Catalytically active nitrogen-doped porous carbon derived from biowastes for organics removal via peroxymonosulfate activation

In this study, N-doped porous carbons (N-doped PCs) were prepared from various biowastes by thermal annealing method under inert atmosphere and compared. Due to the differences in the textural characteristics and % w/w inorganic content, the choice of biowaste influenced the intrinsic (extent of N doping, % graphitic N) and extrinsic (specific surface area) properties of the resultant N-doped PC. The N-doped PCs were employed to activate peroxymonosulfate (PMS) for bisphenol A (BPA) removal. It was found that the N-doped PCs prepared from spent coffee ground (PC-SC) and saw dust, with higher at.% graphitic N (44-46 at.%) and specific surface area (> 400m(2) g(-1)), performed significantly better (apparent rate constant, k(app)= 0.072-0.087 min(-1)) than those prepared from banana peel, orange peel and dried leaves (k(app) < 0.046 min(-1)). The PC-SC was selected to investigate the effects of catalyst loading and PMS dosage on BPA degradation, and the results indicated that increasing the catalyst loading is 1.5 times more beneficial than increasing the PMS dosage. The reactive oxygen species (ROS) was studied using chemical scavengers and electron paramagnetic resonance spectrometer which indicated that the O-1(2) (induced from the interaction between the PC-SC and PMS) was the dominant ROS in the PC-SC/PMS system. The BPA degradation intermediates were also identified using the LC/MS/MS system and the possible BPA degradation pathways are proposed. This study conspicuously shows that biowastes can be used as a sustainable resource to produce PC for application in environmental redox catalysis. However, the right selection of biowaste is crucial to produce high-performance PC for PMS activation.