Pre-coated composite adsorbent material, its preparation method and application

Abstract

The present disclosure provides a pre-coated composite adsorbent material, a preparation method thereof and an application thereof, belonging to the technical field of functional adsorbent materials. The preparation method of the composite adsorbent material includes: pretreating a polymer film material to obtain a polymer substrate; coating both surfaces of the polymer substrate with a coating agent to obtain a coated polymer substrate; sequentially performing stretching treatment and heat treatment on the coated polymer substrate to finally obtain the pre-coated composite adsorbent material. By weight, the coating agent includes 40-60 parts of polyamidoxime, 50-180 parts of a hydrophilic polymer material, 8-30 parts of a plasticizer, and 3-25 parts of a crosslinking agent. The pre-coated composite adsorbent material obtained by using the preparation method of the present disclosure enhances the mechanical properties and thermal stability of the composite adsorbent material itself, while realizing the thinning of the coating layer, thereby increasing the specific surface area of the adsorbent material, exposing more adsorption groups, and enhancing the adsorption efficiency in the process of extracting uranium from seawater.

Description

Technical Field

[0001] The present disclosure relates to the technical field of functional adsorption materials, and particularly relates to a pre-coated composite adsorption material, a preparation method thereof, and an application thereof. Background Art

[0002] Uranium is the foundation and strategic resource for the sustainable development of the nuclear industry and plays a very important role in the development of nuclear power and nuclear energy. However, uranium resources are relatively scarce, and there is a serious gap in the self-sufficiency of uranium fuel. The ocean is a huge repository of uranium. If the uranium resources in seawater can be effectively enriched, it will provide an important supplement and guarantee for the stable supply of fuel for the nuclear power industry. In the extraction of uranium from seawater, adsorption materials are mostly used for extraction. The performance and batch preparation of adsorption materials are important factors affecting the extraction of uranium from seawater. Therefore, researching and developing high-performance adsorption materials for extracting uranium from seawater and their engineering preparation are the technical prerequisites for realizing the industrialization of uranium extraction from seawater.

[0003] Currently, functional polymer materials modified with amidoxime groups (H 2 N-C=N-OH) are considered to be excellent adsorption materials for extracting uranium from seawater because the amidoxime groups can chelate with uranyl ions in seawater.

[0004] One approach in related research is to use electrospinning to prepare amidoxime group-modified functional polymer materials. Although electrospinning can achieve continuous preparation, due to limitations in the porosity, uniformity, and thickness of the micro-nano fibers in the spinning process itself, and potential safety hazards in the production supporting facilities of the corresponding high-voltage electrostatic field, it is difficult to popularize on a large scale.

[0005] Another approach in related technologies is to graft amidoxime groups onto the surface and inside of polymer nanofiber membranes through irradiation treatment, which destroys the overall structure of the polymer nanofiber membranes and reduces their mechanical properties, thereby reducing the saturated adsorption capacity and cyclic stability of the polymer nanofiber membranes and making it unfavorable for further popularization and application.

[0006] In summary, in related technologies, during the preparation process of polymer thin films, problems such as poor uniformity of polymer thin films, high film-forming thickness, poor stability, and difficulty in recycling are likely to occur, making it difficult to invest in practical applications. Summary of the Invention

[0007] Aiming at the problems of high film-forming thickness, poor stability, and difficulty in recycling of the polymer thin films mentioned above, the present disclosure provides a pre-coated composite adsorption material, a preparation method thereof, and an application thereof.

[0008] To achieve the above object, as an aspect of the present disclosure, there is provided a method for preparing a pre-coated composite adsorbent material, including: pretreating a polymer film material to obtain a polymer substrate; coating both surfaces of the polymer substrate with a coating agent to obtain a coated polymer substrate; subjecting the coated polymer substrate to stretching treatment and heat treatment in sequence, and finally obtaining the pre-coated composite adsorbent material; wherein, by weight, the coating agent includes 40-60 parts of polyamidoxime, 50-180 parts of a hydrophilic polymer material, 8-30 parts of a plasticizer, and 3-25 parts of a crosslinking agent.

[0009] According to an embodiment of the present disclosure, the pretreatment includes: sequentially performing extrusion casting, activation treatment to introduce crosslinking groups, water washing, and drying on the polymer film material; the polymer film material includes at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyamide; the activation treatment includes at least one of plasma treatment and corona treatment.

[0010] According to an embodiment of the present disclosure, the pretreatment further includes: longitudinally stretching the polymer film material after extrusion casting before the activation treatment.

[0011] According to an embodiment of the present disclosure, the stretching treatment conditions are: longitudinally and transversely stretching at a temperature of 110-270°C, and the stretching ratio is 1.1-5 for both.

[0012] According to an embodiment of the present disclosure, the heat treatment conditions are: heat treatment reaction for 2-60 s at a temperature of 120-280°C.

[0013] According to an embodiment of the present disclosure, the hydrophilic polymer material includes at least one of polyacrylic acid, polyacrylamide, or polymethacrylic acid.

[0014] According to an embodiment of the present disclosure, the plasticizer includes at least one of glycerol, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, or polyacrylamide.

[0015] According to an embodiment of the present disclosure, the crosslinking agent includes at least one of glutaraldehyde, acetic anhydride, diglycidyl ether, or octamethylenediamine methyl ester.

[0016] According to an embodiment of the present disclosure, the coating agent further includes: a pore-forming agent.

[0017] As another aspect of the present disclosure, there is also provided a pre-coated composite adsorbent material obtained by the preparation method as described above.

[0018] According to an embodiment of the present disclosure, the pre-coated composite adsorbent material includes: a first surface coating layer, a polymer-based film layer, and a second surface coating layer; wherein, the thickness of the first surface coating layer is 1-5 μm; the thickness of the polymer-based film layer is 3-50 μm; the thickness of the second surface coating layer is 1-5 μm.

[0019] As yet another aspect of the present disclosure, there is also provided an application of the pre-coated composite adsorbent material in uranium extraction from seawater.

[0020] Based on the pre-coated composite adsorbent material, its preparation method and application according to the above embodiments of the present disclosure. First, after the polymer thin film material is pretreated to obtain a polymer substrate, a coating agent is used to coat the two surfaces of the polymer substrate to obtain a polymer substrate with coating layers on both surfaces. Among them, the hydrophilic polymer material and the cross-linking agent in the coating agent form a film layer with a three-dimensional network in space on the two surfaces of the polymer substrate through a cross-linking reaction. The hydrophilic polymer material, plasticizer and cross-linking agent in the coating agent act synergistically. The cross-linking agent enables the coating agent to cross-link with the pretreated polymer substrate; the hydrophilic polymer material provides the three-dimensional network structure of the coating layer, forms the supporting framework of the structure, and brings hydrophilic properties to the coating layer; the plasticizer improves the stability and mechanical properties of the coating layer. The three work together to improve the stability and cross-linking of the coating layer on the surface of the polymer substrate, construct the film-forming conditions, and thus provide a better coating effect. The polyamidoxime in the coating agent provides amidoxime groups, and these amidoxime groups are grafted into the coating layers on the two surfaces of the polymer substrate through cross-linking, thereby forming a relatively high selectivity for uranyl ions. The amidoxime groups of the present disclosure are not directly grafted onto the polymer substrate, so the relatively excellent mechanical properties of the polymer substrate are retained, the damage to the polymer substrate is small, and the polymer substrate has good stability and a long service life. Secondly, the coated polymer substrate is stretched to thin both the polymer substrate and the coating layer, obtaining a thinned polymer-based film and coating layer, which increases the specific surface area of the coating layer and exposes more amidoxime groups with high adsorption capacity for uranyl ions, thereby enhancing the adsorption efficiency during the uranium extraction from seawater process. The polymer-based film and the coating layer can be shaped after a heat treatment process to obtain the pre-coated composite adsorbent material, further improving the crystal structure inside the pre-coated composite adsorbent material and enhancing the mechanical properties and thermal stability. The present disclosure realizes a one-time heat treatment process for the polymer-based film and the coating layer through a pre-coating method, realizes the one-time forming of the pre-coated composite adsorbent material, reduces the complexity of subsequent coating processes, and thus has good stability and a long service life. Description of the Drawings

[0021] The following further describes the present disclosure in detail with reference to the accompanying drawings.

[0022] Figure 1 The figure shows a flowchart of a method for a pre-coated composite adsorbent material in an embodiment of the present disclosure;

[0023] Figure 2 The figure shows a schematic cross-sectional view of a pre-coated composite adsorbent material in an embodiment of the present disclosure.

[0024]

Explanation of reference numerals

[0025] 10 - First surface coating layer, 20 - Polymer substrate film layer, 30 - Second surface coating layer, 40 - Hydrophilic polymer material, 50 - Polyamidoxime. Detailed implementation manners

[0026] In the process of implementing the present disclosure, it is found that by using pre-coating treatment, amidoxime groups can be grafted onto the coating layer to ensure the mechanical stability of the polymer substrate material.

[0027] Based on this, the present disclosure provides a pre-coated composite adsorbent material, its preparation method and application. By grafting amidoxime groups onto the coating layer, the excellent mechanical properties of the polymer substrate are retained, and the damage to the polymer substrate is small, so that the polymer substrate has good stability and a long service life. At the same time, the hydrophilic polymer material, plasticizer and cross-linking agent in the coating agent act synergistically, and the three together improve the stability and cross-linking of the coating layer on the surface of the polymer substrate, thus providing a better coating effect. After stretching and heat treatment, the coated composite adsorbent material has a larger specific surface area, exposing more amidoxime groups, thereby enhancing the adsorption efficiency in the process of uranium extraction from seawater.

[0028] To make the purpose, technical solutions and advantages of the present disclosure clearer and more understandable, the following further describes the present disclosure in detail with reference to specific embodiments and the accompanying drawings.

[0029] The following schematically illustrates a pre-coated composite adsorbent material, its preparation method and application. It should be noted that this illustrative example is only a specific embodiment of the present disclosure and does not limit the protection scope of the present disclosure.

[0030] Figure 1 The figure shows a flowchart of a method for a pre-coated composite adsorbent material in an embodiment of the present disclosure.

[0031] As Figure 1 shown, the preparation method of the pre-coated composite adsorbent material includes stages S101 - S103.

[0032] Stage S101, pretreat the polymer thin film material to obtain a polymer substrate.

[0033] Stage S102, coat both surfaces of the polymer substrate with a coating agent to obtain a coated polymer substrate;

[0034] Among them, based on parts by weight, the coating agent includes 40 - 60 parts of polyamidoxime, 50 - 180 parts of hydrophilic polymer material, 8 - 30 parts of plasticizer, and 3 - 25 parts of crosslinking agent.

[0035] In stage S103, the coated polymer substrate is subjected to stretching treatment and heat treatment in sequence, and finally a pre - coated composite adsorbent material is obtained.

[0036] According to the embodiments of the present disclosure, first, after the polymer thin - film material is pretreated to obtain a polymer substrate, the polymer substrate is coated with a coating agent. The hydrophilic polymer material, plasticizer, and crosslinking agent in the coating agent form a three - dimensional spatial network on both surfaces of the polymer substrate through crosslinking. The hydrophilic polymer material, plasticizer, and crosslinking agent in the coating agent act synergistically. The crosslinking agent enables the coating agent to crosslink with the pretreated polymer substrate; the hydrophilic polymer provides the three - dimensional network structure of the coating layer, forms the supporting framework of the structure, and brings hydrophilic groups, such as hydroxyl groups, to the coating layer, which can improve the adhesion of polyamidoxime; the plasticizer improves the mechanical properties of the coating layer. The three work together to improve the stability and crosslinking of the coating layers on both surfaces of the polymer substrate, construct the film - forming conditions, and provide a better coating effect. The polyamidoxime in the coating agent provides amidoxime groups, and these amidoxime groups are grafted into the three - dimensional spatial network of the coating layers on both surfaces of the polymer substrate through crosslinking, thereby forming a high selectivity for uranyl ions. The amidoxime groups of the present disclosure are not directly grafted onto the polymer substrate, so the excellent mechanical properties of the polymer substrate are retained, the damage to the polymer substrate is small, and the polymer substrate has good stability and a long service life. Secondly, the coated polymer substrate is subjected to stretching treatment to obtain a polymer base film and a coating layer, so that both the polymer base film and the coating layer are thinned to increase the specific surface area of the coating layer and expose more amidoxime groups with high adsorption capacity for uranyl ions, thereby exposing more adsorption active sites. The polymer base film is shaped through a heat treatment process to obtain a pre - coated composite adsorbent material, further improving the crystal structure inside the pre - coated composite adsorbent material. While improving the mechanical properties of the pre - coated composite adsorbent material, it also improves the thermal stability. The present disclosure realizes a one - time heat treatment process for the polymer base film and the coating layer through a pre - coating method, realizes the one - time forming of the pre - coated composite adsorbent material, reduces the complexity of subsequent coating processes, and thus has good stability and a long service life.

[0037] According to an embodiment of the present disclosure, the weight fraction of polyamidoxime includes 40 - 60 parts, for example, it can be 40 parts, 45 parts, 50 parts, 55 parts or 60 parts; the weight fraction of the hydrophilic polymer material includes 50 - 180 parts, for example, it can be 50 parts, 90 parts, 120 parts, 150 parts or 180 parts; the weight fraction of the plasticizer includes 8 - 30 parts, for example, it can be 8 parts, 10 parts, 15 parts, 20 parts, 25 parts or 30 parts; the weight fraction of the crosslinking agent includes 3 - 25 parts, for example, it can be 3 parts, 5 parts, 10 parts, 15 parts, 20 parts or 25 parts. The above parts are not limited to the listed values, and other unlisted values within the value range are equally applicable.

[0038] According to an embodiment of the present disclosure, the pretreatment includes: successively performing extrusion casting, activation treatment to introduce crosslinking groups, water washing and drying treatment on the polymer thin film material; the activation treatment includes at least one of plasma treatment and corona treatment.

[0039] According to an embodiment of the present disclosure, after the polymer thin film material is extruded by an extruder and then cooled by a cooling roll, a polymer substrate is obtained. Among them, the extruder can be selected as a twin - screw extruder or a single - screw extruder according to needs. The activation treatment method successively includes at least one of plasma and corona treatment and immersing the polymer thin film material in a solution containing a crosslinking agent. Through the activation treatment, the hydroxyl groups on both surfaces of the polymer substrate react with the groups of the crosslinking agent, so that the crosslinking agent is bonded to both surfaces of the polymer substrate, which is beneficial to better coating effects in the follow - up. Among them, the crosslinking agent used in this activation treatment can be the same as or different from the crosslinking agent in the coating agent.

[0040] According to an embodiment of the present disclosure, the polymer thin film material includes at least one of polyethylene, polypropylene, polyethylene terephthalate or polyamide. For example, it can include: a combination of polyethylene and polypropylene, a combination of polypropylene and polyethylene terephthalate, or a combination of polyethylene terephthalate and polyamide.

[0041] Specifically, polyamidoxime in the coating agent can be prepared by the amidoximation reaction of polyacrylonitrile and hydroxylamine hydrochloride. The conditions for the amidoximation reaction are as follows: at a reaction temperature of 40 - 80 °C, for example, it can be 40 °C, 50 °C, 60 °C, 70 °C, or 80 °C, and adjust the pH of the reaction between polyacrylonitrile and hydroxylamine hydrochloride to 6.5 - 8.5, for example, it can be 6.5, 6.8, 7, 7.5, 8, or 8.5; carry out the reaction for 3 - 36 h, for example, it can be 3 h, 9 h, 12 h, 18 h, 24 h, or 36 h. Among them, the state of polyamidoxime can include any one of slurry, suspension, or solution, and the concentration of the polyamidoxime is 0.02 - 10 g / mL, for example, it can be 0.02 g / mL, 0.2 g / mL, 1 g / mL, 3 g / mL, 5 g / mL, or 10 g / mL. During the process of conducting the relevant preliminary experiments of the present disclosure, it was found that the particle sizes of polyamidoxime in the three states of slurry, suspension, and solution are relatively small, so good coating effects can be achieved. Preferably, when the state of polyamidoxime is solution, the particle size is smaller and the adsorption effect is relatively better.

[0042] According to the embodiments of the present disclosure, the hydrophilic polymer material includes at least one of polyacrylic acid, polyacrylamide, or polymethacrylic acid. For example, it can be a combination of polyacrylic acid and polyacrylamide, a combination of polyacrylamide and polymethacrylic acid, or a combination of polyacrylic acid and polymethacrylic acid; the plasticizer includes at least one of glycerol, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, or polyacrylamide. For example, it can be a combination of glycerol and polyvinyl alcohol, a combination of polyvinyl alcohol and polyethylene glycol, a combination of polyethylene glycol and polyethylene oxide, or a combination of polyethylene oxide and polyacrylamide; the crosslinking agent includes at least one of glutaraldehyde, acetic anhydride, diglycidyl ether, or octamethylenediamine methyl ester. For example, it can be a combination of glutaraldehyde and acetic anhydride, a combination of acetic anhydride and diglycidyl ether, or a combination of diglycidyl ether and octamethylenediamine methyl ester.

[0043] According to the embodiments of the present disclosure, the coating agent further includes: a pore-forming agent. The pore-forming agent can form a multi-level pore structure and a relatively rich pore structure inside the coating layer, improve its contact area, and further increase the adsorption efficiency of the coating layer for uranyl ions. Specifically, the pore-forming agent includes any one or a combination of at least two of lithium carbonate, lithium chloride, ammonium bicarbonate, polyethylene glycol, polyvinyl alcohol, or polyvinylpyrrolidone. For example, it can be a combination of lithium carbonate and lithium chloride, a combination of lithium chloride and ammonium bicarbonate, a combination of polyethylene glycol and polyvinyl alcohol, or a combination of polyvinyl alcohol and polyvinylpyrrolidone.

[0044] Furthermore, the coating method includes at least one of gravure roll coating, dip coating, narrow coating, or spray coating. For example, it can be a combination of gravure roll coating and dip coating, a combination of dip coating and narrow coating, or a combination of narrow coating and spray coating.

[0045] According to an embodiment of the present disclosure, the stretching treatment conditions are as follows: longitudinal and transverse stretching are carried out at a temperature of 110 - 270 °C, and the longitudinal and / or transverse stretching ratios are both 1.1 - 5, for example, they can be 1.1, 1.3, 1.5, 1.8, 2, 3, 4, or 5. Among them, the stretching of the coated polymer substrate may include sequentially performing longitudinal stretching and transverse stretching, or synchronously performing longitudinal stretching and transverse stretching, or sequentially performing transverse stretching and longitudinal stretching, and the value range of the stretching ratio is within the above range to obtain a polymer base film. Specifically, the stretching treatment temperature is 110 - 270 °C, for example, it can be 110 °C, 130 °C, 150 °C, 180 °C, 210 °C, 250 °C, or 270 °C. The present disclosure adopts the method of first coating and then stretching treatment, which can reduce the thickness of the polymer base film and the coating layer, so as to increase the specific surface area of the polymer base film and the coating layer, and more fully expose the adsorption groups.

[0046] According to an embodiment of the present disclosure, the heat treatment conditions are as follows: heat treatment reaction is carried out at a temperature of 120 - 280 °C for 2 - 60 s. Among them, the heat treatment temperature is 120 - 280 °C, for example, it can be 120 °C, 150 °C, 180 °C, 210 °C, 240 °C, or 280 °C, and the heat treatment reaction time is 2 - 60 s, for example, it can be 2 s, 5 s, 10 s, 20 s, 40 s, or 60 s. The stretched polymer base film is subjected to heat setting treatment, thereby further fixing and improving the crystal structure in the polymer base film, while improving its mechanical properties and the thermal stability of the polymer base film.

[0047] According to another embodiment of the present disclosure, the pretreatment further includes longitudinally stretching the polymer substrate after extrusion and calendaring before the activation treatment. This method is basically the same as the preparation method of the above-mentioned pre-coated composite adsorbent material, and will not be elaborated here. Only the differences will be introduced below.

[0048] Specifically, the difference in this treatment method is that during the pretreatment process, the polymer substrate after extrusion and calendaring is first longitudinally stretched before the activation treatment, and the longitudinal stretching ratio is 1.1 - 5, for example, it can be 1.1, 1.3, 1.5, 1.8, 2, 3, 4, or 5, and the longitudinally stretched base film is obtained. Then, the longitudinally stretched base film is sequentially subjected to activation treatment to introduce crosslinking groups, water washing, and drying treatment. Subsequently, when stretching treatment is carried out again, the longitudinally stretched base film is transversely stretched, and the transverse stretching ratio is 1.1 - 5, for example, it can be 1.1, 1.3, 1.5, 1.8, 2, 3, 4, or 5.

[0049] According to an embodiment of the present disclosure, there is also provided a pre-coated composite adsorbent material prepared by the above-mentioned preparation method.

[0050] According to an embodiment of the present disclosure, the obtained pre-coated composite adsorbent material has a high specific surface area, strong mechanical stability, and high adsorption performance.

[0051] Figure 2 The cross-sectional schematic diagram of the pre-coated composite adsorbent material according to an embodiment of the present disclosure is shown. As Figure 2 shown, the pre-coated composite adsorbent material includes: a first surface coating layer 10, a polymer-based membrane layer 20, and a second surface coating layer 30; wherein, the thickness of the first surface coating layer 10 is 1-5 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, preferably, the thickness of the first surface coating layer 10 is 1-3 μm; the thickness of the polymer-based membrane layer 20 is 3-50 μm, for example, it can be 3 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm, preferably, the thickness of the polymer-based membrane layer 20 is 3-20 μm; the thickness of the second surface coating layer 30 is 1-5 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, preferably, the thickness of the second surface coating layer 30 is 1-3 μm. Polyamidoxime 50 is grafted into the coating layer constructed by the hydrophilic polymer material 40 through cross-linking, thereby realizing the adsorption selectivity of the coating layer for uranyl ions.

[0052] According to an embodiment of the present disclosure, an application of the pre-coated composite adsorbent material in uranium extraction from seawater is also provided.

[0053] According to an embodiment of the present disclosure, the obtained pre-coated composite adsorbent material has a large specific surface area, exposing more adsorption active sites of amidoxime groups, thereby enhancing the adsorption efficiency in the process of uranium extraction from seawater, which is beneficial to realizing the large-scale and engineering preparation of the adsorbent material.

[0054] The present disclosure will be further described below through comparative examples, examples, drawings, and related test experiments and their results. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, obviously, one or more embodiments can also be implemented without these specific details. Moreover, without conflict, the details in the following embodiments can be combined arbitrarily into other feasible embodiments.

[0055] It should be noted that the following specific embodiments are only for illustration, and the protection scope of the present disclosure is not limited thereto. The chemical drugs and raw materials used in the following embodiments are all obtained commercially or prepared by recognized preparation methods.

[0056] Example 1

[0057] The preparation of polyamidoxime in the coating agent and the composition of the coating agent include:

[0058] Preparation of polyamidoxime: The polyacrylonitrile solution and hydroxylamine hydrochloride solution were subjected to amidoxime reaction at pH 7.2 and a temperature of 70 °C. After reacting for 16 h, polyamidoxime was prepared, and the prepared polyamidoxime existed in the form of a suspension with a concentration of 1 g / mL.

[0059] Composition of the coating agent: By weight, the coating agent used for coating includes 45 parts of the prepared polyamidoxime, 125 parts of polymethacrylic acid, 18 parts of polyethylene glycol, 20 parts of diglycidyl ether, and 30 parts of polyvinylpyrrolidone.

[0060] Preparation of the pre-coated polyethylene composite adsorbent material by combining polyethylene film material and coating agent, the preparation method includes:

[0061] The polyethylene film material was extruded through a twin-screw extruder or a single-screw extruder, and after being cooled by a cooling roll, a polyethylene substrate material was obtained. The obtained polyethylene substrate material was immersed in a glutaraldehyde solution after being activated by plasma, and then completed the pretreatment after washing with water and drying to obtain a polyethylene substrate.

[0062] The pretreated polyethylene substrate was coated by spraying, and then longitudinally and transversely stretched synchronously. The stretching ratios in the transverse and longitudinal directions were 1.5 and 1.8 respectively, and the temperature of the stretching treatment was 150 °C. Subsequently, heat treatment was carried out at 150 °C for 20 s for shaping to obtain the pre-coated polyethylene composite adsorbent material.

[0063] The composition of the prepared pre-coated polyethylene composite adsorbent material includes an upper surface coating layer with a thickness of 2 μm, an intermediate polyethylene film layer with a thickness of 25 μm, and a lower surface coating layer with a thickness of 1.8 μm.

[0064] Example 2

[0065] Preparation of polyamidoxime in the coating agent and composition of the coating agent, including:

[0066] Preparation of polyamidoxime: The polyacrylonitrile solution and hydroxylamine hydrochloride solution were subjected to amidoxime reaction at pH 6.9 and a temperature of 65 °C. After reacting for 20 h, polyamidoxime was prepared, and the prepared polyamidoxime existed in the form of a slurry with a concentration of 0.5 g / mL.

[0067] Composition of the coating agent: By weight, the coating agent used for coating includes 50 parts of the prepared polyamidoxime, 105 parts of polyacrylic acid, 10 parts of polyethylene oxide, 7 parts of octanediamide methyl ester, and 20 parts of lithium chloride.

[0068] Preparation of the pre-coated polypropylene composite adsorbent material by combining polypropylene film material and coating agent, the preparation method includes:

[0069] The polypropylene film material is extruded by a twin-screw extruder or a single-screw extruder, cooled by a cooling roll and longitudinally stretched to obtain a longitudinally stretched polypropylene base film material, where the longitudinal stretching ratio is 1.8. The obtained longitudinally stretched polypropylene base film material is corona-activated and then immersed in an acetic anhydride solution, and then completed the pretreatment after washing with water and drying to obtain a longitudinally stretched polypropylene base film.

[0070] The pretreated longitudinally stretched polypropylene base film is coated by the method of gravure roll coating, and then transversely stretched, the transverse stretching ratio is 2, the temperature of the stretching treatment is 200 °C, and then heat-treated at 120 °C for 30 s for shaping to obtain a pre-coated polypropylene composite adsorbent material.

[0071] The composition of the prepared pre-coated polypropylene composite adsorbent material includes an upper surface coating layer with a thickness of 1.5 μm, an intermediate polypropylene base film layer with a thickness of 23 μm, and a lower surface coating layer with a thickness of 1.7 μm.

[0072] Comparative Example 1

[0073] The preparation of polyamidoxime in the coating agent and the composition of the coating agent include:

[0074] Preparation of polyamidoxime: The polyacrylonitrile solution and the hydroxylamine hydrochloride solution are subjected to amidoxime reaction under the conditions of pH 7.2 and temperature 70 °C. After reacting for 16 h, polyamidoxime is prepared, and the prepared polyamidoxime exists in the form of a suspension with a concentration of 1 g / L.

[0075] Composition of the coating agent: Calculated by weight, the coating agent used for coating includes 45 parts of the prepared polyamidoxime, 125 parts of polymethacrylic acid, 18 parts of polyethylene glycol, 20 parts of diglycidyl ether, and 30 parts of polyvinylpyrrolidone.

[0076] The preparation method of the pre-coated polyethylene composite adsorbent material jointly prepared by the polyethylene film material and the coating agent includes:

[0077] The polyethylene film material is extruded by a twin-screw extruder or a single-screw extruder, and after being cooled by a cooling roll, a polyethylene sheet material is obtained. The obtained polyethylene sheet material is plasma-activated and then immersed in a glutaraldehyde solution, and then completed the pretreatment after washing with water and drying to obtain a polyethylene sheet.

[0078] First, longitudinal stretching and transverse stretching are carried out synchronously, the transverse and longitudinal stretching ratios are 1.5 and 2 respectively, the temperature of the stretching treatment is 150 °C, and then the pretreated polyethylene sheet is coated by the spraying method, and then heat-treated at 150 °C for 20 s for shaping to obtain a polyethylene composite adsorbent material.

[0079] The composition of the prepared polyethylene composite adsorbent material includes an upper surface coating layer with a thickness of 2 μm, an intermediate polyethylene film layer with a thickness of 25 μm, and a lower surface coating layer with a thickness of 4.8 μm.

[0080] Comparative Example 2

[0081] This comparative example provides a preparation method of an amidoxime-based polyethylene nanofiber membrane, and the preparation method includes:

[0082] (1) Irradiate a polyethylene nanofiber membrane with a porosity of 60% in air at a dose rate of 20 kGy / h, and the absorbed dose is 100 kGy;

[0083] (2) Immerse the irradiated polyethylene nanofiber membrane in a solution containing acrylonitrile and acrylic acid, wherein the volume concentrations of acrylonitrile and acrylic acid are 45% and 15% respectively, and introduce nitrogen, and carry out a grafting reaction in a water bath at 65 °C for 7 h. Wash with DMF and water respectively, and obtain a modified polyethylene nanofiber membrane after vacuum drying;

[0084] (3) Immerse the modified polyethylene nanofiber membrane obtained in step (2) in a methanol / water solution with a volume ratio of 1:1 containing 15 wt% hydroxylamine hydrochloride, and react at 70 °C at pH = 7.0 for 5 h. After the reaction, take out the thin film sample from the solution, wash with water and vacuum dry to obtain the amidoxime-based polyethylene nanofiber membrane.

[0085] Test the adsorption capacity of the pre-coated polyethylene composite adsorbent material obtained in Example 1, the pre-coated polypropylene composite adsorbent material obtained in Example 2, the polyethylene composite adsorbent material obtained in Comparative Example 1, and the amidoxime-based polyethylene nanofiber membrane obtained in Comparative Example 2 under simulated seawater conditions. The specific test process and evaluation results are as follows.

[0086] Preparation process of simulated seawater: Prepare an aqueous solution containing 193 mg of NaHCO 3 , 25.6 g of NaCl, then add 8 mL of a 1000 ppm uranium standard solution to obtain 1 L of an 8 ppm uranium-standard aqueous solution; then drop in a saturated Na 2 CO 3 solution and a 2% HNO 3 solution, and adjust the pH to 8.0 ± 0.1 to obtain uranium-standard simulated seawater.

[0087] The products prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 by alkali activation with 10 mg were respectively used. The products of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 after activation were respectively added to the above-mentioned 1 L of 8 ppm uranium-standard simulated seawater, and adsorption kinetics studies were carried out in a constant-temperature water bath shaker at 25 °C and 100 rpm to test and analyze the uranium concentration. The adsorption performance of uranium was tested using the following formula I. The experiments of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were carried out in parallel three times respectively, and the average values were calculated respectively:

[0088]

[0089] Among them, Q t is the saturated adsorption capacity (mg / g) at adsorption equilibrium, C 0 and C t are the initial uranium concentration (mg / L) and the uranium concentration (g / L) at adsorption equilibrium respectively, V is the volume of the adsorption solution (L), and m is the mass of the adsorbent (g).

[0090] Meanwhile, the regenerability and reusability of the obtained composite adsorbents of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were respectively evaluated, and adsorption-desorption-regeneration cycle tests were continuously carried out on the four of them. The adsorption experimental conditions were to reach adsorption equilibrium in 1 L of 8 ppm uranium-standard simulated seawater; the desorption experimental conditions were to carry out for 30 min in 0.5 mol / L HCl solution; the regeneration experimental conditions were to carry out for 20 min in 5 mmol / L KOH solution, and finally, after washing with water, the adsorption experiment of the next cycle was carried out, and the cycle stabilities of the composite adsorbents of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 after 5 adsorption experiments were tested.

[0091] The mechanical properties of the pre-coated polyethylene composite adsorbent obtained in Example 1, the pre-coated polypropylene composite adsorbent obtained in Example 2, the polyethylene composite adsorbent obtained in Comparative Example 1, and the amidoxime-based polyethylene nanofiber membrane obtained in Comparative Example 2 were respectively tested. The test standards for tensile strength (MPa) and elongation at break (%) both refer to GB / T 1040.3.

[0092] The results are shown in Table 1 below.

[0093] Table 1

[0094]

[0095] As can be seen from the data in Table 1, the adsorption capacity of the pre-coated composite adsorbent material prepared by the preparation method of the present disclosure is about 300 mg / g. After 5 cycle experiments, the adsorption capacity remains above 92.8%, and it has good mechanical properties in terms of tensile strength and elongation at break.

[0096] According to the numerical values of Example 1 and Comparative Example 1, the method of first coating and then stretching can improve the adsorption capacity of the obtained pre-coated composite adsorbent material. This is because by the method of pre-coating and subsequent stretching, while reducing the thickness of the middle polymer thin film layer, the thickness of the upper surface coating layer and the lower surface coating layer can also be reduced, thereby increasing the specific surface area and exposing more adsorption groups. Therefore, in comparison, Example 1 has higher adsorption capacity and better mechanical properties.

[0097] As can be seen from Comparative Example 2, the method of irradiation and grafting reduces the mechanical properties of the obtained amidoxime-based polyethylene nanofiber membrane to a certain extent, causing certain damage to the fibers, resulting in a decrease in both its saturated adsorption capacity and cycle stability; while using the pre-coating method to composite polyamidoxime with the polymer thin film material can not only improve the saturated adsorption capacity and cycle stability of the obtained pre-coated composite adsorbent material in uranium extraction from seawater, but also retain the excellent mechanical properties of the polymer thin film, with higher tensile strength and elongation at break.

[0098] In summary, the present disclosure realizes the one-step forming of the adsorbent material through the pre-coating method, which can reduce the cumbersome subsequent coating process; then subsequent stretching and heat setting treatments are carried out, which can meet the thinning of the functional coating layer, realize the preparation of an ultra-thin coating layer, and at the same time enhance the mechanical properties and thermal stability of the obtained pre-coated composite adsorbent material, which is conducive to the large-scale and engineering preparation of the adsorbent material.

[0099] The above specific embodiments have further elaborated on the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A preparation method of a pre-coated composite adsorbent material, comprising: pre-treating a polymer thin film material to obtain a polymer substrate; coating both surfaces of the polymer substrate with a coating agent to obtain a coated polymer substrate; subjecting the coated polymer substrate to stretching treatment and heat treatment in sequence to finally obtain the pre-coated composite adsorbent material; wherein, by weight parts, the coating agent comprises 40 - 60 parts of polyamidoxime, 50 - 180 parts of hydrophilic polymer material, 8 - 30 parts of plasticizer and 3 - 25 parts of cross-linking agent; the polymer thin film material comprises at least one of polyethylene, polypropylene, polyethylene terephthalate or polyamide; the hydrophilic polymer material is at least one of polyacrylic acid, polyacrylamide or polymethacrylic acid.

2. The method according to claim 1, wherein, the pre-treatment comprises: successively performing extrusion casting, activation treatment to introduce cross-linking groups, water washing and drying on the polymer thin film material; the activation treatment comprises at least one of plasma treatment and corona treatment.

3. The method according to claim 2, wherein, the pre-treatment further comprises: performing longitudinal stretching on the polymer substrate after extrusion casting before the activation treatment.

4. The method according to claim 1, wherein, the conditions of the stretching treatment are: performing longitudinal and transverse stretching at a temperature of 110 - 270 °C, and the stretching ratio is 1.1 - 5 for both.

5. The heat treatment conditions according to the method of claim 1 are: performing a heat treatment reaction at a temperature of 120 - 280 °C for 2 - 60 s.

6. The method according to claim 1, wherein, the plasticizer comprises at least one of glycerol, polyvinyl alcohol, polyethylene glycol, polyoxyethylene or polyacrylamide; the cross-linking agent comprises at least one of glutaraldehyde, acetic anhydride, diglycidyl ether or methyl octanedioimidate.

7. The method according to claim 1, wherein, the coating agent further comprises: a pore-forming agent.

8. A pre-coated composite adsorbent material prepared by using the method according to any one of claims 1 - 7.

9. The pre-coated composite adsorbent material according to claim 8, wherein, the pre-coated composite adsorbent material comprises: a first surface coating layer, a polymer base film layer and a second surface coating layer; wherein, the thickness of the first surface coating layer is 1 - 5 μm; the thickness of the polymer base film layer is 3 - 50 μm; the thickness of the second surface coating layer is 1 - 5 μm.

10. An application of the pre-coated composite adsorbent material according to claim 8 or 9 in uranium extraction from seawater.

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