Efficient degradation of SCP by Co2(OH)2CO3/CuCo2S4-enhanced electron transfer-activated PMS: Dual role of Cu active site

In the activation of peroxymonosulfate by transition metal catalysts, manipulating the formation of high-valent metals facilitates the efficient utilization of persulfates and the removal of organic pollutants. Additionally, the synergistic effect between bimetallic catalysts has been demonstrated to be more advantageous for persulfate activation. In this research, the Co₂(OH)₂CO₃/CuCo₂S₄ (COC/CCS) composite catalyst was successfully prepared by loading CuCo₂S₄ onto Co₂(OH)₂CO₃ using a one-step method. Experimental results showed that the COC/CCS/PMS system could mediate the efficient degradation of various antibiotics through the synergistic action of multiple reactive species, predominantly high-valent metals [Co(IV) = Oxo and Cu(III)], SO₄^•−, and ¹O₂. The larger average pore size and pore volume of COC/CCS exposed more active sites. At the Co active sites, PMS underwent a two-electron transfer to form Co(IV) = Oxo. The Cu active sites played different roles depending on the pH: under acidic conditions, PMS served as an electron donor, transferring electrons to COC/CCS, which favored the reduction of Cu(II) and promoted the Co/Cu bimetallic cycle. Under neutral (alkaline) conditions, the generation of Cu(III) was induced, accelerating the degradation reaction. Additionally, the COC/CCS/PMS system exhibited significant resistance to anions, humic acid, and pH interference, and exhibited superior catalytic performance in actual water conditions. After four cycles, sulfachloropyridazine (SCP) was still completely degraded within 30 min, and the degradation pathway of SCP and the toxicity of the intermediate products were analyzed. This research provided insights into the interaction between bimetallic catalyst active sites and PMS, and the generation of high-valent metals to degrade antibiotics.