Enhanced oxidation and in-situ coagulation Fe(Ⅱ)/peroxymonosulfate-Mn(Ⅶ) process for carbamazepine removal: Multiple promoting effects of Mn and direct/indirect regulation of Cl− on active substances transformation

Slow transformation efficiency of Fe(III)/Fe(II) limits the generation of radicals in peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs), and these radicals was easy to be interfered by the presence of water constituents. In addition, in-situ coagulation during this oxidation process was neglected. This study proposed Fe(II)/PMS-Mn(VII) in the presence of chlorides ions (FPMC) process to reveal multiple promoting effects of Mn on redox cycle of Fe(III)/Fe(II) and different reactive mechanisms of Cl − on types of radicals generation pathways, and the in-situ coagulation enhanced mechanisms was investigated. Results showed that the dual functionality of oxidation and in-situ coagulation in FPMC process was significantly enhanced that carbamazepine (CBZ) could be efficiently and quickly removed. The reduction product Mn(III) of Mn(VII) could promote the redox cycle of Mn(II)/Mn(III) and Mn(III)/Mn(IV) that facilitated Fe(III)/Fe(II), sustaining the reactivity of the system. Cl − could significantly promote the cycling of Mn(Ⅲ)/Mn(Ⅳ) that indirectly affected the cycle of Fe(III)/Fe(II).