RU2410801C1 - Method for processing of oxide-nickel electrodes - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to electrical engineering and may be used to manufacture components of active masses of positive electrodes of alkaline accumulators. According to invention, method for processing of oxide-nickel electrodes includes damage of electrodes, separation of metal component and active mass, leaching of nickel-containing component with solution of sulfuric acid with concentration of 28-32 wt %. Graphite is separated from solution of nickel sulfate by filtration and washed with water on filter. Produced washing solution is evaporated to concentration of nickel sulfate close to saturation. Both solutions, solution of nickel sulfate and washing solution, are cooled down to temperature of 10 - 20°C, are maintained at this temperature until sedimentation of crystals of nickel sulfate, which are separated from solution, mother solutions are combined and treated with concentrated aqueous solution of ammonia to produce main salts of nickel. Afterwards produced deposit is separated by filtration and is treated with solution of sodium hydroxide of 15-20%, to produce nickel hydroxide (II) and solution of sodium sulfate. Hydroxide of nickel (II) is filtered, deposit is washed with water and dried. Washing waters are added to solution of sodium sulfate. Ammonia released in production of nickel hydroxide (II) is absorbed by water and is returned for treatment of mother solution. Sodium hydroxide 15-20 wt % is added to solution left after separation of the main salts of nickel, until iron hydroxide (III) is deposited, which is filtered from solution of sodium sulfate. Produced solutions of sodium sulfate are combined, sodium sulfate is evaporated and crystallised.

EFFECT: improved efficiency of method for processing of oxide-nickel electrodes due to reduction of quantity of used water and reduction of volume of process solutions, increased purity of produced graphite.

1 ex, 1 tbl

Description

The invention relates to electrical engineering and can be used for the manufacture of components of the active masses of the positive electrodes of alkaline batteries.

A known method of restoring the active mass of the positive electrode from spent iron-nickel batteries, including the destruction of the electrodes, the separation of the metal component from the active mass, washing with water, followed by the use of the active mass for reuse in alkaline batteries [as USSR No. 120236]. The disadvantage of this method is the lack of purity of the resulting active mass, which reduces the life of the alkaline battery and does not meet the requirements of TU-48-3-63-90 for nickel (II) hydroxide used in the production of alkaline batteries.

A known method of processing spent alkaline batteries [RF patent No. 2178933], selected for the prototype. The method includes the destruction of the electrodes, the separation of the metal component and the active mass, the separation of graphite by flotation and leaching of the active mass with sulfuric acid, followed by the hydrometallurgical processing of the solution of nickel sulfate into nickel (II) hydroxide according to the known technology [Dasoyan MA, Novoderezhkin VV, Tomashevsky F.F. Manufacture of electric batteries. M.: Higher School, 1970. 428 p.]. The disadvantage of this method is its inefficiency due to the use of a large amount of water for the flotation operation and preparation of technological solutions, the concentration of nickel sulfate in solutions is less than 1% (saturated solution - 27.7%), insufficient purity of the graphite obtained.

The objective of the invention is to increase efficiency by reducing the amount of water used and reducing the volume of technological solutions, increasing the purity of the resulting graphite.

A method for processing oxide-nickel electrodes is proposed, including destruction of the electrodes, separation of the metal component and the active mass, leaching of the nickel-containing component with a solution of sulfuric acid with a concentration of 28-32 wt.%. Graphite is separated from the solution of nickel sulfate by filtration, washed on the filter with water, removed from the filter and dried. The resulting wash solution was evaporated to a concentration of nickel sulfate, close to saturation, approximately two times the volume. Both solutions, a solution of nickel sulfate and a wash solution, are cooled to a temperature of 10-20 ° C, kept at this temperature until precipitation of crystals of Nickel sulfate. Nickel sulfate crystals are separated from the solution, the mother liquors are combined and treated with concentrated aqueous ammonia to obtain basic nickel salts. After that, the precipitate formed is separated by filtration and treated with a sodium hydroxide solution of 15-20% to obtain nickel (II) hydroxide and sodium sulfate solution. Nickel (II) hydroxide is filtered off, the precipitate is washed with water and dried. Wash water is added to the sodium sulfate solution. Ammonia released during the production of nickel (II) hydroxide is absorbed by water and returned to the mother liquor. Sodium hydroxide 15-20 wt.% Is added to the solution remaining after separation of the basic salts of nickel until iron (III) hydroxide precipitates, which is filtered off from sodium sulfate solution. The resulting sodium sulfate solutions are combined, evaporated and crystallized sodium sulfate.

The use of more concentrated solutions of sulfuric acid allows, in comparison with the prototype, to exclude the operation of flotation and subsequent hydrometallurgical purification of the foam product. Using a more concentrated solution of sulfuric acid allows you to increase the degree of extraction of the main component in the solution, resulting in a cleaner graphite compared to the prototype. The proposed method due to the introduction of new operations, in fact, is a closed loop, which significantly reduces losses and leads to increased efficiency.

Thus, the combination of distinctive features is a necessary and sufficient condition for the implementation of the task.

The use of a solution of sulfuric acid with a concentration of 28-32% (wt.) Is due to the completeness of extraction in the solution of the main target component - nickel in the form of sulfate, as well as the neutralization of the residual alkalinity of the active mass. Using for leaching a more concentrated solution of sulfuric acid of more than 32 wt.% Is impractical, since as a result, the resulting solution will be enriched with the accompanying components (impurities). When using less concentrated solutions of sulfuric acid of less than 28 wt.%, The volume of the resulting solution increases and graphite is obtained, contaminated with the components of the active mass.

The cooling of the solution of nickel sulfate formed after leaching is carried out at a temperature of 10-20 ° C, since it is under these conditions that the necessary supersaturation in a solution of this composition is created and the formation of crystal nuclei is observed. At temperatures above 20 ° C, crystal formation in the resulting solutions is not observed. At temperatures less than 10 ° C, intense nucleation of crystals occurs and their contamination with impurities due to capture of the solution is possible.

The concentration range of the sodium hydroxide solution was selected according to the solubility diagram in the Na ₂ SO ₄ -NaOH-H ₂ O system at 25 ° C [M. Pozin Technology of mineral salts (fertilizers, pesticides, industrial salts, oxides and acids) Part I. L .: Chemistry, 1974. 792 p.]. Thus, so that the sodium sulfate formed is in solution at a given ratio of sulfate and sodium hydroxide. When using a solution of sodium hydroxide with a concentration of more than 20%, the solid phase of sodium sulfate precipitates. When using a sodium hydroxide solution with a concentration of less than 15%, a large volume of the technological solution is obtained.

Example

Stage 1. 10 g of the active mass of the oxide-Nickel electrode was leached with sulfuric acid at a concentration of 30% (wt.) In a temperature-controlled reactor at a temperature of 82 ° C. The amount of sulfuric acid required for leaching was determined by the nickel content in the active mass, taking into account the residual alkalinity — the content of carbonates (6.1 ± 1.0)% and hydrocarbons (7.3 ± 1.0)% [Demidov A.I., Kokhatskaya M.S., Sun Lubin Determination of residual alkalinity in the positive and negative electrodes of a spent nickel-iron battery. Journal of Applied Chemistry, 2005.V.5, Issue 8. S.1303-1305]. Sulfuric acid was added portionwise to the dry active mass in order to avoid foaming and spraying of the solution. Then the suspension containing a solution of Nickel sulfate and graphite was filtered at 82 ° C. The graphite washed on the filter was dried at a temperature of 130 ° C, the washing solution was evaporated twice in volume. Both solutions were cooled to a temperature of 17 ° C and kept at this temperature for 3-6 days for the formation and growth of crystals of nickel sulfate. The crystals were separated from the mother liquor using a Schott filter. The resulting final products (graphite, crystalline nickel sulfate) were subjected to x-ray phase analysis to characterize their degree of purity.

The resulting graphite is a powder of the following composition, wt.%:

[C] ≈99.2; [Fe] = 0.01; [Ca] = 0.013; [Si] = 0.008.

Nickel sulfate crystals are single crystals of NiSO ₄ · 6H ₂ O, which were radiographically pure.

Stage 2. The mother liquor remaining after crystallization of Nickel sulfate, was treated with concentrated aqueous ammonia to obtain basic salts of Nickel. The amount of added ammonia was monitored by pH; the addition was carried out to a value of pH ≈ 2.5 to prevent contamination of the resulting salt with iron (III) hydroxide. The solution was kept until complete precipitation of the basic salt. The precipitate was separated from the solution by filtration, washed with water and dried at room temperature. Wash water was added to the stock solution.

Stage 3. 1 g of dried basic Nickel salt was treated with 10 ml of a solution of sodium hydroxide 20% (wt.). The resulting nickel (II) hydroxide was separated by filtration, washed on the filter with water and dried at a temperature of 130 ° C. Wash water was added to sodium sulfate solution containing sodium hydroxide.

Stage 4. To the solution remaining after separation of the basic nickel salts (stage 2), a sodium sulfate solution containing sodium hydroxide obtained from the synthesis of nickel (II) hydroxide (stage 3) was added to remove iron by precipitation in the form iron (III) hydroxide. The precipitate was separated by filtration, followed by washing with water, and washing water was added to the sodium sulfate solution. The solution was evaporated and crystallized to obtain sodium sulfate according to known technology. Ammonia released during the formation of iron (III) hydroxide was absorbed by water for subsequent use in the preparation of basic nickel salts (stage 2).

The following examples were carried out analogously to example 1, changing the concentration of the sulfuric acid solution, the cooling temperature, as well as the concentration of the sodium hydroxide solution. The results are shown in the table.

Table The concentration of H ₂ SO ₄ , wt.% t _cool. ° C The concentration of NaOH, wt.% Notes 28 10 fifteen Received: crystals of NiSO ₄ · 6H ₂ About radiographically pure, graphite is cleaner than the prototype, Nickel hydroxide and sodium sulfate. thirty 17 eighteen Received: crystals of NiSO ₄ · 6H ₂ About radiographically pure, graphite is cleaner than the prototype, Nickel hydroxide and sodium sulfate. 32 twenty twenty Received: crystals of NiSO ₄ · 6H ₂ About radiographically pure, graphite is cleaner than the prototype, Nickel hydroxide and sodium sulfate.

The proposed method allows to exclude the operation of flotation and subsequent hydrometallurgical purification of the foam product, which reduces the volume of water used by 20 m ³ per 1 ton of active mass. The cost of 1 m ^{3 of} water as of January 1, 2009 is 15.45 rubles, water disposal of the same amount is 11.35 rubles. The savings are 536 rubles per 1 ton of active mass. The obtained crystals of NiSO ₄ · 6H ₂ O are radiographically pure and the obtained graphite has high purity. In addition, the proposed method is low-waste, because it additionally allows you to get Nickel hydroxide from the mother liquor, sodium sulfate from the wash solution.

Claims (1)

A method of processing oxide-nickel electrodes, including destruction of the electrodes, separation of the metal component of the electrodes and the active mass, leaching of the nickel-containing component of the active mass with a solution of sulfuric acid, obtaining a solution of nickel sulfate, characterized in that for the leaching take a solution of sulfuric acid with a concentration of 28-32 wt.% after which the suspension is filtered to obtain graphite and solution, graphite is washed with water and dried, and the resulting washing solution is evaporated to a concentration of nickel sulfate mild to saturation, both solutions are cooled to a temperature of 10–20 ° С and kept until crystals precipitate, nickel sulfate crystals are separated from mother liquors, which are combined and treated with concentrated aqueous ammonia, after which the precipitate formed is filtered off, and the precipitate is treated with sodium hydroxide solution 15 -20 wt.% To obtain Nickel (II) hydroxide and sodium sulfate solution, Nickel (II) hydroxide is filtered off, washed with water, dried, washing water is added to the sodium sulfate solution, while yayuschiysya ammonia absorbs water and is returned to the processing of the mother liquor, and thereto is added sodium hydroxide 15-20 wt.% to precipitate iron hydroxide (III), which is filtered from the solution of sodium sulfate, sodium sulfate solutions obtained were combined, evaporated and crystallized sodium sulfate.