The magnetic biochar derived from banana peels as a persulfate activator for organic contaminants degradation

The magnetic biochar (γ-Fe2O3@BC) derived from banana peels was synthesized by a facile one-pot thermal process and used as the cost-effective and recyclable persulfate (PS) activator for organic contaminants degradation. The results showed that the encapsulated iron oxide nanoparticles not only introduced the magnetism into biochar for easy separation, but also influenced the catalytic ability for PS activation. The γ-Fe2O3@BC was found to be highly effective for bisphenol A (BPA) degradation without pH adjustment. A complete removal of BPA was obtained within 20 min with an observed rate constant (kobs) of 0.1849 min−1, which was almost two times as large as that (0.0956 min−1) of pure biochar. Further, it exhibited high mineralization efficiency for the degradation of various organic contaminants. The high catalytic activity could be attributed to large BET surface area, dispersed iron species, abundant oxygen functional groups and rich doped nitrogen. Radical quenching experiments and electron spin resonance (ESR) studies confirmed that OH, SO4− and O2− were all involved in the radical oxidation process which was responsible for BPA degradation. A mechanism of PS activation by the γ-Fe2O3@BC catalyst was proposed based on the synergistic effect of biochar and iron.