Modification of multi-walled carbon nanotubes with tannic acid for the adsorption of La, Tb and Lu ions

We have prepared an environmental friendly sorbent by modifying multi-walled carbon nanotubes with tannic acid. The adsorption of La (III), Tb (III) and Lu (III) as a function of contact time, initial solution pH, and quantity of adsorbent was studied using a batch technique. Both Langmuir and Freundlich isotherms can be used to describe the process. The major adsorption mechanisms were attributed to ion exchange and surface complexation. The kinetics of the adsorption follows a pseudo-second-order model. The thermodynamic functions Delta H, Delta G, and Delta S indicate that the sorption is endothermically driven. The adsorbed ions can be readily desorbed from the surface with 1 M hydrochloric acid.