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

Abstract

• OA favors DEP degradation in VO 2 activation of H 2 O 2 . • The mechanism of OA promoting pollutant degradation was studied. • DEP could be degraded over a wide pH range in VO 2 /H 2 O 2 /OA system. 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 VO 2 -Fenton-like reactions. The results showed that 92% of DEP was degraded in VO 2 /H 2 O 2 /OA system while only 3% and 37% of DEP was degraded with H 2 O 2 and VO 2 /H 2 O 2 respectively, demonstrating that the addition of OA can significantly promote the degradation of DEP in VO 2 /H 2 O 2 system. Electron paramagnetic resonance analysis showed that OH was the dominant reactive species, which increased rapidly with the increase of OA concentration in the range of 0–2 mM. Increasing the VO 2 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 H 2 O 2 /V(IV) and H 2 O 2 /V 2 O 5 systems. This study provides a novel strategy to enhance Fenton-like reactions for pollutant degradation and environmental remediation.