Mechanism And Application On Visible Light Activation Of Persulfate By CoFe₂O₄/MoS₂ For Degradation Of Chloroquine Pollutants

Organic pollutants in water bodies seriously affect the environment and human health.Traditional wastewater treatment methods have problems such as low treatment efficiency,complicated operation and secondary pollution.In recent years,the persulfate non-homogeneous activation technology has become a hot spot for research due to its advantages of high activity,wide applicability conditions and no secondary pollution,however,the slow regeneration rate of metal ion centers,difficulty in recycling and unclear details of the mechanism limit its use.The activation of persulfate is mainly achieved by the loss of electrons of low-valent transition metal ions.Spinel cobalt ferrite（Co Fe2O4）has the advantages of simple preparation,dense active sites and magnetic separation to become an ideal activation material,but the reduction of high valence state is the key to limit the activation rate.To overcome this problem,in this study,highly efficient Co Fe₂O₄/Mo S₂ composites with magnetic separation were prepared by electrostatic self-assembly of molybdenum disulfide（Mo S₂）,which has a co-catalytic effect,and Co Fe₂O₄.Among them,Co Fe₂O₄ has a large number of active sites for rapid activation of peroxymonosulfate（PMS）,while the flower-like Mo S₂ with abundant edge sites and defects can not only provide Mo⁴⁺reduction sites for Co²⁺/Fe²⁺regeneration,but also form type II heterojunctions with Co Fe₂O₄ to provide reduced photogenerated electrons,and the simultaneous existence of the two pathways promotes the active center regeneration.In addition,we have also investigated its performance and mechanism in depth.The main work of the paper is as follows:（1）Preparation and characterization of Co Fe₂O₄/Mo S₂ composites:Co Fe₂O₄/Mo S₂composites were prepared using co-precipitation method,solvothermal method and electrostatic self-assembly method.The preparation process:90%Co Fe₂O₄ by mass,10%Mo S₂by mass,2 h.The successful preparation of Co Fe₂O₄ nanoparticles,flower-like Mo S₂ and composites was confirmed by SEM,TEM,SAED,XRD characterization.The chemical composition and photochemical properties were analyzed using EDS,XPS,and Uv-vis.The results showed that the Co,Fe,O,Mo,and S elements were uniformly distributed in the composites,with a forbidden band width of 1.08 e V for Mo S₂ and 1.24 e V for Co Fe₂O₄.（2）Construction and application of visible light activated persulfate system:The degradation effect of Co Fe₂O₄/Mo S₂ composite on pollutants by visible light activated PMS and its performance under different inorganic ions,water quality and p H were investigated and found that it can degrade 98.6%of chloroquine within 12 minutes and has wide applicability.The magnetic recovery experiments,recycling performance tests and evaluation of energy consumption during use revealed its good economic applicability.（3）Mechanistic investigation of the degradation process of chloroquinolines:The photoelectrochemical properties of Co Fe₂O₄/Mo S₂ composites were found to be superior to those of the monomeric catalysts by photocurrent,EIS and PL characterization.It was determined that SO₄^-·,·OH,·O₂^-,h⁺,and ¹O₂ all contribute to the degradation process by ESR and active substance quenching experiments.A heterojunction model was developed and the differential charge density at the interface was analyzed to probe the adsorption and activation of PMS on the eight crystalline planes and it was found that the（222）crystalline plane of Co Fe₂O₄ has the best catalytic activity.By deducing the mechanism,it was found that the rapid reduction of the Co³⁺/Fe³⁺active center promoted by the dual reduction pathway of Mo S₂greatly increased the activation rate of PMS.Based on quantum chemical calculations,it was found that the frontline orbitals of chloroquine molecule were mainly located in the quinoline ring and side chain part,and the reaction sites were predicted by Fukui function and probably located at N₁₈ and Cl₁₁,and a reasonable degradation pathway was deduced by combining with liquid-mass spectrometry.And based on the quantitative conformational relationship,it was found that the ecotoxicity of the degradation process was significantly reduced.