Aqueous Ion Transport Studies in Stainless Steel Membranes

Aqueous ion transport through unmodified, acid/base resistant, stainless steel membrane material was investigated to determine the feasibility of using the material as a basis for an actinide separation unit operation. The Mott Metal Corporation membrane material used for testing was a sintered 316L stainless steel membrane having a particle size cutoff rating of 0.5 μm and an average pore size of 2.2 ± 0.5 μm. Radiotracer transport experimentation was conducted with 45Ca, 137Cs, 241Am, 152Eu, and 239Pu cations at varying pH and at dilute cation concentrations. Infinite-dilution diffusion coefficients for the cations were measured and had the same order of magnitude (10-6 cm2 s-1). The infinite-dilution diffusivities compared well with values found in the cited literature. These results confirmed bulk diffusion as the controlling mechanism for cation transport through the water-saturated stainless steel membrane pores and support the hypothesis that the membrane, in the unmodified form, does not add any contribution to the removal of selected cations under aqueous conditions. In addition, the infinite-dilution diffusion coefficient for plutonium in solution as Pu(OH)3+ was determined for the first time to be 3.3 ± 1.3 × 10-6 cm2 s-1.