Multiwall carbon nanotubes (MWCNTs) oxidized by nitric acid solution were used to investigate the adsorption behavior of strontium
from aqueous solutions similar to the nuclear waste media. The physical properties of both as produced and oxidized MWCNTs
were studied by Boehm’s titration method and nitrogen adsorption/desorption. The results showed that the surface properties
of MWCNTs such as specific surface area, functional groups and the total number of acid sites were improved after oxidation.
Furthermore, the effect of solution conditions such as initial concentration of strontium(II), pH, ionic strength, MWCNT concentration
and contact time were studied at room temperature. The results of this study showed that the adsorption of strontium(II) was
significantly influenced by the pH value and the solution ionic strength. According to the Langmuir model, the maximum adsorption
capacities of strontium(II) onto the as produced and oxidized MWCNTs were obtained as 1.62 and 6.62 mg g−1, respectively. The contact time to reach equilibrium was 100 min. The good adsorption of strontium(II) on oxidized MWCNTs
at the lower ionic strength, the relatively high pH and the short equilibrium time indicate that the oxidized MWCNTs have
great potential applications in the field of the environmental protection.