Oxygen vacancies-enriched Fe-Cu bimetallic minerals-based magnetic biochar activated peroxydisulfate for durable sulfonamides degradation: pH-dependence adsorption and singlet oxygen evolution mechanism

The construction of oxygen vacancies (Vo) is a promising strategy for designing an efficient catalyst toward peroxydisulfate (PDS) activation. However, the unstable interface electron transfer and deactivation of Vo have been the bottleneck, and Vo-mediated PDS activation mechanisms remain vaguely interpreted. Herein, we innovatively synthesized a low-cost and durable Fe-Cu bimetallic mineral-based magnetic biochar with abundant Vo (Fe-CuFe 2 O 4 @BC). Fe-CuFe 2 O 4 @BC exhibited 6.64, 22.91, and 79.22-fold PDS activation rates for sulfamethazine (SMT) degradation (100%) and mineralization (91.58%) compared with [email protected] , [email protected] , and pristine BC, respectively. The outstanding performance of the Fe-CuFe 2 O 4 @BC/PDS system was ascribed to the Vo-induced sustainable electron transfer and singlet oxygen ( 1 O 2 ) generation, determined by chemical probes and kinetics study. pH-dependence adsorption of SMT dominated by the strengthened H-bonding and π–π EDA interaction was the key rate-limited step to PDS activation. Based on the surface investigation, electronic measurement, and Density functional theory (DFT) calculations, we proposed new insights into the electron-rich Vo and electron-deficient Cu co-induced PDS activation mechanism. Different from conventional perspectives, Vo preferentially activated PDS to generate 1 O 2 , subsequently delocalizing and accumulating residual electrons from the Cu site. Simultaneously, metastable copper intermediates activated PDS through thermodynamically feasible reactions, promoting nano-confinement Vo-triggered 1 O 2 pathway. This study provides a new perspective for synthesizing Vo-rich catalysts and essentially deepens insights into nonradical mechanisms of refractory organics.