High Ion-Accessible Surface Area CNT-Ultracapacitors for Groundwater Desalination

Freshwater is a vital resource for human survival as well as a key component of a wide range of industrial and agricultural needs. However, only 0.65% of the worlds water resources are available as freshwater, and the demand on the worlds water reserves continues to increase, with the demand beginning to outpace the supply in many areas. A water-energy nexus is being reached that requires low-cost and low-energy solutions for various degrees of treated water Seawater and other saline water materials make up around 98% of the available water, representing an almost unlimited supply. The energy, cost, and maintenance to remove salts and other unwanted compounds, however, are barriers to widespread implementation of salt-to- freshwater facilities. These facilities most commonly use reverse osmosis (RO) systems. Because of the required high pressures and moving parts, these facilities consume much grid energy and require constant maintenance, leading to high capital and operational costs. RO also generates highly concentrated bio-hazardous brine that is costly to safely return to the ocean. Capacitive desalination [or capacitive deionization (CDI)] offers a low pressure, low cost high efficiency approach to achieving a stable water supply. Moreover, it can use 1/3 the energy and produces 1/5 the concentrate waste compared to RO systems. In the Phase 1 development Mainstream demonstrated improved electrode structures to significantly enhance the extraction rate and extraction efficiency of capacitive deionization under practical operating conditions. We demonstrated a significant benefit in terms of extraction rate and energy efficiency compared to other prototype capacitive ionization devices being tested in the market. Our capacitive deionization system operates membrane free and is thus not susceptible to the fouling and failures that can occur with RO systems.