Full-chain integrated iron and aluminum slag recovery method and application

Abstract

The invention provides a full-chain integrated iron and aluminum slag recovery method which comprises the following steps: S1, mixing iron and aluminum slag with first alkali liquor to carry out first alkaline leaching reaction, and carrying out solid-liquid separation to obtain first metal hydroxide slag and first alkaline leaching liquor; s2, mixing the first metal hydroxide slag with second alkali liquor, carrying out second alkali leaching reaction, and carrying out solid-liquid separation to obtain an aluminate solution and second metal hydroxide slag; s3, pulping the second metal hydroxide slag, adding acid for acid dissolution, adding phosphate, seed crystal and a complexing agent for iron precipitation reaction, performing solid-liquid separation to obtain iron phosphate slag and nickel-cobalt-manganese extraction pre-liquid, and calcining the iron phosphate slag to obtain anhydrous iron phosphate. According to the method, metal elements can be completely recycled, and the recycled product can be applied to an existing industrial chain.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource recovery, and specifically relates to a method and application of full-chain integrated recovery of iron and aluminum slag. Background Art

[0002] In the current process of recycling waste ternary lithium batteries to prepare ternary positive electrode precursors, the commonly used process flow is: pretreatment - leaching - extraction - synthesis of ternary precursors. Among them, iron and aluminum removal is a very important step in leaching and impurity removal. As the only outlet for iron and aluminum, iron-aluminum slag often has the problem of large output and high processing cost. Therefore, it is of great significance to recover metal elements or recycle them. In the existing technology, the results of wet extraction of metal elements in iron-aluminum slag have the following problems: (1) The metal element recovery rate is low, and nickel, cobalt, manganese and lithium in iron-aluminum slag are not recovered; in order to obtain high-quality single metal element products, another metal element is sacrificed; for example, in one existing technology, iron-aluminum slag is used to prepare hematite, but the aluminum element in the iron-aluminum slag is not recycled; for another existing technology for comprehensive utilization of iron-aluminum slag, the product of the process is sodium aluminum sulfate dodecahydrate, and iron resources are not recycled; (2) The recovered products cannot be stored by themselves, but are sold to other parties. Due to the lack of effective recycling methods, the resource utilization rate is low.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method and application of recycling iron and aluminum slag in a full chain, which can achieve full recycling of metal elements, and the recycled products can be applied to the existing industrial chain.

[0005] According to a first aspect of the present invention, a method for recovering iron-aluminum slag is proposed, comprising the following steps: S1: mixing the iron-aluminum slag with the first alkali solution to perform a first alkali leaching reaction, and after solid-liquid separation, obtaining a first metal hydroxide slag and a first alkali leaching solution; S2: mixing the first metal hydroxide slag with the second alkali solution to perform a second alkali leaching reaction, and obtaining an aluminate solution and a second metal hydroxide slag after solid-liquid separation; S3: slurrying the second metal hydroxide slag, adding acid for acid dissolution, adding phosphate, seed crystals and complexing agent for iron precipitation reaction, and obtaining iron phosphate slag and nickel-cobalt-manganese extraction pre-liquid after solid-liquid separation, and calcining the iron phosphate slag to obtain anhydrous iron phosphate.

[0006] In some embodiments, in step S1, the pH value of the first alkali solution is 9.5-11; and / or the solid-liquid mass ratio of the ferroaluminum slag to the first alkali solution is 1:(5-10).

[0007] In some embodiments, the first alkaline solution is a sodium hydroxide solution.

[0008] In some embodiments, step S1 further comprises: washing the first metal hydroxide slag with the first alkali solution, and the obtained washing solution is incorporated into the first alkali leaching solution.

[0009] In some embodiments, step S1 further comprises: adding sulfuric acid to the first alkaline leaching solution to obtain a neutralized solution, concentrating the neutralized solution to obtain a crystallized solution, freezing and crystallizing the crystallized solution, and obtaining sodium sulfate crystals and lithium precipitation mother liquor after solid-liquid separation. The lithium precipitation mother liquor obtained in this process can be incorporated into the lithium carbonate production workshop.

[0010] In some preferred embodiments, the pH of the neutralization solution is 6.5-7.5.

[0011] In some preferred embodiments, the concentration of sodium ions in the crystallization solution is greater than 1.8 mol / L.

[0012] In some preferred embodiments, the freezing crystallization temperature is 5-10°C.

[0013] In some embodiments, in step S2, the second alkali solution is a sodium hydroxide solution with a pH value of greater than 13, and the molar ratio of the sodium element in the sodium hydroxide solution to the aluminum element in the first metal hydroxide slag is (1.5-3):1.

[0014] In some embodiments, the temperature of the first alkali leaching reaction and the second alkali leaching reaction are independently selected from 60 to 80° C., and the time of the first alkali leaching reaction and the second alkali leaching reaction are independently selected from 2 to 4 hours.

[0015] In some embodiments, step S2 further comprises: washing the second metal hydroxide slag with water, and incorporating the obtained washing water into the first alkaline leaching solution.

[0016] In some embodiments, step S2 further comprises: adding aluminum hydroxide seeds to the aluminate solution for seed separation, and obtaining aluminum hydroxide crystals after solid-liquid separation.

[0017] In some preferred embodiments, the aluminate solution is a sodium aluminate solution, the caustic ratio of the sodium aluminate solution is 1.4-1.65, wherein the concentration of aluminum oxide is 140-180 g / L. The present invention adopts Bayer process crystallization to prepare aluminum hydroxide crystals, wherein the caustic ratio is the molar ratio of sodium oxide to aluminum oxide in the sodium aluminate solution.

[0018] In some preferred embodiments, the feeding ratio of the sodium aluminate solution to the aluminum hydroxide seed crystals is 1 L: (2-10) g.

[0019] In some preferred embodiments, the seeding temperature is 30-60° C. and the seeding time is 24-60 h.

[0020] In some embodiments, in step S3, the slurrying includes: mixing the second metal hydroxide slag with water at a solid-liquid mass ratio of 1:(5-10) to prepare slurry.

[0021] In some embodiments, in step S3, the acid dissolution includes: stirring at a pH of 1-2.5 until the second metal hydroxide slag is completely dissolved; and / or the temperature of the acid dissolution is 25-60°C.

[0022] In some embodiments, in step S3, the acid is selected from at least one of sulfuric acid, phosphoric acid, hydrochloric acid or nitric acid.

[0023] In some embodiments, in step S3, the phosphate is selected from at least one of sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate or ammonium monohydrogen phosphate.

[0024] In some embodiments, in step S3, the phosphate is added in an amount according to a molar ratio of phosphorus to iron in the reaction solution of n(P):n(Fe) of (1.1-1.5):1.

[0025] In some embodiments, in step S3, the seed crystal is ferric phosphate dihydrate with a particle size of less than 1.5 μm; and / or the seed crystal is fed according to a solid-liquid ratio (2-8): 100 g / mL. The above solid-liquid ratio is the solid-liquid ratio of the seed crystal to the acid-dissolved liquid after the second metal hydroxide slag is acid-dissolved.

[0026] In some embodiments, in step S3, the complexing agent is a water-soluble catechol compound; and / or the concentration of the complexing agent in the reaction solution is 5-15 g / L.

[0027] In some preferred embodiments, the complexing agent is selected from at least one of catechol, 4-methylcatechol, 2,3-dihydroxybenzoic acid, dopamine hydrochloride, dopamine, 2,3,4-trihydroxybenzoic acid, pyrogallol or 1,2,4-pyrogallol.

[0028] In some embodiments, in step S3, the temperature of the iron precipitation reaction is 70-90° C., the reaction time is 1-4 hours, and the stirring speed is 200-400 rpm.

[0029] According to the second aspect of the present invention, the application of the method described in the first aspect of the present invention in the recycling of waste lithium batteries is proposed. Since the power batteries on the market are mainly ternary lithium batteries and lithium iron phosphate batteries, most battery recycling industries include recycling production lines for the two types of batteries. The product obtained by the method for recycling iron-aluminum slag proposed in the present invention can be self-incorporated on the production line, which can save many links and improve resource utilization.

[0030] According to one embodiment of the present invention, there are at least the following beneficial effects: 1. The method provided by the present invention recovers a small amount of nickel, cobalt, manganese and lithium elements remaining in the iron-aluminum slag, and can be incorporated into the nickel-cobalt-manganese recovery section and the lithium salt production workshop to further improve the recovery rate of the production line.

[0031] 2. The method provided by the present invention can fully recover the metal elements in the iron-aluminum slag, including nickel, cobalt, manganese, lithium, iron and aluminum.

[0032] 3. The product obtained by the method provided by the present invention can be directly used in the battery recycling production line, avoiding drying and packaging for external sale, thereby improving safety and resource utilization.

[0033] 4. The present invention adopts a one-step iron precipitation method to prepare iron phosphate crystals, and obtains battery-grade anhydrous iron phosphate after calcination. The one-step iron precipitation method has the following advantages: ① The nucleation efficiency of dihydrated iron phosphate is low, so adding seed crystals can accelerate the nucleation efficiency; ② Adding Fe 3+ The complexing agent has good complexing effect, which makes the free Fe in the reaction solution 3+ It decreases the growth rate of crystals, avoids the formation of amorphous ferric phosphate, and reduces the crystal defects of hydrated ferric phosphate crystals, which is beneficial to reduce the amount of nickel, cobalt and manganese elements carried in ferric phosphate slag and improve the separation rate.

[0034] 5. The nickel-cobalt-manganese pre-extraction liquid recovered by the method provided by the present invention contains a chelating agent, which is incorporated into the extraction section of the wet extraction of the ternary positive electrode material, which can improve the distribution coefficient of the iron element in the organic phase, thereby improving the extraction and separation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a process flow chart of Example 1 of the present invention; Figure 2 The figure is a process flow chart of the extraction of nickel, cobalt and manganese pre-extraction solution; Figure 3 The XRD diagrams of the products obtained from the iron precipitation reaction in Example 1, Comparative Example 4 and Comparative Example 5 of the present invention are shown. DETAILED DESCRIPTION

[0036] The concept and technical effects of the present invention will be clearly and completely described below in conjunction with embodiments to fully understand the purpose, features and effects of the present invention.

[0037] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0038] Test description: ICP is used to measure the metal ion concentration of solid and liquid; UV spectrophotometer is used to measure the complexing agent concentration in the solution.

[0039] Example 1 This embodiment provides a method for recycling iron and aluminum slag in a full chain integration, such as Figure 1 As shown, the specific steps include: (1) The ferroaluminum slag and the sodium hydroxide solution with a pH value of 10 are mixed in a mass ratio of 1:8 to prepare a pulp, and then the mixture is heated to 70°C for a first alkali leaching reaction. The reaction time is 3 hours. After solid-liquid separation, a first metal hydroxide slag and a first alkali leaching solution are obtained. The obtained first metal hydroxide slag is rinsed with the above-mentioned sodium hydroxide solution, and the washing solution is incorporated into the first alkali leaching solution.

[0040] The metal element content of iron-aluminum slag measured by ICP is as follows:

[0041] The metal element content of the first metal hydroxide slag measured by ICP is as follows:

[0042] (2) Mixing the first metal hydroxide slag with a sodium hydroxide solution with a pH of 13, wherein the ratio of the molar amount of the sodium element in the sodium hydroxide solution to the molar amount of the aluminum element in the first metal hydroxide slag is 2:1, and heating the mixture to 70°C for a second alkaline leaching reaction for 3 hours. After solid-liquid separation, a sodium aluminate solution and a second metal hydroxide slag are obtained. The obtained second metal hydroxide slag is rinsed with water for standby use, and the washing liquid is incorporated into the first alkaline leaching solution.

[0043] The metal element content of the second metal hydroxide slag measured by ICP is as follows:

[0044] (3) The second metal hydroxide slag obtained in step (2) is mixed with water at a solid-liquid mass ratio of 1:8 to prepare a slurry, and then sulfuric acid is added. The mixture is stirred at a pH of 1.8 and a temperature of 60°C until the second metal hydroxide slag is completely dissolved, and then sodium monohydrogen phosphate, dihydrate iron phosphate seeds (particle size of 800nm~1.2μm) and a complexing agent catechol are added to carry out an iron precipitation reaction. The amount of sodium monohydrogen phosphate added is based on the molar ratio of phosphorus to iron in the reaction solution n(P):n(Fe) of 1.3:1, and the dihydrate iron phosphate seeds are added at a solid-liquid ratio of 5g:100mL (the solid-liquid ratio is the solid-liquid ratio of the acid-dissolved solution after the dihydrate iron phosphate seeds and the second metal hydroxide slag are completely dissolved, the same as in the following embodiments), and the concentration of catechol in the reaction solution is 10g / L. The temperature of the iron precipitation reaction is 80°C, the reaction time is 3h, and the stirring speed is 300rpm. After solid-liquid separation, ferrophosphate slag and nickel-cobalt-manganese extraction pre-liquid were obtained. The XRD pattern of the ferrophosphate slag is as follows: Figure 3 As shown, the iron phosphate slag was washed and calcined at 600°C for 2h to obtain battery-grade anhydrous iron phosphate.

[0045] The metal element content analysis of anhydrous iron phosphate is as follows:

[0046] The concentrations of key components in the pre-extraction solution of nickel, cobalt and manganese are as follows:

[0047] (4) adding sulfuric acid to the first alkaline leaching solution obtained in step (1) to carry out a neutralization reaction until the pH of the solution is 7, thereby obtaining a neutralized solution; heating the neutralized solution and concentrating it until the concentration of sodium ions reaches 2.5 mol / L, thereby obtaining a crystallization solution; cooling the crystallization solution to 10° C. and keeping it warm for 24 h to perform freeze crystallization, and after solid-liquid separation, obtaining sodium sulfate crystals and lithium precipitation mother liquor, and rinsing the sodium sulfate crystals with 10° C. cold water and then drying; and the obtained lithium precipitation mother liquor is incorporated into the lithium carbonate production workshop.

[0048] The metal ion concentration of lithium precipitation mother liquor is as follows:

[0049] (5) Sodium hydroxide was added to the sodium aluminate solution obtained in step (2) to adjust the caustic ratio of the sodium aluminate solution to 1.52, and the concentration of aluminum oxide was 161 g / L, and then aluminum hydroxide seeds were added for seed separation. After solid-liquid separation, the solid phase was washed with pure water and dried to obtain aluminum hydroxide crystals. The remaining solution was returned to the second alkali leaching reactor, and the seed separation rate was 46%. The feeding ratio of sodium aluminate solution to aluminum hydroxide seeds was 1 L: 6 g. The seed separation temperature was 50°C and the time was 24 h.

[0050] The aluminum hydroxide seed crystals are aluminum hydroxide crystals prepared according to the same process flow, collectively referred to as aluminum hydroxide crystals. The parameters measured according to GB / T4294-2010 standard are as follows:

[0051] Example 2 This embodiment provides a method for recycling iron and aluminum slag in a full-chain integrated manner, which specifically includes the following steps: (1) The ferroaluminum slag and the sodium hydroxide solution with a pH value of 9.5 are mixed in a mass ratio of 1:10 to prepare a slurry, and then the mixture is heated to 80°C for a first alkali leaching reaction. The reaction time is 4 hours. After solid-liquid separation, a first metal hydroxide slag and a first alkali leaching solution are obtained. The obtained first metal hydroxide slag is washed with the above-mentioned sodium hydroxide solution, and the washing solution is incorporated into the first alkali leaching solution.

[0052] The metal element content of iron-aluminum slag measured by ICP is as follows:

[0053] The metal element content of the first metal hydroxide slag measured by ICP is as follows:

[0054] (2) Mixing the first metal hydroxide slag with a sodium hydroxide solution with a pH of 14, wherein the ratio of the molar amount of the sodium element in the sodium hydroxide solution to the molar amount of the aluminum element in the first metal hydroxide slag is 1.5:1, heating the mixture to 80°C for a second alkaline leaching reaction, and the reaction time is 2 hours. After solid-liquid separation, sodium aluminate solution and a second metal hydroxide slag are obtained. The obtained second metal hydroxide slag is rinsed with water for standby use, and the washing liquid is incorporated into the first alkaline leaching solution.

[0055] The metal element content of the second metal hydroxide slag measured by ICP is as follows:

[0056] (3) The second metal hydroxide slag obtained in step (2) is mixed with water at a solid-liquid mass ratio of 1:10 to prepare a slurry, and then hydrochloric acid is added. The mixture is stirred at a pH of 1 and a temperature of 40°C until the second metal hydroxide slag is completely dissolved, and then sodium dihydrogen phosphate, dihydrate iron phosphate seeds (particle size of 1-1.5 μm) and a complexing agent 2,3-dihydroxybenzoic acid are added to carry out an iron precipitation reaction. The amount of sodium dihydrogen phosphate added is based on the molar ratio of phosphorus to iron in the reaction solution n(P):n(Fe) of 1.1:1, and the dihydrate iron phosphate seeds are added at a solid-liquid ratio of 8g:100mL. The concentration of 2,3-dihydroxybenzoic acid in the reaction solution is 5g / L. The temperature of the iron precipitation reaction is 70°C, the reaction time is 4h, and the stirring speed is 200rpm. After solid-liquid separation, iron phosphate slag and nickel-cobalt-manganese extraction pre-liquid are obtained. The iron phosphate slag is rinsed and calcined at 600°C for 2h to obtain battery-grade anhydrous iron phosphate.

[0057] The metal element content analysis of anhydrous iron phosphate is as follows:

[0058] The concentrations of key components in the pre-extraction solution of nickel, cobalt and manganese are as follows:

[0059] (4) adding sulfuric acid to the first alkaline leaching solution obtained in step (1) to carry out a neutralization reaction until the pH value of the solution is 6.5, thereby obtaining a neutralized solution; heating the neutralized solution and concentrating it until the concentration of sodium ions reaches 1.84 mol / L, thereby obtaining a crystallization solution; cooling the crystallization solution to 10° C. and keeping it warm for 24 h to perform freeze crystallization, and after solid-liquid separation, obtaining sodium sulfate crystals and lithium precipitation mother liquor, and rinsing the sodium sulfate crystals with 10° C. cold water and then drying; and the obtained lithium precipitation mother liquor is incorporated into the lithium carbonate production workshop.

[0060] The metal ion concentration of lithium precipitation mother liquor is as follows:

[0061] (5) Sodium hydroxide was added to the sodium aluminate solution obtained in step (2) to adjust the caustic ratio of the sodium aluminate solution to 1.4, and the concentration of aluminum oxide was 140 g / L, and then aluminum hydroxide seeds were added for seed separation. After solid-liquid separation, the solid phase was washed with pure water and dried to obtain aluminum hydroxide crystals. The remaining solution was returned to the second alkali leaching reactor, and the seed separation rate was 37%. The feeding ratio of the sodium aluminate solution to the aluminum hydroxide seeds was 1 L: 10 g. The seed separation temperature was 30° C. and the time was 60 h.

[0062] The aluminum hydroxide seed crystals are aluminum hydroxide crystals prepared according to the same process flow, collectively referred to as aluminum hydroxide crystals. The parameters measured according to GB / T4294-2010 standard are as follows:

[0063] Example 3 This embodiment provides a method for recycling iron and aluminum slag in a full-chain integrated manner, which specifically includes the following steps: (1) The ferroaluminum slag and the sodium hydroxide solution with a pH of 11 are mixed in a mass ratio of 1:5 to prepare a pulp, and then the temperature is raised to 60°C for a first alkaline leaching reaction. The reaction time is 2 hours. After solid-liquid separation, a first metal hydroxide slag and a first alkaline leaching solution are obtained. The obtained first metal hydroxide slag is washed with the above-mentioned sodium hydroxide solution, and the washing liquid is incorporated into the first alkaline leaching solution.

[0064] The metal element content of iron-aluminum slag measured by ICP is as follows:

[0065] The metal element content of the first metal hydroxide slag measured by ICP is as follows:

[0066] (2) Mixing the first metal hydroxide slag with a sodium hydroxide solution with a pH of 13.5, wherein the ratio of the molar amount of the sodium element in the sodium hydroxide solution to the molar amount of the aluminum element in the first metal hydroxide slag is 3:1, heating the mixture to 60°C for a second alkaline leaching reaction, and the reaction time is 4 hours. After solid-liquid separation, sodium aluminate solution and the second metal hydroxide slag are obtained. The obtained second metal hydroxide slag is rinsed with water for standby use, and the washing liquid is incorporated into the first alkaline leaching solution.

[0067] The metal element content of the second metal hydroxide slag measured by ICP is as follows:

[0068] (3) The second metal hydroxide slag obtained in step (2) is mixed with water at a solid-liquid mass ratio of 1:5 to prepare a slurry, and then hydrochloric acid is added. The mixture is stirred at a pH of 2.5 and a temperature of 25°C until the second metal hydroxide slag is completely dissolved, and then ammonium dihydrogen phosphate, dihydrate iron phosphate seeds (particle size of 500-800nm) and a complexing agent dopamine hydrochloride are added to carry out an iron precipitation reaction. The amount of ammonium dihydrogen phosphate added is based on the molar ratio of phosphorus to iron in the reaction solution n(P):n(Fe) of 1.5:1, and the dihydrate iron phosphate seeds are added at a solid-liquid ratio of 2g:100mL. The concentration of dopamine hydrochloride in the reaction solution is 15g / L. The temperature of the iron precipitation reaction is 90°C, the reaction time is 1h, and the stirring speed is 400rpm. After solid-liquid separation, iron phosphate slag and nickel-cobalt-manganese extraction pre-liquid are obtained. The iron phosphate slag is rinsed and calcined at 600°C for 2h to obtain battery-grade anhydrous iron phosphate.

[0069] The metal element content analysis of anhydrous iron phosphate is as follows:

[0070] The concentrations of key components in the pre-extraction solution of nickel, cobalt and manganese are as follows:

[0071] (4) adding sulfuric acid to the first alkaline leaching solution obtained in step (1) to carry out a neutralization reaction until the pH value of the solution is 7.5, thereby obtaining a neutralized solution; heating the neutralized solution and concentrating it until the concentration of sodium ions reaches 2.81 mol / L, thereby obtaining a crystallization solution; cooling the crystallization solution to 10° C. and keeping it warm for 24 h to perform freeze crystallization, and after solid-liquid separation, obtaining sodium sulfate crystals and lithium precipitation mother liquor, and rinsing the sodium sulfate crystals with 10° C. cold water and then drying; and the obtained lithium precipitation mother liquor is incorporated into the lithium carbonate production workshop.

[0072] The metal ion concentration of lithium precipitation mother liquor is as follows:

[0073] (5) Sodium hydroxide is added to the sodium aluminate solution obtained in step (2) to adjust the caustic ratio of the sodium aluminate solution to 1.65, and the concentration of aluminum oxide is 180 g / L, and then aluminum hydroxide seeds are added for seed separation. After solid-liquid separation, the solid phase is washed with pure water and dried to obtain aluminum hydroxide crystals, and the remaining solution is continuously returned to the second alkali leaching reactor. The seed separation rate is 42%. The feeding ratio of the sodium aluminate solution to the aluminum hydroxide seeds is 1 L: 2 g. The seed separation temperature is 60° C. and the time is 48 h.

[0074] The aluminum hydroxide seed crystals are aluminum hydroxide crystals prepared according to the same process flow, collectively referred to as aluminum hydroxide crystals. The parameters measured according to GB / T4294-2010 standard are as follows:

[0075] Example 4 This embodiment provides a method for recovering iron-aluminum slag in a full-chain integrated manner, which is different from Embodiment 1 in that the pH value of the sodium hydroxide solution in step (2) is 14.

[0076] The metal element content of the second metal hydroxide slag measured by ICP is as follows:

[0077] Example 5 This embodiment provides a method for recycling iron-aluminum slag in a full-chain integrated manner. The difference from Embodiment 1 is that the amount of iron phosphate dihydrate seed crystals added in step (3) is determined according to a solid-liquid ratio of 2 g:100 mL.

[0078] The metal element content analysis of anhydrous iron phosphate is as follows:

[0079] The concentrations of key components in the pre-extraction solution of nickel, cobalt and manganese are as follows:

[0080] Example 6 This embodiment provides a method for recycling iron-aluminum slag in a full-chain integrated manner. The difference from Embodiment 1 is that the amount of iron phosphate dihydrate seed crystals added in step (3) is determined according to a solid-liquid ratio of 8 g:100 mL.

[0081] The metal element content analysis of anhydrous iron phosphate is as follows:

[0082] The concentrations of key components in the pre-extraction solution of nickel, cobalt and manganese are as follows:

[0083] Example 7 This embodiment provides a method for recovering iron-aluminum slag in a full-chain integrated manner, which is different from Embodiment 1 in that the concentration of the complexing agent in step (3) in the reaction solution is 5 g / L.

[0084] The metal element content analysis of anhydrous iron phosphate is as follows:

[0085] The concentrations of key components in the pre-extraction solution of nickel, cobalt and manganese are as follows:

[0086] Example 8 This embodiment provides a method for recycling iron-aluminum slag in a full-chain integrated manner, which is different from Embodiment 1 in that the concentration of the complexing agent in step (3) in the reaction solution is 15 g / L.

[0087] The metal element content analysis of anhydrous iron phosphate is as follows:

[0088] The concentrations of key components in the pre-extraction solution of nickel, cobalt and manganese are as follows:

[0089] Comparative Example 1 This comparative example provides a method for recovering iron-aluminum slag, which is different from Example 1 in that the pH value of the sodium hydroxide solution in step (1) is 8.5.

[0090] The metal element content of the first metal hydroxide slag measured by ICP is as follows:

[0091] Comparative Example 2 This comparative example provides a method for recovering iron-aluminum slag, which is different from Example 1 in that the pH value of the sodium hydroxide solution in step (2) is 12.

[0092] The metal element content of the second metal hydroxide slag measured by ICP is as follows:

[0093] Comparative Example 3 This comparative example provides a method for recovering iron-aluminum slag, which is different from Example 1 in that step (3) adopts the sodium ferroaluminate method to precipitate iron. The specific process is as follows: water is added to the second metal hydroxide slag for pulping (the mass ratio of the second metal hydroxide slag to water is 1:6), and then concentrated sulfuric acid is added to adjust the pH to 1.5 for acid leaching and dissolution. After solid-liquid separation, sodium carbonate is added to the obtained acid leaching liquid to adjust and maintain the pH to 2.2, and the temperature is raised to 95°C for iron precipitation for 5 hours to obtain ferroaluminate precipitate. The reaction principle is 6Fe 3+ +2Na + +4SO4 2- +12H2O==Na2Fe6(SO4)4(OH) 12 +12H + The iron precipitation mother liquor enters the extraction section as the pre-liquid for nickel, cobalt and manganese extraction.

[0094] Comparative Example 4 This comparative example provides a method for recovering iron-aluminum slag, which is different from Example 1 in that no iron phosphate dihydrate seed crystals are added in step (3).

[0095] The metal element content analysis of anhydrous iron phosphate is as follows:

[0096] The concentrations of key components in the pre-extraction solution of nickel, cobalt and manganese are as follows:

[0097] Since no crystal seeds are added, it is difficult for ferric phosphate dihydrate to crystallize, so most of the ferric phosphate slag is amorphous, and its XRD pattern is as follows: Figure 3 As shown, it has a flocculation effect and carries a large amount of metal elements.

[0098] Comparative Example 5 This comparative example provides a method for recovering iron-aluminum slag, which is different from Example 1 in that no complexing agent is added in step (3).

[0099] The metal element content analysis of anhydrous iron phosphate is as follows:

[0100] The concentrations of key components in the pre-extraction solution of nickel, cobalt and manganese are as follows:

[0101] Since no complexing agent was added, the iron phosphate precipitate formed too quickly, resulting in a large amount of amorphous iron phosphate, which was accompanied by a large amount of metal elements. Its XRD pattern is shown in the figure below. Figure 3 shown.

[0102] Test example (1) Calculation of metal element recovery rate The content of each element is calculated from the iron-aluminum slag as the input amount, and the content of the main elements of each product is measured as the recovery amount, and the recovery rate is taken as the percentage of the recovery amount to the input amount. For example, if the main element of the lithium precipitation mother liquor is Li, the lithium recovery amount is calculated by measuring the concentration of lithium ions in the lithium precipitation mother liquor and the volume of the lithium precipitation mother liquor; for example, if the main element of aluminum hydroxide is Al, the aluminum recovery amount is calculated by measuring the content and total mass of Al in the dry aluminum hydroxide crystals; for example, if the main element of anhydrous iron phosphate is Fe, the iron recovery amount is calculated by measuring the content and total mass of Fe in the anhydrous iron phosphate; for example, if the main elements of the nickel-cobalt-manganese extraction pre-liquid are Ni, Co, and Mn, respectively, the concentration of Ni, Co, and Mn ions in the nickel-cobalt-manganese extraction pre-liquid and the volume of the nickel-cobalt-manganese extraction pre-liquid are measured to calculate the recovery amounts of Ni, Co, and Mn.

[0103]

[0104] (2) Improvement of extraction efficiency The nickel-cobalt-manganese extraction pre-liquid was prepared according to the Figure 2 The process flow is used for extraction, and the content of iron ions in the recovered liquid obtained by the first stripping is studied, as described below: The first extraction uses P204 as the extractant and kerosene as the diluent, the mass ratio of the two is P204: kerosene = 30%: 70%, the saponification degree of P204 is 65%, and five-stage countercurrent extraction is adopted. The obtained organic phase is subjected to five-stage stripping to obtain the first stripping liquid. The stripping agent is dilute sulfuric acid. After the first stripping liquid is deoiled, the iron ion content is detected and the recovery rate is calculated accordingly; the raffinate (inorganic phase) enters the second extraction.

[0105] The second extraction uses P507 as the extractant and kerosene as the diluent, the mass ratio of the two is P507: kerosene = 1:3, the saponification degree of P507 is 65%, and five-stage countercurrent extraction is adopted. The obtained organic phase is subjected to five-stage stripping to obtain the second stripping solution, and the stripping agent is dilute sulfuric acid; after the raffinate (inorganic phase) is adsorbed by resin, the eluate obtained by elution with dilute sulfuric acid is incorporated into the second stripping solution, and the nickel, cobalt and manganese contents in the second stripping solution are detected after deoiling, and the recovery rate of the metal elements in the nickel, cobalt and manganese pre-extraction solution is calculated based on the above.

[0106]

[0107] Principle: catechol compounds form complexes with iron ions, reducing the water solubility of metal ions. Catechol is more lipophilic than hydrophilic, so it acts as a bridge to promote the process of iron ions entering the organic phase, thereby improving the separation of iron from nickel, cobalt and manganese. Referring to the table above, in Comparative Example 5, no complexing agent catechol compounds are added, so the recovery rate of iron decreases.

[0108] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for recovering iron-aluminum slag, characterized in that: The following steps are involved: S1: mixing the iron-aluminum slag with the first alkali solution to perform a first alkali leaching reaction, and after solid-liquid separation, obtaining a first metal hydroxide slag and a first alkali leaching solution; S2: mixing the first metal hydroxide slag with a second alkali solution to perform a second alkali leaching reaction, and obtaining an aluminate solution and a second metal hydroxide slag after solid-liquid separation; S3: slurrying the second metal hydroxide slag, adding acid for acid dissolution, adding phosphate, seed crystals and complexing agent for iron precipitation reaction, and obtaining iron phosphate slag and nickel-cobalt-manganese extraction pre-liquid after solid-liquid separation, and calcining the iron phosphate slag to obtain anhydrous iron phosphate.

2. The method according to claim 1, characterized in that In step S1, the pH value of the first alkali solution is 9.5-11; and / or the solid-liquid mass ratio of the iron-aluminum slag to the first alkali solution is 1:(5-10).

3. The method according to claim 1, characterized in that In step S2, the second alkali solution is a sodium hydroxide solution with a pH value of greater than 13, and the molar ratio of the sodium element in the sodium hydroxide solution to the aluminum element in the first metal hydroxide slag is (1.5-3):

1.

4. The method according to claim 1, characterized in that: The temperature of the first alkali leaching reaction and the second alkali leaching reaction are independently selected from 60 to 80° C., and the time of the first alkali leaching reaction and the second alkali leaching reaction are independently selected from 2 to 4 hours.

5. The method according to claim 1, characterized in that Step S2 also includes: adding aluminum hydroxide seeds into the aluminate solution for seed separation, and obtaining aluminum hydroxide crystals after solid-liquid separation.

6. The method according to claim 1, characterized in that In step S3, the acid dissolution includes: stirring at a pH of 1-2.5 until the second metal hydroxide slag is completely dissolved; and / or the temperature of the acid dissolution is 25-60°C.

7. The method according to claim 1, characterized in that In step S3, the seed crystals are ferric phosphate dihydrate having a particle size of less than 1.5 μm; and / or the seed crystals are fed according to a solid-to-liquid ratio (2-8): 100 g / mL.

8. The method according to claim 1, characterized in that In step S3, the complexing agent is a water-soluble catechol compound; and / or the concentration of the complexing agent in the reaction solution is 5-15 g / L.

9. The method according to claim 1, characterized in that: In step S3, the temperature of the iron precipitation reaction is 70-90° C., the reaction time is 1-4 hours, and the stirring speed is 200-400 rpm.

10. Use of the method according to any one of claims 1 to 9 in the recycling of waste lithium batteries.

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