High pressure differential scanning calorimetry of the hydrothermal salt solutions K2SO4–Na2SO4–H2O and K2HPO4–H2O

Abstract

Aqueous salt solutions under hydrothermal conditions play an important role in geochemistry as well as in processes using hot compressed water as the process medium such as supercritical water oxidation (SCWO) and supercritical water gasification (SCWG). Isochoric high pressure differential scanning calorimetry (HP-DSC) was used as an accurate technique to investigate the phase behavior of such solutions under hydrothermal conditions. New data in the low concentration range (0.14–15.0 mass%) has been collected for the binary systems K₂SO₄–H₂O, Na₂SO₄–H₂O and K₂HPO₄–H₂O. Furthermore we have discovered a liquid–liquid immiscibility in the ternary system K₂SO₄–Na₂SO₄–H₂O, which has not been reported before.