Synthesis of CMK/ LDH and CMK/CLDH for sulfamethoxazole degradation by PS activation: a comparative study of characterization and operating parameter, mechanism pathway

Abstract In recent decades, persulfate activation technology has been used to degrade persistent organic pollutant. Moreover, both transition metal-based catalyst and metal-free catalyst have become more efficient activator. In this study, Cu-Fe LDH was synthesized and calcined at different temperature to form into metal oxides (CLDH). Then, the CMK/LDH and CMK/CLDH composites were fabricated by co-precipitation and sonic treatment, respectively. Furthermore, the prepared samples were used to activate PS for sulfamethoxazole degradation. Based on the several characterizations and degradation experiments, a comparative study of different catalysts was conducted and the results reached the following factors: i CMK/LDH owned the best capacity of PS activation on sulfamethoxazole decomposition, 84.9% SMX of 25 mg/L was degraded with less dosage of persulfate (0.5 g/L) and catalyst (0.15 g/L) being added. ii CMK/CLDH owned the better adaptability of initial pH value compared with CMK/LDH. Meanwhile, based on scavenger quenching experiment and chronoamperometric, it was speculated that non-radical pathway played more role in CMK/LDH composite/PS/SMX system compare with radical pathway. It was interesting to find that SO4•- were mainly generated by LDH while HO• were mainly produced by CMK part. However, the non-radical pathway for SMX decomposition was only ascribed to the electron bridge effect that the CMK owned. This study might provide a theoretical support for further studies on comparison about LDH and the metal oxides originating from calcination of LDH for PS activation.