Advanced oxidation coupled with bioelectrocatalysis toward enhanced toluene removal

Bioelectrocatalysis is a promising strategy for treating wastewater containing benzene derivatives. However, high power consumption, uncertain microbial evolution, and potential free-radical damage limit its application. In this work, a carbon felt (CF) modified with sulfurized Fe species (referred to as "S-ZVI@CF") was developed as an anode for toluene removal. The toluene removal efficiency (RE) of the S-ZVI(4.9)@CF anode exceeded 90% at pH 4-8 when the SO₄^2- concentrations were 1.8-4.5 mg L^-1 and the toluene concentrations were 44-220 mg L^-1. The biodegradation of toluene and its intermediates resulted from the enrichment of the special functional genus Acinetobacter. However, an incomplete removal of toluene was observed when using the S-ZVI@CF anode with an Fe content of 4.9 mg cm^-2 at a toluene concentration of 308 mg L^-1, indicating that biodegradation was limited. Under the catalysis effect of Fe species and at a biovoltage of 0.6 V, SO₄^2- and H₂O in the mineral medium were converted into SO₄^•- and OH^•, respectively, which promoted the conversion of toluene into organic acids. After appropriately cleaning the generated biofilm and exposing more active Fe species, the total RE of toluene increased, reaching 92.6% at a toluene concentration of 308 mg L^-1. This article proposes a novel viewpoint about the application of advanced oxidation and bioelectrocatalysis for treating wastewater containing benzene derivatives.