Extracting agent containing Keggin structure heteropolyacid or heteropolyacid salt co-extracting agent and lithium extraction method

Abstract

The invention discloses an extraction agent containing a Keggin structure heteropolyacid or heteropolyacid salt co-extraction agent and a lithium extraction method. The extraction agent comprises the following steps: S1, taking untreated oilfield brine as an extraction water phase; s2, dissolving a Keggin structure heteropolyacid or heteropolyacid salt co-extraction agent into an organic phosphorus extraction agent, and taking the co-extraction agent as an extraction organic phase after the co-extraction agent is completely dissolved; s3, mixing and extracting the extracted water phase and the extracted organic phase, and after the extraction is balanced, standing and splitting phases to obtain an organic phase and a water phase; step S4, using a LiCl and MgCl2 mixed solution as a washing agent, and washing the organic phase separated in the step S3; s5, dilute hydrochloric acid is used as a stripping agent, and the organic phase obtained through separation in the step S4 is subjected to stripping; and step S6, concentrating the strip liquor separated in the step S5, and then adding a precipitator to prepare Li2CO3. According to the method, the lithium extraction efficiency can be improved, and the lithium can be selectively extracted from the high-sodium and high-calcium oilfield brine.

Description

Technical Field

[0001] The invention relates to a process for selectively extracting lithium from natural oilfield brine, in particular to an extractant containing a Keggin structure heteropoly acid or heteropoly acid salt co-extractant and a lithium extraction method. Background Art

[0002] At present, lithium, as an important basic energy metal for strategic emerging industries, has been widely used in lithium batteries, automobile industry, ceramic glass, medicine, organic synthesis, metal alloys, aerospace and other fields due to its unique excellent physical and chemical properties. With the rapid rise of energy conservation and environmental protection, new energy, new materials and new energy vehicles, the global demand for lithium-ion batteries has increased dramatically, and lithium, as its key raw material, has also increased accordingly.

[0003] In the prior art, lithium resources mainly exist in minerals (such as eucryptite, lithium iron phosphate ore, lithium manganese ore, spodumene, lithium aluminum phosphate, lithium mica, petalite, montmorillonite, etc.) and brine (such as salt lake brine, oil field brine, geothermal brine and seawater). However, the mining of lithium ore faces problems such as insufficient resource reserves, high energy consumption and high cost, and will cause serious damage to the ecological environment during the mining process, and the mining difficulty is also relatively large. Among them, brine is a complex system formed by salts dissolved in water. It has rich lithium reserves, accounting for about 58% of the world's resources. Its lithium ion concentration is easy to concentrate, the mining process is simple and the cost is low, which is suitable for industrial production.

[0004] However, the commonly used extraction systems in existing industrial production, such as TBP / FeCl3, have good extraction effects, but there are still some inherent problems in their extraction mechanism: the extraction process of this system relies on ferric chloride and chloride ions to form ferric chloride anions, and during the entire extraction process, ferric chloride is maintained in the organic phase in the form of ferric chloride anions. To ensure the effectiveness of the extraction process, the chloride ion concentration in the aqueous phase needs to be higher than 6 mol / L, but the high chloride ion concentration brings many problems: first, most brines need to be concentrated, which is time-consuming and energy-consuming; secondly, the equipment is severely corroded during the extraction process; at the same time, the selection of detergents, stripping agents and regeneration agents is limited; in addition, the brine after production is difficult to directly reflux. It can be seen that although the extraction system is suitable for high-chlorine and high-magnesium brines, it has limitations in the separation of sodium ions and calcium ions. The presence of competing ions of calcium leads to extremely low lithium extraction rates. Therefore, how to fully develop and utilize various brine resources is a technical problem that needs to be solved in the prior art. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an extractant and a lithium extraction method containing a Keggin structure heteropoly acid or heteropoly acid salt co-extractant, which are helpful to improve the lithium extraction efficiency and can selectively extract lithium from high-sodium and high-calcium oilfield brine.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0007] An extractant containing a Keggin structure heteropoly acid or heteropoly acid salt co-extractant comprises a composition of an organic phosphorus extractant and a Keggin structure heteropoly acid or heteropoly acid salt co-extractant.

[0008] Preferably, the Keggin structure heteropoly acid or heteropoly acid salt co-extractant comprises A m H n [XM 12 O 40 ], wherein A is any one or more of Li, Na, K, Cs, Mg, Ca, Al and Ce, X is any one or more of Si, Ge, P, As and B, and M is any one or two of W and Mo.

[0009] Preferably, the organophosphorus extractant includes any one or more of tributyl phosphate, triisobutyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, triisopropylphenyl phosphate, butyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate and di(2-ethylhexyl)phenyl phosphate.

[0010] A lithium extraction method based on the extractant containing Keggin structure heteropoly acid or heteropoly acid salt co-extractant, the method comprising the following steps: step S1, using oilfield brine that has not been treated in any way as an extraction water phase; step S2, dissolving the Keggin structure heteropoly acid or heteropoly acid salt co-extractant in an organic phosphorus extractant, and using the extraction organic phase after the co-extractant is completely dissolved; step S3, mixing the extraction water phase and the extraction organic phase for extraction, and obtaining an organic phase and an aqueous phase after extraction equilibrium and static phase separation; step S4, using a mixed solution of LiCl and MgCl2 as a detergent to wash the organic phase separated in step S3; step S5, using dilute hydrochloric acid as a stripping agent to strip the organic phase separated in step S4; step S6, concentrating the stripping solution separated in step S5 and adding a precipitant to obtain Li2CO3.

[0011] Preferably, in step S2, the concentration of the Keggin structure heteropoly acid or heteropoly acid salt co-extractant is 0.3 to 3.0 times the lithium ion concentration in the oilfield brine.

[0012] Preferably, in step S2, the ratio of the extracted organic phase to the oilfield brine is 1:10 to 10:1.

[0013] Preferably, in step S4, the concentration of LiCl in the detergent is 0.00-0.10 mol / L, and the concentration of MgCl2 is 1-5 mol / L.

[0014] Preferably, in step S4, the ratio of the extracted organic phase to the detergent is 1:2 to 30:1.

[0015] Preferably, in step S5, the concentration of the dilute hydrochloric acid solution is 0.1 to 6 mol / L, and the ratio of the organic phase after washing to the stripping agent is 1:10 to 30:1.

[0016] Preferably, the extraction method in step S3 includes single-stage extraction and / or multi-stage countercurrent extraction, the washing method in step S4 includes single-stage washing and / or multi-stage countercurrent washing, and the stripping method in step S5 includes single-stage stripping and / or multi-stage countercurrent stripping.

[0017] The extractant containing Keggin structure heteropoly acid or heteropoly acid salt co-extractant and the lithium extraction method disclosed by the present invention have the beneficial effect compared with the prior art in that the extraction organic phase in the method of the present invention has the characteristics of low water solubility and stability under acid and alkali conditions, and at the same time, the extraction system is applicable to a wide range of brine types, has high selectivity for lithium calcium and lithium sodium, and the oil field brine and salt lake brine of the extraction system do not need any treatment, and the brine after lithium extraction can be directly discharged. Furthermore, the present invention uses Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, which can effectively solve various problems existing in the traditional ferric chloride extraction system. In addition, the extraction system effectively avoids the use of organic solvents as diluents, and can reduce the dissolution loss of organic solvents in the water phase, thus better meeting the process requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of the lithium extraction method of the present invention;

[0019] Figure 2 The extraction rate and separation coefficient chart of Examples 1 to 8 are shown. DETAILED DESCRIPTION

[0020] The present invention is described in more detail below with reference to the accompanying drawings and embodiments.

[0021] The invention discloses an extractant containing a Keggin structure heteropoly acid or heteropoly acid salt co-extractant, which comprises a composition of an organic phosphorus extractant and a Keggin structure heteropoly acid or heteropoly acid salt co-extractant.

[0022] Furthermore, the Keggin structure heteropoly acid or heteropoly acid salt co-extractant includes A m H n [XM 12 O 40 ], wherein A is any one or more of Li, Na, K, Cs, Mg, Ca, Al and Ce, X is any one or more of Si, Ge, P, As and B, and M is any one or two of W and Mo.

[0023] Regarding the specific composition of the organophosphorus extractant, in this embodiment, the organophosphorus extractant includes any one or more of tributyl phosphate, triisobutyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, triisopropylphenyl phosphate, butyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate and di(2-ethylhexyl)phenyl phosphate.

[0024] The present invention proposes a lithium extraction method based on the extractant containing the Keggin structure heteropoly acid or heteropoly acid salt co-extractant, see Figure 1 , the method comprises the following steps:

[0025] Step S1, using untreated oilfield brine as an extraction water phase;

[0026] Step S2, dissolving a Keggin structure heteropoly acid or heteropoly acid salt co-extractant in an organophosphorus extractant, and using the co-extractant as an extraction organic phase after the co-extractant is completely dissolved;

[0027] Step S3, mixing the aqueous extraction phase and the organic extraction phase for extraction, and obtaining an organic phase and an aqueous phase after extraction equilibrium and static phase separation;

[0028] Step S4, using a mixed solution of LiCl and MgCl2 as a detergent to wash the organic phase separated in step S3;

[0029] Step S5, using dilute hydrochloric acid as a stripping agent to strip the organic phase separated in step S4;

[0030] Step S6, concentrating the stripping solution separated in step S5 and adding a precipitant to obtain Li2CO3.

[0031] In the lithium extraction method proposed by the present invention, the extracted organic phase has the characteristics of low water solubility and stability under acidic and alkaline conditions. At the same time, the extraction system is applicable to a wide range of brine types and has high selectivity for lithium calcium and lithium sodium. The oil field brine and salt lake brine of the extraction system do not require any treatment, and the brine after lithium extraction can be directly discharged. Furthermore, the present invention uses Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, which can effectively solve various problems existing in the traditional ferric chloride extraction system. In addition, the extraction system effectively avoids the use of organic solvents as diluents and can reduce the dissolution loss of organic solvents in the aqueous phase, thus better meeting the process requirements.

[0032] As a preferred embodiment, in step S2, the concentration of the Keggin structure heteropoly acid or heteropoly acid salt co-extractant is 0.3 to 3.0 times the lithium ion concentration in the oilfield brine. Furthermore, in step S2, the ratio of the extracted organic phase to the oilfield brine is 1:10 to 10:1.

[0033] Regarding the detergent, in step S4 of the present invention, the concentration of LiCl in the detergent is 0.00-0.10 mol / L, and the concentration of MgCl2 is 1-5 mol / L. Further, in step S4, the ratio of the extracted organic phase to the detergent is 1:2-30:1.

[0034] As a preferred embodiment, in step S5, the concentration of the dilute hydrochloric acid solution is 0.1 to 6 mol / L, and the ratio of the organic phase after washing to the stripping agent is 1:10 to 30:1.

[0035] Regarding the specific process methods in steps S3 to S5: the extraction method in step S3 includes single-stage extraction and / or multi-stage countercurrent extraction, the washing method in step S4 includes single-stage washing and / or multi-stage countercurrent washing, and the stripping method in step S5 includes single-stage stripping and / or multi-stage countercurrent stripping.

[0036] In practical applications, the present invention provides the following embodiments for detailed description.

[0037] Embodiment 1:

[0038] This embodiment provides an extraction system using a Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, wherein the composition of the extraction organic phase includes octyl dibutyl phosphate and silicotungstic acid (concentration: 0.1 mol / L). Specifically, the extraction organic phase using the Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant is used to selectively extract lithium from oilfield brine in the Nanyishan area of ​​the Qaidam Basin, and the components of the lithium-containing brine include: a lithium ion concentration of 0.35 g / L, a sodium ion concentration of 95.44 g / L, a calcium ion concentration of 23.88 g / L, a magnesium ion concentration of 2.11 g / L, a potassium ion concentration of 7.94 g / L, and a chloride ion concentration of 205.9 g / L.

[0039] In this embodiment, the method for selectively extracting lithium includes the following steps:

[0040] Step 1, taking oilfield brine from the Nanyishan area of ​​the Qaidam Basin as the aqueous phase before extraction without any treatment;

[0041] Step 2, weigh a certain amount of silicotungstic acid and dissolve it in dibutyl octyl phosphate extractant, disperse it by ultrasonic, and when the silicotungstic acid is completely dissolved, dilute and fix the volume to prepare the silicotungstic acid concentration to 0.1 mol / L as the organic phase before extraction;

[0042] Step 3, the aqueous phase before extraction and the organic phase are mixed according to O / A=2 / 1, extracted at 25°C, and after the extraction is completed, the layers are allowed to stand and separate to obtain a loaded organic phase and a raffinate phase;

[0043] Step 4: strip the loaded organic phase with 1 mol / L hydrochloric acid solution, O / A = 1 / 1, and remove Li + 、Na + , K + Mg 2+ , Ca 2+ The concentration of 200 μg / ml was tested, and the extraction rate of Li, Na, K, Mg and Ca was calculated to be 58%, 6%, 5.8%, 0.5% and 13% respectively. The organic phase after stripping can be directly recycled.

[0044] Embodiment 2:

[0045] The present embodiment provides an extraction system using a Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, wherein the composition of the extraction organic phase includes octyl dibutyl phosphate and silicomolybdic acid (concentration: 0.1 mol / L). Specifically, the extraction organic phase using the Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant is used to selectively extract lithium from oilfield brine in the Nanyishan area of ​​the Qaidam Basin, and the components of the lithium-containing brine include: a lithium ion concentration of 0.35 g / L, a sodium ion concentration of 95.44 g / L, a calcium ion concentration of 23.88 g / L, a magnesium ion concentration of 2.11 g / L, a potassium ion concentration of 7.94 g / L, and a chloride ion concentration of 205.9 g / L.

[0046] The method for selectively extracting lithium in this embodiment comprises the following steps:

[0047] Step 1, taking oilfield brine from the Nanyishan area of ​​the Qaidam Basin as the aqueous phase before extraction without any treatment;

[0048] Step 2, weigh a certain amount of silicomolybdic acid and dissolve it in dibutyl octyl phosphate extractant, disperse it by ultrasonication, and when the silicomolybdic acid is completely dissolved, dilute and fix the volume to prepare a silicomolybdic acid concentration of 0.1 mol / L as the organic phase before extraction;

[0049] Step 3, the aqueous phase before extraction and the organic phase are mixed according to O / A=2 / 1, extracted at 25°C, and after the extraction is completed, the layers are allowed to stand and separate to obtain a loaded organic phase and a raffinate phase;

[0050] Step 4: strip the loaded organic phase with 1 mol / L hydrochloric acid solution, O / A = 1 / 1, and remove Li + 、Na + , K + Mg 2+ , Ca 2+ The concentration of 2.5 wt% was tested, and the extraction rate of Li, Na, K, Mg and Ca was calculated to be 60%, 2.1%, 3.2%, 0.3% and 7.2% respectively. The organic phase after stripping can be directly recycled.

[0051] Embodiment 3:

[0052] This embodiment provides an extraction system using a Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, wherein the composition of the extraction organic phase includes octyl dibutyl phosphate and phosphotungstic acid (concentration: 0.1 mol / L). Specifically, the extraction organic phase using the Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant is used to selectively extract lithium from oilfield brine in the Nanyishan area of ​​the Qaidam Basin, and the components of the lithium-containing brine include: a lithium ion concentration of 0.35 g / L, a sodium ion concentration of 95.44 g / L, a calcium ion concentration of 23.88 g / L, a magnesium ion concentration of 2.11 g / L, a potassium ion concentration of 7.94 g / L, and a chloride ion concentration of 205.9 g / L.

[0053] The method for selectively extracting lithium in this embodiment comprises the following steps:

[0054] Step 1, taking oilfield brine from the Nanyishan area of ​​the Qaidam Basin as the aqueous phase before extraction without any treatment;

[0055] Step 2, weigh a certain amount of phosphotungstic acid and dissolve it in dibutyl octyl phosphate extractant, perform ultrasonic dispersion, and when the phosphotungstic acid is completely dissolved, dilute and fix the volume to prepare the phosphotungstic acid concentration to 0.1 mol / L as the organic phase before extraction;

[0056] Step 3, the aqueous phase before extraction and the organic phase are mixed according to O / A=2 / 1, extracted at 25°C, and after the extraction is completed, the layers are allowed to stand and separate to obtain a loaded organic phase and a raffinate phase;

[0057] Step 4: strip the loaded organic phase with 1 mol / L hydrochloric acid solution, O / A = 1 / 1, and remove Li + 、Na + , K + Mg 2+ , Ca 2+ The concentration of 2.5 wt% was tested, and the extraction rate of Li, Na, K, Mg and Ca was calculated to be 57%, 4.8%, 4.0%, 2.3% and 7.4% respectively. The organic phase after stripping can be directly recycled.

[0058] Embodiment 4:

[0059] The present embodiment provides an extraction system using a Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, wherein the composition of the extraction organic phase includes octyl dibutyl phosphate and phosphomolybdic acid (concentration: 0.1 mol / L). Specifically, the extraction organic phase using the Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant is used to selectively extract lithium from oilfield brine in the Nanyishan area of ​​the Qaidam Basin, and the components of the lithium-containing brine include: a lithium ion concentration of 0.35 g / L, a sodium ion concentration of 95.44 g / L, a calcium ion concentration of 23.88 g / L, a magnesium ion concentration of 2.11 g / L, a potassium ion concentration of 7.94 g / L, and a chloride ion concentration of 205.9 g / L.

[0060] The method for selectively extracting lithium in this embodiment comprises the following steps:

[0061] Step 1, taking oilfield brine from the Nanyishan area of ​​the Qaidam Basin as the aqueous phase before extraction without any treatment;

[0062] Step 2, weighing a certain amount of phosphomolybdic acid and dissolving it in dibutyl octyl phosphate extractant, ultrasonically dispersing, and when the phosphomolybdic acid is completely dissolved, diluting and constant volume to prepare a phosphomolybdic acid concentration of 0.1 mol / L as an organic phase before extraction;

[0063] Step 3, the aqueous phase before extraction and the organic phase are mixed according to O / A=2 / 1, extracted at 25°C, and after the extraction is completed, the layers are allowed to stand and separate to obtain a loaded organic phase and a raffinate phase;

[0064] Step 4: strip the loaded organic phase with 1 mol / L hydrochloric acid solution, O / A = 1 / 1, and remove Li + 、Na + , K + Mg 2+ , Ca 2+ The concentration of 200 μg / ml was tested, and the extraction rate of Li, Na, K, Mg and Ca was calculated to be 37%, 0.8%, 2.3%, 0.03% and 0.25% respectively. The organic phase after stripping can be directly recycled.

[0065] Embodiment 5:

[0066] This embodiment provides an extraction system using a Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, wherein the composition of the extraction organic phase includes octyl dibutyl phosphate and sodium silicotungstate (concentration: 0.1 mol / L). Specifically, the extraction organic phase using the Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant is used to selectively extract lithium from oilfield brine in the Nanyishan area of ​​the Qaidam Basin, and the components of the lithium-containing brine include: a lithium ion concentration of 0.35 g / L, a sodium ion concentration of 95.44 g / L, a calcium ion concentration of 23.88 g / L, a magnesium ion concentration of 2.11 g / L, a potassium ion concentration of 7.94 g / L, and a chloride ion concentration of 205.9 g / L.

[0067] The method for selectively extracting lithium in this embodiment comprises the following steps:

[0068] Step 1, taking oilfield brine from the Nanyishan area of ​​the Qaidam Basin as the aqueous phase before extraction without any treatment;

[0069] Step 2, weigh a certain amount of sodium silicotungstate and dissolve it in dibutyl octyl phosphate extractant, disperse it by ultrasonic, and when the sodium silicotungstate is completely dissolved, dilute and fix the sodium silicotungstate to a concentration of 0.1 mol / L as the organic phase before extraction;

[0070] Step 3, the aqueous phase before extraction and the organic phase are mixed according to O / A=2 / 1, extracted at 25°C, and after the extraction is completed, the layers are allowed to stand and separate to obtain a loaded organic phase and a raffinate phase;

[0071] Step 4: strip the loaded organic phase with 1 mol / L hydrochloric acid solution, O / A = 1 / 1, and remove Li + , K + Mg 2+ , Ca 2+ The concentration of 200 μg / ml was tested, and the extraction rate of Li, K, Mg and Ca was calculated to be 41.6%, 10.3%, 5.6% and 4.6% respectively. The organic phase after stripping can be directly recycled.

[0072] Embodiment 6:

[0073] The present embodiment provides an extraction system using a Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, wherein the composition of the extraction organic phase includes octyl dibutyl phosphate and sodium silicomolybdate (concentration: 0.1 mol / L). Specifically, the extraction organic phase using the Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant is used to selectively extract lithium from oilfield brine in the Nanyishan area of ​​the Qaidam Basin, and the components of the lithium-containing brine include: a lithium ion concentration of 0.35 g / L, a sodium ion concentration of 95.44 g / L, a calcium ion concentration of 23.88 g / L, a magnesium ion concentration of 2.11 g / L, a potassium ion concentration of 7.94 g / L, and a chloride ion concentration of 205.9 g / L.

[0074] The method for selectively extracting lithium in this embodiment comprises the following steps:

[0075] Step 1, taking oilfield brine from the Nanyishan area of ​​the Qaidam Basin as the aqueous phase before extraction without any treatment;

[0076] Step 2, weigh a certain amount of sodium silicomolybdate and dissolve it in dibutyl octyl phosphate extractant, disperse it by ultrasonication, and when the sodium silicomolybdate is completely dissolved, dilute and fix the sodium silicomolybdate concentration to 0.1 mol / L as the organic phase before extraction;

[0077] Step 3, the aqueous phase before extraction and the organic phase are mixed according to O / A=2 / 1, extracted at 25°C, and after the extraction is completed, the layers are allowed to stand and separate to obtain a loaded organic phase and a raffinate phase;

[0078] Step 4: strip the loaded organic phase with 1 mol / L hydrochloric acid solution, O / A = 1 / 1, and remove Li + , K + Mg 2+ , Ca 2+ The concentration of 200 μg / ml was tested, and the extraction rate of Li, K, Mg and Ca was calculated to be 37.8%, 3.7%, 2.0% and 6.8%, respectively. The organic phase after stripping can be directly recycled.

[0079] Embodiment 7:

[0080] This embodiment provides an extraction system using a Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, wherein the composition of the extraction organic phase includes octyl dibutyl phosphate and sodium phosphotungstate (concentration: 0.1 mol / L). Specifically, the extraction organic phase using the Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant is used to selectively extract lithium from oilfield brine in the Nanyishan area of ​​the Qaidam Basin, and the components of the lithium-containing brine include: a lithium ion concentration of 0.35 g / L, a sodium ion concentration of 95.44 g / L, a calcium ion concentration of 23.88 g / L, a magnesium ion concentration of 2.11 g / L, a potassium ion concentration of 7.94 g / L, and a chloride ion concentration of 205.9 g / L.

[0081] The method for selectively extracting lithium in this embodiment comprises the following steps:

[0082] Step 1, taking oilfield brine from the Nanyishan area of ​​the Qaidam Basin as the aqueous phase before extraction without any treatment;

[0083] Step 2, weigh a certain amount of sodium phosphotungstate and dissolve it in dibutyl octyl phosphate extractant, perform ultrasonic dispersion, and when the sodium phosphotungstate is completely dissolved, dilute and fix the volume to prepare the sodium phosphotungstate concentration of 0.1 mol / L as the organic phase before extraction;

[0084] Step 3, the aqueous phase before extraction and the organic phase are mixed according to O / A=2 / 1, extracted at 25°C, and after the extraction is completed, the layers are allowed to stand and separate to obtain a loaded organic phase and a raffinate phase;

[0085] Step 4: strip the loaded organic phase with 1 mol / L hydrochloric acid solution, O / A = 1 / 1, and remove Li + , K + Mg 2+ , Ca 2+ The concentration of 200 μg / ml was tested, and the extraction rate of Li, K, Mg and Ca was calculated to be 69%, 0.5%, 0.08% and 6.3%, respectively. The organic phase after stripping can be directly recycled.

[0086] Embodiment 8:

[0087] The present embodiment provides an extraction system using a Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, wherein the composition of the extraction organic phase includes octyl dibutyl phosphate and sodium phosphomolybdate (concentration: 0.1 mol / L). Specifically, the extraction organic phase using the Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant is used to selectively extract lithium from oilfield brine in the Nanyishan area of ​​the Qaidam Basin, and the components of the lithium-containing brine include: a lithium ion concentration of 0.35 g / L, a sodium ion concentration of 95.44 g / L, a calcium ion concentration of 23.88 g / L, a magnesium ion concentration of 2.11 g / L, a potassium ion concentration of 7.94 g / L, and a chloride ion concentration of 205.9 g / L.

[0088] The method for selectively extracting lithium in this embodiment comprises the following steps:

[0089] Step 1, taking oilfield brine from the Nanyishan area of ​​the Qaidam Basin as the aqueous phase before extraction without any treatment;

[0090] Step 2, weigh a certain amount of sodium phosphomolybdate and dissolve it in dibutyl octyl phosphate extractant, perform ultrasonic dispersion, wait for the sodium phosphomolybdate to be completely dissolved, dilute and fix the sodium phosphomolybdate concentration to 0.1 mol / L as the organic phase before extraction;

[0091] Step 3, the aqueous phase before extraction and the organic phase are mixed according to O / A=2 / 1, extracted at 25°C, and after the extraction is completed, the layers are allowed to stand and separate to obtain a loaded organic phase and a raffinate phase;

[0092] Step 4: strip the loaded organic phase with 1 mol / L hydrochloric acid solution, O / A = 1 / 1, and remove Li + , K + Mg 2+ , Ca 2+ The concentration of 200 μg / ml was tested, and the extraction rate of Li, K, Mg and Ca was calculated to be 7.7%, 2.4%, 0.01% and 0.5% respectively. The organic phase after stripping can be directly recycled.

[0093] In the above Examples 1 to 8, the extraction process of the Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant from natural oil field brine or salt lake brine is shown in Figure 2 .

[0094] Based on the above embodiments, the present invention uses Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant to selectively extract lithium from oilfield brine. The new extractant provided is a neutral organic phosphorus extractant. Compared with the traditional TBP-FeCl3 extraction system, the present invention uses Keggin structure heteropoly acid or heteropoly acid salt as a co-extractant, which has the advantages of not relying on high concentration chloride ions, being applicable to more complex brine systems, and being more widely practical. At the same time, the method exhibits a higher separation coefficient between lithium and other metal ions in a single-stage extraction, wherein the lithium-magnesium separation coefficient is as high as 6000. In addition, the new extractant provided by the present invention is applicable to natural oilfield brine that does not require treatment, and the extraction system does not need to add a diluent, thereby avoiding the pollution of the water body by organic solvents due to dissolution, and the extraction process is simple, which is conducive to the promotion of industrial production.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the technical scope of the present invention should be included in the scope of protection of the present invention.

Claims

1. An extractant containing a Keggin structure heteropoly acid or heteropoly acid salt co-extractant, characterized in that: The invention discloses a composition comprising an organic phosphorus extractant and a Keggin structure heteropoly acid or heteropoly acid salt co-extractant.

2. The extractant containing Keggin structure heteropoly acid or heteropoly acid salt co-extractant as claimed in claim 1, characterized in that, The Keggin structure heteropoly acid or heteropoly acid salt co-extractant comprises A m H n [XM 12 O 40 ], wherein A is any one or more of Li, Na, K, Cs, Mg, Ca, Al and Ce, X is any one or more of Si, Ge, P, As and B, and M is any one or two of W and Mo.

3. The extractant containing Keggin structure heteropoly acid or heteropoly acid salt co-extractant as claimed in claim 1, characterized in that, The organophosphorus extractant includes any one or more of tributyl phosphate, triisobutyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, triisopropylphenyl phosphate, butyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate and di(2-ethylhexyl)phenyl phosphate.

4. A lithium extraction method based on the extractant containing Keggin structure heteropoly acid or heteropoly acid salt co-extractant according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: Step S1, using untreated oilfield brine as an extraction water phase; Step S2, dissolving a Keggin structure heteropoly acid or heteropoly acid salt co-extractant in an organophosphorus extractant, and using the co-extractant as an extraction organic phase after the co-extractant is completely dissolved; Step S3, mixing the aqueous extraction phase and the organic extraction phase for extraction, and obtaining an organic phase and an aqueous phase after extraction equilibrium and static phase separation; Step S4, using a mixed solution of LiCl and MgCl2 as a detergent to wash the organic phase separated in step S3; Step S5, using dilute hydrochloric acid as a stripping agent to strip the organic phase separated in step S4; Step S6, concentrating the stripping solution separated in step S5 and adding a precipitant to obtain Li2CO3.

5. The lithium extraction method according to claim 4, characterized in that: In the step S2, the concentration of the Keggin structure heteropoly acid or heteropoly acid salt co-extractant is 0.3 to 3.0 times the lithium ion concentration in the oilfield brine.

6. The lithium extraction method according to claim 4, characterized in that: In the step S2, the ratio of the extracted organic phase to the oilfield brine is 1:10 to 10:

1.

7. The lithium extraction method according to claim 4, characterized in that: In the step S4, the concentration of LiCl in the detergent is 0.00-0.10 mol / L, and the concentration of MgCl2 is 1-5 mol / L.

8. The lithium extraction method according to claim 4, characterized in that: In the step S4, the ratio of the extracted organic phase to the detergent is 1:2 to 30:

1.

9. The lithium extraction method according to claim 4, characterized in that: In the step S5, the concentration of the dilute hydrochloric acid solution is 0.1-6 mol / L, and the ratio of the organic phase after washing to the stripping agent is 1:10-30:

1.

10. The lithium extraction method according to claim 4, characterized in that: The extraction method in step S3 includes single-stage extraction and / or multi-stage countercurrent extraction, the washing method in step S4 includes single-stage washing and / or multi-stage countercurrent washing, and the stripping method in step S5 includes single-stage stripping and / or multi-stage countercurrent stripping.

Images