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Synthetic method of cobalt hydroxide

wallpapers Tech 2021-04-09
Cobalt hydroxide is an inorganic substance with the chemical formula Co(OH)2. It is a rose-red monoclinic or hexagonal crystal. It is insoluble in water, slightly amphiphilic, hardly soluble in strong alkalis, but soluble in acid and ammonium salt solutions. . The density is about 3.6g/cm³. Melting point 1100-1200℃ is amphoteric hydroxide. It is mainly used as a colorant for glass and enamel, a raw material for preparing other cobalt compounds, and a drying agent for varnishes and paints. There are mainly the following four synthetic methods.
 
1. Synthesis method: various cobalt-containing waste materials are dissolved in nitric acid and hydrochloric acid, and the obtained cobalt chloride solution is purified with hydrogen peroxide to remove iron. If necessary, sodium carbonate or ammonia water is added to ensure complete purification. The purified cobalt chloride solution is added with sodium hydroxide to generate cobalt hydroxide, which is then washed and centrifuged to obtain a cobalt hydroxide product. The reaction equation is:
Co+2HCl=CoCl2+H2↑
CoCl2+2NaOH=Co(OH)2↓+2NaCl
 
2. Electrolysis method: It is obtained by electrolyzing table salt solution with cobalt as an anode.
 
3. The sulfate or nitrate of divalent cobalt reacts with alkali to form cobalt hydroxide. Dissolve 100 g of CoSO4·7H2O in water to form a nearly saturated solution, and add an alkali solution formed by dissolving 42 g of sodium hydroxide in 60 mL of water under heating and constant stirring. The precipitation reaction is carried out in a long beaker, which is conducive to the clarification of the mixed liquid. The precipitate formed at the beginning was blue, and when heated on a water bath, the precipitate quickly turned red. After clarification, decanted and washed with water several times, then filtered on a Buchner funnel and washed with water until the washing water was neutral. Finally, it is dried in a vacuum dryer equipped with concentrated H2SO4. Since cobalt hydroxide is slowly oxidized in air, the preparation operation is best carried out in an operation box protected by inert gas.
 
4. Use metal cobalt to react with dilute nitric acid at a temperature of 60~70℃. When the reaction basically stops, replenish the lost water and separate the excess metal. Add CoCO3 to make the solution close to neutral, and keep it at this temperature. 2~3h, filter to remove insoluble matter. Then slowly add 2% ammonia water under the condition of constant stirring and heating, so that the blue precipitate that is formed can turn into purple in time, and then into a pale rose red precipitate. After the reaction is completed and clarified, the solution is sucked out with a straw and washed with water until the aqueous solution is neutral, the precipitate is quickly filtered out, and dried in a vacuum dryer equipped with concentrated H2SO4 to obtain cobalt hydroxide

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