Kinetics and equilibrium studies for the removal of cadmium ions from aqueous solutions using Duolite ES 467 resin

Kinetic and equilibrium studies were conducted with cation exchange resin (Duolite ES 467) to investigate the effectiveness of removal of cadmium ions from aqueous solutions in a batch mode. The effect of various parameters was studied, such as contact time, agitation speed, sorbent mass, sorbate concentration, pH, competitive ion and temperature. The kinetic data were analyzed by finding their fitness to the well-known Lagergren and pseudo-second-order models using linear and non-linear curve fitting methods. Equilibrium isotherms generated were tested by applying Langmuir and Freundlich isotherm models using both linear and non-linear methods. The optimum contact time and agitation speed were found to be 60 min and 600 rpm, respectively. The presence of sodium chloride ions in solution drastically reduced the cadmium uptake. On the other hand, higher pH and temperature enhanced sorption. The non-linear curve fitting analysis method was found to fit the data better than the linear method. Similarly the Langmuir isotherm model has an edge over the Freundlich model. The calculated thermodynamic parameters such as Delta G(0), Delta H-0 and Delta S-0 indicate the effectiveness of Duolite ES 467 resin to remove cadmium from solution. (C) 2010 Elsevier B.V. All rights reserved.