Comparative analysis of acid activated nteje clay and two commercially available adsorbents (fuller’s earth and activated carbon)

Project Abstract

<p> The composition and bleaching properties of Nteje clay in comparison with two commercially<br>available adsorbents (activated carbon and fuller’s earth) were investigated to study its<br>competence for use as an alternative to high cost imported adsorbents. The modification of the raw<br>clay sample was carried out by acid activation to enhance the surface area of the clay by exchange<br>of octahedral cations e.g Al3+, Fe3+ and Mg2+ with H+ ions which led to the modification of the<br>clay crystalline structure. The raw clay sample was characterized using X-ray Diffraction (XRD)<br>analysis and Fourier Transfer Infrared Spectroscopy. The acid activated sample was used along the<br>two commercially available adsorbents (activated carbon and fuller’s earth) in adsorptive<br>bleaching of palm oil to study its adsorptive capacity. The bleaching was done at constant<br>temperatures of 60 oC, 80 oC, 100 oC, 120 oC and 140 oC varying time at 10, 20 30, 40 and 50<br>minutes at each constant temperature. The kinetics and thermodynamics of the adsorption reaction<br>was investigated at 333 k, 353 k, 373 k, 393 k and 413 k. To further understand the kinetics, the<br>adsorption data were analyzed by pseudo-second order, elovich and power function equations.<br>Adsorptive bleaching of palm oil was carried out using optimum operating conditions of<br>temperature, clay dosage and reaction time. The results revealed that the adsorption followed<br>power function equation for both activated carbon (A.C) and fuller’s earth (F.E) with linear<br>regression coefficient (R2) values of 0.987 and 0.990 respectively and followed elovich equation<br>for activated Nteje clay (A.N.C) with (R2) value of 0.985. Analysis of the equilibrium data using<br>Langmuir and Freundlich isotherms showed that Langmuir isotherm provided the best fit for the<br>three adsorbents understudy. Furthermore, the evaluation of the adsorption thermodynamic<br>parameters revealed that the adsorption process was spontaneous and exothermic because of the<br>free energy change, negative change in enthalpy and positive change in entropy. A maximum<br>colour reduction of 79 % was obtained for both A.N.C and F.E and 78 % for A.C all at 140 oC.<br>The results from this study reveals that modification of this alumino-silicate increased its<br>adsorptive capacity and produced equal results and responses like their commercially available<br>counterparts. Application of the low cost modification technique Nteje Clay therefore should not<br>be doubted, as this study have establish that it competes and compares favourably with the<br>imported, commercially available adsorbents. <br></p>

Project Overview

<p> INTRODUCTION<br>1.1 Research Background<br>Natural clay minerals are well known and familiar to mankind from the earliest days of<br>civilization1. Because of their low cost, abundance in most continents of the world, high sorption<br>properties, high dissolubility in acidic solutions and potential for ion exchange, clay materials are<br>suitable substances as source of metals and adsorbents. Clay is composed mainly of silica,<br>alumina, water and frequently with appreciable quantities of iron, alkalis as well as alkali earth<br>metals. Two structural units are involved in the atomic lattices of most clay minerals. One unit<br>consists of closely packed oxygen atoms and hydroxyls in which aluminum, iron and magnesium<br>atoms are embedded in an octahedral combination so that they are at equal distant from six oxygen<br>or hydroxyls. The second unit is built of silica tetrahedrons. The silica tetrahedrons (Si4O6(OH)4)<br>are arranged to form a sheet of composition2.<br>Clay deposits are widespread over the regions of Nigeria and are under utilized in the process<br>industries largely because we do not have the technology. These clay deposits can be mined,<br>purified and processed into useful raw materials for the process industries. Naturally occurring<br>clays are alumino-silicate minerals containing sodium, potassium, and calcium, with traces of<br>magnesium and iron which may be substituted for aluminum. The structure of these clays can be<br>altered by heating or reaction with strong acids or alkalis to improve their adsorptive properties<br>and colour. The majority of these clays do not possess such properties, but, may be activated by<br>some forms of treatment and their efficiency in the bleaching of vegetable oils can be improved.<br>24<br>Activation of clays can be accomplished by calcinations, reaction with mineral acids/alkalis, or<br>combination of both techniques.<br>1.2 Research Objective and Scope<br>The aim of this research was to make comparative analysis of the bleaching efficiency of a locally<br>substituted adsorbent, Nteje clay to the imported, commercially available activated carbon and<br>fuller’s earth. Because little or no work has been done in comparing the bleaching efficiency of<br>Nteje clay to its commercial standards, hence the need for the study. This study if found efficient<br>to the imported bleaching efficiencies of activated carbon and fuller’s earth, should be able to<br>operate at various quality of crude palm oil (C.P.O) fed and produce equal results and responses as<br>its commercial standards. By doing so, the purity of the final product including its commercial and<br>health values will be enhanced.<br>Therefore, the specific objectives of the research were:-<br>1. Preparation, characterization of activated and unactivated Nteje clay as well as its<br>activation.<br>2. To carry out adsorption of colour pigment from palm oil<br>3. To study the chemical kinetics, thermodynamics and equilibria of the adsorption process.<br>1.3 Problem Statement<br>1. Despite positive results by researchers of the bleaching capacity of Nteje clay, it is still<br>facing heavy industrial discrimination leading to little or no patronage<br>25<br>2. This study was also motivated by the easy contamination of vegetable and seed oils due to<br>the presence of both physical and chemical impurities.<br>3. The importation of large quantities of adsorbents and at a very high cost.<br>4. There is the problem of few locally substituted earth sources for research compared to<br>activated carbon with several substituted local sources.<br>5. Research have revealed that there are more than enough earth (clays) available that can be<br>used as adsorbent to meet our local demand.<br>1.4 Significance of Study<br>Nteje clay has been reported by several authors to have been successful in the adsorptive<br>bleaching of palm oil and its potency of being an alternative to costly, imported adsorbents.<br>Despite these successful results, it is more valuable when the adsorptive power of these local clays<br>are strong enough to permit it to compete actively with adsorbents already accepted as the standard<br>quality for refining oils. Hence, the main objective of this research which was to compare the<br>widely reported bleaching efficiency of this locally substituted adsorbent (Nteje clay) to the<br>imported, commercially available standards (fuller’s earth and activated carbon). The study will<br>properly validate its use as a local substituent for industrial and scientific applications, if found<br>competent. <br></p>