Coupling electrode aeration and hydroxylamine for the enhanced Electro-Fenton degradation of organic contaminant: Improving H2O2 generation, Fe3+/Fe2+ cycle and N2 selectivity

To improve H2O2 generation and Fe3+/Fe2+ cycle simultaneously for enhancing Electro-Fenton performance, the electrode aeration (EA) and hydroxylamine sulfate (HA) were coupled. With dimethyl phthalate (DMP) as main target contaminant, combination of HA and EA greatly accelerated the degradation of DMP and exhibited a synergy in the pH of 2.0-6.9 through promoting the key reactions, including electrochemical two-electron reduction of O-2 into H2O2 and redox cycles of Fe3+/Fe2+, which then improved the generation of hydroxyl radicals (.OH). The coupling EA and HA reduced the use of HA and converted most of HA into environment friendly N2 (60.1-62.1% of HA products), while HA/solution aeration(SA) system consumed HA rapidly and the generated N-2 only accounted for 5.8-6.7% of HA products. Furthermore, compared with HA/SA and EA Electro-Fenton systems, enhancement degree of DMP degradation in HA/EA Electro-Fenton process was higher in actual waterbody than in ultrapure water. The coupling EA and HA in the Electro-Fenton process could solve the low Fe3+/Fe2+ cycle efficiency and low H2O2 production simultaneously, and improve the N-2 selectivity of HA transformation, which advanced its application in practical environmental remediation.

Automated summary

In this study, the combination of electrode aeration (EA) and hydroxylamine sulfate (HA) was used to improve the generation of H2O2 and the efficiency of Fe3+/Fe2+ cycle, thereby enhancing the performance of Electro-Fenton process. The combination of HA and EA significantly accelerated the degradation of dimethyl phthalate (DMP) and exhibited a synergistic effect within a certain pH range. Furthermore, the coupling of EA and HA reduced the use of HA and improved the selectivity of N2 transformation.