Reactive Extraction of Glutaric Acid from Aqueous Solutions Using Tri- <i>n</i> -octylamine in Deep Eutectic Solvents

Glutaric acid, a value-added dicarboxylic acid with wide applications in food, polymers, pharmaceuticals, and speciality chemicals, is typically produced via fermentation and requires efficient downstream recovery for process viability. In this study, the recovery of glutaric acid via reactive extraction with deep eutectic solvents (DESs) was investigated to intensify the process sustainably. DES was synthesized by combining dl-menthol as the hydrogen bond donor (HBD) and tributyl phosphate (TBP) as the hydrogen bond acceptor (HBA), with tri-n-octylamine (TOA) as the extractant. DES was characterized using FTIR and NMR to investigate structural stability. The effects of operational parameters, including the initial acid concentration, amine concentration, solvent composition, and temperature, were systematically evaluated at 298 K and at atmospheric pressure. Key separation parameters, such as distribution coefficients and loading factors, confirmed the effectiveness of the process. This work establishes a scalable,enviornment-friendly approach fro glutaric acid recovery.The highest reactive extraction efficiency (92.85%) and distribution coefficient (12.99) were observed at the maximum TOA concentration (0.77 mol/L) and at 0.8XT DES (XT represents the mole fraction of TBP in the TBP-TOA DES).