Resource utilization method of waste electrolyte and iron-containing aluminum waste residues

Abstract

The invention discloses a resource utilization method of waste electrolyte and iron-containing aluminum waste residues, and relates to the technical field of resource utilization of lithium battery wastes. According to the method, lithium hexafluorophosphate in the waste electrolyte reacts with water in the iron-containing aluminum waste residues to generate LiF and PF5, and PF5 further reacts with water to generate H3PO4 and HF. Then, HF and an aluminum component in the iron-containing aluminum waste residues react to form an AlF3 precipitate, selective recovery of aluminum is achieved, an iron-containing solution containing Fe < 3 + >, PO4 < 3-> and Li < + > is obtained at the same time, and the AlF3 precipitate is washed and dried to obtain an aluminum fluoride product; the method comprises the following steps: adjusting the pH value of an iron-containing solution, heating to promote the reaction of Fe < 3 + > and PO4 < 3-> to generate an iron phosphate coarse precipitate, aging, cleaning, drying and calcining to obtain an iron phosphate product. The resource utilization method provided by the invention can be used for solving the problem of low resource utilization rate of the waste electrolyte and the iron-containing and aluminum-containing waste slag.

Description

Technical Field

[0001] This invention relates to the field of lithium battery waste resource utilization technology, and in particular to a method for the resource utilization of waste electrolyte and iron-aluminum-containing waste residue. Background Technology

[0002] With the rapid development of new energy vehicles and portable electronic devices, the amount of waste lithium batteries generated is increasing year by year. Waste lithium-ion batteries contain high-value metal resources such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li). If they are not effectively recycled, it will not only waste resources but also pose potential harm to the environment. Therefore, establishing an efficient and environmentally friendly waste lithium battery recycling system has become an important issue in the field of resource recycling.

[0003] In the recycling of spent lithium batteries, wet recycling technology is widely used due to its high processing efficiency and high metal recovery rate. After dismantling and crushing, spent lithium batteries generate waste electrolyte, which is typically treated using high-temperature pyrolysis. This process is characterized by extremely high energy consumption and operating costs, and the potential generation of harmful gases necessitates a dedicated exhaust gas treatment system. Furthermore, the black powder produced after dismantling and crushing contains precious metals such as nickel, cobalt, manganese, and lithium. It requires acid leaching, neutralization, and precipitation to remove impurities such as iron and aluminum, resulting in a solution containing these precious metals and a heavy slag containing iron and aluminum. Currently, this heavy slag, containing impurities such as iron and aluminum, is treated as hazardous waste and is primarily disposed of through landfill or by entrusted disposal to qualified companies. This not only leads to secondary resource waste but also incurs high hazardous waste disposal costs and environmental management pressures. Summary of the Invention

[0004] The main objective of this invention is to propose a method for the resource utilization of waste electrolyte and iron-aluminum-containing waste residue, aiming to solve the problem of low resource utilization rate of waste electrolyte and iron-aluminum-containing waste residue.

[0005] To achieve the above objectives, this invention proposes a method for the resource utilization of waste electrolyte and iron-aluminum-containing waste residue, comprising the following steps: S10. The waste electrolyte is centrifuged, and the upper liquid is collected to obtain pretreated waste electrolyte; wherein, the waste electrolyte contains lithium hexafluorophosphate; S20. Provide iron-aluminum waste residue, and stir the pretreated waste electrolyte and iron-aluminum waste residue to obtain a mixed slurry; wherein, the iron-aluminum waste residue is waste residue containing iron hydroxide and aluminum hydroxide; S30. Heat the mixed slurry to obtain a reactant slurry, then adjust the pH of the reactant slurry to less than 1 with acid, filter it to obtain crude aluminum fluoride and filtrate containing ferric ions. S40. The crude aluminum fluoride is washed with water and dried to obtain the aluminum fluoride product; the pH value of the filtrate containing ferric ions is adjusted with a pH adjuster and heated to generate crude ferric phosphate precipitate from the ferric ions and phosphate in the solution. S50. The crude ferric phosphate precipitate is aged with phosphoric acid solution, filtered to obtain aged ferric phosphate precipitate, washed, and then subjected to solid-liquid separation to obtain solid matter. The solid matter is then dried and calcined to obtain ferric phosphate product.

[0006] In one embodiment, step S20, the preparation step of the iron-aluminum-containing waste residue includes: Waste lithium batteries are crushed and pyrolyzed to obtain black powder. The black powder is then soaked in acid and filtered. The filtrate is collected to obtain an acidic leachate. The acidic leachate is then subjected to a neutralization and precipitation reaction, followed by filtration to obtain iron-aluminum-containing waste residue.

[0007] In one embodiment, step S20, the preparation step of the iron-aluminum-containing waste residue includes: Waste lithium batteries are crushed and pyrolyzed to obtain black powder. The black powder is soaked in acid and then filtered. The filtrate is collected to obtain an acidic leachate. The acidic leachate is subjected to a neutralization and precipitation reaction, and then filtered to obtain an iron-aluminum precipitate residue. An acidic leachate containing ferric ions is provided. The ferric ions in the acidic leachate containing ferric ions are extracted with an extractant to transfer the ferric ions to the organic phase. Then, the leachate is back-extracted with hydrochloric acid solution to obtain an antiferric acid solution. The antiferric acid solution is neutralized and precipitated, and then filtered to obtain an iron-containing precipitate residue. Iron-aluminum precipitate residue and iron-containing precipitate residue are mixed to obtain iron-aluminum waste residue.

[0008] In one embodiment, the waste lithium battery is crushed and pyrolyzed to obtain black powder. The black powder is then soaked in acid and filtered to collect the filtrate to obtain an acidic leachate. The pyrolysis temperature is 100~400℃; and / or, The pyrolysis time is 1-2 hours; and / or, The pH value of the acidic leachate is 1.5 to 2.5.

[0009] In one embodiment, the step of neutralizing and precipitating the acidic leachate includes: The pH of the acidic leachate is adjusted to 4.0-5.0 and heated at 80-90°C for 2-6 hours to allow the ferric and aluminum ions in the acidic leachate to undergo a neutralization and precipitation reaction.

[0010] In one embodiment, in the step of neutralizing and precipitating the antiferric acid solution, the pH value of the antiferric acid solution is adjusted to 4.0~5.0 and heated at 80~90°C for 0.5~2 hours to neutralize and precipitate the ferric ions in the antiferric acid solution.

[0011] In one embodiment, the method further includes the following step before step S20: We provide untreated iron-aluminum waste residue, which is then crushed and screened using a 50-200 mesh screen.

[0012] In one embodiment, in step S20, the mass ratio of the pretreated waste electrolyte to the iron-aluminum waste residue is (2~6):1.

[0013] In one embodiment, in step S30: The heating temperature of the mixed slurry is 20~150℃; and / or, The heating time for the mixed slurry is 2-4 hours.

[0014] In one embodiment, in step S40: The pH of the filtrate containing ferric ions is adjusted to 1.5–3.5 using a pH adjuster; and / or, The pH adjuster includes at least one of ferric hydroxide, ammonium phosphate, diammonium phosphate, and ferric hydroxide; and / or, The heating temperature is 25~40℃; and / or, The heating time is 0.5 to 3 hours.

[0015] In one embodiment, in step S50: The concentration of the phosphoric acid solution is 5% to 10%; and / or, The mass ratio of the phosphoric acid solution to the crude iron phosphate precipitate is (2~3):1; and / or, The aging temperature is 55~65℃; and / or, The aging time is 20-24 hours; and / or, The calcination treatment temperature is 500~600℃; and / or, The calcination treatment time is 2-3 hours.

[0016] In the technical solution of this invention, lithium hexafluorophosphate in the waste electrolyte first reacts with water in the iron-aluminum waste residue to generate lithium fluoride (LiF) and phosphorus pentafluoride (PF5) gas. The highly reactive PF5 further reacts with water to generate phosphoric acid (H3PO4) and highly corrosive hydrogen fluoride (HF). Then, the generated HF preferentially reacts with the aluminum component in the iron-aluminum waste residue to form aluminum fluoride (AlF3) precipitate, which is insoluble in an acidic environment, thereby achieving selective aluminum recovery. Simultaneously, the iron component (mainly Fe) in the iron-aluminum waste residue... 3+ If present, it dissolves into the liquid phase and reacts with PO4 in the system. 3- and Li + Together, they form an iron-containing solution. Subsequently, the separated AlF3 solid (crude aluminum fluoride) is washed and dried to obtain the aluminum fluoride product. The pH of the separated iron-containing solution is adjusted using a pH adjuster, and heating promotes the reaction of ferric ions and phosphates to generate a crude ferric phosphate precipitate. This precipitate is then aged using a phosphoric acid solution to promote the dissolution of small particles and the growth of large particles, thereby achieving impurity desorption and optimizing the ferric phosphate particles. Finally, the aged ferric phosphate precipitate is washed, dried, and calcined to obtain the ferric phosphate product. The resource utilization method provided by this invention not only recovers lithium from the waste electrolyte, keeping it in the form of lithium ions in the solution for easy subsequent extraction, but also utilizes the iron and aluminum in the iron-aluminum waste residue, achieving "multiple recoveries from one material," significantly improving the overall metal recovery rate and solving the problem of low resource utilization of waste electrolyte and iron-aluminum waste residue. Simultaneously, it eliminates the need for adding large amounts of chemical agents, utilizing the components of the waste electrolyte itself to drive the reaction and consume HF, thus removing harmful F... - And Al 3+ The process transforms the material into a stable solid, avoiding the direct discharge of wastewater and exhaust gas, and maximizing resource utilization and environmental friendliness throughout the entire process. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a process flow diagram of the preparation of waste electrolyte and iron-aluminum-containing waste residue in Example 1 of the present invention; Figure 2 This is a process flow diagram of an embodiment of the resource utilization method for waste electrolyte and iron-aluminum-containing waste residue provided by the present invention.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] In the recycling of spent lithium batteries, wet recycling technology is widely used due to its high processing efficiency and high metal recovery rate. After dismantling and crushing, spent lithium batteries generate waste electrolyte, which is typically treated using high-temperature pyrolysis. This process is extremely energy-intensive, has high operating costs, and may produce harmful gases, requiring a corresponding exhaust gas treatment system. Secondly, the black powder from dismantling and crushing contains precious metals such as nickel, cobalt, manganese, and lithium. It needs to undergo acid leaching, neutralization, and precipitation to remove impurities such as iron and aluminum, forming a solution containing these precious metals and a heavy slag containing iron and aluminum. Currently, this heavy slag, containing impurities such as iron and aluminum, is treated as hazardous waste and is mostly disposed of through landfill or by entrusted disposal to qualified companies. This not only causes secondary resource waste but also brings high hazardous waste disposal costs and environmental management pressure.

[0024] In view of this, the present invention proposes a method for the resource utilization of waste electrolyte and iron-aluminum-containing waste residue.

[0025] Please see Figure 1 and Figure 2 The method for resource utilization of the waste electrolyte and iron-aluminum-containing waste residue includes the following steps: S10. The waste electrolyte is centrifuged, and the upper liquid is collected to obtain pretreated waste electrolyte; wherein, the waste electrolyte contains lithium hexafluorophosphate; S20. Provide iron-aluminum waste residue, and stir the pretreated waste electrolyte and iron-aluminum waste residue to obtain a mixed slurry; wherein, the iron-aluminum waste residue is waste residue containing iron hydroxide and aluminum hydroxide; S30. Heat the mixed slurry to obtain a reactant slurry, then adjust the pH of the reactant slurry to less than 1 with acid, filter it to obtain crude aluminum fluoride and filtrate containing ferric ions. S40. The crude aluminum fluoride is washed with water and dried to obtain the aluminum fluoride product; the pH value of the filtrate containing ferric ions is adjusted with a pH adjuster and heated to generate crude ferric phosphate precipitate from the ferric ions and phosphate in the solution. S50. The crude ferric phosphate precipitate is aged with phosphoric acid solution, filtered to obtain aged ferric phosphate precipitate, washed, and then subjected to solid-liquid separation to obtain solid matter. The solid matter is then dried and calcined to obtain ferric phosphate product.

[0026] In the technical solution of this invention, lithium hexafluorophosphate in the waste electrolyte first reacts with water in the iron-aluminum waste residue to generate lithium fluoride (LiF) and phosphorus pentafluoride (PF5) gas. The highly reactive PF5 further reacts with water to generate phosphoric acid (H3PO4) and highly corrosive hydrogen fluoride (HF). Then, the generated HF preferentially reacts with the aluminum component in the iron-aluminum waste residue to form aluminum fluoride (AlF3) precipitate, which is insoluble in an acidic environment, thereby achieving selective aluminum recovery. Simultaneously, the iron component (mainly Fe) in the iron-aluminum waste residue... 3+ If present, it dissolves into the liquid phase and reacts with PO4 in the system. 3- and Li +Together, they form an iron-containing solution. Subsequently, the separated AlF3 solid (crude aluminum fluoride) is washed and dried to obtain the aluminum fluoride product. The pH value of the separated iron-containing solution is adjusted using a pH adjuster, and heating promotes the reaction of ferric ions and phosphates to generate a crude ferric phosphate precipitate. This precipitate is then aged using a phosphoric acid solution to promote the dissolution of small particles and the growth of large particles, thereby achieving impurity desorption and ferric phosphate particle optimization. Finally, the aged ferric phosphate precipitate is washed, dried, and calcined to obtain the ferric phosphate product. The resource utilization method provided by this invention not only recovers lithium from the waste electrolyte, keeping it in the solution as lithium ions for easy subsequent extraction, but also utilizes the iron and aluminum in the iron-aluminum waste residue, achieving "multiple recoveries from one material," significantly improving the overall metal recovery rate and solving the problem of low resource utilization of waste electrolyte and iron-aluminum waste residue. Simultaneously, it eliminates the need for large amounts of additional chemical agents, utilizing the components of the waste electrolyte itself to drive the reaction and consume HF, thus removing harmful F... - And Al 3+ The process transforms the material into a stable solid, avoiding the direct discharge of wastewater and exhaust gas, and maximizing resource utilization and environmental friendliness throughout the entire process.

[0027] It should be noted that when premixing iron-aluminum sludge with electrolyte, deionized water can be added according to the viscosity requirements of the slurry to adjust the solid-liquid ratio to 1: (1~3).

[0028] In an embodiment of the present invention, step S10, the preparation step of the waste electrolyte includes: Waste lithium batteries are crushed, and then the crushed material is placed in a pyrolysis furnace for pyrolysis to vaporize the electrolyte. The liquid in the condensation and recovery system of the pyrolysis furnace is collected to obtain waste electrolyte.

[0029] This invention employs a conventional pyrolysis process to recover waste electrolyte. The organic electrolyte in lithium batteries has a low boiling point (typically in the range of 80-200°C). Heating is performed under an inert atmosphere, with the heating temperature set in a low-temperature range (100-200°C). This temperature is lower than the decomposition temperature of binders (such as PVDF, decomposition temperature 350-400°C), but higher than the boiling point of carbonate organic solvents in the electrolyte (such as dimethyl carbonate 90°C, ethyl carbonate 126°C). When the temperature is raised to this range and held for 1-2 hours, the liquid electrolyte adsorbed on the electrodes and separator rapidly vaporizes into organic solvent vapor without undergoing violent decomposition or combustion. By collecting the liquid in the condensation recovery system of the pyrolysis furnace, crude electrolyte can be obtained, achieving electrolyte recovery.

[0030] In an embodiment of the present invention, in step S10, the centrifugation speed is 800~1200 r / min, and the centrifugation time is 15~30 min. Exemplarily, the centrifugation speed can be 800 r / min, 1000 r / min, or 1200 r / min, and the centrifugation time can be 15 min, 20 min, or 30 min. Centrifugation can remove solid impurities such as electrode powder and metal debris from the electrolyte.

[0031] In an embodiment of the present invention, step S20, the preparation step of the iron-aluminum-containing waste residue includes: Waste lithium batteries are crushed and pyrolyzed to obtain black powder. The black powder is then soaked in acid and filtered. The filtrate is collected to obtain an acidic leachate. The acidic leachate is then subjected to a neutralization and precipitation reaction, followed by filtration to obtain iron-aluminum-containing waste residue.

[0032] Most commercial lithium-ion batteries use aluminum foil as the positive electrode current collector. During acid leaching, the aluminum foil reacts with the acid and dissolves, converting into Al. 3+ The iron in the lithium iron phosphate battery's positive electrode active material, LiFePO4, contains a large amount of iron. After acid leaching, the iron... 2+ / Fe 3+ By adding a small amount of oxidizing agent to the leachate, the Fe in the leachate can be removed. 2+ Oxidized to Fe 3+ It should be noted that the pH range for the formation of hydroxide precipitates from ferric iron and ferric aluminum is 4.0–4.5, while the pH range for the conversion of ferrous iron to hydroxide precipitates is 8.0–8.5. Furthermore, within the pH range of 8.0–8.5, some heavy metals such as nickel and cobalt will precipitate, leading to their loss. Therefore, to improve the subsequent phosphate conversion rate and reduce the loss of heavy metals such as nickel and cobalt, the technical solution of this invention involves adding an appropriate amount of oxidant during the acid leaching process to... 2+ Oxidized to Fe 3+ Then, by adjusting the pH to the range of 4.0 to 4.5, ferric iron and ferric aluminum form hydroxide precipitates, thereby obtaining iron-aluminum-containing waste residue.

[0033] The technical solution of this invention first involves crushing and pyrolyzing waste lithium batteries to obtain black powder, and then soaking the black powder in acid to remove iron ions (Fe). 3+ ) and aluminum ions (Al 3+ The Fe was introduced into an acidic leachate, and then the pH of the acidic leachate was adjusted to allow the Fe to... 3+ And Al 3+ Within this pH range, hydrolysis generates hydroxide precipitate, which is then filtered and the solids collected to obtain iron-aluminum waste residue, which is a precipitate containing iron hydroxide and aluminum hydroxide, i.e., iron-aluminum waste residue.

[0034] In an embodiment of the present invention, step S20, the preparation step of the iron-aluminum-containing waste residue includes: Waste lithium batteries are crushed and pyrolyzed to obtain black powder. The black powder is soaked in acid and then filtered. The filtrate is collected to obtain an acidic leachate. The acidic leachate is subjected to a neutralization and precipitation reaction, and then filtered to obtain an iron-aluminum precipitate residue. An acidic leachate containing ferric ions is provided. The ferric ions in the acidic leachate containing ferric ions are extracted with an extractant to transfer the ferric ions to the organic phase. Then, the leachate is back-extracted with hydrochloric acid solution to obtain an antiferric acid solution. The antiferric acid solution is neutralized and precipitated, and then filtered to obtain an iron-containing precipitate residue. Iron-aluminum precipitate residue and iron-containing precipitate residue are mixed to obtain iron-aluminum waste residue.

[0035] Using the above technical solution, the black powder is first soaked in acid to obtain an acidic leachate. After neutralization and precipitation, and filtration, an iron-aluminum precipitate is obtained from the acidic leachate. Then, the acidic leachate containing ferric ions is extracted with a selective extractant (such as phosphoric acid extractants like P204 or P507) to remove the Fe... 3+ Extraction is performed from the aqueous phase to the organic phase, at which point hydrochloric acid (e.g., 6N hydrochloric acid) is used to react with the supported Fe. 3+ Antiferrolysis occurs through contact with an organic phase, utilizing high concentrations of H₂. + Effectively disrupts the complex structure between iron ions and the extractant, while the Cl- of hydrochloric acid... - Can be with Fe 3+ Formation of stable complex ([FeCl4)) - ), making Fe 3+ The organic phase is returned to the aqueous phase, and the aqueous phase is collected to obtain the antiferric acid solution. This antiferric acid solution is then neutralized and precipitated to remove Fe. 3+ Hydrolysis produces a hydroxide precipitate, yielding a precipitate residue containing iron hydroxide, i.e., an iron-containing precipitate residue. In one embodiment of the present invention, the iron-aluminum waste residue is obtained by mixing the iron-aluminum precipitate residue and the iron-containing precipitate residue in a 1:1 mass ratio.

[0036] It should be noted that because acidic leachates also contain precious metals such as nickel, cobalt, and manganese, selective extraction of these metals will extract not only iron but also these precious metals. Therefore, when using hydrochloric acid (such as 6N hydrochloric acid) with Fe-loaded... 3+Before contacting the organic phase for antiferrore reaction, the organic phase can be washed with sulfuric acid to remove impurities and ensure metal purity. Then, high-concentration sulfuric acid is used to transfer nickel, cobalt, and manganese from the organic phase to the aqueous phase, achieving enrichment and organic phase regeneration. After the above washing and back-extraction, iron-loaded P2O4 and P5O7 are antiferroreted with 6N hydrochloric acid to obtain an antiferric acid solution. In this way, a back-extraction solution containing nickel, cobalt, and manganese, as well as an antiferric acid solution, can be obtained.

[0037] In an embodiment of the present invention, the waste lithium battery is crushed and pyrolyzed to obtain black powder. The black powder is then soaked in acid and filtered to collect the filtrate, yielding an acidic leachate. In this step, the pyrolysis temperature is 100-400°C. For example, the pyrolysis temperature can be 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, or 400°C.

[0038] In an embodiment of the present invention, the waste lithium battery is crushed and pyrolyzed to obtain black powder. The black powder is then soaked in acid and filtered to collect the filtrate, yielding an acidic leachate. In this step, the pyrolysis time is 1-2 hours. Alternatively, the pyrolysis time can be 1 hour, 1.5 hours, or 2 hours.

[0039] The technical solution of this invention first crushes the waste lithium batteries to obtain crushed material, and then places the crushed material in an inert gas-protected pyrolysis furnace for pyrolysis treatment. The organic components (such as electrolyte, separator, and binder) are removed by pyrolysis, reducing the interference of organic impurities in the subsequent acid leaching process (if organic impurities are not removed, problems such as overflow and low reaction efficiency will occur during acid leaching).

[0040] In an embodiment of the present invention, the waste lithium battery is crushed and pyrolyzed to obtain black powder. The black powder is then soaked in acid and filtered to collect the filtrate, resulting in an acidic leachate. The pH value of the acidic leachate is set between 1.5 and 2.5. + The concentration is high enough to efficiently dissolve the target metal.

[0041] In an embodiment of the present invention, the step of neutralizing and precipitating the acidic leachate includes: adjusting the pH value of the acidic leachate to 4.0-5.0 and heating it at 80-90°C for 2-6 hours to allow the ferric ions and aluminum ions in the acidic leachate to undergo a neutralization and precipitation reaction.

[0042] Fe 3+ The pH for complete precipitation is 2.8–3.2, Al 3+ The pH for complete precipitation is 4.0–4.5. Raising the pH to 4.0–5.0 ensures that Fe… 3+ The precipitate leaves no residue and can cover Al. 3+Within the complete precipitation range, the impurity removal rate can reach over 99%. Setting the heating temperature within this range can accelerate the hydrolysis reaction rate and promote Fe... 3+ And Al 3+ The hydrolysis equilibrium shifts towards precipitation. Setting the heating time within the above range ensures that Fe... 3+ And Al 3+ The precipitate is fully converted into hydroxide precipitate, which in turn promotes crystal nucleus growth. The precipitate particles aggregate into clusters, resulting in precipitates with larger particle sizes that are easier to filter.

[0043] In an embodiment of the present invention, the step of neutralizing and precipitating the antiferric acid solution includes: adjusting the pH value of the antiferric acid solution to 4.0~5.0 and heating it at 80~90°C for 0.5~2 hours to neutralize and precipitate the ferric ions in the antiferric acid solution.

[0044] Fe 3+ The pH for complete precipitation is 2.8–3.2. Raising the pH to 4.0–5.0 ensures that Fe… 3+ It is fully converted into precipitate with no residue. Setting the temperature for the neutralization and precipitation reaction within the above range can accelerate the hydrolysis reaction rate and promote Fe... 3+ The hydrolysis equilibrium shifts towards precipitation. Setting the neutralization-precipitation reaction time within the above-mentioned range ensures that Fe... 3+ It is fully converted into hydroxide precipitate.

[0045] In an embodiment of the present invention, before step S20, the method further includes: providing untreated iron-aluminum waste residue, crushing the untreated iron-aluminum waste residue, and sieving it using a 50-200 mesh sieve. Sequentially crushing and sieving the untreated iron-aluminum waste residue can reduce agglomeration problems caused by uneven particle size during subsequent mixing with the electrolyte.

[0046] In an embodiment of the present invention, in step S20, the mass ratio of the pretreated waste electrolyte to the iron-aluminum-containing waste residue is (2~6):1. Exemplarily, the mass ratio of the pretreated waste electrolyte to the iron-aluminum-containing waste residue can be 2:1, 3:1, 4:1, 5:1, or 6:1.

[0047] In an embodiment of the present invention, in step S30, the heating temperature of the mixed slurry is 20~150℃. Exemplarily, the heating temperature of the mixed slurry can be 20℃, 40℃, 60℃, 80℃, 100℃, 120℃ or 150℃.

[0048] In an embodiment of the present invention, in step S30, the heating time of the mixed slurry is 2-4 hours. Exemplarily, the heating time of the mixed slurry can be 2 hours, 2.5 hours, 3 hours, or 4 hours.

[0049] In an embodiment of the present invention, in step S40, the pH value of the filtrate containing ferric ions is adjusted to 1.5-3.5 using a pH adjuster. Within this pH range, ferric phosphate can be stably precipitated.

[0050] In an embodiment of the present invention, in step S40, the pH adjuster includes at least one of ferric hydroxide, ammonium phosphate, diammonium phosphate, and ferric hydroxyphosphate. Using these substances as pH adjusters can reduce the introduction of other impurities.

[0051] In an embodiment of the present invention, in step S40, the heating temperature is 25~40°C. Exemplarily, the heating temperature can be 25°C, 30°C, 35°C, or 40°C. Within the above temperature range, the solubility product of iron phosphate is moderate, ensuring that Fe... 3+ With PO4 3- The rapid combination forms a stable crystal nucleus, which avoids the agglomeration caused by excessively rapid crystal growth. At the same time, impurities are difficult to embed into the crystal lattice, which helps to ensure product purity.

[0052] In an embodiment of the present invention, the heating time in step S40 is 0.5 to 3 hours. Exemplarily, the heating time of the mixed slurry can be 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0053] In an embodiment of the present invention, in step S50, the concentration of the phosphoric acid solution is 5% to 10%. Exemplarily, the concentration of the phosphoric acid solution can be 5%, 7.5%, or 10%.

[0054] In an embodiment of the present invention, in step S50, the mass ratio of the phosphoric acid solution to the crude iron phosphate precipitate is (2~3):1. Exemplarily, the mass ratio of the phosphoric acid solution to the crude iron phosphate precipitate can be 2:1, 2.5:1, or 3:1.

[0055] Using a phosphoric acid solution for aging treatment avoids the introduction of other impurities. During the aging process, the H+ ions provided by the phosphoric acid can slightly dissolve small iron phosphate particles (FePO4+H2O). + =Fe 3+ +HPO4 2- This provides solutes for the growth of large particles; on the other hand, excess PO4 in the system... 3- It can inhibit the dissolution of large-particle iron phosphate, guide the solute to preferentially deposit on the surface of large particles, and achieve uniform grain growth. In addition, the acidic environment of phosphoric acid can promote the deposition of F adsorbed on the precipitate surface. - Li +This process allows impurities to desorb, improving product purity. Therefore, the technical solution of this invention, through aging treatment, allows small particles of ferric phosphate to dissolve and recrystallize on the surface of larger particles, achieving particle growth and impurity desorption, thus improving product purity.

[0056] In an embodiment of the present invention, in step S50, the aging temperature is 55~65°C. Exemplarily, the aging temperature can be 55°C, 60°C, or 65°C.

[0057] In an embodiment of the present invention, in step S50, the aging time is 20-24 hours. Exemplarily, the aging time can be 20 hours, 22 hours, or 24 hours.

[0058] By controlling the aging temperature and aging time within the above range, better aging efficiency and impurity removal effect can be obtained while ensuring the stability of the iron phosphate crystal structure.

[0059] In an embodiment of the present invention, in step S50, the calcination temperature is 500~600℃. Exemplarily, the calcination temperature can be 500℃, 550℃, or 600℃.

[0060] In an embodiment of the present invention, the calcination time in step S50 is 2-3 hours. Exemplarily, the calcination time can be 2 hours, 2.5 hours, or 3 hours.

[0061] Transferring the dried solid to a muffle furnace for high-temperature calcination can remove residual organic matter and improve the purity of ferric phosphate products.

[0062] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0063] Example 1 A method for the resource utilization of waste electrolyte and iron-aluminum-containing waste residue includes the following steps: 1. Preparation of waste electrolyte: Waste lithium batteries are crushed, and then the crushed material is placed in a pyrolysis furnace at 350°C for 2 hours to vaporize the electrolyte. The liquid from the condensation and recovery system in the pyrolysis furnace is collected to obtain waste electrolyte.

[0064] 2. Preparation of iron-aluminum waste residue: 1) After waste lithium batteries are crushed and pyrolyzed, black powder is obtained. 1000 kg of black powder is mixed with 1200 kg of acid (98% concentration sulfuric acid) and 3.3 kg of oxidant (27.5% hydrogen peroxide), stirred and reacted for 4 hours, filtered, and the filtrate is collected to obtain acidic leachate.

[0065] 2) Adjust the temperature of the acidic leachate to 85℃ and adjust the pH of the solution to 4.0-5.0 with 250g of sodium carbonate. React for 4 hours to allow the ferric ions and aluminum ions to undergo a neutralization and precipitation reaction. Then filter to obtain iron-aluminum precipitate residue.

[0066] 3) Extract the acidic leachate with P204 and P507; then wash with sulfuric acid, back-extract with sulfuric acid, and then deferricize the iron-loaded P204 and P507 with 6N hydrochloric acid to obtain a ferric acid solution; adjust the pH of the ferric acid solution to 4.0-5.0 with 32% alkaline solution, and heat at 85℃ for 2 hours to neutralize and precipitate the ferric ions, and then filter to obtain an iron-containing precipitate residue.

[0067] 4) Mix the iron-aluminum precipitate from step 2) and the iron-containing precipitate from step 3) at a mass ratio of 1:1 to obtain iron-aluminum waste residue.

[0068] 3. Resource utilization of waste electrolyte and iron-aluminum-containing waste residue, including the following steps: 1) Pretreatment of waste electrolyte: Centrifuge 150kg of waste electrolyte at 1200r / min for 15min, and collect the supernatant to obtain 142kg of pretreated waste electrolyte.

[0069] 2) Pretreatment of iron-aluminum waste residue: 50kg of the iron-aluminum waste residue obtained above (containing 11kg Fe and 6kg Al) is crushed and screened with a 50-mesh sieve to obtain pretreated iron-aluminum waste residue. 3) Premixing: Add 142kg of pretreated waste electrolyte and 50kg of pretreated iron-aluminum waste residue into the reactor, start stirring, and premix for 15 minutes to form a mixed slurry.

[0070] 4) Separation of aluminum fluoride: The temperature inside the reactor was raised to 120℃ and the reaction was carried out for 2.5 hours to obtain a slurry of reactants. The pH value of the slurry was then adjusted to less than 1 with 98% sulfuric acid and filtered to obtain crude aluminum fluoride and a filtrate containing ferric ions. After washing and drying, 15.6 kg of aluminum fluoride product was obtained (the recovery rate of Al was calculated to be 83.57%).

[0071] 5) Slowly add 99% diammonium phosphate to the filtrate containing ferric ions obtained in step 4) to adjust the pH to 3.0, and heat at 35°C for 1.5 hours to generate crude ferric phosphate precipitate.

[0072] 6) Add 5% phosphoric acid solution (mass ratio of crude ferric phosphate precipitate to phosphoric acid solution is 1:2) to the crude ferric phosphate precipitate and mix and slurry. Then transfer the mixture to an aging tank for aging treatment, control the temperature at 60℃, and let it stand for aging for 24 hours. After aging, filter to obtain aged ferric phosphate precipitate. Wash the aged ferric phosphate precipitate and then filter to obtain solid. Add deionized water (solid-liquid ratio is 1:3) to the solid and slurry and wash again for 20 minutes to obtain washed solid. Then place the washed solid in an oven and dry at 110℃ for 6 hours to remove moisture. Then transfer it to a muffle furnace and calcine at 500℃ for 2 hours. After cooling, 17.9 kg of ferric phosphate product is obtained (the calculated Fe recovery rate is 60.25%).

[0073] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for recycling waste electrolyte and iron-containing aluminum slag, characterized in that, The method comprises the following steps: S10, centrifuging the waste electrolyte to collect the upper liquid to obtain the pretreated waste electrolyte; wherein the waste electrolyte contains lithium hexafluorophosphate; S20, providing iron and aluminum-containing waste residue, stirring the pretreated waste electrolyte and the iron and aluminum-containing waste residue to obtain a mixed slurry; wherein the iron and aluminum-containing waste residue is a waste residue containing iron hydroxide and aluminum hydroxide; S30, heating the mixed slurry to obtain a reactant slurry, then adjusting the pH value of the reactant slurry to less than 1 with an acid, filtering to obtain aluminum fluoride crude product and a filtrate containing trivalent iron ions; S40, washing and drying the aluminum fluoride crude product to obtain aluminum fluoride product; adjusting the pH value of the filtrate containing trivalent iron ions with a pH adjuster, heating to make the trivalent iron ions and phosphate in the solution generate a crude iron phosphate precipitate; S50, using a phosphoric acid solution to age the crude iron phosphate precipitate, filtering to obtain aged iron phosphate precipitate, washing the aged iron phosphate precipitate, then obtaining solid matter through solid-liquid separation treatment, sequentially drying and calcining the solid matter to obtain iron phosphate product.

2. The method according to claim 1, wherein the spent electrolyte and the spent iron-containing aluminum residue are resourcefully utilized. In step S20, the preparation steps of the iron and aluminum-containing waste residue include: After the waste lithium battery is crushed and pyrolyzed, black powder is obtained, the black powder is soaked in acid and then filtered, the filtrate is collected to obtain an acid leaching solution, the acid leaching solution is subjected to neutralization and precipitation reaction, and then filtered to obtain the iron and aluminum-containing waste residue.

3. The method according to claim 1, wherein the spent electrolyte and the spent iron-containing aluminum residue are resourcefully utilized. In step S20, the preparation steps of the iron and aluminum-containing waste residue include: After the waste lithium battery is crushed and pyrolyzed, black powder is obtained, the black powder is soaked in acid and then filtered, the filtrate is collected to obtain an acid leaching solution, the acid leaching solution is subjected to neutralization and precipitation reaction, and then filtered to obtain the iron and aluminum-containing waste residue. An acid leaching solution containing trivalent iron ions is provided, an extractant is used to extract the trivalent iron ions in the acid leaching solution containing trivalent iron ions to transfer the trivalent iron ions to an organic phase, and then a hydrochloric acid solution is used for back extraction treatment to obtain a back iron acid solution, the back iron acid solution is subjected to neutralization and precipitation reaction, and then filtered to obtain an iron-containing precipitate residue; The iron and aluminum-containing precipitate residue and the iron-containing precipitate residue are mixed to obtain the iron and aluminum-containing waste residue.

4. The method for resource utilization of waste electrolyte and iron-aluminum-containing waste residue as described in claim 2 or 3, characterized in that, The pyrolysis temperature is 100-400℃; and / or, The pyrolysis time is 1-2h; and / or, The pH value of the acid leaching solution is 1.5-2.5; And / or, The step of subjecting the acid leaching solution to neutralization and precipitation reaction includes adjusting the pH value of the acid leaching solution to 4.0-5.0 and heating at 80-90℃ for 2-6h to make the trivalent iron ions and aluminum ions in the acid leaching solution undergo neutralization and precipitation reaction.

5. The method for resource utilization of waste electrolyte and iron-aluminum-containing waste residue as described in claim 3, characterized in that, The step of subjecting the back iron acid solution to neutralization and precipitation reaction includes adjusting the pH value of the back iron acid solution to 4.0-5.0 and heating at 80-90℃ for 0.5-2h to make the trivalent iron ions in the back iron acid solution undergo neutralization and precipitation reaction.

6. The method according to claim 1, wherein the spent electrolyte and the spent iron-containing aluminum residue are resourcefully utilized. Before step S20, it further includes: The untreated iron-containing aluminum waste residue is provided, the untreated iron-containing aluminum waste residue is crushed and sieved by a 50-200 mesh sieve.

7. The method according to claim 1, wherein the spent electrolyte and the spent iron-containing aluminum residue are resourcefully utilized. In step S20, the mass ratio of the pre-processed waste electrolyte to the iron-containing aluminum waste residue is (2-6):

1.

8. The method according to claim 1, wherein the spent electrolyte and the spent iron-containing aluminum residue are resourcefully utilized. In step S30: The heating temperature of the mixed slurry is 20-150°C; and / or, The heating time of the mixed slurry is 2-4h.

9. The method according to claim 1, wherein the spent electrolyte and the spent iron-containing aluminum residue are resourcefully utilized. In step S40: The pH value of the filtrate containing ferric ions is adjusted to 1.5-3.5 by using a pH adjuster; and / or, The pH adjuster comprises at least one of iron hydroxide, ammonium phosphate, diammonium phosphate, and iron hydroxyl phosphate; and / or, The heating temperature is 25-40°C; and / or, The heating time is 0.5-3h.

10. The method according to claim 1, wherein the spent electrolyte and the spent iron-containing aluminum residue are resourcefully utilized. In step S50: The concentration of the phosphoric acid solution is 5%-10%; and / or, The mass ratio of the phosphoric acid solution to the crude iron phosphate precipitate is (2-3):1; and / or, The aging temperature is 55-65°C; and / or, The aging time is 20-24h; and / or, The calcination treatment temperature is 500-600°C; and / or, The calcination treatment time is 2-3h.

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