RU2183584C1 - Method of producing magnesium oxide - Google Patents

Abstract

FIELD: separation and purification of magnesium including magnesium enriched with isotopes. SUBSTANCE: method includes dissolving of magnesium-containing concentrate in hydrochloric acid and precipitation of magnesium with ammonium phosphate in ammonia medium in pressure of tartaric acid. Precipitate is separated, calcined and dissolved in hydrochloric acid. Magnesium is sorbed on cationite, washed with water for separation of phosphate ions, and magnesium is eluted with solution of hydrochloric acid. Basic magnesium carbonate is precipitated in purified solution by addition of ammonia solution saturated with ammonium carbonate in presence of ethyl alcohol. Basic magnesium carbonate is subjected to heat treatment in two stages: at 200-400 and 450-850 C. EFFECT: separated of 96.48% magnesium enriched with isotopes in the form of oxide of required degree of purification. 2 cl, 3 ex

Description

 The invention relates to the field of separation and purification of magnesium, including isotopically enriched obtained by electromagnetic separation.

 The task of isolating and purifying isotopically enriched magnesium is to maximize its extraction at all stages of chemical processing and obtain magnesium oxide containing a minimum amount of impurities.

A known method of producing magnesium oxide from a chloride solution (RF patent 2097326, IPC ⁶ C 01 F 5/08), including the deposition of magnesium with ammonia, followed by the precipitation of ammonium carbonate. The main disadvantage of this method is the impossibility of obtaining a pure product, since in solutions containing isotopically enriched magnesium, there is a significant amount of impurities, which are also precipitated by ammonia and ammonium carbonate. In addition, as shown by experimental data, the magnesium content in carbonate filters is ~ 70 mg / l, and such losses during the processing of isotopically enriched magnesium are unacceptable.

There is also known a method for producing magnesium oxide (RF patent 1643463, MPK ⁶ C 01 F 5/02, C 01 F 5/06), including treating the magnesium-containing concentrate with a mixture of hydrochloric and phosphoric acids, separating the impurities with ammonia and thermal decomposition of the purified solution. However, when using this method, impurities that are not precipitated by ammonia will remain in solution, therefore, the required degree of purification of magnesium oxide will not be achieved.

Closest to the claimed technical solution is a method for producing magnesium oxide (RF patent 2128626 IPC ⁶ C 01 F 5/02), comprising dissolving a magnesium-containing concentrate in sulfuric acid, separating the insoluble residue from the obtained sulfate solution by cooling the mixture to crystallization, followed by washing the crystallized mixtures of water; purification of the sulfate solution from impurities by precipitation in the form of hydroxides at pH 5 ... 7, separation of the precipitate, precipitation of magnesium hydroxide from the solution by treatment with an alkaline reagent at pH 10 ... 12, separation of the precipitate of the target product, its heat treatment in two stages: I - at 200 ... 450 ^o С, II - at 450 ... 850 ^o С and washing the calcined product with water.

The main disadvantage of this method is the inability to completely purify calcium by precipitation in the form of sulfate, since CaSO _{4 is} quite soluble even at low temperature. In addition, the purification of a magnesium-containing solution used in this method by precipitation of hydroxides of impurity elements and the release of magnesium in the form of hydroxide will lead to significant losses of magnesium. As shown by experimental data, the volumetric precipitate of hydroxide impurities, the total content of which exceeds the magnesium content by 3 ... 5 times, captures up to 10% of magnesium, and the loss of magnesium with filtrates during the precipitation of its hydroxide is ~ 3%.

 An object of the invention is to obtain pure magnesium oxide, including isotopically enriched, with minimal loss of magnesium at all stages of chemical processing.

The problem is achieved in that the magnesium-containing concentrate is dissolved in hydrochloric acid and magnesium is precipitated with ammonium phosphate in an ammonia medium in the presence of tartaric acid. The precipitate is separated, calcined and dissolved in hydrochloric acid. The solution is cleaned of the remaining impurities by the ion-exchange method, for which magnesium is sorbed on a cation exchange resin, the cation exchange resin is washed with water to separate phosphations and the magnesium is eluted with a hydrochloric acid solution to obtain purified carbonate when using ammonia saturated with ammonium carbonate as a reagent, including in the presence of ethyl alcohol. The precipitate of basic magnesium carbonate is separated and its heat treatment is carried out in two stages: at 200 ... 450 ^o С and 450 ... 850 ^o C.

 In the claimed technical solution, the proposed method for cleaning the solution contributes to the effective separation of impurities and obtaining a pure product, and the used method of precipitation of magnesium in the form of basic carbonate, especially in the presence of ethyl alcohol, allows it to be separated from the purified solution with almost no loss.

 The analysis of publicly available sources of information on the level of technology did not allow to identify a technical solution identical to the declared one, on the basis of which a conclusion is made about the unknownness of the latter, i.e. compliance presented in this application of the invention with the criterion of "novelty."

 A comparative analysis of the claimed solution with known technical solutions revealed that the presented set of distinctive features is unknown to a person skilled in the art and does not follow explicitly from the prior art, on the basis of which it is concluded that the invention presented in this application meets the criterion of "inventive step".

 The proposed method for producing magnesium oxide was implemented as follows.

 Example 1

18 g of a concentrate containing 1.4 g of magnesium and a significant amount of impurities, including copper, iron and calcium, were dissolved in HCl (1: 4) when heated, ammonia was added to pH 10 ... 11, disubstituted ammonium phosphate based 5.5 g per 1 g Mg with an excess of 10 g / l and tartaric acid at the rate of 7 g / l. The solution with the precipitate stood for 16 ... 18 hours. The precipitate was filtered off and the filtrate was analyzed for magnesium content. It was less than 0.1 mg / L. The precipitate was dissolved in HCl (1: 4) upon heating; magnesium was sorbed on KU-2 cation exchange resin. To separate the phosphate ions, the ion exchanger was washed with distilled water, and 94.5% pure magnesium was eluted with a 2N HCl solution; while the allowable calcium content in the eluate was controlled by the atomic adsorption method. NH ₄ OH (2: 1) saturated with ammonium carbonate was added to the resulting hydrochloric acid solution to a pH of 11 ... 12. The solution with the precipitate was thoroughly mixed and stood for 16 hours. The precipitate was filtered off and the filtrates were analyzed for magnesium content. Loss of magnesium during carbonate deposition was 1.63%. The heat treatment of the precipitate was carried out in two stages: first, for 3 hours at 200.. . 450 ^o C, then for 4 hours at 450 ... 850 ^o C. Magnesium oxide was analyzed for impurities. It amounted to 0.088%.

 Example 2

Magnesium oxide was obtained as in Example 1, but when precipitating basic magnesium carbonate after adding ammonia saturated with ammonium carbonate, ethanol was added to the resulting solution with thorough stirring at a ratio of V r-ra: V _cp equal to 1: 1.

 The magnesium content in the ammonia-phosphate filtrate was <0.1 mg / L; after ion-exchange purification, 94.4% of magnesium was isolated, the loss of magnesium during the precipitation of basic carbonate was 0.13%, and the amount of impurities in magnesium oxide was 0.076%.

 Example 3

Dissolution of the concentrate and purification of the solution from impurities was carried out as in Example 1, but magnesium from the purified solution was precipitated as hydroxide by adding KOH to pH 12. The obtained precipitate was heat treated and thoroughly washed with water, i.e., magnesium was extracted from the solution and MgO was prepared according to the RF patent 2128627 IPC ⁶ C 01 F 5/02, selected as the closest technical solution.

 The magnesium content in the ammonia-phosphate filtrate was 0.1 mg / L, 95.8% of magnesium was isolated after ion-exchange purification, losses during the precipitation of magnesium hydroxide were 5.8%, and the sum of impurities in magnesium oxide was 0.28%.

 The results showed that when using the known technical solution, compared with the proposed one, not only increased magnesium losses during its separation from the solution, but magnesium potassium was also contaminated, which led to an increase in the content of impurities in MgO.

 The proposed method for producing magnesium oxide was tested in the production of stable isotopes. It made it possible to isolate 96.48% of isotopically enriched magnesium in the form of oxide with a purification degree of 0.09%, which meets the requirements of TU951234-84, according to which the content of the amount of impurities should not exceed 0.1%.

 The proposed method allows the use of standard equipment, cheap and affordable reagents, does not require large energy consumption. The method is also suitable from an environmental point of view, since the formed ammonia filtrates are easily neutralized by acidic solutions used to regenerate ion-exchange columns.

Claims (2)

1. A method of producing magnesium oxide from a concentrate, including dissolving it in acid, precipitating magnesium from a purified solution by treatment with an alkaline reagent at pH 10-12, separating the precipitate and its heat treatment in two stages: at 200-450 and 450-850 ^o C, characterized the fact that the concentrate is dissolved in hydrochloric acid and magnesium ammonium phosphate is precipitated in ammonia in the presence of tartaric acid, the precipitate is separated, calcined, dissolved in hydrochloric acid, magnesium is sorbed from the solution on cation exchange resin, the cation exchange resin is washed with water to separate phosphate ions and Luiren magnesium hydrochloric acid solution to obtain a purified solution from which magnesium is precipitated as basic carbonate when used as alkaline reagent ammonia solution saturated with ammonium carbonate.  2. The method according to p. 1, characterized in that the deposition of basic ammonium carbonate is carried out in the presence of ethyl alcohol.