Application of Laser-Doppler Velocimetry to the Study of Coagulation and Sedimentation
Richardson, James H.
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https://hdl.handle.net/2142/69748
Description
Title
Application of Laser-Doppler Velocimetry to the Study of Coagulation and Sedimentation
Author(s)
Richardson, James H.
Issue Date
1984
Department of Study
Chemical Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Abstract
The coagulation and subsequent sedimentation of model colloidal systems was measured by laser-Doppler velocimetry. This technique allows for rapid stability tests of dilute suspensions which affords a great savings of material over standard methods. The relative stability of dilute polystyrene latex particle (0.198 (mu)m diameter) suspensions was determined by comparing floc settling velocities. These suspensions are found to be stabilized in basic pH; the addition of sodium dodecyl sulfate (SDS) is insufficient to prevent coagulation of polystyrene suspensions in the presence of an added electrolyte. In a coagulating system of SDS and CaCl(,2), measurement of the time needed for flocs to reach a maximum settling velocity was found to adequately represent coagulation kinetics. Velocity profiles for various depths in a settling cell were recorded for the SDS, CaCl(,2) system. Maximum settling velocity was found to be a constant regardless of concentration or depth in the cell. The upward fluid velocity, emanating from compaction layers at the bottom of the cell and indicated by the slowing of particle settling rates in higher levels of the cell, was approximately equal to the maximum downward particle velocity. This supports the D'Arcian flow assumption made in theoretical settling equation development.
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