Metal Binding Capability of Functionalized Thermo-sensitive Polymer Networks and Application of Hydrogels to Low-level Radioactive Waste Processing


We have investigated hydrogels of thermo-sensitive polymer networks of N-isopropyl-acrylamide(NIPA) containing functional groups for removing and encapsulating metallic cations from aqueous solutions of Co{sup 2+}, Cr{sup 3+}, Cu{sup 2+} and Ni{sup 2+} nitrates. This simulates the situation for mixed radioactive waveforms containing a variety of elements as cations in water. Since hydrogels form a separate phase than water, they can be separated by a simple physical filering. A reversible transition process between the swollen and shrunken states (at 33.4degC) in hydrogels of poly(NIPA) accompanies a tremendous reduction in gel volume and change from an extended conformation of polymer to a compact form with increasing temperature. The above processes were carried out for poly(NIPA) networks containing sodium acrylate, allyl alcohol and allyl cyanide as functional groups. In the swollen state, all cations diffusionally penetrated into all gel pieces to reach equilibrium. With quickly increasing temperature, the encapsulation of cations has been achieved and easily separated from aqueous solutions. Chemical analysis of cations contained in tiny gel show: (1) amide group (NIPA) falls in the middle of ranking for all cations; (2) carboxylic group was most effective for all cations; (2) allyl cyanide removed selectively Ni{sup 2+}; (3) allyl alcohol was basically not effective functional group.



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