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!

JOURNAL OF HAZARDOUS MATERIALS

卷:403

Article

Escudero-Castejon, Lidia¹  Taylor, James¹  Sanchez-Segado, Sergio¹  Jha, Animesh¹ 

[1] Univ Leeds, Sch Chem & Proc Engn, Fac Engn, Woodhouse Lane, Leeds LS2 9JT, W Yorkshire, England

关键词: Chromium;    Chromite ore;    Reductive roasting;    Chromite reduction;    Iron-chromium alloy;    Chromium oxide chemicals;    Cr6+-ion analysis;    Cr6+-ion carcinogen;    Process design;   

DOI  :  10.1016/j.jhazmat.2020.123589

来源: Elsevier

【 摘 要 】

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 hightemperature reduction reaction: FeCr2O4+Na2CO3+2[Cl=[Fel+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 (similar to 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 similar to 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.

【 授权许可】

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