ADSORPTION OF LEAD (II) ION FROM AQUEOUS SOLUTION USING CHEMICALLY TREATED AND UNTREATED COW DUNG ASH

Abstract

Batch experiments have been carried out to evaluate the removal of lead (II) ion from simulated aqueous solutions using chemically treated (CTCA) and untreated (UCA) Cow dung ash under various conditions of initial metal ion concentration, contact time, pH, temperature and adsorbent dosage. The adsorption data have been discussed using Freundlich, Langmuir and Temkin adsorption isotherm models. The kinetics of adsorption has been discussed using pseudo first-order rate equation, pseudo second-order rate equation, intra-particle diffusion and Elovich models. Thermodynamic parameters such as change in Gibbs free energy (ΔG°), change in Enthalpy (ΔH°) and change in Entropy (ΔS°) have been evaluated. The results show that equilibrium was achieved at 180mins and 240mins for UCA and CTCA adsorbents at optimum pH of 5 respectively. The sorption of lead followed pseudo-second-order rate kinetics. Experimental data fitted to Freundlich model very well with high correlation coefficient values. Thermodynamic studies revealed that the sorption process was exothermic and spontaneous, with good affinity toward the sorbent. The sorption capacity decreases with an increase in solution temperature from 28 to 55°C. The results of the present study suggest that Cow dung ash will be an effective and economical adsorbent for Pb2+ removal from wastewater containing lead.