Chloroquine degradation under Fenton-assisted electron beam irradiation in aqueous solution

The removal of pharmaceuticals in the wastewater has been a tough problem. Herein, the Fenton-assisted electron beam radiation was employed to remove chloroquine (CQ) in aqueous solution. The results showed that electron beam removed 63% CQ at 1.5 kGy with •OH, e_aq⁻, and H• contributing to its degradation. Additionally, the presence of CO₃^2-, HCO₃^-, NO₃^-, Fe²⁺, and humic acid decreased the degradation efficiency. Furthermore, the presence of S₂O₈^2- improved efficiency due to the generation of SO₄^•⁻ in addition to •OH. The solely Fenton process removed 57% CQ with 2 mM H₂O₂ and 0.4 mM Fe(II) after 3 h. In comparison, the Fenton-assisted electron beam process effectively increased the removal efficiency of CQ up to 89%, utilizing less amounts of H₂O₂ and Fe²⁺ compared to the pure Fenton process. The molar ratio of the Fenton reagents influenced the efficiency of the Fenton process and the Fenton-assisted electron beam process. The low mineralization of CQ based on TOC and COD measurement was attributed to the formation of lower molecular weight organic compounds that degraded slowly. However, TOC and COD reduction in addition to dechlorination and nitrification under the Fenton-assisted electron beam process were higher, compared to the electron beam process. The degradation byproducts of CQ were identified, and the degradation mechanism was proposed. The degradation products were evaluated and determined to be less toxicity, compared to parent CQ molecule. Overall, the degradation of CQ was higher in the Fenton-assisted electron beam process with better mineralization, dechlorination, and nitrification at comparatively lower absorbed doses, compared to electron beam process and using a lower concentration of Fe²⁺ compared to the Fenton process.