Critical minerals and rare-earth elements are essential to produce the next generation of equipment required for infrastructure to support green energy and electric vehicles.   Due to political tensions and the fast pace of change, there is considerable interest in finding new sources of these critical elements.  Economic sources of critical elements from industrial waste are a growing area of research.  We are characterizing the critical elements and mineralogical phases present in an industrial waste material to analyze its potential economic value and chemical properties. The starting primary ore and processing technique for this material are unknown, but we know that it was processed using a high-temperature plasma extraction technique.  The sample materials range from loose powder to chunks up to 2 cm with the larger chunks containing acicular grains that are metallic and easily friable. Fe, Cr, V, Ti, and P were measured in one of the metallic chunks using energy-dispersive X-ray spectroscopy. Reflected light microscopy showed two different compositions with variations in the amount of V and Ti. Our preliminary hypothesis is that these grains are phosphides, similar to Andreyivanovite and Florenskyite, which have been identified in meteorites. We will present characterization that includes multiple different techniques to characterize the chemical and mineralogical properties, with major mineralogical phases confirmed via X-ray diffraction. We will also discuss electron microprobe measurements to improve the chemical characterization of the two slightly different metallic phases while maintaining their spatial relationships, and diffraction patterns collected using electron backscatter diffraction to confirm the phosphide mineral structure. Critical and trace element measurements are confirmed by inductively coupled plasma-mass spectrometry. This characterization is expected to enable assessment of the economic potential of this material and its behavior in the environment and to provide suggestions for extraction methods during future studies.

Characterization of critical elements in a unique waste material from a plasma extraction technique

ACS Spring 2022

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