Desalination of high salt content mixture by two-stage electrodialysis as the first step of separating valuable substances from grass silage☆

In this study, two-stage electrodialytic separation of valuable substances such as lactic acid and amino acids from grass silage juice was preliminary investigated. Based on the different ionic forms of lactic acid as well as amino acids, which depend on the pH of grass juice, electrodialysis can separate lactic acid and amino acids from mineral ions. At pH = 6.7, most of the amino acids were separated from lactic acid and mineral ions. Current efficiency of this step was η = 0.67. The average mass transfer of inorganic salts was 0.091 kg/m 2 .h. The specific energy consumption for the transportation of ions through the membranes was 0.074 kWh/l of silage juice. The specific energy consumption was 2.11 kWh/kg of lactate transported. More than 97% of sugars and about 90% of amino acids and were separated from the juice in the first separation step. In the next step, lactic acid was separated from the previous concentrate at pH = 2. As expected, the average mass transfer of inorganic salts was 0.490 kg/m 2 .h, which was significantly higher than that of the first step. Current efficiency of the second step was η = 0.88. The specific energy consumption for the transportation of ions through the membranes was 0.038 kWh/l of silage juice. The total lactate recovered by two-stage ED was 91% at a 98% of demineralization level.