Polymer-inorganic coatings containing nanosized sorbents selective to radionuclides. 2. Latex/tin oxide composites for cobalt fixation.

Colloidal tin oxide with an average particle size of 3.5 nm, which was ex-situ synthesized by the sol-gel method, has been attached to the surface of amino-functionalized poly(acrylate-co-silane) latex particles with a diameter of 100 nm to yield a composite with selective sorption properties toward Co(2+) ions. Electrokinetic properties and the colloidal stability of the synthesized latex/SnO2 composites have been evaluated in dependence on SnO2 content and pH; the sorption capacity and distribution coefficients of composites for Co(2+) ions were in accordance with the SnO2 content and its sorption performance as an individual compound. Composite coatings obtained by casting latex/SnO2 dispersions on quartz sand spiked with (57)Co radionuclide have efficiently eliminated radionuclides migration from the surface when the SnO2 volume fraction in the film was 3.5-4.7%. Furthermore, at these SnO2 loadings, the composite coatings retained the coherent structure of the original latex coating with SnO2 particles homogeneously distributed over the film thickness. The presence of competing Ca(2+) ions in the leaching media at a concentration of above 0.01 mol/L results in a decrease of the distribution coefficients of the latex/SnO2 composite and significantly higher (57)Co leaching. The value of the distribution coefficient of the sorption material to be used in latex composite coatings to prevent migration of radionuclides shall be close to 10(6) mL/g.