An effective cobalt imprinted polymer for radioactive waste reduction

Aim

Development of a cobalt specific polymer for use in reducing the volume of radioactive waste. The polymer should be capable of specifically binding cobalt in presence of excess iron and soluble complexing agents. In chemical decontaminations of nuclear reactors, large quantity of ferrous ion which is non-radioactive, is released along with small quantity of radioactive cobaltous ions. Since the ion exchange resins currently used lack selectivity towards the latter ions, it leads to the generation of large amount of radioactive waste which require costly and elaborate disposal procedures.

Approach

Molecular imprinting has been reported widely for achieving selective adsorbents for particular molecules/metal ions. Several examples of bulk and surface metal imprinted polymers have been reported which exhibit pronounced selectivity for particular metal ions eg., Cu, Ni, Cd and UO₂⁺. A survey of the literature however did not reveal any report on cobaltions imprinted polymers tested against a high amount of ferrous ions.

Results

The imprinted polymer (MIP) was synthesized by polymerizing a methanolic solution of the disodium salt of the cobaltous complex of vinylbenzyliminodiacetic acid in presence of a large excess of a crosslinking agent (ethyleneglycol dimethacrylate) by thermal polymerization (Fig. 23).

Figure 23: An ion imprinted polymer designed to specifically bind cobaltions in presence of ironions

As control, non-imprinted polymer (NIP) was synthesized using free ligand in absence of cobalt. Rebinding studies were done by shaking 25 mg of the polymers (MIP or NIP) with 2.5 ml of metal ion solutions in 0.1 M citrate buffer at pH 4.8 (this is the pH that is maintained during a typical clean up operation) for 24 hrs at 30 °C. The supernatant solutions were then analyzed for the metal ion concentration by AAS leading to the results given in the figure 23.
It can be seen that the cobaltions imprinted polymer exhibits a concentration dependent uptake of cobaltions, with a maximum uptake at a concentration of 4.2mM whereas, there is no uptake of ironions. Furthermore, the corresponding non-imprinted polymer showed no evidence of iron - nor cobaltions binding.

Funding

DAAD fellowship to Mr. Anupkumar Bhaskarapillai

Contact

Priv.-Doz. Dr. Börje Sellergren
B.Sellergren@infu.uni-dortmund.de
Phone: +49-(0)231-755-4082

Posters

1. Anupkumar, B.; Sellergren, B. (2006):
   "Metal imprinted polymer for selective removal of cobalt in presence of iron", Cardiff, UK MIP 2006 .