Kinetische Untersuchungen zur Laugung von Erzen und Konzentraten angereichert mit Seltenen Erden


Kinetische Untersuchungen zur Laugung von Erzen und Konzentraten angereichert mit Seltenen Erden

Erben, J.; Balinski, A.

Rare earth elements are an essential part of high-tech devices in the entertainment, automotive and aerospace industry, which is why there is a growing demand for these elements. However, benefication and processing of rare earths is difficult. Thus, there are several studies concerning with the reaction chemistry and the finding of more economical extraction methods for rare earth metals. This study concerns with the liberation and reaction chemistry of a silicate rare earth ore, from the mine Strange Lake, in Canada. The chemical kinetics are focused in order to investigate the chemical behavior of rare earth elements. Therefore, a kinetic model, suggested frequently in literature, is applied and the study’s objective is the examination of the practicality of this model for this specific material. The concentrate was therefore leached for four hours at elevated temperature (50 to 90°C) and with concentrated sulfuric acid (1M to 3M H2SO4). The influence of temperature, acid concentration and pulp density was studied.
It was found that the recovery of the measured rare earth elements could be optimized from around 50 to about 80 Wt% by a temperature increase of 40°C. Hence, it is considered that leaching of rare earth elements is an endothermic process. The highest recovery could be determined for europium and yttrium with around 80 Wt% (90°C, 3M H2SO4). Besides that, a raise in sulfuric acid concentration of 2 mol/l resulted in an increase of recovery of 20 Wt% for the totality of the measured rare earth elements. Aside from agitation and particle size, also the pulp density has important impacts on the leaching process concerning retention time and throughput. In this study pulp density was raised from 5 to 25% (w/v), thereby enhancing the recovery from about 80 Wt% to about 95 Wt%. The kinetic mechanisms are described by the shrinking core model. The rate of reaction versus time and the Arrhenius plots were determined for the measured elements. It was observed that leaching of rare earth elements is controlled by transport mechanisms, which occur by inner diffusion through a porous ash layer. The activation energy EA for the measured rare earth species was respectively determined and it was found that most of these EA values are in the range of 25 kJ/mol to 50 kJ/mol. This order of magnitude allows the assumption, that the rate limiting step of leaching rare earths is inner diffusion.

Keywords: Rare Earth Elements; Leaching

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    Helmholtz-Institut Freiberg für Ressourcentechnologie, 2018
    Mentor: Balinski, Adam; Scharf, Chrisitane
    53 Seiten

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Publ.-Id: 27342