Studies Of Caffeine-Imprinted Phenolic Resin Sorbent

By the technology of inverse suspension polymerization in this topic,caffeine-imprinted phenolic resin sorbent(CIPS) and non-imprinted phenolic resinsorbent(NIPS) have been synthesized. Theirs pore volume, pore size, water content,skeletal density and specific surface area were measured. The results showed that thebasic parameters of CIPS and NIPS are little difference. Theirs morphology wereobserved, the results showed that there are more porous structures in CIPSmicrosphere than in NIPS microsphere.By Static and dynamic adsorption,the adsorption properties of CIPS and NIPSresin on were testde.The results were compared and found that the adsorption amountof CIPS is much larger than the adsorption amount of NIPS.The adsorption amount ofCIPS on caffeine and theophylline were compared,and the results showed that theadsorption amount of caffeine is much larger than the adsorption amount oftheophylline due to CIPS skeleton remain interspace that similar to the imprintingmolecule caffeine shapes and sizes.By Scatchard analysis, the molecular recognition characteristics of CIPS andNIPS were analysised.It was found that CIPS showed two different types of specificbinding sites.The apparent adsorption amount were calculated to be117.69mg/g forhigh affinity binding sites and73.72mg/g for lower affinity binding sites.Whiletheophylline only showed non-specific adsorption and the apparent adsorptionamount was43.14mg/g.The isothermal adsorption behaviors of CIPS and NIPS have been studied, Theresluts showed that the adsorption data are consistent with Langmuir and Freundlichequation in a certain range of concentration, so the adsorption of theophylline onCIPS and NIPS is monolayer adsorption and preferential adsorption.Thermodynamic changes in the process of adsorption of caffeine werestudied,the result show that the adsorption enphalpy change are-21~-27kJ/mol,which was higher than the van der Waals forces,and this showed the adsorption was an exothermic process.And it indicated there was the hydrogen bonding forcebetween the imprinting molecule and a phenolic hydroxyl group.In order to investigate the mechanism between the template molecule and thephenolic hydroxyl group, the functional monomer phenol and imprinting moleculecaffeine were self-assembly firstly.By Gaussian03W B3LYP/6231+G33method formolecular simulation,and the results again showed that there were hydrogen bondingforce between the imprinting molecule and the phenolic hydroxyl, and the most stablestructure was calculated.Under dynamic conditions, the CIPS resin adsorption-desorption propertieswere studied. When400mg/L solution of caffeine at the rate of3BV/h flowed throughCIPS columns, breakthrough point was26th bed volume under dynamic condition. Itwas clear that1mol/L hydrochloric acid at the rate of desorption1.5BV/h forremoving97.5%all the caffeine adsorbed on CIPS were4bed volumes. The averageconcentration of eluent is2498mg/L,which is6.25times than the initialconcentration.This is showed that CIPS possessed excellent desorptionperformance,and can be used to separation or concentration caffeine.