Chloroquine degradation in aqueous solution under electron beam irradiation

Pharmaceutically active compounds are the most widely produced and consumed consumer products that pose a substantial threat to the environment and living organisms owing to their pharmacokinetics, side effects, and contraindications. In this study, the degradation of chloroquine (CQ), a popular antimalarial and recently proposed COVID-19 drug, was investigated under electron beam (EB) irradiation of aqueous solutions. Both the hydroxyl radical and hydrated electron generated in the radiolysis of water contribute to the degradation of CQ in aqueous solution. The overall removal efficiency for 125 mg·L^-1 of the CQ solution under EB treatment is reported to be >80% at neutral pH at a maximum irradiation dose of 7 kGy. Removal efficiency is further favored by acidic and slightly alkaline conditions where reactions with hydroxyl radicals and hydrated electrons are favored, respectively. Additionally, increments in the applied dose resulted in the increased removal efficiency for the same concentration of CQ. Conversely, the removal efficiency decreased with increasing concentration of CQ at the same irradiation dose. The initial solution pH, applied irradiation dose, and initial pollutant concentration play an important role in the EB-induced degradation of CQ by influencing the available oxidizing and reducing species. The chemical oxygen demand (COD) and total organic carbon (TOC) were not significantly decreased during the treatment process and indicated the formation of organic byproducts, which were not further degraded under the current experimental conditions.