Improved azo dye decolorization in a modified sleeve-type bioelectrochemical system

•Azo dye was decolorizated in sleeve-type BES for the first time.•The compact structure configuration showed an almost complete decolorization.•EIS analysis demonstrated the decrease in internal resistance of sleeve-type BES.•Efficient azo dye decolorization was related to the modified configuration. Bioelectrochemical system (BES) that removes recalcitrant pollutant out of wastewater is of special interest for practice. This study modified the configuration of BES to be a sleeve-type with compact structure. Azo dye (acid orange 7, AO7) in the outer cathode chamber performed a complete decolorization by electrons supplied from acetate oxidized with electricigens in the inner anode chamber. The AO7 decolorization efficiency (DEAO7) was enhanced to be higher than 98% from 0.14 to 2.00mM. Electrochemical impedance spectroscopy (EIS) analysis showed that the internal resistance of anode, cathode and the whole cell was 26.4, 38.3, and 64.6Ω, respectively, indicating that the modified configuration with large area and small distance between anode and cathode can result in a lower internal resistance and higher decolorization performance. This is the first study for azo dye decolorization using sleeve-type configuration with highly efficient decolorization by abiotic cathode BES.