ELECTROKINETICALLY ENHANCED SEDIMENTATION OF COLLOIDAL CONTAMINANTS

Electrophoretic clarification of aqueous slurries has been carried out in the laboratory to elucidate the transport process and to explore the application of electrokinetically enhanced sedimentation to large-scale systems such as coal-washing-ponds, Two colloidal systems were investigated: (i) a model system of monodisperse polystyrene latex (PSL) spheres and (ii) heavily contaminated polydisperse suspensions from a coal-washing pond used at a coal-fired power plant. The electrical power requirements and electrokinetic properties of the colloidal suspensions were measured. A light-scattering technique was used to follow the sedimentation process to determine sedimentation rates, which for the PSL system were found to agree with existing theories of electrophoretic mobility. Although flocculation of particles did not occur for, the monodisperse PSL colloids, the coal/mineral particles flocculated after the electric field was applied fora time sufficient to initiate sedimentation. Once flocculation began, gravitational sedimentation dominated the process, and the electrical field could be turned off.