The recovery of critical elements in recycling processes of complex high-tech products is often limited when applying only mechanical separation methods. A possible route is the pyrometallurgical processing that allows transferring of important critical elements into an alloy melt. Chemical rather ignoble elements will report in slag or dust. Valuable ignoble elements such as lithium should be recovered out of that material stream. A novel approach to accomplish this is enrichment in engineered artificial minerals (EnAM). An application with a high potential for resource efficient solutions is the pyrometallurgical processing of Li ion batteries. Starting from comparatively simple slag compositions such as the Li-Al-Si-Ca-O system, the next level of complexity is reached when adding Mg, derived from slag builders or other sources. Every additional component will change the distribution of Li between the compounds generated in the slag. Investigations with powder X-Ray diffraction (PXRD) and electron probe microanalysis (EPMA) of solidified melt of the five-compound system Li2O-MgO-Al2O3- SiO2-CaO reveal that Li can occur in various compounds from beginning to the end of the crystallization. Among these compounds are Li1−x(Al1−xSix)O2, Li1−xMgy(Al)(Al3/2y+xSi2−x−3/2y)O6, solid solutions of Mg1−(3/2y)Al2+yO4/LiAl5O8 and Ca-alumosilicate (melilite). There are indications of segregation processes of Al-rich and Si(Ca)-rich melts. The experimental results were compared with solidification curves via thermodynamic calculations of the systems MgO-Al2O3 and Li2O-SiO2-Al2O3.

Lithium aluminum oxide has previously been identified to be a suitable compound to recover lithium (Li) from Li-ion battery recycling slags. Its formation is hampered in the presence of high concentrations of manganese (9 wt.% MnO2). In this study, mock-up slags of the system Li2O-CaO-SiO2-Al2O3-MgO-MnOx with up to 17 mol% MnO2-content were prepared. The manganese (Mn)-bearing phases were characterized with inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), electron probe microanalysis (EPMA), and X-ray absorption near edge structure analysis (XANES). The XRD results confirm the decrease of LiAlO2 phases from Mn-poor slags (7 mol% MnO2) to Mn-rich slags (17 mol% MnO2). The Mn-rich grains are predominantly present as idiomorphic and relatively large (>50 µm) crystals. XRD, EPMA and XANES suggest that manganese is present in the form of a spinel solid solution. The absence of light elements besides Li and O allowed to estimate the Li content in the Mn-rich grain, and to determine a generic stoichiometry of the spinel solid solution, i.e., (Li(2x)Mn2+(1−x))1+x(Al(2−z),Mn3+z)O4. The coefficients x and z were determined at several locations of the grain. It is shown that the aluminum concentration decreases, while the manganese concentration increases from the start (x: 0.27; z: 0.54) to the end (x: 0.34; z: 1.55) of the crystallization.

The affinity of Nd and Dy to phosphate containing mineral phases was investigated in this study in an Al 2 O 3 -CaO-MgO-P 2 O 5 -SiO 2 slag system. The slags originate from pyrometallurgical recycling of NdFeB magnets. Without addition of phosphate, the distribution of Nd and Dy is more or less arbitrary in the silicate matrix. Addition of phosphate leads to the formation of a silico-phosphate in an early stage of the crystallization process, which scavenges the majority of Nd and Dy. This is due to the strong affinity of these elements to phosphate structures. This phenomenon could be used to produce a rare earth element concentrate by classical mineral beneficiation.

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Rare earth-bearing gypsum tailings from the fertilizer industry are a potential source for an economically viable and sustainable production of rare earth elements. Large quantities are generated inter alia in Catalão, Brazil, as a by-product in a fertilizer production plant. Hitherto, the gypsum has been used as soil conditioner in agriculture or was dumped. The cooperative project, “Catalão Monazite: Economical exploitation of rare earth elements from monazite-bearing secondary raw materials,” intends to extract rare earth elements from these gypsum tailings. In this paper, a chemical process route to obtain a mixed rare earth carbonate from a monazite concentrate, was investigated. The results of the digestion, leaching, and precipitation experiments are presented and discussed herein. This includes reagent choice, process parameter optimization through experimental design, mineralogical characterization of the feed material and residues, purification of the leach solution, and precipitation of the rare earth as carbonates. The results showed that a rare earth extraction of about 90% without the mobilization of key impurities is possible during a sulfuric acid digestion with two heating stages and subsequent leaching with water. In the following purification step, the remaining impurities were precipitated with ammonium solution and the rare earth elements were successfully recovered as carbonates with a mixture of ammonium solution and ammonium bicarbonate.