oa Advanced Treatment Process for Brackish Water Desalination

We aim to develop an energy-efficient, low-cost desalination technology for creating new, affordable water sources from brackish waters. Since Qatar has extremely limited rechargeable water sources, technologies facilitating safe use of impaired and unconventional water sources are needed. Capacitive deionization (CDI) technology can meet the unique, logistical and economic needs for inland desalination. CDI technology, unlike reverse osmosis and nanofiltration, operates under ambient pressure and can be sustained with renewable energy sources. In this process, ions move to the electrode surface and build up an electrical double layer (EDL) when an external potential is applied. Metal oxide nano-particle coatings are widely used in super-capacitors to increase the capacitance. We are employing fourth-generation CDI technology (i.e., alumina, silica nano-particle coated porous carbon) for brackish water treatment. The presence of oxides together with the functional groups on the carbon surface enhances the ion removal process. Sorption capacity of up to 0.05 mM/g electrode has been achieved for monovalent ions with high reversibility and no obvious loss of capacity in long-term operation. During regeneration, up to 50% of the charge can be harvested. Preliminary results indicate that higher sorption capacity exists for divalent cations compared to monovalent ions. Comprehensive tests are underway for various electrolytes (1:2, 2:1, 2:2) and brackish water samples to cover a wide gradient in salt concentration and ionic composition. This project will lead to the development of low-cost inland desalination systems and can be expected to boost Qatar's scientific profile in global and regional water industry.