Microwave irradiation synthesis of CoFe2O4/rGO to activate peroxymonosulfate for the degradation of 2-aminobenzothiazole in water†

Abstract

Reduced graphene oxide modified CoFe₂O₄ (CoFe₂O₄/rGO) magnetic nanoparticles (MNPs) were synthesized by employing an in situ crystallization microwave irradiation method. The morphology and textural properties of CoFe₂O₄/rGO were characterized using SEM, TEM, BET/BJH and XPS. GO was reduced to rGO via the thermal catalysis of Co(acac)₂, which contributed to expanding the effective microwave absorption bandwidth of carbon-based materials. The lattice stability of CoFe₂O₄ effectively improved Snoek's limit and protected the catalytic active site distribution of CoFe₂O₄/rGO nanoparticles. The CoFe₂O₄/rGO composites were selected as a heterogeneous catalyst to initiate the activation of peroxymonosulfate (PMS) for the generation of reactive oxygen species (ROS) and degrade 2-aminobenzothiazole (ABT) in a water sample. Under optimal conditions, the coupling of CoFe₂O₄/rGO and PMS can completely degrade ABT in aqueous solutions within 90 minutes. The effect of inorganic anions, metal cations and humic acid (HA) on the degradation efficiency of ABT was explored. Experimental results showed that the presence of HA and low concentrations of Cu²⁺ enhanced the process performance remarkably, while the addition of NO₃⁻, SO₄²⁻, Zn²⁺, Cd²⁺ and high concentrations of Cu²⁺ suppressed the degradation of ABT. Meanwhile, the absence of Cl⁻ and HCO₃⁻ presented no significant influence on the degradation. Radical quenching experiments indicated that SO₄⁻·, ·OH and non-free radicals of ¹O₂ were involved in the CoFe₂O₄/rGO-PMS system, with the former two being the dominating radical species. A degradation efficiency of 100% was obtained when the proposed method was applied to the degradation of ABT in actual water samples. The CoFe₂O₄/rGO catalyst-activated PMS processes offered a reference to eliminate refractory organics in water.