The controversial role of ascorbic acid in boosting the performance of heterogeneous Fenton-like catalysts for wastewater treatment: the case study of Fe2V4O13

Abstract

In our work, Fe₂V₄O₁₃ was synthesized using a hydrothermal method and characterized using XRD, SEM-EDX, and XPS. The use of Fe₂V₄O₁₃ in advanced oxidation processes (AOPs) via persulfate activation was investigated for the first time. To enhance the performance of the novel heterogeneous Fenton catalyst for sulfamethoxazole (SMX) degradation, ascorbic acid (AA) was employed since it is commonly used to sustain the redox cycle of metal ions. Under UVA irradiation, 55% SMX degradation was observed after 180 min which was significantly better than that of the system without AA. Scavenging experiments and EPR spectroscopy revealed that hydroxyl radicals were the predominant reactive species (RS). However, leaching experiments suggested that the RS generation in AA-assisted systems was predominantly governed by homogeneous Fenton reactions, including iron and vanadium, rather than the heterogeneous catalysis. The findings highlight the fundamental drawbacks of AA-driven strategies in Fenton-based AOPs. Interestingly, EPR spectroscopy confirmed the formation of ascorbyl radicals, thus supporting the drawbacks of using AA. Although rapid degradation was achieved, catalyst instability and inefficiency upon reuse undermine the applicability of such systems for real-world wastewater treatment. This work provides a critical insight into the mechanism emphasizing the necessity of balanced evaluation of AA-enhanced Fenton systems for wastewater treatment.