Adsorptive removal of thorium from aqueous solution using diglycolamide functionalized multi-walled carbon nanotubes
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Multi-walled carbon nanotubes (MWCNTs) were functionalized with diglycolamide (DGA) through chemical covalent route. The adsorption behavior of the DGA-functionalized-MWCNTs (DGA-MWCNTs) towards thorium from aqueous solution was studied under varying operating conditions of pH, concentration of thorium, DGA-MWCNTs dosages, contact time, and temperature. The effective range of pH for the removal of Th(IV) is 3.0–4.0. Kinetic data followed a pseudo-second-order model. The equilibrium data were correlated with the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models. The equilibrium data are best fitted with Langmuir model. The equilibrium Th(IV) sorption capacity was estimated to be 10.58 mg g−1 at 298 K. The standard enthalpy, entropy, and free energy of adsorption of the thorium with DGA-MWCNTs were calculated to be 8.952 kJ mol−1, 0.093 kJ mol−1 K−1 and -18.521 kJ mol−1 respectively at 298 K. The determined value of sticking probability (0.072) and observed kinetic and isotherm models reveal the chemical adsorption of thorium on DGA-MWCNTs.
KeywordsThorium Multi-walled carbon nanotubes Diglycolamide Adsorption isotherm models Kinetics of adsorption
The authors sincerely thank Shri S. C. Chetal, Director, IGCAR for his support during this work. The authors thank Dr. D. Ponraju, Head, PCS, SED, IGCAR for valuable suggestions and Shri H. Krishnan, Shri Shailesh Joshi, RSD, IGCAR for their help during the experiments and analysis.
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