Electro-enhanced heterogeneous activation of peroxymonosulfate via acceleration of Fe(III)/Fe(II) redox cycle on Fe-B catalyst

•Fe-B catalyst was fabricated for electro-assisted heterogeneous activation of PMS.•Electric field could accelerate the Fe(III)/Fe(II) redox cycle.•The direct anodic oxidation and surface-bound radicals were responsible for AO7 decay.•Effects of important operational conditions on the AO7 abatement were explored. Heterogeneous catalytic oxidation based on iron species for peroxymonosulfate (PMS) activation is considered as one of the most attractive strategies for wastewater treatment. However, the rate-limiting regeneration of Fe(II) from Fe(III) heavily hampers the efficient activation of PMS. In this study, the introduction of electric field to the Fe-supported bentonite (Fe-B) activated PMS process was proposed to enhance the Fe(III)/Fe(II) redox cycle. The Fe-B catalyst performed well in the removal of Acid Orange 7 (AO7) through the synergistic effect of electrolysis and the continuous redox cycle of Fe(III)/Fe(II) for PMS activation. The use of 0.5 g L−1 Fe-B catalyst and 10 mM PMS yielded nearly complete removal of the AO7 (50 mg L−1) in 60 min at 2 mA cm−2 of current density. Based on the results of electron paramagnetic resonance (EPR) spectroscopy, chemical quenching tests, X-ray photoelectron spectroscopy (XPS) analysis, and electrochemical measurements, the decolorization of AO7 was dominantly attributed to surface-bound radicals (SO4•−ads and •OHads) and also the direct electron transfer at DSA anode. Moreover, the electro/Fe-B/PMS system showed an effective pH range from 2.6 to 9.0 and the abatement of AO7 was slightly affected in the presence of natural background anions. This work provides a feasible strategy of PMS activation by cost-effective Fe-B catalyst coupling with electric field and gives an insight into the accelerated oxidation of recalcitrant pollutants. [Display omitted]