Measurements and predictions of mineral solubilities in the quaternary systems NaCl + KCl + SrCl2 + H2O, NaCl + MgCl2 + SrCl2 + H2O and KCl + MgCl2 + SrCl2 + H2O at 308 K

Abstract

This paper describes the measurements and predictions for mineral solubilities in the quaternary systems NaCl + KCl + SrCl2 + H2O, NaCl + MgCl2 + SrCl2 + H2O, KCl + MgCl2 + SrCl2 + H2O and subsystem MgCl2 + SrCl2 + H2O at 308 K in detail. The isothermal dissolution equilibrium method was used to determine the solubility of each salt in systems experimentally. Each stable phase diagram was constructed according to the measured results. The ternary system MgCl2 + SrCl2 + H2O has two invariant points, three solubility curves and three crystallization regions (MgCl2·6H2O, SrCl2·2H2O and SrCl2·6H2O). There is one invariant point, three solubility curves and three crystallization regions (NaCl, KCl and SrCl2·6H2O) in the quaternary system NaCl + KCl + SrCl2 + H2O. Two invariant points, five solubility curves and four crystallization regions (NaCl, MgCl2·6H2O, SrCl2·2H2O and SrCl2·6H2O) are included in the quaternary system NaCl + MgCl2 + SrCl2 + H2O. In the quaternary system KCl + MgCl2 + SrCl2 + H2O, the double salts KCl·MgCl2·6H2O were found as its ternary system KCl + MgCl2 + H2O, thus this quaternary system contains three invariant points, seven solubility curves and five crystallization regions (KCl + MgCl2·6H2O + KCl·MgCl2·6H2O + SrCl2·2H2O + SrCl2·6H2O). Using the fitted mixing parameter ΨMg, Sr, Cl and the Pitzer parameters available in literatures, the phase equilibria of four systems listed above were predicted with the Pitzer ion interaction model. The calculations are in adequate agreement with the experimental values.