The wide use of chemicals in modification of kaolinite in order to improve its adsorption capacity is expensive, requires skilled personnel, noxious to the environment and results in secondary contamination. As a result this study investigated an eco and environmental friendly modification of kaolinte using cassava peel to enhance its adsorption for Cr (III) ions. The adsorption capacity of the Unmodified Kaolinite Clay (UKC), Cassava Peel Modified Kaolinite Clay (CPMKC) and Unmodified Cassava Peel (UCP) were compared. The effect of experimental variables such as pH, Cr (III) ion concentration, adsorbent dosage, particle size, agitation time and temperature on sorption was studied using batch methodology. Equilibrium isotherm studies was analyzed by the Langmuir, Freundlich and Halsey isotherm models while the Pseudo First Order (PFO), Pseudo Second Order (PSO) and Intraparticle Diffusion (IPD) models were used for kinetic analysis. All the experimental variables were found to have significant effect on Cr (III) ions sorption on the adsorbents with an optimum pH of 5.0, adsorbent dose 0.1 g, particle size 100 μm and chromium concentration of 375 mg/L obtained. Equilibrium sorption at 25, 20 and 60 min was obtained for UKC, CPMKC and UCP respectively which showed the faster sorption potential of CPMKC. The Langmuir model had the best fit with linear regression (R2) of 0.991 and 0.998 for UKC and UCP. The Freundlich and Halsey models gave the best fit with same R2 of 0.975 for CPMKC and the Sum of Square of Errors (SSE) was slightly lower for the Freundlich (0.833) than the Halsey (0.897). The PFO model gave the best fit (R2>0.980) and lowest SSE than the PSO model. An initial sorption rate h (mg/g min) of 2.16, 3.14 and 1.02 was obtained for UKC, CPMKC and UCP respectively. Thermodynamics revealed an endothermic physical sorption of Cr (III) on all the adsorbents. The sorption was in the order UCP>CPMKC>UKC, which showed the suitability of cassava peel in enhancing the sorption ability of kaolinite for chromium ion from aqueous solution.
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