Adsorption of cesium (I) from aqueous solution using oxidized multiwall carbon nanotubes

Multiwall carbon nanotubes (MWCNTs) were modified by nitric acid solution and then used to study the adsorption of cesium from aqueous solution using a batch technique under ambient conditions. As produced and oxidized MWCNTs were characterized by nitrogen adsorption/desorption, Boehm's titration method and Fourier transform infrared spectroscopy. The physical properties of MWCNTs such as functional groups, total number of acid sites and specific surface area were greatly improved after oxidation, and these were responsible for more sorption of cesium from aqueous solution and made them more dispersible in water. The adsorption of cesium ions as a function of contact time, initial concentration of cesium, pH, ionic strength and oxidized MWCNT concentrations was also investigated. The results showed that cesium adsorption percentage strongly depended on the pH value, oxidized MWCNT content and on the solution ionic strength. Kinetic data indicated that the adsorption process achieved equilibrium within 80 min. Equilibrium data for as produced and oxidized MWCNTs was well described by both Freundlich and Langmuir isotherms. The dominant mechanism of cesium adsorption on oxidized MWCNTs may be mainly attributed to ion exchange. This study suggests that oxidized MWCNTs can be a promising candidate for the removal of cesium from nuclear waste solution.