Method for generating a lithium ion concentrate from an effluent to be treated, lithium recovery method, and associated system

Abstract

The invention relates to a method (100) for generating a lithium ion concentrate (10) from an effluent to be treated (1); the method comprising the following steps: ▪ receiving (110) the effluent to be treated (1), which effluent to be treated comprises at least sulphate ions, lithium ions and calcium ions; ▪ a step of reducing (120) the number of calcium ions in the effluent to be treated (1), then recovering an obtained aqueous solution (5); then ▪ a step of concentrating (130) the lithium ions in the recovered aqueous solution (5) in order to obtain the lithium ion concentrate (10).

Description

[0001] METHOD FOR GENERATING A LITHIUM ION CONCENTRATE FROM AN EFFLUENT TO BE TREATED, METHOD FOR RECOVERING LITHIUM AND ASSOCIATED SYSTEM

[0002] Field of invention

[0003] The present invention relates to the field of recycling battery materials containing at least lithium, and specifically relates to a method for concentrating lithium ions in an effluent. More specifically, the invention aims to provide an efficient and cost-effective method for increasing the lithium concentration of an effluent obtained by leaching, in order to facilitate its subsequent extraction. The invention also relates to methods for producing lithium hydroxide or lithium carbonate from such an effluent concentrated and purified in lithium.

[0004] State of the art

[0005] The market for lithium accumulators (and batteries comprising one or more accumulators), also called Lithium-ion accumulators (or batteries), is currently experiencing strong growth due to new applications linked mainly to the emergence and development of hybrid vehicles, electric vehicles, and portable electrical devices.

[0006] These Li-ion batteries tend to supplant previous technologies such as nickel / cadmium or nickel / metal hydride batteries.

[0007] The main applications of these batteries are the power supply of hybrid vehicles, plug-in hybrid vehicles, station-chargeable urban transport vehicles (trams, buses), electricity storage and charging infrastructure.

[0008] Furthermore, increasing environmental constraints, such as Directive 2006 / 66 / EC of 6 September 2006, require battery producers to ensure the recycling of batteries sold.

[0009] Recently, particular attention has been paid to the issue of resources required for developing technologies, particularly strategic resources such as lithium. There is a growing desire to push for "closed-loop" reuse of materials for certain sectors that are particularly high consumers of such materials.

[0010] In particular, the materials contained in accumulators and whose reuse is of interest are nickel, cobalt, copper and lithium.

[0011] Generally, the treatment of accumulators includes a mechanical treatment step of grinding the accumulator to recover the black mass composed of active materials (iron and lithium, cobalt, etc.). The treatment of accumulators then includes a hydrometallurgical treatment step consisting of dissolving the active materials by acid attack and possibly adding additional reducing reagents, then selectively recovering the different elements put into solution such as Nickel, Cobalt, Copper, Aluminum and / or Manganese.

[0012] Patent US5888463 describes, for example, a complete acid attack with sulfuric acid of waste containing lithium in order to recover a lithium salt, for example in the form of a carbonate.

[0013] However, the purity of the precipitate obtained as well as the lithium recovery rate by this process are insufficient.

[0014] Summary of the invention

[0015] The invention aims to limit at least one drawback of the methods of the prior art by proposing a method for treating an effluent to be treated so as to generate a concentrate whose lithium ion concentration is higher than that of the effluent to be treated.

[0016] Said effluent to be treated comprises at least calcium ions, sulfate ions and lithium ions.

[0017] The effluent to be treated advantageously comes from grinding at least one accumulator.

[0018] The invention solves the technical problem by proposing a method comprising at least one step of concentrating lithium ions to concentrate the solution containing lithium ions as well as a prior step of reducing calcium ions by precipitation in said solution to prevent the precipitation of calcium sulfate and obtain a better lithium concentration in the final concentrate.

[0019] According to a first aspect, the invention relates to a method for generating a lithium ion concentrate from an effluent to be treated.

[0020] Said method comprises a step of receiving an effluent to be treated comprising at least sulfate ions, lithium ions and calcium ions.

[0021] The method further comprises a step of reducing the calcium ions of said effluent to be treated followed by recovery of an aqueous solution obtained. In one embodiment, said reduction step comprises precipitation of the calcium ions.

[0022] The process then comprises a step of concentrating the lithium ions of the recovered aqueous solution to obtain a lithium ion concentrate.

[0023] According to one embodiment, the concentration step comprises a reverse osmosis step to obtain a reverse osmosis concentrate.

[0024] According to one embodiment, the method further comprises a step of evaporation-concentration of the reverse osmosis concentrate obtained.

[0025] According to one embodiment, the concentration step comprises an evaporation-concentration step to obtain the concentrate.

[0026] According to one embodiment, the precipitation of calcium ions is carried out using sodium bicarbonate (NaHCOs).

[0027] According to one embodiment, the precipitation of calcium ions is carried out using sodium carbonate (Na2CO3).

[0028] According to one embodiment, the precipitation of calcium carbonate comprises the addition of a calcium carbonate precipitate to the effluent to be treated to initiate the precipitation reaction.

[0029] According to one embodiment, the reduction step further comprises, after the precipitation of the calcium ions, an additional step of reduction of the calcium ions using an ion exchange resin.

[0030] According to one embodiment, the method comprises, between the reduction and concentration steps, a step of adjusting the pH of the aqueous solution to a pH between 6.5 and 7.5.

[0031] According to one embodiment, the pH adjustment step is carried out using sulfuric acid. According to a second aspect, the invention relates to a method for recovering lithium ions comprising a step of precipitating lithium ions from the concentrate obtained by the method according to the invention in the form of lithium carbonate.

[0032] According to one embodiment, the lithium ion precipitation step is carried out using a water-soluble alkali carbonate such as sodium carbonate.

[0033] According to one embodiment, the lithium carbonate precipitation step comprises heating the osmosis concentrate to a temperature above 35°C.

[0034] According to one embodiment, the lithium carbonate precipitation step comprises the addition of a lithium carbonate precipitate to the osmosis concentrate to increase the kinetics of the precipitation reaction.

[0035] According to a third aspect, the invention relates to a lithium recovery process comprising obtaining a purified lithium osmosis concentrate by implementing a process according to the invention and a step of bipolar membrane electrodialysis of said osmosis concentrate to produce lithium hydroxide.

[0036] According to a fourth aspect, the invention relates to a system comprising means for implementing the method according to the invention. Said means may comprise reactors, reagent addition systems, reverse osmosis devices, an evaporator-concentrator, fluid connection means and / or hydraulic pumps.

[0037] According to one embodiment, the invention relates to a system for generating a lithium ion concentrate designed to implement the method according to the invention.

[0038] According to one embodiment, the system comprises a first reactor intended to receive an effluent to be treated via a first fluid inlet; said effluent comprising the following elements in the form of ions: lithium, calcium and sulfate. Said first reactor is further intended to precipitate the calcium ions of said effluent to be treated.

[0039] According to one embodiment, the system comprises a second reactor comprising a second fluidic inlet fluidly connected to a first fluidic outlet of the first reactor and intended to receive the aqueous solution from the first reactor. Said second reactor is designed for implementing a step of concentrating the lithium ions of said aqueous solution. Said second reactor further comprises a fluidic outlet for extracting the concentrate obtained during said concentration step.

[0040] According to one embodiment, the system further comprises a third reactor intended to receive a concentrate from the second reactor via a third fluidic inlet fluidly connected to the outlet of the second reactor. Said third reactor is designed to carry out a precipitation of the lithium ions of said concentrate into lithium carbonate.

[0041] According to one embodiment, the system comprises fluidic means for continuously receiving a flow of the effluent continuously through the first inlet of the first reactor. According to an alternative embodiment, the different reactors of the system are not fluidically connected and the method is implemented discontinuously by transferring the different products of the process from a first reactor to a second reactor once the reaction of the first reactor is complete or sufficiently advanced.

[0042] Brief description of the figures

[0043] Other characteristics and advantages of the invention will emerge on reading the detailed description which follows, with reference to the appended figures, which illustrate:

[0044] Figure 1: a flowchart representing the different stages of a process according to an embodiment of the invention for purifying an effluent comprising lithium.

[0045] Figure 2: a flowchart representing the different sub-steps of the effluent reception step according to one embodiment of the invention.

[0046] Figure 3: a flowchart representing the different sub-steps of the reduction step according to one embodiment of the invention.

[0047] Figure 4: a flowchart representing the different sub-steps of the concentration step according to one embodiment of the invention.

[0048] Figure 5: A flowchart representing the different stages of a lithium carbonate generation process.

[0049] Figure 6: a flowchart representing the different stages of a lithium hydroxide generation process. Figure 7: a schematic representation of a system according to an embodiment of the invention comprising a first reactor for implementing the stage of reducing calcium ions from the effluent and a second reactor for implementing the stage of concentrating lithium ions in the aqueous solution obtained at the outlet of the first reactor.

[0050] Figure 8: a schematic representation of a system according to a second embodiment comprising a third reactor for implementing the step of precipitation of lithium ions from the concentrate obtained at the outlet of the second reactor.

[0051] Description of the invention

[0052] According to a first aspect, the invention relates to a method 100 for purifying lithium from an effluent to obtain a lithium ion concentrate 10, i.e. a concentrated lithium ion solution.

[0053] This method and various modes of execution are now described below with reference to Figures 1 to 5.

[0054] Reception of an effluent

[0055] The method comprises receiving 110 an effluent 1 to be treated.

[0056] Preferably, the effluent 1 is obtained from a treatment comprising a step of mechanical grinding 111 of one or more lithium-based accumulators to obtain a black mass.

[0057] The black mass is composed of active materials (iron and lithium, cobalt, etc.) and is recovered following mechanical crushing followed by at least one additional physical separation step.

[0058] The treatment also includes a hydrometallurgical treatment step consisting of putting the active materials of the black mass into aqueous solution, then selectively recovering the different elements put into solution such as Nickel, Cobalt, Copper, [Aluminium and / or Manganese.

[0059] In particular, the solutionization preferably includes a sulfuric acid leaching step. Leaching consists of solubilizing active materials, including lithium in particular, in an aqueous solution comprising sulfuric acid and other leaching reagents circulating through the black mass.

[0060] The resulting leachate is therefore an aqueous solution comprising sulfuric acid and elements of the black mass such as solubilized lithium and calcium and other metallic, alkali and alkaline-earth elements.

[0061] Preferably, the leachate may be treated for the extraction of metals other than lithium from the leachate.

[0062] By "effluent to be treated" we mean a solution comprising solubilized lithium as well as sulfate ions from sulfuric acid and solubilized calcium.

[0063] This effluent to be treated is, for example, treated or untreated leachate.

[0064] The lithium concentration in the effluent to be treated 1 is, however, insufficient to cause effective natural precipitation. The main challenge is therefore to treat the said effluent to be treated to increase its lithium concentration as much as possible.

[0065] In one embodiment, the effluent to be treated 1 comprises traces of copper and / or cobalt.

[0066] In one embodiment, the effluent to be treated 1 comprises traces of organic compounds.

[0067] In one embodiment, the effluent to be treated 1 further comprises traces of phosphorus, fluorine, silicate and / or chlorine. These compounds are generally present in an effluent from the grinding and leaching of accumulators.

[0068] As described further, the method comprises a step of concentrating the aqueous solution, for example, by reverse osmosis and / or by evaporative concentration to obtain a lithium-rich concentrate.

[0069] The use of sulfuric acid is advantageously particularly effective for solubilizing lithium in an aqueous solution. However, it is responsible for the precipitation of calcium ions in the form of calcium sulfate under certain conditions, in particular during the reverse osmosis step, at the membrane level, or during evaporation-concentration. This precipitation of calcium sulfate causes a degradation of the quality of any precipitate of calcium carbonate obtained subsequently. It is therefore advantageous to treat the effluent to be treated 1 upstream of the concentration step in order to prevent such precipitation of calcium ions.

[0070] Calcium ion depletion

[0071] The method according to the invention comprises a step 120 of reducing the calcium ions from the effluent to be treated 1.

[0072] In other words, one step of the process consists of reducing the concentration of calcium ions in the effluent to be treated 1 to obtain an aqueous solution 5 depleted in calcium ions Ca 2+ . Preferably, the calcium ion reduction step should be understood as a softening step of the effluent to be treated aimed at reducing the concentration of calcium ions.

[0073] The reduction includes the implementation of a first step of precipitation 121 of calcium ions (Ca 2+ ) present in the effluent to be treated 1 , for example in the form of calcium carbonate. The reduction can be understood as a step of softening the effluent to be treated 1 , in particular by producing a solution whose concentration of calcium ions is lower than that of the effluent to be treated 1 .

[0074] The effluent to be treated 1 is preferably continuously agitated during the first precipitation stage to ensure uniform precipitation.

[0075] In a first embodiment, the precipitation of calcium ions comprises the addition of sodium bicarbonate (NaHCOs) to the effluent to be treated 1 .

[0076] Sodium bicarbonate advantageously allows the precipitation of calcium ions in the form of calcium carbonate.

[0077] Part of the calcium present in the effluent therefore precipitates in the form of calcium carbonate, reducing the residual concentration of calcium ions in the aqueous solution. The aqueous solution 5 obtained therefore has a lower concentration of calcium ions than the effluent to be treated 1.

[0078] Preferably, the pH of the effluent to be treated 1 by the first precipitation step by adding sodium bicarbonate is greater than 9, preferably greater than 10 or greater than 11. In one embodiment, the pH of the effluent is regulated during the reduction so as to maintain a pH greater than 9, preferably greater than 10 or 11.

[0079] Preferably, the temperature of the effluent to be treated during the first stage of precipitation 121 of the calcium ions is greater than 35°C. This advantageously makes it possible to increase the precipitation kinetics.

[0080] According to a second embodiment, the first step of precipitation of calcium ions comprises the addition of sodium carbonate (Na2COs) to the effluent.

[0081] Preferably, the precipitation step 110 also comprises the addition of a calcium carbonate precipitate to the effluent to be treated, such as a seed. The presence of such a precipitate advantageously makes it possible to initiate the precipitation reaction and to increase the kinetics of the precipitation.

[0082] Recovery of the aqueous solution

[0083] The aqueous solution 5 depleted in calcium ions compared to the effluent to be treated 1 is then recovered. The recovery step 122 comprises the separation of a liquid phase from the precipitates formed during the reduction step, in particular from the calcium carbonate precipitates.

[0084] This recovery preferably comprises a decantation step and a supernatant recovery step. Said supernatant can be filtered through different filtration devices to separate the solid compounds from the aqueous solution 5.

[0085] This separation can be achieved by a filtration step with a filter allowing the aqueous solution containing the lithium ions to pass through and retaining the precipitates formed.

[0086] Advantageously, the filtered cake comprising the precipitates formed can be subjected to a washing step so as to optimize the extraction of the lithium ions present in said cake. The lithium ions thus extracted can be reintroduced into the process, for example in the aqueous solution 5 depleted in calcium ions.

[0087] In another embodiment, the separation is achieved by fluidic displacement of the supernatant. This step involves transporting the surface of the liquid from one container. Thus, the denser precipitates remain at the bottom of the container and the upper part of the liquid volume in the container is moved to a second container.

[0088] The recovery may include a centrifugation step. Such filtration and / or centrifugation may be carried out before and / or after the effluent reduction step by resin refining.

[0089] In one embodiment, the precipitation step comprises the addition to the effluent of a calcium carbonate precipitate. The presence of such a precipitate in the effluent advantageously makes it possible to initiate the precipitation reaction and to increase the precipitation kinetics. Another advantage is to obtain similar precipitation kinetics at a lower pH.

[0090] In one embodiment, the first precipitation step is a continuous process: the effluent is introduced into a reactor at a controlled flow rate and the amount of calcium carbonate precipitate is controlled in said reactor.

[0091] Preferably, the reactor comprises a device for recovering the aqueous solution in the reactor at a controlled flow rate.

[0092] Refining on resin

[0093] In one embodiment, the step 120 of reducing the effluent 1 to calcium further comprises a refining 123 on resin of the aqueous solution 5 obtained by the first precipitation step.

[0094] Refining consists of further reducing the concentration of calcium ions in the aqueous solution obtained.

[0095] The aqueous solution obtained by the first precipitation step passes through an ion exchange resin which retains calcium ions from the aqueous solution and in exchange releases its ions, for example sodium ions. Other types of resins can be considered, in particular resins releasing ions other than sodium ions and allowing the selective capture of calcium.

[0096] Preferably, the phase of reducing calcium ions by resin refining is implemented using a resin matrix (for example resin beads) loaded with ions, for example sodium ions, to selectively capture the calcium ions present in the calcium-containing effluent. A resin matrix is ​​prepared using a suitable porous material that allows the percolation of the aqueous solution through the matrix, for example by using resin beads. The resin is loaded with ions, for example sodium ions, by an ion exchange process, thus ensuring the capacity of the matrix to capture calcium ions. Said matrix is ​​installed in a treatment device allowing the percolation of the aqueous solution through said matrix.

[0097] The aqueous solution 5 containing calcium is introduced into the treatment device, where it is directed through the matrix of resin beads loaded with sodium ions.

[0098] The percolation of the aqueous solution 5 through the matrix allows the calcium ions present in the aqueous solution 5 to interact with the ions charged on the resin, which results in the selective capture of the calcium ions by the matrix. The flow rate of the aqueous solution can be controlled to optimize this operation.

[0099] After capturing the calcium ions, the resin matrix gradually becomes saturated with calcium ions. To regenerate the matrix, a suitable regeneration agent is introduced into the treatment device. This agent allows the captured calcium ions to be released and the resin beads to be recharged with ions, for example sodium, ready to be used for further selective capture of calcium ions. In a non-limiting example, the regeneration agent comprises a dilute sodium hydroxide solution (NaOH) or a sodium chloride solution (NaCl) or an acid solution, for example hydrochloric acid.

[0100] This step advantageously allows the selective capture of calcium ions in solution to further reduce the residual calcium concentration in the aqueous solution (which had already been depleted in calcium ions) without impacting the concentration of solubilized lithium in the effluent. Another advantage of this step is that it allows continuous treatment of the effluent with high calcium ion capture efficiency.

[0101] In the case where a refining step on resin 123 is implemented, the separation step also comprises the separation of the aqueous phase from the resin effluent.

[0102] Concentration The method according to the invention further comprises a step 130 of concentrating the recovered aqueous solution 5 depleted in calcium. This step advantageously makes it possible to increase the lithium concentration of the recovered aqueous solution.

[0103] The concentration step makes it possible to generate a lithium ion concentrate 10, said concentrate 10 preferably being an aqueous solution whose lithium ion concentration is greater than the lithium ion concentration of the aqueous solution 5 obtained after the reduction step 120.

[0104] This concentration step 130 advantageously makes it possible to obtain a concentrate 10 sufficiently rich in lithium to promote a lithium precipitation reaction.

[0105] Concentration by reverse osmosis

[0106] In one embodiment, this concentration step 130 comprises removing a portion of the water volume from the recovered aqueous solution.

[0107] In a preferred embodiment, the concentration step 130 comprises a reverse osmosis step 131 of the aqueous solution 5 recovered after the reduction step 120.

[0108] Said aqueous solution 5 is placed in a reverse osmosis system in a device comprising a first compartment and a second compartment on each side of a semi-permeable reverse osmosis membrane.

[0109] The reverse osmosis membrane is designed to allow water to pass through and to retain salts present in the aqueous solution, such as lithium ions. The first compartment and the second compartment are separated by the reverse osmosis membrane.

[0110] Reverse osmosis membranes are well known to those skilled in the art who can easily select the reverse osmosis membrane available on the market compatible with the invention. Preferably, a conventional reverse osmosis desalination membrane is used, in particular of the spiral type.

[0111] For example, the aqueous solution is introduced into the first compartment. Hydrostatic pressure is applied to the liquid in the first compartment of the reverse osmosis system, forcing water from the aqueous solution to leave the first compartment under pressure for the second compartment through the reverse osmosis membrane despite the increased concentration of lithium and other solutes in the first compartment. The aqueous solution then passes through the reverse osmosis membrane to the first compartment and then to the second compartment.

[0112] In the second compartment, we thus obtain purified water and in the first compartment an osmosis concentrate particularly concentrated in lithium which will be recovered, for example through a fluid outlet from the first compartment.

[0113] The previous step of reducing 120 calcium in the effluent to be treated 1 is particularly advantageous. In fact, the increase in the concentration of calcium ions and sulfates promotes the precipitation of calcium sulfate.

[0114] The retention capacity of the reverse osmosis membrane also promotes the formation of such a precipitate.

[0115] However, the formation of a calcium sulfate precipitate, particularly in contact with the reverse osmosis membrane, disadvantageously causes the clogging of the reverse osmosis membrane and an increase in the lithium concentration in the first, less efficient compartment.

[0116] In one embodiment, the permeate, i.e. the liquid present in the second compartment, is extracted regularly, preferably continuously. This advantageously makes it possible to increase the lithium concentration in the concentrate, i.e. the liquid present in the first compartment.

[0117] The pressure exerted on the liquid in the first compartment is greater than the osmotic pressure of said aqueous solution.

[0118] Preferably, the pressure applied to the liquid in the first compartment is greater than 20 bars.

[0119] Double passage or double floor

[0120] In one embodiment, the aqueous solution 5 is subjected to a double-pass reverse osmosis step. In this mode, the permeate obtained in the second compartment of a first reverse osmosis pass is reintroduced into a first compartment of a second reverse osmosis device similar to that described above. The liquid present in the first compartment of the second reverse osmosis pass can then be mixed with the liquid present in the first compartment of the first reverse osmosis pass to form the reverse osmosis concentrate. Such a double-pass reverse osmosis step advantageously makes it possible to improve the recovery rate of lithium ions because it has passed through two successive reverse osmosis devices. In one embodiment, the concentration step comprises a triple-pass reverse osmosis step or more.

[0121] In another embodiment, the aqueous solution 5 is subjected to a two-stage reverse osmosis step. In this embodiment, the concentrate obtained in the first compartment of the first reverse osmosis stage is reintroduced into a first compartment of a second reverse osmosis device (called “second stage”) similar to that described above to carry out a new reverse osmosis step. The reverse osmosis concentrate obtained in the first compartment of the second reverse osmosis stage can then be mixed with the liquid present in the first compartment and then recovered. Such a two-stage reverse osmosis step advantageously makes it possible to improve the lithium ion concentration in the reverse osmosis concentrate because it has passed through two successive reverse osmosis devices. In one embodiment, the concentration step comprises a triple-stage or higher reverse osmosis step.

[0122] Reduction of pH before reverse osmosis

[0123] In a preferred embodiment of the invention, the method comprises, between the reduction steps 120 and the concentration step 130 by reverse osmosis, a step of adjusting the pH of the recovered aqueous solution 5.

[0124] In one example, said treatment step comprises a step of adding sulfuric acid to the aqueous solution 5. Other acids may be envisaged.

[0125] This treatment step aims to achieve a pH range between 6 and 8, more preferably between 6.5 and 7.5. Such a pH range advantageously allows for better separation of the elements and an increase in the lithium concentration in the osmosis concentrate.

[0126] Additionally, a pH above 8 leads to lithium ions passing through the reverse osmosis membrane, increasing lithium ion loss and reducing the lithium ion concentration in the reverse osmosis concentrate.

[0127] The reverse osmosis step 131 advantageously makes it possible to produce an osmosis concentrate whose lithium concentration is higher than that of the aqueous solution recovered at the end of the step of reducing the effluent to be treated in calcium. Another advantage is that this concentrate can be obtained with a high flow rate with lower energy expenditure.

[0128] Concentration by evapoconcentration

[0129] In a first embodiment, the reverse osmosis concentrate is the lithium ion concentrate 10.

[0130] In a second embodiment, the concentration of the aqueous solution 5 further comprises a step of evaporation-concentration 132 of the reverse osmosis concentrate obtained to obtain the concentrate 10.

[0131] The evapo-concentration step 132 makes it possible to increase the lithium ion concentration of the osmosis concentrate.

[0132] The step of evaporation-concentration of the osmosis concentrate comprising lithium, firstly comprises the introduction of said osmosis concentrate into an evaporation-concentration device. This device is equipped with a heating system designed to control the temperature of the solution inside the device.

[0133] Then, said solution is subjected to gradual heating, which causes the evaporation of the water contained in said osmosis concentrate. The evaporation-concentration device is designed to allow the separate collection of water vapor on the one hand and the concentrate on the other.

[0134] Water vapors can be condensed and recovered for future use.

[0135] The evaporation concentrate is advantageously collected and can be used in a subsequent step of the process. To optimize the efficiency of the process, advanced temperature, pressure, and flow rate control techniques are implemented. These techniques allow the evaporation parameters to be regulated so as to obtain a precise and uniform lithium concentration in the concentrate. In one embodiment, the evaporation device includes a heat recovery system, which minimizes energy losses and improves the overall efficiency of the process.

[0136] The increased lithium concentration achieved through the evaporation process facilitates the lithium extraction step and allows for higher yields and better purity of the extracted lithium.

[0137] Adding an evaporation-concentration step after the reverse osmosis step has several advantages. First, it provides a precise and controlled process for increasing the lithium ion concentration, which facilitates its subsequent extraction. In addition, the prior increase in lithium ion concentration through reverse osmosis reduces the amount of energy required for evaporation-concentration and increases the concentrate production rate.

[0138] In one embodiment, the concentrate 10 obtained following said concentration step 130 of the aqueous solution 5 is particularly concentrated in lithium. An advantage is to obtain a liquid phase sufficiently concentrated in lithium ions to allow a precipitation reaction of said lithium ions.

[0139] In one embodiment, the concentrate 10 resulting from the evapo-concentration operations comprises at least 18 g / L and up to 28 g / L of lithium ions.

[0140] Recovery of lithium carbonate

[0141] According to another aspect, the invention relates to a method 200 for recovering lithium in solid form, for example in the form of lithium carbonate 20, from the concentrate 10 produced according to the method 100 described according to the first aspect of the invention. This step makes it possible to transform the lithium ions into a solid form, more easily recoverable and usable in various industrial applications. In addition, this reaction makes it possible to remove and therefore recover a large part of the lithium present in the concentrate 10. Said method comprises a step 210 of precipitation of the lithium ions from the concentrate, for example, in the form of lithium carbonate 20.

[0142] Concentrate 10 is transferred to a reactor. In this reactor, a suitable reagent, such as a soluble alkali carbonate or a powdered alkali carbonate, is added to concentrate 10. The reagent chemically reacts with the lithium ions present in the concentrate, thus forming lithium carbonate 20 as a precipitate.

[0143] Preferably, the soluble alkali carbonate comprises sodium carbonate or sodium bicarbonate. In one embodiment, the added soluble alkali carbonate is sodium bicarbonate and the concentration of said sodium bicarbonate in the reactor is between 100 g / L and 300 g / L. In one embodiment, the alkali carbonate in powder form is sodium carbonate in powder form.

[0144] The precipitation reaction is generally promoted by controlled pH conditions and adequate agitation to ensure homogeneous mixing of the reactants. Parameters such as temperature, reaction time, and reactant concentration can be adjusted to improve the yield and purity of the precipitated lithium carbonate.

[0145] In one embodiment, the second precipitation step 210 is carried out by heating the concentrate 10 to a temperature above 35°C, preferably to a temperature above 55°C, more preferably to a temperature above 75°C or between 75°C and 85°C. An advantage is to improve, with the temperature, the yield of the precipitation reaction and the purity of the lithium carbonate precipitate produced by this reaction.

[0146] Preferably, the precipitation step 210 also comprises the addition of a lithium carbonate precipitate in the concentrate 10, such as a seed. The presence of such a precipitate in the concentrate 10 advantageously makes it possible to initiate the precipitation reaction and to increase the kinetics of the precipitation.

[0147] In a particular embodiment, the lithium carbonate precipitate comes from precipitation step 210.

[0148] The recovery step advantageously includes a step of separating the lithium carbonate from the liquid phase of the concentrate by filtration, decantation and / or centrifugation techniques. The lithium carbonate precipitate can then be washed to remove residual impurities or traces of reagents, which further improves its purity.

[0149] After washing, the precipitated lithium carbonate is preferably subjected to a drying process, generally by controlled heating. This drying eliminates any traces of residual moisture and transforms the precipitate into a dry powder of lithium carbonate 20.

[0150] The resulting lithium carbonate 20 can be used in a variety of applications, including reuse in the battery industry, chemical industry, and ceramic manufacturing. Its high purity and precise composition make it a material of choice for the production of lithium-ion batteries, where it is used as an active material in the battery electrolyte.

[0151] In one embodiment, the remaining liquid phase of the concentrate once the lithium carbonate precipitate has been removed (called the "supernatant") can be reused during one of the steps previously described.

[0152] It can, for example, be introduced into the process line according to the invention. For example, it can be mixed with the leachate to form the effluent to be treated 1.

[0153] Lithium hydroxide production

[0154] According to another aspect, the invention relates to a method for producing lithium hydroxide 300, comprising in particular the method 100 described previously for producing a concentrate 10 of lithium ions. This method comprises the transformation of the lithium ions of the concentrate 10 produced in hydroxide form. Lithium ions in hydroxide form are more valuable and allow applications different from those of lithium carbonate.

[0155] Preferably, lithium hydroxide 30 is produced by a bipolar membrane electrodialysis 310 (designated by the abbreviation “EDBM”).

[0156] Concentrate 10 is introduced into an EDBM device comprising bipolar membranes arranged in an alternating manner, thus creating several electrodialysis compartments. The bipolar membranes are made from selective materials that allow the selective transport of lithium ions into the EDBM device, while limiting the migration of other unwanted ions.

[0157] Once the lithium ion concentrate is placed in the electrodialysis compartments, an electrical voltage is applied across the bipolar membranes. This voltage induces a migration of lithium ions, through the membranes, from the aqueous solution to the appropriate compartments.

[0158] As lithium ions migrate across bipolar membranes, specific chemical reactions occur, promoting the conversion of lithium ions into lithium hydroxide. The reactions can be controlled by adjusting parameters such as electrical voltage and process duration.

[0159] Once the conversion of lithium ions into lithium hydroxide is complete, the lithium hydroxide 30 is recovered in the electrodialysis compartments. The resulting lithium hydroxide can then be crystallized, for example in an evaporative crystallization device.

[0160] The resulting lithium hydroxide 30 has high purity and precise composition, due to the efficiency of the selective separation of lithium ions enabled by bipolar membranes. This lithium hydroxide can then be used in various industrial applications, including the production of the electrolyte for lithium-ion batteries, ceramics and lubricants.

[0161] Another advantage of the EDBM 310 step is the production, as a by-product, of sulfuric acid.

[0162] In one embodiment, the sulfuric acid produced by the EBDM 310 step may be used in the sulfuric acid leaching step for the production of "black mass" to solubilize lithium from the grinding of a battery.

[0163] Continuous process and system

[0164] A system for implementing the method according to the invention is now described with reference to Figure 7. The system 1000 is a fluidic system comprising at least a first reactor 1100 for implementing the calcium ion reduction step and a second reactor 1200 for implementing the concentration step according to the invention.

[0165] The first reactor comprises a fluid inlet 1010 for receiving an effluent 1 into the first reactor.

[0166] The first reactor 1100 is designed to carry out the step of reducing the calcium ions present in the effluent to be treated as described above. Optionally, the first reactor 1100 comprises means 1030 for controlling the quantity of calcium carbonate precipitate in the first reactor 1100.

[0167] The system 1000 may further comprise means for adding, into the first reactor 1100, a precipitation reagent such as sodium bicarbonate or sodium carbonate in a controlled manner.

[0168] In one embodiment, the first reactor comprises a first compartment for carrying out the step of reducing calcium ions and a second compartment comprising a resin matrix for carrying out the step of reducing calcium ions by resin refining. The first and second compartments are preferably fluidically connected to transfer the supernatant from the first compartment into the second compartment.

[0169] The system 1000 further comprises a second reactor 1200 for implementing the concentration step of the method according to the invention.

[0170] The first reactor 1100 comprises a fluid outlet 1020 for extracting the aqueous solution depleted in calcium ions from the first reactor 1100. The system 1000 further comprises means for recovering the aqueous solution 5 from the first reactor 1100 depleted in calcium ions, such as a hydraulic pump.

[0171] The second reactor 1200 comprises a fluid inlet 1021 for receiving the aqueous solution 5 in the second reactor 1200.

[0172] The outlet 1020 of the first reactor 1100 and the inlet 1021 of the second reactor 1200 are fluidically connected to each other, preferably by a second fluidic connection means. Preferably, the system 1000 comprises filtration means designed to remove elements suspended in the aqueous solution fluidly arranged between the outlet 1020 of the first reactor 1100 and the inlet 1021 of the second reactor 1200.

[0173] The second reactor 1200 comprises, as described above, a reverse osmosis device and / or an evapo-concentrator. The second reactor 1200 comprises a first fluid outlet 1040 for extracting the concentrate 10 concentrated in lithium ions and a second fluid outlet 1042 for extracting a solution depleted in lithium ions from the reverse osmosis step and / or the evapo-concentration step. In one embodiment, the fluid inlet 1021 of the second reactor 1200 is fluidically connected to the first compartment of the reverse osmosis device described above. The first fluid outlet 1040 of the second reactor 1200 is also fluidically connected to the first compartment of said reverse osmosis device for extracting the reverse osmosis concentrate. In one embodiment, the second fluid outlet 1042 of the second reactor 1200 is fluidically connected to the second compartment so as to extract the permeate continuously.

[0174] In an embodiment illustrated in FIG. 8, the system 1000 further comprises a third reactor 1300 comprising a fluid inlet 1041 fluidly connected to the first fluid outlet 1040 of the second reactor 1200 so as to receive the concentrate 10 obtained at the outlet of the second reactor 1200.

[0175] The fluidic inlet 1041 of the third reactor 1300 and the first fluidic outlet 1040 of the second reactor 1200 are preferably fluidically connected by fluidic connection means.

[0176] In one embodiment, the third reactor 1300 is designed to carry out the step of precipitating lithium ions from the concentrate into lithium carbonate as described above.

[0177] In this respect, the third reactor 1300 may comprise means for controlling the addition of a reagent allowing the implementation of this precipitation such as a soluble alkali carbonate, preferably a sodium carbonate.

[0178] Preferably, the third reactor 1300 comprises a fluid outlet 1050 for extracting the lithium-depleted concentrate from the third reactor 1300 following the precipitation reaction. In one embodiment, the system 1000 further comprises a second outlet 1060 for extracting in a controlled manner the lithium carbonate precipitate generated in the third reactor 1300. Preferably, the system comprises means for extracting in a controlled manner the lithium carbonate precipitate through the second outlet 1060 of the third reactor 1300.

[0179] Preferably, the system 1000 comprises fluidic means such as one or more fluidic pumps for the continuous transport of the liquid from the fluidic inlet 1010 of the first reactor 1100 to the fluidic outlet 1050 of the third reactor 1300 continuously through the first, second and third reactors.

[0180] Advantageously, the methods according to the invention described above are carried out continuously, that is to say that the successive steps are carried out in continuous flow, without any downtime.

[0181] The effluent is introduced into the system 1000 through the fluid inlet 1010 of the first reactor by a continuous flow and the system thus makes it possible to continuously recover a flow of concentrate 10 at the outlet 1040 of the second reactor and / or to continuously extract a lithium carbonate precipitate through the second outlet 1060 of the third reactor 1300.

[0182] In an alternative embodiment, the system 1000 comprises an EDBM device fluidically connected to the first outlet 1040 of the second reactor for the production of lithium hydroxide from the concentrate obtained at the outlet of the second reactor 1200.

[0183] Example 1

[0184] In a first example, an effluent to be treated (A1) as described above is recovered. A step of precipitation of calcium ions into calcium carbonate is carried out at room temperature by adding sodium carbonate to the reactor at a level of 1.6 g / L. The aqueous solution (B1) depleted in calcium obtained is recovered, treated to adjust the pH to 7 and introduced into a reverse osmosis device to produce the osmosis concentrate. The osmosis concentrate (C1) is finally introduced into a second reactor with sodium carbonate at a level of 200 g / L at different temperatures. The compositions in calcium, sodium, lithium and sulfate ions of the effluent to be treated (A1), of the aqueous solution (B1) resulting from the precipitation step and of the osmosis concentrate (C1) are listed in Table 1.

[0185] Table 1

[0186] The drop in the concentration of calcium ions in the effluent advantageously makes it possible to avoid the precipitation of calcium sulfate during the reverse osmosis stage and the clogging of the reverse osmosis membrane.

[0187] The C1 osmosis concentrate produced thus includes a lithium concentration doubled compared to the concentration of the starting effluent.

[0188] Example 2

[0189] In a second example, the same effluent to be treated (A1) as for example 1 is recovered. A step of precipitation of calcium ions into calcium carbonate is carried out in a reactor heated to 40°C by adding sodium bicarbonate to the reactor at a level of 1 g / L. The aqueous solution (B2) obtained is recovered, treated to adjust the pH to 7 and introduced into a reverse osmosis device to produce the osmosis concentrate (C2) in the same way as for example 1.

[0190] The calcium, sodium, lithium and sulfate ion compositions of the effluent to be treated (A1), of the aqueous solution (B2) resulting from the precipitation stage, and of the osmosis concentrate (C2) are listed in Table 2.

[0191] Table 2 The C2 osmosis concentrate is more concentrated in lithium ions than the C1 osmosis concentrate produced in Example 1.

[0192] The step of precipitation of calcium ions by sodium bicarbonate advantageously allows the production of a concentrated lithium solution compared to the same precipitation with sodium carbonate.

[0193] Example 3

[0194] The osmosis concentrates C1 and C2 produced respectively during example 1 and example 2 are placed in a reactor for the implementation of the step of precipitation of lithium ions into lithium carbonate as described above by addition of sodium carbonate at a level of 200 g / L at temperatures of 40°C, 60°C and 80°C.

[0195] The purity of the lithium carbonate precipitate in mass % and mol % for each temperature, as well as the lithium loss are reported in Table 3.

[0196] The lithium carbonate precipitate produced is advantageously purer when the precipitation step is carried out at a temperature of 80°C. A significant increase in the purity of the precipitate obtained is observed at 80°C, whereas it is substantially the same at 40°C and 60°C.

[0197] The purity of the lithium precipitate produced is also better when the precipitation of calcium ions is carried out by the addition of sodium bicarbonate rather than by the addition of sodium carbonate. When the precipitation of calcium ions is carried out by the addition of sodium bicarbonate and when the precipitation of lithium ions is carried out at a temperature of 80°C, the purity of the lithium carbonate precipitate is satisfactory.

[0198] The lithium loss reported in Table 3 is calculated by measuring the difference between the quantity of lithium present in the effluent to be treated and the quantity of lithium obtained in the lithium carbonate precipitate over the quantity of lithium present in the effluent. The lithium loss decreases when the precipitation step is carried out at a temperature of 80°C. The process according to the invention advantageously makes it possible to recover a large quantity of lithium initially present in the black mass or in the effluent to be treated.

[0199] Example 4

[0200] In a fourth example, the same effluent to be treated is recovered. A step of precipitation of calcium ions into calcium carbonate is carried out at room temperature by adding sodium bicarbonate to the reactor at a rate of 5 g / L.

[0201] A first osmosis concentrate (C3) is obtained by recovering the calcium-depleted aqueous solution and treating said aqueous solution to adjust the pH to 7 before introducing it into a reverse osmosis device to produce the osmosis concentrate (C3) as described above.

[0202] A second osmosis concentrate (C4) is obtained by recovering the calcium-depleted aqueous solution and treating said aqueous solution to adjust the pH to 10 before introducing it into a reverse osmosis device to produce the osmosis concentrate (C4) as described above.

[0203] The rejection values ​​in the first and second osmosis concentrate are reported in Table 4.

[0204] Table 4

[0205] Adjusting the pH to 7 advantageously allows for the recovery of a greater quantity of lithium ions in the osmosis concentrate. The rejection should be understood as the molar or mass concentration of lithium ions present in the osmosis concentrate divided by the lithium ion concentration in the aqueous solution introduced into the reverse osmosis device. In this description, the designated ranges should be understood as including the limits.

Claims

CLAIMS 1. Method (100) for generating a lithium ion concentrate (10) from an effluent to be treated (1); said method comprising the following steps: ■ receiving (110) the effluent to be treated (1) comprising at least sulfate ions, lithium ions and calcium ions; ■ a step of reducing (120) the calcium ions of said effluent to be treated (1) followed by recovery (123) of an aqueous solution (5) obtained; then ■ a step of concentrating (130) the lithium ions of the recovered aqueous solution (5) to obtain the lithium ion concentrate (10).

2. Method (100) according to claim 1, characterized in that the step of reducing the calcium ions comprises a step of precipitating the calcium ions.

3. Method (100) according to any one of claims 1 to 2, characterized in that said concentration step (130) comprises a reverse osmosis step (131) to obtain a reverse osmosis concentrate.

4. Method (100) according to claim 3, characterized in that it further comprises a step of evaporation-concentration (132) of the reverse osmosis concentrate to obtain the lithium ion concentrate (10).

5. Method (100) according to any one of the preceding claims, characterized in that the precipitation (121) of the calcium ions is carried out using a sodium bicarbonate or a sodium carbonate.

6. Method (100) according to one of claims 1 to 5, characterized in that the reduction step (120) further comprises, after the precipitation (121) of calcium ions, an additional step of reduction of calcium ions (123) using an ion exchange resin.

7. Method (100) according to one of claims 1 to 5, characterized in that it comprises, between the reduction (120) and concentration (130) steps, a step of adjusting (125) the pH of the aqueous solution (5) to a pH between 6.5 and 7.

5.

8. Method (100) according to claim 6, characterized in that the pH adjustment step (125) is carried out using sulfuric acid.

9. Method (200) for recovering lithium comprising a step of precipitation (210) of lithium ions, from a lithium ion concentrate (10) obtained by the method according to one of claims 1 to 8, in the form of lithium carbonate.

10. Method (200) according to claim 9, characterized in that the step of precipitation (210) of lithium ions is carried out using a water-soluble alkali carbonate such as sodium carbonate.

11. Method (200) according to claim 9 or claim 10, characterized in that the step of precipitating (210) lithium ions comprises heating the lithium ion concentrate (10) to a temperature above 35°C.

12. A method (300) for recovering lithium comprising obtaining a lithium ion concentrate (10) by implementing a method according to any one of claims 1 to 8 and further comprising a step of bipolar membrane electrodialysis (310) of said lithium ion concentrate (10) to produce lithium hydroxide (30).

13. System (1000) for generating a lithium ion concentrate (10) designed to implement the method according to one of claims 1 to 8, comprising: ■ a first reactor (1100) intended for ■ receive an effluent to be treated (1) via a first fluid inlet (1010), said effluent to be treated (1) comprising at least sulfate ions, lithium ions and calcium ions and intended to ■ precipitate the calcium ions of said effluent to be treated (1); ■ a second reactor (1200) comprising a second fluidic inlet (1021) fluidically connected to a first fluidic outlet (1020) of the first reactor (1100) and intended to receive an aqueous solution (5) from the first reactor (1100); said second reactor being designed for implementing a step of concentrating the lithium ions of said aqueous solution (5).

14. System (1000) according to claim 13, wherein said second reactor (1200) further comprises a second fluid outlet (1040) for extracting the lithium ion concentrate obtained during said concentration step.

15. System (1000) according to claim 13 or claim 14, further comprising a third reactor (1300) for receiving the lithium ion concentrate (10) through a third fluid inlet (1041) fluidly connected to the second fluid outlet (1040) of the second reactor (1200); said third reactor (1300) being adapted for carrying out a precipitation of lithium ions from said concentrate (10) into lithium carbonate.

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