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

• Main Authors: Alexey Mashirin, Ergo Rikmann, Toomas Tenno, Kalev Uiga, Ivar Zekker
• Format: Article
• Language: English
• Published: Estonian Academy Publishers 2020-10-01
• Series: Proceedings of the Estonian Academy of Sciences
• Subjects: solubility product of srs (ksp; srs); dissociation constants of h2s; proton-centric model of the h2o–srs equilibrium system
• Online Access: https://kirj.ee/wp-content/plugins/kirj/pub/proc-2020-4-287-297_20201016111706.pdf
• ISSN: 1736-6046; 1736-7530

This study investigates the H2OâSrS (strontium sulphide) equilibrium system at [SrS] between 0.125 and 88.064 mM (mmol·Lâ1) in a closed oxygen-free test system at 25 ºC (the measured systemâs pH being in the range of 10.0â13.1). 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 H2OâSrS, the dissociation of SrS in aqueous media causes the release of the S2â ions that will accept a certain quantity of protons (â[H+]S2â), originating from the reversible dissociation of water (â[H+]H2O). In the final closed system of H2OâSrS, after adding larger amounts (â¥10 g·Lâ1) 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.