RU2127326C1 - Method of recovery of cobalt from cobalt-containing material - Google Patents

Abstract

FIELD: recovery of cobalt from cobalt-containing materials and its further use for production of various compounds. SUBSTANCE: method includes transfer of cobalt and metal impurities into diluted solution; purification of solution from impurities; filtration and subsequent precipitation of cobalt from solution; washing and squeezing out with subsequent obtaining of final product. Solution is purified from impurities in poison medium containing bicarbonates and carbonates of alkali metal and oxidizer, for instance, hydrogen peroxide at pH 7.8-9.4 and temperature of 15-30 C. EFFECT: high selectivity, provision of production of pure final products without use of complicated equipment. 2 tbl

Description

 The invention relates to the chemical technology of inorganic substances, in particular to chemical and hydrochemical methods for the extraction of cobalt from cobalt-containing materials and its further use for the preparation of various compounds.

 Metallic cobalt is very rare in nature, in the form of complex complex compounds from which it must be extracted.

 The ores from which cobalt is extracted are very diverse in their chemical and mineralogical composition, and the cobalt content in them varies widely - from tenths of a percent to several percent. But non-oxidized ores (sulfide or arsenic), especially complex, are industrial even at a cobalt concentration of 0.15% or less, because they lend themselves to enrichment.

Naturally, poor ores must be pre-enriched, therefore, it is convenient to classify cobalt extraction processes based on ore enrichment, namely:
1. ore enrichment: copper sulfide, arsenic primary, magnetite, nickel sulfide and asbolic;
2. ores not enriched by modern mass methods: oxidized copper, arsenic erythrin, oxidized nickel and solid pyrites or arsenopyrites.

 The initial technological processes for the extraction of cobalt, despite their diversity, are based primarily on phase separation. Usually, it is not possible to obtain a high cobalt content in the extracted phase in one metallurgical processing operation; therefore, the first metallurgical processing product, matte or spice (in hydrometallurgical processes, the first precipitate) must be subjected to several enrichment operations.

 For these purposes, firing and contractile melting or conversion are carried out. The final separation of the accompanying impurities from cobalt is carried out by hydrometallurgical methods by fractional purification of the obtained solutions from impurities with a successive increase in pH. Cobalt hydroxide is precipitated from the purified solution during its oxidation. As a result of enrichment processes, concentrates containing cobalt from a few percent to 40% are obtained.

Further, various paths are possible depending on the task of obtaining a specific product. Thus, the process of hydrometallurgical processing of cobalt-containing materials consists of the following operations:
transfer of cobalt and its accompanying metals into the solution;
purification of the solution from impurities and the allocation of cobalt from it in the form of an independent solid phase;
bringing the solid phase to cobalt metal or some other commercial product.

 Depending on the content of cobalt and other components in the alloy, several methods for dissolving cobalt-containing raw materials are used: chemical, electrochemical, and autoclave (Extraction of cobalt from copper, nickel ores and concentrates.- M .: Metallurgy, 1970).

 The conversion of cobalt into a soluble form and preliminary separation of the bulk of the predominant metals is achieved as a result of various pyrometallurgical processes: oxidative roasting, mine smelting, conversion, sintering with various additives, chlorination and electrolysis.

 After the cobalt is transferred to the solution, it is separated from significant quantities of accompanying metals captured in the processing and leaching: silver, copper or lead, or iron, manganese, nickel and zinc.

Usually, cobalt is used to extract its great tendency to transfer to the trivalent form and to the formation of stable complex compounds; for this purpose, the solution is treated under appropriate conditions with chlorine, sodium hypochlorite, hydrogen peroxide or other oxidizing agents. The final product of the hydrometallurgical stage is Co ₃ O ₄ , from which metallic cobalt is obtained in various ways (Chemical Encyclopedia vol. 2. M: Academy of Sciences, p. 615).

 A known method of producing cobalt oxide by hydrometallurgical dissolution of cobalt-containing material with a mixture of calcium chloride and sulfuric acid, followed by purification of the resulting solution from iron, copper and calcium compounds with soda ash at a pH of 6.1 - 6.5 and the conversion of the purified solution of cobalt chloride to cobalt oxide in accordance with hypochlorite scheme, and then according to the well-known reaction of substitution of chlorine ions for sulfate - ions (ed. St. N 13477, BI N 1 - 61).

A known method of precipitation of cobalt hydroxide from cobalt solutions by blowing them with gaseous chlorine at a temperature of 60 - 74 ^o C with a feed rate of chlorine in the range of 8-16 g / h for each liter of the treated solution, while neutralizing the acid-forming solution with calcined and caustic soda in a ratio from 3: 2 to 1: 1 (ed. St. N 114149).

 A common disadvantage of these methods is that cobalt is released in the form of a precipitate containing impurities of other metals: copper, iron, nickel, zinc, etc. Further separation of these metals due to the proximity of their normal potentials presents a complex problem.

 In addition, the disadvantage of this method is the use of reducing agents and oxidizing agents containing chlorine ions, polluting the environment and affecting human health. Currently, together with hypochlorite, preference is given to chlorine dioxide and hydrogen peroxide.

A known method of extracting cobalt from a spent cobalt-containing catalyst, in which the cobalt-containing material is pretreated with a solution of potassium or sodium hydroxide at a temperature of 50-90 ^o C. After that, the separated precipitate is subjected to heat treatment at a temperature of 260-320 ^o C, and then dissolved in sulfuric acid to form cobalt sulfate (RF patent N 2036841, BI N 23, 1995).

 The disadvantages of this method are: the presence of impurities of organic origin and the high energy intensity of the process.

 Methods for the extraction of cobalt compounds using the autoclave process are most widespread, because provide a more integrated use of the components of the original cobalt-containing material.

 The processes of autoclave leaching of cobalt-containing materials with sulfuric acid or in the presence of ammonia or ammonium salts are widespread.

When leaching in sulfuric acid solutions, a solution is obtained with a high content of free H ₂ SO ₄ (up to ~ 10 g / l). Nickel and cobalt in them are represented by valence ions (Ni ²⁺ , Co ²⁺ ). Such a solution can be processed according to a standard hypochlorite scheme or more correctly hydrated. The solutions after leaching were oxidized with air and iron was isolated from them with ammonia at a temperature of 75 ^o C, a partial pressure of oxygen, 0.35 at and a pH of 4.1 - 4.3. After iron, the solution should be cleaned of copper with cobalt powder at pH 4.2, and cobalt and nickel should be separated in three stages. The selection of cobalt according to the hypochlorite scheme is carried out in excess hypochlorite (200-300%) of the theoretically necessary. Excess hypochlorite was used to neutralize the resulting sulfuric acid. The deposition temperature of 80 - 90 ^o C. the Time 4 to 6 hours. Along with cobalt, a certain part of nickel passes into the solution.

Chlorine precipitation is carried out at a temperature of 65 - 70 ^o C. The acidity of the solution varies from 0.8 - 1 g / l to 0.5 - 0.8 g / l.

 The disadvantage of this method is that the sulfate solution at high temperatures and pressure is very aggressive - it requires the use of titanium or lining of acid-resistant material, and most importantly the use of chlorine.

 The main disadvantage of ammonia solutions is that when leaching mattes with a high cobalt content, insoluble hexamine is formed along with soluble cobalt pentamine, resulting in a decrease in the extraction of cobalt in solution (V. I. Smirnov et al. Extraction of cobalt from copper and nickel ores and concentrates .- M .: 1970, Metallurgy, p. 181-198).

 The hydroxide precipitation process is the final separation operation of nickel and cobalt. As a result, a pure, free from impurities product is obtained.

 Hydroxide is precipitated either with sodium hypochlorite, containing 50-60 g of chlorine and 20-25 g of alkali, or with gaseous chlorine with the simultaneous introduction of a mixture of calcined and caustic soda containing 95 g / l of calcined and 110 g / l of caustic soda into the solution.

 In the hypochlorite method of precipitation of hydroxide in a solution acidified to a pH of 1.5–1.7, sodium hypochlorite is poured through a 5–7 mm diaphragm at a rate of 400–500 l / h in an amount that ensures cobalt precipitation of 85–95% (in depending on the ratio of cobalt to nickel in the initial solution).

 When cobalt hydroxide is precipitated with gaseous chlorine, the pH of the solution is adjusted to 1.9-2.1. Chlorine is passed at a pressure of 0.4 - 0.7 atm and at a flow rate of 40 - 80 kg / h. The constant pH of the solution during the precipitation process is ensured by the supply of soda solution. By the end of the operation, the pH of the solution rises to 2.3-2.5. Chlorination is carried out until the content in the solution of 0.03 - 0.05 g / l of cobalt.

 Its disadvantage is that when precipitating hydroxide with chlorine, fine precipitates are obtained, which are highly dusty during drying.

 The process of electrolytic refining of cobalt is usually carried out in bathtubs with diaphragms, while the solution is removed from the anode space to remove impurities - copper, iron, nickel and then enters the cathode space. Usually, electrolytic cobalt is not sufficiently pure: it contains a significant amount of zinc, so it is subjected to additional refining.

The following operations are used to selectively isolate nickel and cobalt from a solution:
1. oxidation of a solution purified from iron, for the formation of an ammonia complex of cobalt;
2. separation from the solution of Nickel as a result of the formation and allocation of ammonium sulfate salts of Nickel;
3. the conversion of ammonia of trivalent cobalt into compounds of a divalent metal and precipitation from a solution of cobalt with hydrogen.

 When the solution is oxidized with air in the presence of ammonia at elevated temperature and pressure, ammonia-sulfite complexes of cobalt and nickel are formed. After the solution is acidified to a pH of 2.6, the ammonium sulfate complex of trivalent cobalt remains in solution, and a similar complex of divalent nickel (the double sulfate salt of nickel and ammonium) precipitates. As a result, nickel is separated and an almost pure cobalt solution is obtained for subsequent precipitation of the latter with hydrogen in the form of a pure powder.

The oxidation is carried out in a horizontal stainless steel autoclave at a temperature of 71 ^o C and an overpressure of 7 at.

 As mentioned above, the main drawback of an electrolytic metal is the impossibility of obtaining pure cobalt.

 A known method of extracting cobalt from a material containing 10-40% chromium, 10-40% nickel, 5-20% iron, 20-60% tungsten and 0-1% silicon, the rest is cobalt, this material is dehydrated in hydrochloric acid and get a solution containing the entire amount of cobalt, as well as impurity amounts of chromium, nickel, iron, and insoluble material containing tungsten and silicon. The solution is separated from the insoluble material. A compound is added to the solution that produces oxalate in an amount sufficient to convert the entire amount of cobalt to cobalt oxalate. By alkalizing the solution treated with oxalate, the pH is adjusted to a value of 1.5 - 2.0 to form a first precipitate containing all cobalt in the form of cobalt oxalate and an admixture of nickel, and a first mother liquor containing all iron and chromium. The first precipitate is separated from the first mother liquor (US patent N 4594230, 10.06.1986 g).

 The disadvantages of this method are multi-stage and organic pollution of the product.

 Despite the improvements in consideration, the hydration scheme using hypochlorite or chlorine is a complex and cumbersome complex of processes associated with the use of inefficient equipment, high costs of manual labor and reduced metal recovery.

 The closest technical solution to the claimed by the achieved result is a method of separation and purification of metals from impurities by extraction.

 The essence of the method of extraction processing of cobalt-containing solutions is as follows. An aqueous solution containing mineral metal salts (chlorides or sulfates) is brought into contact with an organic liquid that is not miscible with water in extraction columns or box extractors.

 With the appropriate selection of the organic liquid and some additives, metals in the form of complex compounds pass into the organic phase.

 In order to isolate one metal from a solution containing impurities of other metals, it is necessary to select the conditions under which the distribution coefficient of the extracted metal would be greater than for impurity metals.

As extractants for metals present in nickel-cobalt solutions, fatty acids of the C ₇ -C ₉ to C ₁₀ -C ₁₃ fraction are used.

For cobalt production, it is more advantageous to use an acid of the C ₇ -C ₉ fraction, which is less viscous. Fatty acids, as well as their solutions in inert solvents, as a rule, do not extract metals. An intense transition of metals to the organic phase is observed when alkali is added to the solution. By changing the alkali consumption, one can choose the conditions under which all the metal is practically extracted.

 The extraction process proceeds successfully with the simultaneous presence of ions of several metals. If the aqueous solution of cobalt is treated with cobalt soap, then the solution will be cleaned of all metals less alkaline than cobalt, i.e. metals to the left of cobalt in the extraction row.

 The conversion of metal to the organic phase is one half of the process. The second half is the release of metal from this phase - re-extraction, i.e. returning the organic solvent back to the process. Isolation of cobalt from the organic solution is carried out by water (ibid., Pp. 2126-235).

 It is known to use various extractants to extract cobalt from a solution containing it and its impurities. So in US patent N 4882132 for extraction of cobalt from an aqueous solution, this solution is brought into contact at an equilibrium value of pH> 7 with a hydrocarbon solvent containing 1.2% N-alkyl alkanohydraxamic acid containing> 8 carbon atoms. The organic phase saturated with cobalt is separated and cobalt is recovered from it.

 A known method of separating Nickel and cobalt contained in sulfate solutions by extraction with a solvent - phosphonic or phosphinic acid to obtain a saturated organic solution. An organic solution saturated with cobalt is treated with aqueous sulfuric acid to regenerate the extractant and obtain a solution containing cobalt and nickel in the form of sulfates. Then this solution is treated with an organic extractant. For nickel, consisting of a non-chelating oxime with a possible content of di (2-ethyl) hexylphosphoric acid or alpha-bromlauric acid. The result is a raffinate with a Co / Ni ratio> 10,000 and a saturated organic solution containing nickel (US Patent No. 4,900,522, 02/13/90).

 From the above examples of the implementation of the extraction method, it follows that the extraction method for the separation of metals is very flexible. The process technology can be constructed in such a way that cobalt is separated from the main impurities in one step with the release of the sum of polluting elements, for example, iron, copper, nickel can be isolated in one solution by treating the salt solution with cobalt soap or another organic solvent. Pure solutions containing only iron, copper and nickel, i.e. sequential extraction operation.

Regardless of the selected conditions of the extraction method and the organic extractant, the following stages are common:
obtaining one of the known methods above, a solution containing cobalt and impurities:
bringing the resulting solution into contact with an organic solvent (it is possible before that to dilute the initial solution to a certain cobalt content in it) in the extractor;
separation of cobalt from impurities, as a result of which cobalt precipitates or remains in a saturated organic solution:
reextraction of organic extractant;
obtaining the target product is a cobalt compound.

 Common disadvantages of the extraction method are the need to use fairly sophisticated equipment, such as extractors; the complexity of the selection of extraction conditions and the presence of an additional operation - reextraction of the extractant.

 The technical problem solved by the proposed invention is the development of a method for the extraction of cobalt from cobalt-containing solutions without the use of sophisticated equipment with high selectivity and allowing to obtain the final high-quality pure products.

The technical result is achieved due to the fact that in the known method for the extraction of cobalt from cobalt-containing material, including the transfer of cobalt and its accompanying impurities into the solution, purification of the solution from impurities, subsequent filtration and precipitation of the cobalt compound, with further production of the finished product, changes were made, namely: purification of cobalt from impurities is carried out in a buffer medium containing bicarbonates and alkali metal carbonates in the presence of an oxidizing agent, such as hydrogen peroxide, at a pH of 7.8-9.4 and temperature re 15-30 ^o C.

 Using a buffer medium containing alkali metal bicarbonates and carbonates allows you to create the most favorable conditions for the preparation of a complex anion of cobalt tricarbonate in soluble form. When pH values are outside the stated range, the bulk of the cobalt passes into the precipitate, which makes it impossible to separate it from other metals.

The use of an excess of the oxidizing agent (H ₂ O ₂ ) is due to the need for the complete oxidation of bivalent cobalt to a trivalent state and the formation of a stable complex anion [Co (CO ₃ ) ₃ ] ^3- .

The range of acceptable pH values was chosen on the basis that, at pH> 9.4, the probability of formation of Co (OH) ³ hydroxide increases, and at a pH of less than 7.8, the concentration of carbonate ion (CO ₃ ^2- ) in the solution is small and the formation of green the precipitate is probably complexes of the type Co [Co (Co ³ ) ³ ] and Na ₃ [Co (Co ₃ ) ³ ] ^* 3H ₂ O in the crystalline state.

At a temperature of less than 15 ^o C, the oxidation of cobalt to trivalent occurs slowly, there remains a significant amount of cobalt (II).

At temperatures above 30 ^o C, the consumption of an oxidizing agent, for example, deficient hydrogen peroxide, increases, and at temperatures above 35 ^o C the carbonate complex begins to decompose with the formation of Co (OH) ³ due to an increase in the rate of hydrolysis.

 Maintaining the pH in the optimal (declared) range is carried out by changing the supply of soda ash.

 The implementation of the invention will consider the following examples.

 Example 1. As the source of cobalt-containing material, we take cobalt concentrate with the following average content of components, wt.% (In terms of dry matter): cobalt - 12.8, zinc - 6.83, copper - 0.85, sulfur (total. ) - 11.0, sodium - 0.04, potassium - 0.05, calcium - 0.1, nickel - 0.2, iron - 0.5, magnesium - 0.20, manganese - 0.10, cadmium - 0.005, lead - 0.01, HO - 32.3 (Zaire concentrate).

Under certain conditions, a solution containing (wt.%) Was obtained from the initial cobalt concentrate by a wave of extraction: cobalt — 3.32, zinc — 1.39, nickel — 0.04, and other impurities. The density of the solution is 1.136 g / cm ³ .

 Preparation of the buffer solution: 9 kg of sodium bicarbonate and 4.5 kg of sodium carbonate are loaded into a 400-liter device and 80 liters of industrial water are poured from the measuring device. The solution was stirred for 30 minutes, the pH of the resulting buffer system was 9.25 - 9.3.

39 kg of a solution of an aqueous extract of a concentrate of initial composition, i.e. 1.3 kg of cobalt and 0.543 kg of zinc are transferred to the measuring device, 10 l of hydrogen peroxide are poured there. Next, the resulting solution is fed into the buffer system with vigorous stirring, with a feed rate of 0.3 l / min. After feeding about a third of the solution, measure the pH and, if it is less than 8.6, start the parallel flow of sodium carbonate into the apparatus, maintaining a pH of 8.6-9.2. The temperature was 20-25 ^o C.

 At the end of the separation process, the system is stirred for 15 minutes and first filtered through a suction filter into an intermediate container, and then “fungus” into a 400-liter apparatus with a steam jacket.

The resulting solution of cobalt in a device with a steam jacket is heated to a temperature of 90 ^o C at a constant volume for 4 hours, checking the completeness of the destruction of the complex (the solution should be transparent) and left to sediment for 2-3 hours.

The settled mother liquor containing NaHCO ₃ , Na ₂ CO ₃ and NaSO _{4 is} siphoned into a 300-liter apparatus with a steam jacket, where it is evaporated 3 times in volume for reuse.

The precipitate in the apparatus after the destruction of the complex, which is cobalt hydroxide {Co (OH) ³ }, is washed three to four times with hot water to a mass fraction of sodium of not more than 0.07 g / l.

The pressed cobalt hydroxide paste is an intermediate for the preparation of cobalt compounds. The yield of Co (OH) ³ on a dry product was 1.86 kg.

The obtained cobalt hydroxide is used to produce various end products. For example, let a cobalt hydroxide paste from a suction filter be transferred to a steam jacket apparatus. Then 25 l of industrial water and 1 l of sulfuric acid with 94% concentration and about 1.0 l of hydrogen peroxide were fed into it. The solution was heated to 70-80 ^o C, continuing to mix until the cobalt (III) hydroxide was completely dissolved, and then evaporated to p 1.4 g / L. Next, the solution was crystallized by self-cooling. The precipitated crystals were pressed on a suction filter.

As a result, we obtained a product — cobalt (II) seven-water sulfate (CoSO ₄ • 7H ₂ O) of the following quality, table N1. The table for comparison shows the requirements for the quality of the finished product according to TU 6-09-3800-75.

 Thus, we can conclude that the quality of cobalt (II) seven-water sulfate obtained from cobalt (III) hydroxide by the method according to the invention is higher than by known methods.

 As a result of the proposed separation method, the Co / Zn ratio changed from 2.4 / 1 in the initial concentrate to 200: 1 in the final product.

 Other examples of the implementation of the invention, justifying the optimality of the selected parameters are shown in table N 2.

 In order to be able to compare the results obtained, the composition of the initial solutions in Examples 1-6 was the same.

 An analysis of the results obtained in these examples confirms the correctness of the selected parameters of the buffer system.

So in example 2, the temperature of the buffer medium is less optimal and amounted to 13 ^o C. As a result, the cobalt yield was only 47%. This is due to the fact that the process of oxidation of cobalt (II) to cobalt (III) occurs very slowly and part of the cobalt did not oxidize, but precipitated with other metals.

In example 4, on the contrary, the temperature when the cobalt-containing solution was fed into the buffer was higher than optimal and amounted to> 35 ^o C. The cobalt yield was 60%. This is explained by the fact that, as the temperature rises, the hydrolysis process increases and part of the formed Co (OH) ³ precipitates with other metals, i.e., cobalt is lost or its additional extraction is required.

 In Example 5, the pH at the stage of mixing the cobalt-containing solution with the buffer solution is slightly higher than the declared value and amounted to 9.5-9.7, then the cobalt yield will be only 44%. The reason is the formation of cobalt oxide hydrate and its precipitation.

At a pH lower than declared, for example, 7.5-7.8, the cobalt yield is very small - 27%. Cobalt losses are caused by the formation of complexes of the form: Co [Co (Co ₃ ) ₃ ] ^* 3H ₂ O and Na ₃ [Co (Co) ₃ ] ^* 3H ₂ O in crystalline form.

 Examples 7 and 8 show that the most appropriate use of the proposed method for the separation of cobalt is achieved when its content in the initial solution is not more than 5 wt.%. So, in example 7, it exceeded this value and amounted to 5.5 wt.%. The output of cobalt was 60%.

 In example 8, the initial solution was taken very diluted, but despite good quality indicators, this option is not optimal, since low productivity per unit of equipment is obtained.

 In the case of obtaining a solution with a cobalt content of more than 5.0 wt.%, They must first be diluted, but so that the cobalt content is within 2-5 wt.%.

 Example 3 is somewhat different from example 1 in some parameters (temperature and pH value). The output of cobalt is 85%.

 In example 1, the implementation of the proposed invention was brought to obtain the final product - cobalt (II) sulfate heptahydrate. We show in example 3 the production of cobalt oxide.

As in example 1, the precipitate formed after the destruction of the buffer medium and representing CO (OH) ³ , washed three to four times with hot water until the sodium content in the wash water is not more than 0.07 g / L. The last water is siphoned from the apparatus, leaving ~ 25 L of water. Mixing is turned on and the pulp is transferred to a suction filter. The pressed cobalt hydroxide paste is an intermediate for the preparation of cobalt compounds (the yield of Co (OH) ³ in terms of dry product was 1.92 kg).

When calcining at a temperature of 350 ^o C, cobalt (III) hydroxide is converted to cobalt oxide (Co ₃ O ₄ ). Given that at such a calcination temperature the ratio of metals in cobalt hydroxide and oxide does not change, theoretically the product has the following quality indicators, shown in table 3. For comparison, the table shows the quality requirements for pure cobalt oxide according to GOST 4467-70.

 Comparison of the quality of the obtained product according to the proposed invention and obtained by the prototype (extraction method) are almost the same. The extraction of cobalt from the initial solution can be any and depends only on the frequency of contacting it with a buffer medium (invention) or with an extractant (extraction). The extraction method has an advantage in cobalt extraction time, but in terms of hardware design it is much more complicated.

 The advantages of the proposed invention are selectivity, the absence of toxic organic reagents, allow you to create an environmentally friendly and simple process, almost safe.

 Implementation of the alleged invention will be carried out at the factory "Red chemist".

Claims (1)

A method for separating cobalt from a cobalt-containing material, including converting cobalt and related impurities into a solution, purifying the solution from impurities, subsequent filtering and precipitating cobalt compounds, characterized in that the cobalt is purified from impurities in a buffer medium containing alkali metal bicarbonates and carbonates in the presence of an oxidizing agent, at a pH of 7.8 - 9.4 and a temperature of 15 - 30 ^o C.

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