Influence of Reactive Chemical Ions on the Solar-Induced Oxidative Degradation of Chlorophenols in Water

Abstract

Chlorophenolic compounds are persistent pollutants in aquatic systems due to their strong resistance to natural biodegradation, high toxicity, and potential to generate harmful byproducts. Among them, chlorophenol and dichlorophenol are considered priority contaminants in industrial wastewater. This study examined their degradation under solar light, both individually and as a binary mixture, in the presence of iron ions and photocatalyst TiO₂ as well as small quantity of cupper ions. The results showed that iron significantly enhanced degradation compared to direct solar irradiation alone. Under sunlight, Ferric was rapidly reduced to ferrous, maintaining the catalytic cycle and facilitating continuous production of reactive oxygen species (ROS). Several intermediates, including phenol, and 2-chlorocatechol, were identified, along with small amounts of benzoquinone in later stages. The maximum degradation efficiencies of 95% (chlorophenol) and 87% (dichlorophenol) using ferrous ions within 120 minutes were achieved.  These findings highlight the progressive dechlorination pathways and the central role of ferrous in sustaining activity. Overall, the study demonstrates the promise of iron-assisted solar photocatalysis as an efficient and low-cost strategy for treating water contaminated with chlorophenols.