UV-assisted electrochemical oxidation for saline wastewater treatment: Condition optimization and mechanism exploration

Saline wastewater, generated from various industrial processes, poses significant environmental challenges and leads to the waste of valuable saline resources if not properly treated. Traditional treatment methods often fail to achieve efficient removal of organic pollutants in saline wastewater. In this study, a UV-assisted electrochemical oxidation (UV/EO) process was employed to effectively degrade phenol in saline wastewater. The synergistic effects between UV irradiation and electrochemical oxidation (EO) on phenol degradation were systematically demonstrated. Mechanistic insights into the UV/EO process were provided through electron paramagnetic resonance (EPR) analysis and the determination of steady-state concentrations of reactive free radicals. Additionally, the phenol degradation intermediates were identified using gas chromatography–mass spectrometry (GC–MS) and high-performance liquid chromatography (HPLC). The degradation pathways of these intermediates in the UV/EO system were further investigated through free radical inhibition assays. The results revealed that the UV/EO process exhibited a significant synergistic effect, primarily due to the enhanced generation of hydroxyl radicals (OH·) under UV irradiation. Furthermore, the performance of the UV/EO system was evaluated using real saline industrial wastewater containing complex and refractory organic pollutants. Under optimal conditions, the UV/EO system achieved a TOC removal rate of 68.9 %, which was 12.3 % higher than the 56.5 % achieved by the EO process alone. This study provides a deeper understanding of the mechanisms underpinning the UV/EO process and highlights its potential for practical applications in treating saline organic wastewater.