| Metal-organic frameworks(MOFs) has the characteristics of large specific surface area, high porosity, the adjustability of chemical structure and pore size, chemical modification.MOFs has been successfully applied to the field of gas adsorption, but rarely reported in terms of radionuclide adsorption.This article used the azobenzene- 4, 4 ’-dicarboxylic acid as ligand, combined with different chain length of amide functional group to synthesize three kinds of azo type photosensitive MOFs materials, then take them as adsorbent to adsorption study with radioactive uranium ion, the main work is as follows:(1) Take azobenzene- 4, 4 ’- dicarboxylic acid and zinc nitrate as raw materials, combined with N1, N4- di(pyridine – 3 – yl) terephthalamide, N1, N4- di( pyridine – 3 – yl) naphthalene-1,4-dicarboxamide and 4,4’-Vinylenedipyridine to synthesis three kinds of azo type photosensitive MOFs materials named azo-MOFs-1 、 azo-MOFs-2 、azo-MOFs-3 by using hydrothermal method.By single crystal diffraction(SCXRD), scanning electron microscope(SEM) and energy spectrometer(EDS), X-ray powder diffraction(XRD), thermogravimetric(TG) and Fourier transform infrared spectrometer(FTIR), and other characterization methods to characterize, verify the three structures of azo type photosensitive MOFs materials.(2) Take azo-MOFs-1、azo-MOFs-2、azo-MOFs-3 to the static adsorption study on the adsorption behavior of radioactive uranium element, the equilibrium adsorption of the three kinds of materials in the order are 186.92 mg/g, 283.26 mg/g and 366.41 mg/g, it is concluded that MOFs skeleton chain length can effect the adsorption of uranium, in which azo-MOFs-3 has the optimal structure of uranium adsorption configurations.Choose quasi kinetics of primary, secondary and liquid film diffusion model on the dynamic model dynamics research, it is concluded that the adsorption behavior of azo-MOFs-1 、azo-MOFs-2、azo-MOFs-3 are mainly chemical adsorption,which doping with physical adsorption.Using the Langmuir and Freundlich isothermal adsorption model to study the adsorption behavior, it is concluded that azo-MOFs-1、azo-MOFs-2、azo-MOFs-3 are monolayer adsorption;Using thermodynamics and activation energy formula verifies the behavior of three adsorption are chemical endothermic reaction.By observing the IR spectra changes between original materials and adsorptive uranium materials, the effective chemical adsorption sites to uranium of three material is at the C = O bond and N=N location.(3) Using three analytic solution of 0.1 M HNO3, 0.1 M HCl and distilled water under ultraviolet light and dark environment to research the photosensitivity desorption experiments.Found that the best analytic solution of azo-MOFs-1 is 0.1 M HNO3 which the desorption rate is at 70.23%, and light sensitivity gape is at 24.63%; the best analytic solution of azo-MOFs-2 is 0.1 M HCl which the desorption rate is at 71.56%, and light sensitivity gape is at 14.38%; the best analytic solution of azo-MOFs-3 is 0.1 M HCl which the desorption rate is at 59.56%, and light sensitivity gape is at 11.14%.(4) With practical application to the azo-MOFs-1 、 azo-MOFs-2 、 azo-MOFs-3 samples,it is found that: azo-MOFs-1 material adsorption of the tianshan sample is 136 mg/g and the extracting uranium from the simulated seawater can be up to 94.01%; azo-MOFs-2 material adsorption of the tianshan sample is 133.20 mg/g and the extracting uranium from the simulated seawater can be up to 89.17%; azo-MOFs-3 material adsorption of the tianshan sample is 135.85 mg/g and the extracting uranium from the simulated seawater can be up to 80.19%;... |
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