2009 Volume 25 Issue 2 Pages 229-233
A layered manganese oxide film grown electrochemically was applied to remove methylene blue (MB), a cationic dye, from an aqueous solution. A layered MnOx film intercalated with tetraethylammonium (Et4N) cations was deposited potentiostatically at +1.0 V (vs. Ag/AgCl) from an aqueous Mn2+ solution containing Et4NCl. Et4N cations were sandwiched between negatively charged MnOx layers. When the Et4N/MnOx film was immersed in a solution containing MB alone, the intercalated Et4N cations were replaced with MB in a solution phase by an ion-exchange mechanism. The uptake capacity of the Et4N/MnOx film for MB was estimated to be 45.3 mg per 1.0 g of MnO2. In the presence of KCl, the MB sorption was seriously restricted because the interlayer space was occupied by K+ ions. However, the MnOx film anodized at +0.8 V can selectively take up MB molecules from the KCl solution. This can be ascribed to an increase in the interlayer space available to the sorption of MB due to the extraction of K+ ions, where the MnOx surface probably has a specific affinity toward MB molecules.