Abstract
The behavior of oxidized and non-oxidized multiwalled carbon nanotubes (MWCNTs) in the adsorption of lanthanum(III) from aqueous solutions is described. Metal uptake is studied as a function of several variables such as the stirring speed of the system, pH of the aqueous solution and metal and nanomaterial concentrations. The experimental results are fitted to various kinetic and isotherm models, the rate law being fitted to the film diffusion and particle diffusion models, when the non-oxidized and the oxidized nanomaterials are used to remove lanthanum from the solution, respectively. Sulfuric acid solutions seem to be appropriate to recover the metal from La-loaded nanomaterials.
Highlights
Since the 1960s, the applications of rare earths in daily life have increased until they have come to be elements which are critical in industrial developments and modern technologies, in this context, these elements are designated as technology-critical elements [1]
Since the global demand of Rare earths (REs) is increasing and it is expected to experience a notable growth over time [3], the present investigation concerns the adsorption of lanthanum(III) from aqueous solutions with two commercially available adsorbents, in the form of non-oxidized and oxidized multiwalled carbon nanotubes
From the experimental data obtained from this investigation, it can be deduced that both oxidized and non-oxidized multiwalled carbon nanotubes, commercially available materials, can be used to recover lanthanum from aqueous solutions
Summary
Since the 1960s, the applications of rare earths in daily life have increased until they have come to be elements which are critical in industrial developments and modern technologies, in this context, these elements are designated as technology-critical elements [1]. The REs importance are increasing due to their use in green carbon technologies, such as rechargeable car batteries, electronic devices, permanent magnets, wind turbines and so on [4] They are considered by the European Commission as the most critical raw materials group with the highest supply risk [5]. In spite of their great applications and the large amounts of RE-waste, their recycling is still poorly developed, i.e., in the EU only 6% of the heavy REs and 7% of the light REs are recovered [6,7] Among these elements, lanthanum is used in fields such as ceramics, metal alloys, batteries, glass, semiconductors, catalysts, magnetic materials and rechargeable lithium-nickel batteries [8,9]. Since the global demand of REs is increasing and it is expected to experience a notable growth over time [3], the present investigation concerns the adsorption of lanthanum(III) from aqueous solutions with two commercially available adsorbents, in the form of non-oxidized and oxidized (carboxylic groups) multiwalled carbon nanotubes
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