Magnetic CoFe alloy–Co supported on mesoporous carbon as an efficient catalyst for the degradation of bensulfuron-methyl: insight into the effect of calcination temperature on carbon defects and singlet oxygen

Abstract

In this work, a magnetic CoFe alloy and Co supported on mesoporous carbon with abundant defects (CoFe–Co/MC) was prepared by a sol–gel method combined with calcination and applied to activate peroxymonosulfate (PMS) and efficiently remove bensulfuron methyl (BSM) from water. CoFe–Co/MC could degrade 95% of BSM, while Co or Fe without supported mesoporous carbon could only provide degradation efficiencies below 10%, indicating that the introduction of mesoporous carbon could effectively enhance catalytic activity. Moreover, the dissolution of Co²⁺ from CoFe–Co/MC is only 0.22 mg L⁻¹, which is about 20% of Co/MC, indicating that the bimetallic composite effectively inhibits the dissolution. The results of radical scavenger and EPR experiments demonstrated that ¹O₂ played the leading role in degradation process, while SO₄˙⁻ and small amounts of ˙OH and O₂˙⁻ were also involved in the degradation. The results of p-BQ scavenger and N₂ atmosphere experiments showed that ¹O₂ mainly originated from the interaction between carbon defects and dissolved oxygen. The degradation performance of the CoFe–Co/MC/PMS system, carbon defect content and ¹O₂ content all increased with the increase of pyrolysis temperature, which demonstrated that adjusting pyrolysis temperature can regulate carbon defect content and ¹O₂ content, further improving catalytic activity. Possible BSM degradation pathways of CoFe–Co/MC/PMS were investigated in detail. This research provides new insights into the design and construction of metal–carbon catalysts rich in carbon defects and reveals how to regulate carbon defect content, ¹O₂ content and catalytic performance.