Fluoride Removal Methods

Abstract

The present disclosure relates to a method for removing fluoride from an acidic solution that involves a series of precipitation steps that selectively increase the pH using a neutralizing agent.

Description

[Technical field]

[0001] The present disclosure relates to a method for removing fluoride from an acidic solution, which may be part of battery recycling, and in which the acidic solution may be prepared by liquid phase acid leaching of crushed batteries or battery materials. [Background technology]

[0002] Rechargeable batteries, also called secondary batteries, are widely used as power supply and energy storage systems. As a result of pressure from policymakers and global awareness, the number of electric vehicles in the world will increase significantly in the coming years, which will, in turn, lead to a significant increase in the number of secondary batteries. Secondary batteries can be based on different technologies, e.g., nickel-cadmium (NiCd) or nickel metal hydride (NiMH) technologies. In the transportation sector, secondary lithium-ion batteries (LIBs) have become the most used power source. In LIBs, lithium composite oxides, which typically contain lithium and the metals nickel, cobalt and / or manganese (the so-called "NCM metals"), are used as active materials.

[0003] Some of the chemical elements contained in batteries such as LIBs, such as lithium, cobalt, nickel, aluminum, copper and manganese, are valuable, especially considering the growing demand for electric vehicles and batteries on the one hand, and the scarcity of resources on the other hand, making battery recycling crucial to achieve an economical and environmentally friendly production of batteries. Hydrometallurgical recycling, which uses multi-step processing and chemical methods to extract and recover valuable metals from batteries, including acid leaching of feedstocks mainly containing reduced size battery materials (so-called "black mass") or mixed hydroxide precipitates (MHP) or mixed sulfide precipitates (MSP) to obtain valuable metals such as Ni, Co and Mn dissolved in solution, is the most cost-effective and effective recycling method, and is also preferred from an environmentally friendly point of view.

[0004] A battery cell, or simply "cell", generally includes an anode, a cathode, a separator, and an electrolyte. The electrolyte acts as a conductor that allows ions to move between the positive electrode (cathode) and the negative electrode (anode) and vice versa in oxidation and reduction reactions, respectively. LIBs are a type of rechargeable battery in which lithium ions move from the anode to the cathode during discharge. In addition, a battery cell typically includes a casing that houses the electrodes, separator, and electrolyte, current collectors or terminals, and various safety devices such as polymer gaskets, vents, or valves. The positive terminal is connected to the cathode, for example by an aluminum tab, and the negative terminal is connected to the anode, for example by a copper tab. Thus, batteries such as LIBs include many different materials, especially the plastics and metals that make up the housing, the cathode and anode materials, the separator, and the electrolyte. The electrolyte often contains fluorides. Common electrolyte salts used in LIBs are fluoride-containing salts, such as LiPF6. This salt ends up as a black mass after mechanical size reduction of spent batteries, and is offered for recycling together with the active material and impurities. This salt dissolves in acidic solutions, thus introducing fluoride into the solution.

[0005] Removal of fluorides is one of the biggest challenges in the hydrometallurgical process of battery recycling, as high levels of fluoride concentration in the pregnant leach solution (PLS) limit the material of the processing facility and significantly impact capital expenditures (capex) and operational costs (opex). Furthermore, fluorides form salts (LiF), which are sparingly soluble in lithium, if not removed before lithium recovery. The formation of LiF reduces the quality of salts, such as Ni, Co and Mn salts, recovered in later stages of recycling. Therefore, there is a need for a method that can significantly remove fluoride from acidic solutions, minimizing the environmental impact of recycling overall, and battery recycling in particular, opex and capex, and reducing the solution to a concentration that can be safely handled, so that subsequent steps to recover valuable materials can be carried out without fluoride distractions. Summary of the Invention

[0006] In view of this demand for a fluoride removal method, it is an object of the present disclosure to provide a simple and efficient method for removing fluoride from acidic solutions.

[0007] It is further an object of the present disclosure to provide a simple and efficient method for removing fluoride from the acid leach solution prepared by liquid phase acid leaching of crushed batteries or battery materials while minimizing the loss of valuable metals contained in the solution, such as NCM metals.

[0008] Additionally, it is an object of the present disclosure to provide a method for the efficient removal of fluoride from acidic solutions that does not introduce new chemical impurities into the system and allows for the conversion of fluoride to a neutral salt that is easy to handle and dispose of.

[0009] Furthermore, it is an object of the present disclosure to provide a method for removing fluoride from an acidic solution that allows minimizing the opex and capex of battery recycling and is more environmentally friendly, thus ensuring economical and environmentally friendly production of lithium-ion secondary batteries.

[0010] One or more of these objects may be achieved by a method for removing fluoride from an acidic solution according to independent claim 1. The independent claim 1 and the dependent claims may be combined in a technically suitable and expedient manner to provide further aspects of the invention.

[0011] According to the present disclosure, there is provided a method for removing fluoride from an acidic solution, comprising the steps of: a) Preparing an acidic leachate containing fluoride; b) a first precipitation stage of adjusting the pH of the leachate of step a) to 4-5 by addition of a neutralizing agent to form a first fluoride-containing precipitate and separating the first fluoride-containing precipitate to obtain a first fluoride-reduced leachate; c) a second precipitation step of increasing the pH of the first fluoride-reduced leachate to greater than 5 and less than or equal to 6 by addition of a neutralizing agent to form a second fluoride-containing precipitate and separating the second fluoride-containing precipitate to obtain a second fluoride-reduced leachate. A method is provided, comprising:

[0012] The application of a series of precipitation steps according to the disclosed method, which successively increases the pH of the acidic fluoride-containing solution by the addition of neutralizing agents, advantageously results in the formation of insoluble neutral fluoride-containing salts that are easy to handle and can be easily separated and disposed of, thereby significantly reducing the fluoride content. The disclosed method advantageously allows for a simple and efficient removal of fluoride from acidic solutions, in particular from acidic leach solutions prepared by liquid-phase acidic leaching of crushed batteries or battery materials, while minimizing the loss of valuable metals that may be contained in the solution, such as Ni, Co and Mn. The disclosed method further advantageously allows for efficient fluoride removal to be achieved by using agents, such as neutralizing agents, that do not introduce new unwanted chemical or metal impurities into the system. This allows the subsequent steps of recovering valuable battery materials to be carried out with high yields without fluoride distraction. The disclosed method thus allows for the minimization of opex and capex in battery recycling, as well as economical and environmentally friendly battery production.

[0013] Different aspects will be described below with reference to the drawings. The drawings in the following description only show some aspects of the present disclosure, and those skilled in the art can further derive other aspects from the drawings without creative efforts. [Brief description of the drawings]

[0014] [Figure 1]FIG. 1 is a schematic flow diagram showing a method for removing fluoride from an acidic solution according to one embodiment of the present disclosure, comprising three precipitation stages PS1, PS2 and PS3. In the first precipitation stage (PS1), in step A1, a fluoride-containing pregnant leach solution (PLS; pH about 0.5) prepared from reductive acidic leaching of black mass is mixed with nickel manganese cobalt hydroxide (NMC(OH)2) as a neutralizing agent to increase the pH of the leach solution to 4-5 and initiate precipitation. At least a portion of the NMC(OH)2 used in step A1 is recycled back from the second precipitation stage. In the case of black mass obtained from lithium ion batteries, the PLS contains, for example, but not limited to, Ni, Mn, Co, Li, and impurities Al, Cu, Fe, Zn, Mg, K, P and F. Then, in a filtration step B1, the precipitate (P1) formed in step A1, containing mainly Fe(OH)3, Al(OH)3, Cu(OH)3, NMC(OH)2, MgF2, AlFx complexes, is separated and discarded as process waste. The precipitation in the first precipitation stage can be carried out in a series of reaction tanks connected together at 30-60 °C with a residence time of 2-6 hours. In the second precipitation stage (PS2), the leach solution PLS1 obtained after separating the precipitate P1 in the first precipitation stage and with a reduced fluoride concentration is mixed in step A2 with the neutralizing agents NMC(OH)2 and NaOH, and the pH is further increased to >5-<6 to start the precipitation. Then, a filtration step B2 is carried out to separate the precipitate (P2) formed, containing mainly Al(OH)3, Cu(OH)3, MgF2, AlFx complexes and NMC(OH)2. The precipitate P2 separated in step B2 may be isolated and recycled back to the first precipitation stage in order to reuse the coprecipitated NMC(OH)2 as neutralizing agent in step A1. The precipitation in the second precipitation stage can be carried out in a series of interconnected reaction vessels at 30-60°C with a residence time of 2-6 hours. In the third stage of precipitation (PS3), the leach solution PLS2 obtained after separating the precipitate P2 in the second precipitation stage and with a further reduced fluoride concentration is mixed with Mg(SO4) as precipitating agent in step A3 to further precipitate the fluorides.The precipitate (P3) formed in step A3, mainly containing MgF2, is separated in a filtration step B3 and discarded as process waste. The precipitation in the third precipitation stage can be carried out in a series of interconnected reaction vessels at a pH of >5 to <6, preferably the same as in step A2, at 30 to 60°C with a residence time of 2 to 6 hours. The leachate solution PLS3 obtained after separation of P3 in the third precipitation stage, with a further reduced fluoride concentration, may be subjected to subsequent steps for the recovery of valuable battery materials, including for example Ni, Mn, Co and Li. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Detailed Description The technical solutions of the aspects of the present application will be described in more detail with reference to the drawings. It is clear that the described aspects are not all but some of the aspects of the present application. The features of various aspects can be combined to form further representative aspects of the present disclosure that may not be explicitly described or illustrated. All other aspects obtained by those skilled in the art based on the aspects of the present invention without creative efforts shall belong to the protection scope of the present invention. Furthermore, since the scope of the present invention is defined by the claims and their equivalents, it is understood that the words and terms used in this specification are only used to describe certain aspects and are not intended to be limiting.

[0016] Disclosed herein is a method for removing fluoride from an acidic solution, comprising the steps of: a) Preparing an acidic leachate containing fluoride; b) a first precipitation stage of adjusting the pH of the leachate of step a) to 4-5 by addition of a neutralizing agent to form a first fluoride-containing precipitate and separating the first fluoride-containing precipitate to obtain a first fluoride-reduced leachate; c) a second precipitation step of increasing the pH of the first fluoride-reduced leachate to greater than 5 and less than or equal to 6 by addition of a neutralizing agent to form a second fluoride-containing precipitate and separating the second fluoride-containing precipitate to obtain a second fluoride-reduced leachate. The method includes:

[0017] In a preferred embodiment of the method of the present disclosure, the fluoride-containing acid leachate or leach solution, the terms of which are used interchangeably herein, is prepared by liquid-phase acid leaching, in particular by liquid-phase acid leaching of a fluoride-containing feedstock containing mainly crushed batteries or battery materials, commonly referred to as "black mass". More preferably, the fluoride-containing feedstock is black mass. The black mass is preferably obtained by crushing lithium-ion batteries, in particular secondary lithium-ion batteries. However, the fluoride-containing feedstock may be obtained from other sources, for example feedstocks that are fluoride-containing raw or recycled materials such as mixed hydroxide precipitates (MHP) and mixed sulfide precipitates (MSP), combinations thereof, or combinations thereof with black mass.

[0018] In this application, the term "battery" is intended to include battery cells, battery modules that typically usually have multiple battery cells, and battery packs that typically contain multiple battery modules. Additionally, in this application, the term "battery" is intended to include disposable batteries and rechargeable batteries.

[0019] Battery shredding is a step in battery recycling that usually starts with sorting waste batteries according to their chemical composition, then crushing or shredding them to obtain battery materials of reduced size. As explained above, batteries contain various materials, including plastics and metals that make up the battery housing, separators, cathode and anode materials, and electrolytes. After shredding, a series of filtering and sieving steps are performed to separate the plastic and metal fragments, and finally, as a product, a black mass containing mainly electrolyte, cathode and anode materials is obtained. However, the composition of the black mass usually varies depending on the type of battery used as raw material and the chemicals contained therein, and because battery sorting is often difficult or ignored.

[0020] The terms "cathode material" and "cathode active material" are used interchangeably to represent the material or metal that constitutes the main active component of the cathode. In lithium-ion batteries, lithium transition metal composite oxides or lithium iron phosphate (LiFePO4) containing nickel (Ni), cobalt (Co) and / or manganese (Mn) (so-called "NCM metals") are usually used as cathode materials. Representative examples of lithium transition metal composite oxides are lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), lithium nickel cobalt oxide (LiNi x Co 1-x O2(0 < x < 1) or LiNi 1-x-y Co x Al y O2(0 < x ≤ 0.2, 0 < y ≤ 0.1)) and lithium nickel cobalt manganese (NCM) oxide (LiNi 1-x-y Co x Mn y O2(0 < x + y < 1)).

[0021] The terms "anode material" and "anode active material" are used interchangeably to represent the material or metal that constitutes the main active component of the anode. Usually, graphite powder is used as the anode material in lithium-ion batteries. However, in this specification, the term "anode material" is understood to include natural and artificial graphite, activated carbon, carbon black, conductive additives, lithium titanate (LTO), surface-functionalized silicon, and high-performance powdered graphene.

[0022] The electrolyte of a lithium-ion battery is a liquid and typically contains a fluoride-containing salt such as lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(bistrifluoromethanesulfonyl) (LiTFSI) or a lithium fluoroalkylphosphate dissolved in an organic solvent, for example a mixture of C1-C6 alkyl carbonates, e.g., ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate (PC).

[0023] Therefore, the black mass obtained by crushing lithium ion batteries usually contains, for example, about 28 to 40% by weight of Ni, Co and / or Mn, about 3 to 5% by weight of Li, about 30 to 40% by weight of graphite, about 2 to 5% by weight of metallic impurities such as Al, Cu, Fe and / or Mg, about 1 to 2% by weight of organic compounds, about 1% by weight of other impurities such as Ca, P, Si, Zn, K and Na, and about 1 to 2% by weight of fluorides.

[0024] Leaching of the fluoride-containing feedstock may be carried out by any method known to those skilled in the art to be suitable for preparing an acid leach solution, such as, but not limited to, acid leaching or acid roasting, although liquid phase acid leaching using an acid or acid solution as a solvent is preferred for preparing a fluoride-containing acid leach solution.

[0025] Liquid-phase acid leaching of fluoride-containing feedstocks such as black mass dissolves electrode materials, impurities and salts from the electrolyte into solution, leaving graphite, plastic debris and undissolved metals as the insoluble fraction. Thus, the leachate obtained by liquid-phase acid leaching of black mass from crushed lithium-ion batteries may contain lithium (Li) and valuable cathode materials nickel (Ni), cobalt (Co) and / or manganese (Mn) ("NCM metals") as major components, and may contain, in addition to fluoride (F), one or more of the following undesirable impurities, including but not limited to aluminum (Al), copper (Cu), iron (Fe), magnesium (Mg), calcium (Ca), phosphorus (P), silicon (Si), zinc (Zn), potassium (K) and sodium (Na). As explained above, the amount and concentration of each of the electrode materials and impurities in the leachate will vary depending on the composition of the black mass or feedstock used for leaching and the conditions applied during leaching.

[0026] According to a particularly preferred embodiment, which is particularly suitable for leaching black mass, the liquid phase acidic leaching to provide a fluoride-containing acidic leach solution is carried out at atmospheric pressure using sulphuric acid (H2SO4) and hydrogen peroxide (H2O2) as reducing agents.

[0027] In embodiments, the pH of the provided acidic leachate is typically less than 1.5, such as less than 1, and preferably less than 0.5, such as about 0.3 to 0.5.

[0028] The disclosed method includes a first precipitation stage b) in which the pH of the fluoride-containing acidic leachate of step a) is adjusted to 4-5 by addition of a neutralizing agent to form a first fluoride-containing precipitate, followed by separation of the first fluoride-containing precipitate to obtain a first fluoride-reduced leachate. More preferably, in the first precipitation stage the pH of the leachate is adjusted to 4.2-4.7. Adjusting the pH within this range ensures maximum precipitation yield of undesired impurities such as F and Fe or Al, while at the same time minimum amounts of valuable metals such as Ni, Co, Mn are co-precipitated. Thus, the amount of valuable metal loss can be minimized.

[0029] That is, in the first precipitation stage, the pH of the leach solution is increased to 4-5, preferably 4.2-4.7, using a neutralizing agent to initiate precipitation, and then the precipitate formed is separated. Due to the increase in pH and the associated changes in solubility and complexation reactions, fluorides can be precipitated from the solution as insoluble salts until a certain saturation level is reached, leaving a leachate with a reduced fluoride concentration as a supernatant liquid. It is understood that not only fluoride salts are precipitated, but also insoluble salts of other cations and anions that may be contained and dissolved in the acidic leachate may be precipitated or co-precipitated. Thus, the first fluoride-containing precipitate may not only consist of fluoride salts, but may also be a precipitate or co-precipitate of fluoride salts and one or more additional salts. For example, in the particular pH range set in the first precipitation stage b), if present, precipitation of Fe, Al, Cu, Ni, Co and Mn may additionally occur, especially as insoluble hydroxides or phosphates, and F may be, depending on the cations present in the leachate, for example, as magnesium fluoride (MgF2), calcium fluoride (CaF2) and / or aluminium fluoride (AlF x ) complexes may precipitate.

[0030] Thus, in the method of the present disclosure, the fluoride-containing acidic leach solution provided in step a) or the fluoride-containing feedstock or black mass used to provide the acidic leach solution in step a) preferably already contains metal cations that form insoluble salts with fluorides, in particular one or more of Ni, Mn, Co, Al, Na and Mg. Alternatively, such one or more metal cations may be added separately to the acidic solution, for example in the form of a neutralizing agent.

[0031] The neutralizing agents used in the first precipitation stage are preferably selected from sodium hydroxide (NaOH), lithium hydroxide (LiOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), lithium carbonate (Li2CO3), nickel hydroxide (Ni(OH)2), manganese hydroxide (Mn(OH)2), cobalt hydroxide (Co(OH)2), nickel cobalt manganese hydroxide NiCoMn(OH)2 and mixtures of one or more thereof. The use of these neutralizing agents also advantageously avoids the introduction of new metal impurities into the leach solution.

[0032] More preferably, the neutralising agent used in the first precipitation stage comprises at least one or more of nickel hydroxide (Ni(OH)2), manganese hydroxide (Mn(OH)2), cobalt hydroxide (Co(OH)2) and nickel cobalt manganese hydroxide (NiCoMn(OH)2). The use of any one of these neutralising agents is advantageous as it reduces losses of the valuable NCM metals Ni, Co and Mn, especially when these metals are initially contained in the leach solution of step a), e.g. after liquid phase acidic leaching of the feedstock, and when the NCM hydroxide used as neutralising agent in this step is itself a recycled material.

[0033] In a preferred embodiment of the disclosed method, in the first precipitation step b), in addition to the neutralizing agent, phosphoric acid (H3PO4) and / or potassium silicate (K2SiO3) are added to the leachate. The addition of phosphoric acid (H3PO4) allows efficient precipitation of iron (Fe) and aluminum (Al) because Fe and Al as phosphates in the trivalent state have low solubility. Precipitation of Fe and Al as phosphates may be advantageous compared to precipitation in the form of hydroxides because Al and Fe hydroxides tend to absorb NCM metals and lithium. Furthermore, Al and Fe phosphates may be easier to separate and wash, e.g. by filtration, than the corresponding hydroxides, making them easier to recover. The addition of potassium silicate (K2SiO3) allows increased fluoride precipitation in the form of potassium fluorosilicate (K2(SiF6)), which has low solubility and can be easily separated and disposed of.

[0034] In a preferred embodiment of the method of the present disclosure, the first precipitation step is carried out at a temperature between 30° C. and 60° C., more preferably between 40° C. and 50° C. At this temperature, the efficiency of the precipitation can be increased.

[0035] In a further preferred embodiment of the process of the present disclosure, the residence time of the first precipitation stage is between 2 and 12 hours, more preferably between 2 and 6 hours, even more preferably between 3 and 5 hours, which advantageously allows the formation of a large amount of precipitate.

[0036] That is, in the method of the present disclosure, the temperature during precipitation in the first precipitation stage is preferably controlled to be between 30° C. and 60° C., more preferably between 40° C. and 50° C. Alternatively or additionally, preferably additionally, the residence time for precipitation in the first precipitation stage is preferably set to be between 2 and 12 hours, more preferably between 2 and 6 hours, even more preferably between 3 and 5 hours. Since temperature and time are correlated, i.e., a higher temperature results in a shorter residence time and a lower temperature results in a longer residence time, an optimal relationship between precipitation efficiency and energy consumption can be adjusted.

[0037] The separation of the first fluoride-containing precipitate may be carried out by methods known to those skilled in the art. For example, the first fluoride-containing precipitate may be separated from the leachate by filtration using a filter, a centrifuge or a cyclone. The separated precipitate may be discarded as waste, or may be isolated and washed, for example with water, for further recovery of the metals contained therein.

[0038] The disclosed method includes a second precipitation step c) in which the pH of the first fluoride-reduced leachate of step b) is increased to >5-6 by addition of a neutralizing agent to form a second fluoride-containing precipitate, and then the second fluoride-containing precipitate is separated to obtain a second fluoride-reduced leachate. More preferably, in the second precipitation step, the pH of the first fluoride-reduced leachate is adjusted to 5.3-5.7. Adjusting the pH to within this range can further reduce the concentration of undesired impurities such as Fe or Al in the leachate.

[0039] That is, in the second precipitation step, the pH of the first fluoride-reduced leachate obtained from the first precipitation step is further increased to above 5 to below 6, preferably to 5.3 to 5.7, using a neutralizing agent to initiate further precipitation. Due to the further increase in pH and the associated changes in solubility and complexation reactions, fluoride can be further precipitated from the solution in the form of insoluble salts until a certain saturation level is reached, leaving a second fluoride-reduced leachate with a further reduced fluoride concentration as the supernatant. Here again, it is understood that in the second precipitation step c), not only fluoride salts are precipitated, but also insoluble salts of other cations and anions that may be contained and dissolved in the leachate may be precipitated or co-precipitated. Thus, the second fluoride-containing precipitate may also consist of fluoride salts, but may also be a precipitate or co-precipitate of fluoride salts and one or more additional salts. For example, in the particular pH range set in the second precipitation stage c), if present, precipitation of Fe, Al, Cu, Ni, Co and Mn may additionally occur, especially as insoluble hydroxides, and F may be, depending on the cations present in the leachate, for example, as magnesium fluoride (MgF2), calcium fluoride (CaF2) and / or aluminium fluoride (AlF x ) complexes may precipitate.

[0040] The neutralizing agents used in the second precipitation stage are preferably selected from sodium hydroxide (NaOH), lithium hydroxide (LiOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), lithium carbonate (Li2CO3), nickel hydroxide (Ni(OH)2), manganese hydroxide (Mn(OH)2), cobalt hydroxide (Co(OH)2), nickel cobalt manganese hydroxide NiCoMn(OH)2 and mixtures of one or more thereof, more preferably selected from NaOH, Li2CO3, Ni(OH)2, Mn(OH)2, Co(OH)2, NiCoMn(OH)2 and mixtures of one or more thereof. The use of these neutralizing agents also advantageously avoids the introduction of new metal impurities into the leach solution.

[0041] The neutralizing agents used in the first and second precipitation steps can be selected independently, i.e., the neutralizing agent used in the second precipitation step can be the same or different from the neutralizing agent used in the first precipitation step.

[0042] In a further preferred embodiment of the disclosed method, the neutralizing agent used in the second precipitation step comprises at least one or more of nickel hydroxide (Ni(OH)2), manganese hydroxide (Mn(OH)2), cobalt hydroxide (Co(OH)2) and nickel cobalt manganese hydroxide (NiCoMn(OH)2). The use of any one of these neutralizing agents is advantageous because it can reduce the loss of valuable NCM metals Ni, Co and Mn, especially if the NCM metals are already contained in the leach solution.

[0043] In embodiments of the disclosed method, in the second precipitation step c), in order to increase precipitation efficiency, sodium hydroxide (NaOH) and / or lithium carbonate (LiCO) are added to the first fluoride-reduced leachate in addition to one or more of NiCoMn(OH)2, Ni(OH)2, Mn(OH)2 and Co(OH)2 as neutralizing agents.

[0044] In a preferred embodiment of the method of the present disclosure, the second precipitation step is carried out at 30° C. to 60° C., more preferably at 40° C. to 50° C. This temperature can increase the efficiency of precipitation in the second precipitation step and at the same time inhibit the crystallization of Ni, Mn and / or Co salts.

[0045] In a further preferred embodiment of the process of the present disclosure, the residence time of the second precipitation stage is between 2 and 12 hours, more preferably between 2 and 6 hours, even more preferably between 3 and 5 hours, which advantageously allows the formation of a large amount of precipitate in the second precipitation stage.

[0046] That is, in the method of the present disclosure, the temperature during precipitation in the second precipitation stage is preferably controlled within the range of 30° C. to 60° C., more preferably 40° C. to 50° C. Alternatively or additionally, preferably additionally, the residence time for precipitation in the second precipitation stage is preferably set to 2 to 12 hours, more preferably 2 to 6 hours, even more preferably 3 to 5 hours. Since temperature and time are correlated, i.e., a higher temperature results in a shorter residence time and a lower temperature results in a longer residence time, an optimal relationship between precipitation efficiency and energy consumption can be adjusted in the second precipitation stage.

[0047] However, the temperature and residence time in the first and second precipitation stages can be selected independently, which means that the temperature and residence time set in the second precipitation stage can be the same or different from the temperature and residence time set in the first precipitation stage.

[0048] The separation of the second fluoride-containing precipitate may be carried out by methods known to those skilled in the art. For example, the second fluoride-containing precipitate may be separated from the first fluoride-reduced leachate by filtration using a filter, a centrifuge or a cyclone. The separated second fluoride-containing precipitate may be discarded as waste or may be isolated and, for example, washed with water for further recovery of the metals contained therein. However, alternatively, the isolated second fluoride-containing precipitate may be recycled, at least in part, back to the first precipitation stage. As explained above, there may be significant amounts of co-precipitation of Ni, Co and Mn as hydroxides due to the increased pH in the second precipitation stage, and / or significant amounts of undissolved NMC hydroxide neutralizer due to the slow reaction rate at the higher pH applied in the second precipitation stage. Thus, the isolated second fluoride-containing precipitate may contain significant amounts of NMC hydroxide and may be recycled at least in part, but preferably in whole, back to the first precipitation stage as a neutralizing agent without further washing or separation of the NMC hydroxide to recover the NMC content and reduce losses of NCM metals.

[0049] Therefore, in a further preferred embodiment, the method of the present disclosure further comprises a step d) of recycling the separated second fluoride-containing precipitate back to the first precipitation stage.

[0050] The second fluoride-reduced leachate obtained from the second precipitation step may be used directly, for example to provide a subsequent process for the recovery of valuable battery materials. However, AlF x Alternatively, the second fluoride-reduced leachate may be subjected to a further precipitation step, if desired, to further precipitate F in a less soluble form, since some fluoride-containing complexes such as tend to decompose and release F due to the increased pH in the second precipitation step, thereby leaving free F ions in the leachate. This can further reduce the concentration of fluoride in the leachate solution.

[0051] Thus, according to one embodiment, the method of the present disclosure further comprises a third precipitation step, preferably comprising adding an alkaline earth metal salt to the second fluoride-reduced leachate to precipitate inorganic fluoride compounds, which are then separated to obtain a third fluoride-reduced leachate.

[0052] More preferably, in this embodiment, an alkaline earth metal salt is added at a concentration of 100 to 240 g / L in order to initiate precipitation of the inorganic fluorine compound and further reduce the fluoride concentration.

[0053] More preferably according to this embodiment, the alkaline earth metal salt is a magnesium salt such as magnesium sulfate (MgSO4) or magnesium carbonate (MgCO3) to precipitate the fluoride as sparingly soluble magnesium fluoride (MgF2). The inorganic fluorine compound precipitated according to this embodiment is therefore MgF2, which is advantageous as it can be easily separated from the leach solution and disposed of.

[0054] More preferably according to this embodiment, the pH of the second fluoride-reduced leachate is maintained during the third precipitation stage, in other words the pH of the second fluoride-reduced leachate during the third precipitation stage is adjusted to be the same as that during the second precipitation step, thereby preventing, for example, unwanted precipitation or co-precipitation of NCM metals.

[0055] More preferably according to this aspect of the method of the present disclosure, the third precipitation step is carried out at 30-60° C., more preferably at 40-50° C. At this temperature, the efficiency of precipitation of the inorganic fluorine compound can be increased, while at the same time, the crystallization of the Ni, Mn and / or Co salts can be inhibited.

[0056] More preferably according to this embodiment, the residence time in the third precipitation stage is between 2 and 12 hours, more preferably between 2 and 6 hours, even more preferably between 3 and 5 hours, which advantageously allows the formation of a large amount of precipitate in the third precipitation stage.

[0057] That is, in this embodiment of the method of the present disclosure, the temperature during precipitation in the third precipitation stage is preferably controlled to be between 30° C. and 60° C., more preferably between 40° C. and 50° C. Alternatively or additionally, preferably additionally, the residence time for precipitation in the third precipitation stage is preferably set to be between 2 and 12 hours, more preferably between 2 and 6 hours, even more preferably between 3 and 5 hours. Since temperature and time are correlated, i.e., higher temperatures correspond to shorter residence times and lower temperatures correspond to longer residence times, an optimal relationship between precipitation efficiency and energy consumption can be adjusted in the third precipitation stage.

[0058] Separation of the precipitated inorganic fluoride compounds may be performed by methods known to those skilled in the art. For example, the precipitated inorganic fluoride compounds may be separated from the second fluoride-reduced leachate by filtration using a filter or sieve. The isolated inorganic fluoride compounds may then be disposed of as waste.

[0059] In the third precipitation stage, the concentration of residual fluoride in the resulting leachate is even further reduced to a certain saturation level, depending on the pH of the leachate and the concentrations of other ions in the leachate.

[0060] The third fluoride-reduced leachate thus obtained may be used directly, for example to provide for a subsequent process for recovering valuable battery materials.

[0061] Thus, the method disclosed herein advantageously allows for a simple and efficient removal of fluorides from acidic solutions, particularly acidic leach solutions, below concentrations that allow for safe handling of the solution, while minimizing the loss of valuable electrode materials, such as NCM metals, that may be present in the leach solution. Subsequent steps of recovering battery materials can therefore be carried out with high yields without the distraction of fluorides. In addition, the method disclosed herein advantageously does not introduce new chemical or metal impurities into the system, but still allows for the conversion of fluorides into neutral salts that are easy to handle and dispose of. Thus, the method disclosed herein allows for the minimization of opex and capex of battery recycling, making battery production economical and environmentally friendly.

[0062] Without further elaboration, it is believed that one skilled in the art can utilize the present invention to its fullest extent using this specification, including the drawings. Although the present invention has been described herein in terms of its preferred embodiments which are the best modes known to practice the invention, it will be understood that various modifications, which will be apparent to those skilled in the art, can be made therein without departing from the spirit and scope of the present disclosure as set forth in the appended claims. EXAMPLES

[0063] The concept of the present invention was demonstrated in a laboratory scale test using an overhead stirrer, a heating plate with magnetic stirring, a glass beaker (glass reactor, 1 L) and a Buchner funnel to perform 10 cycles of the method to separate solids and liquids.

[0064] These cycles include leaching, a first impurity precipitation stage (impurity precipitation stage 1) and a second impurity precipitation stage (impurity precipitation stage 2), with the cake from the second impurity precipitation stage (recycle cake) being returned to the first impurity precipitation stage.

[0065] First, the black mass was leached by mixing with water, sulfuric acid and hydrogen peroxide in a reactor equipped with an overhead stirrer. This process was carried out at 60°C for a reaction time of 180 minutes until optimal leaching yield was reached. After leaching, a first impurity precipitation stage was carried out, in which recycled cake from the second impurity precipitation stage and NMC-OH slurry were added until a pH close to 4.5 was reached, the hot plate temperature was set at 40°C, and the reaction was allowed to proceed for 4 hours before filtering through a Buchner funnel. After the first impurity precipitation stage, a second impurity precipitation stage was carried out, in which NMC-OH slurry was added until a pH close to 5.5 was reached, the hot plate temperature was set at 40°C, and the reaction was allowed to proceed for 4 hours before filtering through a Buchner funnel. The results are shown in Table 1.

[0066] [Table 1]

[0067] For each cycle, the fluoride content (F) in mg / L of the leaching step, impurity precipitation stage 1 and impurity precipitation stage 2 is specified, the amount of nickel manganese cobalt hydroxide NMC(OH)2 added in grams (g) in impurity precipitation stages 1 (recycled and added) and 2 is specified, and the pH reached at each stage is specified, as per Table 1. It should be noted that this example is only intended to illustrate the concept of the invention rather than an actual industrial implementation, and that in implementation, for example, additional steps or treatments may be added to further reduce the fluoride levels.

Claims

1. 1. A method for removing fluoride from an acidic solution, comprising: a) providing a fluoride-containing acidic leachate; b) a first precipitation stage of adjusting the pH of the leachate of step a) to 4-5 by adding a neutralizing agent to form a first fluoride-containing precipitate and separating said first fluoride-containing precipitate to obtain a first fluoride-reduced leachate; c) a second precipitation step of increasing the pH of said first fluoride-reduced leachate to greater than 5 and less than or equal to 6 by adding a neutralizing agent to form a second fluoride-containing precipitate, and separating said second fluoride-containing precipitate to obtain a second fluoride-reduced leachate. A method comprising:

2. 2. The method of claim 1, wherein in the first precipitation step, the pH of the leachate is adjusted to 4.2 to 4.

7.

3. 2. The method of claim 1, wherein in the second precipitation stage, the pH of the first fluoride-reduced leachate is adjusted to 5.3 to 5.

7.

4. The neutralizing agent in the first and second precipitation steps may be the same or different and may be selected from the group consisting of NaOH, LiOH, KOH, NH ４ OH, Li ２ CO ３ , Ni(OH) ２ , Mn(OH) ２ , Co(OH) ２ , NiCoMn(OH) ２ and mixtures of one or more thereof.

5. The neutralizing agent in the first and second precipitation steps may be the same or different and may be Ni(OH) ２ , Mn(OH) ２ , Co(OH) ２ and NiCoMn(OH) ２ The method of claim 1 , comprising at least one or more of the following:

6. In the first precipitation step, the leachate is added with H ３ P.O. ４ and K. ２ SiO ３ The method of claim 1 , further comprising adding one or both of:

7. 10. The method of claim 1, wherein the first and second precipitation steps are independently carried out at 30 to 60°C.

8. 10. The method of claim 1, wherein the residence times of the first precipitation stage and the second precipitation stage are independently from 2 to 12 hours.

9. The method comprises: d) recycling the separated second fluoride-containing precipitate back to the first precipitation stage. The method of claim 1 further comprising:

10. 10. The method of claim 1, further comprising a third precipitation step of adding an alkaline earth metal salt to the second fluoride-reduced leachate to precipitate inorganic fluoride compounds and separating the precipitated inorganic fluoride compounds to obtain a third fluoride-reduced leachate.

11. 11. The method of claim 10, wherein the alkaline earth metal salt is added at a concentration of 100 to 240 g / L.

12. The alkaline earth metal salt is a magnesium salt, preferably MgSO ４ or MgCO ３ and the inorganic fluorine compound is MgF ２ The method of claim 10, wherein

13. 11. The method of claim 10, wherein the pH of the second fluoride-reduced leachate is maintained during the third precipitation stage.

14. 11. The method of claim 10, wherein the third precipitation step is carried out at 30 to 60°C.

15. 11. The process of claim 10, wherein the residence time of the third precipitation stage is from 2 to 12 hours.

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