Lithium Isotopes Separation By Ordered Mesoporous Silicas Functionalized With Crown Ether:Synthesis And Adsorption Behavior Study

Lithium has two stable isotopes,i.e.,~6Li(I)and ~7Li(I).~6Li is valuable for producing tritium for nuclear fusion reaction,while ~7Li has been used as a thermal carrier and coolant in nuclear reactors.Developing technology for lithium isotopes separation is of strategic value for national defense and nuclear energy industry in our country.According to previous researches,extraction chromatography,based on the coordination ability of crown ether compounds to lithium ion,holds great promise for effective separation of lithium isotopes.However,so far,the developed crown ether functionalized adsorption materials still suffer from low functionalization degree and limited adsorption capacity,leading to poor separation efficiency of lithium isotopes.Herein,in this dissertation,crown ether ligands with excellent coordination ability toward lithium were synthesized.On this basis,different synthetic stra tegies,including surface chemical grafting and surface initiated living radical polymerization(SI-LRP),were employed to develop novel kinds of crown ether functionalized ordered mesoporous silicas(OMSs),which possessed the structural advantages of huge specific surface area,high pore volume and uniform pore-channels.The adsorptive separation performance toward lithium isotopes was systematically investigated.Major achievements of this dissertation are summarized below.Firstly,benzo-15-crown-5 and a series of its derivatives containing different substituents were designed and synthesized,and,the capability of extraction separation for lithium isotopes was evaluated in solvent extraction system.Due to the better complexing ability of 4-aminobenzo-15-crown-5 to lithium isotopes,the crown ether ligand was employed to develop adsorption materials of lithium isotopes.Secondly,large-pore and short-channel OMSs bearing reactive sites were prepared as precursors.Chemical grafting method was used for covalently anchoring the crown ether ligands to the surface and pore-channels of the OMSs,resulting in an effective adsorption and separation of lith ium isotopes.Furthermore,initiators for continuous activator regeneration atom tran sfer radical(ICAR-ATRP)technique was integrated with bio-inspired polydopamine(PDA)chemistry for controlled growth of poly(glycidyl methacrylate)(PGMA)brushes from the outer-and inner-surfaces of OMSs.Taking advantage of the abundant epoxy groups in PGMA brushes of the obtained OMSs/polymer hybrid material,crown ether ligands were introduced with a high functionalization degree.Enhanced adsorption capacity toward lithium was achieved.This research developed methodologies,such as surface chemical grafting and SI-LRP,for preparation of crown ether functionalized OMSs.And,systematical investigation was performed to study the adsorptive separation behavior toward lithium isotopes by using the different types of crown ether functionalized OMSs in batch experiments.Multiple influencing factors on the performance of the adsorption materials,such as solvent,anion,temperature,and so on,were evaluated.Theoretical models regarding adsorption kinetics,thermodynamics,and adsorption isotherms were established.And,adsorption mechanism was examined.Overall,the findings in this dissertation would provide theoretical and experimental supports for development of lithium isotopes separation technology.