Study On The Preparation Of Aluminum-based Metal Organic Frameworks Materials And The Adsorption Properties

With the continuous development of modern society,the energy crisis that we face is becoming serious.Fossil energy is the main energy used in the modern industrial system.As a kind of non-renewable energy,the depletion of the traditional fossil energy will be inevitable.Moreover,fossil fuels will inevitably produce polluting gases which are harmful to the environment during their use.Nuclear energy,a kind of clean and efficient energy,is considered to be one of the best alternative options for fossil energy.Uranium is the most important fuel in the nuclear energy industry,while the land uranium resources in China are scarce and the supply of uranium resources is heavily dependent on imports.Considering the abundance of uranium resources in the ocean,the technology of extracting uranium from seawater can provide guarantee for uranium reserves in China,and contribute to the steady and rapid development of nuclear energy in China.In this paper,the metal-organic-frameworks adsorbents are mainly studied.In this paper four kinds of aluminum-based metal organic frameworks were prepared,and characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Fourier-transform infrared spectroscopy and so on.The adsorption experiment was carried out to study the uranium adsorption properties of the sorbents.Further,the adsorption kinetics data were analyzed by pseudo-first-order kinetic model and pseudo-second-order kinetic model,and the adsorption isotherms of adsorption process were analyzed by Langmuir model and Freundlich model.By the ion competition experiment,the cyclic desorption experiment and the simulated seawater experiment,the comprehensive adsorption properties of the adsorbents were investigated.Via the XPS analysis,the adsorption mechanism were also studied.The metal organic frame material（MIL-68）was successfully prepared by solvothermal method.The specific surface area of the synthesized MIL-68 is 559 m²/g;It has good thermal stability and can be stable at 450℃;The results of uranium adsorption experiments show that the best adsorption pH is 8;And under the laboratory conditions,the maximum adsorption capacity can reach 267.5 mg/g;MIL-68 has good selectivity and recycling efficiency;In the simulated sea water,the adsorption efficiency of low concentration uranium reached 85%.MIL-68/graphite oxide composite was synthesized by one-pot solvothermal method.It has a high performance on uranium adsorption.When pH is 8.0 and initial uranium concentration is 200 mg/L,the maximum adsorption capacity is 370 mg/g.The reusability and selectivity of the MIL-68/graphite oxide composite are excellent.And the removal rate of uranium is above 75%,in the simulated sea water.MIL-53 was successfully prepared by hydrothermal method,and amino-functionalized MIL-53-NH₂ was prepared by solvothermal method.The results of adsorption experiments show that the optimum adsorption pH of the two adsorbents is 8.When the initial uranium concentration is 200 mg/L,the maximum adsorption capacity is 452 and 190 mg/g respectively,which confirms that the amino group can improve the adsorption properties.MIL-53-NH₂ also showed a high adsorption capacity in the simulated sea water.