Determination of diffusion coefficients of uranium in liquid gallium by GITT

In the electrowinning or chemical reductive extraction process, those mass transfer kinetic parameters, for instance the diffusion coefficient in the liquid cathode or medium, have a strong impact upon the practical extraction rate and separation efficiency. This work aims to calculate the diffusion coefficient of uranium in liquid gallium with galvanostatic intermittent titration technique (GITT) and to deduce its corresponding activation energy. By analyzing the data of GITT, before U saturation in liquid gallium at the temperature range of 673-873 K, the temperature dependence of diffusion coefficients of uranium in liquid gallium was measured as ln (D-U(G alpha)) - -(6.90 +/- 1.03) - (1.2 +/- 0.8)x10(3)/T and the corresponding activation energy was determined as E-a = -11.0 +/- 6.7 kJ/mol. The possible source of errors to calculate the diffusion coefficients, such as reference electrode, small solubility of uranium in gallium, side reactions and geometrical approximation of cathode in the theory formula are also presented and discussed.