MEASUREMENT OF PARTITION-COEFFICIENTS OF CARBOXYLIC-ACIDS BETWEEN WATER AND TRIISOOCTYLAMINE DISSOLVED IN VARIOUS DILUENTS

Tertiary amines dissolved in organic diluents are attractive extractan ts for the recovery of carboxylic acids from dilute aqueous solutions. This paper reports experimental results for liquid-liquid equilibrium in organic/aqueous two-phase systems containing a tertiary amine (tri isooctylamine) and five carboxylic acids, aconitic, citric, lactic, ma lic, and oxalic acid. Triisooctylamine (tris[6-methylheptyl]amine) was dissolved in various diluents such as chloroform, a mixture (heptane (50 vol %) + 1-hexanol (50 vol %)), and l-octanol. Partition coefficie nts for individual acids were determined at a temperature of 25 degree s C over a range of amine concentration in each diluent between 2.5 vo l % and 60 vol %. Thus, for aconitic, citric, lactic, malic, and oxali c acid the maximum values of partition coefficient were found to be 92 .7, 47.0, 28.2, 65.2, and 76.0, respectively. For dilute solutions con taining less than 3 mass % of acid, it is energetically preferable to remove the solute from the water through liquid-liquid extraction. Owi ng to the significant partition coefficients obtained with amine dilue nt systems, the process generates a small extract stream for subsequen t regeneration processing. On the other hand, the recovery of solute b y evaporation requires the energy intensive vaporization of water. Liq uid-liquid extraction can be considered as an effective process for th e recovery organic acids present in wastewater from industries such as distilleries, canneries, and wineries.