ZnFe2O4 substituted with Cu atoms for ultra-efficient formation of sulfate radicals: Extremely low catalyst dosage for thiamethoxam degradation

Neonicotinoids as one of the newest major class of insecticides is a kind of persistent pollutants. Herein, copper-substituted zinc ferrites (CuZnFeO) prepared in subcritical aqueous solution has a nanosize of ∼2 nm with high crystallinity and strong magnetic property. At low catalyst dosage of 0.05 g L, peroxymonosulfate (PMS) can be effectively converted into sulfate radicals in CuZnFeO/PMS system. Thiamethoxam (THIA) degradation rate is in the order of CuZnFeO > CuFeO > ZnFeO (124, 84, 21 × 10 min, respectively). At pH ∼7.0, THIA degradation efficiency can be over 99 % in 40 min. The radical species (, HO, SO and O) were demonstrated by EPR spectra using probe molecules. The majority effects in CuZnFeO/PMS system with kinetics modelling were comprehensively investigated as well. This work provides that multi-metal coupling, , Cu(Ⅰ)/Cu(Ⅱ) & Fe(Ⅱ)/Fe(Ⅲ), in spinel structure by polyhedral design is an effective strategy for enhancing the catalytic activity. The CuZnFeO/PMS system has promising for water treatment of neonicotinoid insecticide with ease of recycling catalysts by magnetic separation.