Efficient degradation of N-containing organic wastewater via chlorine oxide radical generated by a photoelectrochemical system

N-containing organic wastewater is harmful to human health and ecosystem while its degradation remains a huge challenge for decarburization and denitrification simultaneously. In this paper, we proposed a new photoelectrochemical method of chlorine oxide radicals production to oxidize mixture wastewater of phenol and N-ammonia into N₂ and CO₂. The chlorine oxide radicals were generated via a rapid reaction of HClO with hydroxyl radicals or chlorine free radicals on a synergistic dual anode, in which hydroxyl radicals and chlorine free radicals generated on WO₃ side, and HClO generated on Sb-SnO₂ side, respectively. Phenol degradation rate on WO₃-Sb/SnO₂ was 2.54 and 4.79 times than that on WO₃ and Sb/SnO₂. Meanwhile, N-ammonia removal rate on WO₃-Sb/SnO₂ was 5.69 and 20 times greater than that on WO₃ and Sb/SnO₂, respectively. The effects of potential, Cl⁻ concentration and initial pH were examined and the optimal conditions were potential 2.0 V vs Ag/AgCl, 0.05 M NaCl, pH = 5. The free radical quenching experiments and electron-spin resonance (ESR) confirmed that chlorine oxide radicals played an important role in the degradation of N-ammonia and phenol. Reasonable pathways of phenol in the WO₃-Sb/SnO₂ system were also proposed. This work provides an exhaustive, novel, environmental-friendly photoelectrochemical system for N-containing organic wastewater treatment.