| This paper is built on the preparation of zero-valent iron/iron oxide composites and their removal properties of U(?)and Cr(?).Fe3O4@HKUST-1,FesO4@HKUST-1/GO,nZVI/MIL-101(Cr)and nZVI@Mg(OH)2 were successfully prepared.The structure,composition and morphology of the target materials were analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier infrared spectroscopy(FT-IR)and thermogravimetric(TG)characterization methods.The above four kinds of composites as a new type of adsorbents used to remove the U(?)ions in aqueous solution and Cr(?)ions.Through a large number of adsorption experiment study the solution pH value,reaction time and temperature adsorbent and target ion concentration on the impact of adsorption performance.According to the experimental data fitting adsorption model and the analysis of the photoelectron spectroscopy(XPS)on the adsorption mechanism of various adsorbent to remove target ion in aqueous solution are explained.(1)Magnetic MOFs composites(Fe3O4@HKUST-1,Fe3O4@HKUST-1/GO)preparation and its adsorption on U(?):Magnetic MOFs has a broader application prospect in the field of pollutant treatment because of the obvious convenience and high efficiency of magnetic separation.In this study,Fe3O4@HKUST-1 and Fe3O4@HKUST-1/GO were successfully prepared by solvent heat and step-by-step synthesis.XRD,TEM,FT-IR and TG were utilized to analyze the composition and content of the composites.SEM analysis results show that the morphology of the two composites is coated spherical structure.Fe3O4@HKUST-1/GO was more uniform and dense than Fe3O4@HKUST-1,indicating that GO enhanced hydrophilicity.TEM test results show that before and after adsorption Fe3O4@HKUST-1/GO core-shell structure basically remain unchanged.The effects of initial adsorption concentration and temperature on Fe3O4@HKUST-1/GO adsorption U(?)were routinely studied by batch adsorption experiments.Through dynamics and thermodynamic research shows that pseudo-second order model and Langmuir model can better explain the relevant adsorption mechanism of U(?).(2)Preparation of nZVI/MOFs and adsorption of U(?):Nanoscale zero-valent iron(nZVI)has a strong reducing property but considering its defects such as easy aggregation.The new MOF base adsorbent modified by nZVI was successfully prepared in this study.According to the characterization results of XRD SEM,HRTEM,FT-IR,XPS and other characteristics,no damage was caused to MIL-101(Cr)structure by nZVI loading;2)the Freundlich model and pseudo-second order kinetic model(PSO)can explain the adsorption process well;3)the adsorption process is exothermic;4)at 298k,the maximum adsorption capacity calculated according to the Langmuir model was 529.1 mg/g.(3)Preparation of nZVI@Mg(OH)2 and adsorption of Cr(VI)and U(?):In this study,a new MOF base adsorbent modified by nZVI was successfully prepared.According to the XRD and SEM characterization,nZVI can form a new compound nZVI@Mg(OH)2 on the surface of Mg(OH)2 with intact load.nZVI@Mg(OH)2 was used to remove contaminated metal ions from wastewater.The results of characterization analysis after adsorption showed that U(?)and Cr(?)were not only absorbed by Mg(OH)2 matrix,but also reduced by nZVI.Through batch adsorption experiments,it is found that:1)The addition of nZVI makes the net negative charge on the adsorbent surface lower than that of Mg(OH)2 and the strong reduction performance of zero-valent iron reduces the toxicity and pollution of high-valent metal ions,thus greatly improving the removal performance of U(?)and Cr(?).2)The pseudo-second-order kinetic model can well explain the adsorption kinetic mechanism of nZVI@Mg(OH)2 on U(?)and Cr(?)and the Langmuir model can well explain the adsorption thermodynamic mechanism of nZVI@Mg(OH)2 on U(?).3)Adsorption of U(?)and Cr(?)by nZVI@Mg(OH)2 was endothermic.4)When the temperature is 318K,the maximum adsorption capacity of nZVI@Mg(OH)2 to U(?)is 529.1 mg/g calculated by Langmuir model.Figure 15 table 17 reference 147... |
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