RU2598444C1 - Method of obtaining beryllium hydroxide from beryllium-containing concentrates - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of beryllium compounds, specifically beryllium hydroxide, widely used in production of metal beryllium, copper-beryllium ligature, ceramics from beryllium oxide and beryllium salts. Described is a method of obtaining beryllium hydroxide from beryllium-containing concentrates through exposure thereof to concentrated sodium hydroxide solution, separation of solution from cake, where after separation of solution from cake, method includes two-step electrochemical neutralisation of excess alkali in anode chambers of electrolytic cells with separation of insoluble residue of hydroxides of iron and manganese after first step with alkali concentration of 170-180 g/dm³, separating beryllium hydroxide precipitate formed as a result of hydrolysis of sodium beryllate after second step of neutralising alkali to concentration of 30 g/dm³, and sodium hydroxide solution is fortified to concentration of 400-600 g/dm³, required for concentrate loosening, When passing through cathode chambers of electrolytic cells, separated from the anode cation-exchange membranes with compensation of losses of alkali addition of solid sodium hydroxide, where current consumption on electrochemical neutralisation of alkali in anode chambers of electrolytic cells at first step is not less than 188 A·h/dm³, and at 2nd step - not less than 93.8 A·h/dm³.

EFFECT: technical result is reduction of power consumption, reduced water consumption, setting up closed water circulation, preventing discharge of liquid wastes at tailing pond reduced load on environment.

3 cl, 2 dwg, 1 tbl, 2 ex

Description

The invention relates to the field of production of beryllium compounds, namely beryllium hydroxide, widely used in the production of metallic beryllium, copper-beryllium ligatures, ceramics from beryllium oxide and beryllium salts.

There are a number of methods described in the source [Bleshinsky S.V., Abramova V.F., Druzhinin I.G. Chemistry of beryllium. Frunze: Academy of Sciences of the Kyrgyz SSR, 1955. P. 193]:

- crushed beryl is treated with concentrated sodium hydroxide solution, taken in relation to beryl in the amount of 1.2-3 weight parts. When the mass is stirred for several hours at a temperature of 100-400 ° C, beryl decomposes;

- decomposition of beryl is carried out by treatment with a solution of caustic soda with a concentration of 50-75% at a temperature of 175-185 ° C. The liquor is diluted with water;

- fusion of crushed beryl ore with alkali, followed by dissolution of the melt in water.

The known method [US Pat. 2264986 RF, IPC C01F 3/02] for the preparation of beryllium hydroxide from beryllium-containing concentrates by exposure to sodium hydroxide, followed by separation of the reaction products. The concentrate or mixture of concentrates is autoclaved with sodium hydroxide with a concentration of 400-450 g / dm ³ in the presence of calcium oxide with a molar ratio of CaO: SiO ₂ = 1.1-1.3, a temperature of 250-260 ° C and a ratio of Na ₂ O: BeO = 12-13 for 4-5 hours

Almost the same parameters for opening the bertrandite-phenakite concentrate are given in the report [Development of alkaline-autoclave purification of beryllium-fluorite product from fluorine and technology for processing beryllium concentrate of the Ermakovskoye deposit with the separation and purification of beryllium hydroxide: Report of Research Institute / FSUE VNIIHT; Head M.L. Kotsar; Inv No TI / 3506, 2006].

The report was adopted as a prototype because it contains the most complete data, both on the technology of alkaline autoclave opening of beryllium-containing concentrates and on further processing of sodium beryllate solutions to produce beryllium hydroxide.

As indicated in the report, the optimal conditions for alkaline autoclave decomposition of bertrandite-phenakite concentrate are:

- the concentration of NaOH - 450 g / DM ³ ;

- caustic module Na ₂ O / BeO ~ 12;

- molar ratio CaO / SiO ₂ = 1.2;

- temperature 260 ° C;

- processing time - 4 hours;

- washing the insoluble residue at a ratio of W: T = 3.5-3.9 at a temperature of 60 ° C for 0.5 hours

The technological solution after separation of the insoluble residue is diluted with condensate to a residual alkalinity of 170-180 g / dm ³ (~ 2.6 times), after which it is treated with hydrogen peroxide to oxidize iron and manganese, followed by separation of the precipitate of these impurities.

The purified sodium beryllate solution is diluted with condensate to a residual NaOH concentration of 29-30 g / dm ³ (~ 5.9 times), heated with boiling steam and kept at this temperature for 1 h. The beryllium hydroxide released by hydrolysis is filtered off and washed condensate from excess alkali. The mother liquor with a concentration of NaOH ~ 30 g / dm ³ together with the washing solution is evaporated to a concentration of NaOH = 450 g / dm ³ and after separation of the soda precipitate by filtration, they are returned to the opening of the concentrate. Extraction of beryllium to hydroxide by this method is 97-98%.

Schematic diagram of the processing of concentrates by the prototype method is shown in Figure 1.

The disadvantages of this method, adopted as a prototype, are:

- high water consumption - 15 times dilution of the main technological solution 450 to 30 g / dm ³ NaOH and the need for its subsequent evaporation from the mother liquor after the isolation of beryllium hydroxide in order to concentrate the alkali from 30 to ~ 450 g / dm ³ NaOH and return it to opening a new portion of the concentrate. The evaporation process is associated with significant energy costs (0.626 kW · h / kg of water);

- a large flooding of the technological process for the production of beryllium hydroxide as a whole due to the formation of juice and heating steam during the evaporation of condensates, which involves the dumping of excess solutions that are not closed in the technological cycle to the tailing dump. This creates an additional burden on the environment;

- the need to use a reagent (hydrogen peroxide) for cleaning the technological solution from impurities of iron and manganese;

- the need to organize a filtration and washing section from an excess of alkali of the soda precipitate formed during the evaporation of the alkaline solution (alkali carbonization).

The technical result of the proposed method is to reduce energy consumption, reduce water consumption, organize closed water circulation, eliminate the discharge of liquid waste to the tailing dump and reduce the load on the environment.

The technical result of this invention is achieved due to the fact that in the method for producing beryllium hydroxide from beryllium-containing concentrates by exposure to concentrated solutions of sodium hydroxide followed by separation of the solution from the cake, two-step electrochemical neutralization of the alkali excess in the anode chambers of the electrolytic cells with the release of insoluble precipitate of iron and manganese hydroxides is carried out between the stages at an alkali concentration of 170-180 g / dm ³ , the precipitate of beryllium hydroxide formed in hydrolysis of sodium beryllate after the second stage of neutralization of alkali, and the solution is strengthened to the concentration required to open the concentrate when passing through the cathode chambers of electrolyzers with compensation for alkali losses by adding solid sodium hydroxide.

The current consumption for electrochemical neutralization of alkali in the anode chambers of the electrolyzers in the first stage is at least 188 A · h / dm ³ , and at the 2nd stage is not less than 93.8 A · h / dm ³ . The cathode and anode chambers of electrolyzers are separated by cation-exchange membranes.

The reduction of energy consumption for the production of beryllium hydroxide is achieved by carrying out electrochemical neutralization of alkali in the anode chambers of electrolyzers with its parallel regeneration in the cathode chambers and eliminating the dilution of the technological solution with water to 30 g / dm ³ and the subsequent evaporation of the mother liquors formed after hydrolysis of sodium beryllate to the initial concentration for the purpose of their further use in the operation of opening the concentrate.

The proposed method simplifies the hardware design of the process by eliminating the areas of evaporation of solutions, filtering and washing soda.

The hydrogen released in the cathode chambers of the electrolytic cells can be accumulated by getter-storages of hydrogen based on intermetallic compounds (IC), for example LaNi ₅ , Zr ₃ Al ₂ , ZrNi, or used to produce steam (3.55 is released when burning 1 m ^{3 of} hydrogen kWh of energy) with its subsequent use for heating technological solutions and pulps in the production of beryllium.

When carrying out electrochemical neutralization of alkali in the anode chamber of the electrolyzer, the concentration of hydroxyl ions decreases due to their discharge on the positively charged anode with conversion to water and oxygen formation:

4 OH ^- -4 e ^- = O ₂ ↑ + 2 H ₂ O.

The decrease in the content of OH ions ^- according to the Faraday law is proportional to the current consumption. When passing 26.8 A · h, the NaOH content decreases by 1 mol-equiv. In this case, no additional reagents are added to the solution. Moreover, there is no need to use hydrogen peroxide to clean the technological solution from impurities of iron and manganese, since their oxidation is carried out by oxygen released in the anode chamber of the electrolyzer.

In the cathode chamber of the electrolyzer, the reverse process of the formation of hydroxyl ions proceeds with the simultaneous evolution of hydrogen at the cathode:

2 H ₂ O + 2 e ^- = H ₂ ↑ + 2 OH ^- .

Thus, the regeneration of the reagent (alkali) occurs.

To prevent the migration of hydroxyl ions formed at the cathode to the anode, the electrode chambers are separated by cation-exchange membranes through which sodium ions pass from the anode to the cathode.

The electrochemical neutralization of alkali in two stages is determined by the need to clean the technological solution from iron and manganese before the isolation of beryllium hydroxide. At the 1st stage of electrochemical neutralization in the anode chamber, the alkali content is reduced to 170-180 g / dm ³ , after which the precipitated precipitate of iron and manganese hydroxides is filtered off, then the 2nd stage of electrochemical neutralization of NaOH is carried out to ≈ 30 g / dm ³ . This alkali concentration is necessary to achieve the most complete release of beryllium hydroxide during the hydrolysis of sodium beryllate, which is carried out at the boiling temperature of the solution for 1 h:

Na ₂ BeO ₂ + 2 H ₂ O → Be (OH) ₂ ↓ + 2 NaOH.

The proposed method for electrochemical neutralization of an alkaline solution and regeneration of a reagent can be used in the processing of waste metal beryllium.

The initial phenakite-bertrandite concentrate after grinding to a particle size of 0.05 mm (95%) in an amount of 110 g was mixed with calcium oxide in a ratio of CaO: SiO ₂ = 1.2 and subjected to treatment with alkali solutions (NaOH concentration of 400-600 g / dm ³ volume 1 dm ³ ) in an autoclave at a temperature of 250-260 ° C for 4 hours

After cooling, the resulting pulp was filtered: the cake was twice washed from water-soluble beryllium, and the alkaline solution was used to obtain beryllium hydroxide according to the prototype and the proposed method.

Example 1. Obtaining beryllium hydroxide according to the prototype method

The technological solution after separation of the insoluble residue was diluted with water 2.3-3.4 times (proportionally to the initial concentration of NaOH) to a residual alkalinity of 170-180 g / dm ³ , after which it was treated with hydrogen peroxide to oxidize iron and manganese, followed by separation of the precipitate specified impurities.

The purified sodium beryllate solution was diluted 5.8 times with distilled water to a residual NaOH concentration of ~ 30 g / dm ³ , heated with boiling steam and kept at this temperature for 1 h. The beryllium hydroxide released by hydrolysis was filtered off and washed from excess alkali . The mother liquor with a concentration of NaOH ~ 30 g / dm ³ together with the washing solution was evaporated 15-20 times to a concentration of NaOH = 400-600 g / dm ³ and filtered to separate the soda precipitate.

Example 2. Obtaining beryllium hydroxide by the proposed method

The technological solution obtained similarly to the prototype, after separation of the insoluble residue, was sent to the anode chamber of the electrolyzer to conduct the 1st stage of electrochemical neutralization of alkali. During the experiment, a direct current source (B5-46) was used. Electrode material: the anode is made of nickel, the cathode is made of stainless steel. The anode and cathode chambers of electrolyzers are separated by MK-40 cation-exchange membranes based on the KU-2 sorbent. When passing direct current in the amount of 188 A · h / dm ³ in the anode chamber, the NaOH content was reduced to ~ 175 g / dm ³ . In this case, due to the evolution of oxygen, the impurities of iron and manganese were oxidized. The resulting suspension was filtered: cake was washed from water-soluble beryllium, and the solution was sent to the anode chamber of the electrolyzer to conduct the 2nd stage of electrochemical neutralization of alkali to a concentration of NaOH ~ 30 g / dm ³ while passing current in an amount of 93.8 A · h / dm ³ , after which the sodium beryllate solution was subjected to hydrolysis during boiling for 1 h. The total current consumption for 2 stages of neutralization was 281.4 A · h / dm ³ .

The precipitated beryllium hydroxide precipitate was separated by filtration and washed from excess alkali. After hydrolysis, the mother liquor was sent to the cathode chamber of the 2nd stage electrolyzer, where the reverse process of the formation of hydroxyl ions occurred under the action of current. In this case, the alkali content increased to 170-180 g / dm ³ NaOH. The resulting solution was sent to the cathode chamber of the electrolyzer of the 1st stage of neutralization, where the reactant was regenerated to the required concentration (400-600 g / dm ³ NaOH).

The technological scheme for producing beryllium hydroxide according to the proposed scheme is shown in Figure 2.

Comparative results of the processing of beryllium-containing concentrate (per 1 kg of beryllium in beryllium hydroxide)

As can be seen from the table, the greatest extraction of beryllium in hydroxide is achieved when the alkali concentration is 400-600 g / DM ³ .

The use of alkaline solutions with a NaOH concentration of less than 400 g / dm ^{3 is} impractical due to the insufficiently high extraction of beryllium in hydroxide, and the use of alkaline solutions with a NaOH concentration of more than 600 g / dm ³ does not significantly increase the extraction of beryllium in hydroxide and is associated with the production of suspensions with high viscosity, which leads to additional losses of beryllium with cake due to high humidity.

The proposed method for the electrochemical neutralization of alkali for the hydrolysis of sodium beryllate with its subsequent regeneration in the cathode chamber of the electrolyzer provides a significant (17-fold) reduction in energy consumption and a decrease in water consumption by an average of 3.4 m ³ / kg of beryllium in hydroxide.

Claims (3)

1. A method of producing beryllium hydroxide from beryllium-containing concentrates by exposing them to a concentrated sodium hydroxide solution, separating the solution from the cake, characterized in that after separating the solution from the cake, two-stage electrochemical neutralization of the alkali excess is carried out in the anode chambers of the electrolytic cells with the release of an insoluble precipitate of iron and manganese hydroxides after the first stage, at an alkali concentration of 170-180 g / dm ³ , a precipitate of beryllium hydroxide is formed, resulting from the hydrolysis of beryl sodium latate after the second stage of alkali neutralization to a concentration of 30 g / dm ³ , and the sodium hydroxide solution is strengthened to the concentration of 400-600 g / dm ³ required for opening the concentrate, when it passes through the cathode chambers of electrolyzers separated from the anode cation exchange membranes, with compensation of alkali losses by the addition of solid sodium hydroxide, where the current consumption for electrochemical neutralization of alkali in the anode chambers of the electrolysers in the first stage is at least 188 A · h / dm ³ , and in the 2nd stage not less than 93.8 A · h / dm ³ . 2. The method according to p. 1, characterized in that the hydrogen released during the electrochemical regeneration of the reagent in the cathode chambers of the electrolytic cells is used to produce steam and heat the technological solutions and pulps in the process of opening the initial concentrates. 3. The method according to p. 1, characterized in that the hydrogen released during the electrochemical regeneration of alkali in the cathode chambers of the electrolytic cells is accumulated on hydrogen storage devices and used for technological purposes.

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