Method of treating lithium-containing materials

Abstract

A method of extracting lithium, the method comprising the steps of subjecting a lithium-containing material to a leaching process in the presence of carbonate ions at atmospheric pressure and elevated temperatures above 50 DEG C but below 160 DEG C to produce a leach slurry containing lithium carbonate; performing a carbonation process on the leached slurry to convert at least a portion of the lithium carbonate to lithium bicarbonate; performing a solid-liquid separation process on the leaching slurry to separate leaching residues from the leaching solution; solid lithium carbonate is obtained from the leaching solution; and separating solid lithium carbonate from the leaching solution.

Description

Technical Field

[0001] The present invention relates to a method for extracting lithium. In particular, the present invention relates to an atmospheric pressure leaching method for extracting lithium from lithium ore or lithium ore concentrate, such as spodumene ore and spodumene concentrate. Background Art

[0002] Lithium and lithium-containing materials have a wide range of industrial uses, such as in heat-resistant glass and ceramics, lithium grease lubricants, flux additives in iron, steel and aluminum production, lithium metal batteries and lithium-ion batteries.

[0003] A significant portion of the lithium mined globally is in the form of spodumene, a mineral containing lithium aluminum silicate. In many conventional extraction processes, spodumene ore is subjected to a leaching process using extraction reagents such as alkali metal sulfates, sulfuric acid, or hydrofluoric acid.

[0004] As described in the widely cited U.S. Patent No. 2,516,109, acid leaching of lithium from spodumene is a traditional extraction process typically characterized by harsh conditions and complex equipment setups. It is not uncommon for these processes to use concentrated sulfuric acid heated to 250°C in a sulfation kiln. Consequently, conventional extraction processes suffer from significant environmental and health hazards associated with the extraction reagents used. Furthermore, these processes contain high levels of impurities such as iron, magnesium, and aluminum, and produce large amounts of waste, such as sodium sulfate and lime-contaminated tailings.

[0005] Additionally, other methods, such as pressure carbonate leaching and acid roasting, require the use of complex equipment that represents significant capital costs and is difficult and expensive to maintain.

[0006] Several attempts have been made to overcome these problems. For example, U.S. Patent No. 11,292,725 discloses a process for extracting lithium from lithium-bearing materials in the form of lithium carbonate under high pressure. However, this process requires a purified lithium-bearing brine stream from a natural lake or from high-temperature leaching of beta spodumene. High-temperature leaching with sodium carbonate produces a solid tailings stream with limited or no commercial use and requires long-term environmental management.

[0007] Alternatively, the Quebec process attempts to overcome the above disadvantages by using alkaline sodium carbonate in a pressure leaching process.While this can reduce the initial reliance on hazardous reagents, the method requires high temperatures and pressures in specially equipped vessels.

[0008] Other methods for processing lithium have been described. For example, U.S. Patent No. 4,588,566 discloses a method for separating lithium from lithium-containing materials. However, this patent discloses a pretreatment process only for lithium-containing clay feeds. This process is not suitable for extracting lithium from hard rock lithium minerals.

[0009] Chinese patent application No. 111593200 discloses a process for recovering lithium cathodes from lithium-ion batteries, which is not suitable for extracting lithium from hard rock lithium materials.

[0010] International Patent Application No. 2023 / 097356 discloses a pyrometallurgical process for carbonizing beta spodumene to produce lithium carbonate powder. However, this process requires mixing carbon dioxide gas with the beta spodumene at high temperatures within a reactor, typically ranging from 400°C to 600°C. These high temperatures significantly increase operating costs and equipment requirements.

[0011] European Patent No. 3981516 discloses the use of CO2 gas to dissolve lithium from primary leaching raw materials (roasted lithium-ion battery materials), followed by recovery of lithium carbonate products through a crystallization process. However, this process is not suitable for extracting lithium from hard rock lithium minerals.

[0012] European Patent No. 4140952 discloses a method for obtaining lithium hydroxide from liquid or solid lithium sulfate. This process is designed for processing spent lithium-ion batteries or various electronic devices and is not suitable for extracting lithium from hard rock lithium minerals. Furthermore, the patent discloses a step of "dissolving" the lithium in a medium (e.g., water). Therefore, the patent does not disclose a leaching process.

[0013] It would therefore be advantageous to provide a method for extracting lithium that produces a relatively high grade lithium product while reducing the use of expensive and harsh conditions and limiting the generation of hazardous waste.

[0014] It should be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art, in Australia or any other country. Summary of the Invention

[0015] The present invention relates to a method for extracting lithium that may at least partially overcome at least one of the above-mentioned disadvantages or provide a useful choice for consumers or a commercial option.

[0016] In a first aspect, the present invention generally resides in a method for extracting lithium from hard rock lithium minerals, the method comprising subjecting a lithium-containing material to a leaching process in the presence of carbonate ions at atmospheric pressure at a temperature greater than 50°C but less than 160°C to produce a leach slurry containing lithium carbonate.

[0017] As previously mentioned, the leaching of the lithium-containing material is carried out at a temperature higher than 50°C but lower than 160°C. More preferably, the leaching of the lithium-containing material can be carried out at a temperature higher than 50°C but lower than 140°C. More preferably, the leaching of the lithium-containing material can be carried out at a temperature higher than 50°C but lower than 120°C. Most preferably, the leaching of the lithium-containing material can be carried out at a temperature higher than 50°C but lower than 100°C.

[0018] Advantageously, conducting the leaching process at temperatures below 160°C reduces or eliminates the need for specialized high-temperature equipment, thereby reducing the investment and operating costs associated with the present invention. In particular, maintaining the temperature below 160°C (particularly below 100°C) reduces or eliminates the need for autoclaves or similar equipment, which add cost and complexity to the process. Autoclaves require precise pressure control and high energy input, as well as stringent safety procedures, all of which increase the initial and ongoing costs of the process. By bypassing these requirements, the process can be operated with more readily available and cost-effective equipment, making it scalable and easier to maintain.

[0019] Alternatively, the leaching of the lithium-containing material is carried out at a temperature between 50°C and about the boiling point of the leach solution.

[0020] As described above, lithium is extracted from hard rock lithium minerals. The hard rock lithium minerals may be of any suitable type, however it is envisaged that the hard rock lithium minerals may include spodumene, lepidolite, eucryptite, petalite, lithium-containing silicate materials, etc. or any suitable combination thereof.

[0021] In a second aspect, the present invention generally resides in a method for extracting lithium, the method comprising the steps of:

[0022] subjecting the lithium-containing material to a leaching process in the presence of carbonate ions at atmospheric pressure and a temperature greater than 50° C. but less than 160° C. to produce a leach slurry containing lithium carbonate;

[0023] subjecting the leach slurry to a carbonation process to convert at least a portion of the lithium carbonate into lithium bicarbonate;

[0024] subjecting the leach slurry to a solid-liquid separation process to separate the leach residue from the leach solution;

[0025] Obtaining solid lithium carbonate from the leach solution; and

[0026] Solid lithium carbonate is separated from the leach solution.

[0027] The lithium-containing material may be in any suitable form. However, preferably, the lithium-containing material comprises a lithium mineral. In particular, the lithium mineral may comprise a hard rock lithium mineral. Specifically, the lithium mineral may comprise one or more of spodumene, lepidolite, eucryptite, and petalite. The lithium-containing material may comprise an ore, a concentrate, a residue, a waste product, or any suitable combination thereof comprising a hard rock lithium mineral. Preferably, at least a portion of the lithium in the lithium-containing material is present in the form of spodumene.

[0028] The spodumene present in the lithium-containing material may be in the form of alpha spodumene, beta spodumene, or a combination thereof. It is envisaged that alpha spodumene is more likely to be present in naturally occurring materials (e.g. lithium ores and mineral concentrates), while beta spodumene is more likely to be present in materials such as thermally treated concentrates.

[0029] In some embodiments of the present invention, the lithium-containing material may be subjected to one or more processing steps prior to the leaching step. Any suitable processing steps may be performed, such as a size reduction step, a separation step, a classification step, etc. In particular embodiments of the present invention, the lithium-containing material may be subjected to a conversion step to convert at least a portion of the alpha spodumene present in the lithium-containing material into beta spodumene.

[0030] The conversion step may take any suitable form, however, in preferred embodiments of the present invention, the conversion step may include a heat treatment step. Specifically, the lithium-containing material may be subjected to a roasting process, a calcining process, or the like at an elevated temperature to convert at least a portion of the α-spodumene to β-spodumene. Any suitable elevated temperature may be used, however, in preferred embodiments of the present invention, the elevated temperature may be between about 800°C and 1200°C. More preferably, the elevated temperature may be between about 900°C and 1100°C.

[0031] The heat treatment step may be carried out for any suitable time, and it will be appreciated that the length of the heat treatment process may depend on many factors, such as the amount of lithium minerals present in the lithium-containing material, the particle size of the lithium-containing material, the minerals present in the lithium-containing material, etc.

[0032] The heat treatment step may be performed as a batch process or a continuous process.In a preferred embodiment of the present invention, the lithium containing material may be cooled after the heat treatment step and before further processing of the lithium containing material.

[0033] In some embodiments of the present invention, the lithium-containing material that has been subjected to the heat treatment step may be subjected to one or more comminution processes and / or one or more classification processes prior to the leaching process. In a preferred embodiment of the present invention, finer particles of the lithium-containing material may be introduced into the leaching process.

[0034] It is envisioned that during the thermal treatment step, a majority of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. In some embodiments of the invention, during the thermal treatment step, at least 70% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. More preferably, during the thermal treatment step, at least 80% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. More preferably, during the thermal treatment step, at least 90% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. In some embodiments of the invention, it is envisioned that during the thermal treatment step, from about 93% to about 96% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. Thus, in this embodiment of the invention, the majority of the lithium present in the lithium-containing material that undergoes the leaching process is in the form of beta spodumene.

[0035] As previously mentioned, the leaching of lithium-containing materials is carried out under atmospheric pressure. It should be understood that the term "atmospheric pressure" refers to a pressure approximately equal to atmospheric pressure, or a pressure less than about 101.325 kPa at sea level. However, it should be understood that relatively small variations in this pressure are intended to be included in the meaning of the term "atmospheric pressure", which can include leaching carried out under a slightly pressurized atmosphere or under a slightly vacuum. For example, the container carrying out the leaching of lithium-containing materials can be operated under a pressure higher or lower than atmospheric pressure.

[0036] The leaching process can be carried out in any suitable container. However, preferably, the container comprises a tank, a reactor, or the like. In a specific embodiment of the present invention, the container can comprise a reactor, such as a tank reactor or a batch reactor. In some embodiments of the present invention, a stirred reactor can be used. In a specific embodiment, a continuously stirred reactor can be used.

[0037] As mentioned above, the leaching process is carried out at an elevated temperature of greater than 50°C but less than 160°C. More preferably, the leaching of the lithium-containing material is carried out at a temperature greater than 50°C but less than 140°C. More preferably, the leaching of the lithium-containing material is carried out at a temperature greater than 50°C but less than 120°C. Most preferably, the leaching of the lithium-containing material is carried out at a temperature greater than 50°C but less than 100°C.

[0038] Preferably, the temperature at which the lithium-containing material is leached is set to be approximately below the boiling point of the leaching solution.

[0039] Any suitable method may be used to control the temperature. In some embodiments of the invention, electric heating devices, direct steam injection (particularly at relatively low pressures), or indirect steam heating may be used for temperature control. In some embodiments, the temperature of the leaching process may be controlled at least in part by heat exchange (and subsequent heat recovery) between a relatively cool leach solution circulated from another point in the process and a relatively hot leach slurry exiting the leaching process.

[0040] It is envisaged that the lithium-containing material may be introduced into the leaching process in the form of a solid material. As previously described, the lithium-containing material is leached in the presence of carbonate ions. Preferably, the lithium-containing material is introduced into a leaching agent containing carbonate ions (particularly an aqueous solution of carbonate ions).

[0041] Preferably, the leaching agent comprises carbonate anions and alkali metal cations. Any suitable alkali metal cation may be present, however, in a preferred embodiment of the present invention, the alkali metal cations may include sodium and / or potassium ions. It should be understood that the leaching agent may comprise anions other than carbonate. For example, the leaching agent may comprise bicarbonate ions.

[0042] The leaching agent can have any suitable carbonate ion concentration. For example, the concentration of carbonate ions in the leaching agent can be between about 6 g / L and 288 g / L. More preferably, the concentration of carbonate ions in the leaching agent can be between about 12 g / L and 230 g / L. Most preferably, the concentration of carbonate ions in the leaching agent can be between about 17 g / L and 173 g / L.

[0043] In a specific embodiment of the present invention, carbonate ions can be added in the form of sodium carbonate. For example, the concentration of sodium carbonate in the leaching agent can be about 10g / L to 500g / L. More preferably, the concentration of sodium carbonate in the leaching agent can be about 20g / L to 400g / L. Most preferably, the concentration of sodium carbonate in the leaching agent can be about 30g / L to 300g / L.

[0044] The leaching agent can have any suitable sodium ion concentration. For example, the concentration of sodium ions in the leaching agent can be between about 4 g / L and 217 g / L. More preferably, the concentration of sodium ions in the leaching agent can be between about 9 g / L and 174 g / L. Most preferably, the concentration of sodium ions in the leaching agent can be between about 13 g / L and 130 g / L.

[0045] In a specific embodiment of the present invention, carbonate ions can be added in the form of potassium carbonate. For example, the concentration of potassium carbonate in the leaching agent can be about 10 g / L to 1000 g / L. More preferably, the concentration of potassium carbonate in the leaching agent can be about 30 g / L to 600 g / L. Most preferably, the concentration of potassium carbonate in the leaching agent can be about 50 g / L to 300 g / L.

[0046] The leaching agent can have any suitable potassium ion concentration. For example, the concentration of potassium ions in the leaching agent can be between about 6 g / L and 566 g / L. More preferably, the concentration of potassium ions in the leaching agent can be between about 17 g / L and 339 g / L. Most preferably, the concentration of potassium ions in the leaching agent can be between about 28 g / L and 170 g / L.

[0047] In particular embodiments of the present invention, leaching of the lithium-containing material (in the form of beta spodumene) may result in the formation of one or more zeolite minerals. The one or more zeolite minerals may have any suitable chemical formula, however, in one embodiment of the present invention, the zeolite mineral may have the chemical formula Na2Al2Si6O 16 7H2O. In this embodiment, the zeolitic material may be formed according to the following reaction:

[0048] 7H2O+2Na2CO3+4LiAlSi2O6+4SiO2=2Na2Al2(Si3O8)2·7H2O+2Li2CO3.

[0049] A similar reaction can occur for the leaching of lithium-containing materials in the presence of potassium carbonate.

[0050] In this embodiment of the invention, it is contemplated that the leaching reaction may result in the extraction of lithium from beta spodumene by the exchange of lithium and sodium ions. The sodium aluminum silicate present in the leach slurry may be in solid form, while the lithium carbonate produced by the leaching reaction may be present in the leach solution as a precipitated solid and / or as an aqueous solution. In some embodiments, the lithium carbonate may be present in the leach slurry as both a solid and an aqueous solution.

[0051] The leaching process can be carried out for any suitable time. However, preferably, the residence time of the leaching process can be from about 1 hour to about 300 hours. More preferably, the residence time of the leaching process can be from about 2 hours to about 200 hours. More preferably, the residence time of the leaching process can be from about 3 hours to about 100 hours. It should be understood that the residence time may depend on many factors, such as the properties of the lithium-containing material, the temperature of the leaching process, the concentration of carbonate ions in the leaching agent, the particle size of the lithium-containing material, the concentration of solids in the solution, etc.

[0052] The leaching process can be carried out as a batch process or a continuous process. However, preferably, the leaching process is carried out as a continuous process.

[0053] In some embodiments of the present invention, at the end of the leaching process, the leach slurry can be treated to recover heat. Any suitable technique can be used to recover heat, but in a preferred embodiment, a heat exchange process can be used to recover heat. The heat exchange fluid used to recover heat from the leach slurry can be in any suitable form. In some embodiments of the present invention, the heat exchange fluid can be a process stream generated or used in another part of the process.

[0054] Most preferably, the heat exchange process exchanges the hot leach slurry discharge with the cooler bicarbonate solution produced by the leaching process.

[0055] As previously mentioned, the leach slurry is subjected to a carbonation process to convert at least a portion of the lithium carbonate in the leach slurry into lithium bicarbonate. The carbonation process can be carried out using any suitable reactant, but in a preferred embodiment of the present invention, the reactant can be a carbonaceous gas. In a specific embodiment, the reactant can include carbon dioxide.

[0056] The lithium carbonate envisioned for conversion to lithium bicarbonate may be solid lithium carbonate in the leach slurry, an aqueous lithium carbonate solution, or a combination of both. Preferably, the lithium carbonate is converted to lithium bicarbonate according to the following reaction:

[0057] Li2CO3+CO2+H2O=2LiHCO3.

[0058] The carbonation process can be carried out at any suitable temperature, and it is contemplated that the temperature can be selected to increase the solubility of the lithium bicarbonate. In a preferred embodiment of the present invention, the carbonation process can be carried out at a temperature not exceeding about 70° C. More preferably, the carbonation process can be carried out at a temperature not exceeding about 60° C. Most preferably, the carbonation process can be carried out at a temperature not exceeding about 50° C.

[0059] The carbonation process can be carried out at any suitable pressure, including at atmospheric pressure, or at pressures above atmospheric pressure.

[0060] Carbonation process can be carried out with continuous process or batch process, and can be carried out in any suitable container (such as but not limited to autoclave, adsorption tower, deep stirred tank or any suitable combination thereof).In a specific embodiment of the invention, container comprises deep atmospheric pressure stirred tank.

[0061] Preferably, the carbonation process can extract at least 70% of the lithium in the leach slurry. More preferably, the carbonation process can extract at least 80% of the lithium in the leach slurry. Even more preferably, the carbonation process can extract at least 90% of the lithium in the leach slurry. In some embodiments, the carbonation process can extract about 95% of the lithium in the leach slurry. It is contemplated that at least a portion of the lithium not extracted by the carbonation process may not be in the form of lithium carbonate, but may instead be present as residual alpha spodumene from the carbonate leaching step and, therefore, may not be available for carbonate dissolution.

[0062] After the carbonation process, the leach slurry from the carbonation process is subjected to a solid-liquid separation process to separate the leach residue from the leach solution. In this way, a lithium leach solution that is relatively free of solids can be obtained. More preferably, the lithium leach solution is substantially completely free of solids.

[0063] Any suitable solid-liquid separation process can be used. For example, the solid-liquid separation process can include a filtration process, an evaporation or drying process, etc. In other embodiments, a sedimentation process or a countercurrent decantation process (such as that performed in a thickener) can be performed to separate the clarified leachate solution from the solid leach residue.

[0064] In some embodiments of the present invention, once the leach residue is separated from the leach solution, it can be washed or otherwise cleaned to remove at least a portion of the soluble materials present thereon. The leach residue can be washed or otherwise cleaned once, or it can be washed or cleaned in two or more steps of the process.

[0065] It is envisaged that the leach residue may form a tailings product from the extraction process. Advantageously, however, it is envisaged that the leach residue may constitute a by-product suitable for transport or storage in the environment rather than being disposed of. Preferably, the tailings from the leach residue are filtered to produce a filtered tailings product.

[0066] Thus, the present invention provides a significant advantage in that it produces a harmless by-product that can be stored in the environment or safely transported for relocation, rather than producing a potentially hazardous tailings product that must be stored or otherwise disposed of.

[0067] In some embodiments of the present invention, the non-hazardous by-products can provide material for the cement fill mixture. The material can be in the form of industrial minerals and can be used for industrial purposes.

[0068] After the solid-liquid separation process, the leach solution is relatively free of solids and has a relatively high concentration of soluble lithium. Lithium can then be obtained from the leach solution in the form of lithium carbonate by modifying the chemical properties of the solution. Although lithium carbonate can be obtained using any suitable technique, in one embodiment of the invention, solid lithium carbonate is obtained by a precipitation reaction.

[0069] Any suitable precipitation reaction can be used, however, in a preferred embodiment of the present invention, a compound can be introduced into the leach solution to convert the soluble lithium bicarbonate into relatively insoluble lithium carbonate. Any suitable compound can be used, however, in a preferred embodiment, the compound is a hydroxide (e.g., sodium hydroxide, potassium hydroxide, etc.). More preferably, the hydroxide can include a sodium compound. In this embodiment of the present invention, the lithium carbonate precipitation is carried out according to the following reaction:

[0070] 2LiHCO3+2NaOH=Li2CO3+Na2CO3+2H2O.

[0071] Advantageously, the use of sodium hydroxide produces a leach solution comprising an aqueous sodium carbonate solution.Thus, once the precipitated lithium carbonate is separated from the leach solution, the leach solution can be returned to the leaching process as a lixiviant.

[0072] In a preferred embodiment of the present invention, the precipitation of lithium carbonate can be carried out at an elevated temperature. Preferably, the precipitation of lithium carbonate can be carried out at a temperature between about 30°C and 99°C. At these temperatures, it is envisioned that other reactions leading to the precipitation of lithium carbonate may occur. This reaction proceeds according to the following reaction:

[0073] 2LiHCO3+heat=CO2(gas)+Li2CO3+H2O.

[0074] In some embodiments of the present invention, a heat source (e.g., a burner, heater, etc.) can be used to increase the temperature of the leach solution. In an alternative embodiment, a heat exchange process can be used to increase the temperature of the leach solution. The heat exchange fluid can be of any suitable type, however, in a preferred embodiment of the present invention, the heat exchange fluid can include the leach slurry exiting the leach process. In this way, the leach slurry exiting the leach process can be cooled and the leach solution undergoing lithium carbonate precipitation can be heated, thereby reducing or eliminating the need for an external heat source.

[0075] The precipitation process can be carried out in any suitable container. However, preferably, the container comprises a reactor or a tank. In a specific embodiment of the present invention, the container comprises a tank reactor or a batch reactor. In some embodiments of the present invention, a stirred reactor can be used. In a specific embodiment of the present invention, a continuous stirred reactor can be used.

[0076] The precipitated lithium carbonate can be separated from the leach solution using any suitable technique. For example, the precipitated lithium carbonate can be separated using a filtration process, evaporation, or drying process. In other embodiments of the present invention, a sedimentation or thickening process can be performed to separate the clarified leach solution from the precipitated lithium carbonate.

[0077] Preferably, the precipitated lithium carbonate is separated using filtration to provide a filter cake.In some embodiments of the present invention, the filtered, precipitated lithium carbonate may be washed with water to provide a moist lithium carbonate filter cake.

[0078] Ideally, the filtrate solution from the separation process can be recycled as the carbonate leach solution. The carbonate solution will contain sodium carbonate and at least trace amounts of lithium carbonate. Advantageously, the carbonate solution can be recycled to the atmospheric leaching process.

[0079] It has been found that the extraction method of the present invention results in at least a comparable lithium recovery from lithium-containing materials compared to conventional extraction methods. In addition, the lithium carbonate product produced by this method has a relatively high purity. In addition, the stream produced by this method can be circulated to other points in the process, thereby reducing reagent costs, and reducing the demand (and the cost associated therewith) for the heat energy provided from an external source. Finally, as previously mentioned, the present invention produces harmless by-products.

[0080] In a third aspect, the present invention resides in a method for extracting lithium, the method comprising the steps of:

[0081] subjecting the lithium-containing material to a first leaching process in the presence of carbonate ions at atmospheric pressure to produce lithium carbonate;

[0082] subjecting the lithium carbonate to a second leaching process in the presence of hydroxide ions to produce a leach slurry comprising an aqueous solution of lithium hydroxide;

[0083] separating a solid leach residue from the leach solution to produce a relatively solids-free lithium hydroxide solution; and

[0084] A solid lithium hydroxide product is produced from a relatively solids-free lithium hydroxide solution.

[0085] The lithium-containing material can be in any suitable form. For example, the lithium-containing material can include ore, concentrate, residue or waste product, etc., or any suitable combination thereof. However, preferably, at least a portion of the lithium in the lithium-containing material exists in the form of spodumene.

[0086] The spodumene present in the lithium-containing material may be in the form of alpha spodumene, beta spodumene, or a combination thereof. It is envisaged that alpha spodumene is more likely to be present in naturally occurring materials (e.g. lithium ores and mineral concentrates), while beta spodumene is more likely to be present in materials such as thermally treated concentrates.

[0087] In some embodiments of the present invention, the lithium-containing material may be subjected to one or more processing steps prior to the leaching step. Any suitable processing steps may be performed, such as a comminution step, a separation step, a classification step, etc. In particular embodiments of the present invention, the lithium-containing material may be subjected to a conversion step to convert at least a portion of the alpha spodumene present in the lithium-containing material into beta spodumene.

[0088] The conversion step may take any suitable form, however, in preferred embodiments of the present invention, the conversion step may include a heat treatment step. Specifically, the lithium-containing material may be subjected to a roasting process, a calcining process, or the like at an elevated temperature to convert at least a portion of the α-spodumene to the β-spodumene. Any suitable elevated temperature may be used, however, in preferred embodiments, the elevated temperature may be between about 800°C and 1200°C. More preferably, the elevated temperature may be between about 900°C and 1100°C.

[0089] The heat treatment step may be carried out for any suitable time, and it will be appreciated that the length of the heat treatment process may depend on many factors, such as the amount of lithium minerals present in the lithium-containing material, the particle size of the lithium-containing material, the minerals present in the lithium-containing material, etc.

[0090] The heat treatment step may be performed as a batch process or a continuous process.In a preferred embodiment of the present invention, the lithium containing material may be cooled after the heat treatment step and before further processing of the lithium containing material.

[0091] In some embodiments of the present invention, the lithium-containing material that has been subjected to the heat treatment step may undergo one or more comminution processes and / or one or more classification processes prior to the leaching process. In a preferred embodiment of the present invention, finer particles of the lithium-containing material may be introduced into the leaching process.

[0092] It is envisioned that during the thermal treatment step, a majority of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. In some embodiments, during the thermal treatment step, at least 70% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. More preferably, during the thermal treatment step, at least 80% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. More preferably, during the thermal treatment step, at least 90% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. In some embodiments of the present invention, it is envisioned that during the thermal treatment step, from about 93% to about 96% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. Thus, in this embodiment, the majority of the lithium present in the lithium-containing material undergoing the leaching process is in the form of beta spodumene.

[0093] As previously mentioned, the leaching of the lithium-containing material is carried out under atmospheric pressure. It should be understood that the term "atmospheric pressure" refers to the atmospheric pressure approximately equal to that at sea level, or a pressure less than about 101.325 kPa. However, it should be understood that the relatively small variation of this pressure is intended to be included in the meaning of the term "atmospheric pressure", which can include leaching carried out under a slightly pressurized atmosphere or under a slightly vacuum. For example, the container carrying out the leaching of the lithium-containing material can be operated under a pressure higher or lower than atmospheric pressure.

[0094] However, it should be understood that the container may comprise a sealed container capable of withstanding pressures above or below atmospheric pressure. In some embodiments of the present invention, the container may comprise a vacuum to control vapor loss and / or air ingress.

[0095] The leaching process can be carried out in any suitable container. However, preferably, the container comprises a tank, a reactor, or the like. In a specific embodiment of the present invention, the container can comprise a reactor, such as a tank reactor or a batch reactor. In some embodiments of the present invention, a stirred reactor can be used. In a specific embodiment, a continuously stirred reactor can be used.

[0096] It is envisaged that the leaching process may be carried out at an elevated temperature. It will be understood that the term "elevated temperature" refers to a temperature above ambient temperature. In a preferred embodiment, the leaching of the lithium-containing material is carried out at a temperature above 50°C but below 160°C. More preferably, the leaching of the lithium-containing material is carried out at a temperature above 60°C but below 160°C. More preferably, the leaching of the lithium-containing material is carried out at a temperature above 70°C but below 160°C. Most preferably, the leaching of the lithium-containing material is carried out at a temperature above 80°C but below 160°C.

[0097] Preferably, the temperature for leaching the lithium-containing material is set to be lower than the boiling point of the leaching solution.

[0098] It is contemplated that the lithium-containing material may be introduced into the leaching process in the form of a solid material. As previously described, the lithium-containing material is leached in the presence of carbonate ions. Preferably, the leaching agent comprises carbonate anions and alkali metal cations. Any suitable alkali metal cation may be present, however, in a preferred embodiment of the present invention, the alkali metal cation may comprise sodium ions. It will be appreciated that the leaching agent may comprise anions other than carbonate. For example, the leaching agent may comprise bicarbonate ions.

[0099] The leaching agent can have any suitable carbonate ion concentration. For example, the concentration of carbonate ions in the leaching agent can be about 17 g / L to 288 g / L. More preferably, the concentration of carbonate ions in the leaching agent can be about 12 g / L to 230 g / L. Most preferably, the concentration of carbonate ions in the leaching agent can be about 6 g / L to 173 g / L.

[0100] The leaching agent can have any suitable carbonate ion concentration. For example, the concentration of carbonate ions in the leaching agent can be about 6 g / L to 288 g / L. More preferably, the concentration of carbonate ions in the leaching agent can be about 12 g / L to 230 g / L. Most preferably, the concentration of carbonate ions in the leaching agent can be about 17 g / L to 173 g / L.

[0101] In a specific embodiment of the present invention, carbonate ions can be added in the form of sodium carbonate. For example, the concentration of sodium carbonate in the leaching agent can be about 10g / L to 500g / L. More preferably, the concentration of sodium carbonate in the leaching agent can be about 20g / L to 400g / L. Most preferably, the concentration of sodium carbonate in the leaching agent can be about 30g / L to 300g / L.

[0102] The leaching agent can have any suitable sodium ion concentration. For example, the concentration of sodium ions in the leaching agent can be between about 4 g / L and 217 g / L. More preferably, the concentration of sodium ions in the leaching agent can be between about 9 g / L and 174 g / L. Most preferably, the concentration of sodium ions in the leaching agent can be between about 13 g / L and 130 g / L.

[0103] In a specific embodiment of the present invention, carbonate ions can be added in the form of potassium carbonate. For example, the concentration of potassium carbonate in the leaching agent can be about 10 g / L to 1000 g / L. More preferably, the concentration of potassium carbonate in the leaching agent can be about 30 g / L to 600 g / L. Most preferably, the concentration of potassium carbonate in the leaching agent can be about 50 g / L to 300 g / L.

[0104] In a particular embodiment of the present invention, leaching of the lithium-containing material (in the form of beta spodumene) may be performed according to the following reaction:

[0105] 4LiAl(SiO3)2+2Na2CO3+4SiO2+7H2O=2Na2Al2(Si3O8)2·7H2O+2Li2CO3.

[0106] In this embodiment, it is contemplated that the leaching reaction may result in the extraction of lithium from beta spodumene by the exchange of lithium and sodium ions. The sodium aluminum silicate present in the leach slurry may be in solid form, while the lithium carbonate produced by the leaching reaction may be present in the leach solution as a precipitated solid and / or as an aqueous solution. In some embodiments, the lithium carbonate may be present in the leach slurry in both solid and aqueous forms.

[0107] The leaching process can be carried out for any suitable time. However, preferably, the residence time of the leaching process can be from about 1 hour to about 300 hours. More preferably, the residence time of the leaching process can be from about 2 hours to about 200 hours. More preferably, the residence time of the leaching process can be from about 3 hours to about 100 hours. It should be understood that the residence time may depend on many factors, such as the properties of the lithium-containing material, the temperature of the leaching process, the concentration of carbonate ions in the leaching agent, the particle size of the lithium-containing material, the concentration of solids in the solution, etc.

[0108] The leaching process can be carried out as a batch process or a continuous process. However, preferably, the leaching process is carried out as a continuous process.

[0109] In some embodiments of the present invention, at the end of the leaching process, the leach slurry can be treated to recover heat. Any suitable technique can be used to recover heat, but in a preferred embodiment, a heat exchange process can be used to recover heat. The heat exchange fluid used to recover heat from the leach slurry can be in any suitable form. In some embodiments of the present invention, the heat exchange fluid can be a process stream generated or used in another part of the process.

[0110] As previously described, the lithium carbonate is subjected to a second leaching process in the presence of hydroxide ions to produce a leach solution comprising an aqueous solution of lithium hydroxide. However, prior to undergoing the second leaching process, the stream exiting the first leaching process may be subjected to one or more process steps.

[0111] In particular, it is envisaged that the stream exiting the first leaching process may comprise leached solids, including lithium carbonate.Thus, in some embodiments of the invention, the stream exiting the first leaching process may be subjected to a solid-liquid separation process.

[0112] Any suitable solid-liquid separation process can be used. For example, the solid-liquid separation process can include a filtration process, an evaporation or drying process, etc. In other embodiments, a sedimentation process or a countercurrent decantation process (such as that performed in a thickener) can be performed to separate the clarified solution from the leached solids.

[0113] In some embodiments of the present invention, once separated from the clarified solution, the leached solids may be washed or otherwise cleaned to remove at least a portion of the soluble matter present thereon.

[0114] The leached solids (including lithium carbonate) can undergo a second leaching process. The second leaching process can be carried out at any suitable pressure, including a pressure above atmospheric pressure. In some embodiments of the present invention, the second leaching process can be carried out at atmospheric pressure.

[0115] The second leaching process may be performed at any suitable temperature, and it is contemplated that the temperature may be selected to increase the solubility of the lithium. In a preferred embodiment of the present invention, the second leaching process may be performed at a temperature not exceeding about 70°C. More preferably, the second leaching process may be performed at a temperature not exceeding about 60°C. Most preferably, the second leaching process may be performed at a temperature not exceeding about 50°C.

[0116] As previously mentioned, the second leaching process is carried out in the presence of hydroxide ions. Preferably, the second leaching process is carried out in the presence of cations that form substantially insoluble carbonate compounds. For example, the second leaching process can be carried out in the presence of cations of barium, calcium, strontium and / or magnesium. Therefore, in this embodiment of the invention, the cationic component of the leaching agent is selected to be substantially insoluble when combined with the carbonate anions from lithium carbonate. In this way, the contamination of the leach solution by carbonate ions and undesirable cations can be reduced or eliminated. In this embodiment of the invention, it is envisioned that at least a portion of the product of the second leaching process can be precipitated into an aqueous solution of calcium carbonate, barium carbonate, strontium carbonate and / or magnesium carbonate and lithium hydroxide.

[0117] The second leaching process can be carried out for any suitable time. However, preferably, the residence time of the second leaching process can be from about 0.5 hours to about 5 hours. More preferably, the residence time of the second leaching process can be from about 1 hour to about 3 hours. More preferably, the residence time of the second leaching process can be from about 1 hour to about 2 hours. It should be understood that the residence time may depend on many factors, such as the nature of the lithium-containing material, the temperature at which the second leaching process is carried out, the concentration of hydroxide ions in the leaching agent, the particle size of the lithium-containing material, the concentration of solids in the solution, etc.

[0118] The second leaching process may be carried out as a batch process or a continuous process. However, preferably, the second leaching process may be a continuous process.

[0119] The step of separating the solid leach residue to produce a relatively solids-free lithium hydroxide solution may be performed using any suitable technique. Preferably, a solid-liquid separation process may be performed to separate the solid leach residue from the relatively solids-free lithium hydroxide solution.

[0120] Any suitable solid-liquid separation process may be used. For example, the solid-liquid separation process may include a filtration process, an evaporation or drying process, etc. In other embodiments, a sedimentation process or a countercurrent decantation process (e.g., a process performed in a thickener) may be performed to separate a relatively solid-free lithium hydroxide solution from the solid leach residue.

[0121] In some embodiments of the present invention, once the solid leach residue is separated from the relatively solids-free lithium hydroxide solution, it may be washed or otherwise cleaned to remove at least a portion of the soluble material present thereon.

[0122] It is envisaged that the solid leach residue may form the tailings product of the extraction process. Advantageously, however, it is envisaged that the solid leach residue may constitute a harmless by-product comprising some calcite and / or one or more zeolites (sodium aluminium silicates).

[0123] As previously mentioned, the solid lithium hydroxide product is produced from a relatively solids-free lithium hydroxide solution. The solid lithium hydroxide product can be in any suitable form and can be anhydrous or hydrated. In some embodiments of the invention, the solid lithium hydroxide product can be in the form of crystalline lithium hydroxide.

[0124] The solid lithium hydroxide product may be produced directly from the relatively solids-free lithium hydroxide solution, or the relatively solids-free lithium hydroxide solution may be subjected to one or more additional processing steps prior to producing the solid lithium hydroxide product.

[0125] For example, a relatively solids-free lithium hydroxide solution can undergo a purification step before producing a solid lithium hydroxide product. Any suitable purification process can be used, however, in some embodiments of the invention, the lithium hydroxide solution can be partially evaporated to crystallize out a relatively high purity lithium hydroxide monohydrate. Alternatively, or in addition, the lithium hydroxide solution can undergo a crystallization process, such as vapor recompression crystallization, to produce lithium hydroxide crystals to form a solid lithium hydroxide product. In some embodiments, the purification step can include an ion exchange process, such as an ion exchange process that removes divalent ions and trivalent cations before the lithium hydroxide solution stream undergoes a crystallization process.

[0126] In a fourth aspect, the present invention resides in a method for extracting lithium, the method comprising the steps of:

[0127] subjecting a material containing alpha spodumene to a conversion process at atmospheric pressure to convert at least a portion of the alpha spodumene to beta spodumene;

[0128] subjecting the beta spodumene to a leaching process in the presence of carbonate ions at atmospheric pressure to produce a leach solution and a leach solid comprising lithium carbonate;

[0129] subjecting the leach solids containing lithium carbonate to a comminution process and / or a classification process in a solution containing carbonate ions to produce a leach slurry containing relatively fine solids;

[0130] subjecting the leach slurry to a carbonation process to convert at least a portion of the lithium carbonate into lithium bicarbonate;

[0131] subjecting the leach slurry to a solid-liquid separation process to separate the leach residue from the leach solution;

[0132] Obtaining solid lithium carbonate from the leach solution; and

[0133] Solid lithium carbonate is separated from the leach solution.

[0134] The lithium-containing material may be in any suitable form. For example, the lithium-containing material may include an ore, a concentrate, a residue, a waste product, or any suitable combination thereof. However, preferably, at least a portion of the lithium in the lithium-containing material is in the form of spodumene, one or more zeolites, or a combination thereof.

[0135] The spodumene present in the lithium-containing material may be in the form of alpha spodumene, beta spodumene, or a combination thereof. It is envisaged that alpha spodumene is more likely to be present in naturally occurring materials (e.g. lithium ores and mineral concentrates), while beta spodumene is more likely to be present in materials such as thermally treated concentrates.

[0136] In some embodiments of the present invention, the lithium-containing material may be subjected to one or more processing steps prior to the leaching step. Any suitable processing steps may be performed, such as a comminution step, a separation step, a classification step, etc. In particular embodiments of the present invention, the lithium-containing material may be subjected to a conversion step to convert at least a portion of the alpha spodumene present in the lithium-containing material into beta spodumene.

[0137] The conversion step may take any suitable form, however, in preferred embodiments of the present invention, the conversion step may include a heat treatment step. Specifically, the lithium-containing material may be subjected to a roasting process, a calcining process, or the like at an elevated temperature to convert at least a portion of the α-spodumene to β-spodumene. Any suitable elevated temperature may be used, however, in preferred embodiments of the present invention, the elevated temperature may be between about 800°C and 1200°C. More preferably, the elevated temperature may be between about 900°C and 1100°C.

[0138] The heat treatment step may be carried out for any suitable time, and it will be appreciated that the length of the heat treatment process may depend on many factors, such as the amount of lithium minerals present in the lithium-containing material, the particle size of the lithium-containing material, the minerals present in the lithium-containing material, etc.

[0139] The heat treatment step may be performed as a batch process or a continuous process.In a preferred embodiment of the present invention, the lithium containing material may be cooled after the heat treatment step and before further processing of the lithium containing material.

[0140] In some embodiments of the present invention, the lithium-containing material that has been subjected to the heat treatment step may undergo one or more comminution processes and / or one or more classification processes prior to the leaching process. In a preferred embodiment of the present invention, finer particles of the lithium-containing material may be introduced into the leaching process.

[0141] It is envisioned that during the thermal treatment step, a majority of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. In some embodiments of the invention, during the thermal treatment step, at least 70% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. More preferably, during the thermal treatment step, at least 80% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. More preferably, during the thermal treatment step, at least 90% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. In some embodiments of the invention, it is envisioned that during the thermal treatment step, from about 93% to about 96% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. Thus, in this embodiment of the invention, the majority of the lithium present in the lithium-containing material that undergoes the leaching process is in the form of beta spodumene.

[0142] As previously mentioned, the leaching of lithium-containing materials is carried out under atmospheric pressure. It should be understood that the term "atmospheric pressure" refers to the atmospheric pressure approximately equal to that at sea level, or a pressure less than about 101.325 kPa at sea level. However, it should be understood that relatively small variations in this pressure are intended to be included in the meaning of the term "atmospheric pressure", which can include leaching carried out under a slightly pressurized atmosphere or under a slightly vacuum. For example, the container carrying out the leaching of lithium-containing materials can be operated under a pressure higher or lower than atmospheric pressure.

[0143] However, it should be understood that the container may comprise a sealed container capable of withstanding pressures above or below atmospheric pressure. In some embodiments of the present invention, the container may comprise a vacuum to control vapor loss and / or air ingress.

[0144] The leaching process can be carried out in any suitable container. However, preferably, the container comprises a tank, a reactor, or the like. In a specific embodiment of the present invention, the container can comprise a reactor, such as a tank reactor or a batch reactor. In some embodiments of the present invention, a stirred reactor can be used. In a specific embodiment, a continuously stirred reactor can be used.

[0145] It is envisaged that the leaching process may be carried out at an elevated temperature. It will be understood that the term "elevated temperature" refers to a temperature above ambient temperature. In a preferred embodiment, the leaching of the lithium-containing material is carried out at a temperature above 50°C but below 160°C. More preferably, the leaching of the lithium-containing material is carried out at a temperature above 60°C but below 160°C. More preferably, the leaching of the lithium-containing material is carried out at a temperature above 70°C but below 160°C. Most preferably, the leaching of the lithium-containing material is carried out at a temperature above 80°C but below 160°C.

[0146] Preferably, the temperature for leaching the lithium-containing material is set to be lower than the boiling point of the leaching solution.

[0147] Any suitable method may be used to control the temperature. In some embodiments of the invention, temperature control may be performed using an electrical heating device, direct steam injection, or indirect steam heating. In some embodiments, the temperature of the leaching process may be controlled at least in part by heat exchange (and subsequent heat recovery) between a relatively cool leach solution circulated from another point in the process and a relatively hot leach slurry exiting the leaching process.

[0148] It is envisaged that the lithium-containing material may be introduced into the leaching process in the form of a solid material. As previously described, the lithium-containing material is leached in the presence of carbonate ions. Preferably, the lithium-containing material is introduced into a leaching agent containing carbonate ions (particularly an aqueous solution of carbonate).

[0149] Most preferably, the lithium-containing material will be beta spodumene. It is envisaged that the beta spodumene may be provided at an elevated temperature. In some embodiments of the invention, the temperature of the beta spodumene may be elevated due to the elevated temperatures used in the roasting or calcining process.

[0150] Preferably, the leaching agent comprises carbonate anions and alkali metal cations. Any suitable alkali metal cation may be present, however, in a preferred embodiment of the present invention, the alkali metal cation may comprise sodium ions. It should be understood that the leaching agent may comprise anions other than carbonate. For example, the leaching agent may comprise bicarbonate ions.

[0151] The leaching agent can have any suitable carbonate ion concentration. For example, the concentration of carbonate ions in the leaching agent can be about 6 g / L to 288 g / L. More preferably, the concentration of carbonate ions in the leaching agent can be about 12 g / L to 230 g / L. Most preferably, the concentration of carbonate ions in the leaching agent can be about 17 g / L to 173 g / L.

[0152] In a specific embodiment of the present invention, carbonate ions can be added in the form of sodium carbonate. For example, the concentration of sodium carbonate in the leaching agent can be about 10g / L to 500g / L. More preferably, the concentration of sodium carbonate in the leaching agent can be about 20g / L to 400g / L. Most preferably, the concentration of sodium carbonate in the leaching agent can be about 30g / L to 300g / L.

[0153] In a particular embodiment of the present invention, leaching of the lithium-containing material (in the form of beta spodumene) may be performed according to the following reaction:

[0154] 4LiAl(SiO3)2+2Na2CO3+4SiO2+7H2O=2Na2Al2(Si3O8)2·7H2O+2Li2CO3.

[0155] In this embodiment of the invention, it is contemplated that the leaching reaction may result in the extraction of lithium from beta spodumene by the exchange of lithium and sodium ions. The sodium aluminum silicate present in the leach slurry from the leaching reaction may be in solid form, while the lithium carbonate produced by the leaching reaction may be present in the leach slurry in the form of a precipitated solid and / or an aqueous solution. In some embodiments of the invention, the lithium carbonate may be present in the leach slurry in both solid and aqueous solution forms.

[0156] The leaching process can be carried out for any suitable time. However, preferably, the residence time of the leaching process can be from about 1 hour to about 300 hours. More preferably, the residence time of the leaching process can be from about 2 hours to about 200 hours. More preferably, the residence time of the leaching process can be from about 3 hours to about 100 hours. It should be understood that the residence time may depend on many factors, such as the nature of the lithium-containing material, the temperature at which the leaching process is carried out, the concentration of carbonate ions in the leaching agent, the concentration of sodium ions in the leaching agent, the particle size of the lithium-containing material, the concentration of solids in the solution, etc.

[0157] The leaching process may be carried out as a batch process or a continuous process. However, preferably, the leaching process may be a continuous process.

[0158] In some embodiments of the present invention, at the end of the leaching process, the leach slurry can be treated to recover heat. Any suitable technology can be used to recover heat, but in a preferred embodiment of the present invention, a heat exchange process can be used to recover heat. The heat exchange fluid used to recover heat from the leach slurry can be in any suitable form. In some embodiments of the present invention, the heat exchange fluid can be a process stream generated or used in another part of the method.

[0159] In some embodiments of the present invention, the leaching slurry containing lithium carbonate in the form of solid and aqueous solution can be subjected to a pulverization process and / or a classification process. The pulverization process can be carried out using any suitable method, such as ball milling, vertical stirred milling, jet milling or any other suitable pulverization technology. The pulverization process can be carried out as a wet process or a dry process, but in a preferred embodiment of the present invention, the pulverization process can be a wet grinding process. Preferably, the pulverization process can produce a stream containing relatively fine particles relative to the feed of the leaching circuit.

[0160] It is envisaged that the comminution process may reduce the particle size of the beta spodumene present in the leach slurry.

[0161] In embodiments of the present invention that utilize a classification process, it is contemplated that any suitable classification process may be utilized. However, it is contemplated that the classification process may classify solid particles based on particle size (e.g., by utilizing a spiral classifier, a conical classifier, a hydrocyclone, a hydroclassifier, etc.). Thus, it is contemplated that the classification process may generate a stream containing relatively fine particles and a stream containing relatively coarse particles.

[0162] In some embodiments of the present invention, the comminution process may include a classification process.

[0163] It is envisaged that a stream of relatively coarse particles from a comminution process and / or a classification process may be recycled to the comminution process and / or the classification process in order to produce further relatively fine particles.

[0164] It is contemplated that the relatively finer particles in the carbonate solution may be subjected to a second leaching process that is substantially identical to the first leaching process.

[0165] As previously mentioned, the leach slurry is subjected to a carbonation process to convert at least a portion of the lithium carbonate in the leach slurry into lithium bicarbonate. The carbonation process can be carried out using any suitable reactant, but in a preferred embodiment of the present invention, the reactant can be a carbonaceous gas. In a specific embodiment, the reactant can include carbon dioxide.

[0166] It is envisaged that the lithium carbonate converted to lithium bicarbonate may come from solid lithium carbonate in the leach slurry, an aqueous lithium carbonate solution, or a combination of both. Preferably, the lithium carbonate is converted to lithium bicarbonate according to the following reaction:

[0167] Li2CO3+CO2+H2O=2LiHCO3.

[0168] The carbonation process can be carried out at any suitable temperature, and it is contemplated that the temperature can be selected to increase the solubility of the lithium bicarbonate. In a preferred embodiment of the present invention, the carbonation process can be carried out at a temperature not exceeding about 70° C. More preferably, the carbonation process can be carried out at a temperature not exceeding about 60° C. Most preferably, the carbonation process can be carried out at a temperature not exceeding about 50° C.

[0169] The carbonation process can be carried out at any suitable pressure, including at atmospheric pressure, or at pressures above atmospheric pressure.

[0170] Carbonation process can be carried out with continuous process or batch process, and can be carried out in any suitable container (such as but not limited to autoclave, adsorption tower, deep stirred tank or any suitable combination thereof).In a specific embodiment of the invention, container comprises deep atmospheric pressure stirred tank.

[0171] Preferably, the carbonation process can extract at least 70% of the lithium in the leach slurry. More preferably, the carbonation process can extract at least 80% of the lithium in the leach slurry. Even more preferably, the carbonation process can extract at least 90% of the lithium in the leach slurry. In some embodiments, the carbonation process can extract about 95% of the lithium in the leach slurry. It is contemplated that at least a portion of the lithium not extracted by the carbonation process may not be in the form of lithium carbonate, but may instead be present as residual alpha spodumene from the carbonate leaching step and, therefore, may not be available for carbonate dissolution.

[0172] In a preferred embodiment of the present invention, in the carbonating process, substantially all of the lithium carbonate in the leach slurry can be converted into lithium bicarbonate aqueous solution. In this way, any solid leaching residue in the leach slurry after the carbonating process can not contain or contain relatively little lithium.

[0173] After the carbonation process, the leach slurry from the carbonation process is subjected to a solid-liquid separation process to separate the leach residue from the leach solution. In this way, a relatively solid-free lithium leach solution can be obtained.

[0174] Any suitable solid-liquid separation process can be used. For example, the solid-liquid separation process can include a filtration process, an evaporation or drying process, etc. In other embodiments, a sedimentation or countercurrent decantation process (such as that performed in a thickener) can be performed to separate the clarified leachate solution from the solid leach residue.

[0175] In some embodiments of the present invention, the leach residue, once separated from the leach solution, may be washed or otherwise cleaned to remove at least a portion of the soluble material present thereon.

[0176] It is envisaged that the leach residue may form a tailings product from the extraction process. Advantageously, however, it is envisaged that the leach residue, rather than being disposed of, may constitute a by-product that may be stored in the environment or safely transported for relocation.

[0177] Preferably, tailings from the leach residue are filtered to produce a filtered tailings product.

[0178] Thus, the present invention provides a significant advantage in that it produces a harmless by-product that can be stored in the environment or safely transported for relocation, rather than producing a potentially hazardous tailings product that must be stored or otherwise disposed of.

[0179] After the solid-liquid separation process, the leach solution is relatively free of solids and has a relatively high lithium concentration. Lithium can then be obtained from the leach solution in the form of lithium carbonate by modifying the chemical properties of the solution. Although lithium carbonate can be obtained using any suitable technique, in one embodiment of the invention, solid lithium carbonate is obtained by a precipitation reaction.

[0180] Any suitable precipitation reaction can be used, however, in a preferred embodiment of the present invention, a compound can be introduced into the leach solution to convert the soluble lithium bicarbonate into relatively insoluble lithium carbonate. Any suitable compound can be used, however, in a preferred embodiment, the compound is a hydroxide (e.g., sodium hydroxide, potassium hydroxide, etc.). More preferably, the hydroxide can include a sodium compound. In this embodiment of the present invention, the lithium carbonate precipitation is carried out according to the following reaction:

[0181] 2LiHCO3+2NaOH=Li2CO3+Na2CO3+2H2O.

[0182] Advantageously, the use of sodium hydroxide produces a leach solution comprising an aqueous solution of sodium carbonate.Thus, once the precipitated lithium carbonate is separated from the leach solution, the leach solution can be returned to the leaching process as a lixiviant.

[0183] In a preferred embodiment of the present invention, the precipitation of lithium carbonate can be carried out at an elevated temperature. Preferably, the precipitation of lithium carbonate can be carried out at a temperature between about 30°C and 99°C. At these temperatures, it is envisioned that other reactions will occur that lead to the precipitation of lithium carbonate. This reaction proceeds according to the following reaction:

[0184] 2LiHCO3+heat=CO2(gas)+Li2CO3+H2O.

[0185] In some embodiments of the present invention, a heat source (e.g., a burner, heater, etc.) can be used to increase the temperature of the leach solution. In an alternative embodiment, a heat exchange process can be used to increase the temperature of the leach solution. The heat exchange fluid can be of any suitable type, however, in a preferred embodiment of the present invention, the heat exchange fluid can include the leach slurry exiting the leach process. In this way, the leach slurry exiting the leach process can be cooled and the leach solution undergoing lithium carbonate precipitation can be heated, thereby reducing or eliminating the need for an external heat source.

[0186] The precipitation process can be carried out in any suitable container. However, preferably, the container comprises a reactor or a tank. In a specific embodiment of the present invention, the container comprises a tank reactor or a batch reactor. In some embodiments of the present invention, a stirred reactor can be used. In a specific embodiment of the present invention, a continuous stirred reactor can be used.

[0187] The precipitated lithium carbonate can be separated from the leach solution using any suitable technique. For example, the precipitated lithium carbonate can be separated using a filtration process, evaporation, or drying process. In other embodiments of the present invention, a sedimentation or thickening process can be performed to separate the clarified leach solution from the precipitated lithium carbonate.

[0188] Preferably, the precipitated lithium carbonate is separated using filtration to provide a filter cake.In some embodiments of the present invention, the filtered, precipitated lithium carbonate may be washed with water to provide a moist lithium carbonate filter cake.

[0189] Ideally, the filtrate solution from the separation process can be recycled as the carbonate leach solution. The carbonate solution will contain carbonate ions and at least trace amounts of lithium carbonate. Advantageously, the carbonate solution can be recycled to the atmospheric leaching process.

[0190] In a fifth aspect, the present invention resides in a method for extracting lithium, the method comprising the steps of:

[0191] subjecting a material containing alpha spodumene to a conversion process at atmospheric pressure to convert at least a portion of the alpha spodumene to beta spodumene;

[0192] subjecting the beta spodumene to a grinding process to produce ground beta spodumene;

[0193] subjecting the ground beta spodumene to a leaching process in the presence of carbonate ions at atmospheric pressure to produce a leach slurry containing lithium carbonate and leach solids;

[0194] subjecting the leach slurry to a carbonation process to convert at least a portion of the lithium carbonate into lithium bicarbonate;

[0195] subjecting the leach slurry to a solid-liquid separation process to separate the leach residue from the leach solution;

[0196] Obtaining solid lithium carbonate from the leach solution; and

[0197] Solid lithium carbonate is separated from the leach solution.

[0198] The lithium-containing material can be in any suitable form. For example, the lithium-containing material can include ore, concentrate, residue or waste product, or any suitable combination thereof. However, preferably, at least a portion of the lithium in the lithium-containing material exists in the form of spodumene.

[0199] The spodumene present in the lithium-containing material may be in the form of alpha spodumene, beta spodumene, or a combination thereof. It is envisaged that alpha spodumene is more likely to be present in naturally occurring materials (e.g. lithium ores and mineral concentrates), while beta spodumene is more likely to be present in materials such as thermally treated concentrates.

[0200] In some embodiments of the present invention, the lithium-containing material may be subjected to one or more processing steps prior to the leaching step. Any suitable processing steps may be performed, such as a comminution step, a separation step, a classification step, etc. In particular embodiments of the present invention, the lithium-containing material may be subjected to a conversion step to convert at least a portion of the alpha spodumene present in the lithium-containing material into beta spodumene.

[0201] The conversion step may take any suitable form, however, in preferred embodiments of the present invention, the conversion step may include a heat treatment step. Specifically, the lithium-containing material may be subjected to a roasting process, a calcining process, or the like at an elevated temperature to convert at least a portion of the α-spodumene to the β-spodumene. Any suitable elevated temperature may be used, however, in preferred embodiments, the elevated temperature may be between about 800°C and 1200°C. More preferably, the elevated temperature may be between about 900°C and 1100°C.

[0202] The heat treatment step may be carried out for any suitable time, and it will be appreciated that the length of the heat treatment process may depend on many factors, such as the amount of lithium minerals present in the lithium-containing material, the particle size of the lithium-containing material, the minerals present in the lithium-containing material, etc.

[0203] The heat treatment step may be performed as a batch process or a continuous process.In a preferred embodiment of the present invention, the lithium containing material may be cooled after the heat treatment step and before further processing of the lithium containing material.

[0204] It is envisioned that during the thermal treatment step, a majority of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. In some embodiments, during the thermal treatment step, at least 70% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. More preferably, during the thermal treatment step, at least 80% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. More preferably, during the thermal treatment step, at least 90% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. In some embodiments of the present invention, it is envisioned that during the thermal treatment step, from about 93% to about 96% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. Thus, in this embodiment, the majority of the lithium present in the lithium-containing material undergoing the leaching process is in the form of beta spodumene.

[0205] Preferably, the beta spodumene is substantially cooled prior to being subjected to the crushing or comminution process. Any suitable process may be used to cool the beta spodumene. The specific manner in which the beta spodumene is cooled is not critical to the present invention, however, in some embodiments of the present invention, the beta spodumene may be subjected to a quenching process, particularly an atmospheric pressure quenching process. In a preferred embodiment of the present invention, the cooling of the beta spodumene may reduce the temperature of the beta spodumene to a temperature of about 60°C to 160°C. More preferably, the cooling of the beta spodumene may reduce the temperature of the beta spodumene to a temperature of about 70°C to 160°C. Most preferably, the cooling of the beta spodumene may reduce the temperature of the beta spodumene to a temperature of about 80°C to 160°C.

[0206] In some embodiments of the present invention, the beta spodumene may be subjected to a pulverization process prior to the leaching process. Any suitable pulverization process may be used, however, in preferred embodiments of the present invention, the pulverization process may include a pulverization process such as crushing, grinding, and the like. The pulverization process may be performed using any suitable method, such as ball milling, vertical agitated milling, jet milling, or any other suitable mechanical milling. The grinding process may be performed as a wet process or a dry process, however, in preferred embodiments, the grinding process may be a wet grinding process using a recycled sodium carbonate leach solution.

[0207] It is envisaged that the grinding process may reduce the particle size of the beta spodumene present in the leach slurry.

[0208] It is envisaged that the ground solids in the carbonate leach slurry may subsequently be subjected to a leaching process.

[0209] As previously mentioned, the leaching of the lithium-containing material is carried out at atmospheric pressure. It should be understood that the term "atmospheric pressure" refers to a pressure approximately equal to atmospheric pressure, or a pressure less than about 101.325 kPa at sea level. However, it should be understood that relatively small variations in this pressure are intended to be included in the meaning of the term "atmospheric pressure", which can include leaching carried out under a slightly pressurized atmosphere or under a slightly vacuum. For example, the container carrying out the leaching of the lithium-containing material can be operated at a pressure higher or lower than atmospheric pressure.

[0210] However, it should be understood that the container may comprise a sealed container capable of withstanding pressures above or below atmospheric pressure. In some embodiments of the present invention, the container may comprise a vacuum to control vapor loss and / or air ingress.

[0211] The leaching process can be carried out in any suitable container. However, preferably, the container comprises a tank, a reactor, or the like. In a specific embodiment of the present invention, the container can comprise a reactor, such as a tank reactor or a batch reactor. In some embodiments of the present invention, a stirred reactor can be used. In a specific embodiment, a continuously stirred reactor can be used.

[0212] It is envisioned that the leaching process may be carried out at an elevated temperature. It will be understood that the term "elevated temperature" refers to a temperature above ambient temperature. In a preferred embodiment, the leaching of the lithium-containing material is carried out at a temperature above 60°C. More preferably, the leaching of the lithium-containing material is carried out at a temperature above 60°C but below 160°C. More preferably, the leaching of the lithium-containing material is carried out at a temperature above 70°C but below 160°C. Most preferably, the leaching of the lithium-containing material is carried out at a temperature above 80°C but below 160°C.

[0213] Preferably, the temperature for leaching the lithium-containing material is set to be lower than the boiling point of the leaching solution.

[0214] Any suitable method can be used to control the temperature. In some embodiments of the present invention, electric heating devices, direct steam injection, or indirect steam heating can be used for temperature control. Preferably, the recycled leach solution is heat exchanged with the leached slurry to recover heat. Most preferably, quenching heat from the calcination process is added to maintain the temperature of the leach slurry at or slightly below the boiling point.

[0215] It is contemplated that the lithium-containing material may be introduced into the leaching process as a solid material suspended in a leaching solution. As previously described, the lithium-containing material is leached in the presence of carbonate ions. Preferably, the ground lithium-containing material is introduced into a leaching agent containing carbonate ions, particularly an aqueous solution of carbonate ions.

[0216] Most preferably, the lithium-containing material will be beta spodumene having a high temperature. It is envisaged that the temperature of the beta spodumene may be elevated due to the high temperatures used in the roasting process or calcining process.

[0217] It will be appreciated that the leaching agent may comprise anions other than carbonate ions. For example, the leaching agent may comprise bicarbonate ions.

[0218] Preferably, the leaching agent comprises carbonate anions and alkali metal cations. Any suitable alkali metal cation may be present, however, in a preferred embodiment of the present invention, the alkali metal cation may comprise sodium ions. It should be understood that the leaching agent may comprise anions other than carbonate. For example, the leaching agent may comprise bicarbonate ions.

[0219] The leaching agent can have any suitable carbonate ion concentration. For example, the concentration of carbonate ions in the leaching agent can be about 6 g / L to 280 g / L. More preferably, the concentration of carbonate ions in the leaching agent can be about 12 g / L to 230 g / L. Most preferably, the concentration of carbonate ions in the leaching agent can be about 17 g / L to 173 g / L.

[0220] In a specific embodiment of the present invention, carbonate ions can be added in the form of sodium carbonate. For example, the concentration of sodium carbonate in the leaching agent can be about 10g / L to 500g / L. More preferably, the concentration of sodium carbonate in the leaching agent can be about 20g / L to 400g / L. Most preferably, the concentration of sodium carbonate in the leaching agent can be about 30g / L to 300g / L.

[0221] In a particular embodiment of the present invention, leaching of the lithium-containing material (in the form of beta spodumene) may be performed according to the following reaction:

[0222] 4LiAl(SiO3)2+2Na2CO3+4SiO2+7H2O=2Na2Al2(Si3O8)2·7H2O+2Li2CO3.

[0223] In this embodiment of the invention, it is contemplated that the leaching reaction may result in the extraction of lithium from beta spodumene by the exchange of lithium and sodium ions. The sodium aluminum silicate present in the leach slurry may be in solid form, while the lithium carbonate produced by the leaching reaction may be present in the leach slurry in the form of a precipitated solid and / or an aqueous solution. In some embodiments of the invention, the lithium carbonate may be present in the leach slurry in both solid and aqueous solution forms.

[0224] The leaching process can be carried out for any suitable time. However, preferably, the residence time of the leaching process can be from about 1 hour to about 300 hours. More preferably, the residence time of the leaching process can be from about 2 hours to about 200 hours. More preferably, the residence time of the leaching process can be from about 3 hours to about 100 hours. It should be understood that the residence time may depend on many factors, such as the properties of the lithium-containing material, the temperature of the leaching process, the concentration of carbonate ions in the leaching agent, the particle size of the lithium-containing material, the concentration of solids in the solution, etc.

[0225] The leaching process may be carried out as a batch process or a continuous process. However, preferably, the leaching process may be a continuous process.

[0226] In some embodiments of the present invention, at the end of the leaching process, the leach slurry can be treated to recover heat. Any suitable technique can be used to recover heat, but in a preferred embodiment of the present invention, a heat exchange process can be used to recover heat. The heat exchange fluid used to recover heat from the leach solution can be in any suitable form. In some embodiments of the present invention, the heat exchange fluid can be a process stream generated or used in another part of the process.

[0227] In some embodiments of the present invention, the leached slurry containing lithium carbonate in the form of solid and aqueous solution will be subjected to grinding in a sodium carbonate solution. Grinding can be performed using any suitable method, such as ball milling, vertical agitation milling, jet milling, or any mechanical grinding. The grinding process can be performed in a wet process or a dry process, but in a preferred embodiment, the grinding process will be a wet grinding process. It should be understood that if a comminution process or a comminution process is performed before the leaching step, the grinding process may not be required.

[0228] It is envisaged that the grinding process will reduce the particle size of the beta spodumene present in the leach solution slurry.

[0229] As previously mentioned, the leach slurry is subjected to a carbonation process to convert at least a portion of the lithium carbonate in the leach slurry into lithium bicarbonate. The carbonation process can be carried out using any suitable reactant, but in a preferred embodiment of the present invention, the reactant can be a carbonaceous gas. In a specific embodiment of the present invention, the reactant can include carbon dioxide.

[0230] The lithium carbonate envisioned for conversion to lithium bicarbonate may be solid lithium carbonate in the leach slurry, an aqueous lithium carbonate solution, or a combination of both. Preferably, the lithium carbonate is converted to lithium bicarbonate according to the following reaction:

[0231] Li2CO3+CO2+H2O=2LiHCO3.

[0232] The carbonation process can be carried out at any suitable temperature, and it is contemplated that the temperature can be selected to increase the solubility of the lithium bicarbonate. In a preferred embodiment of the present invention, the carbonation process can be carried out at a temperature not exceeding about 70° C. More preferably, the carbonation process can be carried out at a temperature not exceeding about 60° C. Most preferably, the carbonation process can be carried out at a temperature not exceeding about 50° C.

[0233] The carbonation process can be carried out at any suitable pressure, including at atmospheric pressure, or at pressures above atmospheric pressure.

[0234] The carbonation process can be carried out as a continuous process or a batch process and can be carried out in any suitable container, such as but not limited to an autoclave, an adsorption tower, a deep stirred tank or any suitable combination thereof. In a specific embodiment of the invention, the container comprises a deep atmospheric stirred tank.

[0235] Preferably, the carbonation process can extract at least 70% of the lithium in the leach slurry. More preferably, the carbonation process can extract at least 80% of the lithium in the leach slurry. Even more preferably, the carbonation process can extract at least 90% of the lithium in the leach slurry. In some embodiments, the carbonation process can extract about 95% of the lithium in the leach slurry. It is contemplated that at least a portion of the lithium not extracted by the carbonation process may not be in the form of lithium carbonate, but may instead be present as residual alpha spodumene from the carbonate leaching step and, therefore, may not be available for carbonate dissolution.

[0236] In a preferred embodiment of the present invention, in the carbonating process, substantially all of the lithium carbonate in the leach slurry can be converted into lithium bicarbonate aqueous solution. In this way, any solid leaching residue in the leach solution after the carbonating process can not contain or contain relatively little lithium.

[0237] After the carbonation process, the leach slurry from the carbonation process is subjected to a solid-liquid separation process to separate the leach residue from the leach solution. In this way, a relatively solid-free lithium leach solution can be obtained.

[0238] Any suitable solid-liquid separation process can be used. For example, the solid-liquid separation process can include a filtration process, an evaporation or drying process, etc. In other embodiments, a sedimentation or countercurrent decantation process (such as that performed in a thickener) can be performed to separate the clarified leachate solution from the solid leach residue.

[0239] In some embodiments of the present invention, the leach residue, once separated from the leach solution, may be washed or otherwise cleaned to remove at least a portion of the soluble material present thereon.

[0240] It is envisaged that the leach residue may form the tailings product from the extraction process. Advantageously, however, it is envisaged that the leach residue may constitute a by-product suitable for transport or storage in the environment, rather than being disposed of.

[0241] Preferably, tailings from the leach residue are filtered to produce a filtered tailings product.

[0242] Thus, the present invention provides a significant advantage in that it produces a harmless by-product that can be stored in the environment or safely transported for relocation, rather than producing a potentially hazardous tailings product that must be stored or otherwise disposed of.

[0243] After the solid-liquid separation process, the leach solution is relatively free of solids and has a relatively high lithium concentration. Lithium can then be obtained from the leach solution in the form of lithium carbonate by modifying the chemical properties of the solution. Although lithium carbonate can be obtained using any suitable technique, in one embodiment of the invention, solid lithium carbonate is obtained by a precipitation reaction.

[0244] Any suitable precipitation reaction may be used, however, in a preferred embodiment of the present invention, a compound may be introduced into the leach solution to convert soluble lithium bicarbonate into relatively insoluble lithium carbonate. Any suitable compound may be used, however, in a preferred embodiment, the compound is a hydroxide (e.g., sodium hydroxide). More preferably, the hydroxide may comprise a sodium compound. In this embodiment, lithium carbonate precipitation proceeds according to the following reaction:

[0245] 2LiHCO3+2NaOH=Li2CO3+Na2CO3+2H2O.

[0246] Advantageously, the use of sodium hydroxide produces a leach solution comprising an aqueous sodium carbonate solution.Thus, once the precipitated lithium carbonate is separated from the leach solution, the leach solution can be returned to the leaching process as a lixiviant.

[0247] In a preferred embodiment of the present invention, the precipitation of lithium carbonate can be carried out at a high temperature. Preferably, the precipitation of lithium carbonate can be carried out at a temperature of about 30°C to 99°C.

[0248] In some embodiments of the present invention, a heat source (e.g., a burner, heater, etc.) can be used to increase the temperature of the leach solution. In alternative embodiments of the present invention, a heat exchange process can be used to increase the temperature of the leach solution. The heat exchange fluid can be of any suitable type, however, in a preferred embodiment of the present invention, the heat exchange fluid can include the leach slurry exiting the leach process. In this way, the leach slurry exiting the leach process can be cooled and the leach solution undergoing lithium carbonate precipitation can be heated, thereby reducing or eliminating the need for an external heat source.

[0249] The precipitation process can be carried out in any suitable container. However, preferably, the container comprises a reactor or a tank. In a specific embodiment of the present invention, the container can comprise a tank reactor or a batch reactor. In some embodiments of the present invention, a stirred reactor can be used. In a specific embodiment of the present invention, a continuous stirred reactor can be used.

[0250] The precipitated lithium carbonate can be separated from the leach solution using any suitable technique. For example, the precipitated lithium carbonate can be separated using a filtration process, evaporation, or drying process. In other embodiments of the present invention, a sedimentation or thickening process can be performed to separate the clarified leach solution from the precipitated lithium carbonate.

[0251] Preferably, the precipitated lithium carbonate is separated using filtration to provide a filter cake.In some embodiments of the present invention, the filtered precipitated lithium carbonate may be washed with water to provide a moist lithium carbonate filter cake.

[0252] Preferably, the filtrate solution from the separation process can be recycled as the carbonate leach solution. The carbonate solution can comprise sodium carbonate and at least trace amounts of lithium carbonate. Advantageously, the carbonate solution can be recycled to the atmospheric leaching process.

[0253] In a sixth aspect, the present invention resides in a method for extracting lithium, the method comprising the steps of:

[0254] subjecting a lithium-containing material containing beta spodumene to a leaching process in the presence of carbonate ions at atmospheric pressure to produce a leach slurry comprising lithium carbonate;

[0255] subjecting the leach slurry to a carbon dioxide leaching process to produce a bicarbonate leach slurry, wherein at least a portion of the lithium carbonate is converted to lithium bicarbonate;

[0256] subjecting the bicarbonate leach slurry to a solid-liquid separation process to separate the leach residue from the leach solution;

[0257] precipitating lithium carbonate from the leach solution; and

[0258] The precipitated lithium carbonate is separated from the leach solution.

[0259] The lithium-containing material may be in any suitable form. However, in a preferred embodiment of the present invention, the lithium-containing material may comprise a hard rock lithium mineral. The lithium-containing material may comprise an ore, a concentrate, a residue or a waste product, or any suitable combination thereof including a hard rock lithium mineral. However, preferably, at least a portion of the lithium in the lithium-containing material is in the form of spodumene.

[0260] The spodumene present in the lithium-containing material may be in the form of alpha spodumene, beta spodumene, or a combination thereof. It is envisaged that alpha spodumene is more likely to be present in naturally occurring materials (e.g. lithium ores and mineral concentrates), while beta spodumene is more likely to be present in materials such as thermally treated concentrates.

[0261] In some embodiments of the present invention, prior to the first leaching step, the lithium-containing material may be subjected to one or more processing steps. Any suitable processing steps may be performed, such as a comminution step, a separation step, a classification step, etc. In particular embodiments of the present invention, the lithium-containing material may be subjected to a conversion step to convert at least a portion of the alpha spodumene present in the lithium-containing material into beta spodumene.

[0262] The conversion step may take any suitable form, however, in preferred embodiments of the present invention, the conversion step may include a heat treatment step. Specifically, the lithium-containing material may be subjected to a roasting process, a calcining process, or the like at an elevated temperature to convert at least a portion of the α-spodumene to the β-spodumene. Any suitable elevated temperature may be used, however, in preferred embodiments, the elevated temperature may be between about 800°C and 1200°C. More preferably, the elevated temperature may be between about 900°C and 1100°C.

[0263] The heat treatment step may be carried out for any suitable time, and it will be appreciated that the length of the heat treatment process may depend on many factors, such as the amount of lithium minerals present in the lithium-containing material, the particle size of the lithium-containing material, the minerals present in the lithium-containing material, etc.

[0264] The heat treatment step may be performed as a batch process or a continuous process.In a preferred embodiment of the present invention, the lithium containing material may be cooled after the heat treatment step and before further processing of the lithium containing material.

[0265] In some embodiments of the present invention, the lithium-containing material that has been subjected to the heat treatment step may undergo one or more comminution processes and / or one or more classification processes prior to the first leaching process. In a preferred embodiment of the present invention, finer lithium-containing material particles may be introduced into the first leaching process.

[0266] It is envisioned that during the thermal treatment step, a majority of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. In some embodiments, during the thermal treatment step, at least 70% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. More preferably, during the thermal treatment step, at least 80% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. More preferably, during the thermal treatment step, at least 90% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. In some embodiments of the present invention, it is envisioned that during the thermal treatment step, from about 93% to about 96% of the alpha spodumene present in the lithium-containing material may be converted to beta spodumene. Thus, in this embodiment, the majority of the lithium present in the lithium-containing material that undergoes the first leaching process is in the form of beta spodumene.

[0267] As previously mentioned, the step of leaching the lithium-containing material is carried out under atmospheric pressure. It should be understood that the term "atmospheric pressure" refers to the atmospheric pressure approximately equal to that on sea level, or is lower than the pressure of about 101.325 kPa. However, it should be understood that the relatively small variation of this pressure is intended to be included in the implication of the term "atmospheric pressure", which can include leaching carried out under a slightly pressurized atmosphere or under a slightly vacuum. For example, the container carrying out the leaching of the lithium-containing material can be operated under a pressure higher or lower than atmospheric pressure.

[0268] However, it should be understood that the container may comprise a sealed container capable of withstanding pressures above or below atmospheric pressure. In some embodiments of the present invention, the container may comprise a vacuum to control vapor loss and / or air ingress.

[0269] The leaching process can be carried out in any suitable container. However, preferably, the container comprises a tank, a reactor, or the like. In a specific embodiment of the present invention, the container can comprise a reactor, such as a tank reactor or a batch reactor. In some embodiments of the present invention, a stirred reactor can be used. In a specific embodiment, a continuously stirred reactor can be used.

[0270] It is envisaged that the leaching process may be carried out at an elevated temperature. It will be understood that the term "elevated temperature" refers to a temperature above ambient temperature. In a preferred embodiment, the leaching of the lithium-containing material is carried out at a temperature above 50°C but below 160°C. More preferably, the leaching of the lithium-containing material is carried out at a temperature above 50°C but below 140°C. More preferably, the leaching of the lithium-containing material is carried out at a temperature above 50°C but below 120°C. Most preferably, the leaching of the lithium-containing material is carried out at a temperature above 50°C but below 100°C.

[0271] Preferably, the leaching temperature of the lithium-containing material is set between 50°C and about the boiling point of the leaching solution.

[0272] It is contemplated that the lithium-containing material may be introduced into the leaching process in the form of a solid material. As previously described, the lithium-containing material is leached in the presence of carbonate ions. Preferably, the leaching agent comprises carbonate anions and alkali metal cations. Any suitable alkali metal cation may be present, however, in a preferred embodiment of the present invention, the alkali metal cation may comprise sodium ions. It will be appreciated that the leaching agent may comprise anions other than carbonate. For example, the leaching agent may comprise bicarbonate ions.

[0273] The leaching agent can have any suitable carbonate ion concentration. For example, the concentration of carbonate ions in the leaching agent can be about 17 g / L to 288 g / L. More preferably, the concentration of carbonate ions in the leaching agent can be about 12 g / L to 230 g / L. Most preferably, the concentration of carbonate ions in the leaching agent can be about 6 g / L to 173 g / L.

[0274] In a specific embodiment of the present invention, carbonate ions can be added in the form of sodium carbonate. For example, the concentration of sodium carbonate in the leaching agent can be about 10g / L to 500g / L. More preferably, the concentration of sodium carbonate in the leaching agent can be about 20g / L to 400g / L. More preferably, the concentration of sodium carbonate in the leaching agent can be about 30g / L to 300g / L. Most preferably, the concentration of sodium carbonate in the leaching agent can be about 30g / L to 200g / L.

[0275] The leaching agent can have any suitable sodium ion concentration. For example, the concentration of sodium ions in the leaching agent can be between about 4 g / L and 217 g / L. More preferably, the concentration of sodium ions in the leaching agent can be between about 9 g / L and 174 g / L. Most preferably, the concentration of sodium ions in the leaching agent can be between about 13 g / L and 130 g / L.

[0276] In a specific embodiment of the present invention, carbonate ions can be added in the form of potassium carbonate. For example, the concentration of potassium carbonate in the leaching agent can be about 10 g / L to 1000 g / L. More preferably, the concentration of potassium carbonate in the leaching agent can be about 30 g / L to 600 g / L. Most preferably, the concentration of potassium carbonate in the leaching agent can be about 50 g / L to 300 g / L.

[0277] In a particular embodiment of the present invention, leaching of the lithium-containing material (in the form of beta spodumene) may be performed according to the following reaction:

[0278] 4LiAl(SiO3)2+2Na2CO3+4SiO2+7H2O=2Na2Al2(Si3O8)2·7H2O+2Li2CO3.

[0279] In this embodiment, it is contemplated that the leaching reaction may result in the extraction of lithium from beta spodumene by the exchange of lithium and sodium ions. The sodium aluminum silicate present in the leach solution may be in solid form, while the lithium carbonate produced by the leaching reaction may be present in the leach solution as a precipitated solid and / or as an aqueous solution. In some embodiments, the lithium carbonate may be present in the leach slurry in both solid and aqueous forms.

[0280] In other embodiments, the leached solids may comprise primarily sodium zeolite P2. Thus, in this embodiment of the invention, in the leaching of lithium-containing material, the conversion of beta spodumene to sodium zeolite P2 may proceed according to the following reaction:

[0281] 7H2O+2Na2CO3+4LiAlSi2O6+4SiO2=2Na2Al2(Si3O8)2·7H2O+2Li2CO3.

[0282] Generally speaking, once the solubility limit is reached under the leaching conditions, lithium may first be leached from the solid and subsequently precipitated as lithium carbonate crystals. At the end of the first leaching process, the leaching solution may be substantially saturated with lithium.

[0283] The leaching process can be carried out for any suitable time. However, preferably, the residence time of the leaching process can be from about 1 hour to about 300 hours. More preferably, the residence time of the leaching process can be from about 2 hours to about 200 hours. More preferably, the residence time of the leaching process can be from about 3 hours to about 100 hours. It should be understood that the residence time may depend on many factors, such as the properties of the lithium-containing material, the temperature of the leaching process, the concentration of carbonate ions in the leaching agent, the particle size of the lithium-containing material, the concentration of solids in the solution, etc.

[0284] The first leaching process may be carried out as a batch process or a continuous process. However, preferably, the leaching process may be a continuous process.

[0285] In some embodiments of the present invention, at the end of the first leaching process, the leach slurry can be treated to recover heat. Any suitable technique can be used to recover heat, but in a preferred embodiment, a heat exchange process can be used to recover heat. The heat exchange fluid used to recover heat from the leach slurry can be in any suitable form. In some embodiments of the present invention, the heat exchange fluid can be a process stream generated or used in another part of the process.

[0286] The stream exiting the first leaching process may be subjected to one or more process steps before the second leaching process occurs.

[0287] In particular, it is envisaged that the stream exiting the first leaching process may comprise leached solids (including lithium carbonate) in a solution having a relatively high potassium content.Accordingly, in some embodiments, the stream exiting the first leaching process may be subjected to a solid-liquid separation process.

[0288] Any suitable solid-liquid separation process can be used. For example, the solid-liquid separation process can include a filtration process, an evaporation or drying process, etc. In other embodiments, a sedimentation process or a countercurrent decantation process (such as that performed in a thickener) can be performed to separate the clarified solution from the leached solids.

[0289] In some embodiments of the present invention, once separated from the clarified solution, the leached solids may be washed or otherwise cleaned to remove at least a portion of the soluble matter present thereon.

[0290] The leached solids may be treated in the presence of a carbonate solution. Any suitable treatment may be used, however, in some embodiments, the treatment may include reslurrying the leached solids with a carbonate solution. Any suitable carbonate solution may be used, such as lithium carbonate, potassium carbonate, or a combination of the two.

[0291] As previously described, the solids in the leach slurry are subjected to a carbon dioxide leaching process to convert at least a portion of the lithium carbonate in the leach slurry into lithium bicarbonate. The carbon dioxide leaching process can be carried out using any suitable reactant, however, in a preferred embodiment of the present invention, the reactant can be a carbonaceous gas. In a specific embodiment, the reactant can include carbon dioxide.

[0292] It is envisaged that the lithium carbonate converted to lithium bicarbonate may be solid lithium carbonate in the leach slurry. Preferably, the lithium carbonate is converted to lithium bicarbonate according to the following reaction:

[0293] Li2CO3+CO2+H2O=2LiHCO3.

[0294] The carbon dioxide leaching process can be carried out at any suitable temperature, and it is contemplated that the temperature can be selected to increase the solubility of the lithium bicarbonate. In a preferred embodiment of the present invention, the carbon dioxide leaching process can be carried out at a temperature of less than about 70°C. More preferably, the carbon dioxide leaching process can be carried out at a temperature of no more than about 50°C. More preferably, the carbon dioxide leaching process can be carried out at a temperature of no more than about 40°C. Most preferably, the carbon dioxide leaching process can be carried out at a temperature of about 25°C.

[0295] The CO2 leaching process may be carried out at any suitable pressure, including at atmospheric pressure, or at pressures above atmospheric pressure.

[0296] The carbon dioxide leaching process can be carried out as a continuous process or a batch process and can be carried out in any suitable vessel, such as, but not limited to, an autoclave, an adsorption tower, a deep stirred tank, an atmospheric stirred tank, or any suitable combination thereof. In a specific embodiment of the present invention, the vessel comprises a deep atmospheric stirred tank.

[0297] Preferably, the CO2 leaching process can dissolve at least 70% of the solid lithium carbonate in the leach slurry. More preferably, the CO2 leaching process can dissolve at least 80% of the solid lithium carbonate in the leach solution. Even more preferably, the CO2 leaching process can dissolve at least 90% of the solid lithium carbonate in the leach solution. In some embodiments, the CO2 leaching process can dissolve about 95% of the solid lithium carbonate in the leach solution. It is contemplated that at least a portion of the lithium may be present as residual alpha spodumene from the carbonate leaching step and, therefore, may not be available for carbonate dissolution.

[0298] After the CO2 leaching process, the leachate solution from the CO2 leaching process is subjected to a solid-liquid separation process to separate the leach residue from the leach slurry. In this way, a concentrated lithium-containing leachate solution can be obtained. The concentrated lithium-containing solution can be collected for subsequent processing.

[0299] Any suitable solid-liquid separation process may be used. For example, the solid-liquid separation process may include a filtration process, an evaporation or drying process, etc. In other embodiments, a sedimentation or decantation process (e.g., a single-stage process or a multi-stage process performed in a thickener) may be performed to separate the clarified leachate solution from the solid leach residue.

[0300] In some embodiments of the present invention, once separated from the leach solution, the leach residue may be washed or otherwise cleaned to remove at least a portion of the soluble material present thereon. The leach residue may be washed or otherwise cleaned once, or may be washed or cleaned in two or more steps of the process.

[0301] It is envisioned that the leach residue may form a tailings product from the extraction process. Advantageously, however, it is envisioned that the leach residue may contain a relatively high concentration of zeolite. Zeolite can be used as an industrial raw material for a range of applications. Therefore, the accumulation of tailings in the environment may not be necessary.

[0302] After solid-liquid separation, the leach solution is relatively free of solids and has a relatively high concentration of soluble lithium. Lithium can then be precipitated from the leach solution as lithium carbonate by altering the solution's chemistry.

[0303] Depending on the specific process requirements, any suitable precipitation reaction can be used to precipitate lithium. For example, additional heat can be applied to accelerate the reaction. However, at higher temperatures, carbon dioxide may be released from the leach solution, resulting in the formation of carbonate ions. The presence of carbonate ions is beneficial to the precipitation of lithium carbonate because lithium carbonate is significantly less soluble in the presence of carbonate ions than bicarbonate ions. As a result, lithium carbonate precipitates from the solution. In this embodiment, the lithium carbonate precipitation is carried out according to the following reaction:

[0304] 2LiHCO3+heat=Li2CO3+CO2+H2O.

[0305] This reaction represents the thermal decomposition of lithium bicarbonate into lithium carbonate, carbon dioxide, and water. The controlled addition of heat ensures that the lithium is efficiently removed from the leach solution in the form of lithium carbonate.

[0306] The precipitation of lithium carbonate can be carried out in any suitable vessel, such as, but not limited to, a stirred tank reactor or a crystallizer with temperature control.

[0307] In a preferred embodiment of the present invention, the precipitation of lithium carbonate can be carried out at an elevated temperature. Preferably, the precipitation of lithium carbonate can be carried out at a temperature of about 30°C to 99°C. More preferably, the precipitation of lithium carbonate can be carried out at a temperature of about 50°C to 90°C.

[0308] In some embodiments, a heat source (e.g., a burner, steam injection, heater, etc.) can be used to increase the temperature of the leach solution. In alternative embodiments, a heat exchange process can be used to increase the temperature of the leach solution. The heat exchange fluid can be of any suitable type, however, in a preferred embodiment of the present invention, the heat exchange fluid can include the leach solution exiting the first or second leach process. In this way, the leach solution exiting the first or second leach process can be cooled, and the leach solution undergoing lithium carbonate precipitation can be heated, thereby reducing or eliminating the need for an external heat source.

[0309] The precipitated lithium carbonate can be separated from the leach solution using any suitable technique. For example, the precipitated lithium carbonate can be separated using a filtration process, evaporation, or drying process. In other embodiments, a sedimentation or thickening process can be performed to separate the clarified leach solution from the precipitated lithium carbonate.

[0310] Preferably, the precipitated lithium carbonate is separated using filtration to provide a filter cake.In some embodiments of the present invention, the filtered precipitated lithium carbonate may be washed with water to provide a moist lithium carbonate filter cake.

[0311] Preferably, the filtrate solution from the separation process may be recycled as a carbonate leach solution. The carbonate leach solution may contain soluble lithium carbonate and trace amounts of sodium carbonate, and advantageously, the carbonate leach solution may be recycled to the leaching process.

[0312] In a seventh aspect, the present invention resides in a method for extracting lithium, the method comprising the steps of:

[0313] subjecting a lithium-containing material containing beta spodumene to a leaching process in the presence of carbonate ions at atmospheric pressure to produce a first leach slurry comprising lithium carbonate;

[0314] performing a solid-liquid separation process on the first leach slurry to separate the first leach residue from the first leach solution;

[0315] subjecting the first leach residue to a reslurry process in the presence of carbonate ions to produce a second leach slurry;

[0316] subjecting the second leach slurry to a carbon dioxide leaching process to produce a bicarbonate leach slurry, wherein at least a portion of the lithium carbonate is converted to lithium bicarbonate;

[0317] subjecting the bicarbonate leach slurry to a solid-liquid separation process to separate a second leach residue from a second leach solution;

[0318] precipitating lithium carbonate from the second leach solution; and

[0319] The precipitated lithium carbonate is separated from the second leach solution.

[0320] Within the scope of the present invention, any feature described herein may be combined in any combination with any one or more other features described herein.

[0321] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge. BRIEF DESCRIPTION OF THE DRAWINGS

[0322] The preferred features, embodiments, and variations of the present invention can be seen from the following detailed description, which provides sufficient information for those skilled in the art to implement the present invention. The detailed description should not be construed as limiting the scope of the foregoing summary of the present invention in any way. The detailed description will refer to the following multiple drawings:

[0323] Figure 1 A method for extracting lithium according to a first embodiment of the present invention is shown;

[0324] Figure 2 A method for extracting lithium according to a second embodiment of the present invention is shown;

[0325] Figure 3 A method for extracting lithium according to a third embodiment of the present invention is shown;

[0326] Figure 4 A method for extracting lithium according to a fourth embodiment of the present invention is shown;

[0327] Figure 5 A method for extracting lithium according to a fifth embodiment of the present invention is shown;

[0328] Figure 6 A method for extracting lithium according to a fourth embodiment of the present invention is shown;

[0329] Figure 7 A method for extracting lithium according to a sixth embodiment of the present invention is shown. DETAILED DESCRIPTION

[0330] Figure 1 A method 2 for extracting lithium according to an embodiment of the present invention is shown. In method 2, a lithium feedstock 4 is converted into a lithium-containing material 5. The conversion of the lithium feedstock 4 into the lithium-containing material 5 is conventional and requires no further discussion. The lithium-containing material 5 is a solid material.

[0331] The lithium-containing material 5 undergoes a leaching process 6 which is carried out in the presence of sodium carbonate at atmospheric pressure. Figure 1In the embodiment of the present invention shown, the lithium-containing material 5 is introduced into a lixiviant containing an aqueous sodium carbonate solution. Generally, the concentration of sodium carbonate in the lixiviant is 30 g / L to 300 g / L, and it will be appreciated that the concentration of sodium carbonate in the lixiviant depends at least in part on the concentration of lithium in the lithium-containing material 5.

[0332] Leaching process 6 is carried out in a continuous stirred tank reactor at 101.325 kPa and a temperature higher than 80° C. but lower than 160° C. The temperature of leaching process 6 is set lower than but relatively close to the boiling point of the leaching agent.

[0333] The residence time and size of the leaching vessel for the lithium-bearing material 5 in the leaching process 6 will depend on many factors, including the amount of lithium in the lithium-bearing material 5, the concentration of sodium carbonate in the lixiviant, the pressure and temperature at which the leaching process 6 is conducted, etc. However, it will be understood that the residence time of the lithium-bearing material 5 in the leaching process 6 will be determined, at least in part, by the time it takes to extract substantially all, or at least a majority, of the lithium from the lithium-bearing material 5.

[0334] At the end of the leaching process 6, the leach slurry 7 is treated to recover heat from the leach slurry 7. To this end, the leach solution 7 is subjected to a heat exchange process using a stream generated in another part of the method 2 (e.g. the sodium carbonate recycle stream 14 entering the leaching process 6).

[0335] In another embodiment of the invention shown, at the end of the leaching process 6, the leach slurry 7 is treated to recover heat from the leach slurry 7. To this end, the leach slurry 7 is subjected to a heat exchange process using a stream generated in another part of the method 2 (e.g., the bicarbonate solution stream 19 containing dissolved lithium entering the leaching process 6).

[0336] At the end of the leaching process 6, the leach slurry 7 containing lithium carbonate (both in aqueous and solid form) and one or more zeolites (sodium aluminum silicate) in solid form is introduced into a carbonation process 8. The purpose of the carbonation process 8 is to convert the lithium carbonate in the leach slurry 7 into soluble lithium bicarbonate by reacting the lithium carbonate with carbon dioxide 12.

[0337] The lithium carbonate converted into lithium bicarbonate can be solid lithium carbonate in the leach slurry 7, an aqueous lithium carbonate solution, or a combination of the two.

[0338] Figure 1 The carbonation process 8 in the illustrated embodiment is carried out at a temperature not exceeding about 50°C and at substantially atmospheric pressure.

[0339] The leach solution 9 exiting the carbonization process 8 is in the form of an aqueous lithium bicarbonate solution and a solid leach residue 20. The leach solution 9 is then subjected to a solid-liquid separation process 16 to separate the solid leach residue 20 from the leach solution 9, thereby producing a leach solution 19 having a high lithium concentration.

[0340] The solid-liquid separation process 16 includes a filtration process that is performed to separate the clarified leach solution 19 from the solid leach residue 20 .

[0341] exist Figure 1 In the embodiment of the invention shown, the solid leach residue 20, once separated from the leach solution 9, is subjected to washing 18 to remove at least a portion of the soluble matter present thereon.

[0342] The solid leach residue 20 forms the tailings product from the extraction process 2. The leach residue 20 contains a relatively high concentration of zeolite 24.

[0343] After the solid-liquid separation process 16, the leach solution 19 is relatively free of solids and has a relatively high lithium concentration. Therefore, the leach solution 19 can be subjected to a precipitation step 26 in the presence of sodium hydroxide 22 to precipitate lithium from the leach solution 19 in the form of relatively insoluble lithium carbonate. Figure 1 In the embodiment, the precipitation step 26 is carried out at a temperature of about 50°C.

[0344] After the precipitation step 26, the leach solution 27 comprises solid lithium carbonate in an aqueous sodium carbonate solution. The leach solution 27 is subjected to a further solid-liquid separation step 28 to produce solid lithium carbonate 31 and a carbonate recycle stream 14 which is recycled to the leaching process 6 for use as a lixiviant.

[0345] exist Figure 1 In the embodiment of the present invention, the temperature of the recycle stream 14 returning to the leaching process 6 is relatively low, allowing the recycle stream 14 to be used in a heat exchange process. Specifically, heat from the relatively hot leach solution 7 leaving the leaching process 6 is exchanged with the recycle stream 19. In this way, the leach solution 7 leaving the leaching process 6 can be cooled and the stream 19 can be heated, thereby reducing or eliminating the need for an external heat source.

[0346] exist Figure 1 In the process, the precipitated lithium carbonate 31 is washed and dehydrated 34 to produce a relatively pure lithium carbonate product 36.

[0347] Figure 2 A method 40 of extracting lithium according to an embodiment of the present invention is shown.

[0348] Specifically, Figure 2 Involving a similar Figure 1 The method uses an original lithium raw material 42 and an atmospheric leaching process 44, but the final product is a lithium hydroxide product 72.

[0349] Figure 2A method 40 for extracting lithium according to an embodiment of the present invention is shown. In this method, a lithium feedstock 42 comprises a solid and a liquid suspension 43. The conversion of the lithium feedstock 42 into the solid and liquid suspended lithium-containing material 43 is conventional and requires no further discussion.

[0350] The lithium-containing material 43 is subjected to a leaching process 44, which is carried out at atmospheric pressure in the presence of sodium carbonate 48. Figure 2 In the embodiment of the present invention shown, the lithium-bearing material 43 is introduced into a lixiviant containing an aqueous sodium carbonate solution 48. Generally, the concentration of sodium carbonate 48 in the lixiviant is between 30 g / L and 300 g / L, it being understood that the concentration of sodium carbonate 48 in the lixiviant depends, at least in part, on the concentration of lithium in the lithium-bearing material 42.

[0351] The leaching process 44 is carried out in a continuous stirred tank reactor at 101.325 kPa and a temperature greater than 80° C. but less than 160° C. The temperature of the leaching process 44 is set to be lower than but relatively close to the boiling point of the leaching agent.

[0352] The residence time of the lithium-containing material 43 in the leaching process 44 will depend on many factors, including the amount of lithium in the lithium-containing material 42, the concentration of sodium carbonate in the leaching agent, the pressure and temperature at which the leaching process 44 is conducted, the size of the leaching vessel, etc. However, it should be understood that the residence time of the lithium-containing material 43 in the leaching process 44 will be determined, at least in part, by the time it takes to extract substantially all, or at least a majority, of the lithium from the lithium-containing material 43.

[0353] However, with Figure 1 Instead, the leach solution 47 is subjected to a solid-liquid separation process 49 (in the form of a filtration process, a countercurrent decantation process (e.g., using a thickener), etc.) to separate the solid leach residue (containing lithium carbonate) from the leach solution 47. The separated liquid 46 (having a relatively high sodium carbonate content) is returned to the leaching process 44 as a leachant.

[0354] In the hydroxide ion (and, in Figure 2 In the embodiment shown, the solid leach residue is subjected to a second leaching process 52 in the presence of calcium hydroxide ions 54 to produce a leach solution 56 comprising an aqueous solution of lithium hydroxide.

[0355] The leach solution 56 also contains solid leach residue, which includes calcium carbonate and sodium compounds. Therefore, the leach solution 56 is subjected to a further solid-liquid separation process 61 (in the form of a filtration process) to separate the solid leach residue 58 from the leach solution 56, thereby producing a lithium leach solution that is relatively free of solids 63.

[0356] exist Figure 2In the illustrated embodiment of the invention, solid leach residue 58 forms a by-product of the extraction process 40. Specifically, solid leach residue 58 comprises, at least in part, calcite and zeolite 60.

[0357] Prior to producing the solid lithium hydroxide product 72, the lithium hydroxide solution 63 undergoes a purification step 64 in the form of partial evaporation to crystallize relatively high purity lithium hydroxide monohydrate 68. Additionally, the lithium hydroxide solution stream 65 undergoes a crystallization process 68 in the form of sublimation or precipitation 66 to produce lithium hydroxide crystals 69, which form the solid lithium hydroxide product 72.

[0358] In another embodiment of the present invention, the lithium hydroxide solution 63 undergoes a purification step 64 in the form of partial evaporation to crystallize relatively high purity lithium hydroxide monohydrate 68. The purification step 64 may include an ion exchange process to remove divalent and trivalent cations before the lithium hydroxide solution stream 65 undergoes the crystallization process 68.

[0359] Figure 3 A method 112 of extracting lithium according to an embodiment of the present invention is shown.

[0360] Specifically, Figure 3 The lithium-containing solid 114 in the embodiment is an alpha spodumene material 114 (e.g., ore). Prior to leaching 116, the alpha spodumene material 114 is converted to a beta spodumene material 120 by roasting or calcining the alpha spodumene material 114 at a temperature between 900° C. and 1100° C. until substantially all of the alpha spodumene 114 is converted to beta spodumene 118.

[0361] The hot beta spodumene 118 may then undergo a leaching process 120 to compare with the reference Figure 1 The same manner as described produces a partially leached and ground lithium carbonate-containing solid 122.

[0362] The partially leached solids 122 comprising lithium carbonate are subjected to a classification process and a grinding process 124. In a specific embodiment 112, the grinding process is a wet grinding process, in particular a ball milling process.

[0363] The partially leached and ground solids in the carbonate solution 125 undergo a secondary leaching process 126 to compare with the reference Figure 1 The same process produces leached solids 122 containing lithium carbonate.

[0364] At the end of the leaching process 126, the leach solution 127 containing lithium carbonate (both in aqueous and solid form) and zeolite (sodium aluminum silicate) is introduced into a carbonation process 130. The purpose of the carbonation process 130 is to convert the lithium carbonate in the leach solution 127 into soluble lithium bicarbonate by reacting the lithium carbonate with carbon dioxide 132.

[0365] The bicarbonate solution containing dissolved lithium 133 is then subjected to solid-liquid separation 134 to obtain a leached residue solid 138 containing zeolite 140 and a bicarbonate solution containing dissolved lithium 143. The bicarbonate solution containing dissolved lithium 143 is heated to a temperature of 100°C in the presence of sodium hydroxide 142. Figure 1 The same manner as described above is followed by the precipitation process 144 .

[0366] The lithium carbonate solids suspended in the leach solution 145 are subjected to a solid-liquid separation process 146 (in the form of a filtration process) to separate the solid leach residue (containing lithium carbonate 150) from the leach solution 146. The separated liquid 136 (relatively high in sodium carbonate) is returned to the leaching process 120 as a leachant.

[0367] The lithium carbonate solids 150 collected from the separation process 146 undergo washing and dehydration 152 to produce relatively pure lithium carbonate solids 156 ready for use as lithium carbonate product 160 .

[0368] Figure 4 A method 162 of extracting lithium according to an embodiment of the present invention is shown.

[0369] Specifically, Figure 4 A method similar to Figure 3 The use of alpha spodumene starting material 164 and conversion process 168, but Figure 4 The method shown is performed using cooled beta spodumene 170.

[0370] Specifically, Figure 4 The lithium source material 166 in the process is an alpha spodumene material 164 (e.g., ore). Prior to leaching 176, the alpha spodumene material 164 is converted to a beta spodumene material 170 by roasting or calcining 168 the alpha spodumene material 166 at a temperature between 900° C. and 1100° C. until substantially all of the alpha spodumene 164 is converted to beta spodumene 170.

[0371] The beta spodumene material 170 exiting the roaster or calciner 168 is cooled before undergoing a crushing (grinding) and classification (screening) process 172 to separate relatively fine beta spodumene particles 174 from relatively coarse beta spodumene particles. The relatively coarse beta spodumene particles can be recycled to the crushing and classification process 172 to produce relatively fine beta spodumene particles 174, or can be discarded depending on the type of material.

[0372] The fine beta spodumene particles 174 can then undergo a leaching process 176 to compare with the reference Figure 1 The same approach ultimately produces relatively high purity lithium carbonate 178.

[0373] Figure 5 A method 74 of extracting lithium according to an embodiment of the present invention is shown.

[0374] Specifically, Figure 5 A method similar to Figure 3 alpha spodumene starting material 76 is used, but in this embodiment, the hot beta spodumene 80 is immediately subjected to an atmospheric leaching process 84.

[0375] For reference Figure 3 The alpha spodumene 76 raw material is converted 78 to hot beta spodumene 80 in the same manner as described.

[0376] To utilize the available thermal energy, the hot beta spodumene 80 is then subjected to a leaching process 84 where it may then be subjected to an optional wet grinding and classification process 86 and then to a reference Figure 1 The same process continues to ultimately produce relatively high purity lithium carbonate 110.

[0377] When the optional wet grinding and classification process 86 is included, the coarse solids separated from the classification process 86 may be recycled 88 back to the atmospheric leaching process 84 for further processing.

[0378] Figure 6 A method 180 of extracting lithium according to an embodiment of the present invention is shown.

[0379] Specifically, Figure 6 A method similar to Figure 4 alpha spodumene starting material 182 is used, but in this embodiment, cooled beta spodumene 188 is subjected to a wet grinding process and a classification process 190 immediately prior to an atmospheric pressure leaching process 194.

[0380] Lithium-containing solid 184 with the previous Figure 4 The same manner is followed by a calcination process 186 to produce cooled beta spodumene 188 .

[0381] The beta spodumene material 188 exiting the roaster or calciner 186 is cooled before undergoing a crushing (grinding) process and a classification (screening) process 190 to separate relatively fine beta spodumene particles 192 from relatively coarse beta spodumene particles. The relatively coarse beta spodumene particles can be recycled to the crushing and classification process 190 to produce relatively fine beta spodumene particles 192, or can be discarded depending on the type of material.

[0382] The fine beta spodumene particles 192 can then undergo a leaching process 194 to compare with the reference Figure 1 The same approach ultimately produces relatively high-purity lithium carbonate 199.

[0383] exist Figure 6 In the depicted embodiment of the invention, the solid-liquid separation process 196 may recycle the carbonate leach solution 198 back to the wet grinding and classification process 190 .

[0384] Figure 7 A method 200 for extracting lithium according to an embodiment of the present invention is shown. In this method, a lithium-containing material 205 containing alpha spodumene is fed to a spodumene conversion process 210 to convert at least a portion of the alpha spodumene present in the lithium-containing material 205 into beta spodumene 215.

[0385] The conversion of a portion of the alpha spodumene present in the lithium-containing material 205 to the beta spodumene 215 includes a calcination process step at a high temperature of about 900°C to 1100°C.

[0386] The lithium-containing material 215 containing beta spodumene is cooled and then undergoes a pulverizing step 220 to reduce the particle size of the lithium-containing material 215 .

[0387] After the comminution step 220, the lithium-containing material 215 undergoes a leaching process 230, which is carried out at atmospheric pressure in the presence of a sodium carbonate solution, preferably an aqueous sodium carbonate solution 221. The leaching process 230 can be carried out at a temperature between about 80°C and 160°C, however, Figure 7 In the illustrated embodiment of the invention, the leaching process 230 may be conducted at a temperature not exceeding 100° C. to avoid the use of an autoclave.

[0388] In the leaching process 230, a leaching reaction occurs, extracting lithium from the beta spodumene by exchanging lithium ions with sodium ions. The lithium carbonate produced in the leaching process 230 exists in the form of a precipitated solid and / or an aqueous solution in the leaching slurry 235.

[0389] The leach slurry 235 is then introduced into a solid-liquid separation process 240 to separate a clarified leach solution 242 from the leached solids 245. At least a portion of the clarified leach solution 242 is recycled to the comminution step 220 to be used again in the leaching process 230.

[0390] The leached solids 245, once separated from the clarified leach solution 242, may be washed or otherwise cleaned to remove at least a portion of the soluble matter present thereon.

[0391] The leached solids 245 are introduced into a reslurry process 250 in the presence of a recycled sodium carbonate solution 252. The reslurry process 250 is carried out at a temperature of about 90° C. The temperature of the reslurry 254 is cooled to a temperature below 40° C. before entering the carbon dioxide leaching process 260.

[0392] Next, the slurry 254 from the reslurry process 250 is subjected to a carbon dioxide leaching process 260 to convert at least a portion of the lithium carbonate in the slurry 254 to lithium bicarbonate. The carbon dioxide leaching process 260 can be performed at atmospheric pressure in a continuous stirred tank reactor or an autoclave.

[0393] After the CO2 leaching process 260, the slurry from the CO2 leaching process 260 is subjected to a solid-liquid separation process 270 to separate the leach residue 275 from the leach slurry. Once separated from the leach slurry, the leach residue 275 is washed or otherwise cleaned to remove at least a portion of the soluble matter present thereon.

[0394] The leach residue 275 contains a relatively high concentration of zeolite.

[0395] After the solid-liquid separation process 270, the leach solution 276 is relatively free of solids and has a relatively high concentration of soluble lithium. Lithium is then precipitated from the leach solution 276 as lithium carbonate by introducing sodium hydroxide 278 into a precipitation process 280.

[0396] Additional heat is applied to promote the reactions of the precipitation process 280. The controlled addition of heat ensures that lithium is effectively removed from the leach solution in the form of lithium carbonate.

[0397] This reaction produces a small amount of soluble sodium carbonate as a by-product. However, the sodium carbonate can be recycled back to the repulping process 250 as a leaching agent, improving the overall efficiency and sustainability of the process by minimizing waste.

[0398] In a subsequent solid-liquid separation process 290, the precipitated lithium carbonate 295 is separated from the carbonate leach solution 252 by thickening and / or filtration. The lithium carbonate 295 is washed 300 with water and filtered to produce a moist lithium carbonate filter cake 305.

[0399] In this specification and claims (if any), the word "comprising" and its derivatives including "comprises" and "comprise" include each stated integer but do not exclude the inclusion of one or more additional integers.

[0400] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner, in one or more combinations.

[0401] The present invention has been described in language that is more or less specific to structural or methodological features, as required by law. It should be understood that the invention is not limited to the specific features shown or described, as the means herein described comprise preferred forms of carrying out the invention. The invention is therefore claimed in any form or modification within the proper scope of the appended claims (if any) as appropriately interpreted by one skilled in the art.

Claims

1. A method for extracting lithium from a hard rock lithium mineral, the method comprising: The lithium-containing material is subjected to a leaching process in the presence of carbonate ions at atmospheric pressure at a temperature above 50°C but below 160°C to produce a leach slurry containing lithium carbonate.

2. The method of claim 1, wherein the hard rock lithium mineral comprises spodumene, lepidolite, eucryptite, petalite, a lithium-containing silicate material, or a combination thereof.

3. A method for extracting lithium, comprising the following steps: subjecting the lithium-containing material to a leaching process in the presence of carbonate ions at atmospheric pressure and at an elevated temperature greater than 50° C. but less than 160° C. to produce a leach slurry containing lithium carbonate; subjecting the leachate slurry to a carbonation process to convert at least a portion of the lithium carbonate into lithium bicarbonate; performing a solid-liquid separation process on the leach slurry to separate the leach residue from the leach solution; obtaining solid lithium carbonate from the leaching solution; and Solid lithium carbonate is separated from the leach solution.

4. The method of claim 3, wherein the lithium-containing material comprises a hard rock lithium material.

5. The method according to claim 3 or 4, wherein at least a portion of the lithium in the lithium-containing material is in the form of spodumene.

6. The method of claim 5, wherein the spodumene present in the lithium-containing material is in the form of alpha spodumene, beta spodumene, or a combination thereof.

7. A method according to any one of the preceding claims, wherein the lithium-containing material is subjected to one or more treatment steps prior to the leaching step.

8. The method of claim 7, wherein one of the one or more processing steps comprises a comminution step, a separation step or a classification step.

9. The method of claim 6, wherein the lithium-containing material undergoes a conversion step to convert at least a portion of the alpha spodumene present in the lithium-containing material to beta spodumene.

10. The method of claim 9, wherein the converting step comprises a heat treatment step.

11. The method according to claim 10, wherein the heat treatment step is a roasting process or a calcining process performed at a high temperature to convert at least a portion of the alpha spodumene into beta spodumene.

12. The method of claim 11, wherein the elevated temperature is about 800°C to 1200°C.

13. The method according to any one of claims 10 to 12, wherein the length of the heat treatment process depends on the amount of lithium minerals present in the lithium-containing material, the particle size of the lithium-containing material or the minerals present in the lithium-containing material.

14. The method according to any one of claims 10 to 13, wherein the lithium-containing material is cooled after the heat treatment step.

15. The method according to any one of claims 10 to 14, wherein the lithium-containing material that has been subjected to the heat treatment step is subjected to one or more comminution processes and / or one or more classification processes prior to the leaching process.

16. A method according to claim 15, wherein relatively fine particles of lithium-containing material are introduced into the leaching process.

17. The method according to any one of claims 3 to 16, wherein the high temperature of the leaching process is controlled using electric heating means, direct steam injection or indirect steam heating.

18. A process according to any one of claims 3 to 17, wherein the elevated temperature of the leaching process is controlled at least in part by heat exchange between relatively cool leach solution recycled from another point in the process and relatively hot leach slurry leaving the leaching process.

19. The method according to any one of claims 3 to 18, wherein In the leaching process, the lithium-containing material is introduced into a leaching agent containing carbonate ions.

20. The method of claim 19, wherein the leaching agent is an aqueous solution of carbonate ions.

21. A method according to claim 19 or 20, wherein the leaching agent comprises an alkali metal cation.

22. The method of claim 21, wherein the alkali metal cations comprise sodium ions and / or potassium ions.

23. The method of any one of claims 19 to 22, wherein the concentration of carbonate ions in the lixiviant is between about 6 g / L and 288 g / L.

24. The method according to any one of claims 3 to 23, wherein the leaching of the lithium-containing material is carried out according to the following reaction: 4LiAl(SiO3)2+2Na2CO3+4SiO2+7H2O=2Na2Al2(Si3O8)2·7H2O+2Li2CO3.

25. A method according to any one of claims 3 to 24, wherein the lithium carbonate is present in the leach slurry in both solid and aqueous form.

26. A method according to any one of claims 3 to 25, wherein at the end of the leaching process the leach slurry is treated to recover heat.

27. The method of claim 26, wherein heat is recovered using a heat exchange process.

28. A method according to any one of claims 3 to 27, wherein a reactant is used in the carbonation process.

29. The method of claim 28, wherein the reactant is a carbon-containing gas.

30. The process according to any one of claims 3 to 29, wherein the lithium carbonate is converted to lithium bicarbonate according to the following reaction: Li2CO3+CO2+H2O=2LiHCO3.

31. The method of any one of claims 3 to 30, wherein the carbonation process is performed at a temperature not exceeding about 70°C.

32. The method of any one of claims 3 to 31 , wherein the carbonation process is carried out at atmospheric pressure.

33. The method of any one of claims 3 to 32, wherein the carbonation process is carried out at a pressure above atmospheric pressure.

34. The method according to any one of claims 3 to 33, wherein the carbonation process is carried out in an autoclave, an adsorption column or a deep stirred tank.

35. The method of any one of claims 3 to 34, wherein the carbonation process extracts at least 70% of the lithium in the leach slurry.

36. The method of any one of claims 3 to 35, wherein the leach solution is relatively free of solids.

37. The method according to any one of claims 3 to 36, wherein the solid-liquid separation process comprises a filtration process, an evaporation process, a drying process, a sedimentation process or a countercurrent decantation process.

38. A method according to any one of claims 3 to 37, wherein Once separated from the leach solution, the leach residue is washed or otherwise cleaned to remove at least a portion of the soluble matter present thereon.

39. The method of any one of claims 3 to 38, wherein the leach residue is filtered to produce a filtered tailings product.

40. The method of claim 39, wherein the filtered tailings product is a non-hazardous by-product.

41. The method of claim 40, wherein the non-hazardous by-product provides material for a cementitious filler mixture.

42. The method according to any one of claims 3 to 41, wherein the solid lithium carbonate is obtained by a precipitation reaction.

43. The method of claim 42, wherein the precipitation reaction introduces a compound into the leach solution to convert soluble lithium bicarbonate into relatively insoluble lithium carbonate.

44. The method of claim 43, wherein the compound is a hydroxide.

45. The method of claim 44, wherein the hydroxide is sodium hydroxide or potassium hydroxide.

46. ​​A method according to any one of claims 3 to 45, wherein Once the solid lithium carbonate is separated from the leach solution, the leach solution is returned to the leaching process.

47. The process of claim 46, wherein the precipitation of lithium carbonate is carried out at an elevated temperature of about 30°C to 99°C.

48. The method of claim 47, wherein the elevated temperature is achieved using a heat exchange process using a heat exchange fluid.

49. The method of claim 48, wherein the heat exchange fluid comprises the leach slurry exiting the leaching process.

50. The method according to any one of claims 3 to 49, wherein the solid lithium carbonate is separated from the leach solution using a filtration process, an evaporation process, a drying process.

51. A method according to any one of claims 3 to 49, wherein the solid lithium carbonate is separated from the leach solution using a settling or thickening process to produce a clarified leach solution.

52. The method of claim 50, wherein the filtration process separates the solid lithium carbonate into a filter cake.

53. The method of claim 52, wherein the filtrate solution produced in the filtration process is recycled to the leaching process as a carbonate leach solution.

54. A method for extracting lithium, the method comprising the steps of: subjecting the lithium-containing material to a first leaching process in the presence of carbonate ions at atmospheric pressure to produce lithium carbonate; subjecting the lithium carbonate to a second leaching process in the presence of hydroxide ions to produce a leach slurry comprising an aqueous solution of lithium hydroxide; separating a solid leach residue from the leach slurry to produce a relatively solids-free lithium hydroxide solution; and A solid lithium hydroxide product is produced from the relatively solids-free lithium hydroxide solution.

55. The method of claim 54, wherein the lithium-bearing material comprises a hard rock lithium mineral.

56. The method of claim 54 or 55, wherein at least a portion of the lithium in the lithium-containing material is in the form of spodumene.

57. The method of claim 56, wherein the spodumene present in the lithium-containing material is in the form of alpha spodumene, beta spodumene, or a combination thereof.

58. A method according to any one of claims 54 to 57, wherein the lithium-containing material is subjected to one or more treatment steps prior to the leaching step.

59. The method of claim 58, wherein one of the one or more processing steps comprises a comminution step, a separation step, or a classification step.

60. The method of claim 57, wherein the lithium-containing material undergoes a conversion step to convert at least a portion of the alpha spodumene present in the lithium-containing material to beta spodumene.

61. The method of claim 60, wherein the converting step comprises a heat treatment step.

62. The method of claim 60 or 61, wherein the converting step is a roasting process or a calcining process performed at a high temperature.

63. The method of claim 62, wherein the elevated temperature is about 800°C to 1200°C.

64. A method according to any one of claims 60 to 63, wherein the lithium-containing material that has been subjected to the conversion step is subjected to one or more comminution processes and / or one or more classification processes prior to the first leaching process.

65. A method according to any one of claims 60 to 64, wherein at least 70% of the alpha spodumene present in the lithium-containing material is converted to beta spodumene in the converting step.

66. A method according to any one of claims 54 to 65, wherein relatively fine particles of the lithium-containing material are introduced into the first leaching process.

67. The method of any one of claims 54 to 66, wherein the first leaching process is performed at an elevated temperature.

68. The method of claim 67, wherein the elevated temperature is greater than 50°C but less than 160°C.

69. The method of any one of claims 54 to 68, wherein the lithium-containing material is leached in the first leaching process using a leaching agent containing carbonate ions.

70. The method of claim 69, wherein the leaching agent comprises carbonate anions and alkali metal cations.

71. The method of claim 70, wherein the alkali metal cation comprises a sodium ion.

72. The method of any one of claims 69 to 71, wherein the concentration of carbonate ions in the lixiviant is between about 17 g / L and 288 g / L.

73. The method of any one of claims 54 to 72, wherein the first leaching process is performed according to the following reaction: 4LiAl(SiO3)2+2Na2CO3+4SiO2+7H2O=2Na2Al2(Si3O8)2·7H2O+2Li2CO3.

74. A process according to any one of claims 54 to 73, wherein the lithium carbonate is present in the leach slurry as a precipitated solid and / or as an aqueous solution.

75. A method according to any one of claims 54 to 74, wherein the leach slurry is treated at the end of the first leaching process to recover heat.

76. The method of claim 75, wherein heat is recovered using a heat exchange process using a heat exchange fluid.

77. The method of claim 76, wherein the heat exchange fluid is a process stream generated or used in another part of the method.

78. The method of claim 54, wherein the stream exiting the first leaching process comprises leached solids comprising lithium carbonate.

79. The method of claim 78, wherein the stream exiting the first leaching process is subjected to a solid-liquid separation process to recover leached solids.

80. The method of any one of claims 54 to 79, wherein the second leaching process is performed at atmospheric pressure.

81. The method of any one of claims 54 to 80, wherein the second leaching process is performed at a temperature not exceeding about 70°C.

82. The method of any one of claims 54 to 81, wherein the second leaching process is carried out in the presence of cations that form substantially insoluble carbonate compounds.

83. The method of claim 82, wherein the cation is a cation of barium, calcium, strontium and / or magnesium.

84. The method of claim 83, wherein at least a portion of the product of the second leaching process is precipitated calcium carbonate, barium carbonate, strontium carbonate and / or magnesium carbonate.

85. A method according to any one of claims 54 to 84, wherein a solid-liquid separation process is performed to separate the solid leach residue from the relatively solids-free lithium hydroxide solution.

86. The method of claim 85, wherein the solid-liquid separation process comprises a filtration process, an evaporation process, a drying process, a sedimentation process, or a countercurrent decantation process.

87. The method according to any one of claims 54 to 86, wherein Once separated from the relatively solids-free lithium hydroxide solution, the solid leach residue is washed or otherwise cleaned to remove at least a portion of the soluble material present thereon.

88. The method of any one of claims 54 to 87, wherein the solid leach residue is a non-hazardous by-product, at least a portion of which comprises calcite and / or one or more zeolites.

89. The process of any one of claims 54 to 88, wherein the solid lithium hydroxide product is in the form of crystalline lithium hydroxide.

90. The process of any one of claims 54 to 89, wherein the relatively solids-free lithium hydroxide solution is subjected to a purification step prior to producing the solid lithium hydroxide product.

91. The method of claim 90, wherein the lithium hydroxide solution is partially evaporated to crystallize relatively high purity lithium hydroxide monohydrate.

92. The method of claim 91, wherein the lithium hydroxide solution undergoes a crystallization process to produce lithium hydroxide crystals to form a solid lithium hydroxide product.

93. The method of claim 92, wherein the crystallization process is vapor recompression crystallization.

94. The method of claim 93, wherein the purification step comprises an ion exchange process to remove divalent and trivalent cations prior to subjecting the lithium hydroxide solution stream to a crystallization process.

95. A method for extracting lithium, the method comprising the steps of: subjecting a material containing alpha spodumene to a conversion process at atmospheric pressure to convert at least a portion of the alpha spodumene to beta spodumene; subjecting the beta spodumene to a leaching process in the presence of carbonate ions at atmospheric pressure to produce a leach solution and a leach solid comprising lithium carbonate; subjecting the leached solid containing lithium carbonate to a comminution process and / or a classification process in a solution containing carbonate ions to produce a leaching slurry containing relatively fine solids; subjecting the leachate slurry to a carbonation process to convert at least a portion of the lithium carbonate into lithium bicarbonate; performing a solid-liquid separation process on the leach slurry to separate the leach residue from the leach solution; obtaining solid lithium carbonate from the leaching solution; and The solid lithium carbonate is separated from the leach solution.

96. A method for extracting lithium, the method comprising the steps of: subjecting a material containing alpha spodumene to a conversion process at atmospheric pressure to convert at least a portion of the alpha spodumene to beta spodumene; subjecting the beta spodumene to a grinding process to produce ground beta spodumene; subjecting the ground beta spodumene to a leaching process in the presence of carbonate ions at atmospheric pressure to produce a leach slurry containing lithium carbonate and leach solids; subjecting the leachate slurry to a carbonation process to convert at least a portion of the lithium carbonate into lithium bicarbonate; performing a solid-liquid separation process on the leach slurry to separate the leach residue from the leach solution; obtaining solid lithium carbonate from the leaching solution; and Solid lithium carbonate is separated from the leach solution.

97. A method for extracting lithium, the method comprising the steps of: subjecting a lithium-containing material containing beta spodumene to a leaching process in the presence of carbonate ions at atmospheric pressure to produce a leach slurry comprising lithium carbonate; subjecting the leach slurry to a carbon dioxide leaching process to produce a bicarbonate leach slurry, wherein at least a portion of the lithium carbonate is converted into lithium bicarbonate; performing a solid-liquid separation process on the bicarbonate leach slurry to separate the leach residue from the leach solution; precipitating lithium carbonate from the leach solution; and The precipitated lithium carbonate is separated from the leach solution.

98. A method for extracting lithium, the method comprising the steps of: subjecting a lithium-containing material containing beta spodumene to a leaching process in the presence of carbonate ions at atmospheric pressure to produce a first leach slurry comprising lithium carbonate; performing a solid-liquid separation process on the first leach slurry to separate a first leach residue from the first leach solution; subjecting the first leach residue to a reslurry process in the presence of carbonate ions to produce a second leach slurry; subjecting the second leach slurry to a carbon dioxide leaching process to produce a bicarbonate leach slurry, wherein at least a portion of the lithium carbonate is converted to lithium bicarbonate; performing a solid-liquid separation process on the bicarbonate leach slurry to separate a second leach residue from a second leach solution; precipitating lithium carbonate from the second leach solution; and The precipitated lithium carbonate is separated from the second leach solution.

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