Capacitive deionization (CDI) is a promising desalination technique that gains more and more attentions worldwide in recent years due to its high efficiency and feasibility. In this work, the sulfuric acid functionalized activated carbon (FAC) is proposed as electrode for CDI. By compared to pristine AC, FAC electrode shows an improved microspores volume from 0.17 to 0.22 m(3) g(-1) and therefore a high electrosorption capacity of 3.54 mg g(-1) as well as a charge efficiency of 0.21. Furthermore, the FAC electrode follows the Langmuir isotherm, indicating the monolayer adsorption. Besides, the pseudo-first-order can describe the adsorption kinetics of FAC electrode as compared to other kinetics models. Additionally, the FAC electrode can be regenerated very well. (C) 2015 Elsevier Ltd. All rights reserved.