Surface Treatment of the Activated Carbon on Capacitive Deionization

The capacitive deionization (CDI) which has huge interest as an energy efficient and eco-friendly desalination process, is an electrochemically water purification technology using electro-static adsorption/desorption of ions on the charged electrode. Activated carbons are commonly used for an electrode material due to its high surface area. The surface condition of activated carbon is a remarkable point on the CDI process that repeats reversible adsorption and desorption of ions on the interface between the carbon electrode and the saline electrolyte. In this experiment, we investigated the effect of surface treatment of activated carbons on CDI performance by two kinds of commercial activated carbons which were Maxsorb-III and P-60 with a surface area of 3000, 1800m²g^-1, respectively. Each activated carbon was treated by two different methods. One was to remove the surface functional groups by heat treatment in hydrogen atmosphere. Another way was to introduce the oxygen functional groups on the surface by H₂O₂ treatment. The characteristics such as the specific surface area and chemical states of carbon surface were evaluated by N₂ adsorption isotherm and FT-IR analysis. The specific capacitance was examined using cyclic voltammetry in saline or acid electrolyte. Unit-cell CDI performances were tested and compared in a view point of surface functional groups of activated carbons