Capacitive deionization technology (CDI) is developing faster as an emerging alternative for desalination. For a good performance of CDI, the electrode material should have a large surface area, dominating mesoporous structure and surface hydrophilicity in addition to a conductive bulk. In this thesis, activated carbon (AC) was prepared from the Mesquite tree using NaOH activation at 800 ºC. AC showed a good graphitic content that was identified with x-ray powder diffraction (XRD) in addition to a surface area of 640 m2 /g and dominating mesoporous structure. AC with 250 m size showed better CDI performance than AC with 500 m size. AC was oxidized to produce oxidized activated carbon (OAC) and was doped with urea to produce UAC. Both OAC and UAC showed less performance in CDI than AC due to their decreased surface area. AC was mixed with reduced graphene oxide to enhance the electrical properties of AC, however, due to its extremely low surface area, an enhancement of such mixture, as electrode material was not achieved. Mixing AC with multiwalled carbon nanotubes (MWCNT1 and MWCNT2) in a ratio of 1: 7 (on a weight basis) showed enhanced salt removal efficiency and salt adsorption capacity than AC. An electrode of AC/MWCNT1 showed the best CDI performance in the desalination of brackish water sample collected from Al-Suwaiq.