A method for recovering lithium from lithium-containing wastewater

Abstract

The application provides a method for recovering lithium from lithium-containing wastewater, which comprises the following steps: pretreating the lithium-containing wastewater to obtain a lithium-containing solution; using an organic phase to extract the lithium-containing solution, and then separating the phases to obtain an oil phase; the organic phase comprises an extractant; during the extraction process, an alkaline substance is added to the extraction system; the oil phase is back-extracted to obtain a lithium-containing aqueous phase; and the lithium-containing aqueous phase is precipitated to obtain a lithium salt. The method has the advantages that the oil-water phases of the extraction system can be well separated, the oil loss is small, the process cost is low, the lithium ions in the wastewater can be recycled and reused, the lithium-sodium selectivity is good, the loading capacity is high, and the process flow is short.

Description

Technical Field

[0001] This invention belongs to the field of battery recycling technology and relates to a method for recovering lithium from lithium-containing wastewater. Background Technology

[0002] Lithium is widely used in pharmaceuticals, glass, ceramics, lubricating greases, alloys, and new energy fields, and is known as "white petroleum." It is one of the most promising metals of the 21st century. Compared to traditional lithium extraction from spodumene solid deposits, lithium extraction from salt lakes has advantages such as abundant resources, simple processes, low development costs, and strong market competitiveness. Currently, lithium extraction from salt lakes has become an important way to obtain lithium salts and a major source of lithium resources.

[0003] In existing technologies, the main methods for lithium extraction include precipitation, adsorption, membrane extraction, electrochemical extraction, and solvent extraction. Among these, solvent extraction technology offers high throughput, simple operation, and low pollution, thus attracting widespread research and development. Currently, the extraction systems used for lithium extraction include the TBP+FeCl3 system and the β-diketone system.

[0004] For example, CN 106636673A discloses a method for extracting lithium from salt lake brine using an extraction method. This method is applicable to the production process of producing lithium carbonate and lithium chloride from high magnesium-to-lithium ratio salt lake brine and lithium-containing concentrated old brine in salt fields. The method uses a co-extractant FeCl3, an extractant, and a diluent for lithium extraction. The extractant is a mixture of neutral phosphorus oxide compound A and a phase modifier B, wherein the phase modifier B is an organic compound that can undergo a protonation reaction with neutral phosphorus oxide compound A during the extraction reaction. Although the extractant TBP in the TBP+FeCl3 extraction system is easy to prepare, inexpensive, and has high selectivity for lithium, TBP has high solubility in water. Furthermore, to prevent iron hydrolysis, the brine needs to maintain a certain acidity, requiring a higher concentration of acid for back-extraction to remove metal ions. However, high concentrations of acid can break the phospho-oxygen bonds of TBP, causing TBP degradation. In addition, ferric chloride needs to be added to the extractant TBP to promote the lithium extraction rate.

[0005] Another lithium extraction system is the β-diketone system. Its advantages are that it is easy to prepare, has good selectivity for lithium, and low acidity during back-extraction. However, the carbon chain of the diketone in this system is relatively short, and its solubility in water is relatively high. Moreover, the system is prone to emulsification, making the interface between the two phases unclear.

[0006] Therefore, since current extraction systems all suffer from problems such as high solubility of the extractant in the aqueous phase and unclear extraction interface due to emulsification of the extraction system, there is an urgent need to provide a lithium recovery method that has good lithium-sodium selectivity, clear phase separation interface, and can slow down the dissolution loss of the extractant. Summary of the Invention

[0007] The purpose of this invention is to provide a method for recovering lithium from lithium-containing wastewater. The extraction system of the method has good oil-water separation, low oil loss, and low process cost. It can recover and recycle lithium ions in wastewater, and has good lithium-sodium selectivity, high loading capacity, and short process flow.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for recovering lithium from lithium-containing wastewater, the method comprising the following steps:

[0010] (1) The lithium-containing wastewater is pretreated to obtain a lithium-containing solution;

[0011] (2) Extraction was performed using the lithium-containing solution described in step (1) of the organic phase, followed by phase separation to obtain the oil phase;

[0012] The organic phase includes an extractant; during the extraction process, an alkaline substance is added to the extraction system;

[0013] (3) The oil phase described in step (2) is back-extracted to obtain a lithium-containing aqueous phase;

[0014] (4) The lithium-containing aqueous phase described in step (3) is precipitated to recover lithium salt.

[0015] This invention first pretreats lithium-containing wastewater before extraction, and adds alkaline substances during the extraction process, which greatly improves the atom utilization rate in the production process and makes the alkalinity of the extracted aqueous phase low. This greatly suppresses the problems of unclear phase separation and extractant loss caused by organic phase emulsification. Therefore, the oil-water phase separation of the entire system of this invention is good, the oil loss is low, the process cost is low, and lithium and sodium ions in the wastewater can be recovered and recycled. At the same time, the method of this invention has good lithium-sodium selectivity, high loading capacity, and short process flow.

[0016] The alkaline substance in step (2) of this invention is added in solution form.

[0017] Preferably, the pretreatment in step (1) includes adjusting the pH of the lithium-containing wastewater to ≥7, for example, it can be 7, 8, 9, 10, 11, 12 or 13, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the pH of the lithium-containing wastewater in step (1) is adjusted using carbonates and / or bicarbonates.

[0019] This invention uses carbonates and / or bicarbonates to adjust the pH of lithium-containing wastewater, achieving low-cost and efficient adjustment of the acidity of the aqueous phase.

[0020] Preferably, in the lithium-containing solution of step (1), the concentration of carbonate is 0.5-1.5 times the concentration of lithium ions, for example, it can be 0.5 times, 1.0 times or 1.5 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the lithium-containing wastewater in step (1) includes the leaching wastewater from the battery powder recycling process.

[0022] The lithium-containing wastewater of this invention is the sulfate leaching wastewater generated during the recycling of ternary battery powder.

[0023] Preferably, the extraction in step (2) includes multi-stage countercurrent extraction.

[0024] Preferably, the number of stages in the multi-stage countercurrent extraction is 1-10, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 stages, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0025] Preferably, the alkaline substance in step (2) is added when the multi-stage countercurrent extraction is carried out to the intermediate stage or the equal-stage stage.

[0026] When the alkaline substance described in this invention is added during the intermediate stage of multi-stage countercurrent extraction, for example, if the number of stages in the multi-stage countercurrent extraction is 2n, the alkaline substance can be added at stage n or between stage n and 2n; or, if the number of stages in the multi-stage countercurrent extraction is 2n+1, the alkaline substance can be added at stage n+1 or between stage n+1 and 2n+1; when the alkaline substance is added during the equal-equal-stage stage of multi-stage countercurrent extraction, for example, if the number of stages in the multi-stage countercurrent extraction is 3n, the alkaline substance can be added at stage n, stage 2n, or stage 3n.

[0027] In addition, the alkaline substance added at the intermediate stage of this invention is in solution form, while the alkaline substances added at other stages can be solid substances or solutions. Furthermore, the alkaline solution added at the intermediate stage can be added from the inlet of the nth stage organic phase or from the inlet of the nth stage aqueous phase.

[0028] In this invention, n is a natural number greater than 1.

[0029] Preferably, the amount of alkaline substance added in step (2) is 0.5-1.5 times the lithium ion concentration in the lithium-containing solution in step (1), for example, it can be 0.5 times, 0.75 times, 1.0 times, 1.25 times or 1.5 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] The present invention adds alkaline substances in stages during the extraction process to avoid unclear phase separation caused by emulsification of the organic phase and the problem of extractant loss. If too little alkaline substance is added, it will affect the extraction effect of the organic phase on lithium. If too much alkaline substance is added, carbonate precipitation and increased oil loss of the organic phase may occur.

[0031] Preferably, the alkaline substance in step (2) includes any one or a combination of at least two of carbonates, bicarbonates, or hydroxides.

[0032] Preferably, the extractant in step (2) includes LiSX extractant.

[0033] This invention uses LiSX as an extractant, and achieves high selectivity and high extraction rate of lithium ions in lithium-containing wastewater under neutral or weakly alkaline conditions without the need to add ferric chloride as a co-extractant.

[0034] Preferably, the LiSX extractant comprises a mixture of phosphorus extractants and ketone extractants.

[0035] The phosphorus (phosphine) extractants of this invention include any one or a combination of at least two of trialkylphosphine oxide (Cyanex 923, TRPO), trioctylphosphine oxide, trinonylphosphine oxide, tridecylphosphine oxide, or tributyl phosphonate (TBP), wherein the alkyl group in trialkylphosphine oxide includes octyl or hexyl. The ketone extractants include any one or a combination of at least two of dodecylphenyl-methyl-β-dione (LIX 54, LIX 54-100, Metrax 54, Metrax 54-100), tetradecylphenyl-methyl-β-dione, dodecylphenyl-ethyl-β-dione, tetradecylphenyl-ethyl-β-dione, decylphenyl-ethyl-β-dione, or decylphenyl-ethyl-β-dione.

[0036] The phosphorus (phosphine) extractants described in this invention are represented by phosphine for extractants containing PC bonds, and by phosphorus for other cases.

[0037] Preferably, in the LiSX extractant, the mass ratio of phosphorus extractant to ketone extractant is (1-9):(1-9), for example, it can be 1:1, 1:5, 5:1, 9:1 or 1:9, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably (1-3):(1-3).

[0038] Preferably, in the organic phase described in step (2), the content of the extractant is 10wt%-80wt%, for example, it can be 10wt%, 30wt%, 50wt%, 70wt% or 80wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the organic phase in step (2) further includes a diluent.

[0040] Preferably, the diluent comprises sulfonated kerosene.

[0041] Preferably, the O / A ratio (extraction ratio) of the extraction in step (2) is (1-5):(1-5), for example, it can be 1:1, 1:3, 3:1, 1:5 or 5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] Preferably, the extraction temperature in step (2) is 20-70℃, for example, 20℃, 40℃, 60℃ or 70℃, the rotation speed is 150-450rpm, for example, 150rpm, 250rpm, 350rpm or 450rpm, and the time is 0.05-0.5h, for example, 0.05h, 0.1h, 0.3h or 0.5h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the oil phase in step (2) is washed before being back-extracted, and the resulting organic phase is then back-extracted.

[0044] Preferably, the washing method includes multi-stage countercurrent washing, wherein the number of stages of multi-stage countercurrent washing is 1-10, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 stages, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0045] Preferably, the detergent used for washing includes any one or a combination of at least two of pure water, lithium salt solution, or acid.

[0046] Preferably, in the detergent, the concentrations of the lithium salt solution and the acid are independently 0-1 mol / L, but not including 0 mol / L. For example, they can be 0.1 mol / L, 0.5 mol / L or 1 mol / L, but are not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, the back-extraction method in step (3) includes multi-stage countercurrent back-extraction, wherein the number of stages of the multi-stage countercurrent back-extraction is 1-10, for example, it can be 1 stage, 2 stages, 3 stages, 4 stages, 5 stages, 6 stages, 7 stages, 8 stages, 9 stages or 10 stages, but is not limited to the listed values, and other unlisted values ​​within the value range are also applicable.

[0048] Preferably, the back-extraction agent used in step (3) includes an inorganic acid back-extraction agent.

[0049] Preferably, the inorganic acid back-extraction agent includes hydrochloric acid and / or sulfuric acid.

[0050] Preferably, the concentration of the inorganic acid back-extraction agent is 0.1-6 mol / L, for example, it can be 0.1 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L or 6 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] The washing phase, temperature, rotation speed, and reaction time of the washing described in this invention are the same as those of the extraction in step (2), and the back-extraction phase, temperature, rotation speed, and reaction time are the same as those of the extraction in step (2); that is, the washing and back-extraction temperatures are independently 20-70℃, for example, 20℃, 40℃, 60℃, or 70℃, the rotation speeds are independently 150-450rpm, for example, 150rpm, 250rpm, 350rpm, or 450rpm, and the times are independently 0.05-0.5h, for example, 0.05h, 0.1h, 0.3h, or 0.5h, but are not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0052] Preferably, the organic phase obtained by back-extraction in step (3) is regenerated and then reused in step (2).

[0053] The extractant used in this invention can be recycled multiple times, and the extraction operation is simple.

[0054] Preferably, the regeneration method includes mixing the organic phase obtained from back-extraction with a regenerating agent.

[0055] Preferably, the regenerant comprises any one or a combination of at least two of water, carbonate, or hydroxide.

[0056] Preferably, the precipitant used in step (4) includes carbonates.

[0057] The carbonates described in this invention are monovalent carbonates, including any one or a combination of at least two of sodium carbonate, potassium carbonate, or rubidium carbonate; the bicarbonates are monovalent bicarbonates, including any one or a combination of at least two of sodium bicarbonate, potassium bicarbonate, or rubidium bicarbonate; the hydroxides include monovalent hydroxides, including sodium hydroxide and / or potassium hydroxide.

[0058] In this invention, the extraction ratio, washing ratio, back-extraction ratio, and addition ratio all refer to the ratio (O / A) of the volume of the organic phase to the volume of the aqueous phase when the organic phase is in contact with the aqueous phase.

[0059] As a preferred embodiment of the method described in this invention, the method includes the following steps:

[0060] (1) Adjust the pH of lithium-containing wastewater to ≥7 using carbonates and / or bicarbonates to obtain a lithium-containing solution;

[0061] In the lithium-containing solution, the concentration of carbonate ions is 0.5-1.5 times the concentration of lithium ions;

[0062] (2) The lithium-containing solution described in step (1) is subjected to multi-stage countercurrent extraction, followed by phase separation to obtain the oil phase;

[0063] The organic phase includes LiSX extractant and diluent; during the multi-stage countercurrent extraction process, an alkaline substance is added to the extraction system, and the amount of alkaline substance added is 0.5-1.5 times the lithium ion concentration in the lithium-containing solution in step (1);

[0064] (3) The oil phase described in step (2) is washed in a multi-stage countercurrent manner with lithium salt solution and / or acid, and the organic phase obtained by washing is back-extracted in a multi-stage countercurrent manner to obtain a lithium-containing aqueous phase and an organic phase;

[0065] (4) The organic phase obtained by back-extraction in step (3) is mixed with a regenerating agent to obtain a regenerated organic phase, which is then reused in step (2).

[0066] The lithium-containing aqueous phase described in step (3) is mixed with a precipitant to recover lithium salt.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] The method described in this invention has good lithium-sodium selectivity, high loading capacity, and short process flow. By adding alkaline substances during the extraction process, the atom utilization rate in the production process is greatly improved, resulting in a lower alkalinity of the aqueous phase during extraction. This significantly suppresses the problems of unclear phase separation and extractant loss caused by organic phase emulsification, resulting in good oil-water phase separation, low oil loss, and low process cost. It can also recover and recycle lithium and sodium ions in wastewater. Attached Figure Description

[0069] Figure 1 In a specific embodiment of the present invention, when the number of multi-stage countercurrent extraction stages is 2n, the flowchart of the method is as follows:

[0070] Figure 2 In a specific embodiment of the present invention, when the number of multi-stage countercurrent extraction stages is 2n+1, the flowchart of the method is as follows:

[0071] Figure 3 In a specific embodiment of the present invention, when the number of multi-stage countercurrent extraction stages is 3n, the flowchart of the method is as follows:

[0072] Figure 4This is a schematic diagram of the raffinate outlet phase in step (3) of Embodiment 1 of the present invention;

[0073] Figure 5 This is a schematic diagram of the raffinate outlet phase in step (3) of Comparative Example 1 of the present invention. Detailed Implementation

[0074] In a specific embodiment of the present invention, a method is provided as follows: Figure 1 The method for recovering lithium from lithium-containing wastewater includes an extraction section, a washing section, a back-extraction section, and a regeneration section. When the number of multi-stage countercurrent extraction stages is 2n, when the extraction reaches the nth stage, an alkaline substance such as carbonate or alkali is added to the organic phase inlet. After the extraction is completed, n-stage washing and n-stage back-extraction are performed. The organic phase obtained from the back-extraction is added to a regenerator to obtain a regenerated organic phase, which is then reused in the extraction stage.

[0075] In one specific embodiment, a method is provided as follows: Figure 2 The method for recovering lithium from lithium-containing wastewater includes an extraction section, a washing section, a back-extraction section, and a regeneration section. When the number of multi-stage countercurrent extraction stages is 2n+1, when the extraction reaches the n+1 stage, an alkaline substance such as carbonate or alkali is added to the organic phase inlet. After the extraction is completed, n-stage washing and n-stage back-extraction are performed. The organic phase obtained from the back-extraction is added to a regenerator to obtain a regenerated organic phase, which is then reused in the extraction stage.

[0076] In one specific embodiment, a method is provided as follows: Figure 3 The method for recovering lithium from lithium-containing wastewater includes an extraction section, a washing section, a back-extraction section, and a regeneration section. When the number of multi-stage countercurrent extraction stages is 3n, alkaline substances such as carbonates or alkalis are added to the organic phase inlet when the extraction reaches the nth and 2nth stages. After the extraction is completed, n-stage washing and n-stage back-extraction are performed. The organic phase obtained from the back-extraction is added to a regenerator to obtain a regenerated organic phase, which is then reused in the extraction stage.

[0077] 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.

[0078] Example 1

[0079] This embodiment provides a method for recovering lithium from lithium-containing wastewater, the method comprising the following steps:

[0080] (1) The pH of the lithium-containing wastewater was adjusted to 10 using saturated sodium carbonate to obtain a lithium-containing solution with Li = 0.65 g / L and Na = 25 g / L.

[0081] In the lithium-containing solution, the concentration of carbonate ions is 1 times the concentration of lithium ions;

[0082] The lithium-containing wastewater is the sulfate leaching wastewater generated during the recovery of ternary battery powder.

[0083] (2) Organic phase preparation: The organic phase was composed of 40 wt% LiSX and 60 wt% sulfonated kerosene;

[0084] The LiSX extractant is dodecylphenyl-methyl-β-dione and trioctylphosphine oxide in a mass ratio of 2:1;

[0085] (3) Extraction: The organic phase described in step (2) is subjected to four-stage countercurrent extraction with an extraction ratio of 1:1 to the lithium-containing solution described in step (1). Liquid alkali is added at the inlet of the third organic phase, with an O / A ratio of 20:1. Then, the phases are separated. The resulting raffinate has a lithium content of 10 mg / L, a sodium content of 24 g / L, and an oil content of 31 mg / L. A schematic diagram of the raffinate outlet phase is shown below. Figure 4 As shown;

[0086] The hydroxide content in the added alkali is 1 times the lithium ion concentration in the lithium-containing solution in step (1);

[0087] The extraction temperature was 35℃, the rotation speed was 350 rpm, and the time was 0.2 h;

[0088] (4) Washing: The organic phase obtained after extraction in step (3) is washed with lithium sulfate solution in a two-stage countercurrent wash at a washing ratio of O / A = 10:1 to remove the trace amount of sodium ions loaded, and to obtain the lithium-loaded organic phase.

[0089] The washing temperature is 35℃, the spin speed is 350rpm, and the time is 0.2h;

[0090] (5) Back-extraction: The lithium-loaded organic phase obtained in step (4) is back-extracted with sulfuric acid solution in a three-stage countercurrent back-extraction ratio of O / A = 10:1 to obtain lithium sulfate solution;

[0091] The back-extraction temperature was 35°C, the rotation speed was 350 rpm, and the time was 0.3 h.

[0092] (6) Precipitation: Add saturated sodium carbonate solution to the lithium sulfate solution described in step (5) to precipitate battery-grade lithium carbonate with a lithium carbonate content of 99.1%.

[0093] Example 2

[0094] This embodiment provides a method for recovering lithium from lithium-containing wastewater, the method comprising the following steps:

[0095] (1) The pH of the lithium-containing wastewater was adjusted to 10.5 using saturated sodium carbonate to obtain a lithium-containing solution with Li = 0.55 g / L and Na = 27 g / L.

[0096] In the lithium-containing solution, the concentration of carbonate ions is 0.5 times the concentration of lithium ions;

[0097] The lithium-containing wastewater is the sulfate leaching wastewater generated during the recovery of ternary battery powder.

[0098] (2) Organic phase preparation: The organic phase was composed of 30 wt% LiSX and 70 wt% sulfonated kerosene;

[0099] The LiSX extractant is a mixture of dodecylphenyl-methyl-β-dione and trioctylphosphine oxide in a mass ratio of 1:3;

[0100] (3) Extraction: The organic phase described in step (2) is used to perform five-stage countercurrent extraction with an extraction ratio of 1:2 to the lithium-containing solution described in step (1). Sodium carbonate solution is added to the inlet of the third organic phase with an O / A ratio of 20:1. Then the phases are separated. The lithium content of the raffinate is 12 mg / L, the sodium content is 26 g / L, and the oil content is 35 mg / L.

[0101] The carbonate content in the added sodium carbonate solution is 0.5 times the lithium ion concentration in the lithium-containing solution in step (1);

[0102] The extraction temperature was 45℃, the rotation speed was 150 rpm, and the time was 0.1 h;

[0103] (4) Washing: The organic phase obtained after extraction in step (3) is washed with lithium sulfate solution in a three-stage countercurrent wash at a washing ratio of O / A = 15:1 to remove trace amounts of loaded sodium ions and obtain an organic phase loaded with lithium.

[0104] The washing temperature is 45℃, the spin speed is 150rpm, and the time is 0.1h;

[0105] (5) Back-extraction: The lithium-loaded organic phase obtained in step (4) is back-extracted with sulfuric acid solution in a three-stage countercurrent back-extraction ratio of O / A = 10:1 to obtain lithium sulfate solution;

[0106] The back-extraction temperature was 45°C, the rotation speed was 150 rpm, and the time was 0.1 h.

[0107] (6) Precipitation: Add saturated sodium carbonate solution to the lithium sulfate solution described in step (5) to precipitate battery-grade lithium carbonate with a lithium carbonate content of 99.6%.

[0108] Example 3

[0109] This embodiment provides a method for recovering lithium from lithium-containing wastewater, the method comprising the following steps:

[0110] (1) The pH of the lithium-containing wastewater was adjusted to 11 using saturated sodium carbonate to obtain a lithium-containing solution with Li = 0.70 g / L and Na = 29 g / L.

[0111] In the lithium-containing solution, the concentration of carbonate ions is 1.5 times the concentration of lithium ions;

[0112] The lithium-containing wastewater is the sulfate leaching wastewater generated during the recovery of ternary battery powder.

[0113] (2) Organic phase preparation: The organic phase was composed of 45 wt% LiSX and 55 wt% sulfonated kerosene;

[0114] The LiSX extractant is a mixture of dodecylphenyl-methyl-β-dione and trioctylphosphine oxide in a mass ratio of 3:1;

[0115] (3) Extraction: The organic phase described in step (2) is used to perform five-stage countercurrent extraction with an extraction ratio of 1:4 to the lithium-containing solution described in step (1). Liquid alkali is added to the inlet of the third organic phase, and the ratio O / A = 20:1 is added. Then the phases are separated. The lithium content of the raffinate is 5 mg / L, the sodium content is 29 g / L, and the oil content is 33 mg / L.

[0116] The hydroxide content in the added alkali is 1.5 times the lithium ion concentration in the lithium-containing solution in step (1);

[0117] The extraction temperature was 20℃, the rotation speed was 450 rpm, and the time was 0.5 h;

[0118] (4) Washing: The organic phase obtained after extraction in step (3) is washed with lithium sulfate solution in a two-stage countercurrent wash at a washing ratio of O / A = 15:1 to remove the trace amount of sodium ions loaded, and to obtain the lithium-loaded organic phase.

[0119] The washing temperature is 20℃, the spin speed is 450rpm, and the time is 0.5h;

[0120] (5) Back-extraction: The lithium-loaded organic phase obtained in step (4) is back-extracted with sulfuric acid solution in a three-stage countercurrent back-extraction ratio of O / A = 10:1 to obtain lithium sulfate solution;

[0121] The back-extraction temperature was 20°C, the rotation speed was 450 rpm, and the time was 0.5 h.

[0122] (6) Precipitation: Add saturated sodium carbonate solution to the lithium sulfate solution described in step (5) to precipitate battery-grade lithium carbonate with a lithium carbonate content of 99.7%.

[0123] Example 4

[0124] This embodiment provides a method for recovering lithium from lithium-containing wastewater, the method comprising the following steps:

[0125] (1) The pH of the lithium-containing wastewater was adjusted to 9 using saturated sodium carbonate to obtain a lithium-containing solution with Li = 0.50 g / L and Na = 21 g / L.

[0126] In the lithium-containing solution, the concentration of carbonate ions is 1 times the concentration of lithium ions;

[0127] The lithium-containing wastewater is the sulfate leaching wastewater generated during the recovery of ternary battery powder.

[0128] (2) Organic phase preparation: The organic phase was composed of 40 wt% LiSX and 60 wt% sulfonated kerosene;

[0129] The LiSX extractant is a mixture of dodecylphenyl-methyl-β-dione and trioctylphosphine oxide in a mass ratio of 1:3;

[0130] (3) Extraction: The organic phase described in step (2) is used to perform four-stage countercurrent extraction with an extraction ratio of 1:4 to the lithium-containing solution described in step (1). Liquid alkali is added to the inlet of the third organic phase, and the ratio O / A = 20:1 is added. Then the phases are separated. The lithium content of the raffinate is 13 mg / L, the sodium content is 22 g / L, and the oil content is 18 mg / L.

[0131] The hydroxide content in the added alkali is 1 times the lithium ion concentration in the lithium-containing solution in step (1);

[0132] The extraction temperature was 50℃, the rotation speed was 300 rpm, and the time was 0.2 h;

[0133] (4) Washing: The organic phase obtained after extraction in step (3) is washed with lithium sulfate solution in a four-stage countercurrent wash at a washing ratio of O / A = 10:1 to remove the trace amount of sodium ions loaded, and to obtain the lithium-loaded organic phase.

[0134] The washing temperature is 50℃, the spin speed is 300rpm, and the time is 0.3h;

[0135] (5) Back-extraction: The lithium-loaded organic phase obtained in step (4) is back-extracted with sulfuric acid solution in a three-stage countercurrent back-extraction ratio of O / A = 10:1 to obtain lithium sulfate solution;

[0136] The back-extraction temperature was 40℃, the rotation speed was 350 rpm, and the time was 0.3 h;

[0137] (6) Precipitation: Add saturated sodium carbonate solution to the lithium sulfate solution described in step (5) to precipitate battery-grade lithium carbonate with a lithium carbonate content of 99.5%.

[0138] Example 5

[0139] This embodiment provides a method for recovering lithium from lithium-containing wastewater. Except for step (3) which involves nine-stage countercurrent extraction, adding liquid alkali at the inlet of the third organic phase, and adding liquid alkali at the inlet of the sixth organic phase, with the addition ratio of O / A = 20:1 each time, the method is the same as in Example 1.

[0140] Example 6

[0141] This embodiment provides a method for recovering lithium from lithium-containing wastewater. The method is the same as in Example 1, except that the addition of liquid alkali in step (3) is different, so that the hydroxide content in the added liquid alkali is 0.3 times the lithium ion concentration in the lithium-containing solution in step (1).

[0142] Example 7

[0143] This embodiment provides a method for recovering lithium from lithium-containing wastewater. The method is the same as in Example 1, except that the addition of liquid alkali in step (3) is different, so that the hydroxide content in the added liquid alkali is twice the lithium ion concentration in the lithium-containing solution in step (1).

[0144] Example 8

[0145] This embodiment provides a method for recovering lithium from lithium-containing wastewater. The method is the same as in Example 1, except that the LiSX extractant in step (2) is replaced by a dodecylphenyl-methyl-β-dione.

[0146] Example 9

[0147] This embodiment provides a method for recovering lithium from lithium-containing wastewater. The method is the same as in Example 1, except that the LiSX extractant in step (2) is replaced by trioctylphosphine oxide.

[0148] Comparative Example 1

[0149] This comparative example provides a method for recovering lithium from lithium-containing wastewater. The method is the same as in Example 1 except that liquid alkali is not added at the inlet of the third organic phase in step (3).

[0150] Comparative Example 2

[0151] This comparative example provides a method for recovering lithium from lithium-containing wastewater. The method is the same as that in Example 1 except that liquid alkali is not added to the inlet of the third organic phase in step (3), and the liquid alkali added in step (3) of Example 1 is added to the lithium-containing wastewater in step (1).

[0152] After extraction in step (3) of this comparative example, a schematic diagram of the raffinate outlet phase is shown below. Figure 5 As shown.

[0153] The solubility loss of the extractant, the organic phase distribution ratio, and the lithium extraction rate of the methods described in the above embodiments and comparative examples are shown in Table 1:

[0154] Table 1

[0155]

[0156]

[0157] As can be seen from Table 1:

[0158] As can be seen from Example 1 and Comparative Example 1, the addition of alkaline substances during extraction in this invention can increase the distribution ratio of lithium ions to sodium ions in the organic phase and increase the extraction rate of lithium ions by the extractant, even with minimal differences in extractant solubility. As can be seen from Example 1 and Comparative Example 2, Figure 4 The corresponding Example 1 is compared to Figure 5 The two-phase separation in Comparative Example 2 was clearer, and the solvent loss was also lower. Figure 5 The liquid alkali is added to the aqueous phase before extraction. The pH value of the pre-liquid is too high (>12.5). When the organic phase and the aqueous phase come into contact for the first time, the extractant is more suitable for the solution with a higher alkalinity, which causes the extractant to enter the aqueous phase. Later, a large amount of acid is needed to break the emulsion when it comes out of the water. However, no acid is used in the extraction stage, which causes the extractant to stay in the aqueous phase and also causes the extractant to dissolve. Therefore, even if the alkaline substances added during the extraction process are added to the lithium-containing wastewater in step (1), the oil loss is still high. From Examples 1 and 6-7, it can be seen that the content of the alkaline substances added during the extraction process of the present invention will affect the extraction effect, and adding too much alkali will result in poor phase separation and high oil loss in the organic phase. From Examples 1 and 8-9, it can be seen that the extractant used in the present invention will affect the extraction effect and the oil loss.

[0159] In summary, the present invention provides a method for recovering lithium from lithium-containing wastewater. The extraction system of the method has good oil-water separation, low oil loss, and low process cost. It can recover and recycle lithium ions in wastewater, and has good lithium-sodium selectivity, high loading capacity, and short process flow.

[0160] 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 method for recovering lithium from lithium-containing wastewater, characterized in that, The method includes the following steps: (1) The lithium-containing wastewater is pretreated to obtain a lithium-containing solution; The pretreatment in step (1) includes adjusting the pH of the lithium-containing wastewater to 7 ≤ pH ≤ 10.5; The lithium-containing wastewater in step (1) includes the raffinate wastewater from the battery powder recycling process, and the lithium-containing solution contains 0.65 g / L of Li and 25 g / L of Na, or 0.55 g / L of Li and 27 g / L of Na, or 0.50 g / L of Li and 21 g / L of Na. The pH of the lithium-containing wastewater described in step (1) is adjusted using carbonates and / or bicarbonates; In the lithium-containing solution, the concentration of carbonate ions is 0.5-1.5 times the concentration of lithium ions; (2) Extraction was performed using the lithium-containing solution described in step (1) of the organic phase, followed by phase separation to obtain the oil phase; The organic phase includes an extractant; during the extraction process, an alkaline substance is added to the extraction system; The extractant in step (2) includes LiSX extractant; The LiSX extractant comprises a mixture of phosphorus extractants and ketone extractants; In the LiSX extractant, the mass ratio of phosphorus extractant to ketone extractant is (1-3):(1-3); (3) The oil phase described in step (2) is back-extracted to obtain a lithium-containing aqueous phase; (4) The lithium-containing aqueous phase described in step (3) is precipitated to recover lithium salt; The extraction in step (2) includes multi-stage countercurrent extraction; The alkaline substance described in step (2) is added when the multi-stage countercurrent extraction reaches the intermediate stage or the equal-stage stage; The amount of alkaline substance added in step (2) is 0.5-1.5 times the lithium ion concentration in the lithium-containing solution in step (1); The organic phase obtained by back-extraction in step (3) is regenerated and then reused in step (2).

2. The method according to claim 1, characterized in that, The number of stages in the multi-stage countercurrent extraction is 1-10.

3. The method according to claim 1, characterized in that, The alkaline substance in step (2) includes any one or a combination of at least two of carbonates, bicarbonates or hydroxides.

4. The method according to claim 1, characterized in that, In the organic phase described in step (2), the content of the extractant is 10wt%-80wt%.

5. The method according to claim 1, characterized in that, The organic phase in step (2) also includes a diluent.

6. The method according to claim 5, characterized in that, The diluent includes sulfonated kerosene.

7. The method according to claim 1, characterized in that, The extraction ratio in step (2) is (1-5):(1-5).

8. The method according to claim 1, characterized in that, The extraction temperature in step (2) is 20-70℃, the rotation speed is 150-450rpm, and the time is 0.05-0.5h.

9. The method according to claim 1, characterized in that, Before the oil phase in step (2) is back-extracted, it is washed, and the resulting organic phase is then back-extracted.

10. The method according to claim 9, characterized in that, The washing method includes multi-stage countercurrent washing.

11. The method according to claim 9, characterized in that, The washing process uses detergents including any one or a combination of at least two of the following: pure water, lithium salt solution, or acid.

12. The method according to claim 11, characterized in that, In the detergent, the concentrations of the lithium salt solution and the acid are independently 0-1 mol / L, but excluding 0 mol / L.

13. The method according to claim 1, characterized in that, The back-extraction method described in step (3) includes multi-stage countercurrent back-extraction.

14. The method according to claim 1, characterized in that, The back-extraction agent used in step (3) includes inorganic acid back-extraction agents.

15. The method according to claim 14, characterized in that, The inorganic acid back-extraction agent includes hydrochloric acid and / or sulfuric acid.

16. The method according to claim 14, characterized in that, The concentration of the inorganic acid back-extraction agent is 0.1-6 mol / L.

17. The method according to claim 1, characterized in that, The regeneration method includes mixing the organic phase obtained from back-extraction with a regenerating agent.

18. The method according to claim 17, characterized in that, The regenerant includes any one or a combination of at least two of water, carbonates, or hydroxides.

19. The method according to claim 1, characterized in that, The precipitant used in step (4) includes carbonates.

20. The method according to claim 1, characterized in that, The method includes the following steps: (1) The lithium-containing wastewater was adjusted to pH 7 ≤ 10.5 using carbonates and / or bicarbonates to obtain a lithium-containing solution; In the lithium-containing solution, the concentration of carbonate ions is 0.5-1.5 times the concentration of lithium ions; (2) The lithium-containing solution in step (1) is subjected to multi-stage countercurrent extraction, followed by phase separation to obtain the oil phase; The organic phase includes LiSX extractant and diluent; during the multi-stage countercurrent extraction process, an alkaline substance is added to the extraction system, and the amount of alkaline substance added is 0.5-1.5 times the lithium ion concentration in the lithium-containing solution in step (1); (3) The oil phase described in step (2) is washed in a multi-stage countercurrent manner with lithium salt solution and / or acid, and the organic phase obtained by washing is subjected to multi-stage countercurrent back-extraction to obtain a lithium-containing aqueous phase and an organic phase; (4) The organic phase obtained by back-extraction in step (3) is mixed with the regenerator to obtain a regenerated organic phase, which is then reused in step (2); The lithium-containing aqueous phase described in step (3) is mixed with a precipitant to recover lithium salt.

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