Robust polystyrene resin-supported nano-CoFe2O4 mediated peroxymonosulfate activation for efficient oxidation of 1-hydroxyethane 1,1-diphosphonic acid

Nanosized spinel cobalt ferrite (CoFe2O4) shows high performance in peroxymonosulfate (PMS) activation for decontamination in water, but is yet challenged by the easily leached Co(II) with high toxicity. Herein, mac-roporous polystyrene resin is used as the support to improve the stability of CoFe2O4 nanoparticles during PMS activation. CoFe2O4@S201 exerted high catalytic activity toward PMS activation for oxidation of 1-hydroxy-ethane 1,1-diphosphonic acid (HEDP), with the apparent rate normalized by Co content 38.2 times higher than that of the unsupported CoFe2O4. Meanwhile, one order of magnitude lower Co leaching (< 2.1 mu g L-1) was detected during the catalytic oxidation. The Co(II)-PMS complex was the primary oxidant responsible for the oxidation of HEDP. The catalytic durability and stability of CoFe2O4@S201 for degradation of HEDP in actual wastewater were systematically evaluated in both batch and continuous-flow mode. It is found that the organic resin, which is often considered to be intolerant to oxidation, is rather stable during the non-radical process. The total cobalt leaching of the fresh CoFe2O4@S201 cannot be ignored in the 100-h continuous-flow run. In contrast, much lower cobalt leaching and slightly higher oxidation efficiency were observed for the regenerated CoFe2O4@S201, which might be due to the removal of unreactive and unstable Co sites on the surface in the first trial. The findings shed light on the potential of organic supports for improving the stability and activity of nanosized CoFe2O4 and other nano-catalysts toward practical application.

Automated summary

This study demonstrates the use of macroporous polystyrene resin as a support to improve the stability of nanosized spinel cobalt ferrite (CoFe2O4) during peroxymonosulfate (PMS) activation for decontamination in water. The supported CoFe2O4 nanoparticles exhibit high catalytic activity and low cobalt leaching. The findings also reveal the stability of the organic resin during the non-radical process and evaluate the catalytic durability and stability of CoFe2O4 in actual wastewater.