Peanut-shell-derived biochar mediated peracetic acid activation for the elimination of acetaminophen via an electron-transfer regime

Biochar-based heterogeneous activation of disinfectant peracetic acid (PAA) is an attractive and promising route for micropollutant elimination in water, yet the underlying activation mechanism is still scarce. In this study, PAA was first catalyzed by peanut shell-derived biochar (PSBC) to degrade acetaminophen (ACP). The enhancement of ACP removal was triggered by PAA activation, while the coexisted H2O2 was unexpected to be an adverse factor owing to its occupation of active sites. Higher dosages of PSBC (0 ∼ 0.30 g/L) and PAA (0 ∼ 4.0 mM) favored the destruction of ACP, and the activation energy (41.8 kJ/mol) of PSBC/PAA system is lower than that of the thermal or microwave activated PAA system. The experimental results demonstrate that the metastable complex PSBC-PAA* dominated ACP elimination through an electron transfer mechanism. The surface –OH group was validated to be the key active site for PAA activation. Surprisingly, the actual water matrices present a negligible effect and the promotion of HCO3− ion on ACP removal was even observed. Based on the identified intermediates, the transformation of ACP was further proposed with the formation of polymeric products via oxidative coupling reactions. The findings not only shed light on the mechanism of PAA activated by the biochar-based catalyst but also contribute to a novel perspective on future PAA studies in contamination remediation.