Zinc removal from aqueous solutions by adsorption onto bentonite

Abstract

Industrial wastewaters contain considerable amounts of metal ions that would endanger public health and the environment if discharged without adequate treatment. The aim of this study is to evaluate, zinc adsorption from aqueous solutions onto Algerian bentonite, kinetics, isotherms, and thermodynamic parameters. The characterization of this bentonite was accomplished by using FT-IR, TGA, and SEM techniques. The effects of contact time, initial metal concentration, agitation speed, and temperature were investigated experimentally. The maximum adsorption was reached at pH 8. Pseudo-first-order, pseudo-second-order, Elovich equation, and intraparticle diffusion models were used to analyze the kinetic data obtained at different concentrations. The pseudo-second-order kinetic model agrees very well with the experimental results. In order to determine the best fit isotherm, in the studied concentration range of Zn²⁺ at 20°C, the experimental equilibrium data were analyzed using four adsorption isotherm models: Langmuir, Freundlich, Temkin, and the Redlich–Peterson. The calculated thermodynamic parameters suggested that the adsorption of zinc was physisorptive, spontaneous, and endothermic in nature. The results indicate that this bentonite is a suitable adsorbent for the removal of heavy metals especially zinc ions.

Keywords:

• Heavy metals
• Zinc
• Adsorption
• Bentonite
• Kinetic
• Isotherm

Notes

Presented at the Conference on Membranes in Drinking and Industrial Water Production. Leeuwarden, The Netherlands, 10–12 September 2012. Organized by the European Desalination Society and Wetsus Centre for Sustainable Water Technology