Взаємодія в системі Ce3+ – WO42– – H+ – H2O за різної кислотності.

Abstract

Formation of Ce(III)-containing isopoly tungstates in acidified to different acidity Z = ν(H+)/ν(WO42–) = 0.00, and 1.00–1.364 solutions of the Na2WO4 – HNO3 – CeCl3 – H2O system was studied.Formation of cerium(III) orthotungstate Ce2(WO4)3·9H2O from non-acidified solution of Na2WO4 (Z = 0.00) was determined by the chemical analysis, XRD, and FTIR spectroscopy. Obtaining of an individual Ce2(WO4)3 phase after Ce2(WO4)3·9H2O calcination at 500 ºC was confirmed by X-ray diffraction analysis. Absence of tetrahedral surrounding of tungsten atoms by oxygen atoms in Ce2(WO4)3∙9H2O salt anion was established by the analysis of FTIR spectroscopy data. From the solution with Z = 1.00 the cerium heptatungstate Ce2W7O24·20H2O was synthesized. Presence of Ce4W9O33 and WO3 phases in products of Ce2W7O24·20H2O thermal decomposition were identified by X-ray diffraction analysis. Conditions for Ce5[HW7O24]3·56H2O synthesis from the Na2WO4 – HNO3 – CeCl3 – H2O system with Z = 1.17 were elaborated. Presence of only WO3 phase in products of Ce5[HW7O24]3·56H2O thermal decomposition at 500 ºC was identified by X-ray diffraction analysis. Crystallization of Ce4W9O33 phase in products of Ce5[HW7O24]3·56H2O thermal decomposition was observed after calcination at 700 ºC. Conditions for the synthesis of Cerium(III) salts with paratungstate B anion, Ce10[W12O40(OH)2]3·94H2O and Na10Ce20[W12O40(OH)2]7·180H2O, from the Na2WO4 – HNO3 – CeCl3 – H2O system with Z = 1.17, and 1.29 respectively were established. Presence of [W12O40(OH)2]10– anion was detected by FTIR spectroscopy. Procedure for the double sodium-cerium(III) salt Na2Ce2[Ce2(H2O)10W22O72(OH)2]·35H2O synthesis from the solution with Z = 1.364 was elaborated. Presence of lacunary metatungstate anion in the salt composition was determined by FTIR spectroscopy. Two Cerium(III) сations in [Ce2(H2O)10W22O72(OH)2]8– are coordinated to polyoxotungstate anion additionally stabilizing two Keggin-type lacunary metatungstate anions, connected by two μ2-O vertices.