The modern theoretical views on the point of zero charge of the oxide hydroxide surface are considered. Methods for determination of the pH of the point of zero charge and the use of this value to characterize the properties of oxide hydroxides are described. Examples of using the pH of the point of zero charge in studies of oxide anodes and amorphous oxide hydroxide sorbents are presented.

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The experimental data on the sorption properties of hydrogels of Fe 1|1, Ti IV, Zr TM, Sn TM, [fl Ill, Cr llI, Sm Ill, Co 11, and Zn II oxide hydroxides are summarized. The data were obtained by the point of zero-charge method and by measuring the rates of the indicator reaction, viz., heterogeneous hydrolysis of the chloro complexes of platinum group metals. The compositions of lhe oxide hydroxides, the pH of the point of zero charge in various ionic media, and the rate constants of the indicator reactions were determined. The values obtained were analyzed in terms of their correlation with the charge, the radius, and the electronic structure of the central ion and with the composition and the preparation conditions of the oxide hydroxide. A data base that allows one to choose an appropriate oxide hydroxide sorbent for extraction of particular complex-forming metals from complexing media is presented. The data obtained confirm the model of the mechanism of heterogeneous hydrolysis and extend its predicting ability. The model was tested experimentally in relation to tin0v) oxide hydroxide.

A series of complexes [ëo(NH 3 ) 6 ] x [ML 6(4) ] y , where M is Fe(III) and Fe(II), Cr(III), Cu(II); L is CN -, NCS -, 1/2C 2 , are synthesized. Their IR spectra and thermal decomposition in air are studied, and interplanar distances in crystalline lattices of the complexes are determined. The compounds can be used as precursors for producing homogeneous bimetallic nanodimensional powders. O 4 2-