Electrochemical enhanced heterogenous activation of peroxymonosulfate using CuFe2O4 particle electrodes for the degradation of diclofenac

CuFe2O4 (CFO) nanoparticles have been used to induce peroxymonosulfate (PMS) for degrading contaminants, while the slow reduction from high valence metals to low valence metals on CFO surface limited its reaction activity. In our study, the introduction of electric field greatly enhanced the activation of PMS by CFO for the degradation of diclofenac (DCF). The removal efficiency and the electrical energy per order of the EC/PMS/CFO system reached 89.9% and 2.12 kWh m−3 order−1 respectively within 60 min under optimal conditions of 0.3 g/L CFO, 2 mM PMS, 8 mA/cm2 current density and initial pH of 6. Electron spin resonance analysis and quenching experiments including ethanol, tertbutyl alcohol, furfuryl alcohol and p-benzoquinone proved that SO4•−, •OH and 1O2 were the main reactive oxygen species in the EC/PMS/CFO system. The cyclic voltammetry test and the X-ray photoelectron spectroscopy demonstrated that both PMS and electric field accelerated the cycles of Fe(III)/Fe(II) and Cu(II)/Cu(I), promoting the generation of reactive oxygen species. Except for the inhibition effect of humic acid and HPO4−, NO3− had no impact on the degradation of DCF, while HCO3− and Cl− accelerated the degradation of DCF in the EC/PMS/CFO system. Furthermore, >90% of DCF in tap water and Houhu lake water was degraded by the EC/PMS/CFO system. The reusability experiment verified that CFO was stable, and the leaching concentrations of copper and iron in each run were less than the legal limits of the U.S. Environmental Protection Agency. This work might provide a feasible strategy for enhancing PMS activation through coupling transition metals with an electric field.