Effects of pore-structure and Surface Acidities of Activated Carbon Electrodes on The Double-layer Adsorption

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It was possible to efficiently remove electrolytes from dilute solution using the flow-through capacitor (FTC), and a greater then 85% removal efficiency was achieved when porous activated carbon electrodes were used. It was confirmed that the amount of removal is generally dependent on the surface area and micropore volume of the activated carbon. Also, surface functional groups had the effect of improving ion removal, but there is a limit to the amount of groups mainly due to the interference of the transport of ions. The mechanisms for removal of the ions is proposed to include 1) adsorption by electrostatic force, 2) electrochemical ion exchange reactions when voltage is applied, and 3) normal ion exchange reactions by contact between the electrolyte and the activated carbon (especially for copper), and 1) electrolysis on the surface of the electrode (for example, for copper and zinc ions). The metal formed by electrolysis affected the pore structure of the activated carbon electrodes during prolonged ion removal. Alkali metals could be recovered and concentrated the easiest, but heavy metals were the most difficult. The latter ions were removed mainly by electrolysis at the interface of the electrode and the metals were being produced on the electrode surface. Therefore it was impossible to concentrate and recover the metal ions by this method.Cations have been demonstrated to be removed and desorbed in the following descending order of ease: alkaline metal > alkaline earth metal > transition metal. A high recovery rate has been obtained in the cycle characteristics of sulfuric acid and nitrates. In both one- and electric double layer are not easily desorbed.In order to increase volume of wastewater treatment, the FTC was large scaled. The optimum running conditions were determined for high efficiency better than small ones.