A simple model of a dry reversed micelle of ionic surfactants is proposed, according to which during the
optimization procedures the ions move over certain closed surfaces in a vacuum at T = 0 K .The electrostatic
interactions of discrete ions in dry, reversed micelles of AOT are calculated as a function of the sizes of the
ions, ion charges, and the optimum positions of the ions in the polar cavity of the micelles. It is shown that
when the counterions penetrate the layer of the potential-determining ions, the electrostatic interaction begins
to favor the self-organization of the ionic surfactants over that of the reversed micelles. The distribution of
the electrostatic potential in the polar cavity of micelles of different shapes (a sphere, a spheroid, a prolate
ellipsoid) is calculated. In the models in which the charge is taken to be discrete, the electrostatic field
extends beyond the double electric layer (DEL); the sign of the potential coincides with that of the counterion.
It is shown that in the analysis of structures of dry, reversed micelles the possibility of the formation of voids
(in the surface layer of polar groups and in the center) as well as the density of packing should be taken into
account by using a specially developed approach. The most probable structural parameters of AOT micelles
are determined for different counterions (Li+, Na+, Cs+, [Co(H2O)6]2+, La3+).
A new method of metal concentration by reversed micelles is described. It differs from traditional solvent extraction concentration in the procedure of metal stripping from an organic phase. Reversed micelles are broken by heating or by adding a polar organic diluent. A concentrated metal solution is produced at surfactant disaggregation; there is no need to use a water-stripping solution. Coefficients of concentration for Fe(III), Pt(IV), and Pd(l1) chloride complexes as high as 150 to 1800 have been seen when nonionic oxyethylated surfactants are used.
The possibility of employing reversed micelles of oxyethylated surfactants to concentrate platinum from acidic aqueous media was investigated. A procedure for reversed micellar concentration is described. Platinum concentration was effected by means of desolubilization in a non-traditional back-extraction stage by dilution of the reversed micellar solution with chloroform or a mixture of chloroform with hexane. In acidic sulfate-chloride media the distribution ratio of Pt IV increased to about 10 2 -5 3 10 3 in the presence of Br 2 and I 2 as complexing agents. In chloride media the distribution ratio could be increased to about 2 3 10 3 by using SnCl 2 . The maximum recovery of platinum from the extract did not exceed 85%. With I 2 as a complexing agent, no back-extraction could be performed. With this back-extraction procedure, the Pt IV concentration factor varied from about 10 2 to 10 3 depending on the aqueous feed composition. It was shown spectrophotometrically that Pt IV complex species were the same in the feed, extract and desolubilized aqueous solution. The possibility of the spectrophotometric determination of platinum with SnCl 2 directly in the reversed micellar solution is demonstrated.
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