Purification of L-Malic Acid from Aqueous Solution by a Method of Reactive Extraction

Malic acid is a C-4-dicarboxylic acid and an intermediate of the tricarboxylic acid cycle. It has been widely used in the polymer, food, and pharmaceutical industries. Malic acid is produced by a fermentation process with a lot of bacteria in about between (8 and 10) % by weight aqueous solution. In this study, malic acid has been extracted from aqueous solution by reactive batch extraction in solvents with and without trioctyl methyl ammonium chloride (TOMAC or Aliquat 336). Five different constant concentrations of TOMAC have been prepared using five different esters (dimethyl phthalate, dimethyl adipate, dimethyl succinate, dimethyl glutarate, diethyl carbonate), five different alcohols (isoamyl alcohol, hexan-1-ol, octan-1-ol, nonan-1-ol, decan-1-ol), and two different ketones (diisobutyl ketone (DIBK), methylisobutyl ketone (MIBK)). The results have been reported as distribution coefficients (K-D), loading factors (T-T), stoichiometric loading factors (T-S), separation factors (S-f), and extraction efficiencies (E). The most effective solvent has been determined to be isoamyl alcohol with a distribution value of 2.674. The maximum values of the overall equilibrium complexation constants in isoamyl alcohol for (acid:amine) (1:1) K-E1 and (2:1) K-E2 are 1.580 and 7.250, respectively. The linear solvation energy relationship (LSER) has been accurately regressed to the experimental distribution coefficients.