On the Adsorption of Cerium(III) Using Multiwalled Carbon Nanotubes

Francisco José Alguacil,Esther Escudero Baquero,Félix Antonio López,Olga Rodríguez Largo,Irene García-Díaz

doi:10.3390/met10081057

Francisco José Alguacil, Esther Escudero Baquero + Show 3 more

Open Access

https://doi.org/10.3390/met10081057

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Abstract

Commercially available oxidized (carboxylic groups) and nonoxidized multiwalled carbon nanotubes were studied as adsorbents of cerium(III) in batch operation mode. Several variables affecting the rare earth adsorption were investigated, including: the stirring speed applied to the system, the pH of the solution, and the metal concentration and carbon dosages. Although the removal of cerium from the solution is different and dependent upon the adsorbent type—(i) adsorption in nonoxidized multiwalled carbon nanotubes, (ii) cation exchange in the case of using oxidized multiwalled carbon nanotubes—the adsorption kinetics, the rate law and the isotherm models are the same for both adsorbents: pseudo-second order, film diffusion, and Langmuir Type-1, respectively. Cerium is desorbed from loaded adsorbents using acidic solutions.

Highlights

In comparison with other separation technologies, adsorption is one of the most used due to its operational characteristics and the possibility of its uses in dilute solutions and even nonclarified ones [1]
The adsorption of cerium(III) by multiwalled carbon nanotubes (MWCNTs) was represented by the general equilibrium: Ce3aq+ ↔ Ce3c +
These results show that Ce3+ adsorption is dependent on the initial metal concentration, since it supplies the major driving force for overcoming limitations of mass transfer between the multiwalled carbon nanotubes and the aqueous phases

Summary

Introduction

In comparison with other separation technologies, adsorption is one of the most used due to its operational characteristics and the possibility of its uses in dilute solutions and even nonclarified ones [1]. From a long time ago, adsorbents of various natures are used as a medium to remove both valuable and nonvaluable, including hazardous, metals or solutes from aqueous solutions [2,3]. Including these adsorbents, carbon nanotubes in various configurations are considered of a particular interest in this task [4,5,6,7]. With a global mine production of 2.1 × 105 ton in 2019 [10], the recovery of these rare earths is of particular interest due to their use in smart technologies and scarce availability of their resources (i.e., here in the European Union); the recycling of these metals became of interest.

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