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 effi ciency 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 effi ciency 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
effi ciency for the same concentration of CQ. Conversely, the removal effi ciency 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 infl uencing the available
oxidizing and reducing species. The chemical oxygen demand (COD) and total organic carbon (TOC) were not
signifi cantly decreased during the treatment process and indicated the formation of organic byproducts, which
were not further degraded under the current experimental conditions.