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

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 center dot were mainly generated by LDH while HO center dot 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.

Automated summary

In this study, Cu-Fe LDH was synthesized and calcined to form metal oxides. CMK/LDH and CMK/CLDH composites were fabricated and used to activate persulfate for sulfamethoxazole degradation. A comparative study showed that CMK/LDH had the best activation capacity, while CMK/CLDH had better adaptability to initial pH values. Additionally, non-radical pathways played a significant role in the degradation process, with sulfate radicals mainly generated by LDH and hydroxyl radicals mainly produced by CMK.