Bio-synthesis of Co-doped FeMnOx and its efficient activation of peroxymonosulfate for the degradation of moxifloxacin

Metal oxides can effectively activate peroxymonosulfate (PMS) to degrade organic contaminants but are usually synthesized via chemical/physical processes involving extreme conditions and hazardous materials. In this study, an innovative bio-synthesis method with a strain of manganese oxidizing bacteria Pseudomonas sp. was developed to prepare multiple metal oxides consisting of iron, manganese, and cobalt (Bio-FeMnCoOx) for degrading moxifloxacin (MOX) with PMS. It was found that the cultivation time, the dosage of Co, the polishing method are the key parameters regulating the PMS activation performance of Bio-FeMnCoOx. Under the optimal preparing conditions, the MOX degradation kinetic constant of obtained Bio-FeMnCoOx was 7 times that of the chemically synthesized peer. Analysis with XRD, EPS and SEM with EDS mapping showed an amorphous structure of Bio-FeMnCoOx with well distributed Fe, Mn, and Co. Radical quenching and EPR spin-trapping tests demonstrated that SO4•- and 1O2 were the main reactive oxygen species. The transformation products of MOX were identified by UPLC-QTOF-MS/MS and the possible degradation pathways were accordingly proposed. The respiratory test showed that the toxicity of MOX was reduced by approximately 69% after the degradation with PMS activated by Bio-FeMnCoOx. The study demonstrates the potential of biogenic metal oxides for efficiently activating PMS.