Enhanced nitrobenzene biotransformation by graphene‐anaerobic sludge composite

BACKGROUND Traditional anaerobic bioprocesses have failed to achieve the efficient biotransformation of nitrobenzene. Thus, graphene‐anaerobic sludge composite as a novel biocatalyst was proposed for the enhancement of nitrobenzene biotransformation . RESULTS Reduced graphene oxide/anaerobic sludge ( RGO / AS ) composite presented good settling performance when graphene oxide ( GO ) was added into an AS system for 24 h cultivation. The presence of RGO resulted in enhanced nitrobenzene biotransformation by AS , and the highest removal efficiency of nitrobenzene was observed with initial GO (3–5 µm) vs sludge ratio of 0.075 (w/w). Dehydrogenase activity in the RGO / AS system increased approximately 2‐fold over that in the AS system and redox active species appeared in supernatant from the RGO / AS system. The ratio of acetate to propionate increased in the RGO / AS system during glucose fermentation, and nitrobenzene biotransformation by both AS and RGO / AS systems was independent of methanogenesis, but dependent on acetogenesis. Moreover, bound and free extracellular polymeric substances ( EPS ) from RGO / AS composite were involved in direct biotransformation of nitrobenzene, and bound EPS might interact with secreted redox active species to accelerate nitrobenzene biotransformation by extracellular electron transfer . CONCLUSION RGO / AS composite was efficient for the treatment of nitrobenzene wastewater. © 2013 Society of Chemical Industry