In Situ Elimination of Water Disinfection Byproducts in the UV/Chlorine Process by Introducing a Faceted Photocatalyst

The ultraviolet (UV)/chlorine process is increasingly applied for water disinfection, enabling efficient pathogen deactivation with the formation of far fewer disinfection byproducts (DBPs) than the conventional chlorine disinfection process. However, many recalcitrant DBPs like 4-chlorophenol (4-CP) still persist in the effluent, threatening water ecosystem safety. Here, we constructed a highly active and stable faceted photocatalyst, consisting of Al-doped SrTiO₃ loaded with spatially separated cobalt oxide (CoO_<i>x</i>) and palladium (Pd) cocatalysts, for efficiently eliminating the halogenated DBPs including 4-CP. This photocatalyst with a dual cocatalyst design enabled efficient photocharge separation and synergized the reductive dechlorination and oxidative degradation processes to augment 4-CP removal, exhibiting 70-fold higher decontamination efficiency than the cocatalyst-free control and 7-fold higher activity than the unfaceted control. Importantly, the high UV activity and singlet oxygen (¹O₂)-dominated oxidation pathway of the photocatalyst rendered it superior in environmental robustness and adaptability to the existing UV/chlorine process. Consequently, by introducing this photocatalyst, a rapid in situ elimination of DBPs during UV/chlorine treatment of the secondary effluent of a municipal wastewater treatment plant (WWTP) was achieved, with the concentrations of several representative DBPs all below the detection limits (<10^-9 g/mL). In addition, it also demonstrated superior stability during cyclic photocatalytic decontamination and during long-term continuous operation in a photocatalytic membrane reactor for UV/chlorine treatment. Our work presents an important advancement to photocatalytic advanced oxidation processes and may inspire further development of photocatalytic water purification and disinfection technologies.