Sorption capacity of Cs⁺ on titania nanotubes synthesized by solution processing

Abstract

Titania nanotubes (TNTs) have nanometer-sized tubular morphologies with layered structures. TNTs are candidate sorbents for the removal of many heavy metals and radionuclides. In this study, we investigated the Cs⁺ sorption capacity of TNTs synthesized by a solution chemical method in comparison with those of zeolite and TiO₂ particles. The TNT powder was shaken in 0.2–4.0 mM CsCl aqueous solution at 10, 25, and 40°C for up to 7 days. The sorption tests showed that the sorption density of Cs⁺ per gram of TNT was lower than that of zeolite. TiO₂ did not show Cs⁺ adsorption. The sorption isotherm of Cs⁺ on TNTs was fitted with the Langmuir model. The sorption of Cs⁺ on zeolite was well described with the Freundlich model. The TNT structure was maintained after sorption testing regardless of the concentration of CsCl aqueous solution. Elemental analysis of the TNTs showed uniformly adsorbed Cs⁺ throughout the TNTs. Na⁺ was also detected in the TNTs both before and after sorption, but the residual Na⁺ concentration decreased with increasing the adsorbed Cs⁺ concentration. These results clearly showed that the Cs⁺ was intercalated into the layered structures of the TNTs by ion-exchange with Na⁺.