Promoted degradation of tetracycline by FeNi alloys embedding in biochar activating peroxydisulfate: Performance and mechanism

Abstract

Bimetallic FeNi alloys embedding into biochar (FeNi-BC) catalysts with different Fe/Ni molar ratio were fabricated using rose petal as biomaterials. The as-fabricated FeNi-BC was employed to activate peroxydisulfate (PDS) toward tetracycline (TC) degradation. The effects of Fe/Ni atomic ratio on the structure feature of FeNi-BC and PDS activation efficiency were explored in detail. Results show that the optimum Fe0.8Ni0.2-BC prepared with Fe/Ni molar being 8:2 exhibited the best PDS activation efficiency toward TC degradation, with 97.01% of TC being removed in 15 min. Combining with the electron paramagnetic resonance (EPR), reactive oxygen species quenching, and electrochemical tests, the direct electron transfer (DET) and singlet oxygen accounted for TC degradation in the Fe0.8Ni0.2-BC activating PDS system. Because of that, the Fe0.8Ni0.2-BC had satisfactory resistance to inorganic anions and natural organic matters (NOMs). Based on the structure-activity relationship, it was found that more Fe0 and pyrrolic N formation in FeNi alloys than single Fe or Ni embedding in BC facilitated in more PDS adsorption, thus more PDS* complex formation on the surface of catalysts to boost the TC degradation through DET mechanism. Moreover, Fe0.8Ni0.2-BC possessed trace Fe and Ni leaching, satisfactory stability, and easy recycling via magnetic separation. This study not only offers new insights for discriminating the catalytic active sites of biochar embedded bimetallic alloys catalysts activating PDS but also developed cost-effective and environment friendly catalysts for high-efficiently remove antibiotics via PS-AOPs.