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Review
. 2019 May 29;9(6):814.
doi: 10.3390/nano9060814.

Recovery of Rare Earth Elements by Carbon-Based Nanomaterials-A Review

Celso E D Cardoso  1 , Joana C Almeida  2 , Cláudia B Lopes  3 , Tito Trindade  4 , Carlos Vale  5 , Eduarda Pereira  6
Affiliations
Review

Recovery of Rare Earth Elements by Carbon-Based Nanomaterials-A Review

Celso E D Cardoso et al. Nanomaterials (Basel). .

Abstract

Modern societies depend strongly on electronic and electric equipment (EEE) which has a side effect result on the large production of electronic wastes (e-waste). This has been regarded as a worldwide issue, because of its environmental impact-namely due to non-adequate treatment and storage limitations. In particular, EEE is dependent on the availability of rare earth elements (REEs), considered as the "vitamins" of modern industry, due to their crucial role in the development of new cutting-edge technologies. High demand and limited resources of REEs in Europe, combined with potential environmental problems, enforce the development of innovative low-cost techniques and materials to recover these elements from e-waste and wastewaters. In this context, sorption methods have shown advantages to pre-concentrate REEs from wastewaters and several studies have reported the use of diverse nanomaterials for these purposes, although mostly describing the sorption of REEs from synthetic and mono-elemental solutions at unrealistic metal concentrations. This review is a one-stop-reference by bringing together recent research works in the scope of the application of carbon nanomaterials for the recovery of REEs from water.

Keywords: E-waste; carbon nanostructures; rare earth elements; solid phase extraction; sorption.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Amount of global e-waste generated from 2014 to 2016 and values estimated for the following years (2017 to 2021) and (b) typology of e-waste produced in 2016. Adapted from Baldé et al. (2017) [18], with permission from ITU, 2017.
Figure 2
Figure 2
Periodic Table of the Chemical Elements showing in full blue squares the technology-critical elements (TCEs).
Figure 3
Figure 3
Criticality assessment of rare earth elements (REEs) and other elements in the medium term (2015–2025). It is represented in green the elements that are not critical, in yellow the near-critical elements and in red the critical elements.
Figure 4
Figure 4
Evolution of global REE demand and supply from 2016 to 2020. Data obtained from [24].
Figure 5
Figure 5
Current consumption of REEs in several applications, as well as the respective susceptibility to be replaced [22].
Figure 6
Figure 6
Steps of a general process of REEs recycling from e-waste.
Figure 7
Figure 7
Carbon allotropic forms: (a) Graphite, (b) graphene, (c) graphene oxide, (d) carbon nanotube, (e) fullerene, (f) carbon nanofibers, (g) carbon dot.
Figure 8
Figure 8
Representation of the general graphene oxide synthesis.
Figure 9
Figure 9
Classification of single-walled carbon nanotubes with distinct geometry and properties: Armchair (orange), zigzag (blue) and chiral (green).
Figure 10
Figure 10
Overview of surface functionalization methods of over carbon nanotubes (CNTs).
Figure 11
Figure 11
Different approaches to CNTs synthesis.
Figure 12
Figure 12
Types of functionalization methods of carbon nanotubes.
See this image and copyright information in PMC

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