Composite adsorption materials, their preparation methods, and applications

Abstract

This disclosure discloses a method for preparing a composite adsorbent material, comprising: mixing and melting a poly(ammonia) oxime with heavy metal ion adsorption properties with a first plasticizer and a first pore-forming agent at a first temperature to obtain a first surface layer melt; melting a polymer film material at a second temperature to obtain an intermediate layer melt; mixing and melting a poly(ammonia) oxime with heavy metal ion adsorption properties with a second plasticizer and a second pore-forming agent at a third temperature to obtain a second surface layer melt; and subjecting the first surface layer melt, the intermediate layer melt, and the second surface layer melt to a co-extrusion casting or co-extrusion blown film process to achieve a tight bond between the first surface layer melt, the intermediate layer melt, and the second surface layer melt, thereby obtaining a composite adsorbent material. This disclosure also discloses a composite adsorbent material prepared based on the aforementioned method and its application.

Description

Technical Field

[0001] This disclosure relates to the field of functional adsorption materials technology, and more specifically, to a composite adsorption material, its preparation method, and its application. Background Technology

[0002] The ocean is a vast reservoir of uranium, with seawater containing up to 4.5 billion tons of uranium. However, due to the sheer volume of seawater and its extremely low uranium concentration, effectively enriching uranium resources from seawater would be a crucial supplement and guarantee for a stable fuel supply for nuclear power. The performance and mass production of adsorbent materials for seawater uranium extraction are key factors determining its economic viability. Therefore, researching and developing high-performance adsorbent materials for seawater uranium extraction and their engineered preparation are essential technological prerequisites for improving the economics of seawater uranium extraction and achieving industrialization.

[0003] In related technologies, due to the ability of the metallo-oxime group (H₂N-C=N-OH) to chelate uranyl ions in seawater, functional polymers modified with metallo-oxime groups are considered superior adsorbents for uranium extraction from seawater. Currently, the main method for preparing metallo-oxime-modified functional polymers is electrospinning. Although continuous preparation is possible, the process itself is limited by factors such as the porosity, size uniformity, and collection thickness of the micro / nanofibers, and the associated safety hazards posed by the high-voltage electrostatic field used in production. Therefore, electrospinning is difficult to use for large-scale engineering preparation of adsorbent materials. Another related technology involves the metallo-oxime gel method for preparing polymer adsorbents. While this method offers superior adsorption performance, the preparation process is relatively complex and difficult to scale up for engineering production. Summary of the Invention

[0004] In view of this, in order to solve at least one technical problem mentioned above and in other aspects of the related art, this disclosure proposes a composite adsorbent material, its preparation method, and its application. By using co-extrusion casting or co-extrusion blown film processes, the complex processes of electrospinning and gel technology in the prior art are overcome, achieving one-time molding of the composite adsorbent material, which is beneficial for large-scale industrial production.

[0005] In one aspect of this disclosure, a method for preparing a composite adsorbent material is proposed, comprising: mixing and melting a poly(ammonia) oxime with heavy metal ion adsorption properties with a first plasticizer and a first pore-forming agent at a first temperature to obtain a first surface layer melt; melting a polymer film material at a second temperature to obtain an intermediate layer melt; mixing and melting a poly(ammonia) oxime with heavy metal ion adsorption properties with a second plasticizer and a second pore-forming agent at a third temperature to obtain a second surface layer melt; and subjecting the first surface layer melt, the intermediate layer melt, and the second surface layer melt to a co-extrusion casting or co-extrusion blown film process, so that the first surface layer melt, the intermediate layer melt, and the second surface layer melt are closely bonded together to obtain a composite adsorbent material.

[0006] According to embodiments of this disclosure, the first plasticizer includes one or more of glycerol, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, or polyacrylamide; the first pore-forming agent includes one or more of lithium carbonate, lithium chloride, ammonium bicarbonate, polyethylene glycol, polyvinyl alcohol, or polyvinylpyrrolidone; in the first surface layer melt, the mass ratio of poly(dimethylamine oxime), the first plasticizer, and the first pore-forming agent is (1-10):1:(0.05-0.8). The second plasticizer includes one or more of glycerol, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, or polyacrylamide; the second pore-forming agent includes one or more of lithium carbonate, lithium chloride, ammonium bicarbonate, polyethylene glycol, polyvinyl alcohol, or polyvinylpyrrolidone; in the second surface layer melt, the mass ratio of poly(dimethylamine oxime), the second plasticizer, and the second pore-forming agent is (1-10):1:(0.05-0.8).

[0007] According to embodiments of this disclosure, the composition of the first surface layer melt and the second surface layer melt may be the same or different.

[0008] According to embodiments of this disclosure, the intermediate layer melt includes at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyamide. Preferably, the intermediate layer melt in the co-extrusion blown film process includes polyethylene and / or polypropylene.

[0009] According to embodiments of this disclosure, the first temperature range is 160–300°C, preferably 170–300°C in the co-extrusion casting process. The second temperature range includes 150–300°C, preferably 180–300°C in the co-extrusion casting process. The third temperature range is 160–300°C, preferably 180–300°C in the co-extrusion casting process.

[0010] According to embodiments of this disclosure, in the co-extrusion blown film process, the screw speed range includes 10 to 200 r / min, the traction rate range includes 2 to 10 m / min, and the blow-up ratio range includes 1 to 8; in the co-extrusion casting process, the screw speed range includes 5 to 150 r / min, the traction rate range includes 10 to 100 m / min, and the cooling roller cooling temperature range includes 5 to 30°C.

[0011] According to the embodiments of this disclosure, the above-mentioned method for preparing composite adsorbent materials further includes stretching, cooling, and heat-setting the composite adsorbent material to improve its adsorption performance and mechanical properties. The cooling temperature range is 10–30°C, the heat-setting temperature is 110–310°C, and the cooling time range is 15–60 min.

[0012] In another aspect of this disclosure, a composite adsorbent material prepared by the above method is proposed, comprising: a first surface layer and a second surface layer having heavy metal ion adsorption properties, and an intermediate layer. The intermediate layer supports the first and second surface layers and improves the mechanical properties and service life of the composite adsorbent material.

[0013] According to embodiments of this disclosure, the thickness of the composite adsorbent material ranges from 200 to 500 μm; the thickness of the first surface layer ranges from 50 to 150 μm; the thickness of the intermediate layer ranges from 100 to 200 μm; and the thickness of the second surface layer ranges from 50 to 150 μm.

[0014] In another aspect of this disclosure, a method for uranium extraction from seawater is proposed, wherein a composite adsorbent material prepared by the above method forms a chelate with uranium in seawater.

[0015] According to embodiments of this disclosure, a surface layer material with adsorption properties is prepared by melt-blending poly(amine oxime) with heavy metal ion adsorption capabilities with a plasticizer and a pore-forming agent. A polymer film material is used as the intermediate layer support material, and the surface layer and intermediate layer are composited through co-extrusion casting or co-extrusion blown film processes to obtain a composite material with heavy metal ion adsorption capabilities. On the one hand, the intermediate layer material improves the mechanical properties of the composite material, ensuring its service life; on the other hand, the co-extrusion casting or co-extrusion blown film process enables one-time molding of the composite adsorption material, which is beneficial for large-scale industrial production. Attached Figure Description

[0016] Figure 1 This is a flowchart of the preparation method of the composite adsorbent material in this disclosure. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0018] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this disclosure.

[0019] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0020] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0021] It should be noted that, unless otherwise defined, the technical or scientific terms used in this disclosure should have the ordinary meaning understood by a person with ordinary skill in the art to which this disclosure pertains. Where the terms "first," "second," etc., are used throughout, they are used only to distinguish similar objects and should not be construed as indicating or implying their relative importance, order of precedence, or implicitly specifying the number of technical features indicated. It should be understood that the data described by "first," "second," etc., can be interchanged where appropriate.

[0022] In the embodiments of this disclosure, on the one hand, the polyamine oxime is obtained by ammonium oxime treatment of polyacrylonitrile material, which effectively avoids the damage to the polymer film material caused by irradiation and grafting, thereby reducing the mechanical properties and service life of the composite material; on the other hand, the complex coating process and harsh and dangerous electric field conditions are avoided by co-extrusion blown film process and / or co-extrusion casting process.

[0023] Figure 1 This is a flowchart of the preparation method of the composite adsorbent material in this disclosure.

[0024] In one aspect of this disclosure, a method for preparing a composite adsorbent material is proposed, such as... Figure 1 As shown, the main steps include S1 to S4, wherein steps S1 to S3 do not have a strict sequential requirement.

[0025] S1, poly(amine oxime) with heavy metal ion adsorption properties is mixed and melted with a first plasticizer and a first pore-forming agent at a first temperature to obtain a first surface layer melt.

[0026] S2, the polymer film material is melted at a second temperature to obtain the intermediate layer melt.

[0027] S3, poly(ammonia oxime) with heavy metal ion adsorption properties is mixed and melted with a second plasticizer and a second pore-forming agent at a third temperature to obtain a second surface layer melt.

[0028] S4, the first surface layer melt, the intermediate layer melt, and the second surface layer melt are co-extruded or co-extruded blown film, so that the first surface layer melt, the intermediate layer melt, and the second surface layer melt are closely bonded together to obtain a composite adsorbent material.

[0029] According to embodiments of this disclosure, a surface layer material with adsorption properties is prepared by melt-blending poly(amine oxime) with heavy metal ion adsorption capabilities with a plasticizer and a pore-forming agent. A polymer film material is used as the intermediate layer support material, and the surface layer and intermediate layer are composited through co-extrusion casting or co-extrusion blown film processes to obtain a composite material with heavy metal ion adsorption capabilities. On the one hand, the intermediate layer material improves the mechanical properties of the composite material, ensuring its service life; on the other hand, the co-extrusion casting or co-extrusion blown film process enables one-time molding of the composite adsorption material, which is beneficial for large-scale industrial production.

[0030] According to embodiments of this disclosure, the first plasticizer includes one or more of glycerol, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, or polyacrylamide; the first pore-forming agent includes one or more of lithium carbonate, lithium chloride, ammonium bicarbonate, polyethylene glycol, polyvinyl alcohol, or polyvinylpyrrolidone.

[0031] In the first surface layer melt, the mass ratio of poly(amine oxime), the first plasticizer and the first pore-forming agent is (1-10):1:(0.05-0.8), for example, 10:1:0.8, 1:1:0.05, 5:1:0.4, 3:1:0.1, 8:1:0.6, etc.

[0032] The second plasticizer includes one or more of glycerol, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, or polyacrylamide; the second pore-forming agent includes one or more of lithium carbonate, lithium chloride, ammonium bicarbonate, polyethylene glycol, polyvinyl alcohol, or polyvinylpyrrolidone.

[0033] In the second surface layer melt, the mass ratio of poly(amine oxime), the second plasticizer and the second pore-forming agent is (1-10):1:(0.05-0.8), for example, 10:1:0.8, 1:1:0.05, 5:1:0.4, 3:1:0.1, 8:1:0.6, etc.

[0034] According to embodiments of this disclosure, a first plasticizer and a second plasticizer are used to reduce the processing temperature of poly(xylene oxime), prevent the high-temperature decomposition of poly(xylene oxime), and increase its plasticity. A first pore-forming agent and a second pore-forming agent are used to increase the specific surface area of ​​poly(xylene oxime) to expose more adsorption and binding active sites.

[0035] According to embodiments of this disclosure, the composition of the first surface layer melt and the second surface layer melt may be the same or different.

[0036] According to embodiments of this disclosure, the specific composition and ratio of the first surface layer melt and the second surface layer melt are adapted to meet the requirements of actual applications for adsorption performance or mechanical performance.

[0037] According to embodiments of this disclosure, the intermediate layer melt includes at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyamide.

[0038] According to embodiments of this disclosure, the use of polymer materials for the intermediate layer improves the mechanical properties of the composite material, such as ductility and toughness.

[0039] According to embodiments of this disclosure, the first temperature range is 160–300°C, for example, 160°C, 200°C, 220°C, 250°C, 280°C, 300°C, etc. Preferably, the first temperature range in the co-extrusion casting process is 170–300°C, for example, 170°C, 200°C, 230°C, 260°C, 280°C, 300°C, etc. The second temperature range includes 150–300°C, for example, 150°C, 190°C, 220°C, 250°C, 280°C, 300°C, etc. Preferably, the second temperature range in the co-extrusion casting process is 180–300°C, for example, 180°C, 200°C, 230°C, 260°C, 280°C, 300°C, etc. The third temperature range is 160 to 300°C, for example, 160°C, 200°C, 220°C, 250°C, 280°C, 300°C, etc. Preferably, the third temperature range in the co-extrusion casting process is 180 to 300°C, for example, 180°C, 200°C, 230°C, 260°C, 280°C, 300°C, etc.

[0040] According to embodiments of this disclosure, the screw speed range in the co-extrusion blown film process includes 10 to 200 r / min, for example, 10 r / min, 50 r / min, 80 r / min, 100 r / min, 150 r / min, 200 r / min, etc.; the traction speed range includes 2 to 10 m / min, for example, 2 m / min, 4 m / min, 5.5 m / min, 7 m / min, 10 m / min, etc.; the blow-up ratio range includes 1 to 8, for example, 1, 3, 4.5, 5, 6.8, 8, etc.

[0041] In the co-extrusion casting process, the screw speed range includes 5 to 150 r / min, such as 5 r / min, 10 r / min, 50 r / min, 100 r / min, 125 r / min, 140 r / min, 50 r / min, etc.; the traction speed range includes 10 to 50 r / min, such as 10 r / min, 15 r / min, 25 r / min, 30 r / min, 50 r / min, etc.; and the cooling roller cooling temperature range includes 5 to 30℃, such as 5℃, 8℃, 10℃, 18℃, 20℃, 25℃, 30℃, etc.

[0042] According to the embodiments of this disclosure, the inventors have verified through extensive experimental testing that the preparation conditions of the co-extrusion blown film process and the co-extrusion casting process balance the adsorption performance and mechanical properties of the composite adsorbent material within this range, thereby maximizing its performance.

[0043] According to embodiments of this disclosure, the above-described method for preparing composite adsorbent materials, such as... Figure 1 As shown, it also includes:

[0044] Step S5: The composite adsorbent material is stretched, cooled, and heat-set to improve its adsorption and mechanical properties. The cooling temperature range is 10–30°C, the heat-setting temperature is 110–310°C, and the cooling time range is 15–60 min.

[0045] According to embodiments of this disclosure, post-treatment of the composite adsorbent material can effectively improve its tensile strength and toughness, wherein the stretching includes longitudinal and transverse bidirectional stretching performed sequentially or simultaneously.

[0046] In another aspect of this disclosure, a composite adsorbent material prepared by the above method is proposed, comprising: a first surface layer and a second surface layer having heavy metal ion adsorption properties, and an intermediate layer. The intermediate layer supports the first and second surface layers and improves the mechanical properties and service life of the composite adsorbent material.

[0047] According to embodiments of this disclosure, the thickness range of the composite adsorbent material includes 200–500 μm; the thickness range of the first surface layer includes 50–150 μm, for example, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, etc.; the thickness range of the intermediate layer includes 100–200 μm, for example, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, etc.; the thickness range of the second surface layer includes 50–150 μm, for example, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, etc.

[0048] According to embodiments of this disclosure, the thickness of the first surface layer and the thickness of the second surface layer can be adjusted to be the same or different depending on the actual application.

[0049] In another aspect of this disclosure, a method for uranium extraction from seawater is proposed, wherein a composite adsorbent material prepared by the above method forms a chelate with uranium in seawater.

[0050] According to the embodiments of this disclosure, the above-mentioned composite adsorbent material needs to be immersed in a 2.5wt% KOH solution and subjected to alkaline activation treatment at 60°C for 3 hours before use, so as to deprotonate and improve the hydrophilicity of the composite adsorbent material.

[0051] It should be noted that the described embodiments are merely some, not all, of the embodiments disclosed herein. Other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are all within the scope of protection of this disclosure.

[0052] Example 1

[0053] Poly(ammoxime), glycerol, and ammonium bicarbonate were mixed in a ratio of 5:1:0.5 and melt-extruded at 180°C to form the first surface layer melt. Polyethylene material was melt-extruded at 200°C to form the intermediate layer melt. Poly(ammoxime), polyethylene oxide, and lithium carbonate were mixed in a ratio of 6.5:1:0.6 and melt-extruded at 175°C to form the second surface layer melt. The poly(ammoxime) was obtained by ammoximation of polyacrylonitrile.

[0054] The first surface layer melt, the intermediate layer melt, and the second surface layer melt were combined using a co-extrusion blown film process, and then cooled at 20°C for 30 minutes to obtain a composite adsorbent material. The thicknesses of the first surface layer, the intermediate layer, and the second surface layer were 80 μm, 150 μm, and 80 μm, respectively.

[0055] Example 2

[0056] Poly(ximetrix), polyethylene glycol, and lithium carbonate were mixed in a ratio of 8:1:0.4 and melt-extruded at 165°C to form the first surface layer melt. High-density polyethylene was melt-extruded at 210°C to form the intermediate layer melt. Poly(ximetrix), glycerol, and ammonium bicarbonate were mixed in a ratio of 4:1:0.2 and melt-extruded at 170°C to form the second surface layer melt. The poly(ximetrix) was obtained by ximetrilation of polyacrylonitrile.

[0057] The first surface layer melt, the intermediate layer melt, and the second surface layer melt were combined using a co-extrusion blown film process, and then cooled at 15°C for 20 minutes to obtain a composite adsorbent material. The thicknesses of the first surface layer, the intermediate layer, and the second surface layer were 75 μm, 175 μm, and 86 μm, respectively.

[0058] Example 3

[0059] Poly(ximetrix), polyethylene glycol, and lithium carbonate were mixed in a ratio of 7:1:0.2 and melt-extruded at 165°C to form the first surface layer melt. High-density polyethylene was melt-extruded at 205°C to form the intermediate layer melt. Poly(ximetrix), polyethylene glycol, and lithium carbonate were mixed in a ratio of 7:1:0.2 and melt-extruded at 165°C to form the second surface layer melt. The poly(ximetrix) was obtained by ximetrilation of polyacrylonitrile.

[0060] The first surface layer melt, the intermediate layer melt, and the second surface layer melt were combined using a co-extrusion blown film process, and then cooled at 15°C for 20 minutes to obtain a composite adsorbent material. The thicknesses of the first surface layer, the intermediate layer, and the second surface layer were 75 μm, 170 μm, and 75 μm, respectively.

[0061] Example 4

[0062] Poly(dimethylamine oxime), glycerol, and ammonium bicarbonate were mixed in a ratio of 6:1:0.5 and extruded at 180°C to form the first surface layer melt. Polyethylene film material was melt-extruded at 195°C to form the intermediate layer melt. Poly(dimethylamine oxime), polyvinyl alcohol, and polyvinylpyrrolidone were mixed in a ratio of 8:1:0.2 and extruded at 175°C to form the second surface layer melt. The poly(dimethylamine oxime) was obtained by the dimethylamine oxime treatment of polyacrylonitrile.

[0063] The first surface layer melt, the intermediate layer melt, and the second surface layer melt are combined using a co-extrusion casting process, and simultaneously subjected to longitudinal and transverse stretching. The mixture is then heat-set at 130°C and wound up to obtain the adsorption film material. The thicknesses of the first surface layer, the intermediate layer, and the second surface layer are 65 μm, 150 μm, and 75 μm, respectively.

[0064] Example 5

[0065] Poly(ximetrix), polyacrylamide, and lithium carbonate were mixed in a ratio of 8:1:0.3 and extruded at 190°C to form the first surface layer melt. Polyethylene terephthalate film material was melt-extruded at 195°C to form the intermediate layer melt. Poly(ximetrix), polyethylene oxide, and polyvinylpyrrolidone were mixed in a ratio of 10:1:0.5 and extruded at 195°C to form the second surface layer melt. The poly(ximetrix) was obtained by ximetrimination of polyacrylonitrile.

[0066] The first surface layer melt, the intermediate layer melt, and the second surface layer melt are combined using a co-extrusion casting process, followed by longitudinal and transverse stretching. The mixture is then heat-set at 140°C and wound up to obtain the adsorption film material. The thicknesses of the first surface layer, the intermediate layer, and the second surface layer are 75 μm, 130 μm, and 65 μm, respectively.

[0067] Example 6

[0068] Poly(ethylene glycol) oxime, polyacrylamide, and lithium carbonate were mixed in a ratio of 5:1:0.3 and extruded at 190°C to form the first surface layer melt. Polyethylene terephthalate film material was melt-extruded at 220°C to form the intermediate layer melt. Poly(ethylene glycol) oxime, glycerol, and polyvinylpyrrolidone were mixed in a ratio of 9.5:1:0.6 and extruded at 185°C to form the second surface layer melt. The poly(ethylene glycol) oxime was obtained by the oximation of polyacrylonitrile.

[0069] The first surface layer melt, the intermediate layer melt, and the second surface layer melt are combined using a co-extrusion casting process, followed by longitudinal and transverse stretching. The mixture is then heat-set at 140°C and wound up to obtain the adsorption film material. The thicknesses of the first surface layer, the intermediate layer, and the second surface layer are 120 μm, 180 μm, and 115 μm, respectively.

[0070] Example 7

[0071] Poly(ammoxime), polyacrylamide, and lithium chloride were mixed in a ratio of 7:1:0.3 and extruded at 180°C to form the first surface layer melt. Polypropylene film material was melt-extruded at 220°C to form the intermediate layer melt. Poly(ammoxime), polyacrylamide, and lithium chloride were mixed in a ratio of 7:1:0.3 and extruded at 185°C to form the second surface layer melt. The poly(ammoxime) was obtained by ammoximation of polyacrylonitrile.

[0072] The adsorption film material is obtained by combining the first surface layer melt, the intermediate layer melt, and the second surface layer melt through a co-extrusion casting process and then cooling. The thicknesses of the first surface layer, the intermediate layer, and the second surface layer are 120 μm, 180 μm, and 120 μm, respectively.

[0073] Comparative Example 1

[0074] This comparative example provides a method for preparing a amine oxime-based polyethylene nanofiber membrane, the method comprising:

[0075] S1: Irradiate a polyethylene nanofiber membrane with a porosity of 55% in air at a dose rate of 15 kGy / h, with an absorbed dose of 120 kGy.

[0076] S2: Immerse the irradiated polyethylene nanofiber membrane in a solution containing acrylonitrile and acrylic acid, wherein the volume concentrations of acrylonitrile and acrylic acid are 55% and 12%, respectively, and argon gas is introduced. The grafting reaction is carried out in a water bath at 68°C for 6 hours. After washing with DMF and water, and vacuum drying, the modified polyethylene nanofiber membrane is obtained.

[0077] S3: The modified polyethylene nanofilm obtained in step S2 is immersed in a methanol / water solution containing 9wt% hydroxylamine hydrochloride at a volume ratio of 0.8:1 and reacted at 72°C for 5 hours at pH 7.1. After the reaction is completed, the film sample is taken out of the solution, washed with water, and vacuum dried to obtain the amylopectin-based polyethylene nanofiber membrane.

[0078] Comparative Example 2

[0079] This comparative example provides a method for preparing a amine oxime-based polyethylene nanofiber membrane, the method comprising:

[0080] S1: Irradiate a polyethylene nanofiber membrane with a porosity of 55% in air at a dose rate of 18 kGy / h, with an absorbed dose of 110 kGy.

[0081] S2: The irradiated polyethylene nanofiber membrane was immersed in a solution containing acrylonitrile and acrylic acid, wherein the volume concentrations of acrylonitrile and acrylic acid were 45% and 12%, respectively, and nitrogen gas was introduced. The grafting reaction was carried out in a water bath at 65°C for 6.5 h. After washing with DMF and water, the modified polyethylene nanofiber membrane was obtained by vacuum drying.

[0082] S3: The modified polyethylene nanofilm obtained in step S2 is immersed in a methanol / water solution containing 12wt% hydroxylamine hydrochloride at a volume ratio of 1.5:1. The reaction is carried out at 65°C for 4.5 h at pH = 7.2. After the reaction is completed, the film sample is taken out of the solution, washed with water and vacuum dried to obtain the amylopectin-based polyethylene nanofiber membrane.

[0083] Test Case

[0084] Under simulated seawater conditions, the adsorption capacity of the composite adsorbent materials prepared in Examples 1-7 and the amylopectin-based polyethylene nanofiber membranes obtained in Comparative Examples 1 and 2 were tested. Specific test methods included:

[0085] S1: Prepare 1L of aqueous solution containing 193mg NaHCO3 and 25.6g NaCl; then add 8mL of 1000ppm uranium standard solution to the above solution to obtain 1L of 8ppm uranium standard simulated seawater;

[0086] S2: Add saturated Na2CO3 solution and 2% HNO3 solution dropwise to adjust the pH to 8.0±0.1;

[0087] S3: 10 mg of the alkali-activated composite adsorbent was added to 1 L of simulated seawater containing 8 ppm uranium standard, and adsorption kinetics were studied in a constant-temperature water bath shaker at 25 °C and 100 rpm. The solution was removed at specified time points, and the uranium concentration was tested and analyzed. The adsorption performance of uranium was calculated according to formula (1). Each experiment was repeated three times, and the average value was used as the saturated adsorption capacity (mg / g) of the composite adsorbent.

[0088]

[0089] Among them, Q t To achieve the adsorption capacity (mg / g) at adsorption equilibrium, C0 and C t The initial uranium concentration (mg / L) and the uranium concentration at adsorption equilibrium (g / L) are respectively, V is the volume of the adsorption solution (L), and m is the mass of the adsorbent (g).

[0090] The regeneration and reusability of the obtained composite adsorbent material were tested by continuously conducting adsorption-desorption-regeneration cycle experiments. Adsorption equilibrium was reached in 1 L of simulated seawater with 8 ppm uranium standard; desorption was carried out in 0.5 mol / L HCl solution for 30 min; regeneration was carried out in 5 mmol / L KOH solution for 20 min. Finally, the material was washed with water before the next cycle of adsorption experiments. The cycle stability was tested after five adsorption experiments.

[0091] The mechanical properties of the composite adsorbent materials prepared in Examples 1-7 and the amylopyridine-based polyethylene nanofiber membranes obtained in Comparative Examples 1 and 2 were tested. The tensile strength (MPa) and elongation at break (%) were tested according to GB / T1040.3. The results are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] As shown in Table 1, the adsorption capacity of the composite adsorbent prepared by the co-extrusion blown film process is about 310 mg / g in the seawater uranium extraction process, while the saturated adsorption capacity of the composite adsorbent prepared by the co-extrusion casting process can reach up to 305 mg / g, which is much higher than the adsorption performance of the comparative example of the amine oxime-based polyethylene nanofiber membrane, and it also has good adsorption stability and mechanical properties.

[0096] In Example 6, biaxial stretching and heat setting were not performed during the post-processing, resulting in a higher thickness of each layer of the composite adsorbent material. This prevented the polyamine oxime active groups from being fully exposed, leading to a slight decrease in the saturated adsorption capacity.

[0097] As can be seen from the comparison between the examples and the comparative examples, compared with the amine oxime-based polyethylene nanofiber membranes prepared by irradiation and grafting, the co-extrusion blown film process and the co-extrusion casting process can effectively utilize the contact area between the adsorption groups on the composite adsorbent material and the uranyl ions in seawater to achieve better adsorption effect. Moreover, the resulting composite adsorbent material has better mechanical properties and further improved cycle stability.

[0098] In the comparative example, irradiation and grafting methods caused some damage to the nanofiber membrane, reducing the material's mechanical properties, service life, and adsorption performance.

[0099] In summary, this disclosure proposes a composite adsorbent material based on a three-layer co-extrusion blown film, its preparation method, and its application. Based on the co-extrusion blown film process and the co-extrusion casting process, the composite adsorbent material can be formed in one step, reducing the complexity of the coating process. The process is short and efficient, and the seawater uranium extraction efficiency is high, which is conducive to the large-scale, industrialized production of the composite adsorbent material.

[0100] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A method for preparing a composite adsorbent material for uranium extraction from seawater, comprising: Polyamine oxime with heavy metal ion adsorption properties is mixed and melted with a first plasticizer and a first pore-forming agent at a first temperature to obtain a first surface layer melt. The polymer film material is melted at a second temperature to obtain an intermediate layer melt. Polyamine oxime with heavy metal ion adsorption properties is mixed and melted with a second plasticizer and a second pore-forming agent at a third temperature to obtain a second surface layer melt. The first surface layer melt, the intermediate layer melt, and the second surface layer melt are co-extruded or co-extruded blown film to make the first surface layer melt, the intermediate layer melt, and the second surface layer melt closely bonded together to obtain a composite adsorbent material.

2. The method according to claim 1, wherein, The first plasticizer includes one or more of glycerol, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, or polyacrylamide; The first pore-forming agent includes one or more of lithium carbonate, lithium chloride, ammonium bicarbonate, polyethylene glycol, polyvinyl alcohol, or polyvinylpyrrolidone; In the first surface layer melt, the mass ratio of the poly(amine oxime), the first plasticizer, and the first pore-forming agent is (1-10):1:(0.05-0.8). The second plasticizer includes one or more of glycerol, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, or polyacrylamide; The second pore-forming agent includes one or more of lithium carbonate, lithium chloride, ammonium bicarbonate, polyethylene glycol, polyvinyl alcohol, or polyvinylpyrrolidone; In the second surface layer melt, the mass ratio of the poly(amine oxime), the second plasticizer and the second pore-forming agent is (1-10):1:(0.05-0.8).

3. The method according to claim 1 or 2, wherein, The composition of the first surface layer melt is the same as or different from that of the second surface layer melt.

4. The method according to claim 1, wherein, The intermediate layer melt comprises at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyamide.

5. The method according to claim 1, wherein, The first temperature range is 160–300°C; The second temperature range includes 150–300°C; The third temperature range is 160–300°C.

6. The method according to claim 1, wherein, In the co-extrusion blown film process, the screw speed range is 10-200 r / min, the traction rate range is 2-10 m / min, and the blow-up ratio ranges from 1 to 8. In the co-extrusion casting process, the screw speed ranges from 5 to 150 r / min, the traction rate ranges from 10 to 100 m / min, and the cooling roller temperature ranges from 5 to 30°C.

7. The method according to claim 1 further comprises subjecting the composite adsorbent material to stretching, cooling, and heat-setting treatments to improve the adsorption performance and mechanical properties of the composite adsorbent material, wherein, The cooling temperature range is 10–30°C, the heat setting temperature is 110–310°C, and the cooling time range is 15–60 min.

8. A composite adsorbent material prepared by the method according to any one of claims 1 to 7, comprising: A first surface layer and a second surface layer with heavy metal ion adsorption properties, and an intermediate layer; The intermediate layer supports the first surface layer and the second surface layer and improves the mechanical properties and service life of the composite adsorption material.

9. The material according to claim 8, wherein, The thickness of the composite adsorption material ranges from 200 to 500 μm; The thickness of the first surface layer ranges from 50 to 150 μm; The thickness of the intermediate layer ranges from 100 to 200 μm; The thickness of the second surface layer ranges from 50 to 150 μm.

10. A method for extracting uranium from seawater, wherein a composite adsorbent material prepared by any one of claims 1 to 7 forms a chelate with uranium in seawater.

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