Electrochemical Adsorption of Cs+ Ions on H-Todorokite Nanorods

Abstract

In this work, manganese oxide with a 3 × 3 tunnel structure was synthesized. Mg-todorokite was treated with HNO3 to obtain H-todorokite, which was used as an electrode for adsorption of Cs+ from aqueous solution by an electrochemical reaction. H-todorokite was electrochemically reduced to lower oxidation state to enhance its negative charge and simultaneously increase the amount of cations because of the charge compensation. The Cs+ adsorption on H-todorokite was completed by a coupled electrochemical reaction (the redox reaction between Mn3+ and Mn4+) and an ion-exchange reaction between Cs+ and H+ ions. Cyclic voltammetry measurements at different pHs and Cs+ concentrations were performed. H-todorokite revealed high electrochemical adsorption capacity for Cs+ because of the high crystallinity and stability of the materials, which reached 6.0 mmol g-1 in 0.1 mol·L-1 Na2SO4 solution.