Development of Adsorbents And Photocatalysts using Nigerian Pindiga Bentonitic Clay.
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.
TABLE OF CONTENT
Cover Page ……………………………………………………………………………………………………………………..i
Title Page ……………………………………………………………………………………………………………………….ii
Declaration ……………………………………………………………………………………………………………………. iii
Certification ………………………………………………………………………………………………………………….. iv
Acknowledgement ………………………………………………………………………………………………………….. v
Abstract ………………………………………………………………………………………………………………………… vi
Table of content ……………………………………………………………………………………………………………. vii
List of Figures ………………………………………………………………………………………………………………. xii
List of Tables ………………………………………………………………………………………………………………. xiv
List of Abbreviations …………………………………………………………………………………………………….. xv
CHAPTER ONE: INTRODUCTION
1.1 Preamble …………………………………………………………………………………………………………….. 1
1.2 Statement of Research Problem ……………………………………………………………………………… 3
1.3 Scope of Research ………………………………………………………………………………………………… 3
1.4 Aim and Objectives ……………………………………………………………………………………………… 3
1.5 Justification of Research ……………………………………………………………………………………….. 4
CHAPTER TWO: LITERATURE REVIEW
2.1 Introduction …………………………………………………………………………………………………………. 5
2.2 Properties of Bentonites ………………………………………………………………………………………… 6
2.2.1 Bentonite synonyms ……………………………………………………………………………………………… 6
2.2.2 Bentonite designations ………………………………………………………………………………………….. 6
2.2.3 Bentonite description ……………………………………………………………………………………………. 7
2.2.4 Typical bentonite chemical properties (wt. %) …………………………………………………………. 8
2.3 Types of Bentonite …………………………………………………………………………………………………… 8
2.3.1 Sodium bentonite …………………………………………………………………………………………………. 9
2.3.2 Calcium bentonite ………………………………………………………………………………………………. 10
2.3.3 Potassium bentonite ……………………………………………………………………………………………. 10
2.4 Applications of Bentonite ………………………………………………………………………………………… 10
2.4.1 Medical ………………………………………………………………………………………………………………… 13
2.4.2 Bentonite slurry walls in modern construction ……………………………………………………….. 13
2.4.3 Foundry …………………………………………………………………………………………………………….. 13
2.4.4 Cat Litter …………………………………………………………………………………………………………… 14
2.4.5 Pelletizing of iron ore pellets ……………………………………………………………………………….. 14
2.4.6 Construction and civil engineering ……………………………………………………………………….. 14
2.4.7 Adsorption ………………………………………………………………………………………………………… 15
2.4.8 Drilling ……………………………………………………………………………………………………………… 15
2.4.9 Agriculture ………………………………………………………………………………………………………… 15
2.4.10 Pharmaceuticals, Cosmetics and Medical Application …………………………………………….. 15
2.4.11 Detergents …………………………………………………………………………………………………………. 16
2.4.12 Paints, Dyes and Polishes ……………………………………………………………………………………. 16
2.4.13 Paper Productions ………………………………………………………………………………………………. 16
2.4.14 Catalysis ……………………………………………………………………………………………………………. 17
2.5 Pindiga Bentonite Clay ……………………………………………………………………………………….. …..17
2.6 Adsorption ……………………………………………………………………………………………………………… 18
2.6.1 Adsorption applications ………………………………………………………………………………………… 19
2.6.2 Sorption dynamics ……………………………………………………………………………………………….. 19
2.6.3 Freundlich isotherm …………………………………………………………………………………………….. 20
2.6.4 Langmuir isotherm ……………………………………………………………………………………………….. 21
2.6.5 Equilibrium isotherm studies …………………………………………………………………………………. 22
2.7 Photocatalysis ………………………………………………………………………………………………………….. 23
2.7.1 Mechanism of Photocatalysis ………………………………………………………………………………….. 24
2.7.2 Application of photocatalysis ……………………………………………………………………………………. 25
2.8 Specific Surface Area of Solids ……………………………………………………………………………………. 28
2.8.1 Brunauer Emmet Teller (BET) surface area measurement ………………………………………….. 29
2.8.2 X-Ray Diffraction …………………………………………………………………………………………………… 32
2.8.3 Scherrer‟s equation ……………………………………………………………………………………………….. 32
2.8.4 X-Ray fluorescence spectroscopy ……………………………………………………………………………. 33
2.9 Langmuir–Hinshelwood Kinetic Model of Photocatalytic Processes ………………………… ……34
2.10 Related Works………………………………………………………………………………………………………… 35
CHAPTER THREE: MATERIALS AND METHODS
3.1 Materials ……………………………………………………………………………………………………………37
3.1.1 Chemicals………………………………………………………………………………………………………….37
3.1.2 Apparatus ………………………………………………………………………………………………………..37
3.1.3 Equipment ……………………………………………………………………………………………………….39
3.2 Methodology ……………………………………………………………………………………………………… 39
3.2.1 Leaching of Pindiga bentonite clay by oxalic acid solutions ……………………………………39
3.2.2 Adsorption experiments ……………………………………………………………………………………. 40
3.2.3 Effect of pH ………………………………………………………………………………………………………. 40
3.2.4 Effect of initial phenol concentration …………………………………………………………………….41
3.2.5 Effect of adsorbent dose ……………………………………………………………………………………… 41
3.2.6 Photocatalytic experiments ………………………………………………………………………………….. 41
3.2.7 Determination of specific surface area of the clay ………………………………………………….. 42
3.2.8 Detailed block diagram of the methodology…………………………………………………………… 43
CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 Leaching of clay…………………………………………………………………………………………………. 44
4.2 Specific Surface Areas and Crystallite Sizes of the Raw and Treated Clays ………………. 44
4.3 Characterization of the Catalysts ………………………………………………………………………….. 45
4.4 Preliminary Photocatalytic Degradation of Phenol before Adsorption Equilibrium was Established…….47
4.5 Adsorption of Phenol on PB, PBC, PB-5 and PB-60 ………………………………………………. 48
4.5.1 Adsorption dynamics ………………………………………………………………………………………….51
4.5.2 Equilibrium Isotherm Studies …………………………………………………………………………….60
4.5.3 Effect of Adsorbent Dosage ………………………………………………………………………………..62
4.5.4 Effect of solution pH………………………………………………………………………………………… 63
4.6 Photocatalytic Degradation of Phenol Using PB, PBC, PB-5 and PB-60 …………………… 64
4.6.1 Effect of pH …………………………………………………………………………………………………….. 65
4.6.2 Effect of catalyst dosage ……………………………………………………………………………………..66
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions ……………………………………………………………………………………………………….. 67
5.2 Recommendations ……………………………………………………………………………………………….68
REFERENCES …………………………………………………………………………………………………………. 69
INTRODUCTION
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.
REFERENCES
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