SEDIMENTATION EQUILIBRIUM OF SUSPENSIONS OF COLLOIDAL PARTICLES AT FINITE-CONCENTRATIONS

Equilibrium concentration profiles of non-dilute colloidal suspensions are calculated by means of the Carnahan-Starling expression for the o smotic compressibility of hard sphere liquids. The profiles depend on the average volume fraction of the suspension, [phi], and on the field interaction parameter, lambda(0) (reciprocal of the Peclet number at infinite dilution). Profiles are computed for values of[phi] and lambd a(0) typical of those encountered in sedimentation field-flow fraction ation experiments. It is found that, in most cases, the volume fractio n at the depletion wail is negligibly small and that the volume fracti on at the accumulation wall, phi(0), depends on the ratio [phi]/lambda (0) only. An inflexion point is found in the concentration profile if phi(0), is larger than 0.13, whatever the value of lambda(0),.