Electroosmosis and streaming in natural and synthetic fibers

Abstract

A critical comparison of the electroosmotic flow rate and stream current over a wide range of solid concentrations was made using softwood bleached sulfite, cotton, cellulose acetate, and glass fibers in the presence of 2.5 × 10 −5 N KCl. ξ E showed a good agreement with ξ S with the sulfite and glass fibers, but was lower than ξ S for the cotton and acetate fibers. It was also found that the electroosmotic flow rate F was not directly proportional to the applied potential at low values of F. It was shown conclusively that the discrepancy was due to the unexpectedly large effect of the air bubble in the capillary flowmeter in resisting electroosmotic flow. When allowance is made for the bubble effect, F is independent of the applied potential and ξ E and ξ S agree within 1%. A series of measurements of electroosmotic pressures is reported. With the glass fibers, agreement between ξ E and ξ S was obtained at solid fractions at low as 0.009, in a region where the resistance to flow of fluid approaches the Stokes resistance of single particles. This is taken to be evidence of an equivalence of the electroosmotic, electrophoretic, and streaming functions.