Bentonites as a Copper Adsorbent: Equilibrium, pH, Agitation, Dose, and Kinetic Effect Studies

Abstract

In landfills, properties of the liner become affected due to the presence of harmful chemicals that, in turn, reduce its efficiency. In this study, two bentonites having different chemical and mineralogical compositions were tested in the presence of various concentrations of copper. The batch adsorption study, effect of pH (range 2–5), agitation speed (0, 50, 150, and 300 rpm), dose study (0.2–5 g), and kinetic study were conducted on both bentonites. The adsorption study showed that bentonite having higher cation exchange capacity and higher specific surface area showed a 10% higher adsorption capacity. The pH study indicated that a maximum adsorption at pH 5 was observed by both bentonites. Agitation speed also influenced the adsorption of Cu2+ on both bentonites. The study indicates that with the increase in bentonite dose, the removal percentage increased and the Cu2+ adsorbed per unit mass decreased. The kinetic study revealed that adsorption process was fast for the initial 120 min and reached equilibrium, and the parameters fitted in the kinetic model indicated that the pseudo-second-order kinetic model fit better. The kinetic study also showed that the removal of Cu2+ by bentonite with a higher specific surface area and cation exchange capacity (CEC) was higher.