Photocatalytic degradation of metronidazole and bacteria disinfection activity of Ag-doped Ni0.5Zn0.5Fe2O4

The health of human beings is threatened by drug-resistant diseases due to excessive antibiotic use. A promising cost-competitive water disinfection technology is photocatalytic disinfection. In this study, Ag-doped Ni0.5Zn0.5Fe2O4 photosensitive catalyst (Ag-d-NZF) was synthesized for disinfection of metronidazole antibiotic and bacteria-contaminated water. Ag-d-NZF was characterized and results revealed it has a bandgap of 2.96 eV, exhibiting a stable photocurrent response of 1.36 mu A cm-2 with a crystallite size of 15.3 nm and crystallinity of 74.5 %. After 360 min of UV-assisted irradiation under optimal conditions (pH 3 and 7 mM H2O2), 10 mg Ag-dNZF degraded 99.9 % of 50 mgL-1 MZ with an apparent rate constant of 0.0103 min- 1. Ag-d-NZF maintained 75.2-80.9 % efficiency in the presence of interfering ions and tylosin antibiotic. After 65 min, 25 mg of Ag-d-NZF demonstrated bactericidal effects (100 % inactivation) in the dark and under UV light against E. coli and S. aureus, respectively. The electrical energy consumed per order revealed that UV/ Ag-d-NZF/H2O2 required 26.84 kW h to degrade MZ which is equivalent to $1.34 per m3 of MZ. A plausible photocatalytic degradation mechanism was established, in which center dot O2- was the dominant radical while center dot OH radicals and h+ contributed moderately to the decomposition processes.