SOLVENT-EXTRACTION OF LACTIC-ACID FROM AQUEOUS-SOLUTION

The equilibrium distribution of lactic acid was studied in a two-phase aqueous-organic system containing various extractants with a view to the separation of lactic acid obtained as a product of lactose degrada tion under the effect of Lactobacillus casei (pH of the aqueous soluti on between 5-6 and temperature 35-degrees-C). ALIQUAT 336 containing a quaternary ammonium salt as an active component was found to be the m ost appropriate extractant. The effect of the experimental conditions on the distribution ratio was followed by varying the concentration of lactic acid in the aqueous solution from 0.001 to 0.033 mol l-1, pH f rom -0.3 to 12.5 and the concentration of extractant in the organic so lution from 0.5 to 20% (vol.). On the basis of the experimental result s the extraction equilibrium constant of lactic acid in the examined t wo-phase system was determined: K(ex) = 0.274. The stripping process o f lactate ions from the organic phase was studied. Alkaline chlorides and carbonates were found to completely destruct the complex of lactat e ions with the extractant which provided their transfer to the stripp ing solution. It was concluded from the obtained results that liquid-m embrane extraction is the most appropriate technique for the simultane ous separation of lactate ions from the medium and their transfer and preconcentration in an aqueous solution containing alkaline chlorides or carbonates.