Insight into the activation of periodate by Mn(II) for rapid degradation of sulfadiazine: Performance and mechanisms

The present study investigated the mechanism of manganese ion (Mn(II))-activated periodate (PI) for rapid removal of sulfadiazine (SDZ). The Mn(II)/PI system showed excellent SDZ degradation results with 99.8 % degradation efficiency within 2 min at pH = 5.5. Mechanism study reveals that the degradation of SDZ in the Mn(II)/PI system takes place mainly through an electron transfer process. Mn(II) can be oxidized by PI to formed the in-situ MnO2, followed by the generation of MnO2-PI complex. Electrochemical methods have confirmed that the generated MnO2-PI complex significantly contributes to the degradation of pollutants. MnO2-PI mediates the transfer of electrons from SDZ to PI surface through surface vacancies, thereby achieving efficient degradation of pollutants. p-methoxyphenyl sulfone (PMSO) is used as a probe compound, and almost 90 % of PMSO is converted into PMSO2 in the Mn(II)/PI/SDZ system, manifesting that excessive PI may oxidize active Mn(IV) to Mn(V). And the generated Mn(V) also contributes to the SDZ degradation. The SDZ degradation pathway is proposed and the transformation of iodine species is detected. The final iodine species in the system are iodate. The chloride culture experiment has confirmed that the production of organic iodine is very low, indicating no significant health risks. This study reveals mechanism of periodate-based process, providing theoretical and technical implementation guidelines of periodate in water treatment.