Process for extracting lithium from carbonic acid type lithium-containing solution

Abstract

The invention provides a process for extracting lithium from a carbonic acid type lithium-containing solution, which comprises the following steps: firstly, adding a calcium-magnesium causticizing agent into the carbonic acid type lithium-containing solution for causticizing reaction to obtain a first lithium-containing feed liquid and a precipitate, and pretreating the precipitate to obtain a product which is used as the causticizing agent again; the first lithium-containing feed liquid is sequentially subjected to pH adjustment, extraction-back extraction-deoiling treatment to obtain second lithium-containing feed liquid, and then a lithium salt product is prepared. According to the method, the calcium-magnesium causticizing agent is added into the carbonic acid type lithium-containing solution, CO3 < 2-> in the raw materials is converted into CaCO3 and / or MgCO3 precipitates, OH <-> is released, alkali consumption is greatly reduced, the causticizing agent can be regenerated, and subsequent supplementation is not needed except the first addition; the method has the advantages of simple process, realization of the cyclic utilization of the CO2 synergistic causticizing agent, great reduction of the production cost and carbon emission, realization of the process at normal temperature, reduction of the energy consumption, further reduction of the operation cost, and suitableness for large-scale application.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology and relates to a process for extracting lithium from a carbonate-type lithium-containing solution. Background Technology

[0002] As a typical example of the development and utilization of new energy, new energy vehicles have developed rapidly in recent years. As an essential metal in new energy vehicles, lithium has seen an increase in market demand. However, existing lithium mines are difficult to mine and cannot meet market demand.

[0003] Brine, especially salt lake brines, contains abundant lithium resources, all in ionic form, offering a natural advantage over lithium extraction from ore. Carbonate-type lithium-containing solutions are widely available, such as salt lake brines, lithium precipitation mother liquor, or pyrolysis mother liquor. Therefore, efficient lithium extraction from carbonate-type lithium-containing solutions is a key approach to meeting the growing demand for lithium. However, current lithium extraction technologies from carbonate-type lithium-containing solutions face the challenge of high alkali consumption in practical applications.

[0004] For example, CN112342407A discloses a method for extracting lithium from a lithium-containing solution. When extracting lithium from the solution, the pH must first be adjusted to 10-13. While higher alkalinity is beneficial for extraction, it undoubtedly increases alkali consumption significantly. The method subsequently uses a combination of carbon dioxide and carbonic acid solution for back-extraction, which reduces back-extraction costs to some extent, but cannot change the large alkali requirement of the extraction process.

[0005] CN103710549A discloses a method for efficient extraction of lithium from salt lake brine. Although the method uses a hydrophobic ionic liquid as a co-extractant to reduce the acidity of back-extraction and improve the lithium-magnesium separation coefficient, the pH and other conditions of the system still need to be adjusted during the extraction stage to ensure the extraction effect, resulting in a large proportion of alkali consumption in the overall process.

[0006] CN111099641A discloses a method for extracting lithium ions to prepare high-purity lithium carbonate. This method uses phosphate ester-type extractants, ketone-type extractants, or macrocyclic polyether extractants, and can extract lithium ions under acidic, neutral, and alkaline pH conditions. However, when the solution is in an alkaline environment, a large amount of alkali is still required to adjust the solution properties to ensure extraction efficiency and selectivity, especially in solutions with a high magnesium-to-lithium ratio, where alkali consumption is even more pronounced.

[0007] The aforementioned patents indicate that the extraction method for lithium extraction from carbonate-containing lithium solutions generally suffers from high alkali consumption. Therefore, effectively reducing alkali consumption in lithium extraction from carbonate-containing lithium solutions is a pressing technical problem that needs to be solved. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a process for extracting lithium from carbonate-containing lithium solutions. This invention involves adding a calcium-magnesium causticizing agent to the carbonate-containing lithium solution, converting carbonate ions in the raw material into calcium carbonate and / or magnesium carbonate precipitates, releasing hydroxide ions, significantly reducing the consumption of alkali solution, thereby substantially lowering costs. Furthermore, the causticizing agent in this invention can be regenerated through calcination; therefore, apart from the initial addition of the causticizing agent, subsequent additions are essentially unnecessary, further reducing costs. The process provided by this invention can be carried out at room temperature and is particularly suitable for extracting lithium from carbonate-containing lithium solutions such as carbonate-containing brines, lithium precipitation mother liquor, or pyrolysis mother liquor, making it suitable for large-scale applications.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a process for extracting lithium from a carbonate-type lithium-containing solution, the process comprising:

[0011] (1) Add a causticizing agent to a carbonate-type lithium-containing solution to carry out a causticizing reaction, and obtain a first lithium-containing solution and precipitate;

[0012] (2) The pH of the first lithium-containing liquid in step (1) is adjusted, and then an extraction-back-extraction process is performed to obtain the back-extraction phase and the back-extraction residue phase;

[0013] (3) The stripping residue from step (2) is subjected to deoiling treatment to obtain a second lithium-containing liquid;

[0014] (4) The lithium-containing liquid from step (3) is subjected to lithium salt extraction treatment to obtain lithium salt;

[0015] The causticizing agent in step (1) includes any one or a combination of at least two of calcium oxide, magnesium oxide, calcium hydroxide, or magnesium hydroxide;

[0016] The precipitate described in step (1) is pretreated, and the pretreated product is used again as a causticizing agent for causticizing reaction.

[0017] This invention targets lithium-containing carbonate solutions. By adding a calcium-magnesium causticizing agent to the system, a large amount of carbonate ions present in the system can be converted into calcium carbonate and / or magnesium carbonate precipitates, releasing hydroxide ions. This avoids the use of alkaline solutions mainly composed of sodium carbonate or sodium hydroxide in traditional methods. Since the calcium-magnesium causticizing agent has a significant price advantage over sodium carbonate or sodium hydroxide, it can greatly reduce production costs. Furthermore, the calcium-magnesium causticizing agent in this invention can be regenerated through calcination, requiring only the initial addition and virtually no subsequent replenishment, further reducing production costs. The process method provided by this invention makes great use of the characteristics of the raw materials themselves and is particularly suitable for extracting lithium from lithium-containing solutions containing carbonate ions, such as carbonated brines, lithium precipitation mother liquor, or pyrolysis mother liquor. Moreover, the process flow is simple and suitable for large-scale applications.

[0018] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0019] As a preferred technical solution, the causticizing agent described in step (1) is activated.

[0020] The activation treatment includes ball milling or ultrasonic treatment.

[0021] In this invention, by activating the causticizer, a fine and uniform crystal structure can be formed, increasing the specific surface area and porosity of the causticizer, increasing the active sites, and improving its activity. Compared with the unactivated causticizer, its reaction rate at room temperature can be increased by 2 to 3 times, thereby significantly reducing the temperature required for the causticizing reaction and greatly reducing the energy consumption in the process.

[0022] The precipitate in step (1) includes calcium carbonate and / or magnesium carbonate.

[0023] The pretreatment includes: first washing the precipitate in step (1), and then calcining it to obtain the calcined product, wherein the calcined product includes calcium oxide and / or magnesium oxide.

[0024] The solution after the first washing treatment is returned to the causticization reaction process described in step (1) for continued use.

[0025] The molar ratio of the causticizing agent to the carbonate in the carbonate-type lithium solution in step (1) is (0.6 to 3):1, for example, 0.6:1, 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] In this invention, the amount of causticizing agent added will affect the lithium extraction effect. By controlling it within the above-mentioned preferred range, the lithium extraction effect can be guaranteed while the alkali consumption can be reduced as much as possible, effectively balancing production efficiency and production cost.

[0027] The temperature of the causticizing reaction in step (1) is 20℃~40℃, for example 20℃, 22℃, 25℃, 27℃, 30℃, 33℃, 35℃ or 40℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] It should be noted that conventional causticization processes in this field are carried out at high temperatures because causticization is relatively slow at low temperatures. However, extraction needs to be performed at room temperature, so a cooling device is required to cool the causticized solution before extraction. However, this invention, by pre-activating the causticizing agent, can significantly improve its causticization efficiency, thus achieving high causticization efficiency at room temperature. This not only reduces the energy consumption of the causticization process but also avoids the energy consumption caused by cooling before extraction in conventional processes.

[0029] As a preferred technical solution, before the extraction-re-extraction process in step (2), a desilication agent is added to the first lithium-containing liquid in step (1) for desilication treatment.

[0030] The desiliconizing agent includes a first precipitant, an inorganic flocculant, and an organic flocculant.

[0031] The first precipitant includes any one or a combination of at least two of calcium, magnesium, or iron agents.

[0032] It should be noted that calcium preparations refer to calcium sulfate and / or calcium chloride, magnesium preparations refer to magnesium sulfate and / or magnesium chloride, and iron preparations refer to ferric sulfate and / or ferric chloride.

[0033] The inorganic flocculant includes any one or a combination of at least two of polyferric sulfate, polyferric chloride, polyaluminum chloride, polyaluminum sulfate, polyferric aluminum sulfate, or polyferric aluminum chloride.

[0034] The organic flocculant includes any one or a combination of at least two of polyacrylamide, polyquaternium salt, or polyether.

[0035] Understandably, industrial-grade causticizing agents are typically used in industrial applications, which introduce some silicon impurities. In this case, the first feed solution needs to be desiliconized to improve the purity of lithium recovery.

[0036] Add the first resin to the first lithium-containing liquid after the desiliconization treatment to perform decalcification and demagnesification treatment; or, before the deoiling treatment in step (3), add the first resin to the back-extraction phase in step (2) to perform decalcification and demagnesification treatment.

[0037] It is understood that, to avoid incomplete calcium and magnesium precipitation, decalcification and demagnesification treatments can be added after desilication or back-extraction to further improve the purity of lithium recovery. This invention does not limit the type of the first resin; resins commonly used in the art for decalcification and demagnesification are applicable to this invention. Exemplarily, the first resin includes any one or a combination of at least two of cation exchange resins, special chelating resins, or adsorbents.

[0038] As a preferred technical solution, the pH in step (2) is 12 to 14, such as 12.0, 12.5, 13.0, 13.5 or 14.0, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] The extraction-back-extraction process in step (2) includes: adding an extractant to the first lithium-containing liquid after pH adjustment in step (2) to obtain an extract phase and a raffinate phase, and then adding a back-extraction agent to the extract phase to obtain the back-extraction phase and the back-raffinate phase.

[0040] Prior to the back-extraction, the extract phase is subjected to a second washing treatment.

[0041] The solution after the second washing treatment is returned to the pH adjustment process described in step (2) for continued use.

[0042] In this invention, the overall lithium recovery rate can be further improved by returning the solutions after the first and second washing treatments to the causticization reaction process and the pH adjustment process, respectively.

[0043] As a preferred technical solution, the extractant includes a main extractant, a synergistic extractant, a diluent, and a modifier.

[0044] The main extractant includes any one or a combination of at least two of the following: β-diketone, carbonylenol, acylimidazolinone, phenolic compounds, salicylates, phenolic ketones, carboxylic acid compounds, hydroxyoxime compounds, aldoxime compounds, or organophosphates.

[0045] The synergistic extractants include neutral phosphorus-oxygen extractants and / or amide extractants.

[0046] The diluent includes any one or a combination of at least two of the following: alkyl kerosene, sulfonated kerosene, aryl kerosene, white oil, 200# solvent oil, or 260# solvent oil.

[0047] The modifier includes any one or a combination of at least two of alcohols, ketones, or esters.

[0048] As a preferred technical solution, the stripping agent includes any one of carbonic acid, hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid.

[0049] The back-extraction phase is then used as an extractant for extraction again.

[0050] Because this extraction system of the present invention requires a certain amount of OH - This method is designed to improve lithium extraction efficiency and is particularly suitable for systems with a pH of 12–14. It can further improve the separation of lithium from other impurity ions, and increase the recovery rate and purity of lithium. Furthermore, the extraction phase obtained using this extraction system only requires a weak acid to back-extract lithium from the lithium-rich organic phase during back-extraction, and the back-extraction phase can also be recycled as an extractant.

[0051] As a preferred technical solution, the deoiling process in step (3) includes: adding a second resin to the back-extraction residue to obtain the second lithium-containing liquid.

[0052] This invention does not limit the type of the second resin; any resin conventionally used for degreasing in the art is suitable for this invention. Exemplarily, the second resin includes macroporous adsorption resins and / or cation exchange resins.

[0053] As a preferred technical solution, when the stripping agent is carbonic acid, the lithium salt extraction process in step (4) is pyrolysis.

[0054] The pyrolysis mother liquor is returned to the back-extraction process in step (2), and / or returned to the causticization reaction process in step (1), and / or returned to the pH adjustment process in step (2) for continued use.

[0055] It should be noted that the sodium content of the mother liquor after pyrolysis is low, which can replace the water and carbon dioxide required for the back-extraction process, greatly reducing water consumption. However, when the mother liquor after pyrolysis is circulated to the back-extraction process for a period of time, the sodium content will be enriched to a high level. If it continues to circulate in the back-extraction process, it will affect the purity of the lithium carbonate produced after pyrolysis. At this time, it is necessary to open this part of the mother liquor after pyrolysis to the causticization reaction process described in step (1) and / or return it to the pH adjustment process described in step (2) for continued use.

[0056] When the stripping agent is any one of hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, the lithium salt extraction process in step (4) is crystallization or lithium precipitation.

[0057] When the lithium salt extraction method is lithium precipitation, a second precipitant is added to the second lithium-containing liquid, and the second precipitant includes sodium carbonate or potassium carbonate.

[0058] Hydrochloric acid or sulfuric acid is added to the mother liquor after lithium precipitation, followed by evaporation and concentration. The evaporated and concentrated solution is returned to the lithium precipitation process, and / or the mother liquor after lithium precipitation is directly returned to the causticization reaction process in step (1), and / or the mother liquor after lithium precipitation is directly returned to the pH adjustment process in step (2) for continued use.

[0059] It should be noted that, since the mother liquor after lithium precipitation has a high carbonate content and a low sulfate content, but the solubility of lithium carbonate is low, the lithium concentration in the mother liquor after lithium precipitation cannot be enriched to a very high level. Therefore, hydrochloric acid or sulfuric acid needs to be added to consume the carbonate, thereby forming a lithium salt solution with high solubility such as lithium sulfate or lithium chloride. Then, the solution is evaporated and concentrated to enrich the lithium to a certain concentration before returning to the lithium precipitation process. When the sodium sulfate concentration is close to saturation after a certain cycle, the cycle in the lithium precipitation process needs to be stopped. At this time, the mother liquor after a certain cycle in the lithium precipitation process can be returned to the causticization reaction process in step (1) and / or returned to the pH adjustment process in step (2) for continued use.

[0060] As a preferred technical solution, the causticizing reaction in step (1) further includes introducing carbon dioxide into the carbonate-type lithium-containing solution.

[0061] When the stripping agent is carbonic acid, the carbonic acid is prepared by dissolving carbon dioxide in water.

[0062] The products of calcination and the products of pyrolysis each independently include carbon dioxide.

[0063] The carbon dioxide in the causticizing reaction in step (1) and the carbon dioxide in the stripping agent each originate independently from the carbon dioxide produced by the calcination and / or the pyrolysis.

[0064] In this invention, the calcium carbonate and / or magnesium carbonate precipitates obtained in step (1) will generate carbon dioxide after calcination. Carbon dioxide can participate in the causticization reaction, increase the concentration of carbonate ions, thereby converting more carbonate ions into hydroxide ions. It also helps to completely convert the causticizing agent into precipitate and reduce its residue in the first feed solution. In practical applications, the concentration of carbonate ions in the raw material or the pH requirements in the subsequent extraction process can be used to select whether to use this part of carbon dioxide for the causticization reaction and the specific utilization ratio. If all of it can be recycled, the process does not need to introduce additional carbon dioxide. The recycling of carbon dioxide and the recycling of the causticizing agent work together to further reduce production costs and carbon emissions.

[0065] In this invention, a suitable back-extraction agent can be selected according to the type of lithium salt required. When the required type of lithium salt is lithium carbonate, the back-extraction agent carbonic acid can be obtained by dissolving carbon dioxide generated by calcination and / or pyrolysis in water as a back-extraction agent. This can reduce the use of carbonate and further reduce production costs.

[0066] The carbonate-type lithium-containing solution in step (1) includes any one of carbonate-type brine, lithium precipitation mother liquor, or pyrolysis mother liquor.

[0067] As a preferred technical solution, the process includes:

[0068] (1) The causticizing agent is activated, and then the activated causticizing agent is added to the lithium carbonate solution according to the molar ratio of the causticizing agent to the carbonate ion in the lithium carbonate solution (0.6-3):1. Carbon dioxide is introduced, and the causticizing reaction is carried out at 20℃-40℃ to obtain a first lithium-containing solution and a precipitate. The precipitate is subjected to a first washing treatment and a calcination treatment in sequence. The calcined product is used as the causticizing agent again for the causticizing reaction. The solution after the first washing treatment is returned to the causticizing reaction process for continued use.

[0069] (2) Add a desilication agent to the first lithium-containing liquid in step (1) for desilication treatment, then add the first resin for decalcification and demagnesification treatment, then adjust the pH of the first lithium-containing liquid to 12-14, add an extractant for extraction treatment, and obtain an extract phase and a raffinate phase. Perform a second washing treatment on the extract phase, add a back-extraction agent (carbonic acid) to the raffinate phase for back-extraction treatment, and obtain a back-extraction phase and a back-extraction phase. Return the solution after the second washing treatment to the pH adjustment process for continued use.

[0070] (3) The stripping residue from step (2) is subjected to deoiling treatment to obtain a second lithium-containing liquid;

[0071] (4) Pyrolyze the second lithium-containing liquid in step (3) to obtain lithium carbonate;

[0072] The causticizing agent in step (1) includes any one or a combination of at least two of calcium oxide, magnesium oxide, calcium hydroxide, or magnesium hydroxide, and the activation treatment includes ball milling or ultrasonic treatment; the calcination product in step (1) includes calcium oxide and / or magnesium oxide, and the calcination product in step (1) and the pyrolysis product in step (4) each independently include carbon dioxide; the carbonic acid in step (2) is prepared by dissolving carbon dioxide in water, and the carbon dioxide in the causticizing reaction in step (1) and the carbon dioxide in the carbonic acid in step (2) each independently originate from the carbon dioxide produced by the calcination and / or pyrolysis.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] This invention primarily targets lithium-containing solutions such as carbonated brine, lithium precipitation mother liquor, or pyrolysis mother liquor. By adding a calcium-magnesium causticizing agent to the solution, the carbonate ions in the raw materials are converted into hydroxide ions, thereby significantly reducing the consumption of alkali solution and substantially lowering costs. Furthermore, the causticizing agent in this invention can be regenerated through calcination, so after the initial addition of the causticizing agent, there is essentially no need to replenish it with new causticizing agent. In addition, the causticizing process can be completed at room temperature, avoiding the energy consumption caused by heating and cooling during high-temperature causticizing and room-temperature extraction, which further reduces costs and makes it suitable for large-scale applications. Attached Figure Description

[0075] Figure 1 This is a process flow diagram of lithium extraction from carbonated brine provided in Example 1.

[0076] Figure 2 This is a process flow diagram of lithium extraction from lithium precipitation mother liquor provided in Example 2.

[0077] Figure 3 This is a process flow diagram of lithium extraction from pyrolysis mother liquor provided in Example 3. Detailed Implementation

[0078] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0079] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0080] Example 1

[0081] This embodiment provides a process for extracting lithium from carbonated brine, such as... Figure 1 As shown, the specific process is as follows:

[0082] (1) At 25°C, calcium oxide and magnesium oxide with a total molar concentration of 0.167 mol / L were added to 100L of carbonate brine with a lithium ion concentration of 0.286 mol / L and a carbonate concentration of 0.167 mol / L as causticizing agents (the molar ratio of causticizing agent to carbonate in carbonate brine is 1:1), and carbon dioxide was introduced to carry out the causticizing reaction. After filtration, the first lithium-containing liquid and precipitate were obtained. The precipitate included magnesium carbonate and calcium carbonate. Water was added to perform the first washing treatment on the precipitate. The aqueous solution after the first washing was returned to the causticizing reaction process for continued use.

[0083] (2) First, magnesium oxide, polyferric oxide and polyacrylamide are added to the first lithium-containing liquid as desilication agents for desilication treatment. Then, cation exchange resin is added as the first resin for decalcification and demagnesification treatment. Then, 0.710L of 10.7mol / L alkaline sodium hydroxide solution is added to adjust the pH to above 12 and then the extractant is added. The extractant system is: dibenzoylmethane + trioctyl phosphate + dodecyl alcohol + alkyl kerosene. The extract phase and raffinate phase are obtained. 10g / L sulfuric acid is added as a washing agent to perform a second washing treatment on the extract phase. Then, carbon dioxide and water are introduced as back-extraction agents to perform back-extraction to obtain a back-extraction phase and a back-extraction phase. The aqueous solution after the second washing treatment is returned to the pH adjustment process for continued use.

[0084] (3) Add macroporous degreasing resin to the back-extraction residue as a second resin for degreasing treatment to obtain a second lithium-containing liquid;

[0085] (4) The second lithium-containing liquid is subjected to pyrolysis to obtain lithium carbonate;

[0086] The precipitate after the first washing treatment in step (1) is calcined to obtain calcined products, which include calcium oxide, magnesium oxide and carbon dioxide. Calcium oxide and magnesium oxide are used as causticizing agents for causticization reaction. The carbon dioxide required in steps (1) and (2) comes from carbon dioxide produced by calcination and pyrolysis.

[0087] In step (2), the back-extraction phase is used as the extractant in step (2). The mother liquor after pyrolysis is first returned to the back-extraction process for continued use, and then returned to the causticization reaction process and pH adjustment process for continued use.

[0088] Example 2

[0089] This embodiment provides a process for extracting lithium from lithium precipitation mother liquor, such as... Figure 2 As shown, the specific process is as follows:

[0090] (1) At 25°C, calcium oxide and magnesium oxide with a total molar concentration of 0.146 mol / L were added as causticizing agents to 100L of lithium precipitation mother liquor with a lithium ion concentration of 0.286 mol / L and a carbonate concentration of 0.243 mol / L (the molar ratio of the causticizing agent to the carbonate in the lithium precipitation mother liquor was 0.6:1), and carbon dioxide was introduced to carry out the causticizing reaction. After filtration, the first lithium-containing liquid and precipitate were obtained. The precipitate included magnesium carbonate and calcium carbonate. Water was added to perform the first washing treatment on the precipitate. The aqueous solution after the first washing was returned to the causticizing reaction process for continued use.

[0091] (2) First, calcium oxide, ferric sulfate and polyacrylamide are added to the first lithium-containing liquid as desilication agents for desilication treatment. Then, chelating resin is added as the first resin for decalcification and demagnesification treatment. Then, 0.751L of 10.7mol / L alkaline sodium hydroxide solution is added to adjust the pH to above 12 and then the extractant is added. The extractant system is: isooctyl salicylate + TRPO + 2-octanone + sulfonated kerosene to obtain the extract phase and raffinate phase. Pure water is added as a washing agent to perform a second washing treatment on the extract phase. Then, sulfuric acid is added as a back-extraction agent to perform back-extraction to obtain the back-extraction phase and back-extraction phase. The aqueous solution after the second washing treatment is returned to the pH adjustment process for continued use.

[0092] (3) Add a special degreasing resin to the back-extraction residue as a second resin for degreasing treatment to obtain a second lithium-containing liquid;

[0093] (4) The second lithium-containing liquid is subjected to crystallization treatment to obtain lithium sulfate;

[0094] The precipitate after the first washing treatment in step (1) is calcined to obtain the calcined product, which includes calcium oxide, magnesium oxide and carbon dioxide. Calcium oxide and magnesium oxide are used as causticizing agents in the causticizing reaction. The carbon dioxide required in step (1) comes from the carbon dioxide produced by calcination. The back-extraction phase in step (2) is used as the extractant in step (2).

[0095] Example 3

[0096] This embodiment provides a process for extracting lithium from pyrolysis mother liquor, such as... Figure 3 As shown, the specific process is as follows:

[0097] (1) At 25°C, calcium oxide and magnesium oxide with a total molar concentration of 0.429 mol / L were added to 100L of pyrolysis mother liquor with a lithium ion concentration of 0.286 mol / L and a carbonate concentration of 0.143 mol / L as causticizing agents to carry out causticization reaction (the molar ratio of causticizing agent to carbonate in pyrolysis mother liquor is 3:1). After filtration, the first lithium-containing liquid and precipitate were obtained. The precipitate included magnesium carbonate, magnesium hydroxide, calcium carbonate and calcium hydroxide. Water was added to perform the first washing treatment on the precipitate. The aqueous solution after the first washing was returned to the causticization reaction process for continued use.

[0098] (2) Add magnesium sulfate, ferric chloride and polyacrylamide as desilication agents to the first lithium-containing liquid for desilication treatment, then add chelating resin as the first resin for decalcification and demagnesification treatment, then add 0.668L of 10.7mol / L alkaline sodium hydroxide solution to adjust the pH to above 12 and then add the extractant. The extractant system is: isooctyl salicylate + trialkylphosphine oxide (TRPO) + 2-octanone + sulfonated kerosene to obtain the extract phase and the raffinate phase. Add 10g / L sulfuric acid as a washing agent to perform a second washing treatment on the extract phase, then add sulfuric acid as a back-extraction agent to perform back-extraction to obtain the back-extraction phase and the back-extraction phase. The aqueous solution after the second washing treatment is returned to the pH adjustment process for continued use.

[0099] (3) Add macroporous resin to the back-extraction residue as a second resin for deoiling treatment to obtain a second lithium-containing liquid;

[0100] (4) Add sodium carbonate as a precipitant to the second lithium-containing liquid to perform lithium precipitation treatment on the second lithium-containing liquid to obtain lithium carbonate;

[0101] The precipitate after the first washing treatment in step (1) is calcined to obtain calcined products, which include calcium oxide, magnesium oxide and carbon dioxide. Among them, calcium oxide and magnesium oxide are used as causticizing agents to carry out causticizing reaction. The carbon dioxide required in step (1) comes from the carbon dioxide produced by calcination.

[0102] In step (2), the back-extraction phase is used as the extractant in step (2). Sulfuric acid is added to the solution after lithium precipitation to eliminate carbonate ions. Then, the solution is evaporated and concentrated. It is first returned to the lithium precipitation process for continued use, and then returned to the causticization reaction process and the pH adjustment process for continued use.

[0103] Example 4

[0104] The difference between this embodiment and embodiment 2 is that in this embodiment, in step (1), calcium oxide and magnesium oxide with a total molar concentration of 0.486 mol / L after activation treatment are added as causticizing agents, and the molar ratio of the causticizing agent to the carbonate in the lithium precipitation mother liquor is 2:1. In step (2), it is not necessary to add alkaline sodium hydroxide solution.

[0105] The remaining preparation methods and parameters are consistent with those in Example 2.

[0106] Example 5

[0107] The difference between this embodiment and embodiment 1 is that in this embodiment, carbon dioxide is not introduced in the causticizing reaction in step (1), and 1.330L of sodium hydroxide is added in step (2).

[0108] The remaining preparation methods and parameters are consistent with those in Example 1.

[0109] Example 6

[0110] The difference between this embodiment and embodiment 1 is that in this embodiment, the carbon dioxide introduced in the causticizing reaction in step (1) comes only from the carbon dioxide produced by pyrolysis, and 0.866L of sodium hydroxide is added in step (2).

[0111] The remaining preparation methods and parameters are consistent with those in Example 1.

[0112] Example 7

[0113] The difference between this embodiment and embodiment 1 is that in this embodiment, the carbon dioxide introduced in the causticizing reaction in step (1) comes only from the carbon dioxide produced by calcination, and 1.022L of sodium hydroxide is added in step (2).

[0114] The remaining preparation methods and parameters are consistent with those in Example 1.

[0115] Example 8

[0116] The difference between this embodiment and embodiment 1 is that in this embodiment, the causticizing agent in step (1) is not activated, and 1.960L of sodium hydroxide is added in step (2).

[0117] The remaining preparation methods and parameters are consistent with those in Example 1.

[0118] Example 9

[0119] The difference between this embodiment and embodiment 1 is that in this embodiment, 0.067 mol / L of causticizing agent is added in step (1), and the molar ratio of causticizing agent to carbonate in carbonate-type lithium solution is 0.4:1. In step (2), 2.086 L of sodium hydroxide is added.

[0120] The remaining preparation methods and parameters are consistent with those in Example 1.

[0121] Comparative Example 1

[0122] The difference between this comparative example and Example 1 is that step (1) is not performed in this comparative example. In step (2), the carbonate brine is decalcified and demagnesified first, and then 3.150L of sodium hydroxide is added. The carbon dioxide required in step (2) comes from the carbon dioxide produced by pyrolysis.

[0123] The remaining preparation methods and parameters are consistent with those in Example 1.

[0124] Comparative Example 2

[0125] The difference between this comparative example and Example 2 is that step (1) is not performed in this comparative example. In step (2), the lithium precipitation mother liquor is decalcified and demagnesified first, and then 3.074L of sodium hydroxide is added.

[0126] The remaining preparation methods and parameters are consistent with those in Example 2.

[0127] Comparative Example 3

[0128] The difference between this comparative example and Example 3 is that step (1) is not performed in this comparative example. In step (2), the pyrolysis mother liquor is decalcified and demagnesified first, and then 3.212L of sodium hydroxide is added.

[0129] The remaining preparation methods and parameters are consistent with those in Example 3.

[0130] Comparative Example 4

[0131] The difference between this comparative example and Example 1 is that in this example, the calcination products calcium oxide and magnesium oxide from step (1) are not reused as causticizing agents, and 3.031L of sodium hydroxide is added in step (2).

[0132] The remaining preparation methods and parameters are consistent with those in Example 1.

[0133] Table 1

[0134] Serial Number Alkali consumption (L) Example 1 0.710 Example 2 0.751 Example 3 0.668 Example 4 0.000 Example 5 1.330 Example 6 0.866 Example 7 1.022 Example 8 1.960 Example 9 2.086 Comparative Example 1 3.150 Comparative Example 2 3.074 Comparative Example 3 3.212 Comparative Example 4 3.031

[0135] The process method provided by this invention, in Examples 1-9, can guarantee a lithium-ion recovery rate of over 99% and a purity of over 99.5%. A comparison of the data from Example 1 and Comparative Examples 1-4 in Table 1 shows that the process method provided by this invention significantly reduces alkali consumption while ensuring lithium-ion recovery rate and purity, thereby substantially reducing production costs and making it suitable for large-scale applications. Furthermore, as shown in Examples 1-4, in practical applications, the amount of causticizing agent can be selected according to the concentration of carbonate ions in the lithium-containing solution. When the amount of causticizing agent added is appropriate, zero alkali consumption can be achieved, thereby significantly reducing costs.

[0136] A comparison of the data from Examples 1 and 5-7 in Table 1 shows that, in this invention, using carbon dioxide generated from calcination and / or pyrolysis for the causticizing reaction can further reduce the amount of alkali solution used. A comparison of the data from Examples 1 and 8 in Table 1 shows that activating the causticizing agent can improve its causticizing efficiency, making it more suitable for room temperature causticizing, thereby reducing energy consumption. A comparison of the data from Examples 1 and 9 shows that the amount of causticizing agent also affects the amount of alkali consumed. By controlling it within the preferred range of this invention, it is more beneficial to balance lithium extraction efficiency and lithium extraction cost.

[0137] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A process for extracting lithium from a carbonate-type lithium-containing solution, characterized in that, The process includes: (1) Add a causticizing agent to a carbonate-type lithium-containing solution to carry out a causticizing reaction, and obtain a first lithium-containing solution and precipitate; (2) The pH of the first lithium-containing liquid in step (1) is adjusted, and then an extraction-back-extraction process is performed to obtain the back-extraction phase and the back-extraction residue phase; (3) The stripping residue from step (2) is subjected to deoiling treatment to obtain a second lithium-containing liquid; (4) The lithium-containing liquid from step (3) is subjected to lithium salt extraction treatment to obtain lithium salt; The causticizing agent in step (1) includes any one or a combination of at least two of calcium oxide, magnesium oxide, calcium hydroxide, or magnesium hydroxide; The precipitate described in step (1) is pretreated, and the pretreated product is used again as a causticizing agent for causticizing reaction.

2. The process for extracting lithium from a carbonate-type lithium-containing solution according to claim 1, characterized in that, The causticizing agent described in step (1) is activated; The activation treatment includes ball milling or ultrasonic treatment; The precipitate in step (1) includes calcium carbonate and / or magnesium carbonate; The pretreatment includes: first washing the precipitate in step (1), and then calcining it to obtain the calcined product, wherein the calcined product includes calcium oxide and / or magnesium oxide; The solution after the first washing treatment is returned to the causticizing reaction process described in step (1) for continued use; The molar ratio of the causticizing agent to the carbonate ions in the carbonate-type lithium-containing solution in step (1) is (0.6-3):1; The temperature of the causticizing reaction in step (1) is 20℃~40℃.

3. The process for extracting lithium from a carbonate-type lithium-containing solution according to claim 1, characterized in that, Before the extraction-back-extraction process described in step (2), a desilication agent is added to the first lithium-containing liquid in step (1) for desilication treatment; The desiliconizing agent includes a first precipitant, an inorganic flocculant, and an organic flocculant; The first precipitant includes any one or a combination of at least two of calcium, magnesium, or iron agents; The inorganic flocculant includes any one or a combination of at least two of polyferric sulfate, polyferric chloride, polyaluminum chloride, polyaluminum sulfate, polyferric aluminum sulfate, or polyferric aluminum chloride. The organic flocculant includes any one or a combination of at least two of polyacrylamide, polyquaternium salt, or polyether. Add the first resin to the first lithium-containing liquid after the desiliconization treatment to perform decalcification and demagnesification treatment; or, before the deoiling treatment in step (3), add the first resin to the back-extraction residue in step (2) to perform decalcification and demagnesification treatment.

4. The process for extracting lithium from a carbonate-type lithium-containing solution according to claim 2, characterized in that, The pH value in step (2) is 12–14; The extraction-back-extraction process in step (2) includes: adding an extractant to the first lithium-containing liquid after pH adjustment in step (2) to obtain an extract phase and a raffinate phase, and then adding a back-extraction agent to the extract phase to obtain the back-extraction phase and the back-extraction phase; Prior to the back-extraction, the extract phase is subjected to a second washing treatment; The solution after the second washing treatment is returned to the pH adjustment process described in step (2) for continued use.

5. The process for extracting lithium from a carbonate-type lithium-containing solution according to claim 4, characterized in that, The extractant includes a primary extractant, a synergistic extractant, a diluent, and a modifier; The main extractant includes any one or a combination of at least two of the following: β-diketone, carbonylenol, acylimidazolinone, phenolic compounds, salicylates, phenolic ketones, carboxylic acid compounds, hydroxyoxime compounds, aldoxime compounds, or organophosphates; The synergistic extractant includes neutral phosphorus-oxygen extractants and / or amide extractants; The diluent includes any one or a combination of at least two of the following: alkyl kerosene, sulfonated kerosene, aryl kerosene, white oil, 200# solvent oil, or 260# solvent oil; The modifier includes any one or a combination of at least two of alcohols, ketones, or esters.

6. The process for extracting lithium from a carbonate-type lithium-containing solution according to claim 4, characterized in that, The stripping agent includes any one of carbonic acid, hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid; The back-extraction phase is then used as an extractant for extraction again.

7. The process for extracting lithium from a carbonate-type lithium-containing solution according to claim 1, characterized in that, The deoiling process in step (3) includes adding a second resin to the back-extraction residue to obtain the second lithium-containing liquid.

8. The process for extracting lithium from a carbonate-type lithium-containing solution according to claim 6, characterized in that, When the stripping agent is carbonic acid, the lithium salt extraction process in step (4) is pyrolysis; The pyrolysis mother liquor is returned to the back-extraction process in step (2), and / or returned to the causticization reaction process in step (1), and / or returned to the pH adjustment process in step (2) for continued use; When the stripping agent is any one of hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, the lithium salt extraction treatment method in step (4) is crystallization or lithium precipitation; When the lithium salt extraction method is lithium precipitation, a second precipitant is added to the second lithium-containing liquid, and the second precipitant includes sodium carbonate or potassium carbonate. Hydrochloric acid or sulfuric acid is added to the mother liquor after lithium precipitation, followed by evaporation and concentration. The evaporated and concentrated solution is returned to the lithium precipitation process, and / or the mother liquor after lithium precipitation is directly returned to the causticization reaction process in step (1), and / or the mother liquor after lithium precipitation is directly returned to the pH adjustment process in step (2) for continued use.

9. The process for extracting lithium from a carbonate-type lithium-containing solution according to claim 8, characterized in that, The causticizing reaction in step (1) further includes passing carbon dioxide into the carbonate-type lithium-containing solution; When the stripping agent is carbonic acid, the carbonic acid is prepared by dissolving carbon dioxide in water; The calcination product and the pyrolysis product each independently include carbon dioxide; The carbon dioxide in the causticizing reaction in step (1) and the carbon dioxide in the stripping agent each originate independently from the carbon dioxide produced by the calcination and / or the pyrolysis; The carbonate-type lithium-containing solution in step (1) includes any one of carbonate-type brine, lithium precipitation mother liquor, or pyrolysis mother liquor.

10. The process for extracting lithium from a carbonate-type lithium-containing solution according to claim 1, characterized in that, The process includes: (1) The causticizing agent is activated, and then the activated causticizing agent is added to the lithium carbonate solution according to the molar ratio of the causticizing agent to the carbonate ion in the lithium carbonate solution (0.6-3):

1. Carbon dioxide is introduced, and the causticizing reaction is carried out at 20℃-40℃ to obtain a first lithium-containing solution and a precipitate. The precipitate is subjected to a first washing treatment and a calcination treatment in sequence. The calcined product is used as the causticizing agent again for the causticizing reaction. The solution after the first washing treatment is returned to the causticizing reaction process for continued use. (2) Add a desilication agent to the first lithium-containing liquid in step (1) for desilication treatment, then add the first resin for decalcification and demagnesification treatment, then adjust the pH of the first lithium-containing liquid to 12-14, add an extractant for extraction treatment, and obtain an extract phase and a raffinate phase. Perform a second washing treatment on the extract phase, add a back-extraction agent (carbonic acid) to the raffinate phase for back-extraction treatment, and obtain a back-extraction phase and a back-extraction phase. Return the solution after the second washing treatment to the pH adjustment process for continued use. (3) The stripping residue from step (2) is subjected to deoiling treatment to obtain a second lithium-containing liquid; (4) Pyrolyze the second lithium-containing liquid in step (3) to obtain lithium carbonate; The causticizing agent in step (1) includes any one or a combination of at least two of calcium oxide, magnesium oxide, calcium hydroxide, or magnesium hydroxide, and the activation treatment includes ball milling or ultrasonic treatment; the calcination product in step (1) includes calcium oxide and / or magnesium oxide, and the calcination product in step (1) and the pyrolysis product in step (4) each independently include carbon dioxide; the carbonic acid in step (2) is prepared by dissolving carbon dioxide in water, and the carbon dioxide in the causticizing reaction in step (1) and the carbon dioxide in the carbonic acid in step (2) each independently originate from the carbon dioxide produced by the calcination and / or pyrolysis.

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