Valorization of Pharmaceutical Waste by Recovery of Active Pharmaceutical Ingredients from Expired or Unused Finished Pharmaceutical Products with Thermodynamic Modeling

This study aims to investigate the possibility of recovering active pharmaceutical ingredients (APIs) from expired or unused finished pharmaceutical products (FPPs). Five pharmaceuticals, including ibuprofen, acetaminophen, lamotrigine, phenobarbital, and carbamazepine, were chosen as FPP models. At the beginning of the study, thermodynamic modeling of pharmaceutical solubility was done by the NRTL-SAC and UNIFAC-DMD activity coefficient models in order to screen the 62 approved solvents as determined by the Food and Drug Administration. These models reduce the time and cost associated with the experimental tries. Solid–liquid extraction, filtration, and crystallization are the three main unit operations that are used to purify pharmaceuticals. Results showed that the efficiency of the active pharmaceutical ingredient recovery is between 47 and 81%, mainly above 50%. Also, the purity of the recovered APIs, as the most important factor, was analyzed using melting point FT-IR, UV, high-performance liquid chromatography, and 1H NMR techniques. Results show that the purity obtained for most recovered APIs is near 100%. So, the purified APIs can be reused in formulation by finished product companies or as starting material in synthesizing derivatives in organic chemistry to obtain new molecules. The present research met the green chemistry criteria and shows significant importance from environmental and economic points of view.