Behavior of bentonite in an aqueous electrolytic solution – evaluation of electrolytic aggregation for adsorption capacity of Cd²⁺ ions onto bentonite

In this study, we used aqueous solutions containing 1 mg/L of Cd²⁺ for electrolysis while varying the current density (CD), amount of bentonite added and the effective submerged area to investigate the adsorption capacity of Cd²⁺ ions onto bentonite by electrolytic aggregation. The adsorption of Cd²⁺ ions increased with increasing amount of bentonite added to the electrolytic solution. The addition of bentonite also regulated the pH of the electrolytic solution during the electrolysis process in addition to the hydrolysis of water. The maximum adsorption capacities at equilibrium (q_e) for current densities of 3.14 and 7.49 mA/cm² (i.e. for 2 and 1 L electrolytic solutions) with 0.2 g of bentonite were 4.54 and 2.92 mg/g, respectively. The removal of Cd²⁺ (R_Cd) clearly depended on the pH of the electrolytic solution. Moreover, q_e decreased with increasing amount of bentonite used for electrolytic aggregation. The findings of this study will be useful for understanding the aggregation of clay particles under electrolysis and their adsorption behaviors.