Study On The Preparation And Adsorption Properties Of Ion Imprinted Materials For Rb(i)and Cr(?)

In recent years,rubidium has shown broad potential in the fields of energy,military industry,medicine and so on,which has great value for development.In China vast amounts of rubidium resources are stored in salt lakes,but the concentration of rubidium is very low,and there are large number of other ions,which bring great difficulties to the extraction and separation of rubidium.Chromium has attracted increasing attention as a widely used heavy metal.Chromium-containing wastewater brings serious water pollution and threatens human health.Therefore,the separation and enrichment of chromium in industrial wastewater is also an urgent problem to be solved.Among numerous adsorbent materials,ion-imprinted materials are widely used in ion detection and ion enrichment due to their good selectivity for template ions.In this paper,ion imprinting technology was used to prepare two kinds of ion-imprinted material that is,selecting alkali rubidium cation ions and dichromate anion ions as the template,respectively.We investigate the adsorption properties of the materials and hope to lay a certain foundation for industrial extraction of rubidium and chromium ions.Firstly,Rb(I)-IIPs were synthesized by bulk polymerization.Using Rb(I)as template ions,methanol and acetonitrile as polymerization solvents,benzene 12 crown 4 ether as ligand and methacrylic acid as functional monomer,The reaction was initiated by 2,2-azobisisobutyronitrile under the crosslinking of ethylene glycol dimethacrylate.In addition to the reaction,benzene 12-crown-4 ether was introduced in order to improve the adsorption performance of polymers,this was done because the crown cavities and metal cations can form complexes,so the template ions can be fixed better.The polymers were characterized by scanning electron microscopy(SEM),infrared spectroscopy(FT-IR),thermal gravity analysis(TGA),energy dispersive spectroscopy(EDS)and ZETA potential.The experimental conditions were also studied,increasing the solution concentration can increase the mass transfer driving force,the maximum adsorption capacity of the polymers is 129.96 mg-g-1 at pH 9.5,the adsorption equilibrium can be reached within 15 min,the adsorption process conforms to the pseudo-second-order kinetic model.The selectivity coefficients for Rb(I)/K(I),Rb(I)/Na(I),Rb(I)/Li(I)are 2.46,1.51 and 1.65,respectively.After 6 repeated cycles of adsorption-desorption,the adsorption decreased only 5%,indicating that the polymers have good regeneration performance.Secondly,Cr(VI)-IIPs were prepared by surface imprinting technique.Using Cr2O72-as template ions,magnetic chitosan as the matrix,isopropyl alcohol and water as solvents and 4-vinylpyridine and 2-(methacryloxy)ethyltrimethyl ammonium chloride as functional monomers,The reaction was initiated by potassium persulfate and 2,2-azobisisobutyronitrile under the crosslinking of ethylene glycol dimethacrylate.The polymers were characterized by SEM,FT-IR and TGA.The polymers had the best adsorption effect at pH 2.0,increasing the adsorption concentration of the solution increased the mass transfer driving force,the maximum adsorption capacity is 219.54 mg·g-1.88%of the equilibrium adsorption capacity can be reached at 2h and at 6h can be fully achieved.The adsorption process conforms to the pseudo-second-order kinetic model.The selectivity coefficients of Cr(VI)-IIPs to Cr(VI)/Cu(?)?Cr(?)/Cr(?)?Cr(VI)/S042-are 346.94,57.71 and 1.72,respectively.After repeating the adsorption-desorption process 10 times,the adsorption capacity can still reach 80%of the initial adsorption capacity.