Study on the Solid–Liquid\nEquilibrium and Thermodynamic\nModel of l‑Histidine + dl-Methionine + Water\nSystem

The solubility of amino acids is\na fundamental characteristic\nthat\nneeds to be determined in order to better understand the design of\nthe production and purification processes. In this study, the solid–liquid\nequilibrium data of the ternary system of 288.15–328.15 K l-histidine + dl-methionine + water at atmospheric\npressure were obtained using the isothermal solution saturation method.\nSubsequently, these data were utilized to develop five precise ternary\nphase diagrams, each detailing the phase relationships at a specific\ncomposition range, in addition to a comprehensive variable-temperature\nphase diagram that captured the phase behavior across the entire temperature\nrange of 288.15–328.15 K. Based on experimental data, a semiempirical\nmodel was employed to derive the thermodynamic equation that described\nthe solid–liquid equilibrium within this system. The model\npredicted solid–liquid equilibrium data for ternary systems\nover a wide range of temperatures. The resulting phase diagram exhibited\nthree distinct crystallization zones, two cosaturation solubility\ncurves, and a single cosaturation point. This comprehensive representation\nof the mutual solubility data and ternary phase diagram holds immense\nsignificance in optimizing the purification process of l-histidine\nand dl-methionine, ultimately leading to improved industrial\napplications and product quality.