Two membrane-less baffled microbial fuel cells (BMFCs) were developed for non-dye (BMFC1) and dye degradation (BMFC2) investigations along with simultaneous bioelectricity generation. The influence of salinity, organic loading, circuit connection, aeration rate, dye concentration and addition of intermediates on BMFCs performances were evaluated systematically. The increase of salinity by 3-fold (0.39 g/L of NaCl) lowered the internal resistance of BMFC1 system by 38%–620 Ω, and the power density increased 49% to 10.55 ± 0.86 mW/m2. While the further increase of salinity (10-fold) adversely affected BMFC1. The power performance of BMFC1 improved with higher organic loading. Whereas, the increment in organic loading enhanced the decolourisation efficiency but deteriorated the power performance of BMFC2 ascribed to the competition between New Coccine (NC) molecules and anode for electrons. This finding corroborates that NC was a preferable electron acceptor than the anode. The addition of 50 mg/L NC increased the power density by 53% to 12.40 ± 1.60 mW/m2, which revealed that NC decolourised intermediates could act as the electron mediator, hence led to the increase of power performance. The electron-mediating mechanism of NC decolourised intermediate, 1-amino-2-naphthol-6,8-disulfonate as electron shuttle was unveiled. The in-depth understanding of the mechanisms involved in dye degradation in MFCs was presented, where a comprehensive degradation pathway of NC was proposed based on the intermediates identified via UV–Visible spectra, Fourier-transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC) and gas chromatograph-mass spectrometer (GC-MS) analyses.
