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

Abstract

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 theexcellent performance of FeOx@GC-NBC to the following attributes: i) a microporous carbon matrix with larger specific surface area (1691.81 m2·g−1) was favorable for adsorption, exposure of catalyst active sites (e.g., Fe-Nx, 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 π-π interaction” mechanism effectively promoted BPA oxidation. In acidic and neutral solutions, the radical oxidation (SO4•–and •OH) processes were responsible for BPA decomposition. In alkaline solution, electron transfer, instead of 1O2 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.