Fe(III) mediated tetracycline degradation by UVA/periodate: Self- coordination driven degradation process

Ultraviolet A (UVA) as the promising light source in disinfection and photochemical applications is less effective in activating peroxides. Iron is wide spread in natural waters, while Fe(III) is less reactive in degrading organics. In this study, Fe(III) was found to be efficient in promoting the effectiveness of UVA/periodate (PI) in degrading various micropollutants, including carbamazepine (CBZ), sulfamethoxazole (SMX), nitrobenzene (NB), benzoic acid (BA) and tetracycline hydrochloride (TC). Among them, TC degraded with the highest rate constants, which was further confirmed to be driven by the generation of Fe(III)-TC complex. Fe(III)-TC complex facilitated the reduction of Fe(III) to Fe(II), and this reduction would be further accelerated by UVA. The generated Fe(II) thereafter enhanced the efficiency of PI activation. Scavenger combined with probing experiments preliminarily demonstrated TC degradation was based on • OH ${}^{•}\mathrm{OH}$ , IO 3 • ${\mathrm{IO}}_3^{•}$ dominated radical oxidation and 1 O 2 , Fe(IV) dominated nonradical oxidation. Electron paramagnetic resonance (EPR) combined with probing test further confirmed the • OH ${}^{•}\mathrm{OH}$ , IO 3 • ${\mathrm{IO}}_3^{•}$ , and 1 O 2 , Fe(IV) involved TC oxidation process. The degradation process was little influenced by water matrices. Cl − and NO 3 − even slightly promoted TC degradation through reduction the solution pH, since acidic condition was more favorable by TC degradation. Excessive humic acid (HA) would hinder TC degradation, as UVA transparency would be reduced by HA. The degradation of TC in the Fe(III)/UVA/PI system proceeded through multiple pathways involving oxidation, deamination, demethylation, ring-opening. Ecotoxicity analysis targeting on E. coli . Found the toxicity of TC intermediates increased, while the end products were nontoxic. Fe(III)/UVA/PI was efficient in inactivating E. coli. , which highlighted the application in water purification as the dual roles of oxidation and disinfection.