Numerical and experimental analysis of the sedimentation of spherical colloidal suspensions under centrifugal force

Abstract

Understanding the sedimentation behaviour of colloidal suspensions is crucial in determining their stability. Since sedimentation rates are often very slow, centrifugation is used to expedite sedimentation experiments. The effect of centrifugal acceleration on sedimentation behaviour is not fully understood. Furthermore, in sedimentation models, interparticle interactions are usually omitted by using the hard-sphere assumption. This work proposes a one-dimensional model for sedimentation using an effective maximum volume fraction, with an extension for sedimentation under centrifugal force. A numerical implementation of the model using an adaptive finite difference solver is described. Experiments with silica suspensions are carried out using an analytical centrifuge. The model is shown to be a good fit with experimental data for 480 nm spherical silica, with the effects of centrifugation at 705 rpm studied. A conversion of data to Earth gravity conditions is proposed, which is shown to recover Earth gravity sedimentation rates well. This work suggests that the effective maximum volume fraction accurately captures interparticle interactions and provides insights into the effect of centrifugation on sedimentation.

Entropy solutions and flux identification of a scalar conservation law modelling centrifugal sedimentation

“…Furthermore, since b is continuous and the solution on both sides of the discontinuity r = b(t) is continuous in a neighbourhood of (r c , t c ), Equation (23) implies that b ′ is continuous. (This can also be established from the formulas (24) and (53). )…”

“…Numerical schemes for the simulation of separation by centrifugation when compression is included, also for polydisperse suspensions, can be found in other works. 6,[21][22][23] Interesting comparisons between numerical simulations of one-dimensional models of centrifugation and real experiments are presented by Antonopoulou et al 24 (with compression) and in other studies 1,2,20 (without compression). In particular, Piao et al 2 use problem (1) with = 0 to model the separation of white blood cells.…”

“…Interesting comparisons between numerical simulations of one‐dimensional models of centrifugation and real experiments are presented by Antonopoulou et al (with compression) and in other studies (without compression). In particular, Piao et al use problem (1) with to model the separation of white blood cells.…”

“…Proof. Equation (42a) can be integrated to get a similar relation as (24) in the following way. We combine (42b) and (42c) and differentiate Q −1 to get…”

Effect of dilution on sedimentational separation of bacteria from blood

“…Many investigators have proposed various semitheoretical and empirical correlations for hindered settling, including monodisperse and polydisperse correlations and corrections. [23][24][25][26][27][28][29] We used the Michaels-Bolger correlation fit experimentally to blood by Lerche et al:…”