Why current research is heading to CDI although it is similar to EDI?
Electrodialysis (ED) is used to transport salt ions from one solution through ion-exchange membranes to another solution under the influence of an applied electric potential difference. This is done in a configuration called an electrodialysis cell. The cell consists of a feed (dilute) compartment and a concentrate (brine) compartment formed by an anion exchange membrane and a cation exchange membrane placed between two electrodes. Capacitive deionization (CDI) is a technology to deionize water by applying an electrical potential difference over two electrodes, which are often made of porous carbon. So, ED is electricity + membrane and CDI is electricity + adsorption.
Does anyone think it matters who invented a technology? I think it is important as a way to discriminate information. In this regard, however, there is a need to improve poor citation hygiene among academic publications. Also great ideas not only have a lot of fathers, but, also, a lot of illegitimate children :). Perhaps the below helps explains this field a little better.- best, Marc
Market details on the commercialization capacitive deionization is described in this webinar https://www.youtube.com/watch?v=Hn7L5JA8AXQ
A paper in MSCE here http://file.scirp.org/pdf/MSCE_2014031817180829.pdf describes a third generation version that works without the most expensive part.
Electrodialysis is the closest cousin of capacitive deionization systems and has been successfully used for the desalination of brackish waters. But CDI is novel, eco-friendly, economically and more flexible. CDI is mainly optimal for diluted or low concentration water.
In the electrodialysis system, inlet flow enters into membranes that are divided into two types of selective anionic and cationic membranes that are interspersed. The application of an electric field leads to the migration of anions and cations to the opposite pole, and through selective membranes, between the membranes, two distinct canals form one in between. One canal is associated with desalinating water, and in the other canal, thick water and salty water are formed. The biggest problem with electrodialysis systems is the use of selective anion and cation membranes, which are expensive to maintain or replace.
In capacitive deionization systems, the salty water passes through a canal, which has electrodes with a high contact surface. By applying the voltage, the ions are absorbed into the electric field at the electrode surface. As a result of this operation, the salinity of the water is reduced and fresh water is exited from another side of the system. To regenerate the electrodes, by reversing the applied voltage, the absorbed ions will be removed from the electrode surface and enter the water flow. This cycle can be repeated many times in capacitive deionization system.
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