Deciphering the simultaneous removal of carbamazepine and metronidazole by monolithic Co2AlO4@Al2O3 activated peroxymonosulfate

Abstract

Reported here is a pioneering work on the co-removal of carbamazepine (CBZ) and metronidazole (MNZ) by Co2AlO4@Al2O3 millispheres activated peroxymonosulfate (PMS). Compared with the single removal, the reduced ratios for the removal kinetics of MNZ (72.16%) are two times higher than that of CBZ (35.41%) within initial pH 3 – 9. This is essentially due to the higher oxidation affinity of SO4•– and 1O2 toward CBZ than MNZ. Cl− facilitated the degradation of CBZ but inhibited the degradation of MNZ, probably ascribed to the formation of HOCl and Cl2•−. HCO3− and PO43− significantly inhibited the removal of CBZ and MNZ by scavenging SO4•– and/or passivating the active sites of Co2AlO4@Al2O3. The degradation of CBZ is mainly due to the electron abstraction and oxygen addition, while the primary oxidation processes of MNZ include the denitration, ring opening and/or N-C cleavage. Because of the competition of CBZ against SO4•−, the simultaneous removal process remarkably changed the main products of MNZ compared with the single removal process. The simultaneous removal of CBZ and MNZ increased the total bioaccumulation potential and mutagenicity risk of degradation products but helped to reduce their total developmental toxicity. The products formed in the co-removal process showed higher total acute toxicity to Daphnia magna than those of the single process, while for the total acute toxicity to Oral rat, the results are reversed. This work will spark more interest of simultaneously removing multiple emerging pollutants with monolithic catalysts-oriented oxidation processes.