CDI is an electrochemical method for ion removal based on electrodes that adsorb ions from water to produce fresh water and later release them as brine. Traditionally, CDI uses a cell design with one porous carbon electrode that adsorbs and releases the cations (cathode), and another electrode that adsorbs and releases the anions (anode). Carbon electrodes naturally do not have preferential adsorption to either cation or anions. The adsorption is solely based on applied potential. By making the electrodes to selectively adsorb either anions or cations, the ion removal efficiency can be increased. Thus in this project, the carbon based materials, for ex. Carbon nanotubes (CNTs) will be chemically modified to induce ion selective adsorption. Also, aligned carbon nanotubes will be chemically modified and tested as ion selective membranes. In addition, the role of faradaic and non-faradaic reactions during the selective ion adsorption will also be probed.