Separation of Taurine and Sodium Sulfate from Simulated Mother Liquor by Electrodialysis and Process Optimization

To address the high energy demand and product losses associated with separating taurine from sodium sulfate (Na2SO4) in the ethylene oxide route to taurine, electrodialytic desalination of a simulated taurine/Na2SO4 mother liquor was investigated. The effects of applied voltage, circulation flow rate, and initial feed concentration on the desalination rate, product purity, taurine recovery, current efficiency, specific energy consumption, and membrane productivity were evaluated. Ion-transport behavior was further examined using COMSOL Multiphysics® 6.3. At 14 V, a circulation flow rate of 200 L/h, and initial taurine and Na2SO4 concentrations of 100 and 68 g/L, respectively, the process achieved a taurine purity of 99.8% and a recovery of 98.9%. The specific electrical energy consumption of the electrodialysis unit was 0.56 kWh/kg Na2SO4, and the membrane productivity was 0.49 kg Na2SO4/(m2·h). One of the key findings of this work is that the low-salt stage plays a dominant role in process economics. This observation led to a simple endpoint-control strategy. The ED operation is stopped when the Na2SO4 concentration in the dilute compartment drops to about 2 g/L. This avoids prolonged operation under inefficient conditions and reduces ED energy consumption by 16.5%. Within the binary simulated system and the defined cost boundary, the proposed process provided a higher taurine recovery and a lower estimated separation cost than the conventional crystallization route. These results demonstrate the laboratory-scale feasibility of electrodialysis for desalting simulated taurine mother liquor.