Removal of pharmaceuticals through UV-C/Performic acid advanced oxidation process: Kinetics and identification of reactive species

Performic acid (PFA), widely recognized for its disinfectant properties in wastewater, shows selective and limited reactivity in oxidizing micropollutants. This study investigates the activation of PFA through UV-C photolysis to generate an advanced oxidation process (UV-C/PFA) and enhance the degradation of six pharmaceuticals: lidocaine, furosemide, sulfamethoxazole, diclofenac, acetaminophen, and carbamazepine. The synergy of UV-C photolysis with PFA enhances the removal of PFA-persistent pharmaceuticals. For instance, diclofenac, acetaminophen, and sulfamethoxazole, initially unreactive with PFA, were entirely degraded within ten minutes under UV-C/PFA in a phosphate buffer solution. This increased reactivity results from generated reactive species like hydroxyl (HO^•), peroxyl (R–O^•) radicals and singlet oxygen (¹O₂), confirmed by electron paramagnetic resonance, with HO^• primarily originating from the background H₂O₂ present in the PFA solution. While UV-C/PFA produced fewer HO^• than UV-C/H₂O₂, it has distinct advantages through the selective action of ¹O₂ and R–O^• in degrading some pharmaceuticals. ¹O₂ was also detected in the PFA solution and could explain its selective reactivity, especially with compounds containing reduced sulfur or tertiary amine groups. Overall, UV-C/PFA yields transformation products of lower molar mass compared to PFA, thus potentially increasing mineralization. In wastewater effluent, UV-C/PFA improved pharmaceutical degradation, though scavenging effects by wastewater constituents reduced removal rates.