Preparation Of Cesium Ion Sieve And Study Of Its Adsorption And Exchange Performance For Cesium

Cesium is a rare alkali metal with strong chemical activity and excellent photoelectric effect,which has a wide application prospect.In China,many salt lake brines contain cesium resources,but the cesium content is low.Inorganic ion exchange method is considered to be one of the most effective methods to separate and extract cesium.In this work,the extraction of cesium from salt lake brine system was studied by ion exchange method.The porous cesium ion sieve with high specific surface area was prepared by the combination of template method and interface regulation method,and its ion exchange performance and adsorption mechanism were studied.Firstly,the mesoporous cesium ion sieve precursor Cs₂Ti₆O₁₃was prepared by the combination of template method and interface regulation method with PMMA polymer microspheres as the template.After acid modification,the cesium ion sieve(HTO/PMMA)was prepared.The structural morphology and adsorption properties of HTO/PMMA were characterized by XRD,SEM,FT-IR,XPS,Raman spectroscopy,nitrogen adsorption-desorption and thermogravimetric analysis.The results showed that the structure of Cs₂Ti₆O₁₃was stable,and the structure was not destroyed even after acid modification and adsorption.The introduction of PMMA microsphere template not only does not change the crystal structure of the ion sieve,but also endodes HTO/PMMA with a larger surface area(67.282m~2/g).The pore size of HTO/PMMA was 10.156nm,which belongs to mesoporous materials.Secondly,the adsorption and exchange performance of cesium ion sieve HTO/PMMA was measured.The saturated adsorption capacity of HTO/PMMA for Cs⁺was 308.8 mg/g,and the adsorption equilibrium was reached after 10 h of adsorption.In the mixed solution with Li⁺?Na⁺?K⁺?Rb⁺?Cs⁺,HTO/PMMA has selective memory for Cs⁺,and the selective sequence of each ion is Li⁺++++.The adsorption process of Cs⁺by HTO/PMMA is affected by temperature,and low temperature is more conducive to the reaction.The initial concentration of the adsorption solution will also affect the adsorption capacity.The higher the initial concentration of the solution,the greater the concentration difference of Cs⁺in the system,the greater the adsorption driving force,and the greater the adsorption capacity of HTO/PMMA.Finally,the ion exchange thermodynamics and ion exchange kinetics of cesium ion sieve HTO/PMMA were studied.The H⁺-Cs⁺exchange isothermal diagram and Kielland diagram of HTO/PMMA at 15?,25?and 35?are obtained.The research showed that the equilibrium constant K_aof H⁺-Cs⁺exchange system decreases with the increase of reaction temperature.At the same time,the?H~0<0 in the ion exchange process,indicating that the H⁺-Cs⁺ion exchange process is an exothermic process,and high temperature was not conducive to the reaction.The H⁺-Cs⁺exchange system?G~0<0 showed that the process of adsorbing Cs⁺by HTO/PMMA can proceed spontaneously,and the H⁺-Cs⁺exchange reaction proceeds in the direction of reducing free energy.When the initial concentration of Cs⁺is 0.001 mol/L,the adsorption process of Cs⁺by HTO/PMMA conforms to Freundlich model,indicating that the adsorption process is multi-layer adsorption.The curve analysis of the intra particle diffusion model showed that the control step of the ion exchange process is mainly controlled by the boundary layer diffusion.At the same time,the preliminary application of HTO/PMMA was studied.Cs Cl product was prepared,and the recovery of Cs⁺was 89.8(wt)%.