阅读说明：本技术 一种萃取-反萃分离纯化提取锂的方法 (Method for extracting lithium by extraction-back extraction separation and purification ) 是由 齐涛 朱兆武 张健 林道勇 于 2019-11-01 设计创作，主要内容包括：本发明涉及一种萃取-反萃分离纯化提取锂的方法,所述方法包括以下步骤：(1)采用含复合萃取剂的萃取体系,在pH＝10-13的条件下对含锂溶液进行萃取、分离,得到锂负载有机相；(2)将步骤(1)得到的锂负载有机相进行气-液-液三相反萃,得到负载锂的反萃液；(3)将步骤(2)得到的反萃液进行热处理,分离,得到锂产品以及分离后的母液。本发明提供的方法,通过采用复合萃取剂实现锂与Na、K和B等杂质元素的高效分离,再通过气-液-液三相连续反萃,锂的反萃率为90％以上,总收率为83％以上,得到锂产品的纯度为96％以上；所述方法处理量大,工艺和设备简单,投资小,有效利用工业尾气,节能环保,连续化生产。(The invention relates to a method for extracting lithium by extraction-stripping separation and purification, which comprises the following steps: (1) extracting and separating the lithium-containing solution by adopting an extraction system containing a composite extracting agent under the condition that the pH value is 10-13 to obtain a lithium-loaded organic phase; (2) carrying out gas-liquid three-phase back extraction on the lithium-loaded organic phase obtained in the step (1) to obtain a back extraction solution loaded with lithium; (3) and (3) carrying out heat treatment on the stripping solution obtained in the step (2), and separating to obtain a lithium product and a separated mother solution. According to the method provided by the invention, the high-efficiency separation of lithium from impurity elements such as Na, K and B is realized by adopting the composite extractant, and then the gas-liquid three-phase continuous back extraction is carried out, wherein the back extraction rate of lithium is more than 90%, the total yield is more than 83%, and the purity of the obtained lithium product is more than 96%; the method has the advantages of large treatment capacity, simple process and equipment, low investment, effective utilization of industrial tail gas, energy conservation, environmental protection and continuous production.)

1. The method for extracting lithium by extraction-stripping separation and purification is characterized by comprising the following steps of:

(1) extracting and separating the lithium-containing solution by adopting an extraction system containing a composite extracting agent under the condition that the pH value is 10-13 to obtain a lithium-loaded organic phase;

(2) carrying out gas-liquid three-phase back extraction on the lithium-loaded organic phase obtained in the step (1) to obtain a back extraction solution loaded with lithium;

(3) and (3) carrying out heat treatment on the stripping solution obtained in the step (2), and separating to obtain a lithium product and a separated mother solution.

2. The method of claim 1, wherein the complex extractant in step (1) comprises a neutral extractant and a chelating extractant, and the extraction system comprises the complex extractant and a diluent;

preferably, the neutral extractant comprises any one of tributyl phosphate TBP, dimethylheptyl methylphosphonate P350, trioctylphosphine oxide TOPO, trioctyl/hexylphosphine oxide Cyanex923 or N, N-bis- (1-methylheptyl) acetamide N503, or a combination of at least two thereof;

preferably, the chelating extractant comprises any one of 2-hydroxy-5-nonylbenzophenone oxime LIX84, dodecylphenyl-methyl- β -diketone LIX54, 2-hydroxy-5-nonylbenzaldehyde oxime LIX860, or an extractant having the same functional group as the extractant, or a combination of at least two thereof;

preferably, the volume ratio of the neutral extractant to the chelating extractant is 0.2:1-2: 1;

preferably, the extraction system further comprises a phase modifier;

preferably, the extraction system comprises a composite extractant, a phase modifier and a diluent, wherein the volume percentages of the composite extractant and the phase modifier are respectively 5-30% and 0-10%.

3. The method according to claim 1 or 2, wherein the lithium-containing solution in step (1) comprises any one or a combination of at least two of lithium ore leachate, lithium precipitation mother liquor, lithium battery waste leachate and salt lake brine;

preferably, the concentration of lithium in the lithium-containing solution is 0.25 to 5 g/L;

preferably, the concentrations of main impurity elements of sodium, potassium and boron in the lithium-containing solution are independently 10-150g/L, 0-50g/L and 0-10g/L respectively;

preferably, the lithium-containing solution further contains metal ions such as rubidium, aluminum, magnesium, cesium and calcium;

preferably, the volume ratio of the lithium-containing solution to the organic phase is from 0.2:1 to 5: 1.

4. The method according to any one of claims 1 to 3, wherein the concentration of lithium in the lithium-loaded organic phase in step (1) is from 0.5 to 3 g/L;

preferably, the lithium-loaded organic phase is washed;

preferably, the washing liquid is water and/or a lithium-containing solution.

5. The process according to any one of claims 1 to 4, wherein the gas-liquid three-phase stripping system in step (2) comprises a first liquid phase, a second liquid phase and a gas phase;

preferably, the gas of the gas phase comprises SO₂、SO₃、CO₂Or Cl₂Preferably SO or a combination of at least two thereof₂And/or CO₂；

Preferably, the first liquid phase comprises water;

preferably, the second liquid phase lithium-containing loaded organic phase;

preferably, the gas-liquid three-phase back extraction is performed under the condition that the pH value is controlled to be 6-9;

preferably, the volume ratio of the first liquid phase to the second liquid phase is from 0.05:1 to 2: 1.

6. The process according to any one of claims 1 to 5, wherein the gas-liquid three-phase stripping in step (2) is carried out by multistage continuous countercurrent operation;

preferably, the equipment for gas-liquid three-phase back extraction comprises any one of a continuous mixer-settler, an extraction tower or a centrifugal extractor, and the stage number of the gas-liquid three-phase back extraction is adjustable between 1 and 10 stages; preferably an extraction column, the size and the number of stages of the extraction column can be adjusted according to the requirements of the actual production process.

7. The process according to any one of claims 1 to 6, wherein the concentration of lithium in the strip liquor in step (2) is > 5 g/L.

8. The method according to any one of claims 1 to 7, wherein the heat treatment in step (3) comprises any one or a combination of at least two of oxidation, evaporative crystallization, or thermal decomposition;

preferably, the temperature of the heat treatment is 60-90 ℃;

preferably, the time of the heat treatment is 0.5-2 h;

preferably, the oxidant used for the oxidation is air, oxygen and ozone gas;

preferably, the evaporative crystallization adopts MVR or multi-effect evaporation;

preferably, the thermal decomposition is performed in a closed or semi-closed vessel.

9. The method according to any one of claims 1 to 8, wherein the manner of separation in step (3) comprises any one or a combination of at least two of filtration, suction filtration or centrifugation;

preferably, the lithium product is lithium sulfate, lithium chloride or lithium carbonate, with a product purity > 96%.

10. The process according to claims 1 to 9, characterized in that the mother liquor after separation in step (3) is returned to step (1) and/or to the first liquid phase in step (2).

Technical Field

The invention relates to the technical field of chemical separation, in particular to a method for extracting lithium by extraction-back extraction separation and purification.

Background

Lithium is the metal with the smallest density, and is widely applied to the fields of electronics, chemistry, new energy, pharmacy and the like, lithium resources are mainly derived from salt lakes, minerals and seawater, and waste lithium batteries also become important sources along with the advance of recycling waste resources in recent years. The process of extracting lithium from the raw materials needs a plurality of purification steps, evaporation concentration, separation and impurity removal and deep removal of calcium and magnesium ions are mostly adopted in the classical process to obtain a lithium-containing solution with high purity, and then the lithium-containing solution is subjected to precipitation treatment to obtain a lithium carbonate product.

CN108423696A discloses a method for extracting high purity lithium salt from lithium-containing solution, comprising the following steps: adding a pH regulator into the lithium-containing solution, and regulating the pH of the solution to be more than 4; concentrating the lithium-containing solution into a lithium-rich solution with the lithium concentration of more than 2 g/L; putting an ultrasonic device into the lithium-rich solution, adding a precipitator, and performing ultrasonic oscillation; and filtering after the ultrasonic treatment is finished, and washing and drying the obtained solid phase to obtain the lithium salt. The method needs to concentrate the lithium-containing solution, and has small treatment capacity; meanwhile, in the process of lithium precipitation, because the lithium-rich solution contains a large amount of sodium ions, potassium ions and the like, the lithium salt has large entrainment, the purity of the lithium salt is influenced, and the lithium salt with high purity is prepared by washing with a large amount of fresh water, so that the water consumption is large. In addition, the lithium salt has a certain solubility in the aqueous phase, and the mother liquor after precipitation still contains a large amount of lithium, resulting in a decrease in the yield of lithium.

CN104884648A provides a method for extracting lithium from a lithium-containing solution, which specifically comprises the following steps: preparing a lithium-containing solution comprising carbonate ions; concentrating the lithium-containing solution to a lithium concentration of less than or equal to 2.481g/L to obtain a first precipitate; subjecting the concentrated lithium-containing solution and the first precipitate to solid-liquid separation; adding a phosphorus supply substance into the concentrated lithium-containing solution to separate out the dissolved lithium into lithium phosphate; concentrating the filtered solution with the lithium phosphate separated out again until the lithium concentration is less than or equal to 2.481g/L to obtain a second precipitate; performing solid-liquid separation on the re-concentrated filtered solution and the second precipitate; and adding core particles to the re-concentrated filtered solution to precipitate dissolved lithium as lithium phosphate. The method has the advantages of repeated concentration and solid-liquid separation, lower lithium yield, longer process flow, larger investment and no contribution to industrial application.

Based on the above documents, how to develop a process with high lithium yield, high lithium product purity, large processing capacity, short flow, low investment and easy industrialization is a problem which needs to be solved urgently at present.

Disclosure of Invention

In view of the problems in the prior art, the invention provides a method for extracting lithium by extraction-stripping separation and purification, which adopts an extraction system containing a composite extractant to extract a lithium-containing solution under the condition of high pH, realizes high-efficiency extraction of lithium, and separates lithium from a large amount of impurity elements such as Na, K, B and the like; and then the tail gas discharged by industry is utilized to carry out gas-liquid three-phase back extraction through a multi-stage continuous countercurrent process, thereby realizing the high-efficiency back extraction of lithium. The method provided by the invention has large treatment capacity, liquid phase recycling and high total lithium yield; the gas phase is recycled to realize zero emission and the utilization rate is high; industrial tail gas can be used as a three-phase back extraction gas source, so that the cost is greatly reduced, and the environment is protected; meanwhile, the process flow is short, the equipment is simple, the investment is small, and the industrial application is easy.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a method for extracting lithium by extraction-stripping separation and purification, which comprises the following steps:

(1) extracting and separating the lithium-containing solution by adopting an extraction system containing a composite extracting agent under the condition that the pH value is 10-13 to obtain a lithium-loaded organic phase;

(2) carrying out gas-liquid three-phase back extraction on the lithium-loaded organic phase obtained in the step (1) to obtain a back extraction solution loaded with lithium;

(3) and (3) carrying out heat treatment on the stripping solution obtained in the step (2), and separating to obtain a lithium product and a separated mother solution.

According to the method provided by the invention, an extraction system containing the composite extracting agent is adopted, lithium is effectively extracted by the composite extracting agent under the condition of higher pH value, and enters a loaded organic phase; the lithium loaded organic phase is then stripped through a gas-liquid three phase stripping using an acid gas as the gas phase, which gas in solution in the liquid phase provides a small amount of H⁺，H⁺In contact with lithium-bearing organic phase and with Li⁺Exchange, Li⁺Back-extracted into aqueous solution, consumed H⁺Replenishment by continuous gas reaction, stripping of Li to aqueous phase⁺Combining with anions generated by the gas-liquid reaction to form a loaded aqueous solution of lithium; and then the lithium product with higher purity is obtained by heat treatment.

Preferably, the complex extractant in step (1) comprises a neutral extractant and a chelating extractant, and the extraction system comprises the complex extractant and a diluent. Under the condition that the pH value is 10-13, lithium forms an inclusion compound with a neutral extractant, and the inclusion compound is extracted by a chelating extractant, so that the high-efficiency extraction of lithium is realized. The extraction reaction is shown as formula (1):

Li_nL+nE_N+nHE_Ch+nOH^-＝nLi·E_NE_Ch+L^n-+nH₂O (1)

in the formula (1), L is Cl^-Or SO₄ ^2-；E_NIs a neutral extractant, E_ChIs a chelating extractant.

Since Na, K and B plasma do not react with E_NThe inclusion is formed, so the extraction is not carried out by the composite extractant, and Li is well separated from impurity elements such as Na, K, B and the like.

In the present invention, the extraction process is carried out under strongly alkaline conditions, and the pH is 10 to 13, and may be, for example, 10, 11, 12, or 13. When the pH is higher<10 hours, inclusion of lithium during extraction with HE_ChGeneration of H⁺It is not effectively neutralized and lithium is not extracted. When the pH is higher>13 hour, a large amount of Na⁺And K⁺Etc. also react with HE_ChForm NaE_ChOr KE_ChLithium is also not extracted efficiently and does not separate well from Na and K.

Preferably, the neutral extractant comprises any one of tributyl phosphate (TBP), dimethylheptyl methylphosphonate (P350), trioctylphosphine oxide (TOPO), trioctyl/hexyl phosphine oxide (Cyanex923), or N, N bis- (1-methylheptyl) acetamide (N503), or a combination of at least two thereof, with typical but non-limiting combinations: p350 and N503, TBP and TOPO, TBP, P350 and Cyanex923, P350, Cyanex923 and N503.

Preferably, the chelating extractant comprises any one or a combination of at least two of 2-hydroxy-5-nonylbenzophenone oxime (LIX84), dodecylphenyl-methyl- β -diketone (LIX54), 2-hydroxy-5-nonylbenzaldehyde oxime (LIX860), or extractants having the same functional groups as it, typically but not limited to combinations of: LIX54 and LIX84I, LIX54 and LIX860, LIX54, LIX84I and LIX 860.

Preferably, the volume ratio of the neutral extractant to the chelating extractant is 0.2:1-2:1, and may be, for example, 0.2:1, 0.3:1, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1 or 2:1, etc., and if the ratio is not within the above range, the extraction process may have an "emulsification" problem that is not conducive to extraction.

Preferably, the extraction system further comprises a phase modifier.

Preferably, the extraction system comprises a composite extractant, a phase modifier and a diluent, wherein the volume percentages of the composite extractant and the phase modifier are respectively 5-30% and 0-10%. For example, the volume percentage of the composite extractant may be 5%, 10%, 15%, 20%, 25%, 30%, or the like; the volume percentage of the phase modifier can be 0%, 0.5%, 1%, 3%, 5%, 8%, 9%, 10%, etc., and the phase modifier is added or not and the volume ratio of the phase modifier is determined according to whether the extraction system has an emulsification problem or not.

In the present invention, the specific types of the diluent and the phase modifier are not particularly limited, and the diluent may be n-dodecane, sulfonated kerosene, or the like, and the phase modifier may be dodecanol, or the like, and any of those commonly used by those skilled in the art can be used in the present invention.

Preferably, the lithium-containing solution in step (1) comprises any one or a combination of at least two of lithium ore leachate, lithium precipitation mother liquor, lithium battery waste leachate and salt lake brine, wherein the combination is typically but not limited to: lithium ore leachate and lithium precipitation mother liquor, salt lake brine and lithium precipitation mother liquor, lithium battery waste leachate and lithium precipitation mother liquor.

Preferably, the lithium-containing solution has a lithium concentration of 0.25 to 5g/L, and may be, for example, 0.25g/L, 0.3g/L, 0.5g/L, 0.8g/L, 1g/L, 1.5g/L, 2g/L, 2.5g/L, 3g/L, 3.5g/L, 4g/L, 4.5g/L, 4.8g/L, or 5 g/L.

Preferably, the concentration of the main impurity elements of sodium, potassium and boron in the lithium-containing solution is independently 10-150g/L, 0-50g/L and 0-10g/L, respectively, for example, the concentration of sodium may be 10g/L, 15g/L, 20g/L, 30g/L, 50g/L, 80g/L, 90g/L, 95g/L, 100g/L, 120g/L, 140g/L or 150g/L, etc.; the concentration of potassium can be 0g/L, 1g/L, 5g/L, 10g/L, 15g/L, 20g/L, 30g/L, 40g/L, 45g/L, 50g/L, or the like; the concentration of boron may be 0g/L, 1g/L, 2g/L, 3g/L, 5g/L, 7g/L, 9g/L, 10g/L, or the like.

Preferably, the lithium-containing solution further contains metal ions such as rubidium, aluminum, magnesium, cesium and calcium.

Preferably, the volume ratio of the lithium-containing solution to the organic phase is 0.2:1 to 5:1, and may be, for example, 0.2:1, 0.3:1, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.5:1, 3:1, 4:1, or 5:1, etc. If the volume ratio is less than 0.2:1, lithium cannot be extracted efficiently and cannot be separated well from Na and K; the volume ratio is more than 5:1, the single-stage extraction effect of lithium is poor, and the extraction yield of lithium is low.

Preferably, the concentration of lithium in the lithium-loaded organic phase in step (1) is 0.5-3g/L, and may be, for example, 0.5g/L, 0.8g/L, 1g/L, 1.2g/L, 1.5g/L, 1.8g/L, 2g/L, 2.2g/L, 2.6g/L, 2.8g/L, 3g/L, or the like.

Preferably, the lithium-loaded organic phase is washed. Although Na, K, B and the like are not extracted by an organic extraction system, phase entrainment is generated in the extraction process, a small amount of impurities such as Na, K, B and the like enter a loaded organic phase along with entrained water and need to be washed, so that the impurities are washed into a water phase, and lithium is further purified.

Preferably, the washing liquid is water and/or a lithium-containing solution.

Preferably, the gas-liquid three-phase stripping system in step (2) comprises a first liquid phase, a second liquid phase and a gas phase.

Preferably, the gas of the gas phase comprises SO₂、SO₃、CO₂Or Cl₂Preferably SO or a combination of at least two thereof₂And/or CO₂。

In the present invention, SO is contained in the gas used for the stripping₂、SO₃Most of the tail gas generated by high-temperature treatment of sulfide ore in metallurgical process is industrially used for preparing by-product sulfuric acid, and SO is treated by adopting catalyst₂Oxidative conversion to SO₃The absorption preparation of sulfuric acid has complex process and high preparation cost. CO 2₂Most of the tail gas of power plants and high-temperature boilers, and a large amount of CO is also generated in the lime burning process₂The tail gas, which is currently purified and discharged, generates greenhouse gases. Cl₂Is a byproduct in the chlor-alkali industry, is currently used for preparing hydrochloric acid or preparing disinfectant and chlorinated plastic industry, but has the byproduct Cl in China₂In severe excess. The invention adopts the tail gas of industrial production or the emitted greenhouse gas to realize the high-efficiency back extraction of lithium, greatly reduces the operation cost and simultaneously lightens the environmental pollution.

Preferably, the first liquid phase comprises water.

Preferably, the second liquid phase comprises a lithium-loaded organic phase.

In the present invention, the dissolution of the gas used for stripping in the first liquid phase can provide a small amount of H⁺，H⁺In contact with a lithium-supporting organic phase and with Li⁺Exchange, Li⁺Back-extracted into aqueous solution, consumed H⁺Replenishment by continuous gas reaction, stripping of Li to aqueous phase⁺Combined with anions generated by the gas-liquid reaction to form a loaded aqueous solution of lithium. The back-extraction of lithium is shown in formula (2):

nLi·E_NE_Ch+G+1/2nH₂O＝Li_nG(O)_1/2n+nE_N+nHE_Ch (2)

in the formula (2), G is a gas used for stripping.

Preferably, the gas-liquid three-phase stripping control pH is 6 to 9, and may be, for example, 6, 7, 8, or 9. The lithium back extraction is realized by gas-liquid continuous three-phase reaction, and Li is generated in the process_nG(O)_1/2nThe system is automatically maintained at near neutrality or weak alkalinity in the back extraction process, the pH value is 6-9, and no other reagent is needed to regulate the pH value.

Preferably, the volume ratio of the first liquid phase to the second liquid phase is 0.05:1-2:1, for example, 0.05:1, 0.1:1, 0.5:1, 1:1, 1.5:1 or 2:1, etc., and if the volume ratio is less than 0.05:1, the back-extraction effect of lithium is poor; the volume ratio is more than 2:1, the concentration of lithium in the back extraction aqueous solution is low, and the recovery rate of lithium is low.

Preferably, the gas-liquid three-phase back extraction in the step (2) adopts multi-stage continuous countercurrent operation.

Preferably, the equipment for gas-liquid three-phase back extraction comprises any one of a continuous mixer-settler, an extraction tower or a centrifugal extractor, and the stage number of the gas-liquid three-phase back extraction is adjustable between 1 and 10 stages. Preferably an extraction column, the size and the number of the stages of the extraction column can be adjusted according to the requirements of the actual production process.

In the invention, the gas-liquid three-phase back extraction equipment can achieve the back extraction rate of lithium by more than 90% by adjusting the quantity of the equipment and/or the process parameters.

Preferably, the concentration of lithium in the strip liquor in step (2) is > 5g/L, and may be, for example, 5.1g/L, 5.2g/L, 5.5g/L, 5.8g/L, 6.0g/L, 6.5g/L, 7.0g/L, 9.0g/L, 10g/L, or the like.

Preferably, the heat treatment in step (3) comprises any one or a combination of at least two of oxidation, evaporative crystallization or thermal decomposition, wherein the combination is typically but not limited to: thermal decomposition and evaporative crystallization, oxidation and evaporative crystallization.

Preferably, the temperature of the heat treatment in the step (3) is 60 to 90 ℃, for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃ or 90 ℃ and the like, and if the temperature is lower than 60 ℃, the lithium product yield is low; the temperature is higher than 90 ℃, and the energy consumption of the heat treatment section is increased.

Preferably, the time of the heat treatment is 0.5 to 2 hours, and may be, for example, 0.5 hour, 1 hour, 1.5 hours, 2 hours, or the like.

In the present invention, the heat treatment is adjusted according to the kind of gas used in the stripping, and SO is used₂Gas stripping to obtain Li₂SO₃Solution, heat oxidation to form Li₂SO₄And then heating for evaporation and crystallization to obtain Li₂SO₄Producing a product; by SO₃Gas stripping to obtain Li₂SO₄Direct evaporative crystallization to obtain Li₂SO₄Producing a product; by using CO₂Gas stripping and heating to obtain Li₂CO₃Producing a product; by Cl₂And carrying out back extraction to obtain a LiCl product.

Preferably, the oxidizing agent used for the oxidation is air, oxygen, and ozone gas.

Preferably, the evaporative crystallization employs MVR or multiple effect evaporation.

Preferably, the thermal decomposition is performed in a closed or semi-closed vessel.

Preferably, the means of separation comprises any one or a combination of at least two of filtration, suction filtration or centrifugation, with typical but non-limiting combinations: centrifugation and filtration, centrifugation and suction filtration.

Preferably, the lithium product is lithium sulfate, lithium chloride or lithium carbonate, with a product purity > 96%, which may be, for example, 96.5%, 97%, 98%, or 99%, etc.

Preferably, the mother liquor separated in the step (3) is returned to the lithium-containing solution in the step (1) and/or returned to the first liquid phase in the step (2), so that the total yield of lithium is improved, and zero discharge of wastewater is realized.

Preferably, the present invention provides a method comprising the steps of:

(1) mixing a neutral extractant and a chelating extractant to form a composite extractant, controlling the volume ratio of the neutral extractant to the chelating extractant to be 0.2:1-2:1, adding a diluent and a phase modifier, and mixing to form an extraction system, wherein the volume percentages of the composite extractant and the phase modifier are controlled to be 5-30% and 0-10% respectively. Extracting with a solution with lithium concentration of 0.25-5g/L under the condition of pH 10-13, controlling the volume ratio of the lithium-containing solution to the organic phase to be 0.2:1-5:1, and then separating to obtain a loaded organic phase with lithium concentration of 0.5-3 g/L;

the neutral extractant comprises any one or the combination of at least two of tributyl phosphate (TBP), dimethylheptyl methylphosphonate (P350), trioctylphosphine oxide (TOPO), trioctyl/hexylphosphine oxide (Cyanex923) or N, N-bis- (1-methylheptyl) acetamide (N503);

the chelating extractant comprises any one or a combination of at least two of 2-hydroxy-5-nonylbenzophenone oxime (LIX84), dodecylphenyl-methyl-beta-diketone (LIX54), 2-hydroxy-5-nonylbenzaldehyde oxime (LIX860) or an extractant having the same functional group;

(2) washing the lithium-loaded organic phase obtained in the step (1), and then carrying out gas-liquid three-phase back extraction in a continuous countercurrent extraction tower, wherein the pH value of a back extraction system is controlled to be 6-9, so as to obtain a back extraction solution with the lithium concentration of more than 5 g/L;

the gas in the gas-liquid three-phase stripping system contains SO₂、SO₃、CO₂Or Cl₂Any one or a combination of at least two of;

(3) and (3) carrying out heat treatment on the stripping solution obtained in the step (2) at the temperature of 60-90 ℃ for 0.5-2h, and separating to obtain a lithium product and a separated mother solution.

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the method for extracting, separating, purifying and extracting lithium by extraction-back extraction, provided by the invention, the lithium is efficiently separated from impurity ions such as Na, K, B and the like by adopting a composite extracting agent, and then the lithium is continuously back extracted by gas-liquid three phases, the back extraction rate of the lithium is more than 90%, the liquid phase and the gas phase are recycled, the total yield of the lithium is more than 83%, and the purity of the obtained lithium product is more than 96%;

(2) the method provided by the invention has the advantages of large treatment capacity, simple process and equipment, low investment, low energy consumption, realization of continuous production and higher application value.

Drawings

FIG. 1 is a flow chart of the process for extracting lithium by extraction-stripping separation and purification provided by the invention.

FIG. 2 is a schematic diagram of a gas-liquid three-phase stripping device provided by the invention. In the figure, 1 is an electric stirrer, 2 is a gas outlet, 3 is a light phase outlet, 4 is a stirring tray, 5 is an extraction column body, 6 is a gas distributor, 7 is a gas inlet, 8 is a heavy phase outlet, 9 is a heavy phase inlet, 10 is a light phase inlet, and 11 is a pulse system.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

The process flow for extracting lithium by extraction-stripping separation and purification provided by the invention is shown in figure 1. The lithium-containing solution is subjected to lithium extraction under the condition that the pH value is 10-13, then an extraction liquid is washed to remove impurities such as Na, K, B and the like, the extraction liquid is subjected to continuous back extraction through a gas-liquid three phase to obtain a back extraction liquid of lithium, and the back extraction liquid is subjected to heat treatment and separation to obtain a lithium product. And returning the separated mother liquor to the Li extraction step according to a circulation mode 1 and/or returning to the Li back-extraction step according to a circulation mode 2, so as to obtain cyclic utilization.

The invention provides a schematic diagram of gas-liquid three-phase stripping equipment, which is shown in figure 2. The device is shown as an extraction tower, gas phase enters the extraction tower through a gas inlet 7 at the bottom of the extraction tower, enters a tower body 5 of the extraction tower through a gas distributor 6 to be in contact reaction with a liquid phase, and unreacted gas is discharged through a gas outlet 2 at the top of the extraction tower; the first liquid phase enters the extraction tower through a tower bottom light phase inlet 10, and is subjected to back extraction through a tower body, and back extraction liquid containing lithium is discharged through a light phase outlet 3; the second liquid phase enters the tower through a heavy phase inlet 9 at the top of the tower to be subjected to back extraction, and the solution after the reaction is discharged through a heavy phase outlet 8. And adjusting the tower plate of the tower body to realize the adjustment of the stage number according to the actual production requirement. The electric stirrer 1 and the stirring tower plate 4 make the gas-liquid three phases fully contact, and the pulse system 11 provides power for the counter flow of the first liquid phase.