AT137319B - Process for removing iron from acidic aluminum salt solutions. - Google Patents

Description

  

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  Process for removing iron from acidic minimum salt solutions.



   In Austrian Patent No. 135054 it has been described that iron-free chromium salts are obtained when the ferrous salt-containing chromium salt solutions are mixed with beta-naphthalene monosulfonic acid or its alkali salts, whereby the iron is precipitated in the form of the insoluble iron salt of this acid and then from the iron-free chromium salt solution can be separated by filtration.



   As has now been found, this new process can also be applied to the separation of iron from the iron-containing aluminum salt solutions. A simple method for solving this important task, where it is a question of the purification of the products obtained by acidic digestion of alumina-containing starting materials, is not known so far. The method according to the invention therefore consists in adding a slight excess of beta-naphthalenesulfonic acid or its soluble salts to the aluminum salt solution after the iron has been converted into the ferroform, and the resulting precipitate is filtered off in the cold.



   The prerequisite for complete separation of the iron is the presence of the same in the ferrous salt form. As a result, the operation of precipitation must be preceded by the complete reduction of the ferric salts present, which can be done with known agents such as sulphurous acid, hydrosulphurous acid, iron powder.



   If soluble salts of naphthalene sulfonic acid are used, the ferrous salt formed of this acid can be converted by reaction with suitable compounds, such as. B. alkali carbonates, can be converted back into soluble salt of beta-naphthalenesulfonic acid which can be used again.



   Example:
100 parts of a bauxite containing 45 "/ o Al 2 O 3, 12" / o SiO 2, 20% Fe 2 O 3, are digested in a known manner in leaded kettles using the calculated amount of 60% sulfuric acid, then diluted with 100-200 parts of water and hot from the silica filtered; the filtrate is diluted to about 600-700 parts by volume with water. In this salt solution, 104 parts of sodium beta-naphthalenesulphonate are dissolved and then slowly 10-12 parts of hydrosulphite (concentrated) or the corresponding amount of sodium sulphite or a mixture of both salts are added, whereby all iron precipitates as a finely crystalline ferrous salt on cooling.

   The solution filtered from the precipitate is neutralized with iron-free aluminum hydroxide, then aluminum sulfate is obtained therefrom by evaporation or crystallization. Aluminum sulphate + 18 H20 obtained in this way contains 0.01-0.020/0 iron and is therefore iron-free, so to speak.

** WARNING ** End of DESC field may overlap beginning of CLMS **.

 

Claims (1)

PATENT CLAIM: Process for removing iron from acidic aluminum salt solutions, characterized in that, after the iron has been converted into the ferroform, a slight excess of beta-naphthalenesulfonic acid or its soluble salts is added to the solution and the resulting precipitate is filtered off in the cold. ** WARNING ** End of CLMS field may overlap beginning of DESC **.