On the positive effect of UVC light during the removal of benzothiazoles by photoelectro-Fenton with UVA light

[Display omitted] •Upgrading of classical UVA-PEF upon part-time use of UVC light (150 last minutes).•Synergy: OH from Fenton’s reaction (UVA) followed by OH from H2O2 photolysis (UVC).•Part-time UVA-/UVC-PEF: similar energy consumption as UVC-PEF, higher TOC removal.•BTH oxidized to 2-OH-BTH and 5 heteroaromatics, along with oxalic, tartronic and oxamic.•Photosensitivity: Fe(III)-oxalate > Fe(III)-tartronate >> Fe(III)-oxamate ≥ Fe(OH)2+. Benzothiazole (BTH) and 2-hydroxybenzothiazole (2-OH-BTH) are ubiquitous pollutants in aquatic ecosystems. This article reports their photoelectro-Fenton (PEF) treatment, either alone or mixed, in sulfate medium at pH 3.0 using an IrO2-based/air diffusion cell that generates H2O2 under UVA and/or UVC irradiation. UVC-PEF was more effective than UVA-PEF to remove the target pollutants, which suggests a positive impact of OH formed via Fenton’s reaction and photo-induced homolysis of H2O2 in the former method. In addition, BTH disappeared more quickly than 2-OH BTH. Full-time UVA-/UVC-PEF outperformed UVC-PEF and UVA-PEF to mineralize the mixtures, although requiring a much higher energy consumption. The evolution of generated H2O2 and homogeneous OH confirmed the positive contribution of UVC photolysis in UVA-PEF. Part-time use of UVC radiation in UVA-PEF yielded a similar total organic carbon removal, with much lower energy consumption. BTH was oxidized to 2-OH-BTH, which was subsequently transformed into other five heteroaromatics.