Nickel recovery methods

Abstract

To provide a recovery method that can recover nickel from raw material powder containing nickel and copper with high efficiency while suppressing copper contamination, without using solvent extraction methods. [Solution] A recovery method for recovering nickel from a raw material powder containing 5% by mass or more nickel and copper, comprising: a dissolution step of dissolving the raw material powder to obtain an aqueous solution containing nickel and copper; a mixing step of mixing the aqueous solution containing nickel and copper with a water-soluble pyrophosphate compound to obtain a mixed slurry; and a solid-liquid separation step of separating the mixed slurry into solid and liquid to obtain an aqueous solution containing nickel.

Description

Technical Field

[0001] The present invention relates to a recovery method for recovering nickel from a raw material powder containing nickel and copper.

Background Art

[0002] In recent years, recycling of valuable materials such as nickel from powders obtained by crushing and incinerating lithium-ion secondary batteries and the like, which contain such valuable materials, has attracted attention.

[0003] Patent Document 1 describes a method for purifying a nickel sulfate solution, in which Fe 2+ , Cu 2+ , Zn 2+ An aqueous nickel sulfate solution containing these elements is subjected to oxidation treatment to convert Fe 2+ to Fe 3+ , then an alkaline substance is added to adjust the pH to 4 to 6 to remove Fe 3+ as a ferric hydroxide precipitate, and subsequently, an inert organic solvent containing a nickel salt of an organic phosphoric acid or a nickel salt of an organic carboxylic acid is added to extract and remove Cu 2+ and Zn 2+ , thus describing a purification method by the so-called solvent extraction method.

[0004] Further, Patent Document 2 describes a recovery method using a solvent extraction method as a method for efficiently separating valuable metals Co, Ni, Li, Mn and impurities Al, Fe, Zn, Cu in the recycling of lithium-ion batteries, and recovering the valuable metals with high purity and high efficiency.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of Invention

[0006] The solvent extraction methods described in Patent Documents 1 and 2 have disadvantages such as requiring special solvents, which are costly, and requiring costly and energy-intensive disposal of the solvents after use. Therefore, there is a need for nickel recovery methods that do not use solvent extraction. Therefore, after diligent research by the inventors, we discovered that by adopting a method that includes a step of mixing an aqueous solution containing nickel and copper with a water-soluble pyrophosphate compound, it is possible to maintain a high nickel recovery rate while reducing copper contamination without using solvent extraction, thus completing the present invention.

[0007] The present invention aims to solve the aforementioned problems in the conventional approach and achieve the following objectives. Specifically, the present invention aims to provide a recovery method that can recover nickel from raw material powder containing nickel and copper with high efficiency while suppressing the inclusion of copper, without using solvent extraction. [Means for solving the problem]

[0008] As a result of diligent research conducted by the inventors to achieve the above objective, they have discovered that it is possible to provide a recovery method that can recover nickel from raw material powders containing nickel and copper with high efficiency while suppressing the inclusion of copper, without using solvent extraction methods.

[0009] The present invention is based on the aforementioned findings by the inventors, and the means for solving the aforementioned problems are as follows: <1> A recovery method for recovering nickel from a raw material powder containing 5% by mass or more nickel and copper, A dissolution step to dissolve the raw material powder to obtain an aqueous solution containing nickel and copper, A mixing step of mixing an aqueous solution containing nickel and copper with a water-soluble pyrophosphate compound to obtain a mixed slurry, The recovery method is characterized by comprising a solid-liquid separation step of the mixed slurry to obtain an aqueous solution containing nickel. <2> The amount of the water-soluble pyrophosphate compound mixed is set to be 0.2 or more in molar ratio to the amount of copper contained in the raw material powder. <1> This is the collection method described in [the relevant document]. <3> Before the mixing step, the pH of the aqueous solution containing nickel and copper is adjusted to 2.0 or higher. <1> This is the collection method described in [the relevant document]. <4> The raw material powder contains at least one of iron and zinc, and in the mixing step, a water-soluble phosphate compound is further mixed, <1> This is the collection method described in [the relevant document]. <5> The amount of the water-soluble phosphoric acid compound mixed is set to be 1.0 or more in molar ratio to the total amount of iron and zinc contained in the raw material powder. <4> This is the collection method described in [the relevant document]. <6> The raw material powder contains iron, and the oxidation-reduction potential of the mixed slurry obtained in the mixing step is adjusted to be between -100mV and 1000mV, based on the silver-silver chloride electrode. <4> This is the collection method described in [the relevant document]. <7> The process includes a neutralization step in which the pH of the nickel-containing aqueous solution is adjusted to 7.0 or higher and 10.0 or lower, followed by solid-liquid separation and washing of the solid components to obtain nickel hydroxide. <1> This is the collection method described in [the relevant document]. <8> A nickel hydroxide dissolution step is performed by mixing the nickel hydroxide and the acid, followed by solid-liquid separation to obtain a nickel hydroxide solution. The crystallization step includes a step in which a nickel salt is precipitated from the nickel hydroxide solution obtained in the nickel hydroxide dissolution step, and then solid-liquid separation is performed to obtain the nickel salt, <7> This is the collection method described in [the relevant document]. <9> The raw material powder contains a water-soluble nickel salt, <1> This is the collection method described in [the relevant document]. <10> The proportion of nickel in the total metal components of the raw material powder is 80% by mass or more. <1> This is the collection method described in [the relevant document]. <11> The cobalt content of the raw material powder is 5% by mass or less. <1> This is the collection method described in [the relevant document]. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a recovery method that can recover nickel with high efficiency from raw material powder containing nickel and copper while suppressing copper contamination, without using a solvent extraction method. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] [Figure 1] Figure 1 is a diagram showing an example of the flow of the recovery method of the present invention. DETAILED DESCRIPTION OF EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0012] (Recovery Method) The recovery method is a method for recovering nickel from raw material powder containing nickel and copper. The recovery method includes a dissolution step, a mixing step, and a solid-liquid separation step, and may further include other steps.

[0013] -Dissolution Step- The dissolution step is a step of dissolving the raw material powder to obtain an aqueous solution containing nickel and copper.

[0014] --Raw Material Powder-- The raw material powder is not particularly limited as long as it contains nickel and copper, and can be appropriately selected according to the purpose, and those containing a water-soluble nickel salt are preferred. The water-soluble nickel salt is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include nickel sulfate, nickel nitrate, nickel chloride, and hydrates thereof. The raw material powder may further contain manganese, lithium, iron, aluminum, zinc, magnesium, and the like. Among these, those further containing iron, or those containing at least one of iron and zinc are preferable.

[0015] As for the lower limit of nickel content in the raw material powder, there are no particular restrictions as long as it is 5% by mass or more, and it can be appropriately selected depending on the purpose, but 10% by mass or more is preferred, 15% by mass or more is more preferred, 18% by mass or more is even more preferred, and 20% by mass or more is particularly preferred. There are no particular restrictions on the upper limit of the nickel content in the raw material powder, and it can be appropriately selected depending on the purpose, but it is preferably 80% by mass or less, more preferably 50% by mass or less, and even more preferably 30% by mass or less. Furthermore, a range of values ​​where one of the values ​​indicated as the lower limit and one of the values ​​indicated as the upper limit are used as the preferred range. Among these, 5% by mass or more and 80% by mass or less is preferred, 10% by mass or more and 50% by mass or less is more preferred, 15% by mass or more and 50% by mass or less is even more preferred, 18% by mass or more and 30% by mass or less is particularly preferred, and 20% by mass or more and 30% by mass or less is most preferred.

[0016] There are no particular restrictions on the copper content in the raw material powder, and it can be appropriately selected depending on the purpose, but it is preferably 10% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0.01% by mass or less.

[0017] There are no particular restrictions on the cobalt content in the raw material powder, and it can be appropriately selected depending on the purpose, but it is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 1% by mass or less, and most preferably 0.1% by mass or less.

[0018] There are no particular restrictions on the iron content in the raw material powder, and it can be appropriately selected depending on the purpose, but it is preferably 10% by mass or less, more preferably 1% by mass or less, even more preferably 0.4% by mass or less, and particularly preferably 0.1% by mass or less.

[0019] There are no particular restrictions on the zinc content in the raw material powder, and it can be appropriately selected depending on the purpose, but it is preferably 10% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0.05% by mass or less.

[0020] There are no particular restrictions on the magnesium content in the raw material powder, and it can be appropriately selected depending on the purpose, but it is preferably 10% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0.05% by mass or less.

[0021] There are no particular restrictions on the nickel content (percentage) in the total metal components of the raw material powder, and it can be appropriately selected depending on the purpose, but 50% by mass or more is preferred, 70% by mass or more is more preferred, 80% by mass or more is even more preferred, 90% by mass or more is particularly preferred, and 95% by mass or more is most preferred.

[0022] There are no particular limitations on the method for obtaining the aqueous solution containing nickel and copper, and a suitable method can be selected depending on the purpose. For example, a method of mixing the raw material powder with water can be used.

[0023] There are no particular restrictions on the water mentioned above, and it can be appropriately selected depending on the purpose. Examples include pure water such as industrial water, tap water, ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, as well as ultrapure water. Among these, ion-exchanged water is preferred because it has relatively low manufacturing costs and relatively low impurity concentrations.

[0024] There are no particular restrictions on the amount of water, and it can be appropriately selected depending on the purpose, but it is preferably 100g to 1000g per 100g of raw material powder, more preferably 200g to 800g, and even more preferably 300g to 500g.

[0025] The raw material powder may also be a powder containing metallic nickel or nickel oxide and copper obtained by incinerating and crushing waste lithium-ion batteries. If the raw material powder is a powder containing metallic nickel or nickel oxide and copper, an aqueous solution containing nickel and copper can be obtained by dissolving the raw material powder in water using an acid such as sulfuric acid or nitric acid, and, depending on the type of raw material powder, an oxidizing agent such as air or sodium hypochlorite as needed, and heating as necessary. Here, the aqueous solution containing nickel and copper may contain 30% by mass or less of solids in the liquid.

[0026] -Mixing process- The mixing step involves mixing an aqueous solution containing nickel and copper with a water-soluble pyrophosphate compound to obtain a mixed slurry.

[0027] --Water-soluble pyrophosphate compound-- The aforementioned water-soluble pyrophosphate compound is not particularly limited as long as it is water-soluble and can be appropriately selected depending on the purpose. For example, pyrophosphate (H4P2O7), sodium pyrophosphate (Na4P2O7), monohydrogen pyrophosphate (Na3HP2O7), dihydrogen pyrophosphate (Na2H2P2O7), trihydrogen pyrophosphate (NaH3P2O7), potassium pyrophosphate (K4P2O7), monohydrogen pyrophosphate (K3HP2O7), dihydrogen pyrophosphate (K2H2P2O7), pyrophosphate Examples include potassium trihydrogen pyrophosphate (KH3P2O7), lithium pyrophosphate (Li4P2O7), lithium monohydrogen pyrophosphate (Li3HP2O7), lithium dihydrogen pyrophosphate (Li2H2P2O7), lithium trihydrogen pyrophosphate (LiH3P2O7), ammonium pyrophosphate ((NH4)4P2O7), ammonium monohydrogen pyrophosphate ((NH4)3HP2O7), ammonium dihydrogen pyrophosphate ((NH4)2H2P2O7), ammonium trihydrogen pyrophosphate (NH4H3P2O7), and their hydrates. Among these, those that do not contain ammonium ions are preferred in order to prevent the formation of complexes between cobalt and nickel and ammonia, which can make recovery difficult. Sodium pyrophosphate (Na4P2O7), potassium pyrophosphate (K4P2O7), or their hydrates are even more preferred as they are readily available.

[0028] There are no particular restrictions on the lower limit of the amount of the water-soluble pyrophosphate compound, and it can be appropriately selected depending on the purpose. However, in terms of suppressing copper contamination, a molar amount of 0.01 times or more the total molar amount of copper in the raw material powder is preferred, more preferably 0.05 times or more, even more preferably 0.1 times or more, even more preferably 0.2 times or more, particularly preferred, and most preferably 0.4 times or more the total molar amount of copper in the raw material powder. There is no particular upper limit to the amount of the pyrophosphate compound, and it can be appropriately selected depending on the purpose. However, from the viewpoint of suppressing the drug cost of the pyrophosphate compound, it is preferable that the amount is 10 times or less the total amount of copper in the raw material powder, more preferably 5 times or less, even more preferably 3 times or less, and particularly preferably 2 times or less. Furthermore, a range of values ​​where one of the values ​​indicated as the lower limit and one of the values ​​indicated as the upper limit are used as the preferred range. Among these, a molar amount of 0.01 to 10 times is preferred, a molar amount of 0.05 to 5 times is more preferred, a molar amount of 0.1 to 3 times is even more preferred, a molar amount of 0.2 to 2 times is particularly preferred, and a molar amount of 0.5 to 2 times is most preferred.

[0029] It is preferable to adjust the pH of the acid leachate obtained in the acid leaching step before the mixing step (before adding the water-soluble pyrophosphate compound).

[0030] There are no particular restrictions on the lower limit of the pH before the mixing step (before the addition of the water-soluble pyrophosphate compound), and it can be appropriately selected depending on the purpose. However, in terms of suppressing the decomposition of pyrophosphate, a pH of 1.0 or higher is preferred, 2.0 or higher is more preferred, 3.0 or higher is even more preferred, 3.5 or higher is particularly preferred, and 4.0 or higher is most preferred. If the pH is low and pyrophosphate decomposes, it becomes necessary to add a larger amount of pyrophosphate compound to prevent a decrease in copper removal efficiency, which leads to increased costs and is therefore undesirable. There are no particular restrictions on the upper limit of the pH before the mixing step (before the addition of the water-soluble pyrophosphate compound), and it can be appropriately selected depending on the purpose. However, in terms of maintaining the dissolution of nickel and cobalt, a pH of 10.0 or less is preferred, 7.0 or less is more preferred, 6.0 or less is even more preferred, 5.0 or less is particularly preferred, and 4.5 or less is most preferred. Furthermore, a range of values ​​where one of the values ​​indicated as the lower limit and one of the values ​​indicated as the upper limit are used as the preferred range. Among these, values ​​of 1.0 to 10.0 are preferred, values ​​of 2.0 to 7.0 are more preferred, values ​​of 3.0 to 6.0 are even more preferred, values ​​of 3.5 to 5.0 are particularly preferred, and values ​​of 4.0 to 4.5 are most preferred.

[0031] It is preferable to adjust the pH of the mixed slurry obtained at the end of the mixing step.

[0032] There are no particular restrictions on the lower limit of the pH of the pyrophosphate mixture obtained at the end of the pyrophosphate addition step, and it can be appropriately selected depending on the purpose. However, from the viewpoint of reducing the residual aluminum content, a pH of 2.0 or higher is preferred, 3.0 or higher is more preferred, and 4.0 or higher is most preferred. There are no particular restrictions on the upper limit of the pH of the pyrophosphate mixture obtained at the end of the pyrophosphate addition step, and it can be appropriately selected depending on the purpose. However, from the viewpoint of reducing the residual aluminum content, a pH of 7.0 or less is preferred, 6.0 or less is more preferred, and 5.5 or less is most preferred. Furthermore, a range of values ​​where one of the values ​​indicated as the lower limit and one of the values ​​indicated as the upper limit are used as the preferred range. Among these, a value of 2.0 to 7.0 is preferred, 3.0 to 6.0 is more preferred, and 4.0 to 5.5 is most preferred.

[0033] If the raw material powder contains iron, it is particularly preferable to adjust the oxidation-reduction potential (ORP) of the mixed slurry obtained at the end of the mixing step.

[0034] The oxidation-reduction potential (ORP) of the mixed slurry obtained at the end of the mixing step, measured relative to the silver-silver chloride electrode, is not particularly limited and can be appropriately selected depending on the purpose. However, in terms of suppressing the inclusion of iron, an ORP of -100mV to 1000mV is preferred, 100mV to 900mV is more preferred, and 300mV to 800mV is even more preferred.

[0035] There are no particular limitations on the means used to adjust the pH and oxidation-reduction potential (ORP) before the mixing step (before the addition of the water-soluble pyrophosphate compound) and at the end of the water-soluble pyrophosphate addition step, and these can be appropriately selected depending on the purpose. Examples include adding an alkali or acid to adjust the pH, and adding an oxidizing agent to adjust the ORP.

[0036] There are no particular restrictions on the alkali, and it can be appropriately selected depending on the purpose. For example, caustic soda (sodium hydroxide) can be used. An oxidizing agent containing alkali, such as sodium hypochlorite, may also be used.

[0037] When the added caustic soda is in solution form, there are no particular restrictions on its concentration, and it can be appropriately selected depending on the purpose. However, a concentration of 10% to 70% by mass is preferred, 20% to 60% by mass is preferred, and 20% to 50% by mass is even more preferred.

[0038] The acid is not particularly limited and can be appropriately selected depending on the purpose; for example, sulfuric acid is an example.

[0039] There are no particular restrictions on the oxidizing agent, and it can be appropriately selected depending on the purpose, but sodium hypochlorite or hydrogen peroxide are preferred in terms of efficiently recovering nickel. An oxidizing gas can also be used as the oxidizing agent. There are no particular restrictions on the oxidizing gas, and it can be appropriately selected depending on the purpose, for example, air or oxygen.

[0040] There are no particular restrictions on the concentration of the sodium hypochlorite, and it can be appropriately selected depending on the purpose. However, in terms of efficiently recovering nickel, a concentration of 5% to 30% by mass is preferred, 10% to 20% by mass is preferred, and 11% to 15% by mass is even more preferred.

[0041] In adjusting the pH and oxidation-reduction potential (ORP) of the pyrophosphate mixture obtained at the end of the mixing step, the timing of adding alkali, acid and oxidizing agent is not particularly limited as long as the pH and oxidation-reduction potential (ORP) of the pyrophosphate mixture obtained at the end of the pyrophosphate addition step are within the desired range, and may be done before or after mixing the water-soluble pyrophosphate compound.

[0042] If the raw material powder contains at least one of iron and zinc, it is preferable to further mix in a water-soluble phosphate compound in the mixing step.

[0043] --Water-soluble phosphoric acid compounds-- The aforementioned water-soluble phosphate compounds are not particularly limited and can be appropriately selected depending on the purpose. Examples include phosphoric acid (H3PO4), sodium phosphate (Na3PO4), monosodium hydrogen phosphate (Na2HPO4), dihydrogen dihydrogen phosphate (NaH2PO4), potassium phosphate (K3PO4), monosodium hydrogen phosphate (K2HPO4), dihydrogen dihydrogen phosphate (KH2PO4), lithium phosphate (Li3PO4), monosodium hydrogen phosphate (Li2HPO4), dihydrogen dihydrogen phosphate (LiH2PO4), ammonium phosphate ((NH4)3PO4), monosodium hydrogen phosphate ((NH4)2HPO4), and dihydrogen dihydrogen phosphate ((NH4)H2PO4).

[0044] There are no particular restrictions on the lower limit of the amount (mixing amount) of the water-soluble phosphoric acid compound, and it can be appropriately selected depending on the purpose. However, in terms of suppressing the inclusion of iron or zinc, a molar amount of 0.1 times or more, more preferably 0.5 times or more, even more preferably 1.0 times or more, particularly preferably 1.5 times or more, and most preferably 1.7 times or more, relative to the total molar amount of iron and zinc in the raw material powder. There is no particular upper limit to the amount of the water-soluble phosphoric acid compound, and it can be appropriately selected depending on the purpose. However, in terms of suppressing the drug cost of the water-soluble phosphoric acid compound, it is preferable that the amount be 10 times or less the total amount of impurity metals other than valuable metals including nickel in the raw material powder, more preferably 5 times or less the total amount of impurity metals other than nickel, and even more preferably 3 times or less the total amount of impurity metals other than nickel. Furthermore, a range of values ​​where one of the values ​​indicated as the lower limit and one of the values ​​indicated as the upper limit are used as the preferred range. Among these, a molar amount of 0.1 to 10 times is preferred, a molar amount of 0.5 to 5 times is more preferred, a molar amount of 1 to 3 times is even more preferred, a molar amount of 1.5 to 3 times is particularly preferred, and a molar amount of 1.7 to 3 times is most preferred.

[0045] There are no particular restrictions on the concentration of the water-soluble phosphoric acid compound to be mixed, and it can be appropriately selected depending on the purpose, but 50% by mass or more and 95% by mass or less is preferred, 70% by mass or more and 95% by mass or less is preferred, and 80% by mass or more and 90% by mass or less is more preferred. In this specification, "phosphoric acid" refers to orthophosphoric acid (H3PO4) and does not include pyrophosphoric acid (H4P2O7). Furthermore, "water-soluble phosphoric acid compound" refers to water-soluble orthophosphoric acid compound and does not include water-soluble pyrophosphoric acid compound.

[0046] -Solid-liquid separation process- The solid-liquid separation step is a step of separating the mixed slurry into solid and liquid components to obtain an aqueous solution containing nickel.

[0047] There are no particular restrictions on the method of solid-liquid separation, and it can be appropriately selected depending on the purpose, for example, filtration.

[0048] -Other processes- The aforementioned other steps are not particularly limited and can be appropriately selected depending on the purpose. Examples include a neutralization step, a nickel hydroxide dissolution step, and a crystallization step. The recovery method of the present invention can be implemented without including a solvent extraction step. In the present invention, nickel can be recovered with high efficiency from raw material powder containing nickel and copper, while suppressing the inclusion of copper, without using solvent extraction, which has high equipment costs due to explosion-proof equipment and solvent costs during operation.

[0049] --Neutralization process-- The neutralization step involves adjusting the pH of the nickel-containing aqueous solution to 7.0 or higher and 10.0 or lower, followed by solid-liquid separation and washing of the solid components to obtain nickel hydroxide. By raising the pH of the nickel-containing aqueous solution to 7.0 or higher, the recovery rate of nickel can be increased, and by raising the pH of the nickel-containing aqueous solution to 10.0 or lower, the removal rate of magnesium can be increased.

[0050] In the neutralization step, the pH of the nickel-containing aqueous solution after adjustment is not particularly limited as long as it is between 7.0 and 10.0, and can be appropriately selected depending on the purpose. However, a pH of 7.0 to 9.0 is preferred, 7.5 to 9.0 is more preferred, and 8.0 to 9.0 is even more preferred.

[0051] In the neutralization step, there are no particular restrictions on the means used to adjust the pH, and they can be appropriately selected depending on the purpose, but examples include adding alkali.

[0052] There are no particular restrictions on the alkali, and it can be appropriately selected depending on the purpose. For example, caustic soda (sodium hydroxide) can be used.

[0053] --Nickel hydroxide dissolution process-- The nickel hydroxide dissolution step involves mixing the nickel hydroxide with an acid, then separating the solid and liquid components to obtain a nickel hydroxide solution.

[0054] The acid is not particularly limited and can be appropriately selected depending on the purpose, but sulfuric acid is preferred.

[0055] There are no particular restrictions on the concentration of the sulfuric acid to be mixed, and it can be appropriately selected depending on the purpose, but it is preferably 5% by mass or more and 99% by mass or less, preferably 50% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 99% by mass or less.

[0056] There are no particular restrictions on the method of solid-liquid separation, and it can be appropriately selected depending on the purpose, for example, filtration.

[0057] --Crystallization process-- The crystallization step involves precipitating a nickel salt from the nickel hydroxide solution obtained in the nickel hydroxide dissolution step, followed by solid-liquid separation to obtain the nickel salt. As for the nickel salt, if sulfuric acid is used as the acid in the nickel hydroxide dissolution step, nickel sulfate or its hydrate can be obtained; if nitric acid is used as the acid, nickel nitrate or its hydrate can be obtained; and if hydrochloric acid is used as the acid, nickel chloride or its hydrate can be obtained.

[0058] There are no particular restrictions on the precipitation method, and it can be appropriately selected depending on the purpose. Examples include heating the nickel hydroxide solution obtained in the nickel hydroxide dissolution step to evaporate the water (concentration), or cooling the solution.

[0059] There are no particular restrictions on the method of solid-liquid separation, and it can be appropriately selected depending on the purpose, for example, filtration. [Examples]

[0060] The following describes embodiments of the present invention, but the present invention is not limited in any way to these embodiments.

[0061] <Nickel recovery> Nickel was recovered from the raw material powder according to the flow shown in Figure 1. From the dissolution step to the mixing step, and from the neutralization step to the nickel hydroxide dissolution step, the temperature of the aqueous solution and slurry was maintained at 40°C, except during solid-liquid separation, and the aqueous solution and slurry were stirred with a stirrer.

[0062] (Example 1) -Dissolution process- 180 g of nickel sulfate hexahydrate containing copper as an impurity was mixed with 600 g of pure water to obtain an aqueous solution containing nickel and copper.

[0063] Using an ICP emission spectrometer (ICP-OES), the grade (content) of nickel and impurities in the nickel sulfate hexahydrate was analyzed and found to be 21.7 mass% nickel, 0.044 mass% cobalt, 0.094 mass% iron, 0.023 mass% zinc, 0.005 mass% copper, and 0.026 mass% magnesium. The proportion of nickel in the total metal components was 99 mass%.

[0064] -Mixing process- To the aqueous solution containing nickel and copper obtained in the dissolution step, 85% by mass phosphoric acid, containing 1.9 times the molar amount of phosphoric acid relative to the total molar amount of iron and zinc contained in the nickel sulfate hexahydrate, was added, and then held for 10 minutes to obtain a slurry. Next, sodium hypochlorite (effective chlorine concentration 12%, manufactured by Kanto Denka Kogyo Co., Ltd.) was added to the obtained slurry as an oxidizing agent until the slurry's ORP reached 600 mV. Furthermore, a 24% by mass aqueous solution of caustic soda was added until the slurry's pH reached 4.0.

[0065] Next, a molar amount of sodium pyrophosphate decahydrate was added in an amount equal to 1.1 times the molar amount of copper contained in the nickel sulfate hexahydrate. Next, a 24% by mass aqueous solution of caustic soda was added to the slurry so that its pH was 5.0. Subsequently, sodium hypochlorite and a 24% by mass aqueous solution of caustic soda were added as appropriate so that the slurry's pH was between 4.8 and 5.3, and its ORP was between 300 mV and 800 mV. The pH and ORP of the slurry were maintained within the above ranges for 120 minutes from the start of adding sodium hypochlorite or the 24% by mass aqueous solution of caustic soda to obtain a mixed slurry.

[0066] The potential of the obtained mixed slurry, measured relative to a silver-silver chloride electrode, was 614 mV. pH and oxidation-reduction potential (ORP) were measured using a pH / ORP meter (Horiba, Ltd., F-73) (the same method was used in the following examples and comparative examples).

[0067] -Solid-liquid separation process- The mixed slurry obtained in the above mixing step was filtered to recover the nickel-containing aqueous solution. The composition (concentrations of various metals) of the recovered aqueous solution was measured using an ICP emission spectrometer (ICP-OES). The measurement results for the concentrations of nickel and impurity elements are shown in Table 1.

[0068] [Table 1]

[0069] (Example 2) The nickel-containing aqueous solution was recovered in the same manner as in Example 1, except that in the mixing step, a molar amount of phosphoric acid equivalent to 2.9 times the total molar amount of iron and zinc contained in nickel sulfate hexahydrate was added, and the composition was measured by ICP-OES. The results are shown in Table 1.

[0070] (Example 3) In the mixing process, an aqueous solution containing nickel was recovered in the same manner as in Example 1, except that 2.9 times the molar amount of phosphoric acid was added relative to the total molar amount of iron and zinc contained in nickel sulfate hexahydrate, and 1.7 times the molar amount of sodium pyrophosphate decahydrate was added relative to the molar amount of copper contained in nickel sulfate hexahydrate. The composition was then measured by ICP-OES. The results are shown in Table 1.

[0071] (Example 4) The nickel-containing aqueous solution was recovered in the same manner as in Example 1, except that in the mixing step, 4.8 times the molar amount of phosphoric acid relative to the total molar amount of iron and zinc contained in nickel sulfate hexahydrate was added, and the composition was measured by ICP-OES. The results are shown in Table 1.

[0072] (Example 5) In the mixing process, instead of adding sodium hypochlorite, phosphoric acid was added and held for 10 minutes, after which air was blown in at a flow rate of 0.5 L / min until a mixed slurry was obtained. Otherwise, the nickel-containing aqueous solution was recovered in the same manner as in Example 4, and its composition was measured by ICP-OES. The results are shown in Table 1.

[0073] (Comparative Example 1) In the mixing process, an aqueous solution containing nickel was recovered in the same manner as in Example 1, except that 1.0 times the molar amount of phosphoric acid relative to the total molar amount of iron and zinc contained in nickel sulfate hexahydrate was added, and sodium pyrophosphate decahydrate was not added. The composition was then measured by ICP-OES. The results are shown in Table 1.

[0074] (Example 2-1) -Neutralization process- In Example 2, a 24% by mass aqueous solution of caustic soda was added to the nickel-containing aqueous solution obtained, so that the pH became 8.6. Subsequently, 24% by mass aqueous solution of caustic soda was added as needed to maintain the pH between 8.4 and 8.9, and the pH of the slurry was maintained within the above range for 60 minutes from the start of adding the 24% by mass aqueous solution of caustic soda, to obtain a slurry containing nickel hydroxide with a pH of 8.6. The obtained slurry containing nickel hydroxide was filtered through a Buchner funnel, and the resulting solid was washed with pure water until the conductivity of the liquid after water passage was 10 mS / m or less to obtain nickel hydroxide.

[0075] The composition of the obtained nickel hydroxide was measured using an ICP emission spectrometer (ICP-OES). The measured concentrations of nickel and impurities in the nickel hydroxide are shown in Table 2.

[0076] -Nickel hydroxide dissolution process- To 80 g of nickel hydroxide obtained in the neutralization step described above, 47% by mass sulfuric acid (prepared using 98% by mass sulfuric acid manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as an acid so that the pH of the slurry after mixing would be 5.8. Subsequently, 47% by mass sulfuric acid was added as needed to bring the pH between 5.5 and 6.0, and the pH of the slurry was maintained within the above range for 5 hours from the start of the addition of 47% by mass sulfuric acid to obtain the slurry. The pH of the obtained slurry was 5.8. Next, the obtained slurry was filtered to recover the nickel hydroxide solution.

[0077] -Concentration / crystallization process- The nickel hydroxide solution obtained in the nickel hydroxide dissolution step was heated and concentrated at 110°C for 3 hours to obtain a concentrated solution with a mass ratio of 0.56. Next, the temperature of the obtained concentrated solution was lowered to room temperature and cooled to 4°C. Then, the cooled solution was filtered to obtain the nickel salt.

[0078] The chemical composition of the obtained nickel salt was measured using an ICP emission spectrometer (ICP-OES), and it was found to contain 22.5% nickel by mass, 0.040% cobalt by mass, less than 0.001% iron by mass, less than 0.001% zinc by mass, less than 0.001% copper by mass, and 0.005% magnesium by mass.

[0079] [Table 2]

[0080] (Example 2-2) Nickel hydroxide was obtained in the same manner as in Example 2-1, except that a 24% by mass aqueous solution of caustic soda was added to the nickel-containing aqueous solution obtained in Example 2 so that the pH became 9.2, and then 24% by mass aqueous solution of caustic soda was added as needed so that the pH was between 9.0 and 9.5, and the pH of the slurry was maintained within the above range for 60 minutes from the start of adding the 24% by mass aqueous solution of caustic soda to obtain a slurry containing nickel hydroxide with a pH of 9.2. The composition of the obtained nickel hydroxide was measured using an ICP emission spectrometer (ICP-OES). The results are shown in Table 2.

[0081] (Example 4-1) Nickel hydroxide was obtained in the same procedure as in Example 2-1, except that a 24% by mass aqueous solution of caustic soda was added to the nickel-containing aqueous solution obtained in Example 4 so that the pH became 8.2, and then 24% by mass aqueous solution of caustic soda was added as needed so that the pH was between 8.0 and 8.5, and the pH of the slurry was maintained within the above range for 60 minutes from the start of adding the 24% by mass aqueous solution of caustic soda to obtain a slurry containing nickel hydroxide with a pH of 8.2. The composition of the obtained nickel hydroxide was measured using an ICP emission spectrometer (ICP-OES) and found to be 50.6 mass% nickel, 0.09 mass% cobalt, less than 0.001 mass% iron, less than 0.001 mass% zinc, less than 0.001 mass% copper, and 0.010 mass% magnesium.

[0082] (Example 5-1) Nickel hydroxide was obtained in the same manner as in Example 2-1, except that a 24% by mass aqueous solution of caustic soda was added to the nickel-containing aqueous solution obtained in Example 5 so that the pH became 8.0, and then 24% by mass aqueous solution of caustic soda was added as needed so that the pH was between 7.8 and 8.3, and the pH of the slurry was maintained within the above range for 60 minutes from the start of adding the 24% by mass aqueous solution of caustic soda to obtain a slurry containing nickel hydroxide with a pH of 8.0. The composition of the obtained nickel hydroxide was measured using an ICP emission spectrometer (ICP-OES) and found to be 51.9% by mass of nickel, 0.10% by mass of cobalt, 0.003% by mass of iron, less than 0.001% by mass of zinc, less than 0.001% by mass of copper, and 0.010% by mass of magnesium.

[0083] The results in Table 1 show that by adopting a method that includes a step of mixing an aqueous solution containing nickel and copper with a water-soluble pyrophosphate compound, the nickel recovery rate can be maintained at a high level while the contamination of copper can be reduced.

Claims

1. A recovery method for recovering nickel from a raw material powder containing 5% by mass or more nickel and copper, A dissolution step to dissolve the raw material powder to obtain an aqueous solution containing nickel and copper, A mixing step of mixing an aqueous solution containing nickel and copper with a water-soluble pyrophosphate compound to obtain a mixed slurry, A recovery method characterized by comprising a solid-liquid separation step of separating the mixed slurry into solid and liquid components to obtain an aqueous solution containing nickel.

2. The recovery method according to claim 1, wherein the amount of the water-soluble pyrophosphate compound mixed is 0.2 or more as a molar ratio to the amount of copper contained in the raw material powder.

3. The recovery method according to claim 1, wherein the pH of the aqueous solution containing nickel and copper is adjusted to 2.0 or higher before the mixing step.

4. The recovery method according to claim 1, wherein the raw material powder contains at least one of iron and zinc, and a water-soluble phosphoric acid compound is further mixed in the mixing step.

5. The recovery method according to claim 4, wherein the amount of the water-soluble phosphoric acid compound mixed is 1.0 or more in molar ratio to the total amount of iron and zinc contained in the raw material powder.

6. The recovery method according to claim 4, wherein the raw material powder contains iron, and the oxidation-reduction potential of the mixed slurry obtained in the mixing step is adjusted to be between -100 mV and 1000 mV, measured with reference to a silver-silver chloride electrode.

7. The recovery method according to claim 1, further comprising a neutralization step to obtain nickel hydroxide by adjusting the pH of the nickel-containing aqueous solution to 7.0 or more and 10.0 or less, followed by solid-liquid separation and washing of solid components.

8. A nickel hydroxide dissolution step is performed by mixing the nickel hydroxide and the acid, followed by solid-liquid separation to obtain a nickel hydroxide solution. The recovery method according to claim 7, comprising a crystallization step of precipitating a nickel salt from the nickel hydroxide solution obtained in the nickel hydroxide dissolution step, and then separating the solid and liquid to obtain the nickel salt.

9. The recovery method according to claim 1, wherein the raw material powder contains a water-soluble nickel salt.

10. The recovery method according to claim 1, wherein the proportion of nickel in the total metal components of the raw material powder is 80% by mass or more.

11. The recovery method according to claim 1, wherein the cobalt content of the raw material powder is 5% by mass or less.

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