Active Site Regulation Of Fe Composite CN Catalyst And Its Non-Free Radical Catalytic Mechanism For PMS

More and more toxic organic pollutants are discharged into the environment,posing a serious threat to the ecosystem,with the development of industry.Persulfate advanced oxidation technology has been considered as an effective solution,which can generate free radicals and non-free radicals to destroy refractory pollutants through different activation methods.Compared with free radical reactions,non-free radicals can overcome the negative effects of p H changes in water,most inorganic anions and different water matrices and achieve better results in the treatment of complex wastewater.However,the mechanism of non-free radical action is still unclear.In order to explore the reaction mechanism of non-radical generated by activated persulfate to the degradation of toxic organic pollutants in heterogeneous systems.Here,we investigated the non-radical oxidation process of activated persulfate（PMS）using Fe composite CN catalysts,and investigated the effects of p H,inorganic anions and different water substrates on the reaction.By adjusting the structure of Fe composite CN catalyst,its catalytic ability and stability are enhanced,and the toxic organic pollutants bisphenol A（BPA）and diclofenac sodium（DCF）can be effectively degraded.The results are as follows:（1）Fe₂O₃ composite CN with heterostructure was prepared by co-precipitation method using carbide nitrogen（g-C₃N₄）and ferric chloride hexahydrate（Fe Cl₃·6H₂O）as precursors.XRD,XPS,FTIR,SEM,TEM,BET and other technologies are used to characterize the catalyst and prove that its heterostructure will lead to the spontaneous migration of electrons and greatly improve the catalytic performance.The quenching experiments and EPR tests show that reactive complexes and singlet oxygen on the catalyst surface are the active substances that cause BPA degradation,and the removal efficiency of BPA reaches 87%within 5 minutes.（2）By adjusting the preparation temperature and the ratio of Fe/CN,the Fe composite CN catalyst was further optimized to prepare a Fe-doped CN catalyst（Fe CN-3）.XPS analysis shows that Fe atoms are doped into the CN skeleton through Fe-N bonds.Due to the change in charge density,the catalytic performance of hybrid catalysts is improved,and the electron transfer rate between catalysts,oxidants and pollutants is promoted.BPA was almost completely degraded within 5 minutes,and the catalytic activity and stability of the catalyst did not change significantly after 6 cycles of experiments.（3）By further doping the S element,the charge density of the Fe-doped CN catalyst was adjusted to prepare an Fe/S co-doped CN catalyst（Fe CNS-1.5）.The experimental results show that S doping enhances the electronegativity of Fe in Fe-N bonds,catalyzes PMS more easily,and significantly enhances the degradation effect of DCF.The reaction mechanism of the Fe CNS-1.5/PMS/DCF system follows the non-radical reaction theory dominated by electron transfer,has strong adaptability to complex water environments,and effectively removes difficult-to-degrade organic substances in a wide p H range.