Separation behaviour of suspensions in polymer solutions studied by multisample analytical centrifugation
In many industrial applications the separation behaviour of dispersions is influenced by the presence of polymeric additives. For example nonadsorbing polymers used as thickeners to stabilise formulations not only increase fluid viscosity but can also induce depletion flocculation. Both viscosity increase and depletion flocculation will modify separation processes. Furthermore the rheological properties of polymer solutions are generally shear dependent.
In this paper we study the shear dependent sedimentation in a centrifugal field for monodisperse (silica) and polydisperse (quartz) dispersions in anionic polymer solutions of varying concentration.
A multisample analytical centrifugation technique with photometric detection (STEP-Technology) is used in this study to trace the sedimentation velocity, velocity and size distributions in-situ. Measurements with monodisperse silica could be used to determine the effective viscosity as function of polymer concentration and centrifugal acceleration. Results revealed depletion flocculation at low polymer concentration but stabilization at higher concentrations. For the polydisperse quartz dispersions the sedimentation velocity of the coarse fraction and the particle size distribution in the supernatant could be determined.
Keywords
sedimentation, analytical centrifugation, velocity distribution, particle size distribution, polymer solutions, depletion flocculation, in-situ measurement, solid-liquid separation
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