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.
TABLE OF CONTENTS
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
4.7 Adsorption kinetics
4.8 Adsorption isotherm
4.9 Adsorption thermodynamics
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, A
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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