Mechanism of significant enhancement of VO2-Fenton-like reactions by oxalic acid for diethyl phthalate degradation

It has been reported that the addition of reducing agents such as ascorbic acid and hydroxylamine to Fenton or Fenton-like systems can accelerate the circulation of Fe(III)/Fe(II), thereby accelerating the degradation of pollutants. However, few studies investigated the effect of reducing agents on pollutant degradation by heterogeneous Fenton-like reactions using other transition metals (e.g. vanadium (V) oxides) as activator. In this study, we investigated the effect of oxalic acid (OA), an inexpensive and environmentally-friendly reducing agent, on diethyl phthalate (DEP) degradation by VO2-Fenton-like reactions. The results showed that 92% of DEP was degraded in VO2/H2O2/OA system while only 3% and 37% of DEP was degraded with H2O2 and VO2/H2O2 respectively, demonstrating that the addition of OA can significantly promote the degradation of DEP in VO2/H2O2 system. Electron paramagnetic resonance analysis showed that center dot OH was the dominant reactive species, which increased rapidly with the increase of OA concentration in the range of 0-2 mM. Increasing the VO2 dosage (0.1-1.0 g L-1) and OA concentration (0.05-2.0 mM) could increase the degradation rate of DEP while the increase of OA concentration was more effective in promoting DEP degradation. Moreover, in the presence of OA, DEP could be efficiently degraded over a wide pH range (pH 3-11), and OA was also found capable of promoting DEP degradation in H2O2/V(IV) and H2O2/V2O5 systems. This study provides a novel strategy to enhance Fenton-like reactions for pollutant degradation and environmental remediation.

Automated summary

This study demonstrates that the addition of oxalic acid can significantly enhance the degradation efficiency of DEP in VO2-Fenton-like reactions, promoting the formation of reactive species such as center ·OH and thus facilitating pollutant degradation. Addition of reducing agents plays a crucial role in enhancing Fenton-like reactions for pollutant degradation and environmental remediation.