Comparison of diester waste treatment by conventional andbipolar electrodialysis Original Research Article

Diester manufacturing plants produce large quantities of glycerol solutions. Their economic development requiressodium sulfate elimination to obtain glycerol rates over 80% of the initial content. Conventional electrodialysis (ED) and bipolar electrodialysis (BED) were investigated for their performances in the demineralisation of effluents. Results indicate that both ED and BED achieve the demineralisation objective with a global loss below 2.5% of the initial glycerol. Salt fluxes are twice as high with a bipolar membrane, bipolar membranes having however a lower efficiency. Hence energetic consumption is higher for BED. This technique also leads to the production of alkali and acid solutions which are useful to the diester process. The glycerol content of the solutions acts, via its viscosity, on the energetic cost of fluid pumping and on energetic efficiency. Therefore, ED or BED has to be used before the preconcentration of the solution.