Study On Production Of Lactic Acid From Lactate Salts Using Electrodialysis

Lactic acid is an important organic acid with wide uses, especially in synthesis of biodegradable materials poly(lactic acid). Currently, the lactic acid recovery process is disadvantageous in terms of elaborate recovery process, exhausting a large amount of raw materials and waste production. To avoid such problems, this research is focused on conversion of lactate salts into lactic acid by electrodialysis using either bipolar or ion exchange membranes. The major advantages of this technology are high recovery efficiency, low energy consumption and having great potential in industrial production. The main goal of this work was to determine the suitable conditions for recovery of lactic acid from model sodium lactate by bipolar or ion exchange membrane electrodialysis, and from calcium lactate in model solution and fermentation broth by ion exchange membrane electrodialysis, and to evaluate the quality of lactic acid produced.In the bipolar membrane electrodialysis(BMED) operation, sodium lactate was converted into lactic acid and sodium hydroxide of high purity was obtained. The yield of lactic acid could exceed 90%, the current efficiency was about 60% and the electric energy consumption was between 2.5-3.5kWh/kg at 95% conversion factor of sodium lactate. During this study, the performance of bipolar membrane made in Beijing and cation membrane JCM-I was better. Current densities, initial concentration of sodium lactate and sodium hydroxide had great influence on the process. During batch operation, the optimal conditions were as follows: electric current was set at 2.5A, and initial concentrations of sodium lactate were 0.70 and 0.10mol/L, respectively.In the process of ion exchange membrane electrodialysis with three compartments, sodium lactate was converted into lactic acid and sodium sulphate was obtained by adding sulphuric acid. Under the conditions of this experiment, the yield of lactic acid and current efficiency exceeded 90%, and the energy consumption was about 0.7kWh/kg. During the process, high initial concentration of sodium lactate had...