Effects of pH on recovery of lactic acid from kitchen garbage fermentation broth by electrodialysis

Recovery of lactic acid from kitchen garbage fermentation broth was carried out by electrodialysis (ED). The effects of pH on permeation ratios of lactic acid, ammonia, reducing sugar were discussed. The experimental results showed that pH was the main factor that affected the permeation of ammonia. The rise of pH changed the equilibrium of NH₄⁺, NH₃ and NH₃·H₂O, and resulted in the increase of NH₃ and NH₃·H₂O, thus the permeation ratio of ammonia increased. Under the conditions of weak acidity, 12 h ED and 2.0 A·dm^-2 current density, the recovery ratio of lactic acid and the average current efficiency were over 89% and 90%, respectively, whereas the permeation ratios of ammonia and reducing sugar were less than 0.15% and 0.95%, respectively. The product could be used as raw material of polylactic acid synthesis if it was further concentrated by distillation.