Synergistic effect for efficient oxidization of refractory organics with high chroma by an innovative persulfate assisted microbial electrolysis ultraviolet cell

UV based advanced oxidation processes including the newly developed microbial electrolysis ultraviolet cell (MEUC) are easy to operate, but always exhibit an ineffective treatment of wastewater with high chroma due to the low UV transmittance. Herein, an innovative persulfate-assisted MEUC process (MEUPS) was developed to treat such wastewaters. The MEUPS can achieve complete decolorization of the selected model compound (40 mg L⁻¹ of methylene blue, MB) within 140 min and a mineralization degree of 97% within 5 h under optimal operating conditions. The hybrid MEUPS process showed a much better treatment performance than that of the individual process and the synergy factor was quantified as 6.42. ^•SO₄⁻, ^•OH, and ^•O₂⁻ were proved to be the major reactive radicals involved in MB degradation, and the degree of contribution was ranked as ^•SO₄⁻, ^•OH, and ^•O₂⁻. Correspondingly, the working mechanism of the MEUPS process was inferred, in which the boosted above listed major reactive radicals can be attributed to the catalytic effect of bioelectrons and UV irradiation, thus the synergistic effect on the efficient treatment of MB-contaminated wastewater. Additionally, the treated effluent exhibited non-toxic by using aquatic plant Lemna minor as an indicator. This research provides a new perspective for the efficient and cost-effective treatment of industrial wastewater with high chroma and refractory organics over a broad pH range together with catalyst-free conditions by using PS-assisted microbial photoelectrochemical technologies.