WO2024224136A1

WO2024224136A1 - Lithium production

Info

Publication number: WO2024224136A1
Application number: PCT/IB2023/000238
Authority: WO
Inventors: Frank DESPINOIS; Christophe BLONDEAU; Rayen FILALI
Original assignee: TotalEnergies Onetech SAS
Current assignee: TotalEnergies Onetech SAS
Priority date: 2023-04-26
Filing date: 2023-04-26
Publication date: 2024-10-31
Anticipated expiration: 2025-10-26

Abstract

It is hereby proposed a method of producing lithium. The method comprises injecting a quantity of a gas into an aquifer; withdrawing water from the aquifer as the gas is injected; and recovering lithium from the withdrawn water. Such a method forms an improved solution for lithium production from an aquifer.

Description

LITHIUM PRODUCTION

TECHNICAL FIELD

The disclosure relates to a method of producing lithium. The disclosure also relates to a lithium production installation configured for producing lithium according to the method.

BACKGROUND

Lithium is a valuable metal that is used in a wide range of applications, including batteries and lubricants. The demand for lithium extraction from its sources has increased significantly in recent years due to the growing popularity of electric vehicles and renewable energy storage systems. For example, lithium recovered from water produced when extracting oil and gas may be used in different fields such as ceramics, greases, aerospace, polymers, metal additives and particularly in the manufacture of lithium-ion batteries.

The lithium extraction from water in an aquifer is generally limited by the withdrawal capacity since the pressure in the aquifer can decrease with time. The preferred strategy for maintaining the pressure is reinjecting treated water, but this causes a financial and energy cost, as the water must be transported far away to avoid dilution and a decrease in the concentration of metals (especially in the case of heterogenous geological formations leading to an early breakthrough of the reinjection water).

Within this context, there is a need for improved solutions notably for producing lithium.

SUMMARY

It is therefore provided a method of producing lithium. The method comprises injecting a quantity of a gas into an aquifer; withdrawing water from the aquifer as the gas is injected; and recovering lithium from the withdrawn water.

The method may comprise any one or more of the following: lithium-depleted water is obtained by the recovering of lithium, and the method further comprises: injecting a part or all of the lithium-depleted water into the aquifer with another quantity of the gas, and/or, injecting a part or all of the lithium-depleted water into a geological structure different from the aquifer and/or transporting a part or all of the lithium-depleted water to another site; the injecting of a part or all of the lithium-depleted water into the aquifer and the injecting of the another quantity of the gas are performed alternately or simultaneously, and/or via a same well or via separate wells; the method comprises injecting all of the lithium-depleted water into the aquifer; the method comprises injecting a part of the lithium-depleted water into the aquifer and injecting another part of the lithium-depleted water into a geological structure different from the aquifer or transporting the another part to another site; the method comprises injecting all of the lithium-depleted water into a geological structure different from the aquifer or transported to another site; the voidage replacement ratio is greater than 0.8, preferably greater than 1, and more preferably greater than 1.4; the method further comprises a post-treatment of purifying the recovered lithium; the post-treatment is carried out by electrodialysis; the method further comprises, before the recovering of lithium, a pretreatment of removing at least a part of suspended solids, hydrocarbons or contaminant ions from the withdrawn water; the pre-treatment comprises precipitating at least a part of the contaminant ions, coagulating and flocculating at least a part of the suspended solids, hydrocarbons or contaminant ions, and/or filtering the withdrawn water; the gas comprises carbon dioxide and/or hydrogen sulfide; the recovering of lithium comprises ion exchange adsorption, electrochemical recovery, liquid-liquid extraction, a membrane extraction, and/or the combination thereof; the ion exchange adsorption comprises passing the withdrawn water through an ion exchange adsorbent, the ion exchange adsorbent comprising a metal oxide, preferably selected from titanium oxide, manganese oxide, and aluminium oxide hydroxide; the metal oxide is in the form of particles fixed on a matrix with a ligand; the metal oxide is fixed on a membrane with a binder; the injecting of the gas into the aquifer is carried out via at least one injection well, and the withdrawing of water from the aquifer is carried out via at least one withdrawal well; the distance between the injection well(s) and the withdrawal well(s) is from 3 km to 40 km, preferably from 5 km to 20 km; the method preliminarily comprises predicting a lithium concentration in the aquifer by a computer-implemented method, and the injecting of a quantity of a gas into the aquifer comprises injecting the gas into an aquifer for which the lithium concentration is equal to or more than a predetermined value; the predetermined value is more than 30 mg/L, preferably between 100 and 200 mg/L; the method preliminarily comprises determining a minimal distance between the injection well(s) and the withdrawal well(s), wherein the behaviour of the injected gas in the aquifer is simulated using a computer to determine the minimal distance required to prevent gas breakthrough; and/or the method further comprises injecting a mobility control agent into the aquifer.

It is further provided a lithium production installation configured for producing lithium according to the above-described method. The installation comprises at least one first well configured for injecting the gas into the aquifer; at least one second well configured for withdrawing the water from the aquifer as the gas is injected; and a lithium recovery unit configured for recovering lithium from the withdrawn water. The lithium production installation may comprise any one or more of the following: the distance between the first well and the second well is from 3 km to 40 km, preferably 5 km to 20 km; and/or the distance between the first well and the second well is obtainable by a process comprising simulating the behaviour of the gas injected to the injection well; and determining the minimal distance required to prevent gas breakthrough.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting examples will now be described in reference to the accompanying drawings, where:

FIG. 1 shows a flowchart of an example of the method of producing lithium;

FIG. 2 shows a flowchart of another example of the method of producing lithium;

FIG. 3 shows a flowchart of another example of the method of producing lithium;

FIG. 4 shows an example of the installation of the present invention;

FIG. 5 shows another example of the installation of the present invention; and

FIG. 6 illustrates an example of lithium production by the installation of the present invention.

DETAILED DESCRIPTION

It is hereby proposed a method of producing lithium, comprising injecting a quantity of a gas into an aquifer, withdrawing water from the aquifer as the gas is injected; and recovering lithium from the withdrawn water.

Such a method forms an improved solution for producing lithium, and more specifically for recovering lithium in a (saline) aquifer. The method builds upon the presence of lithium in aquifers to produce this valuable metal. In addition, the injection of gas helps maintaining the pressure of the aquifer, which ensures the continuous capacity of the water withdrawal. The water withdrawal capacity may be 1000 to 15000 m³/day, for example, 1000 to 5000 m³/day, 5000 to 10000 m³/day, or 10000 to 15000 m³/day.

The term "aquifer" refers to a geological formation consisting of water permeable rocks that are saturated with water, usually saline water called brine.

The aquifer may have pressure and temperature conditions which allow for the geological storage of the injected gas in a dense phase, or supercritical state (for example, above the critical point of 31.1°C and 73 bar for carbon dioxide).

The aquifer may be located at a depth of at least 800 m deep from the ground surface, for example, as deep as 1500 m from the ground surface.

The aquifer may comprise lithium at a sufficient concentration. For example, the water in the aquifer may have a lithium concentration of more than 30 mg/L.

The method obtains lithium-depleted water, that is, the water that has been withdrawn from the aquifer, followed by recovery of lithium therefrom.

The term "lithium-depleted water" refers to water which has a lower concentration of lithium compared to the source water (i.e., withdrawn water) from which lithium is recovered. In other words, the term "lithium-depleted" does not mean that the water is completely free of lithium water, and thus the lithium- depleted water may contain residual lithium.

The method may optionally further comprise injecting a part or all of such lithium-depleted water into the aquifer.

The method may comprise injecting such lithium-depleted water with another quantity of the gas. The term "another quantity of the gas" refers to an additional amount of the same gas that has been initially injected into the aquifer (for example, the method may comprise injecting the gas continuously during the operation of lithium recovery). Injection of such lithium-depleted water with another quantity of the gas results in a better control of the gas mobility as well as higher efficiency in maintaining the pressure in the aquifer.

It is understood that the phrase "injecting a part or all of the lithium-depleted water with another quantity of the gas" means that the action of injecting the lithium- depleted water is accompanied by the action of injecting another quantity of gas, either together (simultaneously) or in close proximity (separately or alternately). The injecting of a part or all of the lithium-depleted water into the aquifer and the injecting of another quantity of the gas may be performed alternately or simultaneously. Additionally or alternatively, the injecting of a part or all of the lithium-depleted water into the aquifer and the injecting of another quantity of the gas may be performed via a same well or via separate wells.

Such water-alternating-gas injection or separated-and-simultaneous-water- and-gas injection allows for the better control of the mobility of the gas plume (volume occupied by gas, or supercritical gas undissolved in water) in order to accelerate the capillary trapping and the dissolution of gas in the saline water in the aquifer.

Furthermore, since the lithium-depleted water injected with another quantity of the gas has a lower concentration in lithium than the withdrawn water (optionally, as well as lower concentrations in other contaminant ions, which will be explained in detail later), the water is less saline than water directly derived from the aquifer. This further facilitates the dissolution of the gas in the lithium-depleted water.

The lithium-depleted water and the other quantity of the gas may be injected simultaneously via, for example, different wells or via the same well(s). In the latter case, they can be injected via distinct inlets (e.g., pipes) within a same injection well or via the same inlet (e.g., pipe).

Alternatively or additionally, the lithium-depleted water and the gas may be injected alternately via, for example, different wells or via the same well(s). In the latter case, they can be injected via distinct inlets within a same injection well or via the same inlet.

The method may further comprise injecting a part or all of the lithium-depleted water into a geological structure different from the aquifer and/or transporting a part or all of the lithium-depleted water to another site.

The geological structure different from the aquifer may be another distinct aquifer, a distinct geological basin, a distinct water-bearing subterranean formation, or an oil and gas reservoir.

The phrase "transporting a part or all of the lithium-depleted water to another site" means that moving the lithium-depleted water from its original location where it was obtained to a different location, where the lithium-depleted water could be then used for industrial or agricultural purposes. The different location may be at least 50 km away from the original location, for example, 100 km or more, 500 km or more, or 1000 km or more away from the original location.

For example, the method may comprise transporting the lithium-depleted water via a pipeline, i.e., through a network of pipes from the original location to the destination location where it will be used. Alternatively or additionally, the method may comprise transporting the lithium-depleted water with a tanker truck or a train, or even transported across large bodies of water by shipping.

Such transported lithium-depleted water can be used for a variety of purposes, e.g., agricultural irrigation (in this case, the other site may be any agricultural setting such as a farm, vineyard, orchard, or a greenhouse), industrial processing, such as cooling, mining or a manufacturing process (in this case; the site may be a plant, factory or an industrial facility).

In some embodiments, the method may comprise injecting all of the lithium- depleted water into a geological structure different from the aquifer or transporting all of the lithium-depleted water to another site (which is also referred to as "open system").

In such an open system, the gas storage capacity may be adjusted (e.g., increased) based on the withdrawal rate. The flow rate for lithium recovery may be stabilized by maintaining the pressure with the help of the injected gas.

In other embodiments, the method may comprise injecting all of the lithium- depleted water into the aquifer (which is also referred to as "closed system").

In such a closed system, in addition to the stable flow rate of lithium recovery, a better control of the mobility of the injected gas may be achieved because, as explained above, the dissolution of the gas in the lithium-depleted water is facilitated compared to water directly derived from the aquifer.

In some other embodiments, the method may comprise injecting a part of the lithium-depleted water into the aquifer and injecting another part of the lithium- depleted water into a geological structure different from the aquifer or transporting the another part to another site (which is also referred to as "semi-open system", which is a combination of the open system and closed system), providing a stable flow rate of lithium recovery and a better control of the mobility of the injected gas.

When a part or all of the lithium-depleted water is injected into the aquifer with another quantity of the gas (open system or semi-open system), the method may comprise premixing the other quantity of the gas with the lithium-depleted water to form a mixture in which the gas is dissolved in the water, and then injecting the mixture into the aquifer (system referred to as "ex-situ dissolution system").

The ex-situ dissolution system provides a better control of the gas dissolution in the lithium-depleted water compared to when the injected gas is dissolved in the lithium-depleted water during the encounter in the aquifer, particularly in the case of shallow aquifers where the gas storage capacity is directly linked to the solubility of the gas in the water. In this system, the gas is not in a gaseous/supercritical state.

The method may optionally comprise adjusting the ratio of the withdrawal rate to the injection rate (called Voidage Replacement Ratio, referred to as "VRR") for the optimization for the storage capacity and the withdrawal capacity.

The VRR is defined as the ratio of injected fluid to produced fluid at the reservoir conditions at a pressure P and a temperature T : the injected volume at P,T (gas and optionally water) / produced volume at P,T, provided that the reservoir is a geological formation containing lithium, and that the injected volume of the gas is more than 0.

The VRR may be greater than 0.8. Such a VRR prevents or at least reduces any imbalance between the withdrawal rate and the injection rate. The VRR may be more preferably greater than 1, and even more preferably greater than 1.4. Such a VRR can ensure that the pressure in the aquifer increases, which benefits a system for withdrawal by minimizing energy demand.

The method may further comprise injecting a mobility control agent into the aquifer.

The mobility control agent may be any agent that can increase the viscosity of the gas by way of in-situ or ex-situ generation of a gas emulsion (also referred to as a "foam") or a polymer solution in which a gas is dissolved. Such a mobility control agent can increase the gas storage capacity, thanks to a better sweeping (piston effect), and increase the duration of water withdrawal from the aquifer before the gas breakthrough, especially in the case where the risk of the gas breakthrough is deemed high (e.g. very heterogeneous geological formation).

The term "gas breakthrough" means that gas injected via an injection well breaks through to one or more of withdrawal wells.

The mobility control agent may comprise, for example, a surfactant or a gassoluble polymer.

For example, when the aquifer is a carbonate formation and is highly saline, the mobility control may be a cationic or switchable cationic surfactant, such as N¹- dodecyl-N³,N³-dimethylpropane-l,3-diamine, N¹-dodecyl-N¹,N³,N³- trimethylpropane-l,3-diamine, N¹-(2,2-diethyloctyl)-N³,N³-dimethylpropane-l,3- diamine, N¹-octyl-N³,N³-dimethylpropane-l,3-diamine, N¹-decyl-N³,N³- dimethylpropane-l,3-diamine, N¹-tetradecyl-N³,N³-dimethylpropane-l,3-diamine, N¹-hexadecyl-N¹,N³,N³-trimethylpropane-l,3-diamine, N¹-heptadecyl-N¹,N³,N³- trimethylpropane-l,3-diamine, N¹-octadecyl-N¹,N³,N³-trimethylpropane-l,3- diamine, or N-dodecyl-l,3-propanediamine.

The method may comprise injecting the mobility control agent and the gas (and optionally the lithium-depleted water) simultaneously or alternately, and/or via a same or via separate wells.

The method may comprise injecting the mobility control agent and the gas via a dedicated well designed to mix the gas and the mobility control agent in situ.

The method may further comprise premixing the mobility control agent and the gas to make a mixture before the injection.

When a part or all of the lithium-depleted water is injected into the aquifer, the method may comprise premixing the mobility control agent and the gas to make a mixture (i.e., the mobility control agent is gas-soluble), and injecting the mixture and the lithium-depleted water simultaneously or alternately, and/or via a same or via separate wells, or comprise premixing the mobility control agent and the lithium- depleted water to make a mixture (i.e., the mobility control agent is water-soluble), and injecting the mixture and the gas simultaneously or alternately, and/or via a same or via separate wells, or comprise premixing the mobility control agent, the gas, and the lithium-depleted water to make a mixture, and injecting the mixture to the aquifer.

The lithium-depleted water may have a pH different from that of the withdrawn water due to, for example, chemical additives used in the lithium recovery and/or the pre-treatment (which will be explained more detail below). Therefore, when a part or all of the lithium-depleted water is injected into the aquifer and/or into a geological structure different from the aquifer, the method may comprise adjusting beforehand the pH of the lithium-depleted water to a suitable pH.

The suitable pH may vary depending on the application of the lithium-depleted water. For example, in the case of injecting a part or all of the lithium-depleted water into the same aquifer or another aquifer, the pH may be, before the injecting, adjusted to a value of from 5 to 6, for example, by adding an acidic solution such as hydrochloric acidic solution at a flow rate of, for example, approximately 200 to 300 L/h.

In the present method, recovering of lithium may comprise performing a direct lithium extraction (DLE) process, which allows for the extraction of lithium from a water of the aquifer.

Compared to conventional lithium extraction by evaporation processes, which results in a lithium recovery efficiency of approximately 40%, the DLE process can optimize lithium recovery performances to over 75%.

Usually, lithium may be recovered as a lithium chloride solution or a lithium hydroxide solution.

The recovering of lithium may comprise ion exchange adsorption, electrochemical recovery, liquid-liquid extraction, a membrane extraction, and/or the combination thereof.

The ion exchange adsorption may comprise passing the withdrawn water through an ion exchange adsorbent.

The ion exchange adsorbent may comprise a resin or polymer that has a high affinity for lithium, or a metal oxide. For example, the recovering of lithium may comprise bringing the withdrawn water into contact with such an ion exchange adsorbent fixed in or on a support, thereby adsorbing lithium on the ion exchange adsorbent, and then desorbing lithium from the ion exchange adsorbent.

The metal oxide is preferably selected from titanium oxide, manganese oxide, and aluminium oxide hydroxide.

In some embodiments, the metal oxide may be in the form of particles fixed on a matrix with a ligand.

For example, the recovering of lithium may comprise passing the withdrawn water through a column containing the resin, the polymer or the metal oxide in the form of particles, adsorbing lithium ions onto the resin, the polymer or the metal oxide, and recovering lithium by washing the resin, the polymer or the metal oxide with a solution that desorbs lithium ions from the resin, the polymer or the metal oxide, allowing them to be collected in the solution.

In other embodiments, the metal oxide may be fixed on a membrane with a binder. In this case, the recovering of lithium may comprise passing the withdrawn water through a channel created between two adjacent membranes on which the metal oxide is fixed, and then passing a solution that desorbs lithium ions from the metal oxide through the channel.

The electrochemical recovery may comprise passing the withdrawn water through an electrochemical cell, and applying an electrical potential to the electrodes in the cell, which results in lithium recovery through a lithium-capturing electrode.

The liquid-liquid extraction may comprise extracting lithium ions into an organic phase, by mixing the withdrawn water with a solvent, and then recovering lithium back into an aqueous solution. Any conventional solvent used for lithium extraction may be used.

The membrane extraction may be an electromembrane extraction or nanofiltration.

The electromembrane extraction may comprise placing the withdrawn water one side of a lithium-selective membrane or a permselective membrane, placing an aqueous solution on the other side, and applying an electrical potential across the membrane, thereby recovering the permeate (lithium-rich solution).

The nanofiltration may comprise pumping the withdrawn water through a semi-permeable membrane, optionally under pressure, and collecting the permeate (lithium-rich solution).

After the lithium recovery, the lithium-depleted water may have an average lithium content of less than 50 mg/L, or less than 30 mg/L.

The method may further comprise, before the recovering of lithium, a pretreatment of removing at least a part of suspended solids, hydrocarbons or contaminant ions from the withdrawn water.

The pre-treatment may comprise precipitating at least a part of the suspended solids, hydrocarbons or contaminant ions.

Examples of the contaminant ions may include iron, magnesium, and calcium.

The precipitating may comprise chemical precipitation. The chemical precipitation is a well-known process in the art. For example, such chemical precipitation may comprise adding a basic solution such as sodium hydroxide or sodium carbonate to the withdrawn water.

The chemical precipitation allows hydrocarbons and/or the majority of contaminating ions, mainly magnesium, to be removed. Since the magnesium is in competition with lithium in terms of affinity, the efficiency of the DLE process may depend on the Mg/Li ratio.

The method may optionally comprise adjusting the feed rate of the basic solution depending on the composition of the withdrawn water or the type of lithium recovery. The feed rate may be about 1 to 500 m³/h, for example, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450 or 500 m³/h.

After such a chemical precipitation, at least 80%, preferably at least 90%, more preferably 95%, and even more preferably at least 99% of contaminant ions present in the withdrawn water prior to the chemical precipitation may be removed. For example, at least 80%, preferably at least 90%, more preferably 95%, and even more preferably at least 99% of the magnesium present in the withdrawn water prior to the chemical precipitation may be removed, and/or at least 80%, preferably at least 90%, more preferably 95%, and even more preferably at least 98% of the iron present in the withdrawn water prior to the chemical precipitation may be removed.

Alternatively or additionally, the pre-treatment may comprise coagulating and flocculating at least a part of the suspended solids, hydrocarbons or contaminant ions.

The coagulating and flocculating of at least a part of the suspended solids, hydrocarbons or contaminant ions may be performed according to a conventional method known in the art, for example, by adding a coagulant in order to destabilize particles through chemical reaction between the coagulant and the particles, and by adding a flocculant to transport the destabilized particles that will form flocs or flakes.

The coagulant used may be an emulsion comprising one or more anionic polyacrylamide such as FLOPAM™ EM 430 commercialized by SNF Floerger.

The flocculant used may be an aqueous solution of aluminum chloride such as FLOQUAT™ PAC 18 commercialized by SNF Floerger.

The method may optionally comprise adjusting the flow rate of the coagulant and the flocculant depending on the composition of the withdrawn water or the type of lithium recovery. As an example, the flow rate of the coagulant may be 0.1 to 10 L/h, for example, 0.1, 0.5, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10 L/h. The flow rate of the flocculant may be 10 to 60 L/h, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 L/h.

The coagulating and flocculating of at least a part of the suspended solids, hydrocarbons or contaminant ions may generate a sludge enriched mainly in magnesium. This sludge may be subjected to a treatment for extracting magnesium (magnesium carbonate or magnesium chloride) by, for example, electrolysis or thermal reduction.

The production rate of the sludge may be 1 to 50 t/h, for example, 1 to 10 t/h, 10 to 20 t/h, 20 to 30 t/h, 30 to 40 t/h, 40 to 50 t/h.

Alternatively or additionally, the pre-treatment may comprise filtering the withdrawn water.

The filtering of the withdrawn water allows at least part of the suspended solids, hydrocarbons or contaminant ions to be removed. The filtering may be performed according to a conventional method known in the art.

Preferably, suspended solids having a volume-average median diameter Dv50 equal to or higher than 50 pm can be separated from the withdrawn water.

Therefore, according to some embodiments, the filtering of the withdrawn water may comprise passing the withdrawn water through a filter or a membrane configured to separate suspended solids having a volume average median diameter Dv50 equal to or higher than 50 pm.

The filter may be a sand filter.

After the filtering of the withdrawn water, the content of contaminant ions may be reduced by at least 30%, for example, 30%, 40%, 50%, 60%, 70%, 80% or 90%, compared to the withdrawn water before the filtering. For example, the content of magnesium in the withdrawn water is reduced by approximately 30%, and the content of iron is reduced by approximately 60%, compared to the withdrawn water before the filtering.

The above pre-treatment (especially the chemical precipitation) may increase the pH of the withdrawn water up to, for example, a value of from 9 to 11. In this case, the method may optionally comprise adjusting the pH pf the withdrawn water, before it is subjected to the lithium recovery, to a pH within the operation range of the lithium recovery.

For example, if the subsequent lithium recovery requires an acidic pH, the method may optionally comprise decreasing the pH of the withdrawn water subjected to the pre-treatment by adding an acidic solution such as hydrochloric acidic solution at the flow rate of, for example, 1 to 2.5 m³/h, 2.5 to 5 m³/h, or 5 to 10 m³/h. If the subsequent lithium recovery does not require an acidic pH, such chemical treatment by addition of acid may not be required.

The precipitation, and the coagulation and flocculation of at least a part of the suspended solids, hydrocarbons or contaminant ions, and filtering of the withdrawn water may be performed in any order. Preferably, the method comprises precipitating at least a part of the suspended solids, hydrocarbons or contaminant ions, coagulating and flocculating at least a part of the suspended solids, hydrocarbons or contaminant ions, and filtering the withdrawn water in this order.

The method may optionally comprise storing the withdrawn water subjected to the pre-treatment in an intermediate tank, thereby allowing for the continuous operation of the lithium recovery.

The method may further comprise a post-treatment of purifying the recovered lithium.

The post-treatment may be carried out by a conventional process known in the art, for example, by electrodialysis, ion exchange polishing, or chemical precipitation.

The post-treatment may allow the lithium to be concentrated (e.g., by removing impurities such as barium and strontium) and/or recovered in the form of lithium hydroxide or lithium carbonate, which is advantageous for battery production or lubricant production, for example.

For example, the chemical precipitation may comprise a conventional conversion of a concentrated lithium hydroxide solution to lithium carbonate by adding sodium carbonate, or of a concentrated lithium chloride solution to lithium carbonate by adding sodium hydroxide with CO2 insufflation.

The chemical precipitation may also comprise the precipitation with sodium phosphate, thereby obtaining lithium phosphate, and optionally an additional electrodialysis or carbonation for the conversion of lithium phosphate into lithium carbonate.

The gas injected into the aquifer is now discussed.

The gas may comprise a greenhouse gas such as carbon dioxide, methane or a mixture thereof, and/or hydrogen sulfide.

The carbon dioxide injected into the aquifer may have been emitted by, for example, the combustion of carbonaceous energy on-site or off-site, or emitted by metal processing facilities on-site or off-site. The method may comprise emitting carbon dioxide (e.g., by combustion or by metal processing).

The methane may have been emitted by, for example, wetlands or livestock, the combustion of carbonaceous energy, or waste management. The method may comprise emitting methane (e.g., by combustion or waste management). The method may further comprise capturing and compressing the emitted carbon dioxide (or methane or a mixture thereof), and optionally transporting the compressed carbon dioxide (or methane or a mixture thereof) to the site of the operation if the carbon dioxide is emitted off-site.

The hydrogen sulfide injected into the aquifer may be obtained from the withdrawn water. In this case, the method may comprise separating the hydrogen sulfide from the withdrawn water. Alternatively or additionally, the hydrogen sulfide may have been be emitted during the processing of natural gas or other fossil fuels. In this case, the method may comprise emitting hydrogen sulfide.

The method may further comprise capturing and compressing the emitted hydrogen sulfide, and optionally transporting the compressed hydrogen sulfide to the site of the operation if the hydrogen sulfide is emitted off-site.

The method may further comprise premixing the carbon dioxide (or methane or a mixture thereof) and the hydrogen sulfide prior to the injection.

Such gas injection in the aquifer alleviates the atmospheric accumulation of the gas, for example, the greenhouse gas (e.g., carbon dioxide, methane) which has a serious impact on the climate change and global warming, and/or hydrogen sulfide, which is toxic and corrosive and can pose risks to human health and the environment.

Injection of gas is mainly conditioned by two factors : the acceptable pressure increase in the subterraneous formation to respect the geomechanical constraints and the migration of the gas plume, which can rise to the top parts of the formation due to the gravity override. In order to respect the acceptable pressure increase, water withdrawal is usually not considered in the context of gas storage due to the costs involved in treating the (saline) water on the surface as well as additional costs of such installations, where water withdrawal wells must be placed far enough from the gas injection wells to delay the arrival of the carbon dioxide to the production areas.

The method allows for both the improved recovery of lithium from aquifer waters and the increased gas storage capacity in aquifers.

The method is also cost-effective because it offsets additional costs of increasing gas storage capacity and maintaining water withdrawal capacity. In the method, the injecting of the gas into the aquifer may be carried out via at least one injection well, and the withdrawing of water from the aquifer may be carried out via at least one withdrawal well.

The distance between the injection well(s) and the withdrawal well(s) may be sufficient to avoid or reduce risks of gas breakthrough during the operation of lithium recovery. The distance may for example be from 3 km to 40 km, preferably from 5 km to 20 km.

Alternatively or additionally, the method may further comprise preliminarily determining a minimal distance between the injection well(s) and the withdrawal well(s).

The determining of the minimal distance may optionally comprise simulating the behaviour of injected gas in the aquifer using a computer to determine the minimal distance required to prevent gas breakthrough.

For example, the determining may comprise creating a numerical model and simulating the flow of injected gas based on the numerical model.

The creating of the numerical model may comprise providing an input, which may include at least one of a geometrical value of the aquifer (e.g., dimension, shape, location), distribution of various properties of the aquifer (e.g., permeability, porosity, temperature, pressure, stress regime), an injection rate, a withdrawal rate, and a voidage replacement ratio.

The creating of the numerical model may then comprise inputting the above input into a computer software which is designed for this purpose, using numerical methods such as the finite difference or finite element method, thereby creating the numerical model.

Subsequently, the determining may comprise using the numerical model to simulate the behaviour of injected gas (e.g., the way the gas displaces in the aquifer, the way gas interacts with the aquifer), and then determining the minimal distance required to prevent gas breakthrough.

The method may further comprise preliminarily predicting a lithium concentration in the aquifer, for example by a computer-implemented method. The prediction may be performed according to the teaching of PCT application No. PCT/IB2021/000845, which is incorporated herein by reference.

In particular, the prediction may comprise providing a dataset comprising, for respective saline aquifer locations, training samples each including a measurement of one or more geochemical variables of a predetermined set, and a respective ground truth value representing a concentration of lithium at the respective saline aquifer location; and learning a predictive aquifer-wise model based on the dataset.

Each predictive aquifer-wise model may be configured for predicting a concentration of lithium at a given location in a saline aquifer.

The predetermined set of one or more geochemical variables may comprise a concentration of any one or any combination of the following chemical elements: Cl, Ca, Na, B, Mg, Sr, and/or K.

The prediction may comprise providing a given measurement of one or more geochemical variables of the predetermined set at a given location, and predicting the concentration of lithium at the given location by applying the predictive aquiferwise model to the given measurement.

The injecting of a quantity of a gas into the aquifer may comprise injecting the gas into an aquifer for which the lithium concentration is equal to or more than a predetermined value.

The predetermined value may be more than 30 mg/L, preferably between 100 and 200 mg/L.

Alternatively, the method may comprise preliminarily predicting a lithium concentration of the several aquifers, and then selecting, for example, an optimal aquifer (for example, an aquifer predicted with the highest lithium concentration), and the injecting of a quantity of a gas into the aquifer may comprise injecting the gas into the optimal aquifer.

Lithium production installation

A lithium production installation configured for producing lithium according to the method as described above comprises at least one first well configured for injecting the gas into the aquifer; at least one second well configured for withdrawing the water from the aquifer as the gas is injected; and a lithium recovery unit configured for recovering lithium from the withdrawn water.

The first and second wells may each comprise a borehole that is drilled into the ground.

The first and second wells may each comprise a casing (e.g., a steel casing) to prevent or reduce leaks, and a screen (perforated section) which allows a fluid to flow out of or into the well.

The first well may further comprise a pipe for injecting a fluid.

The second well may further comprise a pipe for withdrawing water.

The pipe may be connected to surface equipment, such as a pump (e.g., dosimetric pump), a valve (e.g., dosimetric valve), and a tank.

The lithium recovery unit may be a unit configured for a direct lithium extraction (DLE) process, as described above.

The lithium recovery unit may comprise a quantity of an ion exchange adsorbent, a electrochemical unit, a liquid-liquid extraction unit, a membrane extraction unit, and/or a combination thereof.

The ion exchange adsorbent may be the same as the ion exchange adsorbent defined above.

The electrochemical unit may comprise an electrochemical cell, a cathode, an anode, an electrolyte solution, and a power source.

The liquid-liquid extraction unit may comprise a solvent tank, and a vessel for mixing a solvent and the withdrawn water.

The membrane extraction unit may comprise an electromembrane, a power source, electrodes for connecting the power source and the electromembrane, a feeding unit for feeding the withdrawn water, and a permeate tank for collecting the permeate. The electromembrane may be a lithium-selective membrane or a permselective membrane which is selective to anions or cations.

Alternatively, the membrane extraction unit may comprise a nanofiltration membrane, feeding unit, a pump, and a permeate tank. The nanofiltration membrane may be a semi-permeable membrane having pores that selectively allows, based on their size and charge, lithium ions to pass while retaining other larger ions.The lithium recovery unit may be fluidically connected to the second well (via a pipe or a tube for example).

In some embodiments, the first well may be used for injecting the gas and for injecting a part or all of the lithium-depleted water with another quantity of the gas.

In this case, the first well may be fluidically connected to the lithium recovery unit (via a pipe or a tube for example).

In some other embodiments, the lithium production installation of the invention may further comprise a third well for injecting a part or all of the lithium- depleted water into the aquifer with another quantity of the gas, or for injecting a part or all of the lithium-depleted water into a geological structure different from the aquifer.

The third well may have the same structure as the first and second wells.

The third well may further comprise a pipe for injecting a part or all of the lithium-depleted water into the aquifer or the different geological structure.

The third well may be fluidically connected to the lithium recovery unit (via a pipe or a tube for example).

For example, the other quantity of the gas may be injected into the aquifer via the first well while a part or all of the lithium-depleted water may be injected into the aquifer via the third well. In this case, the first well and the third well may exist in the same borehole.

In other examples, the other quantity of the gas may be injected into the aquifer via the first well while a part or all of the lithium-depleted water may be injected into a different geological structure (e.g., another aquifer) via the third well. In this case, preferably, the first well and the third well do not exist in the same borehole.

Alternatively or additionally, the lithium production installation may comprise a pipe for injecting a part or all of the lithium-depleted water into a geological structure different from the aquifer and/or a pipe for transporting a part or all of the lithium-depleted water to another site.

The pipe for injecting a part or all of the lithium-depleted water into a geological structure and the pipe for transporting a part or all of the lithium-depleted water to another site may be fluidically connected to the lithium recovery unit (via a tube for example).

The lithium production installation may further comprise a gas mobility control unit.

The gas mobility control unit may comprise a sensor for monitoring the performance of the gas mobility, a data acquisition system, and a control software for adjusting parameters such as the injection rate to optimize the system.

The gas mobility control unit may be fluidically connected to the first well and/or the third well (via a pipe or a tube for example).

The lithium production installation may further comprise a gas capture and compression unit.

The gas capture and compression unit may comprise a gas capture equipment for capturing gas (for example, carbon dioxide) emitted from metal processing facilities or power plants, and gas compression equipment for compressing the captured gas to a high pressure suitable for transportation and/or storage.

The gas capture and compression unit may be fluidically connected to the first well and/or the third well (via a pipe or a tube for example).

The lithium production installation may further comprise a neutralization tank for adjusting the pH of the lithium-depleted water, especially when a part of the lithium-depleted water may be injected into the aquifer or a geological structure different from the aquifer.

The neutralization tank may be fluidically connected to the lithium recovery unit, and/or to the first well and/or the third well (via a pipe or a tube for example).

The neutralization tank may comprise a feeding unit for feeding the lithium- depleted water to the neutralization tank, a discharge unit for discharging the neutralized lithium-depleted water from the neutralization tank, and a supplying unit for supplying an acidic solution such as hydrochloric acidic solution.

The terms "feeding/discharge/supplying unit" as used herein refers to a device or mechanism that pumps or transfers a fluid to/from the neutralization tank. For example, the feeding/discharge/supplying unit may comprise a pipe, a hose, a valve, or a pump to move the fluid. It may also comprise a sensor or a controller to monitor and regulate the flow of the fluid to/from the neutralization tank.

The lithium production installation may further comprise a pre-treatment unit for removing at least a part of suspended solids, hydrocarbons or contaminant ions from the withdrawn water.

The pre-treatment unit may be present between the second well and the lithium recovery unit in fluid communication (via a pipe or a tube for example).

The pre-treatment unit may comprise a precipitation unit for performing chemical precipitation of contaminant ions.

The process of the chemical precipitation may be as described above.

The precipitation unit may comprise a precipitation tank, a feeding unit for feeding the withdrawn water to the precipitation tank, a discharge unit for discharging the pre-treated withdrawn water from the precipitation tank, and a supplying unit for supplying a basic solution such as sodium hydroxide or sodium carbonate to the precipitation tank.

The feeding/discharge/supplying unit of the precipitation tank may have the same structure as the feeding/discharge/supplying unit of the neutralization tank.

The capacity of the precipitation tank may be suitably determined as long as the capacity ensures the withdrawal rate of the water from the aquifer, i.e., at least five times the basic flow rate.

The precipitation unit may further comprise an auxiliary tank of the same capacity as the precipitation tank. Thus, the continuity of the lithium recovery process can be ensured in case of maintenance and/or cleaning of the precipitation tank.

Alternatively or additionally, the pre-treatment unit may comprise a coagulation and flocculation unit.

The process of the coagulation and flocculation may be as defined above.

The coagulation and flocculation unit may comprise a coagulation/flocculation tank, a feeding unit for feeding the withdrawn water to the tank, a discharge unit for discharging the pre-treated withdrawn water from the coagulation/flocculation tank, and a supplying unit for supplying a coagulant and a flocculant. The feeding/discharge/supplying unit of the precipitation tank may have the same structure as the feeding/discharge/supplying unit of the neutralization tank.

The coagulation and flocculation unit may further comprise an auxiliary tank of the same capacity as the coagulation and flocculation tank, thereby ensuing the continuity of the lithium recovery process in case of maintenance and/or cleaning of the coagulation and flocculation tank.

The coagulation and flocculation unit may further comprise a sludge tank for storing a sludge.

Alternatively or additionally, the pre-treatment unit may further comprise a filtration unit.

The process of the filtration may be as defined above.

The filtration unit may comprise a filtration tank and a filter.

The filter may be a sand filter comprising sand particles.

The filtration unit may further comprise an auxiliary tank of the same capacity as the filtration tank, thereby ensuing the continuity of the lithium recovery process in case of maintenance and/or cleaning of the filtration tank.

When more than one of the precipitation unit, the coagulation and flocculation unit, and the filtration unit is present, the position of the units may be suitably determined, and the units may be f luidica lly connected to each other. For example, when all of the these units are present, the precipitation unit may be positioned downstream of the second well; the coagulation and flocculation unit may be positioned present downstream of the filtration unit; and the filtration unit may be positioned downstream of the coagulation and flocculation unit and upstream of the lithium recovery unit.

The terms "upstream" and "downstream" as used herein refer to the location relative to the flow direction of a fluid. For example, "A is present upstream of B" means that A is located before B in the flow direction (the fluid flows from A to B). Likewise, "A is present downstream of B" means that A is located after B in the flow direction (the fluid flows from B to A).

The pre-treatment unit may further comprise an intermediate tank for storing the pre-treated withdrawn water. The intermediate tank may be fluidically connected to the pre-treatment unit and to the lithium recovery tank (via a pipe or a tube for example).

The lithium production installation may further comprise a storage tank for storing recovered lithium (i.e., a solution rich in lithium, such as a lithium chloride solution).

The storage tank may be fluidically connected to the lithium recovery unit (via a pipe or a tube for example).

The lithium production installation may further comprise a post-treatment unit for purifying the recovered lithium.

The post-treatment unit may be fluidically connected to the lithium recovery unit or the storage tank (via a pipe or a tube for example).

The post-treatment unit may comprise an electrodialysis unit, an ion exchange polishing unit, and/or chemical precipitation unit.

A conventional electrodialysis unit may be used. For example, the electrodialysis unit may comprise a plurality of membranes, a plurality of anodes, a plurality of cathodes, and a power source.

A conventional ion exchange polishing unit may be used. For example, the ion exchange polishing unit may comprise an ion exchange column filled with an ion exchange resin that selectively binds to impurities such as barium or strontium, and a feeding unit for feeding a regeneration solution to displace the bound impurities.

A conventional precipitation unit may be used. For example, the chemical precipitation unit may comprise a precipitation tank, a feeding unit for feeding a solution rich in lithium (e.g., lithium chloride solution or lithium hydroxide solution) to the chemical precipitation tank, a discharge unit for discharging the treated solution from the chemical precipitation tank, and a supplying unit for supplying a reagent such as sodium phosphate, sodium carbonate or sodium hydroxide to the chemical precipitation tank.

The lithium production installation may further comprise a pH adjustment unit which may be fluidically connected to the lithium recovery system, and/or the pretreatment unit. The distance between the first well and the second well may be from 3 km to 40 km, preferably 5 km to 20 km.

This distance between the first well and the second well may be obtainable by a process comprising simulating the behavior of the gas injected to the injection well; and determining the minimal distance required to prevent gas breakthrough.

The process may be performed as defined above.

The method of producing lithium and the lithium production installation are further discussed below by way of examples referring to the Figures.

As shown in FIG. 1, the method of producing lithium may in examples preliminary comprise predicting a lithium concentration in an aquifer by a computer- implemented method (S10).

The method may further comprise determining a minimal distance between the injection well(s) and the withdrawal well(s) (S20).

It is to be understood that, when the method comprises both of the predicting (S10) and the determining (S20), the method may comprise first the determining (S20) and then the predicting (S10).

The method then comprises injecting a quantity of a gas into an aquifer (S30).

The method may further comprise injecting a mobility control agent into the aquifer (S40).

Is it to be understood that the method shown in FIG. 1 is simply an example, and the method may comprise injecting a mobility control agent into the aquifer (S40) before or simultaneously with the injecting of a quantity of a gas into an aquifer (S30).

The method comprises then withdrawing water from the aquifer as the gas is injected (S50).

The method may optionally comprise a pre-treatment of removing at least a part of suspended solids, hydrocarbons or contaminant ions from the withdrawn water (S60).

Then, the method comprises recovering lithium from the withdrawn water

(S70). The method may further comprise injecting all of the lithium-depleted water into the aquifer with another quantity of the gas (S810) (i.e., closed system).

The method mayfurther comprises a post -treatment of purifying the recovered lithium (S90).

In FIG. 2, the method of producing lithium is the same as shown in Fig. 1, except that the method comprises injecting a part of the lithium-depleted water into the aquifer and injecting another part of the lithium-depleted water into a geological structure different from the aquifer or transporting the another part to another site (S811) (i.e., semi-open system) instead of injecting all of the lithium-depleted water into the aquifer with another quantity of the gas (S810).

In FIG. 3, the method of producing lithium is the same as shown in Fig. 1, except that the method comprises injecting all of the lithium-depleted water into a geological structure different from the aquifer or transporting all of the lithium- depleted water to another site (S812) (i.e., open system) instead of injecting all of the lithium-depleted water into the aquifer with another quantity of the gas (S810).

Referring to Fig. 4, the lithium production installation configured for producing lithium according to the method as defined above may comprise a first well 1 configured for injecting the gas into the aquifer, a second well 2 configured for withdrawing the water from the aquifer as the gas is injected; a lithium recovery unit 6 configured for recovering lithium from the withdrawn water, and a third well 3 for injecting a part or all of the lithium-depleted water into a geological structure 4 different from the aquifer (in this case, another aquifer 4), thus implementing the open system.

The first well 1 may comprise a pipe for injecting the gas, which may be f luidica lly connected to, for example, a power plant.

The second well 2 may comprise a pipe for withdrawing water, which may be f I uidica I ly connected to an upstream side of the lithium recovery unit.

The third well 3 may comprise a pipe for injecting a part or all of the lithium- depleted water into another aquifer, the pipe being fluidically connected to a downstream side of the lithium recovery unit. It is understood that the lithium production installation may further comprise a pre-treatment unit 5 and/or a neutralization tank 7 (which will be explained later by reference with Fig. 6). In this case, for example, the second well 2 may be fluidically connected, via the pipe, to an upstream side of the pre-treatment unit; and the lithium recovery unit 6 may be fluidically connected to a downstream side of the pretreatment unit; the neutralization tank may be fluidically connected to a downstream side of the lithium recovery unit 6; and the third well 3 may be fluidically connected to a downstream side of the neutralization tank.

FIG. 5 shows another example of the lithium production installation of the invention.

The lithium production installation comprises a first well 1 configured for injecting the gas into the aquifer, a second well 2 configured for withdrawing the water from the aquifer as the gas is injected; and a lithium recovery unit 6 configured for recovering lithium from the withdrawn water.

The first well 1 may be also used for injecting a part or all of the lithium- depleted water into the aquifer (closed system or semi-open system) with another quantity of the gas. In this case, the first well 1 may be fluidically connected to the lithium recovery unit, as shown in Fig. 5, or a neutralization tank if present (via a pipe or a tube for example).

The rest of the configuration (including a pre-treatment unit if present) may be the same as described in FIG. 1.

FIG. 6 shows a schematic example of the pre-treatment unit 5, a lithium recovery unit 6, and a neutralization tank 7 of the lithium production installation of the invention.

The pre-treatment unit 5 may comprise a chemical precipitation unit 8, a coagulation and flocculation unit 9, a sludge tank 9', a filtration unit 10, and an intermediate tank 11.

The chemical precipitation unit 8 may be fluidically connected to the second well 2 of the lithium production installation.

The lithium production installation may further comprise a pH adjustment unit (not shown) fluidically connected to the pre-treatment unit 5, more specifically, connected to the intermediate tank 11. For example, the pH adjustment unit may comprise a tank for storing an acidic solution and a feeding unit for feeding the acidic solution to the intermediate tank 11.

The neutralization tank 7 may be fluidically connected to the lithium recovery unit 6 on its upstream side, and to the first well, the third well, or a pipeline for injecting to a different geological structure or for transporting to another site on its downstream side (not shown).

The present invention has been described above in the context of lithium production, but it is understood that the present invention is not limited to lithium, and can be applied to the production of other metals, such as magnesium and iron.

EXAMPLES

An example realization of the method was simulated using a computer software ECLIPSE E300 option CO2STORE.

The values presented below were obtained through data extrapolation and analytical measurements from the operation site (United States) where the installation comprises a pre-treatment unit (precipitation unit, coagulation and flocculation unit and filtration unit), a lithium recovery unit and a neutralization tank. The extrapolation was based on average analytical measurements of the water samples collected at the site (Arkansas, United states). The chemical concentration predictions were generated using a software such as AspenTech or Matlab/simulink.

The conditions for the simulation are as follows.

Carbon dioxide is injected into an aquifer located in Arkansas (United States), and water is withdrawn from the aquifer as carbon dioxide is injected.

The withdrawn water has an average pH of 5.3 and contains lithium at an average concentration of 217 mg/L; contaminant ions at high levels (73397 mg/L for sodium, 38113 mg/L for calcium, 2678 mg/L for potassium, 3313 mg/L for magnesium, 2.6 mg/L for iron, 2549 mg/L for strontium) and dissolved solids (total dissolved solids (TDS) of about 313.2 g/L). The water withdrawal capacity is estimated at 8000 m³/day, and the withdrawn water is then subjected to a pre-treatment and lithium recovery process, as shown in

FIG. 6.

The withdrawn water is fed to a chemical precipitation unit 8 by way of a pump at a flow rate of 300 m³/h. The chemical precipitation unit 8 has a precipitation tank having a capacity of 1500 m³, and a feeding unit for feeding the withdrawn water from the second well to the precipitation tank, a discharge unit for discharging the withdrawn water from the precipitation tank to a coagulation and flocculation unit 9, and a supplying unit for supplying a sodium hydroxide solution to the precipitation tank.

The sodium hydroxide solution (50% w/w) is added to the precipitation tank through the supplying unit, thereby causing the precipitation of contaminant ions.

During this precipitation, magnesium removal efficiency and iron removal efficiency are estimated to be 99% and 98%, respectively.

More specifically, at the exit of the chemical precipitation unit 8, the withdrawn water has a pH value of from 10 to 11, and estimated to contain a still high level of lithium (167 mg/L), and contaminant ions at lower levels (73397 mg/L for sodium, 35281 mg/L for calcium, 2199 mg/L for potassium, 1 mg/L for magnesium, 0.06 mg/L for iron, 2376 mg/L for strontium).

The withdrawn water is then fed to the coagulation and flocculation unit 9, in which a coagulant is added at a flow wate of 1.2 L/h and a flocculant is added at a flow wate of 40.8 L/h.

A sludge is stored in a sludge tank 9', at an estimated production rate of 16.2 t/h.

The withdrawn water is then fed to the filtration unit 10 comprising a sand filter.

The filtration is estimated to reduce the impurities, for example, by about 30% for magnesium and about 67% for iron.

Specifically, at the exit of the filtration unit 10, the withdrawn water is estimated to contain a still high level of lithium (164 mg/L), and contaminant ions at lower levels (73397 mg/L for sodium, 34937 mg/L for calcium, 2160 mg/L for potassium, 0.7 mg/L for magnesium, 0.02 mg/L for iron, 2337 mg/L for strontium).

The withdrawn water is then fed to an intermediate tank 11 having a capacity of 25 m³, in which a hydrochloric acidic solution (36 to 50% w/w) is added at a flow rate of 1.2 m³/h to adjust the pH of the withdrawn water.

The withdrawn water is subsequently fed to the lithium recovery unit 6, where lithium is recovered, by way of adsorption (adsorbent such as lithium titanium oxide, lithium manganese oxide, LiCI/AI(OH)3 or an ion exchange material), liquid-liquid extraction, electrochemical recovery, a membrane extraction or combination thereof.

The lithium recovery performed as described above is estimated to result in a production rate of 2275 t/year (corresponding to lithium carbonate).

At the exit of the lithium recovery unit 6, the lithium-depleted water has a pH value of from 8 to 9, and estimated to contain lithium at a concentration of 41 mg/L and contaminant ions (73397 mg/L for sodium, 14673 mg/L for calcium, 2160 mg/L for potassium, 0.7 mg/L for magnesium, 0.02 mg/L for iron, 2337 mg/L for strontium).

The lithium-depleted water is then fed to a neutralization tank 7 having a capacity of 1500 m³. The neutralization of the lithium-depleted water is carried out at a basic flow rate of 300 m³/h, by adding a hydrochloric acidic solution (36 to 50% w/w) at a flow rate of 240 L/h to adjust the pH of the lithium-depleted water to a pH value of from 5 to 6.

The lithium-depleted water is injected to the aquifer (closed system), a different geological structure (open system), or both (semi-open system).

Claims

1. A method of producing lithium, the method comprising: injecting (S30) a quantity of a gas into an aquifer; withdrawing (S50) water from the aquifer as the gas is injected; and recovering (S70) lithium from the withdrawn water.

2. The method of claim 1, wherein lithium-depleted water is obtained by the recovering of lithium, the method further comprising: injecting a part or all of the lithium-depleted water into the aquifer with another quantity of the gas, and/or, injecting a part or all of the lithium-depleted water into a geological structure different from the aquifer and/or transporting a part or all of the lithium-depleted water to another site.

3. The method of claim 2, wherein the injecting of a part or all of the lithium-depleted water into the aquifer and the injecting of the another quantity of the gas are performed alternately or simultaneously, and/or via a same well or via separate wells.

4. The method of claim 2 or 3, wherein the method comprises injecting (S810) all of the lithium-depleted water into the aquifer.

5. The method of claim 2 or 3, wherein the method comprises injecting (S811) a part of the lithium-depleted water into the aquifer and injecting another part of the lithium-depleted water into a geological structure different from the aquifer or transporting the another part to another site.

6. The method of claim 2, wherein the method comprises injecting (S812) all of the lithium-depleted water into a geological structure different from the aquifer or transported to another site.

7. The method of any one of claims 1 to 6, wherein the voidage replacement ratio is greater than 0.8, preferably greater than 1, and more preferably greater than 1.4.

8. The method of any one of claims 2 to 7, further comprising a post-treatment of purifying (S90) the recovered lithium.

9. The method of claim 8, wherein the post -treatment is carried out by electrodialysis.

10. The method of any one of claims 1 to 9, further comprising, before the recovering of lithium, a pre-treatment of removing (S60) at least a part of suspended solids, hydrocarbons or contaminant ions from the withdrawn water.

11. The method of claim 10, wherein the pre-treatment comprises precipitating at least a part of the contaminant ions, coagulating and flocculating at least a part of the suspended solids, hydrocarbons or contaminant ions, and/or filtering the withdrawn water.

12. The method of any one of claims 1 to 11, wherein the gas comprises carbon dioxide, methane and/or hydrogen sulfide.

13. The method of any one of claims 1 to 12, wherein the recovering of lithium comprises ion exchange adsorption, electrochemical recovery, liquid-liquid extraction, a membrane extraction, and/or the combination thereof.

14. The method of claim 13, wherein the ion exchange adsorption comprises passing the withdrawn water through an ion exchange adsorbent, the ion exchange adsorbent comprising a metal oxide, preferably selected from titanium oxide, manganese oxide, and aluminium oxide hydroxide.

15. The method of claim 14, wherein the metal oxide is in the form of particles fixed on a matrix with a ligand.

16. The method of claim 14, wherein the metal oxide is fixed on a membrane with a binder.

17. The method of any one of claims 1 to 16, wherein the injecting of the gas into the aquifer is carried out via at least one injection well, and the withdrawing of water from the aquifer is carried out via at least one withdrawal well.

18. The method of claim 17, wherein the distance between the injection well(s) and the withdrawal well(s) is from 3 km to 40 km, preferably from 5 km to 20 km.

19. The method of any one of claims 1 to 18, preliminarily comprising predicting (S10) a lithium concentration in the aquifer by a computer-implemented method, and the injecting of a quantity of a gas into the aquifer comprises injecting the gas into an aquifer for which the lithium concentration is equal to or more than a predetermined value.

20. The method of claim 19, wherein the predetermined value is more than 30 mg/L, preferably between 100 and 200 mg/L.

21. The method of any one of claims 1 to 20, preliminarily comprising determining (S20) a minimal distance between the injection well(s) and the withdrawal well(s), wherein the behaviour of the injected gas in the aquifer is simulated using a computer to determine the minimal distance required to prevent gas breakthrough.

22. The method of any one of claims 1 to 21, further comprising injecting (S40) a mobility control agent into the aquifer.

23. A lithium production installation configured for producing lithium according to any one of claims 1 to 22, the installation comprising: at least one first well (1) configured for injecting the gas into the aquifer; at least one second well (2) configured for withdrawing the water from the aquifer as the gas is injected; and a lithium recovery unit (6) configured for recovering lithium from the withdrawn water.

24. The lithium production installation of claim 23, wherein the distance between the first well and the second well is from 3 km to 40 km, preferably 5 km to 20 km.

25. The lithium production installation of claim 23 or 24, wherein the distance between the first well and the second well is obtainable by a process comprising: simulating the behaviour of the gas injected to the injection well; and determining the minimal distance required to prevent gas breakthrough.