Preparation method of spherical adsorbent

Abstract

The invention relates to a preparation method of a spherical adsorbent, and belongs to the field of chemical preparation. The invention discloses a preparation method of a spherical adsorbent. The preparation method comprises the following steps: dissolving a hydrophobic base material serving as a forming agent in a preheated organic solvent for mixing; after the forming agent is dissolved, a hydrophilic base material is mixed and dissolved in the organic solvent, and a binder is obtained through stirring; adding adsorbent powder into the binder, and stirring to obtain mixed slurry; and dropping the mixed slurry into a coagulating bath through a pill dropping machine to obtain spherical adsorbent particles. The adsorbent particles are simple in preparation process and high in powder coating rate, the stability of the spherical adsorbent is also remarkably improved, and the spherical adsorbent has certain anti-pollution performance and can be directly applied to extraction of lithium from complex original halide.

Description

Technical Field

[0001] The invention relates to a preparation method of a spherical adsorbent and belongs to the field of chemical preparation. Background Art

[0002] With the rapid development of the lithium battery industry, the demand for lithium resources has increased rapidly. Due to the high cost and high energy consumption of lithium extraction from solid ore, more and more researchers have begun to pay attention to the research on separation and extraction of lithium from salt lake brine. my country is rich in salt lake brine resources. After decades of research, a variety of salt lake lithium extraction technologies have been developed, mainly including adsorption, chemical precipitation, extraction, electrochemical and membrane separation. Among them, the adsorption method is widely used in the separation and extraction of lithium ions from salt lake brine due to its advantages such as high selectivity, simple operation and no secondary pollution. The key to the adsorption method lies in the preparation of adsorbents with high adsorption performance and strong adsorption stability.

[0003] In response to the problems of easy agglomeration, difficult separation and large dissolution loss of powdered adsorbents, researchers have invented a variety of adsorbent granulation methods. For example, directly mix the adsorbent powder with a binder for bonding, and then granulate it after secondary crushing. Common binders include silica gel, water glass, etc.; mix the adsorbent powder with an organic solution, and make it granulate by cross-linking or dripping it into a coagulation bath. Common organic molding agents include polyvinyl chloride, polyacrylamide, polyvinylidene fluoride, etc.; load the adsorbent powder on an inert carrier with a rich pore structure for granulation. Common porous materials are ceramics. Granulating the powder can reduce the powder loss in the adsorption process and solve the problem of difficult solid-liquid separation. The current research focus is mainly on solving the problem that the adsorption performance of the adsorbent after granulation is significantly reduced compared with the powdered adsorbent, and the choice of binder and different granulation methods has a direct impact on the stability of the adsorbent during operation.

[0004] In order to solve the problems of easy agglomeration, difficult separation and large dissolution loss of powdered adsorbents, researchers have invented a variety of adsorbent granulation methods. Although the granulation methods currently developed can improve some of the properties of adsorbents, most of them have complex preparation processes, high cost of modification agents required for polymer modification, low substrate coating, low powder content, and some granulation processes only consider improving hydrophilicity and use natural organic polymer materials. Adsorbent particles prepared from natural organic polymer materials will dissolve to varying degrees after long-term operation, and even the particle structure will collapse. The operation stability is extremely poor, which is not conducive to application in actual production.

[0005] In the actual production process, the composition of salt lake brine is complex, and the temperature and pH of the brine are greatly affected by the external environment. This requires that the adsorbent particles used for lithium extraction from salt lake brine must not only ensure certain adsorption properties but also have strong mechanical stability, so that the adsorbent particles can adapt to long-term stable operation and facilitate recycling.

[0006] Due to the small size of the powder adsorbent particles, it is difficult to separate, easy to agglomerate, and the mass transfer rate is low during the adsorption process. In industrial applications, adsorbents are developed through granulation processes to produce adsorbent particles with excellent adsorption performance and long-term stable operation. However, the current large-scale adsorbent particle preparation process usually has problems such as environmental unfriendliness, cumbersome process flow, irregular particle size, and instability and easy powder loss of adsorbent particles under water flushing during the adsorption process. In addition, the adsorbent particles prepared at this stage have a low powder content, and the granulation process mostly uses hydrophobic materials as binders. These factors make the mass transfer rate of the adsorbent after granulation more prominent.

[0007] Chinese invention patent CN 118217954 A discloses a granular lithium adsorbent and its preparation method and application, wherein the binder is selected from one or more of polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene fluoride, polysulfone, polyether sulfone, polyacrylonitrile, polymethyl methacrylate, polystyrene, polyurethane and cellulose acetate.

[0008] Chinese invention patent CN 117563565 A discloses a method for preparing a lithium ion adsorption material, wherein the high molecular polymer is any one or more mixtures of polyvinyl chloride, chlorinated polyvinyl chloride, polyacrylic acid, polyacrylonitrile, polyacrylamide, polymethyl methacrylate, polystyrene, polysulfone, polyurethane, polyamide, polyimide, polyetheretherketone, polyvinylidene fluoride, polytetrafluoroethylene, nitrile rubber, styrene-butadiene rubber, polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol, cellulose acetate butyrate and chitosan.

[0009] Chinese invention patent CN 115445587 A discloses a high adsorption capacity adsorbent with a hollow composite multi-level pore structure and a preparation method thereof, wherein the polymer is selected from a mixture of one or more of polyvinylidene fluoride, polyether sulfone, polysulfone, polyacrylonitrile, polyvinyl chloride or polyethylene.

[0010] The above three do not solve the polymer blending problem. The main problem of blending is that most polymer pairs are not completely miscible. The miscible phase of polymers occurs in three cases: low molecular weight polymers no longer have negligible mixing entropy; polymers with very similar chemical properties and extremely small unfavorable mixing heat; polymers show specific interactions between molecules, resulting in favorable mixing heat. Failure to solve the polymer blending problem results in low hydrophilicity of the material. Summary of the invention

[0011] In order to solve the above problems, the present invention takes into account the adsorption performance during the adsorbent granulation process, selects a high molecular organic material with strong mechanical stability as the coating substrate, and mixes a hydrophilic substrate in a certain proportion to improve the mass transfer rate of the adsorbent, thereby obtaining a spherical adsorbent particle with high mass transfer rate and strong mechanical stability. The sphericity of the adsorbent particles is effectively improved by controlling the dripping pressure and slurry viscosity during the preparation process. There is no external shear force in the dripping process and no cross-section is generated, which can greatly increase the powder coating amount and reduce the powder loss during the operation process. In actual application, the adsorbent filler with uniform particle size also exhibits more stable mechanical strength during operation.

[0012] Based on the above content, the present invention provides a method for preparing a spherical adsorbent, the steps of which include:

[0013] Dissolving a hydrophobic base material as a forming agent in a preheated organic solvent for mixing;

[0014] After the molding agent is dissolved, the hydrophilic substrate is mixed with the organic solvent and stirred to obtain a binder;

[0015] Adding adsorbent powder to the binder and stirring to obtain a mixed slurry;

[0016] The mixed slurry is dripped into a coagulation bath by a pill dropping machine to obtain spherical adsorbent particles.

[0017] Furthermore, the hydrophobic substrate is one or more of polyvinyl chloride, polyether, polyether sulfone, polycarbonate, and polyvinylidene fluoride; the hydrophilic substrate is one or more of polyacrylonitrile, polymethyl methacrylate, polyvinyl butyral, and polyethylene glycol; and the mass ratio of the hydrophilic substrate to the hydrophobic substrate is 0.05 to 0.5.

[0018] Furthermore, the mass ratio of the hydrophobic substrate to the organic solvent is 0.06 to 0.13.

[0019] Furthermore, the mass ratio of the powder to the mixed slurry is 0.85 to 0.95.

[0020] Furthermore, the adsorbent powder is one of aluminum adsorbent powder, manganese adsorbent powder, titanium adsorbent powder, or other adsorbent powder used in salt lake brine or water treatment.

[0021] Furthermore, the organic solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, ethyl acetate and acetone.

[0022] Furthermore, the coagulation bath is water or an aqueous solution containing the organic solvent.

[0023] Furthermore, the mixing process and the stirring process as a whole adopt a gradient temperature increase from 40°C to 75°C.

[0024] Furthermore, the dripping tank temperature of the dripping pill machine is increased gradually from 70° C. to 85° C.; the dripping tank pressure is 0.001-0.05 MPa; and the dripper aperture is 0.5-1.5 mm.

[0025] The invention also provides a spherical adsorbent with good sphericity and a particle size of 0.5 to 2 mm, which is prepared by the above method.

[0026] The beneficial effects of the present invention are as follows:

[0027] (1) The present invention selects a hydrophobic substrate and a hydrophilic substrate with strong thermal stability and mechanical stability to dissolve in a certain proportion and a certain order to prepare a binder. The blending of the hydrophilic and hydrophobic substrates can improve the mass transfer rate of the adsorbent while ensuring the mechanical strength of the adsorbent.

[0028] (2) In the present invention, two substrates with a high degree of blending are selected for miscibility, the slurry has a high degree of miscibility, and the powder coating is strong. By accurately selecting a blending polymer with a small solubility parameter difference with the hydrophobic substrate and adjusting the mixing ratio, more powders can be coated with the least amount of substrate, thereby improving the hydrophilicity of the material.

[0029] (3) In the preparation process, the present invention selects to control the dripping tank pressure and the dripping head aperture of the dripping pill machine to obtain a spherical particle adsorbent with good sphericity and uniform particle size. The granulation method has no mechanical shear force. After natural dripping, the adsorbent particles are formed by a phase transformation method. The adsorbent particles are spherical with uniform surface. There is no significant powder loss during the operation process, which can ensure the long-term stable operation of the adsorbent.

[0030] (4) The present invention uses a certain proportion of organic solvent miscible aqueous solution as a coagulation bath during the preparation process. The coagulation bath can appropriately slow down the phase conversion rate. Through certain physical methods, the solution is allowed to undergo mass transfer exchange between the solvent and the non-solvent in the surrounding environment, thereby changing the thermodynamic state of the solution so that it undergoes phase separation from a homogeneous polymer solution and transforms into a three-dimensional macromolecular network gel structure, which is finally solidified into a shape, thereby making the phase conversion reaction more complete. The slow phase conversion is more conducive to the formation of pores in the adsorbent spherical particles, and is also greatly beneficial to the improvement of the mass transfer efficiency of the adsorbent.

[0031] (5) The mixing process of the present invention adopts a gradient temperature increase mixing method, and the elongation at break of the substrate is controlled by gradient temperature increase, thereby improving the mechanical strength of the adsorbent particles.

[0032] The present invention selects a hydrophilic and hydrophobic material blend as a coating material, and prepares adsorbent spherical particles by a simple phase inversion method. In the preparation process of the present invention, by controlling the slurry viscosity of the mixing process and the dripping pressure of the dripping pill machine, a spherical adsorbent particle with uniform sphericity is prepared, and the adsorption rate and adsorption capacity are significantly improved. The adsorbent particle preparation process is simple, the powder coverage rate is high, the stability of the spherical adsorbent is also significantly improved, and it has certain anti-pollution performance, and can be directly applied to lithium extraction from complex raw halogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flow chart of the preparation process of an embodiment of the present invention.

[0034] Figure 2 This is a picture of the finished product of the spherical adsorbent particles according to an embodiment of the present invention.

[0035] Figure 3 This is a SEM image of the side section of the finished spherical adsorbent particles according to an embodiment of the present invention.

[0036] Figure 4 Adsorption-desorption cycle data diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention. Figure 1 shown.

[0038] Example 1. Preparation of spherical adsorbent

[0039] The preparation process of the present invention needs to be carried out under specific operating steps and reaction conditions to ensure the effectiveness and safety of the reaction. The operating steps and conditions of this reaction are described below:

[0040] Weigh polyvinyl chloride and dissolve it in dimethylacetamide solvent, the mass ratio of polyvinyl chloride to dimethylacetamide is 7%, stir, and obtain solution A after polyvinyl chloride is completely dissolved. Add polymethyl methacrylate to solution A, the mass ratio of polymethyl methacrylate to polyvinyl chloride is 25%, after strong stirring, polymethyl methacrylate is completely miscible in solution A, and obtain mixed solution B as a binder. Add the prepared aluminum adsorbent powder to mixed solution B, the mass ratio of powder to mixed solution B is 93.5%, after strong stirring, obtain a drip slurry with good dispersion. The total time of the above process is 2h, and the temperature is increased gradually from 50℃ to 70℃.

[0041] The mixed slurry is introduced into the dripping tank of the dripping pill machine. The temperature during drip irrigation is gradually increased from 70℃ to 80℃ for 0.5h. The slurry is evenly injected into the coagulation bath through the dripping tank pressure of 0.025MPa and the dripper aperture of 1mm. The coagulation bath is an aqueous solution containing dimethylacetamide. Spherical adsorbent particles with uniform particle size are prepared by phase inversion method. The finished particles are as follows Figure 2 As shown, the SEM of the particles Figure 3 shown.

[0042] Test item 1. Adsorption performance comparison test

[0043] (1) Adsorption performance test: A certain amount of the adsorbent particles prepared in Example 1 and the adsorbent prepared from a single polyvinyl chloride substrate (other preparation conditions are the same as in Example 1) were measured, and a fixed bed adsorption test was carried out at room temperature. 6 BV of brine from a salt lake was used as the adsorption liquid, and the adsorption time was 2 h. 8 BV of pure water was used as the desorption liquid, and the desorption time was 1 h. The adsorption and desorption process was performed using the top-in and bottom-out process, and 15 adsorption and desorption cycles were performed.

[0044] (2) Adsorption performance test results: The test results are as follows Figure 4 As shown, the adsorption capacity of the adsorbent prepared with the blended substrate as the binder (average value 3.5 g / L) is much higher than that of the adsorbent prepared with the single PVC as the binder (average value 3.1 g / L). Under the same adsorption conditions, the adsorption amount is significantly improved. And no significant powder loss phenomenon occurs during the adsorption operation, which confirms the feasibility of the product of Example 1 to operate stably for a long period in a complex brine system.

[0045] Example 2. Preparation of spherical adsorbent

[0046] The preparation process of the present invention needs to be carried out under specific operating steps and reaction conditions to ensure the effectiveness and safety of the reaction. The operating steps and conditions of this reaction are described below:

[0047] Weigh polyvinylidene fluoride and dissolve it in dimethylformamide solvent, the mass ratio of polyvinylidene fluoride to dimethylformamide is 13%, stir, and obtain solution A after polyvinylidene fluoride is completely dissolved. Add polyacrylonitrile to solution A, the mass ratio of polyacrylonitrile to polyvinylidene fluoride is 50%, after strong stirring, polyacrylonitrile is completely miscible in solution A, and obtain mixed solution B as a binder. Add the prepared aluminum adsorbent powder to mixed solution B, the mass ratio of powder to mixed solution B is 95%, after strong stirring, obtain a well-dispersed drip slurry. The above process takes a total of 2 hours, and the temperature is increased gradually from 40°C to 70°C.

[0048] The mixed slurry was introduced into the dripping tank of the pill machine. The temperature during drip irrigation was gradually increased from 70°C to 80°C for 0.5h. The slurry was evenly injected into the coagulation bath through a dripping tank pressure of 0.05MPa and a dripper aperture of 0.5mm. The coagulation bath was an aqueous solution containing dimethylacetamide. Spherical adsorbent particles with uniform particle size were prepared by phase inversion method.

[0049] Example 3. Preparation of spherical adsorbent

[0050] The preparation process of the present invention needs to be carried out under specific operating steps and reaction conditions to ensure the effectiveness and safety of the reaction. The operating steps and conditions of this reaction are described below:

[0051] Weigh the polyether and dissolve it in N-methyl-2-pyrrolidone solvent at a mass ratio of 6% for polyether to N-methyl-2-pyrrolidone. Stir until the polyether is completely dissolved to obtain solution A. Add polyethylene glycol to solution A at a mass ratio of 5% for polyethylene glycol to polyether. After strong stirring, the polyethylene glycol is completely miscible in solution A to obtain a mixed solution B as a binder. Add the prepared aluminum adsorbent powder to mixed solution B at a mass ratio of 85% for powder to mixed solution B. After strong stirring, a well-dispersed drip slurry is obtained. The above process takes a total of 2 hours, using a gradient temperature increase from 45°C to 75°C.

[0052] The mixed slurry was introduced into the dripping tank of the dripping pill machine. The temperature during drip irrigation was gradually increased from 75°C to 85°C for 0.5 h. The slurry was evenly injected into the coagulation bath through the dripping tank pressure of 0.001 MPa and the dripper aperture of 1.5 mm. The coagulation bath was an aqueous solution containing dimethylacetamide. Spherical adsorbent particles with uniform particle size were prepared by phase inversion method.

[0053] Comparative Example 1. Preparation of spherical adsorbent

[0054] The preparation process of the present invention needs to be carried out under specific operating steps and reaction conditions to ensure the effectiveness and safety of the reaction. The operating steps and conditions of this reaction are described below:

[0055] Weigh polyvinyl chloride and dissolve it in dimethylacetamide solvent, the mass ratio of polyvinyl chloride to dimethylacetamide is 7%, stir, and obtain solution A after polyvinyl chloride is completely dissolved. Add polymethyl methacrylate to solution A, the mass ratio of polymethyl methacrylate to polyvinyl chloride is 25%, after strong stirring, polymethyl methacrylate is completely miscible in solution A, and obtain mixed solution B as a binder. Add the prepared aluminum adsorbent powder to mixed solution B, the mass ratio of powder to mixed solution B is 93.5%, after strong stirring, obtain a well-dispersed drip slurry. The above process takes a total of 2 hours, and the temperature is increased gradually from 30°C to 60°C.

[0056] The mixed slurry was introduced into the dripping tank of the pill machine. The temperature during drip irrigation was gradually increased from 60°C to 70°C for 0.5 h. The slurry was evenly injected into the coagulation bath through the dripping tank pressure of 0.025 MPa and the dripper aperture of 1 mm. The coagulation bath was an aqueous solution containing dimethylacetamide. Spherical adsorbent particles with uniform particle size were prepared by phase inversion method.

[0057] Comparative Example 2. Preparation of spherical adsorbent

[0058] The preparation process of the present invention needs to be carried out under specific operating steps and reaction conditions to ensure the effectiveness and safety of the reaction. The operating steps and conditions of this reaction are described below:

[0059] Weigh polyvinyl chloride and dissolve it in dimethylacetamide solvent, the mass ratio of polyvinyl chloride to dimethylacetamide is 7%, stir, and obtain solution A after polyvinyl chloride is completely dissolved. Add polyvinyl alcohol to solution A, the mass ratio of polyvinyl alcohol to polyvinyl chloride is 25%, after strong stirring, polyvinyl alcohol is completely miscible in solution A, and obtain mixed solution B as a binder. Add the prepared aluminum adsorbent powder to mixed solution B, the mass ratio of powder to mixed solution B is 93.5%, after strong stirring, obtain a well-dispersed drip slurry. The above process takes a total of 2 hours, and the temperature is increased gradually from 50°C to 70°C.

[0060] The mixed slurry was introduced into the dripping tank of the dripping pill machine. The temperature during drip irrigation was gradually increased from 70°C to 80°C for 0.5h. The slurry was evenly injected into the coagulation bath through the dripping tank pressure of 0.025MPa and the dripper aperture of 1mm. The coagulation bath was an aqueous solution containing dimethylacetamide. Spherical adsorbent particles with uniform particle size were prepared by phase inversion method.

[0061] Comparative Example 3. Preparation of spherical adsorbent

[0062] The preparation process of the present invention needs to be carried out under specific operating steps and reaction conditions to ensure the effectiveness and safety of the reaction. The operating steps and conditions of this reaction are described below:

[0063] Weigh polyvinyl chloride and dissolve it in dimethylacetamide solvent, the mass ratio of polyvinyl chloride to dimethylacetamide is 7%, stir, and obtain solution A after polyvinyl chloride is completely dissolved. Add polymethyl methacrylate to solution A, the mass ratio of polymethyl methacrylate to polyvinyl chloride is 25%, after strong stirring, polymethyl methacrylate is completely miscible in solution A, and obtain mixed solution B as a binder. Add the prepared aluminum adsorbent powder to mixed solution B, the mass ratio of powder to mixed solution B is 80%, after strong stirring, obtain a drip slurry with good dispersion. The total time of the above process is 2h, and the temperature is increased gradually from 50℃ to 70℃.

[0064] The mixed slurry was introduced into the dripping tank of the dripping pill machine. The temperature during drip irrigation was gradually increased from 70°C to 80°C for 0.5h. The slurry was evenly injected into the coagulation bath through the dripping tank pressure of 0.025MPa and the dripper aperture of 1mm. The coagulation bath was an aqueous solution containing dimethylacetamide. Spherical adsorbent particles with uniform particle size were prepared by phase inversion method.

[0065] The effect parameters of the above embodiments and comparative examples are shown in Table 1.

[0066] Table 1

[0067]

Claims

1. A method for preparing a spherical adsorbent, comprising the steps of: Dissolving a hydrophobic base material as a forming agent in a preheated organic solvent for mixing; After the molding agent is dissolved, the hydrophilic substrate is mixed with the organic solvent and stirred to obtain a binder; Adding adsorbent powder to the binder and stirring to obtain a mixed slurry; The mixed slurry is dripped into a coagulation bath by a pill dropping machine to obtain spherical adsorbent particles.

2. The method according to claim 1, characterized in that The hydrophobic substrate is one or more of polyvinyl chloride, polyether, polyether sulfone, polycarbonate, and polyvinylidene fluoride; the hydrophilic substrate is one or more of polyacrylonitrile, polymethyl methacrylate, polyvinyl butyral, and polyethylene glycol; and the mass ratio of the hydrophilic substrate to the hydrophobic substrate is 0.05 to 0.

5.

3. The method according to claim 1, characterized in that The mass ratio of the hydrophobic substrate to the organic solvent is 0.06 to 0.

13.

4. The method according to claim 1, characterized in that: The mass ratio of the powder to the mixed slurry is 0.85 to 0.

95.

5. The method according to claim 1, characterized in that The adsorbent powder is one of aluminum adsorbent powder, manganese adsorbent powder, titanium adsorbent powder, or other adsorbent powder used in salt lake brine or water treatment.

6. The method according to claim 1, characterized in that The organic solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, ethyl acetate and acetone.

7. The method according to claim 6, characterized in that The coagulation bath is water or an aqueous solution containing the organic solvent.

8. The method according to claim 1, characterized in that The mixing and stirring processes are carried out in a gradient temperature increase from 40°C to 75°C.

9. The method according to claim 1, characterized in that: The dripping tank temperature of the dripping pill machine is increased gradually from 70° C. to 85° C.; the dripping tank pressure is 0.001-0.05 MPa; and the dripper aperture is 0.5-1.5 mm.

10. A spherical adsorbent with good sphericity and a particle size of 0.5 to 2 mm, prepared by the method of any one of claims 1 to 9.

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