CS242812B1 - A method for removing undesirable components, in particular silicon, from a solution obtained by alkaline decomposition of tungsten ore - Google Patents

Abstract

The purpose of the invention is a method enabling the reduction of the silicon content to lower values than those enabled by previously known methods. The purpose was achieved by adjusting the pH of the solution from a solution obtained by alkaline decomposition of tungsten ore, separation of solids and partial neutralization of the resulting solution by adding hydrochloric acid to the range of 7.7 to 9.7, preferably 7.7 to 8.7, by adding hydrochloric acid, and then adding an aqueous solution of aluminum chloride in a weight ratio of aluminum chloride to tungsten of at least 1:400 and the pH of the solution is again adjusted by adding sodium hydroxide to the above range.

Description

The invention relates to a process for removing undesirable components, in particular silicon, from a solution obtained by the alkaline decomposition of tungsten ore, filtering off the solids and partially neutralizing the resulting solution by the addition of hydrochloric acid at temperatures of 20 to 100 ° C.

In the production of tungstic acid, the alkaline decomposition of tungsten ore takes place in the first stage of the process. After filtering off the solid impurities, in particular the iron and manganese hydroxides, it is necessary to remove dissolved undesirable impurities, in particular the silicon compound present in the solution at a concentration of about 2 to 3 g.dm ^J expressed as silicon from the obtained sodium tungstate solution. To date, partial neutralization of the solution with hydrochloric acid to pH 8.5 to 9.5 at elevated temperature, about 80 to 90 ° C has been used. Most of the silicon is precipitated in the form of hydrated oxide, and its content in solution drops to about 0.1 to 0.3 g.dm @ -1, but this is insufficient for some applications. In another process described, the silicon content is reduced in two steps.

¥ each of which is adjusted to a pH of 9 to 9 with the sodium tungstate solution. »Aluminum sulphate and magnesium sulphate are added, the solution is stirred for 1 hour at 70 to 80 ° C, and the precipitated silicon is then filtered off. In this way, a reduction in the silicon concentration of up to 0.03 to 0.06 g.dm @ 2 (s.V. H. Yih a

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C.T.Vang, Tungsten, Plenum Press, New York 1979 »103.). However, the process is quite laborious and the silicon content is still high for some purposes.

The above-mentioned disadvantages greatly reduce the process of removing undesirable components, in particular silicon, from the solution obtained by alkaline decomposition of tungsten ore, separating the solids after decomposition and partially neutralizing the resulting solution by adding hydrochloric acid at temperatures of 20 to 100 ° C, preferably 70 to 90 ° C. The method consists in adjusting the pH of the solution to a range of 7.7-9.7, preferably 7-7.7, by the addition of hydrochloric acid, and then adding an aqueous solution of aluminum chloride in a weight ratio of aluminum chloride to tungstate of at least 1: 400 and the pH of the solution is readjusted by the addition of an alkali metal hydroxide within the above range. The process according to the invention results in a reduction of the silicon concentration up to about 0.01 g.dm @ 2 as well as a reduced concentration of phosphorus and arsenic. Another advantage of the method according to the invention is the simple implementation.

Example

The starting, strongly basic sodium tungstate solution, containing 10% tungsten and 2.3% silicon, is partially neutralized with hydrochloric acid with stirring (temperature and pH are given in the table below). After 15 min, an aqueous aluminum chloride solution (amount shown in the table) is added with stirring and the pH is adjusted to its original value by the small addition of aqueous sodium hydroxide solution. The table below shows the concentration of silicon in the solution after addition of hydrochloric acid (indicated as a) and after addition of an aqueous aluminum chloride solution (indicated as jako). In the table below, t is heatAa and m is the mass of aluminum chloride (dry matter) added per dm 2 of the solution:

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C. m ^ g.dm “3J tfc) pH Content kre «£ ku / _e . d »* 3 AND (B) 1 0.25 80 8.0 0.12 0.07 2 0.5 80 8.0. 0.14 0.01 3 1.0 80 8.0 0.12 0.01 h 0.5 20 May 9.0 0.14 0.02

SUBJECT OF THE INVENTION

Claims (1)

A process for removing undesirable components, in particular silicon, from a solution obtained by the alkaline decomposition of tungsten ore, separating the solids and partially neutralizing the resulting solution by the addition of hydrochloric acid, characterized in that the pH of the solution is adjusted to 7.7 to 9 by addition of hydrochloric acid. Preferably 7.7 to 8.7, and then an aqueous solution of aluminum chloride in a weight ratio of aluminum chloride to tungsten of at least 1 400 is added and the pH of the solution is again adjusted by adding sodium hydroxide to the above range.