Preparation And Adsorption Properties Of Vitamin E Molecularly Imprinted Polymers

Vitamin E?VE?is essential for human health.Due to its biological activities,clinical application and market potential,the market demand becomes emerging.In order to promote the separation efficiency of VE,a molecular imprinted polymer with specific adsorption capacity for VE was prepared by molecular imprinting technology,and its adsorption performance was studied.The main contents of the study are as follows:?1?Molecularly imprinted polymers?MIPs?were prepared by the precipitation polymerization process.When the optimal imprinting ratio and cross-linking ratio were 1:5and 5:1 respectively,and acetone was used as the solvents,the MIPs was found to reach a high adsorption capacity(38.76 mg.g^-1).The scanning electron micrograph showed that MIP particles form microspheres with relatively uniform size of 2.1?m.The Fourier transform infrared spectroscopy showed that amino group serves as the binding site for VE.The BET specific surface areas of the MIPs were found in the range of 55m²·g^-1.The pore size analysis showed that the adsorbents were mostly macro-porous?d=20-300nm?,with the pore volume range of 0.15-0.2cm³·g^-1.The adsorption mechanism is predominantly chemical in nature.Adsorption experiment showed that the MIPs possesses a high adsorption capacity in chloroform solution while the adsorption time was about 120 minutes.The comparative adsorption experiments of MIPs and NIPs further confirmed that absorption capacity of MIPs are less affected by the other components in the mixture due to the specific binding site of MIPs to VE.?2?The Freundlich equation was found superior to Langmuir to describe the adsorption isotherm data on the MIPs.The adsorption of VE on the MIPs was found to be a heterogeneous process.Scatchard model confirmed that the MIPs got two types of adsorption mechanisms.Thermodynamic analysis showed that the adsorption process on MIPs were exothermic and low temperature?25??was beneficial to the adsorption.The kinetic data were fitted to the pseudo-first order kinetics and pseudo-second order kinetics,respectively.The results indicated that the adsorption kinetic followed the pseudo-second order kinetics.The fitting results of the internal diffusion model showed that the adsorption process was controlled by both film diffusion and internal diffusion.Fixed bed experiments were conducted to investigate the kinetics of adsorption/desorption of VE on the MIPs.About 3g of MIPs was charged into a column of o.d.2.5×L30 cm and pre-equilibrated with VE solution(C0=430.71 mg·L^-1)fed to the column?the ratio of height to diameter:4.5:1?at the flow rate of 0.3m L·min^-1.HPLC analysis showed that the absorption rate of VE was 61.28%.After saturation,the column was eluted with the solution of n-hexane and n-hexane/isopropanol?9:1,v/v?respectively and the recovery rate of MIPs reached to 94%.Cyclic experiments showed that the breakthrough curves changed little after 5 cycles of experiments,proving the good re-usability of the MIPs in practical applications.