Vanadium in phyllosilicate ores: Occurrence, crystal chemistry, and leaching behavior

Maxwell Drexler, Isabel Barton, Pierre Marie Zanetta

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

This article examines the nanoscale occurrence patterns of vanadium in phyllosilicates and correlates them with amenability to leaching. A large fraction of the global vanadium resource is hosted in phyllosilicate ores such as roscoelite and V-bearing chlorites, clays, and micas. Recovery of V from these minerals in acid leaching is typically low but varies widely for unclear reasons. Transmission electron microscopy (TEM) of V-illites, V-chlorites, and roscoelites in leach heads and tails from the La Sal mine (Colorado Plateau) shows that the observed variability in recoveries correlates with intercalations of nanoscale V oxide phases within the phyllosilicate lattice. These are present in some of the V-illites in this study, which displayed higher leach recovery than V-illites without the V oxides. In the latter, as well as in V-chlorites, the V occurs as crystallographic substitutions without oxide intercalations. Electron energy loss spectroscopy (EELS) measurements in the scanning transmission electron microscope (STEM) show that this crystallographic V is mixed-valence, averaging 3.3 in V-chlorite, 3.6 in roscoelite, and 3.8 in V-illite. Unlike the oxide intercalations, this crystallographic type of V corresponds to negligible leaching recoveries irrespective of V siting, oxidation state, or type of phyllosilicate. These results shed light on the causes of a central problem in geometallurgy, which is attempting quantitative predictions of process outcomes from geological inputs. These results show that what appears to be the same mineral (in this case V-illite) can yield wildly disparate leach recoveries depending on nanoscale metal occurrence factors. Similar under-recognized variation in other ore minerals, within or between sites, may explain much of the notorious variability in their leaching behavior.

Original languageEnglish (US)
Article number108205
JournalMinerals Engineering
Volume201
DOIs
StatePublished - Oct 2023

Keywords

  • Geometallurgy
  • Nanomineralogy
  • Silicate dissolution
  • V oxidation state
  • Vanadium in phyllosilicates
  • Vanadium leaching

ASJC Scopus subject areas

  • Control and Systems Engineering
  • General Chemistry
  • Geotechnical Engineering and Engineering Geology
  • Mechanical Engineering

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