Reactive extraction of citric acid using supercritical carbon dioxide

Małgorzata Djas , Marek Henczka

Abstract

This paper presents the results of investigations into reactive extraction of citric acid from an aqueous solution using supercritical carbon dioxide (scCO2) and tri-n-octylamine (TOA). The effect of initial citric acid concentration (0.07–1.04 mol dm−3), pressure (8–16 MPa) and temperature (35–65 °C) on reactive extraction efficiency was identified. The reactive extraction process was conducted in both batch mode and semi-continuous mode. The study concluded that the reactive extraction using TOA as a reactant and scCO2 is an efficient method of citric acid separation. Reactive extraction efficiency increases with an increase in pressure, while an increase in temperature decreases the extraction yield. Reactive extraction of citric acid conducted in semi-continuous mode results in high process efficiency (96.9%). Moreover, the formation of (1,1) acid-amine complexes was reported for the considered initial citric acid (0.01–0.04 mol dm−3) and TOA (0.04–0.07 mol dm−3) concentrations.