Synthesis Of Surface Ion-Imprinted Magnetic Microsphere For Selective Sorption Of Perrhenate

Technetium, one of the radioactive elements commonly in the underground water and geologic sediments, has a long half-life(2.13 ×105 y for 99Tc) and an activity of 629.0 MBq/g for β decay. The most stable form of technetium is pertechnetate, which has good solubility in water and therefore could migrate freely in the environment. The most significant source of 99 Tc is from the nuclear fuel cycle, and approximately 6% of the total fission product is technetium. Once the environment is polluted by technetium, there will be great threat to the health of mankind. At the same time, Technetium is one of the most widely used radioactive elements in biomedicine. Therefore, development of new materials for the adsorption of technetium is significant to environment and human health.Functionalized microsphere possesses large specific surface area and convenient decoration of varying functional groups on the surface, which has demonstrated vast application in wide fields, such as sensor, adsorption, drug delivery and so on. On the other hand, magnetic materials have been one of the hot topics because of its benefit, namely facile separation by external magnetic field. In this work, perrhenate anion as the structural surrogate for the pertechnetate anion, was employed as template to prepare ion-imprinted microsphere based on magnetic Fe3O4 microspheres by “one-pot” radical polymerization, and its selective removal of perrhenate from water was investigated to the prospect of application in pertechnetate removal.Specific studies of this paper are as follows:(1) Synthesis and characterization of surface ion-imprinted magnetic microsphere.In order to prepare ion-imprinted microsphere, N-vinylimidazole and 4-Vinylbenzyl chloride were used as the functional monomers to copolymerize on the surface of Si O2 coated Fe3O4 bearing vinyl groups in the presence of perrhenate ion as template. An imprinted cross-linked network could be formed on the surface of magnetic microspheres. The surface of microspheres became rough with a core-shell structure. As increasing the amount of monomer used in the polymerization, the percentage of nitrogen and zeta potential increased, and particle size became larger. The special saturation magnetization loops showed it could be easily separated by external magnetic.(2) Study of removal of perrhenate from aqueous solutions using surface ion-imprinted magnetic microsphere.Perrhenate was used as a structural surrogate for the pertechnetate anion. The effect of adsorbent dose, coexisting ions, temperature, p H, and initial concentration were evaluated on the removal of perrhenate ions. An adsorption capacity of 62.8 mg/g calculated from Langmuir model could be achieved at 298.15 K, p H = 6. The investigation of adsorption kinetics and thermodynamics indicated that sorption process kinetically followed pseudo-second-order model, and it was exothermic and spontaneous. Compared with non-imprinted composites, imprinted microsphere showed higher affinity, faster kinetics, and larger adsorption capacity of perrhenate ions. All the results indicate the imprinted magnetic composite is a promising adsorbent to selectively remove pertechnetate from aqueous solutions. It is expected that this new material has a good application prospect in the removal of pertechnetate.