A Solid–Solid–Liquid\nQuasi-Ternary Phase\nDiagram Method for Multicomponent Solids Validated by Curcumin Purification\nDesign

Proper process development for solvent-based separation\nand purification\nof multicomponent solid mixtures should be based on a proper understanding\nof the material properties of the product, impurities, and their solid-state\nmixture. The layout of those properties reflected by their mixing\nand demixing behaviors resulting from the molecular interactions can\nneatly be captured in a phase diagram. However, the level of difficulty\nin constructing a phase diagram is dependent on the number of components\nbeing involved. Additionally, a full construction of a phase diagram\nwould be impossible to carry out if the pure standards of the impurities\nare unavailable, making its adoption for the separation of solid mixtures\nto be somewhat limited. In this work, a concept of the quasi-ternary\nphase diagram method is proposed by combining all unknown impurities\ninto one single entity, in effect creating a ternary system of solid\nproduct-solid impurities-liquid solvent. In this way, as long as the\npure product and solvent are available, a ternary phase diagram of\nthis system can be established and used as a guideline for designing\nthe separation process of this product substance. This concept has\nbeen validated against curcumin, where oleoresin obtained from turmeric\nextraction with 25% purity was purified into a curcumin product with\n>98% purity.