Diffusion Coefficients of Aqueous Alkali-Halide Solutions

Diffusion in electrolyte solutions is critical for applications such as seawater desalination, wastewater treatment and energy storage technologies. However, reliable Fick diffusion coefficient data remain scarce. In this work, the self- and Fick diffusion coefficients of 19 aqueous alkali-halide solutions (LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, RbBr, RbI, CsF, CsCl, CsBr, CsI) are sampled with molecular simulation techniques at ambient conditions of temperature and pressure for salt concentrations ranging from c = 0.5 to 5 mol L–1. For seven solutions, where experimental Fick diffusion coefficient data were not available (LiI, RbF, RbBr, RbI, CsF, CsBr, CsI), digital holographic interferometry measurements are presented, covering a total of 29 state points. Molecular dynamics simulation accurately predicts the Fick diffusion coefficient when a consistent methodology is applied, combining the sampled Maxwell-Stefan diffusion coefficient with the thermodynamic factor derived from the same force field combination.