Employing a novel O 3 /H 2 O 2 + BiPO 4 /UV synergy technique to deal with thiourea-containing photovoltaic wastewater.

Photovoltaic wastewater contains a large amount of thiourea that cannot be directly treated by biological methods because of its biotoxicity. In this study, a novel O ₃ /H ₂ O ₂ + BiPO ₄ /UV synergy technique was used as a pre-treatment process to degrade thiourea. The effects of H ₂ O ₂ and catalyst loading were investigated, and the transformation pathway of thiourea was predicted based on the intermediates detected by UPLC-Vion-IMS-QToF. The synergy technique degraded 89.14% thiourea within only 30 min, and complete degradation occurred after 150 min. The TOC removal of O ₃ /H ₂ O ₂ + BiPO ₄ /UV was 1.8, 1.5, and 1.9 times that of O ₃ /H ₂ O ₂ and BiPO ₄ /UV/H ₂ O ₂ single processes and O ₃ /H ₂ O ₂ + UV process, respectively, which was due to the synergy between H ₂ O ₂ residues and BiPO ₄ . In addition, thiourea was mainly degraded by ·OH into thiourea dioxide and melamine (polymerized by other intermediates) and then further degraded into biuret and methyl carbamate by the holes of BiPO ₄ , followed by complete mineralization into H ₂ O and CO ₂ . These results confirm that the O ₃ /H ₂ O ₂ + BiPO ₄ /UV synergy technique is a promising option for the degradation of thiourea.
Competing Interests: The authors have no conflicts of interest to declare.
(This journal is © The Royal Society of Chemistry.)