1070-4272/01/7408-1397 $25.00 C 2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 8, 2001, pp. 1397!1399. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 8, 2001,
Original Russian Text Copyright + 2001 by Kizim, Nesterova, Malyukova.
Structuring in Interphase Layer of Extraction System
N. F. Kizim, O. P. Nesterova, and V. A. Malyukova
Novomoskovsk Institute, Mendeleev Russian University of Chemical Technology, Novomoskovsk, Russia
Received December 26, 2000; in final form, April 2000
Abstract-The results of a study of the rheological properties of the interphase layer formed when an aqueous
phase containing HCl and PrCl
is brought in contact with a solution of an extracting agent (nonoxymethyl-
phosphonic acid) in toluene at varied content of the components in the system are presented.
In extraction of metal ions with organophosphorus
acids, an important role is played by interphase layers
within which chemical reactions between the com-
ponents of the extraction system, giving rise to two-
dimensional structures, can be localized .
The influence exerted by the content of components
on the rheological properties of an interphase layer
formed on bringing in contact the PrCl
system with a solution of nonoxymethylphosphonic
acid (NMPA) in toluene was investigated.
The rheological parameters were found from ki-
netic deformation curves  obtained by the method
of tangential displacement of a plate at 298 K and
from flow curves. A 0.1-mm-thick plate 3 mm in di-
ameter, made of a ferromagnetic material and plati-
num plated to improve its corrosion resistance, was
used in the study.
The method consists in that the displacement of
plate 1 at the phase boundary under the action of an
electromagnet driven by voltage U (V) from a dc
power supply was measured with a microscope at cer-
tain intervals of time t. Preliminary experiments de-
monstrated that the shear stress is proportional to the
electric voltage across the electromagnet terminals.
The measurements were done until the displacement
of 1 became larger than 1 mm. The measurement error
did not exceed 10%. The experimental technique was
described in detail in .
Typical flow curves obtained at varied content of
the components PrCl
and HCl and the extracting
agent NMPA are presented in Fig. 1. An analysis of
the rheological curves demonstrated that, under the
conditions studied, the adsorption layers can be class-
ed as systems of three types : approximately
Newtonian, Newtonian-dilatant, and weakly structured.
With increasing solution acidity, there occurs a
transition from an approximately Newtonian system
in a 10
M solution of HCl to a weakly structured
system, disintegrating in the course of time in a
M solution of HCl and becoming more
stable at C >10
When the NMPA content is varied (0.230.4 M),
weakly structured layers are formed, mainly with
a structure becoming stronger with time.
The structure strengthening is presumably due to
hindered diffusion and orientation of the extracting
agent molecules being adsorbed, which can both dis-
sociate at low HCl concentrations and form a poly-
meric structure at higher HCl concentrations.
Raising the concentration of the extracting agent
makes weaker the contact interaction and leads to
higher flowability and longer time of the elastic after-
Fig. 1. Rheological flow curves for interphase layers.
(l/t) Flow velocity and (U) voltage across electromagnet
terminals. Time of contact between phases (h): (1)9,
(2, 4) 0.5, (3, 9) 4.5, (5) 10, (6)5,(7) 1, and (8) 2.5. Con-
centration (M): HCl: (1, 4!7)10
:(1, 4) 0.05 and (2, 3, 5!9) 0.75; extract-
ing agent: (1, 4) 0.2 and (2, 3, 5-9) 0.4.