Conversion of sodium lactate to lactic acid with water-splitting electrodialysis

The conversion of sodium lactate to lactic acid with water-splitting electr odialysis was investigated. One way of reducing the power consumption is to add a conductive layer to the acid compartment. Doing this reduced the pow er consumption by almost 50% in a two-compartment cell, whereas the electri c current efficiency was not affected at all. Three different solutions wer e treated in the electrodialysis unit: a model solution with 70 g/L of sodi um lactate and a fermentation broth that had been prefiltered two different ways. The fermentation broth was either filtered in an open ultrafiltratio n membrane (cut-off of 100,000 Dalton) in order to remove the microorganism s or first filtered in the open ultrafiltration membrane and then in an ult rafiltration membrane with a cut-off of 2000 Dalton to remove most of the p roteins. The concentration of sodium lactate in the fermentation broth was 70 g/L, as well. Organic molecules present in the broth (peptides and simil ar organic material) fouled the membranes and, therefore, increased power c onsumption. Power consumption increased more when permeate from the more op en ultrafiltration membrane was treated in the electrodialysis unit than wh en permeate from the membrane with the lower cut-off was treated, since the re was a higher amount of foulants in the former permeate. However, the ele ctrodialysis membranes could be cleaned efficiently with a 0.1 M sodium hyd roxide solution.