Adsorptive Removal of Lead from Battery Wastewater by Coconut Coir

Abstract

Abstract The sorption behavior of lead ions on coconut coir has been investigated to decontaminate lead ions from aqueous solutions. Various physico-chemical parameters were optimized to simulate the best conditions in which this material can be used as an adsorbent. Maximum adsorption was observed at 0.0001 to 0.001 mol L−1 of acid solutions (HNO3, HCl and HClO4) using 0.4 g of adsorbent for 4.83 × 10−5 mol L−1 lead concentration in ten minutes equilibration time. The adsorption of lead was decreased with the increase in the concentrations of all the acids used. The kinetic data indicated an intraparticle diffusion process with sorption being pseudo-second order. The determined rate constant k2 was 8.8912 g mg−1 min−1. The adsorption data obeyed the Freundlich isotherm over the lead concentration range of 2.41 × 10−4 to 1.45 × 10−3 mol L−1. The characteristic Freundlich constants i.e., 1/n = 0.44 ± 0.02 and K = 0.184 ± 0.0096 m mol g−1 have been computed for the sorption system. The sorption mean free energy from the Dubinin-Radushkevich isotherm is 10.48 ± 0.72 kJ mol−1 indicating the ion-exchange mechanism of chemisorption. The uptake of lead increases with the rise in temperature (293–333 K). Thermodynamic quantities i.e., ΔG, ΔS, and ΔH have also been calculated for the system. The sorption process was found to be endothermic. The proposed procedure was successfully applied for the removal of lead from battery wastewater samples. Keywords: coconut coirkineticslead adsorptionsorption isothermsthermodynamics