ABSTRACT

The knowledge of the salts solubility in water is of major interest for process design and optimization and for environmental monitoring. The determination of the water solubility of non-aromatic salts or ionic liquids requires the use of specific and expensive analytical equipment. In this work the use of electrical conductivity for the quantification of the solubility of sparingly soluble salts in water is proposed. Novel data for the water solubility of 1-methyl-1-propylpyrrolidinium hexafluorophosphate, 1-methyl-1-propylpiperidinium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, and tetrabutylphosphonium hexafluorophosphate, in the temperature range from 288.15 to 318.15 K, are reported. Using the gathered results, along with literature data, a correlation between the aqueous solubility of [PF6]-based salts with their molar volume is proposed. The COSMO-RS predictive model was also used to estimate the solid liquid equilibrium of the investigated systems. Since all the compounds are solid at room temperature, they were further characterized by differential scanning calorimetry, and the temperatures of solid-solid and solid-liquid phase transitions, as well as the respective enthalpies of phase transition, are presented.

Compounds

#	Formula	Name
1	C8H15F6N2P	1-butyl-3-methylimidazolium hexafluorophosphate
2	C8H18F6NP	1-methyl-1-propylpyrrolidinium hexafluorophosphate
3	C9H20F6NP	1-methyl-1-propylpiperidinium hexafluorophosphate
4	C16H36F6NP	tetrabutylammonium hexafluorophosphate
5	C16H36F6P2	tetrabutylphosphonium hexafluorophosphate
6	H2O	water

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Variable	Constraint	Phase	Method	#Points
POMD	2	Triple point temperature, K ; Crystal 3			Crystal 3 Crystal 2 Air at 1 atmosphere	DTA	1
POMD	2	Triple point temperature, K ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DTA	1
POMD	2	Normal melting temperature, K ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DTA	1
POMD	2	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	2	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	2	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 3			Crystal 3 Crystal 2 Air at 1 atmosphere	DSC	1
POMD	3	Normal melting temperature, K ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DTA	1
POMD	3	Triple point temperature, K ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DTA	1
POMD	3	Triple point temperature, K ; Crystal 3			Crystal 3 Crystal 2 Air at 1 atmosphere	DTA	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 3			Crystal 3 Crystal 2 Air at 1 atmosphere	DSC	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	4	Normal melting temperature, K ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DTA	1
POMD	4	Triple point temperature, K ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DTA	1
POMD	4	Triple point temperature, K ; Crystal 3			Crystal 3 Crystal 2 Air at 1 atmosphere	DTA	1
POMD	4	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 3			Crystal 3 Crystal 2 Air at 1 atmosphere	DSC	1
POMD	4	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	4	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	5	Triple point temperature, K ; Crystal 3			Crystal 3 Crystal 2 Air at 1 atmosphere	DTA	1
POMD	5	Normal melting temperature, K ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DTA	1
POMD	5	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	5	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 3			Crystal 3 Crystal 2 Air at 1 atmosphere	DSC	1
POMD	6 1	Mole fraction - 1 ; Liquid mixture 1	Temperature, K; Liquid mixture 1	Pressure, kPa; Liquid mixture 1	Liquid mixture 1 Liquid mixture 2	Phase equilibration	7
POMD	6 2	Mole fraction - 2 ; Liquid mixture 1	Temperature, K; Liquid mixture 1	Pressure, kPa; Liquid mixture 1	Liquid mixture 1 Liquid mixture 2	Phase equilibration	7
POMD	3 6	Mole fraction - 3 ; Liquid mixture 1	Temperature, K; Liquid mixture 1	Pressure, kPa; Liquid mixture 1	Liquid mixture 1 Liquid mixture 2	Phase equilibration	7
POMD	4 6	Mole fraction - 4 ; Liquid mixture 1	Temperature, K; Liquid mixture 1	Pressure, kPa; Liquid mixture 1	Liquid mixture 1 Liquid mixture 2	Phase equilibration	7
POMD	6 5	Mole fraction - 5 ; Liquid mixture 1	Temperature, K; Liquid mixture 1	Pressure, kPa; Liquid mixture 1	Liquid mixture 1 Liquid mixture 2	Phase equilibration	7

Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

Solubility of non-aromatic hexafluorophosphate-based salts and ionic liquids in water determined by electrical conductivity

Neves, C. M. S. S.[Catarina M.S.S.], Rodrigues, A. R.[Ana R.], Kurnia, K. A.[Kiki A.], Esperanca, J. M. S. S.[Jose M. S. S.], Freire, M. G.[Mara G.], Coutinho, J. A. P.[Joao A. P.]

ABSTRACT