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 SO42- 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, SO42- 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.