Superfast electrophoresis of graphite particles.

It has been shown that the velocity of electrophoretic movement of large graphite particles (d = 100, 150, 200 and 250 mu m) displaced in distilled water or KCl solutions in strong electric fields (100 - 500 V/cm) reaches 0.2 - 1.4 cm/s, which exceeds the electrophoretic movement velocity values typical for non-conducting particles by two orders of magnitude. It means that the so-called superfast electrophoresis (or electrophoresis of the second kind) first observed by us for ion-exchanger particles is realised also for graphite particles with electron conductivity. The velocity of particles changes not only with the electric field but also with the size of particles. The electrophoresis mobility decreases with increasing electrolyte content. The conditions for superfast electrophoresis of electron-type conducting particles are examined. The electric current flows through such particles only if electrochemical oxidation-reduction takes place at the surface of particles. Furthermore, the potential drop on particles has to be high enough to ensure the decomposition of electrolytes, and thus reach the regime of overlimiting current. This is required for the formation of space charge that is a precondition for superfast electrophoresis to occur. A relationship is presented between the superfast electrophoretic velocity and the size of electron-type conducting particles, outer field gradient, electrolyte decomposition voltage and solution parameters.