| Magnetic Fe3O4 nanocomposites are still one of the hot spots in the field of magnetic materials because of their excellent applications in industrial catalysis,adsorption separation,nuclear magnetic imaging and disease diagnosis.In this dissertation,a series of new magnetic Fe3O4 nanocomposites were successfully prepared by optimizing the synthesis method,and their adsorption and catalytic degradation properties of environmental pollutants were studied in detail.The specific contents are as follows:(1)Improved the complex layer by layer coating method,developed a simple one-step method and successfully synthesized magnetic h-Fe3O4@Ag/PDA nanocomposites.The nanocomposite can not only effectively catalyze the degradation of azo dyes,but also significantly inhibit the growth of Bacillus subtilis,and the minimum inhibitory concentration is as low as 12.5 μg/mL.Because silver nanoparticles will not be leached out in the reaction solution under the protection of the PDA shell,the catalytic performance and antibacterial activity of the nanocomposite remain above 90%after five cycles of experiments.More importantly,this simple synthesis method can be used to prepare different multi-functional nanocomposites,such as spherical SiO2@Ag/PDA and rod Fe2O3@Ag/PDA.(2)Magnetic h-Fe3O4@phos-LDH nanocomposite was prepared by modifying h-Fe3O4 with phosphate modified layered double hydroxides.The nanocomposite has rich phosphate groups and large specific surface area,which can be used to remove U(Ⅵ)in wastewater.The saturated adsorption capacity(Qmax=542.60 mg/g,T=298 K,)and adsorption mechanism of the nanocomposite for U(Ⅵ)were investigated by batch adsorption experiments.It was proved that the adsorption process was spontaneous and endothermic,and the adsorption isotherm was consistent with the Langmuir model.XPS analysis confirmed that the phosphate functional groups in the phos-LDH shell play a dominant role in the adsorption process.In addition,the soil purification experiment assisted by electromagnetic separation system was also carried out.The results showed that the h-Fe3O4@phos-LDH nanocomposite could remove more than 90%of U(Ⅵ)in the simulated soil.(3)Magnetic h-Fe3O4@phos-PDA nanocomposite were prepared in situ by one-step method.Due to its rich phosphate and amine functional groups,h-Fe3O4@phos-PDA nanocomposites have excellent adsorption properties for U(Ⅵ).Batch adsorption experiments showed that the isotherm of adsorption of U(Ⅵ)by h-Fe3O4@phos-PDA was consistent with Langmuir model,and the saturated adsorption capacity was 526.35 mg/g(T=298 K).According to the adsorption kinetics experiment,the whole adsorption process can reach equilibrium in only 16 minutes and the adsorption data is consistent with the pseudo-secondary model.XPS analysis showed that phosphate and amine functional groups played an important role in the complexation of phos-PDA shell with U(Ⅵ).In addition,the real uranium-contaminated soil purification experiment showed that h-Fe3O4@phos-PDA nanocomposites could reduce the intensity of α-ray radiation in soil by up to 82.3%.(4)Multifunctional Fe3O4/CNT nanocomposite was synthesized by a simple one-pot method.The Fe3O4/CNT nanocomposite formed by the combination of Fe3O4 and CNT has more excellent electrical properties due to the formation of heterojunction structure conducive to electron transmission.When Fe3O4/CNT is used as the cathode active material of CDI device,its saturated adsorption capacity for U(Ⅵ)reaches 287.53 mg/g.Because of its superparamagnetism,when Fe3O4/CNT is used as the active material of the flow electrode in FCDI device,the magnetic electrode material in the electrode chamber can be quickly recovered by simple magnetic separation.In addition,120 mg/L of U(Ⅵ)waste liquid can be concentrated into 1230 mg/L of small volume and high concentration solution through 9 consecutive stable FCDI adsorption cycle experiments,thus achieving the goal of saving storage space and water resources. |
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