Mass transfer coefficients of uranium and plutonium across aqueous/organic interfaces of solvent extraction

The mass transfer rates of U(VI), U(IV), Pu(IV) and Pu(III) nitrates across aqueous/organic interfaces have been measured by a single drop method in solvent extraction. The overall mass transfer coefficients for rising, falling and jetting drops were related to the individual mass transfer coefficients in the dispersed and continuous phases. The Sherwood numbers in the dispersed and continuous phases, which contain the individual mass transfer coefficients, were correlated with the Peclet numbers in the corresponding phases, on the basis of the boundary layer theory, Handlos-Baron's theory and the penetration theory. This paper presents the experimental results of the mass transfer rates that were analyzed in terms of these theoretical findings. The mass transfers of U and Pu were confirmed to be controlled by molecular diffusion through the organic film layer for the rising or falling drops and the aqueous film layer for the jetting drops. (author)