Synthesis And Preparation Of Magnetic Nanocomposites And Its Functionalization Research

In this thesis,the composite photocatalyst Fe₃O₄@SiO₂@MoS₂/Bi VO₄with semiconductor p-n heterogeneous structure and recyclable was prepared by loading the magnetic Fe₃O₄@SiO₂@MoS₂complex onto the surface of Bi VO₄.The catalytic ability of Fe₃O₄@SiO₂@MoS₂/Bi VO₄to pollutants such as dyes,antibiotics and herbicide under visible light was studied.The possible catalytic mechanism of Fe₃O₄@SiO₂@MoS₂/Bi VO₄was analyzed based on the experimental results.（1）Hydrophobic OA-Fe₃O₄ and hydrophilic Na₃Cit-Fe₃O₄ were prepared by Chemical coprecipitation method and Solvothermal method,respectively.The experiment also explored the effect of reaction conditions on product size,morphology,magnetic saturation strength and crystal form.Through characterization,it can be seen that both methods can synthesize pure phase and uniform morphology of magnetic Fe₃O₄ nanoparticles.（2）The main step in the preparation of Fe₃O₄@SiO₂ material is to coat a SiO₂ shell on the surface of Fe₃O₄ by sol-gel method.The SiO₂ layer can effectively improve biocompatibility,prevent corrosion and agglomeration of Fe₃O₄nanoparticles.It′s also improve its stability in aqueous solution.CTAB is added as a mesoporous template in sol-gel reactions during preparation,and can be used as a stable surfactant for the transfer of Fe₃O₄nanoparticles into the aqueous phase.（3）The MoS₂ was grown in situ on the surface layer of OA-Fe₃O₄@SiO₂ by Hydrothermal method.And a double-layer shell material Fe₃O₄@SiO₂@MoS₂ was prepared.In the preparation process,OA-Fe₃O₄@SiO₂ is put into dilute HNO₃ solution for surface protonation to positively charge the SiO₂ surface,so that negatively charged MoS₂can grow to the SiO₂ surface.Through degradation experiments,it can be seen that Fe₃O₄@SiO₂@MoS₂has the best degradation effect on antibiotics.At 100 min,the degradation efficiency of tetracycline hydrochloride reached 77.83%,and at 80 min,the degradation efficiency of norfloxacin reached 68.39%.（4）The experimental results of Bi VO₄ degradation of cationic dyes,norfloxacin and Cr（VI）further proved that the best conditions for the preparation of Bi VO₄ were p H=5modification and reaction for 12 h.Specifically,the degradation rate of MB was 73.25%at80 min.The degradation rate of norfloxacin at 100 min was72.43%.The degradation rate of glyphosate isopropylamine salt in 100 minutes is 72.05%.The degradation rate of Cr（VI）was 67.00%at 100 min.（5）It can be seen from photocatalytic experiments that when the load capacity of MoS₂is 5%,the photocatalyst has the best degradation efficiency for the target pollutants after modification in the p H value of 5.Specifically,the maximum adsorption efficiency of methylene blue reached 97.22%at 100 min.The degradation rate of methyl orange at 120min was 97.99%.（6）The optimal dosage of Fe₃O₄@SiO₂@MoS₂/Bi VO₄ for composite photocatalysts is20 mg.At 80 min,the maximum degradation efficiency of 20 mg dosage for norfloxacin was83.27%;The maximum degradation efficiency of Cr（VI）with 20 mg was 69.31%at 90 min.（7）Fe₃O₄@SiO₂@MoS₂/Bi VO₄had the largest degradation rate within the p H=5-7range of norfloxacin solution,indicating that it met the acidity environment of human urine metabolites and norfloxacin in medical wastewater.At 80 min,the maximum degradation efficiency was 76.34%.At the solution acidity of p H=3,the degradation efficiency of Cr（VI）reached 75.00%at 90 min.