Leaching of Rare Earth Elements from NdFeB Magnets without Mechanical Pretreatment by Sulfuric (H2SO4) and Hydrochloric (HCl) Acids

A simplified approach for rare earth elements leaching from NdFeB (neodymium-iron-boron) magnets was investigated. The possibility of simplifying the magnet recycling process by excluding grinding, milling and oxidative roasting unit operations was studied. Attempts to skip the demagnetization step were also conducted by using whole, non-demagnetized magnets in the leaching process. The presented experiments were conducted to optimize the operating conditions with respect to the leaching agent and its concentration, leaching time, leaching temperature and the form of the feed material. The use of hydrochloric and sulfuric acids as the leaching agents allowed selective leaching of NdFeB magnets to be achieved while leaving nickel, which is covering the magnets, in a solid state. The application of higher leaching temperatures (40 and 60 °C for sulfuric acid and 40 °C for hydrochloric acid) allowed us to shorten the leaching times. When using broken demagnetized magnets as the feed material, the resulting rare earth ion concentrations in the obtained solutions were significantly higher compared to using whole, non-demagnetized magnets.

Research In The Field Of Intensive Oxidative Roasting Of Molybdenum Sludges

The article deals with the issues of oxidative roasting of sulfide molybdenum-containing materials. The main indicators of production, the recommended parameters for optimal oxidation of sulfides are given as a result of experiments. Also, theoretical foundations and practical data are presented, conclusions on the oxidation of molybdenum sulfide compounds are analyzed and summarized. As a result of numerous laboratory experiments, conclusions have been drawn for the production.

Fluidized Bed Pilot Furnace for Modibdenite Concentrate

In the Rare Metals Processing Shop (CPRM) at the Almalyk MMC JSC, the technology for processing molybdenite concentrate (MOC) provides for the use of kaolin in the granulation charge for oxidative roasting in a drum furnace. Its composition: 8-10% kaolin, the rest is molybdenite concentrate (MOC). Kaolin reduces the Mo content in the cinder. Replacing it with an organic binder eliminates this disadvantage (dilution in Mo), but leads to sticking of the granules in the drum furnace. To avoid sticking, it is proposed to replace it with a furnace of a different design. In addition to kaolin as a binder for MOK, ashless, water-soluble polymers are known. Replacing kaolin with them leads to an enrichment in molybdenum of an industrial product - cinder, by 4-5%. However, for the implementation of such a project, a based selection of the appropriate binder on the local raw material base, modes of its use and replacement of the roasting furnace: drum - with a fluidized (fluidized) bed furnace is required. A binder SK, an alternative to kaolin, and modes of firing granules from a new charge composition with MOC in a fluidized bed furnace have been developed. The design of the fluidized bed furnace has been developed. The introduction of these developments will provide a higher content of Mo in the cinder, better recovery of Mo and Re from it, as well as a lower sulfur content in the cinder, and less time spent on roasting: 1 hour instead of 7 hours in the existing rotary kiln.

OXIDATIVE ROASTING OF INDUSTRIAL SPENT CATALYSTS CO-Mo/Al2O3 HYDROPROCESSING WITH LIM

The oxidative roasting of industrial spent catalyst Co-Mo/Al2O3 for the hydrotreatment of diesel fuel with lime in an air atmosphere was studied. Using the data of DTA, TG and X-ray phase analysis, it was found that during roasting, the sulfur and carbon oxides forms CaSO4 and CaCO3, and Mo is converted to calcium molybdate. Using the filtering fixed bed of reagents, the kinetics of roasting was studied. It was found that in the temperature range of 550 – 600 °C with air, supply rate of 3 l/min the process ends in 38 - 44 min for ground and non-ground catalyst. The optimal parameters (lime consumption, temperature, and time of roasting) of the absorption of sulfur oxides during roasting were determined. The degree of sulfur and carbon oxides adsorption is 96 and 36%, respectively. Separation of roasting products using unmilled spent catalyst is proposed into a small fraction (contains a mixture of CaSO4, CaCO3 and CaO) and a coarse (consists of Al2O3, CaMoO4, CoO) fractions, and their separate processing. It has been shown that in the separate processing of roast fractions by a sodium carbonate solution, it is possible to separately obtain alumina (catalyst base) with cobalt oxide, a molybdenum-containing solution, and also a mixture of sulfate, carbonate and oxide calcium. The used method of roasting the spent hydrotreating catalyst with lime will allow hazardous waste of hazard class 3-4 to be disposed of without hazardous waste gas costs. It allows one to obtain, during further processing, molybdenum and cobalt compounds, as well as finely divided alumina.

Phase evolution and oxidation characteristics of the Nd–Fe–B and Ce–Fe–B magnet scrap powder during the roasting process

Many developed techniques for rare-earths’ (REs) recovery from magnet scraps are highly sensitive to the oxidative roasting process of scraps under high temperature. This study focused on phase evolution, microstructural changes and element distribution during the roasting of the widely used Nd–Fe–B and high-potential Ce–Fe–B scrap powders at 800°C. The sustained oxidation of Fe to Fe2O3 and the constant formation of composite RE oxides were the main reaction processes with increasing roasting cycles for the two scrap powders. The complete oxidation phases consisted of NdBO3, NdFeO3 and Fe2O3 for the Nd–Fe–B scrap powder, while the final products were NdBO3, GdFeO3 and Fe2O3 as well as individual CeO2 for the Ce–Fe–B scrap powder. An oxygen diffusion front was observed, forming a dark gray oxidized layer with almost the same thickness on the large particle surface. Additionally, a Fe2O3 layer covered the particle surface when the oxidation of the two scrap powders was complete. In oxidized Nd–Fe–B particles, the observed white regions corresponded to the oxidized intergranular Nd-rich phase as indicated by the almost same size and position before and after roasting. In Ce–Fe–B particles, the oxidized intergranular phase appeared to gather and grow, and a RE-rich layer appeared between the oxide/unoxidized layer. Conclusively, the iron-outward diffusion and the oxygen-inward diffusion were dominated by the oxidation of both Nd–Fe–B and Ce–Fe–B particles.