Lead bismuth-based sodium-type potassium ion adsorbent and method for preparing the same

Abstract

This invention provides a method for preparing a high-performance potassium adsorbent for potassium extraction from seawater, belonging to the field of ion adsorbent technology. The present invention features a large potassium adsorption capacity, high ion exchange site density, and outstanding enrichment capacity for low-concentration potassium ions. It exhibits very low adsorption capacity for calcium and magnesium ions in the influent, precisely rejecting high concentrations of coexisting sodium, calcium, and magnesium ions, achieving exclusive adsorption only for potassium ions, resulting in high purity of the enriched product. It possesses a highly stable crystal framework structure resistant to acids and alkalis, improving the cycling stability of the potassium adsorbent. The small crystal size is beneficial for increasing the adsorption capacity of the potassium adsorbent; due to the small crystal size, growth is more complete, with fewer crystal defects, which is conducive to improving selectivity and cycling stability. The three-stage calcination crystallization process allows different materials to undergo precise chemical reactions or crystal growth at different temperature stages, facilitating the acquisition of potassium adsorbent crystals with high adsorption capacity, high selectivity, and high cycling stability.

Description

Technical Field

[0001] This invention relates to the field of ion adsorbent technology, specifically to a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent and its preparation method. Background Technology

[0002] Seawater and underground brines contain vast amounts of potassium resources, far exceeding the reserves of terrestrial potassium mines. Therefore, achieving low-cost and efficient potassium extraction from seawater is of great strategic significance. Seawater contains abundant potassium resources (totaling approximately 550 trillion tons), but the concentration is low (approximately 380 mg / L), and it also contains a large number of competing ions such as sodium, magnesium, and calcium, which places extremely high demands on the adsorption capacity and selectivity of adsorbents.

[0003] Currently, research on potassium ion adsorbents mainly focuses on titanium-based (such as sodium titanate and metatitanic acid), aluminosilicate-based (such as zeolites and aluminum phosphate), niobium-based, and ferrocyanide complexes. However, existing materials have significant shortcomings: titanium-based adsorbents (such as the Chinese invention patent application with publication number CN102180521A) typically require strongly alkaline conditions to achieve high capacity and are easily affected by magnesium ions; aluminosilicate-based zeolites (such as the Chinese invention patent application with publication number CN102068958A) have limited selectivity for potassium, and sodium ions compete fiercely; niobium-based materials are expensive and have complex synthesis processes.

[0004] Existing conventional potassium adsorbents generally suffer from three major technical defects: First, their adsorption capacity is low, often below 25 g / L in simulated seawater systems, making it difficult to meet industrial enrichment requirements; second, they exhibit poor selectivity, as the concentrations of sodium, magnesium, and calcium ions in seawater are much higher than those of potassium ions, with the total calcium and magnesium ion content in the eluent reaching several hundred milligrams per liter, making them susceptible to interference from coexisting ions; and third, they suffer from poor cycle stability, with the framework structure collapsing after repeated adsorption-desorption cycles, resulting in an adsorption capacity decay rate exceeding 25%, short service life, and high operating costs. Furthermore, existing potassium adsorbent synthesis processes are mostly simple co-precipitation, one-step hydrothermal treatment, or solid-state sintering, resulting in a single process route, poor precision in material crystal form control, and low ion exchange site density. Summary of the Invention

[0005] The purpose of this invention is to provide a vanadium-bismuth-based sodium-type potassium ion adsorbent and its preparation method, so as to solve at least one of the technical problems existing in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent with the general chemical formula: Na x Pb y VBiO z-SiO2, where x, y, and z are stoichiometric coefficients satisfying 10≤x≤90, 10≤y≤30, and 29≤z≤109; this adsorbent is a layered-porous dual-structure composite inorganic oxide. The framework is a stable three-dimensional network formed by alternating VO-Bi, VO-Pb, and Bi-O-Pb covalent bonds. Sodium ions are uniformly distributed in the interlayer and pores of the framework and, as the only exchangeable ion, undergo a specific ion exchange reaction with potassium ions. Lead, vanadium, and bismuth in the framework are non-exchangeable framework metals, and SiO2 is a binder for powder granulation.

[0008] In a second aspect, the present invention provides a method for preparing a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent as described in the first aspect, comprising:

[0009] Preparation of vanadium-bismuth composite sol: Prepare a vanadium source ammonium metavanadate solution; dissolve bismuth source bismuth nitrate in dilute nitric acid solution, disperse by ultrasonication, and prepare a bismuth source bismuth nitrate solution; add the bismuth source bismuth nitrate solution dropwise to the vanadium source ammonium metavanadate solution to prepare an orange-yellow vanadium-bismuth composite sol;

[0010] Co-precipitation of lead-vanadium-bismuth ternary precursors: Prepare a lead-source lead acetate-alcohol aqueous solution, add the lead-source lead acetate-alcohol aqueous solution to the vanadium-bismuth composite sol, and then add a composite precipitant to obtain a ternary lead-vanadium-bismuth hydroxide precursor slurry. After aging, centrifuge, wash the filter cake, dry, and grind to obtain lead-vanadium-bismuth ternary precursor powder.

[0011] Sodium source introduction: The lead-vanadium-bismuth ternary precursor powder and sodium acetate powder are dry-mixed to obtain a mixed powder with sodium source introduced.

[0012] Segmented gradient sintering crystallization: The mixed powder is sintered using a three-stage gradient heating process. After sintering, it is cooled to room temperature, ground, and sieved to obtain sodium-type lead-vanadium-bismuth ternary oxide-based potassium adsorbent powder, namely lead-vanadium-bismuth-based sodium-type potassium ion adsorbent powder.

[0013] As a further limitation of the second aspect of the present invention, it also includes powder granulation: adding lead-vanadium-bismuth-based sodium potassium ion adsorbent powder, water glass solution, deionized water, and glucose powder into a kneader and kneading them together, then transferring the blend to an extruder for extrusion molding to obtain cylindrical particles, and transferring the cylindrical particles to a calcining furnace for calcination molding to obtain cylindrical lead-vanadium-bismuth-based sodium potassium ion adsorbent particles.

[0014] As a further limitation of the second aspect of the present invention, vanadium source ammonium metavanadate is dissolved in deionized water and stirred until completely dissolved to prepare a vanadium source ammonium metavanadate solution with a concentration of 0.05-0.15 mol / L; bismuth source bismuth nitrate is dissolved in a dilute nitric acid solution with a concentration of 2.5-4.0 mol / L to prepare a bismuth source bismuth nitrate solution with a concentration of 0.05-0.15 mol / L.

[0015] As a further limitation of the second aspect of the present invention, a bismuth-based bismuth nitrate solution is added dropwise to a vanadium-based ammonium metavanadate solution, with the vanadium-bismuth molar ratio controlled at 1:1. During the dropwise addition process, the system is continuously stirred and the system temperature is maintained at 75-85°C. After the dropwise addition is completed, the pH of the system is adjusted to 3.5-5.0 with a 1.5-3.0 mol / L sodium hydroxide solution, and the system is continuously stirred and aged for 2-4 hours to obtain a vanadium-bismuth composite sol.

[0016] As a further limitation of the second aspect of the present invention, lead acetate is dissolved in a mixed solvent of anhydrous ethanol and deionized water in a volume ratio of (1.5-3):1 to prepare an aqueous solution of lead acetate with a concentration of 1-3 mol / L. The aqueous solution of lead acetate is then added dropwise to the vanadium-bismuth composite sol, and the molar ratio of lead:vanadium:bismuth is controlled to be (10-30):1:1.

[0017] As a further limitation of the second aspect of the present invention, lead-vanadium-bismuth ternary precursor powder and sodium acetate powder are added to a high-speed mixer in a molar ratio of Na:Pb=(1-3):1 and dry-mixed to obtain CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder, that is, the mixed powder after the introduction of sodium source.

[0018] As a further limitation of the second aspect of the present invention, the three-stage gradient heating sintering process is as follows: the first stage is low-temperature pretreatment: heating rate of 3-5℃ / min, heating to 200-350℃, constant temperature calcination, to remove the water of crystallization and organic ligands in CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3; the second stage is medium-temperature crystallization: heating rate of 2-4℃ / min, heating to 450-700℃, constant temperature calcination, to initially form a sodium-type lead-vanadium-bismuth ternary oxide framework; the third stage is high-temperature shaping: heating rate of 1-3℃ / min, heating to 800-1000℃, constant temperature calcination, to strengthen the covalent bond connection of the framework and form a stable crystal form.

[0019] As a further limitation of the second aspect of the present invention, the constant temperature calcination time in the first stage of low temperature pretreatment is 2-3 hours; the constant temperature calcination time in the second stage of medium temperature crystallization is 4-6 hours; and the constant temperature calcination time in the third stage of high temperature shaping is 3-5 hours.

[0020] As a further limitation of the second aspect of the present invention, 200-300 kg of lead-vanadium-bismuth-based sodium-type potassium ion adsorbent powder, 30-50 kg of water glass solution with a modulus of 2-2.5, 10-100 kg of deionized water, and 40-80 kg of glucose powder are added to a kneader and kneaded for 3-7 hours. The blend is then transferred to an extruder for extrusion molding to obtain cylindrical particles. The cylindrical particles are then transferred to a calcination furnace and calcined at a temperature of 400-600℃ to obtain cylindrical lead-vanadium-bismuth-based sodium-type potassium ion adsorbent particles.

[0021] The beneficial effects of this invention are: large potassium adsorption capacity, high ion exchange site density, and outstanding enrichment capacity for low-concentration potassium ions; very low adsorption capacity for calcium and magnesium ions in the influent, precisely rejecting high concentrations of coexisting sodium, calcium, and magnesium ions, achieving exclusive adsorption only for potassium ions, resulting in high purity of the enriched product; possessing a very stable crystal framework structure resistant to acids and alkalis, improving the cycle stability of the potassium adsorbent; small crystal size, which is beneficial to improving the adsorption capacity of the potassium adsorbent; due to the small crystal size, the growth is more complete, with fewer crystal defects, which is beneficial to improving selectivity and cycle stability; the three-stage calcination crystallization process allows different materials to undergo precise chemical reactions or crystal growth at different temperature stages, which is beneficial to obtaining potassium adsorbent crystals with high adsorption capacity, high selectivity, and high cycle stability.

[0022] The advantages of additional aspects of the invention will be set forth more clearly in the following description or will be learned by practice of the invention. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart illustrating the preparation method of the lead-vanadium-bismuth-based sodium-type potassium ion adsorbent according to an embodiment of the present invention.

[0025] Figure 2 This is a SEM image of the potassium adsorbent powder prepared in Example 1 of the present invention.

[0026] Figure 3 The image shows the XRD pattern of the potassium adsorbent powder prepared in Example 1 of this invention.

[0027] Figure 4 This is a SEM image of the manganese-based lithium adsorbent precursor described in Example 2 of the present invention.

[0028] Figure 5 The image shows the XRD pattern of the manganese-based lithium adsorbent precursor as shown in Example 2 of this invention.

[0029] Figure 6 This is a SEM image of the manganese-based lithium adsorbent precursor described in Example 3 of the present invention.

[0030] Figure 7 The image shows the XRD pattern of the manganese-based lithium adsorbent precursor as shown in Example 3 of this invention. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0032] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as here.

[0034] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or groups thereof.

[0035] To facilitate understanding of the present invention, the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. However, the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0036] Those skilled in the art should understand that the accompanying drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily essential for implementing the present invention.

[0037] This invention selects lead, vanadium, and bismuth—three unconventional metal elements—as the main adsorbent framework, introduces sodium ions as a specific exchangeable ion, and designs a multi-step gradient synthesis process to prepare a novel potassium adsorbent (lead-vanadium-bismuth-based sodium-type potassium ion adsorbent) with high capacity, high selectivity, and high cycling stability. The lead-vanadium-bismuth-based sodium-type potassium ion adsorbent prepared by this invention has the general chemical formula: Na0 x Pb y VBiO z-SiO2, where x, y, and z are stoichiometric coefficients satisfying 10≤x≤90, 10≤y≤30, and 29≤z≤109; this adsorbent is a layered-porous dual-structure composite inorganic oxide. The framework is a stable three-dimensional network formed by alternating VO-Bi, VO-Pb, and Bi-O-Pb covalent bonds. Sodium ions are uniformly distributed in the interlayer and pores of the framework and, as the only exchangeable ion, undergo a specific ion exchange reaction with potassium ions. Lead, vanadium, and bismuth in the framework are non-exchangeable framework metals, and SiO2 is a binder for powder granulation.

[0038] like Figure 1 As shown, the cylindrical potassium adsorbent Na proposed in this invention x Pb y VBiO z The preparation of SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles involves five steps: “preparation of vanadium-bismuth composite sol”, “co-precipitation of lead-vanadium-bismuth ternary precursors”, “introduction of sodium source”, “segmented gradient sintering crystallization”, and “powder granulation”. The specific process flow is as follows:

[0039] (1) Preparation of vanadium-bismuth composite sol: Ammonium metavanadate (NH4VO3) from the vanadium source was dissolved in hot deionized water at 80-95℃ and stirred until completely dissolved to prepare an NH4VO3 solution with a concentration of 0.05-0.15mol / L; Bismuth nitrate (Bi(NO3)3) from the bismuth source was dissolved in a dilute nitric acid solution with a concentration of 2.5-4.0mol / L and ultrasonically dispersed for 60-90min to prepare a Bi(NO3)3 solution with a concentration of 0.05-0.15mol / L; The Bi(NO3)3 solution was slowly added dropwise to the NH4VO3 solution, controlling the vanadium-bismuth molar ratio to be 1:1. During the dropwise addition process, the system temperature was continuously stirred and maintained at 75-85℃. After the dropwise addition was completed, the pH of the system was adjusted to 3.5-5.0 with 1.5-3.0mol / L sodium hydroxide solution and the system was continuously stirred and aged for 2-4h to obtain an orange-yellow vanadium-bismuth composite sol V-Bi-OH.

[0040] (2) Co-precipitation of lead-vanadium-bismuth ternary precursors: Lead acetate (Pb(CH3COO)2) was dissolved in a mixed solvent of anhydrous ethanol and deionized water in a volume ratio of (1.5-3):1 to prepare a 1-3 mol / L Pb(CH3COO)2 alcohol aqueous solution. The Pb(CH3COO)2 alcohol aqueous solution was added dropwise to the above vanadium-bismuth composite sol at a rate of 100-200 mL / min, controlling the lead:vanadium:bismuth molar ratio to be (10-30):1:1. The system temperature was maintained at 60-70℃ and the stirring speed was 200-300 r / min throughout the dropwise addition. After the dropwise addition was completed, the composite precipitate was slowly added. A precipitant (a mixed solution of oxalic acid and citric acid in a molar ratio of 1:0.8) was used to adjust the pH of the system to 6.5-8.0. The reaction was stirred continuously for 3-5 hours, and then the temperature was raised to 85-95℃ and aged at a constant temperature for 12-24 hours to obtain a ternary lead-vanadium-bismuth hydroxide precursor slurry. After aging, the slurry was centrifuged and the filter cake was washed 5-8 times alternately with deionized water and anhydrous ethanol until the pH of the washing liquid was neutral and there were no nitrate or oxalate residues. The slurry was then dried in a vacuum drying oven at 60-80℃ for 12-18 hours and ground through a 200-mesh sieve to obtain the lead-vanadium-bismuth ternary precursor Pb(OH)2-V(OH)3-Bi(OH)3 powder.

[0041] (3) Sodium source introduction: Pb(OH)2-V(OH)3-Bi(OH)3 powder, a lead-vanadium-bismuth ternary precursor, and sodium acetate CH3COONa powder were added to a high-speed mixer in a molar ratio of Na:Pb=(1-3):1 for dry mixing at a speed of 500-2000 rpm for 1-3 h to obtain CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder.

[0042] (4) Segmented gradient sintering crystallization: CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder is placed in a corundum crucible and then placed in a box-type atmosphere furnace. A three-stage gradient sintering process is adopted. The first stage is low-temperature pretreatment: the heating rate is 3-5℃ / min, the temperature is raised to 200-350℃, and the temperature is kept constant for 2-3 hours to remove the water of crystallization and organic ligands in CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3; the second stage is low-temperature pretreatment: the heating rate is 3-5℃ / min, the temperature is raised to 200-350℃, and the temperature is kept constant for 2-3 hours to remove the water of crystallization and organic ligands in CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3; the third .... Two-stage medium-temperature crystallization: heating rate 2-4℃ / min, heating to 450-700℃, constant-temperature calcination for 4-6 hours, initially forming a sodium-type lead-vanadium-bismuth ternary oxide framework; Third-stage high-temperature shaping: heating rate 1-3℃ / min, heating to 800-1000℃, constant-temperature calcination for 3-5 hours, strengthening the covalent bond connections of the framework, forming a stable crystal form; After sintering, cooling to room temperature in the furnace, grinding through a 300-mesh sieve, obtaining the sodium-type lead-vanadium-bismuth ternary oxide matrix potassium adsorbent Na. x Pb y VBiO z(10≤x≤90,10≤y≤30,29≤z≤109) powder.

[0043] (5) Powder granulation: Add potassium adsorbent Na to the kneader x Pb y VBiO z (10≤x≤90, 10≤y≤30, 29≤z≤109) 200-300 kg of powder, 30-50 kg of water glass solution with a modulus of 2-2.5, 10-100 kg of deionized water, and 40-80 kg of glucose powder are kneaded for 3-7 hours. The blend is then transferred to an extruder for extrusion molding to obtain cylindrical particles with a diameter of 1 mm and a length of 0.5-3 mm. These cylindrical particles are then transferred to a calcination furnace and calcined at 400-600℃ for 2-8 hours to obtain cylindrical potassium adsorbent Na. x Pb y VBiO z -SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles.

[0044] In this invention, the cylindrical potassium adsorbent particles prepared above can be applied in seawater potassium extraction processes to extract potassium ions from seawater. Specifically, the prepared cylindrical potassium adsorbent Na... x Pb y VBiO z SiO2 particles (10≤x≤90, 10≤y≤30, 29≤z≤109) are packed in a fixed-bed adsorption column with an aspect ratio of 8-15:1. The feed flow rate of seawater (or simulated seawater) is controlled at 5-15 BV / h, the temperature at 20-30℃, and the pH of the system is the same as that of natural seawater (7.5-8.5) to dynamically adsorb and enrich potassium ions. After adsorption saturation, a 4 mol / L sodium chloride solution is used as the eluent at an elution flow rate of 3-8 BV / h to complete the desorption of potassium ions and regeneration of the adsorbent. The regenerated adsorbent is directly recycled for the next round of seawater potassium extraction without additional activation treatment.

[0045] In this invention, potassium ion adsorbents with different component contents were prepared through multiple different embodiments and comparative examples. The performance of the different potassium ion adsorbents was compared, and the comparison results are shown in Table 1.

[0046] Table 1

[0047] sample Adsorption capacity (g / L) Total concentration of calcium and magnesium ions in the eluent (mg / L) Lead concentration in adsorbed water (mg / L) Vanadium concentration in adsorbed water (mg / L) Bismuth concentration in adsorbed water (mg / L) Adsorption capacity reduction rate after 500 cycles Example 1 81.6 21 0 0 0 2.4% Example 2 83.4 24 0 0 0 2.7% Example 3 85.7 18 0 0 0 1.9% Comparative Example 1 28.4 324 8.5 0 0 15.3% Comparative Example 2 34.9 426 10.7 4.9 6.2 16.1% Comparative Example 3 19.5 241 20.4 1.6 3.5 14.3% Comparative Example 4 12.7 439 35.2 5.9 10.6 20.7% Comparative Example 5 46.6 237 15.3 4.2 5.6 8.9% Commercially available zeolite 23 845 0 0 0 28.6%

[0048] Example 1

[0049] In this embodiment 1, a cylindrical potassium adsorbent Na is provided. x Pb y VBiOz A method for synthesizing SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles, the method comprising:

[0050] (1) Preparation of vanadium-bismuth composite sol: Ammonium metavanadate (NH4VO3) from vanadium source was dissolved in hot deionized water at 80℃ and stirred until completely dissolved to prepare an NH4VO3 solution with a concentration of 0.05 mol / L; Bismuth nitrate (Bi(NO3)3) from bismuth source was dissolved in dilute nitric acid solution with a concentration of 2.5 mol / L and ultrasonically dispersed for 60 min to prepare a Bi(NO3)3 solution with a concentration of 0.05 mol / L; The Bi(NO3)3 solution was slowly added dropwise to the NH4VO3 solution, controlling the vanadium-bismuth molar ratio to be 1:1. During the dropwise addition process, the system temperature was continuously stirred and maintained at 75℃. After the dropwise addition was completed, the pH of the system was adjusted to 3.5 with 1.5 mol / L sodium hydroxide solution, and the system was continuously stirred and aged for 2 h to obtain an orange-yellow vanadium-bismuth composite sol V-Bi-OH.

[0051] (2) Co-precipitation of lead-vanadium-bismuth ternary precursors: Lead acetate (Pb(CH3COO)2) was dissolved in a mixed solvent of anhydrous ethanol and deionized water in a volume ratio of 1.5:1 to prepare a 1 mol / L Pb(CH3COO)2 alcohol aqueous solution. The Pb(CH3COO)2 alcohol aqueous solution was added dropwise to the above vanadium-bismuth composite sol at a rate of 100 mL / min, controlling the lead:vanadium:bismuth molar ratio to be 10:1:1. The system temperature was maintained at 60℃ and the stirring speed was 200 r / min throughout the dropwise addition. After the dropwise addition was completed, the composite precipitate was slowly added. The pH of the system was adjusted to 6.5 by using a mixture of oxalic acid and citric acid in a molar ratio of 1:0.8. The mixture was stirred continuously for 3 hours, then heated to 85°C and aged at a constant temperature for 12 hours to obtain a ternary lead-vanadium-bismuth hydroxide precursor slurry. After aging, the slurry was centrifuged and the filter cake was washed 5 times with deionized water and anhydrous ethanol alternately until the pH of the washing liquid was neutral and there were no nitrate or oxalate residues. The slurry was then dried in a vacuum drying oven at 60°C for 12 hours and ground through a 200-mesh sieve to obtain the lead-vanadium-bismuth ternary precursor Pb(OH)2-V(OH)3-Bi(OH)3 powder.

[0052] (3) Sodium source introduction: Pb(OH)2-V(OH)3-Bi(OH)3 powder, a lead-vanadium-bismuth ternary precursor, and sodium acetate CH3COONa powder were added to a high-speed mixer in a molar ratio of Na:Pb=1:1 for dry mixing at a speed of 500 rpm for 1 h to obtain CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder.

[0053] (4) Segmented gradient sintering crystallization: CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder was placed in a corundum crucible and placed in a box-type atmosphere furnace. A three-stage gradient sintering process was adopted. The first stage was low-temperature pretreatment: the heating rate was 3℃ / min, the temperature was raised to 200℃, and the temperature was kept constant for 2h to remove the water of crystallization and organic ligands in CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3. The second stage was medium-temperature crystallization: the heating rate was 2℃ / min, the temperature was raised to 450℃, and the temperature was kept constant for 4h to initially form a sodium-type lead-vanadium-bismuth ternary oxide framework. The third stage was high-temperature shaping: the heating rate was 1℃ / min, the temperature was raised to 800℃, and the temperature was kept constant for 3h to strengthen the covalent bond connection of the framework and form a stable crystal form. After sintering, the furnace was cooled to room temperature and ground through a 300-mesh sieve to obtain sodium-type lead-vanadium-bismuth ternary oxide matrix potassium adsorbent Na. x Pb y VBiO z (10≤x≤90,10≤y≤30,29≤z≤109) powder.

[0054] (5) Powder granulation: Add potassium adsorbent Na to the kneader x Pb y VBiO z (10≤x≤90, 10≤y≤30, 29≤z≤109) 200kg of powder, 30kg of water glass solution with a modulus of 2, 10kg of deionized water, and 40kg of glucose powder were kneaded for 3 hours. The blend was then transferred to an extruder for extrusion molding to obtain cylindrical particles with a diameter of 1mm and a length of 0.5-3mm. These cylindrical particles were then transferred to a calcination furnace and calcined at 400℃ for 2 hours to obtain cylindrical potassium adsorbent Na. x Pb y VBiO z -SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles.

[0055] The electron micrograph of the obtained potassium adsorbent powder is shown below. Figure 2 As shown, the potassium adsorbent powder synthesized in this embodiment has a particle size of approximately 200-600 nm, and the powder particles are elongated. A certain mass of potassium adsorbent powder was weighed and dissolved in nitric acid upon heating. Inductively coupled plasma atomic emission spectrometry (ICP) was used to determine the key element ratio of the potassium adsorbent powder to be Na:Pb:V:Bi = 10.01:10.02:1.03:0.98, indicating that the chemical formula of the potassium adsorbent powder is approximately Na. 10 Pb 10 VBiO 29 The potassium adsorbent powder was tested using X-ray diffraction (XRD), and the resulting spectrum is shown below. Figure 3As shown, the sharp peaks in the XRD spectrum indicate good crystal growth and high crystallinity, which is beneficial for improving the selectivity and cycle stability of the potassium adsorbent.

[0056] In this embodiment, the potassium ion adsorbent prepared above is used for potassium extraction from seawater. 50 mL of cylindrical potassium adsorbent Na... 10 Pb 10 VBiO 29 SiO2 was placed in an plexiglass adsorption column, and real seawater (potassium ion concentration of 586 mg / L) was pumped into the column for adsorption for 3 hours at a flow rate of 15 BV / h. The potassium ion concentration in the mixed product water was measured, and the potassium adsorption capacity was calculated based on the potassium concentrations in the influent and product water. The potassium adsorption capacity after 3 hours of adsorption is shown in Table 1, which is 81.6 g / L (under the same conditions, the adsorption capacity of commercially available zeolite potassium adsorbent is 23 g / L). This indicates that the potassium adsorbent synthesized in this embodiment has the advantage of high adsorption capacity. In addition, the total concentration of calcium and magnesium ions in the eluent is 21 mg / L (under the same conditions, the total concentration of calcium and magnesium ions in the eluent of commercially available zeolite potassium adsorbent is 845 mg / L), which is very low. This proves that the potassium extraction process of the potassium adsorbent is not affected by the high concentration of sodium, magnesium, and calcium ions in the seawater system, and can be used for direct potassium extraction from seawater. Furthermore, when adsorption and desorption (using 4 mol / L sodium chloride solution as the desorption solution) were considered as one cycle, it was found that lead, vanadium, and bismuth were undetectable during the adsorption process (the content of lead, vanadium, and bismuth was tested using inductively coupled plasma atomic emission spectrometry (ICP). Moreover, after 500 cycles, the adsorption capacity decreased by only 2.4% (under the same conditions, the adsorption capacity of commercially available potassium zeolite adsorbent decreased by 28.6% after 500 cycles).

[0057] Example 2

[0058] In this embodiment 2, a cylindrical potassium adsorbent Na is provided. x Pb y VBiO z A method for synthesizing SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles, the method comprising:

[0059] (1) Preparation of vanadium-bismuth composite sol: Ammonium metavanadate (NH4VO3) from vanadium source was dissolved in hot deionized water at 95℃ and stirred until completely dissolved to prepare an NH4VO3 solution with a concentration of 0.15 mol / L; Bismuth nitrate (Bi(NO3)3) from bismuth source was dissolved in dilute nitric acid solution with a concentration of 4.0 mol / L and ultrasonically dispersed for 90 min to prepare a Bi(NO3)3 solution with a concentration of 0.15 mol / L; The Bi(NO3)3 solution was slowly added dropwise to the NH4VO3 solution, controlling the vanadium-bismuth molar ratio to be 1:1. During the dropwise addition process, the system temperature was continuously stirred and maintained at 85℃. After the dropwise addition was completed, the pH of the system was adjusted to 5.0 with 3.0 mol / L sodium hydroxide solution, and the system was continuously stirred and aged for 4 h to obtain an orange-yellow vanadium-bismuth composite sol V-Bi-OH.

[0060] (2) Co-precipitation of lead-vanadium-bismuth ternary precursors: Lead acetate (Pb(CH3COO)2) was dissolved in a mixed solvent of anhydrous ethanol and deionized water in a volume ratio of 3:1 to prepare a 3 mol / L Pb(CH3COO)2 alcohol aqueous solution. The Pb(CH3COO)2 alcohol aqueous solution was added dropwise to the above vanadium-bismuth composite sol at a rate of 200 mL / min, controlling the lead:vanadium:bismuth molar ratio to be 30:1:1. The system temperature was maintained at 70 °C and the stirring speed was 300 r / min throughout the dropwise addition. After the dropwise addition was completed, the composite precipitant was slowly added. A mixed solution of oxalic acid and citric acid in a molar ratio of 1:0.8 was prepared. The pH of the system was adjusted to 8.0, and the reaction was stirred continuously for 5 hours. Then, the temperature was raised to 95°C and aged at a constant temperature for 24 hours to obtain a ternary lead-vanadium-bismuth hydroxide precursor slurry. After aging, the slurry was centrifuged and the filter cake was washed 8 times with deionized water and anhydrous ethanol alternately until the pH of the washing liquid was neutral and there were no nitrate or oxalate residues. The slurry was dried in a vacuum drying oven at 80°C for 18 hours and then ground through a 200-mesh sieve to obtain the lead-vanadium-bismuth ternary precursor Pb(OH)2-V(OH)3-Bi(OH)3 powder.

[0061] (3) Sodium source introduction: Pb(OH)2-V(OH)3-Bi(OH)3 powder, a lead-vanadium-bismuth ternary precursor, and sodium acetate CH3COONa powder were added to a high-speed mixer in a molar ratio of Na:Pb=3:1 for dry mixing at a speed of 2000 rpm for 3 h to obtain CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder.

[0062] (4) Segmented gradient sintering crystallization: CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder was placed in a corundum crucible and placed in a box-type atmosphere furnace. A three-stage gradient sintering process was adopted. The first stage was low-temperature pretreatment: the heating rate was 5℃ / min, the temperature was raised to 350℃, and the temperature was kept constant for 3h to remove the water of crystallization and organic ligands in CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3. The second stage was medium-temperature crystallization: the heating rate was 4℃ / min, the temperature was raised to 700℃, and the temperature was kept constant for 6h to initially form a sodium-type lead-vanadium-bismuth ternary oxide framework. The third stage was high-temperature shaping: the heating rate was 3℃ / min, the temperature was raised to 1000℃, and the temperature was kept constant for 5h to strengthen the covalent bond connection of the framework and form a stable crystal form. After sintering, the furnace was cooled to room temperature and ground through a 300-mesh sieve to obtain sodium-type lead-vanadium-bismuth ternary oxide matrix potassium adsorbent Na. x Pb y VBiO z (10≤x≤90,10≤y≤30,29≤z≤109) powder.

[0063] (5) Powder granulation: Add potassium adsorbent Na to the kneader x Pb y VBiO z (10≤x≤90, 10≤y≤30, 29≤z≤109) 300kg of powder, 50kg of water glass solution with a modulus of 2.5, 100kg of deionized water, and 80kg of glucose powder were kneaded for 7 hours. The blend was then transferred to an extruder for extrusion molding to obtain cylindrical particles with a diameter of 1mm and a length of 0.5-3mm. These cylindrical particles were then transferred to a calcination furnace and calcined at 600℃ for 8 hours to obtain cylindrical potassium adsorbent Na. x Pb y VBiO z -SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles.

[0064] The electron micrograph of the obtained potassium adsorbent powder is shown below. Figure 4 As shown, the potassium adsorbent powder synthesized in this embodiment has a particle size of approximately 200-600 nm, and the powder particles are elongated. A certain mass of potassium adsorbent powder was weighed and dissolved in nitric acid upon heating. Inductively coupled plasma atomic emission spectrometry (ICP) was used to determine the key element ratio of the potassium adsorbent powder to be Na:Pb:V:Bi = 90.2:30.4:1.05:1.03, indicating that the chemical formula of the potassium adsorbent powder is approximately Na. 90 Pb 30 VBiO 109 The potassium adsorbent powder was tested using X-ray diffraction (XRD), and the resulting spectrum is shown below. Figure 5As shown, the sharp peaks in the XRD spectrum indicate good crystal growth and high crystallinity, which is beneficial for improving the selectivity and cycle stability of the potassium adsorbent.

[0065] In this embodiment, the potassium ion adsorbent prepared above is used for potassium extraction from seawater. 50 mL of cylindrical potassium adsorbent Na... 10 Pb 10 VBiO 29 SiO2 was placed in an plexiglass adsorption column, and real seawater (potassium ion concentration of 586 mg / L) was pumped into the column for adsorption for 3 hours at a flow rate of 15 BV / h. The potassium ion concentration in the mixed product water was measured, and the potassium adsorption capacity was calculated based on the potassium concentrations in the influent and product water. The potassium adsorption capacity after 3 hours of adsorption is shown in Table 1, which is 83.4 g / L (under the same conditions, the adsorption capacity of commercially available zeolite potassium adsorbent is 23 g / L). This indicates that the potassium adsorbent synthesized in this embodiment has the advantage of high adsorption capacity. In addition, the total concentration of calcium and magnesium ions in the eluent is 24 mg / L (under the same conditions, the total concentration of calcium and magnesium ions in the eluent of commercially available zeolite potassium adsorbent is 845 mg / L), which is very low. This proves that the potassium extraction process of the potassium adsorbent is not affected by the high concentration of sodium, magnesium, and calcium ions in the seawater system, and can be used for direct potassium extraction from seawater. Furthermore, when adsorption and desorption (using 4 mol / L sodium chloride solution as the desorption solution) were considered as one cycle, it was found that lead, vanadium, and bismuth were undetectable during the adsorption process (the content of lead, vanadium, and bismuth was tested using inductively coupled plasma atomic emission spectrometry (ICP). Moreover, after 500 cycles, the adsorption capacity decreased by only 2.7% (under the same conditions, the adsorption capacity of commercially available potassium zeolite adsorbent decreased by 28.6% after 500 cycles).

[0066] Example 3

[0067] In this embodiment 3, a cylindrical potassium adsorbent Na is provided. x Pb y VBiO z A method for synthesizing SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles, the method comprising:

[0068] (1) Preparation of vanadium-bismuth composite sol: Ammonium metavanadate (NH4VO3) from vanadium source was dissolved in hot deionized water at 87.5℃ and stirred until completely dissolved to prepare an NH4VO3 solution with a concentration of 0.1 mol / L; Bismuth nitrate (Bi(NO3)3) from bismuth source was dissolved in dilute nitric acid solution with a concentration of 3.25 mol / L and ultrasonically dispersed for 75 min to prepare a Bi(NO3)3 solution with a concentration of 0.1 mol / L; The Bi(NO3)3 solution was slowly added dropwise to the NH4VO3 solution, controlling the vanadium-bismuth molar ratio to be 1:1. During the dropwise addition process, the system temperature was continuously stirred and maintained at 80℃. After the dropwise addition was completed, the pH of the system was adjusted to 4.25 with 2.25 mol / L sodium hydroxide solution, and the system was continuously stirred and aged for 3 h to obtain an orange-yellow vanadium-bismuth composite sol V-Bi-OH.

[0069] (2) Co-precipitation of lead-vanadium-bismuth ternary precursors: Lead acetate (Pb(CH3COO)2) was dissolved in a mixed solvent of anhydrous ethanol and deionized water in a volume ratio of 2.25:1 to prepare a 2 mol / L Pb(CH3COO)2 alcohol aqueous solution. The Pb(CH3COO)2 alcohol aqueous solution was added dropwise to the above vanadium-bismuth composite sol at a rate of 150 mL / min, controlling the lead:vanadium:bismuth molar ratio to be 20:1:1. The system temperature was maintained at 65℃ and the stirring speed was 250 r / min throughout the dropwise addition. After the dropwise addition was completed, the composite precipitate was slowly added. The pH of the system was adjusted to 7.25 by using a mixture of oxalic acid and citric acid in a molar ratio of 1:0.8. The mixture was stirred continuously for 4 hours, then heated to 90°C and aged at a constant temperature for 18 hours to obtain a ternary lead-vanadium-bismuth hydroxide precursor slurry. After aging, the slurry was centrifuged and the filter cake was washed 7 times with deionized water and anhydrous ethanol alternately until the pH of the washing liquid was neutral and there were no nitrate or oxalate residues. The slurry was then dried in a vacuum drying oven at 70°C for 15 hours and ground through a 200-mesh sieve to obtain the lead-vanadium-bismuth ternary precursor Pb(OH)2-V(OH)3-Bi(OH)3 powder.

[0070] (3) Sodium source introduction: Pb(OH)2-V(OH)3-Bi(OH)3 powder, a lead-vanadium-bismuth ternary precursor, and sodium acetate CH3COONa powder were added to a high-speed mixer in a molar ratio of Na:Pb=2:1 for dry mixing at a speed of 1250 rpm for 2 h to obtain CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder.

[0071] (4) Segmented gradient sintering crystallization: CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder was placed in a corundum crucible and placed in a box-type atmosphere furnace. A three-stage gradient sintering process was adopted. The first stage was low-temperature pretreatment: the heating rate was 4℃ / min, the temperature was raised to 275℃, and the temperature was kept constant for 2.5h to remove the water of crystallization and organic ligands in CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3. The second stage was medium-temperature crystallization: the heating rate was 3℃ / min, the temperature was raised to 575℃, and the temperature was kept constant for 5h to initially form a sodium-type lead-vanadium-bismuth ternary oxide framework. The third stage was high-temperature shaping: the heating rate was 2℃ / min, the temperature was raised to 900℃, and the temperature was kept constant for 4h to strengthen the covalent bond connection of the framework and form a stable crystal form. After sintering, the furnace was cooled to room temperature and ground through a 300-mesh sieve to obtain sodium-type lead-vanadium-bismuth ternary oxide matrix potassium adsorbent Na. x Pb y VBiO z (10≤x≤90,10≤y≤30,29≤z≤109) powder.

[0072] (5) Powder granulation: Add potassium adsorbent Na to the kneader x Pb y VBiO z (10≤x≤90, 10≤y≤30, 29≤z≤109) 250kg of powder, 40kg of water glass solution with a modulus of 2.3, 55kg of deionized water, and 60kg of glucose powder were kneaded for 5 hours. The blend was then transferred to an extruder for extrusion molding to obtain cylindrical particles with a diameter of 1mm and a length of 0.5-3mm. These cylindrical particles were then transferred to a calcination furnace and calcined at 500℃ for 5 hours to obtain cylindrical potassium adsorbent Na. x Pb y VBiO z -SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles.

[0073] The electron micrograph of the obtained potassium adsorbent powder is shown below. Figure 6 As shown, the potassium adsorbent powder synthesized in this embodiment has a particle size of approximately 200-600 nm, and the powder particles are elongated. A certain mass of potassium adsorbent powder was weighed and dissolved in nitric acid upon heating. Inductively coupled plasma atomic emission spectrometry (ICP) was used to determine the key element ratio of the potassium adsorbent powder to be Na:Pb:V:Bi = 40.05:20.03:1.04:0.99, indicating that the chemical formula of the potassium adsorbent powder is approximately Na. 40 Pb 20 VBiO 64 The potassium adsorbent powder was tested using X-ray diffraction (XRD), and the resulting spectrum is shown below. Figure 7As shown, the sharp peaks in the XRD spectrum indicate good crystal growth and high crystallinity, which is beneficial for improving the selectivity and cycle stability of the potassium adsorbent.

[0074] The potassium ion adsorbent prepared in this embodiment was used for potassium extraction from seawater. 50 mL of cylindrical potassium adsorbent Na... 10 Pb 10 VBiO 29 SiO2 was placed in an plexiglass adsorption column, and real seawater (potassium ion concentration of 586 mg / L) was pumped into the column for adsorption for 3 hours at a flow rate of 15 BV / h. The potassium ion concentration in the mixed product water was measured, and the potassium adsorption capacity was calculated based on the potassium concentrations in the influent and product water. The potassium adsorption capacity after 3 hours of adsorption is shown in Table 1, which is 85.7 g / L (under the same conditions, the adsorption capacity of commercially available zeolite potassium adsorbent is 23 g / L). This indicates that the potassium adsorbent synthesized in this patent has the advantage of high adsorption capacity. In addition, the total concentration of calcium and magnesium ions in the eluent is 18 mg / L (under the same conditions, the total concentration of calcium and magnesium ions in the eluent of commercially available zeolite potassium adsorbent is 845 mg / L), which is very low. This proves that the potassium extraction process of the potassium adsorbent is not affected by the high concentration of sodium, magnesium, and calcium ions in the seawater system and can be used for direct potassium extraction from seawater. Furthermore, when adsorption and desorption (using 4 mol / L sodium chloride solution as the desorption solution) were considered as one cycle, it was found that lead, vanadium, and bismuth were undetectable during the adsorption process (the content of lead, vanadium, and bismuth was tested using inductively coupled plasma atomic emission spectrometry (ICP). Moreover, after 500 cycles, the adsorption capacity decreased by only 1.9% (under the same conditions, the adsorption capacity of commercially available potassium zeolite adsorbent decreased by 28.6% after 500 cycles).

[0075] Comparative Example 1

[0076] In this comparative example 1, a cylindrical potassium adsorbent Na was provided. x Pb y O z A method for synthesizing SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles, wherein the synthesis method omits the vanadium-bismuth composite sol preparation step described in the above embodiments, and the synthesis method of the comparative example includes:

[0077] (1) Lead precipitation: Lead acetate (Pb(CH3COO)2) was dissolved in a mixed solvent of anhydrous ethanol and deionized water in a volume ratio of 1.5:1 to prepare a 1 mol / L Pb(CH3COO)2 alcohol aqueous solution. A composite precipitant (a mixed solution of oxalic acid and citric acid in a molar ratio of 1:0.8) was slowly added to the Pb(CH3COO)2 alcohol aqueous solution to adjust the pH of the system to 6.5. The reaction was stirred continuously for 3 h, and then the temperature was raised to 85 °C and aged at a constant temperature for 12 h to obtain lead hydroxide precursor slurry. After aging, the slurry was centrifuged and the filter cake was washed 5 times with deionized water and anhydrous ethanol alternately until the pH of the washing liquid was neutral and oxalate was residual. The slurry was dried in a vacuum drying oven at 60 °C for 12 h and ground through a 200-mesh sieve to obtain lead precursor Pb(OH)2 powder.

[0078] (2) Sodium source introduction: Same as in Example 1.

[0079] (3) Segmented gradient sintering crystallization: Same as Example 1.

[0080] (4) Powder granulation: Same as in Example 1.

[0081] A certain mass of potassium adsorbent powder was dissolved in nitric acid by heating. Inductively coupled plasma atomic emission spectrometry (ICP) was used to determine the key element ratio of the potassium adsorbent powder to be Na:Pb = 10.04:10.05. Therefore, the chemical formula of the potassium adsorbent powder is approximately Na. 10 Pb 10 O 25 .

[0082] The difference between the potassium adsorbent synthesis method of Comparative Example 1 and Example 1 is that the potassium adsorbent synthesis in Example 1 was doped with vanadium and bismuth, while the potassium adsorbent of Comparative Example 1 was not doped with vanadium and bismuth.

[0083] The potassium adsorption capacity after 3 hours of adsorption is shown in Table 1, which is 28.4 g / L (under the same conditions, the adsorption capacity of commercially available zeolite potassium adsorbent is 23 g / L). This indicates a significant decrease in the adsorption capacity of the potassium adsorbent synthesized in Comparative Example 1. Furthermore, the total concentration of calcium and magnesium ions in the eluent is 324 mg / L (under the same conditions, the total concentration of calcium and magnesium ions in the eluent of commercially available zeolite potassium adsorbent is 845 mg / L), indicating a significant increase in impurity ions and poor selectivity. In addition, considering adsorption and desorption (using 4 mol / L sodium chloride solution as the desorption solution) as a single cycle, it was found that during adsorption (lead content was measured using inductively coupled plasma atomic emission spectrometry (ICP)), the lead concentration was 8.5 mg / L, indicating poor structural stability. Moreover, after 500 cycles, the adsorption capacity decreased by 15.3% (under the same conditions, the adsorption capacity of commercially available zeolite potassium adsorbent decreased by 28.6% after 500 cycles), demonstrating poor cycle performance.

[0084] The reason is that the chemical framework of the potassium adsorbent uses lead atoms as the core atoms and vanadium and bismuth atoms as auxiliary atoms. The beneficial effects are: lead atoms as core atoms can form a very stable crystal framework structure that is resistant to acids and alkalis, thus improving the cycle stability of the potassium adsorbent; the doping of vanadium and bismuth atoms can inhibit the rapid continuous growth of Pb-O-Pb chemical bonds, avoid the formation of ultra-large crystals, and reduce the crystal size, which is conducive to improving the adsorption capacity of the potassium adsorbent. Because the crystals are small, the growth is more complete and there are fewer crystal defects, which is conducive to improving selectivity and cycle stability.

[0085] Comparative Example 2

[0086] In this comparative example 2, a cylindrical potassium adsorbent Na is provided. x Pb y VBiO z A method for synthesizing SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles, the method comprising:

[0087] (1) Preparation of vanadium-bismuth composite sol: Same as in Example 1.

[0088] (2) Co-precipitation of lead, vanadium and bismuth ternary precursors: The molar ratio of lead:vanadium:bismuth was controlled at 10:5:5, and other conditions were the same as in Example 1.

[0089] (3) Sodium source introduction: Same as in Example 1.

[0090] (4) Segmented gradient sintering crystallization: Same as in Example 1.

[0091] (5) Powder granulation: Same as in Example 1.

[0092] A certain mass of potassium adsorbent powder was dissolved in nitric acid by heating. The key element ratio of the potassium adsorbent powder was determined by inductively coupled plasma atomic emission spectrometry (ICP) to be Na:Pb:V:Bi = 10.01:10.02:5.07:5.05. Therefore, the chemical formula of the potassium adsorbent powder is approximately Na. 10 Pb 10 V5Bi5O 45 .

[0093] The difference between the potassium adsorbent synthesis method in this comparative example and that in Example 1 is that in Example 1, the potassium adsorbent synthesis controlled the lead:vanadium:bismuth molar ratio to be 10:1:1 (meeting the requirement of controlling the lead:vanadium:bismuth molar ratio (10-30):1:1) during the co-precipitation of the lead-vanadium-bismuth ternary precursor; while in Comparative Example 2, the potassium adsorbent synthesis controlled the lead:vanadium:bismuth molar ratio to be 10:5:5 (not meeting the requirement of controlling the lead:vanadium:bismuth molar ratio (10-30):1:1), significantly increasing the vanadium and bismuth content.

[0094] The potassium adsorption capacity after 3 hours of adsorption was measured as shown in Table 1, which was 34.9 g / L (under the same conditions, the adsorption capacity of commercially available zeolite potassium adsorbent was 23 g / L). It can be seen that the adsorption capacity of the potassium adsorbent synthesized in Comparative Example 2 was significantly reduced. In addition, the total concentration of calcium and magnesium ions in the eluent was 426 mg / L (under the same conditions, the total concentration of calcium and magnesium ions in the eluent of commercially available zeolite potassium adsorbent was 845 mg / L), indicating a significant increase in impurity ions and poor selectivity. Furthermore, when adsorption and desorption (using 4 mol / L sodium chloride solution as the desorption solution) were considered as one cycle, it was found that during the adsorption process (lead content was measured using inductively coupled plasma atomic emission spectrometry (ICP)), the lead concentration was 10.7 mg / L, the vanadium concentration was 4.9 mg / L, and the bismuth concentration was 6.2 mg / L. The structure was unstable, and after 500 cycles, the adsorption capacity decreased by 16.1% (under the same conditions, the adsorption capacity of commercially available potassium zeolite adsorbent decreased by 28.6% after 500 cycles), indicating poor cycle performance.

[0095] The reason is that vanadium and bismuth atoms, as auxiliary dopants, can improve adsorption capacity, selectivity, and cycle stability by controlling the lead:vanadium:bismuth molar ratio (10-30):1:1. However, excessive doping with vanadium and bismuth leads to a relative lack of Pb, a growth element in the Pb-O host framework, preventing the formation of the basic structure of the potassium adsorbent and resulting in a significant drop in performance.

[0096] Comparative Example 3

[0097] In this comparative example 3, a cylindrical potassium adsorbent Na is provided. x Pb y VBiO z A method for synthesizing SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles, the method comprising:

[0098] (1) Preparation of vanadium-bismuth composite sol: Same as in Example 1.

[0099] (2) Co-precipitation of lead, vanadium and bismuth ternary precursors: The molar ratio of lead:vanadium:bismuth was controlled at 10:0.25:0.25, and other conditions were the same as in Example 1.

[0100] (3) Sodium source introduction: Same as in Example 1.

[0101] (4) Segmented gradient sintering crystallization: Same as in Example 1.

[0102] (5) Powder granulation: Same as in Example 1.

[0103] A certain mass of potassium adsorbent powder was dissolved in nitric acid by heating. The key element ratio of the potassium adsorbent powder was determined by inductively coupled plasma atomic emission spectrometry (ICP) to be Na:Pb:V:Bi = 10.01:10.02:0.26:0.24. Therefore, the chemical formula of the potassium adsorbent powder is approximately Na. 10 Pb 10 V 0.25 Bi 0.25 O 26 .

[0104] The difference between the potassium adsorbent synthesis method of Comparative Example 3 and Example 1 is that: in Example 1, the potassium adsorbent synthesis controlled the lead:vanadium:bismuth molar ratio of 10:1:1 (meeting the requirement of controlling the lead:vanadium:bismuth molar ratio (10-30):1:1) during the co-precipitation of the lead-vanadium-bismuth ternary precursor; while in Comparative Example 1, the potassium adsorbent synthesis controlled the lead:vanadium:bismuth molar ratio of 10:0.25:0.25 (not meeting the requirement of controlling the lead:vanadium:bismuth molar ratio (10-30):1:1), thus reducing the content of vanadium and bismuth.

[0105] The potassium adsorption capacity after 3 hours of adsorption was measured as shown in Table 1, which was 19.5 g / L (under the same conditions, the adsorption capacity of commercially available zeolite potassium adsorbent was 23 g / L). It can be seen that the adsorption capacity of the potassium adsorbent synthesized in Comparative Example 3 was significantly reduced. In addition, the total concentration of calcium and magnesium ions in the eluent was 241 mg / L (under the same conditions, the total concentration of calcium and magnesium ions in the eluent of commercially available zeolite potassium adsorbent was 845 mg / L), indicating a significant increase in impurity ions and poor selectivity. Furthermore, when adsorption and desorption (using 4 mol / L sodium chloride solution as the desorption solution) were considered as one cycle, it was found that during the adsorption process (lead content was measured using inductively coupled plasma atomic emission spectrometry (ICP)), the lead concentration was 20.4 mg / L, the vanadium concentration was 1.6 mg / L, and the bismuth concentration was 3.5 mg / L. The structure was unstable, and after 500 cycles, the adsorption capacity decreased by 14.3% (under the same conditions, the adsorption capacity of commercially available potassium zeolite adsorbent decreased by 28.6% after 500 cycles), indicating poor cycle performance.

[0106] The reason is that vanadium and bismuth atoms, as auxiliary dopants, can improve adsorption capacity, selectivity, and cycling stability by controlling the lead:vanadium:bismuth molar ratio (10-30):1:1. Doping with vanadium and bismuth atoms can suppress the rapid, continuous growth of Pb-O-Pb bonds, preventing the formation of ultra-large crystals. Reducing crystal size is beneficial for improving the adsorption capacity of potassium adsorbents. Smaller crystals result in more complete growth and fewer crystal defects, which in turn improves selectivity and cycling stability. However, if the doping of vanadium and bismuth is too low, the Pb-O backbone will grow very rapidly, leading to a significant decrease in performance.

[0107] Comparative Example 4

[0108] Comparative Example 4 provides a cylindrical potassium adsorbent, Na. x Pb y VBiO z A method for synthesizing SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles, wherein the comparative synthesis method does not include the preparation of vanadium-bismuth composite sol, and includes:

[0109] (1) Co-precipitation of lead, vanadium, and bismuth ternary precursors: Lead acetate (Pb(CH3COO)2), ammonium metavanadate (NH4VO3), and bismuth nitrate (Bi(NO3)3) were dissolved in a mixed solvent of anhydrous ethanol and deionized water at a volume ratio of 1.5:1 to prepare an alcohol-water solution with a concentration of 1 mol / L Pb(CH3COO)2, 0.05 mol / L NH4VO3, and 0.05 mol / L Bi(NO3)3. The molar ratio of lead:vanadium:bismuth was controlled at 10:1:1. The composite precipitant (oxalic acid) was slowly added. A mixed solution with citric acid in a molar ratio of 1:0.8 was prepared. The pH of the system was adjusted to 6.5, and the reaction was stirred continuously for 3 hours. Then, the temperature was raised to 85°C and aged at a constant temperature for 12 hours to obtain a ternary lead-vanadium-bismuth hydroxide precursor slurry. After aging, the slurry was centrifuged and the filter cake was washed 5 times with deionized water and anhydrous ethanol alternately until the pH of the washing liquid was neutral and there were no nitrate or oxalate residues. The slurry was dried in a vacuum drying oven at 60°C for 12 hours and then ground through a 200-mesh sieve to obtain the lead-vanadium-bismuth ternary precursor Pb(OH)2-V(OH)3-Bi(OH)3 powder.

[0110] (2) Sodium source introduction: Same as in Example 1.

[0111] (3) Segmented gradient sintering crystallization: Same as Example 1.

[0112] (4) Powder granulation: Same as in Example 1.

[0113] A certain mass of potassium adsorbent powder was dissolved in nitric acid by heating. The key element ratio of the potassium adsorbent powder was determined by inductively coupled plasma atomic emission spectrometry (ICP) to be Na:Pb:V:Bi = 10.03:10.01:1.03:1.04. Therefore, the chemical formula of the potassium adsorbent powder is approximately Na. 10 Pb 10 VBiO 29 .

[0114] The difference between the potassium adsorbent synthesis method of Comparative Example 4 and Example 1 is that the potassium adsorbent synthesis in Example 1 includes a "vanadium-bismuth composite sol preparation" step, in which vanadium-bismuth composite sol is prepared first, followed by the preparation of the lead-vanadium-bismuth ternary precursor; while the potassium adsorbent synthesis in Comparative Example 4 does not include the "vanadium-bismuth composite sol preparation" step, and directly synthesizes the lead-vanadium-bismuth ternary precursor in one step.

[0115] The potassium adsorption capacity after 3 hours of adsorption was measured as shown in Table 1, which was 12.7 g / L (under the same conditions, the adsorption capacity of commercially available zeolite potassium adsorbent was 23 g / L). It can be seen that the adsorption capacity of the potassium adsorbent synthesized in Comparative Example 4 was significantly reduced. In addition, the total concentration of calcium and magnesium ions in the eluent was 439 mg / L (under the same conditions, the total concentration of calcium and magnesium ions in the eluent of commercially available zeolite potassium adsorbent was 845 mg / L), indicating a significant increase in impurity ions and poor selectivity. Furthermore, when adsorption and desorption (using 4 mol / L sodium chloride solution as the desorption solution) were considered as one cycle, it was found that during the adsorption process (lead content was measured using inductively coupled plasma atomic emission spectrometry (ICP)), the lead concentration was 35.2 mg / L, the vanadium concentration was 5.9 mg / L, and the bismuth concentration was 10.6 mg / L. The structure was unstable, and after 500 cycles, the adsorption capacity decreased by 20.7% (under the same conditions, the adsorption capacity of commercially available potassium zeolite adsorbent decreased by 28.6% after 500 cycles), indicating poor cycle performance.

[0116] The reason is that the beneficial effects of preparing a "vanadium-bismuth composite sol" first, followed by the preparation of a "lead-vanadium-bismuth ternary precursor co-precipitation" are as follows: First, a uniform vanadium-bismuth composite sol V-Bi-OH is prepared, and then the lead-vanadium-bismuth ternary precursor Pb(OH)2-V(OH)3-Bi(OH)3 powder is prepared based on the composite sol V-Bi-OH, instead of preparing Pb(OH)2-V(OH)3-Bi(OH)3 powder by co-precipitation of the three salts in one step. This is because vanadium and bismuth are relatively small in quantity compared to lead, and are used as dopants. Therefore, their dispersibility during the synthesis process is crucial. Preparing Pb(OH)2-V(OH)3-Bi(OH)3 powder by co-precipitation of the three salts in one step makes it difficult to obtain a uniform precipitation system. Uneven dispersion of vanadium and bismuth elements leads to numerous defects in the subsequent calcination and crystallization process, resulting in a significant reduction in adsorption capacity, selectivity, and cycle stability.

[0117] Comparative Example 5

[0118] In this comparative example 5, a cylindrical potassium adsorbent Na is provided. x Pb y VBiO z A method for synthesizing SiO2 (10≤x≤90, 10≤y≤30, 29≤z≤109) particles, the method comprising:

[0119] (1) Preparation of vanadium-bismuth composite sol: Same as in Example 1.

[0120] (2) Co-precipitation of lead-vanadium-bismuth ternary precursors: Same as in Example 1.

[0121] (3) Sodium source introduction: Same as in Example 1.

[0122] (4) Segmented gradient sintering crystallization: CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder was placed in a corundum crucible and then placed in a box-type atmosphere furnace. A single-stage temperature-controlled sintering process was adopted, with a heating rate of 1℃ / min, and the temperature was raised to 800℃ and calcined at a constant temperature for 3h. After sintering, the mixture was cooled to room temperature with the furnace and ground through a 300-mesh sieve to obtain sodium-type lead-vanadium-bismuth ternary oxide-based potassium adsorbent Na. x Pb y VBiO z (10≤x≤90,10≤y≤30,29≤z≤109) powder.

[0123] (5) Powder granulation: Same as in Example 1.

[0124] A certain mass of potassium adsorbent powder was dissolved in nitric acid by heating. The key element ratio of the potassium adsorbent powder was determined by inductively coupled plasma atomic emission spectrometry (ICP) to be Na:Pb:V:Bi = 10.01:10.04:1.04:1.02. Therefore, the chemical formula of the potassium adsorbent powder is approximately Na. 10 Pb 10 VBiO 29 .

[0125] The difference between the potassium adsorbent synthesis method of Comparative Example 5 and Example 1 is that the potassium adsorbent synthesis in Example 1 adopts a three-stage calcination crystallization process with three temperature gradients in the calcination process, and each temperature gradient is subjected to constant temperature calcination; the potassium adsorbent synthesis in Comparative Example 1 adopts a one-stage temperature-controlled sintering process, directly raising the temperature to 800℃ in one step and calcining at a constant temperature for 3 hours.

[0126] The potassium adsorption capacity after 3 hours of adsorption was measured as shown in Table 1, which was 46.6 g / L (under the same conditions, the adsorption capacity of commercially available zeolite potassium adsorbent was 23 g / L). It can be seen that the adsorption capacity of the potassium adsorbent synthesized in Comparative Example 4 was significantly reduced. In addition, the total concentration of calcium and magnesium ions in the eluent was 237 mg / L (under the same conditions, the total concentration of calcium and magnesium ions in the eluent of commercially available zeolite potassium adsorbent was 845 mg / L), indicating a significant increase in impurity ions and poor selectivity. Furthermore, when adsorption and desorption (using 4 mol / L sodium chloride solution as the desorption solution) were considered as one cycle, it was found that during the adsorption process (lead content was measured using inductively coupled plasma atomic emission spectrometry (ICP)), the lead concentration was 15.3 mg / L, the vanadium concentration was 4.2 mg / L, and the bismuth concentration was 5.6 mg / L. The structure was unstable, and after 500 cycles, the adsorption capacity decreased by 8.9% (under the same conditions, the adsorption capacity of commercially available potassium zeolite adsorbent decreased by 28.6% after 500 cycles), indicating poor cycle performance.

[0127] The reason is that a three-stage calcination crystallization process is used, instead of a one-step process of heating from room temperature to the maximum temperature for high-temperature calcination. This allows different materials to undergo precise chemical reactions or crystal growth at different temperature stages, facilitating the acquisition of potassium adsorbent crystals with high adsorption capacity, high selectivity, and high cycle stability. If a constant heating rate is maintained until the maximum temperature is reached, followed by isothermal treatment without intermediate isothermal zones, the sodium-form lead-vanadium-bismuth ternary oxide framework lacks a isothermal growth period. This results in numerous defects in the growth of the sodium-form lead-vanadium-bismuth ternary oxide framework, which cannot be repaired at high temperatures, ultimately leading to low adsorption capacity, poor selectivity, and poor cycle stability of the potassium adsorbent.

[0128] In summary, the potassium ion adsorbent and its preparation method provided by this invention have the following advantages compared with the prior art:

[0129] (1) Excellent adsorption capacity: Under simulated seawater system, the potassium adsorption capacity can reach 85g / L, which is far greater than the existing zeolite potassium adsorbent (23g / L under the same conditions). It has a high density of ion exchange sites and outstanding ability to enrich low concentration potassium ions.

[0130] (2) Extremely strong potassium selectivity: Under simulated seawater system, the adsorption capacity of calcium and magnesium ions in the influent is very low. The total content of calcium and magnesium ions in the eluent is less than 25 mg / L (under the same conditions, the total content of calcium and magnesium ions in the eluent of zeolite potassium adsorbent is 845 mg / L). It does not adsorb sodium ions, can accurately reject high concentrations of coexisting sodium ions and calcium and magnesium ions, and achieves exclusive adsorption of potassium ions only, resulting in high purity of enriched products.

[0131] (3) Excellent cycle stability: After 500 adsorption-desorption cycles, the adsorption capacity decay rate is less than 3% (under the same conditions, the adsorption capacity decay rate of zeolite potassium adsorbent is 28.6%). The skeleton structure does not collapse, no metal ions are dissolved, the service life is long, and the industrial operation cost is low.

[0132] (4) The synthesis process is highly controllable: a multi-step gradient synthesis process is adopted to precisely control the crystal form, pore structure and ion exchange sites of the material. The process has good repeatability, no toxic and harmful substances remain, and it is suitable for large-scale production.

[0133] (5) The chemical framework of the potassium adsorbent uses lead atoms as the core atoms and vanadium and bismuth atoms as auxiliary atoms. The beneficial effects are: lead atoms as core atoms can form a very stable crystal framework structure that is resistant to acids and alkalis, thus improving the cycle stability of the potassium adsorbent; the doping of vanadium and bismuth atoms can inhibit the rapid continuous growth of Pb-O-Pb chemical bonds, avoid the formation of super-large crystals, and reduce the crystal size, which is conducive to improving the adsorption capacity of the potassium adsorbent. Since the crystal is small, the growth is more perfect and there are fewer crystal defects, which is conducive to improving selectivity and cycle stability.

[0134] (6) The beneficial effects of preparing "vanadium-bismuth composite sol" first and then "lead-vanadium-bismuth ternary precursor co-precipitation": The method of first preparing a uniform vanadium-bismuth composite sol V-Bi-OH and then preparing lead-vanadium-bismuth ternary precursor Pb(OH)2-V(OH)3-Bi(OH)3 powder based on the composite sol V-Bi-OH, instead of preparing Pb(OH)2-V(OH)3-Bi(OH)3 powder by co-precipitation of lead, vanadium and bismuth salts in one step, is because vanadium and bismuth elements are in small amounts compared to lead elements and are used as dopants. Therefore, their dispersibility in the synthesis process is very critical. It is difficult to obtain a uniform precipitation system by co-precipitating lead, vanadium and bismuth salts in one step. The uneven dispersion of vanadium and bismuth elements will lead to a large number of defects in the subsequent calcination and crystallization process, which will result in a significant reduction in adsorption capacity, selectivity and cycle stability.

[0135] (7) Beneficial effects of segmented gradient calcination crystallization: The use of a three-stage calcination crystallization method, instead of a one-step method of raising the temperature from room temperature to the highest temperature for high-temperature calcination, aims to allow different materials to undergo precise chemical reactions or crystal growth at different temperature stages, which is beneficial for obtaining potassium adsorbent crystals with high adsorption capacity, high selectivity, and high cycle stability. If a constant heating rate is maintained until the highest temperature is reached and then isothermalized, without setting an isothermal zone in between, the sodium-type lead-vanadium-bismuth ternary oxide framework will not have an isothermal growth period, resulting in a large number of defects in the growth of the sodium-type lead-vanadium-bismuth ternary oxide framework. These defects cannot be repaired at high temperatures, ultimately leading to low adsorption capacity, poor selectivity, and poor cycle stability of the potassium adsorbent.

[0136] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solutions disclosed in the present invention, various modifications or variations that can be made by those skilled in the art without creative effort should be included within the scope of protection of the present invention.

Claims

1. A lead-vanadium-bismuth-based sodium-type potassium ion adsorbent, characterized in that, The general chemical formula is: Na x Pb y VBiO z -SiO2, where x, y, and z are stoichiometric coefficients satisfying 10≤x≤90, 10≤y≤30, and 29≤z≤109; this adsorbent is a layered-porous dual-structure composite inorganic oxide. The framework is a stable three-dimensional network formed by alternating VO-Bi, VO-Pb, and Bi-O-Pb covalent bonds. Sodium ions are uniformly distributed in the interlayer and pores of the framework and, as the only exchangeable ion, undergo a specific ion exchange reaction with potassium ions. Lead, vanadium, and bismuth in the framework are non-exchangeable framework metals, and SiO2 is a binder for powder granulation.

2. A method for preparing a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent, characterized in that, include: Preparation of vanadium-bismuth composite sol: Preparation of ammonium metavanadate solution as a vanadium source; Bismuth-based bismuth nitrate was dissolved in dilute nitric acid solution and ultrasonically dispersed to prepare a bismuth-based bismuth nitrate solution. A bismuth-based bismuth nitrate solution was added dropwise to a vanadium-based ammonium metavanadate solution to prepare an orange-yellow vanadium-bismuth composite sol. Co-precipitation of lead-vanadium-bismuth ternary precursors: Prepare a lead-source lead acetate-alcohol aqueous solution, add the lead-source lead acetate-alcohol aqueous solution to the vanadium-bismuth composite sol, and then add a composite precipitant to obtain a ternary lead-vanadium-bismuth hydroxide precursor slurry. After aging, centrifuge, wash the filter cake, dry, and grind to obtain lead-vanadium-bismuth ternary precursor powder. Sodium source introduction: The lead-vanadium-bismuth ternary precursor powder and sodium acetate powder are dry-mixed to obtain a mixed powder with sodium source introduced. Segmented gradient sintering crystallization: The mixed powder is sintered using a three-stage gradient heating process. After sintering, it is cooled to room temperature, ground, and sieved to obtain sodium-type lead-vanadium-bismuth ternary oxide-based potassium adsorbent powder, namely lead-vanadium-bismuth-based sodium-type potassium ion adsorbent powder.

3. The method for preparing a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent according to claim 2, characterized in that, It also includes powder granulation: lead-vanadium-bismuth-based sodium potassium ion adsorbent powder, water glass solution, deionized water, and glucose powder are added to a kneader and kneaded. Then, the blend is transferred to an extruder for extrusion molding to obtain cylindrical particles. The cylindrical particles are then transferred to a calcining furnace for calcination molding to obtain cylindrical lead-vanadium-bismuth-based sodium potassium ion adsorbent particles.

4. The method for preparing a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent according to claim 2, characterized in that, Dissolve ammonium metavanadate (vanadium source) in deionized water and stir until completely dissolved to prepare a vanadium source ammonium metavanadate solution with a concentration of 0.05-0.15 mol / L; dissolve bismuth nitrate (bismuth source) in dilute nitric acid solution with a concentration of 2.5-4.0 mol / L to prepare a bismuth nitrate solution with a concentration of 0.05-0.15 mol / L.

5. The method for preparing a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent according to claim 4, characterized in that, Bismuth nitrate solution was added dropwise to ammonium metavanadate solution, vanadium source, with the vanadium-bismuth molar ratio controlled at 1:

1. The addition process was continuously stirred and the system temperature was maintained at 75-85℃. After the addition was completed, the pH of the system was adjusted to 3.5-5.0 with 1.5-3.0 mol / L sodium hydroxide solution. The system was then continuously stirred and aged for 2-4 hours to obtain vanadium-bismuth composite sol.

6. The method for preparing a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent according to claim 2, characterized in that, Lead acetate, a lead source, is dissolved in a mixed solvent of anhydrous ethanol and deionized water in a volume ratio of (1.5-3):1 to prepare a 1-3 mol / L aqueous solution of lead acetate. This aqueous solution is then added dropwise to the vanadium-bismuth composite sol, with the lead:vanadium:bismuth molar ratio controlled at (10-30):1:

1.

7. The method for preparing a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent according to claim 2, characterized in that, Lead-vanadium-bismuth ternary precursor powder and sodium acetate powder were added to a high-speed mixer in a molar ratio of Na:Pb=(1-3):1 and dry-mixed to obtain CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3 powder, which is the mixed powder after the introduction of sodium source.

8. The method for preparing a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent according to claim 2, characterized in that, The three-stage gradient heating sintering process is as follows: The first stage is low-temperature pretreatment: heating rate is 3-5℃ / min, heating to 200-350℃, and constant temperature calcination to remove the water of crystallization and organic ligands in CH3COONa-Pb(OH)2-V(OH)3-Bi(OH)3; The second stage is medium-temperature crystallization: heating rate is 2-4℃ / min, heating to 450-700℃, and constant temperature calcination to initially form a sodium-type lead-vanadium-bismuth ternary oxide framework; The third stage is high-temperature shaping: heating rate is 1-3℃ / min, heating to 800-1000℃, and constant temperature calcination to strengthen the covalent bond connection of the framework and form a stable crystal form.

9. The method for preparing a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent according to claim 8, characterized in that, The constant temperature calcination time in the first stage of low-temperature pretreatment is 2-3 hours; the constant temperature calcination time in the second stage of medium-temperature crystallization is 4-6 hours; and the constant temperature calcination time in the third stage of high-temperature shaping is 3-5 hours.

10. The method for preparing a lead-vanadium-bismuth-based sodium-type potassium ion adsorbent according to claim 3, characterized in that, Add 200-300 kg of lead-vanadium-bismuth-based sodium potassium ion adsorbent powder, 30-50 kg of water glass solution with a modulus of 2-2.5, 10-100 kg of deionized water, and 40-80 kg of glucose powder to a kneader and knead for 3-7 hours. Transfer the blend to an extruder for extrusion molding to obtain cylindrical particles. Transfer the cylindrical particles to a calcination furnace and calcine them at a temperature of 400-600℃ to obtain cylindrical lead-vanadium-bismuth-based sodium potassium ion adsorbent particles.

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