Recyclable positive azeotropes for the purification of curcumin with optimum purity and solvent capacity

Purification of curcumin (CUR) from crude CUR, which is referred to as curcuminoids, has been conducted by cooling crystallization with the use of two azeotropes of ethyl acetate/ethanol (AZE-EA/EtOH) and ethyl acetate/isopropyl alcohol (AZE-EA/IPA), as compared to the use of single solvents, including acetone, EA, EtOH, and IPA. According to the determination of crude CUR solubility in those solvents, the effects of stirring, crystallization time, and seeding on the induction time, purity, and yield of CUR product were investigated on a small scale. Especially the effects of the purity of CUR seed crystals have a positive trend on the CUR purity. Seeding at a high temperature is suggested. The use of AZE-EA/EtOH shows the optimum purity of 94.0% and solvent capacity of 16.0 mg/mL with a yield of 29.0% by seeded cooling crystallization in a single step. Similar results are observed in the larger scale purification of CUR with a higher purity of 94.9%. After purification, the azeotropes can easily be recovered for reuse without changing their compositions, confirmed by GC, density, and boiling point determination.