A novel reductive alkali roasting of chromite ores for carcinogen-free Cr<sup>6+</sup>-ion extraction of chromium oxide (Cr<inf>2</inf>O<inf>3</inf>) ¿ A clean route to chromium product manufacturing!

Journal ar
Journal of Hazardous Materials
  • Volumen: 403
  • Fecha: 05 febrero 2021
  • ISSN: 18733336 03043894
  • Tipo de fuente: Revista
  • DOI: 10.1016/j.jhazmat.2020.123589
  • Tipo de documento: Artículo
  • Editorial: Elsevier B.V.
© 2020 Elsevier B.V.A novel reduction reaction for extracting Cr2O3 from chromite ores is demonstrated by excluding the formation of carcinogenic chromate (Cr6+) intermediates. We have investigated in detail the underpinning high-temperature reduction reaction: FeCr2O4+Na2CO3+2[C]=[Fe]+Na2Cr2O4+3CO(g), which defines the process chemistry for the formation of sodium chromite (Na2CrO2) as an intermediate product for Cr2O3 extraction. After high-temperature reduction, the magnetic separation, aqueous and acid leaching of reaction products yielded 81 wt% and 70 wt% pure Cr2O3 from low (~4 wt%) and high (>8 wt%) silica-containing chromite ores, respectively. The process diagram explains the extraction of Cr2O3, Fe-Cr alloy, Al2O3, and MgO-Al2O3-silicate, reuse of CO2 for Na2CO3 recovery, and energy generation from CO combustion for demonstrating Cr6+-free extraction of metallic and mineral values from chromite ores. The process chemistry demonstrates the extraction of 75¿80 % pure Cr2O3 from NaCrO2 by leaching with 0.05¿0.5 M dilute H2SO4 in controlled pH conditions. The detailed chemical analysis of leachates after Cr2O3 extraction shows that the acid leachates with residual concentrations of ~150 ppm Cr3+-ions can be recycled in situ for reusing water, for eliminating the risk of Cr6+-ion formation from atmospheric oxidation. The novel extraction route may be able to displace the current oxidative process for chromite ore processing by retrofitting.

Palabras clave del autor

    Palabras clave indexadas

      Detalles de financiación