A facial strategy to efficiently improve catalytic performance of CoFe2O4 to peroxymonosulfate

Cobalt iron spinel (CoFe2O4) has been considered as a good heterogeneous catalysis to peroxymonosulfate (PMS) in the degradation of persistent organic pollutants due to its magnetic properties and good chemical stability. However, its catalytic activity needs to be further improved. Here, a facial strategy, "in-situ substitution", was adopted to modify CoFe2O4 to improve its catalytic performance just by suitably increasing the Co/Fe ratio in synthesis process. Compared with CoFe2O4, the newly synthesized Co1.5Fe1.5O4, could not only significantly improve the degradation efficiency of phenol, from 50.69 to 93.6%, but also exhibited more effective mineralization ability and higher PMS utilization. The activation energy advantage for phenol degradation using Co1.5Fe1.5O4 was only 44.2 kJ/mol, much lower than that with CoFe2O4 (127.3 kJ/mol). A series of related representations of CoFe2O4 and Co1.5Fe1.5O4 were compared to explore the possible reasons for the outstanding catalytic activity of Co1.5Fe1.5O4. Results showed that Co1.5Fe1.5O4 as well represented spinel crystal as CoFe2O4 and the excess cobalt just partially replaced the position of iron without changing the original structure. Co1.5Fe1.5O4 had smaller particle size (8.7 nm), larger specific surface area (126.3 m2/g), which was more favorable for exposure of active sites. Apart from the superior physical properties, more importantly, more reactive centers Co (Ⅱ) and surface hydroxyl compounds generated on Co1.5Fe1.5O4, which might be the major reason. Furthermore, Co1.5Fe1.5O4 behaved good paramagnetism, wide range of pH suitability and strong resistance to salt interference, making it a new prospect in environmental application.