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Preparation of cobalt oxide

wallpapers Industry 2021-04-09
Cobalt oxide is a high-valent oxide of cobalt. The theoretical cobalt content is 71.06%, the oxygen content is 28.94%, and the density is 6.079/cm3. It is a black amorphous powder that will generate cobalt tetroxide (Co304) when heated. Cobalt oxide is an unstable and impossible to be a free compound. The commonly referred to as cobalt oxide actually still contains a certain amount of cobalt tetroxide. Co203 is stable only when it is in a hydrated state, and this hydrate will be dehydrated at 265°C to transform into the intermediate oxide cobalt tetroxide (Co304). Cobalt oxide can be reduced to cobalt tetroxide (Co304) by H2 at 125°C, reduced to CoO at 200°C, and reduced to metallic cobalt at 250°C. Cobalt oxide is insoluble in water, but soluble in acid to form the corresponding salt.

Cobalt metal method: Add metal cobalt to hydrochloric acid, add nitric acid appropriately according to the dissolution, and heat to 80 ℃ to react. Add hydrogen peroxide to the resulting cobalt chloride solution to purify iron. After precipitation and filtration, sodium carbonate is added for displacement reaction. Cobalt carbonate is produced, washed, centrifuged, and the net cobalt carbonate is burned and sieved to obtain cobalt oxide.
The process of the waste recovery method is basically the same as the aforementioned metal cobalt method, except that the removal of impurities with sodium carbonate and caustic soda for iron removal and sodium hypochlorite for nickel removal is added.
Co3O4 can be decomposed to produce CoO when the temperature is higher than 900℃. The metal cobalt powder is oxidized and roasted in air. In order to avoid the formation of Co3O4, increase the oxidation temperature above 900℃ to produce CoO. Alternatively, Co3O4 can be heated to 960°C in air to cause thermal decomposition to obtain CoO. After the reaction is completed, the temperature should be lowered and cooled under the condition of introducing inert gas.
Cobalt nitrate, cobalt carbonate or cobalt hydroxide is calcined in a vacuum or inert atmosphere to cause thermal decomposition, and the product of decomposition is CoO. After roasting the cobalt nitrate in an argon stream, it is heated in an argon stream containing wet HCl at 950°C for 10 h, and then heat-treated in a dry argon stream to obtain a deep dark red CoO. When cobalt hydroxide is used for decomposition, the heating temperature in vacuum or nitrogen flow is 200°C or the heating temperature in CO2 flow is 900°C, and the decomposition products are all CoO. Cobalt carbonate is easier to decompose than cobalt nitrate, and CoO can be obtained by decomposing cobalt carbonate below 900°C in a vacuum. In order to avoid the oxidation of the product during the cooling process to produce Co3O4, the cooling process should be carried out in an inert atmosphere.
Cobalt oxide is obtained by heating and decomposing cobalt carbonate or cobalt nitrate in an inert atmosphere.

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Tag: cobalt oxide