Title page for ETD etd-08282012-144921


Type of Document Master's Thesis
Author Guzman, Francisco J
Author's Email Address guzman@vt.edu, fcoman@vt.edu
URN etd-08282012-144921
Title Separation of Colloidal Particles in a Packed Column using Depletion Forces
Degree Master of Science
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Walz, John Y. Committee Chair
Ducker, William A. Committee Member
Martin, Stephen M. Committee Member
Keywords
  • Colloid Transport; Depletion Forces; Depletion Int
Date of Defense 2012-08-27
Availability unrestricted
Abstract
Depletion forces were used to separate an equinumber density binary dispersion of 1.5 and 0.82 µm polystyrene sulfate (PS) particles. Experiments consisted of injecting a pulse of a binary dispersion of PS particles into the inlet of a packed bed of 0.5 mm silica collector beads. Prior to injection, a carrier fluid of either KCl and KOH electrolyte or a silica nanoparticle dispersion was flowing through the column at steady state. When the carrier fluid was a dispersion of silica nanoparticles, the ratio of PS particles in the column outlet would change from 1:1 big to small particles to slightly over 2:1. This implies that more of the smaller 0.82 µm particles were being trapped on the surface of the collector beads due to depletion forces. Experiments with a single particle type (either 1.5 or 0.82 µm PS particle) were also done and correlated with the binary dispersion measurements. Potential energy profiles between a PS particle and a flat silica plate were calculated. The secondary energy barrier for the 1.5 µm particles was two times greater than for the 0.82 µm particles. Hence, the 0.82 µm particles were more likely to overcome the energy barrier and get trapped on the surface of the collector beads. Although the potential energy profiles were calculated at equilibrium, they can be used as a tool in finding the optimal conditions for separation.
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