Rod-shaped lithium extraction adsorbent and preparation method thereof

Abstract

The invention relates to a rod-like lithium extraction adsorbent and a preparation method thereof, and belongs to the field of energy materials and technologies. The preparation method comprises the following steps: mixing an inorganic adsorbent with a hydrophilic material and a dispersing agent to form a precursor, blending and banburying the precursor with a polymer, a pore-foaming agent and a surface coalescing agent, carrying out extrusion molding, carrying out surface crosslinking curing treatment, forming a compact protective layer in a coagulating bath, and finally carrying out size stabilization, water washing and drying. The adsorbent has the characteristics of high wear resistance, high pressure resistance and high adsorption capacity, the problem of pulverization loss in recycling can be effectively prevented by the surface protection layer, and the cycling stability is remarkably improved. The problems that a conventional adsorbent is prone to compaction and pulverization, high in column pressure, low in capacity and the like are solved, the service life is prolonged, energy consumption is reduced, and the method is suitable for industrial continuous adsorption-desorption processes such as salt lake lithium extraction.

Description

Technical Field

[0001] The present invention relates to a rod-shaped lithium extraction adsorbent and a preparation method thereof, belonging to the technical field of adsorbent preparation. Background Art

[0002] Lithium metal and its compounds have important applications in the fields of lithium batteries, pharmaceutical and chemical industries, ceramics, glass, atomic energy thermonuclear fusion, etc. Especially in recent years, the rapid development of the new energy industry has led to a sharp increase in the demand for lithium. Lithium resources are mainly stored in hard rocks and salt lake brines, among which the "salt lake type" lithium ore reserves account for more than 70%. Therefore, how to develop the lithium resources in salt lake brines has become increasingly important.

[0003] At present, the adsorption method is considered to be the most promising method for extracting lithium from salt lake brines in industrial applications. In the adsorption method, first, an adsorbent selective to lithium adsorbs lithium ions in the salt lake brine, and then the lithium ions are eluted to achieve the separation of lithium ions from other ions. This method is suitable for the separation of lithium in high-magnesium and low-lithium brines and is also suitable for brines with relatively low lithium content. The greatest advantage of the adsorption method is its great superiority in terms of economy and environmental protection, with simple process, high recovery rate, and good selectivity. The key to this process is the lithium ion adsorbent, which is required to selectively adsorb lithium ions in the brine and have the characteristics of high adsorption capacity and high strength. However, most of the currently developed lithium ion sieve adsorbents are in powder or spherical-like shapes, with poor fluidity and permeability, and the performance of the adsorbent itself cannot be fully utilized, resulting in low adsorption efficiency and increased energy consumption, which is not conducive to industrial applications; the dissolution loss rate is too high during the soaking and lithium stripping process, the cycle stability is poor, and metal ions are likely to cause environmental pollution. After multiple adsorption and desorption processes, the effective cost of the spherical-like adsorbent will quickly lose, and it is prone to compaction, flattening, and pulverization during application, resulting in an increase in tower pressure, further exacerbating the decline in performance and service life, and increasing energy consumption. Summary of the Invention

[0004] The technical problems to be solved by the present invention are as follows: Existing adsorbents generally have problems such as poor mechanical strength, easy pulverization and loss, poor cycle stability, and low adsorption capacity, which seriously affect their industrial application effects. The present invention forms a precursor by mixing an inorganic adsorbent with a hydrophilic material and a dispersant, and then co-blending and kneading it with a polymer, a pore-forming agent, and a surface film-forming aid. After extrusion molding, a dense protective layer is constructed on the surface of the rod-shaped adsorbent through a special surface cross-linking and curing process. This protective layer can effectively prevent the pulverization and loss problems of the adsorbent caused by mechanical friction and hydraulic scouring during multiple cycles of use. The rod-shaped adsorbent prepared through processes such as continuous granulation, water washing, and drying not only has high mechanical strength, excellent wear and pressure resistance performance, and high adsorption capacity, but also significantly improves the cycle stability, fundamentally solves the problems of traditional adsorbents such as easy compaction, deformation, pulverization, increased column pressure, and capacity attenuation, greatly extends the service life, and reduces the operating energy consumption.

[0005] A rod-shaped lithium extraction adsorbent, which has a rod-shaped structure, a length of 0.2 - 2 mm, a diameter of 0.4 - 1 mm, and is a porous structure. The rod-shaped adsorbent contains a polymer and an inorganic adsorbent.

[0006] The inorganic adsorbent is selected from aluminum-based adsorbents, titanium-based adsorbents, or manganese-based adsorbents; the polymer is selected from one or more mixtures of polysulfone, polyethersulfone, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyacrylic acid, polyvinyl acetate, polyvinyl alcohol, or vinyl chloride-vinyl acetate resin, etc.

[0007] The weight ratio of the inorganic adsorbent to the polymer is 20 - 100:15; the particle size range of the inorganic adsorbent is 0.5 - 20 μm.

[0008] Its surface is distributed with a protective layer obtained by cross-linking chitosan and polyphosphate.

[0009] A preparation method of the rod-shaped lithium extraction adsorbent, comprising the following steps:

[0010] Step 1, fully mixing the inorganic adsorbent with a hydrophilic material and a dispersant to obtain a precursor;

[0011] Step 2, dispersing the precursor, polymer, and pore-forming agent in a solvent and carrying out internal mixing;

[0012] Step 3, feeding the mixture obtained in Step 2 into an extruder, adding a cross-linking agent to the extruder at the same time, extruding through a die into a shaping bath for curing and forming, and obtaining the finished lithium extraction adsorbent through sieving, washing, drying, and screening equipment.

[0013] In the preparation method, in Step 1, the mixing ratio of the inorganic adsorbent, hydrophilic material, and dispersant is 20 - 68:0.5 - 5:0.02 - 0.5; in Step 2, the mixing ratio of the precursor, polymer, pore-forming agent, and solvent is 20 - 68:15:6 - 12:30 - 70; in Step 3, the ratio of the internally mixed mixture to the cross-linking agent is 1:0.02 - 0.2.

[0014] The solvent is one or more mixtures of acetone, ethyl acetate, carbon tetrachloride, water, xylene, dioctyl phthalate, epoxidized soybean oil, dimethylacetamide, dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, etc.; the hydrophilic material is one or more mixtures of polyvinyl alcohol, polyethylene glycol, chitosan, sodium alginate, polyvinylpyrrolidone, polyacrylic acid, etc.; the dispersant is one of Tween-80, sodium dodecylbenzenesulfonate, or dodecyl phosphate; the pore-forming agent is one or more mixtures of calcium carbonate, sodium carbonate, sodium bicarbonate, sodium chloride, lithium chloride, polyethylene glycol, glycerol, diethylene glycol, etc.; the cross-linking agent is one of glutaraldehyde or carbodiimide.

[0015] The kneading temperature is 60 - 120 °C and the time is 6 - 12 h; the extruder is a twin-screw extruder with a frequency of 60 - 300 r / min and a temperature of 60 - 150 °C.

[0016] The structure of the die includes a slurry nozzle, and on both sides of the liquid nozzle there are compressed cold air slits. The exhaust direction of the compressed cold air slits is parallel to the slurry extrusion direction. The flow rate of the slurry in the die is 2 - 10 L / min, and the flow rate of the compressed cold air is 8 - 20 m / s.

[0017] In step 3, after the slurry is extruded, it is held in the air for 10 - 20 s and then enters the setting bath. The setting bath is water or an aqueous solution containing 0.1 - 1% polyphosphate, with a temperature of 15 - 50 °C and a pH range of 4 - 6.

[0018] The polyphosphate is selected from tripolyphosphate, tetrapolyphosphate or pyrophosphate; the cations therein are selected from sodium, potassium, calcium or ammonium.

[0019] In the described use, in the brine composition, it contains Mg 2+ and Li + , and the mass ratio of Mg / Li is 1 - 200:1, preferably 5 - 100; the desorbing liquid used in the desorption process is water or dilute hydrochloric acid with a pH range of 1.0 - 5.0.

[0020] Through innovative material combinations and process designs, the present invention significantly enhances the performance of rod-shaped adsorbents. The dispersant evenly disperses and fully mixes the inorganic adsorbent powder and the hydrophilic material, avoiding agglomeration and improving hydrophilicity. In particular, during the kneading process of the precursor, polymer, and pore-forming agent, the polymer initially interconnects the precursors. After the pore-forming agent enters the setting bath and dissolves, a surface porous structure is formed, improving surface roughness and surface porosity. The hydrophilic monomer undergoes a cross-linking reaction with the cross-linking agent to form a semi-interpenetrating network structure with the polymer, wrapping and bonding the inorganic adsorbent powder to prevent the inorganic adsorbent powder from falling off, being lost, and pulverizing. The core is to form a three-dimensional network structure through ionic cross-linking reactions, effectively preventing the pulverization and loss of the adsorbent during the recycling process. Based on the formation mechanism of the polyelectrolyte composite membrane of chitosan (amino) and sodium tripolyphosphate (TPP), an excellent protective layer is constructed on the surface of the adsorbent. Meanwhile, the polyelectrolyte composite membrane formed on the surface further strengthens the protection effect, significantly enhancing the mechanical strength of the entire rod-shaped adsorbent, making it not easily broken or compacted. This unique porous network structure design not only increases the contact sites of the adsorbent powder, improves the penetration rate and adsorption rate of the brine, but also ensures the structural stability of the adsorbent during long-term use through the protective effect of the surface membrane. The rod-shaped adsorbent extruded through a customized die is treated with high-speed compressed cold air, undergoes rapid stretching, the polymer crystallizes, and the crystal regions gradually separate to form a porous structure with a smaller diameter. It is cured and shaped in the setting bath. The finally prepared rod-shaped adsorbent with high strength, hydrophilicity, and a porous structure is coated with a protective film on the surface. When placed in the adsorption tower, it can form a stable multi-layer rod-shaped skeleton structure, is not easily compacted, flattened, or pulverized, has a small tower pressure, the brine can quickly penetrate into the adsorbent, fully exerting the performance of the adsorbent itself, and has a high exchange rate and long-term use stability. Description of the Drawings

[0021] Figure 1 is the electron micrograph of the rod-shaped adsorbent prepared by this patent.

[0022] Figure 2 is the structure of the mold.

[0023] Figure 3 is the curve graph of mass loss and adsorption capacity. Detailed Embodiments

[0024] In the following examples, an aluminum-based adsorbent is taken as an example to illustrate the preparation and application of this rod-shaped adsorbent. The aluminum-based adsorbent used here has a good selectivity for lithium ions, and its particle size distribution is 0.5 - 20 μm.

[0025] A rod-shaped lithium extraction adsorbent and its preparation method, with a rod-shaped structure, a length of 0.2 - 2 mm, a diameter of 0.4 - 1 mm, and a porous structure. The rod-shaped adsorbent contains a polymer and an inorganic adsorbent.

[0026] The inorganic adsorbent described above is selected from aluminum-based adsorbents, titanium-based adsorbents or manganese-based adsorbents; the polymers described above are selected from one or more mixtures of polysulfone, polyethersulfone, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyacrylic acid, polyvinyl acetate, polyvinyl alcohol or vinyl chloride-vinyl acetate resin, etc.

[0027] The weight ratio of the inorganic adsorbent to the polymer is 20-100:15; the particle size range of the inorganic adsorbent is 0.5-20 μm.

[0028] The preparation method of the rod-shaped lithium extraction adsorbent described above includes the following steps:

[0029] Step 1, fully mix the inorganic adsorbent with the hydrophilic material and the dispersant to obtain a precursor;

[0030] Step 2, disperse the precursor, the polymer and the pore-forming agent in a solvent and carry out internal mixing;

[0031] Step 3, feed the mixture obtained in Step 2 into an extruder, and at the same time add a cross-linking agent to the extruder, extrude through a die into a shaping bath for curing and forming, and obtain the finished lithium extraction adsorbent through sieving, washing, drying and screening equipment.

[0032] In the preparation method described above, in Step 1, the mixing ratio of the inorganic adsorbent, the hydrophilic material and the dispersant is 20-68:0.5-5:0.02-0.5, in Step 2, the mixing ratio of the precursor, the polymer, the pore-forming agent and the solvent is 20-68:15:6-12:30-70, and in Step 3, the ratio of the internally mixed mixture to the cross-linking agent is 1:0.02-0.2.

[0033] The solvent is one or more mixtures of acetone, ethyl acetate, carbon tetrachloride, water, xylene, dioctyl phthalate, epoxidized soybean oil, dimethylacetamide, dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, etc., the hydrophilic material is one or more mixtures of polyvinyl alcohol, polyethylene glycol, chitosan, sodium alginate, polyvinylpyrrolidone, polyacrylic acid, etc.; the dispersant is one of Tween-80, sodium dodecylbenzenesulfonate, dodecyl phosphate; the pore-forming agent is one or more mixtures of calcium carbonate, sodium carbonate, sodium bicarbonate, sodium chloride, lithium chloride, polyethylene glycol, glycerol, diethylene glycol, etc.; the cross-linking agent is one of glutaraldehyde and carbodiimide.

[0034] The internal mixing temperature is 60-120 °C and the time is 6-12 h;

[0035] The extruder is a twin-screw extruder, with a frequency of 60-300 r / min and a temperature of 60-150 °C;

[0036] The structure of the die includes a slurry nozzle 1, and compressed cold air slits 2 are provided on both sides of the liquid nozzle. The flow rate of the slurry in the die is 2 - 10 L / min, and the flow rate of the compressed cold air is 8 - 20 m / s;

[0037] The setting bath is water or an aqueous solution containing 0.1 - 1% polyphosphate, with a temperature of 15 - 50 °C and a pH range of 4 - 6.

[0038] The polyphosphate is selected from tripolyphosphate, tetrapolyphosphate or pyrophosphate.

[0039] In step 3, after the slurry is extruded, it is kept in the air for 10 - 20 s and then enters the setting bath.

[0040] Use of the rod-shaped lithium extraction adsorbent in extracting lithium from brine.

[0041] In the said use, it is characterized in that in the said use, the composition of the brine contains Mg 2+ and Li + , and the mass ratio of Mg / Li is 1 - 200:1, preferably 5 - 100; the desorbing liquid used in the desorption process is water or dilute hydrochloric acid with a pH range of 1.0 - 5.0.

[0042] Example 1

[0043] Mix the inorganic adsorbent, polyvinyl alcohol and Tween - 80 evenly according to the mass ratio of 35:2:0.2 to form a precursor. Mix the precursor, polysulfone, sodium carbonate, polyethylene glycol and acetone according to the mass ratio of 25:15:6:2:45, and carry out internal mixing. The temperature is set at 90 °C and the time is 8 h.

[0044] Feed the internally mixed mixture into a twin-screw extruder, set the frequency at 200 r / min and the temperature at 120 °C. At the same time, add glutaraldehyde as a cross-linking agent to the extruder, and add it according to the ratio of the internally mixed mixture to the cross-linking agent of 1:0.1. Extrude through a die with compressed cold air slits, control the slurry flow rate at 5 L / min, and the compressed cold air flow rate at 15 m / s.

[0045] After the extruded rod-shaped lithium extraction adsorbent stays in the air for 15 s, it quickly enters a pure water setting bath at a temperature of 30 °C for solidification and forming. Finally, it is processed through sizing, water washing, drying and screening equipment to obtain the finished lithium extraction adsorbent.

[0046] Example 2

[0047] Mix the inorganic adsorbent, polyethylene glycol, and sodium dodecylbenzenesulfonate according to a mass ratio of 40:3:0.1 to form a precursor. Mix the precursor, polyacrylonitrile, calcium carbonate, glycerol, ethyl acetate, and epoxidized soybean oil according to a mass ratio of 30:15:5:3:35:25 and conduct internal mixing. Set the internal mixing temperature at 80 °C and the time at 6 h.

[0048] Feed the mixture into a twin-screw extruder, set the frequency at 150 r / min, and the temperature at 120 °C. Add carbodiimide as a crosslinking agent and add it according to the ratio of the internally mixed mixture to the crosslinking agent of 1:0.05.

[0049] Extrude through a die, control the slurry flow rate at 3 L / min, and the compressed cold air flow rate at 10 m / s. After the extruded rod-shaped lithium extraction adsorbent stays in the air for 12 s, quickly enter a pure water setting bath at 25 °C for curing. Finally, obtain the finished product through processes such as granulation, washing, drying, and screening.

[0050] Example 3

[0051] Mix the inorganic adsorbent, polyvinyl alcohol, and Tween-80 evenly according to a mass ratio of 35:2:0.2 to form a precursor. Mix the precursor, polysulfone, sodium carbonate, polyethylene glycol, and acetone according to a mass ratio of 25:15:6:2:45 and conduct internal mixing. Set the temperature at 90 °C and the time at 8 h.

[0052] Feed the internally mixed mixture into a twin-screw extruder, set the frequency at 200 r / min, and the temperature at 120 °C. At the same time, add glutaraldehyde as a crosslinking agent to the extruder and add it according to the ratio of the internally mixed mixture to the crosslinking agent of 1:0.1. Extrude through a die with a compressed cold air slit, control the slurry flow rate at 5 L / min, and the compressed cold air flow rate at 15 m / s.

[0053] After the extruded rod-shaped lithium extraction adsorbent stays in the air for 15 s, quickly enter a setting bath containing 0.5% sodium tripolyphosphate (pH 5 - 6) at 30 °C for curing. Finally, obtain the finished lithium extraction adsorbent through processes such as granulation, washing, drying, and screening.

[0054] Example 4

[0055] Mix the inorganic adsorbent, polyethylene glycol, and sodium dodecylbenzenesulfonate according to a mass ratio of 40:3:0.1 to form a precursor. Mix the precursor, polyacrylonitrile, calcium carbonate, glycerol, ethyl acetate, and epoxidized soybean oil according to a mass ratio of 30:15:5:3:35:25 and conduct internal mixing. Set the internal mixing temperature at 80 °C and the time at 6 h.

[0056] Feed the mixture into a twin-screw extruder, set the frequency to 150 r / min and the temperature to 120 °C. Add carbodiimide as a crosslinking agent and add it according to the ratio of the kneaded mixture to the crosslinking agent of 1:0.05.

[0057] Extrude through a die, control the slurry flow rate at 3 L / min, and the compressed cold air flow rate at 10 m / s. After the extruded rod-shaped lithium extraction adsorbent stays in the air for 12 s, quickly enter a setting bath containing 0.5% sodium tripolyphosphate (pH 5-6) at 25 °C to cure. Finally, after sizing, washing, drying and screening equipment treatment, the finished product is obtained.

[0058] Comparative Example 1

[0059] Mix the inorganic adsorbent, polyethylene glycol and sodium dodecylbenzenesulfonate into a precursor according to a mass ratio of 40:3:0.1. Mix the precursor, polyacrylonitrile, calcium carbonate, glycerol, ethyl acetate and epoxidized soybean oil according to a mass ratio of 30:15:5:3:35:25 for kneading. Set the kneading temperature to 80 °C and the time to 6 h.

[0060] Feed the mixture into a twin-screw extruder, set the frequency to 150 r / min and the temperature to 120 °C. Add carbodiimide as a crosslinking agent and add it according to the ratio of the kneaded mixture to the crosslinking agent of 1:0.05.

[0061] Extrude through a die, control the slurry flow rate at 3 L / min, and the compressed cold air flow rate at 0 m / s. After the extruded rod-shaped lithium extraction adsorbent stays in the air for 12 s, quickly enter a pure water setting bath at 25 °C to cure. Finally, after sizing, washing, drying and screening equipment treatment, the finished product is obtained.

[0062] Morphology characterization:

[0063] The cross-sectional morphology of the rod-shaped lithium extraction adsorbent prepared in Example 1 above is as Figure 1 , as can be seen from the figure, the cross-section is circular, the adsorbent powder particles are small in size, evenly distributed in the polymer fiber network and there is no obvious agglomeration. The cross-sectional structure is loose, with a semi-interpenetrating porous network structure, which not only locks the adsorbent powder particles to avoid loss, but also has a loose fiber network structure with high porosity, ensuring the stability of the overall structure of the adsorbent and the high exchange rate. This is because the dispersant evenly disperses the adsorbent powder particles, and the hydrophilic material undergoes a crosslinking reaction in the polymer and adsorbent powder mixture to form a semi-interpenetrating fiber network structure. Through further cooling and stretching with compressed cold air, the polymer crystal regions are stretched to form an open-cell structure, and the preliminary network structure is shaped to form a fiber network structure.

[0064] Adsorption experiment:

[0065] The brine used in the adsorption experiment contains Li+ 0.35 g / L, Mg 2+ 16 g / L, Na + 80 g / L, K + 80 g / L, SO4 2- 1.2 g / L, Cl - 1.2 g / L. Add 50 mL of the adsorbent prepared in the above examples and comparative examples to 700 mL of brine, and continuously stir. After 2 h, take out and measure the adsorption capacity. The adsorption capacity is calculated by the following formula: adsorption amount A = (C0 - C1)V / 1000, where C0 is the ion concentration in the initial solution, C1 is the ion concentration in the solution after adsorption, and V is the solution volume.

[0066]

[0067] Strength and adsorption loss rate test:

[0068] ① After washing and drying the adsorbent prepared in the above examples and comparative examples, take 50 mL of the dry adsorbent and weigh it. Immerse it in a sample bottle containing 200 mL of pure water, and place it on a shaker bed with a shaking frequency of 20 Hz. After shaking for 4 h, filter out, wash, dry and bake, and conduct adsorption performance tests. Repeat the test 20 times to obtain the mass loss and adsorption capacity change curves as Figure 3 shown.

[0069] ② Take 50 mL of the adsorbent prepared in the above examples and comparative examples and place it in an ion exchange column. Pump 10 L of water into the ion exchange column at a speed of 3.0 through a peristaltic pump, measure the column pressure and calculate the actual flow rate, and observe the state of the adsorbent.

[0070]

[0071] It can be seen that the adsorption amount of lithium in the examples of the present invention can reach more than 3.7 g / L, while that in the comparative example is only 2.6 g / L, and it has low adsorption for other ions, indicating that the adsorbent prepared by the present invention has high adsorption performance and high selectivity. Through the dynamic strength and loss rate test, it can be found that the rod-shaped adsorbent prepared in the examples has a low mass loss rate and maintains a relatively high adsorption capacity, indicating that the rod-shaped adsorbent with a semi-interpenetrating fiber network-like porous structure has high strength and high permeation rate performance, and can extend the service life and reduce energy consumption during application.

[0072] Influence of adsorption agent use cycle loss:

[0073] Adsorption experiments were carried out using the adsorbents prepared in the examples and comparative examples. Brine simulation solution: Li+ 0.35 g / L, Mg 2+ 16 g / L, Na + 80 g / L, K+ 80 g / L; the desorbing solution is dilute hydrochloric acid with pH 2.0.

[0074] The process of the dynamic column experiment is as follows: The adsorbent is filled into an ion exchange column (column volume 50 mL), and brine is pumped in at a flow rate of 3.0 L / min, and the initial column pressure and flow rate are recorded; the amount of brine adsorbed is 700 mL, the amount of desorbing solution is 500 mL, and the amount of washing water is 1500 mL. After each cycle, it is desorbed with dilute hydrochloric acid with pH 2.0 and regenerated with water washing. Repeat 30 times, and monitor the change of column pressure and the attenuation of adsorption capacity.

[0075] Number of cycles Example 1 Example 2 Example 3 Example 4 Comparative Example 1 10 cycles 2.1％ 2.1％ 1.1％ 1.4％ 4.6％ 20 cycles 4.0％ 3.8％ 2.1％ 2.7％ 8.1％ 30 cycles 5.0％ 5.4％ 3.2％ 3.8％ 11.2％

[0076] As can be seen from the above table, the rod-shaped lithium extraction adsorbent obtained by the method of this patent has the advantage of good cycling performance. Compared with the comparative example, the stability of the adsorbent is significantly improved after crosslinking treatment; at the same time, comparing Example 1 and 2 with Example 3 and 4, since the chitosan molecular chain is rich in amino groups (-NH2), the amino groups are protonated in an acidic solution to form -NH3 + , carrying a positive charge; while the phosphate group (P3O 10 5- ) in the TPP molecule carries a negative charge, and the two form an ionic crosslinking network through electrostatic attraction. This interaction is the main driving force for the formation of the composite membrane. Under acidic conditions (pH 4 - 6), the amino groups of chitosan can be fully protonated, and the binding efficiency with the phosphate groups of TPP is the highest, with a large crosslinking density, and the crosslinking effect obtained under alkaline conditions is relatively low. As a multivalent anion crosslinking agent, TPP forms crosslinking points by "bridging" multiple chitosan molecular chains. This crosslinking not only enhances the mechanical strength of the membrane, but also inhibits water penetration by reducing the mobility of molecular chains, thereby improving the pulverization and loss of the adsorbent during multiple adsorption / desorption / elution processes. A dense and ordered chitosan / TPP membrane can be prepared through the crosslinking process, and its structural stability is significantly improved.

Claims

1. A rod-shaped lithium extraction adsorbent, characterized in that: The shape is a rod-like structure with a length of 0.2-2 mm, a diameter of 0.4-1 mm, and a porous structure. The rod-like adsorbent contains a polymer and an inorganic adsorbent.

2. The rod-shaped lithium extraction adsorbent according to claim 1, characterized in that: The inorganic adsorbent is selected from aluminum adsorbent, titanium adsorbent or manganese adsorbent; the polymer is selected from polysulfone, polyethersulfone, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyacrylic acid, polyvinyl acetate, polyvinyl alcohol or chloroacetic acid resin or one or more mixtures thereof.

3. The rod-shaped lithium extraction adsorbent according to claim 1, characterized in that: The weight ratio of the inorganic adsorbent to the polymer is 20-100:15; the particle size range of the inorganic adsorbent is 0.5-20 μm; and a protective layer obtained by cross-linking chitosan and polyphosphate is distributed on its surface.

4. The method for preparing the rod-shaped lithium extraction adsorbent according to claim 1, characterized in that: The steps include: Step 1, fully mixing an inorganic adsorbent, a hydrophilic material and a dispersant to obtain a precursor; Step 2, dispersing the precursor, polymer and porogen in a solvent and performing mixing; Step 3, the mixture obtained in step 2 is fed into an extruder, a cross-linking agent is added to the extruder, and the mixture is extruded through a die into a shaping bath for solidification and forming, and a finished lithium extraction adsorbent is obtained through granulation, water washing, drying and screening equipment.

5. The preparation method according to claim 4, characterized in that: In step 1, the mixing ratio of inorganic adsorbent, hydrophilic material and dispersant is 20-68:0.5-5:0.02-0.5, in step 2, the mixing ratio of precursor, polymer, porogen and solvent is 20-68:15:6-12:30-70, and in step 3, the mixing ratio of the mixture and the crosslinking agent is 1:0.02-0.

2.

6. The preparation method according to claim 4, characterized in that: The solvent is a mixture of one or more of acetone, ethyl acetate, tetrachloromethane, water, xylene, dioctyl phthalate, epoxy soybean oil, dimethylacetamide, dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, etc.; the hydrophilic material is a mixture of one or more of polyvinyl alcohol, polyethylene glycol, chitosan, sodium alginate, polyvinylpyrrolidone, polyacrylic acid, etc.; the dispersant is one of Tween-80, sodium dodecylbenzene sulfonate, and dodecyl phosphate; the porogen is a mixture of one or more of calcium carbonate, sodium carbonate, sodium bicarbonate, sodium chloride, lithium chloride, polyethylene glycol, glycerol, diethylene glycol, etc.; the crosslinking agent is one of glutaraldehyde and carbodiimide.

7. The preparation method according to claim 4, characterized in that: The mixing temperature is 60-120°C and the mixing time is 6-12h; the extruder is a twin-screw extruder with a frequency of 60-300r / min and a temperature of 60-150°C; the structure of the die includes a slurry nozzle (1), and compressed cold air slits (2) are provided on both sides of the slurry nozzle, the exhaust direction of the compressed cold air slits (2) is parallel to the slurry extrusion direction, the flow rate of the slurry in the die is 2-10L / min, and the flow rate of the compressed cold air is 8-20m / s.

8. The preparation method according to claim 4, characterized in that: In step 3, after extrusion, the slurry is kept in the air for 10-20 seconds before entering a setting bath, wherein the setting bath is water or an aqueous solution containing 0.1-1% polyphosphate, the temperature is 15-50° C., and the pH range is 4-6; the polyphosphate is selected from tripolyphosphate, tetrapolyphosphate or pyrophosphate; and the cation is selected from sodium, potassium, calcium or ammonium.

9. Use of the rod-shaped lithium extraction adsorbent according to claim 1 in extracting lithium from brine.

10. The use according to claim 9, characterized in that The composition of brine contains Mg 2+ and Li + , and the mass ratio of Mg / Li is 1-200:1, preferably 5-100; the desorption liquid used in the desorption process is water or dilute hydrochloric acid with a pH range of 1.0-5.0.

Images