(335z) Removal of Salt Impurities From Glycerol Using Electrodeionization Technique

The demand and production of biodiesel is growing to meet the regulatory requirements of the Energy Independence and Secuirty Act of 2007. The principal co-product of biodiesel production is glycerol (or glycerin). Approximately, 100 kg of glycerol is produced per ton of biodiesel. Most biodiesel is produced by transesterification with homogeneous catalysts, which leaves inorganic salts in the process streams. After separating the biodiesel layer, the glycerol layer is obtained that contains around 70-75 % glycerol along with 20-25 % methanol, 4-5 % inorganic salts and 1-2 % water as impurities. Removal of these impurities is critical to convert the crude glycerol into a high value pure glycerol for further uses in food, pharmaceutical and cosmetics industries. The existing technologies, such as, distillation and chemical addition are inefficient and energy intensive. Therefore an efficient glycerol purification technique is required to enhance the sustainability and economics of biodiesel production.

We developed a crude glycerol purification technology using an electrodeionization (EDI) system. EDI combines electrodialysis and ion-exchange technologies, and used for desalination of low conductive process streams. In this study, Argonne National Laboratory's proprietary ion-exchange resin wafers were used in the EDI stack (RW-EDI) for desalination of low conductive crude glycerol. Ion exchange resin beads were fabricated into porous resin wafers using a patented technique to improve the flow distribution and increase the conductivity of the process stream inside the device. We report the removal of >99 % of catalyst salts from the crude glycerol stream using the RW-EDI technology. The energy consumption for the desalination using RW-EDI is significantly lower than the currently available technologies. In this presentation, the effects of flow rates and applied voltages on the salt removal efficiency will be discussed.