Redox mediator as cathode modifier for enhanced degradation of azo dye in a sequential dual chamber microbial fuel cell-aerobic treatment process

The electron transfer from cathode to azo dye Acid Blue 29 (AB29) using thionine (TH) and anthraquinone-2-sulfonate (AQS) redox mediators were investigated in dual chamber microbial fuel cells (DCMFCs). More than 90% of color was removed using electropolymerized TH (192 h) and AQS (264 h) cathodes. Chemical oxygen demand (COD) removal after anaerobic treatment in cathode chamber of TH-MFC, AQS-MFC and unmodified-MFC were 76.6 ± 1.7, 70.8 ± 2.5 and 18.3 ± 2.9%, respectively, which increased to 85.4 ± 1.5, 79.8 ± 3 and 20.6 ± 2.1%, respectively, after aerobic post treatment. Gas chromatography–mass spectrometry (GC–MS) investigations revealed the formation of aromatic amines in DCMFCs which were further degraded into low molecular-weight products in the aerobic post treatment. Electrochemical impedance spectroscopic (EIS) analysis showed lowest charge transfer resistance of TH-cathode which increased the electrochemical reactions and electron transfer rates. These results indicated that AB29 can be efficiently degraded by utilizing modified cathode based DCMFC-aerobic post treatment process along with bioelectricity generation.