Kinetics and equilibrium studies for the removal of cadmium ions by ion exchange resin

• High cadmium exchange capacity, greater than 2 mmole per gram resin.
• Much higher exchange capacities at pH 5 than pH 2.5.
• Excellent correlation of kinetic data using the pseudo-second order model.

Cadmium is a highly toxic metal which is found in the effluent of battery manufacturing plants. In this study, the ability to remove cadmium ions using an ion exchange resin has been studied in single component sorption-exchange systems.The maximum sorption capacity of resin for cadmium ions has been reached at pH 5 and the value is 2.20 mmole/g resin. This value shows that resin can effectively remove cadmium ions. The equilibrium isotherms have been analyzed using the Langmuir, Freundlich and Redlich–Peterson isotherm equations and the experimental data are best described by the Redlich–Peterson model.A series of kinetics studies have been conducted in an agitated batch reactor. Two variables have been studied under two different pH values, namely, 2.5 and 5.0, – different initial metal ion concentrations and different masses of resin. The kinetics of sorption of the cadmium ions have been analyzed by three kinetic models, the pseudo-first order, pseudo-second order and Elovich models. The rate constants and the correlation coefficients of the three kinetic models have been calculated. The experimental data were compared on the basis of SSE values and the pseudo-second model order provides the best fit to the experimental data.