Thermodynamic properties calculation of perrhenates and their application in the simulation of sample pretreatment for the chemical analysis

Abstract

Thermodynamic properties, namely standard molar enthalpy of formation (Δ H f ° 298 ), standard molar entropy ( S ° 298 ), and temperature dependence of heat capacity ( С р ( Т )) of crystalline metal perrhenates, were assessed by the semi-empirical methods. In this work, Δ H f ° 298 , S ° 298 and coefficients a , b and c for C p = а + 0.001× b × T + 10 5 × c × T – 2 equation were calculated using several methods and averaged. These thermodynamic properties were calculated for the following perrhenates metals: Li, N, K, Rb, Cs, Cu, Ba, Fe, Ca, Cd, Co, Mg, Mn, Pb, Sr, Zn, Al, Crи Fe. The calculated values of the thermodynamic properties were in good accordance with the known literature data. New data were applied to the thermodynamic simulation of rhenium-containing sample pretreatment processes for the chemical analysis. The thermodynamic simulation of the sintering sample with the magnesium oxide with/without oxidizing agents was carried out using HSC 6.1 software with new data about the perrhenates. According to the calculated results, the addition of the oxidizing agent (NaNO 3 or K 2 S 2 O 7 ) to the magnesium oxide was needed and its presence ensured the rhenium transition into the solution without losses. In this case, rhenium was present at the temperature of the sintering predominantly as NaReO 4 c or KReO 4 c . Calculation results and estimation of perrhenates thermodynamic properties could be used for the thermodynamic simulation of different processes as well as in analytical chemistry and in metallurgy. Keywords : perrhenates, thermodynamic properties, thermodynamic simulation, sintering, oxidizing agent, rhenium (Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.4.015 O.V. Melchakova 1 , P.V. Zaitceva 1 , A.V. Maiorova 1,2 , T.V. Kulikova 1,2 , N.V. Pechishcheva 1 , K.Yu. Shunyaev 1,2 1 Institute of Metallurgy of the Ural Branch of the Russian academy of Sciences, 101, Amundsen street, Ekaterinburg, 620016, Russian Federation, 2 Ural Federal University named after the first President of Russia B.N. Yeltsin, 19, Mira street, Ekaterinburg, 620002, Russian Federation