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.

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

Recovery of rare earths from spent NdFeB magnets of wind turbine: Leaching and kinetic aspects.

Identification and recovery of rare-earth permanent magnets from waste electrical and electronic equipment

Separation efficiency of valuable and critical metals in WEEE mechanical treatments

Increasing recovery of critical raw materials (CRMs) from waste electrical and electronic equipment (WEEE) is a strategic priority to mitigate supply risks Today, CRM recovery rates are generally low, with increases requiring new recovery processes and interface optimisation with pre-processing to ensure appropriate material flows for efficient recovery are generated Here, results from an industrial trial to increase CRM recovery from WEEE are presented to inform development of pre-processing strategies which generate such material flows Au, Ag, Co, Ga, Mg, Nb, Ru, Pd, Ir, Y, Nd, Sb, Ta and W are identified with XRF in components of a range of WEEE samples including within individual printed circuit board (PCB) components CRM distribution in PCBs is mapped by visual inspection with reference to this data Cost-effective methods to disassemble WEEE; isolate CRM bearing components, and upgrade/concentrate CRMs are evaluated for industrial adoption A guillotine is found most suitable for LCD disassembly and separation of Au edge-contacts from PCBs, while cryocracking is best for isolation of internal components of digital media devices Thermal PCB disassembly with a solder bath for simultaneous SMD removal and subsequent sieving to sort SMDs thereby concentrating CRMs for recovery is a promising approach Microwave ashing of PCBs to concentrate CRMs is promising although off-gas treatment would be required Recovery potential of identified CRMs from material streams generated is found to be poor due to lack of suitable recovery infrastructure except for precious and platinum group metals in PCBs, but available pyrometallurgical recovery permanently dissipates other CRMs present

Towards Increased Recovery of Critical Raw Materials from WEEE– evaluation of CRMs at a component level and pre-processing methods for interface optimisation with recovery processes

Neodymium as the main feature of permanent magnets from hard disk drives (HDDs).

Eco-Friendly Electronics—A Comprehensive Review

Rare earth elements (REE) are among the Critical Raw Materials classified by the European Commission due to unbalanced supply and demand. Neodymium and praseodymium belong to the REE group that plays a significant role in NdFeB magnets, which are applied in green technology devices such as wind turbines and hybrid cars, besides hard disk drives. Recent data estimate that demand for these magnets will increase in the next years, causing insufficient metals availability. Recycling is an alternative to solve the problem, however there are many difficulties, mainly economics, since there is no profitable process developed yet. This study was mainly focused on the evaluation of neodymium and praseodymium leaching efficiency from post-consumer NdFeB magnets. Three factors (solid/liquid ratio, temperature, and time) were studied to evaluate the process. Statistical design of experiments and analysis of variance were performed in order to determine the main effects and interactions among the investigated factors for the leaching efficiency of neodymium and praseodymium in sulfuric acid 2 mol/L. The results showed that the highest leaching efficiencies for neodymium and praseodymium were 90.3 and 89.6%, respectively, and they were obtained at 1/20, 70 °C and 15 min. The ANOVA showed no significant factors for praseodymium. On the contrary, temperature and time were the significant main factors with positive effect, and the interaction between the three factors had a significant negative effect for neodymium.

Evaluation of Neodymium and Praseodymium Leaching Efficiency from Post-consumer NdFeB Magnets

Besides neodymium, the chemical composition of Neodymium–Iron–Boron (NdFeB) permanent magnets possibly contains other rare earth elements (REEs) such as praseodymium, dysprosium, and terbium. Among its applications, NdFeB magnets are essential for Hard Disk Drives (HDDs) in computers for data storage, in Mobile Phones (MPs), and in acoustic transducers. Because REEs were classified as critical raw materials by the European Union and the USA, the recycling of them has become an important strategy to diminish supply risk. Therefore, in this publication, the authors have uncovered the recycling potential estimate (RPE) of these four REEs from both end-of-life (EoL) secondary sources. The results were based on the time-step method, using in-use stock and sales data from Brazil over the last decade (2010–2019). Moreover, the NdFeB magnets were characterized by content and weight to a more accurate RPE. The EoL generation over the decade studied showed different scenarios for MPs and HDDs, mainly due to lifespan, social behavior regarding storage and usage, and resources. Under those circumstances, the RPE revealed 211.30 t of REEs that could return as raw materials in the last decade, of which approximately 80% is neodymium. Unfortunately, recycling rates are still too low, even more so in Brazil, which is problematic for the future REE supply chain and electronic waste figures.

Daniel Dotto München

Papers

Neodymium as the main feature of permanent magnets from hard disk drives (HDDs).

Eco-Friendly Electronics—A Comprehensive Review

Evaluation of Neodymium and Praseodymium Leaching Efficiency from Post-consumer NdFeB Magnets

Rare Earth Elements Recycling Potential Estimate Based on End-of-Life NdFeB Permanent Magnets from Mobile Phones and Hard Disk Drives in Brazil

Materials Used in Electronic Equipment and Manufacturing Perspectives