Method for recovering lithium from lithium-containing stream

Abstract

The present invention relates to a process for recovering lithium from a lithium-containing stream, the process comprising contacting the stream or a pretreated solution obtained from said stream with sodium aluminate at an alkaline pH to form a slurry comprising a lithium aluminate precipitate; and recovering the slurry containing the lithium aluminate or a precipitate thereof.

Description

Technical Field

[0001] The present invention relates to a method for recovering lithium from a lithium-containing stream obtained by processing ores, brines or recycled materials such as battery waste.

[0002] Specifically, the present invention relates to the above method related to a soda-leaching process, wherein the lithium-containing stream is a part obtained from the soda-leaching process, lithium is recovered from this stream by the above method for recovering lithium, and the recovered lithium is returned to the soda-leaching process. Background Art

[0003] Lithium (Li) is a metal used in batteries and currently, the mining and processing of lithium have attracted much attention. The main sources of lithium include brines and ores, and at the same time, the recycling of various lithium-containing materials (such as battery waste) is also increasing.

[0004] Processes for treating lithium-containing mineral raw materials (such as rocks, ores, clays or concentrates) generally include first heat-treating these rocks at high temperature and then performing water leaching to release lithium into the solution. Brines are usually concentrated before further processing. Then the leachate or concentrated brine is further treated using precipitation, ion exchange, etc. to remove residual contaminants. Carbonation using soda ash or carbon dioxide usually precipitates lithium carbonate as the final product, while lithium hydroxide (LiOH) is usually recovered by crystallization or electrodialysis, for example using bipolar membranes.

[0005] However, especially in the LiOH route, after crystallization and removal of the main product in solid form, a large amount of lithium still remains in the solution, and the remaining solution usually still contains about 30 g / l of lithium. A possible method for recovering the remaining lithium from this solution is to use lithium carbonate and / or phosphate precipitation, which can reduce the lithium concentration in the solution. When using a combination of carbonate and phosphate precipitation, a level of 250 mg / l can be achieved, which seems to be the lowest level guaranteed by this method. However, current environmental issues mean that lower lithium levels in the process effluent would be beneficial. In addition, the effluent from lithium phosphate precipitation usually contains residual phosphate, which should not be released into nature.

[0006] Other existing techniques for treating effluents from lithium processing mainly involve evaporation and crystallization of the final waste and effluents. However, this method is known to be very expensive and requires more space than simple precipitation processes. In addition, evaporation and crystallization can take a long time, which also increases the risk of leakage into nature, for example due to heavy rain. Ion exchange can also be used, but its disadvantage is that the effluent may contain other harmful components, such as chlorides. Ettringite can also be used, but it is usually not even considered because it produces a mixture of impurities in the sludge, and the treatment of which is another problem.

[0007] Document EP 963950 describes a method for preparing layered AlLiO 2 by reacting an aqueous solution containing at least one lithium salt produced on zeolite by industrial ion exchange with a sodium aluminate solution, and then separating the formed layered lithium aluminate at pH 6 - 13. The pH value can be adjusted with sulfuric acid. However, this method requires a high-purity aqueous solution in order to be able to synthesize a clean (pristine) layered product.

[0008] Therefore, current solutions are generally not very efficient in recovering lithium, and usually recover lithium containing different impurities (such as chlorides or sulfates), which cannot be completely washed out from the obtained lithium precipitate, and these impurities will eventually enter the further processes using the recovered lithium.

[0009] Therefore, there is a need to provide a suitable method for effectively recovering lithium without carrying unwanted impurities, while reducing the amount of lithium in the lithium-containing solution to a level below 200 mg / l, and in particular without generating new problematic effluents or wastes. Another objective is to provide such a method that simultaneously uses the smallest amount of materials not yet used in current methods. Preferably, the method will be applicable to existing processes using existing equipment, and furthermore, it will preferably help to minimize the use of harmful chemicals (which may be used in other known processes), and avoid any other harmful compounds in the recovered lithium precipitate and the final waste / effluent. In addition, such a method will maximize the recovery of lithium from common raw materials. Summary of the Invention

[0010] The present invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0011] According to a first aspect, there is provided a method for recovering lithium from a lithium-containing stream, the method comprising:

[0012] - contacting the stream or a pre-treated solution obtained from the stream with sodium aluminate at an alkaline pH to form a slurry containing a lithium aluminate precipitate;

[0013] - Adjust the pH value of the obtained slurry to a level of 8 - 13 using carbon dioxide to promote the precipitation of lithium aluminate; and

[0014] - Recover the slurry containing the lithium aluminate or the precipitate separated therefrom.

[0015] According to a second aspect, there is provided a method for soda leaching a lithium-containing raw material and recovering lithium therefrom, the method comprising the following steps:

[0016] - Pulping a lithium-containing raw material selected from optionally calcined ores, recycled materials or combinations thereof to form a water-containing slurry containing lithium;

[0017] - Leaching the slurry to form a partially dissolved lithium-containing slurry;

[0018] - Optionally performing further processing steps to adjust the lithium content of the formed lithium-containing slurry; and

[0019] - Product recovery, thereby precipitating lithium and leaving a solution containing trace amounts of lithium,

[0020] wherein at least a portion of one or more lithium-containing slurries or solutions is separated from the method and subjected to a method for recovering lithium, and thereafter, the recovered slurry containing lithium aluminate or the precipitate separated therefrom is returned to the pulping or leaching step of the method. Detailed Embodiments

[0021] As used herein, the term "mineral" includes materials obtained from the processing of metal-containing ores or rocks. The present invention particularly relates to lithium-containing minerals such as spodumene, petalite, lepidolite or zinnwaldite, or mixtures thereof. Unless otherwise stated, any percentages are weight percentages (wt-%, weight / weight). The term "stream" is used to describe the flow of any substance, whether solid or liquid, preferably a water-containing stream such as a slurry, solution, filtrate or mass flow, most preferably a water-containing slurry or solution. The term "effluent" is used to denote any liquid stream obtained from a process, which is usually further processed. The final liquid effluent of the method may also be referred to as the final wastewater.

[0022] The present invention relates to a method for recovering lithium from a lithium-containing stream, the method comprising:

[0023] - At an alkaline pH, contacting the stream or a pre-treated solution obtained from the stream with sodium aluminate to form a slurry containing lithium aluminate precipitate;

[0024] - Adjust the pH value of the obtained slurry to a level of 8 - 13 using carbon dioxide to promote the precipitation of lithium aluminate; and

[0025] - Recycling the slurry containing the lithium aluminate, or the precipitate separated therefrom.

[0026] Accordingly, the present invention provides a method for recovering lithium from a lithium-containing stream to effectively recover lithium without undesirable impurities and further provide a final liquid effluent with a lithium content that meets the strictest environmental specifications. The lithium content in the liquid effluent of this method can be as low as 10 mg / l (i.e., 10 ppm). An optimized method can also remove aluminum in the stream to the extent required by the specifications.

[0027] In particular, the present invention is based on the idea that when sodium aluminate is used as a reagent for a lithium-containing stream to recover lithium in the form of lithium aluminate (LiAlO 2 ), the pH during the lithium precipitation process is controlled and optimized by using carbon dioxide as a pH regulator. Generally, the adjustment of the pH value during the precipitation process significantly enhances the precipitation of lithium aluminate, making the precipitation more efficient. It has been unexpectedly found in the present invention that in the context of lithium precipitation and recovery, this combination of sodium aluminate and carbon dioxide enables the effective recovery of lithium aluminate without generating undesirable impurities, especially considering the soda ash leaching process.

[0028] Therefore, the present invention achieves significant advantages. First, the present invention provides an effective method for recovering lithium in the form of lithium aluminate because it has been found that using carbon dioxide as a pH regulator significantly promotes precipitation by adjusting the pH value to a preferred precipitation level, thereby making the precipitation more effective.

[0029] Typically, hydrochloric acid (HCl) or sulfuric acid (H 2 SO 4 ) is used as a possible pH regulator, and / or an aluminum compound containing chloride or sulfate is used as a reagent to precipitate lithium, where chloride and / or sulfate or other harmful compounds are introduced into the lithium-containing precipitate and they cannot all be washed out of the precipitate. Then, these carried impurities are recycled into further processes that utilize the recovered lithium and are ultimately recycled into the resulting effluent. This results in a high concentration of these impurities in the further processes and the wastewater loop. When sodium aluminate and carbon dioxide are used, only sodium carbonate and sodium bicarbonate are formed as impurities during the precipitation process and thus ultimately enter the slurry containing lithium aluminate or its precipitate. This is particularly advantageous in the soda ash leaching process because when sodium carbonate is used as a reagent in the soda ash leaching, there is already an excessive carbonate load in the loop, and the recovered lithium aluminate does not introduce any new impurities into the soda ash leaching process. Generally speaking, the present invention avoids the use and formation of commonly harmful compounds such as sulfates and chlorides.

[0030] Thus, in a preferred embodiment, the advantage of the method is that it utilizes the same reagents and products that have already been used in the process of treating lithium-containing materials. Thus, the method avoids any further harmful compounds in the final wastewater and other effluents. Additionally, if the stream contains aluminum, it can be removed by the same method.

[0031] Furthermore, according to a preferred embodiment, the method can be used with minimal or no changes to existing process equipment. Additionally, as described below, the final product of the method can be used as-is in further one or more processes.

[0032] The method can be used, for example, as an alternative to lithium phosphate precipitation and achieves a much lower lithium concentration in the final liquid effluent, since this would simply mean replacing the phosphate reagent with an aluminum reagent, namely sodium aluminate, and adding carbon dioxide, without requiring any other process updates. Known lithium phosphate precipitation methods can only achieve a lithium concentration of approximately 250 mg / l in the final wastewater, and residual phosphate is also typically found in the final wastewater (which is also undesirable). The present invention also does not introduce any harmful or unnecessary compounds into the final effluent by using the reaction of sodium aluminate and carbon dioxide.

[0033] Another advantage of the method is that when used to treat the effluent from a lithium recovery device, an increase in the total yield of lithium products is achieved. The combined lithium recovery rate can reach 90% or even higher.

[0034] Compared with traditional waste stream treatment (evaporation and crystallization), another advantage of the method is that it is significantly faster, does not require as much space, has lower environmental risks and lower investment and operating costs. Additionally, the method does not result in the formation of any large amounts of waste like the ettringite process.

[0035] As described above, the method includes the step of contacting a lithium-containing stream or a pretreated solution obtained from said stream with sodium aluminate to form a slurry containing lithium aluminate precipitate, i.e., allowing the reaction to occur. The pH during this step is alkaline, preferably 8 - 13.5, and the reaction time is preferably less than 1 hour, for example 10 - 30 minutes. The reaction can be carried out at any suitable temperature, for example at a temperature of 0 - 100 °C, preferably 0 - 90 °C, more preferably 50 - 90 °C.

[0036] According to one embodiment, the alkaline pH can be provided by the stream or solution itself, or the pH can be adjusted to a suitable level in the form of a pretreatment step, particularly by adding an acid, particularly carbon dioxide, to the stream or solution.

[0037] In one embodiment, the pH of the stream or solution is adjusted to a level of 8 - 12, preferably 8.1 - 12, or 8.2 - 12, or 8.3 - 12, more preferably 8.5 - 11 and most suitably 9 - 11.

[0038] Thus, according to a preferred embodiment, the step of contacting the stream or solution with sodium aluminate is carried out at an alkaline pH of 8 - 12, preferably 8.1 - 12, or 8.2 - 12, or 8.3 - 12, more preferably 8.5 - 11, most suitably 9 - 11. According to one embodiment, such a pH is achieved with carbon dioxide.

[0039] The present invention also includes the step of using carbon dioxide to adjust the pH of the obtained slurry. The pH value of the slurry is adjusted to a level of 8 - 13 with carbon dioxide to promote the precipitation of lithium aluminate. In particular, the pH value of the obtained slurry is adjusted to a level of 8 - 12, preferably 8.1 - 12, or 8.2 - 12, or 8.3 - 12, more preferably 8.5 - 11 and most suitably 9 - 11.

[0040] In one embodiment, the carbon dioxide for pH adjustment is added after the stream or solution has contacted sodium aluminate, and the precipitation reaction continues after the pH is lowered to a suitable level by adding carbon dioxide. In another embodiment, the carbon dioxide for pH adjustment is added at least partially simultaneously with sodium aluminate, such as 20 wt.%, 40 wt.%, 60 wt.%, 80 wt.% or 100 wt.% of carbon dioxide, where the carbon dioxide has been present since the start of precipitation. Thus, in one embodiment, carbon dioxide can be added simultaneously with sodium aluminate and / or after adding sodium aluminate. In both cases, carbon dioxide promotes the precipitation of lithium aluminate.

[0041] In a preferred embodiment, the pH value is adjusted within the range of 9 - 11 with carbon dioxide after the lithium-containing stream or solution has contacted sodium aluminate or simultaneously with the addition of sodium aluminate.

[0042] According to a preferred embodiment, the carbon dioxide for pH adjustment is added in gaseous form, usually using a pressure of 0 - 15 bar(g), more typically using a pressure of 0 - 10 bar(g).

[0043] According to one embodiment, carbon dioxide is gradually added to the obtained slurry, for example, within a time period of 10 - 60 minutes, such as 20 - 40 minutes, such as within 30 minutes.

[0044] As described above, according to one embodiment, the initial pH of the lithium-containing stream can also be adjusted with an acid, in particular carbon dioxide, to obtain the preferred alkaline pH for the step of contacting the stream with sodium aluminate. Thus, in one embodiment, carbon dioxide can be added before and after / simultaneously with the addition of sodium aluminate.

[0045] In a preferred embodiment, only carbon dioxide is used as the pH control agent in the present invention.

[0046] At the end of the process, lithium aluminate precipitate formed in the reaction between the lithium-containing stream or solution and sodium aluminate is typically recovered in the form of a slurry. Lithium aluminate can also be recovered in the form of a precipitate separated from the slurry containing the lithium aluminate.

[0047] Thus, the method includes the step of recovering the slurry containing the lithium aluminate or the precipitate separated therefrom.

[0048] In fact, lithium aluminate is insoluble in water. In one embodiment, the slurry containing lithium aluminate can be recovered by, for example, solid / liquid separation such as filtration, sedimentation or flotation. An exemplary recovery method is dissolved air flotation (DAF).

[0049] In one embodiment, the method can further include a solid / liquid separation step after recovering the slurry, so as to recover the lithium product in the form of a precipitate. Alternatively, the product can be further reacted with another lithium product or further processed, for example, by washing and drying.

[0050] According to one embodiment, the lithium-containing stream is an industrial stream, in particular an effluent from a lithium recovery facility. The lithium recovery facility can include high-temperature conversion of lithium-containing ore and leaching with water, or treatment of brine or recycled materials such as battery waste. When recovering lithium from ore, the lithium recovery facility can, for example, include high-temperature conversion of lithium-containing ore and leaching with water. Such conversion typically includes:

[0051] - calcining the mineral in one or more calcination steps to obtain a calcined lithium-containing material;

[0052] - pulping the calcined material into a slurry, preferably in an aqueous solution together with a leaching reagent;

[0053] - subjecting the formed slurry to water leaching; and

[0054] - separating the lithium-containing solid from the solution containing the leaching reagent in a solid-liquid separation step.

[0055] In one embodiment, the lithium-containing ore is selected from ores containing lithium-containing materials. The lithium-containing materials are preferably selected from spodumene, petalite, lepidolite or triphylite, or mixtures thereof, more preferably spodumene. When the preferred option spodumene is calcined, it becomes more soluble beta-spodumene (β-spodumene). In a particular embodiment, the lithium-containing material is selected from lithium-containing clay materials such as lepidolite, triphylite, masutomilite, swinefordite, hectorite or jadarite, or mixtures thereof.

[0056] The liquid stream obtained from the solid-liquid separation step of the above conversion process is preferably an alkaline solution, more preferably a solution with a pH of 8 - 11.5. As described above, the solution contains one or more carbonates, preferably one or more alkali metal carbonates, such as sodium carbonate (Na 2 CO 3 ).

[0057] In one embodiment, the lithium-containing stream is obtained from a device for soda leaching of a lithium-containing raw material and recovering lithium therefrom.

[0058] However, the lithium-containing stream treated according to the present invention can be obtained from any other industrial process, even if the stream to be treated contains high concentrations of impurities. Common impurities in such industrial lithium-containing streams include, but are not limited to, ions and solutes of sodium (Na), calcium (Ca) or other alkaline earth metals, potassium (K), borates and carbonates. Other possible impurities include soluble silica and silicate substances, phosphates (and hydrogen phosphates) and fluorides (F - ). Generally, silica / silicate, carbonate ions (CO 3 2- ), sodium ions (Na + ) and potassium ions (K + ) are present in the highest amounts. Minor metals that may be present include arsenic (As), vanadium (V), molybdenum (Mo), manganese (Mn) and iron (Fe). None of these prevent the achievement of the above advantages of the present invention, namely achieving a sufficiently low lithium content in the resulting final effluent.

[0059] In one embodiment, the step of contacting the lithium-containing stream or solution with sodium aluminate can be carried out by electrochemical water treatment (EWT), preferably by electrocoagulation, to obtain a solution free of undesirable solutes.

[0060] In another embodiment, EWT is used as a pre-treatment step or a post-treatment step for the contacting step. Thus, according to one embodiment, the lithium-containing stream or the slurry containing lithium aluminate is pre-treated or post-treated respectively, and the pre-treatment or post-treatment includes electrochemical water treatment (EWT), preferably electrocoagulation, aiming to provide a pre-treated or post-treated solution free of undesired solutes.

[0061] As a pre-treatment step, EWT can be used to reduce the content of undesired solutes in the lithium-containing stream before lithium precipitation, or to precipitate an initial portion of lithium. As a post-treatment step, EWT can be used to reduce the content of undesired solutes in the slurry containing lithium aluminate, or to precipitate a further portion of lithium.

[0062] EWT is a technique for treating water-containing streams to reduce the content of undesired components therein without further addition of chemicals by utilizing processes such as electrodesinfection, electrochemical reduction, electrocoagulation, electroflotation, and electrodialysis. As described above, electrocoagulation is the preferred option used in the present invention.

[0063] Electrocoagulation can be used in the contacting step of the present method or can be used as a pre-treatment or post-treatment step. It is known per se and is carried out using aluminum-containing metal electrodes. Power is supplied to the metal electrodes serving as anodes-cathodes. The material selection is determined individually according to the water quality. The operating principle is to destabilize the charges of the dissolved pollutants and generate flocs suitable for mechanical removal. Although the electrode material is still regarded as a consumable, chemical treatment is eliminated. Those skilled in the art can easily determine the settings of electrocoagulation, and an exemplary charge load is 73 MC / m 3 。

[0064] The present method can be used as a main step for recovering lithium from the process stream in the process, or can be used as a polishing step after another step for removing lithium from the process effluent. This decision generally depends on the amount of lithium in the process stream, the existing process equipment, and the possibility of further using lithium aluminate at a reasonable cost. As described above, the present method can even be used for streams and effluents containing high concentrations of impurities.

[0065] In addition, the present invention relates to a method for soda leaching a lithium-containing raw material and recovering lithium therefrom. In one embodiment, the method comprises the following steps:

[0066] - Pulping a lithium-containing raw material selected from optionally calcined ores, recycled materials, or combinations thereof, thereby forming a water-containing slurry containing lithium;

[0067] - Leaching the slurry, thereby forming a partially dissolved slurry containing lithium;

[0068] - Optionally, further processing steps are carried out to adjust the lithium content of the formed lithium-containing slurry; and

[0069] - Product recovery, whereby lithium is precipitated, leaving a solution containing trace amounts of lithium,

[0070] wherein at least a portion of one or more lithium-containing slurries or solutions is separated from the process and subjected to the lithium recovery process of the present invention, and thereafter, the recovered slurry containing lithium aluminate or the precipitate separated therefrom is returned to the pulping or leaching step of the process.

[0071] Accordingly, the present invention also relates to a combination of a soda ash leaching process of a lithium-containing raw material and the above-described lithium recovery method. Accordingly, all of the above-described embodiments of the lithium recovery method are also applicable to the soda ash leaching process. Thus, in such a method, the lithium recovery method of the present invention is used to recover lithium from a portion obtained from the soda ash leaching process, wherein the recovered lithium can be recycled back into the soda ash leaching process.

[0072] The above-described embodiments and variations related to methods, uses, and / or equipment are applicable to the system with appropriate modifications. Accordingly, the present system allows for the production of commercial lithium products, such as lithium carbonate and lithium hydroxide, even as battery-grade products, while reducing the lithium content in industrial effluents from, for example, these production processes or other processes to levels that meet the most stringent requirements. All products from the system can be used for a certain purpose, and only water is released or recycled into the system.

[0073] As is well known in the art, the above-described equipment and systems can be automated, including any control and tracking of process efficiency and the quality and quantity of the products produced by each step.

[0074] It should be understood that the disclosed embodiments are not limited to the specific structures, process steps, or materials disclosed herein, but extend to equivalents thereof that would be recognized by those skilled in the relevant art. It should also be understood that the terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting.

[0075] References to an embodiment throughout this specification mean that the particular features, structures, or characteristics described in connection with that embodiment are included in at least one embodiment of the present invention. Thus, the phrases "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily all refer to the same embodiment. When terms such as about or substantially are used to refer to a numerical value, the exact numerical value is also disclosed.

[0076] As used herein, for convenience, multiple items, structural elements, compositional elements, and / or materials may be presented in a common list. However, these lists should be construed such that each member of the list is individually identified as a separate and unique member. Additionally, this document may refer to various embodiments and examples of the present invention and alternatives to its various components. It should be understood that these embodiments, examples, and alternatives should not be construed as de facto equivalents of one another, but rather as separate and autonomous representatives of the present invention.

[0077] In addition, the features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In this specification, numerous specific details are provided to facilitate a thorough understanding of the embodiments of the present invention. However, those skilled in the relevant art will recognize that the present invention may be practiced without one or more of the specific details.

[0078] While the foregoing examples illustrate the principles in one or more specific applications, it will be apparent to those of ordinary skill in the art that various modifications may be made to the form, use, and details of the embodiments without exercising creativity and without departing from the principles and concepts of the present invention. Accordingly, the present invention is limited only by the following claims.

[0079] The following non-limiting examples are only intended to illustrate the advantages obtained through the embodiments of the present invention.

[0080] Experimental Section

[0081] Example 1

[0082] The method for recovering lithium of the present invention was tested in a laboratory setup. The composition of the raw feed solution (i.e., the effluent solution) for the lithium recovery tests (1 - 4) is given in Table 1. Plasma emission spectrometry (ICP - OES; ISO 11885) was used to analyze a group of 9 different elements, namely Li, B, Al, Si, P, S, K, and Ca.

[0083] Table 1. Feed Solution Analysis

[0084] Element Unit Test 1 Test 2 Test 3 Test 4 Li mg / l 1900 1850 1880 1900 B mg / l 4 4 5 5 Na mg / l 3880 3850 3950 3780 Al mg / l 2 <5 4 <5 Si mg / l 685 385 625 678 P mg / l <10 <10 4 4 S mg / l 241 223 339 341 K mg / l 676 649 689 682 Ca mg / l 209 210 200 3

[0085] The feed solutions had very similar compositions with relatively high Li concentrations. The initial sulfate concentration levels varied between 223 and 339 mg / l.

[0086] The tests were conducted in a stirred reactor at a temperature of 40 °C. The lithium precipitation reagent used was prepared by dissolving solid sodium aluminate (NaAlO 2 ) in water to form a solution of 120 grams per liter. 96% liquid concentrated sulfuric acid (H 2 SO4 ) as a reference pH control reagent, and carbon dioxide gas (CO 2 ) was used in the tests conducted according to the method of the present invention (Test 4).

[0087] As a pretreatment step, the effluent solution was heated to 40 °C and the pH was adjusted to an initial target of 9.5 using a pH control reagent; the pH control reagent was H 2 SO 4 (in Tests 1-3) or the pH control reagent of the present invention, i.e., CO 2 gas (in Test 4). Then the lithium precipitation reagent NaAlO 2 was added to the effluent solution. The amount of the reagent NaAlO 2 was equal to 3 times the stoichiometric amount of lithium in the solution. After adding the NaAlO 2 reagent, the pH control reagent H 2 SO 4 or CO 2 was immediately added to further adjust the pH of the mixture to the target pH value of 10.0 within a reaction time of 30 minutes. Finally, the solid and the solution were separated on a filter, and the precipitate obtained was washed with a washing ratio of an average of 3 m 3 / ton (dry solid) of water to provide a washed solid cake. The compositional analysis of the filtrate and the washed solid cake is listed in Tables 2 and 3.

[0088] Table 2. Solution analysis of lithium precipitation tests

[0089] Element Unit Test 1 Test 2 Test 3 Test 4 Li mg / l 2 <5 2 1 B mg / l 2 2 3 3 Na mg / l 15200 16200 15000 13900 Al mg / l 32 82 20 13 Si mg / l 4 3 2 3 P mg / l <10 <10 <2 <2 S mg / l 8550 8730 7960 204 K mg / l 420 439 464 449 Ca mg / l 2 2 2 <2 Cl mg / l 2160 2110 2240 2313

[0090] Table 3. Solid analysis of lithium precipitation tests

[0091]

[0092]

[0093] It can be seen that all the tests were equally successful in terms of lithium recovery. Almost 100% of the lithium could be recovered by aluminate precipitation. The current results show that the performance of carbon dioxide as a pH control reagent is at least as effective as sulfuric acid. Compared with Tests 1-3, the solids in Test 4 naturally contain the lowest sulfate level, achieving a reduction of >75%.

[0094] Furthermore, it can be seen that the method according to the present invention also provides a final solution (final effluent) with a lithium concentration significantly less than 10 mg / l (i.e., 10 ppm), thus providing an effective method for recovering lithium.

Claims

1. A method for recovering lithium from a lithium-containing stream, the method comprising: - contacting the stream or a pretreated solution obtained therefrom with sodium aluminate at an alkaline pH to form a slurry containing a lithium aluminate precipitate; - adjusting the pH of the obtained slurry to a level of 8-13 using carbon dioxide to promote the precipitation of lithium aluminate; and - Recovering the slurry containing the lithium aluminate, or the precipitate separated therefrom.

2. The method according to claim 1, wherein the pH of the stream or solution is adjusted to a level of 8-12, preferably 8.1-12, or 8.2-12, or 8.3-12, more preferably 8.5-11, and most suitably 9-11.

3. The process according to claim 1 or 2, wherein the step of contacting the stream or solution with sodium aluminate is carried out at a temperature of 0-100°C, preferably 0-90°C, more preferably 50-90°C.

4. The process according to any one of the preceding claims, wherein at least a portion of the carbon dioxide used for pH adjustment is added simultaneously with the sodium aluminate.

5. A process according to any one of the preceding claims, wherein the carbon dioxide used for pH adjustment is added in gaseous form, typically using a pressure of 0 to 15 bar(g), more typically using a pressure of 0 to 10 bar(g).

6. A method according to any one of the preceding claims, wherein the lithium-containing stream is a stream containing sodium ions (Na + ), calcium ions (Ca 2+ ) or potassium ion (K + ), borate ions, carbonate ions, soluble silica and silicate species, phosphate (and hydrogen phosphate) ions, and fluoride (F - ) a flow in which one or more of the ions are present as impurities.

7. A method according to any one of the preceding claims, wherein the lithium-containing stream is an industrial stream, preferably a stream originating from a lithium recovery plant.

8. A method according to any one of the preceding claims, wherein the lithium-bearing stream is obtained from an apparatus for soda ash leaching of a lithium-bearing raw material and recovering lithium therefrom.

9. A method according to claim 7 or 8, wherein the lithium recovery equipment includes high temperature conversion of lithium-containing ores and recovery of lithium using water leaching, brine treatment or from recycled materials such as battery waste.

10. The method according to claim 9, wherein the lithium-containing ore is selected from an ore containing lithium-containing materials, such as spodumene, petalite, lepidolite or ferrolithium mica, or a mixture thereof.

11. The method according to any one of the preceding claims, wherein the slurry containing lithium aluminate is recovered by solid / liquid separation.

12. A method according to any one of the preceding claims, wherein the lithium-containing stream or the slurry containing lithium aluminate is subjected to a pretreatment or posttreatment, respectively, the pretreatment or posttreatment comprising an electrochemical water treatment, preferably electrocoagulation, aimed at providing a pretreated or posttreated solution free of undesirable solutes.

13. A method for leaching lithium-containing raw materials with soda ash and recovering lithium therefrom, the method comprising the following steps: - slurrying a lithium-containing raw material selected from an optionally calcined ore, a recycled material or a combination thereof, thereby forming an aqueous slurry containing lithium; - leaching the slurry to form a partially dissolved lithium-containing slurry; - optionally carrying out further treatment steps to adjust the lithium content of the formed lithium-containing slurry; and - product recovery, whereby lithium is precipitated, leaving a solution containing trace amounts of lithium, wherein at least a portion of one or more lithium-containing slurries or solutions is separated from the process and subjected to a method for recovering lithium as claimed in any one of the preceding claims, after which the recovered slurry containing lithium aluminate or the precipitate separated therefrom is returned to the pulping or leaching step of the process.

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