Kinetics and mechanisms for the degradation of pharmaceutical and personal care product pollutants in the process of electrochemistry-driven in-situ chlorination coupled with solar photocatalysis

The ultraviolet (UV)/chlorine advanced oxidation process, which generates hydroxyl radical ( OH) and chlorine radicals (Cl ), is considered to be an efficient technology for pollutant removal. In this study, the in-situ generation of hypochlorous acid (HOCl) using an electrode as the source of active chlorine was employed, in which electrochemical/chlorine (EC) and solar photocatalytic technologies were combined to form the Solar/E/catalyst system. In this process, HOCl not only served as the precursor for generating OH but also continuously generate OH and regenerating under TiO 2 driving. Additionally, the chlorine ions generated in the reaction were reconverted to HOCl through electrode oxidation. Under the optimal conditions of [ibuprofen] 0  = 20 μmol/L, I 0  = 150 mA, [Cl − ] 0  = 100 mg/L, and pH 0  = 7.0, the degradation rate increased from 22 % in the Solar/E condition to 91 % in the Solar/E/TiO 2 condition. The kinetic rate constants were 13.1 and 3.2 times higher than those in the Solar/E and Solar/TiO 2 conditions, respectively, indicating a significant synergistic effect (by a factor of 2.6) in the Solar/E/TiO 2 system. The significant enhancement effect disappeared when ZnO and Fe-gC 3 N 4 catalysts were used for comparison instead of TiO 2 . In addition, this process has broad application prospects in the treatment of pharmaceutical and personal care product pollutants such as atenolol and sulfamethoxazole, as well as in practical water treatment applications. In conclusion, this study provides an efficient, energy-saving method for the degradation of organic pollutants.