Preparation Of Nickel-Iron Hydrotalcite Composites And Study On The Performance Of Activated Persulfate To Degrade Tetracycline

With the development of commerce and agriculture,the global water pollution problem is becoming increasingly serious.The use of tetracycline hydrochloride（TCH）has become quite common.Due to its stable structure and difficulty in degradation under natural conditions,it has posed a serious threat to the water environment and human health.How to remove TCH from water has always been a focus of attention.In recent years,the Advanced oxidation process that uses catalysts to activate peroxymonosulfate（PMS）to generate a large number of sulfate radical（SO₄^-·）and hydroxyl radical（·OH）has the advantages of simple operation,wide application range,stable reaction process,strong oxidation ability,and high efficiency,and stands out in the application of oxidative degradation of organic pollutants.The bimetallic hydroxide is called LDH for short.It has low production cost,high specific surface area,strong adsorption to pollutants when used as a catalyst,and adjustable advantages such as size,thickness,morphology,main layer cation,and interlayer anion,which can be used as an efficient catalyst.Among them,Ni Fe-LDH has a stable structure,a wide range of light responses to visible light,and simple material preparation.However,conventional synthetic Ni Fe-LDH is easy to stack together,which reduces the contact area between the catalyst and pollutants and reduces the number of active sites,limiting the application of hydrotalcite in photocatalysis.Layered bismuth-based photocatalysts have a unique layered crystal structure,and their combination with hydrotalcite can make up for this deficiency.At the same time,the favorable band structure of bismuth-based materials has also attracted widespread attention from researchers.Therefore,this article takes nickel iron hydrotalcite as the research object,composite different bismuth-based materials to prepare heterojunctions,and explores its activation PMS to improve the catalytic performance of the catalyst,in order to achieve efficient degradation using low-dose catalysts,The main research content is as follows:（1）A composite material of Ni Fe-LDH and Bi₂WO₆ was prepared by the hydrothermal method:z-type heterojunction Ni Fe-LDH/BWO.The composition and morphology of the heterojunction were analyzed by XRD,XPS,SEM,TEM,and other characterization methods.The results showed that the hexagonal nanosheet Ni Fe LDH was successfully composited onto non-stacked bismuth tungstate nanosheets.The performance of the Ni Fe-LDH/BWO catalyst was evaluated by degrading the target pollutant tetracycline hydrochloride（TCH）.The optimal composite ratio of the catalyst was Ni Fe-LDH/BWO-30%,and its degradation rate of TCH reached 88%within 120 minutes.The reaction kinetics constant was 6.4 times that of Ni Fe-LDH.Electrochemical testing showed that its photo-induced carrier separation efficiency was 2.3and 5.8 times that of a single material,This indicates a lower interfacial electron transfer resistance and higher photoelectric response density.The prepared catalyst exhibits good stability,and after three cycles of experiments,the degradation rate of TC can still reach 79%.Finally,free radical capture experiments were conducted and possible reaction mechanisms were analyzed.The results showed that the main reactive oxygen species in the system were·OH and·O₂^-（2）A composite material of Ni Fe-LDH and Bi₅O₇I was prepared using a two-step hydrothermal method:type II heterojunction LDH/BOI.Introducing PMS photocatalytic degradation of tetracycline hydrochloride in an aqueous medium,and systematically studying the structure,composition,morphology,optical performance,and corresponding electrochemical performance of the catalyst.The photocatalytic activity of LDH/BOI is higher than that of its single component,and it has a good photodegradation effect on TCH under visible light.Under 80 min sunlight,about 94%of tetracycline is degraded by LDH/BOI（1:0.5）,and the kinetic reaction rate constant k=0.0352 min^-1 is far higher than that of other complex systems.LDH/BOI（1:0.5）also shows excellent stability.After three cycles of degradation,the degradation efficiency remains at 90%,This composite system has a good ability to separate and transport photogenerated electrons and holes and belongs to a type II heterojunction system.Through the capture analysis of key free radicals such as·OH、SO₄^-·and·O₂^-in the LDH/BOI（1:0.5）activated PMS degradation experiment,the mechanism of heterojunction-activated PMS degradation of TCH was revealed,laying a theoretical foundation for improving the photocatalytic performance of catalyst activated PMS.（3）The composites of Ni Fe-LDH and Bi₄Ti₃O₁₂ were prepared by a two-step hydrothermal method:n-n heterojunction LDH/BTO.Bi₄Ti₃O₁₂ loose flower-like microsphere structure is conducive to light absorption while providing enough load space for LDH,through the EDX element mapping map can be seen that Bi,Ti,O,Ni,Fe uniformly distributed in the photocatalyst,LDH/BTO-1.5 sample shows the highest photocurrent intensity,its intensity is 3.1 times that of Bi₄Ti₃O₁₂.In the degradation experiment,Under the conditions of 30mg/L at the initial concentration of TCH,0.2 g/L for PMS,and 30 mg for catalyst with optimal degradation,the degradation rate of TCH by LDH/BTO-1.5+VIS+PMS system reached 96.5%,and the degradation efficiency remained at 90%through three cycles of testing,ensuring the reusability of the catalyst.