Near-Ultraviolet Light-Driven Photocatalytic Chlorine Activation Process with Novel Chlorine Activation Mechanisms

In this study, the near-ultraviolet (near-UV) light-driven TiO2 photocatalytic chlorine activation process, termed as the UV365/TiO2/chlorine process, degrades a representative recalcitrant micropollutant, carbamazepine (CBZ), at an apparent first-order rate constant (k(CBZ)') that is 34.2 and 3.9 times higher than those without TiO2 and chlorine, respectively. In this process, chlorine serves a more important role as a catalyst to enhance the yield of hydroxyl radicals (HO center dot) without being consumed, in addition to its role as a radical precursor to produce HO center dot and reactive chlorine species. k(CBZ)' increased with increasing TiO2 dosages from 1.0 to 20.0 mg/L and light intensities from 0.1 to 0.33 mW/cm(2) and with decreasing chlorine dosages from 5.0 to 1.0 mgCl(2)/L. Increasing pH increased the overall radical concentrations but transformed HO center dot and Cl center dot to less reactive ClO center dot, leading to a decreasing k(CBZ)' from pH 6.0 to 9.0. The dual roles of chlorine in the process enabled the rapid CBZ degradation at a chlorine dosage about 1/20 to that of the conventional UVC/chlorine process, at a TiO2 dosage about 1/200 to that of the UVC/TiO2 process and at an electrical energy per order of CBZ degradation at least 2-order of magnitude lower than those of the existing UVC-based processes.

Automated summary

This study highlights the significant enhancement in carbamazepine (CBZ) degradation in the UV365/TiO2/chlorine process, where chlorine plays a dual role in catalyzing the production of hydroxyl radicals and reactive chlorine species. The use of chlorine in this process enables rapid CBZ degradation at significantly lower dosages compared to conventional methods, providing a more energy-efficient and effective approach for micropollutant removal.