Rational design and synthesis of hollow Co3O4@Fe2O3 core-shell nanostructure for the catalytic degradation of norfloxacin by coupling with peroxymonosulfate

Abstract

Rational design and synthesis of efficient catalyst for the generation of sulfate radicals (SO4−) through heterogeneous approach is highly desirable. In the present study, a magnetic cobalt-based catalyst, Co3O4@Fe2O3 was successfully synthesized by using metal-organic frameworks (MOFs) as a template. A hollow core-shell structure possessing moderate specific surface area (22.8 m2 g−1) and pore volume (0.18 cm3 g−1) was obtained. The catalyst performed high efficiency for the degradation of norfloxacin (NOR) by coupling with peroxymonosulfate (PMS). And the process was kinetically favorable in neutral (0.43 min−1 at pH of 7.5) and weak acidic/basic conditions, whilst significantly inhibited at acidic condition (0.12 min−1 at pH of 4.5). Catalyst loading showed a more remarkable effect on the degradation process than PMS dose. Interestingly, chloride, phosphate and bicarbonate ions clearly promoted the degradation process while humic acid showed a detrimental effect. Cl2/HOCl oxidation system was demonstrated when massive Cl− was added into the reaction system. As evidenced by electron paramagnetic resonance (EPR) analysis, both hydroxyl and sulfate radicals contributed to the degradation and the latter one played a crucial role. Eventually, degradation pathway was tentatively proposed based on the HPLC-ESI-MS/MS analysis of the detected intermediates. This study would be very meaningful to promote the applications of sulfate radical based advanced oxidation processes (SR-AOPs) for the environmental remediation.