| Heterogeneous transition metal oxide-activated peroxymonosulfate（PMS）can be used for the treatment of emerging contaminants in water.Among them,the photosynthetic catalysis technology based on peroxymonosulfate advanced oxidation technology（SR-AOP）combines the advantages of the two technologies.At the same time,the photogenerated electrons accelerate the reduction reaction process of high-valence transition metal ions,which greatly improves the catalytic performance of pollutants.Among the catalysts for activating PMS,spinel manganese cobaltate（MnCo2O4）not only has excellent activation performance,but also has the advantages of low cost and low ion dissolution.However,the catalysts cannot be widely used for degrading pollutants due to the disadvantages of low charge separation efficiency and easy accumulation of catalysts in solution.In addition,MnCo2O4 also has a narrow band gap and can be excited by visible light to generate electrons and holes.However,the high charge recombination rate still limits its direct application in the field of photocatalysis.Therefore,it is necessary to further study the rational modification strategy of MnCo2O4.It is an effective method to combine photocatalyst,co-catalyst and MnCo2O4 to form a composite catalyst with heterostructure.In this study,a MnCo2O4/g-C3N4composite catalyst was prepared,which successfully improved the effect of the catalyst.On this basis,a three-way high-efficiency catalyst MnCo2O4/g-C3N4/CDots was synthesized,and its performance was compared with that of MnCo2O4/CDots/g-C3N4,and the difference in catalytic performance was summarized and analyzed.Through some characterization methods and key experiments,the composition and morphology of the three-way catalyst were proved,and the influencing factors of the reaction process were explored.Finally,the reaction mechanism and degradation pathway were analyzed.The test results are as follows:（1）In this work,MnCo2O4 nanoparticles anchored on graphitic carbon nitride（g-C3N4）flakes were successfully prepared as MnCo2O4/g-C3N4 catalysts and showed high PMS activation efficiency under visible light（Vis）.The resulting catalyst degraded 96.1%of tetracycline hydrochloride（TCH）through the synergistic effect of PMS and photocatalysis.The reaction rate constants(0.2505 min-1)in the MnCo2O4/g-C3N4/PMS/Vis system are 5.3 and 1.8 times that of pristine g-C3N4(0.0471 min-1)and MnCo2O4(0.1435 min-1),respectively.The main free radicals in the reaction system are singlet oxygen and persulfate radicals.（2）In the study of three-way catalysts,we used bottom-up and top-down methods to synthesize MnCo2O4/g-C3N4/CDots and MnCo2O4/CDots/g-C3N4,respectively.The designed ternary material MnCo2O4/g-C3N4/CDots has better light absorption properties.Compared with monomer materials and binary materials,it has a wider light absorption range and high electron-hole separation rate,which greatly improves the material.Catalytic ability to better deal with high concentrations of pollutants.MnCo2O4/g-C3N4/CDots can degrade 90%of high-concentration TCH within 16minutes,which is a 3-fold improvement in the degradation rate constant compared to binary materials.Experiments with different influencing factors proved that pollutant concentration,PMS concentration,catalyst amount and initial p H value had different effects on the degradation performance.Different kinds of cations and anions had no significant effect on the degradation effect.The main active species ROS in the system were also verified by free radical quenching experiments to be 1O2 and SO4-·.g-C3N4acts as an electron donor in photocatalytic heterojunction system to transfer a large number of photogenerated electrons to MnCo2O4,and then the electrons are further transported and gathered around CDots,which inhibits the recombination of electron holes and improves the efficiency of divalent and trivalent metal ions.cycle rate.The composite exhibits good stability and cation/anion tolerance. |
