Desalination and Waste Water Treatment by Capacitive Deionization (CDI)
Source: Lawrence Livermore National Laboratory
Date: 1/1/95    Record No.: 10085
Contact: Joe Farmer, 510-423-6574; Craig Savoye, 510-422-9919

Desalination and Waste Water Treatment by Capacitive Deionization (...
On December 20, 1994, LLNL announced a new way to deionize water. The huge effective surface area of carbon aerogels makes feasible the straightforward and well-known process of capacitive deionization. Water containing salts, heavy metals or even radioactive isotopes flows through a series of electrochemical cells. An electric potential is applied across the electrodes, which attract the charged ions.

The electrodes are metal plates coated with the aerogel, the high surface area of which allows them to absorb large quantities of ions, which are released later into a small volume "rinse" stream. CDI offers significant benefits over traditional deionization processes, such as reverse osmosis, ion exchange or evaporation. These involve high energy use, reliance on acids and bases, production of corrosive secondary wastes, and use of troublesome membranes. Compared with traditional desalination techniques, CDI could reduce the energy requirement by as much as 100-1000 times.

Potential applications include: treatment of boiler water in power plants, electric residential water softeners, desalination of sea water, waste water treatment (i.e., volume reduction, notably of radioactive wastewater, by a factor of 1000), and more.

A desktop test unit has been operating at LLNL for some time. A patent was filed in May 1994. Aerojet may become a supplier of the aerogel material, based on its experience with silicon aerogels.

Topics: END USE