According to surveys, the toxic residue of industrial chromium salts is mainly linked to sodium dichromate production. The preparation of one ton of sodium dichromate can generate ~2.5 tons of residue, in which the Cr (VI) content is ≥0.4%, present in the carcinogenic calcium chromate phase [ 18, 19 ].
Abstract. Sodium chromate is produced via the soda-ash roasting of chromite ore with sodium carbonate. After the reaction, nearly 15 pct of the chromium oxide remains …
The ore used in this study was S. African chromite ore of the following composition 48.8% Cr2O3, 31.3% Fe2O3, 7.03% MgO, 7.15% Al2O3, 3.45% SiO2 and 0.54% CaO. Sodium carbonate (Na2CO3) and activated charcoal of analytical grade were also employed in alkali reduction experiments. For the reduction experiments, the as-received mineral was …
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! | Semantic Scholar
A solid reduction process is described whereby chromite is reduced with the help of calcium chloride to produce ferrochrome alloy powders with high metal recovery. The process involves segregation reduction of chromite using graphite as the reductant and calcium chloride as the segregation catalyst. Experiments were performed in the …
The chromite ore and the salt mixture of sodium carbonate - sodium chromate were mixed in the stoichiometric ratios. In the sodium chromate - sodium carbonate mixture, the ratio of carbonate to chromate was varied between 0 and 80 % with an increment of 20 %. Pellets were prepared using a 2 g powder mixture.
A method of producing sodium chromate from chromite ore which involves mixing the ore with sodium carbonate and a refractory diluent, pelleting the mixture at a temperature of at least 36* C. using a pelleting liquid which may be water or water containing dissolved substances, drying and roasting the pellets under oxidizing conditions, then …
When roasting with sodium or potassium hydroxide, the main reaction taking place is shown in equation (2): 2 FeCr2O4 + 8 MOH + 7/2 O2(g) s 4 M2CrO4 + Fe2O3 + 4 …
The traditional chromate production process used in China presently consists of three procedures: roasting of chromite ore, water leaching, and multi-stage …
The phrase analysis of the sinter in lime-free roasting process shows that Na2O·Fe2O3, Na2O·Al2O3 and Na2O·SiO2 can be …
A method of producing sodium chromate from chromite ore which involves mixing the ore with sodium carbonate and a refractory diluent, pelleting the mixture at a temperature of at least...
Soda-ash roasting of the chromite mineral is commonly used worldwide for the production of watersoluble sodium chromate. The formation of sodium chromate …
Soda-ash roasting of the chromite mineral is commonly used worldwide for the production of watersoluble sodium chromate. The formation of sodium chromate during the soda-ash roasting...
Roasting in Metallurgy. In metallurgy, the operation of roasting, as a preliminary to chlorination, has for its object the expulsion of the sulphur, arsenic, antimony and other volatile substances existing in …
For reductive roasting of chromite ores with alkali, the presence of a reducing agent, e.g. carbon is necessary, which is in contrast with the oxidation process, shown in reaction 1. Under the reducing condition, the alkali complexes with chromium oxide in 3+-state and forms water-insoluble sodium chromite (Na 2 O∙Cr 2 O 3).
Several researchers have used sodium carbonate with chromite ore in the soda-ash roasting reaction. Temperatures used are above 1073 K in air. The …
Sodium chromate is produced commercially by roasting chromite ore with sodium carbonate, or with sodium carbonate and calcium oxide, and leaching to dissolve the sodium chromate. After treatment to remove …
In the process of roasting, chromite is mixed with sodium carbonate and a large amount of limestone and dolomite additives, and then calcined at 1200 °C in a rotary kiln. The utilization of reagents and energy in the calcination process is quite low.
The phrase analysis of the sinter in lime-free roasting process shows that Na2O·Fe2O3, Na2O·Al2O3 and Na2O·SiO2 can be formed in the first 20 min, but they decrease in contents and finally...
The soda-ash roasting of chromite ore processing residue for the reclamation of chromium - NASA/ADS Sodium chromate is produced via the soda-ash roasting of chromite ore with sodium carbonate. After the reaction, nearly 15 pct of the chromium oxide remains unreacted and ends up in the waste stream, for landfills.
Iron (II) chromite react with sodium carbonate and oxygen to produce sodium chromate, iron (III) oxide and carbon dioxide. This reaction takes place at a temperature of 1000-1200°C. Find another reaction Thermodynamic properties of substances The solubility of the substances Periodic table of elements Picture of reaction:
Chromite ores are industrially treated with sodium carbonate (above 1100 °C) however, to ensure that the extraction process is carried out at rela tively low temperatures (500-700 °C), sodium ...
Iron(II) chromite react with sodium carbonate and oxygen to produce sodium chromate, iron(III) oxide and carbon dioxide. This reaction takes place at a temperature of 1000-1200°C. Find another reaction. Thermodynamic properties of substances The solubility of the substances Periodic table of elements.
The existence of leachable Cr(Ⅵ) in chromite ore processing residue (COPR) makes it hazardous waste. Therefore, resourceful utilization of COPR is nec…
molten phase formed during alkali roasting of chromite ore with sodium carbonate [12]. The liquid phase mainly consists on the formation of an eutectic mixture at 928 K between Na2CO3 and Na2CrO4 with a 62.5 wt.% sodium chromate. It …
Four chromite samples (120–180 ± 0.01 g) were roasted with sodium carbonate in clay crucibles at about 1160 °C in air for 2 h. Iron in chromite roast reacts with sodium carbonate to produce NaFeO 2 + NaAlSiO 4 and other complex sodium-aluminium silicate according to the following reaction [ 1, 26 ]:
African chromite ore is processed for the extraction of chro- stoichiometric amount of sodium carbonate required for the mium as sodium chromate. The oxide constituents of South formation of sodium chromate. The mixture was roasted African chromite ore were determined by chemical analysis; isothermally in an alumina crucible in a temperature-con-
As explained above, the traditional process for treating chromite ores is based on alkali roasting with soda ash, lime and dolomite under an oxidizing atmosphere at 1200 °C, which yields water soluble sodium chromate. 9 The sodium chromate is acidified with sulphuric acid to make sodium dichromate, which is crystallized and sold or roasted ...
Sodium chromate is produced via the soda-ash roasting of chromite ore with sodium carbonate. After the reaction, nearly 15 pct of the chromium oxide remains unreacted and ends up in the waste stream, for landfills. In recent years, the concern over environmental pollution from hexavalent chromium (Cr6+) from the waste residue has become a major …
Sodium chromate is produced via the soda-ash roasting of chromite ore with sodium carbonate. After the reaction, nearly 15 pct of the chromium oxide remains unreacted and ends up in the waste stream, … Expand
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 (Na 2 CO 3 -Na 2 CrO 4 binary …
According to surveys, the toxic residue of industrial chromium salts is mainly linked to sodium dichromate production. The preparation of one ton of sodium dichromate can generate ~2.5 tons of …
As explained above, the traditional process for treating chromite ores is based on alkali roasting with soda ash, lime and dolomite under an oxidizing atmosphere at 1200 °C, which yields water soluble …
ilmenite and chromite, respectively. As a consequence, the amount of roasting of ilmenite mineral concentrates and chromite ores, using sodi- waste generated and the energy required to treat the mineral feedstock um and potassium hydroxides. The thermodynamics of alkali roasting
A method of producing sodium chromate from chromite ore which involves mixing the ore with sodium carbonate and a refractory diluent, pelleting the mixture at a temperature of at least 36° C. using a pelleting liquid which may be water or water containing dissolved substances, drying and roasting the pellets under oxidizing conditions, then …
The essence of the green process is that traditional oxidation roasting of chromite ore with sodium carbonate at 1200° C is replaced by continuous liquid-phase oxidation of chromite ore in the submolten salt …
In this study, the roasting of Tunga Kaduka (Nigeria) chromite ore concentrate with sodium carbonate in the absence of airflow, while preventing interference of nitrogen and other atmospheric gases in the air yielded maximum chromium recovery of 97.06% at 900 °C within 2 h.
Chromium salt manufacturing is a typical extraction process, which takes chromite, sodium carbonate, and dolomite as raw materials. After high-temperature oxidation roasting, chromium oxides are transformed into water-soluble sodium chromate, and the remaining tailings become chromium slag after water leaching [ 4, 5 ].
A method of producing sodium chromate from chromite ore which involves mixing the ore with sodium carbonate and a refractory diluent, pelleting the mixture at a temperature of …
Exercise 10.3 - Percent yield:The raw material used as a source of chromium and chromium compounds is a chromium-iron ore called chromite. For example, sodium chromate, Na2CrO4, is made by roasting chromite with sodium carbonate, Na2CO3. (Roasting means heating in the presence of air or oxygen.)