Study On Preparation And Adsorption Properties Of Ion Imprinted Polymers For Cu(Ⅱ) And Cr(Ⅵ)

With increasing wide application of heavy metals in industrial manufacture in recent years,the consequent heavy metal wastewater pollution becomes increasingly severe.Heavy metal ions like copper（Ⅱ）and chromium（Ⅵ）are very harmful to bones,organs and nervous system.Therefore,it is of great significance to study and develop an effective treatment technology of heavy metal wastewater.In this paper,Cu（Ⅱ）and Cr（Ⅵ）ion imprinted polymers were synthesized by ion imprinted technology,which showed high adsorption capacity and good adsorption selectivity.The details are as follows:1、A Cu（Ⅱ）ion imprinted polymer（Cu（Ⅱ）-IIP）was synthesized by ion imprinted technology in combination with sol-gel process.In this work,Cu（Ⅱ）ion was chosen as template ion,water as solvent,and N-[3-（2-aminoethylamino）propyl]trimethoxysilane（AAPTMS）was selected as monomer,tetraethyl orthosilicate（TEOS）was used as cross-linker.Effects of preparation conditions including solvent type and volume,molar ratio of functional monomer to template ion,and amount of cross-linker on adsorption properties of polymers were studied systematically.Characterization methods,including FT-IR,SEM,XPS and Zeta potential were used.Not only concentration and pH of Cu（Ⅱ）solution,but also adsorption time have great effects on adsorption performance of ion imprinted polymers.The maximum adsorption capacity of Cu（Ⅱ）-IIP is up to 39.82 mg·g^-1.Adsorption equilibrium can be reached within 60 min.The results indicate that adsorption process fits well with the Freundlich isotherm and pseudo-second-order model.Moreover,the relative selectivity coefficients for Cu（II）/Pb（II）,Cu（Ⅱ）/Ni（Ⅱ）,Cu（Ⅱ）/Co（Ⅱ）,and Cu（Ⅱ）/Cd（Ⅱ）are 1.76,25.71,21.94 and 18.41,respectively.In addition,Cu（II）-IIP shows very stable adsorption performance and good reuseability after five adsorption/regeneration cycles and the reduction of adsorption capacity is less than 3%.2、Magnetic Fe₃O₄ nanoparticles were prepared by hydrothermal method and then coated with a silica shell to form Fe₃O₄@SiO2 by a sol-gel process.The Cr（Ⅵ）ion imprinted polymer was prepared by surface imprinting technique using Cr₂O₇^2-as template ion,4-VP as monomer,isopropanol as solvent,EGDMA as cross-linker,and AIBN as initiator.Effects of solvent type,the additive amounts of template ion and cross-linker on the adsorption properties of prepared ion imprinted polymers were studied.FT-IR,transmission electron microscope（TEM）,XPS and thermal gravity analysis（TGA）were used for characterization of prepared polymers.When 10 mg imprinted polymers are used in 100 mg L-1 Cr（VI）aqueous solution at pH 2.0,the maximum adsorption capacity reaches up to 131.40 mg·g^-1 and adsorption equilibrium can be reached within 50 min.Resutls of isotherm study show that the adsorption process fits well with Langmuir model with high correlation coefficient（R2=0.9877）,indicating that the adsorption process is monolayer adsorption.In addition,kinetics study indicates that the adsorption process fits well with pseudo-first order model.KMnO4,KCrO4and KAIF4 were selected for the study of adsorption selectivity of ion imprinted polymers.Prepared ion imprinted polymers show good adsorption selectivity for Cr₂O₇^2-in Cr₂O₇^2-/AIF4-and Cr₂O₇^2-/CrO42-solutions and the relative selectivity coefficients are 6.91 and 5.99,respectively.The reduction of adsorption capacity is about 8.2%after six adsorption/regeneration cycles,indicating that the prepared ion imprinted polymer has good stability and reuseability.