ETUK, ANYANIME CHRISTOPHER

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COMPARATIVE ANALYSIS OF ACID ACTIVATED NTEJE CLAY AND TWO COMMERCIALLY AVAILABLE ADSORBENTS (FULLER’S EARTH

AND ACTIVATED CARBON)

BY

ETUK, ANYANIME CHRISTOPHER

PG/M.SC./12/62662

DEPARTMENT OF PURE AND INDUSTRIAL CHEMISTRY FACULTY OF PHYSICAL SCIENCE

UNIVERSITY OF NIGERIA, NSUKKA

JANUARY, 2015

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COMPARATIVE ANALYSIS OF ACID ACTIVATED NTEJE CLAY AND TWO COMMERCIALLY AVAILABLE ADSORBENTS (FULLER’S EARTH AND ACTIVATED CARBON)

BY


PG/M.SC./12/62662

RESEARCH PROJECT

SUBMITTED TO THE DEPARTMENT OF PURE AND INDUSTRIAL CHEMISTRY, FACULTY OF PHYSICAL SCIENCES, UNIVERSITY OF NIGERIA, NSUKKA IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF MASTER OF SCIENCE (M.Sc.) DEGREE IN INDUSTRIAL CHEMISTRY

JANUARY, 2015

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DECLARATION

This Project contains the report of an original work that was carried out by me and has not

been presented in any previous application for any degree or diploma. All literatures cited,

information from other sources have been acknowledged by means of references.

Sign: ------------------------ Date: -------------------


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CERTIFICATION This is to certify that the research work titled, “COMPARATIVE ANALYSIS

OF ACID ACTIVATED NTEJE CLAY AND TWO COMMERCIALLY

AVAILABLE ADSORBENTS (FULLER’S EARTH AND ACTIVATED

CARBON)” was carried out by Etuk, Anyanime Christopher with registration

number: PG/M.Sc/12/62662 and has been approved by the undersigned as

having met the standard for the Department of Pure and Industrial Chemistry,

University of Nigeria, Nsukka in partial fulfillment of the requirements for the

award of Master of Science (M.Sc.) degree in Industrial Chemistry.

-------------------------------------- ---------------------- Prof. Linus E. Aneke Date Supervisor

------------------------------------------------------ ----------------------------- Dr. A. E. Ochonogor Date Head of Department ------------------------------------------------------- -------------------------------- External Examiner Date

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DEDICATION

With reference to God, I dedicate this work to my dear family (Dad, Mum and siblings) whose

support and love to me has been immeasurable.

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ACKNOWLEDGMENT

The success of this work wasn’t without challenges. It is therefore necessary to

acknowledge contributors and facilitators to this fruition. And in so doing, I thank God for His

mercies and grace that qualify me to this lofty height. I am humbled at His protection, journey

mercies and provisions I enjoyed throughout the period of this study. May his name be praised.

It is compulsory within my spirit to acknowledge my supervisor, Prof. Linus Enemor

Aneke. Untiring he was correcting my mistakes, happily he was bearing my disturbances to his

telephone lines and would always be there for me. Thank you. I am not ungrateful to the head,

Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka, Dr. A. E. Ochonogor

for his fatherly response and contributions which were strategic to this success.

I acknowledge the immense contribution of all the staffs (teaching and non-teaching) of the

Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka. Amongst whom are

Prof. P. O. Ukoha who has been elevated to the position of the Dean, Faculty of Physical

Sciences, Dr. J. Asegbeloyn, Dr. P. M. Ejikeme. Specially, I acknowledge and appreciate the effort

of Engr. J. U. Ani. His contribution and advice speaks volume to the success of this work. Thank

you. Let me acknowledge in advance the external examiner, who will do another good but tedious

job to the overall success of this study. Thank you, Sir.

I acknowledge and appreciate the efforts of my parent, bearing the entire cost of this study,

my siblings for their love and patience, friends and donors who stood by me throughout the period

of this work.

Finally, I appreciate Christ Church Chapel, University of Nigeria, Nsukka, its Choir (C4)

and Methodist Campus Fellowship (MCF) for their moral support and all those whose

contribution(s) and efforts made this work a success.

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ABSTRACT

The composition and bleaching properties of Nteje clay in comparison with two commercially available adsorbents (activated carbon and fuller’s earth) were investigated to study its competence for use as an alternative to high cost imported adsorbents. The modification of the raw clay sample was carried out by acid activation to enhance the surface area of the clay by exchange of octahedral cations e.g Al3+, Fe3+ and Mg2+ with H+ ions which led to the modification of the clay crystalline structure. The raw clay sample was characterized using X-ray Diffraction (XRD) analysis and Fourier Transfer Infrared Spectroscopy. The acid activated sample was used along the two commercially available adsorbents (activated carbon and fuller’s earth) in adsorptive bleaching of palm oil to study its adsorptive capacity. The bleaching was done at constant temperatures of 60 oC, 80 oC, 100 oC, 120 oC and 140 oC varying time at 10, 20 30, 40 and 50 minutes at each constant temperature. The kinetics and thermodynamics of the adsorption reaction was investigated at 333 k, 353 k, 373 k, 393 k and 413 k. To further understand the kinetics, the adsorption data were analyzed by pseudo-second order, elovich and power function equations. Adsorptive bleaching of palm oil was carried out using optimum operating conditions of temperature, clay dosage and reaction time. The results revealed that the adsorption followed power function equation for both activated carbon (A.C) and fuller’s earth (F.E) with linear regression coefficient (R2) values of 0.987 and 0.990 respectively and followed elovich equation for activated Nteje clay (A.N.C) with (R2) value of 0.985. Analysis of the equilibrium data using Langmuir and Freundlich isotherms showed that Langmuir isotherm provided the best fit for the three adsorbents understudy. Furthermore, the evaluation of the adsorption thermodynamic parameters revealed that the adsorption process was spontaneous and exothermic because of the free energy change, negative change in enthalpy and positive change in entropy. A maximum colour reduction of 79 % was obtained for both A.N.C and F.E and 78 % for A.C all at 140 oC. The results from this study reveals that modification of this alumino-silicate increased its adsorptive capacity and produced equal results and responses like their commercially available counterparts. Application of the low cost modification technique Nteje Clay therefore should not be doubted, as this study have establish that it competes and compares favourably with the imported, commercially available adsorbents.

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LIST OF ABBREVIATIONS AND SYMBOLS

ANC - Activated Nteje Clay

AC - Activated carbon

FE - Fuller’s Earth

XRD - X-ray Diffraction

EDTA - Ethylene di-amime tetraacetic acid

UANC - Unactivated Nteje Clay

CPO - Crude Palm Oil

RBDPO - Refined, bleached, deodorized palm oil

FTIR - Fourier transform infrared

SEM - Scanning electron microscope

DBPO - Deodorized, bleached palm oil

FFA - Free fatty acid

PFAD - Palm fatty acid distillate

NHP - Non-hydratable phosphatide

RBD - Refined, bleached and deodorized

PV - Peroxide value

DOBI - Deterioration of bleachability index

IR - Infrared

Å - Angstrom

M - meter

λ - lambda

F - Fahrenheit

% - Percentage

mmHg - millimeters mercury

ppm - Parts per million

γ - Gamma

wt% - weight percent

KJ/mol - Kilojoules per mole

K - Kelvin

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μm - Micrometer oC - Degrees centigrade

M - Molar

N - Normal

m2/g - Meters square per grams

ml - mills

meq - milli equivalent

S/N - Serial number

etc - et cetera

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TABLE OF CONTENT

Title page

Certification

Approval page

Dedication

Acknowledgement

Table of content

List of Tables

Abstract

List of Figures

List of Abbreviations and Symbols

CHAPTER ONE: INTRODUCTION

1.1 Research background

1.2 Research objectives and scope

1.3 Significant of study

CHAPTER TWO: LITERATURE REVIEW

2.1 Introduction

2.2 Clays

2.2.1 Classification of clays

2.2.2 Modification of clays-

2.2.3 Methods of modification of clay minerals

2.1.3.1 Thermal activation

2.1.3.2 Acid activation

2.1.3.2.1Mechanism of acid activation

2.3 Characterization techniques for clay

2.3.1 X-ray fluorescence

2.3.2 Fourier transform infrared spectroscopy (FTIR)

2.3.3 Powdered X-ray diffraction analysis

2.3.4 Scanning electron microscope

2.4 Use of clay in decolourizing and refining oil

2.4.1 Types of clays used in decolourizing

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2.4.2 Properties required of decolourizing clays

2.5 Activated carbon

2.5.1 Production

2.5.2 Physical reactivation

2.5.3 chemical reactivation

2.6 Pre-treatment – Degumming, deodorization and bleaching

2.6.1 Degumming process

2.6.2 Deodorization

2.6.3 Bleaching process

2.7 What is degumming?

2.7.1 Types of degumming

2.7.1.1 Dry degumming

2.7.1.2 Water degumming

2.7.1.3 Acid degumming

2.7.1.4 Enzymatic degumming

2.7.1.5 EDTA – degumming

2.7.1.6 Membrane degumming

2.7.2 Process theory of degumming

2.8 What is bleaching?

2.8.1 Types of bleaching

2.8.1.1 Heat bleaching

2.8.1.2 Chemical oxidation

2.8.1.3 Adsorption

2.8.2 Process theory of bleaching

2.8.3 Palm oil (Elaeis guineensis)

2.8.3.1 Composition of crude palm oil (CPO)

2.9 Survey of related literature

CHAPTER THREE: EXPERIMENTAL

3.1 Modification of clay by chemical activation

3.2 Physical and chemical characterization of Nteje clay

3.2.1 Surface area measurement

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3.2.2 Bulk density

3.2.3 Specific Gravity

3.2.4 Oil retention

3.2.5 pH and acidity measurement

3.2.6 Cation exchange capacity (CEC)

3.3 Pretreatment - degumming and neutralization

3.3.1 Degumming process

3.3.2 Neutralization process

3.4 Bleaching process

3.5 Adsorption kinetics

3.6 Adsorption isotherm

3.7 Adsorption thermodynamics

CHAPTER FOUR: RESULTS AND DISCUSSION

4.1 Physico-chemical characterization of Nteje clay

4.2 FTIR characterisation

4.3 XRD analysis

4.4 Effect of activation

4.5 Effect of bleaching time

4.6 Effect of temperature


4.8 Adsorption isotherm


CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusion

5.2 Recommendations

5.3 Contribution to knowledge

REFERENCES

APPENDICES

APPENDICES

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Appendix A: Table of Values for the Amount of Pigment Adsorbed (Percentage Bleaching) and

Isotherm Parameters at Various Constant Temperatures.

Appendix B: Table of Values for the Adsorption Thermodynamic Plot at Constant Time.

Appendix C: Table of Values for the Adsorption Kinetic Plots at Constant Temperatures.

Appendix D: Detailed X-ray Diffraction (XRD) Analysis Result as Obtained from Physics

Advanced Laboratory, Sheda Science and Technology, Abuja

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LIST OF FIGURES

Figure 2.1: Flow Diagram of Dry Degumming

Figure 2.2: Flow Diagram of Water Degumming

Figure 2.3: Flow Diagram of Acid Degumming

Figure 2.4: Flow Diagram of EDTA Degumming

Figure 2.5: Chemical Structure of Phosphatide

Figure 2.6: Mechanism of Adsorption

Figure 4.1: FTIR Spectrum Of Natural Nteje Clay

Figure 4.2: FTIR Spectrum Of Activated Nteje Clay

Figure 4.3: Charts of Percentage Bleaching with Time at Various Constant Temperatures

Figure 4.4: Pseudo-second Order Plot for AC, FE and ANC at 10 min



Figure 4.7: Pseudo-second order Plot for AC, FE and ANC at 40 min


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Figure 4.9: Elovich Plot for AC, FE and ANC at 10 min


Figure 4.11: Elovich plot for AC, FE and ANC at 30 min



Figure 4.14: Power Function Equation Plot for AC, FE and ANC at 10 min





Figure 4.19: Freundlich Isotherm Plot for AC, FE and ANC at 10 oC





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Figure 4.24: Langmuir Isotherm Plot for AC, FE and ANC at 10 oC





Figure 4.29: Plot of �� versus 1 �� for AC, FE and ANC at 10 min





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LIST OF TABLES

Table 2.1: Compositions of Phospholipids of Palm Oil (mole %)

Table 4.1: Physical Properties of AC, FE, ANC and UANC

Table 4.2: XRD Analysis Result of Nteje Clay

Table 4.3: Effect of Bleaching Time at 60 oC





Table 4.8: Pseudo-second Order Parameters for AC, FE and ANC

Table 4.9: Elovich Parameters for AC, FE and ANC

Table 4.10: Power Function Equation Parameters for AC, FE and ANC

Tables 4.11: Freundlich and Langmuir Isotherm Parameters evaluated for AC, FE and ANC at 60 oC

Table 4.12: Freundlich and Langmuir Isotherm Parameters evaluated for AC, FE and ANC at 80 oC

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Table 4.13: Freundlich and Langmuir Isotherm Parameters evaluated for AC, FE and ANC at

100 oC



Table 4.16: Thermodynamic Parameters Evaluated for AC, FE and ANC at 10 Mins.





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CHAPTER ONE

INTRODUCTION

1.1 Research Background

Natural clay minerals are well known and familiar to mankind from the earliest days of

civilization1. Because of their low cost, abundance in most continents of the world, high sorption

properties, high dissolubility in acidic solutions and potential for ion exchange, clay materials are

suitable substances as source of metals and adsorbents. Clay is composed mainly of silica,

alumina, water and frequently with appreciable quantities of iron, alkalis as well as alkali earth

metals. Two structural units are involved in the atomic lattices of most clay minerals. One unit

consists of closely packed oxygen atoms and hydroxyls in which aluminum, iron and magnesium

atoms are embedded in an octahedral combination so that they are at equal distant from six oxygen

or hydroxyls. The second unit is built of silica tetrahedrons. The silica tetrahedrons (Si4O6(OH)4)

are arranged to form a sheet of composition2.

Clay deposits are widespread over the regions of Nigeria and are under utilized in the process

industries largely because we do not have the technology. These clay deposits can be mined,

purified and processed into useful raw materials for the process industries. Naturally occurring

clays are alumino-silicate minerals containing sodium, potassium, and calcium, with traces of

magnesium and iron which may be substituted for aluminum. The structure of these clays can be

altered by heating or reaction with strong acids or alkalis to improve their adsorptive properties

and colour. The majority of these clays do not possess such properties, but, may be activated by

some forms of treatment and their efficiency in the bleaching of vegetable oils can be improved.

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Activation of clays can be accomplished by calcinations, reaction with mineral acids/alkalis, or

combination of both techniques.

1.2 Research Objective and Scope

The aim of this research was to make comparative analysis of the bleaching efficiency of a locally

substituted adsorbent, Nteje clay to the imported, commercially available activated carbon and

fuller’s earth. Because little or no work has been done in comparing the bleaching efficiency of

Nteje clay to its commercial standards, hence the need for the study. This study if found efficient

to the imported bleaching efficiencies of activated carbon and fuller’s earth, should be able to

operate at various quality of crude palm oil (C.P.O) fed and produce equal results and responses as

its commercial standards. By doing so, the purity of the final product including its commercial and

health values will be enhanced.

Therefore, the specific objectives of the research were:-

1. Preparation, characterization of activated and unactivated Nteje clay as well as its

activation.

2. To carry out adsorption of colour pigment from palm oil

3. To study the chemical kinetics, thermodynamics and equilibria of the adsorption process.

1.3 Problem Statement

1. Despite positive results by researchers of the bleaching capacity of Nteje clay, it is still

facing heavy industrial discrimination leading to little or no patronage

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2. This study was also motivated by the easy contamination of vegetable and seed oils due to

the presence of both physical and chemical impurities.

3. The importation of large quantities of adsorbents and at a very high cost.

4. There is the problem of few locally substituted earth sources for research compared to

activated carbon with several substituted local sources.

5. Research have revealed that there are more than enough earth (clays) available that can be

used as adsorbent to meet our local demand.

1.4 Significance of Study

Nteje clay has been reported by several authors to have been successful in the adsorptive

bleaching of palm oil and its potency of being an alternative to costly, imported adsorbents.

Despite these successful results, it is more valuable when the adsorptive power of these local clays

are strong enough to permit it to compete actively with adsorbents already accepted as the standard

quality for refining oils. Hence, the main objective of this research which was to compare the

widely reported bleaching efficiency of this locally substituted adsorbent (Nteje clay) to the

imported, commercially available standards (fuller’s earth and activated carbon). The study will

properly validate its use as a local substituent for industrial and scientific applications, if found

competent.

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CHAPTER TWO

LITERATURE REVIEW

2.1 Introduction

The use of local raw materials in the process industries has been an age old practiced which

so many researchers have dealt with in the last twenty decades. These locally available raw

materials ranging from agricultural wastes to naturally occurring materials like clays have been

found to be useful in such areas like cement production, resins, polishes, metal manufacturing,

ceramics industries, cosmetics, textiles, confectionaries, leather industries, etc. The enormous

availability of these raw materials has necessitated further research work into their alternate uses

other than the ones already developed. Clay, which is one of the most readily available of these

materials, has been found useful in so many areas of life ranging from refractory to metal

processing. Much work has been carried out on the possibility of leaching out some of the metallic

oxides that form the base constituents of clay minerals- alumina, magnesia, ferric oxide, calcium

oxide, and titanium oxide3. The various works are reviewed to see the extent of work done and find

out the lapses which this work will fill and also improvement on the established processes.

2.2 Clays

The word clay is used in ceramics to mean several different kinds of material(s). It is often

taken to mean one of a particular group of purified true clay minerals, each having a definite

composition and a characteristic crystal structure. At other times, it refers to a natural or

manufactured mixture of materials that contains some true clay minerals, which can be made

workable by the addition of water4. The true clay minerals occur in great varieties in nature and are

found in commercial workable deposits of various purities all over the world. True clay minerals

are hydrated aluminum silicates that have been formed by alteration and breakdown of parent

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igneous rocks5. The most important source rocks for clay formation are feldspathic rocks or

granites (typically mixtures of feldspars, quartz, and mica).

The gradual alteration of parent rocks to form clay minerals has usually taken place over

very long time periods within the earth’s crust under the chemical action of heat, high-pressure

gases and water. Deposits of clays formed by such a hydrothermal process are frequently found

still mixed with fragments of unaltered parent rock. These are called residual or primary clay

deposits. A long ago, erosion exposed many primary clay deposits, and streams and rivers washed

much of the clays out from their original deposits. The actions of the moving water tended to

partially purify the material by separating out some of the heavier parent rock fragments. The

resulting finer particles were washed downstream to settle out in the calm waters of lakes or where

rivers emptied into ancient seas. Clays deposited in such a manner are called sedimentary or

secondary clays6. These deposits still contain some finely divided mineral impurities and often also

contain organic material resulting from decaying vegetation entrapped in the clays as they settled

out of the water. The most abundant true clay mineral is Kaolinite, which is a hydrated aluminum

silicate with the chemical formula Al2Si2O5(OH)4. A clay raw material that consist primarily of

Kaolinite is called kaolin. The name kaolin comes from the Chinese word kauling, which means

“high-ridge,” the name of a hill near Jauchau Fu where an important ancient deposit was located7.

Kaolinite occurs in nature in relatively thick beds made up of billions of these tiny Kaolinite

crystals, which typically measure about 1 millionth of a meter (1 μm), or approximately 40

millionths of an inch, across the plate face by about 0.1 μm in thickness. Several structural

variations of the fixed Kaolinite formula exist, depending on differences in internal arrangement of

the Al, Si, and O atoms in the crystal. Montmorillonite is a true clay mineral with a crystal

structure completely different from Kaolinite but fairly closely related to the structure of the

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mineral mica. The general chemical formula for montmorillonite is Al2Si4O10(OH)2 but there are

always significant amounts of iron, magnesium, and potassium atoms present within the crystals8.

The crystal structure of montmorillonite consists of layers, and large amounts of water which can

be accommodated between the layers, leading to the possibility of considerable swelling when the

dry clay contacts water. Montmorillonite is the major mineral in deposits of very fine-grained,

highly weathered, volcanic glass called bentonite.

2.2.1 Classification of Clays

The classification of clays have been organized about the origin of clays (geological

viewpoint), their chemical compositions (chemical viewpoint), or their uses (technological

viewpoint). As an example of the first classification, one finds categories such as residual clays,

lake clays, glacial clays, sedimentary clays, etc., and examples of the second viewpoint are

siliceous clays, high-alumina clays, manganiferous clays, etc. A mineralogical classification of

clays includes both the clay minerals (Kaolinite, montmorillonite, etc.) and additional rock forming

and other minerals5. For technological purposes, factors which determine the technological

classification of clay (rock deposit) take into account the following: (1) the dominant clay-mineral

type including breakdown into its polymorphs, the sites and amount of charge on it, and shape of

clay crystal and particle. (2) The clay minerals present in minor quantities, but perhaps coating the

surface of the major constituent. (3) The particle size distribution of the clay and other minerals.

(4) Ion-exchange capacity (cat ion, anion) and neutral molecule sorption. (5) The kind of

exchangeable ions present on the clay and degree of saturation of exchange sites. (6)

Hygroscopicity of the clay. (7) Reactivity of the clay with organic compounds. (8) Expansion

potentialities of the clay mineral lattice. (9) Electrolytes and solutions in association with the clay

deposit. (10) The accessory minerals, or mineral “impurities,” their sizes, homogeneity of mixture,

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and their ion-exchange capacity. (11) Content of organic matter and especially its occurrence—

size and discreteness of particles, its adsorption on and/or within the clay crystal units, and

protective colloid action. (12) Presence or absence of bacteria or other living organisms. The pH

and other properties of a clay deposit may vary notably within a short time where bacteria are

growing. (13) Content of hydrated alumina and/or silica, which are relatively soluble in ground

water or in dilute acid or alkali. (14) The texture and structure of the clay deposit, such as

lamination, orientation of mineral particles, and other gross features. Clay minerals are classified

preferably on a structural basis5.

2.2.2 Modification of Clays

Modification can alter the clay structure to enlarge its surface area, thereby increasing the

adsorptive and dissolution capacities9. Modification of clay is vital to increase the range of

applicability of clays for the adsorption of colour pigments and extraction of metals10. The

chemical composition of clay minerals varies depending upon the origin influencing the layer

charge, cation exchange capacity, adsorption capacity, dissolution capacity, and morphology.

These factors play a significant role in the modification of the natural clays11. After modification

with cationic surfactants the organic groups are attached to the surface of the natural clays and

largely change the surface properties9. The physical, chemical and biological properties of

modified adsorbents are different from the original adsorbent12.

2.2.3 Methods of Modification of Clay Minerals

The term activation refers to chemical and physical treatments employed to enhance the

adsorption and dissolution capacities of clays. 13 There are various methods for modification of

clay minerals, such as, acid activation11, thermal treatment14, treatment with cationic surfactant[15],

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polymer modification, pillaring by different types of poly (hydroxo metal) cations, intra-particle

and inter-particle polymerization, de-hydroxylation and calcination, de-lamination and re-

aggregation of smectites, and lyophilisation, etc.

2.2.3.1 Thermal Activation

The thermal activation of clay is a physical treatment which involves calcination of clays at

high temperature14. The change in structure and composition upon heating is different for different

clays and largely depends on the particle size and the heating regime16. Furthermore, the clay

minerals are generally calcined prior to their use in order to remove any impurities or moisture

attached to the clay particles11. The thermal activated clays are extensively used in textile, oil and

sugar industries to remove colour and other impurities17. Initially, in the dehydration stage, the

adsorbed and hydrated water and impurities attached to the clay particles are removed. This results

in the weight loss of the clay particles and increase in surface area, providing access to more sites

for adsorption16. Further heating corresponds to the de-hydroxylation. If heating is continued

beyond de-hydroxylation the clay structure and the surface functional groups are altered.

Breakdown of the bonds within the clay structure takes place resulting in the collapse of structure

and reduction in surface area.Vimonses et al (2009)18 studied the adsorption of cadmium and zinc

ions on bentonite. The modification of bentonite was conducted by simple heating at 100 and 200

oC and acid activation was carried in the range from 0.5 to 2.5M H2SO4. The thermal activated

clay at 200 oC was much more effective compared to other activated clay. Chaari et al (2008)19

studied the adsorption of lead on thermal activated clays. The results revealed that adsorption of

lead on the smectite clay increased with the increase in calcination temperature due to the removal

of physico-sorbed water and then decreased with further increase in temperature because of

decrease in surface area.

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2.2.3.2 Acid Activation

The clay formulated by treating it with inorganic acids at high temperatures is termed acid

activated clays20. The acid activation of the clays is normally done by treating it with HCl or

H2SO4 or HNO321 and the cost of production of these acid activated clays is low. The acid

activation of the clays alters the physical properties, such as enhancing the surface area and

average pore volume22. It can also change the chemical properties such as cation exchange

capacity and the surface acidity of the clays, thus, generating the desirable characteristics required

for an effective adsorbent23.

2.2.3.2.1 Mechanism of Acid Activation

The acid activation of clay is a two-step procedure in which the splitting of particles within

the octahedral sheet takes place. In the first step the exchangeable cations are replaced by protons

(H+). The second step involves the leaching of octahedral cations such as Al3+, Mg2+, and Fe3+

from the octahedral and the tetrahedral sheets[11]. The octahedral Al3+ cations could be more easily

leached by acid attack than the tetrahedral Si4+ cations. However, to prevent the excessive leaching

of Al3+ at high concentration, which results in rupture of the lattice structure and decrease in the

surface area of the clay, it is essential to use the appropriate amount of acid. Hajjaji M. et al

(2009)24 investigated the adsorption of methylene blue on raw and acid activated bentonite. The

adsorption capability can decrease after acid activation using certain acid at a high concentration.

The acid activation of bentonite was carried out by treating it with 6.7 M HCl at boiling

temperature for 3 hours. The high acid strength and temperature may have caused the

decomposition of the montmorillonite structure and formation of excess amorphous silica.

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Apart from leaching of cations from octahedral and tetrahedral sheets, acid activation also

removes impurities like calcite and exposes the edges of platelets leading to an increase in surface

area. The acid activated clays have a lower layer charge, lower cation exchange efficiency and

higher surface area than the natural clays, and could be desired for adsorption. Jovanovic and

Jonackovic (1991)25 activated bentonite with HCl over a concentration range of 0.5 – 4 M. It was

found that surface area of bentonite increased with severity of acid. The maximum surface area

and optimal porosity is achieved by activation with 2 M HCl and decreases with further increase in

acid concentration. The increase in surface area at a low concentration is attributed to cation

exchange and removal of impurities; however, the decrease in surface area beyond 2 M HCl is due

to structural changes and the decomposition of samples. The properties of the acid activated clays

are controlled by the following factors: acid concentration, temperature, treating time, and dry

acid/clay ratio, drying temperature of the clay, washing procedure. Bhattacharyya K. G. et al

(2006)26 activated Kaolinite and montmorillonite by acid activation with 0.25 M H2SO4 for 3

hours. On acid activation, the surface area of Kaolinite increased from 3 to 15 m2g-1, whereas the

surface area of montmorillonite increased from 19 to 52 m2g-1. The adsorption of Fe (III) ions on

montmorillonite was more than Kaolinite and acid activation enhanced the activation capacity

adsorbing more Fe (III) ions on the acid activated forms. A comparative study of the effect of acid

activation with H2SO4 and HCl has been reported by Pushpaletha et. al, (2005)27. The results

revealed that modification of clay by sulphuric acid was proven to be more efficient than

hydrochloric acid. The activation was carried out over a concentration range of 0.35 to 10 N. The

maximum conversion of benzene was obtained by sample treated with 1.5 N for both acid and

significant increase in conversion of acid activated bentonites was observed compared to raw

bentonite. Kara M. et. al. (2003)28 analyzed the effect of HNO3, HCl, and H2SO4 on the

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modification of sepiolite. The surface area evaluation revealed that surface area of sepiolite

increased with acid activation and followed the order H2SO4 > HCl > HNO3. Furthermore, the

results showed that acid activation followed by thermal activation drastically increases the surface

area.

2.3 Characterization Techniques for Clay

In this study, various characterization techniques were used to analyze the properties of the clay

samples. In this section, a brief overview of the characterization techniques is described.

2.3.1 X-ray Fluorescence

The X-ray fluorescence (XRF) is widely used to measure the elemental composition of

materials. Since this method is fast and non-destructive to the sample, it is the method of choice for

field applications and industrial production for control of materials. Depending on the application,

XRF can be performed by using not only X-rays but also other primary sources like alpha

particles, protons or high energy electron beams. When a primary X-ray excitation source from an

X-ray tube or a radioactive source strikes a sample, the X-ray can either be absorbed by the atom

or scattered through the material. The process in which an X-ray is absorbed by the atom by

transferring all of its energy to an innermost electron is called the photoelectric effect. During this

process, if the primary X-ray had sufficient energy, the electron is ejected from the inner shell,

creating a vacancy. The vacancy presents an unstable condition for the atom. As the atom returns

to its stable condition, electron from the outer shell is transferred to the inner shell and in the

process give off a characteristic X-ray whose energy is the difference between the two binding

energies of the corresponding shells. Because each element has a unique set of energy levels, each

element produces X-rays at a unique set of energies, allowing one to nondestructively measure the

elemental composition of a sample. The process of emissions of characteristic X-rays is called "X-

34

ray Fluorescence," or XRF. Analysis using X-ray fluorescence is called "X-ray Fluorescence

Spectroscopy." In most cases the innermost K and L shells are involved in XRF detection. A

typical X-ray spectrum from an irradiated sample will display multiple peaks of different

intensities. The identification of atom can be done by comparing the spectrum with the standard

value stored in the look-up table. Also, the quantitative analysis can be done using the intensities

of the peaks.

2.3.2 Fourier Transform Infrared Spectroscopy

The region of the infrared spectrum which is of great interest to most of the chemists is the

wavelength range 2.5 to 15 μm. In practice, units proportional to frequency, (wave number in units

of cm-1) rather than wavelength, are commonly used and the region 2 to 15 μm corresponds to

approximately 4000 to 400 cm-1. The atoms in a molecule are constantly oscillating around

average positions. Bond lengths and bond angles are continuously changing due to this vibration.

A molecule absorbs infrared radiation when the vibration of the atoms in the molecule produces an

oscillating electric field with the same frequency as the frequency of incident infrared radiation

when they are in resonance. Each molecule has its own characteristic spectrum. The bands that

appear depend on the types of bonds and the structure of the molecule. Fourier transform infrared

(FTIR) spectroscopy measures dominantly vibrations of functional groups and highly polar bonds.

Thus these chemical fingerprints are made up of the vibration features of all the samples

components. FTIR spectrometer records the interaction of IR radiation with experimental samples,

measuring the frequencies at which the sample absorbs the radiation and the intensities of the

absorptions. Determining these frequencies allows identification of the sample's chemical makeup,

since chemical functional groups are known to absorb light at specific frequencies. FTIR

experiments generally can be classified into the following two categories: (a) qualitative analysis,

35

where the aim is to identify the sample and (b) quantitative analysis, where the intensity of

absorptions is related to the concentration of the component.

2.3.3 Powder X-ray Diffraction

X-rays are electromagnetic radiation of wavelength about 1 Å (10 - 100 m), which is about

the same size as atomic distances in solid thus it can be used to probe the crystalline structure at

atomic level. X-ray diffraction has been used in two main areas, for the fingerprint characterization

of crystalline materials and the determination of their structure. Each crystalline solid has its

unique characteristic X-ray powder pattern which may be used as a "fingerprint" for its

identification. Once the material has been identified, X-ray crystallography may be used to

determine its structure, i.e. how the atoms pack together in the crystalline state and what the inter-

atomic distance and angle are. These unique properties made X-ray diffraction one of the most

important characterization tools used in solid state chemistry and material science. An important

equation for X-ray diffraction is Bragg’s equation which shows a relationship between X-ray.

wavelength (λ) with lattice point distance (d) and the incident diffraction angle (θ).

nλ = 2 d sinθ .

Different crystal plane in the crystal will diffract X-ray at different angle according to the

Bragg’s equation. By rotating the sample plane with respect to the incident X-ray therefore,

diffracted angles can be recorded by a detector and the diffraction pattern is obtained. The

identification of the sample structure can be done by comparing the spectrum with the pattern

stored in the database.

2.3.4 Scanning Electron Microscopy

36

Scanning electron microscope (SEM) is a type of microscope that uses electrons rather than

light to form an image. There are many advantages in using the SEM instead of a light microscope.

The SEM has a large depth of field, which allows a large amount of the sample to be in focus at

one time. The SEM also produces images of high resolution, which means that small spaced

features can be examined at a high magnification. Preparation of the samples is relatively easy

since most SEM instruments only require the sample to be conductive. The combination of higher

magnification, larger depth of focus, greater resolution, and ease of sample observation makes the

SEM one of the most heavily used instruments in present-day research. By using the wave-particle

duality, SEM creates the magnified images by using electrons instead of light waves. The SEM

shows very detailed 3-dimensional images at much higher magnifications than is possible with a

light microscope. The images created without light waves are rendered black and white. By the

nature of electron beam, a vacuum is required during the operation; therefore the sample has to be

prepared carefully to withstand the vacuum inside the microscope. The samples must be

conductive material in order to be able to interact with electron; SEM samples are coated with a

very thin layer of gold by a machine called a sputter coater. The sample is placed inside the

microscope's vacuum column through an air-tight door. After the air is pumped out of the column,

an electron gun emits a beam of high energy electrons. This beam travels downward through a

series of magnetic lenses designed to focus the electrons to a very fine spot. Near the bottom, a set

of scanning coils moves the focused beam back and forth across the specimen, row by row. As the

electron beam hits each spot on the sample, secondary electrons and back scattered electrons are

knocked loose from its surface. A detector counts these electrons and sends the signals to an

amplifier. The final image is built up from the number of electrons emitted from each spot on the

sample. By this way the morphology of the sample can be seen directly from the micrograph.

37

2.4 Use of Clay in Decolourizing and Refining Oil

Clay materials are used widely to decolourize oils. Decolourization is applied to mineral,

vegetable, and animal oils. Clay materials are used extensively to refine such oils as cotton seed,

soy, palm, and lard oils prior to the manufacture of soaps, paints, and various edible oils. The clay

may serve to deodorize, dehydrate, and neutralize as well as decolourize the oil, but

decolourization is generally the major objective of such processes. Clay may be used in

decolourizing and purifying processes in two ways. The oils may be filtered through a granular

product of 10 to 60 mesh particles, or the oil may be placed into contact with finely ground clay of

approximately –200 meshes; then the oil is separated from the clay by some sort of filter pressing

operations. The percolation process is essentially a low-temperature process, whereas the contact

process uses temperatures in the range of 300—6000 F.

2.4.1 Types of Clays used in Decolourizing

A wide range of clay materials have been used for decolourizing, ranging from fine grained

silts to clays composed of almost pure clay minerals. The materials may be substantially crude clay

or clay that has been prepared by chemical and physical treatment. In earlier times crude clays

called fuller’s earths were used. The name comes from the use of these clays in cleaning or fulling

wool. At the present time, the term fuller’s earth is applied to any clay that has adequate

decolourizing and purifying capacity to be used commercially in oil refining without chemical

treatment. It means nothing so far as the composition and origin of the earth is concerned. Various

silty materials have moderate decolourizing and adsorptive capacities that have permitted their use

38

in the past. It was soon found that many types of clay composed of Attapulgite and some

Montmorillonite possess superior decolourizing powers and such clays supplanted the silts. In the

preparation of these clays, they are dried at 400- 6000 F and ground to various sizes. The activity

of the Attapulgite clay can be substantially enhanced by extrusion under high pressure at low

moisture contents. So far as is known, Montmorillonite clays are not improved by such extrusion.

It is generally recognized that only some Montmorillonite clays possess substantial decolourizing

properties, and that this is not solely a matter of the purity of the Montmorillonite. The explanation

for this variation in the decolourizing ability of these clays is not known and they can be evaluated

only by actually decolourizing tests. Zvanut F. J. (1937)8 have shown that Halloysite clays may

have high decolourizing power. Kaolinite clay from southern Illinois has high decolourizing

power. Diaz F. et al (2001)21 have reported that unusual Illitic clay from Northern Illinois also has

high decolourizing power. Chambers, G. P. (1959)5 has indicated that some Sepiolite clays from

Spain are excellent decolourizing materials. So far as is known, however, at the present time only

Attapulgite and Montmorillonite clays are used commercially for decolourizing. It is well-known

that acid activation enhances the decolourizing power of some Montmorillonite clays several-fold.

2.4.2 Properties Required of Decolourizing Clays

For satisfactory use, the ability of the material to decolourize must be high, that is, a

relatively small amount of earth must have a large amount of colour reduction. In addition, the

earth must have low oil retention, that is, only a small amount of oil is retained by the earth in the

course of the decolourizing process. This property is particularly critical if the oil is of the sort that

cannot be reclaimed from the spent earth by the use of a solvent or by distillation. The clay must

have good filtration characteristics—in the percolation process there must be fairly rapid

movement of oil through the earth, and in the contact process the earth must not unduly bind the

39

filters. Any change in the composition or the character of the oil during the process of

decolourizing is very important. The change may be desired or may be detrimental, depending on

the particular oil and the desired use. In the case of edible oils, the earth must not impart an

obnoxious odour or taste to the oil.

2.5 Activated Carbon

Activated carbon, also called activated charcoal or activated coal, or carbo activatus, is a

form of carbon processed to be riddled with small, low-volume pores that increase the surface area

available for adsorption or chemical reactions. The term “activated” is sometimes substituted with

active.

Due to its high degree of microporosity, just one gram of activated carbon has a surface area in

excess of 500 m2, as determined by adsorption isotherms of carbon dioxide gas at room or 0.0 °C

temperature. An activation level sufficient for useful application may be attained solely from high

surface area, however, further chemical treatment often enhances adsorption properties.

All activated carbons contain some micropores, mesopores and macropores characteristics but

their proportions to one another vary substantantially depending upon the kind of starting material

and the production procedures29. The bleaching action seems to be due to the large adsorbent

surface of carbon. This large surface held in a small volume, would influence the surface tension

of the compounds with which it will come into contact, thus causing adsorption. There are a large

number of commercial grades of activated carbon that are used for adsorbing gasses and vapours,

odours and colouring materials30.

40

2.5.1 Production

Activated carbon is carbon produced from carbonaceous source materials such as nutshells,

coconut husk, peat, wood, coir, lignite, coal, and petroleum pitch. It can be produced by one of the

following processes:

2.5.2 Physical Reactivation

The source material is developed into activated carbon using hot gases. This is generally done by

using one or a combination of the following processes:

• Carbonization: Material with carbon content is pyrolyzed at temperatures in the range 600–

900 °C, in absence of oxygen (usually in inert atmosphere with gases like argon or

nitrogen)

• Activation/Oxidation: Raw material or carbonized material is exposed to oxidizing

atmospheres (oxygen or steam) at temperatures above 250 °C, usually in the temperature

range of 600–1200 °C.

2.5.3 Chemical Activation

Prior to carbonization, the raw material is impregnated with certain chemicals. The

chemical is typically an acid or a strong base, or a salt (phosphoric acid, potassium hydroxide,

sodium hydroxide, calcium chloride, and zinc chloride. Then, the raw material is carbonized at

lower temperatures (450–900 °C). It is believed that the carbonization / activation step proceeds

41

simultaneously with the chemical activation. Chemical activation is preferred over physical

activation owing to the lower temperatures and shorter time needed for activating material.

2.6 Pre-treatment – Degumming, Deodorization and Bleaching

2.6.1 Degumming Process

The main objective of this degumming is to remove the unwanted gums from the oil, which

will interfere with the stability of the final product in later stage. The objective is achieved by

treating the crude palm oil (CPO) with the specified quantity of food grade acid normally

phosphoric or citric acid of certain concentration. The main component contained in the gums,

which has to be removed, is phosphatide. It is vital to remove the phosphatide content in the crude

oil because the presence of this component will impart undesirable flavor and color, and shorten

the shelf life of oil. The phosphatides emulsifying action is the main culprit that causes the

oxidative instability of the crude palm oil (CPO). In this unit operation, the incoming crude palm

oil is first heated up to a temperature of about 90 oC – 110 oC before it is treated with phosphoric

acid. The dosage of phosphoric acid normally used is within the range of 0.05 – 0.1 % of oil

weight with acid concentration approximately about 80 - 85 %. It is meant to decompose the non-

hydratable phosphatides as well as to coagulate the phosphatides making them insoluble and thus

easily removed during bleaching. Excessive amount of phosphoric acid needs to be avoided as it

may cause rise in phosphorus acid and this excessiveness may be difficult to be removed and

contribute to further refining problems.

42

2.6.2 Deodorisation

The filtered Deodorised Bleached Palm Oil (DBPO) is then channeled into the deodorizer

for the deacidification and deodorisation treatment. This process utilizes a combination of high

temperature heating approximately about 240 – 260 oC, under vacuum (2 – 4 mmHg) and direct

steam injection of about 2.5 - 4.0 % by weight of oil31. During this deodorization process, free fatty

acid (FFA) in the form of palm fatty acid distillate (PFAD) is removed as refining waste at the

upper section of deodorizer. Apart from FFA, carotenoid pigment, primary and secondary

oxidation products are also being removed as it may contribute to off-flavour. The deodorized oil

is then cooled before it is filtered by means of a polishing filter and sent to storage tanks.

2.6.3 Bleaching Process

During bleaching process in palm oil refinery, degummed oil is treated with bleaching

earth and heated up to a temperature of about 100 oC before entering the vacuum bleacher. The

dosage of acid activated clay used is typically within the range of 0.5 – 2.0 % by weight of oil and

the contact time with continuous agitation is about 30 minutes.

During this stage, trace metal complexes such as iron and copper, pigments, phosphatides and

oxidation products are removed by adsorptive effect of the bleaching earth. Any residual of

phosphoric acid are removed during this stage too. The bleached oil is then filtered on industrial

filters such as plate and frame filter press or vertical leaf pressure filter.

2.7 Degumming

Technically, degumming is referred as an operation of purification of seed oils, which

normally contain impurities in the colloidal state or dissolved in them31. Fats and oils contain

43

complex organo-phosphorus compound referred to as phospholipids (phosphatides) or more

usually, as gums. Phospholipids should be removed because of their strong emulsifying action and

if they are not removed, the oil will go through undue darkening during deodorization at high

temperature32. The phospholipids (phosphatides) are removed during processing by a variety of

treatments collectively referred to as degumming. The treatment usually involves hydration with

water, orthophosphoric acid, and polybasic organic acids either singly or in combination, followed

by centrifuging the precipitated material.

2.7.1 Types of Degumming

There are 6 types of degumming process in vegetable oil industry. The differences between

all these types are based on methods of processing, chemicals used and the content of phosphatides

in the crude vegetable oil. The types of degumming process are as follows;

2.7.1.1 Dry Degumming

Dry degumming process involves the removal of gums through precipitation by acid

conditioning and via filtration during the bleaching process, not via centrifugal separation. This

process is used for low-phosphatides oil such as palm oil, lauric oils, edible tallow and suitable to

be used for preparing oils for subsequent physical refining. This type of process eliminates

bleaching, as separate processing step, thus, it is cost-advantageous and it is a well-proven process.

44

LOW PHOSPHATIDE OIL

Figure 2.1: Schematic Diagram of Dry Degumming

2.7.1.2 Water Degumming

Water degumming is a process of removing gums through precipitation by pure water

hydration of crude oil via centrifugal separation. This method is used when extracting gums for

production of lecithin, soybean oil and for crude oil with 200 ppm phosphorus content. In this

process, water is the main agent used to remove the hydratable phosphatides from vegetable oils

and it can be carried out in batch or continuous procedure depending on the type of the oil to be

degummed and amount of oil to be processed. This process is insufficient to be used for

subsequent physical refining.

Mixing

Bleaching

Mixing

Filtration

Heating 90 -100 0C

Under Vacuum

Dry-Degummed Oil

Spent Earth

Phosphoric Acid

Bleaching Earth

45

Figure 2.2: Schematic Diagram of Water Degumming

2.7.1.3 Acid Degumming

In this acid degumming process, gums are precipitated by some form of acid conditioning

process and subsequently removed by centrifugal separation. In this process method, the gums can

be hydrated at temperature higher than 40 oC and the process may lead to dewaxing which is

usually associated with processing of sunflower and rice brand oils. In organic refining process,

dilute organic (citric) acid is normally used and the removal of residual phosphatides is by

bleaching using silica hydrogel.

Crude Oil

Water Degummed Oil

Mixing

Separating

Holding

Drying

Heating 80 -100 0C

Water 15 -30 Minutes

Wet Gums

Drying

Commercial Lecithin

46

Figure 2.3: Schematic Diagram of Acid Degumming

2.7.1.4 Enzymatic Degumming

Enzymatic degumming is a special degumming that is enhanced by using some food-grade

enzymes. Types of oil that uses this process method are soybean oil and rapeseed oil. The

advantage of enzymatic degumming is that no soap stock is produced so there are no oil losses due

to soap stock separation.

2.7.1.5 EDTA- Degumming

EDTA degumming is a physico-chemical degumming process. It involves a complete

elimination of phospholipids by a chelating agent, Ethylene Diamine Tetraacetic Acid (EDTA), in

the presence of an emulsifying additive.

Crude oil

Mixing

Separating

Holding

Drying

Heating >40 0C

Acid degummed Oil

Gums

Citric Acid/Dilute Acid

47

Figure 2.4: Schematic Diagram of EDTA Degumming

2.7.1.6 Membrane Degumming

Membrane degumming process is usually used in extraction plant. According to Lin L. et.

al. (1997)33, membrane separation is primarily a size-exclusion-based, pressure-driven process. It

separates different components according to the molecular weight or particle sizes and shapes of

individual components and dependent on their interactions with membrane surfaces and other

components of the mixture. During oil processing, miscella, which contain 25-30 % of crude oil

and 70- 75 % hexane are obtained from extraction prior to solvent removal. Phospholipids can be

separated from triglyceride in the miscella stage using appropriate membrane. The membrane-

based crude oil degumming produces permeate and retentate containing triglyceride and

phospholipids, respectively. The majority of the coloring materials and some of the FFAs and

other impurities are included in phospholipids micelles and are removed as well33. This processing

method is typically used for cottonseed oil.

Crude oil

Mixing

Separating

Holding

Drying

Heating 75-80 0C

EDTA-Degummed Oil

Gums

EDTA (Wetting Agent)

20 - 30 Minutes

48

2.7.2 Process Theory of Degumming

Phospholipids, proteins and carbohydrates, vegetable gums and colloidal components have

negative influence towards the storage of oil. They are considered as undesirable substances in

refining because they increase the oil loss and hamper other operations. Oils that have certain

amount of these substances should be degummed in order to remove all those substances. There

are two kinds of phospholipids that exist, those that are hydratable and those that cannot be

hydrated (non-hydratable phosphatides -NHP). Hydratable phospholipids can be removed easily by

the addition of water where the process can be conducted rapidly at elevated temperature or slowly

at low temperature. However, the temperature should stay below the temperature at which the

phospholipids hydrate starts to become liquid crystals (usually ~ 40 oC). By taking up water,

phospholipid lose their lipophilic character and become lipophobic and thus precipitate from oil34.

Whereas, for non-hydratable phospholipids, they have to be converted to hydratable ones. The

conversion of non-hydratable phospholipids to hydratable is done usually through acidulation

followed by neutralisation. Traditionally, acids that are being used are usually sufficiently strong to

hydrate phospholipids without hydrolyzing the triglycerides. At present, citric or phosphoric acid

is normally used for any type of vegetable oil. However, phosphoric acid is more preferred by the

palm oil refiners because of lower unit cost and easier handling35.

49

Table 2.1: Composition of Phospholipids of Palm Oil (mole %)

Phospholipid Percentage

Phosphatidylcholine (PC) 36

Phosphatidylethanolamine (PE) 24

Phosphatidylinositol (PI) 22

Phosphatidylglycerol 9

Disphosphatidylglycerol 4

Phosphatidic Acid (PA) 3

Lysophosphatidylethanolamine 2

Phosphatidylserine Trace

Lysophosphatidylcholine Trace

Phospholipids are present in relatively small quantities of about 5 – 130 ppm in palm oil as

compared with other vegetable oils. Sambanthamurthi R. et. al. (1991)36 mentioned that the

solvent extracted mesocarp oil usually contained 1000-2000 ppm phospholipids , however it is

only present at level of 20-80 ppm in commercial crude palm oil. Phospholipids have been

reported to show antioxidant effects. Their antioxidant-synergistic effects can be attributed to the

sequestering of soluble pro-oxidant metal ions to form inactive species. Hudson and Maghoub also

showed a synergism between phospholipids and naturally occurring antioxidants such as α-

tocopherol and quercetin. Hydratable insoluble metal ions can also be dispersed by phospholipids

through miscellar action. Since phospholipids and glycolipids cause reverse micelle, vesicle or

emulsion droplet formation, phospholipids can remove metal ions and their hydrophilic salts from

the lipid phase to reduce oxidation.

50

2.8 Bleaching

The term bleaching refers to the treatment that is given to remove colour producing

substances and to further purify the fat or oil. The usual method of bleaching is by adsorption of

the colour producing substances on an adsorbent material. There are lot of adsorbent materials that

are used in vegetable oil industry, for examples, acid activated bleaching earth, natural bleaching

earth, activated carbon and synthetic silicates. Acid activated bleaching earth (fuller’s earth) or

clay, sometimes called bentonite, is the adsorbent material that has been used most extensively.

This substance consists primarily of hydrated aluminium silicate. Usually, bleaching earth does not

remove all the colour producing materials, much of which are actually removed by thermal

destruction during the deodorization process.

Fig. 2.6: Adsorption Mechanism

51

2.8.1 Types of Bleaching Methods

There are three types of bleaching methods that can be used in the edible oil industry, (Gunstone F.

D. (1983)37). They are described below:

2.8.1.1 Heat Bleaching

Some pigments, such as the carotenes become colorless if heated sufficiently. However this

will leave the pigment molecules in the oil and may have adverse effect on oil quality. According

to Gunstone F. D. (1983)37, if this oil comes into contact with air. colored degradation products

such as chroman-5,6-quinones from γ- tocopherol present, may be formed. These are very difficult

to remove.

2.8.1.2 Chemical Oxidation

Some pigments for example carotenoids are made colorless or less colored by oxidation.

But such oxidation invariably affects the glycerides and destroys the natural antioxidants.

Consequently, it is never used for edible oil but restricted to oils for technical purposes, such as

soap-making

2.8.1.3 Adsorption

Adsorption is the common method usually used for bleaching the edible oil by using

bleaching agents. Examples of bleaching agents are bleaching earths, activated carbon and silica

gel. Bleaching agents normally posses a large surface that has a more or less specific affinity for

pigment-type molecules, thus removing them from oil without damaging the oil itself

2.8.2 Palm Oil (Elaeis guineensis)

In 1434, a Portuguese sailor, Gil Eannes first reported about oil palms (Elaeis guineesis)34.

Today, they flourish mainly in the western part of Africa, Indonesia, and Malaysia and most

52

recently in Brazil and Colombia. Oil palm tree grow up to 20 m in height and grow best at

temperature of 24 – 27 oC. Oil palm tree requires a humid climate and the cultivated oil palm

carries fruits from their fourth year onward and can be harvested for 40 – 50 years34. Palm oil is

derived from the fleshy part or the mesocarp of the fruit of the palm species Elaeis guineesis. The

commercial value of this crop mainly lies in the oil that can be obtained from the mesocarp of the

fruit- palm oil and the kernel of the nut- palm kernel oil. In fact, oil palm is the only fruit that can

give these two types of oil. Both are edible oils but with very different chemical composition,

physical properties and applications. As mentioned, the oil palm produces two types of oils, palm

oil from the fibrous mesocarp and palm kernel oil from the palm kernel. Palm oil and palm kernel

oil have a wide range of applications; about 80% are used for food applications while the rest is

feedstock for a number of non-food applications39. Among the food uses, refined, bleached and

deodorized (RBD) olein is used mainly as cooking and frying oils, shortenings and margarine

while RBD stearin is used for the production of shortenings and margarine. RBD palm oil, which

is the un-fractionated palm oil, is used for producing margarine, shortenings, vanaspati, frying fats

and ice cream39.

2.8.2.1 Composition and Constituents of Crude Palm Oil (CPO)

Salmiah A. (2000)39 stated that crude vegetable oil commonly consists of desirable

triglycerides, unsaponifiable matter together with small amount of impurities. Most of these

impurities contribute undesirable effects to the oil, for instance, colour, flavor, odour, instability

and foaming. These impurities should be removed by a purification step in order to produce good

quality refine oil with minimal possible oil loss or damage to the oil and desirable materials such

as tocophenols and carotenes. The compositions of crude palm oil can be classified as a mixture of

five main chemical groups40. They are oil, oxidized products, non-oil (but oil soluble), impurities,

53

water soluble. Some of these chemical groups need to be removed partially or completely through

the refining process in order to produce good edible oil that has better stability and storage. Thus,

in palm oil refineries the CPO produced undergoes degumming, bleaching and deodorization in

order to obtain refined, bleached and deodorized palm oil (RBDPO).

2.9 Survey of Related Works

Onukwuli et. al. (1995)41 reported that the bleaching or adsorptive properties of Nigerian

local clays can be improved by thermal and acid activation. They also found that the bleaching

performance of the clays, measured in terms of the percentage colour reduction of palm oil

depended on the temperature and length of time of activation, with Ukpor clay giving the highest

colour reduction (92 %), while that of acid activated clays depended on the acid used, the type of

clay, acid concentration, temperature, time of activation, and quantity of the acid relative to clay.

They established that Nsu clay was not easily activated by thermal and acid activation, and that

HNO3 was not suitable as an activating agent for the clays investigated. The acids used were

H2SO4, HCl, and HNO3 and it was concluded that H2SO4 gave the best bleaching ability at a low

concentration of 0.5 M with 82 % maximum colour reduction, followed by HCl at a concentration

of 1M with 58 % colour reduction while HNO3 gave the lowest at a concentration of 2.5 M with

about 32 % colour reduction.

Okwara and Osoka (2006)42 in their work using sodium hydroxide (NaOH) as the

activating agent found out that local clay from Mbano, Ohaozara, and Bauchi can be activated with

the alkali at various concentrations. They concluded that the clay from Mbano (kaolin) can be

activated using 3 M of NaOH to give a maximum colour reduction of 76.38 %, clay from Bauchi

(Fuller’s earth) could be activated with 2.9 M NaOH solutions to give a maximum colour

54

reduction of 80.69 %, while the clay from Ohaozara (Bentonite) could be activated with 1M NaOH

to give a maximum colour reduction of 78.66 %. They also estimated that the percentage colour

reduction of the clays from Mbano and Bauchi could be adequately modeled using a third order

polynomial with correlation coefficient of unity within the range of the experimental data, while

that of Ohaozara could be modeled using a logarithmic function with a correlation coefficient of

0.9866.

Salawudeen et. al. (2007)43 reported that acid activation increased the bleaching power of

Nigerian clays and that hydrochloric acid activated clays proved more effective than those of

sulphuric acid. They also reported that the bleaching efficiency increased with increase in the

concentration of the acids irrespective of the type and that the optimal concentration lies in the

range of 35 % and 45 %, while the clay dosage for the bleaching process was in the range between

5 to 10 % mass of the oil.

Nnadozie et. al. (1989)44 investigated the applicability of local clays from Nsu and Okija

areas of Eastern Nigeria in the bleaching of Nigerian crude palm oil. They reported that the clays

from Okija possess some potential as an adsorptive cleanser in the refining of the said crude palm

oil when activated with various concentrations of sulphuric acid. They found out that best result

was obtained when 3 M H2SO4 was used in the activation of Okija clay while the Nsu clay showed

little or no effect at such concentration. The comparison of Okija with an imported bentonite

purchased from Baroid Nigeria limited, Warri, showed that the Okija clay can compete favourably

with imported bleaching earth.

55

Makhoukhi et. al. (2009)45 studied the acid activation of Algerian bentonite by means of 33

factorial designs. They concluded that the acid concentration and activation time influenced greatly

the bleaching capacity of the investigated bentonite, while the temperature exerted no significant

individual effect on the activation. They also reported that the investigated process parameters

exert binary interactions and that the highest bleaching capacity was found to be 99 % under

optimum activation conditions of acid concentration (34 %), contact time (7 h), and temperature

(90 oC).

James et. al. (2008)46 investigated the bleaching performance of a Nigerian Yola bentonite.

They found out that the bleaching performance was enhanced upon activation and that the

predominant active sites on the raw clay are Lewis acid sites, while those on the activated clay are

Bronsted acid sites. They also reported that the best bleaching performance was obtained with clay

sample activated with 5M H2SO4 at acid/clay ratio of 0.7, bleaching temperature of 120 oC and at

10 minutes stirring time.

Nde-Aga et. al. (2007)47 investigated the adsorption of carotene and free fatty acid from

palm oil onto activated Cameronian clay, activated with sulphuric acid. They reported that the time

required to attain adsorption equilibrium decreased as the temperature increased and that the clay

activated with 1M sulphuric acid solution was the most efficient in the adsorption experiment.

They found out that the Freundlich equation is applicable to the adsorption isotherm and the

Brimberg model used to determine the activation energy of the adsorption process gave the values

72 ± 11, 74 ± 11, and 37 ± 6 kJ/mol, for 0.5, 1, and 2M H2SO4 activated clays, respectively.

CHAPTER THREE

EXPERIMENTAL

56

3.1 Modification of Clay by Chemical Activation

The clay sample was obtained on 24th February, 2014. The clay was mined at Achallaku

village, Nteje, Oyi local government area of Anambra state. The clay was ground to fineness, and

then activated. Activation was done using 45 % hydrochloric acid (HCl). 200 g of the ground clay

sample was charged into a 500 ml beaker and slurry of it was made with distilled water. The

activation was carried out by adding the 45 % HCl to the clay slurry and the mixture was boiled for

90 minutes at a regulated temperature of 100 oC. After slow cooling, the slurry was filtered

through a big filter paper. The filtered clay was thoroughly washed with distilled water and re-

filtered to remove the residual acid used in the activation. The sample was then dried in an oven

until the weight of the clay remained constant. The lumps of the activated dried clay was re-ground

using a morter and pestle. Both the activated and the unactivated clay samples were sieved to an

extreme Geologic fineness known as silt.

3.2 Physical and Chemical Characterization of Nteje Clay

3.2.1 Surface Area Measurement: The surface area of each adsorbent was determined according

to the method of Inglethorpe S. D. J., (1993)48. In the process, 1.5 g of each adsorbents was

agitated in 100 ml of HCl that has been diluted to pH of 3. Then 30 g of NaCl was added while

stirring the suspension. The volume was then made up to 150 ml with de-ionized water resulting in

the change of the pH to 4. 0.10 N NaOH was used to raise the pH from 4 to 9 and the volume of

NaOH used, V; recorded. The surface area was then calculated using the equation:

S = 32V – 25 3.00

Where, S is the surface area (m2/g)

57

3.2.2 Bulk Density: The bulk density was carried out according to the method described by Nde-

Aga, B. J. et .al. (2007)49. Done by the tapping procedure. A known weight of each sample after

being dried at 105 0C, was charged into a 10 ml capacity graduated cylinder. The bottom of the

cylinder was tapped gently on the laboratory bench top several times until there was no further

diminution of the sample level. The bulk density was then calculated using the equation below;

Bulk Density (g/ml) = Wmat/Vmat 3.10

Where, Wmat is the weight of the dry material (g) and Vmat is the volume of the dry material (ml).

3.2.3 Specific Gravity: The specific gravity of the clay samples were determined as specified by

the British Standard BS 1377:90. A 50 ml density bottle with the stopper on was dried in an oven

and weighed (m1). Twenty five grams of the samples were oven-dried at105 oC for 24 hours. The

samples were transferred into the density bottle and the bottle with its content and the stopper

weighed again (m2). Then the sample in the bottle was covered with kerosene of known specific

gravity. With the stopper removed, the container was placed in a vacuum dessicator, and the air

gradually evacuated. When no more air was seen to be released, the bottle was removed from the

dessicator and filled with de-aired kerosene. The stopper was again inserted and the bottle

immersed in a water bath until a constant temperature of 25 oC was attained. The bottle was then

wiped dry and weighed (m3). The bottle was afterwards emptied of its contents, cleaned and

completely filled with kerosene, covered with stopper and re-weighed (m4). The specific gravity

(Gs) of the sample was calculated as:

�� = ��(� �� )�� (� �� )

3.11

�� = Specific gravity of kerosene = 0.80

58

3.2.4 Oil Retention: This was done according to the method described by Achife, E. C et al

(1989)50. One hundred grams of oil and 10 g of each of the samples were mixed together and heated

up to 120 oC for 5 minutes. The mixture was filtered using a vacuum system for 30 minutes. The

filtered cake was then weighed. The percentage oil retention was calculated as:

% OR = Wc [(100 - % H2O in Cake) – 10 (100 - % H2O in Clay)]/ 10 3.12

Where OR represents oil retention, Wc is the weight of cake (g). The percentage of H2O in cake

and in clay was determined by drying them in an oven at 110 oC until a constant weight was

attained.

3.2.5 pH and Acidity Measurement: 10 g of each clay samples were added to 100 ml of distilled

water. The mixture was stirred vigorously. The pH of the clay suspension was then measured via

pH meter. In the acidity test, 10 g of clay was boiled for 3 minutes with 10 ml distilled water then

filtered and washed with another 100 ml of distilled water. The combined filtrate and washed

liquid were then titrated with 0.1 N NaOH solutions to phenolphthalein end point.

The acidity was then calculated as percentage weight of NaOH per gram as:

Clay Acidity = [(V x N x 40) / Wc] x 100 3.13

Where V is the volume of sodium hydroxide used in titration (ml), N is normality of sodium

hydroxide and W is weight of clay (g).

59

3.2.6 Cation Exchange Capacity (CEC): This was done according to the method described by

Dias M. I. et. al. (2003)51. Five grams of the clay sample was weighed into the 250 ml polythene

bottle with a magnetic stirrer. The bottle and its content was weighed (M1). One hundred millilitres

of buffered barium chloride solution was added to the bottle and was placed on a magnetic stirring

plate and agitated for 1 hour. At the end of the period, the bottle was centrifuged at 1500 rpm for

15 minutes and the supernatant solution was discarded. Further 200 ml of the buffered barium

chloride solution was added and the mixture was agitated on a magnetic stirring plate for another 1

hour. The bottle and its contents were left overnight. The following day, the bottle and its contents

were centrifuged at 1500 rpm for 15 minutes and the supernatant solution discarded. Two hundred

millilitres of distilled water was added and agitated for few minutes on the magnetic stirring plate.

It was centrifuged for further 15 minutes and the supernatant solution discarded. The bottle and its

content was weighed (M2). One hundred millilitres of MgSO4 solution was pipette into the bottle

and stirred well and was left to stand for 2 hours with occasional agitation on the magnetic stirring

plate. After 2 hours the content was centrifuged at 1500 rpm for 15 minutes and the supernatant

solution decanted into the stoppered bottle. Five millilitres aliquot of this solution was pipetted into

a 100 ml conical beaker and 5 ml of ammonia buffer and 6 drops of indicator were added to it.

This mixture was titrated with standard EDTA (titer A1 ml). Another titration was done with a 5 ml

of aliquot of 0.05 M MgSO4 solution (titer B ml). The end point was indicated by a blue to pink

colour change. The cation exchange capacity was calculated as follows:

CEC = 8{B – ([A1 x (100 + M2 – M1)] / 100)} meg/100 g 3.14

Where M1 = weight of bottle plus dry content (g)

M2 = weight of bottle plus wet content (g)

60

A1 = titration end-point of sample (ml)

B = titration end-point of MgSO4 solution (ml)

3.3 Pre-treatment – Degumming and Neutralisation

3.3.1 Degumming Process: The oil used for degumming and bleaching was obtained at Ogige

market, Nsukka on the 25th of February, 2013. One thousand millilire of melted crude palm oil

(CPO) was accurately measured into a 3000 ml beaker. The oil in the beaker was then heated to a

temperature of 40 oC. Phosphoric acid, 1 % of the oil weight was then added to the oil with

adequate stirring. The oil was later left to stand to enable the precipitation and settlement of the

phosphatide (gums) and subsequent separation of same. The degummed oil was stored for further

use.

3.3.2 Neutralisation: The acid degummed oil was neutralized by adding an alkali of 1.7 M. 0.5

cm3 of sodium hydroxide (NaOH) solution was used per gram of degummed oil charged. The

mixture was then stirred at a regulated temperature of 75 oC for 20 minutes to break the emulsion

formed. Two layers were formed after centrifuging, oil and soap. The soap stock was then filtered

off and the neutralized oil was stored for the next phase of the bleaching process.

3.4 Bleaching Process

Bleaching of the degummed-neutralized oil was carried out according to the method

described by Preeti S. N., et. al. (2007)52. Fifty grams of the degummed-neutralized palm oil was

charged into a 250 ml beaker and then heated up to 100 oC on a magnetic hot plate. The dosage of

the bleaching earth fed at each charge was 10 % of the oil weight. At the end of the bleaching

process, the content of the flask was filtered with a Whatmann filter paper at a regulated

temperature of 30-35 oC to allow for ease of filtration at the end of each bleaching process, and the

61

concentration of pigment of filtrate was determined. The absorbance of the palm oil was measured

using a UV Spectrophotometer. The samples were diluted in hexane to a concentration of 10 %

(v/v), and the absorbances of the samples were determined at a wavelength of 450 nm. The

absorbance of the unbleached palm oil was also measured, to enable the calculation of the amount

of pigment adsorbed at each run. The bleaching performance of the adsorbents was determined

using the equation:

�� ℎ�� %�= 100 − ��

× 100 3.15


The kinetic models used in the analysis of the data are as follows: pseudo-second order,

Elovich and power function equations. The respective linear forms of the equations are as given

below:

� �� = 1��

�� + � �� – Pseudo − second order 3.16

�� = �1�� ln��+ �1

�� − Elovich model 3.17

�� = �� + �� - Power function equation 3.18

qt = q = adsorption capacity at time (t)

qe = adsorption capacity at equilibrium

K = rate constant for pseudo-second order model

(gmg-1 min-1)

α = initial adsorption rate (mg/min)

62

β = is related to the extent of surface coverage and the activated

energy for chemisorption (g/mg)

a & b = power function constants

t = time in seconds

3.6 Adsorption Isotherms

The Freundich and Langmuir equations as reported by Ho, Y. S. et. al (2000)53 were used

for isotherm study. Freundlich adsorption equation is given as: ��

= �� 3.19

Taking log of both sides gives

log ��

= �� + �� 3.20

Where, x = the amount of substance adsorbed, m = the amount of adsorbent (clay), Xe = the

residual amount at equilibrium which is mathematically equal to 1 – x. The plot of log x/m versus

log �� gives n as slope and log K as intercept.

Langmuir adsorption equation is given as

��/�

= ��

+ ��

�� 3.21

Where, a and b are Langmuir constants. The plot of Xe/(x/m) versus Xe was used to evaluate the

values of a and b.


63

Thermodynamic behavior of the adsorption process was evaluated by the following

thermodynamic parameters including the change in free energy (ΔG), enthalpy (ΔH), and entropy

(ΔS).These parameters were obtained using the equation:

∆�� = − �� 3.22

where ∆�� is the standard free energy change (J/mol), R the universal gas constant (8.314 J/mol

K), and T is the absolute temperature (K). Considering the relationship between ∆�� and ��,

change in equilibrium constant with temperature can be obtained in the differential forms.

64

CHAPTER FOUR

RESULTS AND DISCUSSION

4.0 Physico-chemical Characteristics of Nteje Clay

Table 4.1 demonstrates the effect of hydrochloric acid activation of Nteje clay on its physical

parameters. The surface area of the activated Nteje clay was observed to increase with activation

(84.5 m2/g) while the unactivated Nteje clay (UANC) gave a value of (229 m2/g) indicating a

lower surface area. The increase in the surface area from natural to activated samples is related to

the elimination of the exchangeable cations, de-lamination of clays, and the generation of micro-

porosity during the activation process54. Surface area is important in chemical kinetics. The rate of

reaction is increased by increasing the surface area and vice versa. It is one of the factors that

affects chemical reactions.

The bulk density of the activated sample was also observed to have decreased drastically

from1214.3 to 706.2, 699.89 and 710.15 with activation for AC, FE and ANC respectively. This

may be due to the destruction of the clay crystalline structure, following the elimination of the clay

octahedral cations. R. O. Ajembe et. al. (2012)3 studied the Kinetics, Equilibrium and

Thermodynamics of Colour pigment Removal from Palm Oil using Activated Ukpor Clay and obtained

bulk density values ranging from 874, 838.5, 753.9, 715.8, 864.9 Kg/m3 for varying acid

concentrations.

The cation exchange capacity also decreased from 98 to 55, 61 and 58 meq/100g for AC,

FE and ANC respectively after activation of the sample with 1.7 M HCl. This result conforms to

the results obtained by R. O. Ajemba et. al. (2012)3, who got 97, 84, 68, 59, 50, 48 meq/100g at

varying strength of acid concentration. And concluded that the result indicate the extent of removal

of the octahedral cations (Al3+, Fe3+ and Mg2+) from the clay structure. Significant effects were

also observed for oil retention and pH. All results obtained for activated Nteje clay on account of

its physical parameters are without significant difference with the commercially obtained

adsorbents (fuller’s earth and activated carbon).

Table 4.1: Physical Properties of AC, FE, ANC and UANC

Parameters AC FE ANC UANC Surface area (m2/g) 225 231 229 84.5 Bulk density 706.2 699.89 710.15 1214.3

65

(kg/m3) Cation exchange capacity (meq/100g) 55 61 58 98 Oil retention (%) 50.9 52.6 52.8 30 pH 1.5 1.7 1.4 7.3

4.1 FTIR Characterization

Fourier Transform Infra-red (FTIR) analysis of the raw and activated material were

investigated, to study the effect of acid activation on the clay and help in the identification of

various forms of the minerals present in the clay samples. Both the spectra of the raw and acid

activated Nteje clay are presented in Figures 4.1 and 4.2 respectively. The coupled vibrations are

appreciable due to the availability of various constituents. In the IR study of the clays, the Si-O

stretching vibrations were observed at 445.57 cm-1, 559.38 cm-1, 565.16 cm-1, 783.13 cm-1, and

788.91 cm-1 showing the presence of quartz in the clay samples. The appearance of v (Si-O-Si) and

δ (Si-O) bands also support the presence of quartz[55], a strong band at 3694.77 cm-1, 3692.84 cm-1,

3623.4 cm-1, 3442.8 cm-1, 3432.44 cm-1, and 3419.9 cm-1 indicate the possibility of the hydroxyl

linkage. However, broad band at 3449.8 cm-1, 3432.44 cm-1, 3419.9 cm-1, and band at 1643.41 cm-

1, 1641.48 cm-1, and 1639.55 cm-1 in the spectrum of the clay suggests the possibility of water of

hydration in the samples. Most of the bands such as 3694.77 cm-1, 3692.84 cm-1, 3623.4 cm-1,

1066.67 cm-1, 1046.42 cm-1, 1037.74 cm-1, 920.08 cm-1, 788.91 cm-1, 783.13 cm-1, 525.62 cm-1,

518.87 cm-1, 472.58 cm-1 show the presence of Kaolinite. The vibrations observed at 525.62 cm-1,

518.87 cm-1, and 472.58 cm-1 indicate the possibility of the presence of montmorillonite3. The

presence of bands at 3694.77 cm-1, 3692.84 cm-1, 3623.4 cm-1, 3449.8 cm-1, 3432.44 cm-1, 3419.9

cm-1, 2376.38 cm-1, 1643.41 cm-1, 1641.48 cm-1, 1639.55 cm-1, 1066.67 cm-1, 1046.42 cm-1,

1037.74 cm-1 and 792.77 cm-1 indicate the possibility of the presence of parlygorskite3, whereas

3623.4 cm-1, and 998.2 cm-1 are indicative of gypsum and 70 690.54 cm-1 shows the possibility of

the presence of dickite.

66

The changes in the functional groups gives the indication of the modifications that occurred

during the activation process. During the acid activation of the clay sample, it appears that the

protons from the acid medium penetrated into the clay structures attacking the OH groups thereby

causing the alteration in the adsorption bands attributed to the OH vibrations and octahedral

cations. The intensities of the stretching bands observed at 3623, 3432, 1641, and 920 cm-1

(associated with O-H, along with Al-OH stretch) decreased after acid activation. The increase in

the severity of acid caused the disappearance of the stretching bands at 4660, 3694, 2376, and 998

cm-1 assigned to the H-O-H stretching. The peak assigned to Si-O-Si stretch at 788 and 1066 cm-

1 remained after acid activation of the clay signifying that, similar result was reported by others56.

The bands at 525, 690, and 998 cm-1 disappeared after the acid treatment of the clay sample

implying that the transformation of the tetrahedral structure occurred at 788 cm-1 which was

increased after the acid treatment.

Figure 4.1: FTIR Spectrum Of Natural Nteje Clay

67

Figure 4.2: FTIR Spectrum Of Activated Nteje Clay

4.2 XRD Analysis

Table 4.2 is the X-ray Diffraction (XRD) analysis of powdered Nteje clay which was done

at Physics Advanced Laboratory, Sheda Science and Technology, Sheda, FCT, Abuja. The XRD

analysis was necessary in order to obtain information on the mineral composition of the clay, to

enable its comparison with the mineral compositions of the commercially available activated

carbon and fuller’s earth. The XRD analysis of Nteje clay reveals that its composition are of four

minerals namely: Dickite, Kaolinite, montmorillonite and palygorskite. Dickite, kaolinite, nacrite

and halloysite have the same composition but with different crystalline structure (Polymorph).

These compositions of Nteje clay will not exactly compare with the compositions of the imported,

commercially available fuller’s earth and activated carbon. Variance in the composition of these

adsorbents, does not affect their bleaching efficiencies. According to Siew W. L. (1991)57 analysis

of various samples of fuller’s earth varies so greatly that chemical analysis is no more a criterion in

determining whether or not a particular clay shall be classified as a fuller’s earth. Like all other

clays, fuller’s earth is hydrous, aluminium silicate containing small proportions of other

substances. Most fuller’s earth materials contain a higher percentage of water than most clays, but

68

this water is not an essential factor in the bleaching properties of all fuller’s earth materials; some

bleach fully as well after they have been driven off of their water as before, and others lose much

of their bleaching power when this water is removed. To determine whether or not a particular clay

is a fuller’s earth is no simple matter, for its bleaching power is practically the only characteristic

by which it may be identified. Among the properties formerly attributed to fuller’s earth are

nonplasticity, disintegrating in water, detergent action, large water content and the property of

adhering to the tongue. Hence, why the mineral composition of Nteje clay would vary with its

commercially available counterparts.

Same can also be said of the chemical composition of activated carbon being at variance

with that of Nteje clay. It is obvious that the high temperature employed in carbonization, drives

off organic and inorganic minerals present in the source material, leaving a porous carbonaceous

product.

Table 4.2: XRD Analysis Summarised Result for Nteje Clay

S/N MINERAL NAME

PDF INDEX NAME EMPIRICAL FORMULA

CHEMICAL FORMULA

1 Dickite Aluminium Silicate Hydroxide

Al2H4O9Si2

Al2 Si2O5(OH)4

2 Kaolinite Aluminium Silicate Hydroxide

Al2H4O9Si2

Al2 Si2O5(OH)4

3 Palygorskite Magnesium Aluminium Silicate Hydroxide

H18Mg5O30Si8

(Mg, Al)5 (Si, Al)8 (OH)2 . 8H2O

4 montmorillonite Sodium Magnesium Aluminum Silicate Hydroxide Hydrate

Al2H4Na0.3O13Si4 Na0.3(Al, Mg)2 Si4O10(OH)2 xH2O

4.3 Effect of Activation

69

Acid activation was carried out using optimum operating conditions described by Berbesi,

R. (2006)58. The structural features of the clay were modified by treatment with a food grade acid

(concentrated hydrochloric acid). During this process the physical structure and chemical

compositions are altered in a controlled manner to maximize specific properties. The adsorption

process was influenced by some factors as follows:

• particle size

• adsorbent polarity

• surface area

• pore volume

• pore size.

4.4 Effect of Oil Degumming and Neutralization

4.5 Effect of Bleaching Time

The effect of contact time on the bleaching efficiencies of the clays were also investigated

as shown in Tables 4.3 to 4.7. The percentage colour reduction was observed to have improved

from 30–45 minutes. No further improvement was observed in percentage colour reduction after

this time. The highest bleaching time established for hydrochloric acid activated Nteje clay was

between 30 to 45 minutes (Tables 4.5 to 4.7). This result is in agreement with the result of

Hymore F. K., et. al. (1989)60 which stated that the contact time for effective bleaching typically

ranges from 15 to 45 minutes. According to James, O.O., et. al. (2008)61 the quality of crude palm

oil is of utmost importance to the refiners as it relates directly to the bleaching time and product’s

shelf life. Establishing optimum bleaching time is therefore important as prolonged bleaching time

may lead to colour deterioration. Howes P. D., et. al. (1991)62 made similar observation while

bleaching palm oil using local clays to prepare adsorbents. Similar trend was also obtained for

70

fuller’s earth and activated carbon which dictates the competence of the hydrochloric acid

activated Nteje clay compared to the standards (AC and FE).


A.C F.E A.N.C S/N Time % Bleaching % Bleaching % Bleaching 1 0-10 14.815 17.581 20.021 2 10-20 20.021 29.730 29.930 3 20-30 31.411 30.531 32.432 4 30-40 35.836 34.434 36.136 5 40-50 38.338 40.041 38.939






A.C F.C A.N.C S/N Time % Bleaching % Bleaching % Bleaching 1 0-10 38.839 39.940 39.940 2 10-20 50.451 49.950 49.449

71

3 20-30 75.876 70.071 74.975 4 30-40 76.076 75.676 76.877 5 40-50 77.878 78.879 78.579


A.C F.E A.N.C S/N

Time % Bleaching % Bleaching % Bleaching

1 0-10 44.044 39.940 42.843 2 10-20 58.358 56.757 51.852 3 20-30 77.377 76.476 77.778 4 30-40 77.978 78.879 78.979 5 40-50 78.478 79.079 79.079

4.6 Effect of Temperature

Figures 4.3 shows the effect of temperature on the performance of AC, FE and ANC used

in bleaching palm oil. The highest bleaching efficiency wasn’t obtained within the range 90 to 125

oC according to Hymore F. K., et. al. (1989)60. This contradiction can best be explained by Howes

P. D. et. al. (1991)63. They reported that the optimum bleaching temperature is specific for a

particular adsorbent and oil, which is between 100 to 120 oC for palm oil and gave no range for

adsorbents. The highest bleaching efficiency was obtained at 140 oC with percentage bleaching of

78.478 for AC, 79.079 for FE and 79.079.079 for ANC. This result conforms to the result obtained

by Mustapha et. al. (2013)56 who reported a temperature of 140 oC for adsorptive bleaching of

palm oil. Like the commercially available standards (activated carbon and fuller’s earth), activated

Nteje clay was observed to yield its highest bleaching efficiency at similar temperature. The

viscosity of the oil was also observed to have decreased with increasing temperature. Hamilton R.

J. (1995)57 reported that oil viscosity decreases with increasing temperature, resulting in better

dispersion of particles, improved clay interactions and flowability.

72

73

Figure(s). 4.3: Charts of Percentage Bleaching with Time at Various Constant Temperatures

0

10

20

30

40

50

10 20 30 40 50

% B

leac

hing

Time (S)

At 60oC

AC

FE

ANC 0102030405060

10 20 30 40 50

% B

leac

hing

Time (S)

At 80oC

AC

FE

ANC

0

20

40

60

80

100

10 20 30 40 50

% B

leac

hing

Time (S)

At 100oC

AC

FE

ANC0

20

40

60

80

100

10 20 30 40 50

% B

leac

hing

Time (S)

At 120oC

AC

FE

ANC

0

20

40

60

80

100

10 20 30 40 50

% B

leac

hing

Time (s)

At 140oC

AC

FE

ANC

74


In order to examine the mechanism of adsorption process such as mass transfer and

chemical reaction, some suitable kinetic models are needed to analyse the rate data64. A study of

adsorption kinetics provides information about the mechanism of adsorption, which is important

for the efficiency of the process65. These kinetic models are useful for the design and optimisation

of effluent – treatment process66.

Figures 4.4 to 4.18 illustrate the amount of colour pigment adsorbed as a function of time for AC,

FE and ANC. The experimental data were analyzed using known kinetic models in order to

examine the controlling mechanism of the adsorption process. The models are: pseudo-second

order, elovich model and power function equation. The associated kinetic parameters have been

evaluated for the slopes and intercepts of the respective linear plots and presented in Tables 4.3 to

4.5, respectively. Comparison of the analysed data based on their linear regression coefficient (R2)

values shows that the experimental data were best described by the power function equation for

both AC and FE with (R2) values of 0.987 and 0.990, respectively and elovich model for ANC

with a correlation value (R2) of 0.985. The models which the adsorbents followed do not form any

significant difference in their adsorption efficiencies since the elovich model has equally given a

nice correlation for ANC as the power function equation for AC and FE.

75

Figure 4.4: Pseudo-second Order Plot for AC, FE and ANC at 10 min.


y = -0.06x + 4.968R² = 0.176

y = -0.068x + 5.619R² = 0.752

y = -0.054x + 4.983R² = 0.789

0

1

2

3

4

5

6

7

8

0 10 20 30 40 50 60

1/q t

t (s)

AC

FE

ANC

y = -0.071x + 5.159R² = 0.850

y = -0.051x + 4.297R² = 0.861

y = -0.036x + 3.690R² = 0.947

0

1

2

3

4

5

6

0 10 20 30 40 50 60

1/q t

t (s)

AC

FE

ANC

76



y = -0.038x + 2.924R² = 0.775

y = -0.031x + 2.634R² = 0.838

y = -0.034x + 2.751R² = 0.834

0

0.5

1

1.5

2

2.5

3

3.5

0 10 20 30 40 50 60

1/q t

t (s)

AC

FE

ANC

y = -0.032x + 2.671R² = 0.804

y = -0.031x + 2.652R² = 0.870

y = -0.031x + 2.644R² = 0.827

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 60

1/q t

t (s)

AC

FE

ANC

77



y = -0.018x + 2.025R² = 0.425

y = -0.029x + 2.515R² = 0.769

y = -0.028x + 2.458R² = 0.810

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 60

1/q t

t (s)

AC

FE

ANC

y = 0.156x - 0.228R² = 0.951

y = 0.126x - 0.108R² = 0.946

y = 0.113x - 0.054R² = 0.985

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 1 2 3 4 5

q t

ln t

AC

FE

ANC

78


Figure 4.11: Elovich Plot for AC, FE and ANC at 30 Min

y = 0.192x - 0.254R² = 0.968

y = 0.161x - 0.137R² = 0.982

y = 0.134x - 0.034R² = 0.958

0

0.1

0.2

0.3

0.4

0.5

0.6

0 1 2 3 4 5

q t

ln t

AC

FE

ANC

y = 0.292x - 0.324R² = 0.939

y = 0.261x - 0.217R² = 0.924

y = 0.275x - 0.267R² = 0.949

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 1 2 3 4 5

q t

ln t

AC

FE

ANC

79



y = 0.269x - 0.239R² = 0.908

y = 0.261x - 0.223R² = 0.952

y = 0.268x - 0.235R² = 0.908

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 1 2 3 4 5

q t

ln t

AC

FE

ANC

y = 0.234x - 0.091R² = 0.926

y = 0.265x - 0.202R² = 0.942

y = 0.257x - 0.178R² = 0.886

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 1 2 3 4 5

q t

ln t

AC

FE

ANC

80

Figure 4.14: Power Function Plot for AC, FE and ANC at 10 Min


y = 0.639x - 1.483R² = 0.968

y = 0.478x - 1.209R² = 0.933y = 0.405x - 1.086

R² = 0.967

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

00 0.5 1 1.5 2

log

q

log t

AC

FE

ANC

y = 0.592x - 1.289R² = 0.987

y = 0.464x - 1.081R² = 0.990

y = 0.354x - 0.904R² = 0.979

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

00 0.5 1 1.5 2

log

q

log t

AC

FE

ANC

81



y = 0.551x - 1.000R² = 0.950

y = 0.462x - 0.866R² = 0.938

y = 0.528x - 0.936R² = 0.728

-0.5

-0.45

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

00 0.5 1 1.5 2

log

q

log t

AC

FE

ANC

y = 0.480x - 0.891R² = 0.926

y = 0.462x - 0.869R² = 0.963

y = 0.472x - 0.877R² = 0.926

-0.45

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0 0.5 1 1.5 2

log

q

log t

AC

FE

ANC

82

Figure 4.18: Power Function for AC, FE and ANC at 50 Min

Table 4.8: Pseudo-second Order Parameters for AC, FE and ANC

S/N To C AC FE ANC

qe K2 * 10-

3

R2 qe K2 * 10-3 R2 qe K2 * 10-3 R2

1 60 0.201 -2.42 0.176 0.178 -2.15 0.752 0.201 -2.18 0.789

2 80 0.194 -2.67 0.850 0.233 -2.77 0.861 0.271 -2.64 0.947

3 100 0.342 -4.44 0.775 0.379 -4.45 0.838 0.364 -4.50 0.834

4 120 0.374 -4.48 0.804 0.377 -4.41 0.804 0.378 -4.43 0.827

5 140 0.494 -4.39 0.425 0.398 -4.59 0.769 0.407 -4.64 0.810

Table 4.9: Elovich Parameters for AC, FE and ANC

S/N To C AC FE ANC

y = 0.389x - 0.735R² = 0.934

y = 0.461x - 0.845R² = 0.946

y = 0.436x - 0.811R² = 0.906

-0.45

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

00 0.5 1 1.5 2

log

q

log t

AC

FE

ANC

83

B a R2 b a R2 b a R2

1 60 -4.36 1.169 0.951 -9.259 1.134 0.946 -18.52 1.011 0.985

2 80 -3.94 1.212 0.968 -7.299 1.175 0.982 -29.41 1.143 0.958

3 100 -3.08 1.340 0.939 -4.608 1.298 0.924 -3.745 1.317 0.949

4 120 -4.18 1.308 0.908 -4.484 1.298 0.952 -4.255 1.307 0.908

5 140 -10.99 1.264 0.926 -4.950 1.303 0.942 -5.618 1.293 0.886

Table 4.10: Power Function Equation Parameters for AC, FE and ANC

S/N To C AC FE ANC

B a R2 b a R2 b a R2

1 60 -1.483 -0.194 0.968 -1.209 -0.321 0.933 -1.086 -0.393 0.967

2 80 -1.289 -0.228 0.987 -1.081 -0.333 0.990 -0.904 -0.451 0.979

3 100 -1.000 -0.259 0.950 -0.866 -0.335 09.38 -0.936 -0.277 0.728

4 120 -0.891 -0.319 0.926 -0.869 -0.335 09.63 -0.877 -0.326 0.926

5 140 -0.735 -0.410 0.934 -0.845 -0.336 0.946 -0.811 -0.361 0.906

4.8 Adsorption Isotherm

A sorption isotherm (also adsorption isotherm) describes the equilibrium of the sorption of

a material at a surface (more general at a surface boundary) at constant temperature. It represents

the amount of material bound at the surface (the sorbate) as a function of the material present in

the gas phase and/or in the solution.

84

Figures 4.19 to 4.28 are Freundlich and Langmuir isotherm plots for AC, FE and ANC describing

the equilibrium of the sorption of palm oil impurities at constant temperatures. The associated

isotherm parameters are calculated and presented in Tables 4.6 to 4.10. To evaluate the nature of

adsorption, the experimental isotherm data were fitted by model isotherm equations namely;

Freundlich and Langmuir models.

Isotherm study of the three adsorbents were best described by Langmuir adsorption isotherm with

linear correlation coefficient (R2) values of 0.982 for AC and 0.999 for both FE and ANC. The

forces of attraction existing between the adsorbent and adsorbate were almost the same strength as

chemical bonds. This type of adsorption can be said to be Chemical adsorption (Chemisorption),

and is always attributed to Langmuir adsorption. Consequently, the following can be deduced of

the adsorption process:

(1) It has high heat of adsorption in the range of 40-400kJ/mol

(2) Forces of attraction were chemical bonds

(3) Took place at high temperature

(4) It is irreversible

(5) It is highly specific

(6) Required activation energy

(7) The adsorption of colour pigment on the three adsorbents was monolayer.

(8) The surfaces of the adsorbents were uniform, that is, all the adsorption sites were

equivalent.

(9) All the adsorption occurred through the same mechanism.

(10) Adsorbed molecules did not interact

85

Figure 4.19: Freundlich Isotherm Plot at 60 oC

y = -2.913x - 2.304R² = 0.977

y = -1.929x - 2.116R² = 0.753

y = 0.704x - 0.062R² = 0.907

-2.5

-2

-1.5

-1

-0.5

0-0.25 -0.2 -0.15 -0.1 -0.05 0 0.05

log(

x/m

)

log(Xe)

AC

FE

ANC

y = -1.895x - 2.149R² = 0.965

y = -1.441x - 2.026R² = 0.947

y = -1.188x - 1.956R² = 0.973

-2.5

-2

-1.5

-1

-0.5

0

-0.35 -0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0 0.05

log(

x/m

)

logXe

AC

FE

ANC

86




y = -0.732x - 1.871R² = 0.967

y = -0.613x - 1.803R² = 0.996

y = -0.646x - 1.823R² = 0.989

-2

-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0-0.8 -0.6 -0.4 -0.2 0 0.2

log(

x/m

)

logXe

AC

FE

ANC

y = -0.675x - 1.839R² = 0.977

y = -0.646x - 1.832R² = 0.967

y = -0.683x - 1.849R² = 0.989 -2

-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0-0.8 -0.6 -0.4 -0.2 0 0.2

log(

x/m

)

logXe

AC

FE

ANC

87


Figure 4.24: Langmuir Isotherm Plot at 60 oC

y = -0.576x - 1.784R² = 0.975

y = 1.085x + 0.050R² = 0.996

y = 1.113x + 0.064R² = 0.986

-2

-1.5

-1

-0.5

0

0.5

-0.8 -0.6 -0.4 -0.2 0 0.2

log(

x/m

)

logXe

AC

FE

ANC

y = 340.6x - 183.8R² = 0.953

y = 208.1x - 98.52R² = 0.72

y = 166.1x - 72.18R² = 0.785

0

20

40

60

80

100

120

140

0 0.2 0.4 0.6 0.8 1

Xe/(

x/m

)

Xe

AC

FE

ANC

88



y = 191.8x - 80.25R² = 0.937

y = 120.9x - 41.84R² = 0.96

y = 98.74x - 29.91R² = 0.977

0

10

20

30

40

50

60

70

80

90

0 0.2 0.4 0.6 0.8 1

Xe/(

x/m

)

Xe

AC

FE

ANC

y = 72.46x - 11.60R² = 0.965

y = 56.08x - 6.993R² = 0.999

y = 61.16x - 8.353R² = 0.992

0

5

10

15

20

25

30

35

40

45

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Xe/(

x/m

)

Xe

AC

FE

ANC

89



Table 4.11: Freundlich and Langmuir Isotherm Parameters Evaluated for AC, FE and ANC at 60 oC.

ISOTHERM FREUNDLICH LANGMIUR

y = 64.57x - 9.315R² = 0.976

y = 61.78x - 7.971R² = 0.974

y = 64.74x - 9.239R² = 0.990

0

5

10

15

20

25

30

35

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Xe/(

x/m

)

Xe

AC

FE

ANC

y = 55.86x - 6.962R² = 0.982

y = 71.81x - 10.74R² = 0.962

y = 64.59x - 8.742R² = 0.999

0

5

10

15

20

25

30

35

0 0.1 0.2 0.3 0.4 0.5 0.6

Xe/(

x/m

)

Xe

AC

FE

ANC

90

PARAMETER K n R2 a b R2 AC 0.344 -2.304 0.977 0.0029 -0.539 0.953 FE 0.513 -2.116 0.753 0.0048 -0.473 0.72 ANC 0.708 -0.062 0.907 0.0060 -0.435 0.785

Table 4.12: Freundlich and Langmuir Isotherm Parameters Evaluated for AC, FE and ANC at 80 oC

ISOTHERM FREUNDLICH LANGMIUR PARAMETER K n R2 a b R2 AC 0.527 -2.149 0.965 0.0052 -0.418 0.937 FE 0.692 -2.026 0.947 0.0083 -0.346 0.96 ANC 0.841 -1.956 0.973 0.010 -0.222 0.977

Table 4.13: Freundlich and Langmuir Isotherm Parameters Evaluated for AC, FE and ANC at 100 oC


Tables 4.14: Freundlich and Langmuir Isotherm Parameters Evaluated for AC, FE and ANC at 120oC


Tables 4.15: Freundlich and Langmuir Isotherm Parameters Evaluated for AC, FE and ANC at 140oC

ISOTHERM FREUNDLICH LANGMIUR PARAMETER K n R2 a b R2 AC 0.577 -1.784 0.975 0.0179 -0.125 0.982 FE 1.084 0.050 0.996 0.0139 -0.149 0.962 ANC 1.112 0.064 0.986 0.0155 -0.135 0.999

4.9 Adsorption Thermodynamics

91

The reaction rate can be calculated from the knowledge of kinetic studies. But the changes

in reaction that can be expected during the sorption process require the knowledge of

thermodynamic parameters. Thermodynamic considerations of an adsorption process are necessary

to conclude whether the process is spontaneous or not.

Figures 4.29 to 4.33 show the thermodynamic linear plots of �� versus 1 �� . The values of the

thermodynamic parameters of AC, FE and ANC were calculated and presented in Tables 4.11 to

4.15. The values of the Gibbs free energy change of adsorption (∆��) are all negative and

decreases as the temperature increases. According to Puah, C. W. et. al. (2004)69, a decrease in the

negative value of ∆�� with an increase in temperature indicates that the adsorption process is more

favourable at higher temperatures. This is possible because the mobility of adsorbate

ions/molecules in the solution increases with increase in temperature, and the affinity of the

adsorbate on the adsorbent is high at higher temperatures. This can be seen in the effect of

temperature on the adsorption efficiencies of the adsorbents (figures 4.3). As the temperature of

the reaction was increased, the adsorption of colour pigments onto the adsorbent also increased.

The values of the enthalpy (∆��) and entropy (∆��) calculated from the plot of �� versus 1��

are presented in Tables 4.11 to 4.15. The values for the change in enthalpy are negative and this

implies that the adsorption process of colour pigments from palm oil onto locally activated clay is

exothermic. In an exothermic process, the total energy absorbed in bond breaking is less than the

total energy released in bond making between adsorbate and adsorbent thereby resulting in the

release of extra energy in the form of heat. The magnitude of ∆�� gives an idea about the type of

sorption. The heat evolved during physical adsorption falls in the range of 2.1–20.9 KJ/mol while

that evolved during chemical sorption is in the range of 40 to 400 KJ/mol. As can be seen from

thermodynamic parameters, therefore, in Tables 4.11 to 4.15, it can be deduced that the adsorption

92

of colour pigments onto acid activated Nteje clay can be attributed to a physico-chemical

adsorption process rather than a pure physical or chemical adsorption process69. The entropy (∆��)

calculated and presented in Tables 4.11 to 4.15 is positive and this reflects the affinity of the

adsorbent towards the adsorbate species. A positive value of ∆�� suggests increased randomness at

the solid/solution interface with some structural changes in the adsorbate and adsorbent. The

adsorbed solvent molecules which are displaced by the adsorbate species gain more translational

entropy than is lost by the adsorbate ions/molecules, thus allowing for the prevalence of

randomness in the system. The same result was also reported by (R. O. Ajemba et. al. 2012)3.

Figure 4.29: Plot of �� Versus � �� for AC, FE and ANC at 10 min

y = -2207.x + 4.922R² = 0.921

y = -1695.x + 3.687R² = 0.896

y = -1453.x + 3.095R² = 0.918

-2

-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

00 0.001 0.002 0.003 0.004

ln K

f

1/T

AC

FE

ANC

93

Figure 4.30: Plot of �� Versus � �� for AC, FE and ANC at 20 Min


y = -2342.x + 5.719R² = 0.963

y = -1879.x + 4.560R² = 0.961

y = -1545x + 3.737R² = 0.996

-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0 0.001 0.002 0.003 0.004

ln K

f

1/T

AC

FE

ANC

y = -3230x + 9.229R² = 0.850

y = -2945.x + 8.491R² = 0.869

y = -3114.x + 8.926R² = 0.895

-1

-0.5

0

0.5

1

1.5

2

0 0.001 0.002 0.003 0.004

ln K

f

1/T

AC

FE

ANC

94



Table 4.16: Thermodynamic Parameters Evaluated for AC, FE and ANC at 10 Mins. AC FE ANC

y = -2981.x + 8.612R² = 0.817

y = -2480.x + 7.424R² = 0.749

y = -3026.x + 8.740R² = 0.840

-1

-0.5

0

0.5

1

1.5

2

0 0.001 0.002 0.003 0.004

ln K

f

1/T

AC

FE

ANC

y = -2631.x + 7.825R² = 0.819

y = -2993.x + 8.756R² = 0.850

y = -2928.x + 8.582R² = 0.800

-1

-0.5

0

0.5

1

1.5

2

0 0.001 0.002 0.003 0.004

ln K

f

1/T

AC

FE

ANC

95

T(K) ∆G0 ∆S0 ∆H0 R2 T(K) ∆G0 ∆S0 ∆H0 R2 T(K) ∆G0 ∆S0 ∆H0 R2

333 -22.37 0.59

-26.55

0.92

333 -16.79 0.44

-20.39

0.896

333 -14.14 0.37

-17.48

0.918

353 -23.55 353 -17.68 353 -14.88 373 -24.74 373 -18.56 373 -15.62 393 -25.92 393 -19.45 393 -16.38 413 -27.10 413 -20.33 413 -17.11 Table 4.17: Thermodynamic Parameters Evaluated for AC, FE and ANC at 20 Mins.

AC FE ANC


333 -25.72 0.69

-28.17

0.963

333 -20.51 0.55

-22.60

0.961

333 -16.81 0.45

-18.58

0.996

353 -27.16 353 -21.60 353 -17.71 373 -28.48 373 -22.70 373 -18.06 393 -29.86 393 -23.79 393 -19.50 413 -31.23 413 -24.89 413 -20.40 Table 4.18: Thermodynamic Parameters Evaluated for AC, FE and ANC at 30 Mins.

AC FE ANC


333 -40.85

1.11

-38.85

0.850

333 -37.24

0.55

-22.60

0.961

333 -16.81

1.074

-37.45

0.895

353 -43.07 353 -39.58 353 -17.71 373 -45.29 373 -41.63 373 -18.06 393 -47.51 393 -43.67 393 -19.50 413 -52.43 413 -45.71 413 -20.40 Table 4.19: Thermodynamic Parameters Evaluated for AC, FE and ANC at 40 Mins

AC FE ANC T(K) ∆G0 ∆S0 ∆H0 R2 T(K) ∆G0 ∆S0 ∆H0 R2 T(K) ∆G0 ∆S0 ∆H0 R2

333 -38.08 1.04

-35.86

0.817

333 -32.72 0.89

-29.83

0.749

333 -38.64 1.05

-36.39

0.840

353 -40.16 353 -34.51 353 -40.73 373 -42.23 373 -36.19 373 -42.84 393 -44.30 393 -38.08 393 -45.24 413 -46.37 413 -39.86 413 -47.05 Table 4.20: Thermodynamic Parameters Evaluated for AC, FE and ANC at 50 Mins

AC FE ANC T(K) ∆G0 ∆S0 ∆H0 R2 T(K) ∆G0 ∆S0 ∆H0 R2 T(K) ∆G0 ∆S0 ∆H0 R2

333 -34.50 0.94

-31.65

0.819

333 -38.66 1.05

-35.99

0.850

333 -37.89 1.032

-35.22

0.800

353 -36.38 353 -40.77 353 -39.95 373 -38.26 373 -42.88 373 -42.06 393 -40.15 393 -44.98 393 -44.08 413 -42.03 413 -47.09 413 -46.14

96

97

CHAPTER FIVE

CONCLUSIONS, RECOMMENDATIONS AND CONTRIBUTIONS TO KNOWLEDGE

5.1 Conclusion

The comparative analysis of the bleaching efficiency of activated Nteje clay with the imported,

commercially available adsorbents (activated carbon and fuller’s earth) has been successfully

investigated, and the following conclusions are made:

(1) Like other earth-mined adsorbents, activated Nteje clay retain its specific mineral

composition having hydrous aluminium silicate as its base which must be common in all

the earth adsorbents.

(2) The bleaching (adsorption) efficiency of this activated Nteje clay effectively competes

favourably with the imported, commercially available adsorbents (activated carbon and

fuller’s earth). Like the later, activated Nteje clay bleaches at similar conditions and

produce equal results and responses.

(3) The Nteje clay was kinetically best described by the elovich model with linear

regression coefficient (R2) value of 0.985 which is as good as activated carbon and fuller’s

earth which both followed power function equation with (R2) values of 0.987 and 0.990,

respectively.

(4) Like the standard adsorbents, activated Nteje clay was best described by the Langmuir

isotherm with (R2) value of 0.999 well competing with the activated carbon and fuller’s

earth having 0.982 and 0.999, respectively.

98

(5) Thermodynamics of this clay (activated Nteje clay) shows similar trend with the

commercially available adsorbents, which includes negative free energy change (∆G),

negative enthalpy change (∆H) and positive entropy change (∆S), thereby implying that

adsorption was feasible at all temperatures.

5.2 Recommendation

The effects of the various activating methods of Nteje clay should be advanced into the concept of

defect chemistry, to understand the kind of defect caused by the various activating agents/methods

on the crystalline structure of the clay and applying the Gibbs-Duhem equation in studying the

thermodynamics of the various defects.

5.3 Contribution to knowledge

The bleaching potential of Nteje clay has long been established, but contrary to its resourcefulness,

lacks patronage. This could be traced to doubts arising from its competitative efficiency to the

commercially, imported, available adsorbents.

This work has therefore established that Nteje clay, naturally occurring in nature equally produce

results and responses comparable to the imported, commercially available adsorbents. The

conviction of this work will therefore furnish industries and research institutions with the trust for

the industrial and scientific application of Nteje clay.

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99

2 J. T. Nwabanne and F. C. Ekwu (2013) - Decolourisation of palm oil by Nigerian local clay: A study of adsorption isotherms and bleaching isotherms. International Journal of multidisciplinary Sciences and Engineering, Vol. 4, No. 1, January 2013

3 R. O. Ajemba and Okechukwu D. Onukwuli (2012) – Adsorptive removal of colour pigments from palm oil using acid activated Nteje clay. Kinetics, Equilibrium and Thermodynamics. Physicochem. Probl. Miner. Process 49(1), 2013, 369-381

4 Sleppy, W. C., (2002) - Aluminum compounds- introduction. Kirk-Othmer Encyclopedia of Chemical Technology (online).

5 Chambers, G. P. C., (1959) - Some industrial applications of the clay mineral, sepiolite. Silicates Inds. 24, 3 – 11.

6 Amira International limited, (2001) - Alumina technology roadmap.

http://www.amira.com.au/documents/alumina/index. 7 International Aluminum Institute, (2003) - Statistics, alumina production.

http://www.world-aluminium.org/iai/stats. 8 Zvanut F. J., (1937) - X-ray investigation of the pyro-chemical changes in Missouri halloysite.

J. Am. Ceram. Soc. 20, 251 – 256. 9 Dai J. C., Huang J. T., (1991) - Surface modification of clays and clay-rubber composite.

Applied Clay Science, 15, 51 – 65. 10 An J. H., Dultz S., (2007) - Adsorption of tannic acid on chitosan-montmorillonite as a

function of pH and surface charge properties. Applied Clay Science, 36, 256 – 264. 11 Steudel A., Batenburg L. F., Fischer H. R., Weidler P. G., Emmerich K., (2009) -

Alteration of swelling clay minerals by acid activation. Applied Clay Science, 44, 105 –115.

12 Jiuhui Q. U., (2008). Research progress of novel adsorption processes in water purification.

A review. J. Environ. Sci. 20, 1 – 13. 13 Christidis G. E., Scott P. W., Dunham A. C., (1997) - Acid activation and bleaching

capacity of bentonites from the islands of Milos and Chios, Aegean and Greece. Applied Clay Science, 12, 329 – 347.

14 Al-Asheh S., Banat F., Abu-Aitah L., (2003) - Adsorption of phenol using different typesN

of activated bentonites. Separation Purification Technology, 33, 1 – 10. 15 He H., Frost R. F., Bostrom T., Yuan P., Duong L., Yang D., Xi Y., Kloprogge T., (2006) -

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104

APPENDIX A

TABLE OF VALUES FOR THE AMOUNT OF PIGMENT ADSORBED (PERCENTRAGE BLEACHING) AND ISOTHERM PARAMETERS AT VARIOUS

CONSTANT TEMPERATURES

TABLES A1: Values for the Plot of Percentage Bleaching Versus Time, Log � �⁄ Versus Log(��) for Freundlich Isotherm, and ��

� �⁄ Versus �� for Langmuir Isotherm at 60

oC.

A. C.

S/N Time Absorbance Amount Adsorbed(X)

% Bleaching

x/m logx/m xe (1 – x)

log(xe) xe/x/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.851 0.148 14.815 0.007 -2.131 0.852 -0.069 115.135 2 20 0.799 0.200 20.021 0.010 -2.000 0.800 -0.097 80.000 3 30 0.685 0.314 31.411 0.016 -1.796 0.686 -0.164 42.875 4 40 0.641 0.358 35.836 0.018 -1.745 0.642 -0.192 35.667 5 50 0.616 0.383 38.338 0.019 -1.721 0.617 -0.209 32.474

F. E.


% Bleaching

X/m LogX/m Xe (1 – x)

LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.824 0.175 17.581 0.009 -2.058 0.825 -0.084 94.286 2 20 0.702 0.297 29.730 0.015 -1.824 0.703 -0.153 46.867 3 30 0.694 0.305 30.531 0.015 -1.824 0.695 -0.158 46.333 4 40 0.655 0.344 34.434 0.017 -1.769 0.656 -0.183 38.588 5 50 0.599 0.400 40.041 0.020 -1.699 0.600 -0.222 30.000

A. N. C.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.799 0.200 20.021 0.010 -2.000 0.800 -0.097 80.000 2 20 0.700 0.299 29.930 0.015 -1.824 0.701 -0.152 46.733 3 30 0.675 0.324 32.432 0.016 -1.769 0.676 -0.170 42.250 4 40 0.638 0.361 36.136 0.018 -1.745 0.639 -0.194 35.500

105

5 50 0.610 0.389 38.939 0.019 -1.721 0.611 -0.214 32.158


� �⁄ Versus �� for Langmuir Isotherm at 80

oC

A. C.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.799 0.200 20.021 0.010 -2.000 0.800 -0.097 80.000 2 20 0.697 0.302 30.231 0.015 -1.824 0.698 -0.156 46.533 3 30 0.618 0.381 38.138 0.019 -1.721 0.619 -0.208 32.579 4 40 0.511 0.488 48.849 0.024 -1.619 0.512 -0.291 21.333 5 50 0.509 0.490 49.049 0.025 -1.602 0.510 -0.292 20.400

F. E.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.759 0.240 24.024 0.012 -1.921 0.760 -0.119 58.333 2 20 0.665 0.334 33.433 0.017 -1.769 0.666 -0.177 39.176 3 30 0.598 0.401 40.141 0.020 -1.699 0.599 -0.223 29.950 4 40 0.520 0.479 47.948 0.024 -1.619 0.521 -0.283 21.708 5 50 0.513 0.486 48.649 0.024 -1.619 0.514 -0.289 21.417

A. N. C.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.711 0.288 28.829 0.014 -1.854 0.712 -0.148 50.857 2 20 0.647 0.352 35.235 0.018 -1.745 0.648 -0.188 36.000 3 30 0.601 0.398 39.840 0.019 -1.721 0.602 -0.220 31.684 4 40 0.524 0.475 47.548 0.024 -1.619 0.525 -0.279 21.875 5 50 0.499 0.500 50.051 0.025 -1.602 0.500 -0.301 20.000

106


� �⁄ Versus �� for Langmuir Isotherm at 100 oC

A. C.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.654 0.345 34.535 0.017 -1.769 0.655 -0.184 38.529 2 20 0.490 0.509 50.951 0.025 -1.602 0.491 -0.309 19.640 3 30 0.255 0.744 74.474 0.037 -1.432 0.256 -0.592 6.919 4 40 0.239 0.760 76.076 0.038 -1.420 0.240 -0.619 6.316 5 50 0.229 0.777 77.077 0.039 -1.409 0.223 -0.652 5.718

F. E.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.599 0.400 40.041 0.020 -1.699 0.600 -0.222 30.000 2 20 0.502 0.497 49.750 0.025 -1.602 0.503 -0.298 20.120 3 30 0.272 0.727 72.773 0.036 -1.440 0.273 -0.564 7.583 4 40 0.234 0.765 76.577 0.038 -1.420 0.235 -0.629 6.184 5 50 0.223 0.776 77.678 0.039 -1.409 0.224 -0.649 5.744

A. N. C.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.621 0.378 37.838 0.019 -1.721 0.622 -0.206 32.737 2 20 0.498 0.501 50.151 0.025 -1.602 0.499 -0.302 19.960 3 30 0.277 0.722 72.272 0.036 -1.444 0.278 -0.556 7.722 4 40 0.244 0.755 75.576 0.038 -1.420 0.245 -0.611 6.447 5 50 0.211 0.788 78.879 0.039 -1.409 0.212 -0.674 5.436

107



A. C.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.611 0.388 38.839 0.019 -1.721 0.612 -0.213 32.211 2 20 0.495 0.504 50.451 0.025 -1.602 0.496 -0.305 19.840 3 30 0.241 0.758 75.876 0.038 -1.420 0.242 -0.616 6.368 4 40 0.239 0.760 76.076 0.038 -1.420 0.240 -0.619 6.316 5 50 0.221 0.778 77.878 0.039 -1.409 0.222 -0.654 5.692

F. E.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.600 0.399 39.940 0.019 -1.721 0.601 -0.221 31.632 2 20 0.500 0.499 49.950 0.025 -1.602 0.501 -0.300 20.040 3 30 0.299 0.700 70.071 0.035 -1.456 0.300 -0.523 8.571 4 40 0.243 0.756 75.676 0.038 -1.420 0.244 -0.613 6.421 5 50 0.211 0.788 78.879 0.039 -1.409 0.212 -0.674 5.436

A. N. C.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.600 0.399 39.940 0.019 -1.721 0.601 -0.221 31.632 2 20 0.505 0.494 49.449 0.024 -1.619 0.506 -0.296 21.083 3 30 0.250 0.749 74.975 0.037 -1.432 0.251 -0.600 6.784 4 40 0.231 0.768 76.877 0.038 -1.420 0.232 -0.635 6.105 5 50 0.214 0.785 78.579 0.039 -1.409 0.215 -0.668 5.513

108



A. C.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.559 0.440 44.044 0.022 -1.658 0.560 -0.252 25.455 2 20 0.416 0.583 58.358 0.029 -1.538 0.417 -0.379 14.379 3 30 0.226 0.773 77.377 0.039 -1.409 0.227 -0.644 5.821 4 40 0.220 0.779 77.978 0.039 -1.409 0.221 -0.656 5.667 5 50 0.215 0.784 78.478 0.039 -1.409 0.216 -0.666 5.538

F. E.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.600 0.399 39.940 0.019 -1.721 0.601 -0.221 31.632 2 20 0.432 0.567 56.757 0.028 -1.553 0.433 -0.364 15.464 3 30 0.235 0.764 76.476 0.038 -1.420 0.236 -0.627 6.211 4 40 0.211 0.788 78.879 0.039 -1.409 0.212 -0.674 5.436 5 50 0.209 0.790 79.079 0.039 -1.409 0.210 -0.678 5.385

A. N. C.


% Bleaching


LogXe Xe/X/m

0 0 0.999 0 0 0 0 0 0 0 1 10 0.571 0.428 42.843 0.021 -1.678 0.572 -0.243 27.238 2 20 0.481 0.518 51.852 0.026 -1.585 0.482 -0.317 18.538 3 30 0.222 0.777 77.778 0.039 -1.409 0.223 -0.652 5.718 4 40 0.210 0.789 78.979 0.039 -1.409 0.211 -0.676 5.410 5 50 0.209 0.790 79.079 0.039 -1.409 0.210 -0.678 5.385

109

APPENDIX B

TABLE OF VALUES FOR THE ADSORPTION THERMODYNAMIC PLOT AT CONSTANT TIME

TABLES B1: Values for the Plot of �� Versus 1 �� at 10 min

A.C

S/N Tempt (K) Tempt (K-

1) lnKf = ln(X/Xe)

1 333 0.0030 -1.749 2 353 0.0028 -1.386 3 373 0.0027 -0.781 4 393 0.0025 -0.583 5 413 0.0024 -0.476

F.E


1) lnKf = ln(X/Xe)

1 333 0.0030 -1.551 2 353 0.0028 -0.863 3 373 0.0027 -0.823 4 393 0.0025 -0.646 5 413 0.0024 -0.405

A.N.C


1) lnKf = ln(X/Xe)

1 333 0.0030 -1.386 2 353 0.0028 -0.851 3 373 0.0027 -0.736 4 393 0.0025 -0.571 5 413 0.0024 -0.451

110

TABLES B2: Values for the Plot of �� Versus 1 �� at 20 mins

A.C


1) lnKf = ln(X/Xe)

1 333 0.0030 -1.386 2 353 0.0028 -0.837 3 373 0.0027 -0.485 4 393 0.0025 -0.048 5 413 0.0024 -0.039

F.E


1) lnKf = ln(X/Xe)

1 333 0.0030 -1.152 2 353 0.0028 -0.689 3 373 0.0027 -0.402 4 393 0.0025 -0.084 5 413 0.0024 -0.056 A.N.C


1) lnKf = ln(X/Xe)

1 333 0.0030 -0.906 2 353 0.0028 -0.599 3 373 0.0027 -0.414 4 393 0.0025 -0.099 5 413 0.0024 0


A.C


1) lnKf = ln(X/Xe)

1 333 0.0030 -0.641 2 353 0.0028 0.036 3 373 0.0027 1.067 4 393 0.0025 1.153 5 413 0.0024 1.248

111

F.E


1) lnKf = ln(X/Xe)

1 333 0.0030 -0.405 2 353 0.0028 -0.012 3 373 0.0027 0.979 4 393 0.0025 1.180 5 413 0.0024 1.242

A.N.C


1) lnKf = ln(X/Xe)

1 333 0.0030 -0.498 2 353 0.0028 0.004 3 373 0.0027 0.954 4 393 0.0025 1.126 5 413 0.0024 1.313


A.C


1) lnKf ln(X/Xe)

1 333 0.0030 -0.456 2 353 0.0028 0.016 3 373 0.0027 1.142 4 393 0.0025 1.153 5 413 0.0024 1.254

F.E


1) lnKf = ln(X/Xe)

1 333 0.0030 -0.409 2 353 0.0028 0.996 3 373 0.0027 0.847 4 393 0.0025 1.131 5 413 0.0024 1.313

112

A.N.C


1) lnKf = ln(X/Xe)

1 333 0.0030 -0.409 2 353 0.0028 -0.024 3 373 0.0027 1.093 4 393 0.0025 1.197 5 413 0.0024 1.295


A.C


1) lnKf = ln(X/Xe)

1 333 0.0030 -0.241 2 353 0.0028 0.335 3 373 0.0027 1.225 4 393 0.0025 1.259 5 413 0.0024 1.289

F.E


1) lnKf = ln(X/Xe)

1 333 0.0030 -0.409 2 353 0.0028 0.269 3 373 0.0027 1.175 4 393 0.0025 1.313 5 413 0.0024 1.325

A.N.C


1) lnKf = ln(X/Xe)

1 333 0.0030 -0.290 2 353 0.0028 0.072 3 373 0.0027 1.248 4 393 0.0025 1.319 5 413 0.0024 1.325

113

APPENDIX C

TABLE OF VALUES FOR THE ADSORPTION KINETIC PLOTS AT CONSTANT TEMPERATURES

KINETIC PARAMETERS

TABLES C1: Values for the Plots of 1 �� Versus �(�) for Pseudo-second Order, �� Versus Ln � for Elovich Model and Log � Versus Log � for Power Function Equation at 60 oC

AC

S/N Time (s) log t ln t qt 1/qt log qt 1 10 1 2.30 0.148 6.757 -0.829 2 20 1.30 2.99 0.200 0.5 -0.699 3 30 1.48 3.40 0.314 3.184 -0.503 4 40 1.60 3.69 0.358 2.793 -0.446 5 50 1.69 3.91 0.383 2.611 -0.417

FE


ANC


114

TABLES C2: Values for the Plots of 1 �� Versus �(�) for Pseudo-second Order, �� Versus Ln � for Elovich model and Log � Versus Log � for Power Function Equation at 80 oC

AC


FE


ANC


TABLES C3: Values for the Plots of 1 �� Versus �(�) for Pseudo-second Order, �� Versus Ln � for Elovich Model and Log � Versus Log � for Power Function Equation at 100 oC

AC


115

FE


ANC

S/N Time (s) log t ln t qt 1/qt log qt 1 10 1 2.30 0.378 2.646 -0.423 2 20 1.30 2.99 0.501 1.996 -0.300 3 30 1.48 3.40 0.722 1.385 -0. 141 4 40 1.60 3.69 0.755 1.326 -0.122 5 50 1.69 3.91 0.788 1.269 -0.103

TABLES C4: Values for the Plots of 1 �� Versus � (�) for Pseudo-second Order, �� Versus Ln � for Elovich Model and Log � Versus Log � for Power Function Equation at 120 oC

AC


FE


116

ANC


TABLES C5: Values for the Plots of 1 �� Versus � (�) for Pseudo-second Order, ��Versus Ln � for Elovich Model and Log � Versus Log � for Power Function Equation at 140 oC

AC


FE


ANC


117

APPENDIX D DETAILED X-RAY DIFFRACTION ANALYSIS (XRD) RESULT

Appendix D 1

Name and Formula Reference code: 00-058-2002 Mineral name: Dickite-2M1 PDF index name: Aluminum Silicate Hydroxide Empirical formula: Al2H4O9Si2 Chemical formula: Al2Si2O5 ( OH )4 Crystallographic Parameters Crystal system: Monoclinic Space group: Cc Space group number: 9 a (Å): 5.1477 b (Å): 8.9396 c (Å): 14.4164 Alpha (°): 90.0000 Beta (°): 96.7182 Gamma (°): 90.0000 Measured density (g/cm^3): 2.58 Volume of cell (10^6 pm^3): 658.86 Z: 4.00 RIR: - Subfiles and Quality Subfiles: Inorganic Mineral Common Phase Forensic Pharmaceutical Excipient Quality: Indexed (I) Comments

118

General comments: Data collected using a 0.02° step scan with a count time of 0.5

seconds. Sample source: Sample from Thomaston section of Pinecolliery, Schulykill Co.,

Pennsylvania, USA. Sample preparation: The sample was settled in water for 4 hours to obtain <2

micrometer particles. Specimen was an oriented preparation on a glass slide.

Unit cell: Cell and hkl values were assigned using data from PDF 00-058-2003. Unit cell refinement was not possible because too few peaks were identified.

Temperature: Pattern taken at 298 K. References Primary reference: Smith, D., Pennsylvania State Univ., University Park, PA, USA.,

Private Communication, (1983) Peak List No. h k l d [A] 2Theta[deg] I [%] 1 0 0 2 7.16160 12.349 100.0 2 1 1 0 4.45970 19.893 0.4 3 0 0 4 3.58310 24.829 78.3 4 0 0 6 2.38820 37.634 11.1 Stick Pattern

119

APPENDIX D 2 Name and Formula Reference code: 00-021-0958 Mineral name: Palygorskite PDF index name: Magnesium Aluminum Silicate Hydroxide Hydrate Empirical formula: H18Mg5O30Si8 Chemical formula: ( Mg , Al )5 ( Si , Al )8O20 ( OH )2 ·8H2O Crystallographic Parameters Crystal system: Monoclinic Space group: Pn Space group number: 7 a (Å): 12.7800 b (Å): 17.8300 c (Å): 5.2400 Alpha (°): 90.0000 Beta (°): 95.7700

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Gamma (°): 90.0000 Calculated density (g/cm^3): 2.40 Volume of cell (10^6 pm^3): 1187.98 Z: 2.00 RIR: - Subfiles and Quality Subfiles: Inorganic Mineral Common Phase Quality: Star (S) Comments Color: White, grayish white. Optical Data Specimen location: Optical data

on specimen from Noss Hill, South Mainland, Shetland Isles, Scotland, UK.

Sample source: Specimen from Metaline, Washington, USA. Additional pattern: To replace 00-005-0099. Unit cell data source: Powder Diffraction. References Primary reference: Christ, C., Hathaway,J., Hostetler, P., Shepard, A., Am. Mineral.,

54, 198, (1969) Optical data: Stephen, I., Mineral. Mag., 30, 471, (1954) Peak List No. h k l d [A] 2Theta[deg] I [%] 1 1 1 0 10.40000 8.495 100.0 2 2 0 0 6.36000 13.913 20.0 3 1 3 0 5.38000 16.464 16.0 4 0 4 0 4.46000 19.891 20.0 5 -1 2 1 4.36000 20.352 4.0 6 1 2 1 4.14000 21.446 18.0 7 2 4 0 3.65000 24.367 10.0 8 1 5 0 3.44000 25.879 4.0 9 2 3 1 3.23000 27.594 14.0 10 4 0 0 3.18000 28.037 18.0 11 0 0 2 2.60900 34.345 6.0 12 4 4 0 2.58500 34.674 10.0

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13 -1 6 1 2.55500 35.094 10.0 14 1 6 1 2.50600 35.803 12.0 Stick Pattern

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APPENDIX D 3 Name and Formula Reference code: 00-001-0527 Mineral name: Kaolinite PDF index name: Aluminum Silicate Hydrate Empirical formula: Al2H4O9Si2 Chemical formula: Al2Si2O5 ( OH )4 Crystallographic Parameters Crystal system: Anorthic a (Å): 5.1400 b (Å): 8.9300 c (Å): 7.3700 Alpha (°): 91.8000 Beta (°): 104.5000 Gamma (°): 90.0000 Measured density (g/cm^3): 2.58 Volume of cell (10^6 pm^3): 327.34 RIR: - Status, Subfiles and Quality Status: Marked as deleted by ICDD Subfiles: Inorganic Mineral Pharmaceutical Excipient Quality: Indexed (I) Comments Deleted by: Deleted by 00-005-0143, replaced by 00-014-0164, 00-012-0447. Color: Colorless. Additional pattern: See PDF 00-006-0221. References

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Primary reference: Hanawalt. et al., Anal. Chem., 10, 475, (1938) Optical data: Ross, Kerr., U.S. Geol. Surv. Prof. Paper, 165, (1930) Unit cell: Brindley, Robinson., Mineral. Mag., 27, 42, (1946) Peak List No. h k l d [A] 2Theta[deg] I [%] 1 0 0 1 7.20000 12.283 80.0 2 0 2 0 4.45000 19.936 80.0 3 1 1 0 4.30000 20.639 64.0 4 -1 -1 1 4.20000 21.136 48.0 5 -1 1 1 4.04000 21.984 32.0 6 0 0 2 3.59000 24.780 100.0 7 1 -3 0 2.56000 35.023 48.0 8 -1 3 1 2.50000 35.892 48.0 9 1 -3 1 2.34000 38.439 80.0 10 1 -3 2 1.99000 45.547 32.0 11 2 3 0 1.90000 47.835 8.0 12 -2 -3 2 1.85000 49.212 8.0 13 -2 2 3 1.80000 50.674 8.0 14 1 4 2 1.67000 54.937 40.0 15 -1 3 4 1.54000 60.026 16.0 16 1 -5 2 1.49000 62.260 56.0 17 3 2 2 1.31000 72.033 8.0 18 1 0 5 1.29000 73.330 16.0 19 2 -6 1 1.24000 76.809 16.0 Stick Pattern

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APPENDIX D 4 Name and Formula Reference code: 00-013-0259 Mineral name: Montmorillonite-14A PDF index name: Sodium Magnesium Aluminum Silicate Hydroxide Hydrate Empirical formula: Al2H4Na0.3O13Si4 Chemical formula: Na0.3 ( Al , Mg )2Si4O10 ( OH )2 ·xH2O Crystallographic Parameters Crystal system: Unknown Measured density (g/cm^3): 2.50 RIR: - Subfiles and Quality Subfiles: Inorganic Mineral Common Phase Educational pattern Forensic Quality: Doubtful (O) Comments Color: White, yellow, green. Sample source: Specimen from Polkville mine, Polkville, Mississippi, USA. Analysis: Chemical analysis (wt.%): ''Si O2'' 50.95, ''Al2 O3'' 16.54, ''Fe2 O3''

1.36, FeO 0.26, MgO 4.65, CaO 2.26, ''Na2 O'' 0.17, ''K2 O'' 0.47, ''H2 O'' 23.29.

CAS Number: 1318-93-0. Unit cell data source: Powder Diffraction. Reason "O" quality: O assigned because unindexed. References Primary reference: Molloy, Kerr., Am. Mineral., 46, 583, (1961)

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Peak List No. h k l d [A] 2Theta[deg] I [%] 1 13.60000 6.494 100.0 2 4.47000 19.846 18.0 3 3.34000 26.668 10.0 4 3.23000 27.594 10.0 5 2.92000 30.591 8.0 6 2.59000 34.605 5.0 7 2.49000 36.041 5.0 Stick Pattern

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