RU2431691C1 - Procedure for processing grinding wastes from manufacture of permanent magnets - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: invention refers to procedure of extraction of rare earth elements (REE) from grinding wastes of manufacture of permanent magnets. The procedure consists in dissolving grinding wastes in sulphuric acid, in extraction of double salts and sodium REE-Na by sedimentation and in washing double salts. Further, double salts are conversed in hydroxide of REE and hydroxides of REE are washed. Upon washing hydroxides of REE are oxalate conversed, dried and burned producing sum of REE oxides. After sedimentation of double salts of rare earth elements and sodium REE-Na mother solutions are processed producing ferriferous and cobalt cakes. ^ EFFECT: production of sum of oxides REE with high content of REE by hydro-metallurgical procedure, production of ferriferous and cobalt concentrates as by-products. ^ 4 cl, 1 dwg

Description

The invention relates to the field of chemical technology of inorganic substances and can be used in cases where it is necessary to obtain rare earth elements (REE), purified from impurities. The invention can be used to obtain a mixture of REE oxides for their reuse in various fields of science and technology.

There is a method of extracting rare earth elements from grinding waste from the production of permanent magnets (1), which includes dissolving grinding waste in sulfuric acid, precipitation of double salts of rare earth elements and sodium (REE-Na), obtaining REE oxalates, drying and calcination of oxalates to obtain the sum of REE oxides processing of mother solutions of precipitation of REE-Na double salts to obtain glandular cake and the release of cobalt.

A known method of separating REE oxides from grinding waste production of permanent magnets (2), which includes mixing grinding waste with ammonium fluoride hydrofluoride, which is taken in excess of 20% of the stoichiometric ratio. The mixture is heated to 230 ° C and maintained at this temperature until the complete separation of volatile fluorides of carbon, boron and other non-metals. The solid residue of fluoride compounds of REE, silicon, aluminum and iron is heated to a temperature of more than 320 ° C for sublimation separation of silicon compounds. The resulting solid residue is subjected to aqueous leaching to separate iron compounds. Insoluble fluorides of REE and aluminum are converted into the oxide form by pyrohydrolysis and then ground. REE oxides are separated from alumina by magnetic separation.

The method described above involves the use of high temperatures, leading to high energy consumption, as well as aggressive fluoride compounds in the gaseous state, leading to the use of equipment with high corrosion resistance and the presence of a special gas cleaning system.

In addition, this method cannot ensure the complete separation of impurities (in particular aluminum) from the target product (according to (1), the final aluminum content in the finished product is in the range of 0.11-0.15%).

Also known is a method of processing grinding wastes (3), including drying, oxidation at 550-650 ° C, magnetic separation of a mixture of oxides and subsequent fluorination with elemental fluorine at temperatures of 200-350 ° C. The resulting fluoride mixture is metallothermally reduced by an out-of-furnace process to produce alloys and magnetic alloys.

The disadvantage of this processing method is the use of an expensive and extremely aggressive fluorinating reagent - elemental fluorine, as well as the use of drying and calcining operations at the initial stage of processing, since grinding waste is a fire hazardous material.

The present invention is the development of hydrometallurgical technology (all operations are carried out in aqueous solutions at temperatures less than 100 ° C) processing grinding waste production of permanent magnets, eliminating the disadvantages described above.

The problem is solved by the method of processing grinding waste, including the following stages:

- dissolution of the initial grinding waste in sulfuric acid to obtain a solution of REE, iron, cobalt, etc .;

- separation of insoluble impurities;

- separation of REE compounds from other elements by the deposition of double salts by crystalline sodium sulfate;

- washing the double salts of REE from the mother liquor deposition;

- the conversion of the washed double salts in REE hydroxide by the action of a NaOH solution;

- washing of REE hydroxides from excess alkali;

- oxalate conversion of REE hydroxides;

- drying of REE oxalates at 250 ° C;

- calcination of oxalates at 900-1000 ° C to obtain REE oxides.

With this method of producing REE oxide, fluoride compounds are not used (in particular, elemental fluorine and its volatile compounds). The method is as follows.

Grinding waste after rough sifting is pulped up in water at a ratio of T: W = 1: 10. The pulp is opened with concentrated sulfuric acid, gradually dosing it into the pulp of grinding wastes. After the introduction of acid, the pulp is kept at a temperature of 60-70 ° C for 1 hour and filtered, separating the insoluble precipitate of silicon, aluminum, abrasive materials, etc.

This method of opening grinding waste eliminates the use of fluoride reagents and high temperatures to separate silicon-aluminum and other compounds, since they are insoluble in sulfuric acid. Also, this opening method eliminates the energy-intensive operation of drying and calcining grinding waste.

The solutions obtained after dissolution contain, on average, g / l:

∑РЗО Fe Co H ₂ SO ₄ 30-35 55-70 3-6 25-30

After dissolution, the filtrate is heated to 70-80 ° C and crystalline sodium sulfate is introduced into it with an excess of 150-200% of the stoichiometric amount. The resulting pulp of double sulfate salts of REE-Na is incubated for an hour and is separated from the mother liquor, which is a sulfate solution of iron, cobalt, boron, etc. by filtration. The precipitate of double salts is washed on the filter with water, acidified to pH ~ 1 with sulfuric acid in order to displace the mother liquor from the sediment layer.

Washing on the filter is not enough to separate the mother liquor, therefore, at least two repulpations of the double salt in water acidified with sulfuric acid to pH ~ 1, a temperature of 50 ° C and a ratio of T: W = 1: 3 are carried out. After each repulpation, filtration followed by washing the precipitate on the filter with acidified water. The filtrates are supplied to obtain glandular and cobalt cake (see drawing).

The washed double salt is converted to REE hydroxide, which is carried out as follows: the salt is loaded into a NaOH solution (200 g / l) preheated to 60-70 ° C at a ratio of T: W = 1: 3 and kept under stirring for 1 -1.5 hours. The resulting hydroxide precipitate is filtered and washed with water on a filter from the mother liquor conversion. A mother liquor containing an excess of alkali is directed to the deposition of cobalt cake (see drawing). Rinsing on the filter is not enough, therefore, at least one hydroxide is repulped in water at a temperature of 50 ° C and a ratio of T: W = 1: 3. After each repulpation, filtration and washing of the filter cake with water follows. Filtrates after repulpation, containing small amounts of alkali, are wrapped to neutralize and then merge.

The washed hydroxide is loaded into a solution of oxalic acid (150-200 g / l) at a temperature of 80 ° C and T: W = 1: 3. After exposure for 2-3 hours, the precipitate of REE oxalates is filtered, washed on the filter from excess acid. The filtrate is sent to neutralize.

The resulting REE oxalate is dried at 250 ° C to remove the bulk of the moisture, and then calcined at 900-1000 ° C for 3 hours to obtain the oxide of the sum of REE.

Obtained by this method, the oxide contains,%:

∑РЗО Fe Co B Ca Na Al Si 99-99.2 0.001 0.001 0.01 0.08-0.1 0.01-0.03 0.01 0.001

The mother liquor after precipitation of the REE-Na double salt, as well as the filtrates after washing the double salt, are fed to the isolation of glandular and cobalt cake (see drawing).

The precipitation of iron from the solution is carried out at pH = 4.5-5.0, oxidizing it at a temperature of 60-70 ° C with hydrogen peroxide taken in excess of 10% of the stoichiometric amount (or with atmospheric oxygen for 15-17 hours), and neutralizing a solution of soda ash (150-200 g / l). The pulp obtained during the deposition is filtered, the cake is washed from the solution on the filter.

After precipitation of iron, the filtrate is neutralized to pH = 10-11 with NaOH solution (200 g / l) or reverse filtrate after the separation of REE hydroxides (see drawing), highlighting cobalt cake. The precipitate is filtered, washed. The resulting cake contains 30-50% cobalt.

At low cobalt contents in the solution or at the inappropriateness of its isolation, it is possible to obtain a joint iron-cobalt cake by raising the pH at the stage of iron evolution to 10-11.

The main scheme of the method is presented in the drawing. Thus, the proposed hydrometallurgical method for processing grinding wastes makes it possible to obtain REM oxides purified from basic impurities, as well as iron and cobalt compounds suitable for use.

Information sources

1. US patent No. 5129945, 19923

2. RF patent No. 2369561, 2009

3. RF patent No. 2111833, 1998

Claims (4)

1. The method of separation of rare earth elements (REE) from grinding waste from the production of permanent magnets, including the dissolution of grinding waste in sulfuric acid, the allocation of double salts of rare earth elements and sodium REE-Na by precipitation, the washing of double salts, the conversion of double salts to REE hydroxides, the washing of REE hydroxides, the washing of hydroxides of RE oxalate conversion of REE hydroxides, drying and calcination of oxalates to obtain the sum of REE oxides, and also processing of the mother liquors of the deposition with obtaining ferrous and cobalt cakes. 2. The method according to claim 1, characterized in that during the processing of grinding wastes, aqueous solutions of sulfuric, oxalic acid, sodium sulfate, soda ash and caustic soda are used. 3. The method according to claim 1, characterized in that the operations of dissolving the allocation of double salts, washing the double salts, the conversion of double salts to hydroxides and the conversion of hydroxides to REE oxalates are carried out in aqueous solutions and at significantly lower temperatures, less than 100 ° C. 4. The method according to claim 1, characterized in that after the precipitation of the double salts, they are washed, after which the conversion of the double salts to REE hydroxides and their washing, the production of oxalates is carried out by loading the washed REE hydroxides in a solution of oxalic acid, and the selection of cobalt from the mother solutions are carried out by deposition in the form of cobalt cake.