Theory of sedimentation and diffusion in multicomponent suspensions

A theory of sedimentation and diffusion in multicomponent hard-sphere suspensions is developed within the framework of linear non-equilibrium thermodynamics. Expressions for the chemical potentials are obtained using Santos' theory of hard-sphere mixtures, and the phenomenological coefficients are obtained via a proposed extension of Batchelor's theory of sedimentation. The model is tested against several steady-state and transient bidisperse sedimentation experiments. Good agreement is obtained in non-colloidal suspensions by taking account of hydrodynamic dispersion, and in charged colloidal suspensions by utilizing an effective hard-sphere radius.