Ni2+ Removal from Aqueous Solutions Using Conditioned Clinoptilolites: Kinetic and Isotherm Studies

The aim of this study is to investigate the effects of conditioning with NaCl and HCl solutions on removal of Ni2+ ions from aqueous solutions using natural clinoptilolite. Batch studies were performed to evaluate the effects of various parameters such as chemically conditioning, adsorbent amount, contact time, initial pH of the solution, mixing temperature, and initial metal ions. The results clearly showed that the conditioning improved both the exchange capacity and the removal efficiency. Langmuir, Freundlich, Temkin, and Dubinin-kaganer-Radush-kevich (DKR) isotherm models were adopted to describe the adsorption isotherms. Adsorption isotherms of Ni2+ ions could be best modeled by Langmuir equation. Three simplified models including pseudo-second-order, intraparticle diffusion and Elovic were used to test the adsorption kinetics. These results indicate a significant potential for the natural and conditioned clinoptilolites as an adsorbent/io-exchange material for heavy metal removal. (C) 2008 American Institute of Chemical Engineers Environ Prog, 28: 162-172, 2009