Liquid-Liquid Equilibria of Lactic Acid between Water and Tris(6-methylheptyl)amine and Tributyl Phosphate in Various Diluents

Abstract

Separation of an organic solute from dilute aqueous solution is difficult when the solute is not sufficiently volatile for distillation and furthermore is very soluble in the water phase. In this case, it is economically preferable to remove the solute by solvent extraction. In this work, the possibility of the extraction of lactic acid from agroindustrial aqueous effluent was studied. Two type of organic solvents such as organophosphorus extractant and a long-chain tertiary amine dissolved in various diluents of varying polarity were chosen for their abilities to extract lactic acid. Owing to their very low solubilities in the aqueous phase which limit the environmental pollution, the use of these solvents in biotechnology and food processing was reported in previous works (Yu-Ming, J.; Dao-Chen, L.; Yuan-Fu, S. Proc. ZSEC 1980, ZZ, 517. Wennersten, R. J. Proc. ZSEC 1980, ZZ, 63). The solubility of tris(6-methylhepty1)amine (triisooctylamine) in water (0.002 mass %) is less than the solubility of tributyl phosphate in water (0.039 mass %). Tie line data were determined a t a temperature of 25 C. For the selected solvents tributyl phosphate + dodecane, triisooctylamine + 1-octanol, and triisooctylamine + heptane + hexanol the partition coefficients defined as the ratio of lactic acid concentration (mass %) in the organic phase to lactic acid concentration (mass %) in the aqueous phase were found to be equal to average values of 0.77, 1.37, and 0.53, respectively.