FeOx@graphitic carbon core-shell embedded in microporous N-doped biochar activated peroxydisulfate for removal of Bisphenol A: Multiple active sites induced non-radical/radical mechanism

The development of novel carbocatalysts with high activity and stability is important for the rapid degradation of emerging pollutants. Fe/N co-doped biochar (FeOx@GC-NBC) was innovatively synthesized with a pyrolytic carbonization method and then used as a functional peroxydisulfate (PDS) activator to degrade Bisphenol A (BPA). FeOx@GC-NBC with an optimized Fe/N ratio modification exhibited 23.16 and 8.65-fold great activity for BPA removal compared to pristine BC and N-doped BC, respectively. Approximately 93% of total organic carbon (TOC) could be removed in the heterogeneous activation system. We attributed the excellent performance of FeOx@GC-NBC to the following attributes: i) a microporous carbon matrix with larger specific surface area (1691.81 m(2).g(- 1)) was favorable for adsorption, exposure of catalyst active sites (e.g., Fe-N-x, Graphitic N) and electron transfer; ii) the C-O-Fe bond and highly core-shell structure of graphitic nanosheets (FeOx@GC) enhanced the N retention ability and durability of the catalyst; iii) organics adsorption dominated by a pore filling and 7C-7C interaction mechanism effectively promoted BPA oxidation. In acidic and neutral solutions, the radical oxidation (SO4 center dot and (OH)-O-center dot) processes were responsible for BPA decomposition. In alkaline solution, electron transfer, instead of O-1(2) or a high-valent iron species, was the dominant pathway. This study proposes a simple and feasible strategy to synthesize the FeOx@GC-NBC catalyst, which provides insights into catalyst design and the internal active sites involved in the purification mechanism of refractory organics.

Automated summary

The development of novel carbocatalysts is crucial for the degradation of emerging pollutants. In this study, FeOx@GC-NBC was synthesized and used as a functional activator to enhance the degradation of Bisphenol A. The optimized Fe/N ratio modification significantly improved the activity of FeOx@GC-NBC, and the catalyst showed excellent adsorption and oxidation abilities. This study provides insights into catalyst design and the purification mechanism of refractory organics.