Three-dimensional multi-level porous phosphorylated chitosan / microalgae-based aerogel as well as preparation method and application thereof

Abstract

The application provides a three-dimensional multi-stage hole phosphonated chitosan / microalgae-based aerogel and a preparation method and application thereof, and belongs to the technical field of aerogel preparation. The three-dimensional multi-stage hole phosphonated chitosan / microalgae-based aerogel (aCSP / CP) is prepared by taking chitosan (CS), phosphonated chitosan (CSP) and chlorella pyrenoidosa powder (CP) as raw materials. The selectivity of CP to U(VI) is low, but the total ion adsorption capacity is higher, and more coexisting ions can be adsorbed. The selectivity of CSP to U(VI) is greatly improved. The high affinity and high selectivity between the phosphorus functional groups in CSP and U(VI) can improve the selective adsorption of U(VI). In the application, CP and CSP synergistically act together to realize the high selective adsorption of U(VI).

Description

Technical Field

[0001] This invention relates to the field of aerogel preparation technology, and in particular to a three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel, its preparation method, and its application. Background Technology

[0002] Uranium is an important raw material for the nuclear industry. In order to cope with the dual pressures of environmental problems and uranium resource shortage, it is urgent to properly treat acidic uranium-containing wastewater from uranium mining and metallurgy, and to achieve highly selective separation and recovery of uranium. This will not only improve the comprehensive utilization rate of uranium resources and alleviate the shortage of uranium resources, but also reduce the harm of radioactive pollution to the environment and protect human health and ecological security.

[0003] Uranium mining and metallurgical acidic uranium-containing wastewater has a complex composition, containing not only radioactive substances such as uranium, strontium, and cerium, but also metallic ions such as calcium, magnesium, iron, aluminum, manganese, cobalt, and nickel. Conventional treatment methods have low selectivity for uranium separation, making it difficult to separate uranium from coexisting ions and achieve uranium recovery. Therefore, selective enrichment of uranium has become a research challenge. Adsorption methods, due to their high efficiency, low cost, low emissions, ease of operation, and high enrichment factor, have long been considered one of the most effective methods for uranium enrichment and separation. Currently, scholars both domestically and internationally have reported some uranium-selective adsorbents; however, the raw materials used are carbon nanomaterials such as graphene oxide, which also suffer from poor selective adsorption performance. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel, its preparation method, and its applications. The three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel prepared by this invention achieves highly selective adsorption of U(VI).

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogels, comprising the following steps:

[0007] Chitosan is mixed with a solvent to obtain chitosan sol;

[0008] Phosphorylated chitosan was mixed with water to obtain a phosphorylated chitosan solution;

[0009] The chitosan sol was mixed with the phosphorylated chitosan solution and then mixed with Chlorella pyrenoidosa powder and a foaming agent to obtain phosphorylated chitosan-based microalgae gel.

[0010] The phosphorylated chitosan-based microalgae gel was freeze-dried to obtain the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel.

[0011] Preferably, the mass ratio of chitosan in the chitosan sol to phosphorylated chitosan in the phosphorylated chitosan solution is 0.275–0.825: 0.173–0.346.

[0012] Preferably, the mass ratio of chitosan to Chlorella powder in the chitosan sol is 0.275–0.825:0.1–0.2.

[0013] Preferably, the foaming agent is an aqueous solution of NH4HCO3 or an aqueous solution of sodium dodecyl sulfate.

[0014] Preferably, the ratio of chitosan to foaming agent in the chitosan sol is 0.275-0.825g:1-1.5mL, and the volume fraction of the foaming agent is 10%.

[0015] Preferably, the freeze-drying temperature is -80 to -90°C and the time is 10 to 15 hours.

[0016] Preferably, the freeze-drying process further includes thawing the resulting dried material with anhydrous ethanol and then extracting the water.

[0017] Preferably, the degree of deacetylation of chitosan in the chitosan sol is ≥95%, and the viscosity is 100-400 mP·s.

[0018] The present invention also provides a three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel prepared by the preparation method described above, wherein the porosity of the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel is 80% to 85%.

[0019] This invention also provides the application of the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel described above in the field of uranium adsorption.

[0020] This invention provides a method for preparing a three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel, comprising the following steps: mixing chitosan with a solvent to obtain a chitosan sol; mixing phosphorylated chitosan with water to obtain a phosphorylated chitosan solution; mixing the chitosan sol with the phosphorylated chitosan solution and then with Chlorella vulgaris powder, adding a foaming agent to obtain a phosphorylated chitosan-based microalgae gel; and freeze-drying the phosphorylated chitosan-based microalgae gel to obtain the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel.

[0021] This invention prepares a three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel (aCSP / CP) using chitosan (CS), phosphorylated chitosan (CSP), and Chlorella vulgaris powder (CP) as raw materials. CP exhibits low selectivity for U(VI) but possesses a higher total ion adsorption capacity, enabling the adsorption of more coexisting ions. CSP significantly improves the selectivity for U(VI), as the phosphorus functional groups in CSP have high affinity and high selectivity for U(VI), thereby enhancing the selective adsorption of U(VI). In this invention, CP and CSP work synergistically to achieve highly selective adsorption of U(VI). Data from the examples show that the aCSP / CP prepared in this invention has a selectivity of 80.53% for U(VI) and a maximum adsorption capacity of 1393.338 mg / g for U(VI).

[0022] This invention also provides the application of the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel described above in the field of uranium adsorption. In this invention, the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel not only has a large adsorption capacity for U(VI), but also maintains an adsorption capacity of over 18 mg / g for U(VI) after 5 cycles, and is easily recyclable with a resolution rate of 73.51%. Attached Figure Description

[0023] Figure 1 SEM image of aCSP / CP;

[0024] Figure 2 (a) The adsorption capacity of aCSP / CP and aCS / CP for U(VI) in the nine-element solution, and (b) The effect of competing ions on the adsorption of U(VI) by aCSP / CP in the binary solution;

[0025] Figure 3 The effect of pH on the adsorption of U(VI) by aCSP / CP and aCS / CP;

[0026] Figure 4 NO3 - Effect on the adsorption of U(VI) by aCSP / CP;

[0027] Figure 5 The fitting plot of the adsorption kinetics of U(VI) on aCSP / CP;

[0028] Figure 6 Fitting plot of the U(VI) adsorption isotherm for aCSP / CP;

[0029] Figure 7 The recycling performance curve of aCSP / CP is shown. Detailed Implementation

[0030] This invention provides a method for preparing three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel, comprising the following steps;

[0031] Chitosan is mixed with a solvent to obtain chitosan sol;

[0032] Phosphorylated chitosan was mixed with water to obtain a phosphorylated chitosan solution;

[0033] The chitosan sol was mixed with the phosphorylated chitosan solution and then mixed with Chlorella pyrenoidosa powder and a foaming agent to obtain phosphorylated chitosan-based microalgae gel.

[0034] The phosphorylated chitosan-based microalgae gel was freeze-dried to obtain the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel.

[0035] Unless otherwise specified, all raw materials used in this invention are commercially available products in the field.

[0036] This invention involves mixing chitosan with a solvent to obtain a chitosan sol.

[0037] In this invention, the degree of deacetylation of chitosan in the chitosan sol is preferably ≥95%, and the viscosity of the chitosan sol is preferably 100-400 mP·s.

[0038] In this invention, the solvent is preferably an aqueous solution of acetic acid. This invention does not impose any particular limitation on the amount or concentration of the aqueous solution of acetic acid. In a specific embodiment of this invention, preferably, 0.2750–0.8250 g of chitosan is dispersed in 4.00–4.50 mL of an aqueous solution of acetic acid and stirred to obtain the chitosan sol. The volume fraction of acetic acid in the aqueous solution of acetic acid is preferably 0.5–2%. This invention does not impose any particular limitation on the specific stirring parameters; methods well known to those skilled in the art can be used.

[0039] This invention involves mixing phosphorylated chitosan with water to obtain a phosphorylated chitosan solution.

[0040] In this invention, 0.1730–0.3460 g of phosphorylated chitosan is preferably dissolved in 4.00–4.50 mL of deionized water to obtain the phosphorylated chitosan solution. This invention does not impose any specific limitations on the mixing parameters; methods well-known to those skilled in the art can be used.

[0041] In this invention, the phosphorylated chitosan is preferably prepared by a method comprising the following steps: dispersing chitosan in methanesulfonic acid, then adding P2O5, bathing in an ice-water mixture for one hour, manually stirring once every 5 minutes, then washing with diethyl ether, acetone and methanol three times each, and freeze-drying the resulting solid material at low temperature to obtain the phosphorylated chitosan.

[0042] In this invention, the preferred ratio of chitosan, methanesulfonic acid, and P2O5 is 1g:7mL:1g. Preferably, the chitosan is dispersed in methanesulfonic acid in multiple fractions, and the number of fractions is preferably ≥3.

[0043] After obtaining chitosan sol and phosphorylated chitosan solution, the present invention mixes the chitosan sol and phosphorylated chitosan solution and then mixes them with Chlorella pulveratum powder and foaming agent to obtain phosphorylated chitosan-based microalgae gel.

[0044] In this invention, the mass ratio of chitosan in the chitosan sol to phosphorylated chitosan in the phosphorylated chitosan solution is preferably 0.275-0.825:0.173-0.346, more preferably 0.825:0.173.

[0045] In this invention, the mass ratio of chitosan to Chlorella powder in the chitosan sol is preferably 0.275-0.825:0.1-0.2, more preferably 0.825:0.2.

[0046] In this invention, the protein-core Chlorella powder has low selectivity for U(VI) but higher total ion adsorption capacity, enabling it to adsorb more coexisting ions.

[0047] In this invention, the foaming agent is preferably an aqueous solution of NH4HCO3 or an aqueous solution of sodium dodecyl sulfate, and the foaming agent serves to create pores.

[0048] In this invention, the preferred ratio of chitosan to foaming agent in the chitosan sol is 0.275-0.825g:1-1.5mL, and the preferred volume fraction of the foaming agent is 10%.

[0049] In this invention, the preferred order of adding the chitosan sol and phosphorylated chitosan solution, followed by mixing with Chlorella nucleatum powder and a foaming agent, is as follows: The chitosan sol and phosphorylated chitosan solution are mixed, then the Chlorella nucleatum powder is incorporated, stirred, and the foaming agent is added. The mixture is stirred for 2-5 minutes to obtain the phosphorylated chitosan-based microalgae gel. This invention does not impose specific limitations on the stirring parameters; methods well-known to those skilled in the art can be used.

[0050] After obtaining the phosphorylated chitosan-based microalgae gel, the present invention freeze-dries the phosphorylated chitosan-based microalgae gel to obtain the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel.

[0051] In this invention, the freeze-drying temperature is preferably -80 to -90°C, more preferably -85.8°C, and the time is preferably 10 to 15 hours, more preferably 12 hours.

[0052] In this invention, the freeze-drying process further includes thawing the resulting dried material with anhydrous ethanol and then extracting the water.

[0053] In this invention, it is preferable to extract water from the dried material by mixing it with anhydrous ethanol, and the mixing is preferably performed ≥2 times. In this invention, the first mixing with anhydrous ethanol serves to thaw the material, and the second mixing serves to extract water.

[0054] In this invention, the preferred ratio of chitosan to anhydrous ethanol in the chitosan sol is 0.275-0.825 g: 30-50 mL, and the preferred mass fraction of the anhydrous ethanol is 95%.

[0055] After obtaining the composite aerogel with extracted water, the present invention preferably places the obtained composite aerogel in dilute hydrochloric acid water with pH=2 for 30-60 minutes and observes that it does not dissolve, thus verifying the acid resistance of the composite aerogel.

[0056] After the acid resistance performance is verified, the present invention preferably washes the obtained acid-resistant composite aerogel repeatedly with deionized water 5 times to keep the composite gel material neutral, and finally dries it in a vacuum freeze dryer at -45 to -60°C for 20 to 24 hours to obtain the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel.

[0057] The present invention also provides a three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel prepared by the preparation method described above, wherein the porosity of the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel is 80% to 85%, more preferably 81.7%.

[0058] This invention also provides the application of the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel described above in the field of uranium adsorption.

[0059] In this invention, the uranium is preferably derived from acidic wastewater from uranium mining and metallurgy, and the concentration of uranium in the acidic wastewater is preferably 1 to 10 mg / L.

[0060] In this invention, the acidic wastewater from uranium mining preferably also includes competing ions, which preferably include one or more of Cu(II), Co(II), Ca(II), Mg(II), Zn(II), Mn(II), Pb(II) and Ni(II), and the concentration of the competing ions in the acidic wastewater from uranium mining is preferably 1 to 5 mg / L.

[0061] In this invention, the preferred ratio of the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel to uranium mining acidic wastewater is 0.045 g: 90 mL.

[0062] In this invention, after the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel adsorbs uranium from acidic wastewater in uranium mining, the process preferably includes desorption. The desorption preferably uses a mixture of H2O2 and Na2CO3 as the desorption solution, wherein the volume fraction of H2O2 in the desorption solution is preferably 2%, and the concentration of Na2CO3 is preferably 0.1 mol / L.

[0063] In this invention, the solid-liquid ratio during the analysis is preferably 1:1000.

[0064] To further illustrate the present invention, the following detailed description, in conjunction with examples, of the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel, its preparation method, and its applications, should not be construed as limiting the scope of protection of the present invention.

[0065] Example 1

[0066] Synthetic CSP

[0067] First, 2.0000g of chitosan was dispersed in 14mL of methanesulfonic acid in three portions. Then, 2.000g of P2O5 was added in three portions and stirred until homogeneous. The mixture was then placed in an ice-water bath for one hour, with manual stirring every 5 minutes. Afterward, the mixture was washed three times each with ether, acetone, and methanol. The resulting product was then freeze-dried at low temperature for later use.

[0068] Synthesis of aCSP / CP

[0069] 0.8250 g of CS was dispersed in 4.25 mL of 1% acetic acid and stirred until homogeneous to obtain chitosan sol. 0.1730 g of CSP was dissolved in 4.25 mL of deionized water. The chitosan sol and phosphorylated chitosan solution were mixed and then 0.2000 g of Chlorella nucleoprotein powder was added. After stirring until homogeneous, 1.50 mL of 10% NH4HCO3 solution was added and stirred for 2 min to obtain phosphorylated chitosan-based microalgae gel. The gel was frozen at -85.8℃ for 12 h to form a three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based gel (three-dimensional porous composite gel). After removal, the water in the composite gel was extracted twice with anhydrous ethanol. Then, the gel was soaked in dilute hydrochloric acid water with pH=2.0 for 1 h to verify the acid resistance of the composite gel. The gel was then washed repeatedly with deionized water 5 times and finally freeze-dried under vacuum to obtain composite aerogel for later use.

[0070] Preparation of aCS / CP

[0071] aCS / CP is an unphosphorylated chitosan microalgae-based gel, prepared using the same method as aCSP / CP, the only difference being the absence of phosphorylated chitosan solution.

[0072] Batch adsorption experiment

[0073] In batch experiments, the adsorbent (three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel) concentration was 0.5 g / L (0.0450 g of three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel was added to 90 mL of U(VI) solution). The pH of the solution was adjusted with 0.01 M HCl and 0.01 M NaOH. The experiment was conducted under constant oscillation at 175 r / min. All experimental values ​​were obtained by two replicates, with an error within 1.0%.

[0074] Selective adsorption experiment

[0075] Selectivity experiments were conducted using 9-membered and 2-membered mixed solutions to study the selective adsorption of U(VI) by the adsorbent and the promoting / inhibiting effects of competing ions. Selective adsorption was calculated using the following formula:

[0076]

[0077] Where, q e-U(VI) It is the adsorption capacity of the adsorbent for U(VI), q e-Total The adsorption capacity of an adsorbent for all competing ions.

[0078] Selective adsorption of uranium by aCSP / CP

[0079] Characterization of hierarchical porous aCSP / CP

[0080] Figure 1 The image shows a SEM image of aCSP / CP. It reveals that the aCSP / CP surface exhibits continuous pores ranging from hundreds of nanometers to hundreds of micrometers, making it rough and continuously undulating, filled with irregular protrusions; these hierarchical pores allow for efficient uranyl ion transport and maximize the utilization of the aCSP / CP active sites. Mercury porosimetry results show that the aCSP / CP has an average pore size of 4831.17 nm, a maximum pore size of 0.121 mm, a minimum pore size of 46.77 nm, a density of 0.202 g / mL, a permeability of 92.197 d, and a porosity of 81.7%, indicating high porosity (>80%). This test also confirms the three-dimensional porous structure of aCSP / CP.

[0081] Selective adsorption of U(VI) by hierarchical porous aCSP / CP

[0082] Selectivity experiments of aCSP / CP and aCS / CP aerogels were conducted in nine-element solutions with concentrations of 11.837 mg / L L (VI) and 1 mg / L (competing ions Cu(II), Co(II), Ca(II), Mg(II), Zn(II), Mn(II), Pb(II), and Ni(II)). The results are as follows: Figure 2As shown in (a), in this mixed solution, the adsorption capacity and selectivity of aCSP / CP for U(VI) were 23.67 mg / g and 80.53%, respectively, while those of aCS / CP were 22.95 mg / g and 64.77%, respectively. aCS / CP exhibited a higher total ion adsorption capacity than aCSP / CP because its lower selectivity for U(VI) allowed it to adsorb more coexisting ions under the same conditions. CSP showed a significant improvement in selectivity for U(VI) (an increase of 15.76%), fully demonstrating the high affinity and high selectivity between phosphorus functional groups and U(VI).

[0083] To explain the effect of competing ions on U(VI) adsorption, binary solutions were prepared by mixing 11.837 mg / L U(VI) with a higher concentration (5 mg / L) of each of the aforementioned competing ions. Results ( Figure 2 (b) shows that the adsorption capacity of aCSP / CP for cations is in the order: U(VI) > Cu(II) > Zn(II) > Pb(II) > Ni(II) > Co(II) > Mg(II) > Ca(II) > Mn(II). The high selectivity for U(VI) can be attributed to two main reasons: 1) aCSP / CP contains abundant functional groups with high affinity for U(VI), such as amino, hydroxyl, carboxyl, and phosphate groups, especially the latter, which can significantly improve the selectivity and adsorption capacity of U(VI); 2) the autoxidation and hydrolysis complexation affinity of U(VI) is higher than that of other ions.

[0084] Effect of initial pH

[0085] pH is a crucial factor affecting the zeta potential and ionic speciation of U(VI) in solution. Therefore, this study investigated the effect of pH values ​​(2–7) on the adsorption of U(VI) by aCSP / CP, measuring the zeta potential at each pH value to evaluate the performance of aCSP / CP in aqueous solution. Since most processes in the nuclear fuel cycle utilize NO3... - Or nitric acid, in which NO3 is also considered. - The impact.

[0086] Figure 3 The effect of pH on the adsorption of U(VI) by aCSP / CP and aCS / CP was investigated. The Zeta potentials of aCSP / CP and aCS / CP decreased rapidly from pH 2 to 7, then decreased slowly and stabilized, indicating that they have higher stability at higher pH values. The positively charged surface of the adsorbents may be due to the addition of nitrogen groups on the CS monomer and NH4HCO3; NH4HCO3 not only promotes the formation of cavities in the composite aerogel, but also increases its total alkalinity.

[0087] The adsorption capacity of both aerogels for U(VI) increased rapidly with increasing pH, then tended to stabilize, consistent with the trend of the Zeta potential. At lower pH values, a large amount of H₂... + The adsorption sites were occupied, reducing the adsorption capacity of aCSP / CP; as the pH value increased, H... + As the amount of adsorbent gradually decreases, the adsorption sites of aCSP / CP bind to U(VI), leading to a rapid increase in the adsorption rate. When the pH exceeds 4, the protonation of the adsorbent weakens, and U(VI) begins to form uranyl / hydroxyl complexes, such as UO2(OH)2(aq) and UO2(OH). + (UO2)2(OH)2 2+ (UO2)3(OH) 5+ and (UO2)4(OH) 7+ Its adsorption gradually slows down and eventually stops increasing, mainly due to H + The content decreases. On the one hand, the protonation degree of aCSP / CP weakens, and the competition between H+ and U(VI) gradually weakens. On the other hand, the lone pair electrons from oxygen atoms from P-OH and P=O begin to increase and gradually occupy the electron orbitals of U atoms, promoting the formation of uranyl complexes.

[0088] Figure 4 NO3 - The effect of aCSP / CP adsorption on U(VI), when NO3 - When the concentration increased from 0.0084 mol / L to 0.084 mol / L, the adsorption rate of U(VI) by aCPS / CP remained above 96%, indicating that the adsorption rate of U(VI) at high concentrations of NO3 was still high. - The environmental impact is minimal, laying a solid foundation for the practical application of aCSP / CP.

[0089] Effect of reaction time on adsorption kinetics

[0090] Time is an important influencing factor in adsorption experiments. The adsorption of U(VI) by aCSP / CP is represented by pseudo-first-order kinetic equation (2) and pseudo-second-order kinetic equation (3), respectively. The results are as follows: Figure 5 As shown.

[0091]

[0092]

[0093] The synthesized aCSP / CP aerogels adsorbed U(VI) at concentrations of 0.998, 4.998, and 9.253 mg / L at pH 4 and 278 K. Due to the unique structure and functional groups on the aCSP / CP surface, all aerogel samples rapidly adsorbed U(VI) within 1 h and reached adsorption equilibrium within 4 h.e The concentrations were 2.208, 9.987, and 18.295 mg / g, respectively. After fitting pseudo-first-order and pseudo-second-order kinetics, the kinetic models for the three concentrations better conformed to pseudo-second-order kinetics, indicating that aCSP / CP adsorbs U via strong surface complexation and chemisorption. In the pseudo-second-order kinetics, k2 decreased with increasing concentration of uranium (VI), consistent with existing studies on pseudo-second-order kinetic parameters.

[0094] Effect of initial concentration on isothermal adsorption

[0095] In calculating the theoretical adsorption capacity of adsorption isotherms, adsorption isotherm studies can infer the interaction between the adsorbate and the adsorbent. Adsorption isotherm experiments were conducted at 278, 298, and 318 K with initial concentrations of U(VI) of 1, 10, 25, 50, 100, 300, 500, 700, and 900 mg / L. The calculated CU(VI)... e q e and K d Experimental data on the adsorption of U(VI) by aCSP / CP were nonlinearly fitted using Langmuir and Freundlich models (represented by equations (4) and (5), respectively); the fitting parameters and results are shown in Tables 1 and 2. Figure 6 .

[0096]

[0097]

[0098] C e It increases with increasing initial concentration, while K d They show the opposite trend. At 318K and 1 mg / L, K d Reaching the maximum value (1.37 × 10) 6 Fitting at different temperatures showed that the correlation coefficient (R0.05) of the Langmuir model was [mL / g]. 2 The correlation coefficient of aCSP / CP is higher than that of the Freundlich model, indicating that the former dominates the U(VI) adsorption mechanism of aCSP / CP, representing a uniform monolayer adsorption rather than multilayer physisorption. According to the Langmuir model, the maximum adsorption capacities at 318 K and pH = 4 and 5 are 769.268 and 1393.338 mg / g, respectively, while the corresponding experimental values ​​are 726.448 and 1167.120 mg / g. A continuous comparison with other composite aerogels (Table 1) demonstrates the outstanding advantage of aCSP / CP in adsorbing low concentrations of uranium in wastewater.

[0099] Table 1. Isothermal adsorption data in the temperature range of 278–318 K.

[0100]

[0101] Reusability of aCSP / CP and uranium recovery

[0102] The cyclic performance of the adsorbent is of great significance. At 318 K, using 0.1 mol / L Na₂CO₃ added to 2% H₂O₂ as the eluent (45 mL volume), eluting aCSP / CP (0.0450 g mass) after adsorption of 10 mg / L LU(VI) at a solid-liquid ratio of 1:1000, the results are as follows: Figure 7 As shown, the initial elution rate was 83.58% U(VI). After 5 cycles, the adsorption capacity for U(VI) remained above 18 mg / g, with a desorption rate of 73.51%, which is attributed to the gradual loss of phosphate groups in aCSP / CP during elution. Furthermore, the desorbed uranium solution was used for subsequent extraction and purification to prepare uranium products, making a significant contribution to uranium solution recovery.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel, characterized in that, Includes the following steps: Chitosan is mixed with a solvent to obtain chitosan sol; Phosphorylated chitosan was mixed with water to obtain a phosphorylated chitosan solution; The chitosan sol was mixed with the phosphorylated chitosan solution and then mixed with Chlorella pyrenoidosa powder and a foaming agent to obtain phosphorylated chitosan-based microalgae gel. The phosphorylated chitosan-based microalgae gel was freeze-dried to obtain the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel. The mass ratio of chitosan in the chitosan sol to phosphorylated chitosan in the phosphorylated chitosan solution is 0.275~0.825:0.173~0.346; The mass ratio of chitosan to Chlorella vulgaris powder in the chitosan sol is 0.275~0.825:0.1~0.2; The freeze-drying temperature is -80~-90℃, and the time is 10~15h.

2. The production method according to claim 1, characterized by, The foaming agent is an aqueous solution of NH4HCO3 or an aqueous solution of sodium dodecyl sulfate.

3. The production method according to claim 1 or 2, characterized by, The ratio of chitosan to foaming agent in the chitosan sol is 0.275~0.825g:1~1.5mL, and the volume fraction of the foaming agent is 10%.

4. The method of claim 1, wherein, The freeze-drying process also includes thawing the resulting dried material with anhydrous ethanol and then extracting the water.

5. The preparation method according to claim 1, characterized in that, The chitosan has a degree of deacetylation ≥95% and a viscosity of 100~400 mPa·s.

6. The three-dimensional hierarchically porous phosphonated chitosan / microalgae-based aerogel prepared by the method of any one of claims 1 to 5, characterized in that, The porosity of the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel is 80%~85%.

7. The application of the three-dimensional hierarchical porous phosphorylated chitosan / microalgae-based aerogel according to claim 6 in the field of uranium adsorption.

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