A method is disclosed of immobilizing actinide metal oxide ions. A liquid composition is prepared of the actinide metal oxide ions and a monomer which is capable during electropolymerization of complexing with the actinide metal ions. An optional polar solvent may be included in the composition if it is necessary to dissolve a solid monomer. The monomer is then electropolymerized to form a polymeric complex with the actinide metal oxide ion. The polymeric complex can be separated from the remainder of the liquid composition by the addition of a non-solvent for the polymeric complex which results in its precipitation. Vinylimidazoles have been found to be suitable monomers for use in this process.