Pomelo peel biochar supported nZVI@Bi0 as a persulfate activator for the degradation of acetaminophen: Enhanced performance and degradation mechanism

Due to the contradiction between superior reaction kinetics and imperfect reproducibility of nanoscale zero-valent iron (nZVI) in persulfate oxidation systems, how to improve the reusability of nZVI while highly guaranteeing efficiency is an important but challenging matter. Hence, we took a hydrothermal-assisted carbon reduction to synthesize nZVI encapsulated with Bi being loaded on pomelo peel biochar (nZVI@Bi0/PPBC), and the results indicated that the presence of Bi could improve the reproducibility of nZVI and facilitate the removal of acetaminophen (ACE) in the persulfate (PDS) system. The degradation rate constant of the nZVI@Bi0/PPBC800 composite for ACE was approximately 1.5 times higher than that of the nZVI/PPBC800. nZVI exhibited synergistic effects with Bi on PDS activation through electron transfer. Interestingly, the Bi(0) became increasingly pure as the pyrolysis temperature increased, and the catalytic performance of ZVI@Bi0/PPBC became better. In addition, electron spin resonance and quenching experiments revealed that 1O2 and O2·− were the predominant reactive oxygen species in nZVI@Bi0/PPBC/PDS system. The nZVI@Bi0/PPBC/PDS system showed excellent oxidation ability across a broad pH range (3.0–9.0) and resisted interference from certain anions. This work reveals the possible role of Bi(0) in nZVI based PDS system, and provides an idea for the protection of nZVI.