A novel reductive alkali roasting of chromite ores for Carcinogen-free Cr6+-ion Extraction of chromium oxide (Cr2O3) – a clean route to chromium product manufacturing!
| Autor: | Sergio Sanchez-Segado, L. Escudero-Castejon, Animesh Jha, James E. Taylor |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
021110 strategic
defence & security studies Environmental Engineering Aqueous solution Chromate conversion coating Health Toxicology and Mutagenesis 0211 other engineering and technologies chemistry.chemical_element 02 engineering and technology 010501 environmental sciences 01 natural sciences Pollution Redox Chromium chemistry Environmental Chemistry Leaching (metallurgy) Chromite Waste Management and Disposal Mineral processing 0105 earth and related environmental sciences Nuclear chemistry Roasting |
| ISSN: | 0304-3894 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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