Efficient and synergistic decolourization and nitrate removal using a single-chamber with a coupled biocathode-photoanode system.

Abstract

With the continuous development of the chemical industries, synergistic removal of carbon and nitrogen contaminants has drawn much attention. In this work, a novel strategy for the synergistic removal of methyl orange (MO) and nitrate was developed in a single reactor by combining a TiO2/g-C3N4 nanosheet/graphene photoanode and denitrifying biofilm cathode. Under xenon light illumination, the photocatalytic MO decolorization rate exceeded 90% (the initial concentration of MO was as high as 100\xa0mg·L-1) with a biocathode potential bias of -0.5\xa0V vs Ag/AgCl; additionally, the decolourization rate apparently followed first-order kinetics with a constant of 0.11\xa0±\xa00.02\xa0h-1. The improved MO decolourization rate was mainly because the biocathode effectively enhanced the charge separation of the photogenerated charge at the TiO2/g-C3N4 nanosheet/graphene photoanode interface. In the meantime, the effluent nitrate was lower than 1\xa0mg·N·L-1 at a biocathode potential of -0.5\xa0V vs Ag/AgCl. The results indicated that the coupled biocathode-photoanode system could serve the purpose of simultaneously degrading MO and accomplishing nitrate reduction. Considering the sustainability of sunlight and the use of a biocathode, the coupled biocathode-photoanode system is a promising alternative for the simultaneous removal of biorefractory organics and nitrate.