ABSTRACT
The contamination of water sources with toxic metals and semi-metallic elements, including arsenic and selenium, is a matter of great concern worldwide, because of their potential negative impact on the ecosystems. While in very small amounts, many of these metals are necessary to support life, in larger amounts, they can become extremely toxic. Since, usually there are no detectable organoleptic changes in drinking water in the presence of toxic metal ions in trace levels, it is rather possible that some of them may easily remain undetected, thus additionally increasing possible health risks. Since most metal-containing species in water are either positively or negatively charged, use of electro-membrane processing for their removal appears as natural choice. Membrane processes that use ion-exchange membranes and electric potential difference as the driving force for ionic species transport are referred to as electromembrane processes. Various electro-membrane separation processes include electrodialysis, including variations such as electrodialysis reversal, electro-electrodialysis and bipolar membrane electrodialysis, electrodeionization, and Donnan dialysis.
