Preparation And Characteristic Of Thermo-sensitive Metal Ion Imprinted Polymers

Carbon dioxide is inexpensive, nontoxic, and non-flammable, and it has an easily accessible critical temperature of 31.1°C and critical pressure of 7.38 MPa, and it has both liquid and gas like characteristic. So the use of supercritical carbon dioxide (scCO₂) as an alternative to traditional aqueous and organic solvents has attracted much attention in the fields of extraction, polymer synthesis and materials processing. In the present study , molecular imprinting technology was applied to the preparation of the metal ion imprinting polymer(MIIP) using scCO₂ as a polymerization medium. Based on unique identification of the imprinted polymers to the template molecular(ion), the high selective of metal ion imprinted polymer for the target molecular(ion) have received much attention. So MIIP are having extensive application in many field. The present study contain the following three research works:(1) Metal ion imprinted polymers were synthesized for Cu(â…¡) ions adopting precipitation polymerization in scCO₂, which in the study, copper ion was used as a model template, a simple both as monomer and complexing ligand, Ethylene Dimethacry(EDMA) and 2,2-azobisisobutyronitrile(AIBN) were added as a crosslinker and free radical initiator, respectively. Removal of target copper ion from the polymer was accomplished with 1.0% H2SO4. It can be concluded that the adsorption capacity of the Cu(â…¡)-imprinted polymers for Cu(â…¡) ions was higher than non-imprinted polymers and the adsorption capacity of the Cu(â…¡)-imprinted polymers and non-imprinted for Cu(â…¡) ions were 21.25 mg·g^-1, 7.5 mg·g^-1 respectively. In addition, the Cu(â…¡)-imprinted polymers for Cu(â…¡) ions showed excellent selectivity under competitive conditions. It can be concluded that the Cu(â…¡)-imprinted polymers show the following metal ion affinity order:Cu(â…¡) >Zn(â…¡) >Co(â…¡),and also the selectivity coefficient of Cu²⁺/Zn²⁺ and Cu²⁺/Co²⁺ was 2.13. (2) Ion imprinted polymers of temary complexes metal were synthesized in scCO₂ by precipitation polymerization , with addition of small amount of methanol as coselvent, using copper ion as model template, MAA and NIPA as funcional monomer, EDMA and AIBN as crosslinker and free radical initiator, respectively. Removal of target copper ion from the polymer was accomplished with 3.0% H2SO4. Moreover, we have also characterized very extensively the synthesized Cu(â…¡)-MIIP in terms of SEM, FTIR, XRD and TGA. At the same time, the adsorption capacity of the Cu(â…¡)-imprinted polymers for Cu(â…¡) ions was studied in different conditions(pH,temperature) and selectivity adsorption for different metal ions. The results were shown that the imprinted polymers had excellent selectivity for copper ions.(3) Thermo-sensitive Ni(â…¡) ion mprinted polymers were prepared throught seeded emulsion polymerization with different doses of EDMA(0%,2%,5%)in order to regulate the a lower critical solution temperature(LCST) of the polymer, in which Ni(â…¡) ion was used as the imprinting ion, NIPA was the thermo-sensitive monomer, adding the hydrophilic monomer N-hydroxymethylacrylamide in the reaction system. Moreover, the adsorption capacity of the Ni(â…¡)-imprinted polymers for Ni(â…¡) ions was researched. The results were shown that the adsorption capacity of the imprinted polymers for Niâ…¡) ions was higher than non-imprinted polymers.