Optimization of working cathode position in sleeve-type bioelectrochemical system with inner chamber/outer chamber for azo dye treatment

• Working position in sleeve-type BES was evaluated and optimized for decolorization.
• Cathode in outer chamber performed better both at Vcathode:Vanode = 1:1 and 3:1.
• Current and EIS analysis showed outer cathode benefited proton/electron transfer.
• Lower decolorization with increased Vcathode might be due to less substrate supply.
• It would be further improved through increasing substrate concentration at anode.

In this study, the optimization of working cathode position in sleeve-type bioelectrochemical system (BES) was evaluated with inner/outer chamber for azo dye decolorization. Results showed that the working position in outer chamber performed better with decolorization efficiencies of 97.8 ± 2.1% (7 h) and 94.0 ± 2.3% (16 h) than that in inner chamber as the volume ratio Vcathode:Vanode = 1:1 and 3:1, respectively. The current and electrochemical impedance spectroscopy (EIS) analysis indicated that the proton/electron transfer and anolyte diffusion could be improved using outer chamber as working position. The decolorization with increased volume ratio could be further improved through the strategy of increasing substrate concentration, which would provide enough electrons and decrease diffusion resistance, further improving the whole performance with increased outer cathode volume. It has the great potential in sleeve-type configuration application and would create more challenges for process optimization and maintenance.