Separation behaviour of suspensions in polymer solutions WFC 10 World Filtration Conference 10

Contribution to 10th World Filtration Conference April 14-18 2008 Leipzig/Germany
Separation behaviour of suspensions in polymer solutions studied by multisample analytical centrifugation

T. Sobisch*, T. Detloff, D. Lerche

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

Evaluation of beverage cloud emulsion stability - Food Colloids 2008

Contribution to Food Colloids 2008 - Le Mans
Evaluation of traditional and new methods determining beverage cloud emulsion stability
C. Cherbit, S. Reiner, G. Reineccius
Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave., Saint Paul, MN 55108 USA
T. Sobisch, D. Lerche LUM, Berlin, Germany

Emulsions are inherently unstable. This is an ongoing problem for the food and flavor industries. The objective of this work was to evaluate two instruments (LUMiSizer® and LUMiReader®) designed to characterize dispersion stability thereby potentially replacing lengthy and costly traditional methods.
Several beverage cloud emulsions were prepared using orange terpenes or medium chain triglycerides as the oil phase, emulsifiers (gum acacia or a chemically modified starch), in the presence or absence of a weighing agent (ester gum). Results obtained with the analytical centrifuge LUMiSizer® and the separation analyser LUMiReader® were compared to those obtained using traditional methods (visual observations of creaming, measurement of absorbance to obtain the opacity and droplet size index, and particle size analysis).
For the systems investigated application of high resolution photometric detection compared to traditional methods resulted in more detailed information in shorter time.