Open-cell adsorbent prepared by solid particle foam template synergistic chemical foaming and its application in rapid removal of uranium from wastewater

Abstract

The present invention belongs to the field of adsorbents and provides an open-cell adsorbent prepared by using a solid particle foam template in conjunction with chemical foaming, and its application in rapidly removing uranium from wastewater. The invention comprises the following steps: adding soy protein isolate and hydroxyapatite to a solution containing a chemical foaming agent, a polymerization monomer, a crosslinking agent, a thermal initiator, and polyamidooxime, vortexing and mixing, stirring and foaming, to obtain a foam sample with stable solid particles; heating the foam sample with stable solid particles in a water bath at 80°C to 90°C for 25 to 35 minutes to initiate monomer polymerization and thermal decomposition of the chemical foaming agent; after the reaction is completed, drying and removing excess water, to obtain an open-cell adsorbent; the present invention combines the foam template with the chemical foaming method to prepare an open-cell hydrophilic adsorbent functionalized with amidoxime and having a high permeability flux by a more energy-saving and environmentally friendly technology.

Description

Technical Field

[0001] The invention belongs to the field of adsorbents, and particularly relates to an open-pore adsorbent prepared by solid particle foam template coordinated chemical foaming and application of the open-pore adsorbent in rapidly removing uranium from wastewater. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] The use of nuclear energy has effectively alleviated the problem of energy shortage, but the rapid development of the nuclear industry has generated a large amount of radioactive wastewater. Uranium, as one of the main radioactive elements in wastewater, is easily migrated in aqueous media and poses the risk of high radioactivity and toxicity. Therefore, the removal and recovery of radioactive uranium is of great significance to protecting the ecological environment, human health, and promoting the sustainable development of energy. Uranium exhibits different valence states and existence modes in different pH environments, which also poses a considerable challenge to its recovery. Currently, commonly used uranium recovery methods include ion exchange, ultrafiltration, electrochemical method, flocculation method, adsorption method, etc. Among them, adsorption method is considered to be a more environmentally friendly and safe method with convenient operation, low secondary pollution and higher efficiency. The functional groups that can usually play an adsorption role include amino group, phosphate group, amide oxime, etc. Among them, the oxime nitrogen, amino nitrogen and oxime oxygen in the amide oxime (AO) structure can act as electron donors to coordinate with uranyl ions. Therefore, in a complex wastewater environment where multiple ions coexist, amide oxime is considered to be the most effective method for extracting uranyl ions (UO2 2+) is the most effective and chelating functional group. Many researchers have also demonstrated through DFT theoretical calculations, XRD, XPS and other techniques that amidoxime can preferentially interact with uranium ions in a complex environment where multiple ions coexist. Therefore, amidoxime-functionalized materials with multiple active adsorption sites and strong selectivity have been developed one after another. According to the material's existing form, the earliest materials to be studied were fibers and resins. The amidoxime groups were mainly introduced into the fiber and resin matrix through radiation-induced polymerization (RIGP) and atom transfer radical polymerization (ATRP) techniques. However, the structure of such materials is dense and the introduced amidoxime polymer segments are hydrophobic, which hinders the improvement of the overall adsorption capacity of the material. Some workers have also modified amidoxime on materials such as mesoporous silica or inorganic minerals to prepare powder materials, but the recycling of such materials is relatively difficult. In recent years, amidoxime-functionalized thin films and hydrogel materials have attracted people's attention. Due to their hydrophilicity and three-dimensional network, hydrogel materials can attract large amounts of water and allow the amidoxime polymer chains to fully extend, thereby accelerating the migration rate of uranyl ions to the adsorption sites and improving the binding ability of uranium ions with the adsorbent. This can effectively alleviate the problems existing in the current amidoxime-functionalized fiber and powder materials. For example, it has been reported that integrating the hydrophilic substance acrylamide with amidoxime can increase the adsorption capacity of amidoxime polymers and promote binding with uranium ions. However, the uranium adsorption capacity of such macroporous gel materials is usually lower than the maximum theoretical value. This may be because the closed-pore or semi-open-pore structure of the material prevents the AO hydrophobic polymer chains from fully extending, hindering the full contact between uranium ions and functional AO groups. Therefore, in order to enhance the ability of such hydrophilic materials to interact with uranium ions, it is urgent to construct new adsorbents with rich chemical specific sites and highly permeable transport channels. Currently, commonly used methods for constructing high-throughput macroporous materials include freeze-drying, 3D printing, pore-forming agent etching, and emulsion template technology. However, these construction methods are energy-intensive, cumbersome, and subject to significant secondary pollution, making them unsuitable for large-scale production. Therefore, it is urgent to develop a greener and simpler construction method to prepare hydrophilic macroporous amidoximated functional materials with high permeability flux and apply them to the removal and recovery of radioactive uranium in wastewater. Summary of the Invention

[0004] Based on the problems of low mass transfer efficiency of current amidoxime-functionalized hydrophilic macroporous adsorbents and high energy consumption, complicated steps and large secondary pollution in the reported methods for constructing interconnected pore adsorbents, the present invention combines foam templates and chemical foaming methods to prepare amidoxime-functionalized open-pore hydrophilic adsorbents with high permeation flux using a more energy-saving and environmentally friendly technology.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention provides a method for preparing an open-cell adsorbent by using a solid particle foam template in conjunction with chemical foaming, comprising:

[0007] The soy protein isolate and hydroxyapatite are added to a solution containing a chemical foaming agent, a polymerizable monomer, a cross-linking agent, a thermal initiator, and a polyamidooxime, vortexed to mix, and stirred to foam to obtain a foam sample with stable solid particles;

[0008] The solid particle-stabilized foam sample is heated in a water bath at 80° C. to 90° C. for 25 to 35 minutes to initiate monomer polymerization and thermal decomposition of the chemical foaming agent. After the reaction is complete, the sample is dried to obtain an open-cell adsorbent.

[0009] The mass ratio of soy protein isolate, hydroxyapatite, chemical foaming agent, polymerization monomer, cross-linking agent, thermal initiator and polyamidooxime is 0.1-0.2: 0.2-0.4: 0.1-0.2: 0.18-0.36: 0.75-1.5: 0.020-0.040: 0.75-1.5.

[0010] The present invention adopts a method that combines foam templates and chemical foaming. The foam is a gas-liquid dispersion system, with the liquid as the continuous phase and the gas as the dispersed phase. This method can introduce polymerized monomers into the liquid phase to form the skeleton of the porous material, and the pore structure mainly depends on the size and shape of the foam bubbles. There is no need to remove the dispersion medium or pore-forming agent and other subsequent steps, which is a more energy-saving and environmentally friendly method. However, there are relatively few studies on the preparation of materials using foam systems as templates. The main reason is that foam is a thermodynamically unstable gas-liquid dispersion system, and the stability of the foam is difficult to maintain during the formation of the material skeleton, which makes it impossible to play the role of the foam template. Compared with foams stabilized by traditional surfactants, foams stabilized by solid particles can provide a more stable elastic barrier by effectively "irreversibly adsorbing" at the gas-liquid interface, thereby effectively preventing bubble shrinkage and gas diffusion. Selecting a suitable particle stabilizer can make the foam stabilized by solid particles have excellent stability, making it possible to use it to prepare foam materials. The secondary foaming of chemical reagents is beneficial to increase the porosity of the material, expose more active adsorption sites and increase the contact speed with the target substance.

[0011] In some embodiments, the chemical foaming agent is sodium bicarbonate.

[0012] In some embodiments, the polymerizable monomer is acrylamide.

[0013] In some embodiments, the cross-linking agent is N,N′-methylenebisacrylamide.

[0014] In some embodiments, the thermal initiator is azobisisobutylamidine hydrochloride.

[0015] In some embodiments, the specific conditions for the stirring and foaming are 18000 r / min to 22000 r / min, and the foaming time is 0.8 to 1.2 min.

[0016] In some embodiments, the synthesis method of the polyamidoxime includes: dissolving NH2OH·HCl in DMF and stirring at 45°C to 50°C for 30 to 40 minutes; adding Na2CO3 and NaOH while continuing to stir, and reacting the mixture at 45°C to 50°C for 3 to 4 hours; adding PAN to the reacted solution and reacting at 65°C to 70°C for 24 to 32 hours; then, adding Na2CO3 and NaOH and continuing to react at 65°C to 70°C for 24 to 32 hours; then, centrifuging and collecting the supernatant and dripping it into water; collecting the obtained white flocs and drying them to obtain.

[0017] More specifically, soy protein isolate (SPI) and hydroxyapatite (HAP) are added to a solution containing sodium bicarbonate, acrylamide (AAm), a crosslinker N,N′-methylenebisacrylamide (MBA), and polyamidooxime (PAO). Under high-speed stirring, the amphiphilic soy protein isolate particles stabilize the gas-liquid interface to obtain a solid particle-stabilized foam. The foam sample is then heated at 80°C. While the monomers polymerize to form the material skeleton, the sodium bicarbonate in the liquid phase thermally decomposes to produce carbon dioxide for secondary foaming. In this way, during the process of monomer polymerization to obtain a solid skeleton, both the particle-stabilized foam and the bubbles produced by the carbon dioxide can achieve the purpose of pore formation, thereby obtaining a material with open and interconnected pore structures. Hydroxyapatite also serves as part of the material skeleton, enhancing the material's mechanical strength while working together with PAO to perform adsorption functions. This improves the problem of difficult recycling of granular materials and the low theoretical adsorption capacity of amidoxime block materials.

[0018] The second aspect of the present invention provides an open-pore adsorbent prepared by the above method.

[0019] The third aspect of the present invention provides the use of the above-mentioned open-pore adsorbent in the rapid removal of uranium from wastewater.

[0020] In some embodiments, the wastewater has a pH value of 2-8.

[0021] Beneficial effects of the present invention

[0022] (1) Based on the structure-activity relationship, this invention innovatively utilizes an environmentally friendly and simple solid particle-stabilized foam template in conjunction with a chemical foaming method to prepare an adsorbent with an interconnected open-pore structure, thus improving the structural construction problems of current hydrophilic materials. The introduction of a hydrophilic open-pore structure allows the material to fully expose adsorption sites, allowing HAP and PAO to fully contact uranium ions, thereby improving the material's adsorption rate and adsorption capacity.

[0023] (2) The amphiphilic particles SPI used in the present invention are low-cost and simple to synthesize. HAP, as a hydrophilic functional mineral particle, can exert its adsorption function while reinforcing the skeleton of the material. Together with the hydrophilic monomer, it imparts hydrophilicity to the material, thereby accelerating the binding process between the adsorption active sites and the uranyl ions.

[0024] (3) The preparation method of the present invention is simple, practical, and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 Schematic diagram of the preparation process of the hydrophilic open-porous structure adsorbent in the present invention;

[0027] Figure 2 The morphological characterization results of the amphiphilic particles SPI and the functional adsorption particles HAP in Example 1; wherein A is the TEM image of the amphiphilic particles SPI; B is the particle size distribution diagram of the amphiphilic particles SPI; C is the isoelectric point potential diagram of the amphiphilic particles SPI; D is the TEM image of the functional adsorption particles HAP; E is the particle size distribution diagram of the functional adsorption particles HAP; F is the isoelectric point potential diagram of the functional adsorption particles HAP; G is the surface activity results of the amphiphilic particles SPI and the functional adsorption particles HAP; H is the solid-liquid-gas three-phase contact angle characterization results of the amphiphilic particles SPI and the functional adsorption particles HAP;

[0028] Figure 3 : is the characterization result of the functional polymer; A is a schematic diagram of the PAN-PAO reaction process; B is the Fourier transform infrared spectrum of the functional polymer;

[0029] Figure 4 Properties of solid particle-stabilized foam samples constructed with amphiphilic SPI particles. Figure A is a physical image, with a and a1 representing SPI concentrations of 0.03 g / g, b and b1 representing SPI concentrations of 0.11 g / g, and c and c1 representing SPI concentrations of 0.17 g / g. Figure a represents an unfoamed sample, a1 represents a foamed sample, and similarly for b and c. Figure B is a micrograph, with a representing SPI concentrations of 0.03 g / g, b representing SPI concentrations of 0.11 g / g, and c representing SPI concentrations of 0.17 g / g. Figure C shows rheological characterization, with a representing a stress-strain sweep, b representing a frequency sweep, and c representing steady-state shear.

[0030] Figure 5 Rheological characterization of foams prepared for functional particles HAP and functional polymer PAO;

[0031] Figure 6 This is a study on the stability of foam samples, where A is a physical image, a1, a2, and a3 are unfoamed samples, b1, b2, and b3 are foamed samples, and c1, c2, and c3 are foamed samples after being placed at room temperature for 4 hours; B is a microscopic photograph of the foamed sample, and C is a microscopic photograph of the sample placed at room temperature for 4 hours; the sample compositions are a1: SPI-0.15 g / g, a2: SPI-0.05 g / g, HAP-0.1 g / g, a3: SPI-0.05 g / g, HAP-0.1 g / g, PAO-3 wt %, and the compositions of b1 and c1 samples are the same as a1, the compositions of b2 and c2 samples are the same as a2, and the compositions of b3 and c3 samples are the same as a3, that is, samples with the same Arabic numeral subscripts have the same composition;

[0032] Figure 7 The following are photos of samples placed at 80°C for 30 minutes and optical microscope images of the samples. a, b, and c are foamed samples, with compositions of a: SPI-0.15 g / g, b: SPI-0.05 g / g, HAP-0.1 g / g, and c: SPI-0.05 g / g, HAP-0.1 g / g, PAO-3 wt%.

[0033] Figure 8 The figure shows the physical image of SPI / HAP / PAO / NaHCO3 sample and the water absorption curve of the sample within 30 minutes.

[0034] Figure 9 SEM images of samples obtained by chemical foaming, particle-stabilized foam template, and chemical foaming combined with particle-stabilized foam template (sample composition: a: HAP / PAO / NaHCO3, b: SPI, c: SPI / HAP / PAO / NaHCO3);

[0035] Figure 10 Mercury intrusion test results for samples obtained from foam templates and chemical foaming synergistic foam templates;

[0036] Figure 11 a is the adsorption of uranyl ions by SPI / HAP / PAO / NaHCO3 materials at different pH values, b is the Zeta potential of SPI / HAP / PAO / NaHCO3 materials at different pH values, and c is a comparison of the adsorption of uranyl ions by materials constructed with different compositions and foaming methods.

[0037] Figure 12 Dynamics of open-cell adsorbents constructed by chemical foaming and particle stabilization foam templates;

[0038] Figure 13The adsorption isotherm of open-cell adsorbent constructed by chemical foaming and particle stabilization foam template method and model fitting were performed;

[0039] Figure 14 The selective adsorption capacity and recycling of open-cell adsorbents constructed by chemical foaming and particle stabilization foam templates;

[0040] Figure 15 XPS (a), XRD (b), FTIR (c) spectra of the samples before and after adsorption, as well as high-resolution XPS spectra of N / O / Ca / P elements. DETAILED DESCRIPTION

[0041] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0042] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0043] Example 1 Synthesis of polyamidoximes

[0044] Dissolve 4.17 g of NH₂OH·HCl in 45 mL of DMF and stir vigorously at 45°C for 30 minutes. Subsequently, add 2.87 g of Na₂CO₃ and 0.72 g of NaOH while stirring. The mixture is reacted at 45°C for 3.0 hours. To the resulting solution, add 3.18 g of PAN and react at 65°C for 24 hours. Then, add 1.43 g of Na₂CO₃ and 0.36 g of NaOH, and continue reacting at 65°C for an additional 24 hours. The supernatant is then centrifuged and dripped into 500 mL of pure water. Finally, collect the resulting white flocculent and dry it to obtain PAO.

[0045] Example 2 Amphiphilic Particles SPI Stabilized Foam

[0046] Dissolve a certain amount of N,N′-methylenebisacrylamide (MBA) in water at 80°C to obtain a 1% MBA aqueous solution for later use. Place 1.5g of this 1% MBA solution in a 7mL plastic centrifuge tube. Dissolve 0.18g of the polymerization monomer AAm and 0.020g of the thermal initiator azobisisobutylamidine hydrochloride (AIBA) in the MBA solution. Disperse 0.3g of soy protein isolate particles in the aqueous solution and vortex for 30 seconds to evenly disperse them. Use a high-speed disperser to foam the sample at a constant speed of 20,000 rpm for 1 minute to obtain a solid particle-stabilized foam sample stabilized by amphiphilic particles. The preparation method for foams stabilized by amphiphilic particles SPI at different concentrations is the same as the above steps.

[0047] Example 3: Foam stabilized by solid particles containing HAP and PAO

[0048] Preparation of a foam containing adsorbent HAP and PAO: PAO was added to a 0.15 mol / L sodium hydroxide solution and heated at 80°C for 30 minutes to dissolve, yielding a 6% (mass fraction) PAO precursor solution. 0.75 g of the dissolved PAO solution was mixed with 0.75 g of an aqueous MBA solution in a 7 mL plastic centrifuge tube. 0.18 g of the polymerization monomer AAm and 0.020 g of azobisisobutylamidine hydrochloride (AIBA) as a thermal initiator were added to the mixture. 0.1 g of soy protein isolate and 0.2 g of hydroxyapatite particles were dispersed in the aqueous solution and vortexed for 30 seconds to achieve uniform dispersion. The sample was foamed using a high-speed disperser at a constant speed of 20,000 rpm for 1 minute to yield a solid particle-stabilized foam containing HAP and PAO stabilized by amphiphilic particles.

[0049] Example 4: Solid particle-stabilized foam containing HAP, PAO, and a chemical blowing agent

[0050] Preparation of a foam sample containing the chemical foaming agent sodium bicarbonate: 0.75g of PAO solution and 0.75g of MBA aqueous solution were mixed in a 7mL plastic centrifuge tube, followed by the addition of 0.1g of sodium bicarbonate to dissolve. 0.18g of the polymerization monomer AAm and 0.020g of the thermal initiator azobisisobutylamidine hydrochloride (AIBA) were added to the mixed solution. 0.1g of soy protein isolate and 0.2g of hydroxyapatite particles were dispersed in the aqueous solution and vortexed for 30 seconds to achieve uniform dispersion. The sample was foamed using a high-speed disperser at a constant speed of 20,000 rpm for 1 minute to obtain a foam sample containing HAP and PAO stabilized by amphiphilic particles and the chemical foaming agent.

[0051] Example 5 Preparation of adsorbent sample

[0052] The foam samples obtained in Examples 2-4 were placed in an 80°C waterbath and heated for 30 minutes. This heat initiated polymerization of the AAm monomers and simultaneously induced the thermal decomposition of sodium bicarbonate to produce carbon dioxide. This polymerization formed the skeleton while also achieving secondary pore formation. The post-polymerization samples were oven-dried to remove excess moisture, yielding adsorbent samples for subsequent characterization and adsorption experiments.

[0053] Experimental Example 1 Characterization of Particles

[0054] The microstructure, isoelectric point, surface activity, and solid-liquid-gas contact angle of the two particles used were characterized. Figure 2 .

[0055] pass Figure 2 Particle size statistics indicate that the amphiphilic SPI particles are irregularly spherical with a size of approximately 10 nm, while the functional adsorbent HAP particles are rod-shaped with a size of approximately 80 nm. Both have acidic isoelectric points. Surface tension measurements revealed that SPI has the ability to reduce surface tension, while HAP has virtually no surface activity. Three-phase contact angle measurements revealed that the contact angle of SPI with liquid and air is approximately 90°, indicating similar wettability with both water and air phases, suggesting potential for foam stabilization. Furthermore, SPI can adjust the contact angle of the hydrophilic HAP particles with both air and liquid.

[0056] Experimental Example 2 Characterization of functional polymers

[0057] Related results are shown in the PAN-PAO reaction process and Fourier transform infrared spectrum (FTIR) ( Figure 3 ).

[0058] Depend on Figure 3 It can be seen that the reacted substance has a wavelength of 2242 cm -1 The characteristic peak of cyano group disappears at 1664cm -1 , 964cm -1 The appearance of stretching vibration peaks of -C=N- and -NO- indicates that this method of preparing functional polymer PAO is feasible.

[0059] Experimental Example 3 Preparation of solid particle stabilized foam

[0060] First, the properties of the foam samples stabilized by solid particles constructed only by amphiphilic particles were investigated. Figure 4 , which are the actual pictures, microscope photos and rheological characterization of the samples of foam stabilized by solid particles with SPI concentrations of 0.03g / g, 0.11g / g and 0.17g / g respectively.

[0061] It can be seen that particle-stabilized foams can be formed at all three concentrations. Furthermore, stress-strain sweeps show that the yield stress of the foam increases with increasing particle dosage, enhancing its ability to resist external forces. Frequency sweeps reveal that the storage modulus (G') of all three samples is greater than the loss modulus (G"), indicating a solid-like state. Steady-state shear analysis of sample viscosity reveals that increasing the amount of amphiphilic particles increases sample viscosity, thereby slowing down drainage and improving foam stability.

[0062] The present invention fixes the amount of amphiphilic particles, adds functional particles HAP and functional polymer PAO to the sample to prepare foam, and conducts rheological characterization on the sample. The relevant results are shown in Figure 5 (Stress-strain sweep, frequency sweep, and steady-state shear of SPI, SPI / HAP, and SPI / HAP / PAO foam samples) The present invention analyzed the effects of the amphiphilic particles, finding that the addition of functional mineral particles and polymers, when used at a fixed dosage, enhanced the yield stress and viscosity of the samples, thereby increasing the stability of the foam samples.

[0063] Since the stability of foam has a great influence on the application of foam template construction materials, the present invention has investigated the stability of foam samples that will be used to prepare macroporous materials. The relevant results are shown in Figure 6 : Sample physical pictures (a, b, c are respectively the samples before foaming, samples after foaming and foam samples after being placed at room temperature for 4 hours, and the sample compositions are respectively a1: SPI-0.15g / g, a2: SPI-0.05g / g, HAP-0.1g / g, a3: SPI-0.05g / g, HAP-0.1g / g, PAO-3wt%), microscope pictures of the samples after foaming and samples placed at room temperature for 4 hours. It can be seen from the sample physical pictures and microscope pictures that the prepared foam samples have a certain stability at room temperature. Since the foam will be placed at 80°C to initiate monomer polymerization in the later stage, the present invention has conducted high temperature stability tests on these three samples, and the results are shown in FIG. Figure 7 : The actual picture and microscope picture of the sample placed at high temperature for 30 minutes show that the sample can still maintain the overall structure of the foam at 80°C, which can meet the conditions for use as a template in the future.

[0064] Experimental Example 4 Preparation and characterization of adsorbent

[0065] The stable foam obtained above is heated to initiate polymerization of the liquid monomer, and excess water is dried to obtain a solid material. Figure 8The following is a picture of the sample and its water absorption. It can absorb up to 20 times its own weight of water within 1 minute. It has the ability to absorb water quickly, which is conducive to the rapid adsorption of target substances in aqueous solution. In order to explore the effect of the double foaming method on the pore structure, the present invention used SEM to observe the pore structure of samples obtained by different foaming methods. Figure 9 : Samples obtained by chemical foaming, particle-stabilized foam template, and chemical foaming with particle-stabilized foam template (the sample compositions are HAP / PAO / NaHCO3, SPI, SPI / HAP / PAO / NaHCO3, respectively). It can be seen that only chemical foaming can obtain a closed-cell structure, while the closed cells and open cells obtained by the foam template coexist, with most of them being closed cells. When the two foaming methods are combined, the skeleton presents an interconnected open-cell structure, which is conducive to fully exposing active sites, accelerating the mass transfer process, and effectively combining with the target substance. The samples obtained by the foam template and the chemical foaming with foam template were characterized by mercury intrusion experiments. The pore size distribution of the samples obtained by the two foaming methods is relatively concentrated, and both are large pores of 200-300μm. Compared with the material obtained by using only the foam template, the porosity of the material is improved after the two foaming methods are combined, which can reach 85%. The relevant results are shown in Figure 10 .

[0066] Experimental Example 5: Conducting the adsorption experiment

[0067] Since the existence form of uranyl ions is highly dependent on the environmental pH, the effect of pH on the adsorption capacity of the material was first explored. 0.01g of adsorbent was placed in 5mL of 85ppm uranium solution and stirred at 200r / min (all adsorption experiments were fixed at this speed) for 8h. By testing the uranium concentration after adsorption, it was found that the adsorption capacity was stronger under acidic conditions. The Zeta potential of the material was measured and it was found that the material was negatively charged in a wide pH range. Therefore, the present invention speculates that the reason why the material has better adsorption capacity under acidic conditions is that the uranium ions are positively charged under acidic conditions, and there is electrostatic attraction between them and the negatively charged adsorbent, which is conducive to their adsorption under acidic conditions. The present invention compared the adsorption capacity of adsorbents obtained with different material compositions and foaming methods (50mL 280ppm solution, 0.02g adsorbent, adsorption 8h), and concluded that SPI has a certain adsorption capacity. The addition of HAP and PAO enhanced the overall adsorption capacity of the material. After adding sodium bicarbonate for foaming, due to the presence of the open-pore structure, the exposure of the adsorption site increased, and the adsorption capacity was further improved. Related results are shown in Figure 11 : The adsorption of uranyl ions by materials at different pH values, the Zeta potential of materials at different pH values, and the comparison of the adsorption of uranyl ions by materials constructed with different compositions and foaming methods.

[0068] Table 1

[0069]

[0070]

[0071] The present invention uses an open-cell adsorbent constructed by a foam template method with chemical foaming and particle stabilization as a model, and investigates the adsorption process of adsorption kinetics (100 mL of 85 ppm solution, 0.035 g of adsorbent adsorbed for 8 h), adsorption isotherms (50 mL of uranium-containing solution with different initial concentrations, 0.02 g of adsorbent adsorbed for 4 h, with initial concentrations of 56, 112.8, 225.6, 282, 470, 570, and 800 ppm, respectively), and adsorption thermodynamics (50 mL of 300 ppm uranium-containing solution, 0.02 g of adsorbent adsorbed for 4 h), and performs relevant model fitting. Figure 12 (Kinetic process of adsorbent) and Table 1 (Kinetic model fitting) show that the material can reach adsorption equilibrium within 4 h, and it can be seen from the model fitting that the R 2 The larger the value, the better the fitting degree, indicating that the adsorption process is related to the concentration of both the adsorbent and the adsorbent phase. In addition, the fitting line passes through the origin from the intragranular diffusion model, indicating that the internal diffusion of uranium ions is the main process controlling the adsorption rate. The adsorption isotherm was examined and the model was fitted ( Figure 13 ), and found that it is more consistent with the Langmuir model, indicating that the process is monolayer adsorption, and the adsorption capacity can be as high as 1203 mg / g. The present invention also investigates the adsorption thermodynamics. At 298K, the Gibbs free energy ΔG of the adsorption process is <0, and as the temperature increases, the ΔG becomes smaller, indicating that the process is spontaneous, and increasing the temperature is conducive to the development of the adsorption process. The relevant results are shown in Table 2. The present invention investigates the selective adsorption capacity of the adsorbent (50mL of solution containing different initial metal ion concentrations, 0.02g of adsorbent adsorbed for 4h) and the recycling use (50mL of 50ppm uranium-containing solution, 0.02g of adsorbent adsorbed for 4h), and the results are shown in Table 2. Figure 14 When multiple ions such as monovalent and divalent ions coexist, the material can still efficiently and specifically adsorb uranyl ions, and the adsorption capacity can still be maintained after 4 cycles of adsorption-desorption, indicating that the material has good selective adsorption capacity and recyclability.

[0072] Table 2

[0073]

[0074] Experimental Example 6 Investigation of adsorption mechanism

[0075] Related results can be found in Figure 15: XPS, XRD, FTIR spectra of samples before and after adsorption and peak fitting of high-resolution XPS spectra of N / O / Ca / P elements.

[0076] The spectra obtained by XPS peak fitting show that the N / O / Ca / P elements all move to high binding energy positions, indicating that the amino nitrogen, oxime nitrogen and oxime oxygen on the functional polymer PAO can act as electron-donating groups to bind to the central uranium element of the uranyl ion. The Ca in the functional particle HAP 2+ PO4 2+ The group also participates in the capture process of uranium ions and forms a complex. Through infrared characterization of the present invention, it can be seen that the characteristic vibration peak of uranium and oxygen appears in the material after adsorption, which also shows that the material has captured uranium.

[0077] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing an open-cell adsorbent by using a solid particle foam template in conjunction with chemical foaming, characterized in that: include: The soy protein isolate and hydroxyapatite are added to a solution containing a chemical foaming agent, a polymerizable monomer, a cross-linking agent, a thermal initiator, and a polyamidooxime, vortexed to mix, and stirred to foam to obtain a foam sample with stable solid particles; The solid particle-stabilized foam sample is heated in a water bath at 80° C. to 90° C. for 25 to 35 minutes to initiate monomer polymerization and thermal decomposition of the chemical foaming agent. After the reaction is complete, the sample is dried to obtain an open-cell adsorbent. The mass ratio of soy protein isolate, hydroxyapatite, chemical foaming agent, polymerization monomer, cross-linking agent, thermal initiator and polyamidooxime is 0.1-0.2: 0.2-0.4: 0.1-0.2: 0.18-0.36: 0.75-1.5: 0.020-0.040: 0.75-1.5; The chemical foaming agent is sodium bicarbonate; the specific conditions for the stirring and foaming are 18000 r / min~22000 r / min, and the foaming time is 0.8~1.2 min.

2. The method for preparing an open-cell adsorbent by using a solid particle foam template in synergistic chemical foaming as claimed in claim 1, characterized in that: The polymerizable monomer is acrylamide.

3. The method for preparing an open-cell adsorbent by using a solid particle foam template in synergistic chemical foaming as claimed in claim 1, characterized in that: The cross-linking agent is N,N'-methylenebisacrylamide.

4. The method for preparing an open-cell adsorbent by using a solid particle foam template in synergistic chemical foaming as claimed in claim 1, wherein: The thermal initiator is azobisisobutylamidine hydrochloride.

5. The method for preparing an open-cell adsorbent by using a solid particle foam template in synergistic chemical foaming as claimed in claim 1, wherein: The synthesis method of the polyamidoximate comprises: dissolving NH2OH•HCl in DMF, stirring at 45°C-50°C for 30-40 minutes; adding Na2CO3 and NaOH while continuing to stir, reacting the mixture at 45°C-50°C for 3-4 hours, adding PAN to the reaction solution, reacting at 65°C-70°C for 24-32 hours, then adding Na2CO3 and NaOH, and continuing to react at 65°C-70°C for 24-32 hours; then, collecting the supernatant by centrifugation and dripping it into water; collecting the obtained white flocs and drying them to obtain the product.

6. An open-pore adsorbent prepared by the method according to any one of claims 1 to 5.

7. Use of the open-pore adsorbent according to claim 6 in the rapid removal of uranium from wastewater.

8. The use according to claim 7, characterized in that The pH value of the wastewater is 2-8.

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