Ionic sodium sulfonate-based covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses an ionic sodium sulfonate-based covalent organic framework material and a preparation method and application thereof, the method comprises the following steps: S1, placing an aqueous solution of a surfactant in a reaction container, and adding 4, 4 '-diaminostilbene-2, 2'-sulfonic acid while stirring; s2, dissolving 2, 4, 6-trihydroxybenzene-1, 3, 5-tricarboxaldehyde in a solvent, slowly dropwise adding the solution into the aqueous solution in the step S1, carrying out a heating reaction, precipitating a solid after the reaction is finished, and centrifuging to obtain a precipitate of a crude product; s3, washing and drying the precipitate obtained in the step S2; s4, placing the dried product in a sodium hydroxide solution for modification, and then performing centrifugal treatment; and S5, washing and drying the precipitate obtained in the step S4 to obtain the product. The ionic sodium sulfonate-based covalent organic framework material disclosed by the invention realizes efficient adsorption of potassium ions.

Description

Technical Field

[0001] This invention belongs to the field of water treatment and environmental protection technology, specifically relating to an ionic sodium sulfonate-based covalent organic framework material, its preparation method, and its application in effectively capturing and removing potassium ions from water. Background Technology

[0002] Controlling metal ion pollution has always been a challenging issue in water treatment and environmental protection. Metal ions can enter the human body through the food chain, and long-term accumulation can lead to various health problems, including nervous system damage and kidney disease. Furthermore, metal ions can react with other chemicals in water to form toxic compounds, further exacerbating water pollution. Therefore, developing effective metal ion removal technologies is crucial for ensuring water safety and human health. Potassium ions (K+) are one of the essential electrolytes for the human body, but excessive intake can also have health effects. In the human body, hyperkalemia can lead to heart problems, such as arrhythmia or even cardiac arrest. Environmentally, excessive potassium ions in wastewater and soil also pose serious hazards. Excessive potassium ion discharge into water bodies can cause imbalances in aquatic ecosystems, affecting the growth and reproduction of aquatic organisms and even triggering algal blooms. In soil, excessive accumulation of potassium ions can affect soil structure, reduce soil fertility, and consequently affect crop growth and yield. Currently, potassium ion removal technologies mainly include ion exchange, membrane separation, and adsorption. While ion exchange is effective, it is costly and requires regular resin replacement. Membrane separation technology suffers from problems such as membrane fouling and high energy consumption. Covalent organic frameworks (COFs), as a novel type of porous material, exhibit great potential in removing metal ions due to their highly ordered porous structure, uniform and adjustable pore size, large specific surface area, and the ability to be precisely designed and constructed through organic synthesis methods to achieve diverse functions. However, the synthesis of COF materials typically requires high temperature and pressure, resulting in high energy consumption, environmental unfriendliness, and inconsistencies with the principles of green chemistry. Strict control of synthesis conditions and long overall time consumption also limit their large-scale production and application. Therefore, developing novel, green, and efficient covalent organic framework materials for the efficient removal of potassium ions from water and soil is of great significance not only for improving water and soil quality and protecting human health but also for promoting environmental protection and sustainable development. Summary of the Invention

[0003] The present invention aims to solve one of the technical problems in the related art to a certain extent. To this end, one object of the present invention is to provide an ionic sodium sulfonate-based covalent organic framework material.

[0004] Another objective of this invention is to provide a green and efficient method for preparing ionic sodium sulfonate-based covalent organic framework materials.

[0005] Another object of the present invention is to provide the application of ionic sodium sulfonate-based covalent organic framework materials in capturing and / or removing potassium ions from water.

[0006] The technical solution adopted in this invention is as follows: Firstly, This invention provides a method for preparing an ionic sodium sulfonate-based covalent organic framework, comprising the following steps: S1: Place the aqueous solution of the surfactant in a reaction vessel and add 4,4'-diaminostilbene-2,2'-sulfonic acid while stirring; S2: Dissolve 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde in a solvent and slowly add it dropwise to the aqueous solution of step S1 for heating reaction. After the reaction is completed, a solid precipitate is formed and centrifuged to obtain the precipitate of crude product. S3: Wash and dry the precipitate obtained in step S2; S4: After drying, the product was placed in a sodium hydroxide solution for modification, and then centrifuged. S5: Wash and dry the precipitate obtained in step S4 to obtain the final product.

[0007] In some embodiments, the surfactant in step S1 is hexadecylpyridine bromide, and the aqueous solution concentration of hexadecylpyridine bromide is 0.8~1.2 mg / mL, preferably 1 mg / mL.

[0008] In some embodiments, in step S1, the stirring speed is 400~600 r / min, preferably 500 r / min.

[0009] In some embodiments, the molar ratio of 4,4'-diaminostilbene-2,2'-sulfonic acid and 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde is 3:2.

[0010] In some embodiments, the solvent in step S2 is one of o-dichlorobenzene, dichloromethane, and n-butanol, the reaction temperature is the azeotropic point of the system, and the reaction time is 120~240 min.

[0011] In some preferred embodiments, the solvent in step S2 is n-butanol, the reaction temperature is the azeotropic point of the system (about 90°C), the reaction time is 120 min, and the solid is precipitated with ethanol after the reaction is completed.

[0012] In some embodiments, the volume ratio of n-butanol to hexadecylpyridine bromide aqueous solution is 1:(3~5), more preferably 1:(3.5~4).

[0013] In some embodiments, the dropping rate in step S2 is 0.4~0.6 mL / min, preferably 0.5 mL / min.

[0014] In some embodiments, step S3 is as follows: the precipitate is washed three times by centrifugation with tetrahydrofuran, then washed three times by centrifugation with methanol, and then dried at 45~80°C for 4-6 hours to obtain COF-SO3H.

[0015] In some embodiments, the concentration of the sodium hydroxide solution in step S4 is 0.1M, and the stirring time is 6-12 hours, preferably 12 hours.

[0016] In some embodiments, step S5 is as follows: the precipitate is washed by centrifugation with distilled water 3 to 5 times until the supernatant is neutral, then frozen in a refrigerator at -20°C for 12 hours, and then dried in a freeze dryer at -40 to -60°C for 24 hours to obtain COF-SO3Na.

[0017] Secondly, This invention also provides an ionic sodium sulfonate-based covalent organic framework prepared by the above method.

[0018] Thirdly, The present invention also provides the application of the above-mentioned ionic sodium sulfonate-based covalent organic framework in the adsorption and removal of metal ions in water.

[0019] In some embodiments of the application, the metal ion is a potassium ion.

[0020] In some embodiments of the application, the pH is adjusted to 5-6, the concentration of the ionic sodium sulfonate-based covalent organic framework material is 1-3 mg / mL, the temperature is 20-25℃, and the adsorption time is 10 min.

[0021] More preferably, the pH is adjusted to 6, the concentration of the ionic sodium sulfonate-based covalent organic framework material is 2 mg / mL, the temperature is 25°C, and the adsorption time is 10 min.

[0022] In some embodiments of the application, the ionic sodium sulfonate-based covalent organic framework material is reused 2-8 times to adsorb and remove potassium ions, more preferably 2-5 times.

[0023] In some embodiments of the application, after the ionic sodium sulfonate-based covalent organic framework material adsorbs potassium ions, it is immersed in a 0.1 M NaNO3 solution for 6 hours, and then repeatedly washed with deionized water until the solution becomes neutral, thereby regenerating the adsorbent.

[0024] The advantages and beneficial effects of this invention are as follows: (1) The method for synthesizing the ionic sodium sulfonate-based covalent organic framework material of the present invention is simple and fast, does not require high pressure, and is a green and fast synthesis method.

[0025] (2) The ionic sodium sulfonate-based covalent organic framework material of the present invention achieves efficient adsorption of metal ions (potassium ions), with a maximum adsorption capacity of up to 113.06 mg / g.

[0026] (3) The adsorption of potassium ions by the ionic sodium sulfonate-based covalent organic framework material of the present invention can reach equilibrium within 10 minutes, showing the ability to respond quickly to pollutants and is suitable for dealing with emergency water pollution events.

[0027] (4) The ionic sodium sulfonate-based covalent organic framework material of the present invention can maintain high adsorption performance even in complex water bodies containing high concentrations of salt, showing good selectivity and anti-interference ability.

[0028] (5) The ionic sodium sulfonate-based covalent organic framework material of the present invention can be recycled multiple times through a simple washing and regeneration process, with a slight decrease in adsorption performance, indicating that it has good stability and sustainability. Attached Figure Description

[0029] Figure 1 The characterization results of the COF-SO3Na material prepared in Example 1 are presented.

[0030] Among them, (a): PXRD pattern of COF-SO3Na; (b): FT-IR spectrum of COF-SO3Na and its synthetic monomers; (c): thermogravimetric analysis diagram of COF-SO3Na and FT-IR diagrams after treatment with acid, alkali, water and tetrahydrofuran; (d): N2 adsorption-desorption isotherm and pore size distribution diagram of COF-SO3Na.

[0031] Figure 2 The morphology and elemental analysis results of the COF-SO3Na material prepared in Example 1 are shown.

[0032] Wherein, (a) and (b): scanning electron microscopy images of COF-SO3Na; (c) and (d): transmission electron microscopy images of COF-SO3Na; (e): scanning electron microscopy-elemental mapping analysis of COF-SO3Na before adsorption; (f): scanning electron microscopy-elemental mapping analysis of COF-SO3Na after adsorption; (g): EDX spectrum of COF-SO3Na before adsorption; (h): EDX spectrum of COF-SO3Na after adsorption.

[0033] Figure 3 The results of a batch adsorption experiment of potassium ions on COF-SO3Na prepared in Example 1 are presented.

[0034] Among them, (a): the effect of pH value on the adsorption of potassium ions by COF-SO3Na; (b): the effect of adsorbent concentration on the adsorption of potassium ions by COF-SO3Na; (c): the adsorption kinetic curve of potassium ions by COF-SO3Na; (d): the adsorption isotherm of potassium ions by COF-SO3Na; and (e): the effect of temperature on the adsorption of potassium ions by COF-SO3Na.

[0035] Figure 4 This demonstrates the adsorption of potassium ions in paddy soil samples from different regions by COF-SO3Na prepared in Example 1.

[0036] Figure 5 The experimental results of the COF-SO3Na cyclic adsorption of potassium ions prepared in Example 1 are presented.

[0037] Figure 6 The following images are presented: (a) XPS total spectrum; (b) K 2p fine spectrum; (c) Na 1s fine spectrum.

[0038] Figure 7 The maximum adsorption capacity and adsorption time of potassium ions prepared in Example 1 were compared with those of different adsorbents reported in other literature. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0040] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0041] Unless otherwise stated, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art.

[0042] In this article, the term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0043] In this document, the term "about" means a specified value of + / -10%, more preferably + / -5%, and even more preferably + / -1%.

[0044] When a value is described as a range, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as the specific numerical value falling within that range, regardless of whether the specific numerical value or specific subrange is explicitly specified.

[0045] It should be noted that all the following adsorption experiments were performed three times, and the average value was taken.

[0046] Example 1

[0047] The synthesis method of ionic sodium sulfonate-based covalent organic framework material (COF-SO3Na) includes the following steps: (1) Add 15 mL of 1 mg / mL hexadecylpyridine bromide aqueous solution to a 50 mL round bottom flask, stir at 500 r / min, and add Stb-SO3H (4,4'-diaminostilbene-2,2'-sulfonic acid, 111.12 mg, 0.3 mmol).

[0048] (2) Tp (2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde, 42.0 mg, 0.2 mmol) was dissolved in 4 mL of n-butanol by sonication (40 kHz) and added dropwise to the aqueous solution of step (1) at a rate of 0.5 mL / min. The mixture was heated to boiling (about 90 °C) and stirred (500 r / min) for 120 minutes. After the reaction was completed, the solid was precipitated with 15 mL of ethanol and centrifuged to obtain a reddish-brown powder.

[0049] (3) The solid reddish-brown powder was washed three times by centrifugation with tetrahydrofuran, then washed three times by centrifugation with methanol, and then dried at 60°C for 6 hours to obtain COF-SO3H. The dried powder was dispersed in 100 mL of 0.1 M NaOH solution and stirred at room temperature for 12 hours. Subsequently, the obtained product was centrifuged and washed three times with distilled water until the supernatant was neutral. Finally, the collected solid was placed in a refrigerator and frozen at -20°C for 12 hours, and then placed in a freeze dryer and dried at -50°C for 24 hours to obtain the target product COF-SO3Na.

[0050] Example 2

[0051] The difference from Example 1 is that in step (2) of Example 2, the solvent used is dichloromethane (DCM), the system is heated to the azeotropic point (about 47°C), and the stirring time is 120 min.

[0052] Example 3

[0053] The difference from Example 1 is that in step (2) of Example 3, the solvent used is dichloromethane (DCM), the system is heated to the azeotropic point (about 47°C), and the stirring time is 240 min.

[0054] Example 4

[0055] The difference from Example 1 is that the solvent used in step (2) of Example 4 is o-dichlorobenzene. （o -DCB ） Heat to the azeotropic point of the system (approximately 112°C) and stir for 120 minutes.

[0056] Comparative Example 1 The difference from Example 1 is that in step (2) of Comparative Example 1, the solvent used is dichloromethane (DCM), the temperature is 20°C, and the stirring time is 10 min.

[0057] Comparative Example 2 The difference from Example 1 is that in step (2) of Comparative Example 2, the solvent used is dichloromethane (DCM), the temperature is 40°C, and the stirring time is 10 min.

[0058] Comparative Example 3 The difference from Example 1 is that in step (2) of Comparative Example 3, the solvent used is dichloromethane (DCM), the system is heated to the azeotropic point, and the stirring time is 10 min.

[0059] Comparative Example 4 The difference from Example 1 is that in step (2) of Comparative Example 4, the solvent used is dichloromethane (DCM), the system is heated to the azeotropic point, and the stirring time is 20 min.

[0060] Comparative Example 5 The difference from Example 1 is that in step (2) of Comparative Example 5, the solvent used is dichloromethane (DCM), the system is heated to the azeotropic point, and the stirring time is 30 min.

[0061] Comparative Example 6 The difference from Example 1 is that in step (2) of Comparative Example 6, the solvent used is dichloromethane (DCM), the system is heated to the azeotropic point, and the stirring time is 60 min.

[0062] Comparative Example 7 The difference from Example 1 is that in step (2) of Comparative Example 7, the solvent used is 1,4-dioxane, the system is heated to the azeotropic point, and the stirring time is 120 min.

[0063] Comparative Example 8 The difference from Example 1 is that in step (2) of Comparative Example 8, the solvent used is mesitylene, the system is heated to the azeotropic point, and the stirring time is 120 min.

[0064] Comparative Example 9 The difference from Example 1 is that in step (2) of Comparative Example 9, the solvent used is tetrahydrofuran (THF), the system is heated to the azeotropic point, and the stirring time is 120 min.

[0065] Comparative Example 10 The difference from Example 1 is that in step (2) of Comparative Example 10, the solvent used is N,N-dimethylformamide (DMF), the system is heated to the azeotropic point, and the stirring time is 120 min.

[0066] Comparative Example 11 The difference from Example 1 is that in step (2) of Comparative Example 11, the solvent used is methanol (MeOH), the system is heated to the azeotropic point, and the stirring time is 120 min.

[0067] Comparative Example 12 The difference from Example 1 is that in step (2) of Comparative Example 12, the solvent used is ethanol (EtOH), the system is heated to the azeotropic point, and the stirring time is 120 min.

[0068] Table 1 shows the effects of different temperatures, times, and solvents on the reaction yields of Examples 1-4 and Comparative Examples 1-12. As can be seen from Table 1, Example 1, using n-butanol as a solvent and heating to boiling for 120 minutes, achieved the highest reaction yield.

[0069] Table 1. Effects of different temperatures, times, and solvents on the reaction.

[0070] Figure 1 The characterization results of the COF-SO3Na material prepared in Example 1 are presented. First, the crystallinity of COF-SO3Na was evaluated using powder X-ray diffraction (PXRD). Figure 1 (a) A strong diffraction peak corresponding to the crystal plane (100) was observed at 2.9°, indicating that the prepared COF-SO3Na material has good crystallinity. The Fourier transform infrared (FT-IR) spectrum of COF-SO3Na is shown in (a). Figure 1 (b) Figure 1 In (b), observations were made at 1175, 1592, and 1618 cm. -1 Characteristic peaks corresponding to CN, C=C, and C=O bonds were observed nearby, indicating that a Schiff base reaction occurred between the monomers, and that COF-SO3Na maintained a stable state. βIt exists in the form of ketene-enamine. COF-SO3Na exhibits good thermal and chemical stability. Thermogravimetric analysis (TGA) under N2 atmosphere, from 30℃ to 800℃ at a heating rate of 10℃ / min, shows that COF-SO3Na has good thermal stability below 300℃, with a weight loss of about 10%, and maintains the integrity of its crystal structure in acid (1M HCl), alkali (1M NaOH), water, and the organic solvent DMF. Figure 1 (c)). Specific surface area and pore size of COF-SO3Na N2 adsorption-desorption experiments are shown below. Figure 1 As shown in (d), the COFs adsorption-desorption curve is a type IV isotherm, indicating the presence of mesopores in the material. The specific surface area of ​​COF-SO3Na calculated using the BET equation is 38.71 m². 2 / g, with an average pore size of 17.56 nm ( Figure 1 (d) Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that COF-SO3Na is composed of a large number of irregular granular structures aggregated together. Figure 2 (a)-(d)). Scanning electron microscopy-elemental mapping analysis (SEM-EDX) shows that C, N, O, S and Na are uniformly distributed on the COF-SO3Na surface. Figure 2 (e)

[0071] Example 5

[0072] Example 1: Method for potassium ion removal by adsorption of ionic sodium sulfonate-based covalent organic framework prepared in Example 1 First, the effect of pH on the adsorption of potassium ions by COF-SO3Na was investigated. Figure 3 In step (a), 10 mg of COF-SO3Na was added to 5 mL of a potassium ion solution (1 mg / L) with pH = 2-12. The solution was shaken for 10 min at room temperature (25℃). The supernatant was centrifuged to determine the concentration of potassium ions. The results showed that the adsorption efficiency first increased and then decreased with increasing pH. The adsorption performance of COF-SO3Na for potassium ions was optimal at pH 6. After centrifuging to remove COF-SO3Na, the concentration of residual potassium ions in the solution after adsorption was measured by ICP-MS. The adsorption efficiency was calculated using formula (1).

[0073] (1) in c 0 (mg / L) and c e (mg / L) is the concentration of potassium ions in the solution before and after COF-SO3Na adsorption.

[0074] Then the effect of COF-SO3Na feed concentration on adsorption efficiency was investigated. Figure 3 In (b), 5, 10, and 15 mg of COF-SO3Na were added to 5 mL of a potassium ion solution (1 mg / L) at pH 6. The mixture was stirred for 10 min at room temperature (25℃), and the potassium ion concentration was determined by centrifugation of the supernatant. The results showed that the adsorption efficiency increased with the increase of COF-SO3Na adsorbent concentration. To ensure that COF-SO3Na can effectively remove potassium ions in practical applications while avoiding waste and cost control caused by excessive adsorbent, batch adsorption experiments were conducted at pH 6 and a COF-SO3Na feed concentration of 2 mg / mL.

[0075] Next, the effect of contact time on the adsorption of potassium ions by COF-SO3Na was investigated. Figure 3 In step (c), 40 mg of COF-SO3Na was added to 20 mL of a 600 mg / L potassium ion solution at pH 6 and the process was carried out at room temperature (25 °C), with samples taken periodically. After centrifugation, the concentration of potassium ions in the supernatant was measured. The rapid adsorption in the initial stage can be attributed to the large number of available binding sites on COF-SO3Na and the concentration gradient at the solution-material interface. The adsorption of potassium ions by COF-SO3Na reached equilibrium within 10 minutes.

[0076] To investigate the saturated adsorption capacity of COF-SO3Na, adsorption isotherms were examined at different initial potassium ion concentrations (0.5-1000 mg / L, pH=6, COF-SO3Na feed concentration of 2 mg / mL, and stirring at room temperature (25℃) for 10 min). Figure 3 (d) The Langmuir saturated adsorption capacity of COF-SO3Na is 113.06 mg / g, close to the experimental maximum adsorption capacity of 108.54 mg / g. Adsorption capacity q e (mg / g) is calculated using formula (2).

[0077] (2) Where V (L) is the solution volume and m (g) is the mass of COF-SO3Na.

[0078] like Figure 3As shown in Figure (e), to investigate the effect of temperature on the adsorption of potassium ions by COF-SO3Na, the adsorption efficiency of COF-SO3Na for potassium ions was tested under different temperature conditions. 10 mg of COF-SO3Na was added to 5 mL of a potassium ion solution (1 mg / L) at pH 6, and the mixture was stirred for 1 h at different temperatures. After centrifugation, the concentration of potassium ions in the supernatant was measured. With increasing temperature, the adsorption capacity of COF-SO3Na for potassium ions decreased significantly, indicating that the adsorption reaction has exothermic characteristics. The thermodynamic parameters of the reaction were calculated according to the Gibbs-Helmholtz equation, where the Gibbs free energy change (… Δ G 0 The value of COF-SO3Na is negative, and the negative value becomes smaller and smaller as the temperature increases, indicating that the adsorption of potassium ions by COF-SO3Na is thermodynamically spontaneous, but the degree of spontaneity of the adsorption reaction decreases as the temperature increases.

[0079] Example 6

[0080] A method for removing potassium ions from paddy soil by adsorption of ionic sodium sulfonate-based covalent organic framework. In real-world environments, especially in soil systems, potassium ions often coexist with various metal ions, such as Na+. + Mg 2 + Ca 2+ Cu 2+ Zn 2+ To investigate the feasibility of COF-SO3Na in practical applications in soil, the adsorption efficiency of COF-SO3Na for potassium ions in real paddy soil digestate (provided by the Environmental Protection Research and Monitoring Institute (Tianjin)) from different regions (Tianjin, Sichuan, Guizhou, and Hunan) was tested. Figure 4 Weigh 0.2 g of dried soil sample (passed through a 100-mesh sieve) into a 50 ml PTFE tube. Add a few drops of ultrapure water to moisten the soil, then add 5 mL of hydrofluoric acid (HF), followed by 5 mL of perchloric acid (HClO4). Place the PTFE tube on a porous graphite furnace and heat to dryness at 200-250℃. When the contents are nearly dry and the residue in the crucible is viscous, remove it and let it cool slightly. Rinse the inner wall of the crucible with a small amount of dilute hydrochloric acid (HCl) or water, and heat to dryness again to completely remove residual fluoride ions (F). -Finally, the remaining residue was dissolved by heating with dilute hydrochloric acid (1:1 HCl), transferred to a volumetric flask, and diluted to the mark to obtain the soil digestion solution. 20 mg of COF-SO3Na was added to 5 mL of the soil digestion solution at pH=6, stirred at room temperature for 10 min, and the potassium ion concentration was determined by centrifugation of the supernatant. The results showed that the adsorption performance of COF-SO3Na was slightly affected, but the removal rate of potassium ions remained above 80%. The recoverability and reusability of the adsorbent are another key factor in evaluating its actual performance. After adsorbing potassium ions, COF-SO3Na was immersed in a 0.1 mol / L NaNO3 solution and stirred for 6 hours, then repeatedly washed with deionized water until the solution became neutral, thus easily regenerating the adsorbent. Figure 5 It can be seen that the adsorption capacity of COF-SO3Na for potassium ions decreases with increasing number of reuses. After 8 adsorption-elution cycles, the removal rate of potassium ions by COF-SO3Na decreased by 13%, which may be due to the structural collapse of COF-SO3Na and the loss of adsorbent mass caused by washing during the regeneration process. These experimental results demonstrate that COF-SO3Na possesses good anti-interference ability and great application potential as an adsorbent for removing potassium ions from soil.

[0081] Example 7

[0082] A Mechanism Analysis Method for the Adsorption of Potassium Ions by an Ionic Sodium Sulfonate-Based Covalent Organic Framework To investigate the adsorption mechanism of COF-SO3Na, various characterization methods were used to explore the adsorption mechanism of potassium ions by COF-SO3Na. Figure 2 Images (e) and (f) show the elemental spectra of COF-SO3Na before and after potassium ion adsorption using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). A comparison reveals that after potassium ion adsorption, COF-SO3Na exhibits a more uniformly distributed K signal, while the Na signal is significantly weakened. Further analysis of the EDX images of COF-SO3Na before and after potassium ion adsorption... Figure 2 Analysis of the (g)-(h) spectrum showed that the mass percentage of Na decreased, while the mass percentage of K increased significantly from zero. These results confirm that potassium ions were successfully adsorbed by COF-SO3Na, thus preliminarily determining that the adsorption mechanism is ion exchange.

[0083] To further elucidate the adsorption mechanism of potassium ions on COF-SO3Na, X-ray photoelectron spectroscopy (XPS) was used to characterize the samples before and after adsorption. The XPS spectra further confirmed that potassium ions were adsorbed onto COF-SO3Na. Figure 6In (a), the characteristic peak of K is clearly visible in the full XPS spectrum, and the characteristic peak signals of K 2p1 / 2 (296.03 eV) and K 2p3 / 2 (293.31 eV) are detected in the fine spectrum. Figure 6 (b)). From Figure 6 The fine spectrum of Na 1s in (c) clearly shows that after COF-SO3Na adsorbs potassium ions, the peak area of ​​the characteristic Na 1s peak is significantly reduced. This phenomenon further confirms that there is an ion exchange mechanism in the process of COF-SO3Na adsorbing potassium ions.

[0084] To more fully and intuitively evaluate the adsorption performance of COF-SO3Na, as shown in Table 2 and... Figure 7 The maximum adsorption capacity and adsorption time of potassium ions by the COF-SO3Na prepared in this invention were compared with those of other adsorbents reported in the literature. Comparative analysis revealed that the prepared COF-SO3Na exhibits superior adsorption capacity for potassium ions compared to most reported adsorbents.

[0085] Table 2. Adsorption capacity of potassium ions by different adsorbent materials

[0086] [1] Zhang X, Liu H, Xing H, et al. Investigation of potassium vaportime-resolved adsorption and potassium-sodium competitive adsorption by modified kaolinite[J]. Fuel, 2019, (258): 116124. [2] Chen K, Li L, Yang K, et al. Efficient adsorptive removal of potassium from potassium perrhenate solution using a cationic ion exchangeresin[J]. RSC Adv, 2025, (15): 1604. [3] Pan L, Zhang A, Sun J, et al. Application of ocean manganesenodules for the adsorption of potassium ions from seawater[J]. MineralsEngineering, 2013, (49): 121. [4] Liu Y, Duan X, Cao X, et al. Experimental study on adsorption ofpotassium vapor in flue gas by coal ash [J].Powder Technology, 2017, (318):170. [5] Casadella A, Kuntke P, Schaetzle O, et al. Clinoptilolite-basedmixed matrix membranes for the selective recovery of potassium and ammonium[J]. Water Research, 2016, (90): 62. [6] Naidu G, Jeong S, Choi Y, et al. Valuable rubidium extractionfrom potassium reduced seawater brine[J].Journal of Cleaner Production, 2018,(174): 1079. [7] Jiang D, Hill J P, Henzie J, et al. Selective electrochemicalcapture of monovalent cations using crown ether-functionalized COFs[J].Journal of the American Chemical Society, 2025, (147): 12460. Furthermore, the terms "first" and "second" in this invention are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0087] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0088] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing an ionic sodium sulfonate-based covalent organic framework, characterized in that, Includes the following steps: S1: Place the aqueous solution of the surfactant in a reaction vessel and add 4,4'-diaminostilbene-2,2'-sulfonic acid while stirring; S2: Dissolve 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde in a solvent and slowly add it dropwise to the aqueous solution of step S1 for heating reaction. After the reaction is completed, a solid precipitate is formed and centrifuged to obtain the precipitate of crude product. S3: Wash and dry the precipitate obtained in step S2; S4: After drying, the product was placed in a sodium hydroxide solution for modification, and then centrifuged. S5: Wash and dry the precipitate obtained in step S4 to obtain the final product.

2. The method for preparing an ionic sodium sulfonate-based covalent organic framework according to claim 1, characterized in that, The surfactant in step S1 is hexadecylpyridine bromide, and the concentration of the aqueous solution of hexadecylpyridine bromide is 0.8~1.2 mg / mL, preferably 1 mg / mL.

3. The method for preparing an ionic sodium sulfonate-based covalent organic framework according to claim 1, characterized in that, The molar ratio of 4,4'-diaminostilbene-2,2'-sulfonic acid and 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde is 3:

2.

4. The method for preparing an ionic sodium sulfonate-based covalent organic framework according to claim 2, characterized in that, The solvent in step S2 is one of o-dichlorobenzene, dichloromethane, and n-butanol. The reaction temperature is the azeotropic point of the system, and the reaction time is 120-240 min. Preferably, the solvent in step S2 is n-butanol, the reaction temperature is the azeotropic point of the system, the reaction time is 120 min, and the solid is precipitated with ethanol after the reaction is completed.

5. The method for preparing an ionic sodium sulfonate-based covalent organic framework according to claim 4, characterized in that, The volume ratio of n-butanol to hexadecylpyridine bromide aqueous solution is 1:(3~5), preferably 1:(3.5~4).

6. The method for preparing an ionic sodium sulfonate-based covalent organic framework according to claim 1, characterized in that, In step S4, the concentration of the sodium hydroxide solution is 0.1M, and the stirring time is 6-12 hours, preferably 12 hours.

7. The method for preparing an ionic sodium sulfonate-based covalent organic framework according to claim 1, characterized in that, In step S1, the stirring speed is 400~600 r / min, preferably 500 r / min; And / or, the dropping rate in step S2 is 0.4~0.6 mL / min, preferably 0.5 mL / min; And / or, step S3 is: the precipitate is washed three times by centrifugation with tetrahydrofuran, then washed three times by centrifugation with methanol, and then dried at 45~80℃ for 4-6 hours to obtain COF-SO3H; And / or, step S5 is as follows: the precipitate is washed by centrifugation with distilled water 3 to 5 times until the supernatant is neutral, then frozen in a refrigerator at -20°C for 12 hours, and then dried in a freeze dryer at -40 to -60°C for 24 hours to obtain COF-SO3Na.

8. An ionic sodium sulfonate-based covalent organic framework, characterized in that, The ionic sodium sulfonate-based covalent organic framework is prepared by the method comprising any one of claims 1-7.

9. The application of the ionic sodium sulfonate-based covalent organic framework of claim 8 in the adsorption and removal of potassium ions in water.

10. The application according to claim 9, characterized in that, The pH is adjusted to 5-6, the concentration of the ionic sodium sulfonate-based covalent organic framework material is 1-3 mg / mL, the temperature is 20-25℃, and the adsorption time is 10 min; more preferably, the pH is adjusted to 6, the concentration of the ionic sodium sulfonate-based covalent organic framework material is 2 mg / mL, the temperature is 25℃, and the adsorption time is 10 min. And / or, the ionic sodium sulfonate-based covalent organic framework material can be reused 2-8 times to adsorb and remove potassium ions; And / or, after the ionic sodium sulfonate-based covalent organic framework material adsorbs potassium ions, it is immersed in a 0.1 M NaNO3 solution for 6 hours, and then repeatedly washed with deionized water until the solution becomes neutral, thereby regenerating the adsorbent.

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