Simultaneous removal of pyridine and denitrification in an integrated bioelectro-photocatalytic system utilizing N-doped graphene/α-Fe2O3 modified photoanode

In order to realize simultaneous removal of pyridine and denitrification, an integrated bioelectrophotocatalytic system (IBPS) equipped with N-doped graphene/alpha-Fe2O3 modified graphite felt (GF) photoanode and GF biocathode was constructed and operated in ON-OFF illumination mode. Compared to alpha-Fe2O3 modified GF electrode, N-doped graphene/alpha-Fe2O3 modified photoanode showed superior stability, photo-electrochemical and catalytic activity owing to the excellent electron transporting properties of N-doped graphene and unique structure of N-doped graphene/alpha-Fe2O3 composite. In IBPS, ammonia produced from pyridine photocatalytic degradation diffused from anode to biocathode through the cation-exchange membrane. Simultaneous nitrification and denitrification were realized in the biocathode chamber under limited dissolved oxygen. At the same time, the harvested photo-electrons derived from photoanode were delivered to the biocathode via an external circuit for enhanced denitrification. Complete removal of pyridine and high TOC removal efficiency of 85.90 +/- 5.48% in the anode and complete denitrification in the biocathode after four ON-OFF cycles (96 h) reaction were achieved. Furthermore, the underlying mechanism for the enhanced removal of pyridine and denitrification was proposed preliminarily. This integrated reactor synergically utilized photoenergy, electrical energy and bioenergy for removal of pyridine and denitrification, showing a promising future in designing new systems for water environmental remediation from solar energy. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

An integrated bioelectrophotocatalytic system was developed for simultaneous removal of pyridine and denitrification. The system showed excellent stability, photo-electrochemical and catalytic activity, achieving complete removal of pyridine and high TOC removal efficiency. Simultaneous nitrification and denitrification were realized through ammonia diffusion and external circuit for enhanced denitrification.