Equilibrium studies of the extraction and re-extraction of lactic acid

Equilibrium studies on the extraction of lactic acid in various organic phases and its re-extraction into aqueous solutions have been carried out. This includes a variety of experimental situations: using only solvents, single carriers with solvent, mixed carriers with solvent and with mixed solvents. The organic phase consists of a carrier (or a mixture of carrier) dissolved in a solvent (or a mixture of solvents). The extraction and re-extraction processes have been characterized by using distribution coefficient for the respective processes. The values of the distribution coefficient have been obtained by varying the operating conditions (i) for extraction: feed solution pH, types of carrier and its concentrations, solvent and its concentration in the organic phase; and (ii) for re-extraction: the type, pH, and concentration of recovery solution. It was found that 20 wt % of trioctylamine (an ionic carrier) dissolved in tributyl phosphate (an active solvent) was found to be the best extracting phase. For re-extraction, an aqueous solution of sodium carbonate gave the best recovery from the organic phase.