Optimizing Iron Dosage in Photo-Fenton Treatment of 2,6-Dichlorobenzoquinone for Sustainable Wastewater Remediation

Chlorinated benzoquinones, such as 2,6-dichlorobenzoquinone (DCBQ), are toxic disinfection byproducts of growing concern in aquatic environments. Advanced oxidation processes, particularly photo-Fenton treatment, provide sustainable alternatives for their degradation. However, optimization is required to ensure not only the removal of the parent compound but also the reduction in harmful intermediates. This study evaluated the degradation of DCBQ (1.0 mM H2O2, 150 W UV, pH 3.0, 25 °C) with ferrous ion between 0 and 1.0 mg/L. DCBQ removal followed a second-order kinetic model, reaching complete degradation. Aromaticity-loss and water color degradation adjusted to kinetics of second-order, reflecting the sequential reduction in chlorinated hydroquinones and chlorophenols type intermediates, with marked decreases after 120 min at 0.8 mg/L. Results showed that increasing iron dosage enhanced both the rate of DCBQ disappearance and the removal of aromaticity, with complete pollutant degradation. Importantly, optimal ferrous ion dosages (20 mol DCBQ: 70 mol H2O2: 1 mol Fe2+) effectively limited the persistence of intermediates, as evidenced by significant decreases in color and aromaticity, while avoiding excessive turbidity. These findings demonstrate that fine-tuning iron dosage in photo-Fenton systems can maximize contaminant elimination and minimize secondary byproducts, reinforcing their role as sustainable solutions for wastewater remediation.