Synergy between MgFe2O4 and biochar derived from banana pseudo-stem promotes persulfate activation for efficient tetracycline degradation

Exploiting environment-friendly and cost-effective catalysts and understanding their catalytic mechanisms are a great challenge in persulfate-based advanced oxidation processes (PS–AOPs). Herein, a simple sol–gel pyrolysis procedure was employed to generate a novel magnesium ferrite/biochar (MgFe2O4/BC), exhibiting excellent degradation abilities to tetracycline (TC) (94.70% within 90 min). Characterization results demonstrated that biochar (BC) increased the dispersibility, surface area, and electronic transfer capability of MgFe2O4. Compared with the single MgFe2O4 and BC, the TC degradation efficiency of the novel MgFe2O4/BC was significantly improved by 78.49% and 45.97%, which ascribed to the synergies causing the composite possessed large specific surface area and exposing more active sites. The quenching test and electron spin resonance revealed the dominance of 1O2 and O2•− among the identified reactive oxygen species. Oxygen vacancy and carbonyl were identified as the main active sites. A possible TC degradation pathway has been proposed, and reduced toxicity of intermediates was observed. This study provides a new perspective on understanding the persulfate activation mechanism by spinel-biochar composites.