Comparative Adsorption Studies Prof MR Gidde

7/27/2019 Comparative Adsorption Studies Prof MR Gidde

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INTERNA TIONAL CONGRESS ON ENVIRONMENTAL RESEARCH AT BITS PILANI GOA, 08-09Comparative adsorption studies on Activated Rice Husk and Rice HuskAsh by using Methylene Blue as dye

Milind R.Oidde1 , Julie Dutta', Snehal Jadhav3

AbstractActivated Rice Husk (ARH) and Rice Husk Ash (RHA) were used as adsorbents for

decolourisation. ARH was prepared from rice husk treated with nitric acid and RHA wascollected directly from mill. There adsorption capacity was evaluated for the decolourisation ofwastewater containing methylene blue. The effect of system variables such as pH, contact time,initial concentration and adsorbent dose were investigated. The result shows that efficiencyvaries with the variation in adsorbate concentrations and adsorbent. Colour removal efficiencywas found to be 88 % to 94 % at the dose of 20 g/l for ARH and 80 % to 95 % at the adsorbent.dose of 2.5 g/l for RHA. The studies were carried out at methylene blue concentration of 50 mg/l,30 mg/l and 10 mg/l. On the basis of adsorption isotherm graphs, R-square values weredetermined and found to fit the adsorption data. The Linear, Langmuir and Freundlichadsorption isotherms are good fitted for the experimental data.Keywords: Rice husk, ARH, RHA, Methylene blue, Adsorption isotherms

1. Professor, Department of Civil Engineering, Bharati Vidyapeeth University College ofEngineering, Pune - 411043, Maharashtra, India. [email protected]. PO students, Vasant Dada Sugar Institute, Manjari, Pune.

1. INTRODUCTIONPollution is a serious problem ever sincesewage and industrial effluents are disposedinto the water bodies and on land. Thewastewater contain a wider variety ofmaterials of both organic and inorganic natureincluding toxic substances and are usually

discharged with or without treatment intothe surface water such as rivers, streams,lakes or into oceans or on land or in sewers.One of the most common water pollutant iscolour. They find there way into the waterby the discharge of dyes from paper andpulp industries, textile industries, tanning

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industries and many other industries. Colors inthe water affect the nature of water, inhibitsunlight penetration and reduce photosyntheticaction. Some of the dyes cause rapid depletionof dissolved oxygen affecting aquatic lifeadversely. Some of the dyes are toxic andcarcinogenic. Thus, uses of dye contaminatedwater without any treatment may causeadverse effect on human health, domesticanimals, wildlife and on the environment. Soit is necessary to treat or remove color fromthe wastewater before discharge.Various treatment methods for removal ofcolour and dye are co-agulation using alum,lime, ferric chloride and ferric sulphate,oxidation, flocculation, ozonation, biologicaltreatment, adsorption and membraneprocesses. Among these methods, adsorptionmethod appears to offer the best prospect foroverall treatment of colour removal.Use of Granulated Activated Carbon (GAC)or Powdered Activated Carbon (PAC) is morecommon. However, they are expensive andthe regeneration or disposal of it has severalproblems. Thus, to make the process customerfriendly, the use of several low costadsorbents has been studied. Locally availablenatural material can minimize or avoid theconcerns and significantly reduce treatmentcost.

Being India an agricultural country, a largeamount of agro-waste is generated everyyear. The use of these agricultural solidwastes such as coir pith, banana pith,coconut shell, rice husk and straw, bagasses,saw dust, bamboo dust, groundnut shell, etc.as an adsorbent for removal of colour fromwastewater will be customer friendly.Rice is the second largest produced cereal inthe world. Worldwide, India stands first inrice area and second in rice production, afterChina. During milling of paddy about 78 %of weight is received as rice, broken rice andbran. Rest 22 % of the weight of paddy isreceived as husk. The total quantity of ricehusk produced annually in the country isabout 19.5 million tones. The possibleutilization of rice husk and rice husk ash asan adsorbent for methylene blue dye or othercolour from aqueous solutions can beinvestigated because of its effectiveadsorption properties.

2. MATERIALS AND METHODSa. Collection and Preparation of

AdsorbentsRice husk and rice husk ash were collectedfrom Roha rice mill situated in Raigaddistrict of Maharashtra state. The rice huskwas screened and washed with water toremove the dirt and was sun dried for a day.

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Then the dried rice husk was soaked in 2.0mol/L of nitric acid for an hour. It was thenrinsed with distilled water for 2-3 times andoven dried at 105C for 2 hours. The ovendried rice husk was ground and sieved throughBSS-30 mesh size particle. The name given tothe adsorbent was Activated rice husk (ARH).Another adsorbent rice husk ash (RHA) wasdirectly used without treatment. Only fine ashwas used as adsorbent.

b. Preparation of dye solutionMethylene blue is a heterocyclic aromaticchemical compound with molecular formula:C16HlSCIN3S. It was chosen because of itsknown strong adsorption onto solids. The dyeis regarded as acutely toxic, but it can havevarious harmful effects. The structure ofmethylene blue is as given below-

r:Figure 2: Structure of Methylene blueMethylene blue (S.D. fine chern. Ltd) wascollected from laboratory. The stock solutionof dye was prepared by dissolving 10 g ofmethylene blue in 1000ml of distilled water.The working solutions were prepared by serialdilution of this stock solution.

c. Equipment

The Spectrophotometer (HACH DR/2000)was used for methylene blue analysis. Therotary incubator shaker (model RIS,manufactured by Steelment industries),Microprocessor pH meter (CERT),Centrifuge machine (REMI R8C laboratorycentrifuge), etc. were used for all adsorptionexperiments.

d. ExperimentsThe working solution of differentconcentrations 50 mg/l, 30 mg/l, and 10mg/1were prepared by serial dilution of stocksolution. The four factors initialconcentration of dye, pH, contact time andadsorbent dose were varied. The batchadsorption tests were carried out by shaking100ml working dye solution in a stopperedconical flask. The conical flasks were placedon rotary shaking machine for one hour at150 rpm. The progress of adsorption duringthe experiment was determined by removingthe flask after desired contact time,centrifuging and analyzing the supernatantsolution spectrophotometrically at 610nm.Adsorption tests were performed attemperature 29C 2.The spectrophotometric readings wererecorded and further calculations were doneto see the removal efficiency of theadsorbents. The removal efficiency wascalculated using following formulae:

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% Removal efficiency ( 1 1 ) = (Ci-Ct) x 100Cf

Where, Ci is the initial concentration ofmethylene blue in solution and Cf is finalconcentration of methylene blue in solution.Adsorption isotherms were used to modelcolour adsorption. The adsorption isothermswere tried to fit to the experimental adsorptiondata. The isotherms used in this study were:

i. Linear Adsorption Isothermq=K*Ce 1

Where, q is the amount of methylene blueadsorbed on adsorbents, Ce is the amount ofMethylene blue present in the solution and Kis the constant given by the slope. For Linearadsorption isotherm, graphs of q vis Ce wereplotted.

ii. Langmuir Adsorption Isothermqm * K* Ce

....... 2=--------------1 + K*Ce

Where, q is the amount of methylene blueadsorbed per unit weight of adsorbent, qm isthe maximum amount of methylene blueadsorbed per unit weight of adsorbent, K is theadsorption equilibrium constant and Ce is theconcentration of methylene blue in liquidphase at adsorption equilibrium. Evaluation ofthe coefficients qm and K can be obtainedusing linearized form of equation 2 as-lIq = (l/b*K) (lICe) + lib .3

In the case of Langmuir adsorptionisotherm, graphs of II q vis liCe wereplotted.

iii. Freundlich AdsorptionIsotherm

q = K*Cel/n . . . . . . . .Here, K is the measure of the capacity of theadsorbent (mass adsorbatel mass adsorbent)and n is a measure of how affinity for theadsorbate changes with changes IIIadsorption density. Evaluation of thecoefficient K and n can be accomplishedusing linearized form of equation 4.log q = log K + (lIn) log Ce 5For Freundlich isotherm, graphs of log q vislog Ce were plotted.

The adsorption isotherms were triedto fit to the experimental adsorption data.Linear regression analysis was conducted todetermine the goodness of fit for thedifferent adsorption isotherms. For Linearadsorption isotherm, a plot of q vis Ce wasplotted. Linear regression analysis wasperformed to determine whether the givenisotherm is a good fit for experimentaladsorption data. Based on the R-squarevalues, the isotherm that explains theexperimental adsorption data the best wasselected.3. RESULTS AND DISCUSSIONS

A. Effect of pH

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a) For different concentrationsThe graph (a) shows that as pH increases theremoval efficiency increases. Considering 50mg/l of methylene blue solution 93 %efficiency is achieved at pH 11 for ARH. AtpH 7, 78 % efficiency is achieved. From graph(b), the maximum efficiency is 91 % at pH 7for RHA. Therefore by observing both thegraphs pH at 7 was optimized for solutionhaving concentration 50 mg/l of methyleneblue.

For concentration 30 mg/l of solution,the efficiency is 87 % for ARH and 96 % forRHA at pH 7. Thus colour removal efficiencyis quite high at pH 7 and as the dischargestandard for wastewater is neutral pH at 7 wasoptimized for concentration 30 mg/l ofsolution.

From graph (a) and graph (b), theefficiency is 88 % and 79 % at pH 7 forconcentration 10 mg/l of methylene blue forARH and RHA. After pH 7 the efficiency isnearly equilibrium. Therefore for allconcentrations of methylene blue solution thepH is optimized at 7.

b) For different adsorbentsBy comparing graph (a) and graph (b)

we have observed that at low pH i.e. 3 theefficiency is 91 to 93 % for RHA whereas forARH it is only 36 to 73 %. Considering allconcentrations of solution, at pH 7 the

efficiency is 78 % to 88 % for ARH and 79to 96 % for RHA

If the solution is acidic andhave pH 3 to 5 then RHA canprove good adsorbent for allconcentration.

And if the nature of solutionis neutral or alkaline and theconcentration of solution is10 mg/l then, ARH isapplicable.

For high concentration ofsolution RHA is a goodadsorbent even if the pH islow or high.

B. Effect of Contact Timea) For different concentrationsFrom graph C and D for

concentration 50 mg/l of methylene bluesolution it is observed that the efficiencyincreases with increase in contact time. Theefficiency is 84 % at contact time 60minutes for ARH and 91 % for RHA. Afterdoubling the contact time i.e. 120 minutesthe efficiency is reached upto 88 % for ARHand 94 % for RHA. The difference is about3-4 % only. Therefore, contact time wasoptimized at 60 minutes for 50 rng/l ofmethylene blue solution.

The efficiency is same for theconcentration 30 mg/l of solution as that of

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concentration 50 mg/l of solution. Thereforeoptimum contact time is 60 min forconcentration 30 mg/l of solution for ARH.From graph (d), the efficiency for 30 mg/l ofsolution is 92 % at contact time 40 minute andafter 40 min it attains equilibrium. Therefore,optimum contact time is 40 min for RHA for30 mg/l of methylene blue solution.

The equilibrium attained at 40 min forconcentration 10 mg/l of solution for ARH.Therefore, considering concentration 10 mg/lof solution, the optimum contact time is 40minute for ARH. From graph (d), theefficiency is 91 % for concentration 10 mg/lof solution at 40 min. And equilibrium isattained after it. Therefore, the optimumcontact time is 40 min for concentration 10mg/l of solution for RHA.

b) For different adsorbentsThe graph (c) shows optimum contact

time for Activated Rice Husk and graph (d)shows that of Rice Husk Ash. By comparingboth the graphs, it is observed that ARH canremove colour to about 84 to 89 % from thesolution in 60 minutes and RHA can removecolour about 88 to 92 % from solution in 40min. Thus, by considering all concentrations ofsolution RHA can prove a good adsorbent toremove colour in less time i.e. in 40 min.e. Effect of Adsorbent Dose

a) For different concentrations

From graph (e), it is observed thatfor concentration 50 mg/l of methylene bluesolution the efficiency increases withincrease in adsorbent dose. The efficiency is65% to 93 % when the adsorbent dosevaried from 2.5 g/l to 40 g/l for ARH. Theefficiency is about 88 % for 20 g/l of ARH.From graph (f), it is observed that 95 %efficiency is achieved at the dose of 2.5 g/lof RHA. And equilibrium is attained afterthis. Therefore, optimum adsorbent dose is2.5 gll of RHA and 20 g/l of ARH forconcentration 50 mg/l of solution.

From graph (e), as compared toconcentration 50 mg/l, for 30 mg/l ofsolution efficiency about 86 % is achieved atdose 10 g/l of ARH. At 20g/1 dose theefficiency is 91 %. The difference is of 5 %.Therefore optimum dose can be consideredas 10 g/l of ARH. From graph (f), 95 %efficiency is achieved at dose 5 gll of RHA.Therefore, optimum adsorbent dose forconcentration 30 mg/l of solution is 10 g/l ofARH and 5 gll ofRHA.

For concentration 10 mg/l of solutionthe efficiency is 92 % for 5 g/l of ARH asshown in graph (e). The increase inefficiency is about only 1 % after doublingthe adsorbent. While from graph (f), it isobserved that the efficiency is about 93 % atdose 10 g/l of RHA. Highest efficiency is

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about 97 % at dose 20 g/l of RHA. Therefore,optimized adsorbent dose is 5 gll of ARH and10 g/l of RHA for concentration 10 mg/l ofsolution.

b) For different adsorbentsThe removal efficiency form 88 % to

94 % is achieved at the dose of 20 g/l ofadsorbent having concentration of 50 mgll, 30mg/l and 10 mg/l. For low concentration ofmethylene blue (i.e. 10 mgll), 92 % efficiencycan be achieved for 5 g/l of ARH dose.Considering all concentration of methyleneblue, optimum adsorbent dose is 20 g/l ofARH.

The removal efficiency from 80 % to95 % is achieved at the dose of 2.5 gll of RHAfor all concentration of methylene blue. Withincrease in adsorbent dose the efficiency up to98 % can be achieved. To minimize thevolume of waste, it is necessary to use lessamount of adsorbent. Also the efficiency ishigh at low adsorbent dose. Therefore, theoptimum adsorbent dose is 2.5 g/l of RHA.

By comparing graph (e) and graph (f),it is observed that for high concentrations thatis 50 mg/l and 30 mg/l , RHA can prove goodadsorbent. But for low concentration of 10mg/l of solution ARH is a good adsorbent. Byconsidering all concentrations of solutionRHA can prove to be good adsorbent.

D. Application of Adsorption isotherm

The R-square values of the linearregression performed were used todetermine whether the isotherm was a goodfit for the given experimental adsorptiondata. The R-square value close to 1 indicatesa good fit by the model for the givenexperimental data whereas R-square valuenear 0 indicates that the model is not a goodfit for the given experimental data.

Linear Adsorption IsothermFrom the Graph No.1 and 4 for

adsorption data, it can be seen that the R2values are greater than 0.7 for adsorption ofmethylene blue on ARH and RHA. Theseindicate that the linear adsorption isothermis good fit for experimental adsorption data.

Langmuir Adsorption IsothermLangmuir adsorption isotherm graph

is plotted with l/q vis liCe. Trend lines forthe adsorption data of differentconcentration of methylene blue usingdifferent adsorbents are plotted in graph (2)and graph (5). The linear regression wasconducted using plot lIq vis liCe, it wasfound that R2 values are closer to 1 (i.e. 0.9),indicating that the Langmuir adsorptionisotherm is a good fit for both of theadsorption data.

Freundlich Adsorption IsothermFrom graph 3 and 6 the Freundlich

adsorption isotherm can be said to be good

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fit for the given experimental adsorption data,since the linear regression of log q vis log Cegave R2values in the range of 0.89 to 0.92 forthe different concentration of methylene bluewith different adsorbents.

E. Application of adsorbents fordifferent effluent samples

To understand the actual application ofthis adsorption method on the results obtainedthe experiments were conducted on differentwaste water samples collected from differentindustries. The ARH did not show goodaffinity towards adsorption for all effluent.But for some of the effluent (sample 5) showsgood removal efficiency. Activated rice huskis effective for organic dyes as it showed 86 %to 94 % efficiency. The removal efficiencyfor sample 3 is 22 % to 24 %. The treatmentwith other samples shows negative results asactivated rice husk releases colour into theeffluent.

The rice husk ash shows good removalefficiency for the sample 1, sample 3 andsample 5 i.e. 65 to 84 %, 45 to 53 % and 75 to98 % respectively. The colour removalefficiency for other samples are very low i.e. 1to 4 % only. Thus, it reveals that rice husk ashcan be used as good adsorbent for organiccolour.

The activated rice husk and rice huskash can be used as good adsorbent forselected effluent having specificconcentration of adsorbate (colour/organicmatter).

5. CONCLUSIONThe result of present study clearly showsthat acid treated rice husk and RHA iseffective in removal of methylene blueand can provide an economical solutionfor removal of such colour from theaqueous solution. 88 % to 94 % colourremoval efficiency can be achieved atthe dose of 20 g/l of ARH havingmethylene blue concentration of 50 mg/l,30 mgll and 10 mg/I. 80 % to 95 %colour removal efficiency is achieved atthe adsorbent dose of 2.5 g/l of RHA formethylene blue concentration of 50 mg/l,30 mg/l and 10 mg/I. With increase inRHA dose the efficiency increased upto98 %. RHA also shows good efficiencyin less time than that of ARH. Theefficiency varies with the variation inadsorbate concentrations and adsorbentdose. From the results of theexperiments conducted in presentinvestigation, it is evident thatexperimental adsorption data for theadsorption of colour in this research can

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be explained by more than one adsorptionisotherms. The result shows that the R-square values are closer to 1 for alladsorption isotherm plots. Thus, Linear,Langmuir and Freundlich isotherm modelsare good fitted to the experimental data.Thus full utilization of agro-waste andtreatment of wastewater is one of the goodprospective for good environment. Therice husk can be proved as good, effectiveand eco friendly adsorbent.

6. REFERENCES1. Aydun A Haluk and Orner Yavuz,

Removal of acid red 183 from aqueoussolution using clay and activatedcarbon, Indian Journal of ChemicalTechnology., 11 (01), 89-94, (2004)

2. Balasubramanian M. R. andMuralisankar 1., Utilisation of fly ashand tea-waste ash as decolourisingagents for dye effluents, IndianJournal of Technology, 25, 471-474,(1987)3. Dhar N.R., Khoda A.K.M.B., KhanA.H., Bala P., Karim M.F., A study ofEffects of Acid Activated Saw dust onthe removal of different dissolvedTannery Dyes (Acid dye) fromaqueous solution, Journal ofEnvironmental Science and Engg., 47(02), 103, (2005)

4. Gokarm A.N., S. Mayadevi, GawandeSunayana, Jacob Nalini, A costeffective sorbent for decolorisation oftreated spent wash, 8th JointConvention of Three Association-2005, 137

5. Gokarn A. N., Mayadevi S., Activecharcoal from Agro-wastes for colour

removal of treated spent-wash,D.S.TA. Part 1" B1-B7, (2002)6. Gokam A. N., Oswal Namita,

Sankpal Narendra, Studies on the useof Natural Polyelectrolytes fortreatment of distillery effluent,DSTA, Part I, BI-BI0, (1999)7. Jadhav D. N. and Vanjara A.K.,Adsorption equilibrium study:Removal of dyestuff effluent usingsawdust, polymerized sawdust andsawdust carbon-I, Indian Journal ofChemical Technology., 11 (03), 194,(2004)8. Jadhav D.N. and Vanjara A.K.,Adsorption kinetics study: Removalof dyestuff effluent using sawdust,polymerized sawdust and sawdustcarbon-II, Indian Journal ofChemical Technology., 11, 42,(2004)

9. Jyoti D. Mane, Shweta Modi, SwatiNagawade, Phadnis S.P., BhandariV.M., Treatment of spentwash usingchemically modified bagasse andcolour removal studies, BioresourceTechnology, 97, 1752-1725, (2006)

10. Khattri S D and Singh M K,Adsorption of basic dyes fromaqueous solution by naturaladsorbent, Indian Journal ofChemical Technology, 6 (03), 112,(1999)11. Mall 1.D. and Upadhyay S.N.,Removal of basic dyes from wastewater using boiler bottom ash, IndianJournal of Environmental Health.,37 (1), 1, (1995)

12. Manaskom Rachakornkij, SirawanRuangchuay and SumateTeachakulwiroj, Removal of reactivedyes from aqueous solution usingbagasse fly ash, Journal of ScienceTechnology., 26 (1),13-24, (2004)

13. Ramteke D.S., Wate S.R. and Moghec.A., Comparative adsorption

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studies of Distillery waste onActivated carbon, Indian Journal ofEnvironmental Health, 31, 17, (1989)14. Sarioglu M. and Atay U.A., Removalof Methylene blue by using biosolid,Global NEST Journal, 8 (02), 113-120,(2006)

15. Singh D. K. and Srivastava Bhavana,Basic dyes removal from waste water

Optimum pH for Adsorbent Activated Rice Husk(ARH)

,., 100 T'""~~~~""""~"""-"""-~--"""""""""''''. ~ 80 t - - - - - - - - - ~~~~~~~~~~~~IE ~ w+- - - ~~~- - - - ~~- - - - - - - - - - - - - - ~>o~ 40+-~~--~L---------------------~0 : :~ 20+- - - ~- - - - _ r - - - - , _ - - - - r _ - - ~- - - - ~

2 5 pH 7 9 II

-It- Concentration 01methylene blue SOmgJ1-+- Concentration 01methylene blue 3OmgJ1-->+-Concentra tion 01methy lene blue 10mgJ1

Graph (a): Optimum pH for Activated Rice HuskOptimum contact time for Activated Rice

Husk~ 95e.9! 90~ 85- 80~ 75& 70~ 65

~> -: ~.r> -:/..--r"V10 20 40 60 120Time in minute 240

___ Concentration of methyiene blue 50mgll-..- Concentration of methylene blue 30mgll~ Concentration of methylene blue 10mgJ l

Graph (c): Optimum contact time for Activated Rice Husk Graph (d): Optimum contact time for Rice Husk AshOptimum Adsorbent dose of Rice Husk Ashptimum Adsorbent dose of Activated Rice

Husk100

I.. ..:..~~---0

~ .~ -. ."," . .. . . .~.'.'"J 80 . . . . . .- - ....70 .>. ,. . . . .. . . .. . .60

2.5 5Adsorbent ~s. In gml20 40

I___ Concentration of met hylene blue SOmglL

I.- Concentration of methylene blue 30mg/L~ Concentration of methylene blue 1Omg/LGraph (e): Optimum adsorbent dose for ARH

by adsorption on rice husk carbon,Indian Journal of ChemicalTechnology ,133, 03 (2001)

16. Stephen Inbaraj B. and SulochanaN, Basic dye adsorption on low costcarbonaceous sorbent - Kinetic andequilibrium studies, Indian Journalof Chemical Technology., 201, 05(2002)

Optimum pH for Adsorbent Rice Husk Ash (RHA)l OOr - ~- ' ; : ~~~===: ~~l. ,c; W+---~T7~--------~~----~~----~'us~ W' ~- - ~- - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4>oE~ 40+- ~- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~~20+-----~----~----r_----r_----r_--~

2 3 5 pH 7 9 II___ Concentration 01methylene blue SOmgJ1-+- Concentrat ion 01methylene b lue 3OmgJ1___ Concentration 01methylene b lue 1OmgJ1

Graph (b): Optimum pH for Rice Husk AshOptimum Contact time for Rice Husk Ash (RHA)

1001 :- .. . c:. .U 90E --- .----w ~~ . .-;>0 W~ ./. ,.

7010 20 40 W 120 240Tlmoln mln-4.Concentration of methylene blue SOmgll___ Concentrat ion of methyl ene blue 30mgll___ Concentration of methylene blue 10mgll

100 ..~~~ __ ~~ ~ ,i0 t------7"-=~-----iI80+- ~~- - - - - - - - - - - - - - - - - - - - - - - - - - ~. .. .70+- - - - -_ _ - - - - ~- - - - - - _ _- - - - - - - - - - ~

2.5 5 10 20AdsOf"bent dose in gml1

40

_Concentration of meth)'tene blue 50mgll-.- Concentration of meth)'tene b lu e 30m gIL-


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For all graphs the legend are same as given bellow: Concentration of methylene blue is 50m g/l Concentration of methylene blue is 30m g/l" Concentra tion of methylene blue is 10mgll- Linear !concentration of methylene blue is 10mg/ll- Linear Concentration of methylene blue is 30m g/l- Linear (Concentration of methylene blue is 50mg/l)Linear adsorption isotherm for ARH Langmuir isotherm for ARH

14.000R" 0.9933 "2.000 - . 5.000R' =0 9313 ./' 4.000 R' = 0.6879 0.000 / He = 0.99018.000 3.000 R' = 0.9972. , . / /" .:.000 I / !!2.000 . . -:.000 , I / 1.000 . . . . 2.000 ~ ./.1/'-/ 0.000 I/0.000 _1.008COO 0.500 1.000 1.500 2. 000.000 5.000 10.000 15.000 20.000

Co 1/Ce

Graph I: Linear plot for ARHFreundlich isotherm for ARH

-0

R' = 0.8967R" = 0.893 "R .. 0.9746 ./

/. .-~. .c .// ~].., ~v'7 . . ,./1:'

log CeGraph 3: Freundlich plot for ARH

Langmuir isotherm for RHA----4600. ------------------ ..-- ---- .I n, R' 0.8429 ~O,~~R~,~=~02.9~46~7-------~--~. . /

R'=0.9498 /~OO~- - - - - - - - - - - - ~~- - - - - - ~- - -2~~-- - - -_,~~-- -~/

. " '--l.Q!& ..~H;O"' Inn 1.0001/Ce

..3.000.000

Graph 5: Langmuir plot for RHA

4. 00

Graph 2: Langmuir plot for ARHLinear adsorption isotherm for RHA

20.000 . R' = 0.610315.000 R? ': 07565

R' = 0.9131

10.000

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Comparative Adsorption Studies Prof MR Gidde