ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2013, Vol. 87, No. 5, pp. 840–845. © Pleiades Publishing, Ltd., 2013. Original Russian Text © Yu.S. Dzyazko, V.V. Trachevskii, L.M. Rozhdestvenskaya, S.L. Vasilyuk, V.N. Belyakov, 2013, published in Zhurnal Fizicheskoi Khimii, 2013, Vol. 87, No. 5, pp. 857–862. 840 INTRODUCTION Multivalent metal hydrophosphates and their derivatives have a set of functional properties that are important from a practical point of view [1]. These materials are characterized by considerable proton conductivity at temperatures of up to 423 K, allowing us to use them as fillers in polymer membranes intended for fuel elements [2]. Introducing an inor- ganic component into the polymer phase prevents its dehydration at elevated temperatures. The ability of hydrophosphate groups to associate with functional polymer groups by means of hydrogen bonds deter- mines the compatibility of organic and nanosized inorganic components and, correspondingly, the strength and elasticity of nanocomposites [2, 3]. The ion exchange ability of multivalent metal hydro- phosphates, particularly their high exchange capacity, is worthy of attention [1]. Amorphous modifications are thus promising, since exchanges on such ionites occur much faster than those on crystalline ionites. The order of the values of the effective diffusion exchange coeffi- cient for hydrogel and xerogel samples of zirconium hydrogen phosphate (ZHP) (e.g., Ni(II) → H + and Cu(II) → H + ) is 10 –11 –10 –14 m 2 s –1 [4, 5]. In addition, ionites of this type are characterized by high selectivity with respect to nonferrous metal ions [1, 6–8]. Selec- tivity is based on the possibility of insoluble com- pounds forming in the ionite phase [7] (in our opinion, the formation of ion pairs localized on the surface is more likely [9]), as along with the geometric corre- spondence of the micropores of the matrix and sorbed ions [8]. The ability of the phosphate groups of poly- mer ionites to form complexes [10] leads us to suspect a similar mechanism of sorption on amorphous ZHP as well. This work is aimed at establishing the compo- sition of the formed complexes. EXPERIMENTAL ZHP samples were synthesized with different molar Zr : P ratios. The methods for preparing mate- rials with high phosphorus concentrations included precipitation of the hydrogel of hydrated zirconium dioxide from sol by a saturated NaOH solution with subsequent phosphatization as in [4]. ZHP-1 hydrogel was obtained in the form of durable glass-like trans- parent granules, and part of the material was preserved in deionized water. The rest of the hydrogel was dried at 298 K to a constant mass (xerogel ZHP-2). Our ZHP-3 sample was synthesized by mixing equimolar ZrOCl 2 and H 3 PO 4 solutions (100 mol m –3 ) with the subsequent dispersion of the gel-like hydrogel in decane and the hydrogel transitioning into xerogel during drying. Since the hydrogel granules obtained in the latter manner were not mechanically durable, we studied only the xerogel. The chemical composition of the samples was determined from their dissolution in concentrated H 2 SO 4 , and the solution was analyzed by photometry [5]. The exchange capacity on Na + at dif- ferent pH values of the solution was determined according to [5]. The porometric studies of xerogels were performed on a Quantachrome AS1Win unit via the thermal desorption of nitrogen. PHYSICAL CHEMISTRY OF SURFACE PHENOMENA Interaction of Sorbed Ni(II) Ions with Amorphous Zirconium Hydrogen Phosphate Yu. S. Dzyazko a , V. V. Trachevskii b , L. M. Rozhdestvenskaya a , S. L. Vasilyuk a , and V. N. Belyakov a a Vernadskii Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine, Kiev, 03680 Ukraine b Kurdyumov Institute of Metallophysics, National Academy of Sciences of Ukraine, Kiev, 03680 Ukraine e-mail: dzyazko@ionc.kiev.ua Received August 22, 2012 Abstract—Samples of amorphous zirconium hydrogen phosphate with different zirconium and phosphorus concentrations in hydrogen and nickel-substituted forms are studied by means of electronic, 31 P NMR, and impedance spectroscopy. It is shown that Ni(II) → H + ion exchange is accompanied by the hydrolysis of sorbed cations and the formation of complexes with the dihydro- and hydrophosphate groups of the inorganic ionite. It is found that the coordination environment of Ni(II) in the sorbent phase includes 2–4 fragments of phosphate groups, along with OH groups and water molecules. Keywords: amorphous zirconium hydrogen phosphate, nickel, ion exchange, complexation. DOI: 10.1134/S0036024413050063