Role of modified activated carbon by H₃PO₄or K₂CO₃from natural adsorbent for removal of Pb(II) from aqueous solutions

Most heavy metals are well-known toxic and carcinogenic agents and when discharged into wastewater represent a serious threat to the human population and the fauna and flora of the receiving water bodies. The present study aims to develop a procedure for Pb(II) removal. The study was based on using powdered activated carbon, which was prepared from walnut shells generated as plant wastes and modified with potassium carbonate or phosphoric acid as chemical agents. The main parameters, such as effect of pH, effect of sorbent dosage, Pb(II) concentrations, and various contact times influence the sorption process. The experimental results were analyzed by using Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich adsorption models. The kinetic study of Pb(II) on activated carbon from walnut shells was performed based on pseudo-first order and pseudo-second order equations. The data indicate that the adsorption kinetics follow the pseudo-second order rate. The procedure was successfully applied for Pb(II) removal from aqueous solutions.