A novel bioelectrode and anaerobic sludge coupled system for p-ClNB degradation by magnetite nanoparticles addition

A novel laboratory-scale bioelectrode and anaerobic sludge coupled system was established for the enhancement of p-chloronitrobenzenes (p-ClNB) reductive transformation with addition of magnetite nanoparticles. In this coupled system, the bioelectrodes were supplied with a voltage of 0.8 V and the amount of magnetite nanoparticles was set at 7.4 mL/400 mL. Results showed that high p-ClNB transformation rate of 0.284 h^-1 and high p-chloroaniline (p-ClAn) dechlorination rate of 0.082 h^-1 were achieved in the coupled system at p-ClNB initial concentration of 30 mg L^-1, and p-ClAn is one of the reductive products of p-ClNB. The cyclic voltammetry curve showed that when the potential was -1000 mV, the magnetite-biocathode current was about 10.7 times of the abiotic cathode. Also, a shift in the reductive peak potential and a dramatic increase in reductive peak current were observed. These findings suggest that magnetite nanoparticles could enhance the electrocatalytic activity and may act as electron conduits between microorganisms or between electrodes and microorganisms to promote the extracellular electron transfer.