Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 5, pp. 680686.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © N.F. Kizim, E.N. Golubina, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 5, pp. 734739.
Effect of External Factors on the Increase in the Extraction Rate
in a Vibration Treatment on the Dynamic Interfacial Layer
N. F. Kizim and E. N. Golubina
Novomoskovsk Institute, Mendeleev University of Chemical Technology of Russia, Novomoskovsk,
Tula oblast, Russia
Received December 18, 2012
Abstract—Vibration treatment of a dynamic interfacial layer in the extraction system constituted by an aqueous
solution of a salt of a rare-earth element and a solution of di-(2-ethylhexyl)phosphoric acid in heptane (toluene)
results in an increase in the process rate. This increase is characterized by an acceleration coefﬁ cient deﬁ ned as
the ratio between the lanthanide concentrations in the organic phase after equal intervals of time in systems with
and without vibrations. It is shown that the acceleration coefﬁ cient depends on the concentration of the extractive
agent, initial concentration of an element being extracted, solution pH, and phase contact duration. The observed
behavior is explained in terms of the process model suggested by the authors. According to this model, the effect
depends on the relative contributions made by a number of interfacial phenomena accompanying the extraction of
a lanthanide with solutions of di-(2-ethylhexyl)phosphoric acid in diluents and, in particular, by the spontaneous
surface convection and structuring in the interfacial layer.
Commonly, liquid extraction is performed in the
emulsion mode by using rabbles and pulsators. A
shortcoming of these methods is in their intricate
equipment and increased energy expenditure by stirring
devices dispersing one ﬂ uid in another, i.e., creating
a developed phase contact surface. In addition, the
extraction should be followed by phase separation,
which may be very slow if substances present in a
system (or appearing products) possess surface-active
properties and form cruds. In this case, the throughput
of settlers decreases and additional energy is required
for making faster the drop coalescence process [1, 2].
In devices having no stirrers, the mass-transfer rate
is low. In this case, it is necessary to look for ways to
reduce the resistance to the transfer across the interfacial
To raise the “permeability” of the interfacial layer in
an extraction system, Tarasov et al. have suggested to
draw a band reciprocating across the phase boundary at
a frequency of 0–2 Hz. In general, the observed effect
is accounted for by a change of the mechanism of mass-
transfer across the phase boundary; however, details of
this mechanism remain unclear.
Another way to intensify the mass transfer in liquid
extraction is by applying an external electric ﬁ eld. It has
been shown  that the increase in the extraction rate is
due to a change in the composition of the interfacial layer.
However, the mass-transfer rate of the substance being
extracted may both increase and decrease. In particular,
it follows from  that an electric ﬁ eld applied in the
direction normal to the phase boundary destabilizes
the surface, whereas that in the tangential direction
stabilizes this surface. The authors of  state that the
increase in the mass-transfer rate of a component from
one liquid phase into another is due to the turbulization
of the phase boundary. Consequently, a local delivery
of energy into the interfacial layer may give rise to, or
enhance, the surface convection.
The effect of vibration on the interfacial layer may
give rise to a resonance and, as a consequence, also to a