Development of kinetic and equilibrium models for removal of Cd2+and Zn2+ions from aqueous solutions by clinoptilolite

Abstract

The ability of clinoptilolite to remove Cd2+and Zn2+from aqueous solution was studied. In this regard, the effects of important parameters such as initial concentration, initial pH, chemical conditioning, environmental temperature, and contact time on the Zn2+and Cd2+sorption were investigated. The results showed that the Zn2+and Cd2+sorption behavior was highly dependent on the pH. Sorption data were interpreted in terms of Langmuir and Freundlich equations. As a result, sorption isotherms of Zn2+and Cd2+ions could be best modeled by the Langmuir equation. The maximum capacity of Zn2+and Cd2+using modified clinoptilolite was found to be 229 and 72.30 mg/g. Furthermore, kinetic investigations showed that the adsorption rate was best described by a pseudo-second-order kinetic model. With respect to the results, clinoptilolite has a particularly high potential for Cd2+and Zn2+removal. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 633–641, 2016.