The structure of the electrical double layer (EDL) of colloidal system
s is discussed. The methods of determination of the most important par
ameters of the EDL, i.e. the value of the surface-potential psi(0), th
e Stern-potential psi(delta) and the electrokinetic-potential delta, t
he surface charge density sigma(0), the electrokinetic charge sigma(ze
ta) as well as the specific surface conductance kappa(sigma) and Rel p
arameter are described. The application of the theory of non-linear el
ectrosurface phenomena developed by Dukhin, Derjaguin and Shilov for c
alculation of the EDL parameters is discussed. The above data of the E
DL characteristics for polystyrene and melamin-formaldehyde latices, s
uspensions of AgI, Sb2S3, Fe2O3, ZrO2, hydromica, palygorskyte, yeast
cells as well as kerosene-in-water, ET grade lubricating oil technical
emulsions in different electrolyte solutions are discussed. It has be
en shown that in the most of cases (with the exception of AgI solution
) psi(0) or psi(delta) > zeta and sigma(0) >> sigma(zeta). It indicate
s the presence of a considerable free charge between the surface and s
lipping plane due to the formation of hydrodynamically immobile water
layers on the surface in which the ions retain high mobility. The nece
ssity of complex (integrated) electrosurface measurements for the desc
ription of the electrical double layer structure is stressed. A new ki
nd of non-linear electrokinetic phenomena, namely the superfast electr
ophoresis is described. The phenomenon was predicted theoretically by
Dukhin and Mishchuk and investigated experimentally in detail in the a
uthor's laboratory. It has been shown that the electrophoretic mobilit
y of large (hundreds mu m) ion-type conducting particles like ion-exch
anger grains/fibres or electron-type conducting particles like Al/Mg a
lloy, graphite and activated carbon in strong electric fields (100-100
0 V/cm) exceeds the electrophoretic mobility values typical for non-co
nducting particles by 1-2 orders of magnitude. The mobility of such pa
rticles depends on the conductivity ratio between the particles and me
dium and strongly increases with the electric field gradient and the p
article size. This is in contrast to classical electrophoresis. The su
perfast electrophoresis is due to the interaction of a strong electric
field with the space charge near the surface of unipolar conducting p
articles. This space charge is induced by the strong external field be
cause of the concentration polarisation. (C) 1998 Elsevier Science B.V
.