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VELIKANOVA et al.
the fact that energetically simlar active centers on the
metal surface adsorb both the solvent and the ligand.
Thus, the increase in the ligand concentration should be
acceptable and individual for each metal.
technological solution of leaching metals from waste is
simple, proceeds at low temperatures, which is unusual
for pyrometallurgical processes, and is characterized by
the kinetic selectivity in the separation of metals and
possibility of recovering the solvent.
The nature of the organic solvent plays the essential
role. Reliable criterion for its choice may be the
Dimroth– Reichardt electrophilicity parameter ЕТ, which
is a quantitative measure of the capability of aprotonic
solvent–ligand system to coordination leaching of
metal. For systems with large ЕТ value, the tendency
to chelate formation is larger. The obtained empiric
equation depicting the dependence of the logarithm
of the reaction rate constant on ЕТ is log k = –10.49 +
0.19ЕТ.
The advantages of the technological methods using
organic reagents and their ability to extract metals from
industrial waste and poor ores with a low concentration
of d-elements demonstrate wide possibilities of solvate-
metallurgical processes and, presumably, will lead
to a radical change in the classical schemes used in
extraction of non-ferrous metals.
CONCLUSIONS
The extraction rate as a function of temperature
within 20–80°С is described by the exponential
Arrhenius equation. The apparent activation energy of
the process was determined from the ln V0 == f(1/τ)
graphs (V0 is dissolution rate (mol g–1 h–1) and τ, time
(h). Experimental data suggest that the reaction of an
ore metal with the ligand is kinetically limited under
agitation conditions (activation energy 40–70 kJ mol–1).
Exception is chalcosine (apparent activation energy
18 ± 1 kJ mol–1). For this mineral, a temperature
increase is less efficient than for other minerals, whereas
the agitation intensity, on the contrary, increases with
the extraction rate (diffusion control). For ores with
other mineral components, the increase in the agitation
intensity has no effect.
(1) The products formed in the reaction of 2-oxy-
1-benzylideneaniline with poor ores containing native
copper and different sulfide and oxide minerals upon
leaching in the dimethylformaldehyde–azomethine
system were determined
(2) The kinetic parameters of the process were
studied. The rate constants of concecutive reactions,
the optimum concentration of the ligand, and the
mechanism of the recovery of copper in oxidation
state 0 were determined. The reaction proceeds by the
Langmuir–Hinshelwood mechanism, when the reagent
and the solvent are adsorbed on energetically similar
surface centers.
(3)Studyofthekineticsandmechanismoftheprocess
and determination of the limiting stage gives ground to
choose the processing conditions (pressure, temperature,
time, solvent, and concentration of complexing agent)
and determine ways for leaching intensification.
As the s : l ratio decreases to 5 : 1, the extraction
degree and leaching rate decrease and then remain
constant at larger ratios (60 : 1 or 30 : 1).
Analysis of the kinetic data warrants a conclusion
to be made that these ores can be processed in non-
aqueous solvents, but each type of the ore requires
individual choice of the solvato-processing conditions
in order to select the best parameters of the process.
Solvato-processing can be carried out in leaching vats
with agitation and by heap leaching without stirring.
In the latter case however, the leaching time, at which
an acceptable degree of metal recovery is reached,
increases from 3 h to 5 days.
REFERENCES
1. Abramov, A.A., Tekhnologiya pererabotki i obogashche-
niya rud tsvetnykh metallov (Technology of Processing and
Concentration of Ores of Non-Ferrous Metals), Moscow:
Mosk. Gos. Univ., 2005, vol. 2.
2. Yurtov, E.V., Murasheva, N.M., and Simonov, A.I., Khim.
Tekhnol., 2004, no. 8, pp. 35–39.
3. Barbin, N.M., Processing of Secondary Raw and Wastes
of Industrial Origin in Ionic Melts of Chrorides and
Carbonates, Doctoral Dissertation, Ekaterinburg, 2004.
The mechanism of the chemical coordination
extraction of metals with organic reagents, proceeding
without dissociation, hydration, and hydrolysis at larger
solubility of oxygen, is less complicated in comparison
with the extraction with aqueous solutions. The proposed
4. Sal’nikova, Yu.I., Boos, G.A., Ryzhkina, I.S., et al.,
Kolloid. Zh., 2007, vol. 69, no. 5, pp. 673–679.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011