Diffusion in the system water + tri-n-butyl phosphate. Effect of aqueous electrolytes, and of organic phase water concentration

Abstract

The interfacial permeability coefficient k for the transfer of water across the water/tri-n-butyl phosphate (TBP) interface has been determined as a function both of aqueous electrolyte concentration, and of the initial water concentration in the TBP. The diffusion coefficient D of water in the organic phase has also been measured. Both k and D are found to be independent of electrolyte concentration over the range 0–1 mol dm^–3 aqueous NaCl, and for 1.25 mol dm^–3 aqueous Cr(NO₃)₃. The coefficient D is dependent on the initial water concentration in the TBP phase, with a maximum value at a TBP/H₂O mole ratio ≈2. The results are discussed in terms of possible diffusion mechanisms.