KINETIC-STUDY OF ELECTRODIALYSIS OF ACETIC-ACID AND PHOSPHATE IN FERMENTATION BROTH

Ion fluxes of acetic acid and phosphate in the electrodialysis of a mo del fermentation broth were examined using a solution of acetic acid a nd potassium dihydrogenphosphate. As the molar fraction of the phospha te was increased the ion flux of the acetic acid decreased, which was as predicted theoretically. As the influent pH was increased the flux also increased notably, reached a maximum, and then decreased slightly . The maximum flux was obtained in a pH range from 5.2 (near pK(a)) to 6.6. The pH at the exit of the electrodialyzer became markedly alkali ne when the influent pH was in the range of 6 to 7 in the absence of t he phosphate. The pH range shifted to the alkaline side and the degree of alkalinity reduced as the molar fraction of phosphate increased. T his may be ascribed to the buffering effect of the phosphate. It is co ncluded that the optimum pH for the electrodialysis of an organic acid fermentation broth is around (pKa + 1), where a relatively high ion f lux with high current efficiency and a small pH increase at the exit o f the electrodialyzer are established.