Preparation And Adsorption Separation Properties Research Of ReO₄^- Ion Imprinted Polymer

With the rapid development of the defense,aerospace and other industries,higher requirements were imposed on the high temperature resistance of high-temperature alloys.In order to meet requirements of high temperature resistance,various high-temperature alloy elements need to be added to high-temperature alloys.Among many high-temperature alloy elements,Rhenium(Re),a rare metal materials,were widely favored because it could significantly improve the high temperature resistance of high-temperature alloys.Since the second generation of high temperature alloys,Rewere added to high-temperature alloys in our country.Among the widely used third/fourth-generation single-crystal high-temperature alloys,the addition amount of Rehad reached about 6%.With the expansion of high-temperature alloy applications,the demand of Reis increasing.However,the natural reserves of Rewere seriously insufficient,the quality of minerals were low and the distribution of minerals was extremely unbalanced,which resulted in a shortage of Reand seriously hinder the development of high-temperature alloy industries and downstream industries.At present,the metallurgical process of Remainly include d dissolution,oxidation,separation and purification,reduction.The metallurgical process was complicated,and the separation and purification as an important process had many disadvantages of low purification efficiency and low purity.Therefore,the development of new technologies to achieve accurate ly separation and recycling of Refrom complex environments could not only shorte the metallurgical process of Reand reduce production costs,but also alleviate d the serious supply and demand contradictions and ensured strategic security.Imprinted polymer,due to its special preparation process by imprinting technology,have a specific property of template recognition,and it is expected to accurately separate the template from complex environments.Similarly,based on its special preparation process,imprinted polymer materials have many advantages of the long-term stability,structural presupposition and wide applicability,and have become a research hotspot in the field of separation and purification.In this work,ReO₄^-ion imprinted polymer(ReO₄^--IIP)was synthesized with ReO₄^-as template and synthesis conditions were optimized.At the same time,the structure and morphology of ReO₄^--IIP were characterized.The preparation and separation performance of ReO₄^--IIP were studied.The kinetics and thermodynamic mechanism of ReO₄^--IIP in adsorption process were studied.Some meaningful results were obtained.The specific research contents and results are summarized as follows:1.ReO₄^--IIP was synthesized,which seclected ReO₄^-as template ion,N-vinylpyrrolidone(NVP)and acrylic acid(AA)as functional monomers,N,N-methylenebisacrylamide(NMBA)as crosslinkers,H₂O₂-Vc as initiators and water assolvent,respectively.The synthesis conditions were optimized by adsorption capacity and separation degree in the equimolar concentration mixture solutions of NH₄ReO₄ and KMn O₄,and the desorption ratio in aqueous solution as index.The optimum conditions were obatined:the molar ratios of NMBA,NH₄ReO₄,AA,H₂O₂and V_C to NVP were 2.08,0.03,1.95,0.03 and 0.003,the temperature and time of polymerization were 35? and 24h.The adsorption capacity,separation degree and desorption ratio of ReO₄^--IIP under optimal conditions were 0.037 mmol/g,2.35 and68.33%.Good adsorption selectivity was maintained after repeated 6 times.Adsorption kinetics and thermodynamics were also studied.The results of adsorption kinetics demonstrated that the Zero-order kinetic model could better describe the adsorption process.The results of adsorption thermodynamic documented that Langmuir model was more suitable for describing the isothermal ad sorption process of IIP,and Scatchard model indicated that there were two binding sites in the IIP.2.Since acrylamide(AM)was superior to NVP for the effect of self-assembly by the amide bond and intermolecular forces.Moreover,the methanol-water mixed solution could increase the solubility of N,N-methylenebisacrylamide(NMBA),which would increase the rigidity of the IIP,maintain the shape of imprinted pores,and improve the performance of the IIP.So,ReO₄^--IIP was prepared,which selected ReO₄^-as template ion,AM and acrylic acid(AA)as functional monomers,NMBA as crosslinkers,H₂O₂-Vc as initiators,V_water:V_methanol=3:7 mixed solution as solvent.The synthesis conditions were optimized by adsorption capacity and separation degree in the equimolar concentration mixture solutions of NH₄ReO₄ and KMn O₄,and the desorption ratio in aqueous solution as index.The optimum conditions were obtained:the molar ratios of NMBA,NH₄ReO₄,AA,H₂O₂,Vc to AM were 5.73,0.052,1.29,0.02 and 0.003,the temperature and time of polymerization were 40? and 28h.The adsorption capacity,separation degree and desorption ratio of ReO₄^--IIP under optimal conditions were 0.060 mmol/g,3.11 and 69.70%.Good adsorption selectivity was maintained after repeated 8 times.Adsorption kinetics and thermodynamics were also studied.The results of adsorption kinetics demonstrated that the Zero-order kinetic model could better describe the adsorption process.The results of adsorption thermodynamic documented that Langmuir model was more suitable for describing the isothermal adsorption process of IIP,and Scatchard model indicated that there were two binding sites in the IIP.3.The adsorption desorption performance of IIP prepared by the conventional method was difficult to improve simultaneously.We introduced Poly N,N-diethyl acrylamide(PDEA)synthesized by Reversible Addition-Fragmentation Chain Transfer(RAFT)polymerization into IIP to design and synthesize IIP with a"rolling curtain"structure.ReO₄^--IIP containing the temperature-sensitive block PDEA was prepared with ReO₄^-as template ions,acrylamide(AM)and acrylic acid(AA)as functional monomers,N,N-methylenebisacrylamide(NMBA)as crosslinkers,H₂O₂-Vc as initiator,and the mixed solution of V_water:V_methanol=3:7 as solvent.The optimal molecular weight(3600)of PDEA was determined by the adsorption capacity and separation degree of IIP in the equimolar concentration of NH ₄ReO₄ and KMn O₄mixed solution,and the desorption ratio in aqueous solution as index.The synthesis process conditions were optimized under the molecular weight(3600)of PDEA.The optimum conditions were obtained:the molar ratios of NMBA,NH₄ReO₄,AA,H₂O₂,Vc to AM were:5.97,0.040,1.54,0.021 and 0.003,the temperature and time of polymerization were 35? and 20h.The adsorption and desorption performance of IIP above or below the lower criticalsolution temperature(LCST)of PDEA were studied in detail.The result showed that the effect of separation and purification was best at the adsorption of 40? and the desorption of 25?.The adsorption capacity,separation degree and desorption ratio of ReO₄^--IIP under optimal conditions were0.068mmol/g,3.35 and 77.86%.