Removal of cadmium from aqueous solutions by adsorption on granular red mud (GRM)

This study puts forward a novel method to prepare granular red mud (GRM) and evaluates its potential use to remove cadmium ions from aqueous solutions as a low-cost adsorbent. The properties of the novel adsorbent were examined and then used for cadmium adsorption experiments. Batch experiments were conducted and equilibrium isotherms at different temperatures (20 °C, 30 °C, 40 °C) have been determined and analyzed with a Freundlich model. Kinetics data at initial pH 6.0 and 3.0 were fitted with Pseudo-second-order model and external mass transfer coefficients, effective particle diffusion coefficients were subsequently calculated for cadmium–GRM system at initial pH 6.0. Column breakthrough curves were depicted and the data were analyzed with a Thomas model. The column adsorption was reversal and the regeneration operation was accomplished by pumping 0.1 mol/L hydrochloric acid through the adsorbed column.