Kinetics and equilibrium modeling of lead(II) and chromium(III) ions' adsorption onto clay from Kono-bowe, Nigeria


Abstract: Clay from Kono-bowe, Nigeria, was activated thermally and chemically and used to remove lead(II) and chromium(III) ions from aqueous solution. The effects of adsorption process variables were studied as well as the kinetics and equilibrium of the process. Analysis of the activated samples showed that the surface area, cation exchange capacity, and adsorption performance were positively favored by both activation processes. It was observed that the adsorption rate increased with an increase in temperature, contact time, adsorbent dosage, initial ion concentration, and solution pH values. The pH$_{PZC}$ of the adsorbents was determined to be 6.5, 7.4, and 7.2, for KBR, KBTA, and KBAA, respectively. It was observed that sample KBAA yielded maximum adsorption efficiency of 99.9% for the removal of chromium(III), and gave maximum adsorption efficiency of 98.7% for lead(II) removal. The results of the kinetics analysis of the adsorption data revealed that adsorption follows pseudo-second-order kinetics. Analysis of the equilibrium data showed that the Langmuir isotherm provided a better fit to the experimental data for KBR, while the Freundlich isotherm fitted the experimental data of KBTA and KBAA. Evaluation of the thermodynamic parameters revealed that the adsorption process is spontaneous and endothermic.

Keywords: Adsorption, clay activation, modeling, kinetics, equilibrium, isotherm

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