N-doped coal-based carbon membrane coupling peroxymonosulfate activation for bisphenol A degradation: The role of micro-carbon structure and nitrogen species

Herein, a novel N-doped coal-based carbon membrane (N-CCM) was prepared by using melamine as N source with high-temperature pyrolysis assistance. Through reasonable regulation of membrane micro-carbon structure and N species by varying pyrolysis temperature, the N-CCM integrated with peroxymonosulfate (PMS) activation under membrane filtration (MFPA) process showed excellent bisphenol A (BPA) removal of 98.3%. The excellent performance of N-CCM MFPA process was mainly owing to the following reason: For one thing, the more orderly micro-carbon structure of N-CCM possessed high defect density and boundary active sites under suitable pyrolysis temperature (700 °C), contributing to PMS activation (enhanced generation of reactive oxygen species (ROS) and electron transfer). For another, pyrrolic N, pyridinic N and C=C were beneficial to PMS adsorption and facilitate the electrons transfer from BPA to PMS. While C–O and graphitic N were responsible for the generation of ROS (SO4•−, •OH and 1O2). Theoretical calculations showed that the bond length of O–O, O–H and O–S in PMS adsorbed on C atom near N sites was significantly lengthened, corresponding to the generated ROS. Overall, the co-effect of radical process (SO4•− and •OH) and non-radical process (1O2 and electron transfer) achieved efficient BPA degradation in system.