The method of producing cerium oxide

 

(57) Abstract:

The invention relates to the production of cerium oxide used as the material for polishing glass or in the production of catalysts. The method involves the calcination of carbonates of rare earth metals with getting their oxides, processing of oxides acid to obtain a precipitate of cerium dioxide and a solution of rare-earth metals. Processing of rare-earth metal oxides is carried out in the presence of fluoride ion to the final content of the acid in the solution is 0.1-1 m at 70-100C, the concentration of fluoride ion is 2-12 g/l Method allows us to simplify the process and increase the degree of purity of the cerium oxide. 1 C.p. f-crystals, 1 table.

The invention relates to the field of hydrometallurgy of rare earth elements, in particular to a technology for pure cerium oxide.

A method of obtaining pure cerium oxide, comprising the oxidation of cerium solution of chlorides of rare-earth metals with chlorine and subsequent precipitation of Ce(+4) in the form of a hydroxide solution of caustic soda. During annealing get the precipitate of oxides containing 90 to 95% CeO2- (Rare earth metals. Mikhailichenko A. I., Mikhlin E. E., patrikeeva Y. B. M.: metallurgy, 1987, 146 S.).

A disadvantage of the known the clients.

The closest in technical essence to the achieved result is a method of producing cerium oxide, including oxidative calcination of carbonates REM containing cerium, with the subsequent dissolution of trivalent REE in dilute acids, separating and washing the precipitate, containing cerium. Thus obtained cerium oxide with a purity of up to 95% (Chemistry and technology of rare and scattered elements, including 2. Under.ed. K. A. Bolshakova. The textbook. manual for schools. Ed. 2nd, Rev. and ext. M., "Above. school". 1976, 113 - 114 C.).

The disadvantage of this method is the complexity and duration of the leaching trivalent REE, lack of purity cerium compounds.

Features a method of producing cerium oxide, allows to simplify the process and increase the degree of purity of the cerium oxide. For this purpose, the method including oxidative calcination of carbonates REM obtaining oxides, processing of oxides by acid solution to obtain a solution of trivalent rare-earth metals and precipitate cerium dioxide, separation of cerium dioxide from the solution and washing the precipitate, the processing of REE oxides is carried out in the presence of fluoride ions with a concentration of 2 to 12 g/l to excessive acidity of 0.1 - 1 M when heated to 70 volume the use of these reagents in the declared modes contributes to the selective dissolution of trivalent rare-earth metals and impurities of other metals while leaving CeO2in the sediment. While fluoride ions play a role of catalyst for the dissolution of the oxides of rare-earth metals, and low acidity and high temperature solution create conditions for hydrolysis of dissolved Ce(+4), culminating in the formation of hydrated oxide of cerium CeO2H2O.

Fluoride ions are used in the form of salts or hydrofluoric acid. The concentration of fluoride ions in the reaction system depends on the content of CeO2in the calcined oxides and is 2 to 5 g/l when the contents CeO2less than 85% of RSA and 5 to 12 g/l when the contents CeO2- 85-90%. The concentration of fluoride ions is a critical factor and should not be below the specified value. If the concentration is lower, the weight leaching trivalent REE is not achieved. Increasing the concentration of fluoride ions above the specified value leads to unnecessary costs fluorine-containing reagent, since it does not enhance the purity of cerium dioxide. Consumption of fluoride ions does not depend on the temperature of annealing oxides.

The use of acid in Coney trivalent rare-earth metals and impurities of other metals while leaving CeO2in the sediment. Excessive acidity more than 1M extraction of Ce(+4) in the sediment decreases sharply due to its solubility.

Lowering the temperature of the reaction system is less than 70oC leads to an increase in the duration of the process and insufficient leaching trivalent REE.

Hydrated ceria washed from the mother liquor, dried and calcined to CeO2. Calcined pure ceria is used as a material for polishing glass or in the production of catalysts.

Example.

One kilogram of total carbonates REM calcined in a furnace for 3 hours while blowing air. Get 0,55 - 0,56 kg of REE oxides. The oxide is treated with a solution of nitric acid in the presence of HF, creating a concentration of fluoride ion 2 - 12 g/L. the Treatment is carried out at a temperature of 70 - 100oC for 30 minutes. The final content of the acid solution of 0.1 - 1M. The resulting slurry is filtered, the precipitate CeO2washed successively with 0.3 M solution of ammonium nitrate and 0.15 M solution of ammonium carbonate. The washed precipitate is dried and calcined at a temperature of 950oC. receive CeO2with a basic substance content of more than 99%. The result is a single stage to obtain high-purity cerium, to use the REE oxides, calcined at various, including high temperature, which when using the known method is poorly soluble. The resulting product does not require modification which significantly reduces the consumption of reagents and labor.

1. The method of producing cerium oxide, comprising the calcination of carbonates of rare earth metals (REM) with getting their oxides, processing of REE oxides by acid solution to obtain a precipitate of cerium dioxide and a solution of rare-earth metals, characterized in that the processing of REE oxides is carried out in the presence of fluoride ion concentration of not less than 2 g/l to a final content of the acid in the solution is 0.1 - 1 M at 70 - 100oC.

2. The method according to p. 1, characterized in that the concentration of fluoride ion is 2 to 12 g/L.

 

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