Application of Laser-Doppler Velocimetry to the Study of Coagulation and Sedimentation

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Richardson, James H.

• Engineering, Chemical

Identifier

(UMI)AAI8502280

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/69748