A resource-saving method and system for extracting lithium from salt lake brine

Abstract

The present invention provides a resource-saving method for extracting lithium from salt lake brine, comprising: mixing an extractant with an acidic NaCl-FeCl3 solution, and then clarifying and separating the mixture to obtain an activated extractant; mixing the activated extractant with salt lake brine and clarifying the mixture to obtain an extract containing a lithium extractant; and stripping the extract containing the lithium extractant to finally obtain a high-lithium solution. The present invention also provides a system suitable for the resource-saving method for extracting lithium from salt lake brine, comprising an activation section, an extraction section, and a stripping section circulated along the flow direction of the extractant. The resource-saving method for extracting lithium from salt lake brine of the present invention reduces the amount of FeCl3 used, the activator can be reused, the acid consumption is low, the extraction rate is improved, the brine has a wide range of uses, the properties of the brine after extraction are slightly changed, and the environmental pollution is small.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction, and in particular to a resource-saving method and system for extracting lithium from salt lake brine. Background Art

[0002] With the rapid development of new energy vehicles and new energy storage industries, the demand for lithium resources is rapidly increasing. Currently, the main methods for industrial lithium extraction include precipitation, ion exchange adsorption, membrane extraction, calcination leaching, salting out, and solvent extraction. Solvent extraction has been widely used due to its advantages such as continuous operation, high enrichment ratio, high yield, simple equipment, low cost, and safe operation. Solvent extraction utilizes the special extraction properties of organic solvents for lithium extraction. The key to this is finding a suitable extraction agent.

[0003] Currently, the extractants known to have strong selectivity for lithium are primarily crown ethers, including carboxylic acid crown ether compounds and crown ether phosphonate compounds. However, these are limited to experimental research, with no reports of industrial application. Furthermore, neutral phosphorus extractants in organophosphorus extraction systems are also a method for extracting lithium that is currently being widely studied both domestically and internationally. Neutral phosphorus extractants are categorized into three types: phosphate esters (TRPs), phosphinate esters (RDRPs), and trialkylphosphine oxides (TRPOs). Tributyl phosphate (TBP), dibutyl phosphate (DBBP), and trioctylphosphine oxide (TOPO) are currently the most studied. DBBP and TOPO exhibit lower lithium extraction abilities than TBP.

[0004] In the prior art, the TBP-FeCl3 extraction system generally assists in the extraction by adding FeCl3 to the lithium-containing solution. In order to prevent FeCl3 from forming Fe(OH)3 precipitation, the pH value of the brine needs to be adjusted to 2~3. After disassembly and acid leaching, lithium batteries are acidic, and the lithium ion content is usually around 5g / L. The lithium content is high, which is convenient for subsequent extraction. Therefore, the TBP-FeCl3 extraction system is widely used in the field of lithium battery recovery lithium industrialization. However, since brine contains a large amount of buffer substances, the acid consumption is increased. At the same time, the H + Will be with Li + This creates a competitive relationship, reducing the lithium extraction rate. Due to the low chloride ion content in some original brines, additional MgCl2 needs to be added to increase the chloride ion concentration. Under the same lithium production conditions, the amount of acid and ferric chloride used is much higher than that of battery recycling and lithium extraction, resulting in a higher overall cost of brine extraction and lithium extraction. Therefore, it limits the industrialization process of TBP-FeCl3 extraction system in salt lake brine extraction and lithium extraction.

[0005] Therefore, developing a resource-saving extraction process for lithium extraction from salt lake brine has important industrial application value. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a resource-saving method and system for extracting lithium from salt lake brine, which is used to solve the problems of the prior art such as the great environmental harm of the raffinate, high brine requirements, large acid consumption, and waste of extraction agent.

[0007] To achieve the above-mentioned and other related purposes, the present invention provides a resource-saving method for extracting lithium from salt lake brine, comprising the following steps:

[0008] S1. Mixing the extractant with the acidic NaCl-FeCl3 solution and then clarifying and separating to obtain an activated extractant, the reaction formula is:

[0009] Fe 3+ + 4Cl - → FeCl4 - （a） ;

[0010] FeCl4 - + Na + + S （o） → NaFeCl4·S （o） ;

[0011] Among them, the subscript （a） represents the aqueous phase, subscript （o） represents the oil phase, and S represents the extractant;

[0012] S2, the activated extractant is mixed with salt lake brine and clarified to obtain an extract containing a lithium extractant, and the reaction formula is as follows:

[0013] NaFeCl4·S （o） + Li + → LiFeCl4·S （o） + Na + ;

[0014] S3, stripping the extract containing the lithium extractant to finally obtain a high-lithium solution.

[0015] Preferably, the pH of the acidic NaCl-FeCl3 solution in step S1 is 0-4, 0-1, 1-2, 2-3 or 3-4, the concentration of sodium chloride solution in the acidic NaCl-FeCl3 solution is 2-6 mol / L, 2-3 mol / L, 3-3.5 mol / L, 3.5-4 mol / L, 4-4.5 mol / L, 4.5-5 mol / L, 5-5.5 mol / L or 5.5-6 mol / L, and the concentration of ferric chloride is 0.5-2 mol / L, 0.5-0.7 mol / L, 0.7-0.9 mol / L, 0.9-1 mol / L, 1-1.2 mol / L, 1.2-1.4 mol / L, 1.4-1.6 mol / L, 1.6-1.8 mol / L or 1.8-2 mol / L.

[0016] Preferably, the extractant in step S1 comprises a phosphate ester. In the present invention, a phosphate ester is an ester derivative of phosphoric acid and belongs to a class of phosphoric acid derivatives. The present invention does not specifically limit the phosphate ester, and those skilled in the art may select one based on actual circumstances. More preferably, the phosphate ester in step S1 of the present embodiment may be selected from tributyl phosphate, tripentyl phosphate, 2-ethylhexyl phosphate, or other phosphate esters.

[0017] More preferably, the extractant in step S1 further contains a diluent. The present invention does not specifically limit the components of the diluent, for example, the diluent can be sulfonated kerosene, toluene, dodecane or amyl acetate, etc., and those skilled in the art can select the diluent according to actual conditions.

[0018] Preferably, the acidic NaCl-FeCl3 solution in step S1 can be reused.

[0019] More preferably, the flow ratio of the extractant to the acidic NaCl-FeCl3 solution in step S1 is 1:0.5 to 1:2, for example, 1:0.5 to 1:1, 1:1 to 1:1.5, or 1:1.5 to 1:2.

[0020] More preferably, the flow ratio of the activated extractant to the salt lake brine in step S2 is 1:0.5-1:3, for example, 1:0.5-1:1, 1:1-1:1.5, 1:1.5-1:2, 1:2-1:2.5 or 1:3.5-1:3.

[0021] Preferably, the salt lake brine in step S2 is salt lake brine that has been precipitated and filtered.

[0022] Preferably, before the stripping in step S3, the extract is washed with a detergent, wherein the detergent is a lithium-containing aqueous solution or pH-neutral water. The sodium extract and brine contained in the extract are removed by washing; the reaction formula is as follows:

[0023] NaFeCl4·S （o） + Li + → LiFeCl4·S （o） + Na + ;

[0024] NaFeCl4·S （o） + H + → HFeCl4·S （o） + Na + .

[0025] More preferably, the lithium concentration in the lithium-containing aqueous solution is 0.1-2 g / L, for example, 0.1-0.5 g / L, 0.5-1 g / L, 1-1.5 g / L, or 1.5-2 g / L.

[0026] More preferably, the flow ratio of the detergent to the extract is 1:5-1:30, for example, 1:5-1:10, 1:10-1:15, 1:15-1:20, 1:20-1:25 or 1:25-1:30.

[0027] Preferably, in step S3, the stripping agent used in the stripping is an acid with a concentration of 0.1 to 6 mol / L. For example, it is 0.1 to 1 mol / L, 1 to 2 mol / L, 2 to 3 mol / L, 3 to 4 mol / L, 4 to 5 mol / L, or 5 to 6 mol / L. The stripping process reaction formula is as follows:

[0028] LiFeCl4·S （o） → S （o） + LiCl + FeCl3.

[0029] More preferably, the acid is hydrochloric acid, sulfuric acid or nitric acid.

[0030] More preferably, the flow ratio of the acid to the extract is 1:5 to 1:20, for example 1:5 to 1:10, 1:10 to 1:15 or 1:15 to 1:20.

[0031] Preferably, after the stripping in step S3, an oil phase is obtained, and the oil phase is returned to step S1 and mixed with the acidic NaCl-FeCl3 solution. 。

[0032] The present invention also provides a system suitable for the resource-saving salt lake brine extraction method for lithium extraction as described above, the system comprising an activation section, an extraction section, and a stripping section circulated along the flow direction of the extractant;

[0033] The activation section includes 1st to fth-stage activation tanks arranged in series, where f≤5, for example, f=1, 2, 3, 4 or 5; the oil phase inlet of the first-stage activation tank is connected to the extractant storage tank, the water phase inlet of the f-stage activation tank is connected to the activator storage tank, the water phase outlets of each stage of the activation tank are connected to the water phase inlet of the previous stage of the activation tank, and only the water phase outlet of the first-stage activation tank is connected to the water phase inlet of the f-stage activation tank; the oil phase outlets of each stage of the activation tank are connected to the oil phase inlet of the next-stage activation tank, and only the oil phase outlet of the f-stage activation tank is connected to the oil phase inlet of the extraction section;

[0034] The extraction section is connected to a salt lake brine storage tank to provide salt lake brine to the extraction section, and the extraction section is also connected to a raffinate storage tank to collect the raffinate generated by the extraction section;

[0035] The stripping section is connected to a stripping solution storage tank to provide stripping solution to the stripping section. The stripping section is also connected to a high-lithium solution storage tank to collect high-lithium solution from the stripping section.

[0036] Preferably, the system further comprises a washing section, which is provided between the extraction section and the stripping section and is connected to the extraction section and the stripping section respectively. The washing section is also connected to a washing liquid storage tank to provide washing liquid to the washing section.

[0037] Preferably, the extraction section comprises 1st to nth stage extraction tanks arranged in series, n≤8, for example, n=1, 2, 3, 4, 5, 6, 7 or 8; the oil phase inlet of the 1st stage extraction tank is connected to the oil phase outlet of the fth stage activation tank, the water phase inlet of the nth stage extraction tank is connected to the salt lake brine storage tank, the water phase outlet of each stage extraction tank is connected to the water phase inlet of the previous stage extraction tank, only the water phase outlet of the 1st stage extraction tank is connected to the raffinate storage tank, the oil phase outlet of each stage extraction tank is connected to the oil phase inlet of the next stage extraction tank, and only the oil phase outlet of the nth stage extraction tank is connected to the oil phase inlet of the washing section.

[0038] Preferably, the washing section comprises 0 to x-th washing tanks arranged in series, x≤6, for example, x =1, 2, 3, 4, 5 or 6; the oil phase inlet of the 1st-stage washing tank is connected to the oil phase outlet of the n-stage extraction tank, the water phase inlet of the x-stage washing tank is connected to the washing liquid storage tank, the water phase outlets of each stage of the washing tank are connected to the water phase inlet of the previous stage of the washing tank, only the water phase outlet of the 1st-stage washing tank is connected to the water phase inlet of the n-stage extraction tank, the oil phase outlets of each stage of the washing tank are connected to the oil phase inlet of the next stage of the washing tank, and only the oil phase outlet of the x-stage washing tank is connected to the oil phase inlet of the stripping section.

[0039] Preferably, the stripping section comprises 1 to y stage stripping tanks arranged in series, y≤8, for example, y =1, 2, 3, 4, 5, 6, 7 or 8; the oil phase inlet of the 1st stage stripping tank is connected to the oil phase outlet of the xth stage washing tank, the water phase inlet of the yth stage stripping tank is connected to the stripping liquid storage tank, the water phase outlet of each stage stripping tank is connected to the water phase inlet of the previous stage stripping tank, only the water phase outlet of the 1st stage stripping tank is connected to the high lithium liquid storage tank, the oil phase outlet of each stage stripping tank is connected to the oil phase inlet of the next stage stripping tank, and only the oil phase outlet of the yth stage stripping tank is connected to the inlet of the 1st stage activation tank.

[0040] As described above, the resource-saving method and system for extracting lithium from salt lake brine of the present invention has the following beneficial effects:

[0041] The resource-saving method for extracting lithium from salt lake brine of the present invention is as follows: an extractant containing a phosphate ester organic compound is first activated by an acidic NaCl-FeCl3 solution to form a sodium iron extract; the activated aqueous phase can be recycled; only hydrochloric acid, sodium chloride and ferric chloride need to be added in the activation section; in the prior art, ferric chloride and hydrochloric acid are directly added to the brine; the acid and ferric chloride in the brine are finally discharged with the raffinate; as the amount of brine treated increases, the consumption of ferric chloride and hydrochloric acid also increases synchronously; compared with the prior art, the present invention greatly reduces the amount of hydrochloric acid and ferric chloride used, saves resources, and does not require the addition of hydrochloric acid in the extraction section, that is, H + Low content, Li + will be extracted preferentially, thereby increasing the lithium extraction rate.

[0042] The resource-saving salt lake brine extraction method and system of the present invention has no requirements for the chlorine content in the brine. After the extractant is activated, it can be directly used for extraction with the brine. It has a wide range of applications and does not require the addition of chemical agents to the brine. It can be used directly. The properties of the brine after extraction are not greatly changed, and the pollution to the environment is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic structural diagram of the resource-saving salt lake brine lithium extraction system of the present invention; M in the figure represents stirring.

[0044] 100 Activation section 200 Extraction section 300 Washing section 400 Stripping section 101 Extractant storage tank 102 Activator storage tank 11 Level 1 Activation Tank 12 Level f activation tank 201 Salt lake brine storage tank 202 Raffinate storage tank 21 1st stage extraction tank 22 nth stage extraction tank 301 Washing liquid storage tank 31 1st stage sink 32 Class x sink 401 Stripping liquid storage tank 402 High lithium liquid storage tank 41 1st stage stripping tank 42 The yth stage stripping tank DETAILED DESCRIPTION

[0045] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0046] When a numerical range is disclosed herein, the above range is deemed to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges therein. For example, a specified range from "1 to 10" should be deemed to include any and all subranges between a minimum of 1 and a maximum of 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0047] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; and, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of implementation of the present invention. Changes or adjustments in their relative relationships, without substantially changing the technical content, should also be regarded as the scope of implementation of the present invention.

[0048] Example 1

[0049] This embodiment provides a resource-saving salt lake brine extraction system and method for lithium extraction, wherein the system includes an activation section 100, an extraction section 200, a washing section 300, and a stripping section 400 arranged in a circular manner along the flow direction of the extractant.

[0050] The activation section 100 includes a first-stage activation tank, the oil phase inlet of the first-stage activation tank 11 is connected to the extractant storage tank, the water phase inlet of the first-stage activation tank 11 is connected to the activator storage tank, and the oil phase outlet of the first-stage activation tank 11 is connected to the oil phase inlet of the extraction section 200. The activation tank can be set in multiple levels to balance production efficiency.

[0051] The extraction section 200 includes 1st to 6th stage extraction tanks arranged in series, the oil phase inlet of the 1st stage extraction tank 21 is connected to the oil phase outlet of the 1st stage activation tank 11, the water phase inlet of the 6th stage extraction tank is connected to the salt lake brine storage tank 201, the water phase outlet of each stage extraction tank is connected to the water phase inlet of the previous stage extraction tank, the water phase outlet of the 1st stage extraction tank 21 is connected to the raffinate storage tank 202, the oil phase outlet of each stage extraction tank is connected to the oil phase inlet of the next stage extraction tank, and the oil phase outlet of the 6th stage extraction tank is connected to the oil phase inlet of the washing section 300.

[0052] The washing section 300 includes 1st to 6th stage washing tanks arranged in series, the oil phase inlet of the 1st stage washing tank 31 is connected to the oil phase outlet of the 6th stage extraction tank, the water phase inlet of the 6th stage washing tank is connected to the washing liquid storage tank 301, the water phase outlet of each stage washing tank is connected to the water phase inlet of the previous stage washing tank, the water phase outlet of the 1st stage washing tank 31 is connected to the water phase inlet of the 6th stage extraction tank, the oil phase outlet of each stage washing tank is connected to the oil phase inlet of the next stage washing tank, and the oil phase outlet of the 6th stage washing tank is connected to the oil phase inlet of the stripping section 400.

[0053] The stripping section 400 includes 1st to 6th stage stripping tanks arranged in series, the oil phase inlet of the 1st stage stripping tank 41 is connected to the oil phase outlet of the 6th stage washing tank, the water phase inlet of the 6th stage stripping tank is connected to the stripping liquid storage tank 401, the water phase outlet of each stage stripping tank is connected to the water phase inlet of the previous stage stripping tank, the water phase outlet of the 1st stage stripping tank 41 is connected to the high lithium liquid storage tank 402, the oil phase outlet of each stage stripping tank is connected to the oil phase inlet of the next stage stripping tank, and the oil phase outlet of the 6th stage stripping tank is connected to the inlet of the 1st stage activation tank 11.

[0054] Concentration of each ion in salt lake brine: Na + :50g / L、Li + :1.2g / L、Cl - :180g / L、Mg 2+ :20g / L.

[0055] The extraction agent is: tributyl phosphate: sulfonated kerosene = 1:1.

[0056] Activator: acidic NaCl-FeCl3 solution, pH 2, sodium chloride solution concentration of 3 mol / L, ferric chloride concentration of 1 mol / L.

[0057] The detergent is: 2g / L lithium solution.

[0058] The stripping agent is: 0.1 mol / L hydrochloric acid.

[0059] The resource-saving method for extracting lithium from salt lake brine comprises the following steps:

[0060] S1. The extractant and the activator are mixed in the stirring chamber of the first-stage activation tank 11, with the flow rate of the extractant being 80 ml / min and the flow rate of the activator being 40 ml / min; the mixed solution of the extractant and the activator is separated in the clarifying chamber of the first-stage activation tank 11, and the activated extractant is obtained in this process. The remaining activator solution is refluxed in the first-stage activation tank 11; when the concentration of the activator in the activation tank decreases, the raw material for replenishing the activator is regularly added to ensure that the H in the activator is + 、Na+ 、Cl - 、Fe 3+ concentration; the reaction formula for obtaining the activated extractant is:

[0061] Fe 3+ + 4Cl - → FeCl4 - （a） ;

[0062] FeCl4 - + Na + + S （o） → NaFeCl4·S （o） ;

[0063] Among them, the subscript （a） represents the aqueous phase, subscript （o） represents the oil phase, and S represents the extractant;

[0064] S2, the activated extractant enters the extraction section 200 from the first-stage extraction tank 21, and the flow rate of the activated extractant is 80 ml / min; the salt lake brine enters the extraction section from the sixth-stage extraction tank, and the flow rate of the salt lake brine is 120 ml / min. The activated extractant extracts lithium ions in the salt lake brine by countercurrent extraction. The raffinate is discharged from the first-stage extraction tank 21 to the raffinate storage tank, and the sixth-stage extraction tank obtains an extract containing lithium extractant. The reaction formula of the extraction process is:

[0065] NaFeCl4·S （o） + Li + → LiFeCl4·S （o） + Na + ;

[0066] S3, the extract containing lithium complex enters the washing section 300 from the first washing tank 31, and the extract containing lithium complex flows into the sixth washing tank in turn; the flow rate of the detergent is 10 ml / min, and the detergent enters the first washing tank 31 from the sixth washing tank, and the washed oil phase enters the stripping section 400; the reaction formula of the washing process is:

[0067] NaFeCl4·S （o） + Li + → LiFeCl4·S （o） + Na + ;

[0068] NaFeCl4·S （o） + H + → HFeCl4·S （o） + Na + ;

[0069] S4, the washed oil phase enters the stripping section 400 from the first-stage stripping tank 41, and the stripping agent enters the stripping section 400 from the sixth-stage stripping tank from the stripping liquid storage tank. The flow rate of the stripping agent is 10 ml / min; the oil phase after stripping enters the first-stage activation tank 11 from the sixth-stage stripping tank for reactivation for recycling, and the aqueous phase obtained after stripping enters the high-lithium liquid storage tank 402; the reaction formula of the process is:

[0070] LiFeCl4·S （o） + H + → S （o） + LiCl + FeCl3 + H + .

[0071] Example 2

[0072] Compared with Example 1, the difference is:

[0073] The extraction agent is: tripentyl phosphate: sulfonated kerosene = 1:1.

[0074] Activator: acidic NaCl-FeCl3 solution, pH 1, sodium chloride solution concentration of 4 mol / L, ferric chloride concentration of 0.8 mol / L.

[0075] The detergent is: 0.1g / L lithium chloride solution.

[0076] The stripping agent is: 0.5 mol / L hydrochloric acid.

[0077] The remaining steps are the same as in Example 1.

[0078] Example 3

[0079] Compared with Example 1, the difference is:

[0080] The extractant is: 2-ethylhexyl mono-2-ethylhexyl phosphate: sulfonated kerosene = 1:1.

[0081] Activator: acidic NaCl-FeCl3 solution, pH 3, sodium chloride solution concentration of 5 mol / L, ferric chloride concentration of 0.5 mol / L.

[0082] The detergent is: pure water with pH=6.

[0083] The stripping agent is: 6 mol / L hydrochloric acid.

[0084] The remaining steps are the same as in Example 1.

[0085] Example 4

[0086] Compared with Example 1, the concentrations of ions in the salt lake brine are: Na+ :60g / L、Li + :1g / L、Cl - :150g / L、Mg 2+ :40g / L.

[0087] The remaining steps are the same as in Example 1.

[0088] Example 5

[0089] Compared with Example 1, the structure of the washing section is not included. The rest is the same as Example 1.

[0090] Example 6

[0091] Compared with Example 1, the pH of the acidic NaCl-FeCl3 solution in the activation stage is 3, the concentration of the sodium chloride solution is 2 mol / L, and the concentration of ferric chloride is 0.2 mol / L. The rest is the same as in Example 1.

[0092] Comparative Example 1

[0093] Compared with Example 1, the system does not include an activation section, and the extractant is not first activated with an acidic NaCl-FeCl3 solution. Instead, acid and FeCl3 are directly added to the salt lake brine. The pH of the extraction section is the same as that of the activation section in Example 1, the concentration of FeCl3 is 42 g / L, and then extraction is carried out using the extractant. The rest is the same as in Example 1.

[0094] Comparative Example 2

[0095] Compared with Example 1, only the activation stage of step 1 was omitted, and severe emulsification occurred during the extraction process, making extraction impossible.

[0096] Comparative Example 3

[0097] Compared with Example 1, when the extractant was replaced with a diketone extractant, selected from the extractant in Example 1 of Patent Publication No. CN 118241039 A, emulsification occurred and extraction could not be achieved.

[0098] Comparative Example 4

[0099] Compared with Example 1, the sodium chloride in the activator was replaced by magnesium chloride of the same concentration.

[0100] Comparative Example 5

[0101] Compared with Example 1, the addition of sodium chloride solution is omitted in S1, and a new step is added between S1 and S2, that is, the organic phase obtained in S1 is mixed with a sodium chloride solution with a concentration of 3 mol / L. The flow rate of the organic phase is 80 ml / min, and the flow rate of the sodium chloride solution is 40 ml / min.

[0102] The high-lithium solutions obtained in the above examples and comparative examples were tested, and the results are shown in Table 1 below.

[0103] Table 1

[0104] The content of ferric chloride in the raffinate after a single cycle g / L Lithium yield (%) Example 1 3.1g / L 95.4% Example 2 3.1g / L 95.2% Example 3 2.7g / L 95.4% Example 4 2.5g / L 95.3% Example 5 3.4g / L 94.2% Example 6 2.3g / L 70.1% Comparative Example 1 17.6g / L 90.6% Comparative Example 4 5.3g / L 80.2% Comparative Example 5 3.1g / L 85.6%

[0105] By comparing Example 1 and Example 4, it can be seen that the change in the concentration of components in the brine has no significant effect on the extraction rate of the present application.

[0106] By comparing Example 1 and Example 5, it can be seen that when the washing stage is omitted, the extraction rate decreases because the extractant carries some sodium ions.

[0107] By comparing Example 1 with Example 6, it can be seen that the concentrations of chloride ions and iron ions in the activation stage are relatively low, and the NaFeCl4·mS (0) Smaller amounts are produced, resulting in lower extraction yields.

[0108] By comparing Example 1 and Comparative Example 1, it can be seen that the content of ferric chloride in the raffinate of Comparative Example 1 is much higher than that in Example 1. The content of ferric chloride in Example 1 is relatively small, mainly ferric chloride entrained in the raffinate, while the content in Comparative Example 1 is mainly ferric chloride added to the brine. At the same time, in order to maintain the stable presence of iron ions in the brine, the hydrogen ion content is relatively high, and the hydrogen ions occupy the extractant, resulting in a decrease in the extraction rate.

[0109] By comparing Example 1 and Comparative Example 4, it can be seen that when magnesium chloride is used instead of sodium chloride under the same conditions, the loss of iron ions in the raffinate increases due to the lower complexing ability of magnesium with the extractant than that of sodium, the extractant is not fully utilized, and the loss of active substance iron ions leads to a decrease in lithium yield.

[0110] By comparison of Example 1 and Comparative Example 5, it can be seen that the acidic ferric chloride solution and the sodium chloride solution are added separately. Due to the use of sodium chloride, the iron ion loss rate does not change significantly. However, due to the relatively low chloride ion concentration and the reduced hydrogen ion concentration, the iron ions are lost in the sodium chloride solution, which ultimately leads to a decrease in the lithium yield relative to Example 1.

[0111] In the actual operation process of Comparative Example 5, the hydrogen ion concentration in the ferric chloride solution will continue to decrease, while the hydrogen ion concentration in the sodium chloride solution will continue to increase. The hydrogen ion concentration fluctuates greatly, and hydrogen ions need to be continuously added to the ferric chloride solution.

[0112] Therefore, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0113] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A resource-saving method for extracting lithium from salt lake brine, characterized in that: The following steps are involved: S1. Mixing an extractant with an acidic NaCl-FeCl3 solution and then clarifying and separating the mixture to obtain an activated extractant, wherein the extractant comprises a phosphate ester, the pH of the acidic NaCl-FeCl3 solution is 0-4, and the reaction formula is: Fe 3+ + 4Cl - → FeCl4 - （a） ; FeCl4 - + In + + S （o） → NaFeCl4·S （o） ; Among them, the subscript （a） represents the aqueous phase, subscript （o） represents the oil phase, and S represents the extractant; S2, the activated extractant is mixed with salt lake brine and clarified to obtain an extract containing a lithium extractant, and the reaction formula is as follows: NaFeCl4·S （o） + Li + → LiFeCl4·S （o） + On + ; S3, stripping the extract containing the lithium extractant to finally obtain a high-lithium solution.

2. The resource-saving method for extracting lithium from salt lake brine according to claim 1, characterized in that: The concentration of sodium chloride solution in the acidic NaCl-FeCl3 solution in step S1 is 2-6 mol / L, and the concentration of ferric chloride is 0.5-2 mol / L.

3. The resource-saving method for extracting lithium from salt lake brine according to claim 1, characterized in that: Before the back extraction in step S3, the extract is washed with a detergent, wherein the detergent is a lithium-containing aqueous solution or pH-neutral water.

4. The resource-saving method for extracting lithium from salt lake brine according to claim 3, characterized in that: The concentration of lithium in the lithium-containing aqueous solution is 0.1-2 g / L.

5. The resource-saving method for extracting lithium from salt lake brine according to claim 1, characterized in that: In step S3, the stripping agent used in the stripping is 0.1-6 mol / L acid.

6. The resource-saving method for extracting lithium from salt lake brine according to claim 5, characterized in that: The acid is hydrochloric acid, sulfuric acid or nitric acid.

7. The resource-saving method for extracting lithium from salt lake brine according to claim 1, characterized in that: In step S3, an oil phase is obtained after the stripping, and the oil phase is returned to step S1 to be mixed with the acidic NaCl-FeCl3 solution.

8. A system suitable for the resource-saving method of extracting lithium from salt lake brine according to any one of claims 1 to 7, characterized in that: The system comprises an activation section (100), an extraction section (200) and a stripping section (400) which are circulated along the flow direction of the extractant; The activation section (100) comprises 1st to fth stage activation tanks arranged in series, f≤5, the oil phase inlet of the first stage activation tank (11) is connected to the extractant storage tank (101), the water phase inlet of the fth stage activation tank (12) is connected to the activator storage tank (102), the water phase outlets of each stage activation tank are connected to the water phase inlet of the previous stage activation tank, only the water phase outlet of the first stage activation tank (11) is connected to the water phase inlet of the fth stage activation tank (12), the oil phase outlets of each stage activation tank are connected to the oil phase inlet of the next stage activation tank, and only the oil phase outlet of the fth stage activation tank (12) is connected to the oil phase inlet of the extraction section (200); The extraction section (200) is connected to a salt lake brine storage tank (201) to provide salt lake brine to the extraction section. The extraction section (200) is also connected to a raffinate storage tank (202) to collect the raffinate generated by the extraction section. The stripping section (400) is connected to a stripping solution storage tank (401) to provide stripping solution to the stripping section. The stripping section (400) is also connected to a high-lithium solution storage tank (402) to collect high-lithium solution from the stripping section.

9. The system suitable for the resource-saving method of extracting lithium from salt lake brine according to claim 8, characterized in that: The system further comprises a washing section (300), wherein the washing section (300) is arranged between the extraction section (200) and the stripping section (400) and is connected to the extraction section (200) and the stripping section (400), respectively. The washing section (300) is also connected to a washing liquid storage tank (301) to provide washing liquid to the washing section.

10. The system suitable for the resource-saving method of extracting lithium from salt lake brine according to claim 9, characterized in that: The extraction section (200) includes 1st to nth stage extraction tanks arranged in series, n≤8, the oil phase inlet of the 1st stage extraction tank (21) is connected to the oil phase outlet of the fth stage activation tank (12), the water phase inlet of the nth stage extraction tank (22) is connected to the salt lake brine storage tank (201), the water phase outlets of each stage extraction tank are connected to the water phase inlet of the previous stage activation tank, only the water phase outlet of the 1st stage extraction tank (21) is connected to the raffinate storage tank (202), the oil phase outlets of each stage extraction tank are connected to the oil phase inlet of the next stage extraction tank, and only the oil phase outlet of the nth stage extraction tank (22) is connected to the oil phase inlet of the washing section (300).

11. The system suitable for the resource-saving method of extracting lithium from salt lake brine according to claim 10, characterized in that: The washing section (300) comprises 0 to x-th washing tanks arranged in series, where x≤6, the oil phase inlet of the first-stage washing tank (31) is connected to the oil phase outlet of the n-th-stage extraction tank (22), the water phase inlet of the x-th-stage washing tank (32) is connected to the washing liquid storage tank (301), the water phase outlets of each washing tank are connected to the water phase inlet of the previous-stage washing tank, only the water phase outlet of the first-stage washing tank (31) is connected to the water phase inlet of the n-th-stage extraction tank (22), the oil phase outlets of each washing tank are connected to the oil phase inlet of the next-stage washing tank, and only the oil phase outlet of the x-th-stage washing tank (32) is connected to the oil phase inlet of the stripping section (400).

12. The system suitable for the resource-saving method of extracting lithium from salt lake brine according to claim 11, characterized in that: The stripping section (400) includes 1 to y stage stripping tanks arranged in series, y≤8, the oil phase inlet of the 1 stage stripping tank (41) is connected to the oil phase outlet of the x stage washing tank (32), the water phase inlet of the y stage stripping tank (42) is connected to the stripping liquid storage tank (401), the water phase outlets of each stage stripping tank are connected to the water phase inlet of the previous stage stripping tank, only the water phase outlet of the 1 stage stripping tank (41) is connected to the high lithium liquid storage tank (402), the oil phase outlets of each stage stripping tank are connected to the oil phase inlet of the next stage stripping tank, and only the oil phase outlet of the y stage stripping tank (42) is connected to the inlet of the 1 stage activation tank (11).

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