Thesis Abstract

Abstract
Kaolinite is a naturally occurring clay mineral that has been widely used in various applications due to its abundance and low cost. However, pristine kaolinite has limitations in its sorption capacity and selectivity for certain pollutants. In this study, a novel organokaolinite material was synthesized by modifying kaolinite with cetyl trimethyl ammonium bromide (CTAB) to enhance its sorption characteristics. The synthesis process involved the intercalation of CTAB into the kaolinite interlayer spaces through cation exchange reactions. The resulting organokaolinite material exhibited improved hydrophobicity and increased surface area compared to pristine kaolinite. The characterization of the organokaolinite was carried out using techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis. The sorption characteristics of the organokaolinite were evaluated using various pollutants, including organic dyes and heavy metal ions. The results demonstrated that the organokaolinite exhibited enhanced sorption capacity and selectivity towards these pollutants compared to pristine kaolinite. The increased hydrophobicity of the organokaolinite played a significant role in improving the sorption efficiency for organic pollutants, while the increased surface area facilitated the sorption of heavy metal ions. Furthermore, the regeneration studies indicated that the organokaolinite material could be effectively regenerated and reused multiple times without significant loss in sorption capacity. The stability and reusability of the organokaolinite make it a promising candidate for environmental remediation applications. Overall, the synthesis of the novel organokaolinite material through the modification of kaolinite with CTAB represents a significant advancement in the field of sorbent materials. The enhanced sorption characteristics, stability, and reusability of the organokaolinite make it a potential candidate for various environmental remediation applications, including wastewater treatment and pollution control. Further research can focus on optimizing the synthesis parameters to tailor the properties of the organokaolinite for specific pollutant removal applications.

Thesis Overview

INTRODUCTION AND LITERATURE REVIEW

1.0     General Introduction

            Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried or fired. Clay deposits are mostly composed of clay minerals (phyllosilicate minerals) and variable amounts of water trapped in the mineral structure by polar attraction. Organic materials which do not impart plasticity may also be a part of clay deposits.   Clay is a widely distributed, abundant mineral resource of major industrial importance for an enormous variety of uses (Ampian, 1985). In both value and amount of annual production, it is one of the leading minerals worldwide. In common with many geological terms, the term “clay” is ambiguous and has multiple meanings: a group of fine-grained minerals which show plasticity through a variable range of water content, and which can be hardened when dried or fired i.e., the clay minerals; a particle size (smaller than silt); and a type of rock i.e., a sedimentary deposit of fine-grained material usually composed largely of clay minerals (Patterson & Murray, 1983; Bates & Jackson, 1987). Clays find wide range of applications, in various areas of science, due to their natural abundance and the propensity with which they can be chemically and physically modified to suit practical technological needs (Xi et al., 2005).

Clays are distinguished from other fine-grained soils by various differences in composition. Silts, which are fine grained soils which do not include clay minerals tend to have large particle sizes than clays but there is some overlap in both particle size and other physical properties, and there are many naturally occurring deposits which include both silts and clays. The distinction between silts and clay varies by discipline.Geologists and soil scientists usually consider the separation to occur at a particle size of 2µm (clays being finer than silts), sedimentologists often use 4-5µm, and colloid chemists use 1um. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, ISO 14688 grades; clay particles as being smaller than 0.063mm and silts one larger.

There are three or four main groups of clays; kaolinite, montmorillonite-smecite, illite and chlorite. Chlorites are not always considered clay, sometimes being classified as a separate group within the phyllosilicates. There are approximately thirty different types of “pure” clays in these categories but most “natural” clays are mixtures of these different types along with other weathered minerals (Lagaly, 1984).

1.1                    Clay Minerals

Clay minerals likely are the most utilized minerals not just as the soils that grow plants for foods and garment, but a great range of applications, including oil absorbants, iron casting, animal feeds, pottery, china, pharmaceuticals, drilling fluids, waste water treatment, food preparation, paint e.t.c.

Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations. Clays form flat hexagonal sheets similar to the micas. Clay minerals are common weathering products (including weathering of feldspar) and low temperature hydrothermal alteration products. Clay minerals are very common in fine grained sedimentary rocks such as shale, mudstone, and siltstone and in fine grained metamorphic slate and phyllite. Clay minerals are usually (but not necessarily) ultrafine-grained (normally considered to be less than 2µm in size on standard particle size classifications) and so may require special analytical techniques for their identification/study. These include x-ray diffraction, electron diffraction methods, various spectroscopic methods such as Mössbauer spectroscopy, infrared spectroscopy, and SEM-EDX or automated mineralogy solutions. These methods can be enlarged by polarized light microscopy, a traditional technique establishing fundamental occurrences or petrologic relationships.

Clay minerals can be classified as 1:1 or 2:1clays; this originates from the fact that they are fundamentally built of tetrahedral silicate sheets and octahedral hydroxide sheets, as described in Figure 1 below. A 1:1 clay would consist of one tetrahedral sheet and one octahedral sheet, for example, kaolinite and serpentine. A2:1 clay consists of an octahedral sheet sandwiched between two tetrahedral sheets, for example, talc, vermiculite and montmorillonite.

Clay minerals include the following groups:

Other 2:1 clay types exist such as sepiolite or attapulgite, which areclays with long water channels internal to their structure.

Typically, the structural formula for kaolinite is Al4Si4O10(OH)8 and the theoretical chemical composition given in Table 1.