The effect of fermentation broth composition on removal of carboxylic acids by reactive extraction with Cyanex 923

Abstract

This paper presents results of liquid-liquid extraction of carboxylic acids, particularly succinic acid (Suc), from one-, two-and multi-component model solutions, and from a fermentation broth with 0.1 and 0.4 mol/L Cyanex 923 (solvating extractant, mixture of trialkylphosphine oxides). As the idea of the extraction is to concentrate Suc in the organic phase, thus, the optimum conditions of extraction are proposed, i.e. 0.4 mol/L Cyanex 923) at low volume of the organic phase (o/w = 1/2), to obtain high extraction efficiency (64%) and to enrich Suc in the organic phase (almost 8 g/L in relation to 6 g/L in the feed). The presence of polyols (propane-1,3-diol, glycerol) in Suc model solutions does not affect Suc extraction efficiency, while the presence of such carboxylic acids as lactic (Lac), acetic (Ac) or formic (For) results in a competition between Suc and other acids. Extraction efficiency of the acids from the real fermentation broth decreases in the following order: But ≫ For ≈ Ac > Lac, which is consistent with their increasing hydrophilicity. The total yield of the proposed extraction-stripping process amounts to 70% recovery of succinic acid. The results prove that the extraction with Cyanex 923 is effective for separation of carboxylic acids from polyols (propane-1,3-diol, glycerol).