Separation and Purification of LA

LA solution obtained initially from a fermentation medium or any other source cannot be used directly, which need to be concentrated and purified. 

LA can be purified either by precipitation of metal lactates followed by a neutralizing reaction with sulfuric acid [8] or by esterification with alcohol, distillation and hydrolysis of the formed ester, or by electro-dialysis. A more recent purification process is to extract LA by liquid-liquid extraction making use of at least one organic solvent not miscible with water in the presence or not of at least one Lewis base such as a ternary amine for instance. With this process, lactic acid must be recovered in a second step with a liquid-liquid back-extraction. This step allows to re-transfer the lactic acid to water. Finally, LA in acid- and/or ammonium lactate or metal lactate-form may be purified by processing it on cationic and/or anionic ion-exchange columns. 

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