Water
Within the research community, many are beginning to realize the need to develop a technological solution that combats the growing problem of water scarcity. Presently, over half of the world´s population is affected by a severe water shortage. In many developing countries, water shortage is responsible for 80 to 90 percent of diseases, as well as 30 percent of all deaths. Since 97 percent of the world´s water supply is sea water, creating new and improving existing water desalination techniques is the logical choice to surmount this problem. With the global population on the rise, one of the biggest problems our society will face this century is maintaining an appropriate level of drinking water through highly efficient, low cost methods of desalination.
Membrane separation, specifically separation by reverse osmosis, is the current state of the art technology in sea water desalination. While the process of desalination though reverse osmosis is being used more and more in countries throughout the world, problems still exist due to the current membranes involved with the process. The non-selective membrane used relies on the high applied pressure for separating the salt and organics from the sea water while allowing water to diffuse across the active layer, thus requiring a large membrane (high surface area to volume) in order to achieve high fresh water output. However, this type of membrane is highly prone to fouling, thus requiring periodic replacement in order to maintain maximum efficiency. A goal of our research is to determine whether the membrane can be modified by selectively tuned materials in order to achieve high ion rejection and water permeability without using extreme pressure. Another goal is to create a new membrane composed solely of these tunable materials.
Capacitive deionization is a non-membrane-based, electrochemical separation process to reduce the salt concentration in a solution. Based off the principles of electrochemical capacitors, the salt water is passed between two electrodes with an applied voltage. The ions in the solution adsorb onto the surface of the respective electrode (capacitive charging) thereby reducing the bulk concentration of the solution. Once the electrodes are saturated, the voltage is reversed by allowing the ions to return to the solution in a purge stream (capacitive discharging). The energy returned in the discharging process can simultaneously help power another set of electrodes. We are currently working on better understanding the ion transport mechanisms during this process to design more efficient capacitive deionization desalination systems.
