| Polymeric microsphere is a kind of new functional materials, which can be appliedin the adsorption of heavy metal ions, bio-separation and other fields. The functionalparticles could be obtained by grafting or modification reaction on the surfaces ofparticles, but the steps are usually more complicated. In recent years, the amphiphilicblock polymer has received more and more attention as emulsifier to prepare functionalpolymer microspheres by “one-pot” emulsion polymerization. At the same time, moreand more researchers pay attention to synthesize novel magnetic polymericmicrospheres. On the other hand, Uranium is the major composition of nuclear waste,and may pose the great threat to human health and environment owing to its chemicaltoxicity and radioactivity. It is important to synthesize novel materials to separate andenrich Uranium from aqueous solution. Uranium is one of the heaviest elements innature with multiple ligand sites, it could induce inter-chain coordination of polymers,and the uranyl ion-polymer hybrid functional materials could have sophisticatedarchitectures. Therefore, it is desirable to design and synthesize polymeric microspheresand smart polymers for uranium enrichment from aqueous solution.Specific studies of this paper are as follows:(1) Highly efficient removal of Uranium (VI) from aqueous solutions usingpoly(acrylic acid)-functionalized microspheres.Uranium (VI) is highly toxic and radioactive in water, and may pose the great riskto human health and environment. A new adsorbent is reported here for highly efficientremoval of uranyl ions from aqueous solution. Specifically, poly(acrylicacid)-block-polystyrene (PAA-b-PSt) block copolymers were synthesized asmacromolecular surfactant for the emulsion polymerization of styrene. The obtained PStmicrospheres had the controlled density and length of PAA chain on the surface, whichlead to a controlled high adsorption capacity. The effects of pH, adsorbent dose, coexisting ions, temperature, contact time, initial concentration were evaluated on theremoval of uranyl ions. Adsorption equilibrium could be achieved within4h, and thekinetic data could be well described by pseudo-second-order kinetics equation, and themaximum adsorption capacity calculated from Langmuir equation was~990mg/g at298.15K and pH4.5. This work indicates that PAA-functionalized microspheres can beused as a new adsorbent for highly efficient removal of uranium (VI) from aqueoussolutions.(2) Rapid removal of Uranium from aqueous solutions using imprinted magneticparticles with “well-defined” composites.A novel imprinted magnetic composite is reported here for highly efficient andrapid removal of uranyl ions from aqueous solution. Specifically,N-hydroxyethylacrylamide and1-vinylimidazole were used as functional monomers tocopolymerize uranyl ion-imprinted polymer modified on Fe3O4. The effect of pH,adsorbent dose, coexisting ions, competing ions and initial concentration were evaluatedon the removal of uranyl ions. In addition, adsorption kinetics and thermodynamicswere also investigated. Adsorption equilibrium could be achieved within1min, and thekinetic data could be well described on pseudo-second-order kinetics equation, themaximum adsorption capacity calculated from Langmuir model was~146.41mg/g.Compared with non-imprinted composites, imprinted one showed higher affinity, fasterkinetics, and larger adsorption capacity of uranyl ions. This work indicates that theimprinted magnetic composites could be a potential candidate as an adsorbent to removeU (VI) from aqueous solution effectively, selectively and rapidly.(3) Removal of Uranium from aqueous solutions using temperature-sensitivebiocompatible copolymers.We first synthesized biocompatible copolymers from the copolymerization of2-(adenin-9-yl) ethanol methacrylate (EAM) and n-dimethylammoniumbetaine (DMAB,which had an upper critical solution temperature (UCST) behavior. The effect ofmonomer ratios on phase transition temperature and self-assembly was studied. Phasetransition temperature increased with the increasing of adenine monomer ratio, andnanotubes and micro-phase separation were observed for self-assembly of thecopolymer in water at room temperature. When uranyl ion participated in theself-assembly progress, it could induce inter-chain coordination of polymer andfascinating snow-flake like morphologies. Above UCST, polymer chains extend to solution and contact with uranyl ions efficiently; under UCST, uranyl ion was wrappedin polymer. This property enable that the copolymers could be used to separate smartlyuranium from aqueous solutions after self-assembly of uranyl ions and polymer. |
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