SU2165A1 - The method of separation of hafnium and zirconium - Google Patents

Description

The invention relates to a process for the separation of hafnium from zirconium, elements that are often found in ore together and possess similar chemical properties.

The proposed method is based on the fact that hafnium, having the highest atomic weight, has more clearly expressed basic properties than zirconium. Therefore, if alkalies are added to the solution of their salts in an amount insufficient for complete precipitation, then in the resulting precipitate, hydrates of hafnium oxides are contained relatively less, and zirconium in a larger percentage ratio than in the initial mixture.

In addition, a mixture of hydrates of oxides of hafnium and zirconium can be divided into fractions by fractional dissolution in an insufficient amount of acid - then the resulting solution will be relatively richer in hafnium than the initial mixture.

Both mentioned methods can be combined together.

When applying the proposed method, it is very important that the salt solution and the mixture of hydrates of oxides or oxides be free from impurities of other metals, such as titanium, niobium, tantalum, aluminum, iron, etc. If such metals are contained in a mixture of hafnium and zirconium, then This method is associated with great difficulties, since these metals also have different degrees of basicity. Therefore, it is recommended to first remove impurities of these metals, which can be produced by any known method, for example, according to a method adopted to remove such impurities from zircon compounds.

In the process, the insoluble mineral is converted into a mixture of soluble salts by fusion with potassium dichloride.

whereby zirconium and hafnium are converted to soluble double fluoride compounds. The ore can also be fused with sodium hydrogen sulphate, whereby zirconium and hydrate are converted to soluble sulphate 1.

Upon removal of other metals, either a base is added to the solution, for example, ammonia water, caustic soda, or a salt, which acts as a base in an aqueous solution, for example, sodium sulfate. These substances are added to the solution in such an amount that a fraction of the metals precipitates as a mixture of their hydrates with oxides. Hafnium, the oxide of which is more basic, is thus concentrated in solution, while the precipitate contains a relatively smaller amount of hafnium. The precipitate, the aqueous oxides, is separated by filtration and dissolved in acid, after which the base is again added to the solution. This treatment is repeated until the separation is completed to the desired degree.

On the other hand, the base or the appropriately reactive compound can be added to the mother liquor, causing a new partial precipitation of metals to occur. In this way, the content of hafnium in the mother solution can be gradually increased. Finally, from the last mother liquor, which contains almost no zirconium. It is possible to precipitate the aqueous oxide of hafnium by adding an excess of base or, by using hydrolysis, by treating with superheated steam. The oxide hydrate, when heated to the proper temperature, is converted into oxide, the reduction of which, for example, according to the method adopted for the reduction of zirconium oxide, produces metallic hafnium either in pure form or with a small admixture of zirconium.

If we start from a pure mixture of soluble salts of hafnium and zirconium, as it can be directly obtained from some minerals containing, for example, 5% hafnium, the latter can be precipitated in its pure form using twelve successive treatments with caustic soda, and it turned out that the fourth precipitate contains gafni approximately twice less than the initial solution, and the eighth - only about a quarter of the initial amount.

The same principle can be used differently: from a solution of a mixture of hafnium and zirconium salts, a mixture of hydrates of oxides is obtained either by precipitation from a solution of whole hafnium and zirconium by adding excess base, or by hydrolysis of salts by treatment with superheated steam. To the precipitate of hydrates obtained in this way with oxides, a certain amount of acid is added, which is insufficient to completely dissolve them. The resulting solution contains a relatively larger amount of hafnium than the initial mixture. Thus, adding to the mixture of aqueous oxides an amount of HC1 insufficient for complete dissolution, a solution of oxychloride containing relatively more hafnium is obtained than the initial mixture. The residue can be re-treated with acid to remove new amounts of hafnium from it. On the other hand, an excess base is again added to the solution to obtain a mixture of hydrates of zirconium and hafnium oxides, however, more rich in hafnium than the original mixture. This mixture is treated with acid, causing a new enrichment of the solution of hafnium and, by doing so further, the desired degree of concentration is obtained.

Finally, it is possible to combine both methods, for which a base or a compound giving the appropriate reaction is added to a solution of the salts of hafnium and zirconium, as a result of which a mixture of oxides hydrates is partially precipitated. An excess base is added to the mother liquor containing a relatively larger amount of hafnium than the original mixture, so that the metals are completely precipitated in the form of hydrates of oxides. The resulting mixture of hydrate oxides is then treated with an insufficient amount of acid, which is why the metals partially transfer

in solution. The residue of the hydrates of the oxides is separated by filtration, and the mother liquor, which is richer in hafnium than the mixture of the hydrates of the oxides, is subjected to a new treatment with a base or the corresponding compound. The operation is repeated until the desired degree of concentration is achieved with respect to hafnium.

In a suitable manner, a mixture with a high content of zirconium can be obtained Continuing to act in the same way, zirconium hydroxide is obtained, from which zirconium metal or the desired zirconium compound can be obtained by a method already known.

The resulting compound of hafnium, containing only a small percentage of qi, rconi or not at all containing such, can be translated

to the oxide of hafnium or to the metallic hafnium in the manner already described. Similarly, other hafnium compounds can be obtained by using methods accepted for zirconium.

SUBJECT OF THE PATENT.

The method of separation of hafnium and zirconium, characterized in that the solution of a mixture of salts of hafnium and zirconium is subjected to fractional precipitation by adding a base or salt, acting in an aqueous solution as a base, or a mixture of hydrates of oxides of hafnium and zirconium is subjected to fractional dissolution in acid, or use a combination of fractional precipitation of hafnium and zirconium hydrates with fractional dissolution of hydrates in acid