Modelling and experimental measurement of the closed equilibrium system of H2O–SrS

Abstract

This study investigates the H 2 O-SrS (strontium sulphide) equilibrium system at [SrS] between 0.125 and 88.064 mM (mmol•L −1 ) in a closed oxygenfree test system at 25 ºC (the measured system's pH being in the range of 10.0-13.1). The distribution of ions and molecules in this system is described in a structural scheme. A proton transfer model was developed to calculate the pH, concentrations of formed ions and molecules in the system by using an iteration method. In the formation of the basic equilibrium system of H 2 O-SrS, the dissociation of SrS in aqueous media causes the release of the S 2− ions that will accept a certain quantity of protons (Δ[H + ] S 2-), originating from the reversible dissociation of water (Δ[H + ] H 2 O ). In the final closed system of H 2 O-SrS, after adding larger amounts (≥10 g•L −1 ) of salt into MilliQ water, strontium hydroxide was formed as a precipitate. Proton transfer parameters, pH, and equilibrium concentrations of ions and molecules in the liquid phase were calculated and experimentally validated.