A manganese ion specific adsorbent, its preparation method and use

Abstract

This invention discloses a manganese ion-specific adsorbent, its preparation method, and its applications, belonging to the field of heavy metal adsorption technology. The preparation method involves amylating dendritic fibrous nano-silica, followed by an amidation reaction to introduce naphthic anhydride groups, thus obtaining the manganese ion-specific adsorbent. This invention also successfully prepared an FL-DFNS probe through organic functionalization modifications such as silanization, amidation, and substitution reactions. Its adsorption on Mn2+ was systematically studied. 2+ The FL-DFNS probe exhibits good recognition and adsorption properties for Mn. The results show that the FL-DFNS probe effectively targets Mn. 2+ It has good selective recognition ability and good anti-interference ability against other ions.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal adsorption technology, specifically relating to a manganese ion specific adsorbent, its preparation method, and its applications. Background Technology

[0002] Porous materials play a crucial role in materials science. Among them, morphology-controllable silica-based materials have attracted much attention due to their low density, good biocompatibility, and ease of surface modification. In 2010, Polshettiwar et al. first prepared DFNS, a type of mesoporous silica with a branched fibrous morphology. Their research opened up new directions for the study of mesoporous silica with special morphologies. Compared with traditional mesoporous silica, DFNS has a more open and permeable pore structure. This structure can support a wide range of active materials, such as metals, metal oxides, and organic molecules, significantly enhancing the accessibility of active sites. In addition, its hierarchical pore structure with abundant micropores and macropores can further optimize the adsorption and diffusion efficiency of guest molecules. Furthermore, the particle size of DFNS silica microspheres can be precisely controlled by adjusting the reaction process. In summary, these outstanding characteristics fully highlight the enormous application potential of DFNS in related fields.

[0003] The original DFN is monodisperse and lacks some of the functional properties we expect. Therefore, it is necessary to modify silica, i.e., functionalize silica. Specifically, DFNs can be modified through three main approaches: (1) loading metals or metal oxides to give them catalytic or adsorption activities; (2) constructing an internal magnetic core-shell structure; or (3) grafting functional groups or chemical monomers to impart specific surface chemical properties. After such modifications, DFNs have been widely used in many cutting-edge fields, including catalysis, drug delivery, energy storage, sensors, and carbon dioxide capture. However, the application research of DFNs in the field of adsorption separation is relatively limited at present. In particular, the research on the detection and adsorption of heavy metal ions still needs further in-depth exploration.

[0004] Manganese is an essential trace element for humans, animals, and plants. However, excessive intake of manganese can have adverse effects on the body. Specifically, manganese accumulation threatens communities of fish, amphibians, and invertebrates. Furthermore, long-term exposure can lead to a decline in ecosystem services and further impair overall biodiversity. In humans, excessive intake of manganese ions through drinking water or food can cause a range of neurological disorders. This effect is particularly pronounced in children, potentially interfering with their neurodevelopment. Therefore, developing efficient technologies for identifying and removing manganese ions is of paramount importance.

[0005] Several analytical methods have been developed for the detection of Mn in aqueous systems. 2+Ion analysis methods, including inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS), colorimetry, electrochemistry, and mass spectrometry, are conventional techniques that demonstrate excellent precision and reliability in quantitative analysis. However, they are inherently limited by factors such as cumbersome procedures, the high cost of complex instruments, and relatively long detection cycles. This makes them unsuitable for on-site and rapid screening of actual water samples. In contrast, fluorescence analysis, with its advantages of fast detection speed, high specificity, simple operation, and suitability for rapid screening of large numbers of water samples, has become a promising alternative. Thanks to these superior performance characteristics, fluorescent probes have been widely used in scientific research, food safety, medical technology, and other research and practical fields in recent years. In our previous research, we also designed and prepared a series of functional fluorescent probes, some of which have been successfully applied to the removal of heavy metal ions in the aquatic environment.

[0006] Methods for removing heavy metals are currently classified into three main categories: physical, chemical, and biological. Chemical methods utilize the inherent properties of heavy metal ions to initiate chemical reactions for their removal, such as precipitation and chelation, and these methods have shown extremely high efficiency in removing mercury ions. Physical methods employ simple physical techniques, such as distillation, to remove heavy metal ions without altering their chemical state. Among these methods, adsorption is considered one of the most promising due to its simplicity, low cost, and environmental friendliness. Summary of the Invention

[0007] To address the aforementioned shortcomings in the prior art, this invention provides a manganese ion-specific adsorbent, its preparation method, and its uses, which can specifically adsorb manganese ions without adsorbing other heavy metal ions.

[0008] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is as follows: The purpose of this invention is to provide a method for preparing a manganese ion-specific adsorbent, specifically: aminated dendritic fibrous nano-silica, followed by the introduction of naphthalene anhydride groups via an amidation reaction to obtain the manganese ion-specific adsorbent.

[0009] Furthermore, the preparation method of dendritic fibrous nano-silica is as follows: Using hexadecylpyridine bromide, siloxane and urea as raw materials, the mixture is stirred in a solvent and reacted at 70~80℃ for 1~3h, then heated to 90~105℃ and reacted for 10~16h. The crude product is collected by centrifugation and then calcined at 500~650℃ for 10~14h to obtain dendritic fibrous nano silica.

[0010] Furthermore, the mass ratio of hexadecylpyridine bromide, siloxane, and urea is 1:2~3:0.5~1.

[0011] Furthermore, the siloxane is tetraethyl orthosilicate.

[0012] Furthermore, the reaction was first carried out at 70℃ for 1 hour, then the temperature was increased to 90℃ for 12 hours, and finally calcined at 550℃ for 12 hours.

[0013] Further, after ultrasonically dispersing the dendritic fibrous nano-silica, APTES was added, and the mixture was refluxed at 110~120℃ for 10~12h. After the reaction, the product was taken out and washed, and then vacuum dried to obtain the amino-modified product N-DFNS.

[0014] Further, after ultrasonically dispersing N-DFNS, 4-bromo-1,8-naphthalenedicarboxylic anhydride was added, and the mixture was stirred evenly and reacted at 80~95℃ for 10~12h. After the reaction, the product was taken out and washed, and then vacuum dried to obtain H-DFNS.

[0015] Another object of the present invention is to provide a manganese ion specific adsorbent, which is prepared by the above method.

[0016] Furthermore, the manganese ion-specific adsorbent also contains a fluorescent group; the fluorescent group is 8-aminoquinoline.

[0017] Another object of the present invention is to provide the use of the above-mentioned manganese ion specific adsorbent in wastewater treatment or in the preparation of manganese ion specific adsorption reagents and manganese ion detection reagents.

[0018] The beneficial effects of this invention are: This invention successfully prepared FL-DFNS probes through organic functionalization modifications such as silanization, amidation, and substitution reactions. Its effect on Mn was also systematically investigated. 2+ The results showed that the FL-DFNS probe exhibited good recognition and adsorption properties for Mn. 2+ It exhibits good selective recognition capability and excellent resistance to interference from other ions. The probe is related to Mn. 2+ Fluorescence energy transfer during the binding process is considered the core reason for fluorescence quenching. Mechanistic studies show that the specific recognition of Mn² by FL-DFNs is achieved through the interaction of the lone pair electrons of the N atom with Mn². 2+ This is achieved through empty orbital coordination. Furthermore, the high adsorption efficiency stems from the interaction between the protons of the NH bonds and Mn. 2+ The weak interactions between them, and the rich porous structure of FL-DFNs for Mn 2+ The FL-DFNS prepared by this invention can be used as a novel adsorbent material for the detection and removal of MMN. 2+ This has important reference value for the detection and treatment of heavy metal polluted water bodies. Attached Figure Description

[0019] Figure 1 Electron micrographs of the original DNFS and different particles prepared in Example 1; Figure 2 The N2 adsorption-desorption isotherms and BJH pore size distribution curves of different particles during the preparation of the original DNFS and Example 1 are shown. Figure 3 XPS analysis chromatogram of FL-DFNs prepared in Example 1; Figure 4 Infrared spectra of the original DNFS and different particles prepared in Example 1; Figure 5 FL-DFNs prepared in Example 1 for Mn 2+ Specific adsorption; Figure 6 FL-DFNs prepared in Example 1 for Mn 2+ The adsorption detection limit; Figure 7 FL-DFNs prepared in Example 1 for Mn 2+ Its specific adsorption and recognition mechanism. Detailed Implementation

[0020] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0021] 1. Materials The hexadecylpyridine bromide (CTPB), tetraethyl orthosilicate (TEOS), urea, isopropanol, cyclohexane, cesium carbonate, (3-aminopropyl)triethoxysilane (APTES), and 8-aminoquinoline used in this invention were purchased from Aladdin Chemical Ltd. Chitosan (average molecular weight: 100,000-300,000) (CS), trimesoyl chloride (TMC), N,N-dimethylformamide (DMF), and 4-bromo-1,8-naphthalenedicarboxylic anhydride were purchased from J&K Scientific Chemical Ltd. Ethanol (EtOH) and glacial acetic acid (HAc), such as K... + Ba 2+ Ni 2+ Mg 2+ Ag + Fe 2+ Cd 2+ Ca 2+ Pd 2+ Fe3+ Cu 2+ Cr 3+ Na + Mn 2+ Zn 2+ Co 2+ Hg 2 + Hg + And Al 3+ Purchased from Sinopharm Chemical Reagent Co., Ltd. All were used as received. All solvents used in the synthesis were first distilled under a nitrogen atmosphere before subsequent use.

[0022] 2. Instruments Scanning electron microscopy (SEM, SU8600) was performed on an instrument from Hitachi, Japan. Transmission electron microscopy (TEM, Jem-2100) images were obtained using an instrument from Japan. Simultaneous thermal analysis (STA, STA449F3) was performed on an instrument from Netzsch, Germany. Contact angle measurements were performed using a Hack-SPCA measuring instrument from Beijing Hack Experimental Instrument Factory, China. Fourier transform infrared spectroscopy (FT-IR, Nicolet 380) was recorded on a Thermo Fisher Scientific Instrument, USA. X-ray photoelectron spectroscopy (XPS) measurements were performed using a PHI-5300 ESCA spectrometer. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed on an STA449F3 instrument. Fluorescence spectra were recorded using an F97 PRO fluorescence spectrophotometer from Lengguang, China. Mn in solution was determined by atomic absorption spectrometry (AAS, ICE 3500) on a Thermo Fisher Scientific Instrument, USA. 2+ The concentration of nitrogen was determined. Nitrogen adsorption-desorption tests for surface analysis were performed using a Micromeritics ASAP 2020HD88 instrument. Specific surface area and pore structure parameters were calculated using the Brunauer-Emmett-Teller (BET) method and the Barrett-Joyner-Halenda (BJH) model, respectively. Fluorescence lifetime was measured using a fully integrated fluorescence spectrometer (FLS920P) from Edinburgh Instruments.

[0023] 3. Hg 2+ / Hg + Adsorption test In the adsorption experiment, the adsorbent FL-DFNS was added to a total volume of 4 mL of Mn with the same concentration. 2+In aqueous solution, the mixture was shaken and sonicated to ensure complete adsorption, followed by determination of Mn in the solution by atomic absorption spectrometry (AAS). 2+ The accurate concentration.

[0024] Equations (3) and (4) used to evaluate the adsorption performance are given below: (3) (4) In the formula, E Indicates adsorption efficiency (%) C i This is the initial concentration. C e To balance the concentration, q e Adsorption capacity (G / mg) m This refers to the mass of the adsorbent.

[0025] Example 1 A manganese ion-specific adsorbent, the preparation method of which is as follows: (1) CTPB (700 mg), urea (0.42 g), and deionized water (21 mL) were mixed uniformly and sonicated for 30 min to form an aqueous phase. The aqueous phase was transferred to a 100 mL three-necked flask. Then, cyclohexane (21 mL) and isopropanol (0.644 mL) were slowly added dropwise and stirred for 5 min. Then, TEOS (1.75 g) was slowly added dropwise while stirring continuously for 30 min. The temperature was raised to 70 °C and reacted for 1 h, then raised to 90 °C and reacted for another 12 h until the solution turned milky white. Finally, the reaction mixture was centrifuged at 8000 rpm and washed repeatedly with ethanol and water to obtain a crude product. The crude product was calcined at 550 °C for 12 h to remove the surfactant and named DFNS, a white powder.

[0026] (2) Add 0.3 g of DFNS to 15 mL of DMF in a three-necked flask and sonicate for 30 min to achieve uniform dispersion. Add 300 μL of APTES dropwise under magnetic stirring and reflux at 120 °C for 12 h. After the reaction, remove the product and wash it repeatedly with DMF, ethanol and distilled water. Finally, dry the product in a vacuum oven at 40 °C for 24 h and name it N-DFNS, a light yellow product with a yield of 84%.

[0027] (3) N-DFNS (0.213 g) was added to anhydrous ethanol (12 mL) in a three-necked flask and sonicated for 30 min to achieve uniform dispersion. Then, 4-bromo-1,8-naphthalenedicarboxylic anhydride (234.13 mg) was added and mixed thoroughly. The temperature was then raised to 80 °C and maintained for 10 h with stirring. The product was washed successively with ethanol, DMF, and distilled water. Finally, the product was dried in an oven at 40 °C for 24 h and named H-DFNS, TAN powder, with a yield of 62%.

[0028] (4) H-DFNS (0.3 g) and DMF (10 mL) were mixed in a three-necked flask and sonicated for 30 min to achieve uniform dispersion. Then 8-aminoquinoline (30 mg) and cesium carbonate as a catalyst were added, and the mixture was stirred evenly. The mixture was then reacted in an oil bath at 80 °C for 10 h. The product was removed and washed repeatedly with ethanol and distilled water. Finally, the product was dried in an oven at 60 °C for 4 h and named FL-DFNS, a yellow powder with a yield of 46%.

[0029] Test case 1. SEM and TEM images of silica particles of different sizes are shown below. Figure 1 As shown.

[0030] exist Figure 1 As seen in the SEM images (a) and (d), the original silica spheres are uniformly dispersed spherical particles with a perfect hydrangea-like structure. After organic functionalization, the silica microspheres retained the original spherical morphology of the DFNs, but the particle surface became rougher. This is likely due to surface changes caused by the grafting of fluorescent components during the functionalization process. Figure 1 In the TEM images of (b) and (c), the particles exhibit good dispersion and a unique dendritic / fibrous hierarchical structure. Figure 1 Following the modifications shown in (e) and (f), the dendritic fiber structure remained intact, indicating that the modifications did not disrupt the hierarchical structure of the DFN. The fluorescent components were grafted only onto the surface or within the pores of the DFN. The successful introduction of the new structure preserved a high specific surface area. This structural stability is crucial for subsequent adsorption and fluorescence sensing applications.

[0031] 2. Detection of N2 adsorption-desorption isotherms and BJH pore size distribution curves for different particles N2 adsorption analysis nitrogen adsorption-desorption isotherms, such as... Figure 2As shown in (a), all silica microspheres exhibited typical Type IV isotherms with a distinct hysteresis loop between P / P = 0.4 and 1.0. This indicates the presence of mesoporous channels in the material and capillary condensation under higher relative pressures. This is characteristic of mesoporous materials. Compared to the original DFNS, which had the highest nitrogen adsorption capacity, the modified DFNS showed a decrease in adsorption capacity. This suggests that the introduction of functional groups partially occupied the pores, leading to a reduction in the effective specific surface area. Figure 2 In sample b, the pore sizes of all materials are mainly concentrated in the 2-4 nm (sharp peak) and 10-50 nm (broad peak). The pore volume of the fluorescently modified FL-DFN is significantly reduced in the 2-4 nm range, while the intensity of the broad peak in the 10-50 nm range weakens. This indicates that the introduction of the fluorescent group not only occupies part of the mesoporous channels but also has a certain impact on the macroporous structure.

[0032] As shown in Table 1, the first step is amination modification. The specific surface area of ​​BET increased from 345.14 m² / g. 2 / g increased to 374.28m 2 / g, while the specific surface area of ​​BJH is 440.74m². 2 / g decreased to 372.35m 2 / g. This indicates that the amination modification of N-DFNS mainly introduces amino groups on the particle surface, and primarily occurs on the particle surface. It has little effect on the pore structure, and may even form new microstructures on the surface, thereby increasing the specific surface area. The second step is amidation modification. The BET specific surface area drops sharply to 195.99m². 2 / g, the specific surface area of ​​BJH also decreased to 250.08m². 2 / g. This indicates that the functionalization reaction penetrates deep into the channels and occurs inside the silica microspheres, leading to a significant decrease in specific surface area. The third step is a substitution reaction. The BET specific surface area slightly recovers to 224.44m². 2 / g, the specific surface area of ​​BJH also recovered to 286.07m². 2 / g. This may be because the grafting of fluorescent groups onto the pore surface mitigated the pore-filling effect, leading to a slight recovery in pore volume and specific surface area. In summary, the trends in pore volume and pore size are highly consistent with the trends in specific surface area, reflecting the process of pores being gradually occupied and partially recovered during modification.

[0033] Table 1. Porosity of DFNS, N-DFNS, H-DFNS, and FL-DFNS according to the BET, Langmuir, and BJH equations.

[0034] 3. XPS analysis of L-DFNs XPS analysis was used to characterize DFNS, H-DFNS, and FL-DFNS to confirm the successful functionalization of silica microspheres. Figure 3 The full spectrum in (d) clearly shows the evolution of the elemental signals. DFNS shows only peaks for Si 2p, O 1s, and C 1s, matching the composition of pure silica. H-DFNS introduces a new Br 3d signal, confirming the grafting of the bromide precursor. FL-DFNS exhibits an additional N1s peak, while the Br 3d signal is significantly reduced, indicating that bromine is partially substituted by the fluorescent component.

[0035] Figure 3 The high-resolution O1s spectra in (a) further reveal the structural changes. For DFNS, Si-O-Si (532.6 eV) and Si-OH (533.2 eV) represent the silica framework and surface hydroxyl groups. H-DFNS shows a novel CO (533.3 eV) peak, originating from the ether / ester bond in the bromide precursor. Meanwhile, FL-DFNS introduces a C=O (531.2 eV) peak. This peak corresponds to the carbonyl group in the fluorescent moiety, providing direct evidence of the final modification.

[0036] Figure 3 The C1s spectrum in (b) also reflects the sequential grafting process. DFNS shows only CC / CH (284.7 eV) and CO (286.5 eV) peaks, originating from surface-adsorbed carbon and hydroxyl-related carbon. H-DFNS adds C=O and C-Br (288.3 eV) peaks, confirming the introduction of aromatic rings and bromine atoms. FL-DFNS shows a stronger C=C peak, confirming that bromine is substituted by fluorescent aromatic groups.

[0037] Figure 3 The N1s spectrum in (c) provides final confirmation of the reaction pathway. H-DFNS exhibits a novel NH (399.9 eV) peak, originating from the amino group remaining after initial amination. FL-DFNS shows an additional CN (400.6 eV) peak. This peak corresponds to the covalent bond formed between the fluorescent moiety and the precursor, confirming successful final functionalization.

[0038] Overall, XPS results showed that the silica framework remained intact throughout the functionalization process. The gradual changes in elemental signals fully validated the designed reaction route, confirming the successful preparation of FL-DFNs.

[0039] Table 2 DFNS, H-DFNS, FL-DFNS, FL-DFNS+Mn 2+ Content of different elements

[0040] 4. FT-IR analysis of DFNS, N-DFNS, H-DFNS and FL-DFNS like Figure 4 As shown, 467cm -1 803cm -1 and 1090cm -1 The characteristic peaks at these locations correspond to the bending vibrations of the Si-O-Si bond, the symmetric stretching vibrations of Si-O, and the asymmetric stretching vibrations of Si-O-Si, respectively. These peaks remain clear and stable in the spectra of all products. The siloxane framework structure of DFNS remains intact throughout the modification process.

[0041] In the N-DFNS spectrum: 3440 ccm -1 The peak at [value] corresponds to the stretching vibrations of the -NH2 and -OH groups. Meanwhile, at 1664 cm⁻¹... -1 A new NH bending vibration peak appeared at 1775 cm⁻¹, confirming that the amino group had been successfully grafted onto the surface of the silica microspheres. For the H-DFNS spectrum, a new peak was observed at 1775 cm⁻¹. -1 A new peak appears at 1732 cm⁻¹, corresponding to the stretching vibration of the C=O bond. -1 Another new peak appears at 660 cm⁻¹, which is a characteristic vibration of the C=C double bond. -1 A third new peak was observed, attributed to the stretching vibration of the C-Br bond. These characteristic peaks confirm the successful grafting process via the amidation reaction. In the FL-DFNS spectrum: 660 cm⁻¹ -1 The C-Br peak at 1732 cm⁻¹ weakens, while the peak at 1732 cm⁻¹ weakens. -1 The enhanced C=C peak at the point indicates that the fluorescent group has been grafted onto the surface of the silica microspheres through a substitution reaction.

[0042] 5. FL-DFNS for Mn 2+ Specific adsorption recognition FL-DFNS (5 mg) powder was dispersed in 100 mL of DMF to form a mother liquor. A mixture was prepared at 25 °C by mixing 1.5 mL of the mother liquor with 970 μL of deionized water. 30 μL of various metal ion solutions (K₂O₃, K₂O₃, K₂O₃) were then added to this mixture. + Ba 2 + Ni 2+ Mg 2+ Ag + Fe 2+ Cd 2+ Ca 2+ Pd 2+ Fe 3+ Cu 2+ Cr 3+ Na + Mn2+ Zn 2+ Co 2+ Hg 2+ Hg + And Al 3+ The samples were added separately. Additionally, 30 μL of pure water and natural lake water were used as control groups for comparison. For all samples, the excitation wavelength in the fluorescence spectrum was set to 380 nm.

[0043] Mn 2+ Detection such as Figure 5 As shown, the FL-DFNS fluorescent probe has a λ-front of 380 nm and a maximum emission wavelength of 523 nm. The FL-DFNS probe exhibits advantages such as low background interference and high detection sensitivity, with a Stokes shift of 132 nm. When the FL-DFNS probe is mixed with 19 other ions, its maximum fluorescence emission peak intensity reaches 4470 nm, while the addition of Mn... 2+ Subsequently, the maximum fluorescence intensity dropped sharply to 1727, exhibiting a significant "fluorescence quenching" effect. This indicates that the probe is effective against Mn. 2+ It has a unique selective response.

[0044] Interference from metal ions was evaluated through a competition experiment to assess their anti-interference capabilities. In the presence of other metal ions at the same concentration, 30 μL of Mn was added. 2+ In combination with other metal ions (such as Cr) 2+ Pb 2+ Cu 2+ In a system where Mn and others coexist, 2+ Afterwards, FL-DFNs still maintained a significant fluorescence quenching effect. This indicates that even in the presence of multiple interfering ions, the FL-DFN probe can still selectively target Mn. 2+ It produces a fluorescent response and exhibits good anti-interference ability. Figure 5 ).

[0045] 6. FL-DFNs on Mn 2+ Adsorption detection limit To further clarify the relationship between the FL-DFNS probe and Mn 2+ To investigate the interaction mechanism between Mn and Mn, this study conducted fluorescence titration experiments to determine the concentration response characteristics and detection limit (LOD) of the fluorescence sensor. Different Mn groups were examined. 2+ The detection range at a given concentration is calculated using the following formula: the limit of detection (LOD) of the probe. LOD = 3σ / K(1) Where K represents the slope of the standard curve, and σ represents the standard deviation of the fluorescence intensity of the blank sample.

[0046] like Figure 6As shown in (a), with Mn 2+ With increasing concentration, the fluorescence intensity of the probe at its maximum absorption wavelength gradually decreases, and the fluorescence quenching effect becomes more pronounced. Figure 6 In the CIE chromaticity diagram in (c), the fluorescence color of the probe changes with Mn. 2+ The concentration change exhibited a clear color shift, confirming that the fluorescent probe can effectively target Mn. 2+ Rapid and intuitive detection. Multiple fluorescence measurements were performed on the blank sample, and the standard deviation σ of the blank fluorescence value was calculated to be 2.62. Based on... Figure 6 (b) Fluorescence intensity of Mn 2+ The linear fitting equation for concentration was obtained, and the absolute value of the slope K (8.4177) was taken and substituted into the LOD calculation formula (LOD=3σ / K) to calculate the probe-to-Mn concentration. 2+ The LOD is 0.93 μM.

[0047] like Figure 6 As shown in (d), in the absence of Mn 2+ Under the condition of adding Mn, the fluorescence lifetime of FL-DFNS is 4.9 ns; 2+ Subsequently, its fluorescence lifetime shortened to 4.17 ns. Therefore, it can be inferred that the fluorescence lifetime of the FL-DFNS probe and Mn... 2+ During binding, a fluorescence resonance energy transfer occurs, which quenches the fluorescent donor signal of the probe, thereby shortening the fluorescence lifetime.

[0048] Table 3 FL-DFNS probe and FL-DFNS+Hg 2+ / Hg + fluorescence lifetime data

[0049] In summary, the FL-DFNS probe for Mn 2+ It exhibits good linear concentration response and low detection limit, while also possessing visual detection capability and a stable recognition mechanism.

[0050] 7. FL-DFNs on Mn 2+ Specific adsorption and recognition mechanisms To further confirm the adsorption mechanism, the adsorption of Hg was investigated. 2+ / Hg + XPS analysis was performed by combining the elemental composition of the FL-DFNs before and after the analysis. The overall spectrum is as follows: Figure 7 As shown in (b). From Figure 7 The FTIR spectrum in (a) shows that FL-DFNS and Mn 2+After the interaction, the peak shape and intensity of characteristic peaks such as Si-O-Si in the siloxane framework remained stable, indicating that its matrix structure was not destroyed during recognition and adsorption. Conversely, at 1410 cm⁻¹... -1 The infrared absorption peak at that location underwent a significant change. Considering the coordination mechanism of the N atom, this change can be attributed to the formation of an N-Mn coordination bond, confirming that FL-DFNs interact with Mn via the lone pair electrons of the N atom. 2+ empty orbital coordination to achieve Mn 2+ Specific identification.

[0051] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a manganese ion-specific adsorbent, characterized in that, Ammoniated dendritic fibrous nano-silica was modified by aminoation, and then naphthalene anhydride groups were introduced by amidation reaction to obtain the manganese ion specific adsorbent.

2. The preparation method according to claim 1, characterized in that, The preparation method of dendritic fibrous nano-silica is as follows: Using hexadecylpyridine bromide, siloxane and urea as raw materials, the mixture is stirred in a solvent and reacted at 70~80℃ for 1~3h, then heated to 90~105℃ and reacted for 10~16h. The crude product is collected by centrifugation and then calcined at 500~650℃ for 10~14h to obtain dendritic fibrous nano silica.

3. The preparation method according to claim 2, characterized in that, The mass ratio of hexadecylpyridine bromide, siloxane, and urea is 1:2~3:0.5~1.

4. The preparation method according to claim 3, characterized in that, The siloxane is tetraethyl orthosilicate.

5. The preparation method according to claim 2, characterized in that, First, react at 70℃ for 1 hour, then raise the temperature to 90℃ and react for 12 hours, and finally calcine at 550℃ for 12 hours.

6. The preparation method according to claim 1, characterized in that, Dendritic fibrous nano-silica was ultrasonically dispersed, then APTES was added, and the mixture was refluxed at 110-120℃ for 10-12 h. After the reaction, the product was removed, washed, and then vacuum dried to obtain the amino-modified product N-DFNS.

7. The preparation method according to claim 1, characterized in that, After ultrasonic dispersion of N-DFNS, 4-bromo-1,8-naphthalenedicarboxylic anhydride was added, and the mixture was stirred evenly and reacted at 80-95℃ for 10-12 hours. After the reaction, the product was removed, washed, and then vacuum dried to obtain H-DFNS.

8. A manganese ion-specific adsorbent, characterized in that, It is prepared by the method described in any one of claims 1 to 7.

9. The manganese ion-specific adsorbent according to claim 8, characterized in that, The manganese ion-specific adsorbent also contains a fluorescent group; the fluorescent group is 8-aminoquinoline.

10. The use of the manganese ion specific adsorbent according to claim 8 or 9 in wastewater treatment or in the preparation of manganese ion specific adsorption reagents and manganese ion detection reagents.

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