Application of amide functionalized carbon nanotube for the sorption of U and Th

The strength and flexibility of carbon nanotubes makes them of potential use in controlling other nanoscale structures having an important role in nanotechnology engineering. Recently, several studies have highlighted the prospect of using carbon nanotubes as building blocks to fabricate three-dimensional macroscopic all-carbon devices. Due to the high surface area, carbon nano tube is expected to be a better sorbent of the metal ions. Moreover the anchoring of amide functionality improves its sorption capacity as well as selectivity. The k_d values of both U and thorium was found to increase with feed acidity followed by the plateau. The k_d values of Th⁴⁺ (11 x 10³) was found to be more than that of U (2 x 10³) while only negligibly small amount of lanthanides were found to be sorbed on the amide functionalized carbon nano tube. The sorption kinetics data were fitted into Lagergren first order rate kinetics and rate of sorption was calculated for both U and Th. The sorption behavior was also analyzed comparing Langmuir, Dubinin-Radushkevich, Temkin and Freundlich isotherm. Dilute nitric acid was found to be inefficient for quantitative stripping of uranium and thorium from the functionalized CNT. Therefore aqueous phase complexing agents (0.05 M Na₂CO₃ and 0.05 M oxalic acid) were used to serve the purpose. Oxalic acid was found to strip thorium effectively from sorbent while for uranium Na₂CO₃ was found to be effective. (author)