Single and Binary Adsorption of Heavy Metal Ions from Aqueous Solutions Using Coirpith as the Adsorbent

Abstract

The adsorption of nickel and zinc ions onto coir pith was studied using batch experiments at 30 ℃ and 40 ℃. Adsorption kinetics and equilibrium isotherms were obtained for both single component adsorption and binary adsorption. The kinetics of single system and binary system adsorption of nickel and zinc was studied using Lagergren pseudo first order model, pseudo second order model and the intraparticle diffusion model. The experimental data showed all of the systems could be described using pseudo second order model. In the single system the coir pith had a higher capacity for zinc than nickel. In both the nickel and zinc single systems the adsorption decreased when temperature increased from 30 ℃ to 40 ℃. In the binary system at 30 ℃ the coir pith had a larger capacity for zinc adsorption then nickel but at 40 ℃ coir pith had a larger capacity for nickel than zinc. Equilibrium data were satisfactorily fitted to Langmuir and Freundlich isotherms. When comparing the adsorption capacity, qmax, the experimental data showed the binary system had a lesser capacity (qmax 13.6 mg g−1) than the single systems nickel (qmax 27 mg g−1) and zinc (qmax 22.7 mg g−1) under similar conditions. This suggests the competitive nature of the systems decreases the overall adsorption.