Structure and crystallization behavior of aqueous KCl–MgCl2 solutions†

Abstract

Potassium resources are abundant in the brine of chloride-type salt lakes. The main challenge in the efficient separation and extraction of potassium from salt lakes lies in the insufficient understanding of the structure and crystallization behavior of brine solutions and their correlation. In the present work, X-ray scattering (XRS) and computational simulation methods were used to study the microstructure of KCl and MgCl₂ mixed solutions, including the hydration and association structures of ions in the solutions. Furthermore, infrared (IR) spectroscopy was used to further study the crystallization behavior of solution droplets. The results indicate that the hydrogen bond network structure is disrupted as the mass fraction of MgCl₂ increases. The addition of MgCl₂ causes Mg²⁺ to compete with K⁺ for Cl⁻ in solutions, hindering K⁺–Cl⁻ association and forming contact K⁺–Cl⁻–Mg²⁺ clusters, which results in a slower precipitation and crystallization rate of mixed solutions compared with that of aqueous KCl solutions. This study is expected to provide theoretical guidance for the efficient separation and extraction process of potassium resources in salt lake brine.