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