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

1.2       Research objectives and scope

1.3       Significant of study

CHAPTER TWO:                LITERATURE REVIEW

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

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

• Modification of clay by chemical activation

3.2       Physical and chemical characterization of Nteje clay

3.2.1    Surface area measurement

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

• 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

 

 

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. 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
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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