Study On The Construction Of ZIFs Metallic Composites And The Performance Of Its PMS Activation For Degradation Of Tetracycline In Water

Tetracycline as a broad spectrum antibiotic has been widely used in the treatment of bacterial infections.In order to improve the life span and quality of human and animal life,the large amount of residual water in groundwater,surface water and drinking water has become an important environmental problem.Sulfate radical based advanced oxidation technology（SR-AOPs）is a new advanced oxidation technology which can effectively degrade most organic pollutants.In practical application,it is very important to select the appropriate persulfate and catalytic mode.Since the activation of persulfate（PMS）by homogeneous metal ions is easy to cause secondary pollution,the use of heterogeneous transition metal catalysts to activate PMS to degrade emerging antibiotics pollutants has attracted the attention of many researchers.However,how to prepare catalysts with high catalytic activity,low cost and excellent regeneration performance to remove antibiotic residues in water remains to be studied.In this paper,a metal composite based on ZIFs was constructed to activate PMS to degrade tetracycline in water.A series of characterization methods and scientific experiments were used to further study the performance and mechanism of ZIFs metal composite to activate PMS to degrade tetracycline,and good degradation effect was achieved in a short time.It also shows great potential in the degradation of different antibiotics and actual water bodies.The main research contents and results are as follows:（1）Zn/Co-ZIFs catalysts with different Zn,Co doping proportions were prepared by mixed solvothermal method,and the Zn/Co-ZIFs were characterized to analyze its morphology,crystal structure,elemental composition and valence state.The results show that Zn/Co-ZIFs does not change the basic structure of ZIFs series materials.Like ZIF-67 and ZIF-8,Zn/Co-ZIFs presents polyhedral shape and has the same functional group,but also retains the characteristics of high specific surface area and large porosity of ZIFs materials.In view of the difficulty in separating Zn/Co-Zifs metal composite catalyst from the liquid phase,Fe-Zn/Co-ZIFs catalyst with strong magnetic properties was prepared by introducing Fe₃O₄nanoparticles into Zn/Co-ZIFs material by solvothermal method,and the electron transfer between Fe₃O₄and catalyst was used to promote the effective circulation of Co.Finally,Fe₃O₄nanoparticles were successfully loaded on the surface of Zn/Co-ZIFs materials through a series of characterization.（2）The prepared Zn/Co-ZIFs was used to activate PMS to catalyze the degradation of TC in wastewater.The results showed that the degradation rate of TC with a concentration of 20mg/L reached 82.81%in 30 minutes under the condition of0.5 m M PMS and 5mg catalyst.The removal rate of TC remained above 75%after the material was recycled for 5 times,and the catalyst showed good stability and reusability.By studying the effects of different inorganic anions on TC removal,HCO₃-has a significant inhibitory effect on TC removal,while NO₃-has the least effect on TC degradation efficiency.Through the free radical quenching experiment found that 2Zn/Co-ZIFs/PMS system is one of the main active species in the degradation of TC for sulfate radicals（SO₄·^-）and hydroxyl radical（·OH）.（3）The degradation performance and mechanism of Fe-Zn/Co-ZIFs catalyst on TC were studied.The results showed that the degradation rate of TC with a concentration of 20mg/L reached 99.83%in 30min under the condition of0.5m MPMS and 5mg catalyst.The degradation efficiency of TC remained above 89%after 5 catalytic cycles,and the catalyst had good magnetic separation ability（12.6emu/g）.Fe-Zn/Co-ZIFs catalyst is suitable for a wide pH range,and has good TC degradation effect in the pH range of 5-9.Most interference ion HCO₃-and H₂PO₄-and humus（HA）has inhibitory effect on the degradation of TC rate,and low concentration Cl-although can inhibit the degradation of TC,but high concentration can promote its degradation,NO₃^-influence on TC degradation is negligible.From the practical application,Fe-Zn/Co-ZIFs/PMS system has a better performance in the degradation of different antibiotics and in actual water.Experiment in quenching free radicals,produced in the process of degradation of SO₄·^-and·OH,the SO₄·^-dominant role.