Selective Separation Of Rubidium By Ion Exchange Dsorption And Electro-driven Liquid Membrane Technology

Due to the coexistence of lithium,potassium and sodium with similar properties in solid ores such as lithium mica,cesium-neptunium and Salt Lake brine,the separation of precious metal rubidium from them is difficult.The traditional separation technology has been difficult to meet the demand of rubidium resources in aerospace and some new modern industrial fields.Therefore,the development of efficient separation and enrichment technology of rubidium has practical significance.Using rubidium,potassium and sodium coexisting solution and the reside solution of acid leaching of lithium mica after lithium extraction(Rb+: 80mg/L;K+: 5.67g/L;Na+: 17.46g/L,p H=7)as rubidium extraction solution,the selective adsorption and separation methods of rubidium by a novel highly efficient adsorption material(PVA@AMP)based on polyvinyl alcohol(PVA)embedding ammonium molybdate(AMP),and selective mass transfer behavior of rubidium by three series of polymer incusion membranes based on dicyclohexane-18-crown-6 ether(DC18C6)as carriers coupled with external electric field.The main research contents and results are as follows:(1)PVA@AMP is prepared by using polyvinyl alcohol(PVA)as the polymer substrate and ammonium phosphomolybdate(AMP)as the ion exchanger.The morphology,structure and adsorption performance of PVA@AMP influenced by AMP content,pore-forming additives polyethylene glycol 200/acetone/ethanol and its content,and the cross-linking reaction time in 3% glutaraldehyde aqueous solution are investigated by single factor method under the condition of single column dynamic adsorption with1 m L/min flow rate.The results show that the maximum embedding amount of AMP to PVA@AMP is not more than 45%.Within this range,the saturated adsorption amount of Rb(I)QRb increases with the increase of AMP content.The porogenic effect of PEG200 is better than that of acetone and ethanol.The 20-minute glutaraldehyde cross-linking reaction effectively solves the swelling behavior of PVA.Under the optimal preparation conditions of AMP content of 45%,PEG200 dosage of 2m L/0.25 g PVA and crosslinking time of 20min(3% glutaraldehyde aqueous solution),the adsorption amount of PVA@AMP for Rb(I)is 24.21 mg/g,and the separation coefficients of rubidium/potassium and rubidium/sodium SRb/K and SRb/Na are 19.8 and 54.3,respectively.(2)The adsorption kinetics of PVA@AMP for Rb(I),K(I)and Na(I)and the isothermal adsorption behavior of PVA@AMP for Rb(I)are investigated using simulating the rubidium-containing solution as the adsorption solution under the optimized single column dynamic adsorption process.The results show that the adsorption of K(I)and Na(I)by PVA@AMP is more consistent with the pseudo first-order kinetic model,while the adsorption kinetics for Rb(I)is consistent with the quasi-second-order kinetic model,indicating that the adsorption of PVA@AMP for Rb(I)is a chemisorption process,while that of K(I)and Na(I)are physical adsorption processes;the adsorption of PVA@AMP for Rb(I)conforms to the Freundlich adsorption isotherm model and is a multi-molecular layer adsorption.With deionized water as eluent,the elution percentage of K(I)and Na(I)on the surface of PVA@AMP are over 98%,and the loss percentage of Rb(I)are less than 5%.With 20% NH4 Cl as the desorption solution,the desorption percentage of Rb(I)can reach99% at a flow rate of 0.5 m L/min.(3)Three series of polymer incusion membranes PDA-PIM,PDO-PIM and PDT-PIM are prepared by using polyvinyl chloride(PVC)as based polymer,dicyclohexane-18-crown-6 ether(DC18C6)as carrier,trimethyloctyl ammonium chloride(Aliquat 336),n-octanol(OCT),trioctylphosphine oxide(TOPO)as auxiliary respectively.The simulated solution of 30mg/L Rb(I),K(I)and Na(I)is used as the solution.The permeability coefficient P and the selectivity coefficient S are used as indicators for the investigation of the influence of electric field voltage,PIM composition and stripping phase environment on mass transfer behaviors of three series of PIM.The results show that the permeability coefficients of three PIMs for Rb(I),K(I)and Na(I)increase with the increase of external electric field voltage.Mass transfer performance of PDA-PIM with the membrane composition of P25D3.5A25(w/w/w)is the best.Under the condition that the stripping phase is deionized water,the selectivity of PDA-PIM to rubidium increases with the increase of external electric field voltage,and at 180 V,PRb=12,SRb/Na=11.2,SRb/K=2.4,However,the stability was insufficient;PRb=2.59,SRb/Na=14.44,and SRb/K=1.88 for PDT-PIM under the optimal experimental conditions of voltage of 180 V and membrane phase of P25D3.5T10.However,the mass transfer performance of PDT-PIM was stable.The PRb and SRb/Na of PDT-PIM decrease only 4.6% and 0.5% after four cycles of experiments,and the enrichment factor of rubidium and sodium in 350 m L simulated solution are 3.02 and 0.50 respectively in 81.5h.PDO-PIM coupling external electric field has a high mass transfer coefficient for all three metal ions.The mass transfer coefficient P of PDO-PIM with P25D2.0O40 membrane composition can reach 115.93 for Rb(I)at 180 V.However,SRb/Na is only 3.89.