Organic acids constitute a key group among the building-block chemicals since they are extremely useful as starting materials for the chemical industry. However, the extraction processes of these acids from dilute waste water and fermentation broths normally use organic solvents which imply additional environmental hazards. In this work we have tested the efficiency of hydrophobic ionic liquids, namely phosphonium-based, to extract three short-chain organic acids (L-lactic, L-malic, and succinic acids) from dilute aqueous solutions, as model systems for the use of ionic liquids to extract bioproducts from fermentation broths. The effect of the anion's nature and the concentration of the acid in the aqueous solution on the partition coefficients was evaluated. Two different approaches to recover the organic acid from the ionic liquid, viz, reduced pressure distillation and pH variation were assessed. The results gathered in this work proved that phosphonium-based ILs can be better extractants than the organic solvents traditionally used. In addition, the predictive capacity of the COSMO-RS for the ternary systems water + - organic acid + ionic liquid was evaluated. (C) 2011 Elsevier B.V. All rights reserved.