A method for detecting and removing Hg 2+ / Hg + Ion adsorbents and their preparation methods

Abstract

This invention discloses a method for detecting and removing Hg. 2+ / Hg + This invention relates to ion adsorbents and their preparation methods, belonging to the field of environmental science and engineering technology. Specifically, chitosan is introduced into dendritic fibrous nano-silica, and a naphthalimide fluorophore is embedded into chemically modified DFNS to prepare an adsorbent for detecting and removing Hg. 2+ / Hg + An adsorbent for ions (fluorescent dendritic fiber nano-silica@chitosan porous composite microspheres) has a high affinity for Hg. 2+ / Hg + The ions exhibit excellent adsorption and separation properties. This invention confirms that fluorescent dendritic fiber nano-silica@chitosan porous composite microspheres can effectively identify and remove Hg. 2+ / Hg + Practical applications in the field of ions.

Description

Technical Field

[0001] This invention belongs to the field of environmental science and technology, specifically relating to a method for detecting and removing Hg. 2+ / Hg + Ion adsorbents and their preparation methods. Background Technology

[0002] Currently, the pervasive nature of heavy metals poses a serious threat to ecosystems and human health. Mercury, a harmful heavy metal, accumulates unnoticed in organisms and through the food chain, ultimately leading to neurological and developmental effects. Unborn infants and young children, in particular, face considerable risk; their developing brains are vulnerable to the destructive effects of mercury, potentially causing irreversible damage, manifesting as cognitive and motor impairments. Therefore, the identification and isolation of mercury ions from the environment and biological systems is of paramount importance.

[0003] Current strategies for mercury removal primarily include physical, chemical, and biological technologies. Physical methods, such as adsorption and membrane separation, are favored due to their simplicity and relatively low cost. However, in practical applications, these methods face challenges in selecting adsorbents and membrane materials. Chemical methods, including chemical precipitation and ion exchange technologies, have demonstrated high efficiency in mercury removal but may cause secondary pollution problems, increasing the complexity and risk of pollution management. Therefore, seeking more environmentally friendly methods for identifying and removing mercury remains a scientific challenge.

[0004] In recent years, porous materials have shown great potential in improving the adsorption capacity and selectivity of pollutant separation. They are renowned for their high specific surface area, customizable pore size and shape, selective permeability, and excellent transport properties, making them ideal for developing novel adsorbents. Chitosan (CS), derived from biological sources, is an excellent bio-based adsorbent, with its potential anchored to (-OH) and (-amino) functional groups that interact with heavy metal ions. Chitosan is known for its unique properties, including bioactivity, biocompatibility, sustainability, non-toxicity, and biodegradability. However, its resistance to mass transfer, low porosity, limited surface area, low solubility, and mechanical brittleness all contribute to its reduced efficiency in adsorbing pollutants from water systems. Summary of the Invention

[0005] In view of the above-mentioned prior art, the present invention provides a method for detecting and removing Hg. 2+ / Hg + The ion adsorbent and its preparation method solve the problems of weak detection of mercury ions and poor enrichment and adsorption capacity of mercury ions in existing mercury removal technologies.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is to provide a method for detecting and removing Hg. 2+ / Hg + The ion adsorbent includes a substrate, which is a dendritic fiber nano-silica with an NH2-naphthalimide fluorescent probe and chitosan bonded to it.

[0007] The beneficial effects of this invention are: it achieves a close combination of organic and inorganic materials, and at the same time endows the invention with the ability to detect heavy metals.

[0008] Furthermore, dendritic fiber nano-silica is prepared through the following steps:

[0009] Carboxyl-terminated polybutadiene and urea are co-dispersed in ultrapure water to form an aqueous phase; cyclohexane, isopropanol and ethyl silicate are mixed to form an organic phase; the organic phase is then added dropwise to the aqueous phase, stirred at 65-75°C for 10-15 hours, the reactants are washed, and calcined in air at 500-600°C for 8-10 hours to obtain the final product.

[0010] Furthermore, the mass ratio of carbonyl-based liquid polybutadiene to urea is 1.5–2:1, the concentration of urea in the aqueous phase is 0.02 g / mL, the amount of cyclohexane, isopropanol and ethyl silicate is 40–45 mL: 1–2 mL: 3–4 g, and the volume ratio of organic phase to aqueous phase is 1:0.8–1.2.

[0011] The beneficial effects of adopting the above-mentioned further technical solutions are: dendritic fiber nano silica has a unique dendritic fiber structure. This radially oriented pore structure extends from the center of the sphere to the outer surface, which helps to increase the loading of active sites on the silica surface without clogging the pores. More importantly, dendritic fiber nano silica is characterized by its overall porosity and inclusion of mesopores, which allows guest molecules to be effectively adsorbed and diffused with minimal constraints.

[0012] Furthermore, the NH2-naphthalimide fluorescent probe was prepared through the following steps:

[0013] S1: Dissolve 4-bromo-1,8-naphthalenedicarboxylic anhydride in the first solvent, then add 1-(4-hydroxyphenyl)piperazine to the resulting solution, keep the reaction at 130℃ for 8-10 hours, then wash, centrifuge, and purify by column chromatography to obtain the intermediate;

[0014] S2: Dissolve the intermediate in a second solvent, then add hydrazine hydrate to the resulting solution, reflux at 78–82 °C for 8–10 hours, and then purify by column chromatography to obtain the final product.

[0015] Furthermore, the first solvent is ethylene glycol monomethyl ether, and the second solvent is ethanol.

[0016] The beneficial effects of adopting the above-mentioned further technical solutions are: the NH2-naphthalimide fluorescent probe has high sensitivity, high selectivity and real-time monitoring capability, and is a highly efficient fluorescent labeling tool.

[0017] Furthermore, the molar ratio of 4-bromo-1,8-naphthoic anhydride to 1-(4-hydroxyphenyl)piperazine was 1:1; column chromatography purification in S1 used silica gel as the stationary phase and PE:EA = 10:1 as the mobile phase.

[0018] Furthermore, the molar ratio of the intermediate to hydrazine hydrate was 1:3; column chromatography purification in S2 used silica gel as the stationary phase and PE:EA = 5:1 as the mobile phase.

[0019] The beneficial effects of adopting the above-mentioned further technical solutions are: using suitable column chromatography stationary phase and mobile phase can improve the separation effect, speed and stability of column chromatography, and minimize damage to the column packing.

[0020] Furthermore, detection and removal of Hg 2+ / Hg + The preparation method of the ion adsorbent includes the following steps:

[0021] S1: Dendritic fiber nano-silica was dissolved in a third solvent, and glycidyl propargyl ether and trifluoroacetic acid were added to the resulting solution under a protective atmosphere. The mixture was reacted at 35-40°C for 48 hours. The product was then washed and dried to obtain TB-DFNS.

[0022] S2: Dissolve TB-DFNS in a fourth solvent, add NH2-naphthalimide fluorescent probe to the resulting solution under a protective atmosphere, react at 80℃ for 8-10 hours, then wash and dry the product to obtain FL-DFNS;

[0023] S3: Dissolve FL-DFNS in the fifth solvent, add sebacyl chloride to the resulting solution under a protective atmosphere, stir at 30°C for 2 hours, then add chitosan, continue stirring for 4-6 hours, and then wash to obtain FL-DFNS@CS.

[0024] The beneficial effects of adopting the above-mentioned further technical solution are as follows: This invention successfully synthesizes FL-DFNS by embedding a naphthalimide fluorophore into chemically modified DFNS. The prepared FL-DFNS is rich in C≡C bonds, possesses fluorescent recognition ability, and can be used as Hg... 2 The fluorescent probe for Hg+ ions is activated, and due to the synergistic effect of chitosan and FL-DFNS, the FL-DFNS@CS composite microspheres not only have good recognition of mercury, but also have a high adsorption capacity.

[0025] Furthermore, the third solvent is toluene, and the fourth and fifth solvents are both N,N-dimethylformamide.

[0026] Furthermore, the ratio of dendritic fiber nano-silica, glycidyl propargyl ether, and trifluoroacetic acid is 20 mg: 20 μL: 4–5 μL; the mass ratio of TB-DFNS to NH2-naphthalimide fluorescent probe is 5:1; and the ratio of FL-DFNS, sebacate chloride, and chitosan is 40–100 mg: 0.5 mL: 100–160 mg.

[0027] The beneficial effects of adopting the above-mentioned further technical solutions are: an appropriate ratio can maximize the utilization of synthetic raw materials, so that the final product can achieve the desired use effect.

[0028] The beneficial effects of this invention are as follows: First, an NH2-naphthalimide fluorescent probe was synthesized. Subsequently, DFNS was precisely chemically modified to enrich its surface with triple bonds and hydroxyl groups. Then, the reaction between -C≡C and the NH2-naphthalimide fluorescent probe allowed for the effective integration of the modified DFNS with amino groups, enabling the DFNS to detect heavy metal ions fluorescently. Finally, utilizing the abundant hydroxyl and amino groups on the surface of the modified DFNS and chitosan, stable covalent bonds were formed under the action of sebacate chloride. This method innovatively synthesizes a novel FL-DFNS@CS composite material while achieving a close combination of organic and inorganic materials. The resulting composite microspheres will be endowed with fluorescence-based heavy metal detection capabilities, as well as the inherent high-efficiency adsorption characteristics of porous materials. Attached Figure Description

[0029] Figure 1 Synthesis route of FL-DFNS@CS microspheres;

[0030] Figure 2 SEM image of DFNS;

[0031] Figure 3 A 200nm TEM image of DFNS;

[0032] Figure 4 A 100nm TEM image of DFNS;

[0033] Figure 5 SEM images of TB-DFNS;

[0034] Figure 6 A 200nm TEM image of TB-DFNS;

[0035] Figure 7 A 100nm TEM image of TB-DFNS;

[0036] Figure 8SEM images of FL-DFNS;

[0037] Figure 9 A 200nm TEM image of FL-DFNS;

[0038] Figure 10 A 100nm TEM image of FL-DFNS;

[0039] Figure 11 This is a nitrogen adsorption-desorption isotherm diagram;

[0040] Figure 12 BJH pore size distribution curves for DFNS, TB-DFNS, and FL-DFNS;

[0041] Figure 13 The O1s spectra of DFNS, TB-DFNS, and FL-DFNS are shown.

[0042] Figure 14 C1s spectra of DFNS, TB-DFNS, and FL-DFNS;

[0043] Figure 15 The overall spectra of DFNS, TB-DFNS and FL-DFNS;

[0044] Figure 16 The N1s spectrum of FL-DFNS;

[0045] Figure 17 Fluorescence intensity curves of FL-DFNs with different ions;

[0046] Figure 18 To add Hg + Then, a bar chart showing the fluorescence intensity of other metal ions and FL-DFNs;

[0047] Figure 19 To add Hg 2+ Then, a bar chart showing the fluorescence intensity of other metal ions and FL-DFNs;

[0048] Figure 20 For FL-DFNS in different equivalents of Hg 2+ The fluorescence intensity change graph;

[0049] Figure 21 For FL-DFNS in different equivalents of Hg + The fluorescence intensity change graph;

[0050] Figure 22 fluorescence intensity and Hg 2+ Linear relationship graph between concentrations;

[0051] Figure 23fluorescence intensity and Hg + Linear relationship graph between concentrations;

[0052] Figure 24 The energy storage modulus (G′) and loss modulus (G″) of FL-DFNS@CS-1 are functions of the oscillation frequency (ω).

[0053] Figure 25 The energy storage modulus (G′) and loss modulus (G″) of FL-DFNS@CS-2 are functions of the oscillation frequency (ω).

[0054] Figure 26 The storage modulus (G′) and loss modulus (G″) of FL-DFNS@CS-3 are functions of the oscillation frequency (ω).

[0055] Figure 27 The storage modulus (G′) and loss modulus (G″) of FL-DFNS@CS-4 are functions of the oscillation frequency (ω).

[0056] Figure 28 For comparison of water loss rates between CS and FL-DFNS@CS-3;

[0057] Figure 29 For FL-DFNS and FL-DFNS+Hg 2+ FT-IR spectrum;

[0058] Figure 30 For FL-DFNS and FL-DFNS+Hg 2 +XPS-total spectrum;

[0059] Figure 31 For FL-DFNS and FL-DFNS+Hg 2 + XPS-stage spectrum. Detailed Implementation

[0060] The specific embodiments of the present invention will be described in detail below with reference to examples.

[0061] Example 1

[0062] A method for detecting and removing Hg 2+ / Hg + The ion adsorbent includes a dendritic fiber nano-silica substrate on which NH2-naphthalimide fluorescent probe and chitosan are bonded;

[0063] The adsorbent preparation process in this embodiment is as follows: Figure 1 As shown, the specific steps include:

[0064] S1: Synthesis of the first intermediate (6-(4-(4-hydroxyphenyl)piperazin-1-yl)-1H,3H-benzo[de]isochromene-1,3-dione): 138 mg (0.5 mmol) of 4-bromo-1,8-naphthalenedicarboxylic anhydride was placed in a three-necked flask, and 5 mL of ethylene glycol monomethyl ether was added as a solvent. The mixture was purged with nitrogen and stirred to obtain a homogeneous mixture. Then, 89 mg (0.5 mmol) of 1-(4-hydroxyphenyl)piperazine was added, and the temperature was raised to 130 °C. The reaction was maintained for 8 hours. The product was washed with 1% HAc and deionized water, centrifuged, and then purified by column chromatography with silica gel as the stationary phase and PE:EA = 10:1 as the mobile phase to obtain a yellow powder.

[0065] S2: Synthesis of the second intermediate (NH2-naphthalimide fluorescent probe: 2-amino-6-(4-(4-hydroxyphenyl)piperazin-1-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione): 187 mg (0.5 mmol) of the first intermediate was placed in a three-necked flask, 5 mL of ethanol was added as solvent, and the mixture was purged with nitrogen. Then 74 mg (1.5 mmol) of hydrazine hydrate was added. The mixture was stirred and heated to 80 °C. The reaction was refluxed for 8 hours and then purified by column chromatography with silica gel as the stationary phase and PE:EA = 5:1 as the mobile phase to obtain an orange-yellow powder.

[0066] S3: Synthesis of DNFS: Carboxyl-terminated polybutadiene (1.4 g), urea (0.84 g), and ultrapure water (42 mL) were mixed and sonicated for 30 min to form an aqueous phase. This phase was then transferred to a three-necked flask. Subsequently, a premixed organic phase consisting of cyclohexane (42 mL), isopropanol (1.3 mL), and ethyl silicate (3.5 g) was added dropwise to the aqueous phase. The mixture was stirred vigorously at 70 °C for 12 hours. The reaction mixture was washed with acetone and water. Finally, the product was calcined in air at 550 °C for 9 hours to remove the surfactant.

[0067] S4: Synthesis of TB-DNFS: DFNS (200 mg) was added to a three-necked flask containing 30 mL of toluene. Under nitrogen protection and continuous stirring, glycidyl propargyl ether (200 μ L) was gradually introduced, and one drop of trifluoroacetic acid was added as a catalyst. The reaction temperature was 37 °C and the reaction time was 48 hours. Subsequently, the product was washed with ethanol and distilled water, and then dried in a vacuum oven at 40 °C for 24 hours to obtain a light yellow powder of TB-DFNS.

[0068] S5: Synthesis of FL-DNFS: TB-DFNS was placed in a three-necked flask containing 30 ml of DMF. Under nitrogen protection and stirring, 20 mg of the second intermediate was added. The mixture was reacted at 80 °C for 8 hours, followed by washing with ethanol, DCM, and distilled water. The final product was dried in a vacuum oven at 40 °C for 24 hours to obtain a yellow powder of FL-DFNS.

[0069] S6: Preparation of fluorescent dendritic fiber nanofibers of silica@chitosan microspheres (FL-DFNS@CS): 100 mg of dried FL-DFNS was placed in a three-necked flask, and 10 mL of DMF was used as a solvent. Under nitrogen protection, the mixture was stirred to ensure uniform dispersion. Then, 0.5 mL of sebacate chloride was added and the mixture was stirred for 2 hours. After that, 100 mg of chitosan was added and the mixture was stirred for 5 hours. Finally, the product was washed with EtOH, DCM and water to remove unreacted small molecules to obtain FL-DFNS@CS-1. FL-DFNS@CS-1 was dissolved in 1% acetic acid solution, and the solution was dripped into sodium hydroxide solution using a syringe to form a solution of FL-DFNS@CS-1 microspheres.

[0070] Example 2

[0071] The difference between this embodiment and Example 1 is that in S6, the mass of FL-DFNS is 66 mg and the mass of chitosan is 133 mg. The remaining operations are the same as in Example 1, and the resulting product is FL-DFNS@CS-2.

[0072] Example 3

[0073] The difference between this embodiment and embodiment 1 is that the mass of FL-DFNS in S6 is 50 mg and the mass of chitosan is 150 mg. The rest of the operation is the same as in embodiment 1, and the product obtained is FL-DFNS@CS-3.

[0074] Example 4

[0075] This embodiment is basically the same as embodiment 1, except that the mass of FL-DFNS in S6 is 40mg and the mass of chitosan is 160mg. The rest of the operation is the same as in embodiment 1, and the product obtained is FL-DFNS@CS-4.

[0076] Comparative Example 1

[0077] A method for detecting and removing Hg 2+ / Hg + The ion adsorbent includes a dendritic fiber nano-silica substrate with an NH2-naphthalimide fluorescent probe bonded to it.

[0078] The preparation method of the adsorbent in this comparative example includes the following steps:

[0079] S1: Synthesis of the first intermediate (6-(4-(4-hydroxyphenyl)piperazin-1-yl)-1H,3H-benzo[de]isochromene-1,3-dione): 138 mg (0.5 mmol) of 4-bromo-1,8-naphthalenedicarboxylic anhydride was placed in a three-necked flask, and 5 mL of ethylene glycol monomethyl ether was added as a solvent. The mixture was purged with nitrogen and stirred to obtain a homogeneous mixture. Then, 89 mg (0.5 mmol) of 1-(4-hydroxyphenyl)piperazine was added, and the temperature was raised to 130 °C. The reaction was maintained for 8 hours. The product was washed with 1% HAc and deionized water, centrifuged, and then purified by column chromatography with silica gel as the stationary phase and PE:EA = 10:1 as the mobile phase to obtain a yellow powder.

[0080] S2: Synthesis of the second intermediate (NH2-naphthalimide fluorescent probe): 187 mg (0.5 mmol) of the first intermediate was placed in a three-necked flask, 5 ml of ethanol was added as solvent, and the mixture was purged with nitrogen. Then, 74 mg (1.5 mmol) of hydrazine hydrate solution was added. The mixture was stirred and heated to 80 °C. The reaction was refluxed for 8 hours and then purified by column chromatography with silica gel as the stationary phase and PE:EA = 5:1 as the mobile phase to obtain an orange-yellow powder.

[0081] S3: Synthesis of DNFS: Carbonyl-based liquid polybutadiene (1.4 g), urea (0.84 g), and ultrapure water (42 mL) were mixed and sonicated for 30 min to form an aqueous phase. This phase was then transferred to a three-necked flask. Subsequently, a premixed organic phase consisting of cyclohexane (42 mL), isopropanol (1.3 mL), and ethyl silicate (3.5 g) was added dropwise to the aqueous phase. The mixture was stirred vigorously at 70 °C for 12 hours. The reaction mixture was washed with acetone and water. Finally, the product was calcined in air at 500–600 °C for 8–10 hours to remove the surfactant.

[0082] S4: Synthesis of TB-DNFS: DFNS (200 mg) was added to a three-necked flask containing 30 ml of toluene. Under nitrogen protection and continuous stirring, glycidyl propargyl ether (200 μ L) was gradually introduced, and one drop of trifluoroacetic acid was added as a catalyst. The reaction temperature was 37 °C and the reaction time was 48 hours. Subsequently, the product was washed with ethanol and distilled water, and then dried in a vacuum oven at 40 °C for 24 hours to obtain a light yellow powder of TB-DFNS.

[0083] S5: Synthesis of FL-DNFS: TB-DFNS was placed in a three-necked flask containing 30 ml of DMF. Under nitrogen protection and stirring, 20 mg of the second intermediate was added. The mixture was reacted at 80 °C for 8 hours, followed by washing with ethanol, DCM, and distilled water. The final product was dried in a vacuum oven at 40 °C for 24 hours to obtain a yellow powder of FL-DFNS.

[0084] S6: Dissolve 200 mg FL-DNFS in 1% acetic acid solution, and use a syringe to drop the solution into sodium hydroxide solution to form a solution of FL-DFNS microspheres.

[0085] Comparative Example 2

[0086] S1: Add 200 mg of chitosan to a three-necked flask containing 10 mL of 3% HAc solution and stir until fully dissolved. Then adjust the pH of the solution to be close to neutral.

[0087] S2: Add 14 mL of formaldehyde (3.7% crosslinking agent) to the chitosan solution and stir to mix.

[0088] S3: The above solution is dripped into anhydrous ethanol using a syringe to form chitosan microbeads.

[0089] Experimental Example 1

[0090] Comparison of silica particle morphology: DFNS, TB-DFNS, and FL-DFNS were scanned using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results are as follows: Figures 2-10 As shown, the three types of particles are uniform in size and perfectly spherical. This spherical shape exhibits a unique dendritic fibrous structure, formed by multi-level branching extending from the center outwards. Between these branches, radially oriented central channels are formed, with the pore size increasing from the inside out. Furthermore, the original size of DFNS was 80 nm, which increased to 116 nm after the first modification step. This size increase, coupled with the increased dendritic branching shown in the TEM results, indicates a successful reaction of glycidyl propargyl ether. Therefore, it can be inferred that the surface of the modified TB-DENS is loaded with a large number of triple bonds and hydroxyl groups. After the second modification step, there was no significant change in size, indicating a low loading of fluorescent groups, which is consistent with our experimental requirements; a small amount of fluorescent group grafting is sufficient to achieve fluorescent recognition.

[0091] Nitrogen adsorption-desorption tests were also performed on DFNS, TB-DFNS, and FL-DFNS, such as... Figure 11 As shown, DFNS, TB-DFNS, and FL-DFNS all exhibit typical type IV nitrogen adsorption-desorption isotherms. The curves saturate when P / P0 = 1.0. The surface area, pore volume, and average pore size of DFNS, TB-DFNS, and FL-DFNS were determined according to the BET, Langmuir, and BJH equations; the experimental results are shown in Table 1 and... Figure 12 As shown.

[0092] Table 1. Determination of surface area, pore volume, and average pore size of DFNS, TB-DFNS, and FL-DFNS

[0093]

[0094]

[0095] exist Figure 12 The size distribution of the silica spheres observed was mainly in the range of 2-20 nm, with a sharp peak in the 2-4 nm range and a broader peak in the 6-18 nm range. This size distribution pattern is highly consistent with the results obtained from our electron microscopy analysis. The data in Table 1 show that the porosity of the TB-DFNS obtained after the first modification did not change significantly compared to the original DFNS, indicating that the initial modification process was mainly concentrated on the particle surface, as confirmed by the increase in silica sphere size observed in the electron microscopy results. However, after the second modification, a decrease in both the specific surface area and pore volume of the silica was observed. This change suggests that the chemical modification in the second step mainly occurred within the internal structure of the silica microspheres, potentially leading to pore blockage.

[0096] Experiment Example 2

[0097] Formation mechanism study of FL-DFNs: To further investigate the formation mechanism, X-ray photoelectron spectroscopy (XPS) was used to characterize the prepared DFNs, TB-DFNs and FL-DFNs. Figure 15 The broad-scan XPS spectra revealed binding energies of 109.9 eV, 297.9 eV, 409.9 eV, and 544.9 eV, corresponding to Si 2p, C 1s, N 1s, and O 1s, respectively. In both DFNS and TB-DFNS, only Si, C, and O elements are present. With the introduction of the naphthimide fluorophore, FL-DFNS showed the addition of N element.

[0098] Figure 13 The O1s spectrum of the original DFNS consists of three peaks: from left to right, O-Si, OH, and CO. Figure 14 The C1s spectrum of the original DFNS consisted of two peaks: CC / CH and CO from left to right; after the first modification, significant changes in the binding energies of these components were observed. Figure 13 In the middle, the peak position of O1s remains unchanged, but the area of ​​the OH peak at 533.2 eV increases; in Figure 14 In the figure, the binding energy of CO changed from 284.7 eV to 284.9 eV, and a new C=C peak appeared at 284.2 eV, providing further evidence of the successful reaction with glycerol ether. After the second revision, for Figure 13 In the O1s region, when the peak position remains unchanged, a new C=O bond peak appears at 534.2 eV; for Figure 14A new CN bond peak appears at 283.6 eV in the C1s region. More significantly, Figure 16 The peaks in the N1s spectrum at 398.5 and 399.8 eV correspond to CN and NN bonds, respectively. These transitions further confirm the successful preparation of TB-DFNS and FL-DFNS, and affirm the expected successful design and fabrication of FL-DFN.

[0099] Experimental Example 3

[0100] FL-DFNS particles as a sensor for detecting Hg 2 Experiment with Hg+ / Hg+ ions: FL-DFNS (5 mg) powder was dispersed in 100 mL of DMF as the stock solution. At 25 °C, the stock solution (1.5 mL) was mixed with deionized water (970 μL), and then 30 μL of various metal ion solutions (K+) were added. + Ba 2+ Ni 2+ Mg 2+ Ag + Fe 2+ CD 2+ Ca 2 +, PD 2 +, Fe 3 +, Cu 2 +、Cr 3 +, Na+, Mn 2 +、Zn 2 +、Co 2 +、Hg 2 +, Hg+ and Al 3 +) served as the control group. In addition, experimental group 1 consisted of stock solution (1.5 mL), deionized water (970 μL), metal ion solution (30 μL), and Hg+ ion solution (30 μL); experimental group 2 consisted of stock solution (1.5 mL), deionized water (970 μL), metal ion solution (30 μL), and Hg+ ion solution (30 μL). 2 + Ionic solution (30 μL); set the excitation wavelength in the fluorescence spectrum to 380 nm to detect the experimental group and the control group.

[0101] Test results as follows Figure 17 As shown, the FL-DFNS fluorescent probe has a λex of 380 nm and a maximum emission wavelength of 612 nm. The FL-DFNS probe exhibits advantages such as low background interference and high detection sensitivity, with a Stokes shift of 132 nm. (The text then abruptly shifts to a seemingly unrelated topic: "Adding Hg...") 2After Hg+ / Hg+, the maximum fluorescence intensity significantly increased to 4.7 / 5.3 times the initial intensity. Simultaneously, the maximum wavelength exhibited a redshift from 512 nm to 525 nm, a shift of approximately 13 nm. In contrast, the presence of other metal ions had no significant effect on the fluorescence spectrum. Therefore, the FL-DFNS sensor demonstrates good fluorescence response to Hg+. 2 The specific transduction ability of Hg+ ions plays a role in "activating" the fluorescent probe. And... Figures 18-19 The results showed that fluorescence enhancement was maintained even in the presence of other metal ions. Therefore, FL-DFNS can selectively and sensitively detect Hg from fluorescence. 2+ / Hg + Without any obvious interference.

[0102] Experiment Example 4

[0103] Detection limit fluorescence titration experiment: FL-DFNS (5 mg) powder was dispersed in 100 mL of DMF as the stock solution. At 25 °C, the stock solution (1.5 mL) was mixed with deionized water (970 μL). Hg+ ion solution was added dropwise to the mixture as experimental group 1, and its fluorescence intensity was detected. Hg+ ion solution was then added dropwise to the mixture. 2 The + ion solution was used as experimental group 2, and its fluorescence intensity was detected.

[0104] The results are as follows Figure 20 and Figure 21 As shown, the fluorescence intensity is highest at 525 nm; when Hg 2 When the Hg+ / Hg+ ion concentration increased from 0 μM to 30 μM, fluorescence intensity was observed to correlate with Hg+ / Hg+ ion concentration. 2 The linear relationship between Hg+ and Hg+ concentrations, such as Figure 22 and 23 As shown, Hg was measured by fluorescence titration. 2+ / Hg + The LODs were 0.47 μM and 0.61 μM, respectively. Therefore, the FL-DFNS probe exhibits good recognition specificity, anti-interference ability, and linear response capability.

[0105] Experimental Example 5

[0106] Comparative experiment on storage modulus (G') and loss modulus (G”) of FL-DFNS@CS: Rheological analysis showed that the storage modulus (G') and loss modulus (G”) of the polymer solution are functions of angular frequency. The functional relationship of storage modulus (G') and loss modulus (G”) of FL-DFNS@CS-1 to 4 prepared in Examples 1 to 4 is as follows: Figures 24-27 As shown, in Figure 24 and 25In the studies, FL-DFNS@CS-1 and FL-DFNS@CS-2 showed that at lower frequencies, the loss modulus significantly exceeded the storage modulus, indicating liquid-like behavior in these hybrid systems. Notably, FL-DFNS@CS-2 transitioned to a gel-like structure at higher frequencies, where the storage modulus exceeded the loss modulus. Conversely, Figure 26 and 27 FL-DFNS@CS-3 and FL-DFNS@CS-4 were shown, with the storage modulus consistently exceeding the loss modulus across the detected frequency range. This suggests that increased CS component concentration promotes gel formation. This gelation is likely due to the diacyl chloride esterification of hydroxyl groups in CS and FL-DFNS. However, after a certain reaction threshold, the remaining unreacted FL-DFNS particles become incompatible within the complex, leading to phase separation and hindering further gelation. On the other hand, the amino- and hydrogen-bonded CS chains form hydrogen bonds, promoting the formation of a robust cross-linked network along with water. Therefore, FL-DFNS@CS-3 consistently exhibits gel-like properties at lower angular frequencies, making it the best candidate for constructing composite hydrogels. Subsequent experiments focused on FL-DFNS@CS-3.

[0107] Experimental Example 6

[0108] Water retention capacity test experiment: The microspheres prepared in Example 3 and Comparative Example 2 were placed at room temperature, and the water content inside the microspheres was tested every 5 hours to compare their dehydration rates. The water retention capacity is as follows: Figure 28 As shown, under the same conditions, the dehydration rate of the FL-DFNS@CS-3 composite hydrogel was significantly lower than that of the pure chitosan hydrogel. The dense porous structure of the FL-DFNS@CS-3 composite hydrogel plays a crucial role in preventing water molecule evaporation and subsequent loss. The tight network structure acts as a barrier, limiting the diffusion of water molecules from the hydrogel matrix. Therefore, compared to the pure chitosan hydrogel, the FL-DFNS@CS-3 composite hydrogel exhibits better moisture retention.

[0109] Experimental Example 7

[0110] Hg 2+ / Hg + Adsorption performance experiment: At room temperature, 5 mg of the microbeads prepared in Example 3, Comparative Example 1 and Comparative Example 2 were placed in 4 ml of Hg solution with an initial concentration of 222.77 mg / L. 2+ Solution and Hg with an initial concentration of 235.69 mg / L + Hg was detected in the solution after shaking and sonication for 20 minutes. 2+ Solution and Hg + The equilibrium concentration of the solution, and the equation used to evaluate the adsorption performance, are as follows:

[0111] Removal efficiency RE = (CI - CE) / CI × 100%;

[0112] Adsorption capacity QE=(CI-CE) / m×V;

[0113] In the formula, RE represents adsorption efficiency, CI represents initial concentration, CE represents equilibrium concentration, QE represents adsorption capacity, m represents mass of adsorbent, and V represents solution volume.

[0114] The experimental results are shown in Table 2.

[0115] Table 2 Adsorption efficiency and adsorption capacity of FL-DFNS@CS, FL-DFNS and CS

[0116]

[0117]

[0118] This experiment combined the detection mechanism of FL-DFNS and used Fourier transform infrared spectroscopy to study Hg. 2+ / Hg + Fluorescent probes for ions, such as Figure 29 As shown, in relation to Hg 2+ / Hg + Before the interaction, the spectrum of FL-DFNS showed a characteristic peak at 1682 cm⁻¹ corresponding to the C=C bond. However, when interacting with Hg... 2+ / Hg + Upon recombination, the absorption peak associated with the C=C stretching vibration disappears, indicating that the C=C bond is broken. This breakage may be due to the lone pair orbitals on the paired electrons of the C=C bond and the Hg... 2+ / Hg + The interaction between the empty orbitals leads to the formation of the coordination compound. Simultaneously, the breaking of the C=C bond disrupts the original naphthalimide conjugate structure, resulting in enhanced fluorescence. This fluorescence enhancement can be attributed to a photoinduced electron transfer (PET) mechanism: during the interaction between the probe and Hg... 2+ / Hg + During the binding process, the lone pair electrons on the C=C group are transferred to the naphthalimide fluorescent group, ultimately leading to enhanced fluorescence.

[0119] To further confirm the adsorption mechanism, XPS analysis was performed on the elemental composition of FL-DFNs before and after binding with Hg2+ / Hg+. The overall spectrum is shown below. Figure 30 As shown. Figure 31As shown, the results revealed a new Hg 4f peak in the XPS spectrum. The double binding energies of the Hg 4f peak were determined at 100.2 eV (Hg4F7 / 2) and 104.8 eV (Hg4F5 / 2), indicating the formation of a new mercury-containing substance on the FL-DFNS particles. In the FL-DFN@CS microspheres, the particle composition is FL-DFNS and CS, rich in triple bonds and C=C, enabling it to bind with Hg. 2+ / Hg + Furthermore, the original chitosan structure contains N and O elements and also adsorbs a small amount of Hg. 2+ / Hg + Most importantly, the prepared adsorbent exhibits a porous structure, as shown in the SEM image. When containing Hg... 2+ / Hg + When the solution of the particles flows through this porous structure, Hg 2+ / Hg + The ions effectively bind to the abundant adsorption sites within the hydrogel. Therefore, Hg can be effectively removed from aqueous solutions using this adsorbent. 2+ / Hg + ion.

[0120] In summary, this invention successfully synthesized FL-DFNS by embedding a naphthalimide fluorophore into chemically modified DFNS. Subsequently, FL-DFNS was crosslinked with chitosan via acyl chloride to prepare FL-DFN@CS microspheres. Due to the synergistic effect of chitosan and FL-DFNS, the FL-DFNS@CS composite microspheres not only exhibit excellent mercury recognition but also possess high adsorption capacity. Furthermore, these microspheres demonstrate good reusability, being recyclable at least seven times, excellent thermal stability, and a rapid adsorption rate.

[0121] Although specific embodiments of the present invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of this patent.

Claims

1. A method for detecting and removing Hg 2+ / Hg + An ion adsorbent, characterized in that, The substrate is a dendritic fiber nano-silica, on which an NH2-naphthalimide fluorescent probe and chitosan are bonded; the detection and removal of Hg... 2+ / Hg + The ion adsorbent is prepared by the following steps: S1: Dendritic fiber nano-silica was dissolved in a third solvent, and glycidyl propargyl ether and trifluoroacetic acid were added to the resulting solution under a protective atmosphere. The mixture was reacted at 35-40°C for 48 hours. The product was then washed and dried to obtain TB-DFNS. S2: Dissolve TB-DFNS in a fourth solvent, add NH2-naphthalimide fluorescent probe to the resulting solution under a protective atmosphere, react at 80℃ for 8-10 hours, then wash and dry the product to obtain FL-DFNS; S3: Dissolve FL-DFNS in the fifth solvent, add sebacyl chloride to the resulting solution under a protective atmosphere, stir at 30°C for 2 hours, then add chitosan, continue stirring for 4-6 hours, and then wash to obtain the final product.

2. The detection and removal of Hg according to claim 1 2+ / Hg + An ion adsorbent, characterized in that: The dendritic fiber nano-silica is prepared through the following steps: Carboxyl-terminated polybutadiene and urea are co-dispersed in ultrapure water to form an aqueous phase; cyclohexane, isopropanol and ethyl silicate are mixed to form an organic phase; the organic phase is then added dropwise to the aqueous phase, stirred at 65-75°C for 10-15 hours, the reactants are washed, and calcined in air at 500-600°C for 8-10 hours to obtain the final product.

3. The detection and removal of Hg according to claim 2 2+ / Hg + An ion adsorbent, characterized in that: The mass ratio of the carboxyl-terminated polybutadiene to urea is 1.5~2:1, and the concentration of urea in the aqueous phase is 0.02g / mL; the ratio of the amounts of cyclohexane, isopropanol, and ethyl silicate is 40~45mL:1~2mL:3~4g; and the volume ratio of the organic phase to the aqueous phase is 1:0.8~1.

2.

4. The detection and removal of Hg according to claim 1 2+ / Hg + An ion adsorbent, characterized in that, The NH2-naphthalimide fluorescent probe was prepared by the following steps: S1: Dissolve 4-bromo-1,8-naphthalenedicarboxylic anhydride in the first solvent, then add 1-(4-hydroxyphenyl)piperazine to the resulting solution, keep the reaction at 130℃ for 8-10 hours, then wash, centrifuge, and purify by column chromatography to obtain the intermediate; S2: Dissolve the intermediate in a second solvent, then add hydrazine hydrate to the resulting solution, reflux at 78-82℃ for 8-10 hours, and then purify by column chromatography to obtain the final product.

5. The detection and removal of Hg according to claim 4 2+ / Hg + An ion adsorbent, characterized in that: The first solvent is ethylene glycol monomethyl ether, and the second solvent is ethanol.

6. The detection and removal of Hg according to claim 4 2+ / Hg + An ion adsorbent, characterized in that: The molar ratio of 4-bromo-1,8-naphthoic anhydride to 1-(4-hydroxyphenyl)piperazine is 1:1; column chromatography purification in S1 uses silica gel as the stationary phase and PE:EA = 10:1 as the mobile phase.

7. The detection and removal of Hg according to claim 4 2+ / Hg + An ion adsorbent, characterized in that: The molar ratio of the intermediate to hydrazine hydrate is 1:3; column chromatography purification in S2 uses silica gel as the stationary phase and PE:EA = 5:1 as the mobile phase.

8. The detection and removal of Hg according to any one of claims 1 to 7 2+ / Hg + A method for preparing an ion adsorbent, characterized in that, Includes the following steps: S1: Dendritic fiber nano-silica was dissolved in a third solvent, and glycidyl propargyl ether and trifluoroacetic acid were added to the resulting solution under a protective atmosphere. The mixture was reacted at 35-40°C for 48 hours. The product was then washed and dried to obtain TB-DFNS. S2: Dissolve TB-DFNS in a fourth solvent, add NH2-naphthalimide fluorescent probe to the resulting solution under a protective atmosphere, react at 80℃ for 8-10 hours, then wash and dry the product to obtain FL-DFNS; S3: Dissolve FL-DFNS in the fifth solvent, add sebacyl chloride to the resulting solution under a protective atmosphere, stir at 30°C for 2 hours, then add chitosan, continue stirring for 4-6 hours, and then wash to obtain the final product.

9. The preparation method according to claim 8, characterized in that: The third solvent is toluene, and the fourth and fifth solvents are both N,N-dimethylformamide.

10. The preparation method according to claim 8, characterized in that: The ratio of dendritic fiber nano-silica, glycidyl propargyl ether, and trifluoroacetic acid is 20 mg: 20 μL: 4~5 μL; the mass ratio of TB-DFNS to NH2-naphthalimide fluorescent probe is 5:1; and the ratio of FL-DFNS, sebacate chloride, and chitosan is 40~100 mg: 0.5 mL: 100~160 mg.

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