Enhanced biodecolorization of azo dyes by electropolymerization-immobilized redox mediator

The biodecolorization rate of azo dyes can be improved by the addition of some soluble quinoid redox mediators, but continuous dosing and discharge of these mediators will result in the secondary contamination due to their recalcitrant trait. In this study, the effect of anthraquinone-2,6-disulfonate (AQDS) bound into polypyrrole (PPy) on activated carbon felt (ACF) on anaerobic biodecolorization of azo dyes was investigated and compared with that immobilized on platinum (Pt). The results showed that in the presence of AQDS/PPy/ACF, the biodecolorization efficiency of azo dye RR15 reached over 80% at the optimal pH 7 in 8 h and kept stable during successive 10 times repeated experiments. In contrast, in the presence of AQDS/PPy/Pt biodecolorization efficiency of RR15 was less than 60% under the above conditions, and the PPy doped by AQDS desquamated from the substrate material Pt at the third biodecolorization experiment. In addition, in the presence of AQDS/PPy/ACF biodecolorization efficiencies of 5 reactive dyes, 4 acid dyes and 2 direct dyes increased more than 3-fold than that without AQDS. This indicates that electropolymerization-immobilized AQDS (AQDS/PPy/ACF) has potential applications in accelerating the anaerobic biodecolorization of azo dyes.