Highlights Hydroxychloroquine (HCQ) has the potential to be a persistent pollutant in water. Electrochemical oxidation with BDD anode (EO) degraded HCQ in all tested conditions. EO led to the release of Cl − ions and conversion of organic nitrogen to NO 3 − and NH 4 +. EO combined with UV light or ultrasound enhanced degradation kinetics and efficiency. Due to higher production of oxidants, EO combined with UV light used much less energy.

In this work, the degradation of chloroquine (CLQ), an antiviral and antimalarial drug, using electro-Fenton oxidation was investigated. Due to the importance of hydrogen peroxide (H 2 O 2 ) generation during electro-Fenton oxidation, effects of pH, current density, molecular oxygen (O 2 ) flow rate, and anode material on H 2 O 2 generation were evaluated. H 2 O 2 generation was enhanced by increasing the current density up to 60 mA/cm 2 and the O 2 flow rate up to 80 mL/min at pH 3.0 and using carbon felt cathode and boron-doped diamond (BDD) anode. Electro-Fenton-BDD oxidation achieved the total CLQ depletion and 92% total organic carbon (TOC) removal. Electro-Fenton-BDD oxidation was more effective than electro-Fenton-Pt and anodic oxidation using Pt and BDD anodes. The efficiency of CLQ depletion by electro-Fenton-BDD oxidation raises by increasing the current density and Fe 2+ dose; however it drops with the increase of pH and CLQ concentration. CLQ depletion follows a pseudo-first order kinetics in all the experiments. The identification of CLQ degradation intermediates by chromatography methods confirms the formation of 7-chloro-4-quinolinamine, oxamic, and oxalic acids. Quantitative amounts of chlorides, nitrates, and ammonium ions are released during electro-Fenton oxidation of CLQ. The high efficiency of electro-Fenton oxidation derives from the generation of hydroxyl radicals from the catalytic decomposition of H 2 O 2 by Fe 2+ in solution, and the electrogeneration of hydroxyl and sulfates radicals and other strong oxidants (persulfates) from the oxidation of the electrolyte at the surface BDD anode. Electro-Fenton oxidation has the potential to be an alternative method for treating wastewaters contaminated with CLQ and its derivatives.