9 research outputs found
Water activity and freezing points in aqueous solutions of manganese nitrate: experimental and modeling
The water activities of manganese nitrate solutions were measured using a
humidity sensor instrument up to almost the saturation molality at 298.15 K; the thermodynamic
properties of the system were described by the Pitzer model and specific
interaction theory (SIT). The evaluation of the ion interaction parameters for the Pitzer
model and SIT were carried out using experimental freezing points and osmotic coefficients
of manganese nitrate aqueous solutions, collected from the open literature, and the
water activity data measured in this work. A set of Pitzer and SIT parameters were
estimated using a temperature dependency, that enables us to cover wider temperature
ranges, and consequently calculate system properties to higher molalities. Both approaches
represent very satisfactorily, and with similar accuracy, the experimental data and the
calculated manganese nitrate molal activity coefficients are comparable to those already
published for analogous systems. Additionally, the Pitzer model was also able to calculate
the ice curve and the solubility branch of manganese nitrate hexahydrate up to a salt
solution 6.5 mol-kg-1.This work was developed in the scope of the projects POCI-01-0145-FEDER-
006984—Associate Laboratory LSRE-LCM both funded by European Regional Development Fund (ERDF)
through COMPETE2020—Programa Operacional Competitividade e Internacionalização (POCI)—and by
national funds through FCT—Fundação para a Ciência e a Tecnologia. This work is also a result of project
‘‘AIProcMat@N2020—Advanced Industrial Processes and Materials for a Sustainable Northern Region of
Portugal 2020’’, with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal
Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through
ERDF.info:eu-repo/semantics/publishedVersio
Thermodynamic modeling using Extended UNIQUAC and COSMO-RS-ES models: Case study of the cesium nitrate - water system over a large range of temperatures
A comparison of two thermodynamic models is presented using the water-cesium nitrate system as case study. Both models were able to model the thermodynamic properties such as the osmotic coefficient, vapor pressure, mean activity coefficient and solubility with good accuracy. We show that it is possible to reproduce the temperature dependency of the properties using a simple set of parameters in the case of Extended UNIQUAC. Furthermore, COSMO-RS-ES is a completely predictive model adjusted to data at 298.15 K, which is applied for the first time to other temperatures