TABLE OF CONTENT
Title Page
Abstract
Table of content
List of Abbreviations
CHAPTER ONE: INTRODUCTION
1.1 Preamble
1.2 Statement of Research Problem
1.3 Scope of Research
1.4 Aim and Objectives
1.5 Justification of Research
CHAPTER TWO: LITERATURE REVIEW
2.1 Introduction
2.2 Properties of Bentonites
2.2.1 Bentonite synonyms
2.2.2 Bentonite designations
2.2.3 Bentonite description
2.2.4 Typical bentonite chemical properties (wt. %)
2.3 Types of Bentonite
2.3.1 Sodium bentonite
2.3.2 Calcium bentonite
2.3.3 Potassium bentonite
2.4 Applications of Bentonite
2.4.1 Medical
2.4.2 Bentonite slurry walls in modern construction
2.4.3 Foundry
2.4.4 Cat Litter
2.4.5 Pelletizing of iron ore pellets
2.4.6 Construction and civil engineering
2.4.7 Adsorption
2.4.8 Drilling
2.4.9 Agriculture
2.4.10 Pharmaceuticals, Cosmetics and Medical Application
2.4.11 Detergents
2.4.12 Paints, Dyes and Polishes
2.4.13 Paper Productions
2.4.14 Catalysis
2.5 Pindiga Bentonite Clay
2.6 Adsorption
2.6.1 Adsorption applications
2.6.2 Sorption dynamics
2.6.3 Freundlich isotherm
2.6.4 Langmuir isotherm
2.6.5 Equilibrium isotherm studies
2.7 Photocatalysis
2.7.1 Mechanism of Photocatalysis
2.7.2 Application of photocatalysis
2.8 Specific Surface Area of Solids
2.8.1 Brunauer Emmet Teller (BET) surface area measurement
2.8.2 X-Ray Diffraction
2.8.3 Scherrer‟s equation
2.8.4 X-Ray fluorescence spectroscopy
2.9 Langmuir–Hinshelwood Kinetic Model of Photocatalytic Processes
2.10 Related Works
CHAPTER THREE: MATERIALS AND METHODS
3.1 Materials
3.1.1 Chemicals
3.1.2 Apparatus
3.1.3 Equipment
3.2 Methodology
3.2.1 Leaching of Pindiga bentonite clay by oxalic acid solutions
3.2.2 Adsorption experiments
3.2.3 Effect of pH
3.2.4 Effect of initial phenol concentration
3.2.5 Effect of adsorbent dose
3.2.6 Photocatalytic experiments
3.2.7 Determination of specific surface area of the clay
3.2.8 Detailed block diagram of the methodology
CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 Leaching of clay
4.2 Specific Surface Areas and Crystallite Sizes of the Raw and Treated Clays
4.3 Characterization of the Catalysts
4.4 Preliminary Photocatalytic Degradation of Phenol before Adsorption Equilibrium was Established
4.5 Adsorption of Phenol on PB, PBC, PB-5 and PB-60
4.5.1 Adsorption dynamics
4.5.2 Equilibrium Isotherm Studies
4.5.3 Effect of Adsorbent Dosage
4.5.4 Effect of solution pH
4.6 Photocatalytic Degradation of Phenol Using PB, PBC, PB-5 and PB-60
4.6.1 Effect of pH
4.6.2 Effect of catalyst dosage
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions
5.2 Recommendations
REFERENCES
APPENDICES
ABSTRACT
The potential of Pindiga bentonitic clay for phenol adsorption from aqueous solution and photocatalytic degradation was studied. Pindiga bentonic clay was treated with oxalic acid and calcined at a temperature of 1000oC and was successfully used as an adsorbent and for the degradation of phenol under visible light illumination. The processes were investigated by X-Ray Fluorescence (XRF), X-Ray diffraction (XRD), and surface area analysis. The clay treated with acid for 60 min (PB-60) and 5 min (PB-5) gave higher surface areas of 363.61 m2/g and 265.99 m2/g respectively compared with the raw (PB) and the raw calcined (PBC) with surface areas of 151.69 m2/g and 47.13 m2/g respectively. The adsorptions of phenol by the acid treated clays were studied using pseudo-first order, pseudo-second order kinetic models and intra-particle diffusion model. The adsorption data does not fit well with pseudo-second order kinetic model. The Freundlich and Langmuir adsorption models were used for the mathematical description of adsorption equilibrium and it was found that the experimental data fitted very well to the Freundlich model. The clay treated with acid for 60 minutes (PB-60) showed a better monolayer coverage capacity and greater affinity for phenol compared with the PB, PBC and PB-5. The increase in pH values from 5 – 11 was observed to hinder adsorption processes. Better adsorption was observed at lower pH value. Increase in catalyst dosage increases the adsorption rate. Langmuir-Hinshelwood kinetic model was employed for photocatalysis processes and the values of krand KLH were calculated as 6.8483 mgl-1min-1 and 0.0034lmg-1 for PB-60. PB-60 degraded phenol better than PB, PBC and PB-5 under visible light illumination. Catalyst dosages of 1.5, 2.0, 2.5 and 3.0g were used and the optimum catalyst dosage was found to be 2.5g/l for the photocatalytic degradation.
CHAPTER ONE
INTRODUCTION
1.1 Preamble
Bentonite is an absorbent aluminium phyllosilicate, impure clay consisting mostly of montmorillonite. The absorbent clay was given the name bentonite by Wilbur C. Knight in 1898, after the Cretaceous Benton Shale near Rock River, Wyoming (Hosterman and Patterson, 1992).
There are different types of bentonite, each named after the respective dominant element, such as potassium (K), sodium (Na), calcium (Ca), and aluminium (Al). Experts debate a number of nomenclatorial problems with the classification of bentonite clays. Bentonite usually forms from weathering of volcanic ash, most often in the presence of water. However, the term bentonite, as well as similar clay called tonstein, has been used to describe clay beds of uncertain origin. For industrial purposes, two main classes of bentonite exist: sodium and calcium bentonite.
Photocatalysis, one of the advanced physico-chemical technology applicable in photodegradation of organic pollutants, has attracted much attention in recent years. Photocatalysis can generally be described as a process in which light is used to activate a substance.The photocatalyst that aid this process is itself not involved in the chemical transformation. Photocatalytic reactions are classified into homogeneous photocatalysis in which both the photocatalyst and the substrate are of the same phase and the heterogeneous photocatalysis in which both the both the photocatalyst and the substrate are of different phases. Heterogeneous photocatalysis is mainly used in cases where a light-absorbing.....
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