Mineral Composition Of Soil In Ado Ekiti Metropolis
Abstract
Mineralogical evaluation of soil involves the study of soil in terms of their chemical and physical properties. This is done either to identify the type of soil been evaluated or its mineral contents. The present study investigated the physicochemical properties and evaluated the major mineral content of Ado Ekiti soil. The mineralogical evaluation of the clay and physicochemical characterization of the clay include determination of particle size distribution, surface morphology, pH, moisture content, chemical composition, elemental composition, functional group elucidation, cation exchange capacity, soil organic matter, bulk density and moisture content. Result of the chemical composition determined by the XRF showed that silica (SiO2) and alumina (Al2O3) are the major chemical components of the clay with percentage composition of 58.65 and 23.55% respectively which is a major property of kaolin. In support of the XRF, the PIXE showed that Al (254444 ppm) and Si (568138 ppm) are the most abundant elements of the clay. The EDX together with the FTIR showed that the metallic constituents of the clay exist in their oxide form which is consistent to the result of the XRF. This study therefore showed that the clay is typically kaolin having kaolinite as its major mineral content.
CHAPTER ONE
INTRODUCTION
A soil is a complex mixture of different minerals, water, air, organic matter, and remains of decayed organisms (flora, fauna and human) capable of supporting plant and animal life on earth. As a result, soil differs from its parent materials in physical, biological, mechanical and chemical properties (Seini et al., 2019). Sand, silt, and clay are the particles that make up soil. Sand particles are the largest while clay particles are the smallest (Eric et al., 2014). According to ASTM (2016), clays belong to the family of minerals called phyllosilicates which is made up of tetrahedral silicate sheets and octahedral metal oxide (or hydroxide) sheets with particle size less than 2 μm. Clay is composed of different minerals and the clay minerals are generally classified into three layer types based upon the number and arrangement of tetrahedral and octahedral sheets in their basic structure. They are 1:1 (e.g. kaolinite), 2:1 (e.g. mica, smectite, and vermiculite groups) and 2:1:1 (e.g. Chlorite) clay minerals (Braddy, 1990). Several techniques have been developed for mineralogical evaluation and identification of different types of minerals present in clay. For instance, X-ray Diffractometry (XRD) among other techniques has been solely used to identify the mineral contents of soil and such is reported in a study by (Akinola et al., 2014). They were able to show that kaolinite, illite and quartz are the clay minerals present in Ishan clay. Recent work by Akinola and Obasi (2014) showed that kaolinite is the major mineral component of kaolin. Some of the most important techniques that have been used for the mineralogical evaluation of soil minerals include scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray fluorescence (XRF), Thermogravimetry (TGM), energy dispersive X-ray emission technique (EDX) and proton induced X-ray emission technique (PIXE) (Cook, 2000; Akinola and Obasi, 2014; Sanusi et al., 2016; Awokunmi and Asaolu, 2017; Sanou et al., 2019). Ado Ekiti a town located in Ekiti State, Southwestern Nigeria has abundant clay deposits. The clay deposits have been mined for several years for its application in pottery, ceramics and architecture. Mineralogical evaluation and physicochemical characterization of this clay is therefore important and has become the aim of this study in order to understand the nature and other possible future application of the clay.
Laterites and lateritic soils abound in tropical and subtropical regions of the world. They are largely products of intense physico-chemical decomposition of rocks under hot and humid climatic conditions. On tropical African shields, lateritization processes have led to the development of weathering mantles ten of meter thick often capped with ferricretes at the expense of all kinds of parent rocks that may reflect a long and complex evolution including climatic geomorphological changes (Aleva 1994). Such lateritization processes commonly involve preferential leaching and concentration of valuable deposits, such as ores of aluminium, iron, nickel, chromium, cobalt, manganese, gold, tin, niobium and tantalum. Other minerals include bauxites, phosphate, industrial clays and gemstones. The clayey residues generated from the chemical decomposition of rocks within these areas are sometimes found to be suitable for industrial applications.
In the south western Nigeria, extensive occurrences of such residual bodies have been reported by various workers (Kehinde-Phillip 1991, Elueze and Bolarinwa 1994, Emofurieta et al 1994, Bolarinwa 2001, Ige et al., 2005, Bolarinwa 2006, Adegbuyi et al., 2015). Profile investigation reveals erratic variation in the major oxide composition and pronounced dissimulation in mineralogical characteristics in line with the parent rock and chemical environments. Hence, translocation and redistribution of the weathering products through groundwater and percolating rain water under appropriate Eh and pH conditions (Norton, 1973), result in lateritization or duricrust formation. Thick lateritic deposits overly and blanket bedrock in most part of Nigeria (Durotoye and Malomo, 1982). The studying of the removal of mobile elements by meteoric water from the well established crystalline rocks, the resulted chemical variation along the profile and subsequent concentration of stable weathering products is the focus of present investigation.
1.2 Objectives of study
The objectives of this study is to examine the composition of mineral resources in Ado Ekiti.
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