Efficient degradation of norfloxacin using a novel biochar-supported CuO/Fe3O4 combined with peroxydisulfate: Insights into enhanced contribution of nonradical pathway

Nonradical persulfate oxidation techniques have evolved as a new contaminated water treatment approach due to its great tolerance to water matrixes. The catalysts of CuO-based composites have received much attention in that aside from SO4•-/•OH radicals, the nonradicals of singlet oxygen (1O2) can be also generated during persulfate activation via CuO. However, the issues regarding particles aggregation and metal leaching from the catalysts during the decontamination process remain to be addressed, which could have a remarkable impact on the catalytic degradation of organic pollutants. Accordingly in the present study, a novel biochar-supported bimetallic Fe3O4-CuO catalyst (CuFeBC) was facilely developed to activate peroxodisulfate (PDS) for the degradation of norfloxacin (NOR) in aqueous solution. The results showed CuFeBC has a superior stability against metal ions Cu/Fe leaching, and NOR (30 mg L-1) was degraded at 94.5% within 180 min in the presence of CuFeBC (0.5 g L-1) and PDS (6 mM) in pH 8.5. The scavenging of reactive oxygen species and electron spin resonance analysis revealed that 1O2 dominated the degradation of NOR. Compared with pristine CuO-Fe3O4, the interaction between biochar substrate and metal particles could significantly enhance the contribution of the nonradical pathway to NOR degradation from 49.6% to 84.7%. Biochar substrate could efficiently reduce the leaching of metal species from the catalyst, thereby maintaining excellent catalytic activity and lasting reusability of the catalyst. These findings could enlighten new insights into fine-tuning radical/nonradical processes from CuO-based catalysts for the efficient remediation of organic contaminants in polluted water.