Evaluation of the influence of clay montmorillonite content on the aqueous uptake of lead and zinc

This study investigated the influence of montmorillonite content in a natural clay on the aqueous uptake of lead and zinc, using factorial design analysis. The effects of initial pH, montmorillonite content, initial metal concentration, and adsorbent mass on the sorption capacity of lead and zinc were evaluated using variance analysis. Increasing montmorillonite content had an insignificant effect on lead adsorption capacity whilst significantly influencing that of zinc. Comparable equilibrium sorption capacities for lead and zinc were achieved when the retention time for zinc adsorption was significantly increased and montmorillonite content was high. Under experimentally verified operating conditions, pseudo-second-order and pseudo-first-order kinetics, respectively, described the ions adsorption process with intraparticle diffusion not the sole rate-controlling step. These results suggest that the montmorillonite content in natural clays exhibits distinct affinity behaviors towards the uptake of different heavy metals. This is expected to divergently influence processes such adsorption and electrokinetic remediation, for clays with differing montmorillonite content.