Reactive extraction of citric acid was studied using tri-n-octylamine (TOA) in methyl isobutyl ketone (MIBK). Extraction using pure diluent was not found to be very high (degree of extraction E = 2%). Using the mixtures of extractant-diluents, the extraction was significantly improved (E_(TOA+MIBK) = 90%). For interpretation of equilibrium data, the modified Langmuir isotherm and Linear Solvation Energy Relationship (LSER) model were used. The values of extraction equilibrium constants assure the best fit of measured and calculated equilibrium concentrations. Citric acid-TOA was found to form (1:1) complex with no overloading in any case. TOA-MIBK system was found to provide K_D (average) value of 90 and K_E value of 234 m³/kmol.

Citric acid is one of the most important carboxylic acids produced commercially by the fermentation route. Global production of citric acid in 2004 was about 1.4 million tons estimated by Business Communications Co. (BCC) in a recent study of fermentation chemical markets (Soccol et al., 2006). Citric acid is widely used to impart a pleasant, tart flavor to foods and beverages. Citric acid is used in cosmetics and toiletries as a buffer, and in a wide variety of industrial applications as a buffering and chelating agent. Citric acid is also a reactive intermediate in chemical synthesis. In addition, its carboxyl and hydroxyl groups permit the formation of a variety of complex molecules and reactive products of commercial interest.

Production of citric acid by bioroute has its own advantages: operations are simple and stable, the plant is generally less complicated and needs less sophisticated control systems, technical skills required are lower, energy consumption is lower and frequent power failures do not critically affect the functioning of the plant. The only problem associated with production is the costly and difficult recovery step. Because of its hydrophilic nature, citric acid is poorly extractable by common organic solvents; so, for recovering it from aqueous solutions, a good recovery technique is required.

Chemistry Journal, Reactive Extraction, Citric Acid, Carboxylic Acids, Business Communications, Industrial Applications, Conventional Recovery Method, Extraction Equilibrium Experiments, Organic Compounds, Aqueous Phases, Hydrogen Bonding, Linear Solvation Energy Relationship, Langmuir Extraction Model.