Recent developments of electromembrane desalination processes

Electromembrane processes use the electric potential difference as the driving force to move charged ions through ion-selective membranes. These membranes have negative or positive charged functional groups and can be named as cation- and anion-exchange membranes (CEM and AEM) depending on the sign of the permeating ions. As the electrical force is applied, the membranes allow the permeation of oppositely signed ions and separate the ionic species from an aqueous solution and from other uncharged species. Electromembrane processes are well-established techniques and have gained importance in many areas such as desalination processes, energy production, food processing, molecular separation, water treatment and recovery and membrane concentrate treatment. The desalination with electromembrane process is widely used today for the production of high-quality water from seawater or brackish water. The main electromembrane desalination processes are categorized as electrodialysis (ED), electrodeionization (EDI), capacitive deionization (CDI), reverse electrodialysis (EDR), electrodialysis with bipolar membranes (EDBM). In this review article, the most popular electromembrane desalination processes have been evaluated with their theoretical basis and technological background. The main objectives of the review are (1) to describe the technological background of electromembrane processes (2) to summarize past and present attempts towards scaling up and commercialization of electromembrane desalination process (3) to present a critical review of their advantages and limitations (4) to outline the R&D activities with cost analysis.