Preparation And Performance Of Adsorption And Separation For DEHP Surface Molecularly Imprinted Polymer With Magnetic Nanoparticles

As an important phthalate,di（2-ethylhexyl）phthalate（DEHP）is often used as plasticizer to improve the flexibility and toughness of plastic products,and it has been widely used in our daily life.However,DEHP can be easily transfered into the environment,and for a certain concentration,it can cause harm to people’s health even with teratogenicity,carcinogenicity,and mutagenicity.At present,DEHP has been detected in food packaging,children toys,cosmetics and people’s body fluids.Therefore,developing a newly efficient method for determining and separating DEHP in diverse environmental matrices becomes highly significant.The spatial structure of molecularly imprinted materials can well match the structure of templates,which can be used for specific adsorption for templates.Molecularly imprinted polymers are often prepared by bulk polymerization,which have many problems such as low utilization rate of binding sites and difficulty of templates removal.However,surface molecular imprinting technology establishes the imprinting sites on the surface of carrier and can be used to make up for the deficiencies.The stimulus-responsive molecularly imprinted polymers are the focus of molecular imprinting technique,and they can response to external conditions such as magnetic field,temperature,light and pH.Hence,molecularly imprinted polymers can show controllable movement,adsorption and release behavior,and they have broader application prospect.In this paper,three nano-sized molecularly imprinted polymers were prepared by surface molecular imprinting with for DEHP as template.The details are described as follows:（1）Preparation and properties of DEHP molecularly imprinted polymer by surface-grafting method（SMIP）The SMIP was synthesized by surface-grafting method with silica nanoparticles as carrier which prepared by St?ber method.The preparation conditions of molecularly imprinted shells were optimized to get the best adsorption performance.The results show that under the conditions with the ratio of functional monomer of methacrylic acid（MAA）,template molecule and crosslinker of 1:4:20,the self-assembly time of 12 hours and the polymerization time of 24 hours at 65°C,the optimum adsorption performance of SMIP can be obtained.According to the TEM images,the molecularly imprinted layer on the silica particle surface is about 50 nm with obvious core-shell structure.The maximum adsorption capacity of SMIP for template molecule DEHP is 8.42mg/g.The Langmuir model is more suitable for fitting the static adsorption process of SMIP,indicating that the adsorption is monolayer adsorption.The dynamic adsorption process of SMIP shows that the adsorption of SMIP can reach equilibrium in about 80min.The Pseudo-second-order kinetic model fits the whole adsorption process well,which indicates that the adsorption mainly depends on chemical action.The SMIP has good selectivity to DEHP with selectivity coefficient of 2.485,and the SMIP also has good reproducibility.（2）Preparation and properties of DEHP magnetic molecularly imprinted polymer（MMIP）Fe₃O₄ magnetic nanoparticles were synthesized by hydrothermal method,and the silicon layer was coated on the surface of Fe₃O₄ nanoparticles by St?ber method.The surface of silicon layer was modified by silane coupling agent MPS,and then through surface molecular imprinting technique,coating magnetic carriers with molecularly imprinted polymers,a novel MMIP was successfully fabricated for the convenient separation of DEHP with methacrylic acid as functional monomer,ethylene glycol dimethacrylate（EGDMA）as cross linker and 2,2-azobis（isobutyronitrile）（AIBN）as initiator.According to the TEM images,the synthesized Fe₃O₄ nanoparticles are regularly spherical and dispersed well.The thickness of the surface silicon layer is about 20 nm,and the thickness of molecularly imprinted layer is about 20 nm.The prepared MMIP shows superparamagnetic property with the maximum saturation magnetic intensity of 43.97emu/g,and it can be conveniently separated in 20S by external magnetic field.The maximum equilibrium adsorption capacity of MMIP is5.23mg/g,and the adsorption equilibrium can be achieved in about 40min.The Langmuir model and the Pseudo-second-order kinetic model are more suitable for fitting the static and dynamic adsorption process of MMIP,respectively.MMIP has good adsorption selectivity and recyclability.（3）Preparation and properties of thermosensitive DEHP magnetic molecularly imprinted polymer（TMMIP）The TMMIP was synthesized by adding thermosensitive monomers of N-isopropylacrylamide（NIPAM）and hydrophilic crosslinker of N,N-methylene bisacrylamide（MBA）during the preparation of MMIP.The prepared TMMIP has good magnetic separation performance with saturation magnetic intensity of31.05emu/g.TMMIP has different adsorption behaviors at different temperatures.Dynamic light scattering（DLS）analysis shows that the Lower Critical Solution Temperature（LCST）of TMMIP is around 34°C.At 35°C,TMMIP reaches adsorption equilibrium in about 60 min,and the pseudo-second-order kinetic model can fit the adsorption well.The adsorption selectivity coefficient of TMMIP for DAP and DBP to are 3.05 and 1.97,respectively.TMMIP can be recycled more than five times and has good practical value.