Electrokinetic sedimentation: A theoretical and experimental study

Electrokinetic sedimentation is discussed from both theoretical and experimental aspects. A theory of electrokinetic sedimentation is proposed based on the combined action of electrophoretic, Stokesian, and interparticle forces on fine clay particles suspended in water under the influence of an external direct current electric field. The theory predicts that the sedimentation velocity of solid suspensions is proportional to the applied current density in the free settling stage and is dominated by the porosity of the suspensions in the following hindered settling stage. The results of electrokinetic sedimentation tests on three natural clay suspensions were examined to verify the theory. The results show that the sedimentation velocity of clay suspensions was increased and the porosity of the sediments formed after electrokinetic sedimentation was reduced significantly and yielded good agreement with the theory after the application of a direct current electric field, attributable to electrokinetic sedimentation.