SUPERFAST ELECTROPHORESIS OF GRAPHITE PAR TICLES

It has been shown that the velocity of electrophoretic movement of lar ge graphite particles (d = 100, 150, 200 and 250 mu m) displaced in di stilled 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-excha nger particles is realised also for graphite particles with electron c onductivity. The velocity of particles changes not only with the elect ric field but also with the size of particles. The electrophoresis mob ility decreases with increasing electrolyte content. The conditions fo r superfast electrophoresis of electron-type conducting particles are examined. The electric current flows through such particles only if el ectrochemical oxidation-reduction takes place at the surface of partic les. Furthermore, the potential drop on particles has to be high enoug h to ensure the decomposition of electrolytes, and thus reach the regi me of overlimiting current. This is required for the formation of spac e charge that is a precondition for superfast electrophoresis to occur . A relationship is presented between the superfast electrophoretic ve locity and the size of electron-type conducting particles, outer field gradient, electrolyte decomposition voltage and solution parameters.