Download pdf - A review on applicability of naturally available adsorbents for the removal of hazardous dyes from aqueous waste

Environ Monit Assess (2011) 183:151–195DOI 10.1007/s10661-011-1914-0

A review on applicability of naturally available adsorbentsfor the removal of hazardous dyes from aqueous waste

Pankaj Sharma · Harleen Kaur ·Monika Sharma · Vishal Sahore

Received: 29 March 2010 / Accepted: 27 January 2011 / Published online: 10 March 2011© Springer Science+Business Media B.V. 2011

Abstract The effluent water of many industries,such as textiles, leather, paper, printing, cosmetics,etc., contains large amount of hazardous dyes.There is huge number of treatment processes aswell as adsorbent which are available for theprocessing of this effluent water-containing dyecontent. The applicability of naturally availablelow cast and eco-friendly adsorbents, for the re-moval of hazardous dyes from aqueous waste byadsorption treatment, has been reviewed. In thisreview paper, we have provided a compiled listof low-cost, easily available, safe to handle, andeasy-to-dispose-off adsorbents. These adsorbents

P. Sharma (B) · H. KaurDepartment of Chemistry, Lovely School of Sciences,Lovely Professional University, Phagwara 144402,Punjab, Indiae-mail: [email protected]

P. SharmaEnergy and Environment Fusion Technology Center,Department of Environmental Engineeringand Biotechnology, Myongji University, San 38-2,Nam-dong, Cheoin-Gu, Yongin-Si 449-728,Republic of Korea

M. SharmaDepartment of Chemistry, Kurukshetra University,Kurukshetra 136119, India

V. SahoreDepartment of Microelectronics & Photonics,University of Arkansas, Fayetteville, AR 72701, USA

have been classified into five different categorieson the basis of their state of availability: (1) wastematerials from agriculture and industry, (2) fruitwaste, (3) plant waste, (4) natural inorganic mate-rials, and (5) bioadsorbents. Some of the treatedadsorbents have shown good adsorption capaci-ties for methylene blue, congo red, crystal violet,rhodamine B, basic red, etc., but this adsorptionprocess is highly pH dependent, and the pH of themedium plays an important role in the treatmentprocess. Thus, in this review paper, we have madesome efforts to discuss the role of pH in thetreatment of wastewater.

Keywords Adsorption · Low-cost adsorbents ·Dyes · Wastewater treatment · Column studies

Introduction

With the discovery of the synthetic dyes, the thingsbegan to change. Cheaper to produce, brighter,more color-fast, and easy to apply to fabric aresome of the characteristic of these new dyes.Scientists have competed to formulate gorgeousnew colors, and synthetic dyes had become obso-lete for most applications. No doubt, this bright-colored material has changed the world; however,the chemicals used to produce dyes are oftentoxic, carcinogenic, or even explosive. Among thedifferent pollutants of aquatic ecosystem, dyes are

152 Environ Monit Assess (2011) 183:151–195

a major group of chemicals (Attia et al. 2008;Namasivayam and Kavita 2002; Goyal et al. 2004;Khattri and Singh 1998). Many industries liketextiles, leather, cosmetics, paper, printing, plas-tics, etc., use many synthetic dyes to color theirproducts. Thus, effluents from these industriescontain various kinds of synthetic dye stuffs. Forinstance dyes used in the textile industries areclassified into three classes: (a) Anionic (direct,acid, and reactive dyes), (b) Cationic (all basicdyes), and (c) Non-ionic (dispersed dyes). Basicand reactive dyes are extensively used in the tex-tile industry because of their favorable character-istics of bright color, being easily water soluble,cheaper to produce, and easier to apply to fabric(Karadag et al. 2007; Karcher et al. 2002; Purkaitet al. 2005). Presence of color and color-causingcompounds has always been undesirable in waterfor any use. It is, therefore, not at all surprisingto note that the color in wastewater has now beenconsidered as a pollutant that needs to be treatedbefore discharge. Thus, color removal is one ofthe most difficult requirements to be faced bythe textile finishing, dye manufacturing, pulp andpaper industries, among others. These industriesare major water consumers and are, therefore,a source of considerable pollution. In order toimplement an appropriate treatment process, it isof utmost importance to minimize pollution, andto do that, it is necessary to know its exact nature.Robinson et al. (2001) made some good effortsto give some collective information related tocurrent available technologies and have suggestedan effective, cheaper alternative for dye removaland decolorization applicable on large scale. Theyhave also provided some important data relatedto the desorption of individual textile dyes anda synthetic dye effluent from dye-adsorbed agri-cultural residues using solvents (Robinson et al.2002a, b, c), which is also important in designingthe adsorption treatment process.

Various physical and chemical techniques,other than adsorption, like coagulation, chemicaloxidation, froth floatation, oxidation or ozona-tion, membrane separation, and solvent extrac-tion processes have been used by a number ofresearchers for the removal of organics as well asinorganics from the wastewater; however, theseprocesses are effective and economic, only in the

case where the solute concentrations are relativelyhigh (Panswed and Wongchaisuwan 1986; Malikand Saha 2003; Koch et al. 2002; Ciardelli et al.2000; Gupta and Suhas 2009). Also, these treat-ments involve high operational cost and aerobicdigestion. For instance, photocatalytic degrada-tion processes have shown considerable successin the removal of organic dyes from wastewater(Li et al. 2008; Pauporte and Rathousky 2007; Jainet al. 2007; Marugan et al. 2007); however, therehave certain shortcomings. Coagulation processproduces large amount of sludge leading to highdisposal costs. Ion-exchange process has no lossof adsorbent on regeneration; however, it cannotaccommodate wide range of dyes and is expensive.Membrane separation process is also effective inthe removal of dyes; however, due to relativelyhigh investment and membrane fouling problem,its application is restricted as there is a widerange in pH of dyes and even the conventionalbiological methods are not effective to treat dyebearing wastewaters (Lakshmi et al. 2009). Ad-sorption has been found to be a superior tech-nique as compared to other methods of wastetreatment in terms of cost, simplicity of designand operation, availability, effectiveness, and theirinsensitivity to toxic substances (Choy et al. 2000;Namasivayam et al. 1996). The more recent meth-ods for the removal of synthetic dyes from wa-ter and wastewater were complied and reportedin the form of review article by Forgacs et al.(2004). The advantages and disadvantages of thevarious methods were also discussed and theirefficacies were compared. Adsorption is a physio-chemical wastewater treatment in which dissolvedmolecules are attached to the surface of an ad-sorbent by physical/chemical forces. Dependingon the nature of the interactions ionic speciesand molecular species carrying different func-tional groups may be held to the surface throughelectrostatic attraction to sites of opposite chargeat the surface or physiosorbed due to action ofvan der Waals forces or chemisorbed involvingstrong adsorbate–adsorbent bonding. So, it maylead to attachment of adsorbate molecules atspecific functional group on adsorbent surface.It is true that choice of adsorbent plays a veryimportant role (Sarma et al. 2008). This techniqueis quite popular due to its simplicity as well as

Environ Monit Assess (2011) 183:151–195 153

the availability of a wide range of adsorbents,and it proved to be an effective and attractiveprocess for the removal of non-biodegradable pol-lutants (including dyes) from wastewater (Hanet al. 2006; Aksu 2005). Most commercial systemsuse activated carbon as adsorbent to remove dyesin water because of its significant adsorption ca-pacity. Although activated carbon is a preferredadsorbent, its widespread use is restricted due toits cost. In order to decrease the cost of treat-ment, some attempts have been made to find lowcost alternative adsorbents. Recently, numerousstudies have been conducted to develop cheaperand effective adsorbents from a variety of startingmaterials such as wheat bran carbon (Weng andPan 2006), sludge ash (Rozada et al. 2003), mangoseed kernel (Kumar and Kumrana 2005; Kumarand Porkodi 2006), perlite and clay (Acemioglu2005), sawdust (Shukla et al. 2002; Garg et al.2004), sugarcane (Ho et al. 2005a), jute fiber(Senthilkumaar et al. 2005), bagasse pith (McKayet al. 1987), and carbons from agricultural wastes.The effectiveness of a combined reduction–biological treatment system for the decoloriza-tion of non-biodegradable textile dyeing wastewa-ter was investigated by Ghoreishi and Haghighi(2003). In this treatment system, a bisulfite-catalyzed sodium borohydride reduction is fol-lowed by activated sludge technique in order toremove the color at ambient temperature andpressure, and this experimental study consistedof two major parts: reduction treatment and bi-ological oxidation. Joo et al. (2007) reported thedecolorization of reactive dyes using inorganiccoagulants and synthetic polymer, and they foundthat the use of inorganic coagulant alone appearedlittle effective in the removal of reactive dyes fromthe real wastewater. However, alum/polymer andferric salt/polymer combinations improved colorremoval up to 60% and 40%, respectively.

In this review, an extensive list of adsorbentsobtained from different sources has been com-piled, and this review also reports the optimumprocessing parameters for getting maximum dyeremoval for effluent water. Main emphasis is onthe pH and initial dye concentration in the solu-tion as these two parameter affects the adsorptionprocess more. The other objective to write this re-view paper is to make some comparisons between

the adsorbent capacity of chemically modified,pretreated, and untreated adsorbents.

Low cost and easily available adsorbents

Keeping all the above points in view, our labora-tories are contributing more towards the directionof adsorption by cheap adsorbents. Cost is actu-ally an important parameter for comparing theadsorbent materials. Certain waste products fromindustrial and agricultural operations, natural ma-terials, and biosorbents represent potentially eco-nomical alternative sorbents. Many of them havebeen tested and proposed for dye removal.

Waste materials from agriculture and industries

A number of agricultural wastes/by-products andindustrial waste products have been proposed bya number of researchers for the dye removalfrom aqueous wastewater (Namasivayam andKadirvelu 1994; Pala and Tokat 2002; Crini 2006).These low-cost adsorbents are abundant in na-ture, inexpensive, require little processing, and areeffective for dye removal. The recently reportedadsorbents obtained from the industrial waste andagricultural by products with their adsorption ca-pacities (milligrams per gram) are tabulated inTable 1.

Activated carbon

Activated carbon adsorption is one such methodwhich has great potential for the removal of dyesfrom aqueous waste. The adsorption capacity ofactivated carbon depends on various factors, suchas surface area, pore size distribution, and surfacefunctional groups on the adsorbent, polarity, sol-ubility, and molecular size of the adsorbate, solu-tion pH and the presence of other ions in solution,and so on. The most widely used activated carbonsare microporous and have high surface areas, andas a consequence, show high efficiency for theadsorption of low molecular weight compoundsand for larger molecules. Zhi-yuan (2008) carriedout an adsorption study of methylene blue onactivated carbon fiber (ACF). It has been used inadsorption systems including removal of noxious


Table 1 Reviewed results representing the adsorption capacity of agriculture and industrial waste materials for theadsorption of dyes and their optimized pH values for maximum adsorption

Adsorbent Dye pH Adsorption capacity References

Rice husk Indigo carmine 5.4 65.90 mg g−1 Lakshmi et al. (2009)Activated carbon - RHC Acid yellow 36 3.0 86.90 mg g−1 Malik (2003)Rice husk α-picoline 7.0 15.46 mg g−1 Lataye et al. (2009)Activated carbon Crystal violet 10.8 64.80 mg g−1 Mohanty et al. (2006)Activated carbon - RHS Crystal violet 10.8 61.60 mg g−1 Mohanty et al. (2006)Activated carbon - RHZ Acid blue 2.0 55.40 mg g−1 Mohamed (2004)Rice husk Congo red 6.0 ≈14.00 mg g−1 Han et al. (2008)Rice husk Safranine 7.0 178.10 mg g−1 Kumar and Sivanesan (2007)Rice husk ash Brilliant green 3.0 26.20 mg g−1 Mane et al. (2007a)Sugarcane bagasse Methylene blue 5.8 34.20 mg g−1 Filho et al. (2007)Sugarcane bagasse Methylene blue 7.0 99.60 mg g−1 Raghuvanshi et al. (2004)Sugarcane bagasse Methyl red 7.0 54.60 mg g−1 Azhar et al. (2005)Activated carbon Acid orange 10 7.0 5.78 mg g−1 Tsai et al. (2001)Sugarcane bagasse Basic violet 3 7.0 3.79 mg g−1 Khattri and Singh (2000)Sugarcane dust Basic green 4 7.0 3.99 mg g−1 Khattri and Singh (1999)Activated carbon Acid blue 80 7.0 112.30 mg g−1 Choy et al. (2000)Activated carbon Acid red 114 7.0 103.30 mg g−1 Choy et al. (2000)Activated carbon Acid yellow 117 7.0 155.80 mg g−1 Choy et al. (2000)Activated carbon Reactive blue 2 7.0 0.27 mmol g−1 Al-Degs et al. (2008)Activated carbon Reactive yellow 2 7.0 0.24 mmol g−1 Al-Degs et al. (2008)Activated carbon Reactive red 4 7.0 0.11 mmol g−1 Al-Degs et al. (2008)Activated carbon Methylene blue 3.0 0.93 mmol g−1 Wang and Zhu (2007)Activated carbon Crystal violet 3.0 0.43 mmol g−1 Wang and Zhu (2007)Activated carbon Rhodamine B 3.0 0.48 mmol g−1 Wang and Zhu (2007)Fly ash SFA Methylene blue 5.0 2.40 × 10−3 mol g−1 Janoš et al. (2003)Fly ash SFA Rhodamine B 5.0 0.60 × 10−3 mol g−1 Janoš et al. (2003)Fly ash CFA Methylene blue 5.0 3.60 × 10−3 mol g−1 Janoš et al. (2003)Fly ash CFA Rhodamine B 5.0 1.00 × 10−3 mol g−1 Janoš et al. (2003)Fly ash CFA Egacid orange II 5.0 4.70 × 10−3 mol g−1 Janoš et al. (2003)Fly ash CFA Egacid red G 5.0 2.20 × 10−3 mol g−1 Janoš et al. (2003)Fly ash CFA Egacid yellow G 5.0 1.50 × 10−3 mol g−1 Janoš et al. (2003)Fly ash CFA Midlon black VL 5.0 3.10 × 10−3 mol g−1 Janoš et al. (2003)Cotton waste Basic blue 7.0 277.00 mg g−1 McKay et al. (1999)Fly ash Acid orange 7 7.0 4.00 μg g−1 Albanis et al. (2000)Fly ash Acid yellow 23 7.0 23.90 μg g−1 Albanis et al. (2000)Fly ash Direct yellow 28 7.0 816.00 μg g−1 Albanis et al. (2000)Fly ash Basic yellow 28 7.0 288.00 μg g−1 Albanis et al. (2000)Fly ash Disperse blue 79 7.0 0.06 μg g−1 Albanis et al. (2000)Fly ash Pyridine 6.0 31.06 mg g−1 Lataye et al. (2006)Fly ash Brilliant green 3.0 65.9 mg g−1 Mane et al. (2007b)Fly ash Metomega chrome 7.0 742.80 μg g−1 Gupta and Shukla (1996)Sludge ash Methylene blue 4.0 3.5 × 10−6 mol g−1 Weng and Pan (2006)Sludge ash Reactive blue 2 7.0 250.00 mg g−1 Aksu (2001)Sludge ash Reactive yellow 2 7.0 333.30 mg g−1 Aksu (2001)Activated carbon (sludge based) Basic red 46 11.0 188.00 mg g−1 Martin et al. (2003)Activated carbon (sludge based) Acid brown 283 3.0 20.50 mg g−1 Martin et al. (2003)Activated carbon (sludge based) Direct red 89 3.2 49.20 mg g−1 Martin et al. (2003)Activated carbon (sludge based) Direct black 3.0 28.90 mg g−1 Martin et al. (2003)Activated carbon (Chemviron GW) Basic red 46 11.0 106.00 mg g−1 Martin et al. (2003)Activated carbon (Chemviron GW) Acid brown 283 3.5 22.00 mg g−1 Martin et al. (2003)Activated carbon (Chemviron GW) Direct red 89 4.0 8.40 mg g−1 Martin et al. (2003)


Table 1 (continued)


Activated carbon (Chemviron GW) Direct black 3.0 18.70 mg g−1 Martin et al. (2003)Sugar industry mud Basic red 22 7.0 519.00 mg g−1 Magdy and Daifullah (1998)Activated carbon (oil palm shell) Methylene blue 6.5 243.90 mg g−1 Tan et al. (2008)Granular activated carbon Basic blue 4 7.0 58.82 mmol g−1 Noroozi et al. (2008)Granular activated carbon Basic red 18 7.0 116.27 mmol g−1 Noroozi et al. (2008)Silkworm pupa Basic blue 4 7.0 6.33 mmol g−1 Noroozi et al. (2008)Silkworm pupa Basic red 18 7.0 0.42 mmol g−1 Noroozi et al. (2008)Activated carbon W20 Bisphenyl A 9.0 392.00 mg g−1 Liu et al. (2009)Activated carbon W20N Bisphenyl A 8.0 438.00 mg g−1 Liu et al. (2009)Activated carbon Reactive red 6.1 181.90 mg g−1 Senthilkumaar et al. (2006)

(coconut tree flower)Activated carbon (Jute fiber) Reactive red 6.1 200.00 mg g−1 Senthilkumaar et al. (2006)Activated carbon (rice husk) Malachite green 10.2 1.49 mmol g−1 Guo et al. (2003)Metal hydroxide sludge Reactive red 2 8.6 61.73 mg g−1 Netpradit et al. (2004a)Metal hydroxide sludge Reactive red 120 8.6 45.87 mg g−1 Netpradit et al. (2004a)Metal hydroxide sludge Reactive red 141 8.6 51.55 mg g−1 Netpradit et al. (2004a)Activated carbon (newspaper) Methylene blue 7.0 390.00 mg g−1 Okada et al. (2003)Powdered activated sludge Direct yellow 12 7.0 98.00 mg g−1 Kargi and Ozmıhcı (2004)Charfines Direct brown 7.0 6.40 mg g−1 Mohan et al. (2002b)Lignite coal Direct brown 7.0 4.10 mg g−1 Mohan et al. (2002b)Bituminous coal Direct brown 7.0 2.04 mg g−1 Mohan et al. (2002b)Activated carbon Direct brown 7.0 7.69 mg g−1 Mohan et al. (2002b)Activated carbon (Cassava peel, Rodamine B 5.6 100% Rajeshwarisivaraj et al. (2001)

physical 700◦C) Direct brown 6.9 10.4% Rajeshwarisivaraj et al. (2001)Activated carbon (Cassava peel, Procion orange 6.7 5.3% Rajeshwarisivaraj et al. (2001)

physical 700◦C) Acid violet 6.8 83.0% Rajeshwarisivaraj et al. (2001)Activated carbon (Cassava peel, Malachite green 6.8 100% Rajeshwarisivaraj et al. (2001)

physical 700◦C) Methylene blue 6.8 100% Rajeshwarisivaraj et al. (2001)Activated carbon (Cassava peel, Rodamine B 7.5 100% Rajeshwarisivaraj et al. (2001)

chemical H3PO4) Direct brown 8.3 100% Rajeshwarisivaraj et al. (2001)Activated carbon (Cassava peel, Procion orange 8.3 100% Rajeshwarisivaraj et al. (2001)

chemical H3PO4) Acid violet 8.4 86.3% Rajeshwarisivaraj et al. (2001)Activated carbon (Cassava peel, Malachite green 8.3 100% Rajeshwarisivaraj et al. (2001)

chemical H3PO4) Methylene blue 8.2 100% Rajeshwarisivaraj et al. (2001)Activated carbon (bagasses) Basic red 22 4.1 608.00 mg g−1 Juang et al. (2002a)Activated carbon (bagasses) Acid blue 25 5.9 548.00 mg g−1 Juang et al. (2002a)Activated carbon (beds) Yellow dye 7.0 551.00 mg g−1 Chern and Wu (2001)Activated carbon fiber (pitch) Acid blue 9 9.0 5.0 × 10−4 mol g−1 Tamai et al. (1999)Activated carbon fiber (pitch) Acid blue 74 9.0 9.0 × 10−4 mol g−1 Tamai et al. (1999)Activated carbon fiber (pitch) Acid orange 10 9.0 8.0 × 10−4 mol g−1 Tamai et al. (1999)Activated carbon fiber (pitch) Acid orange 51 9.0 1.8 × 10−4 mol g−1 Tamai et al. (1999)Activated carbon fiber (pitch) Direct black 19 9.0 1.1 × 10−4 mol g−1 Tamai et al. (1999)Activated carbon fiber (pitch) Direct yellow 11 9.0 1.8 × 10−4 mol g−1 Tamai et al. (1999)Activated carbon fiber (pitch) Direct yellow 50 9.0 2.2 × 10−4 mol g−1 Tamai et al. (1999)Activated carbon fiber (pitch) Basic brown 1 9.0 1.4 × 10−3 mol g−1 Tamai et al. (1999)Activated carbon fiber (pitch) Basic yellow 9.0 2.2 × 10−3 mol g−1 Tamai et al. (1999)


Table 1 (continued)


Waste Fe(III)/Cr(III) hydroxide Congo red 3.0 44.00 mg g−1 Namasivayam et al. (1994)Activated carbon (filtrasorb 400) Ramazol reactive 5.7 1111.00 mg g−1 Al-Degs et al. (2000)

yellowActivated carbon (filtrasorb 400) Ramazol reactive 5.7 434.00 mg g−1 Al-Degs et al. (2000)

blackActivated carbon (filtrasorb 400) Ramazol reactive 5.7 400.00 mg g−1 Al-Degs et al. (2000)

redSewage sludge ASSg1 Crystal violet 7.0 263.20 mg g−1 Otero et al. (2003a)Sewage sludge ASSg1 Indigo carmine 7.0 60.00 mg g−1 Otero et al. (2003a)Sewage sludge ASSg2 Crystal violet 7.0 270.90 mg g−1 Otero et al. (2003a)Sewage sludge ASSg2 Indigo carmine 7.0 54.40 mg g−1 Otero et al. (2003a)Sewage sludge PSSg2 Crystal violet 7.0 184.70 mg g−1 Otero et al. (2003a)Sewage sludge PSSg2 Indigo carmine 7.0 30.80 mg g−1 Otero et al. (2003a)Waste carbon slurries Basic red 2.0 10.2 × 10−5 mol g−1 Gupta et al. (2003)Blast furnace slag Basic red 10.0 1.11 × 10−5 mol g−1 Gupta et al. (2003)Metal hydroxide sludge Reactive red 141 8.5 45.00 mg g−1 Netpradit et al. (2004b)Fly ash Methylene blue 5.0 3.47 mmol kg−1 Woolard et al. (2002)Sewage sludge – Ud Methylene blue 7.0 114.90 mg g−1 Otero et al. (2003b)Sewage sludge – Ad Methylene blue 7.0 87.00 mg g−1 Otero et al. (2003b)Sewage sludge – Up Methylene blue 7.0 31.70 mg g−1 Otero et al. (2003b)Sewage sludge – Ap Methylene blue 7.0 28.70 mg g−1 Otero et al. (2003b)Sewage sludge – Ua Methylene blue 7.0 24.90 mg g−1 Otero et al. (2003b)Sewage sludge – Aa Methylene blue 7.0 28.30 mg g−1 Otero et al. (2003b)Activated carbon (pinewood) AC1.5 h Basic blue 69 8.0 598.00 mg g−1 Tseng et al. (2003)Activated carbon (pinewood) AC1.5 h Acid blue 264 8.0 983.00 mg g−1 Tseng et al. (2003)Activated carbon (pinewood) AC1.5 h Methylene blue 8.0 484.00 mg g−1 Tseng et al. (2003)Activated carbon (pinewood) AC2.7 h Basic blue 69 8.0 761.00 mg g−1 Tseng et al. (2003)Activated carbon (pinewood) AC2.7 h Acid blue 264 8.0 1014.00 mg g−1 Tseng et al. (2003)Activated carbon (pinewood) AC2.7 h Methylene blue 8.0 507.00 mg g−1 Tseng et al. (2003)Activated carbon (pinewood) AC4.0 h Basic blue 69 8.0 1119.00 mg g−1 Tseng et al. (2003)Activated carbon (pinewood) AC4.0 h Acid blue 264 8.0 1176.00 mg g−1 Tseng et al. (2003)Activated carbon (pinewood) AC4.0 h Methylene blue 8.0 556.00 mg g−1 Tseng et al. (2003)Wheat straw Remazol red 7.0 2.50 mg g−1 Nigam et al. (2000)Wheat straw Remazol black B 7.0 2.10 mg g−1 Nigam et al. (2000)Corn-cob shreds Remazol red 7.0 0.60 mg g−1 Nigam et al. (2000)Corn-cob shreds Remazol black B 7.0 0.60 mg g−1 Nigam et al. (2000)Activated carbon CC-1 Acid blue 80 7.4 333.30 mg g−1 Valix et al. (2004)Activated carbon CC-3 Acid blue 80 7.4 59.90 mg g−1 Valix et al. (2004)Activated carbon CC-5 Acid blue 80 7.4 75.20 mg g−1 Valix et al. (2004)Activated carbon CC-7 Acid blue 80 7.4 169.50 mg g−1 Valix et al. (2004)Activated carbon CC-10 Acid blue 80 7.4 277.80 mg g−1 Valix et al. (2004)Activated carbon CC-15 Acid blue 80 7.4 384.60 mg g−1 Valix et al. (2004)Parthenium hysterophorus - SWC Methylene blue 7.0 39.70 mg g−1 Lata et al. (2007)Parthenium hysterophorus - PWC Methylene blue 7.0 88.50 mg g−1 Lata et al. (2007)Linseed oil cake Basic blue 41 7.0 303.10 mg g−1 Liversidge et al. (1997)Fly ash: coal Omega chrome 2.0 0.77 mg g−1 Gupta et al. (1990)

red MEFe(III)/Cr(III) hydroxide Direct red 12b 3.0 5.00 mg g−1 Namasivayam and

Sumithra (2005)Fe(III)/Cr(III) hydroxide Methylene blue 10.0 10.00 mg g−1 Namasivayam and

Sumithra (2005)Corncob Dye mixture 7.0 4.60 mg g−1 Robinson et al. (2002b)


Table 1 (continued)


Barley husk Dye mixture 7.0 8.30 mg g−1 Robinson et al. (2002b)Activated carbon Acid red 114 7.0 101.00 mg g−1 Choy et al. (1999)Activated carbon Polar yellow 7.0 128.80 mg g−1 Choy et al. (1999)Activated carbon Polar blue RAWL 7.0 100.90 mg g−1 Choy et al. (1999)Activated sludge Basic red 18 7.0 285.70 mg g−1 Gulnaz et al. (2004)Activated sludge Basic blue 9 7.0 256.40 mg g−1 Gulnaz et al. (2004)White ash Congo red 7.0 171.00 mg g−1 Chou et al. (2001)Pellet adsorbent Congo red 7.0 31.70 mg g−1 Chou et al. (2001)White ash Congo red 7.0 171.00 mg g−1 Chou et al. (2001)Pellet adsorbent Congo red 7.0 31.70 mg g−1 Chou et al. (2001)Coir pith carbon Rhodamine B 11.1 2.56 mg g−1 Namasivayam et al. (2001a)Coir pith carbon Acid violet 1.5 8.06 mg g−1 Namasivayam et al. (2001a)Slag Basic blue 9 11.0 9.95 mg g−1 Ramakrishna and

Viraraghavan (1997)Slag Acid blue 29 2.0 4.86 mg g−1 Ramakrishna and

Viraraghavan (1997)Slag Acid red 91 7.0 2.36 mg g−1 Ramakrishna and

Viraraghavan (1997)Slag Disperse red 1 2.0 33.20 mg g−1 Ramakrishna and

Viraraghavan (1997)Carbonaceous adsorbent Ethyl orange 7.0 198.40 mg g−1 Jain et al. (2003)Carbonaceous adsorbent Methylene yellow 7.0 211.90 mg g−1 Jain et al. (2003)Carbonaceous adsorbent Acid blue 113 7.0 221.20 mg g−1 Jain et al. (2003)Silk cotton carbon Rhodamine B 6.1 70.00 mg g−1 Kadirvelu et al. (2003)Silk cotton carbon Congo red 6.7 250.00 mg g−1 Kadirvelu et al. (2003)Silk cotton carbon Methylene blue 5.1 120.00 mg g−1 Kadirvelu et al. (2003)Silk cotton carbon Methyl violet 5.0 225.00 mg g−1 Kadirvelu et al. (2003)Silk cotton carbon Malachite green 4.9 222.50 mg g−1 Kadirvelu et al. (2003)Coconut tree sawdust carbon Rhodamine B 3.2 247.50 mg g−1 Kadirvelu et al. (2003)Coconut tree sawdust carbon Congo red 3.5 239.00 mg g−1 Kadirvelu et al. (2003)Coconut tree sawdust carbon Methylene blue 3.6 225.50 mg g−1 Kadirvelu et al. (2003)Coconut tree sawdust carbon Methyl violet 3.9 240.00 mg g−1 Kadirvelu et al. (2003)Coconut tree sawdust carbon Malachite green 3.3 225.00 mg g−1 Kadirvelu et al. (2003)Maize cob carbon Rhodamine B 3.2 206.60 mg g−1 Kadirvelu et al. (2003)Maize cob carbon Congo red 5.0 191.40 mg g−1 Kadirvelu et al. (2003)Maize cob carbon Methylene blue 4.0 233.40 mg g−1 Kadirvelu et al. (2003)Maize cob carbon Methyl violet 4.3 93.60 mg g−1 Kadirvelu et al. (2003)Maize cob carbon Malachite green 2.1 120.50 mg g−1 Kadirvelu et al. (2003)Banana pith carbon Rhodamine B 3.2 206.60 mg g−1 Kadirvelu et al. (2003)Banana pith carbon Congo red 5.0 191.40 mg g−1 Kadirvelu et al. (2003)Banana pith carbon Methylene blue 4.0 233.40 mg g−1 Kadirvelu et al. (2003)Banana pith carbon Methyl violet 4.3 93.60 mg g−1 Kadirvelu et al. (2003)Banana pith carbon Malachite green 4.1 120.50 mg g−1 Kadirvelu et al. (2003)Wheat straw Methylene blue 7.0 312.50 mg g−1 Gong et al. (2008)Wheat straw Citric acid 7.0 227.27 mg g−1 Gong et al. (2008)Sunflower oil cake – AC1 Methylene blue 6.0 10.21 mg g−1 Karagöz et al. (2008)Sunflower oil cake – AC2 Methylene blue 6.0 16.43 mg g−1 Karagöz et al. (2008)Sunflower oil cake – AC3 Methylene blue 6.0 15.80 mg g−1 Karagöz et al. (2008)Activated carbon (almond shell) Methylene blue 7.0 1.33 mg g−1 Aygün et al. (2003)Activated carbon (apricot stone) Methylene blue 7.0 4.11 mg g−1 Aygün et al. (2003)Activated carbon (hazelnut shell) Methylene blue 7.0 8.82 mg g−1 Aygün et al. (2003)Activated carbon (walnut shell) Methylene blue 7.0 3.53 mg g−1 Aygün et al. (2003)


Table 1 (continued)


Metal hydroxide sludge Reactive red 2 8.5 62.50 mg g−1 Netpradit et al. (2003)Metal hydroxide sludge Reactive red 120 8.5 48.30 mg g−1 Netpradit et al. (2003)Metal hydroxide sludge Reactive red 141 8.5 56.20 mg g−1 Netpradit et al. (2003)Bark Safranine 7.0 1119.00 mg g−1 McKay et al. (1999)Rice husk Safranine 7.0 838.00 mg g−1 McKay et al. (1999)Cotton waste Safranine 7.0 875.00 mg g−1 McKay et al. (1999)Hair Safranine 7.0 190.00 mg g−1 McKay et al. (1999)Coal Safranine 7.0 120.00 mg g−1 McKay et al. (1999)Bark Methylene blue 7.0 914.00 mg g−1 McKay et al. (1999)Rice husk Methylene blue 7.0 312.00 mg g−1 McKay et al. (1999)Cotton waste Methylene blue 7.0 270.00 mg g−1 McKay et al. (1999)Hair Methylene blue 7.0 158.00 mg g−1 McKay et al. (1999)Coal Methylene blue 7.0 250.00 mg g−1 McKay et al. (1999)Core pith Acid violet 3.0 1.60 mg g−1 Namasivayam et al. (2001b)Core pith Acid brilliant blue 3.0 16.60 mg g−1 Namasivayam et al. (2001b)Core pith Rhodamine B 3.0 203.20 mg g−1 Namasivayam et al. (2001b)Activated carbon (rice husk) Acid blue 2.0 50.00 mg g−1 Mohamed (2004)Activated carbon fibers Methylene blue 7.0 99.30 mg g−1 Zhi-yuan (2008)Rice husk Safranine 7.0 838.00 mg g−1 McKay et al. (1999)Cotton waste Safranine 7.0 875.00 mg g−1 McKay et al. (1999)Hair Safranine 7.0 190.00 mg g−1 McKay et al. (1999)Coal Safranine 7.0 120.00 mg g−1 McKay et al. (1999)Bark Methylene blue 7.0 914.00 mg g−1 McKay et al. (1999)Rice husk Methylene blue 7.0 312.00 mg g−1 McKay et al. (1999)Cotton waste Methylene blue 7.0 270.00 mg g−1 McKay et al. (1999)Hair Methylene blue 7.0 158.00 mg g−1 McKay et al. (1999)Coal Methylene blue 7.0 250.00 mg g−1 McKay et al. (1999)Sugarcane dust Basic violet 10 7.0 50.4 mg g−1 Ho et al. (2005a)Sugarcane dust Basic violet 1 7.0 13.9 mg g−1 Ho et al. (2005a)Sugarcane dust Basic green 4 7.0 20.6 mg g−1 Ho et al. (2005a)Activated carbon (rice husk) Acid blue 2.0 50.00 mg g−1 Mohamed (2004)Cotton Direct red 28 7.0 1 × 10−2 kg−1 Sawada and Ueda (2003)Calcium rich - fly ash Congo red 5.0 4.47 × 105 mol g−1 Acemioglu (2004)Activated carbon (sewage – sludge) Methylene blue 7.0 6.08 mg g−1 Rozada et al. (2003)Activated carbon (sewage – sludge) Saphranine 7.0 11.05 mg g−1 Rozada et al. (2003)Commercial activated carbon Methylene blue 7.4 980.30 mg g−1 Kannan and Sundaram (2001)Bamboo dust carbon Methylene blue 7.4 143.20 mg g−1 Kannan and Sundaram (2001)Coconut shell carbon Methylene blue 7.4 277.90 mg g−1 Kannan and Sundaram (2001)Groundnut shell carbon Methylene blue 7.4 164.90 mg g−1 Kannan and Sundaram (2001)Rice husk carbon Methylene blue 7.4 343.50 mg g−1 Kannan and Sundaram (2001)Straw carbon Methylene blue 7.4 472.10 mg g−1 Kannan and Sundaram (2001)Sugarcane baggase Methylene blue 7.0 96.56 mg g−1 Raghuvanshi et al. (2004)Activated sugarcane baggase Methylene blue 7.0 99.63 mg g−1 Raghuvanshi et al. (2004)Lignin (sugarcane baggase) Methylene blue 4.5 16.50 mg g−1 Filho et al. (2007)Activated carbon PKN2 Methylene blue 7.0 765.00 mg g−1 Tseng (2007)Activated carbon PKN2 Acid blue 74 7.0 549.00 mg g−1 Tseng (2007)Activated carbon PKN2 Basic brown 1 7.0 1453.00 mg g−1 Tseng (2007)Activated carbon PKN3 Methylene blue 7.0 785.00 mg g−1 Tseng (2007)Activated carbon PKN3 Acid blue 74 7.0 561.00 mg g−1 Tseng (2007)Activated carbon PKN3 Basic brown 1 7.0 1529.00 mg g−1 Tseng (2007)Activated carbon PKN4 Methylene blue 7.0 828.00 mg g−1 Tseng (2007)Activated carbon PKN4 Acid blue 74 7.0 567.00 mg g−1 Tseng (2007)


Table 1 (continued)


Activated carbon PKN4 Basic brown 1 7.0 1845.00 mg g−1 Tseng (2007)Activated carbon (oil palm wood) Methylene blue 7.0 90.9 mg g−1 Ahmad et al. (2007)Activated carbon C1 Methylene blue 7.0 198.00 mg g−1 Attia et al. (2008)Activated carbon C2 Methylene blue 7.0 309.00 mg g−1 Attia et al. (2008)Activated carbon C3 Methylene blue 7.0 362.00 mg g−1 Attia et al. (2008)Activated carbon C4 Methylene blue 7.0 412.00 mg g−1 Attia et al. (2008)Activated carbon C5 Methylene blue 7.0 306.00 mg g−1 Attia et al. (2008)Activated carbon C6 Methylene blue 7.0 316.00 mg g−1 Attia et al. (2008)Activated carbon Rhodamine B 2.1 5.34 × 10−5 mg g−1 Jain et al. (2007)Rice husk Rhodamine B 2.1 5.87 × 10−5 mg g−1 Jain et al. (2007)Wheat bran carbon Methylene blue 2.5 222.20 mg g−1 Özer and Dursun (2007)I-GLYTAC-Cotton Acid blue 25 7.0 0.26 mmol g−1 Bouzaida and Rammah (2002)I-GLYTAC-Cotton Acid yellow 99 7.0 0.18 mmol g−1 Bouzaida and Rammah (2002)I-GLYTAC-Cotton Reactive yellow 23 7.0 0.19 mmol g−1 Bouzaida and Rammah (2002)II-GLYTAC-Cotton Acid blue 25 7.0 0.60 mmol g−1 Bouzaida and Rammah (2002)II-GLYTAC-Cotton Acid yellow 99 7.0 0.39 mmol g−1 Bouzaida and Rammah (2002)II-GLYTAC-Cotton Reactive yellow 23 7.0 0.39 mmol g−1 Bouzaida and Rammah (2002)III-GLYTAC-Cotton Acid blue 25 7.0 0.64 mmol g−1 Bouzaida and Rammah (2002)III-GLYTAC-Cotton Acid yellow 99 7.0 0.41 mmol g−1 Bouzaida and Rammah (2002)III-GLYTAC-Cotton Reactive yellow 23 7.0 0.41 mmol g−1 Bouzaida and Rammah (2002)IV-GLYTAC-Cotton Acid blue 25 7.0 0.59 mmol g−1 Bouzaida and Rammah (2002)IV-GLYTAC-Cotton Acid yellow 99 7.0 0.37 mmol g−1 Bouzaida and Rammah (2002)IV-GLYTAC-Cotton Reactive yellow 23 7.0 0.37 mmol g−1 Bouzaida and Rammah (2002)V-GLYTAC-Cotton Acid blue 25 7.0 0.59 mmol g−1 Bouzaida and Rammah (2002)V-GLYTAC-Cotton Acid yellow 99 7.0 0.36 mmol g−1 Bouzaida and Rammah (2002)V-GLYTAC-Cotton Reactive yellow 23 7.0 0.36 mmol g−1 Bouzaida and Rammah (2002)Porous carbon Rhodamine B 3.45 0.90 mmol g−1 Guo et al. (2005)

gases because of its extensive specific surfacearea, high adsorption capacity, well-developed mi-cropores, reproducibility, and processability. Theeffects of various experimental parameters, suchas the initial methylene blue (MB) concentra-tion and the ACF mass, on the adsorption rateswere investigated. Equilibrium data was fit wellby a Freundlich isotherm equation. Adsorptionmeasurement shows that the process is very fast.Moreover, thermodynamic parameters �Go, �So,and �Ho were calculated (Wang and Zhu 2007).

Nakagawa et al. (2004) made attempt to eval-uate the porous properties and hydrophobicityof activated carbons obtained from several solidwastes, namely, waste PET, waste tires, refusederived fuel, and wastes generated during lacticacid fermentation from garbage. Activated car-bons having various pore size distributions wereobtained by the conventional steam-activationmethod and via the pretreatment method (i.e.,mixture of raw materials with a metal salt, car-

bonization, and acid treatment prior to steamactivation). The liquid-phase adsorption charac-teristics of organic compounds from aqueous solu-tion on the activated carbons were determined toconfirm the applicability of these carbons, wherereactive dye, Black5, were employed as repre-sentative adsorbates. Authors reported that theactivated carbons with plentiful mesopores pre-pared from PET and waste tires had quite highadsorption capacity for large molecules. There-fore, they are useful for wastewater treatment,especially for removal of bulky adsorbates. Liet al. (2002) reported the displacement of atrazineby the strongly competing fraction of naturalorganic matter (NOM) in batch and continuous-flow powdered activated carbon (PAC) adsorp-tion system. The extent of atrazine displacementby NOM was found to be dependent on the typeof PAC, while the rate of displacement was afunction of PAC type as well as carbon dose.Choy et al. (2000) reported the adsorption of


three acidic dyes, Acid Blue 80 (AB80), AcidRed 114 (AR114), and Acid Yellow 117 (AY117)onto activated carbon. In the same paper, theyhave also reported the adsorption isotherms forthe three single components (AB80, AR114, andAY117) and three binary component (AB80 +AR114, AB80 + AY117, and AR114 + AY117),dyes adsorption on activated carbon. Four mod-els for predicting the multicomponent equilibriumsorption isotherms have been compared in or-der to determine the best to predict or corre-late binary adsorption data. These four modelsare the extended Langmuir isotherm, the sim-plified model based on single-component equi-librium factors, a modified extended Langmuirisotherm with a constant interaction factor, anda modified extended Langmuir isotherm incorpo-rating a surface coverage-dependent interactionfactor. Adsorption of trichloroethylene (TCE) bytwo ACFs and two granular activated carbons pre-loaded with hydrophobic and transphilic fractionsof NOM was examined by Tanju Karanfil et al.(2006) ACF10. The most microporous activatedcarbon used in this study had over 90% of itspore volume in pores smaller than 10 Å. It alsohad the highest volume in pores 5–8 Å, which isthe optimum pore size region for TCE adsorption,among the four activated carbons. Adsorption ofNOM fractions by ACF10 was, in general, negli-gible. Therefore, ACF10, functioning as a mole-cular sieve during preloading, exhibited the leastNOM uptake for each fraction, and subsequentlythe highest TCE adsorption. The other three sor-bents had wider pore size distributions, includinghigh volumes in pores larger than 10 Å, whereNOM molecules can be adsorbed. As a result, theyshowed higher adsorption efficiency for all NOMfractions, and subsequently lower adsorption ca-pacities for TCE, as compared to ACF10.

Adsorption of congo red (CR) dye on bitu-minous coal-based mesoporous activated carbon(AC) from aqueous solutions was reported byGrabowska and Gryglewicz (2007). The mesoporecontribution to the total pore volume ranged from52% to 83%. The adsorption tests were performedunder static conditions at solution pH 7.8–8.3.Itwas found that the higher the fraction of meso-pores with a size between 10 and 50 nm, theshorter the time to achieve the equilibrium stage

for CR adsorption. The kinetics of adsorptionin view of three kinetic models, i.e., the first-order Lagergren model, the pseudo-second-ordermodel, and the intraparticle diffusion model,was discussed. The pseudo-second-order kineticmodel describes the adsorption of CR on meso-porous activated carbon very well. The correla-tion coefficients ranged from 0.980 to 0.991. Theintra-particle diffusion into small mesopores wasfound to be the rate-limiting step in the adsorptionprocess. The equilibrium adsorption data were in-terpreted using Langmuir and Freundlich models.The adsorption of CR was better represented bythe Langmuir equation. The monolayer adsorp-tion capacity of ACs was found to increase withincreasing both the mesopore volume and themesopore contribution to their porous texture.The effect of solution ionic strength on the up-take of CR by two different mesoporous car-bons was also investigated. Also, the kinetics andmechanism of MB adsorption on commerciallyactivated carbon and indigenously prepared acti-vated carbons from bamboo dust, coconut shell,groundnut shell, rice husk, and straw have beenreported by the Kannan and Sundaram (2001).The effects of various experimental parametershave been investigated using a batch adsorp-tion technique to obtain information on treatingeffluents from the dye industry. The extent ofdye removal increased with decrease in the ini-tial concentration of the dye and particle size ofthe adsorbent and also increased with increasein contact time, amount of adsorbent used andthe initial pH of the solution. Adsorption datawere modeled using the Freundlich and Lang-muir adsorption isotherms and first-order kineticequations. The kinetics of adsorption was foundto be first order with regard to intra-particlediffusion rate. The adsorption capacities of in-digenous activated carbons have been comparedwith that of the commercially activated carbon.The results indicate that such carbons could beemployed as the low-cost alternatives to com-mercially activated carbon in wastewater treat-ment for the removal of color and dyes. Jirankovaet al. (2007) contribution deals with study of thecombined adsorption-membrane process for or-ganic dye removal. Adsorption equilibrium andkinetics of Egacid red sorption on PAC were stud-


ied in batch experiments. During the combinedhollow fiber membrane microfiltration operatedin dead-end mode, it was found that membranewas effective for removal of PAC particles fromwater suspensions and PAC tendency for irre-versible membrane fouling was extremely low.The presented combined adsorption-membraneprocess has a potential application for organicdye removal. Tapered bed adsorption columns,using activated carbon, have been used to studythe removal of two organic pollutants, an aciddye and para-chlorophenol, from aqueous effluentby McKay et al. (2008). Equilibrium sorptionisotherms were measured to provide the satura-tion capacity (qe) of each pollutant by ChemvironFiltrasorb 400 carbon, for operating continuousadsorption columns. The Redlich–Peterson (R–P) isotherm gives the best fit model to describethe sorption process of these organic pollutants.The conventional bed depth service time (BDST)model has not been applied to tapered beds be-fore, as the linear velocity of fluid is continuallychanging along the column. Several others authors(Al-Degs et al. 2008; Wang and Zhu 2007; Nassarand Magdy 1997) have also tested activated car-bon for the adsorption of various dyes.

Pereira et al. (2003) reported that the sur-face chemistry of a commercially activated carbonhas been selectively modified, without changingsignificantly its textural properties, by means ofchemical treatments, using HNO3, H2O2, NH3,and thermal treatments under a flow of H2 orN2, and they found that the surface chemistry ofthe activated carbon plays a key role in dye ad-sorption performance. The basic sample obtainedby thermal treatment under H2 flow at 700◦C isthe best material for the adsorption of most ofthe dyes tested. For anionic dyes (reactive, direct,and acid), a close relationship between the surfacebasicity of the adsorbents and dye adsorption isshown, the interaction between the oxygen-freeLewis basic sites and the free electrons of thedye molecule being the main adsorption mecha-nism. For cationic dyes (basic), the acid oxygen-containing surface groups show a positive effectbut thermally treated samples still present goodperformances, showing the existence of two paral-lel adsorption mechanisms involving electrostaticand dispersive interactions. The conclusions ob-

tained for each dye individually were confirmedin the color removal from a real textile processeffluent.

Rice husk/rice husk ash

Rice husk is insoluble in water, has good chem-ical stability, high mechanical strength, and pos-sesses a granular structure, making it a goodadsorbent material. Rice husk consists of cel-lulose (32.24%), hemicelluloses (21.34%), lignin(21.44%), and mineral ash (15.05%) and highpercentage of silica in its mineral ash, which isapproximately 96.34%. Pretreatment of rice huskcan remove lignin and hemicelluloses, decreasecellulose crystallinity, and increase the porosityand surface area. Rice husk can easily be con-verted into rice husk ash (RHA) at 300◦C whichcontains 92% to 95% silica. The adsorbent ob-tained by this treatment is light weight with avery external surface area. Lakshmi et al. (2009)carried out study of the adsorptive characteristicsof Indigo Carmine (IC) dye from aqueous solu-tion onto RHA. Batch experiments were carriedout to determine the influence of parameters likeinitial pH, contact time, adsorbent dose, and ini-tial dye concentration on the removal of IC. Theoptimum conditions were found to be: pH = 5.4,t = 8 h, and m = 10.0 g L−1. The pseudo-second-order kinetic model represented the adsorptionkinetics of IC on to RHA. Equilibrium isothermswere analyzed by Freundlich, Langmuir, Temkin,and Redliche Peterson models using a nonlinearregression technique. Adsorption of IC on RHAwas favorably influenced by an increase in thetemperature of the operation. The positive valuesof the change in entropy (�So) and heat of ad-sorption (�Ho); and the negative value of changein Gibbs free energy (�Go) indicate feasible andspontaneous adsorption of IC on to RHA.

Adsorption onto activated carbon is a potentmethod for the treatment of dye-bearing effluentsbecause it offers various advantages as reportedby Mohanty et al. (2006). In this study, activatedcarbons, prepared from low-cost rice husk bytwo different processes: physical activation andchemical activation, were used as the adsorbentfor the removal of crystal violet. The effects ofvarious experimental parameters, such as adsor-


bent dosage and size, initial dye concentration,pH, contact time, and temperature, were investi-gated in batch mode. The kinetic data were wellfitted to the Lagergren, pseudo-second order, andintra-particle diffusion models. It was found thatintra-particle diffusion plays a significant role inthe adsorption mechanism. The isothermal datacould be well described by the Langmuir andFreundlich equations. The maximum uptakes ofcrystal violet by sulfuric acid activated (RHS) andzinc chloride activated (RHZ) rice husk carbonwere found to be 64.875 and 61.575 mg g−1 ofadsorbent, respectively. The results indicate thatRHS and RHZ could be employed as low-costalternatives to commercially activated carbon inwastewater treatment for the removal of basicdyes. It has been reported in one of the papersby Dhalan et al. (2006) that the materials, such asRHA, have the potential to be utilized as high-performance sorbents for the flue gas desulfur-ization process in small-scale industrial boilers.This study presents findings on identifying the keyfactor for high desulfurization activity in sorbentsprepared from RHA. Initially, a systematic ap-proach using central composite rotatable designwas used to develop a mathematical model thatcorrelates the sorbent preparation variables tothe desulfurization activity of the sorbent. Hanet al. (2008) reported a continuous bed study byusing rice husk as a biosorbent for the removalof CR from aqueous solution. The effects of im-portant factors, such as the value of pH, existingsalt, the flow rate, the influent concentration ofCR, and bed depth, were studied. Data confirmedthat the breakthrough curves were dependenton flow rate, initial dye concentration, and thebed depth. Thomas, Adams–Bohart, and Yoon–Nelson models were applied to the experimentaldata in order to predict the breakthrough curvesusing nonlinear regression and to determine thecharacteristic parameters of the column useful forprocess design, while BDST model was used toexpress the effect of bed depth on breakthroughcurves. The results showed that Thomas modelwas found suitable for the normal description ofbreakthrough curve at the experimental condi-tion, while Adams–Bohart model was only foran initial part of dynamic behavior of the ricehusk column. The data were in good agreement

with BDST model. It was concluded that the ricehusk column can remove CR from solution (Malik2003; McKay et al. 1999; Mohamed 2004; Hanet al. 2008; Guo et al. 2005; Kumar and Sivanesan2007; Mane et al. 2007a).

Sugarcane dust

The adsorption potential of agricultural (sugar-cane) by-product, the baggase was investigatedin batch experiments with two different formsi.e., raw and chemically activated forms, for theremoval of MB dye, with different parameters likedye concentration, contact time, temperature, andadsorbent dose is reported by Raghuvanshi et al.(2004). The removal is better and more effectivewith chemically activated baggase in comparisonto the raw baggase. An average percent removaldifference between the two adsorbents of around18% was achieved under the different experimen-tal conditions. The data fit well in the Freundlichisotherm. Azhar et al. (2005) in one of his pa-pers has reported that adsorbents prepared fromsugarcane baggase-an agro industries waste weresuccessfully used to remove the methyl red froman aqueous solution in a batch reactor. This studyinvestigates the potential use of sugarcane bag-gase, pretreated with formaldehyde (PCSB) andsulfuric acid (PCSBC), for the removal of methylred from simulated wastewater. Formaldehyde-treated and sulfuric acid-treated sugarcane bag-gase were used to adsorb methyl red at varyingdye concentration, adsorbent dosage, pH, andcontact time (Tsai et al. 2001). Similar experimentwas conducted with commercially available PAC,in order to evaluate the performance of PCSB andPCSBC. The adsorption efficiency of different ad-sorbents was in the order PAC>PCSBC>PCSB.The initial pH of 6–10 flavors the adsorption ofboth PCSB and PCSBC. Adsorbents are veryefficient in decolorized diluted solution. It is pro-posed that PCSB and PCSBC, in a batch or stirredtank reactors, could be employed as a low-costalternative in wastewater treatment for the dyeremoval.

Filho et al. (2007) carried out an experiment inwhich the adsorption kinetics and equilibrium ofMB onto reticulated formic lignin from sugar canebaggase was studied. The adsorption process is


pH, temperature, and ionic strength (μ) dependentand obeys the Langmuir model. Conditions forhigher adsorption rate and capacity were deter-mined. The faster adsorption (12 h) and higheradsorption capacity (34.20 mg g−1) were observedat pH = 5.8 (acetic acid-sodium acetate aque-ous buffer), 50◦C, and 0.1 ionic strength. Theseinteractions between binding sites were detectedthrough Scatchard analysis. Under temperature(50◦C) control and occasional mechanical stirring,it took from 1 to 10 days to reach equilibrium(Khattri and Singh 1999). The sorption of threebasic dyes, named basic violet 10, basic violet 1,and basic green 4, from aqueous solutions ontosugarcane dust was studied by Ho et al. (2001).The results revealed the potential of sugarcanedust, a waste material, to be a low-cost sorbent.Equilibrium isotherms were analyzed using theLangmuir, Freundlich, and the three-parameterRedlich–Peterson isotherms. In order to deter-mine the best-fit isotherm for each system, twoerror analysis methods were used to evaluate thedata: the linear coefficient of determination andthe Chi-square statistic test for determination of anonlinear model. Results indicated that the Chi-square test provided a better determination forthe three sets of experimental data.

Cotton waste

Cotton is one of the most widely used fibersby the agriculturists. Cotton found naturally andconsisting cellulose exhibits excellent physical andchemical properties in terms of stability, water ab-sorbency, and dye removal ability. Bouzaida andRammah (2002) reported the adsorption of aciddyes on treated cotton in a continuous system.It has been concluded that at 20◦C and for thegrafted support at 1.25% of nitrogen, the capacityis around 589, 448, and 302 mg of adsorbed dye,respectively, for acid blue 25, acid yellow 99, andReactive yellow 23 dyes. Sawada and Ueda (2003)studied the solubilization and adsorption behaviorof direct dye on cotton in Aerosol-OT reveremicellar system. Cotton fabrics could be dyed indeep shade with direct dye from reverse micellarsystem without adding auxiliaries. Exhaustion ofdye was almost perfect and was very superior tothat in aqueous system. High exhaustion of the

dye in reverse micellar system was attributed tothe very low bath ratio (water–fabric ratio) com-pared to the conventional aqueous dyeing process.It has become obvious that adsorption of di-rect dye on cotton in reverse micellar system issimilar to that in aqueous system and follows aFreundlich manner.

Fly ash

Adsorption and removal of commercial dyes werestudied in aqueous suspensions of fly ash mixtureswith a sandy clay loam soil of low organic mattercontent. The commercial dyes, acid orange 7, acidyellow 23, disperse blue 79, basic yellow 28, anddirect yellow 28 represent the widely used ni-troazo structures. Batch and column experimentswere carried out by Albanis et al. (2000) at equi-librium conditions for concentrations of dyes be-tween 5 and 60 mg L−1. The logarithmic formof Freundlich equation gave a high linearity andthe K constants are increasing with the increaseof fly ash content in adsorbent mixtures and theaffinity between the adsorbent surface and ad-sorbed solute. The mean amount of removed dyesby adsorption batch experiments in soil mixturewith 20% fly ash content were up to 53.0% foracid yellow 7, 44.9% for acid yellow 23, 99.2%for direct yellow 28, 96.8% for basic yellow 28,and 88.5% for disperse blue 79. The removal ofdyes from column experiments decrease with theincrease of the solution concentration form 10to 50 mg L−1 at 20◦C, showing the process tobe highly dependent on the concentration of thesolution. The mean removed amounts of dyes byadsorption on columns of soil mixture with 20%fly ash content and for initial concentration ofdye solutions 50 mg L−1 were up to 33.8% foracid yellow 7, 59.4% for acid yellow 23, 84.2%for direct yellow 28, 98.2% for basic yellow 28,and 60.3% for disperse blue 79. Moreover, Latayeet al. (2009) reported adsorption of pyridine (Py)from aqueous solutions, using bagasse fly ash(BFA), which is a solid waste that is generatedfrom bagasse-fired boilers as an adsorbent. Batchadsorption studies have been performed to eval-uate the influence of various parameters, on theremoval of Py from the aqueous solutions. Themaximum removal of Py is determined to be 99%


at lower concentrations (<50 mg L−1) and 95%at higher concentrations (600 mg L−1), using aBFA dosage of 25 kg m−3at normal temperature.Studies on Py adsorption equilibrium and kineticsby BFA also have been conducted. The adsorp-tion equilibrium analyses are performed, usingthe Langmuir, Freundlich, Redlich–Peterson, andTemkin isotherm equations. The Langmuir equa-tion is determined to best represent the equilibri-um sorption data. Thermodynamic studies revealedthat the adsorption of Py on BFA is endothermicin nature and that the isosteric heat of adsorptiondecreases as the equilibrium uptake of Py on theBFA surface increases.

Adsorption studies were carried out for different temperatures, particle sizes, pHs, and adsor-bent doses by Mohan et al. (2002a). The ad-sorption of each dye was found to increase withincreasing temperature, thereby indicating thatthe process is endothermic in nature. The re-moval of each dye was found to be inverselyproportional to the size of the fly ash particles,as expected. Both the linear and nonlinear formsof the Langmuir and Freundlich models havefitted the adsorption data. The results indicatethat the Freundlich adsorption isotherm fittedthe data better than the Langmuir adsorptionisotherm. Further, the data were better corre-lated with the nonlinear than the linear form ofthis equation. Thermodynamic parameters suchas the free energies, enthalpies, and entropies ofadsorption of the dye-fly ash systems were alsoevaluated. The negative values of free energy in-dicate the feasibility and spontaneous nature ofthe process, and the positive heats of enthalpysuggest the endothermic nature of the process.The adsorptions of crystal violet and basic fuschinfollow first-order rate kinetics. In comparison toother low-cost adsorbents, the sorption capacityof the material under investigation is found to becomparable to that of other commercially avail-able adsorbents used for the removal of cationicdyes from wastewater (Mane et al. 2007b; Guptaand Shukla 1996). Hsu (2008) carried out ex-periment in which they found that raw coal flyash (CFA) that has not been subjected to anypretreatment process have a superior adsorbingability for the anionic dye Acid red 1 (AR1) thanthe two modified coal fly ashes (CFA-600 and

CFA-NaOH). The adsorption capacities followedthe order CFA > CFA-600 > CFA-NaOH, andthe capacities for all of them increased upon in-creasing the temperature (60◦C > 45◦C > 30◦C).The adsorptions of AR1 onto CFA, CFA-600,and CFA-NaOH, all followed pseudo-second-order kinetics. The isotherms for the adsorptionof AR1 onto the raw and modified coal fly ashesfit the Langmuir isotherm quite well; the ad-sorption capacities of CFA, CFA-600, and CFA-NaOH for AR1 were 92.59–103.09, 32.79–52.63,and 12.66–25.12 mg g−1, respectively. Accordingto the positive values of �H◦ and �S◦, these ad-sorptions were endothermic processes. The AREand EABS error function methods provided thebest parameters for the Langmuir isotherms andpseudo-second-order equations, respectively, inthe AR1–CFA adsorption system.

Sludge ash/bottom ash

Weng and Pan (2006) reported that the kinet-ics and equilibrium adsorption experiments wereconducted to evaluate the adsorption characteris-tics of a cationic dye (MB) onto bio-sludge ash.Results show that the ash could remove the dyeeffectively from aqueous solution. The adsorptionrate was fast and about 80% of absorbed MBwas removed in 10 min. The adsorption kineticscould be expressed by the modified Freundlichequation and intra-particle diffusion model. It wasfound that both the initial MB concentration andionic strength could affect the rate of adsorption.The effect of electrical double layer thicknesson the adsorption kinetics was discussed. Theequilibrium adsorption data was correlated wellto the nonlinear multilayer adsorption isotherm.The maximum adsorption capacities for MB were7.3 × 10−6, 6.3 × 10−6, 5.0 × 10−6, and 3.5 ×10−6 mol g−1, respectively, at temperature of 4◦C,14◦C, 24◦C, and 34◦C. Values of the first-layeradsorption energy, �Go, ranged from −6.62 to−7.65 kcal mol−1, suggesting that the adsorptioncould be considered as a physical process, whichis simultaneously enhanced by the electrostaticeffects. The multilayer adsorption energy, �Go,ranged from -4.51 to -5.02 kcal mol−1, suggest-ing that the adsorption was of the typical phys-ical type. On the basis of the monolayer dye


adsorption capacity, the specific surface area ofthis ash sample was estimated as 2.1–2.9 m2 g−1

which is close to the value (3.7 m2 g−1) obtainedvia BET nitrogen gas adsorption measurements.Mittal et al. (2006a) carried out an inexpensiveadsorption method for the removal of indigocarmine, a highly toxic indigoid class of dye fromwastewater by bottom ash. Attempts have beenmade through batch and bulk removal of the dye,and both the adsorbents have been found to ex-hibit good efficiency to adsorb indigo carmine.Under batch technique effect of temperature,pH, concentration, dosage of adsorbents, sievesize of adsorbents, etc. have been observed. Thedye uptake on to both the adsorbents is foundto validate Langmuir and Freundlich adsorptionisotherms models. Different thermodynamic pa-rameters, like Gibb’s free energy, enthalpy, andentropy of the ongoing adsorption process, havealso been evaluated (Aksu and Tezer 2000). TheBatch technique employed for kinetic measure-ments, and the adsorption follows a first-order-rate kinetics for both the adsorbents. The kineticinvestigations also reveal for both the adsorbentsfilm diffusion and particle diffusion mechanismsare operative in the lower and higher concentra-tion ranges, respectively. Under the bulk removal,indigo carmine has been adsorbed through thecolumn beds of bottom ash and de-oiled soya, andmore than 90% of the dye material has been re-covered by eluting dilute NaOH solution throughexhausted columns.

Tartrazine a highly toxic dye can be adsorbedby bottom ash as demonstrated by Mittal et al.(2006b). Through the batch technique, equilib-rium uptake of the dye is observed at differentconcentrations, pH of the solution, dosage of ad-sorbents, and sieve size of adsorbents. Langmuirand Freundlich adsorption isotherms are success-fully employed on both the adsorbents, and on thebasis of these models, the thermodynamic para-meters are evaluated. Kinetic investigations revealthat more than 50% adsorption of dye is achievedin about 1 h in both these cases, whereas equilib-rium establishment takes about 3 to 4 h. The linearplots obtained in rate constant and mass transferstudies further confirm the applicability of firstorder rate expression and mass transfer model,respectively. The kinetic data treated to identify

rate controlling step of the ongoing adsorptionprocesses indicate that for both the systems, par-ticle diffusion process is predominant at higherconcentrations, while film diffusion takes place atlower concentrations. The column studies revealthat about 96% saturation of both the columnsis attained during their exhaustion, while about88% and 84% of the dye material is recovered byeluting dilute NaOH solution through exhaustedBottom Ash.

Fruit waste

In this part of the review article, we have tried todiscuss the cellulose-based waste (fruit waste) forthe removal of different types of dyes from water(Table 2). Fruit peel and pith is discarded in thejuice and soft-drink industries all over the world,and India is the second largest consumer and pro-ducer of fruits which also leads to the generationof million tones of fruit waste. Such fruit waste canbe effectively used for the wastewater treatment(Hameed et al. 2008; Kumar and Porkodi 2006;Youssef 1993).

Yellow passion fruit

Pavan et al. (2008a) reported that the use ofyellow passion fruit (YPFW), a powdered solidwaste, was tested as biosorbent for the removalof a cationic dye MB from aqueous solution. Ad-sorption of MB onto this low-cost natural adsor-bent was studied by batch adsorption at 25◦C.The effects of shaking time, biosorbent dosage,and pH on adsorption capacities were studied.In alkaline pH region, the adsorption of MB isfavorable. The contact time required to obtainthe maximum adsorption was 48 h at 25◦C. Fourkinetic models were tested, being the adsorptionkinetics better fitted to pseudo-first-order and ionexchange kinetic models. The ion exchange andpseudo-first-order constant rates were 0.05594and 0.05455 h−1, respectively. The equilibriumdata was fitted to Langmuir, Freundlich, Sips, andRedlich–Peterson isotherm models. Taking intoaccount the analysis of the normal distribution ofthe residuals (difference of qmeasured − qmodel), thedata were best fitted to Sips isotherm model. Themaximum amount of MB is absorbed by YPFW


Table 2 Reviewed results representing the adsorption capacity of fruit waste for the adsorption of dyes and their optimizedpH values for maximum adsorption


Yellow passion fruit Methylene blue 9.0 16.00 mg g−1 Pavan et al. (2007)Yellow passion fruit Methylene blue 8.0 44.70 mg g−1 Pavan et al. (2008a)Mandarin peel Methylene blue 11.0 15.20 mg g−1 Pavan et al. (2007)Orange peel Rhodamine B 3.0 3.22 mg g−1 Namasivayam et al. (1996)Orange peel Congo red 5.0 22.40 mg g−1 Namasivayam et al. (1996)Orange peel Procion orange 3.0 1.30 mg g−1 Namasivayam et al. (1996)Orange peel Acid violet 17 6.3 19.88 mg g−1 Sivaraj et al. (2001)Orange peel Direct red 28 8.0 14.00 mg g−1 Annadurai et al. (2002)Orange peel Direct red 23 2.0 10.72 mg g−1 Arami et al. (2005)Orange peel Direct red 80 2.0 21.05 mg g−1 Arami et al. (2005)Orange peel Basic violet 10 8.0 14.30 mg g−1 Annadurai et al. (2002)Orange peel Methyl orange 5.7 20.50 mg g−1 Annadurai et al. (2002)Orange peel Methylene blue 7.2 18.60 mg g−1 Annadurai et al. (2002)Orange peel Rhodamine B 5.8 14.30 mg g−1 Annadurai et al. (2002)Orange peel Congo red 7.9 14.00 mg g−1 Annadurai et al. (2002)Orange peel Methyl violet 5.3 11.50 mg g−1 Annadurai et al. (2002)Orange peel Amido black 10B 5.8 7.90 mg g−1 Annadurai et al. (2002)Banana pith Direct red 28 8.0 18.20 mg g−1 Annadurai et al. (2002)Banana pith Basic blue 9 8.0 20.80 mg g−1 Annadurai et al. (2002)Banana pith Basic violet 10 8.0 20.60 mg g−1 Annadurai et al. (2002)Banana pith Methyl orange 5.7 21.00 mg g−1 Annadurai et al. (2002)Banana pith Methylene blue 7.2 20.80 mg g−1 Annadurai et al. (2002)Banana pith Rhodamine B 5.8 20.60 mg g−1 Annadurai et al. (2002)Banana pith Congo red 7.9 18.20 mg g−1 Annadurai et al. (2002)Banana pith Methyl violet 5.3 12.20 mg g−1 Annadurai et al. (2002)Banana pith Amido black 10B 5.8 6.50 mg g−1 Annadurai et al. (2002)Banana pith Rhodamine B 4.0 8.50 mg g−1 Namasivayam et al. (1993)Banana pith Direct red 3.0 5.92 mg g−1 Namasivayam et al. (1998)Banana pith Acid brilliant blue 3.0 4.42 mg g−1 Namasivayam et al. (1998)Garlic peel Methylene blue 6.0 142.86 mg g−1 Hameed and Ahmad (2009)Raw date pits Methylene blue 8.0 80.29 mg g−1 Banat et al. (2003)Activated date pits (500◦C) Methylene blue 8.0 12.94 mg g−1 Banat et al. (2003)Activated date pits (900◦C) Methylene blue 8.0 17.27 mg g−1 Banat et al. (2003)Bagasse pith Acid blue 25 7.0 21.70 mg g−1 McKay et al. (1999)Bagasse pith Acid red 114 7.0 22.90 mg g−1 McKay et al. (1996)Bagasse pith Basic blue 69 7.0 157.40 mg g−1 McKay et al. (1996)Bagasse pith Basic red 22 7.0 76.60 mg g−1 McKay et al. (1996)Bagasse pith Acid blue 25 7.0 17.50 mg g−1 Chen et al. (2001)Bagasse pith Acid red 114 7.0 20.00 mg g−1 Chen et al. (2001)Bagasse pith Basic blue 69 7.0 152.00 mg g−1 Chen et al. (2001)Bagasse pith Basic red 22 7.0 75.00 mg g−1 Chen et al. (2001)Bagasse pith Basic blue 69 7.0 158.00 mg g−1 McKay et al. (1987)Bagasse pith Basic red 22 7.0 77.00 mg g−1 McKay et al. (1987)Bagasse pith Acid blue 114 7.0 22.00 mg g−1 McKay et al. (1987)Bagasse pith Acid red 25 7.0 23.00 mg g−1 McKay et al. (1987)Apple pomace Reactive dye mixture 7.0 2.79 mg g−1 Robinson et al. (2002c)Brazilian pine fruit shell - PW Methylene blue 8.5 185.00 mg g−1 Royer et al. (2009)Brazilian pine fruit shell - C-PW Methylene blue 8.5 413.00 mg g−1 Royer et al. (2009)Barley straw Acid blue 40 – 1.02 × 10−4 mol g−1 Oei et al. (2009)Barley straw Reactive black 5 – 2.54 × 10−5 mol g−1 Oei et al. (2009)Olive pomace Reactive red 198 2.0 1.08 × 10−4 mol g−1 Akar et al. (2009)


Table 2 (continued)


Pith Acid blue 25 5.0 14.30 mg g−1 Ho and McKay (2003)Pith Basic blue 69 5.0 150.00 mg g−1 Ho and McKay (2003)Palm fruit bunch Basic yellow 21 7.0 327.00 mg g−1 Nassar and Magdy (1997)Palm fruit bunch Basic red 22 7.0 180.00 mg g−1 Nassar and Magdy (1997)Palm fruit bunch Basic blue 3 7.0 92.00 mg g−1 Nassar and Magdy (1997)Jack fruit peel Basic blue 9 7.0 285.71 mg g−1 Hameed (2009)

biosorbent was 44.70 mg g−1. In one of his pa-pers, he also reported that the total number ofexperiments for achieving the highest removal ofMB from aqueous solutions using yellow passionfruit peel (Passif lora edullis f. f lavicarpa) andmandarin peel (Citrus reticulata) as biosorbentstwo independent sets of full 23 factorial designswith two central points (10 experiments) were ex-perimented. In order to continue the optimizationof the system, a new full 22 factorial design withtwo central points (six experiments) and a cen-tral composite surface analysis (13 experiments,divided into four cube points, five center points,and four axial points) were employed for yellowpassion fruit peel (PFP) and mandarin peel (MP),respectively. Using these statistical tools, the bestconditions for MB removal from aqueous solutionwere initially methylene blue (Co) of 3.20 mg L−1,pH 9.0 for PFP and 11.0 for MP, and time ofcontact higher than 48 h for PFP and 42.9 h forMP (Hameed 2009).

Garlic peel

Hameed and Ahmad (2009) reported the poten-tial of garlic peel, an agricultural waste to re-move MB from aqueous solution. Experimentswere carried out as function of contact time, ini-tial concentration (25–200 mg L−1), pH (4–12),and temperature (303, 313, and 323 K). Adsorp-tion isotherms were modeled with the Langmuir,Freundlich, and Temkin isotherms. The data fittedwell with the Freundlich isotherm. The maximummonolayer adsorption capacities were found tobe 82.64, 123.45, and 142.86 mg g−1 at 303, 313,and 323 K, respectively. The kinetic data wereanalyzed using pseudo-first-order and pseudo-second-order models. The results indicated that

the garlic peel could be an alternative for morecostly adsorbents used for dye removal isothermmodel. In order to reduce the total number ofexperiments for achieving the highest removal ofMB from aqueous solutions using yellow passionfruit peel (P. edullis f. f lavicarpa) and mandarinpeel (C. reticulata) as biosorbents, two indepen-dent sets of full 23 factorial designs with two cen-tral points (10 experiments) were experimented.

Orange peel and Banana pith

Orange peel waste was studied as a very goodadsorbent for the adsorption of many dyes.Namasivayam et al. (1996) reported the adsorptionof Congo red, Procion orange, and RhodamineB dyes. The process was studied at differentconcentrations of dyes, adsorbent dosage, agita-tion time, and pH was found to obey Langmuirand Freundlich isotherms. Orange peels havealso been investigated as an adsorbent by Sivarajet al. (2001) for the removal of an acid dye:acid violet17. The adsorption capacity Q0 was19.88 mg g−1 at initial pH of 6.3. The equilib-rium time was found to be 80 min for 10, 20, 30,and 40 mg L−1 dye concentration, respectively.A maximum removal of 87% was obtained atpH 2.0 for an adsorbent dose of 600 mg 50 mL−1

of 10 mg L−1 dye concentration. Adsorption in-creases with increase in pH. Maximum desorptionof 60% was achieved in water medium at pH of 10.Namasivayam et al. (1998) reported the adsorp-tion of direct red and acid brilliant blue withwaste banana pith by varying the agitation time,dye concentration, adsorbent dosage, and pH 9(Annadurai et al. 2002). The adsorption capac-ity was 5.92 and 4.42 mg dye per gram of theadsorbent for direct red and acid brilliant blue,


respectively. Also the adsorption of Rhodamine-Bhas been reported by Namasivayam et al. (1993).A maximum removal of 87% of the dye was ob-served at pH 4. Orange peel is also tested as anadsorbent by Arami et al. (2005), Ardejaniet al. (2007), and Annadurai et al. (2002). Aramiet al. (2005) reported the adsorption capacity ofdirect red 23 and direct red 80 to be 10.72 and21.05 mg g−1, respectively.

Plant waste

The obvious advantage of above discussed adsor-bent for the dyes removal by adsorption treatmentis the lower costs involved. Hence, there is a needto search for more economical and effective ad-sorbents. Tree fern is naturally and commerciallyavailable in all over the world. This variety oftree fern is generally marketed for horticulturalpurposes because of its character of adsorbabilityto retain water and manure for plants. Tree fernis generally dark brown in color and is a complexmaterial containing lignin and cellulose as ma-jor constituents (Newman 1997). Chemical sorp-tion can occur via the polar functional groups oflignin, which include alcohols, aldehydes, ketones,acids, phenolic hydroxides, and ethers as chemicalbonding and ion exchange (Adler and Lundquist1963). Tree fern, an agricultural by-product, hasbeen currently investigated to remove dyes fromaqueous solutions (McKay et al. 1981; Ofomaja2007; Ofomaja and Ho 2007; Han et al. 2006).Moreover, after cutting off the “fruit bunch,” mostof the residues are either used as manure or simplythrown away or burnt off to reduce the volume.The approximate amount of dry matter producedper banana plant is about 1.0, 1.3 and 5.0 g of leaf,pseudostem, and fruits, respectively (Hegde andSrinivas 1991).

Plant leaf powder

Sarma et al. (2008) reported the removal of a basicdye called Rhodamine B from aqueous solutionby adsorption onto a biosorbent, Azadirachta in-dica (neem) leaf powder (AILP). Removal wastested in a batch process with concentration ofdye solution, AILP load, pH, temperature, andcontact time as the working variables. The adsorp-

tion was favored by an acidic pH range and wasbest described by a second-order rate equation.The experimental data were verified by fittinginto both Freundlich and Langmuir isotherms.Thermodynamically, the process was found to beexothermic accompanied by a decrease in entropyand increase in Gibbs energy as the temperatureof adsorption was increased from 303 to 333 K.The effect of solution temperature and the de-termination of the thermodynamic parameters ofadsorption of RB on AILP enthalpy of activa-tion, entropy of activation, and free energy ofactivation, on the adsorption rates are impor-tant in understanding the adsorption mechanism.The rate and the transport/kinetic processes ofdye adsorption onto the adsorbents are describedby applying various kinetic adsorption models.This would lead to a better understanding of themechanisms controlling the adsorption rate. Thepseudo-second-order model was the best choiceamong all the kinetic models to describe theadsorption behavior of RB onto AILP, suggest-ing that the adsorption mechanism might be achemisorption process. The negative value of theenthalpy change suggested that the rise in thesolution temperature did not favor RB adsorptiononto AILP (Bhattacharyya and Sharma 2004).Bestani et al. (2008) identify the effectivenessof a local desert plant characteristic of South-west Algeria and known as Salsola vermiculata,which was pyrolyzed and treated chemically with a50% zinc chloride solution, to remove methyleneblue and iodine. The natural plant adsorption ca-pacities were respectively 23 and 272 mg g−1formethylene blue and iodine. Corresponding re-sults for the pyrolyzed plant uptakes were 53and951 mg g−1, while those for the pyrolyzed plant,chemically treated and activated at 650◦C, were130and 1,178 mg g−1, respectively. In comparison,the standard Merck-activated carbon capacitieswere 200 mg g−1 for MB and 950 mg g−1 for io-dine. Consequently, this low-cost local plant mayalso prove useful for the removal of large organicmolecules as well as potential inorganic conta-minants. The sorption of methylene blue ontountreated guava leaf powder has been studied byPonnusami et al. (2008). The kinetics of sorptionof methylene blue is described by pseudo-second-order model. Effects of initial dye concentration,


solution temperature, and adsorbent dosage havebeen studied. The pseudo-second-order rate con-stant has been correlated as a function of thesystem variables. Statistical tools like Student’st test, F test, ANOVA, and lack of fit have beenemployed to determine the significance of eachcoefficient that appeared in the model. Model ad-equacy has been checked by residual distribution.The proposed model explains 95.1% of the totalvariation in the response. The development, char-acterization, and application of adsorbents pre-pared from avocado kernel seeds were discussedby Elizalde-González et al. (2007), and they cometo the conclusion that a mayor adsorption capacityof the non-carbonized adsorbent in comparisonwith carbonized samples is due to the greateramount of surface acidic groups.

Plant f iber

The use of Palm kernel fiber, a readily avail-able agricultural waste product, for the sorptionof MB from aqueous solution and the possiblemechanism of sorption has been investigated byOfomaja (2008b). The extent of dye removaland the rate of sorption were analyzed usingtwo kinetic rate models (pseudo-first and pseudo-second-order kinetic models) and two diffusionmodels (intra-particle and external mass transfermodels). Analysis of the kinetic data at differentsorbent dose revealed that the pseudo-first-orderkinetics fitted to the kinetic data only in the first5 min of sorption and then deviated from theexperimental data. The pseudo-second-order ki-netic model was found to better fit the experi-mental data with high correlation and coefficientsat the various fiber dose used. The dye sorptionwas confirmed to follow the pseudo-second-ordermodel by investigating the relationship betweenthe amount of dye sorbed and the change inhydrogen ion concentration of the dye solutionand also the dependence of dye uptake with so-lution temperature. It was found that the changein hydrogen ion concentration and increase insorption temperature were directly related to theamount of dye sorbed, and activation energy wascalculated to be −39.57 kJ mol−1, indicating thatthe dye uptake is chemisorption, involving valenceforces through sharing or exchange of electrons

between sorbent and sorbate as covalent forces.The intra-particle diffusion and mass transfer rateconstants were observed to be well correlated withsorbent dose in the first 5 min of sorption, indi-cating that sorption process to be complex. It wasfound that at low sorbent dose, the mass transferis the main rate controlling parameter. However,at high sorbent dose, intra-particle diffusion be-comes rate controlling.

Wu et al. (1999) reported some results of plumkernels on MB. The activation temperature andtime tested were in the ranges 750–900◦C and1–4 h, respectively. Adsorption isotherms of twocommercial dyes and phenol from water on suchactivated carbons were measured at 30◦C. Theexperimental results indicated that the preparedactivated carbons were economically promisingfor adsorption removal of dyes and phenol, incontrast to the other commercial adsorbents.

The kinetics and mechanism of adsorption oftwo commercial dyes basic red 22 and acid blue2, phenol, and 3-chlorophenol from water on acti-vated carbons were studied at 30◦C by Juang et al.(2000). Three simplified kinetic models includinga pseudo-first-order, a pseudo-second-order, andan intra-particle diffusion model were tested. Itwas shown that the adsorption of both phenolscould be fitted to a pseudo-second-order ratelaw and that of both dyes could be fitted to anintra-particle diffusion model. Kinetic parameterswere calculated and correlated with the physicalproperties of the adsorbents. Tseng (2007) re-ported that activated carbon was prepared fromplum kernels by NaOH activation at six differentNaOH/char ratios. The physical properties includ-ing the BET surface area, the total pore volume,the micropore ratio, the pore diameter, the burn-off, and the scanning electron microscope (SEM)observations as well as the chemical properties,namely elemental analysis and temperature pro-grammed desorption, were measured. The resultsrevealed a two-stage activation process: Stage 1activated carbons were obtained at NaOH/charratios of 0–1, surface pyrolysis being the mainreaction; Stage 2 activated carbons were obtainedat NaOH/char ratios of 2–4, etching and swellingbeing the main reactions. The physical propertiesof stage 2 activated carbons were similar, andspecific area was from 1478 to 1887 m2 g−1. The


results of reaction mechanism of NaOH activationrevealed that it was apparently because of the lossratio of elements C, H, and O in the activatedcarbon, the variations in the surface functionalgroups and the physical properties. Three kindsof dyes (MB, BB1, and AB74) were used foran isotherm equilibrium adsorption study. Thedata fitted well to the Langmuir isotherm equa-tion. In this work, activated carbons preparedby NaOH activation were evaluated in terms oftheir physical properties, chemical properties, andadsorption type, and the activated carbon plumkernel was found to have most application po-tential. Kumar and Kumrana (2005) in one oftheir papers reported the sorption of MB ontomango seed kernel particles. The operating vari-ables studied were the initial solution pH, temper-ature, adsorbent mass, initial dye concentration,and contact time. Equilibrium data were fittedto Freundlich and Langmuir isotherm equation,and the equilibrium data were found to be wellrepresented by Langmuir isotherm equation. Themonolayer sorption capacity of mango seed kernelfor MB sorption was found to be 142.857 mg g−1 at303 K. The sorption kinetics was found to followpseudo-first-order kinetics model. The MB uptakeprocess was found to be controlled by both sur-face and pore diffusion with surface diffusion atthe earlier stages, followed by pore diffusion atlater stages. The average effective diffusion co-efficiency was calculated and found to be 5.66 ×10−4 cm2 s−1. Analysis of sorption data using Boydplot confirms that the external mass transfer is therate limiting step in the sorption process. Vari-ous thermodynamic parameters such as enthalpyof sorption �Ho, free energy change �Go, andentropy �So were estimated. The positive valueof �Ho and negative values of �Go show thatthe sorption process is endothermic and sponta-neous. Jute stick powder has been found to be apromising material for adsorptive removal of CR(C.I. 22120) and RB (C.I. 45170) from aqueoussolutions demonstrated by Panda et al. (2008).Physiochemical parameters like dye concentra-tion, solution pH, temperature, and contact timehave been varied to study the adsorption phe-nomenon. Favorable adsorption occurs at aroundpH 7.0, whereas temperature has no significanteffect on adsorption of both the dyes. The max-

imum adsorption capacity has been calculatedto be 35.7 and 87.7 mg g−1 of the biomass forCR and RB, respectively. The adsorption processis in conformity with Freundlich and Langmuirisotherms for RB whereas CR adsorption fitswell to Langmuir isotherm only. In both cases,adsorption occurs very fast initially and attainsequilibrium within 60 min. Kinetic results suggestthe intra-particle diffusion of dyes as rate limitingstep.

Wood shaving

Janoš et al. (2008) reported that spruce woodshavings from Picea abies were used for an ad-sorptive removal of both basic as well as aciddyes from waters. The sorption properties of thesorbents were modified by treating with HCl,Na2CO3, and Na2HPO4. The treatment of thewood sorbents with alkaline carbonate solutionas well as with phosphate solution increased thesorption ability for the basic dye (MB), whereasthe treatment with mineral acid decreased thesorption ability for MB to some extent. The op-posite is true for the sorption of the acid dye—Egacid Orange. The maximum sorption capac-ities estimated from the Langmuir–Freundlichisotherms ranged from 0.060 to 0.165 mmol g−1 forMB and from 0.045 to 0.513 mmol g−1for EgacidOrange. The basic dye sorption decreased at lowpH values in accordance with a presupposed ion-exchange mechanism of the sorption. The sorp-tion of acid dye, on the other hand, decreased withincreasing pH. The presence of inorganic salts aswell as surfactants exhibited only minor effects onthe dye sorption. Similar kind of study has alsobeen reported by Ho and McKay (1998a).

Tea waste

The potentiality of tea waste for the adsorptiveremoval of MB, a cationic dye, from aqueous so-lution was reported by Uddin et al. (2008). Batchkinetics and isotherm studies were carried outunder varying experimental conditions of contacttime, initial MB concentration, adsorbent dosage,and pH. The nature of the functional groups of ad-sorbent and their corresponding frequencies areshown by FTIR spectra. The pH of the adsorbent


was estimated by titration method and a value of4.3 ± 0.2 was obtained. An adsorption–desorptionstudy was carried out resulting the mechanism ofadsorption was reversible and ion exchange. Ad-sorption equilibrium of tea waste reached within5 h for MB concentrations of 20–50 mg L−1. Thesorption was analyzed using pseudo-first-orderand pseudo-second-order kinetics models, and thesorption kinetics was found to follow a pseudo-second-order kinetics model. The extent of thedye (milligrams per gram) removal increased withincreasing initial dye concentration. The equilib-rium data in aqueous solutions were well rep-resented by the Langmuir isotherm model. Theadsorption capacity of MB onto tea waste wasfound to be as high as 85.16 mg g−1, which isseveral folds higher than the adsorption capacityof a number of recently studied in the litera-ture potential adsorbents. Tea waste appears asa very prospective adsorbent for the removal ofmethylene blue from aqueous solution.

Oil palm wood

Activated carbons were prepared from the bio-mass of oil palm wood via two stages, pyrolysisand physical activation, using an environmentfriendly pyrolysis pilot plant, and an activationpilot plant; it was studied by Ahmad et al. (2007).The latter uses the outlet flue gases from limestonecalcination process as activating agents. Experi-mental results showed that pyrolysis and activa-tion conditions leading to various final averagetemperatures had significant effects on the prop-erties of activated carbons prepared. Methyleneblue adsorption was tested and 90.9 mg g−1 maxi-mum adsorption capacity was found. The high mi-cropore fraction, N2 adsorption isotherm, and SEMshowed that these activated carbons possessedintricate pore network comprising micropores andnarrow mesopores. FTIR characterization indi-cated that pyrolysis and activation temperaturesaffected the surface functional groups, and max-imum methylene blue adsorption was dependenton BET surface area.

Activated carbon prepared from low-cost palmoil fiber has been utilized as the adsorbent for theremoval of basic dye; methylene blue is studied byDarus et al. (2005). Experiments were conducted

at different pH, different adsorbent dose, differentinitial concentration of dye, and different contacttime. The most effective of color removal wasoptimum at pH 7 and the percentage removal in-creased with the increase in carbon dose while thepercentage removal decreased with the increase ininitial dye concentration. The adsorption equilib-rium for color reached at 90 min of contact time.The results indicated that palm oil fiber could beemployed as low cost alternatives to commerciallyactivated carbon in wastewater treatment for dyeremoval.

Sawdust

Sawdust is composed of fine particles of wood.This material is produced from cutting with a saw,hence its name. Garg et al. (2004) investigates thepotential use of Indian Rosewood (Dalbergia sis-soo) sawdust, pretreated with formaldehyde andsulfuric acid, for the removal of methylene bluedye from simulated wastewater. Higher adsorp-tion percentages were observed at lower concen-trations of methylene blue. Optimum pH value fordye adsorption was determined as 7.0 for both theadsorbents. Maximum dye was sequestered within30 min after the beginning for every experiment.The adsorption of methylene blue followed a first-order rate equation and fit the Lagergren equa-tion well.

In another case, Ibrahim et al. (1997) studiedthe factors affecting preparation of wood saw-dust and used the obtained adsorbents for the re-moval of anionic dyestuffs. Sawdust was modifiedby reacting with cross-linked polyethylenimine(CPEI) to create aminated adsorbent. Modifiedsawdust was added to acidic dye (pH 3.0) andshook for 30 min at 25◦C. The filtrate was col-lected, and its concentration was determined witha UV spectrophotometer. The results showed thatmodification with CPEI increased the adsorptivityof the sawdust, since the CPEI introduced positivesorptive sites in the form of reactive amino groupsonto the wood material, thus improving the saw-dust reactivity and anionic dye uptake. Similarresults are also studied by Ferrero (2007), Malik(2003), and Özacar and Sengil (2003). The adsorp-tion capacities of plant waste were summarized inTable 3.


Table 3 Reviewed results representing the adsorption capacity of plants waste for the adsorption of dyes and their optimizedpH values for maximum adsorption


Azadirachta indica (neem) Rhodamine B 7.2 25.80 mg g−1 Sarma et al. (2008)leaf powder

Azadirachta indica (neem) Congo red 6.7 128.30 mg g−1 Bhattacharyya and Sharmaleaf powder (2004)

Activated desert plant Methylene blue 6.4 23.00 mg g−1 Bestani et al. (2008)Guava leaf powder Methylene blue 7.0 95.10 mg g−1 Ponnusami et al. (2008)Tea waste Methylene blue 4.3 85.16 mg g−1 Uddin et al. (2008)Oil palm wood Methylene blue 7.0 90.90 mg g−1 Ahmad et al. (2007)Oil palm wood Methylene blue 7.2 25.0 mg g−1 Darus et al. (2005)Palm kernel fiber Methylene blue 7.1 49.96 mg g−1 Ofomaja (2008b)Mango seed kernel Methylene blue 8.0 142.90 mg g−1 Kumar and Kumrana (2005)Jute stick powder Congo red 7.0 35.70 mg g−1 Panda et al. (2008)Jute stick powder Rhodamine B 7.0 87.70 mg g−1 Panda et al. (2008)Tree fern Basic red 13 7.0 408.00 mg g−1 Ho et al. (2005b)Saw dust-Walnut Acid blue 25 7.0 36.98 mg g−1 Ferrero (2007)Saw dust- cherry Acid blue 25 7.0 31.98 mg g−1 Ferrero (2007)Saw dust- oak Acid blue 25 7.0 27.85 mg g−1 Ferrero (2007)Saw dust- pitch pine Acid blue 25 7.0 26.19 mg g−1 Ferrero (2007)Sawdust carbon Acid yellow 36 3.0 183.80 mg g−1 Malik (2003)Pine sawdust (raw) Acid yellow 132 3.5 398.80 mg g−1 Özacar and Sengil (2005)Pine sawdust (raw) Acid blue 256 3.5 280.30 mg g−1 Özacar and Sengil (2005)Avocado kernel seeds - AGAP Basic blue 41 7.0 72.60 mg g−1 Elizalde-González et al. (2007)Avocado kernel seeds - AGAP1 Basic blue 41 7.0 43.40 mg g−1 Elizalde-González et al. (2007)Avocado kernel seeds - AGAP800 Basic blue 41 7.0 67.10 mg g−1 Elizalde-González et al. (2007)Avocado kernel seeds - AGAP1000 Basic blue 41 7.0 130.20 mg g−1 Elizalde-González et al. (2007)Avocado kernel seeds - AGAP-P-800 Basic blue 41 7.0 125.30 mg g−1 Elizalde-González et al. (2007)Avocado kernel seeds - Basic blue 41 7.0 86.60 mg g−1 Elizalde-González et al. (2007)

AGAP-P-N-800Sawdust (Formaldehyde treated) Malachite green 7.0 27.00 mg g−1 Garg et al. (2003)Sawdust (Sulphuric acid treated) Malachite green 9.0 59.70 mg g−1 Garg et al. (2003)Wood Basic blue 69 7.0 77.00 mg g−1 Ho and McKay (1998a)Wood Acid blue 25 7.0 6.14 mg g−1 Ho and McKay (1998a)Mansonia wood Methtlene blue 10.0 33.44 mg g−1 Ofomaja (2008a)Sawdust Methylene violet 10.0 21.65 mg g−1 Ofomaja (2008a)Eucalyptus bark Remazol BB 2.0 34.10 mg g−1 Morais et al. (1999)Wood chips Remazol red 7.0 2.80 mg g−1 Nigam et al. (2000)Wood chips Remazol black B 7.0 3.30 mg g−1 Nigam et al. (2000)Beech sawdust (CaCl2 treated) Methylene blue 11.0 13.02 mg g−1 Batzias and Sidiras (2004)Beech sawdust (CaCl2 treated) Red basic 22 11.0 23.90 mg g−1 Batzias and Sidiras (2004)Beech sawdust (original) Methylene blue 11.0 9.78 mg g−1 Batzias and Sidiras (2004)Beech sawdust (original) Red basic 22 11.0 20.20 mg g−1 Batzias and Sidiras (2004)Neem leaf powder Brilliant green 7.0 0.55 mmol g−1 Bhattacharyya and Sharma

(2003)Wood shaving – untreated Methylene blue 5.0 55.00 μmol g−1 Janoš et al. (2008)Wood shaving – HCl treated Methylene blue 5.0 39.00 μmol g−1 Janoš et al. (2008)Wood shaving – Na2CO3treated Methylene blue 5.0 184.00 μmol g−1 Janoš et al. (2008)Wood shaving – NaHPO4treated Methylene blue 5.0 91.00 μmol g−1 Janoš et al. (2008)Wood shaving – untreated Egacid orange 5.0 33.00 μmol g−1 Janoš et al. (2008)Wood shaving – HCl treated Egacid orange 5.0 36.00 μmol g−1 Janoš et al. (2008)Wood shaving – Na2CO3treated Egacid orange 5.0 211.00 μmol g−1 Janoš et al. (2008)Wood shaving – NaHPO4treated Egacid orange 5.0 111.00 μmol g−1 Janoš et al. (2008)Saw dust Methylene blue 7.0 62.40 mg g−1 Garg et al. (2004)


Natural inorganic materials

Most recently, the clay minerals and zeolites werereported to be unconventional adsorbents for theremoval of dyes from aqueous solutions due totheir cheap and abundant resources, higher sur-face areas (Liu and Zhang 2007). Furthermore,the regeneration of these low-cost substitutes isnot necessary whereas regeneration of activatedcarbon is essential because of the abundant re-sources. Clay materials with sheet-like structures(Arbeloa et al. 2002a; Orthman et al. 2003; Liet al. 2004; Tahir and Rauf 2006) and needle-like structure (Ozdemir et al. 2006; Alkan et al.2007; Liu and Guo 2006; Huang et al. 2007) havebeen increasingly gaining attention because theyare cheaper than activated carbons, and they alsoprovide highly specific surface area (Zhao andLiu 2008). On the other hand, zeolites are threedimensional, microporous, crystalline solids withwell-defined structures that can absorb dyes witha capacity of up to more than 25% of their weightin water. For zeolite, their unique properties suchas the existence of high intra-crystalline surfacearea, the microporous/mesoporous character ofthe uniform pore dimensions, the ion exchangeproperties, the ability to develop internal acid-ity, the thermal stability, and the high internalsurface area along with their ability to absorbmolecules/ionic species in to their structure giverise to great variety of applications which makeszeolites special when compared with other inor-ganic materials (Davis 2002). They separate ions,complex ions, and molecules based on size, shape,polarity, and degree of unsaturation.

Clay

Clay material possesses a layered structure and isconsidered to be host material. They are classifiedon the basis of layered structures. There are sev-eral classes of clays such as smectites, kalonite,serpentine, vermiculite, and sepiolite (Shichi andTakagi 2000). Gürses et al. (2006) investigatedadsorption kinetics of a cationic dye, methyleneblue, onto clay from aqueous solution with respectto the initial dye concentration, temperature, pH,mixing rate, and sorbent dosage in this study. Inorder to understand the adsorption mechanism

in detail, zeta potentials and the conductivities ofclay suspensions at various pH (1–11) and cationexchange capacity were measured. Porosity andBET surface area of clay studied were deter-mined. The results showed that the adsorptionhas been reached the equilibrium in 1 h. It wasfound that the amount adsorbed of methyleneblue increases with decreasing temperature andalso with increasing both sorbent dosage and in-creasing initial dye concentration. Adsorption ca-pacity decreases with increasing pH, except forthe natural pH (5.6) of clay suspensions. Theadsorption kinetics of methylene blue has beenstudied in terms of pseudo-first-order, pseudo-second-order sorption, and intra-particle diffusionprocesses thus comparing chemical sorption anddiffusion sorption processes. It was found thatthe pseudo-second-order mechanism is predomi-nant and the overall rate of the dye adsorptionprocess appears to be controlled by the morethan one step. McKay et al. (1985) reported theadsorption capacity of fuller’s earth for basic andacid blue to be 220 and 120 mg g−1, respectively.Similar results are also investigated by Ho et al.(2001) and Gürses et al. (2006). Clays are naturalenvironment-friendly materials with high specificsurface area are now widely used for the adsorp-tion and removal of the organic pollutants. Liuand Zhang (2007) have reviewed the adsorptionproperties of the raw clays, activated clays byacid treatment or calcinations, organic-modifiedclays with small molecules or polymers for the ad-sorption, and removal of organic dyes from aque-ous solutions. The development perspectives arealso proposed. Arbeloa et al. (1998, 2002b) andChaudhuri et al. (2000) investigated the hy-drophobic effect on the adsorption of rhodamine3B dye on laponite particles, hectorite, and mont-morillonite in aqueous suspensions with electronicabsorption and fluorescence spectroscopies. Clayminerals exhibit a strong affinity for both het-eroatomic cationic and anionic dyes (Table 4).

Sepiolite

Sepiolite has been tested as an adsorbent by manyresearchers (Ozdemir et al. 2004). Sepiolite, as anadsorbent, may be a good alternative to these sys-tems. Sepiolite is a natural hydrated magnesium


Table 4 Reviewed results representing the adsorption capacity of naturally available inorganic minerals for the adsorptionof dyes and their optimized pH values for maximum adsorption


Clay Methylene blue 7.0 6.30 mg g−1 Gürses et al. (2004)Clay Basic blue 69 7.0 1200.00 mg g−1 McKay et al. (1985)Clay Acid blue 25 7.0 220.00 mg g−1 McKay et al. (1985)Clay Acid blue 9 3.0 57.80 mg g−1 Ho et al. (2001)Clay Basic red 18 3.0 157.00 mg g−1 Ho et al. (2001)Clay Basic blue 69 7.0 585.00 mg g−1 El-Guendi et al. (1995)Clay Basic red 22 7.0 488.40 mg g−1 El-Guendi et al. (1995)Sepiolite Reactive red 239 11.0 108.80 mg g−1 Ozdemir et al. (2004)Sepiolite Reactive yellow 176 11.0 169.10 mg g−1 Ozdemir et al. (2004)Sepiolite Reactive black 5 11.0 120.50 mg g−1 Ozdemir et al. (2004)Sepiolite Reactive blue 221 6.7 55.9 × 10−4 mol g−1 Alkan et al. (2005)Sepiolite Acid blue 62 6.7 32.9 × 10−4 mol g−1 Alkan et al. (2005)Sepiolite Methylene blue 6.6 1.87 × 10−4 mol g−1 Dogan et al. (2007)Am-SiO2 Methylene blue 5.0 70.86 mmol kg−1 Woolard et al. (2002)Red mud Congo red 2.0 4.05 mg g−1 Namasivayam and Arasi (1997)Spent activated clay Methylene blue 8.0 3.41 × 10−4 mol g−1 Weng and Pan (2007)Zeolite Reactive black 5 11.0 60.50 mg g−1 Ozdemir et al. (2004)Zeolite Reactive red 239 11.0 111.10 mg g−1 Ozdemir et al. (2004)Zeolite Reactive yellow 176 11.0 88.50 mg g−1 Ozdemir et al. (2004)Zeolite Methylene blue 7.0 0.045 mmolg−1 Wang et al. (2005)Zeolite Methylene blue 5.0 33.83 mmol kg−1 Woolard et al. (2002)Zeolite Alizarin sulphonate 8.0 7.13 mmol kg−1 Woolard et al. (2002)Perlite Methylene blue 11.0 9.1 × 10−6 mol g−1 Dogan et al. (2004)Perlite Methyl violet 9.0 1.4 × 10−5 mol g−1 Dogan and Alkan (2003)Ca – Montmorillonite Basic green 5 7.0 156.30 mg g−1 Wang et al. (2004)Ca - Montmorillonite Basic violet 10 7.0 414.90 mg g−1 Wang et al. (2004)Ti - Montmorillonite Basic green 5 7.0 170.50 mg g−1 Wang et al. (2004)Ti – Montmorillonite Basic violet 10 7.0 961.50 mg g−1 Wang et al. (2004)Glass powder Carminic acid 7.0 8.2 × 10−3 mmol g−1 Atun and Hisarli (2003)Raw kaolin Methylene blue 4.0 13.99 mg g−1 Ghosh and Bhattacharyya (2002)Pure kaolin Methylene blue 4.0 15.55 mg g−1 Ghosh and Bhattacharyya (2002)Calcined raw kaolin Methylene blue 4.0 7.59 mg g−1 Ghosh and Bhattacharyya (2002)Calcined pure kaolin Methylene blue 4.0 8.88 mg g−1 Ghosh and Bhattacharyya (2002)NaOH treated raw kaolin Methylene blue 4.0 16.34 mg g−1 Ghosh and Bhattacharyya (2002)NaOH treated pure kaolin Methylene blue 4.0 20.49 mg g−1 Ghosh and Bhattacharyya (2002)Calcined alunite Reactive blue 114 2.0 170.70 mg g−1 Özacar and Sengil (2003)Calcined alunite Reactive yellow 64 10.0 236.00 mg g−1 Özacar and Sengil (2003)Calcined alunite Reactive red 124 10.0 153.00 mg g−1 Özacar and Sengil (2003)Fuller’s earth 1 Methylene blue 7.0 4.48 × 10−4 mol g−1 Atun et al. (2003)Fuller’s earth 2 Methylene blue 7.0 6.11 × 10−4 mol g−1 Atun et al. (2003)Fuller’s earth 3 Methylene blue 7.0 6.00 × 10−4 mol g−1 Atun et al. (2003)Fuller’s earth 4 Methylene blue 7.0 6.34 × 10−4 mol g−1 Atun et al. (2003)Balkaya lignite Methylene blue 7.0 40.00 mg g−1 Karaca et al. (2004)Diatomaceous clay Methylene blue 7.0 4.2 × 10−4 mmol g−1 Shawabkeh and Tutunji (2003)Clay Methylene blue 7.0 0.15 meq g−1 Neumann et al. (2002)Halloysite nanotubes Methylene blue 10.0 84.32 mg g−1 Zhao and Liu (2008)Dolomite Brilliant red 7.0 900.00 mg g−1 Walker et al. (2003)Charred dolomite Brilliant red 7.0 110.00 mg g−1 Walker et al. (2003)Fly ash Methylene blue 5.2 1.4 × 10−5 mol g−1 Wang et al. (2005)Red mud Methylene blue 5.2 7.8 × 10−6 mol g−1 Wang et al. (2005)Kaolinite Safranin - O 9.2 10.45 μmol m−2 Harris et al. (2001)


Table 4 (continued)


Kaolinite Azure - A 9.2 8.80 μmol m−2 Harris et al. (2001)Kaolinite 3,6-diamino acridine 9.2 7.18 μmol m−2 Harris et al. (2001)Kaolinite 9-amino acridine 9.2 4.85 μmol m−2 Harris et al. (2001)QAL alumina Safranin - O 9.2 0.55 μmol m−2 Harris et al. (2001)QAL alumina Azure - A 9.2 0.45 μmol m−2 Harris et al. (2001)QAL alumina 3,6-diamino acridine 9.2 0.34 μmol m−2 Harris et al. (2001)QAL alumina 9-amino acridine 9.2 0.02 μmol m−2 Harris et al. (2001)Gibbsite Safranin - O 9.2 1.40 μmol m−2 Harris et al. (2001)Gibbsite Azure - A 9.2 0.90 μmol m−2 Harris et al. (2001)Gibbsite 3,6-diamino acridine 9.2 0.70 μmol m−2 Harris et al. (2001)Gibbsite 9-amino acridine 9.2 0.80 μmol m−2 Harris et al. (2001)Silica Safranin - O 9.2 1.40 μmol m−2 Harris et al. (2001)Silica Azure - A 9.2 0.88 μmol m−2 Harris et al. (2001)Silica 3,6-diamino acridine 9.2 1.15 μmol m−2 Harris et al. (2001)Silica 9-amino acridine 9.2 0.40 μmol m−2 Harris et al. (2001)Diatomaceous earth Methylene blue 11.0 198.00 mg g−1 Al-Ghouti et al. (2003)Activated bentonite SELLA FAST Brown H 7.0 0.36 mg g−1 Espantaleón et al. (2003)Anion clay hydrotalcite Acid blue 29 7.0 34.00 mg g−1 Orthman et al. (2003)Bentonite – HDMTA 2 nitrophenol 10.0 18.64 mg g−1 Navarro et al. (2009)Bentonite – HDMTA 2 chlorophenol 10.0 9.95 mg g−1 Navarro et al. (2009)Bentonite – BTEA 2 nitrophenol 4.0 23.02 mg g−1 Navarro et al. (2009)Bentonite – BTEA 2 chlorophenol 4.0 10.04 mg g−1 Navarro et al. (2009)Bentonite – Na Acid blue 193 1.5 67.10 mg g−1 Özcan et al. (2004)Bentonite – DTMA Acid blue 193 1.5 740.50 mg g−1 Özcan et al. (2004)Bentonite Basic red 2 274.00 mg g−1 Hu et al. (2006)Bentonite Basic blue 9 7.9 1667.00 mg g−1 Özacar and Sengil (2006)Crude clay Basic red 46 9.0 54.00 mg g−1 Karim et al. (2009)Sand Methylene blue 7.0 0.64 mol g−1 Bukallah et al. (2007)Raw bentonite Crystal violet 7.0 0.32 mmol g−1 Eren (2009)Modified bentonite Crystal violet 7.0 1.12 mmol g−1 Eren (2009)Fly ash Reactive Blue 21 2.0 106.71 mg g−1 Demirbas and Nas (2009)Sepiolite Reactive Blue 21 2.0 66.67 mg g−1 Demirbas and Nas (2009)Clinoptilolite Amido Black 10B 7.0 55.13 μg g−1 Qiu et al. (2009)Clinoptilolite Safranine T 7.0 11.20 μg g−1 Qiu et al. (2009)Natural zeolite Basic red 46 7.0 8.56 mg g−1 Karadag et al. (2007)Modified zeolite – CTAB Reactive yellow 176 7.0 5.54 mg g−1 Karadag et al. (2007)Modified zeolite – HDTMA Reactive yellow 176 7.0 13.15 mg g−1 Karadag et al. (2007)Bentonite Methylene blue 7.0 33.00 mg g−1 Al-Bastaki and Banat (2004)Anilinepropylsilica xerogel Congo red 7.0 22.62 mg g−1 Pavan et al. (2008b)Na-Bentonite Methylene blue 7.0 0.75 mmol g−1 Kahr and Madsen (1995)Ca-Bentonite Methylene blue 7.0 0.65 mmol g−1 Kahr and Madsen (1995)Arizona Methylene blue 7.0 1.15 mmol g−1 Kahr and Madsen (1995)Illite Methylene blue 7.0 0.25 mmol g−1 Kahr and Madsen (1995)Kaolinite Methylene blue 7.0 0.06 mmol g−1 Kahr and Madsen (1995)Zeolite Everzol black B 7.0 2.90 mg g−1 Armagan et al. (2004)Zeolite Everzol red 3BS 7.0 3.70 mg g−1 Armagan et al. (2004)Zeolite Everzol yellow 3RS H/C 7.0 7.60 mg g−1 Armagan et al. (2004)Bentonite Malachite green 7.0 7.72 mg g−1 Tahir and Rauf (2006)Silica Basic blue 3 8.9 11.16 mg g−1 Ahmed and Ram (1992)Sand Methylene blue 7.0 0.64 mol g−1 Bukallah et al. (2007)Sepiolite Acid red 57 6.0 11.99 μmol g−1 Alkan et al. (2004)Sepiolite Methyl violet 6.6 1.76 × 10−4 mol g−1 Dogan et al. (2007)


silicate clay mineral, (Si12)(Mg8)O30(OH6)–(OH2)4.8H2O Structurally, it is formed by blocksand channels extending in the fiber direction.Each structural block is composed of two tetrahe-dral silica sheets and a central octahedral sheetcontaining magnesium. The removal of reactiveblue 221 and acid blue 62 anionic dyes ontosepiolite from aqueous solutions has been inves-tigated by Alkan et al. (2005) using parameterssuch as calcination temperature, pH, ionicstrength, and temperature. After 200◦C calcina-tion temperature, the specific surface area ofsepiolite decreased with increasing calcinationtemperature. The amount adsorbed of reactiveblue 221 and acid blue 62 on sepiolite in-creased with the increased ionic strength andtemperature and decreasing pH. The sepiolitesample calcinated at 200◦C has the maximumadsorption capacity. However, calcination athigher temperature caused a decrease in theamount adsorbed of dye. Also, Sepiolite wasused as an adsorbent for the removal of methylviolet and MB from aqueous solutions byDogan et al. (2007). The rate of adsorption wasinvestigated under various parameters such ascontact time, stirring speed, ionic strength, pH,and temperature for the removal of these dyes.Kinetic study showed that the adsorption ofdyes on sepiolite was a gradual process. Quasi-equilibrium reached within 3 h. Adsorption rateincreased with the increase in ionic strength, pH,and temperature. The adsorption of acid red 57 bynatural mesoporous sepiolite has been examinedby Alkan et al. (2004) in order to measure theability of this mineral to remove colored textiledyes from wastewater.

Bentonite

Bentonite is an absorbent aluminumphyllosilicate, generally impure clay consistingmostly of montmorillonite. Combining ultra-filtration (UF) and adsorption is an advancetechnique for the treatment of colored wastesproposed by researchers. Bentonite can be usedto adsorb dyes and UF can be used to purifywastewaters from colloidal matters. Combiningboth processes in a one-step treatment process canachieve both goals concurrently. The suitability

of such a combined process for the removalof color caused by MB dye was investigated(Al-Bastaki and Banat 2004; Özacar andSengil 2006; Hu et al. 2006). Effects of feedconcentration, feed temperature, bentonite dose,and operating pressure on the permeate fluxand color removal were investigated. Permeateflux increased linearly with increasing pressurewhile the permeate concentration remained almostconstant (Kahr and Madsen 1995). The additionof bentonite significantly increased the rejectioncoefficient of MB but decreased the permeateflux. The results obtained in this study revealedthat such a combined process could beneficiallybe used for the treatment of dye effluents. Ozcanet al. (2004) prepared Dodecyltrimethylammo-nium bromide-modified bentonite (DTMA–bentonite) and tested it as an adsorbent for anacid dye (Acid Blue 193, AB193) removal fromaqueous solution in comparison to Na–bentonite.Results of this study show that a pH value of 1.5is favorable for the adsorption of Acid Blue 193.The isothermal data could be well described bythe Freundlich equation. The dynamical data fitwell with the pseudo-second-order kinetic model.The adsorption capacity of DTMA–bentonite(740.5 mg g−1) was found to be around 11 timeshigher than that of Na–bentonite (67.1 mg g−1)at 20◦C. Tahir and Rauf (2006) reported that themaximum adsorption of the dye, i.e. >90% hasbeen achieved in aqueous solutions using 0.05 gof bentonite at a pH of 9.

Zeolites

Zeolites are microporous, aluminosilicate min-erals commonly used as commercial adsorbents.Zeolites (Dabrowski 2001) are the only exist-ing crystalline materials with a well-defined porestructure in the microporous range. Zeolites, withtheir permanent negative charges as well as theinterconnection of channels and cages that runthrough their secondary framework structure, areefficient adsorbents for positively charged pollu-tants such as heavy metals. Zeolites are easily syn-thesized from industrial wastes such as coal fly ashand paper sludge ash. Several studies have beenconducted on the sorbent behavior of natural ze-olites (Armagan et al. 2004; Karcher et al. 2001).


Similar conclusions have been found by Ozdemiret al. (2004) and Wang et al. (2008). Benkli et al.(2005) reported the uptake of three types of reac-tive dyes i.e. CI Reactive Black 5, Red 239, andyellow 176 onto modified zeolite. Modification ofzeolite (clinoptilolite) surface with a quaternaryamine, hexadecyl trimethyl ammonium bromide,had been made to improve the removal efficiencyof reactive azo dyes.

Bioadsorbent

The degradation of azo dyes by algae was eval-uated by Jinqi and Houtian (1992), and it wasfound that certain algae can degrade a numberof azo dyes to some extent. The reduction rateappears to be related to the molecular struc-ture of the dyes and the species of algae used.The azo reduclase of algae is responsible for de-grading azo dyes into aromatic amine by breakingthe azo linkage. The aromatic amine is then sub-jected to further metabolism by algae. The abilityof microorganisms to carry out dye decolorizationhas been received by Alhassani et al. (2007), andBanat et al. (1996). Microbial decolorization anddegradation of dyes has been seen as a cost-effective method for removing organic pollutantsfrom the environment. Recent fundamental workhas revealed the existence of a wide variety of mi-croorganisms capable of decolorizing an equallywide range of dyes. In this review, they have alsoexamined biological decolorization of dyes usedin textile industries and report on progress andlimitations.

A simple and practical biological process forthe decolorization of colored effluent from a tex-tile company was described by Nigam et al. (1996)in his research paper. Potential applications ofthe cultures obtained in textile dye stuff effluentdecolorization and treatment were discussed, andthey made the following outcomes; a number ofaerobic and anaerobic cultures able to decolorizedyes in textile effluent samples were isolated aftera prolonged enrichment of the culture from textiledye-effluent samples. The decolorization of somecomponent dyes of the effluent and of a mixtureof dyes was achieved under anaerobic conditions,indicating that the bacteria were able to break thechromophoric bonds in the dye molecules. Several

bacterial cultures capable of total decolorizationof some effluent component dyes under anaerobicliquid fermentation conditions were isolated. Oneof the cultures decolorized Cibacron Red (reac-tive dye), Remazol Golden Yellow (azo dye), andRemazol Red (diazo dye) completely within 24–30 h fermentation process; Remazol Navy Blue(diazo dye) and Cibacron Orange (reactive dye)within 48 h; and Remazol Blue within 54 h. Thesedecolorizations were permanent with no colorchange upon exposure to air: Only one dye, Re-mazol Turquoise Blue (a phthalocynaine dye),was partially reversibly decolorized.

Chitin and chitosan

Chitin is a natural polysaccharide found partic-ularly in the shells of crustaceans such as craband shrimp, the cuticles of insects, and the cellwalls of fungi. It is the second most abundantpolysaccharide after cellulose. It has gained im-portance in environmental biotechnology due toits very good adsorption capacity towards dyes(Annadurai et al. 1999) and metal ions. The ad-sorption of reactive yellow 2 (RY2) and reactiveblack 5 (RB5) by chitin (Sigma C 9213) was in-vestigated by Akkaya et al. (2007). Experimentaldata obtained at different temperatures for theadsorption of each dyestuff by chitin were appliedto pseudo-first-order, pseudo-second-order, andWebere Morris equations, and the rate constantsof first-order adsorption (k1), the rate constants ofsecond-order adsorption (k2), and pore diffusionrate constants (kp) at these temperatures werecalculated, respectively. In addition, the adsorp-tion isotherms of each dyestuff by chitin werealso determined at different temperatures. Physic-ochemical investigation on adsorption of congored, an anionic azo dye by chitosan hydrobeads,has been carried out by Chatterjee et al. (2007).The main difference between chitin and chitosanis that the chitin has two hydroxyl groups whilechitosan has one amino group and two hydroxylgroups in the repeating hexosamide residue. Ad-sorption process has been found to be dependenton temperature with optimum activity at 30◦C.Both ionic interaction and physical forces are re-sponsible for binding of congo red with chitosan.The kinetic results follow pseudo-second-order


rate equation. Influence of pH on the adsorptionprocess was studied over a range of 3.0 to 12.0, anddye concentration was measured after 10 h.

The enhancement of abilities for the removalof reactive dyes and immobilization of tyrosinaseonto highly swollen chitosan beads was demon-strated compared to the use of common chitosanflakes by Wu et al. (2001a, b). Chitosan wasprepared from natural cuttlebone wastes. It wasshown that the adsorption capacity of dyes at30◦C using swollen chitosan beads was around fivetimes greater than that using common chitosanflakes. The adsorption of dyes using swollen beadswas faster by 10–40% depending on the types ofdyes. Finally, the capacity of tyrosinase immobi-lization onto swollen beads was about 14 timesgreater than chitosan flakes, which was reflectedby the higher yield of 3,4-dihydroxyphenylalaninefrom tyrosine and ascorbic acid in the heteroge-neous catalytic system.

The sorption of reactive dye RR222, as wellas the immobilization of acid phosphatase andglucosidase onto swollen chitosan beads was in-vestigated by Juang et al. (2002b). In this study,they prepared the chitosan from cuttlefish wastesand cross-linked with different dosages of glu-taraldehyde and glyoxal. The conclusions drawnfrom this study was that the amounts of sorptionof solutes and the immobilization capacities ofenzymes onto the swollen chitosan beads were sig-nificantly affected by the degrees of cross-linking.Activities and lifetimes of the immobilized en-zymes were measured to evaluate the potential ofpractical applications.

Chiou and Li (2003) reported batch study forthe adsorption of reactive dye (reactive red 189)from aqueous solutions by cross-linked chitosanbeads. The ionic cross-linking reagent sodiumtripolyphosphate was used to obtain more rigidchitosan beads. To stabilize chitosan in acid solu-tions, chemical cross-linking reagent epichlorohy-drin (ECH), glutaraldehyde, and ethylene glycoldiglycidyl ether was used and ECH shows ahigher adsorption capacity. In this study, Lang-muir model agrees very well with experimentaldata, and its calculated maximum monolayer ad-sorption capacity has very large value of 1,802–1,840 g kg−1 at pH 3.0, 30◦C. The kinetics ofthe adsorption with respect to the initial dye con-

centration, temperature, pH, ionic strength, andwet/dry beads were investigated. The pseudo-first-order, second-order kinetic models, and intra-particle diffusion model were used to describe thekinetic data, and the rate constants were evalu-ated. The dynamical data fit well with the second-order kinetic model, except for the dry beadsfitting better with the first-order model. The ad-sorption capacity increases largely with decreasingsolution pH or with increasing initial dye con-centration. The desorption data shows that theremoval percent of dye RR 189 from the cross-linked chitosan beads is 63% in NaOH solutionsat pH 10.0, at 30◦C. The desorbed chitosan beadscan be reused to adsorb the dye and to reachthe same capacity as that before desorption. Inanother paper Chiou et al. (2004) also reportedabout the adsorption of four reactive dyes Re-active Blue 2, Reactive Red 2, Reactive Yellow2, Reactive Yellow 86, three acidic dyes AcidOrange 12, Acid Red 14, Acid orange 7, and onedirect dye direct Red 81. The adsorption capaci-ties had very large values of 1,911–2,498 g kg−1 atpH 3–4, 30◦C, which were 3.4–15.0 and 2.7–27.4times those of the commercially activated carbonand chitin, respectively. Chitosan was also testedas an adsorbent (Wong et al. 2004; Wu et al. 2000;Wang and Wang 2007).

Fungi

In the recent years, there has been an inten-sive research in fungal decolorization of dyewastewater. It is becoming a promising alterna-tive to replace or supplement present treatmentprocesses. Fu and Viraraghavan (2001) in their re-viewed results said that they have examine variousfungi, living or dead cells, which are capable ofdecolorizing dye wastewaters, discuss variousmechanisms involved, report some elution andregeneration methods for fungal biomass, summa-rize the present pretreatment methods for increas-ing the biosorption capacity of fungal biomass,and discuss the effects of various factors on dec-colorization. From these studies, they made thefollowing conclusions: (a) there are many fungalstains capable of decolorization dye wastewater.There is a need to develop these fungal strainswhich can grow in simple, inexpensive medium,


and have high production rate and possesses highbiosorption capacity; (b) decolorization by livingcells involves more complex mechanisms such asintracellular, extracellular oxidases, and biosorp-tion, than by dead cells. The process involvingliving cells is closely related to the operationalconditions, such as nutrition requirements, theinfluent concentration, and toxicity. In contrast,decolorization involving dead biomass is easierto operate, and dead cells may possess higherbiosorption capacity in certain conditions. Theycan be effective biosorbents. Some bacterial andfungal species have been reported that are capa-ble of biodegradation of dyes. The present studyreports preliminary findings on the removal ofazo dyes from solutions using white rot basid-iomycetes. The ability of four different speciesof white rot fungi i.e. Coriolus versicolor, Terme-tomyces sp., Pleurotus ostreatus, and Schizophyl-lum commune to remove azo dyes from aqueoussolutions were evaluated in batch culture underlaboratory conditions by Nasreen et al. (2007). C.versicolor was found to be the most efficient colorremoving species for the three dyes investigated.Maximum removal capacity of C. versicolor foracid green, disperse red, and basic orange was98%, 76%, and 61%, respectively. Glucose as thecarbon source in growth medium is more suit-able for the decoloration of dyes in comparisonto starch at the same concentration. Preliminarystudies indicate that C. versicolor has the potentialto remove color from aqueous solutions and maybe used as an efficient biological agent for thedecoloration of dyes in industrial effluents. Thetwo species of white rot fungi were evaluatedfor their ability to decolorize Blue CA, BlackB133, and Corazol Violet SR by Sathiya moorthiet al. (2007). Trametes hirsute and Pleurotusf lorida displayed the greatest extent of decol-orization. Laccase is the ligneolytic enzyme fromthese fungi. The laccase activity was measuredusing both solid and aqueous state assays. The dyeabsorption ability of the mycelium was studiedusing appropriate medium containing dyes at theconcentration of 75 mg L−1. The effective decol-orization of Blue CA and Corazol Violet SR dyesby both microorganisms were observed in the fifthday of incubation. Further decolorization activitywas verified using various concentrations of dyes

such as 25, 50 and 75 mg L−1. Maximum decol-orization was observed in Blue CA and CorazolViolet SR dyes. The effluent from the dye housewas treated using both organisms with differentconcentration of glucose (1% and 2%). Effectivedecolorization was found to be more by the P.

f lorida in 2% glucose.Swamy and Ramsay (1999) reported five

species of white rot fungi for their ability to de-colorize Amaranth, Remazol Black B, RemazolOrange, Remazol Brilliant Blue, Reactive Blue,and Tropaeolin O in agar plates, Bjerkandera sp.BOS55, Phanerochaete chrysosporium, and Tram-etes versicolor displayed the greatest extent ofdecoloration. In static aqueous culture, the threecultures formed fungal mats which did not de-colorize any dye beyond some mycelial sorption.When agitated at 200 rpm, the biomass grew asmycelial pellets. Bjerkandera sp. BOS55 pelletsdecolorized only Amaranth, Remazol Black B,and Remazol Orange. P. chrysosporium and T.versicolor pellets were capable of decolorizingmost dyes with decoloration by T. versicolor be-ing several times more rapid. Batch cultures ofBjerkandera sp. BOS55 and P. chrysosporium hada limited ability to decolorize repeated dye addi-tions; however, T. versicolor rapidly decolorizedrepeated additions of the different dyes and dyemixtures without any visual sorption of any dyeto the pellets. The choice of buffer had a pro-found effect on pH stability upon dye additionand, consequently, decoloration. The use of 2,29-dimethylsuccinic acid allowed for excellent pHcontrol and resulted in high decoloration ability.

Fu and Viraraghavan (2002a) reported someelution and regeneration methods for fungal bio-mass and summarize the pretreatment methodsfor fungal biomass. Kaushik and Malik (2009) intheir study conclude that the fungal decolorizationhas a great potential to be developed further asa decentralized wastewater treatment technologyfor small textile or dyeing units. However, fur-ther research work is required to study the tox-icity of the metabolites of dye degradation andthe possible fate of the utilized biomass in or-der to ensure the development of an eco-friendlytechnology. Wesenberg et al. (2003) summarizethe state-of-the-art in the research and prospec-tive use of white-rot fungi and their enzymes


(lignin-modifying enzymes) for the treatment ofindustrial effluents particularly dye containingeffluents. The decolorization and detoxificationpotential of white-rot fungi can be harnessedthanks to emerging knowledge of the physiologyof these organisms as well as of the biocatalysisand stability characteristics of their enzymes. Thisknowledge will need to be transformed into reli-able and robust waste treatment processes.

Peat

The suitability of peat as a natural adsorbentis supported by a number of studies whichhave reported the successful treatment of manydifferent types of effluent. Peat compares favor-ably with other adsorbents such as carbon, silicaand alumina, both in terms of adsorption capacityand cost (Allen et al. 1994; Viraraghavan andAyyaswami 1987). Peat has been widely used inthe treatment of wastewaters. The potential ofusing peat in wastewater treatment is reviewedby Couillard (1994) with special attention to thefollowing topics: (1) the properties of peat; (2)the pretreatment of peat; (3) the principles in-volved in the removal of wastewater pollutantsby peat; and (4) the applications of peat to theremoval of impurities from wastewater. Peat ispartially fossilized plant matter, usually of a darkbrown color. It is formed in poorly oxygenatedwetlands, where the rate of accumulation of plantmatter is greater than that of decomposition.The sorption of three basic dyes, namely Basicblue 3, Basic yellow 21, and Basic red 22, ontopeat is reported by Allen et al. (2004). Equi-librium sorption isotherms have been measuredfor the three single-component systems. Equilib-rium was achieved after 21 days. The experimen-tal isotherm data were analyzed using Langmuir,Freundlich, and Redlich–Peterson, Tempkin, andToth isotherm equation. The Redlich–Petersonmodel also yielded the best fit to experimentaldata for all three dyes using the nonlinear errorfunctions. An extended Langmuir model has beenused to predict the isotherm data for the binarysystems using the single component data. Thecorrelation between theoretical and experimentaldata had only limited success due to competitiveand interactive effects between the dyes and the

dye–surface interactions. The adsorption of TelonBlue on peat has been investigated by Poots et al.(1976).

The sorption of two dyes, namely, Basic Blue69 and Acid Blue 25, onto peat has been stud-ied by Ho and McKay (1998b) in terms ofpseudo-second-order and first-order mechanismsfor chemical sorption as well as an intra-particlediffusion mechanism process. The batch sorptionprocess, based on the assumption of a pseudo-second-order mechanism has been developed topredict the rate constant of sorption, the equilib-rium constant and initial sorption rate with theeffect of agitation, initial dye concentration, andtemperature. Activation energy of sorption hasalso been evaluated with the pseudo-second-orderrate constants. A comparison of the equilibriumsorption capacity evaluated has been made frompseudo-second-order rate constant. The adsorp-tive capacity of sphagnum moss peat for a rangeof adsorbates has been studied by Allen (1987).The adsorption of acid dyes, basic dyes, and zincions is reported. The adsorption isotherms are de-scribed by means of the Freundlich and Langmuirisotherms. High adsorptive capacities for some ba-sic dyes were found. Modified peat was preparedby mixing thoroughly raw peat with sulfuric acid,and modified peat–resin particle was obtained, bymixing modified peat with solutions of polyvinylalcohol and formaldehyde. Sun and Yang (2003)reported the adsorption of Basic Magenta andBasic Brilliant Green onto modified peat–resinparticle.

Rhizopus

Rhizopus is a genus of molds that includes cos-mopolitan filamentous fungi found in soil, decay-ing fruit and vegetables, animal feces, and oldbread. Aksu and Tezer (2000) demonstrated up-take of 588.2 mg g−1 of reactive black 5 per g usingRhizopus arrhizus biomass. The fungal biomassexhibited the highest dye uptake capacity at 35◦C,at the initial pH value of 2.0, and at the initialdye concentration of 800 mg L−1. O’Mahony etal. (2002) also reported the biosorption of threereactive dyes cibacron red, remazol blue, rema-zol orange on R. arrhizus biomass. The biomassexhibited maximum dye uptake at pH 2 due to its


Table 5 Reviewed results representing the adsorption capacity of bioadsorbents for the adsorption of dyes and theiroptimized pH values for maximum adsorption


Chitin and Chitosan Acid green 25 4.0 645.1 mg g−1 Wong et al. (2004)Chitin and Chitosan Acid orange 10 4.0 922.9 mg g−1 Wong et al. (2004)Chitin and Chitosan Acid orange 12 4.0 973.3 mg g−1 Wong et al. (2004)Chitin and Chitosan Acid red 18 4.0 693.2 mg g−1 Wong et al. (2004)Chitin and Chitosan Acid orange 12 3.0 1954 mg g−1 Chiou et al. (2004)Chitin and Chitosan Acid red 14 3.0 1940 mg g−1 Chiou et al. (2004)Chitin and Chitosan Acid orange 7 4.0 1940 mg g−1 Chiou et al. (2004)Chitin and Chitosan Direct red 81 4.0 2383 mg g−1 Chiou et al. (2004)Chitin and Chitosan Reactive blue 2 3.0 2498 mg g−1 Chiou et al. (2004)Chitin and Chitosan Reactive red 2 3.0 2422 mg g−1 Chiou et al. (2004)Chitin and Chitosan Reactive yellow 2 4.0 2436 mg g−1 Chiou et al. (2004)Chitin and Chitosan Reactive yellow 86 3.0 1911 mg g−1 Chiou et al. (2004)Chitin and Chitosan Direct red 28 7.0 81.23 mg g−1 Wang and Wang (2007)Chitosan bead (crab) Reactive red 222 7.0 1106 mg g−1 Wu et al. (2000)Chitosan flake (crab) Reactive red 222 7.0 293 mg g−1 Wu et al. (2000)Chitosan bead (lobster) Reactive red 222 7.0 1037 mg g−1 Wu et al. (2000)Chitosan flake (lobster) Reactive red 222 7.0 398 mg g−1 Wu et al. (2000)Chitosan bead (shrimp) Reactive red 222 7.0 1026 mg g−1 Wu et al. (2000)Chitosan flake (shrimp) Reactive red 222 7.0 494 mg g−1 Wu et al. (2000)Giant duckweed Methylene blue 9.0 144.93 mg g−1 Waranusantigul et al. (2003)

(Spirodela polyrrhiza)White rot Fungi (C. versicolor) Acid green 7.0 98.00 mg g−1 Nasreen et al. (2007)White rot Fungi (C. versicolor) Disperse red 7.0 76.00 mg g−1 Nasreen et al. (2007)White rot Fungi ( C. versicolor) Basic orange 7.0 61.00 mg g−1 Nasreen et al. (2007)Modified fungal biomass Disperse red 1 4.0 5.59 mg g−1 Fu and Viraraghavan (2002a)

(Aspergillus niger) Acid blue 29 4.0 45.96 mg g−1 Fu and Viraraghavan (2002a)Peat Acid blue 25 7.0 12.7 mg g−1 Ho and McKay (1998b)Peat Basic blue 69 7.0 195 mg g−1 Ho and McKay (1998b)Peat Basic violet 14 7.0 400 mg g−1 Sun and Yang (2003)Peat Basic green 4 7.0 350 mg g−1 Sun and Yang (2003)Biomass (Rhizopus arrhizus) Reactive blue 19 2.0 90 mg g−1 O’Mahony et al. (2002)Biomass (Rhizopus arrhizus) Reactive orange 16 2.0 190 mg g−1 O’Mahony et al. (2002)Biomass (Rhizopus arrhizus) Reactive red 4 2.0 150 mg g−1 O’Mahony et al. (2002)Biomass (Rhizopus arrhizus) Reactive black 5 2.0 500.7 mg g−1 Aksu and Tezer (2000)Yeast (Candida sp.) Remazol blue 2.0 167.0 mg g−1 Aksu and Dönmez (2003)Yeast (C. lipolytica) Remazol blue 2.0 250.0 mg g−1 Aksu and Dönmez (2003)Yeast (C. tropicalis) Remazol blue 2.0 182.0 mg g−1 Aksu and Dönmez (2003)Yeast (C. quilliermendii) Remazol blue 2.0 154.0 mg g−1 Aksu and Dönmez (2003)Yeast (C. utilis) Remazol blue 2.0 114.0 mg g−1 Aksu and Dönmez (2003)Native white rote fungus Direct blue 1 6.0 101.1 mg g−1 Bayramoglu and Arıca (2007)

(Trametes versicolor) Direct red 128 3.0 189.7 mg g−1 Bayramoglu and Arıca (2007)Heat-treated white rote fungus Direct blue 1 6.0 152.3 mg g−1 Bayramoglu and Arıca (2007)

(Trametes versicolor) Direct red 128 3.0 225.4 mg g−1 Bayramoglu and Arıca (2007)Macrocystis integrifolia Bory 2 nitrophenol 4.0 97.37 mg g−1 Navarro et al. (2009)Macrocystis integrifolia Bory 2 chlorophenol 4.0 24.18 mg g−1 Navarro et al. (2009)Lessonia nigrescens Bory 2 nitrophenol 3.0 71.28 mg g−1 Navarro et al. (2009)Lessonia nigrescens Bory 2 chlorophenol 3.0 17.33 mg g−1 Navarro et al. (2009)Kudzu (Peuraria lobata ohwi) Basic yellow 21 7.0 860.0 mg g−1 Allen et al. (2003)Kudzu (Peuraria lobata ohwi) Basic red 22 7.0 720.0 mg g−1 Allen et al. (2003)Chitosan swollen bead Reactive red 222 7.0 1653.0 mg g−1 Wu et al. (2001a)Chitosan swollen bead Reactive blue 222 7.0 1009.0 mg g−1 Wu et al. (2001a)


Table 5 (continued)


Chitosan swollen bead Reactive yellow 145 7.0 885.0 mg g−1 Wu et al. (2001a)Chitosan flake Reactive red 222 7.0 339.0 mg g−1 Wu et al. (2001a)Chitosan flake Reactive blue 222 7.0 199.0 mg g−1 Wu et al. (2001a)Chitosan flake Reactive yellow 145 7.0 188.0 mg g−1 Wu et al. (2001a)Chitosan – BA Crystal violet 7.0 44.76 mmol kg−1 Chao et al. (2004)Chitosan – BA Bismarck brown Y 9.0 45.77 mmol kg−1 Chao et al. (2004)Chitosan – DBA Crystal violet 7.0 66.76 mmol kg−1 Chao et al. (2004)Chitosan – DBA Bismarck brown Y 9.0 67.39 mmol kg−1 Chao et al. (2004)Chitosan – PA Crystal violet 7.0 99.70 mmol kg−1 Chao et al. (2004)Chitosan – PA Bismarck brown Y 9.0 101.09 mmol kg−1 Chao et al. (2004)Chitosan – CA Crystal violet 7.0 104.69 mmol kg−1 Chao et al. (2004)Chitosan – CA Bismarck brown Y 9.0 107.28 mmol kg−1 Chao et al. (2004)Cross linked chitosan beads Reactive red 189 3.0 1936.0 mg g−1 Chiou and Li (2002)Non-cross-linked chitosan beads Reactive red 189 6.0 1189.0 mg g−1 Chiou and Li (2002)Dried seagrape Astrazon blue FGRL 6.0 80.7 mg g−1 Punjongharn et al. (2008)

(Caulerpa lentillifera)Dried seagrape Astrazon red GTLM 6.0 113.6 mg g−1 Punjongharn et al. (2008)

(Caulerpa lentillifera)Dried seagrape Astrazon golden yellow 6.0 35.5 mg g−1 Punjongharn et al. (2008)

(Caulerpa lentillifera)Eggshell membrane Direct red 80 2.0 0.124 mmol g−1 Arami et al. (2006)Eggshell membrane Acid blue 25 2.0 1.736 mmol g−1 Arami et al. (2006)Chitosan Reactive red 222 7.0 185.0 mg g−1 Wu et al. (2001b)Chitosan Reactive yellow 145 7.0 78.0 mg g−1 Wu et al. (2001b)Chitosan Reactive blue 222 7.0 41.0 mg g−1 Wu et al. (2001b)Peat Basic blue 3 7.0 427.52 mg g−1 Allen et al. (1988a)Peat Basic red 22 7.0 248.33 mg g−1 Allen et al. (1988a)Peat Basic yellow 21 7.0 306.25 mg g−1 Allen et al. (1988a)Saccharomyces cerevisiae Remazol blue 3.0 84.0 mg g−1 Aksu (2003)Saccharomyces cerevisiae Remazol black B 3.0 88.5 mg g−1 Aksu (2003)Saccharomyces cerevisiae Remazol red RB 3.0 48.8 mg g−1 Aksu (2003)Fungus (Aspergillus niger) Congo red 6.0 14.72 mg g−1 Fu and Viraraghavan (2002b)Chitin gels Acid blue 74 3.3 40.0 mg g−1 Vachoud et al. (2001)Chitin gels Reactive violet 5 3.3 32.5 mg g−1 Vachoud et al. (2001)Peat Basic blue 41 7.0 536.6 mg g−1 Liversidge et al. (1997)Peat Acid blue 25 7.0 45.0 mg g−1 Allen et al. (1988b)Peat Basic blue 3 7.0 555.61 mg g−1 Allen et al. (2004)Peat Basic yellow 21 7.0 666.56 mg g−1 Allen et al. (2004)Peat Basic red 22 7.0 312.50 mg g−1 Allen et al. (2004)Hen feather Malachite Green 5.0 2.9 × 10−5 mol g−1 Mittal (2006)Dried Chlorella vulgaris (an alga) Remazol black B 2.0 555.60 mg g−1 Aksu and Tezer (2005)Dried Chlorella vulgaris (an alga) Remazol red RR 2.0 196.10 mg g−1 Aksu and Tezer (2005)Dried Chlorella vulgaris (an alga) Remazol golden yellow 2.0 71.90 mg g−1 Aksu and Tezer (2005)Peat Acid blue 25 3.5 35.00 mg g−1 Allen (1987)Peat Basic blue 3 5.5 410.00 mg g−1 Allen (1987)Peat Basic blue 69 5.5 605.00 mg g−1 Allen (1987)Chitin Reactive yellow 2 8.0 2.83 mg g−1 Akkaya et al. (2007)Chitin Reactive black 5 6.0 1.88 mg g−1 Akkaya et al. (2007)Peat Acid blue 25 5.0 14.40 mg g−1 Ho and McKay (2003)Peat Basic blue 69 5.0 168.00 mg g−1 Ho and McKay (2003)White rot fungi Amarant 4.9 50.00 mg g−1 Swamy and Ramsay (1999)White rot fungi Remazol black B 5.0 60.00 mg g−1 Swamy and Ramsay (1999)


Table 5 (continued)


White rot fungi Remazol orange 4.8 60.00 mg g−1 Swamy and Ramsay (1999)White rot fungi Remazol brilliant blue 4.7 40.00 mg g−1 Swamy and Ramsay (1999)White rot fungi Reactive blue 4.6 20.00 mg g−1 Swamy and Ramsay (1999)White rot fungi Tropaeolin O 4.7 20.00 mg g−1 Swamy and Ramsay (1999)Peat Acid blue 25 7.0 43.49 μmol g−1 Poots et al. (1976)Chitosan Acid red 73 7.0 728.2 mg g−1 Wong et al. (2004)

positively charged nature at acidic pH and the an-ionic nature of the reactive dyes. Reactive orange16 dye was adsorbed most effectively to a max-imum of approximately 200 mg g−1. Chitin andchitosan exhibits strong affinity for acid/reactivedyes, and peat is shown to be a particularlyeffective adsorbent for basic dyes (Table 5).

Conclusions

After reviewing the collected data, we have madesome conclusions as discussed in the followingparagraphs:

The treatment of industrial effluent that con-tains the large number of organic dyes by ad-sorption process, using these easily available lowcost adsorbents, such as natural materials, wastematerials from industrial and agriculture, plantwaste, fruit waste, and bioadsorbents are aninteresting alternative to the traditionally avail-able aqueous waste processing techniques (chemi-cal coagulation/flocculation, ozonation, oxidation,photodegradation, etc.). Undoubtedly, low-costadsorbents offer a lot of promising benefits forcommercial purposes in the future.

As we knew that the distribution of size, shape,and volume of voids species in the porous ma-terials is directly related to the ability to per-form the adsorption application, there are onlya few papers where they have studied the mor-phology of the adsorbent. The comparison of ad-sorption performance of different adsorbents notonly depend on the experimental conditions andanalytical methods (column, reactor, and batchtechniques) but also depends on the surface mor-phology of the adsorbent, surface area, particlesize and shape, micropore and mesopore volume,

etc. Many researchers have made comparison be-tween the adsorption capacities of the adsorbents,but they have nowhere discussed anything aboutthe role of morphology of the adsorbent, even incase of the inorganic material where it plays amajor role in the adsorption process.

The pH value of the solution is an importantfactor which must be considered during design-ing adsorption process. The pH has two kindsof influences on dye: an effect on the solubilityand speciation of dye in the solution. It is wellknown that surface charge of adsorbent can bemodified by changing the pH of the solution andthe chemical species in the solution depend onthis parameter. The high adsorption of cationic oracidic dyes at higher pH may be due to the surfaceof adsorbent becomes negative which enhancesthe positively charged dyes through electrostaticforce of attraction and vice versa in case of an-ionic or basic dyes. In case of adsorbents obtainedfrom the industries and agriculture by-products,fruit, and plant waste, the literature reveals thatmaximum removal of dyes from aqueous wastecan be achieved in the pH range of 5–8. But themajor role of pH was seen in the paper in whichinorganic and bioadsorbents are used for the dyewaste treatment.

We also agree with the discussions made byCrini (2006) in the review article that the adsorp-tion process will provide an attractive technologyif the low-cost sorbent is ready for use. However,physical and chemical processes such as drying,autoclaving, crosslinking reactions, or contactingwith organic or inorganic chemicals proposed forimproving the sorption capacity and the selectiv-ity. For example, for the industrial applicationof biosorption, immobilization of biomass is nec-essary (Aksu 2005). These pretreatment meth-ods are not cost effective at large scale. The


production of chitosan also involves a chemicaldeacetylation process. Commercial production ofchitosan by deacetylation of crustacean chitin withstrong alkali appears to have limited potentialfor industrial acceptance because of difficultiesin processing, particularly with the large amountof waste concentrated alkaline solution causingenvironmental pollution. However, several yeastsand filamentous fungi have been recently reportedas containing chitin and chitosan in their cell walland septa. They can be readily cultured in sim-ple nutrients and used as a source of chitosan.With advances in fermentation technology chi-tosan preparation from fungal cell walls couldbecome an alternative route for the production ofthis biopolymer via an ecofriendly pathway.

At last, we have tried to make a comparisonbetween the adsorption capacities of adsorbentsfor three commonly used dyes, methylene blue(Fig. 1), basic blue (Fig. 2), and acid blue (Fig. 3).On analyzing these results, we have reached to aconclusion that there is a lack of data concerningthe reproducibility of the adsorption isotherms; itmay be due to the differences in the physical and

chemical characteristic adsorbents obtained fromdifferent resources and locations. We have seenthat peat shows different adsorption capacities forsingle dye (Figs. 2 and 3) (Allen 1987; Allen et al.1988a, b; Ho and McKay 2003; Poots et al. 1976).In view of industrial developments of the variouskinds of adsorbents described in the literature, thephysical and chemical stability of the materialsand the reproducibility of the adsorption prop-erties are of great concern. Although commer-cially activated carbon show maximum adsorptionpotential for methylene blue (Fig. 1), the bark(McKay et al. 1999) and activated carbon obtainedfrom plum kernels (Tseng 2007) may prove to bean important alternative for the methylene blueremoval from aqueous waste.

The common adsorbent, commercially avail-able activated carbon has good capacity for theremoval of pollutants. But its main disadvantagesare the high price of treatment and difficult re-generation, which increases the cost of wastewatertreatment. Thus, there is a demand for other ad-sorbents, which are of inexpensive material and donot require any expensive additional pretreatment

Fig. 1 Comparison of adsorption capacities of different adsorbents for the removal of cationic dye methylene blue


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(m

g g-1

)

Pea

t

Pea

t

Pea

t

Pea

t

Pea

t

Pea

t

Pea

t

BB 69

BB 3 BB 41

BB 3 BB 3 BB 69

BB 69

Fig. 2 Comparison of adsorption capacities for the adsorption of basic blue (BB) dyes onto the different adsorbents

0

200

400

600

800

1000

1200

Act

ivat

ed c

arbo

n -

RH

Z

Act

ivat

ed c

arbo

n

Act

ivat

ed c

arbo

n (b

agas

ses)

Act

ivat

ed c

arbo

n fi

ber

(pit

ch)

Act

ivat

ed c

arbo

n C

C-1

Act

ivat

ed c

arbo

n C

C-3

Act

ivat

ed c

arbo

n C

C-5

Act

ivat

ed c

arbo

n C

C-7

Act

ivat

ed c

arbo

n C

C-1

0

Act

ivat

ed c

arbo

n C

C-1

5

Slag

Car

bona

ceou

s ad

sorb

ent

Act

ivat

ed c

arbo

n P

KN

2

Act

ivat

ed c

arbo

n P

KN

3

Act

ivat

ed c

arbo

n P

KN

4

Bag

asse

pit

h

Bag

asse

pit

h

Pit

h

Saw

dus

t-W

alnu

t

Saw

dus

t-ch

erry

Saw

dus

t-oa

k

Saw

dus

t-pi

tch

pine

Pin

e sa

wdu

st (

raw

)

Woo

d

Cla

y

Cla

y

Ani

on c

lay

hydr

otal

cite

Ben

toni

te -

Na

AB AB 80

AB 25

AB 264

AB 80

AB 80

AB 80

AB 80

AB 80

AB 80

AB 29

AB 113

AB 74

AB 74

AB 74

AB 25

AB 114

AB 25

AB 25

AB 25

AB 25

AB 25

AB 256

AB 25

AB 25

AB 9

AB 29

AB 193

Ads

orpt

ion

capa

city

(m

g g-1

)

Ben

toni

te -

Na

Ben

toni

te -

DT

MA

Fun

gal

Pea

t

Chi

tin

gels

Pea

t

Pea

t

Pea

t

AB 193

AB 193

AB 29

AB 25

AB 74

AB 25

AB 25

AB 25

Fig. 3 Comparison of adsorption capacities for the adsorption of acid blue (AB) dyes onto the different adsorbents


step. So now, most of the adsorption studies havebeen focused on untreated industrial, agricultural,fruit, plant wastes because of low cost, easy avail-ability, easy to handle. But we found that only afew untreated adsorbents show good adsorptionpotential (Tables 1, 2, 3, and 5), and performanceof these adsorbents has been remarkably affectedupon physical and chemical treatment. Pretreat-ment of plant wastes can remove soluble organiccompounds and increase chelating efficiency andin case of cellulose base adsorbents pretreatmentcan also remove lignin, hemicelluloses, decreasecellulose crystallinity and increase the porosity orsurface area. The excellent ability and economicpromise of the activated carbon prepared fromby-products after physical and chemical treatmenthave been recently presented and well describedby the researches. The non-conventional activatedcarbons exhibited good adsorption properties andcharacteristics as reported in Table 1. However,the adsorption characteristics of carbon dependon the source of raw material, the treatment con-ditions, activation time, etc.

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