Comparative anaerobic decolorization of AZO dyes by carbon-based membrane bioreactor

Abstract

This study used a novel integrated technology of ceramic supported carbon membrane(CSCM) to degrade azo dyes through an anaerobic mixed culture. The CSCM worked simultaneouslyas biofilm support, redox mediator, and nano-filter to enhance the dye decolorization efficiency. Thedecolorization of Acid Orange 7 (AO7) was initially investigated with and without microorganismsin both ceramic support (CS) and CSCM reactors. The CSCM bioreactor (B-CSCM), operated withmicroorganisms, gave a maximum decolorization of 98% using a CSCM evolved from 10% weight(wt.) of Matrimid 5218 solution. To know the influence of permeate flow, feed concentration, anddye structure on the decolorization process, different B-CSCMs for dye removal experiments werestudied over monoazo AO7, diazo Reactive Black 5 (RB5), and triazo Direct Blue 71 (DB71). Thehighest color removal, operated with 50 mg·L-1feed solution and 0.05 L·m-2·h-1of permeate flux,was 98%, 82%, and 72%, respectively, for AO7, RB5, and DB71. By increasing these parameters to100 mg·L-1and 0.1 L·m-2·h-1, the decolorization rate of dye solution still achieved 37% for AO7,30% for RB5, and 26% for DB71. In addition, the system was run for weeks without apparent loss ofactivity. These findings make evident that the combined phenomena taking place in CSCM bioreactorresult in an efficient, cost-effective, and ecofriendly azo dye decolorization method.