Green solvent‐based reactive extraction of glutaric acid: performance of natural oils in tri‐n‐butyl phosphate

Background Recovery of glutaric acid from dilute aqueous streams such as fermentation broths and process wastewaters remains challenging because of its high water solubility and the high cost of conventional downstream separation. This study investigates the reactive extraction of glutaric acid using tri‐ n ‐butyl phosphate (TBP) dissolved in green vegetable oils, namely sunflower, soybean, and sesame oils. Results The extraction performance was evaluated in terms of the distribution coefficient ( K D ), extraction efficiency ( E %), equilibrium complexation constant ( K E ), and loading ratio ( z ). At the highest TBP concentration (3.614 mol L −1 ), sunflower oil exhibited the highest extraction performance, with a maximum distribution coefficient of 4.61 and extraction efficiency of 85.9%, followed by soybean oil ( K D = 4.61, E = 82.2%) and sesame oil ( K D = 3.59, E = 78.15%). The diffusivity of glutaric acid towards the organic‐aqueous interface was estimated as 1.78 × 10 −6 cm 2 s −1 using the Wilke‐Chang equation and 2.02 × 10 −6 cm 2 s −1 using the Reddy‐Doraiswamy correlation. The minimum solvent‐to‐feed ( S / F ) ratio and the required number of theoretical stages for counter‐current extraction were determined from the equilibrium data, while negligible water co‐extraction confirmed the hydrophobic nature of the vegetable oils. Conclusion Reactive extraction of glutaric acid using TBP in vegetable oils demonstrated that sunflower oil was the most effective green diluent, followed by soybean oil and sesame oil. The diffusivity data and process design parameters obtained in this study provide useful information for the design and scale‐up of continuous reactive extraction systems for sustainable glutaric acid recovery.