Preparation And Characterization Of Cr(Ⅵ) And 4,4’-diaminodiphenylmethane Imprinted Polymer

The content of harmful substances in food contact materials is low.In order to effectively avoid the interference of a large number of coexisting ions and matrix factors,it is necessary to improve the anti-interference ability in the detection process,which requires the separation and enrichment of target substances.However,most of the sample pretreatment technologies are lack of selectivity at present.In order to ensure the accuracy and efficiency of the actual detection,it is still necessary to develop pretreatment technologies with high adsorption efficiency and selectivity at the same time.In this project,molecularly imprinted polymers were prepared with Cr（Ⅵ）and 4,4’-diaminodiphenylmethane as template molecules and Fe₃O₄@m SiO₂ as magnetic carriers.Through a variety of characterization methods and adsorption test experiments,the structure and adsorption properties of the two molecularly imprinted polymers were analyzed.The main research contents and achievements are as follows:（1）Preparation and characterization of magnetic carrier.The magnetic particles were prepared by different methods and different particle sizes of Fe₃O₄.The effects of different methods and different magnetic core sizes on magnetic composite microspheres were investigated by TEM and XRD.The results show that the magnetic carrier prepared by the two-step method has a clear core-shell structure,and the magnetic carrier shows a better dispersion with the magnetic core of 200 nm.The magnetic support has larger specific surface area,which can provide more active sites for subsequent reactions.（2）Preparation and adsorption properties of chromium ion imprinted polymer.The template ion potassium dichromate,functional monomer salicylaldoxime,comonomer-methacrylic acid and crosslinking agent EGDMA were used as the main factors for the preparation of Cr（Ⅵ）-IIPs.The orthogonal experiment was designed and the optimal experimental scheme for the preparation of Cr（Ⅵ）-IIPs was obtained as follows:the amount of potassium dichromate was 0.1 mmol,salicylaldoxime was 0.6 mmol,-methacrylic acid was0.5 mmol,EGDMA was 1.5 m L and Fe₃O₄@m SiO₂ was 0.1 g respectively.The adsorption properties of the imprinted polymer were investigated by designing single factor adsorption experiments.The results showed that at room temperature,when the p H of the solution was 2,the imprinted polymer could reach the adsorption equilibrium in 2 h,and the maximum adsorption capacity was 145 mg/g.The relative selectivity coefficients of Cr（Ⅵ）-IIPs for Cr O₄^2-,Cr³⁺,Pb²⁺and Cu²⁺were 6.32,4.21,3.00 and 3.30,respectively,indicating that Cr（Ⅵ）-IIPs had strong selective ability for target ions.After being reused for 6 times,there were no obvious changes in adsorption capacity of the polymer.（3）Preparation and adsorption properties of 4,4’-diaminodiphenylmethane molecularly imprinted polymer.The effects of the types of functional monomers,the ratio of template molecules to functional monomers,and the amount of crosslinking agent on the adsorption capacity of molecularly imprinted materials were investigated.The results of the experiments of the adsorption properties showed that the molecularly imprinted polymer reached adsorption equilibrium at 25℃in 80 min,and the maximum adsorption capacity was 56.5mol/g.And the results showed that the adsorption process conformed to the pseudo second order kinetic model and Langmuir model.The selectivity coefficients of imprinted polymers for4,4’-methylene bis（2-chloroaniline）,4-aminobiphenyl and4,4’-tetramethyldiaminodiphenylmethane were 2.2、5.84和3.68,respectively.After being reused for 6 times,the adsorption capacity of the molecularly imprinted polymer can still be maintained at about 83.5%,with a certain repeatability.