Enhanced extraction of rare earth elements by novel tuned diglycolamides

International audienceRare earth elements (REE) are essential for our modern economy, in relation to the development of new energy and communication technologies, however their recycling from electronic waste and end-of-life products (such as permanent NdFeB magnets, Ni-MH batteries, etc.) is still not sufficiently developped.1 Although substitution of these materials by less critical ones is growing faster and faster especially in Japan efficient and eco-designed recycling processes will be of great importance in a near middle term. Depending on their technoeconomics efficiency and environmental footprint, hydrometallurgical processes enabling the recovery of separated elements could be of particular interest.Typically these processes include a first pretreatment (crushing, milling, sieving,) followed by an acidic leaching step (with possibly selective precipitation substeps) and a solvent extraction step (SX) in order to separate and purify the REE.2 Recently, diglycolamides (DGAs) appeared as a very interesting group of extractants for the recovery of trivalent lanthanides from nitric acid solutions, particularly in the presence of metal ions commonly found in waste products.3 The TODGA extractant (N,N,N',N'-tetraoctyl diglycolamide) was successfully used for designing a full REE recycling SX process from used permanent magnets.4 Nevertheless its performances have not yet been validated against upscaling tests.Most works concerning the group of DGAs dealt with symmetrical extractants exhibiting different separation efficiencies for REE in nitric acid media. The chain length modification on one side of the DGA (asymmetrical DGAs) can lead to important variation in selectivity during the Eu/Am separation.5 Recently, new dissymmetrical DGAs with very short chains were reported for REE extraction, such as for instance MODGA (N,N'-dimethyl-N,N'dioctyl-diglycolamide),6 however their solubility in industrial diluents is rather limited.The present work describes the organic synthesis of several novel DGAs and their solvent extraction behaviour towards REE in several aqueous acid media which could increase the industrial interest of such SX process. These new ligands displayed a remarkable improvement of REE extraction efficiency compared to reference TODGA in acid media, while presenting a good solubility in industrial aliphatic diluents. Furthermore, the separation factors of REE towards major impurities such as Fe3+ are substantially improved. Figure Distribution ratio of a novel DGA compared to TODGA in an acid solutionNevertheless it will be of primary importance to check whether the REE can be quantitatively de-extracted from the organic phase without any impurity. These promising results will also contribute to the design of an optimized SX process for the separation of REE

A combined process for the selective rare earth recovery and separation from used permanent magnets

International audienceRare earth elements (REE) have become essential for our modern economy, in relation to the development of new energy and communication technologies. Albeit being considered today as the most critical raw materials group with the highest supply risk, the recycling of REE from electronic waste and end-of-life products (permanent NdFeB magnets, Ni-MH batteries etc.) is almost inexistent.[1] Therefore, a large research effort is needed for over-coming the current scientific and technological barriers and improving the recycling efficiency. Innovative, eco-designed processes have to be developed, which require extensive RandD effort from basic research to technological developments.The CEA has gained a world-class expertise in the field of separation processes by hydrometallurgy and pyrometallurgy, several solvent extraction processes being developed and industrially implemented for the nuclear fuel cycle. In this communication, an efficient combined hydro- and pyrometallurgical process aimed at REE recovery and separation from used NdFeB permanent magnets will be presented.[2] The process integrates the mechanical and physico-chemical treatment of NdFeB magnets, followed by a liquid-liquid solvent extraction step for the recovery and intra-separation of REE using a selective extractant with excellent affinity for heavy REE which are today the most expensive REE. Experimental liquid-liquid extraction and modeling data allowing the recovery of a 99.9 per cent pure Dysprosium solution will be discussed in this paper. A subsequent pyrometallurgical treatment via molten chloride salt electrolysis allowed the isolation of pure Dy metal with 80 per cent faradic yield. This is one of the first examples of an effective, closed-loop REE recovery and separation process, starting from magnet scrap down to individual pure REE as metals, which paves the way for future developments in the field.Following this successful demonstration, a new project aimed at the separation of rare earths and nickel from Ni-MH batteries is currently being developed in our department, and preliminary results concerning the evaluation of new molecules for liquid-liquid extraction will be presented in this paper

A combined process for the selective rare earth recovery and separation from used permanent magnets

International audienceRare earth elements (REE) have become essential for our modern economy, in relation to the development of new energy and communication technologies. Albeit being considered today as the most critical raw materials group with the highest supply risk, the recycling of REE from electronic waste and end-of-life products (permanent NdFeB magnets, Ni-MH batteries etc.) is almost inexistent.[1] Therefore, a large research effort is needed for over-coming the current scientific and technological barriers and improving the recycling efficiency. Innovative, eco-designed processes have to be developed, which require extensive RandD effort from basic research to technological developments.The CEA has gained a world-class expertise in the field of separation processes by hydrometallurgy and pyrometallurgy, several solvent extraction processes being developed and industrially implemented for the nuclear fuel cycle. In this communication, an efficient combined hydro- and pyrometallurgical process aimed at REE recovery and separation from used NdFeB permanent magnets will be presented.[2] The process integrates the mechanical and physico-chemical treatment of NdFeB magnets, followed by a liquid-liquid solvent extraction step for the recovery and intra-separation of REE using a selective extractant with excellent affinity for heavy REE which are today the most expensive REE. Experimental liquid-liquid extraction and modeling data allowing the recovery of a 99.9 per cent pure Dysprosium solution will be discussed in this paper. A subsequent pyrometallurgical treatment via molten chloride salt electrolysis allowed the isolation of pure Dy metal with 80 per cent faradic yield. This is one of the first examples of an effective, closed-loop REE recovery and separation process, starting from magnet scrap down to individual pure REE as metals, which paves the way for future developments in the field.Following this successful demonstration, a new project aimed at the separation of rare earths and nickel from Ni-MH batteries is currently being developed in our department, and preliminary results concerning the evaluation of new molecules for liquid-liquid extraction will be presented in this paper

Phosphine-Coordinated Pure-Gold Clusters: Diverse Geometrical Structures and Unique Optical Properties/Responses

Synthetic techniques, geometrical structures, and electronic absorption spectra of phosphine-coordinated pure-gold molecular clusters (PGCs) accumulated over 40 years are comprehensively collected especially for those with unambiguous X-ray crystal structures available. Inspection of the electronic absorption spectra from geometrical aspects reveals that their optical properties are highly dependent on the cluster geometries rather than the nuclearity. Recent examples of unusual clusters that show unique color/photoluminescence properties and their utilization for stimuli-responsive modules are also presented

Wafer-sized multifunctional polyimine-based two-dimensional conjugated polymers with high mechanical stiffness

One of the key challenges in two-dimensional (2D) materials is to go beyond graphene, a prototype 2D polymer (2DP), and to synthesize its organic analogues with structural control at the atomic- or molecular-level. Here we show the successful preparation of porphyrin-containing monolayer and multilayer 2DPs through Schiff-base polycondensation reaction at an air–water and liquid–liquid interface, respectively. Both the monolayer and multilayer 2DPs have crystalline structures as indicated by selected area electron diffraction. The monolayer 2DP has a thickness of∼0.7 nm with a lateral size of 4-inch wafer, and it has a Young's modulus of 267±30 GPa. Notably, the monolayer 2DP functions as an active semiconducting layer in a thin film transistor, while the multilayer 2DP from cobalt-porphyrin monomer efficiently catalyses hydrogen generation from water. This work presents an advance in the synthesis of novel 2D materials for electronics and energy-related applications