Sorption profile of cadmium ions onto styrene-divinylbenzene copolymer beads

Abstract

The sorption behavior of cadmium ions from aqueous media was investigated on styrene-divinylbenzene copolymer beads (StDVB) as an adsorbent. Various physico-chemical parameters were optimized to simulate the best conditions which can be used to decontaminate cadmium ions from aqueous media using StDVB beads as an adsorbent. Maximum adsorption was observed at 0.001 mol L^-1 acid solutions (HNO₃, HCl, H₂SO₄ and HClO₄) using 0.2 g of adsorbent for 8.89×10^-5 mol L^-1 of cadmium ions within three minutes equilibration time. The adsorption data followed the Freundlich, Langmuir and Dubinin–Radushkevich (D–R) isotherms over the cadmium concentration range of 8.89×10^-4 to 8.01×10^-3 molL^-1. The characteristic Freundlich constants, i.e. 1/n=0.243±0.007 and A=1.783×10^-3±2.069×10^-5 mol g^-1 have been computed for the sorption system. Langmuir isotherm gave a saturated capacity of 0.334±0.0123 mmol g^-1. The sorption mean free energy from D–R isotherm was found to be 16.31±0.31 kJ mol^-1 indicating chemisorption involving chemical bonding for the adsorption process. The uptake of cadmium increased with the rise in temperature. Thermodynamic parameters, i.e. ΔG, ΔH and ΔS have also been calculated for the system. The sorption process was found to be endothermic. The proposed procedure was applied to remove cadmium from tap water and industrial effluent.