Stabilizing effect of ethylene glycol for iso- and heteropolytungstates from aqueous-ethylene glycol solutions

Abstract

In this master's thesis, by the methods of pH-potentiometric titration and mathematical modeling using the CLINP 2.1 program in the acidity Z = ν(HCl) : ν(Na2WO4) = 0.0 ÷ 2.5 the processes of complexation in acidified aqueous-ethylene glycol solutions WO4 2- – H2O – H+ – NaCl – C2H4(ОН)2 with a volume fraction φ(C2H4(OH)2) = 10 ÷ 50 vol. % and ionic strengths range I(NaCl) = 0.1 ÷ 0.5 mol/L at a temperature of 25ºC were investigated. Models of equilibrium processes that adequately describe the experimental dependences pH = f(Z) were determined, for which logarythms of thermodynamic constants by the Pitzer method were calculated and the standard Gibbs energies of isopoly tungstate anions formation reactions from WO4 2- and Н+ at mixed organic-inorganic media were calculated. Two previously undescribed in the literature salts were synthesized and structurally characterized – isopoly tungstate with the anion of paratungstate-B [Na(C2H4(OH)2)]2Na8W12O40(OH)2∙C2H4(OH)2∙11H2O, and and heteropoly tungstate with Anderson-type anion [Na(C2H4(OH)2)]2Na2[Ni(OH)6W6O18]∙6H2O. Using the density functional theory (DFT), the FT-IR spectrum was refined and the structure of the Anderson-type anion in the compound Na3Mn0,5[Mn(OH)6W6O18]∙nC2H4(OH)2∙mH2O was determined. For the first time, isopoly tungstate anions cross-junction schemes for WO4 2- – H+ – H2O – NaCl – C2H4(OH)2 systems were proposed.