Electrokinetic phenomena

Electrokinetic phenomena are a family of several different effects that occur in heterogeneous fluids, or in porous bodies filled with fluid, or in a fast flow over a flat surface. The term heterogeneous here means a fluid containing particles. Particles can be solid, liquid or gas bubbles with sizes on the scale of a micrometer or nanometer. There is a common source of all these effects — the so-called interfacial 'double layer' of charges. Influence of an external force on the diffuse layer generates tangential motion of a fluid with respect to an adjacent charged surface. This force might be electric, pressure gradient, concentration gradient, or gravity. In addition, the moving phase might be either continuous fluid or dispersed phase.

Family of electrokinetic phenomena

Various combinations of the driving force and moving phase determine various electrokinetic effects. According to J.Lyklema, the complete family of electrokinetic phenomena includes:^[1]

• electrophoresis, as motion of particles under influence of electric field;
• electro-osmosis, as motion of liquid in porous body under influence of electric field;
• diffusiophoresis, as motion of particles under influence of a chemical potential gradient;
• capillary osmosis, as motion of liquid in porous body under influence of the chemical potential gradient;
• sedimentation potential, as electric field generated by sedimenting colloid particles;
• streaming potential/current, as either electric potential or current generated by fluid moving through porous body, or relative to flat surface;
• colloid vibration current, as electric current generated by particles moving in fluid under influence of ultrasound;
• electric sonic amplitude, as ultrasound generated by colloidal particles in oscillating electric field.

Further reading

There are detailed descriptions of electrokinetic phenomena in many books on interface and colloid science. ^{[1] [2] [3] [4] [5] [6] [7] [8]}

See also

• Surface charge
• Onsager reciprocal relations
• Isotachophoresis

References

1. Lyklema, J. (1995) Fundamentals of Interface and Colloid Science, Vol. 2, p. 3.208.
2. Hunter, R.J. (1989) Foundations of Colloid Science, Oxford University Press.
3. Dukhin, S.S. and Derjaguin, B.V. (1974) Electrokinetic Phenomena, J. Willey and Sons.
4. Russel, W.B., Saville, D.A., and Schowalter, W.R. (1989) Colloidal Dispersions, Cambridge University Press.
5. Kruyt, H.R. (1952) Colloid Science, Elsevier. Volume 1, Irreversible systems.
6. Dukhin, A.S. and Goetz, P.J. (2002) Ultrasound for characterizing colloids. Elsevier.
7. Kirby, B.J. (2010). Micro- and Nanoscale Fluid Mechanics: Transport in Microfluidic Devices. Cambridge University Press. ISBN 978-0-521-11903-0.
8. Anand Plappally, Alfred Soboyejo, Norman Fausey, Winston Soboyejo and Larry Brown,"Stochastic Modeling of Filtrate Alkalinity in Water Filtration Devices: Transport through Micro/Nano Porous Clay Based Ceramic Materials" J Nat Env Sci 2010 1(2):96-105.