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Journal ArticleDOI

Kinetics of roasting of chromium oxide with sodium nitrate flux

TL;DR: In this article, low temperature isothermal kinetic studies were performed on alkali roasting of Cr2O3 with progressive replacement of Na2CO3 in the reaction mixture by NaNO3 in a temperature range of 573 to 873 K. The influence of the nitrate on the course of the reactions was studied.
Abstract: Low temperature isothermal kinetic studies were performed on alkali roasting of Cr2O3 with progressive replacement of Na2CO3 in the reaction mixture by NaNO3 in the temperature range of 573 to 873 K. The influence of the nitrate on the course of the reactions was studied. Statistical design of experiments was employed to asses the relative influence of different process variables. Kinetic analysis of the experimental data shows that the reaction with NaNO3 follows a simple first-order model, and the activation energy of the reaction is 22.7 kJmol-1, as compared to 72 kJmol−1 for Na2CO3 flux.
Citations
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Journal ArticleDOI
TL;DR: In this article, a novel alkali-based oxidative roasting and aqueous leaching is explained in the context of the original work of Le Chatelier in 1850, which was unsuccessful in the industrialization of bauxite processing for alumina extraction.

47 citations

Journal ArticleDOI
TL;DR: Reduction of Cr(VI) by hydrazine in aqueous solutions saturated with potassium bicarbonate was studied and showed that the overall reaction was third-order, i.e. first-order with respect to hydrazin and second-orderWith respect to Cr( VI).

10 citations

Book ChapterDOI
31 Jan 2013
TL;DR: Chromium is mainly used for the production of stainless steel, in electroplating, as pigments and in leather and refractory industries as discussed by the authors, and the natural resource of chromium is the chromite ore, which is a spinel (Fe2+, Mg), and is often present with gangue minerals such silicates.
Abstract: Chromium is mainly used for the production of stainless steel, in electroplating, as pigments and in leather and refractory industries. The natural resource of chromium is the chromite ore, which is a spinel (Fe2+, Mg)[Cr,Al,Fe3+]2O4, and is often present with gangue minerals such silicates. Traditionally chromium chemical extraction has been carried out with alkali and CaO roasting, which led to major environmental issues due to CaCrO4/Na2CrO4 release.

5 citations

Journal ArticleDOI
TL;DR: The phase relationship of complex multi-component systems in the liquid-phase oxidization and separation process related with the chromate cleaner production is investigated theoretically and experimentally in this paper, where the phase diagram of main system FeCr2O4-KOH-O-2 of oxidization process and the relationship of its standard Gibbs free energy change with temperature are calculated.
Abstract: The phase relationships of the complex multi-component systems in the liquid-phase oxidization and separation process related with the chromate cleaner production are investigated theoretically and experimentally. The phase diagram of main system FeCr2O4-KOH-O-2 of oxidization process and the relationship of its standard Gibbs free energy change with temperature are calculated. A series of phase diagrams of the separation process at different temperatures, such as K(Na)OH-K(Na)(2)CrO4-H2O, KOH-KAlO2-H2O, K(Na)OH-K(Na)(2)CO3-H2O, K(Na)OH-K(Na)HCO3-H2O and K(Na)HCO3-K(Na)(2)CrO4-H2O have also been calculated. Some experiments are carried out to verify the calculated results. Our results showed that the sub-molten salt media are suitable for the oxidization and separation processes; FeCr2O4 can be oxidized across a wide range of temperature; K(Na)(2)CrO4 can be separated from K(Na)AlO2 system at appropriate temperature and proper concentration; the crystallization of carbonate is easier than that of K(Na)(2)CrO4.
References
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Book
01 Jan 1972

2,557 citations

Journal ArticleDOI
TL;DR: In this paper, the initial stages of reduction of Fe 2 O 3, leading to the formation of wustite, have been investigated using thermal analysis and the activation energy for isothermal reduction is an overall average for overlapping reactions.

24 citations

Book
01 Jan 1956

13 citations

Journal ArticleDOI
TL;DR: In this paper, the reduction of iron ore-coal pellets is compared with similar data for lump ore, and it is shown that, when ore and coal are mixed intimately, the reduction reactions are accelerated considerably.
Abstract: Kinetic data on the reduction of iron ore-coal pellets are compared with similar data for lump ore. It is shown that, when ore and coal are mixed intimately, the reduction reactions are accelerated considerably. Ore-coal pellets offer some additional advantages, as discussed in the text. It is shown that the kinetics of ore-coal reduction can be studied by using a pseudo kinetic parameter,f (fraction of reaction), defined as the instantaneous weight loss divided by the maximum possible weight loss. Plots off versust have been analysed to establish the kinetic equations and evaluate the kinetic parameters.

12 citations

Journal ArticleDOI
TL;DR: In this article, thermal decomposition studies of intimate mixtures of different molar ratios of potassium nitrate and chromium(III) oxide were made by employing thermogravimetry differential thermal analysis, chemical analysis, infrared spectral measurements and X-ray powder diffraction patterns.

11 citations