FORMATION OF ROLYOXOMETALATE ANIONS IN THE SYSTEMS M(NO3)2 – Na2WO4 – HNO3 – H2O (M = Co, Ni; ν(M) : ν(WO42–) : ν(H+) = 1 : 6 : 6)
Nadiya Gumerova, Ksenia Semenova, Georgiy Rozantsev, Sergii Radio
Abstract
The interaction in the system of М2+ - WO42- - H+ - H2O (М = Co, Ni; СW = 
= 0,01 mol/L; СM = 0,00167 mol/L) acidified up to Z = ν(Н+)/ν(WO42-) = 1,00 by adding acid (alkali) in the interval Z = 0,6-2,5 at 298 ± 0,1К with the background electrolyte KNO3 (I = 0,1 mol/L) is investigated using the methods of UV-Vis. spectroscopy, pH-potentiometry and mathematical modeling. The models of equilibrium processes of polyoxotungstate-anions formation and transformation, adequately describing the experimental dependence рН = f(Z), are proposed. The difference in the processes occurring in solutions of Co(II) and Ni(II) is established. The concentration equilibrium constants of reactions of polyanions formation are calculated and diagrams of ions distribution are plotted. The results of the modeling are proven by successful synthesis of Co5[W12O40(OH)2]∙34H2O, and Na4[Ni(OH)6W6O18]∙16H2O at Z = 1,00. The composition of synthesized salts is established based on the data of chemical analysis and FTIR spectroscopy.
= 0,01 mol/L; СM = 0,00167 mol/L) acidified up to Z = ν(Н+)/ν(WO42-) = 1,00 by adding acid (alkali) in the interval Z = 0,6-2,5 at 298 ± 0,1К with the background electrolyte KNO3 (I = 0,1 mol/L) is investigated using the methods of UV-Vis. spectroscopy, pH-potentiometry and mathematical modeling. The models of equilibrium processes of polyoxotungstate-anions formation and transformation, adequately describing the experimental dependence рН = f(Z), are proposed. The difference in the processes occurring in solutions of Co(II) and Ni(II) is established. The concentration equilibrium constants of reactions of polyanions formation are calculated and diagrams of ions distribution are plotted. The results of the modeling are proven by successful synthesis of Co5[W12O40(OH)2]∙34H2O, and Na4[Ni(OH)6W6O18]∙16H2O at Z = 1,00. The composition of synthesized salts is established based on the data of chemical analysis and FTIR spectroscopy.