Preparation Of Rare Earth Ion Imprinted Membranes And Studies On The Adsorption And Separation Of Heavy Rare Earths

Rare Earths(REs)are widely used in the fields of communications,medical care,energy,and national defense,and are listed as key strategic resources by many countries.One of its characteristics is that the incorporation of trace high-purity rare earths will significantly improve product performance.Although my country has rich abundant rare earth resources,the demand for a single high-purity heavy rare earth element depends on high-priced imports.The reason is that the physical and chemical properties of adjacent rare earth ions are extremely similar.At the same time,rare earth elements often coexist in rare earth minerals,making it difficult to separate adjacent rare earth elements.Solvent extraction technology,as the main process for the production of single high-purity rare earth products in my country,still has the disadvantages of low efficiency,incomplete stripping,large consumption of acid and alkali,and large amount of volatile organic solvents for the separation of heavy rare earths.Membrane separation method integrates extraction and stripping processes,with less acid,alkali and volatile organic solvents,and is highly efficient and green.However,when applied to the separation of adjacent rare earth ions,it still needs to strengthen its performance in terms of selectivity.Ion imprinting technology has the advantage of specifically identifying target ions.Combining it with the membrane separation method to construct a rare earth ion imprinted membrane material is expected to achieve high-efficiency and green separation of adjacent heavy rare earth ions.In this thesis,firstly,the PVDF-Cyphos IL 104 polymer inclusion membrane(Polymer Inclusion Membranes,PIMs)was prepared by using the bifunctional ionic liquid Cyphos IL 104,which has good selectivity to heavy rare earth ions.Adsorption and separation behavior and mechanism of ytterbium and lutetium;then using polymer inclusion membrane as the base membrane,using surface aqueous ion imprinting and sol-gel imprinting methods,respectively,to prepare two different ion imprinted membranes(Ion Imprinted Membranes,IIMs),The separation behavior mechanism of heavy rare earth yttrium ion was studied.The specific research content is as follows:1.Preparation of PVDF-Cyphos IL 104 polymer inclusion membrane and its separation behavior and mechanism of heavy rare earth lutetium and ytterbium.Using the bifunctional ionic liquid Cyphos IL 104 with good selectivity to heavy rare earth ions,a PVDF-Cyphos IL 104 polymer inclusion membrane was prepared,and the adsorption and separation behavior and mechanism of the adjacent heavy rare earth ytterbium and lutetium were studied.The chemical composition of the PIM was verified by attenuated total reflection Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.It was confirmed that only P=O and P-O groups were involved in the formation of RE-Cyphos IL 104 complex.Scanning electron microscopy observed that the PIM has a typical thumb-like asymmetric structure.The decrease in water contact angle proves that the addition of Cyphos IL 104 improves the hydrophilicity of PIM.The results of dynamic transport experiments show that the permeability coefficients of lutetium and ytterbium are 156?m s^-1 and 114.82?m s^-1,respectively,and the corresponding initial membrane fluxes are 90.17?mol m^-2 s^-1and 65.61?mol m^-2 s^-1,respectively.The calculated separation coefficient of Yb(III)and Lu(III)is 1.37.2.Preparation of yttrium ion aqueous phase imprinted membrane and its adsorption and separation thermodynamics and kinetic behavior of heavy rare earth holmium,yttrium and erbiumUsing ion imprinting technology,a rare earth ion imprinting membrane material is constructed on the surface of the PIM base membrane.First,add hydrophilic ethylene-vinyl alcohol copolymer(EVOH)to the PIM base membrane,mix PVDF,EVOH and Cyanex 272 to prepare the PIM base membrane by the phase inversion method.Then,using yttrium ion as the template ion,itaconic acid as the imprinting functional monomer,and N,N'-methylenebisacrylamide as the crosslinking agent,polymerization is initiated by redox in the water phase to prepare the yttrium ion imprinting Membrane(Y-IIMs).The composition and surface morphology of Y-IIMs were studied by FTIR,XPS,SEM and other characterization methods.The results showed that P=O and P-O are the groups mainly involved in the formation of RE-Cyanex 272 complex.After the imprinting process,a layer of imprinted polymer is attached to the inner wall and surface of the membrane pores.After EVOH and Cyanex 272 are added and the hydrophilic imprinted polymer layer is formed,the hydrophilicity of the Y-IIMs is improved.The adsorption capacity of Y-IIMs to yttrium is three times that of non-imprinted membranes(NIMs),indicating that the Y-IIMs exhibits the expected specific recognition ability for yttrium.The obtained separation coefficients?(Y/Ho)and?(Y/Er)increased from 1.27 and 0.88 without imprinting to 1.66 and 1.36 after imprinting,and yttrium was preferentially permeated and transported.The relative separation factors?_r(Y/Ho)and?_r(Y/Er)of the imprinting process were 1.32 and 1.45,respectively.3.The preparation of yttrium ion imprinted spinning membranes and the thermodynamic and kinetic behaviors of the adsorption and separation of heavy rare earth holmium,yttrium and erbiumThe PVDF-Cyanex 272 electrospinning membrane modified by dopamine was used as the base membrane,and the yttrium ion was used as the template ion to prepare the Yttrium Ion Imprinted Electrospinning Membranes(Yttrium Ion Imprinted Electrospinning Membranes,Y-IIEMs).Through different characterization test methods,static adsorption thermodynamics,kinetics and dynamic transport experiments,the composition,morphology and adsorption and separation performance of the membrane material were studied.The results show that only P=O and P-O participate in the formation of rare earth complexes.The addition of Cyanex272 and the formation of hydrophilic imprinted polymer improve the hydrophilicity of the membrane material.The adsorption capacity of Y-IIEMs for yttrium ions is seven times that of NIMs,and it shows excellent adsorption performance for Y(?).Similarly,due to the imprinting process,the membrane preferentially transports yttrium,and the obtained separation coefficients?(Y/Ho)and?(Y/Er)are increased from 1.24 and 0.85 for unprinted to 2.01 and 1.77 after imprinting.The imprinting process The relative separation factors?_r(Y/Ho)and?_r(Y/Er)are 1.83 and 2.08,respectively.