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

Abstract

Abstract 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 μA 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–d-NZF 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 O2− was the dominant radical while OH radicals and h+ contributed moderately to the decomposition processes.