Cerium-regulated Mg3FeO4@biochar activated persulfate to enhance degradation of aqueous tetracycline: The dominant role of cerium

Abstract

The role of cerium (Ce) in Ce-regulated Mg₃FeO₄@biochar (CMF@BC) and the mechanism by which CMF@BC activates persulfate (PS) remain unclear. In this work, a novel CMF@BC was synthesized through the simple impregnation–pyrolysis process and utilized as a PS activator for the removal of aqueous tetracycline (TC). Under the optimal degradation conditions, the removal efficiency and mineralization rate of TC reached 92.7 % and 84.2 % within 60 min, respectively, the corresponding rate constant was 0.0487 min⁻¹. The CMF@BC catalyst exhibited extremely high stability and excellent reusability after five cycles. The characterization results identified Fe²⁺ and oxygen vacancies as major catalytic sites. The Ce dopant inhibited the aggregation of metal ions of Mg₃FeO₄ during the high-temperature pyrolysis process and the Ce³⁺/Ce⁴⁺ redox cycle promoted Fe²⁺ regeneration, thus improving the catalyst performance. The degradation process was dominated by non-free radical (¹O₂) pathways. The possible TC-removal pathway was inferred from liquid chromatography–mass spectrometry results and density functional theory calculations. The toxicity of the degradation products was also evaluated. The CMF@BC catalyst displayed excellent catalytic performance and recyclability, wide pH adaptability, and a low ion-leaching rate, confirming its broad application prospects as a PS activator in antibiotic wastewater treatment.