Citrate-regulated synthesis of hydrotalcite-like compounds as peroxymonosulfate activator - Investigation of oxygen vacancies and degradation pathways by combining DFT

This work investigated the triggering mechanism of peroxymonosulfate (PMS) activated by an oxygen vacancy (Ov)-rich cobalt (Co)-based hydrotalcite-like compound (CA-LDH). CA-LDH was synthesized by a urea-hydrothermal process with ammonium citrate (CA) as the reducing agent. The PMS activation mechanism was investigated by combining batch experiments, characterization techniques, and DFT calculations. Over 98 % of CIP (20 mg/L) was degraded by the CA-LDH/PMS system within 60 min, which remained efficient in the presence of common interfering substances or over a wide pH range. DFT showed that CA was beneficial for introducing the electron transfer intermediate, namely, Ov, on CA-LDH, thereby allowing for the unique electron transfer performance of CA-LDH. Specifically, electron transfer from Co-Ov to PMS triggered the radical pathway, while electron transfer from PMS to Co-Ov triggered the nonradical pathway. Overall, this study provides a reference for the rational catalyst synthesis and the investigation of the triggering mechanism of PMS activation.