Amorphous Co3O4 nanoparticles-decorated biochar as an efficient activator of peroxymonosulfate for the removal of sulfamethazine in aqueous solution

In this study, amorphous Co3O4 nanoparticles-decorated biochar was synthesized and employed to activate peroxymonosulfate (PMS) for sulfamethazine (SMT) degradation in aqueous solution. Hydrochar of corn straw obtained from hydrothermal carbonization was impregnated in CoCl2 solution for anchoring cobalt nanoparticles onto biochar surface before pyrolysis. Application conditions of as-prepared cobalt-loaded biochar (Co-BC) involving dosage, pyrolysis temperature, cobalt loading, solution pH and groundwater components were examined; and the stability of the catalyst was investigated by examining its performance in recycling experiments (3 rounds) and the variation of catalytic mechanism in recycling experiment was investigated. 100% SMT was removed under the optimum condition within 60 min: 1.0 mmol/L CoCl2 aqueous solution, 800 °C of pyrolysis temperature, 400 mg/L Co-BC, 0.06 mM PMS, solution pH 8. The results turned out that the amorphous Co3O4 nanoparticles were favorable for the activation of PMS. BC not only played as a support for dispersion of Co3O4 nanoparticles but also acted as an electron shuttle between Co3O4 and PMS/SMT molecules. During the recycling use, the key free radicals changed from ▪OH and SO4▪- to SO4▪- and only low degree of cobalt ions leaching was monitored. Additionally, the mixed groundwater components exerted trivial influence on the reaction system.