Method for removing iron and copper from solution using metal reagents

Abstract

The present invention relates to a method for removing Cu and Fe from an acidic aqueous solution also containing one or more of Ni and Co, the method comprising the steps of: - adding a metal reagent comprising one or more of Ni and Co to the acidic solution under oxidizing conditions, thereby neutralizing the acidic solution and forming a precipitate comprising Cu and Fe, wherein at least a portion of the Cu and Fe are in the form of hydroxides; and - separating the Cu and Fe precipitate from the solution, thereby obtaining a Cu and Fe depleted solution. The method significantly reduces the need for an external neutralizing agent, thereby limiting or even completely avoiding the introduction of additional impurities into the method. The invention is advantageously applied to an acidic aqueous solution obtained by leaching a material having the same composition as the metal reagent.

Description

[0001] The invention relates to the field of hydrometallurgy and describes a method for purifying acidic solutions containing different metals by oxidative hydrolysis using metallic reagents.

[0002] Many cobalt and nickel-containing raw materials and intermediates also contain significant amounts of iron and copper, which end up in the leach solution after dissolution of these materials. Examples include: mattes from primary smelting of ores; intermediate hydroxide and sulphide products from mining of Cu, Co and Ni; deep-sea nodules containing certain metals, Co, Ni and Mn; white alloys produced during smelting of Co and Ni products; and waste and scrap generated during the production or use of lithium-ion or nickel metal hydride batteries.

[0003] Therefore, the removal of iron and copper from aqueous solutions containing cobalt, nickel and other metals is a common hydrometallurgical operation. Purification is usually accomplished in two separate unit operations, one focused on removing the bulk of the copper from solution and the other focused on removing the iron from solution.

[0004] In many hydrometallurgical schemes, the extraction of copper from solutions containing Ni and Co is based on electrowinning. CG Anderson (book chapter: Optimization of Industrial Copper Electrowinning Solutions. In: Prime Archives in Chemical Engineering. Hyderabad, India: Video Leaf. 2019) describes the direct electrowinning of copper on industrial solutions containing Cu and Ni ("direct electrowinning"), where the cathode is immersed in the solution. By applying an electric current, Cu is deposited on the cathode, separating it from other elements in the solution such as Co, Ni, Fe or Mn. Large amounts of Cu may require multiple operations, circulating the solution on a single electrolytic cell. An alternative to this arrangement is a series of electrowinning electrolytic cells in series, each operating in a manner that reduces the Cu concentration. Electrolytic cells for electrowinning can have different designs. The most widely used are electrolytic cells with flat parallel electrodes. WO2020078779 suggests the use of a microparticle cathode for direct electrolytic deposition of Cu from a solution containing Co, Ni and Mn, while Siegmund et al. (Replacement of liberator cells-pilot test study at AurubisHamburg using the EMEW technology: Proceedings of Copper 2013: Santiago, Chile, December 1-4, 2013: Volume V, pages 275-283) describe the use of a cylindrical electrolytic cell for the selective removal of Cu from a Ni-containing solution.

[0005] In other cases, electrowinning is combined with solvent extraction ("SX-electrowinning"). Examples are found by Cheng et al. (Thecovery of nickel and cobalt from leach solutions by solvent extraction: Process overview, recent research and development; Proceedings of ISEC 2005). In this approach, Cu is first extracted from an impure feed solution by solvent extraction (SX), which is typically highly selective for Cu. The extracted Cu ions are transferred to a separate Cu solution from which they are collected in a subsequent electrowinning operation that is not limited by the elements present in the initial solution, such as Co, Ni, Fe, or Mn.

[0006] In both cases, the electrowinning operation will typically remove most, but not all, of the Cu, as reduced efficiency at lower Cu concentrations is a drawback of such processes. Therefore, this must be combined with other operations to avoid loss of the remaining Cu.

[0007] WO2019121086 describes an alternative method for removing copper and more precious metals, which is based on selective precipitation by displacement precipitation using a reducing agent. In this method, Cu is precipitated in its metallic form. This is generally applicable when the quality and value of the Cu product are not important, or when lower Cu concentrations are not suitable for more expensive electrolytic deposition-type solutions.

[0008] In this operation based on displacement precipitation, the Cu-containing solution is contacted with a reducing agent, such as a more electronegative metal compound such as Ni, Co, Fe, Zn, Mn, or with hydrogen. In the latter case, the operation is generally referred to as hydrogen reduction. For example, Togashi and Nagai (Hydrogen reduction of spent copper electrolyte, Hydrometallurgy, 11: 149-163, 1983) describe it. The effect is, for example, to convert soluble Cu into 2+ Cu 1+ ions are reduced to insoluble elemental copper:

[0009] H2+CuSO4→Cu 0 ↓+H2SO4

[0010] In the case of using a metal compound as reducing agent, this compound eventually goes into solution, for example, according to the following formula:

[0011] Ni 0 +CuSO4→Cu 0 ↓+NiSO4

[0012] Mn 0 +2CuCl → 2Cu 0 ↓+MnCl2

[0013] Elemental copper is precipitated as solid metal. When an excess of metal reagent is used, this can result in an impure displacement precipitate consisting of a mixture of precipitated copper and unreacted metal reducing reagent.

[0014] Operations based on displacement precipitation usually avoid the introduction of oxidizing compounds such as air, oxygen or hydrogen peroxide into the solution to be treated. The reason is that oxidizing compounds can react directly with the reducing agent, causing them to oxidize without reacting with the Cu ions in solution, or react with the already precipitated elemental Cu, causing the Cu to redissolve. In both cases, the presence of oxidizing compounds will have a negative impact on the performance of the displacement precipitation operation. Therefore, this displacement precipitation method must sometimes be carried out under an inert atmosphere.

[0015] GB2011476 has described the multi-step method with coprecipitation step and displacement precipitation step, and coprecipitation step and displacement precipitation step are separated by solid / liquid filtration.In this process, multiple oxides, hydroxides, carbonates and bicarbonates can be used as alkali, but metal is not used to neutralize.Iron is unacceptable, therefore avoids or removes it with some coppers in the coprecipitation step.Remaining copper is removed from iron-free solution by classical displacement precipitation.

[0016] In general, processes based on displacement precipitation have in common that Cu and more noble metals are removed as metal displacement precipitates. Since iron is less noble, it is usually removed in a separate operation.

[0017] EP0262964 discloses another option, in which Cu is precipitated as a sulfide compound using a sulfide reagent under reducing conditions. Common reagents are H2S, Na2S and NaHS. Similar to displacement precipitation, this technique is suitable for reducing Cu to low concentrations.

[0018] Neither of the above operations is suitable for handling the iron that is also usually present. Therefore, a separate Fe removal step is required to purify such Ni and / or Co containing solutions. Sometimes this is done by ion exchange, but most Fe removal operations rely on the removal of insoluble Fe at low free acid concentrations. 3+Compound precipitation. For example, this is explained in Monhemius et al. (The iron elephant: A brief history of hydrometallurgists'struggles with element no.26, CIM Journal 8(4): 197-206, 2017). This type of method uses a combination of an oxidizing agent and an alkaline agent, the oxidizing agent promoting the conversion of ferrous compounds to ferric compounds, and the alkaline agent neutralizing the free acid and promoting the precipitation of ferric compounds at low free acid concentrations. Common oxidizing agents are air, O2, H2O2 and Cl2. Stronger oxidizing agents such as hypochlorites, persulfate compounds or permanganates can also be used. The acid to be neutralized may be present in the feed solution or may be generated during the precipitation reaction of the iron. Hydroxides or carbonates are generally used as neutralizing agents, especially NaOH, Na2CO3, Mg(OH)2, Ca(OH)2, CaCO3, NH4OH or (NH4)2CO3.

[0019] In addition to Fe, many other impurities such as Cr, Al, As, Sb, Sn, W or Cu may also be present in the feed solution. These elements can be hydrolyzed and precipitated together with Fe. This is as mentioned in, for example, WO2019121086 cited above, which describes a scheme in which most of Cu is first removed by displacement precipitation and then by a hydrolysis operation to remove Fe and trace impurities. The proposed hydrolysis operation uses sodium hydroxide, lithium hydroxide, ammonia, potassium hydroxide or calcium hydroxide. WO2020212546 discloses a similar operation. However, in all these cases, other elements such as K, Ca, Na, Li or NH4 are introduced into the solution by a neutralizing agent, which is an obvious disadvantage when used for high-purity operations.

[0020] WO2019090389 provides a method for avoiding the introduction of additional contaminants by neutralizing compounds. As part of a flow chart for converting a Ni metal powder feed into a nickel sulfate solution, hydrolysis is described to remove impurities including iron as a whole by neutralization. Nickel hydroxide is used as a neutralizing agent instead of a more conventional alkali metal base. It is particularly important to mention that the use of sodium hydroxide or potassium hydroxide bases is avoided because these bases typically cause alkali metal contamination. This nickel hydroxide is prepared in a separate operation by precipitating Ni from a portion of the refined solution using sodium hydroxide. In this way, sodium can be prevented from entering the main process, but the consumption of sodium hydroxide still exists. Although a Ni-containing feed is used in the main process, the additional device for making nickel hydroxide makes this essentially a two-step process.

[0021] In summary, known precipitation methods for removing Cu generally rely on hydrolysis or displacement precipitation using caustic reagents.Precipitation methods for Fe generally rely on hydrolysis.

[0022] When performing a displacement precipitation to remove copper, a reducing agent is added to convert copper or cuprous ions into metallic copper. Avoid using an oxidizing agent to prevent oxidation and redissolution of the compound of the displacement precipitation. When performing a hydrolysis to remove Fe and / or Cu, an oxidizing agent is usually added to avoid reduction and redissolution of Fe, especially ferric oxide or ferric hydroxide. These different requirements result in the need for two separate process steps to remove most of Cu and Fe.

[0023] In contrast to the above, the present invention discloses an alternative scheme involving a single unit operation for precipitating Cu and Fe from a solution containing Ni and / or Co. The key to the method is to combine the hydrolysis and precipitation of Cu and Fe in one operation by using a reducing metal reagent containing Ni and / or Co for neutralization, combined with an oxidizing agent required to promote the oxidation of ferrous iron to iron. The method thus advantageously combines materials and reaction conditions that are not usually used or used in combination. The introduction of additional impurities in the process is limited or even completely avoided.

[0024] The Cu compound precipitated by hydrolysis under oxidizing conditions is very different from the compound precipitated by conventional methods based on displacement precipitation under reducing conditions. In the method based on displacement precipitation, Cu is removed as a metal displacement precipitation product, while in the present invention, Cu is removed as Cu 2+ The Cu compounds are precipitated in the form of a compound. Such compounds may be, for example, oxides, hydroxides, alkaline sulfates or alkaline chlorides. This also depends on the anions in the solution. Compared with the precipitation of Fe compounds, the precipitation of these Cu compounds usually occurs at lower acid concentrations.

[0025] In the present method, it is assumed that the starting solution is acidic, as it is when it is provided by the leaching operation using acid. The purpose and effect of the addition of the metal reagent is to consume the acid, not to replace the precipitate. For this purpose, the addition of the metal reagent is combined with the addition of an oxidizing agent: in this case, no metal replacement precipitate is formed. With increasing pH, insoluble hydroxides of certain metals, in particular of Fe and Cu, precipitate; other metals such as Ni and / or Co remain at least partially in solution.

[0026] This is in contrast to conventional neutralization and hydrolysis operations, which use caustic compounds such as hydroxides of Na, K, Mg, Ca, Li, or ammonia, thereby introducing other impurities into the solution.

[0027] The process optimizes itself by selecting a metal reagent containing elemental Ni and / or Co which at least partially dissolves, thereby increasing the value of the solution.

[0028] The optimized process achieves optimal use of the acid remaining after leaching and the acid generated by the precipitation reaction of Cu and Fe. The acid is effectively used to dissolve the additional Ni and / or Co present in the metal reagent. No neutralizing reagent is required and no dilution is caused by the addition of such reagent.

[0029] The application of the proposed hydrolysis operation using a metal reagent or metal alloy containing Ni and / or Co as an acid neutralizing agent to remove Fe and Cu from the leaching solution under oxidizing conditions has several advantages compared to conventional methods based on hydrolysis to remove Fe and / or Cu.

[0030] Conventional hydrolysis methods for removing Fe also have the disadvantage of introducing other elements that are not yet present in the leaching solution. Typically, these elements are introduced as caustic compounds for neutralization. However, it is also possible that the oxidizing agent applied also introduces such undesirable or even obstructive compounds, such as chloride ions when chlorine is used as an oxidizing agent in a sulfate solution, or sulfate when persulfate is used as an oxidizing agent in a chloride solution. The introduction of any such elements generally requires additional downstream purification operations to prevent them from entering the final product. In addition, this may be particularly disadvantageous, for example, in battery applications requiring very high purity. This operation increases the cost and complexity of the entire refining scheme. Another disadvantage is that these elements can increase the total concentration of ions in the solution.

[0031] Therefore, in order to avoid supersaturation and undesirable precipitation of solid salt products in such operations, the total concentration of metals in the leaching solution must be limited, or such solutions must be diluted, which increases the volume flow and reduces the capacity of a given plant. Another disadvantage is that the net consumption of neutralizing reagents is equivalent to the amount of Cu and Fe to be removed. Therefore, in conventional hydrolysis processes, the consumption of reagents for Fe removal always comes at a cost.

[0032] In contrast, in a flowsheet configuration aimed at converting an impure feedstock containing Ni and / or Co into a high purity final product, the use of a metal reagent containing Ni and / or Co and optionally also Mn will advantageously contribute to the net capacity by introducing additional Co, Ni and / or Mn that ultimately ends up in the final product. Thus, in a typical Co and Ni refining configuration according to the invention, the use of Co or Ni as a neutralizing agent is of particular interest, since it not only avoids the introduction of additional impurities, but also increases the overall yield of high purity valuable metals. In such a configuration, the feedstock fed into the pre-leaching operation and the metal or alloy used for neutralization in the hydrolysis operation may be similar or even identical.

[0033] It is therefore an object of the present invention to provide a process for the selective precipitation of Cu and Fe from a Ni and / or Co containing solution, wherein a metallic reagent such as an alloy is used under oxidizing conditions.

[0034] According to a first embodiment, a method for removing Cu and Fe from an acidic aqueous solution that also contains one or more of Ni and Co comprises the steps of:

[0035] - adding a metal reagent comprising one or more of Ni and Co to the acidic solution under oxidizing conditions, thereby neutralizing the acidic solution and forming a precipitate comprising Cu and Fe, wherein at least a portion of the Cu and Fe are in the form of hydroxides; and

[0036] - Separating the Cu and Fe precipitates from the solution, thereby obtaining a Cu and Fe depleted solution.

[0037] "Acidic aqueous solution" refers to a solution in which at least some free acid is present, as determined, for example, by titration.

[0038] Typically, the pH value of the feed solution is lower than 2, while the pH value of the neutralized solution of the method should preferably be higher than 2. In particular, in H2SO4 medium, the pH value of the feed solution is generally less than 3.5, more preferably less than 3. The pH value of the treated neutralized solution should preferably be higher than 3.5, more preferably higher than 4.0, and even more preferably higher than 4.5. In particular, in HCl medium, the pH value of the feed solution is generally less than 2.0, more preferably less than 1.5. The pH value of the treated neutralized solution should preferably be higher than 2.0, more preferably higher than 2.2, even more preferably higher than 2.5, and most preferably higher than 3.0. The higher the pH value of the output stream, the lower the residual concentration of Fe and Cu will be. However, the pH value is preferably less than 7.

[0039] Oxidizing conditions are required for the formation of ferric ions and promote dissolution of the metal reagent while consuming free acid to effectively neutralize the solution. Neutralization is important to ensure precipitation of ferric compounds and copper or cuprous compounds, the solubility of which decreases with increasing pH.

[0040] "Metallic reagent" refers to a material in which the majority of the elements are present in the zero oxidation state. In addition to the metals Ni, Co and Mn, other metallic elements may also be present, in particular Cu and Fe. The metallic reagent preferably comprises a total of at least 25% by weight of Co and Ni.

[0041] On the other hand, mattes or slags in which a large portion of the metal is present in an oxidized state and chemically bonded to, for example, sulfur or oxygen are not considered to be suitable "metal reagents" according to the present invention.

[0042] In addition to Co and Ni, Mn may also be advantageously present in the acidic aqueous solution. Mn does often occur together with Ni and Co, especially when processing materials related to battery recycling ("NMC-batteries").

[0043] In contrast to conventional displacement precipitation, this method produces a residue containing oxidized metal compounds, in particular containing, for example, Cu 2+ and Fe 3+ "Hydroxide" refers to a compound containing one or more OH groups. These can therefore be pure hydroxides, oxyhydroxides or more complex compounds such as alkaline sulfates or alkaline chlorides.

[0044] "Cu and Fe depleted" refers to a solution with reduced Cu and Fe content compared to an acidic aqueous solution, i.e., preferably containing less than 50% Cu and less than 50% Fe in an acidic aqueous solution. Alternatively, it may refer to a solution having a content of any one of Cu and Fe of less than 10 g / L, preferably less than 6 g / L, more preferably less than 1 g / L, still more preferably less than 500 mg / L and most preferably less than 100 mg / L. Solutions of higher concentration are more suitable for methods of harvesting pure Cu products, while solutions of more or most preferred lower concentrations are increasingly suitable for post-processing, such as post-processing by solvent extraction.

[0045] The Cu and Fe precipitates can be separated from the solution, for example, using decantation, filtration or centrifugation.

[0046] In another embodiment, the acidic aqueous solution contains HCl or H2SO4. However, HNO3 or other inorganic acids may also be suitable.

[0047] In another embodiment according to any of the above embodiments, the metal agent is a metal alloy.

[0048] "Alloy" refers to a mixture of metals that retains the properties of a metal. Metal chalcogenides such as mattes or slags are not considered alloys.

[0049] In another embodiment according to any of the above embodiments, the metal reagent comprising one or more of Ni and Co is substantially free of sulfur.

[0050] Sulfur-containing feeds such as compounds known as "mattes" in smelting operations or sulfides precipitated by hydrometallurgical means are generally not preferred, whether they enter the process via solid starting materials and acid leaching or via metal reagents used in hydrolysis operations.

[0051] Sulfur in such feeds limits the efficiency and applicability of the process, since it can be oxidized to sulfate under oxidative conditions, which is important for the claimed process. Such sulfur oxidation will consume the oxidant introduced for the oxidation of iron, without consuming free acid to raise the pH of the solution. To compensate for this, it is necessary to add, for example, more neutralizing agent, which is not required in the claimed process.

[0052] Another potential disadvantage is that sulfur oxidation introduces sulfate into the solution, which is undesirable, for example when refining chloride solutions.

[0053] In another embodiment according to any of the above embodiments, the metal reagent is in the form of a metal powder.Using a powder can increase the reactivity of the reagent, which is advantageous because it can enhance the reaction kinetics.

[0054] In another embodiment according to any of the above embodiments, the metal powder has a particle size distribution as follows: the equivalent particle size d90 of the particles is less than 500 μm; or the average equivalent particle size d50 of the particles is less than 200 μm. This allows for better suspension of the powder and implementation of the method in a common stirred reactor.

[0055] In another embodiment according to any of the above embodiments, oxidizing conditions are obtained by adding H2O2 and / or an O2-containing gas. The O2-containing gas may be, for example, air, concentrated air or pure O2 gas. Air has a lower electrical potential and therefore requires a larger volume. This air volume may even be a disadvantage in some cases because it introduces cooling. Pure oxygen has a stronger oxidizing property and therefore requires a smaller volume. Peroxide is very strong and thus more efficient per mole, but it is more expensive than the above alternatives. Chlorine injection, for example in the form of Cl2 gas, may also be used, particularly when the acidic aqueous solution is based on HCl.

[0056] In another embodiment according to any of the above embodiments, the method is carried out at atmospheric / ambient pressure. This is a general advantage because the method does not require high pressure or very high temperatures (as found, for example, in some autoclave settings) to operate efficiently. However, the use of an autoclave, for example at 15 bar and 180° C., is still a viable alternative.

[0057] In another embodiment according to any of the above embodiments, in the step of adding the metal reagent, the pH value of the solution after neutralization is higher than 2.0 under the condition that the acidic aqueous solution contains HCl, or the pH value of the solution after neutralization is higher than 3.5 under the condition that the acidic aqueous solution contains H2SO4. The choice of working in HCl medium or H2SO4 medium can be advantageously adapted to the type of metal reagent and / or oxidant used in the method, for example.

[0058] In another embodiment according to any of the above embodiments, the metal reagent is added to the acidic solution in a stoichiometric excess relative to the sum of the free acid in the solution and the acid produced in the precipitation reaction.

[0059] The stoichiometric amount used to neutralize the metal reagent can be estimated based on the composition of the solution and the metal reagent by considering the following reaction scheme. The balance of the acid can be estimated by considering the following factors:

[0060] 1. The starting solution usually contains free acid.

[0061] 2. Assume that there is dissolved Cu in the sulfuric acid medium 2+ and Fe 3+ , the precipitation reaction generally produces an acid according to the following exemplary formula:

[0062] 4CuSO4+6H2O→Cu4(SO4)(OH)6(s)+3H2SO4

[0063] Fe2(SO4)3+4H2O→2FeOOH(s)+3H2SO4

[0064] The hydrolysis of other elements such as Al may generate additional acid according to reactions similar to those of Cu and Fe. A metal reagent should be used to neutralize this additional acid.

[0065] 3. Dissolution reactions usually consume acid.

[0066] Assuming an M-based metal reagent, M is one or more divalent metals such as Ni or Co, where O2 is used as an oxidant in a sulfuric acid medium:

[0067] 2M 0 (s)+O2+2H2SO4→2MSO4+2H2O

[0068] In order to reach the desired pH values ​​of greater than 2 in the HCl medium and greater than 3.5 in the H2SO4 medium, respectively, it is essentially necessary to neutralize all free acids, i.e. the acids present in the starting solution (1) and the acids originating from the precipitation reaction (2) will be consumed by the acid required for the dissolution reaction (3).

[0069] When the composition is known with reasonable accuracy, the acid balance can be predicted.In other cases, the skilled person will rely directly on the measurement of pH to determine the stoichiometric amount of the metal reagent.

[0070] Adding a metal reagent in excess of the stoichiometric ratio is considered an excess. This excess reagent can benefit the overall process. The excess reagent will be collected in the residue along with Fe and Cu. The upper limit of the excess is not critical: unreacted metal reagent will remain undissolved, and this will not affect the purity of the solution depleted of Cu and Fe.

[0071] In another embodiment according to any of the above embodiments, the precipitate comprising Cu and Fe further comprises unreacted metal reagent.

[0072] When introducing excessive metal reagent, when finishing described method, the residual component of unreacted metal reagent and the hydroxide component of precipitation may still exist.Unreacted metal reagent can be separated from solution.This can be completed in a single operation together with hydroxide precipitation, for example, by filtering or decantation.Or, this can also be completed in a separate solid-liquid separation operation.In this case, unreacted metal component and hydroxide component can be separated according to the difference of its specific gravity, for example, by selective decantation or centrifugation.Or, they can be selectively separated according to different magnetic properties.Because the composition and property of unreacted metal reagent and the hydroxide of precipitation can be different, the separation of two components advantageously makes each component be carried out to the aftertreatment selection with larger difference.

[0073] In another embodiment according to any of the above embodiments, the acidic aqueous solution is obtained by a step of acid leaching a solid starting material containing at least one of Ni and Co, Cu and Fe. Optionally, a step of removing part of Cu and / or Fe is subsequently performed.

[0074] The leaching step may be operated at a temperature of 50°C or higher. Pressure leaching is also suitable. When leaching with H2SO4, the acid leaching step preferably provides an acidic solution with a pH value of less than 3.5. When leaching with HCl, the acid leaching step preferably provides an acidic solution with a pH value of less than 2.

[0075] The leaching step may be oxidation using, for example, H2O2 and / or an O2-containing gas. Iron ions may also be used. This will promote oxidation of the metal species into its soluble ionic form. When the metal in the solid starting material is already in an oxidized form, no oxidizing conditions are required. Optional removal of a portion of Cu may be performed by, for example, sulfide precipitation, displacement precipitation, electrolytic deposition, ion exchange or solvent extraction, thereby removing most of the Cu. The removal of the remaining / residual Cu is then performed according to the first embodiment as described above.

[0076] The optional removal of a portion of Fe can be accomplished, for example, by ion exchange, solvent extraction, or in a separate hydrolysis operation. This operation is then preferably performed under oxidizing conditions using a neutralizing agent that does not introduce additional impurities into the solution. Examples of such agents include NiCO3 and Co(OH)2.

[0077] Alternatively, partial Fe removal can already be performed during the leaching process by dissolving only part of the Fe in the feed and retaining another part in the leaching residue. This can be achieved by controlling the supply of acid for leaching: only a substoichiometric amount of acid is added compared to the feed so that other elements react with the acid first. These elements will then be brought into solution in preference to Fe. This is the case for Ni, Co, Mn and Cu. This is promoted by applying oxidizing conditions during the leaching process to support the formation of iron compounds that have a lower solubility than ferrous compounds.

[0078] The first way to control the supply of acid is to calculate in advance the acid consumed by other elements. This requires a good understanding of the composition of the feed. There is still some uncertainty, which may lead to overdosing of acid, resulting in undesired dissolution of Fe, or underdosing of acid, resulting in reduced dissolution yield of other elements.

[0079] The second way to control the supply of acid is the control of the pH value. This is feasible when the feed dissolves quickly at very low acidity and / or when the acid is supplied at a slow rate, so that the supply of acid lags behind the consumption of the acid. In this way, the system is always close to equilibrium and no excess acid is supplied. When leaching with H2SO4, pH values ​​of 1.5 to 3 are observed to ensure selectivity for Fe. When working with HCl, pH values ​​of 0.5 to 2 are observed to ensure selectivity for Fe. The disadvantage of this method is that the total duration of leaching can be long because the leaching rate at low acidity is generally lower.

[0080] The third way to control the supply of acid is to work in stages. In the first stage, a first amount of acid is supplied, wherein the first amount is less than the stoichiometric amount relative to the total amount of metal (excluding Fe) contained in the solid starting material. In the second stage, the reaction is allowed to reach equilibrium. At the end of this stage, substantially all of the Fe is oxidized to iron ions and is aggregated to the solid component together with a portion of other elements. This depends in part on the lack of acid not supplied in the first stage. When working with H2SO4, the pH value is generally higher than 2.5, preferably higher than 3, at the end of the second stage. When working with HCl, the pH value is generally higher than 1, preferably higher than 2, at the end of the second stage. In the third stage, an additional amount of acid is supplied by controlling the pH value. This supply is completed at a sufficiently slow rate to avoid oversupply of acid. The third stage is completed when the target pH value can be maintained without the supply of additional acid. When leaching with H2SO4, the target pH value is 1 to 3. When leaching with HCl, the target pH value is 0.5 to 2. The higher the pH value, the less Fe is residual in the solution.

[0081] This "three-step leaching" of adding a first amount of acid, balancing, and adding a second amount of acid has distinct advantages:

[0082] - Reduce the time required for the entire method;

[0083] -Flexibility to use metal reagents whose composition is not 100% precisely known; and

[0084] - avoid reducing the efficiency of the process by supplying too much acid,

[0085] By precisely controlling only the second addition of acid, the first (bulk) addition of acid can be accomplished fairly quickly and is believed to be relatively uncritical to the high selectivity and efficiency of the process.

[0086] In another embodiment, the solid starting material is substantially free of sulfur. This is particularly true when leaching in HCl to avoid the introduction of impurity sulfur.

[0087] In another embodiment, the Cu and Fe precipitates are at least partially recycled to the acid leaching step of the solid starting material. This embodiment achieves the recovery of the undissolved excess neutralizer described above. In addition, potential co-precipitated Ni and / or Co are recovered. By adding this "recycling loop", the loss of potential valuable metals is minimized.

[0088] As an alternative to acid leaching, the precipitate can be processed in a pyrometallurgical process and used as a valuable feed material.

[0089] In another embodiment, the metal reagent and the solid starting material have substantially the same composition. From a logistical point of view, the use of the same material in the acid leaching step and the hydrolysis operation is particularly interesting, since, for example, separate procurement, storage or pre-processing is no longer necessary. In addition, this combination limits or even avoids the introduction of additional impurities during the process and advantageously contributes to the output of high purity metals from the process.

[0090] In another embodiment, the solid starting material comprises batteries, battery waste and / or products derived therefrom. The method is suitable for recovering metals from batteries, in particular from scrapped Li-ion batteries, and from any kind of production waste generated in the production of these batteries.

[0091] The following examples are provided to further illustrate embodiments of the present invention.

[0092] Example 1

[0093] The mixed hydroxide product was processed and is an intermediate in primary Co mining. The product contained 62% moisture and was determined to have the following composition on a dry basis.

[0094] element weight% Co 42％ Ni 2.3％ Mn 7.7％ Mg 8.5％ Fe 2.7％ Cu 1.3％

[0095] 600 g of the wet product was placed in a beaker with 1 L of water and mixed into a slurry. The slurry was heated to 70°C. The pH of the slurry was recorded as being above 7. Dilute sulfuric acid (500 g / l H2SO4) was pumped into the beaker to establish and maintain a pH of around 2 while the solids were dissolved. When no more acid was consumed to maintain the target pH, the slurry was cooled to 40°C and the solid and liquid components were separated by filtration. 1.9 L of leaching solution was obtained, and the measured composition is shown below. Titration showed that the concentration of free H2SO4 was 14.7 g / L. The solid component still contained some Ni, Co and Mn, indicating that the starting material had not been completely dissolved under the current leaching conditions.

[0096] element Composition (g / l) Co 36.8 Ni 2.1 Mn 1.1 Mg 9.8 Fe 2.8 Cu 1.4

[0097] The leaching solution was heated to 80°C in a beaker. Oxygen was injected into the solution through the immersion tube at a rate of 100 l / h, while vigorous stirring was performed to ensure good oxygen dispersion and complete suspension of the solids. Next, 85 g of dry atomized NiCoMnCuFe alloy was added. The alloy had the following composition:

[0098] element Composition (weight %) Co 20 Ni 46 Mn 8 Mg <0.1 Fe 6 Cu 23

[0099] The particle size distribution of the alloy is characterized by a d50 of 110 μm and a d90 of 280 μm. The conditions in the beaker are maintained for 13 hours to allow precipitation of Fe and Cu. No reagent is added except demineralized water to compensate for the volume loss due to evaporation. During these 13 hours, the pH value is monitored and an increase from an initial value of 2 to a value of 5.1 is observed. The slurry is then cooled to 40°C and the solid and liquid components are separated by filtration. 1.8 L of a solution are obtained, the composition of which is as shown below.

[0100] element Composition (g / l) Co 42 Ni 10 Mn 3.9 Mg 10 Fe <0.001 Cu 0.023

[0101] After washing the solid component with 2 L of demineralized water, 287 g of a wet cake was obtained. The moisture content was measured to be 53%, and the composition of the measured dry component was as shown below.

[0102] element Composition (weight %) Co 9 Ni 18 Mn 1 Mg <0.1 Fe 8 Cu 16

[0103] This example shows how to use a NiCoMnCuFe alloy to remove substantially all of the iron and most of the copper from the solution obtained after leaching the initial Co feed by hydrolysis. This enables further downstream processing of the solution to separate cobalt and nickel, for example by solvent extraction. The solid component obtained in the hydrolysis operation is rich in Cu and Fe, while still containing corresponding amounts of Ni and Co. Other processes can be applied to recover this residual Ni, Co and / or Cu.

[0104] This example demonstrates the removal of 99.97% of the Fe and 98% of the Cu present in the starting solution.

[0105] Example 2

[0106] The alloy containing CoNiMnFeCu was processed. The alloy was obtained by melting scrap batteries and then atomizing into a powder component with a measured particle size distribution D50 of less than 162 μm and D90 of less than 361 μm. The composition of this dry alloy is shown below.

[0107] element Composition (weight %) Co 41 Ni 7.8 Mn 2.2 Fe 23 Cu 21 Ca <0.1 Cr 0.590

[0108] 6110g of this material was introduced into a 50L reactor along with 36L of demineralized water. Intense mixing was used to suspend the alloy and distribute oxygen, which was blown into the reactor using a dip tube at a rate of 600L / h. The reactor was heated to 60°C. Over the next 4 hours, 8300g of 78% by weight H2SO4 solution was pumped into the reactor at a constant flow rate of 2075g / h. This is approximately 90% of the stoichiometric amount required to dissolve Co, Ni, Mn and Cu in the alloy. During the addition process, the pH value dropped from 5.6 to 1.2. Then, the oxygen flow rate was reduced to 300L / h and the reactor temperature was raised to 80°C. These conditions were maintained for another 8 hours, and then the pH value was raised to 3.6. Again, a pH-based controller was used and the dosage rate was limited to 500ml / h to supply 78% by weight H2SO4 solution. The target pH value was set to 2.7. This pH value was reached after 3 hours, and essentially no more acid was consumed. Another 877 g of 78 wt % H2SO4 solution was added in this step. At this point, most of the Ni, Co, Mn and Cu dissolved, while most of the Fe precipitated. Water was added throughout the process to compensate for the volume loss caused by evaporation, keeping the total volume at about 40 L. The reactor was cooled to 40 ° C and the reaction mixture was filtered using a vacuum filter. After filtration, 37 L of leached solution was obtained, and the composition was determined as shown below.

[0109] element Composition (g / l) Co 62 Ni 12 Mn 3.2 Fe 1.5 Cu 29 Ca 0.053 Cr 0.018

[0110] The measured composition of the solid residue after drying is as follows.

[0111] element Composition (wt % based on dry weight) Co 6.3 Ni 1.0 Mn 0.5 Cu 6.6 Fe 43

[0112] In the next step, the leached solution is subjected to an electrolytic deposition (EW) of copper, wherein the Cu concentration in the solution is reduced to 5.4 g / L, which means that 23.6 g / L of Cu is deposited on the cathode and extracted from the solution. In this operation, a stoichiometric amount of free acid is also generated in the solution. After the EW operation, the concentration of free H2SO4 is 38 g / L as measured by titration. The complete composition after EW is as follows. Note that, except for Cu, the minor deviations in the concentration of other elements can be explained by the limited precision of the analytical technique, the minor volume loss caused by evaporation during the EW operation, and possible precipitation during the EW operation.

[0113] element Composition (g / l) Co 61 Ni 12 Mn 2.8 Fe 1.6 Cu 5.4 Ca 0.040 Cr 0.018

[0114] The 30L solution obtained after EW was introduced into a 50L reactor and heated to 80°C while blowing oxygen into the reactor at a rate of 600L / h using a dip tube. Vigorous mixing was performed. 5726g of the same CoNiMnFeCu alloy was introduced, which was also used as a starting material in the leaching step of the present embodiment. The reactor was kept in this state for 16 hours, while water was added to compensate for the volume loss caused by evaporation. Thereafter, almost all free acid was consumed, and the pH value was therefore increased to 5.0. The slurry was then cooled to room temperature. Stirring and oxygen injection were stopped to separate the liquid and solid components by decantation. After 24 hours, 20L of overflow liquid was taken out from the reactor and filtered to remove the remaining trace solids. The composition of the liquid is as follows. About 10L of underflow remained in the reactor, and the underflow contained most of the solids and the remaining leaching solution.

[0115] element Composition (g / l) Co 83 Ni 14 Mn 5.8 Fe 0.001 Cu 0.035 Ca 0.069 Cr <0.001

[0116] This example demonstrates how a Co-rich CoNiMnFeCu alloy obtained by smelting a cell can be transformed in a purified sulphate solution containing Co, Ni and Mn. This is achieved using a combination of a majority removal operation of both Fe and Cu and a hydrolysis operation for removal of residual Cu and Fe according to the invention.

[0117] In the leaching operation, the majority of the iron removal is achieved by limiting the amount of acid introduced, resulting in a lower free acid concentration at the end of the leaching operation. Under these conditions, Ni, Co, Mn and Cu tend to dissolve in preference to Fe, separating most of the Fe in the feed into the leaching residue. By leaving a certain amount of Fe in the solution after leaching, good selectivity can be achieved and contamination of Ni and Co in the leached filter cake can be limited.

[0118] Most of the removal of Cu is accomplished by electrowinning (EW), producing high purity cathodes with essentially no loss of Ni and Co. Because the current efficiency and quality of Cu cathodes drop dramatically at lower Cu concentrations, EW is not suitable for complete depletion of Cu.

[0119] Through the proposed hydrolysis operation, the CoNiMnFeCu alloy feed itself is used as a reagent in combination with oxygen as an oxidant to remove residual amounts of Cu and Fe. In this scheme, in addition to the feed material, only sulfuric acid and oxygen are used as reagents, thereby substantially avoiding the introduction of impurities.

[0120] Example 3

[0121] The residual components from the earlier hydrolysis operation were processed. This was demonstrated for the underflow component remaining in the reactor after the hydrolysis operation in Example 2. It was a combination of solution and solids. Based on the analysis provided in Example 2, the metal content of this component was evaluated as shown below.

[0122] element Mass(g) Co 2518 Ni 527 Mn 94 Fe 1365 Cu 1364

[0123] This component is the starting material for the new operation and is leached in the same reactor. To this end, 25L of demineralized water is added and mixed to suspend the alloy and distribute oxygen, which is blown into the reactor using a dip tube at a rate of 600L / h. The reactor is heated to 80°C. Over the next 16 hours, the pH value of the slurry is reduced to 2.7 by pumping a 78% by weight H2SO4 solution into the reactor. The pumping is carried out at a maximum rate of 0.5L / h. Demineralized water is added to compensate for the volume loss caused by evaporation, keeping the total volume at about 40L. After 16 hours, most of Ni, Co, Mn, Cu and a small amount of Fe are dissolved. The reactor is cooled to 40°C and the reaction mixture is filtered using a vacuum filter. After filtration, about 38L of leached solution is obtained, and the composition measured is as follows.

[0124] element Composition (g / l) Co 62 Ni 13 Mn 2.0 Fe 1.4 Cu 32

[0125] In the next step, part of the Cu is removed by displacement precipitation. To this end, the leaching solution is heated to 90°C in the reactor and stirred thoroughly. A nitrogen flow into the reactor headspace avoids the introduction of oxygen into the tank. Metallic nickel powder is added step by step, and samples are taken in between to measure the Cu concentration. The pH value is stabilized at 2.0 by pumping a 78 wt % H2SO4 solution. It is observed that a layer of metallic Cu is precipitated by displacement on the surface of the Ni powder. Ni powder is added until a residual Cu concentration of 14 g / L is obtained. It is balanced by increasing the concentration of Ni. The composition of the solution is measured again and is shown below.

[0126] element Composition (g / l) Co 60 Ni 28 Mn 2.1 Fe 1.4 Cu 14

[0127] 2L of solution obtained after the displacement precipitation operation was introduced into a beaker. Oxygen was injected into the solution through a dip tube at a rate of 100L / h while vigorous stirring was performed to ensure that the oxygen was well dispersed and the solids were completely suspended. 200g of dry atomized Ni-rich NiCoCuFe alloy was added.

[0128] This alloy has the composition shown below.

[0129] element Composition (weight %) Cu 22 Fe 1 Co 21 Ni 56

[0130] The particle size distribution of the alloy is characterized by a d50 of 143 μm and a d90 of 296 μm. The conditions in the beaker are maintained for 8 hours to allow the precipitation of Fe and Cu. No reagent is added except demineralized water to compensate for the volume loss caused by evaporation. During these 8 hours, the pH value in the beaker is monitored and it is observed that the initial value of 2.0 increases to a value of 5.2. The slurry is then cooled to 40°C and the solid and liquid components are separated by filtration. 1.7 L of solution is obtained. The measured composition is as shown below.

[0131] element Composition (g / l) Co 66 Ni 35 Mn 2.0 Fe <0.001 Cu 0.01

[0132] This example demonstrates the treatment of the residual solids and solutions of the previous examples, wherein Ni, Co and Mn are recovered as a mixed sulfate solution free of Fe and with very low residual Cu concentration. In this case, most of the Cu in the starting material is selectively removed by displacement precipitation using Ni powder. The remaining Cu and all Fe are subsequently removed using a Ni-rich NiCoCuFe alloy in the proposed hydrolysis operation.

[0133] Example 4

[0134] The wet impure mixed FeCuNi hydroxide filter cake was processed. The moisture content was determined to be 63% and the metal content of the filter cake on a dry weight basis was as follows.

[0135] element Composition (weight %) Cu 20 Fe 24 Ni 9

[0136] 400 g of wet cake was placed in a beaker with 1.5 L of water and 250 ml of 36 wt % hydrochloric acid solution. While mixing, the slurry was heated to 70°C for 3 hours while adding demineralized water to compensate for volume loss due to evaporation, keeping the total volume at 2 L. At this point, all solids were visually dissolved and leaching was complete. Samples were taken and the liquid composition was measured. The composition was as follows.

[0137] element Composition (g / l) Ni 6 Fe 17 Cu 15

[0138] In the next step, Fe and most of Cu are removed from the solution by hydrolysis using nickel-iron alloy in microparticle form. These dry microparticles are nearly spherical in shape and have a diameter of 1 to 4 mm. The composition is as follows.

[0139] element Composition (weight %) Co 1.2 Cu <0.1 Fe 73 Ni 25

[0140] 308 g of nickel-iron particles were added to a glass beaker containing the leaching solution. Oxygen was injected at a rate of 75 L / h. Mixing was performed using a turbine-shaped impeller at 500 rpm to ensure good homogeneity of the liquid and good distribution of oxygen while avoiding suspension of the particles. The solution temperature was raised to 85°C. These conditions were maintained for 12 hours while demineralized water was added to compensate for the volume loss caused by evaporation. After this period of time, the pH value of the solution increased from less than 0 to a value of 2.9. Most of the particles dissolved while suspended solid fines were formed in the beaker. The slurry was then cooled to 40°C and the solid and liquid components were separated by filtration. 1.2 L of solution was recovered, the composition of which was as shown below.

[0141] element Composition (g / l) Co 2.6 Cu 3.2 Fe 0.01 Ni 57

[0142] This embodiment shows how to apply the proposed hydrolysis operation to chloride-based solutions. In this case, the mixed hydroxide feed is processed. After leaching the starting material, most of the Cu and almost all of the Fe are discharged from the leaching solution by ferronickel neutralization. In this operation, a part of the Co and Ni in the ferronickel metal dissolves, substantially replacing the Cu and Fe in the leaching solution. In this way, the total amount of metal in the solution is maintained and dilution is avoided.

[0143] Example 5

[0144] 181 g of CoSO4·7H2O crystals, 311 g of NiSO4·6H2O crystals, 16 g of MnSO4·H2O crystals, 58 g of CuSO4·5H2O crystals and 10 g of FeSO4·7H2O crystals were added to 1.60 L of demineralized water in a 3 L beaker. The beaker was equipped with a reflux cooler to avoid volume loss due to evaporation. 10 g of concentrated H2SO4 (98% solution) was also added. The mixture was heated to 80°C while stirring at 700 rpm using a turbine mixer. After 1 hour, the material dissolved and a leaching solution having the following composition was obtained.

[0145] element Composition (g / l) Co 29 Ni 50 Mn 3 Cu 10 Fe 1.5

[0146] The pH value of the measured solution is 2.6. In the next step, a commercially available metal Ni powder is used to hydrolyze the solution. The powder is a pure Ni with a content of >99.9% and a D50 particle size of 107 μm. 114 g of the powder is added to a beaker, which is maintained at 80 ° C and stirred at 700 rpm for a total of 50 hours. Oxidation is performed by adding hydrogen peroxide (35% commercial solution). The addition of hydrogen peroxide is controlled by the redox potential of the solution, which is maintained at more than 400 mV relative to an Ag / AgCl reference electrode. A total of 356 g of hydrogen peroxide solution is added.

[0147] After 4 hours, the composition of the solution was measured. The Fe concentration dropped to <10 mg / l and Cu to 4.0 g / l. After 25 hours, Fe remained below 10 mg / l, while Cu dropped to 3.4 g / l. After 50 hours, Fe was measured to be 3 mg / l, while Cu dropped to 1.8 g / l. The pH of the solution was measured to be 4.1. The contents of the beaker were filtered and the residue was dried at 105°C for 16 hours. After drying, 128 g of solid were recovered, the composition of which was shown below.

[0148] element Composition (weight %) Ni 69 Cu 14 Fe 2.5 Co <0.1 Mn <0.1

[0149] In this case, during the hydrolysis, no Cu and Fe are introduced by the metallic reagent consisting entirely of Ni. Therefore, the efficiency of removing Cu and Fe from the solution can be calculated as the ratio of the amount of Cu and Fe in the residue relative to the amount of Cu and Fe entering the impure solution. For Cu, this ratio is equal to 80%, and for Fe, this ratio is equal to 99.8%.

Claims

1. A method for removing Cu and Fe from an acidic aqueous solution also containing one or more of Ni and Co, the method comprising the steps of: - adding a metal reagent comprising one or more of Ni and Co to the acidic aqueous solution under oxidizing conditions, thereby neutralizing the acidic aqueous solution and forming a precipitate comprising Cu and Fe, wherein at least a portion of the Cu and Fe are in the form of hydroxides, and wherein the metal reagent is in the form of a metal powder and the metal reagent does not contain sulfur; and - separating the Cu and Fe precipitates from the solution, thereby obtaining a Cu and Fe depleted solution.

2. The method according to claim 1, wherein the acidic aqueous solution contains HCl or H2SO4.

3. The method according to claim 1 or 2, wherein the metal reagent is a metal alloy. 4 . The method according to claim 1 , wherein the metal powder has the following particle size distribution: the equivalent particle size d90 of the particles is less than 500 μm; or the average equivalent particle size d50 of the particles is less than 200 μm.

5. The method according to claim 1 or 2, wherein the oxidizing conditions are obtained by adding H2O2 and / or an O2-containing gas.

6. The method according to claim 1 or 2, wherein the method is carried out under atmospheric pressure.

7. The method according to claim 2, wherein in the step of adding the metal reagent, under the condition that the acidic aqueous solution contains HCl, the pH value of the solution after neutralization is higher than 2.0, or under the condition that the acidic aqueous solution contains H2SO4, the pH value of the solution after neutralization is higher than 3.

5.

8. The method according to claim 1 or 2, wherein the metal reagent is added to the acidic aqueous solution in a stoichiometric excess amount relative to the sum of the free acid in the solution and the acid generated in the precipitation reaction.

9. The method of claim 1 or 2, wherein the precipitate comprising Cu and Fe further comprises unreacted metal reagents.

10. The method according to claim 1 or 2, wherein the acidic aqueous solution is obtained by a step of acid leaching a solid starting material containing at least one of Ni and Co, Cu and Fe.

11. The process according to claim 10, wherein the precipitate comprising Cu and Fe is at least partly recycled to the acid leaching step of the solid starting material.

12. The method of claim 10, wherein the solid starting material and the metal reagent have the same composition.

13. The method of claim 10, wherein the solid starting material or the metal reagent comprises batteries, spent batteries, battery waste and / or waste derived from battery production.