Study On Synthesis Of Molecularly Imprinted Hypercrosslinked Resin Modified By Phenolic Hydroxyl And Its Adsorption Properties For Matrine

Alkaloid is one of the most effective components in Chinese herbal medicine,of which matrine is widely used.There are many similar compounds of matrine,hence,it is important to identify and extract matrine effectively.To achieve high adsorption capacity and selectivity of matrine,the hypercrosslinked resin was combined with molecular imprinting technique to prepare phenolic hydroxyl modified hypercrosslinked resin(NIP)and molecularly imprinted hypercrosslinked resin(MIP).The lower crosslinked styrene-divinyl benzene polymer was prepared by suspension polymerization,and the harmfulless chloromethyl ethyl ether was used as chloromethylation reagent to prepare chloromethyl styrene.By post-crosslinking reaction,phenol was modified to obtain hypercrosslinked adsorption resin(NIP).Using matrine as template molecular to react with phenol for some time and then react with chloromethyl styrene,matrine was removed to obtain hypercrosslinked molecularly imprinted polymer(MIP).The prepared resins were characterized by specific surface area and pore size analyzer and fourier transform infrared spectroscopy,and the adsorption properties of NIP resin in water system were also investigated.The effects of temperature,concentration,pH value and solvent type on the adsorption performance were analyzed.The results showed that phenolic hydroxyl groups are successfully modified onto the resin skeleton,and NIP resin has high specific surface area of 605.79m~2/g.At the temperature of 288 K with initial concentration of 100mg/L,the equilibrium adsorption capacity of NIP resin for matrine and cytisine are 22.24mg/g and 21.02mg/g,respectively,which indicates that the adsorption capacity of NIP resin for matrine is close to that for cytisine.Langmuir and Freundlich equations can well fit the adsorption isotherm of NIP resin for two kinds of adsorbate.With the increasing of pH value,the adsorption capacities of NIP for matrine and cytisine are increased with latter decreasing and reach the maximum value at about 9 of pH value.Under the same conditions,the adsorption enthalpy change of matrine and cytisine on NIP resin are similar,which indicates that the adsorption capacities of the resin for the two adsorbates are similar.The kinetic study shows that the adsorption rates of matrine and cytisine on NIP resin are similar.In the aqueous solution,the adsorption ability of matrine on NIP resin is the highest with the decreasing sequence in chloroform solvent and ethanol solvent.The surface topography of MIP resin was determined by SEM,and the adsorption selectivity of MIP resin in water system was also investigated.The results show that the holes on MIP resin are more regular than those of NIP resin.Compared with cytisine,the adsorption selectivity coefficient of MIP resin for matrine can reach about 15,while that of NIP resin is only about 1.At the temperature of 288 K with initial concentration of 100mg/L,the adsorption capacity of MIP resin for matrine reaches 35.48mg/L,while that for cytisine is only 15.33mg/L.The adsorption capacity comparison indicates that the adsorption ability of MIP resin for matrine is greater than that of cytisine.Thermodynamic analysis also shows that MIP resin is more easily adsorb matrine than cytisine.When the adsorption amount is 20mg/g,the adsorption enthalpies of matrine and cytisine onto MIP resin are-31.742kJ/mol and-19.394kJ/mol,respectively.Kinetic analysis shows that the diffusion rate of matrine in MIP resin particles is higher than that of cytisine.All these are due to the cavities of MIP resin matching matrine molecular very well after molecular imprinting.