首页|Thermodynamic modeling of ammoniacal nickel sulphate solutions
Thermodynamic modeling of ammoniacal nickel sulphate solutions
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NSTL
The aim of this study was to build a thermodynamic model to extrapolate the system NiSO_4-(NH_4)_2SO_4-NH_3-H_2O which exists in aqueous hydrogen reduction processes of nickel. These solutions are relatively concentrated, and the temperature for solution preparation and reduction stages might range from room temperature up to 180-200 deg C. Temperature has a great effect on solution equilibria and the equilibrium solubility of simple and complex crystalline salts such as sulphates and hydroxides known to exist in the system. In this work, the role of kinetics is recognized, but only equilibrium phenomena reconsidered. The main focus of the study was on the modeling of salt solubility. In cases of a process solution where the precipitation of solid crystalline salts is highly undesirable it is important to know the safe limits for a 'clear solution' to operate even if the kinetics are unfavorable. Relatively concentrated solutions are strongly non-ideal and realistic calculations on solution equilibria necessitate the modeling of excess thermodynamic properties of these solutions. The excess model selected for aqueous species was Pitzer's ion-interaction model and for the gas phase Tsonopoulos' model. Emphasis in data assessment was on the thermodynamic modeling of various binaries and ternaries to create a substantial database for the approximation of the quaternary system.
NSTL
