A composite lithium extraction adsorbent, a preparation method and application thereof

Abstract

The application provides a composite lithium extraction adsorbent and a preparation method and application thereof, and the preparation method comprises the following steps: (1) electrospinning treatment is performed on silica sol, calcination is performed to obtain silica nanofibers, the silica nanofibers are broken in a solvent to obtain a silica nanofiber suspension; (2) a hydrophilic polymer material is dissolved in deionized water to obtain a hydrophilic polymer mucilage, the hydrophilic polymer mucilage, lithium ion sieves, a crosslinking agent and the silica nanofiber suspension are mixed to obtain a composite liquid through stirring; (3) the composite liquid is frozen, then freeze-drying treatment is performed, and after drying is completed, the composite lithium extraction adsorbent is obtained through a heating crosslinking reaction. The lithium ion sieves and the oleophilic silica nanofibers are compounded, the oleophilic silica nanofibers can promote the aggregation of oil droplets and can also enhance the mechanical strength of the sponge-like adsorbent, and the cyclic stability is improved.

Description

Technical Field

[0001] This invention belongs to the field of adsorption materials technology, and relates to a composite lithium extraction adsorbent, its preparation method, and its application. Background Technology

[0002] Lithium is the lightest metallic element in nature and has a wide range of applications. With the rise of the new energy industry, lithium has become another strategic resource after petroleum and rare earth elements. Lithium in nature is mainly found in spodumene, lepidolite, and brine. Currently, there are two main lithium extraction technologies: the calcination method using lithium ore as raw material and the adsorption method extracting lithium resources from brine. While ore-based lithium extraction is a mature technology, it is also costly. In contrast, brine-based lithium extraction does not require a calcination process and is relatively cheaper.

[0003] The current technical challenge in lithium extraction from brine lies in the separation of impurities from salt lake brine. Ion sieves, as a novel separation material, have significant advantages in selective adsorption separation. Oilfield brine, as one of the raw materials for lithium resources, contains a large amount of lithium to be extracted, but it also has a high COD content. Simple filtration is insufficient to fully separate oil and water, resulting in a high COD content in the obtained lithium-rich solution, which affects the quality of the lithium-rich solution.

[0004] CN108584995A discloses a method for the comprehensive extraction of lithium, potassium, and boron from oilfield brine. The process includes: pretreatment; evaporation and crystallization to precipitate sodium salt to obtain sodium extraction mother liquor; evaporation and crystallization of potassium salt from the sodium extraction mother liquor to obtain potassium extraction mother liquor; purification of the potassium extraction mother liquor with lime milk and Glauber's salt to obtain purified potassium extraction mother liquor; addition of hydrochloric acid or sulfuric acid to the purified potassium extraction mother liquor to obtain crude boric acid and crude lithium-containing mother liquor; evaporation and concentration of the crude lithium-containing mother liquor and purification by chelation or adsorption to obtain refined lithium-rich mother liquor; and addition of alkali to the refined lithium-rich mother liquor for precipitation and washing to obtain crude lithium carbonate.

[0005] CN116790910A discloses a method for extracting lithium from oilfield brine with high sodium chloride content. The method includes the following steps: (1) using an evaporation crystallization method to precipitate sodium chloride from the oilfield brine with high sodium chloride content to obtain a lithium-enriched mother liquor; (2) adding hydrochloric acid to the lithium-enriched mother liquor to adjust the pH, and introducing chlorine gas to convert bromide ions in the solution into bromine gas to obtain a bromine byproduct and a debromine-removed mother liquor; (3) adding liquid alkali to the debromine-removed mother liquor, and using an adsorbent to adsorb and desorb lithium elements in the solution to obtain a lithium chloride solution.

[0006] The above-mentioned methods are difficult to separate the oil and water phases in emulsified oil and dispersed oil, which will not only cause the loss of lithium resources but also affect the quality of lithium-rich desorption solution. Summary of the Invention

[0007] The purpose of this invention is to provide a composite lithium extraction adsorbent, its preparation method, and its application. This invention combines a lithium ion sieve with oleophilic silica nanofibers. The oleophilic silica nanofibers can promote oil droplet aggregation while also enhancing the mechanical strength of the sponge-like adsorbent and improving cycle stability.

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

[0009] In a first aspect, the present invention provides a method for preparing a composite lithium extraction adsorbent, the method comprising the following steps:

[0010] (1) The silica sol is electrospun and calcined to obtain silica nanofibers. The silica nanofibers are then broken in a solvent to obtain a silica nanofiber suspension.

[0011] (2) Dissolve the hydrophilic polymer material in deionized water to obtain a hydrophilic polymer viscous liquid, mix the hydrophilic polymer viscous liquid, lithium ion sieve, crosslinking agent and silica nanofiber suspension, and stir to obtain a composite liquid;

[0012] (3) After freezing the composite liquid, freeze-dry it, and after drying, heat cross-linking reaction is carried out to obtain the composite lithium adsorbent.

[0013] This invention prepares a sponge-like hydrophobic / hydrophilic composite adsorbent by combining lithium-ion sieves with oleophilic silica nanofibers. The protrusions on the surface of the lithium-ion sieve particles break up the emulsion droplets. After the droplets are broken up in the channels, the aqueous phase of the droplets gathers on the surface of the hydrophilic adsorbent, while the oil phase gathers on the surface of the hydrophobic particles. The small oil phase particles collide with each other, grow larger, and float to the surface, thus achieving more complete oil-water separation.

[0014] Preferably, the silica sol in step (1) is prepared by the following method:

[0015] Tetraethyl silicate, methyltrimethoxysiloxane, hydrochloric acid, water and anhydrous ethanol are mixed and heated and stirred until the total mass loss of the substances in the system reaches more than 50%, then heating is stopped to obtain silica sol.

[0016] Preferably, the mass ratio of tetraethyl silicate, methyltrimethoxysiloxane, hydrochloric acid, water, and anhydrous ethanol is (10-15):(3-5):(1-3):(3-5):(0.1-0.5), for example: 10:3:1:3:0.1, 12:4:2:4:0.3, 11:3:3:4:0.2, 13:4:1:3:0.4, or 15:5:3:5:0.5, etc.

[0017] Preferably, the heating and stirring temperature is 70-90°C, for example: 70°C, 75°C, 80°C, 85°C or 90°C.

[0018] Preferably, the voltage of the electrospinning treatment in step (1) is 5 to 10 kV, for example: 5 kV, 6 kV, 8 kV, 9 kV or 10 kV.

[0019] Preferably, the distance between the needle and the receiving plate in the electrospinning process is 10-15cm, for example: 10cm, 11cm, 12cm, 13cm or 15cm.

[0020] Preferably, the calcination temperature is 700-800℃, for example: 700℃, 720℃, 750℃, 780℃ or 800℃, etc.

[0021] Preferably, the calcination time is 3 to 5 hours, for example: 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0022] Preferably, the solvent includes pure water.

[0023] Preferably, the lithium-ion sieve in step (2) is prepared by the following method:

[0024] Persulfate and manganese nitrate were dissolved in deionized water to obtain a mixed salt solution. The mixed salt solution was heated and stirred, and a cationic surfactant was added. After hydrothermal reaction, a precursor was obtained. The precursor was mixed with a lithium source, sintered, and then acid-washed to obtain the lithium ion sieve.

[0025] The lithium-ion sieve prepared by the method of the present invention has a raised surface structure, which can better achieve oil-water separation.

[0026] Preferably, the molar ratio of persulfate to manganese nitrate is (0.8 to 1.2):1, for example: 0.8:1, 0.9:1, 1:1, 1.1:1 or 1.2:1, etc.

[0027] Preferably, the total concentration of persulfate and manganese nitrate in the mixed salt solution is 0.2 to 0.5 mol / L, for example: 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, etc.

[0028] Preferably, the heating and stirring temperature is 60-80°C, for example: 60°C, 65°C, 70°C, 75°C or 80°C.

[0029] Preferably, the heating and stirring time is 20 to 30 minutes, for example: 20 minutes, 22 minutes, 25 minutes, 28 minutes or 30 minutes.

[0030] Preferably, the cationic surfactant comprises any one or a combination of at least two of hexadecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, octadecyltrimethylammonium chloride, or polyquaternium-16.

[0031] Preferably, the molar volume ratio of the cationic surfactant to the mixed salt solution is 0.05 to 0.1 mmol / L, for example: 0.05 mmol / L, 0.06 mmol / L, 0.08 mmol / L, 0.09 mmol / L or 0.1 mmol / L, etc.

[0032] Preferably, the temperature of the hydrothermal reaction is 140-180°C, for example: 140°C, 150°C, 160°C, 170°C or 180°C.

[0033] Preferably, the hydrothermal reaction time is 2 to 5 hours, for example: 2 hours, 2.5 hours, 3 hours, 4 hours or 5 hours.

[0034] Preferably, the molar ratio of manganese in the precursor to lithium in the lithium source is (1.5-2):1, for example: 1.5:1, 1.6:1, 1.8:1, 1.9:1 or 2:1, etc.

[0035] Preferably, the sintering temperature is 700-800℃, for example: 700℃, 720℃, 750℃, 780℃ or 800℃.

[0036] Preferably, the sintering time is 4 to 8 hours, for example: 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0037] Preferably, the pickling agent for pickling includes hydrochloric acid with a concentration of 0.01 to 0.1 mol / L (e.g., 0.01 mol / L, 0.02 mol / L, 0.05 mol / L, 0.08 mol / L, or 0.1 mol / L).

[0038] Preferably, the pickling time is 10 to 60 minutes, for example: 10 minutes, 20 minutes, 30 minutes, 50 minutes or 60 minutes.

[0039] Preferably, the hydrophilic polymer material in step (2) includes any one or a combination of at least two of polyvinyl alcohol, sodium alginate, polyacrylic acid, or polyacrylonitrile.

[0040] Preferably, the crosslinking agent comprises butanetetracarboxylic acid and / or ethylenediamine.

[0041] Preferably, the mass ratio of the crosslinking agent to the hydrophilic polymer material is 1:(4-5), for example: 1:4, 1:4.2, 1:4.5, 1:4.8 or 1:5, etc.

[0042] Preferably, the mass fraction of the hydrophilic polymer material in the composite liquid is 5% to 10%, for example: 5%, 6%, 8%, 9% or 10%, etc.

[0043] Preferably, the mass fraction of lithium ion sieve in the composite liquid is 5% to 20%, for example: 5%, 8%, 10%, 15% or 20%, etc.

[0044] Preferably, the mass fraction of silica nanofibers in the composite liquid is 0.5% to 2%, for example: 0.5%, 0.8%, 1%, 1.5% or 2%.

[0045] Preferably, the stirring time is 30 to 60 minutes, for example: 30 minutes, 35 minutes, 40 minutes, 50 minutes or 60 minutes.

[0046] Preferably, the freezing time in step (3) is 3 to 5 hours, for example: 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0047] Preferably, the temperature of the heating crosslinking reaction is 80-90°C, for example: 80°C, 82°C, 85°C, 88°C or 90°C.

[0048] In a second aspect, the present invention provides a composite lithium extraction adsorbent, which is prepared by the method described in the first aspect.

[0049] Thirdly, the present invention provides a lithium extraction method, characterized in that the lithium extraction method includes the following steps:

[0050] (A) The composite lithium extraction adsorbent as described in the second aspect is placed in the lithium extraction tank, and after the oilfield brine is injected, it is left to stand. The liquid inlet, upper outlet and lower outlet of the lithium extraction tank are opened to control the liquid flow rate and carry out the lithium extraction reaction.

[0051] (B) After the lithium extraction is completed, the lithium-extracted adsorbent is added to the lithium extraction tank containing hydrochloric acid solution. The inlet, upper outlet and lower outlet are opened to control the liquid flow rate to carry out the delithiation reaction, and a lithium-rich solution and a delithiation adsorbent are obtained. The delithiation adsorbent is reused in step (A) as a composite lithium extraction adsorbent.

[0052] The lithium extraction tank includes a tank body and an inlet and an outlet respectively disposed at both ends of the tank body. The outlet includes an upper outlet and a lower outlet. In step (A), the liquid discharged from the lower outlet of the lithium extraction tank is introduced into the inlet of the lithium extraction tank. In step (B), the liquid introduced into the inlet is a mixed solution of the liquid discharged from the lower outlet in step (A) and hydrochloric acid.

[0053] In the lithium extraction method of the present invention, during the lithium extraction reaction in step (A), the liquid flowing out of the lower outlet of the lithium extraction tank continues to flow into the inlet of the lithium extraction tank to repeatedly extract lithium. After the lithium extraction is completed, the mixed solution of the liquid flowing out of the lower outlet and hydrochloric acid is used to delithiate the lithium in the delithiation reaction in step (B) and then flows into the inlet of the lithium extraction tank, thus avoiding the generation of waste liquid and improving the utilization rate of materials.

[0054] The lithium extraction method described in this invention can achieve efficient oil-water separation while simultaneously extracting lithium through adsorption, resulting in a high-quality lithium-rich desorption solution with a long adsorbent lifespan.

[0055] Preferably, the stacking height of the composite lithium extraction adsorbent in step (A) is less than or equal to the height of the upper outlet of the lithium extraction tank.

[0056] Preferably, the stacking height of the composite lithium extraction adsorbent is greater than the height of the lower outlet of the lithium extraction tank.

[0057] Preferably, the contents of silica nanofibers and lithium ion sieves in the composite lithium extraction adsorbent in the lithium extraction tank are distributed in a gradient.

[0058] Preferably, the content of silica nanofibers in the composite lithium extraction adsorbent near the upper outlet increases from the inlet to the outlet.

[0059] Preferably, the lithium ion sieve content in the composite lithium extraction adsorbent near the lower outlet increases from the inlet to the outlet.

[0060] The composite lithium extraction adsorbent of this invention is placed in a lithium extraction tank. The highest point of the cross-section of the composite lithium extraction adsorbent is lower than the upper outlet but higher than the lower outlet. The composite lithium extraction adsorbent contains silica nanofibers and lithium ion sieves, with their contents set in a gradient, such as... Figure 3 As shown, the present invention sets up a lithium extraction adsorbent with a gradient of components in the lithium extraction tank, which is more conducive to oil-water separation after demulsification of oilfield brine and improves the quality of lithium-rich solution.

[0061] Preferably, the settling time is 1 to 2 hours, for example: 1 hour, 1.2 hours, 1.5 hours, 1.8 hours or 2 hours.

[0062] Preferably, the liquid flow rate at the inlet is 50–200 mL / min, for example: 50 mL / min, 80 mL / min, 100 mL / min, 150 mL / min or 200 mL / min, etc.

[0063] Preferably, the liquid flow rate at the upper outlet is 10 to 100 mL / min, for example: 10 mL / min, 20 mL / min, 50 mL / min, 80 mL / min or 100 mL / min, etc.

[0064] Preferably, the liquid flow rate at the lower outlet is 50-200 mL / min, for example: 50 mL / min, 80 mL / min, 100 mL / min, 150 mL / min or 200 mL / min, etc.

[0065] Preferably, the lithium extraction reaction time is 3 to 10 hours, for example: 3 hours, 5 hours, 6 hours, 8 hours or 10 hours.

[0066] Preferably, the concentration of the hydrochloric acid solution in step (B) is 0.01 to 0.1 mol / L, for example: 0.01 mol / L, 0.02 mol / L, 0.05 mol / L, 0.08 mol / L or 0.1 mol / L, etc.

[0067] Preferably, the liquid flow rate at the inlet is 50–200 mL / min, for example: 50 mL / min, 80 mL / min, 100 mL / min, 150 mL / min or 200 mL / min, etc.

[0068] Preferably, the liquid flow rate at the upper outlet is 10 to 100 mL / min, for example: 10 mL / min, 20 mL / min, 50 mL / min, 80 mL / min or 100 mL / min, etc.

[0069] Preferably, the liquid flow rate at the lower outlet is 50-200 mL / min, for example: 50 mL / min, 80 mL / min, 100 mL / min, 150 mL / min or 200 mL / min, etc.

[0070] Preferably, the delithiation reaction time is 10 to 30 minutes, for example: 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] (1) The present invention combines lithium ion sieves with oleophilic silica nanofibers. The oleophilic silica nanofibers can promote oil droplet aggregation and enhance the mechanical strength of sponge-like adsorbents, thereby improving cycle stability. The resulting composite lithium extraction adsorbent can be used in the lithium extraction method described in the present invention to achieve efficient oil-water separation while adsorbing and extracting lithium. The resulting lithium-rich desorption liquid has good quality and the adsorbent has a long lifespan.

[0073] (2) The lithium extraction adsorbent prepared by the method of the present invention can be used in the lithium extraction method of the present invention. The adsorption capacity can reach more than 25.53 mg / g, the capacity retention rate can reach more than 98.62% after 100 cycles, and the COD content of the lithium-rich liquid can reach less than 26.9 mg / L. Among them, the composite adsorbent with different lithium ion sieves and silica nanofiber contents is set in the lithium extraction tank in a gradient. The adsorption capacity of the oilfield brine can reach 25.71 mg / g, the capacity retention rate can reach 98.69% after 100 cycles, and the COD content of the lithium-rich liquid can reach 16.8 mg / L. Attached Figure Description

[0074] Figure 1 This is a SEM image of the composite lithium extraction adsorbent prepared in Example 1 of the present invention.

[0075] Figure 2 This is a SEM image of the lithium-ion sieve described in Embodiment 1 of the present invention.

[0076] Figure 3 This is a schematic diagram of the lithium extraction method described in Example 1 of the present invention. Detailed Implementation

[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 composite lithium extraction adsorbent, and the SEM image of the composite lithium extraction adsorbent is shown below. Figure 1 As shown, the preparation method of the composite lithium extraction adsorbent is as follows:

[0080] (1) Tetraethyl silicate, methyltrimethoxysiloxane, hydrochloric acid, water, and anhydrous ethanol were mixed in a mass ratio of 12:3:2:4:0.2 and heated and stirred at 80°C until the mass loss reached 55%, at which point heating was stopped to obtain silica sol. The silica sol was transferred to an electrospinning apparatus for spinning to obtain nanofibers. The electrospinning voltage was 8kV and the distance between the needle and the receiving plate was 12cm. The collected nanofibers were then calcined at 750°C in air for 4h to obtain silica nanofibers. The obtained silica nanofibers were then broken up in pure water to obtain a silica nanofiber suspension.

[0081] (2) Sodium persulfate and manganese nitrate were dissolved in deionized water to obtain a mixed salt solution with a salt concentration of 0.3 mol / L and a molar ratio of sodium persulfate to manganese nitrate of 1:1. The mixed salt solution was stirred at 70°C for 20 min, and hexadecyltrimethylammonium bromide with a concentration of 0.06 mmol / L was added simultaneously. The mixed salt solution was then placed in a hydrothermal reactor and reacted at 160°C for 3 h. After the reaction, the mixture was washed with pure water and dried to obtain a precursor. The precursor was mixed with a lithium source at a molar ratio of lithium:manganese = 1:2, and sintered at 750°C for 6 h to obtain a lithium-ion sieve precursor. The lithium-ion sieve precursor was eluted in 0.05 mol / L hydrochloric acid for 30 min to obtain a lithium-ion sieve (SEM image of the lithium-ion sieve is shown in Figure 1). Figure 2 As shown, by Figure 2 It can be seen that the lithium-ion sieve obtained by this invention has a raised surface structure.

[0082] (3) Polyvinyl alcohol (PVA) was dissolved in deionized water in a water bath at 80°C to obtain a PVA viscous solution. The PVA viscous solution, lithium-ion sieve, butanetetracarboxylic acid (TTCA), and silica nanofiber suspension were mixed and stirred to obtain a composite solution. In the composite solution, the mass fraction of lithium-ion sieve particles was 20 wt%, the mass fraction of PVA was 6 wt%, the mass fraction of silica nanofiber was 0.5 wt%, and the mass ratio of TTCA to PVA was 1:4.5. The composite solution was stirred at room temperature for 30 min, then frozen in a -40°C refrigerator for 4 h, and then placed in a freeze dryer. After drying, it was thermally crosslinked in an oven at 80°C to obtain the composite lithium-extraction adsorbent. Figure 1 As can be seen, the composite lithium extraction adsorbent of the present invention has a sponge-like structure.

[0083] Example 2

[0084] This embodiment provides a composite lithium extraction adsorbent, and the preparation method of the composite lithium extraction adsorbent is as follows:

[0085] (1) Tetraethyl silicate, methyltrimethoxysiloxane, hydrochloric acid, water, and anhydrous ethanol were mixed in a mass ratio of 10:4:1:3:0.3 and heated and stirred at 80°C until the mass loss reached 52%, at which point heating was stopped to obtain silica sol. The silica sol was transferred to an electrospinning apparatus for spinning to obtain nanofibers. The electrospinning voltage was 5kV and the distance between the needle and the receiving plate was 10cm. The collected nanofibers were then calcined at 700°C in air for 5h to obtain silica nanofibers. The obtained silica nanofibers were then broken up in pure water to obtain a silica nanofiber suspension.

[0086] (2) Sodium persulfate and manganese nitrate were dissolved in deionized water to form a mixed salt solution with a concentration of 0.2 mol / L and a molar ratio of sodium persulfate to manganese nitrate of 1:1. The mixed salt solution was stirred at 60°C for 30 min, and hexadecyltrimethylammonium bromide with a concentration of 0.08 mmol / L was added simultaneously. The mixed salt solution was then placed in a hydrothermal reactor and reacted at 140°C for 5 h. After the reaction, the mixture was washed with pure water and dried to obtain a precursor. The precursor was mixed with a lithium source at a molar ratio of lithium:manganese = 1:1.5, and sintered at 700°C for 8 h to obtain a lithium-ion sieve precursor. The lithium-ion sieve precursor was eluted in 0.01 mol / L hydrochloric acid for 60 min to obtain a lithium-ion sieve.

[0087] (3) Polyvinyl alcohol was dissolved in deionized water in a water bath at 80°C to obtain a polyvinyl alcohol viscous solution. The polyvinyl alcohol viscous solution, lithium ion sieve, ethylenediamine, and silica nanofiber suspension were mixed and stirred to obtain a composite solution. In the composite solution, the mass fraction of lithium ion sieve particles was 15 wt%, the mass fraction of polyvinyl alcohol was 6 wt%, the mass fraction of silica nanofiber was 1 wt%, and the mass ratio of ethylenediamine to polyvinyl alcohol was 1:4. The composite solution was stirred at room temperature for 30 min, then placed in a refrigerator at -40°C for 3 h, and then placed in a freeze dryer. After drying, it was thermally crosslinked in an oven at 85°C to obtain a sponge-like composite lithium extraction adsorbent.

[0088] Example 3

[0089] This embodiment provides a composite lithium extraction adsorbent, and the preparation method of the composite lithium extraction adsorbent is as follows:

[0090] (1) Tetraethyl silicate, methyltrimethoxysiloxane, hydrochloric acid, water, and anhydrous ethanol were mixed in a mass ratio of 15:5:3:5:0.5 and heated and stirred at 90°C until the mass loss reached 56%, at which point heating was stopped to obtain silica sol. The silica sol was transferred to an electrospinning apparatus for spinning to obtain nanofibers. The electrospinning voltage was 10kV and the distance between the needle and the receiving plate was 15cm. The collected nanofibers were then calcined at 800°C in air for 3h to obtain silica nanofibers. The obtained silica nanofibers were then broken in pure water to obtain a silica nanofiber suspension.

[0091] (2) Sodium persulfate and manganese nitrate were dissolved in deionized water to form a mixed salt solution with a concentration of 0.5 mol / L and a molar ratio of sodium persulfate to manganese nitrate of 1:1. The mixed salt solution was stirred at 80°C for 20 min, and hexadecyltrimethylammonium bromide with a concentration of 0.1 mmol / L was added simultaneously. The mixed salt solution was then placed in a hydrothermal reactor and reacted at 180°C for 2 h. After the reaction, the mixture was washed with pure water and dried to obtain a precursor. The precursor was mixed with a lithium source at a molar ratio of lithium:manganese = 1:2, and sintered at 800°C for 4 h to obtain a lithium-ion sieve precursor. The lithium-ion sieve precursor was then eluted in 0.1 mol / L hydrochloric acid for 10 min to obtain a lithium-ion sieve.

[0092] (3) Polyvinyl alcohol was dissolved in deionized water in a water bath at 80°C to obtain a polyvinyl alcohol viscous solution. The polyvinyl alcohol viscous solution, lithium ion sieve, butanetetracarboxylic acid, and silica nanofiber suspension were mixed and stirred to obtain a composite solution. In the composite solution, the mass fraction of lithium ion sieve particles was 10 wt%, the mass fraction of polyvinyl alcohol was 6 wt%, the mass fraction of silica nanofiber was 2 wt%, and the mass ratio of butanetetracarboxylic acid to polyvinyl alcohol was 1:5. The composite solution was stirred at room temperature for 30 min, then placed in a refrigerator at -40°C for 3 h, and then placed in a freeze dryer. After drying, it was thermally crosslinked in an oven at 85°C to obtain a sponge-like composite lithium extraction adsorbent.

[0093] Example 4

[0094] The only difference between this embodiment and Example 1 is that the mass fraction of silica nanofibers in the composite liquid is 0.1%, while the other conditions and parameters are exactly the same as in Example 1.

[0095] Example 5

[0096] The only difference between this embodiment and Example 1 is that the mass fraction of silica nanofibers in the composite liquid is 4%, while the other conditions and parameters are exactly the same as in Example 1.

[0097] Example 6

[0098] The only difference between this embodiment and Embodiment 1 is that the crosslinking temperature is 70°C, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0099] Example 7

[0100] The only difference between this embodiment and Embodiment 1 is that the heating crosslinking temperature is 100°C, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0101] Comparative Example 1

[0102] The only difference between this comparative example and Example 1 is that silica nanofibers are not added; all other conditions and parameters are exactly the same as in Example 1.

[0103] Application Example 1

[0104] This application example provides a lithium extraction method, and a schematic diagram of the lithium extraction method is shown below. Figure 3 As shown, the lithium extraction method includes the following steps:

[0105] (A) The composite lithium extraction adsorbent prepared in Examples 1-3 was placed in a lithium extraction tank, with the upper outlet located above the adsorbent and the lower outlet located below the adsorbent. Oilfield brine was introduced from left to right to fill the lithium extraction tank, and the tank was left to stand for 1.5 hours.

[0106] The adsorbent in the lithium extraction tank is assembled from the composite lithium extraction adsorbents prepared in Examples 1-3 according to the following rules. The compositional variation from the inlet to the outlet is as follows: near the upper outlet, the content of hydrophobic silica nanofibers gradually increases from the inlet to the outlet; near the lower outlet, the content of lithium-ion sieve particles gradually increases from the inlet to the outlet; and from top to bottom, the content of lithium-ion sieve particles gradually increases while the content of hydrophobic silica nanofibers gradually decreases. Then, the inlet and both outlets are opened. Liquid discharged from the lower outlet of the lithium extraction tank is introduced into the inlet at a flow rate of 100 mL / min, 80 mL / min at the lower outlet, and 20 mL / min at the upper outlet, for a 6-hour lithium extraction cycle.

[0107] (B) After lithium extraction is complete, remove the sponge-like lithium extraction adsorbent and reuse the brine in the lithium extraction tank in step (A). Place the lithium-extracted sponge-like lithium extraction adsorbent into the lithium extraction tank and inject 0.05 mol / L hydrochloric acid to fill the tank. Then open the inlet and the upper and lower outlets. Pour a mixture of the liquid discharged from the lower outlet and hydrochloric acid from step (A) into the inlet. The inlet flow rate is 150 mL / min, the lower outlet flow rate is 140 mL / min, and the upper outlet flow rate is 10 mL / min. The flow rate at the upper outlet is lower than that at the inlet. Circulate for 15 minutes to remove lithium. Remove the desorbed sponge-like lithium extraction adsorbent to obtain a lithium-rich solution. The obtained sponge-like lithium extraction adsorbent is reused in step (A).

[0108] Application Example 2

[0109] The only difference between this application example and application example 1 is that the composite lithium extraction adsorbent prepared in example 1 is used, while the other conditions and parameters are exactly the same as in application example 1.

[0110] Application Example 3

[0111] The only difference between this application example and application example 1 is that the composite lithium extraction adsorbent prepared in example 2 is used, while the other conditions and parameters are exactly the same as in application example 1.

[0112] Application Example 4

[0113] The only difference between this application example and application example 1 is that the composite lithium extraction adsorbent prepared in example 3 is used, while the other conditions and parameters are exactly the same as in application example 1.

[0114] Application Example 5

[0115] The only difference between this application example and application example 2 is that the composite lithium extraction adsorbent prepared in example 4 is used, while the other conditions and parameters are exactly the same as in application example 1.

[0116] Application Example 6

[0117] The only difference between this application example and application example 2 is that the composite lithium extraction adsorbent prepared in example 5 is used, while the other conditions and parameters are exactly the same as in application example 1.

[0118] Application Example 7

[0119] The only difference between this application example and application example 2 is that the composite lithium extraction adsorbent prepared in example 6 is used, while the other conditions and parameters are exactly the same as in application example 1.

[0120] Application Example 8

[0121] The only difference between this application example and application example 2 is that the composite lithium extraction adsorbent prepared in example 7 is used, while the other conditions and parameters are exactly the same as in application example 1.

[0122] Comparative Application Example 1

[0123] The only difference between this application example and application example 2 is that only the composite lithium extraction adsorbent prepared by comparative example 1 is used; all other conditions and parameters are exactly the same as in application example 1.

[0124] Performance testing:

[0125] Measure the concentration of brine before and after adsorption, and calculate the adsorption capacity according to the following formula.

[0126] The adsorption capacity of the adsorbent is: Q = V(C0 - C) / m;

[0127] Q is the adsorption capacity, mg / g; V is the adsorption liquid volume, L; m is the adsorbent mass, g; C0 and C are the lithium ion concentrations in the brine before and after adsorption, mg / L, respectively.

[0128] The lithium ion concentration in the brine is 30 mg / L.

[0129] The capacity retention rate after 100 cycles is obtained by comparing the adsorption capacity after 100 cycles with the initial adsorption capacity. The test results are shown in Table 1.

[0130] Table 1

[0131]

[0132] As shown in Table 1, based on Application Examples 1-4, the lithium extraction adsorbent prepared by the method of the present invention, when used in the lithium extraction method of the present invention, has an adsorption capacity of over 25.53 mg / g, a capacity retention rate of over 98.62% after 100 cycles, and a COD content of lithium-rich liquid below 26.9 mg / L. Among them, when a composite adsorbent with different lithium ion sieve and silica nanofiber contents is set in a gradient in the lithium extraction tank, the adsorption capacity of oilfield brine can reach 25.71 mg / g, the capacity retention rate can reach 98.69% after 100 cycles, and the COD content of lithium-rich liquid can reach 16.8 mg / L.

[0133] A comparison of Application Examples 2 and 5-6 shows that the mass fraction of silica nanofibers in the composite liquid affects the performance of the composite lithium extraction adsorbent described in this invention. Controlling the mass fraction of silica nanofibers in the composite liquid to 0.5-2% results in a composite lithium extraction adsorbent with better performance. If the mass fraction of silica nanofibers in the composite liquid is too high, the proportion of lithium ion sieves in the adsorbent will be too low, affecting the specific capacity. If the mass fraction of silica nanofibers in the composite liquid is too low, the enhancement of adsorbent strength will be less, affecting cycle stability. Furthermore, the reduction in oleophilic substances will lead to a worse water-oil separation effect.

[0134] A comparison of Application Examples 2 and 7-8 shows that the heating crosslinking temperature affects the performance of the composite lithium extraction adsorbent during its preparation. Controlling the heating crosslinking temperature at 80-90°C results in a composite lithium extraction adsorbent with better performance. If the heating crosslinking temperature is too high or too low, it will affect the crosslinking effect. If the temperature is too high, the crosslinking will be excessive, affecting the adsorbent capacity. If the temperature is too low, the degree of crosslinking will be insufficient, affecting the adsorbent's cycle stability.

[0135] By comparing Application Example 2 and Comparative Application Example 1, it can be seen that the present invention prepares a sponge-like hydrophobic / hydrophilic composite adsorbent by combining lithium ion sieves and oleophilic silica nanofibers. The protrusions on the surface of lithium ion sieve particles break up the emulsion droplets. After the droplets are broken up in the channels, the aqueous phase of the droplets gathers on the surface of the hydrophilic adsorbent, while the oil phase gathers on the surface of the hydrophobic particles. The small oil phase particles collide with each other, grow larger, and float to the surface, thus achieving more complete oil-water separation.

[0136] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a composite lithium extraction adsorbent, characterized in that, The preparation method includes the following steps: (1) The silica sol was electrospun and calcined to obtain silica nanofibers. The silica nanofibers were crushed in a solvent to obtain a silica nanofiber suspension. The silica sol was prepared by the following method: Tetraethyl silicate, methyltrimethoxysiloxane, hydrochloric acid, water and anhydrous ethanol are mixed and heated and stirred until the total mass loss of the substances in the system reaches more than 50%, then heating is stopped to obtain the silica sol. (2) The hydrophilic polymer material is dissolved in deionized water to obtain a hydrophilic polymeric mucus. The hydrophilic polymeric mucus, lithium ion sieve, crosslinking agent and silica nanofiber suspension are mixed and stirred to obtain a composite liquid. The mass fraction of silica nanofibers in the composite liquid is 0.5%~2%. The lithium-ion sieve is prepared by the following method: Persulfate and manganese nitrate were dissolved in deionized water to obtain a mixed salt solution. The mixed salt solution was heated and stirred, and a cationic surfactant was added. After hydrothermal reaction, a precursor was obtained. The precursor was mixed with a lithium source, sintered, and then acid-washed to obtain the lithium ion sieve. (3) After freezing the composite liquid, freeze-dry it. After drying, the composite lithium adsorbent is obtained by heating and cross-linking reaction. The temperature of the heating and cross-linking reaction is 80~90℃.

2. The preparation method according to claim 1, characterized in that, The mass ratio of tetraethyl silicate, methyltrimethoxysiloxane, hydrochloric acid, water and anhydrous ethanol is (10~15): (3~5): (1~3): (3~5): (0.1~0.5).

3. The preparation method according to claim 1, characterized in that, The heating and stirring temperature is 70~90℃.

4. The preparation method according to claim 1, characterized in that, The voltage for the electrospinning process in step (1) is 5~10kV.

5. The preparation method according to claim 1, characterized in that, The distance between the needle and the receiving plate in the electrospinning process is 10-15 cm.

6. The preparation method according to claim 1, characterized in that, The calcination temperature is 700~800℃.

7. The preparation method according to claim 1, characterized in that, The calcination time is 3-5 hours.

8. The preparation method according to claim 1, characterized in that, The solvent includes pure water.

9. The preparation method according to claim 1, characterized in that, The molar ratio of persulfate to manganese nitrate is (0.8~1.2):

1.

10. The preparation method according to claim 1, characterized in that, The total concentration of persulfate and manganese nitrate in the mixed salt solution is 0.2~0.5 mol / L.

11. The preparation method according to claim 1, characterized in that, The heating and stirring temperature is 60~80℃.

12. The preparation method according to claim 1, characterized in that, The heating and stirring time is 20-30 minutes.

13. The preparation method according to claim 1, characterized in that, The cationic surfactant includes any one or a combination of at least two of hexadecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, octadecyltrimethylammonium chloride, or polyquaternium-16.

14. The preparation method according to claim 1, characterized in that, The molar volume ratio of the cationic surfactant to the mixed salt solution is 0.05~0.1 mmol / L.

15. The preparation method according to claim 1, characterized in that, The temperature of the hydrothermal reaction is 140~180℃.

16. The preparation method according to claim 1, characterized in that, The hydrothermal reaction takes 2 to 5 hours.

17. The preparation method according to claim 1, characterized in that, The molar ratio of manganese in the precursor to lithium in the lithium source is (1.5~2):

1.

18. The preparation method according to claim 1, characterized in that, The sintering temperature is 700~800℃.

19. The preparation method according to claim 1, characterized in that, The sintering time is 4 to 8 hours.

20. The preparation method according to claim 1, characterized in that, The pickling agent used in the pickling process includes hydrochloric acid with a concentration of 0.01~0.1 mol / L.

21. The preparation method according to claim 1, characterized in that, The pickling time is 10-60 minutes.

22. The preparation method according to claim 1, characterized in that, The hydrophilic polymer material in step (2) includes any one or a combination of at least two of polyvinyl alcohol, sodium alginate, polyacrylic acid or polyacrylonitrile.

23. The preparation method according to claim 1, characterized in that, The crosslinking agent includes butanetetracarboxylic acid and / or ethylenediamine.

24. The preparation method according to claim 1, characterized in that, The mass ratio of the crosslinking agent to the hydrophilic polymer material is 1:(4~5).

25. The preparation method according to claim 1, characterized in that, The mass fraction of hydrophilic polymer material in the composite liquid is 5%~10%.

26. The preparation method according to claim 1, characterized in that, The mass fraction of lithium ion sieve in the composite liquid is 5%~20%.

27. The preparation method according to claim 1, characterized in that, The stirring time is 30-60 minutes.

28. The preparation method according to claim 1, characterized in that, The freezing time in step (3) is 3 to 5 hours.

29. A composite lithium extraction adsorbent, characterized in that, The composite lithium extraction adsorbent is prepared by the method described in any one of claims 1-28.

30. A method for lithium extraction, characterized in that, The lithium extraction method includes the following steps: (A) The composite lithium extraction adsorbent as described in claim 29 is placed in a lithium extraction tank, oilfield brine is injected and allowed to stand, and the inlet, upper outlet and lower outlet of the lithium extraction tank are opened to control the liquid flow rate for lithium extraction reaction. (B) After lithium extraction is completed, the lithium-extracted adsorbent is added to a lithium extraction tank containing hydrochloric acid solution. The inlet, upper outlet and lower outlet are opened to control the liquid flow rate to carry out the delithiation reaction, and a lithium-rich solution and a delithiation adsorbent are obtained. The delithiation adsorbent is reused in step (A) as a composite lithium extraction adsorbent. The lithium extraction tank includes a tank body and an inlet and an outlet respectively disposed at both ends of the tank body. The outlet includes an upper outlet and a lower outlet. In step (A), the liquid discharged from the lower outlet of the lithium extraction tank is introduced into the inlet of the lithium extraction tank. In step (B), the liquid introduced into the inlet is a mixed solution of the liquid discharged from the lower outlet in step (A) and hydrochloric acid.

31. The lithium extraction method as described in claim 30, characterized in that, In step (A), the stacking height of the composite lithium extraction adsorbent is less than or equal to the height of the upper outlet of the lithium extraction tank.

32. The lithium extraction method as described in claim 30, characterized in that, The stacking height of the composite lithium extraction adsorbent is greater than the height of the lower outlet of the lithium extraction tank.

33. The lithium extraction method as described in claim 30, characterized in that, The content of silica nanofibers and lithium ion sieves in the composite lithium extraction adsorbent in the lithium extraction tank is distributed in a gradient.

34. The lithium extraction method as described in claim 30, characterized in that, The content of silica nanofibers in the composite lithium extraction adsorbent near the upper outlet increases from the inlet to the outlet.

35. The lithium extraction method as described in claim 30, characterized in that, The lithium ion sieve content in the composite lithium extraction adsorbent near the lower outlet increases from the inlet to the outlet.

36. The lithium extraction method as described in claim 30, characterized in that, The settling time is 1 to 2 hours.

37. The lithium extraction method as described in claim 30, characterized in that, The liquid flow rate at the inlet is 50~200mL / min.

38. The lithium extraction method as described in claim 30, characterized in that, The liquid flow rate at the upper outlet is 10~100mL / min.

39. The lithium extraction method as described in claim 30, characterized in that, The liquid flow rate at the lower outlet is 50~200mL / min.

40. The lithium extraction method as described in claim 30, characterized in that, The lithium extraction reaction takes 3 to 10 hours.

41. The lithium extraction method as described in claim 30, characterized in that, The concentration of the hydrochloric acid solution in step (B) is 0.01~0.1 mol / L.

42. The lithium extraction method as described in claim 30, characterized in that, The liquid flow rate at the inlet is 50~200mL / min.

43. The lithium extraction method as described in claim 30, characterized in that, The liquid flow rate at the upper outlet is 10~100mL / min.

44. The lithium extraction method as described in claim 30, characterized in that, The liquid flow rate at the lower outlet is 50~200mL / min.

45. The lithium extraction method as described in claim 30, characterized in that, The delithiation reaction takes 10-30 minutes.

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