Reclamation of reactive metal oxides from complex minerals using alkali roasting and leaching – an improved approach to process engineering

Sánchez-Segado, Sergio; Makanyire, Terence; Escudero‐Castejon, L.; Hara, Yotamu R. S.; Jha, Animesh

doi:10.1039/c4gc02360a

Cited by 57 publications

(34 citation statements)

References 46 publications

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“…During the early stages of reaction, extraction kinetics are slower for NaOH compared with KOH reaction as shown in Figure 20, which might be due to extensive fracture of particles caused by potassium ions. The fractured surface area is larger in K + ions than with Na + ions, [38]. Eventually, the two extraction curves converge and the final chromium extraction is quite similar for both the hydroxides, yielding slightly above 95% extraction efficiency at 1000 o C for 2 hours, respectively.…”

Section: Roasting Time Effect On Chromium Extractionmentioning

confidence: 93%

“…Chromium is present in complex oxide minerals, occasionally combined with iron oxides and other transition metals oxides such as manganese, titanium, vanadium, niobium and tantalum [38]. Chromite ore belongs to the spinel group with the general chemical formula of XY 2 O 4 , where X and Y represent divalent and trivalent metal ions, respectively.…”

Section: Characterisation Of Chromite Orementioning

confidence: 99%

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Comparative study of alkali roasting and leaching of chromite ores and titaniferous minerals

et al. 2016

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Extraction of titanium and chromium oxides may be achieved via roasting the respective minerals with alkali at high temperatures, followed by water and organic acid leaching. In this study, sodium and potassium hydroxides are used as alkali for roasting of chromite ores and ilmenite mineral concentrates. The thermodynamic analysis of the roasting process is discussed in terms of designing the process. Samples of chromite and titaniferous minerals were roasted with NaOH and KOH in a temperature range of 400˚C -1000˚C in an oxidizing atmosphere. The roasted chromite and ilmenite samples were further processed in order to extract water-soluble Na 2 CrO 4 from the reacted chromite and purify titanium dioxide from titaniferous minerals, respectively. The TiO 2 purity obtained after roasting at 400 o C with NaOH and double leaching was 49.2 wt.% , whereas when using KOH the purity was 54.5 wt.%. The highest TiO 2 purity obtained after roasting at 1000 o C for 2 hours and double leaching with water and organic acids was 84 wt.%. At low temperature (400 o C) the recovery of chromium was higher for chromite roasted with KOH than for chromite roasted with NaOH. However, at high temperatures (700 o C and 1000 o C) chromium recoveries were similar when roasting with both hydroxides. Around 95% chromium extraction yield was achieved when chromite was roasted with sodium and potassium hydroxides at 1000 o C for 2 hours and water leached.

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Section: Roasting Time Effect On Chromium Extractionmentioning

confidence: 93%

Section: Characterisation Of Chromite Orementioning

confidence: 99%

Comparative study of alkali roasting and leaching of chromite ores and titaniferous minerals

et al. 2016

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“…Sodium ferrite undergoes the hydrolysis as described in equation (4) to form Fe2O3, which is in agreement with the Eh-pH diagram presented in figure 5b. Hematite precipitates as Fe(OH)3 according to reaction (5), but heating of the residues converted this phase into Fe2O3 as observed in the XRPD patterns.…”

Section: Effect Of Roasting On Phases Formedmentioning

confidence: 97%

“…The application of alkali roasting in oxidative conditions dates back to the days of Le Chatelier in the 19 th century, where he initially used this method for the treatment of bauxite and chromite ores [4]. More recently, the alkali roasting technique has been employed for the physicochemical separation of reactive metal oxides from complex minerals [5]. Foley and Mackinnon [6], reported the formation of Na/K-Fe-Ti-O and Fe2O3 oxides after the alkali roasting of ilmenite with potassium and sodium carbonates at 860 o C in air atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Molten Salt Phase Formation during Alkali Roasting of Titaniferous Minerals with Sodium and Potassium Hydroxide

Parirenyatwa¹,

Escudero‐Castejon²,

Sánchez-Segado³

et al. 2016

Journal for Manufacturing Science and Production

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“…This discovery formed the basis for the industrial process which is still practiced today. The application of the alkali roasting process to the extraction of different metal oxides, such as Ti, Al or V, from complex minerals has also been investigated with satisfactory results [3][4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Formation of Chromium-Containing Molten Salt Phase during Roasting of Chromite Ore with Sodium and Potassium Hydroxides

Escudero‐Castejon

Sánchez-Segado

Parirenyatwa

et al. 2016

Journal for Manufacturing Science and Production

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Chromium has a wide range of applications including metals and alloys manufacturing, pigments, corrosion resistance coatings and leather tanning. The production of chromium chemicals is based on the oxidative alkali roasting of chromite ores, which leads to the formation of water-soluble alkali chromates. Previous investigations reported that when chromite is roasted with soda-ash, a molten salt containing chromium, which is mainly composed of sodium carbonate and sodium chromate (Na2CO3-Na2CrO4 binary mixture), forms under typical roasting conditions. The physical properties of the liquid phase, which are dependent on the temperature, charge and gangue compositions, play an important role on the oxidation reaction and may limit the chromate recovery by hindering the oxygen transport to the reaction interface.This investigation focuses on the alkali roasting of chromite ore at 1000 o C using NaOH and KOH, followed by water leaching. The influence of the alkali ratio on the chromium extraction yield is analysed, and the results obtained with both hydroxides are compared. Sample characterisation and thermodynamic analysis, including phase diagrams, equilibrium calculations and computation of liquidus curves, are combined with the purpose of studying the formation of the molten salt phase under different roasting conditions and its effect on the final chromium recovery.

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Reclamation of reactive metal oxides from complex minerals using alkali roasting and leaching – an improved approach to process engineering

Abstract: This review highlights the alkali roasting of aluminium, chromium and titanium minerals as an alternative to mitigate the environmental pressure associated with their mineral processing.

Cited by 57 publications

References 46 publications

Comparative study of alkali roasting and leaching of chromite ores and titaniferous minerals

Comparative study of alkali roasting and leaching of chromite ores and titaniferous minerals

Investigation of Molten Salt Phase Formation during Alkali Roasting of Titaniferous Minerals with Sodium and Potassium Hydroxide

Formation of Chromium-Containing Molten Salt Phase during Roasting of Chromite Ore with Sodium and Potassium Hydroxides

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