Kinetic modeling and mechanistic insights into chloroquine phosphate degradation by UV-activated peroxymonosulfate

Abstract

Chloroquine phosphate (CQP), a widely utilized antimalarial and anti-COVID-19 medication, exhibits persistence and ecotoxicity in aquatic environments. This study systematically investigated the CQP degradation in the UV-activated peroxymonosulfate (UV/PMS) process, focusing on influencing factors, degradation pathways, and constructs the first-principle kinetic model describing this degradation. The UV/PMS process effectively degraded CQP with a pseudo-first-order reaction rate constant of 0.271 min^− 1, sulfate radicals (SO₄•⁻, 62.4%) and hydroxyl radicals (HO•, 27.3%) were the dominant reactive species. Increasing PMS concentration enhanced radical generation and degradation efficiency. Furthermore, the UV/PMS process exhibited excellent pH adaptability, when the pH value was 10.8, the maximum pseudo-first-order reaction rate constant was 2.894 min^− 1 due to the sharp increase in HO• contribution. Cl⁻ slightly inhibited degradation by consuming SO₄•⁻, while HCO₃⁻ had no obvious effect due to the non-negligible role of CO₃•⁻. Additionally, a kinetic model simulated the radical dynamics and degradation trends, showing a strong correlation with experiments. Several potential degradation pathways involved N-deethylation, C-N bond cleavage, hydrogen abstraction, and N-oxidation. An economic analysis revealed that the total cost reached the minimum of 0.33 USD/(m³∙order) when the concentration of PMS was 0.14 mM. This study provides theoretical support for UV/PMS-based CQP removal from water.