A magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent and its preparation method

Abstract

This invention discloses a magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material and its preparation method, belonging to the field of adsorbent material preparation technology. The method first prepares a clay-based mineral polymer, then further prepares a magnetic precursor, and subsequently prepares magnetic lithium saponite. This magnetic lithium saponite is then combined with hydroxyethyl cellulose / polyvinyl alcohol through cyclic freezing and freeze-drying methods to obtain the magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material. The magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material obtained by this invention has the characteristics of high adsorption efficiency and good regeneration performance. Furthermore, the preparation process is suitable for industrial production and can be used in the field of water pollution control.

Description

Technical Field

[0001] This invention belongs to the field of adsorption material preparation technology, specifically relating to a magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorption material and its preparation method. Background Technology

[0002] With rapid industrialization, water pollution has become increasingly serious, especially the pollution of water bodies by heavy metal ions and organic pollutants, which has become a global concern. Traditional wastewater treatment methods, such as chemical precipitation, ion exchange, and membrane separation, can remove pollutants from water to some extent, but they suffer from high costs, low efficiency, and the potential for secondary pollution. Therefore, the development of efficient, environmentally friendly, and reusable adsorption materials has become a research hotspot in the field of water treatment.

[0003] Lithium saponite is a layered silicate mineral with a large specific surface area and abundant surface active sites, exhibiting excellent adsorption properties for heavy metal ions and organic pollutants. However, lithium saponite suffers from problems such as easy agglomeration and difficulty in recycling in practical applications, limiting its widespread use. Furthermore, traditional lithium saponite preparation processes generally rely on high-purity lithium salts, magnesium salts, and silicates as chemical raw materials, resulting in high raw material costs and complex synthesis routes (typically using hydrothermal synthesis methods, which lead to low yields, large waste discharges, and low synthesis efficiency due to low solid-liquid ratios in a single reactor). To overcome these drawbacks, researchers have attempted to develop low-cost lithium saponite preparation processes and have tried to combine lithium saponite with other materials to improve its dispersibility and recyclability.

[0004] Hydroxyethyl cellulose (HEC) is a water-soluble polymer compound with good biocompatibility and film-forming properties, and is often used as a thickener, stabilizer, and adhesive. Polyvinyl alcohol (PVA) is a synthetic polymer material with good mechanical properties and chemical stability, and is widely used in textiles, papermaking, and pharmaceuticals. Combining lithium saponite with HEC and PVA not only improves the dispersibility and stability of lithium saponite but also enhances the mechanical and adsorption properties of the composite material.

[0005] Magnetic composite materials have attracted widespread attention in the field of adsorption materials in recent years due to their ease of separation and recycling. By introducing magnetic nanoparticles into composite materials, rapid separation and recycling of adsorbent materials can be achieved, thereby improving material utilization and reducing processing costs. However, the preparation of magnetic adsorbent materials still faces significant challenges. For example, the self-aggregation of magnetic materials and the random distribution of functional groups (or defects) on the surface of adsorbent materials make it difficult to ensure uniform and efficient loading of magnetic materials. In addition, since the interaction between magnetic materials and adsorbent materials is mostly weak, magnetic materials are prone to detachment during the regeneration and recycling of adsorbent materials, resulting in a significant reduction in the regeneration performance of magnetic adsorbent materials. How to avoid complex magnetization material synthesis steps and cumbersome magnetic modification processes, and achieve uniform distribution of magnetic materials on the adsorption medium in a low-cost and simple manner, while simultaneously ensuring strong interfacial interactions between the two, is the key to the low-cost preparation of adsorbent materials with high adsorption performance, high separation performance, and high regeneration performance.

[0006] In conclusion, developing magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbents with high adsorption performance and easy separation and recovery is of great significance for solving water pollution problems. Summary of the Invention

[0007] To address the problems existing in the preparation of magnetic composite materials in current technologies, this invention provides a magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent and its preparation method. The method involves first preparing a fly ash-based mineral polymer and a magnetic precursor, then preparing magnetic lithium saponite, and finally combining it with hydroxyethyl cellulose / polyvinyl alcohol through cyclic freezing and freeze-drying to obtain the magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent. The magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent obtained by this invention features high adsorption efficiency and good regeneration performance. Furthermore, the preparation process is suitable for industrial production and can be used in the field of water pollution control.

[0008] This invention is achieved through the following technical solution:

[0009] A method for preparing a magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material specifically includes the following steps:

[0010] S1. Add polyvinyl alcohol to deionized water to prepare a polyvinyl alcohol solution with a mass ratio of 5%-15%. Stir the polyvinyl alcohol solution with a magnetic stir bar, and at the same time heat the polyvinyl alcohol solution in a water bath to 90°C and maintain it for 2-3 hours until the polyvinyl alcohol is completely dissolved. Then stop heating and cool the solution. The resulting solution is denoted as solution A.

[0011] S2. Add hydroxyethyl cellulose to deionized water and prepare a hydroxyethyl cellulose solution by mass ratio of hydroxyethyl cellulose to deionized water = 1-5:180. Stir the hydroxyethyl cellulose solution with a magnetic stir bar until it dissolves naturally. The resulting solution is denoted as solution B.

[0012] S3. Add magnetic lithium soapstone to solution B according to the mass ratio of deionized water to magnetic lithium soapstone = 1:0.1-0.01; stir the solution with a magnetic stirrer to fully dissolve the magnetic lithium soapstone in the solution, and the resulting solution is called solution C.

[0013] S4. Mix solution A and solution C in a mass ratio of 1:1 and stir with a stirrer under the following conditions: stirring speed of 1000-3000 rpm, stirring temperature of 25-40℃, and stirring time of 0.5-2 h. The resulting mixture is denoted as solution D.

[0014] S5. Freeze solution D at -80℃ for 12 hours. After freezing, thaw it at 20-25℃ for 12 hours. Repeat the freezing and thawing steps 3-5 times. Then freeze it at -80℃ for 3 hours. The obtained substance is denoted as substance E.

[0015] S6. Substance E is freeze-dried to obtain a magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material. The freeze-drying process conditions are: freeze-drying temperature: -80℃, freeze-drying time: 48-72h.

[0016] Furthermore, in step S3, the magnetic lithium saponite is prepared by the following method, specifically including the following steps:

[0017] A1. Mix the lithium source, magnesium source and magnetic precursor in a molar ratio of 1.0:3.0:1.7-3.0 and stir thoroughly. The resulting mixture is denoted as Mixture I.

[0018] A2. Transfer the above mixture I to a polytetrafluoroethylene hydrothermal reactor lined tank, and add 3-5 ml of ammonia solution to the bottom of the polytetrafluoroethylene hydrothermal reactor lined tank;

[0019] A3. Place the prepared polytetrafluoroethylene hydrothermal reactor liner into the stainless steel reactor, and put it in a constant temperature oven to react for 24-72 hours at a temperature of 110-200℃.

[0020] A4. After the reaction is complete, remove the inner liner of the polytetrafluoroethylene hydrothermal reactor, centrifuge and wash the solid product until it is neutral, transfer the solid product with deionized water, and freeze-dry the obtained substance. The resulting solid powder is magnetic lithium soapstone.

[0021] Furthermore, in step A1, the lithium source is one or a mixture of two of lithium fluoride, lithium carbonate, and lithium hydroxide monohydrate; the magnesium source is one or a mixture of two of magnesium chloride, magnesium carbonate, and magnesium hydroxide.

[0022] Furthermore, in step A2, the ammonia water used is concentrated ammonia water with a laboratory-labeled concentration of 25%; mixture I and the ammonia water solution are isolated by a polytetrafluoroethylene mesh, that is, during the reaction process, only the alkaline vapor formed by heating the ammonia water serves as the reaction medium.

[0023] Furthermore, in step A4, the freeze-drying conditions are: freezing temperature -80℃, freeze-drying time 1-3 days.

[0024] Furthermore, in step A1, the magnetic precursor is prepared by the following method, specifically including:

[0025] B1. Mix the fly ash base mineral polymer and magnetic material at a mass ratio of 1:0.05-1 until homogeneous. The resulting mixture is referred to as mixture II.

[0026] B2. Transfer the above mixture II to the inner liner of the polytetrafluoroethylene hydrothermal reactor, and add 3-5 ml of ammonia solution to the bottom of the inner liner of the polytetrafluoroethylene hydrothermal reactor;

[0027] B3. Place the polytetrafluoroethylene hydrothermal reactor liner prepared in step B2 into a stainless steel reactor, and place it in a constant temperature oven to react for 3-6 hours at a temperature of 150-170℃.

[0028] B4. After the reaction is complete, remove the inner liner of the polytetrafluoroethylene hydrothermal reactor and take out the solid product from the inner liner of the reactor. The resulting mixture is called mixture III.

[0029] B5. Place the mixture III obtained in step B4 into a microwave digestion vessel, and add 3-5 ml of ammonia solution to the bottom of the microwave digestion vessel;

[0030] B6. Place the assembled microwave digestion vessel into a microwave digester and irradiate it at a certain temperature under specific irradiation conditions. The irradiation conditions are: irradiation temperature 120-150℃, irradiation cycle 3-8.

[0031] B7. After the reaction is complete, remove the microwave digestion vessel after microwave irradiation, filter the solid product until it is neutral, and place it in a vacuum oven at 90°C for 12 hours. The vacuum degree of the vacuum oven is 0.07 MPa. The resulting solid powder is the magnetic precursor.

[0032] Furthermore, in step B1, the magnetic material is one or a combination of more of the following: Fe2O3, Fe3O4, FeCl2, Co3O4, CoCl2, and NiCl2.

[0033] In step B2, the ammonia water used is an ammonia solution obtained by mixing 25% concentrated ammonia water (with a laboratory label) and deionized water at a volume ratio of 1:1. The mixture II and the ammonia solution are separated by a polytetrafluoroethylene mesh, meaning that the reaction in step B3 relies solely on the alkaline vapor formed by heating the ammonia solution as the reaction medium.

[0034] In step B5, the ammonia water used is a 25% concentrated ammonia water with a laboratory-labeled concentration; the mixture III and the ammonia water solution are isolated by a polytetrafluoroethylene mesh, that is, the reaction in step B6 relies solely on the alkaline vapor formed by heating the ammonia water as the reaction medium.

[0035] In step B6, the irradiation cycle specifically consists of 100W irradiation for 10s, 150W irradiation for 10s, 200W irradiation for 10s, 250W irradiation for 10s, 300W irradiation for 10s, followed by a 10s pause.

[0036] Furthermore, in step B1, the fly ash-based mineral polymer is prepared by the following method, specifically including:

[0037] C1. After selecting fly ash for flotation and impurity removal, grind it into powder and sieve it through an 80-mesh sieve to obtain refined fly ash powder.

[0038] C2. The refined fly ash and acid solution are loaded into a microwave digestion vessel at a certain solid-liquid ratio. The mass-volume ratio of the refined fly ash to the acid solution is in the range of 1:2.5-5 g / ml.

[0039] C3. Place the microwave digestion vessel prepared in step C2 into a microwave digester and irradiate it at a certain temperature under specific irradiation conditions, specifically an irradiation temperature of 150-200 ℃ and an irradiation cycle of 30-60 cycles.

[0040] C4. Remove the microwave digestion vessel after microwave irradiation, filter the solid product until it is neutral, and place it in a constant temperature oven at 80-90℃ for 12 hours to dry. The resulting solid powder is the fly ash base mineral polymer.

[0041] In step C2, the acid solution is hydrochloric acid with a concentration of 2-4 mol / L;

[0042] In step C2, the refined fly ash and the acid solution are separated by a polytetrafluoroethylene mesh, meaning that during microwave irradiation, the acid solution is heated to form acidic vapor as the reaction medium.

[0043] In step C3, the irradiation cycle specifically consists of 200W irradiation for 10s, 230W irradiation for 10s, 270W irradiation for 10s, 330W irradiation for 10s, 350W irradiation for 10s, followed by a 10s pause.

[0044] Compared with the prior art, the advantages of the present invention are as follows:

[0045] 1. Excellent Adsorption Performance and Regeneration Capacity: The material used in this invention combines the adsorption properties of three adsorbents: magnetic lithium saponite, hydroxyethyl cellulose, and polyvinyl alcohol. Magnetic lithium saponite not only provides a certain adsorption capacity but also acts as a spatial crosslinking point for hydroxyethyl cellulose and polyvinyl alcohol, giving the composite material a complex spatial network. This not only increases the specific surface area of ​​the material but also provides more active sites. Furthermore, the addition of magnetic lithium saponite endows the material with higher regeneration capacity, making it more advantageous in the adsorption field.

[0046] 2. In the preparation of magnetic lithium saponite, fly ash-based mineral polymers produced by acid hydrolysis of fly ash are used as synthetic raw materials. This mitigates the upstream pollution problem caused by the use of silicon-containing chemicals (such as silica gel) to a certain extent, and also reduces the synthesis cost of lithium saponite. Secondly, for the process of obtaining fly ash-based mineral polymers, this invention adopts a superimposed composite process of a solid-phase method and a microwave progressive irradiation method. This allows low-concentration acid solutions to achieve the effects of high-concentration acid solutions, effectively improving the utilization efficiency of the acid solution. Furthermore, it allows for multiple recycling by appropriately adding small amounts of acid solution. In addition, it ensures that the acid solution contains a large number of high-value elements, such as aluminum. On the other hand, direct microwave irradiation of fly ash, due to the different microwave absorption characteristics of different chemical bonds, promotes their direct activation and leads to uniformity in the activation and breakage of chemical bonds. These broken chemical bonds can better and more firmly and uniformly bind with magnetic particles through chemical interactions.

[0047] 3. In the process of preparing the magnetic precursor, a solid-phase preparation method and a microwave progressive irradiation screening method are adopted. This process minimizes the influence of the synthesis process on the magnetic properties of the magnetic particles, while using microwave irradiation technology to quickly screen the chemical loading behavior between the magnetic particles and the polymers from fly ash base minerals.

[0048] 4. In the process of preparing magnetic lithium saponite, the combination of solid-phase preparation method and freeze-drying process not only eliminates the various inconveniences of hydrothermal synthesis of lithium saponite, but also significantly reduces the loss of magnetic particles, thus maximizing the efficiency of magnetic lithium saponite preparation. Attached Figure Description

[0049] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0050] Figure 1 XRD pattern of fly ash-based active silicon source for Case 1;

[0051] Figure 2 XRD pattern of the magnetic precursor in Case 1;

[0052] Figure 3 XRD patterns of magnetic lithium saponite from Case 1-3;

[0053] Figure 4 The image shows the physical product obtained in Case 1 after it has absorbed water. Detailed Implementation

[0054] To clearly and completely describe the technical solution and its specific working process of the present invention, the specific embodiments of the present invention are as follows, in conjunction with the accompanying drawings:

[0055] Example 1

[0056] This embodiment provides a method for preparing a magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material, the specific steps of which are as follows:

[0057] S1. Add polyvinyl alcohol to deionized water to prepare a 5% polyvinyl alcohol solution by mass. Stir the polyvinyl alcohol solution with a magnetic stir bar, and heat the polyvinyl alcohol solution in a water bath to 90°C and maintain it for 2 hours until the polyvinyl alcohol is completely dissolved. Then stop heating and cool the solution. The resulting solution is denoted as solution A.

[0058] S2. Add hydroxyethyl cellulose to deionized water at a mass ratio of hydroxyethyl cellulose:deionized water = 1:180 to prepare a hydroxyethyl cellulose solution. Stir the hydroxyethyl cellulose solution with a magnetic stir bar until it dissolves naturally. The resulting solution is denoted as solution B.

[0059] S3. Add magnetic lithium soapstone to solution B according to the mass ratio of deionized water to magnetic lithium soapstone of 1:0.1. Stir the solution with a magnetic stirrer until the magnetic lithium soapstone is fully dissolved. The resulting solution is denoted as solution C.

[0060] S4. Mix solution A and solution C in a mass ratio of 1:1 and stir with a stirrer under the following conditions: stirring speed of 1000 rpm, stirring temperature of 25℃, and stirring time of 2 h. The resulting mixture is denoted as solution D.

[0061] S5. Freeze solution D at -80℃ for 12 hours. After freezing, thaw it at 20℃ for 12 hours. Repeat the freezing and thawing steps 5 times. Freeze it at -80℃ for 3 hours. The obtained substance is denoted as substance E.

[0062] S6. Substance E is freeze-dried to obtain the magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material. The freeze-drying process conditions are: freeze-drying temperature: -80℃, freeze-drying time: 48h.

[0063] In this embodiment, in step S3, the magnetic lithium saponite is prepared by the following method, specifically including the following steps:

[0064] A1. Mix the lithium source, magnesium source, and magnetic precursor in a molar ratio of 1.0:3.0:3.0 and stir thoroughly. The resulting mixture is referred to as Mixture I.

[0065] A2. Transfer the above mixture I to a 100 ml polytetrafluoroethylene hydrothermal reactor liner, and add 3 ml of ammonia solution to the bottom of the polytetrafluoroethylene hydrothermal reactor.

[0066] A3. Place the polytetrafluoroethylene hydrothermal reactor liner prepared in step A2 into the stainless steel reactor, and place it in a constant temperature oven at 200℃ for 24 hours.

[0067] A4. After the reaction is complete, remove the inner liner of the polytetrafluoroethylene hydrothermal reactor, centrifuge and wash the solid product until neutral, then transfer the solid product with deionized water, and freeze-dry the resulting substance to obtain a solid powder, which is magnetic lithium soapstone.

[0068] In this embodiment, in step A1, the lithium source is lithium hydroxide monohydrate; the magnesium source is magnesium hydroxide.

[0069] In this embodiment, the ammonia water used in step A2 is a concentrated ammonia water with a laboratory-labeled concentration of 25%; the mixture I and the ammonia water solution are isolated by a polytetrafluoroethylene mesh, that is, during the reaction process, only the alkaline vapor formed by heating the ammonia water is used as the reaction medium.

[0070] In this embodiment, in step A4, the freeze-drying conditions are: freezing temperature -80℃, and freeze-drying time is 1 day.

[0071] In this embodiment, in step A1, the magnetic precursor is prepared by the following method, specifically including:

[0072] B1. Mix the fly ash base mineral polymer and magnetic material at a mass ratio of 1:0.05 until homogeneous. The resulting mixture is referred to as mixture II.

[0073] B2. Transfer the above mixture II to a 100 ml polytetrafluoroethylene hydrothermal reactor liner, and add 3 ml of ammonia solution to the bottom of the polytetrafluoroethylene hydrothermal reactor liner;

[0074] B3. Place the polytetrafluoroethylene hydrothermal reactor liner prepared in step B2 into the stainless steel reactor, and place it in a constant temperature oven at 170℃ for 3 hours.

[0075] B4. After the reaction is complete, remove the inner liner of the polytetrafluoroethylene hydrothermal reactor and take out the solid product from the inner liner of the reactor. The resulting mixture is called mixture III.

[0076] B5. Place the mixture III obtained in step B4 into a microwave digestion vessel, and add 3 ml of ammonia solution to the bottom of the microwave digestion vessel;

[0077] B6. Place the assembled microwave digestion vessel into a microwave digester and irradiate it at a certain temperature under specific irradiation conditions, specifically an irradiation temperature of 150 ℃ and an irradiation cycle of 8.

[0078] B7. After the reaction is complete, remove the microwave digestion vessel after microwave irradiation, filter the solid product until it is neutral, and place it in a vacuum oven at 90°C for 12 hours (vacuum degree is 0.07MPa). The resulting solid powder is the magnetic precursor.

[0079] In this embodiment, the ammonia water used in step B2 is an ammonia solution obtained by mixing concentrated ammonia water with a laboratory-labeled concentration of 25% and deionized water at a volume ratio of 1:1; the mixture II and the ammonia solution are isolated by a polytetrafluoroethylene mesh, that is, the reaction in step B3 relies solely on the alkaline vapor formed by heating the ammonia solution as the reaction medium.

[0080] In this embodiment, the ammonia water used in step B5 is a 25% concentrated ammonia water with a laboratory-labeled concentration; the mixture III and the ammonia water solution are isolated by a polytetrafluoroethylene mesh, that is, the reaction in step B6 relies solely on the alkaline vapor formed by heating the ammonia water as the reaction medium.

[0081] In this embodiment, the irradiation cycle mentioned in step B6 is specifically 100W irradiation for 10s, 150W irradiation for 10s, 200W irradiation for 10s, 250W irradiation for 10s, 300W irradiation for 10s, and then a 10s pause.

[0082] In this embodiment, FeCl2 is selected as the magnetic material in step B1.

[0083] In this embodiment, in step B1, the fly ash base mineral polymer is prepared by the following method, specifically including:

[0084] C1. After selecting fly ash for flotation and impurity removal, grind it into powder, and then sieve it through an 80-mesh sieve to obtain refined fly ash powder.

[0085] C2. The refined fly ash and acid solution are loaded into a microwave digestion vessel at a certain solid-liquid ratio, the ratio range being refined fly ash: acid solution = 1:5g / ml;

[0086] C3. Place the microwave digestion vessel prepared in step C2 into a microwave digester and irradiate it at a certain temperature under specific irradiation conditions, specifically an irradiation temperature of 200 ℃ and an irradiation cycle of 30 cycles.

[0087] C4. After microwave irradiation, remove the microwave digestion vessel, filter the solid product until it is neutral, and place it in a constant temperature oven at 80°C for 12 hours to dry. The resulting solid powder is the fly ash base mineral polymer.

[0088] In this embodiment, in step C2, the acid solution is hydrochloric acid with a concentration of 2 mol / L;

[0089] In step C2, the fly ash and acid are separated by a polytetrafluoroethylene mesh, meaning that during microwave irradiation, only the acid vapor formed by the heating of the acid serves as the reaction medium.

[0090] In step C3, the irradiation cycle specifically consists of 200W irradiation for 10s, 230W irradiation for 10s, 270W irradiation for 10s, 330W irradiation for 10s, 350W irradiation for 10s, followed by a 10s pause.

[0091] from Figure 1 As can be seen, the polymer in fly ash base minerals exhibits an amorphous structure, indicating that its inherent crystal structure has been completely depolymerized.

[0092] from Figure 2 As can be seen from the diffraction peaks, it can be determined that the magnetic particles have been combined with the fly ash base mineral polymer.

[0093] from Figure 3 As can be seen from the diffraction peaks, the lithium saponite used in Examples 1-3 can be identified as magnetic lithium saponite.

[0094] Figure 4 The image shows the composite material obtained in Case 1 after it has absorbed water.

[0095] Example 2 is the same as Example 1 except that, in the preparation of solution A, the mass ratio of the polyethylene solution is 15% and the water bath heating time is 3 hours; in the preparation of solution B, the mass ratio of hydroxyethyl cellulose to deionized water is 5:180; in the preparation of solution C, the mass ratio of deionized water to magnetic lithium saponite is 1:0.01; the stirring conditions for solution D are: stirring speed of 3000 rpm, stirring temperature of 40°C, and stirring time of 0.5 hours; in the process of obtaining substance E, after solution D is frozen, it is placed in an environment at 25°C, and the above freezing and thawing steps are repeated 3 times; in step S6, the freeze-drying process conditions are: freeze-drying temperature: -80°C, freeze-drying time: 72 hours.

[0096] Example 3 is the same as Example 1 except that in the preparation steps of magnetic lithium saponite, the lithium source, magnesium source, and magnetic precursor are in a molar ratio of 1.0:3.0:1.7; in step A2, 5 ml of ammonia solution is added to the bottom of the polytetrafluoroethylene hydrothermal reaction vessel; in step A3, the reaction temperature is 110°C and the reaction time is 72 h; in step A1, the lithium source is lithium carbonate and the magnesium source is magnesium hydroxide; in step A4, the freeze-drying conditions are: freezing temperature -80°C and freeze-drying time is 3 days.

[0097] Example 4 is the same as Example 1 except that, in step B1, the fly ash base mineral polymer and magnetic material are mixed at a mass ratio of 1:0.05; in step B2, 5 ml of ammonia solution is added to the bottom of the PTFE hydrothermal reactor liner; in step B3, the reaction temperature is 150°C and the reaction time is 6 h; in step B5, 5 ml of ammonia solution is added to the bottom of the PTFE hydrothermal reactor liner; and in step B6, the irradiation temperature is 150°C and the irradiation cycle is 3 times.

[0098] Example 5 is the same as Example 1 except that the magnetic material Fe3O4 is used.

[0099] Example 6 is the same as Example 1 except that in step C2, the ratio of refined fly ash to acid solution is 1:2.5 g / ml; in step C3, the irradiation temperature is 150 ℃ and the irradiation cycle is 60 cycles; in step C4, the solid product is filtered until neutral and placed in a constant temperature oven at 90 ℃ for 12 h to dry; and in step C2, the acid solution used is hydrochloric acid with a concentration of 4 mol / L.

[0100] Experimental data

[0101] Table 1 shows the test results of the first adsorption performance and the adsorption performance after 9 regenerations of the magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent materials in Implementation Cases 1-8.

[0102] serial number Adsorption efficiency (first time) Adsorption efficiency (tenth time) Implementation Case 1 99% 94% Implementation Case 2 98% 92% Implementation Case 3 98% 93% Implementation Case 4 99% 92% Implementation Case 5 97% 91% Implementation Case 6 98% 93%

[0103] Adsorption experiment

[0104] Each time, a certain mass of magnetic lithium soapstone / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material (0.2 g) was weighed and placed into an Erlenmeyer flask, and a certain volume of lead ion-containing solution (100 mL) was added. The mixture was shaken at 30℃ for 2 h. After adsorption, the supernatant was collected and centrifuged at 8000 r / min for 15 min. The concentration of heavy metal ions in the wastewater before and after adsorption was determined by X-ray fluorescence diffraction (initial concentration C0 was 1000.0 mg·L¹, C...). t (where R is the concentration of heavy metal ions in the solution after adsorption), and then calculate the removal rate (R,%) of heavy metal ions using the following formula.

[0105]

[0106] The adsorbed material after adsorption is collected under the action of an external magnetic field, and then a regeneration adsorption experiment is carried out. Before each regeneration adsorption, it needs to be ultrasonically treated at room temperature (20-30℃) (the ultrasonic frequency used is 40KHz, and the ultrasonic time is 15min). After ultrasonic treatment, the adsorption experiment is carried out.

[0107] As can be seen from the adsorption results of lead ions in Table 1, the prepared magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material has excellent adsorption and regeneration performance.

[0108] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0109] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0110] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent, characterized in that, Specifically, the following steps are included: S1. Add polyvinyl alcohol to deionized water to prepare a polyvinyl alcohol solution with a mass ratio of 5%-15%. Stir the polyvinyl alcohol solution with a magnetic stir bar, and at the same time heat the polyvinyl alcohol solution in a water bath to 90°C and maintain it for 2-3 hours until the polyvinyl alcohol is completely dissolved. Then stop heating and cool the solution. The resulting solution is denoted as solution A. S2. Add hydroxyethyl cellulose to deionized water and prepare a hydroxyethyl cellulose solution by mass ratio of hydroxyethyl cellulose to deionized water = 1-5:

180. Stir the hydroxyethyl cellulose solution with a magnetic stir bar until it dissolves naturally. The resulting solution is denoted as solution B. S3. Add magnetic lithium soapstone to solution B according to the mass ratio of deionized water to magnetic lithium soapstone = 1:0.1-0.01; stir the solution with a magnetic stirrer to fully dissolve the magnetic lithium soapstone in the solution, and the resulting solution is called solution C. S4. Mix solution A and solution C in a mass ratio of 1:1 and stir with a stirrer under the following conditions: stirring speed of 1000-3000 rpm, stirring temperature of 25-40℃, and stirring time of 0.5-2 h. The resulting mixture is denoted as solution D. S5. Freeze solution D at -80℃ for 12 hours. After freezing, thaw it at 20-25℃ for 12 hours. Repeat the freezing and thawing steps 3-5 times. Then freeze it at -80℃ for 3 hours. The obtained substance is denoted as substance E. S6. Substance E is freeze-dried to obtain a magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material. The freeze-drying process conditions are: freeze-drying temperature: -80℃, freeze-drying time: 48-72h. In step S3, the magnetic lithium saponite is prepared by the following method, specifically including the following steps: A1. Mix the lithium source, magnesium source and magnetic precursor in a molar ratio of 1.0:3.0:1.7-3.0 and stir thoroughly. The resulting mixture is denoted as Mixture I. A2. Transfer the above mixture I to the inner liner of the polytetrafluoroethylene hydrothermal reactor, and add 3-5 ml of ammonia solution to the bottom of the inner liner of the polytetrafluoroethylene hydrothermal reactor; A3. Place the prepared polytetrafluoroethylene hydrothermal reactor liner into the stainless steel reactor, and put it in a constant temperature oven to react for 24-72 hours at a temperature of 110-200℃. A4. After the reaction is complete, remove the inner liner of the polytetrafluoroethylene hydrothermal reactor, centrifuge and wash the solid product until it is neutral, transfer the solid product with deionized water, and freeze-dry the obtained substance. The resulting solid powder is magnetic lithium soapstone. In step A1, the magnetic precursor is prepared by the following method, specifically including: B1. Mix the fly ash base mineral polymer and magnetic material at a mass ratio of 1:0.05-1 until homogeneous. The resulting mixture is referred to as mixture II. B2. Transfer the above mixture II to the inner liner of the polytetrafluoroethylene hydrothermal reactor, and add 3-5 ml of ammonia solution to the bottom of the inner liner of the polytetrafluoroethylene hydrothermal reactor; B3. Place the polytetrafluoroethylene hydrothermal reactor liner prepared in step B2 into a stainless steel reactor, and place it in a constant temperature oven to react for 3-6 hours at a temperature of 150-170℃. B4. After the reaction is complete, remove the inner liner of the polytetrafluoroethylene hydrothermal reactor and take out the solid product from the inner liner of the reactor. The resulting mixture is called mixture III. B5. Place the mixture III obtained in step B4 into a microwave digestion vessel, and add 3-5 ml of ammonia solution to the bottom of the microwave digestion vessel; B6. Place the assembled microwave digestion vessel into a microwave digester and irradiate it at a certain temperature under specific irradiation conditions. The irradiation conditions are: irradiation temperature 120-150℃, irradiation cycle 3-8. B7. After the reaction is complete, remove the microwave digestion vessel after microwave irradiation, filter the solid product until it is neutral, and place it in a vacuum oven at 90°C for 12 hours. The vacuum degree of the vacuum oven is 0.07 MPa. The resulting solid powder is the magnetic precursor.

2. The preparation method of the magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material as described in claim 1, characterized in that, In step A1, the lithium source is one or a mixture of two of lithium fluoride, lithium carbonate, and lithium hydroxide monohydrate; the magnesium source is one or a mixture of two of magnesium chloride, magnesium carbonate, and magnesium hydroxide.

3. The preparation method of the magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material as described in claim 1, characterized in that, In step A2, the ammonia water used is a 25% concentrated ammonia water with a laboratory-labeled concentration; the mixture I and the ammonia water solution are isolated by a polytetrafluoroethylene mesh, that is, during the reaction process, only the alkaline vapor formed by heating the ammonia water is used as the reaction medium.

4. The preparation method of the magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material as described in claim 1, characterized in that, In step A4, the freeze-drying conditions are: freezing temperature -80℃, freeze-drying time 1-3 days.

5. The preparation method of the magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material as described in claim 1, characterized in that, In step B1, the magnetic material is one or a combination of more of Fe2O3, Fe3O4, and Co3O4; In step B2, the ammonia water used is an ammonia solution obtained by mixing 25% concentrated ammonia water (with a laboratory label) and deionized water at a volume ratio of 1:

1. The mixture II and the ammonia solution are separated by a polytetrafluoroethylene mesh, meaning that the reaction in step B3 relies solely on the alkaline vapor formed by heating the ammonia solution as the reaction medium. In step B5, the ammonia water used is a 25% concentrated ammonia water with a laboratory-labeled concentration; the mixture III and the ammonia water solution are isolated by a polytetrafluoroethylene mesh, that is, the reaction in step B6 relies solely on the alkaline vapor formed by heating the ammonia water as the reaction medium. In step B6, the irradiation cycle specifically consists of 100W irradiation for 10s, 150W irradiation for 10s, 200W irradiation for 10s, 250W irradiation for 10s, 300W irradiation for 10s, followed by a 10s pause.

6. The preparation method of the magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material as described in claim 1, characterized in that, In step B1, the fly ash-based mineral polymer is prepared by the following method, specifically including: C1. After selecting fly ash for flotation to remove impurities, grind it into powder, and then sieve it through an 80-mesh sieve to obtain refined fly ash powder. C2. The refined fly ash and acid solution are loaded into a microwave digestion vessel at a certain solid-liquid ratio. The mass-volume ratio of the refined fly ash to the acid solution is in the range of 1:2.5-5 g / ml. C3. Place the microwave digestion vessel prepared in step C2 into a microwave digester and irradiate it at a certain temperature under specific irradiation conditions, specifically an irradiation temperature of 150-200 ℃ and an irradiation cycle of 30-60 cycles. C4. Remove the microwave digestion vessel after microwave irradiation, filter the solid product until it is neutral, and place it in a constant temperature oven at 80-90℃ for 12 hours to dry. The resulting solid powder is the fly ash base mineral polymer.

7. The preparation method of the magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material as described in claim 6, characterized in that, In step C2, the acid solution is hydrochloric acid with a concentration of 2-4 mol / L; In step C2, the refined fly ash and the acid solution are isolated by a polytetrafluoroethylene mesh, meaning that during microwave irradiation, the acid solution is heated to form acidic vapor as the reaction medium. In step C3, the irradiation cycle specifically consists of 200W irradiation for 10s, 230W irradiation for 10s, 270W irradiation for 10s, 330W irradiation for 10s, 350W irradiation for 10s, followed by a 10s pause.

8. A magnetic lithium saponite / hydroxyethyl cellulose / polyvinyl alcohol composite adsorbent material, characterized in that, Prepared by the method described in any one of claims 1-7.

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