Utilizing the “memory effect” of bimetallic-supported hydrotalcites for adsorption and reduction of perchlorate in water

Abstract

In this study, calcined Mg/Fe hydrotalcite (CHT) and hydrotalcite-based Pd/Co catalyst (Pd/Co-CHT, with Pd/Co of 1/2 wt.%) was successfully synthesized and employed to remove perchlorate from aqueous solution. The adsorption performances of CHT and Pd/Co-CHT were compared, and the hydrogen reduction performance of Pd/Co-CHT was explored. The adsorption kinetics and isotherms data satisfactorily followed the pseudo-second-order kinetics model and the Langmuir model, respectively. The adsorption capacity of Pd/Co-CHT (73.91 mg/g) is slightly lower than CHT (91.33 mg/g, 298 K), because of the decreased average pore diameter and pore volume. Hydrogen reduction of perchlorate by Pd/Co-CHT involved both adsorption and reduction processes, and its removal efficiency achieved 3 times higher than that of a single adsorption process. Results of XPS, XRD and FTIR revealed that the perchlorate was firstly adsorbed onto the positive surface of Pd/Co-CHT by “memory effect”, and then reduced to chloride. Notably, Cl− was the only product of the reduction process. After a chemical regeneration, the reuse efficiency of catalyst was 90.90 %, thus paving a way to effective regulation of perchlorate.