An adsorbent for organic amine flotation and its preparation method

Abstract

This invention relates to an adsorbent for organic amine flotation and its preparation method, based on the design of polar microporous TpPa-NO2COF. Batch adsorption experiments showed that TpPa-NO2COF reaches adsorption equilibrium within 20 minutes, with a maximum adsorption capacity of 128.5 mg / g for ODA. The adsorption mechanism between TpPa-NO2COF and ODA mainly involves electrostatic interactions, polar interactions, van der Waals forces, hydrogen bonding, and hydrophobic effects. Furthermore, by in-situ deposition of TpPa-NO2COF powder on an organic nylon membrane substrate, rapid removal of ODA from sample solutions was achieved under dynamic pressure-driven membrane filtration conditions. Dynamic adsorption experiments showed that TpPa-NO2COF achieved an ODA extraction rate exceeding 90%, and the membrane material maintained a regeneration rate of over 93% after hydrochloric acid washing.

Description

Technical Field

[0001] This technology belongs to the field of organic pollutant adsorption and removal technology, specifically involving an adsorbent for organic amine flotation and its preparation method. The method of this invention obtains an excellent organic amine flotation adsorbent, TpPa-NO2. By precisely customizing the polarity and pore size of COFs at the molecular level, this method achieves efficient adsorption and rapid removal of long-chain alkylamine pollutants, providing a new solution for water treatment, environmental remediation, and organic pollutant removal. Background Technology

[0002] With the development of the chlor-alkali industry, a large amount of amine-rich reagents, such as octadecylamine (ODA), are consumed annually in the flotation process of potash fertilizer. These amines continuously diffuse and accumulate during production, leading to increased amine content in the brine system and potash fertilizer products. Excessive amine levels negatively impact fertilizer efficiency, pose safety risks, and hinder the development of high-quality potassium chloride products. Therefore, research on amine removal technologies is imperative. Currently, significant progress has been made in ammonia nitrogen removal research in the wastewater treatment industry both domestically and internationally. However, in-depth research on amine removal technologies in potash fertilizer production (including amine removal in brine systems and potash fertilizer products, as well as the improvement, removal, and recovery of flotation reagents) is still lacking, especially industrialization technologies suitable for large-scale production. Due to its hydrophobic and long-chain structure, ODA is difficult to degrade naturally once it enters water bodies, causing serious impacts on aquatic ecosystems, including affecting the growth and reproduction of aquatic organisms and posing a potential threat to human health. Therefore, developing effective ODA removal technologies is crucial for environmental protection and public health. Currently used methods for ODA removal include physical adsorption, chemical oxidation, and biodegradation. However, these methods suffer from high costs, low efficiency, and secondary pollution, especially when treating large-scale industrial wastewater. Therefore, exploring a new, efficient, economical, and environmentally friendly method for ODA removal has become an important research direction in the fields of environmental governance and potash fertilizer refining. Summary of the Invention

[0003] The present invention aims to overcome the shortcomings of the prior art. To this end, the present invention provides an adsorbent for organic amine flotation and a method for preparing the same.

[0004] The technical solution adopted in this invention is as follows:

[0005] This invention provides a method for preparing an adsorbent for an organic amine flotation agent, comprising the following steps:

[0006] 2-Nitrophenyl-1,4-diamine (Pa-NO2) was added to a first solvent to form a first solution; 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde (Tp) was added to a second solvent to form a second solution. The second solution was mixed with glacial acetic acid solution to form a mixed solution. The first solution was heated to 60-100°C, and then the mixed solution was added dropwise to the first solution. After stirring for 1 hour, a large amount of reddish-brown precipitate was formed. Then, the mixture was sealed under vacuum and the reaction was carried out at 120°C for 24-72 hours to obtain a reddish-brown solid. The solid was collected by centrifugation, washed, and dried to obtain TpPa-NO2 COF.

[0007] Furthermore, the molar ratio of 2-nitrobenzene-1,4-diamine (Pa-NO2) to 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde (Tp) is 3:(2-2.5).

[0008] Furthermore, the first solvent is o-dichlorobenzene or N,N-dimethylformamide.

[0009] Furthermore, the second solvent is n-butanol or dichloromethane.

[0010] Furthermore, the concentration of the glacial acetic acid solution is 6-9M, and the volume ratio of the second solvent to the glacial acetic acid solution is (3-10):1.

[0011] Furthermore, the molar ratio of 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde (Tp) to glacial acetic acid is 1:(20-60).

[0012] Furthermore, the washing refers to washing with dichloromethane for 6-12 hours, washing with anhydrous ethanol for 6-12 hours, and then washing with tetrahydrofuran for 6-12 hours in a Soxhlet extractor.

[0013] Furthermore, the drying refers to vacuum drying at 60-100°C for 6-12 hours.

[0014] Furthermore, the preparation method also includes uniformly loading TpPa-NO2 COF onto an organic nylon membrane substrate material using a vacuum-assisted in-situ deposition method.

[0015] Furthermore, using tannic acid as a crosslinking agent, 10 mg TpPa-NO2COF was uniformly deposited on a nylon substrate with a diameter of 25 mm through a vacuum-assisted in-situ deposition process, ultimately producing a nylon@COF composite membrane.

[0016] The present invention also provides an adsorbent obtained by the above preparation method.

[0017] This invention also provides the application of the above-mentioned adsorbent in the adsorption and removal of organic amine flotation agents in water.

[0018] In the above applications, the water body can be brine from a salt lake.

[0019] In the above application, the organic amine flotation agent is octadecylamine (ODA).

[0020] In the above applications, the pH was adjusted to 5-6, the feed concentration of TpPa-NO2 COF was 0.16-0.2 mg / mL, the temperature was room temperature, and the adsorption time was 20 min.

[0021] This invention relates to a novel nitro-modified microporous covalent organic framework (COF) material, specifically designed for the adsorption removal and membrane filtration separation of organic amine flotation agents, such as octadecylamine (ODA), in chlor-alkali industrial salt lake brine. It offers the following advantages and beneficial effects:

[0022] (1) This invention relates to a highly efficient adsorbent for organic amine flotation agents, based on the design of TpPa-NO2COF with polar micropores. Through batch adsorption experiments, it was found that TpPa-NO2 COF can reach adsorption equilibrium within 20 minutes, and the maximum adsorption capacity for octadecylamine (ODA) is 128.5 mg / g, demonstrating a rapid response capability to organic amine flotation agents. The adsorption mechanism between TpPa-NO2 COF and ODA mainly involves electrostatic interaction, polar interaction, van der Waals forces, hydrogen bonding, and hydrophobic effects.

[0023] (2) Furthermore, TpPa-NO2 COF powder was deposited in situ onto an organic nylon membrane substrate, enabling rapid removal of ODA from the sample solution under dynamic conditions of pressure-driven membrane filtration. Dynamic adsorption experiments showed that TpPa-NO2 COF achieved an ODA extraction rate exceeding 90%, and the membrane material maintained a regeneration rate of over 93% after hydrochloric acid washing. This invention provides an effective approach for the removal of organic amine pollutants in environmental remediation and industrial applications.

[0024] (3) The TpPa-NO2 COF material of the present invention exhibits high ODA adsorption performance in complex water bodies containing high concentrations of salt, demonstrating good selectivity and anti-interference ability. Furthermore, after simple acid washing and regeneration treatment, the adsorption performance remains at a high level, providing the possibility for the sustainable use of the material. Attached Figure Description

[0025] Figure 1 The characterization results are for the TpPa-NO2 COF material of Example 1.

[0026] a represents the FT-IR spectrum of TpPa-NO2 COF and its synthetic monomers.

[0027] b is the PXRD pattern of TpPa-NO2 COF.

[0028] c is a simulated pore structure diagram of TpPa-NO2 COF.

[0029] solid-state NMR of d for TpPa-NO2 COF 13 C spectrum,

[0030] e is the thermogravimetric analysis diagram of TpPa-NO2 COF.

[0031] f represents the N2 adsorption-desorption isotherm and pore size distribution of TpPa-NO2 COF.

[0032] Figure 2 The image shows the morphology and elemental mapping results of the TpPa-NO2 COF material from Example 1.

[0033] a is a scanning electron microscope image of TpPa-NO2 COF.

[0034] b is a transmission electron microscope image of TpPa-NO2 COF.

[0035] c is the elemental analysis diagram of TpPa-NO2 COF.

[0036] Figure 3 The results of the batch adsorption experiment of ODA by TpPa-NO2 COF in Example 1 are shown.

[0037] a represents the effect of pH on the adsorption of ODA by TpPa-NO2 COF, and the inset shows the Zeta potential of TpPa-NO2 COF.

[0038] b represents the effect of adsorbent concentration on the adsorption of ODA by TpPa-NO2 COF.

[0039] c represents the adsorption kinetics curve of ODA by TpPa-NO2 COF.

[0040] d represents the adsorption isotherm of ODA at TpPa-NO2 COF.

[0041] e represents the effect of temperature on the adsorption of ODA by TpPa-NO2 COF.

[0042] f represents the effect of salt lake brine matrix, KCl, and NaCl on the adsorption of ODA by TpPa-NO2 COF.

[0043] Figure 4 The results are from the reuse test of TpPa-NO2 COF adsorbed ODA in Example 1.

[0044] Figure 5The results are from the experiment of TpPa-NO2 COF adsorbing ODA under dynamic conditions of pressure-driven membrane filtration in Example 1.

[0045] in,

[0046] a is a schematic diagram of the preparation process of the nylon@TpPa-NO2 COF membrane.

[0047] b represents the effect of membrane flux on the adsorption of ODA by TpPa-NO2 COF.

[0048] c represents the penetration curve of ODA through the nylon@TpPa-NO2 COF membrane.

[0049] Figure 6 The results are from molecular dynamics simulations of ODA adsorption at TpPa-NO2 COF.

[0050] a represents the side and top views of the initial configuration of the simulation system.

[0051] b is a side view of the TpPa-NO2 COF+ODA system at different simulation times.

[0052] c represents the statistical count of the number of ODA cations adsorbed by TpPa-NO2 COF.

[0053] d represents the number density distribution of ODA cations, and the orange dashed line represents the solution / COF interface.

[0054] e represents the curves showing the changes in Coulomb interaction energy and LJ potential energy during the molecular dynamics simulation.

[0055] f represents the H2O and Cl- concentrations during the molecular dynamics simulation. - The mean square shift of the ODA cation is shown in the figure. The red dashed line in the inset represents the hydrophobic effect between TpPa-NO2 COF and the ODA cation.

[0056] Figure 7 The results are from density functional theory calculations of ODA adsorbed by NO2 COF at TpPa.

[0057] a represents the surface area of ​​the van der Waals surface of the TpPa-NO2 COF model molecule within different ESP ranges.

[0058] b shows the optimized molecular structure of the TpPa-NO2 COF+ODA complex. The blue area represents the Hirshfeld surface, and the red and white areas represent the hydrogen bonds and C-H σ-π interactions between TpPa-NO2 COF and ODA, respectively.

[0059] c is the fingerprint image of Hirshfeld surface analysis.

[0060] Table 1 provides the thermodynamic parameters for the adsorption of ODA by NO2 COF at TpPa.

[0061] Table 2 shows descriptors for measuring the molecular polarity of TpPa-NO2 COF and ODA. polar V min and V max These represent the percentage of polar surface area to the total molecular area, and the minimum and maximum values ​​of the molecular surface electrostatic potential, respectively.

[0062] Table 3 provides information on the hydrogen bond lengths and bond angles between TpPa-NO2 COF and ODA. 1 O represents the oxygen atom in the carbonyl group of TpPa-NO2COF. 2 O represents the oxygen atom in the nitro group of TpPa-NO2 COF.

[0063] Table 4 provides information on the bond energies of hydrogen bonds between TpPa-NO2 COF and ODA. ρ(r BCP The electron density at the critical point of the bond is denoted as E. The hydrogen bond energy (E) is calculated using a formula reported in the literature. HB (kcal / mol)=-223.08×ρ(r BCP (+0.7423). Detailed Implementation

[0064] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0065] This invention provides a method for preparing an adsorbent for an organic amine flotation agent, comprising the following steps:

[0066] 2-Nitrophenyl-1,4-diamine (Pa-NO2) is added to a first solvent to form a first solution; 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde (Tp) is added to a second solvent to form a second solution. The second solution is mixed with glacial acetic acid solution to form a mixture. The first solution is heated to 60-100℃ (non-limiting examples include temperatures of 60℃, 70℃, 75℃, 80℃, 90℃, 95℃, 100℃, etc.), and then the mixture is added dropwise to the first solution. After stirring for 1 hour, a large amount of reddish-brown precipitate is formed. Then, the mixture is sealed under vacuum and the reaction is carried out at 120℃ for 24-72 hours (non-limiting examples include times of 24 hours, 30 hours, 40 hours, 50 hours, 60 hours, 72 hours, etc.) to obtain a reddish-brown solid. The solid is collected by centrifugation, washed, and dried to obtain TpPa-NO2 COF.

[0067] Further, the molar ratio of 2-nitrobenzene-1,4-diamine (Pa-NO2) to 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde (Tp) is 3:(2-2.5). Non-limiting examples include molar ratios of 3:2, 3:2.1, 3:2.2, 3:2.3, 3:2.4, 3:2.5, etc.

[0068] Furthermore, the first solvent is o-dichlorobenzene or N,N-dimethylformamide.

[0069] Furthermore, the second solvent is n-butanol or dichloromethane.

[0070] In a specific example, the first solvent is o-dichlorobenzene and the second solvent is n-butanol.

[0071] In another specific example, the first solvent is N,N-dimethylformamide and the second solvent is dichloromethane.

[0072] Further, the concentration of the glacial acetic acid solution is 6-9M, and the volume ratio of the second solvent to the glacial acetic acid solution is (3-10):1. Non-limiting examples include: the concentration of the glacial acetic acid solution can be 6M, 7M, 8M, 9M, etc., and the volume ratio of the second solvent to the glacial acetic acid solution can be 3:1, 4:1, 5:1, 7:1, 10:1, etc.

[0073] Further, the molar ratio of 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde (Tp) to glacial acetic acid is 1:(20-60). Non-limiting examples include: the molar ratio can be 1:20, 1:25, 1:30, 1:40, 1:50, 1:60, etc.

[0074] Furthermore, the washing refers to washing in a Soxhlet extractor with dichloromethane for 6-12 hours (non-limiting examples, such as washing time can be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 12 hours, etc.), washing with anhydrous ethanol for 6-12 hours (non-limiting examples, such as washing time can be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 12 hours, etc.), and then washing with tetrahydrofuran for 6-12 hours (non-limiting examples, such as washing time can be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 12 hours, etc.).

[0075] Furthermore, the drying refers to vacuum drying at 60-100°C for 6-12 hours. Non-limiting examples include: the temperature can be 60°C, 70°C, 75°C, 80°C, 90°C, 95°C, 100°C, etc., and the time can be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 12 hours, etc.

[0076] Furthermore, the preparation method also includes uniformly loading TpPa-NO2 COF onto an organic nylon membrane substrate material using a vacuum-assisted in-situ deposition method.

[0077] Furthermore, using tannic acid as a crosslinking agent, 10 mg TpPa-NO2COF was uniformly deposited on a nylon substrate with a diameter of 25 mm through a vacuum-assisted in-situ deposition process, ultimately producing a nylon@COF composite membrane.

[0078] The present invention also provides an adsorbent obtained by the above preparation method.

[0079] This invention also provides the application of the above-mentioned adsorbent in the adsorption and removal of organic amine flotation agents in water.

[0080] In the above applications, the water body can be brine from a salt lake.

[0081] In the above application, the organic amine flotation agent is octadecylamine (ODA).

[0082] In the above applications, the pH was adjusted to 5-6, the feed concentration of TpPa-NO2 COF was 0.16-0.2 mg / mL, the temperature was room temperature, and the adsorption time was 20 min.

[0083] In this embodiment of the invention,

[0084] Instrumentation Testing: The crystallinity of the material was assessed using a Bruker D2PHASE RX diffractometer (Germany). Fourier transform infrared (FTIR) spectra of the COF powder were obtained using a Thermo Scientific Nicoleti S20 Fourier transform infrared spectrometer (USA) against a potassium bromide background. Nitrogen adsorption and desorption isotherms were obtained at 77 K using a Micromeritics APSP2460 four-station fully automated surface area analyzer (USA). The specific surface area, pore volume, and pore size of the material were determined using the Brunauer-Emmett-Teller (BET) method. Solid-state carbon NMR spectra were acquired using a Bruker 400M high-resolution solid-state NMR spectrometer (Germany). Thermal stability was assessed using a Rigaku TG-DTA8122 thermogravimetric analyzer (Japan). Surface morphology was examined using a Czech Tescan Miralm scanning electron microscope (SEM) with an accelerating voltage of 3 kV and an SE2 secondary electron detector. High-resolution imaging and elemental analysis were performed using a FEITalos F200XG2AEM transmission electron microscope (USA). Surface elemental composition and relative abundance were analyzed using Al Kα rays (hv = 1486.6 eV) at an operating voltage of 12 kV and a filament current of 6 mA using a Thermo Scientific K-Alpha X-ray photoelectron spectrometer (XPS, USA) at an operating voltage of 12 kV and a filament current of 6 mA. The binding energy was calibrated to a C1s reference value of 284.8 eV.

[0085] Reagent sources: 2,4,6-Trihydroxybenzene-1,3,5-tricarboxaldehyde (Tp) was provided by Jilin Zhongke Science & Technology Co., Ltd. 2-Nitrobenzene-1,4-Diamine (Pa-NO2) was provided by Shanghai Bide Pharmaceutical Technology Co., Ltd. Octadecylamine (ODA) and bromocresol green were provided by Tianjin Xiens Biochemical Technology Co., Ltd. o-Dichlorobenzene, n-Butanol, N,N-Dimethylformamide, and dichloromethane were purchased from Lianyungang Bohua Pharmaceutical Chemical Co., Ltd. Anhydrous ethanol, tetrahydrofuran, dichloromethane, chloroform, hydrochloric acid, sulfuric acid, and glacial acetic acid were purchased from Tianjin Jiangtian Chemical Technology Co., Ltd. Sodium hydroxide, potassium chloride, magnesium chloride, and sodium chloride were provided by Kaimate (Tianjin) Chemical Technology Co., Ltd. Homemade brine was prepared from NaCl (2.5%), KCl (2.5%), and MgCl2 (25%). Real salt lake brine was provided by Qinghai Salt Lake Industry Co., Ltd. (Qinghai, China), with Li as its main component. + Na + K + 、Rb + Cs + Ca 2+ Mg 2+ and Cl -ODA was dissolved in double-distilled water to obtain an initial stock solution of ODA (100 mg / L). The pH was adjusted to 5 with 0.5 M HCl solution. Before each use, the solution must be stirred at 60°C for 1 hour to ensure complete dissolution of ODA. A series of ODA standard solutions of different concentrations were prepared by diluting the initial stock solution with double-distilled water. All chemical reagents used were analytical grade and unpurified. Commercial organic nylon filter membranes (0.22 μm) were provided by Haining Delv New Material Technology Co., Ltd. All aqueous solutions were prepared using double-distilled water.

[0086] Example 1

[0087] The synthesis method of TpPa-NO2 COF includes the following steps:

[0088] In a 10 mL thick-walled pressure tube, a solution of o-dichlorobenzene (3 mL) of Pa-NO2 (46.0 mg, 0.3 mmol) was heated to 60 °C. Then, a mixture of n-butanol solution (3 mL) of Tp (42 mg, 0.2 mmol) and 1 mL of 6 M glacial acetic acid solution was added dropwise to the above solution. After stirring for 1 hour, a large amount of reddish-brown precipitate formed. The tube was then sealed under vacuum by evacuating the air from the tube. The reaction was carried out at 120 °C for 72 hours to obtain a reddish-brown solid. The solid was collected by centrifugation and then washed in a Soxhlet extractor with dichloromethane, anhydrous ethanol, and tetrahydrofuran for 6 hours each. Finally, it was dried under vacuum at 60 °C for 12 hours to obtain TpPa-NO2 COF powder.

[0089] Example 2

[0090] The synthesis method of TpPa-NO2 COF includes the following steps:

[0091] In a 10 mL thick-walled pressure tube, a solution of Pa-NO2 (46.0 mg, 0.3 mmol) in N,N-dimethylformamide (3 mL) was heated to 60 °C. Then, a mixture of Tp (42 mg, 0.2 mmol) in dichloromethane (3 mL) and 1 mL of 6 M glacial acetic acid solution was added dropwise to the above solution. After stirring for 1 hour, a large amount of reddish-brown precipitate formed. The tube was then sealed under vacuum by evacuating the air from the tube. The reaction was carried out at 120 °C for 72 hours to obtain a reddish-brown solid. The solid was collected by centrifugation and then washed for 6 hours each with dichloromethane, anhydrous ethanol, and tetrahydrofuran in a Soxhlet extractor. Finally, it was dried under vacuum at 60 °C for 12 hours to obtain TpPa-NO2COF powder.

[0092] Figure 1The characterization results of the TpPa-NO2 COF material prepared in Example 1 are shown. First, Fourier transform infrared (FT-IR) spectroscopy was used to confirm the successful synthesis of TpPa-NO2 COF. Figure 1 (a) FT-IR spectrum at 3324 cm⁻¹ -1 and 3444cm -1 An absorption peak for the amino NH stretching vibration of the Pa-NO2 monomer appears at 1646 cm⁻¹. -1 An absorption peak for the C=O stretching vibration of the aldehyde group of the Tp monomer appears at 1400-1600 cm⁻¹, while the characteristic peaks of the amino and aldehyde groups of the above monomers disappear in TpPa-NO₂COF. -1 The characteristic absorption peak of β-ketoenamine appears at the (100) crystal plane. A distinct diffraction peak appears at a small corner in the powder X-ray diffraction (PXRD) pattern of TpPa-NO2 COF, indicating that the TpPa-NO2COF material has good crystallinity. Figure 1 (b) The PXRD experimental results are very close to the simulation results under the AA stacking mode, with a consistency factor R. wp Below 5%, the simulated pore size of TpPa-NO2 COF in AA packing mode is ( Figure 1 (c) Solid-state NMR C-spectroscopy further confirmed the presence of β-ketoenamine, showing characteristic β-ketoenamine signals at 135 and 146 ppm. Figure 1 (d). Thermogravimetric analysis (TGA) results showed that when heated to 300℃ in a N2 atmosphere, TpPa-NO2 COF still retained more than 90% of its weight. Figure 1 The result (e) indicates that the material possesses good thermal stability. The N2 adsorption-desorption isotherm at 77 K reveals the porous nature of the TpPa-NO2 COF, with a specific surface area and average pore size of 176.8 m² / kJ. 2 / g and 1.74nm ( Figure 1 (f)

[0093] Morphological characterization using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the porous nanofiber structure of TpPa-NO2 COF. Figure 2 (a) The TEM image shows the morphology of the cross-linked fiber aggregates. Figure 2 (b) This is likely due to strong interlayer π-π stacking interactions. TEM combined with energy-dispersive X-ray diffraction (TEM-EDX) analysis confirmed the uniform distribution of C, N, and O elements in TpPa-NO2 COF. Figure 2(c) The above characterization results jointly verify the successful synthesis of TpPa-NO2 COF and demonstrate its application potential in porous materials requiring high specific surface area, excellent thermal stability, and chemical stability.

[0094] The TpPa-NO2 COF material prepared in Example 2 was characterized and its ODA adsorption was investigated. The TpPa-NO2 COF prepared in Example 2 also exhibited good crystallinity, with a specific surface area of ​​109.4 m². 2 / g. Its saturated adsorption capacity for ODA is 106.5 mg / g.

[0095] Example 3: Organic Amine Removal Method Using TpPa-NO2 COF Adsorption of Octadecylamine by Flotation Agent

[0096] This embodiment quantitatively evaluates the adsorption efficiency of TpPa-NO2 COF by detecting the ODA concentration in the aqueous medium before and after TpPa-NO2 COF treatment. First, a systematic study was conducted on the correlation between adsorption efficiency and solution pH. 8 mg of TpPa-NO2 COF was added to 50 mL of ODA solution (20 mg / L) at different pH values, stirred at room temperature (25℃) for 1 h, and the supernatant was centrifuged. The ODA concentration was then measured. The results are shown below. Figure 3 In highly acidic conditions, the amino groups in ODA undergo protonation, resulting in significant electrostatic repulsion between the generated cationic ODA species and the positively charged TpPa-NO2COF, thus hindering adsorption. Above the isoelectric point, TpPa-NO2COF acquires a negative charge due to the deprotonation of surface acidic groups. Under weakly acidic conditions, the amino groups in ODA are protonated, generating positively charged ODA molecules, thereby enhancing the electrostatic attraction with the protonated ODA. This interaction leads to peak adsorption efficiency. However, with further increases in pH, the protonation of the ODA amino groups weakens, thus reducing its positive charge. Therefore, the electrostatic binding between TpPa-NO2COF and ODA weakens, thereby reducing adsorption capacity. This weakening is related to the acidic environment, which reduces the protonation of the ODA amino groups, thereby reducing the electrostatic interaction crucial for adsorption. Subsequently, we carefully investigated the effect of different TpPa-NO2COF feed concentrations on adsorption efficiency. Figure 3In step b), 5, 8, 10, 15, and 20 mg of TpPa-NO2 COF were added to 50 mL of an ODA solution (20 mg / L) at pH 5. The mixture was stirred at room temperature (25°C) for 1 h, and the supernatant was centrifuged to determine the concentration of ODA. The results showed that increasing the adsorbent concentration inevitably leads to an increase in adsorption efficiency. To achieve efficient ODA removal by TpPa-NO2 COF in practical applications while avoiding the inefficiency and cost associated with using excessive adsorbent, subsequent adsorption experiments were conducted at the optimal pH of 5, with the TpPa-NO2 COF concentration fixed at 0.16 mg / mL.

[0097] After centrifugation to remove TpPa-NO2 COF, bromocresol green and chloroform were used as colorimetric and extraction reagents, respectively, and the residual ODA concentration in the solution after adsorption was measured by ultraviolet-visible spectrophotometry (UV-Vis). The adsorption efficiency was calculated by formula (1).

[0098]

[0099] Where c0 (mg / L) and c e (mg / L) is the concentration of ODA in the solution before and after TpPa-NO2 COF adsorption.

[0100] Figure 3 The study revealed the time-dependent adsorption kinetics of ODA by TpPa-NO2 COF. 8 mg of TpPa-NO2 was added to 50 mL of 20 mg / L ODA solution at pH 5, and the process was carried out at room temperature (25 °C), with samples taken periodically. After centrifugation, the concentration of ODA in the supernatant was measured. The initial rapid adsorption phase can be attributed to the large number of unoccupied adsorption sites on TpPa-NO2 COF and the significant concentration gradient at the solution / material interface. TpPa-NO2 COF reached equilibrium within 20 minutes, and its pore size is close to the molecular size of ODA, which may improve adsorption efficiency. To reveal the potential adsorption mechanism, a pseudo-second-order adsorption kinetic model was used to fit the experimental data. The fitting results showed that adsorption was dominated by chemisorption. To investigate the equilibrium adsorption capacity of TpPa-NO2 COF, detailed isothermal studies were conducted at different initial ODA concentrations. Figure 3(d), 5-30 mg / L (pH=5, TpPa-NO2 COF feed concentration was 0.16 mg / mL, stirred at room temperature (25℃) for 1 h). The Langmuir isotherm adsorption model was used to describe the interaction between TpPa-NO2 COF and ODA, and a monolayer chemisorption mechanism was hypothesized on the adsorbent surface. According to the Langmuir model calculations, the saturated adsorption capacity of TpPa-NO2 COF was 129.8 mg / g. The effect of temperature on the adsorption of ODA by TpPa-NO2 COF is as follows. Figure 3 As shown in Figure e, 8 mg of TpPa-NO2 COF was added to 50 mL of ODA solution (20 mg / L) at pH = 5. The solution was stirred for 1 h at different temperatures, centrifuged, and the concentration of ODA in the supernatant was measured. A negative correlation was found between temperature and saturated adsorption capacity; that is, the higher the temperature, the lower the saturated adsorption capacity, indicating that the adsorption reaction is exothermic. With increasing temperature, the Gibbs free energy change (ΔG) calculated according to the Gibbs-Helmholtz equation... 0 The adsorption rate (ΔG) showed a decreasing trend (Table 1). Although the spontaneity of adsorption decreased with increasing temperature, ΔG... 0 The values ​​are all negative, confirming the thermodynamic spontaneous nature of the ODA adsorption process.

[0101] Table 1

[0102]

[0103]

[0104] Example 4: TpPa-NO2 COF method for removing octadecylamine from salt lake brine using organic amine flotation.

[0105] In complex environmental matrices, especially in brine environments, ODA often coexists with large amounts of inorganic salts (including but not limited to potassium chloride, sodium chloride, and magnesium chloride). To determine the applicability of TpPa-NO2 COF under these practical conditions, the adsorption efficiency of the material from various aqueous media (distilled water, self-made simulated brine, real Qinghai salt lake brine, and saturated solutions of potassium chloride and sodium chloride) was evaluated through systematic batch adsorption experiments. Figure 3(f) Different 5 mg / L ODA reserve reaction solutions were prepared by diluting the initial ODA reserve solution (100 mg / L) with pure water, saturated potassium chloride solution, saturated sodium chloride solution, homemade brine, and real salt lake brine, respectively. 8 mg of COFs were added to 50 mL of the reaction solution at pH 5, stirred at room temperature for 1 h, and the ODA concentration was determined by centrifugation of the supernatant. Empirical results show that the adsorption performance of the nitro-modified microporous covalent organic framework TpPa-NO2 COF was almost unaffected, retaining over 95% of the original ODA removal rate in various interfering matrices. The superior anti-interference ability of TpPa-NO2 COF is attributed to its smaller microporous structure and the large number of hydrogen bonding sites provided by the nitro functional groups within the pores, giving it a stronger ability to capture long-chain alkylamine ODA molecules. The sustainable availability and stability of the adsorbent are important indicators for evaluating its potential in practical applications. After adsorbing ODA, TpPa-NO2COF can be easily regenerated by immersing it in a 0.5 mol / L HCl solution for 6 hours. Figure 4 As shown in the continuous adsorption-elution cycle experiment, the saturated adsorption capacity of TpPa-NO2 COF decreased by only 13.7% after five regeneration cycles. These findings confirm that TpPa-NO2 COF has good anti-interference ability and reusability, and can be used to remediate complex water systems containing organic amine flotation pollutants.

[0106] Example 5: Dynamic adsorption of octadecylamine using TpPa-NO2 COF membrane filtration

[0107] To further elucidate the practical application potential of TpPa-NO2 COF, its enrichment capacity was evaluated through dynamic membrane filtration permeation experiments. Nylon membranes, possessing flexibility, chemical stability, and hydrophilicity, have been widely studied and reported as adsorption media for the efficient extraction of organic pollutants from aqueous phases. Using tannic acid as a crosslinking agent, 10 mg of TpPa-NO2 COF was uniformly deposited on a 25 mm diameter nylon substrate via vacuum-assisted in-situ deposition, ultimately fabricating a nylon@COF composite membrane. Figure 5 (a) Due to the numerous hydrogen bonds formed between the tannic acid on the nylon membrane and the COF, its bonding with the nylon matrix is ​​very strong. This structural fusion provides a feasible approach for developing adsorbent materials for the efficient and targeted removal of contaminants from water. The nylon@COF composite membrane is placed in the middle interlayer of a stainless steel filter housing. One end of the filter is connected to a peristaltic pump and an inflow pipe containing ODA (5 mg / L, pH=5), while the other end is connected to a filtrate collection device.

[0108] First, the effects of solution flow rate and flux on ODA removal efficiency were investigated. A peristaltic pump was used to adjust the liquid flow rate, thereby regulating the flux of the solution through the membrane. It was observed that the ODA removal efficiency of TpPa-NO2COF gradually decreased with increasing membrane flux. Figure 5 (b) This phenomenon is attributed to the increased flow rate, which shortens the interaction time between ODA molecules and COF on the membrane surface. To optimize removal efficiency, the liquid flow rate was adjusted using a peristaltic pump, and the concentration of ODA in the solution was measured for 30 minutes at different flow rates. A membrane flux of 2.0 mL / min·cm was ultimately selected. 2 This ensures effective ODA extraction by COF loaded on the membrane. Dynamic membrane breakthrough experiment results ( Figure 5 Figure c) shows that the TpPa-NO2 COF achieved an ODA removal rate exceeding 90% in the first 100 mL of solution treated. Subsequently, as the available adsorption sites on the COF became saturated, the ODA concentration in the effluent gradually increased. After treating 225 mL of solution, the COF on the membrane reached adsorption equilibrium, at which point the ODA concentration in the collected filtrate was close to the feed ODA concentration, indicating complete membrane permeation. After adsorption saturation, the adsorbed ODA was replaced with 0.5 mol / L HCl solution, thus regenerating the membrane. Based on the ODA concentration in the eluent, the regeneration efficiency of the TpPa-NO2 COF was calculated to be 93.1%, indicating that the ODA captured by the COF loaded on the membrane can be easily and efficiently recovered. These experimental results confirm the feasibility and potential application prospects of TpPa-NO2 COF as an adsorbent for organic amine flotation.

[0109] Example 6: Mechanism analysis of TpPa-NO2 COF adsorption of octadecylamine

[0110] Although TpPa-NO2 COF exhibits excellent ODA adsorption capacity, the underlying factors contributing to this phenomenon, such as the influence of pore size and the role of microscopic interactions, remain unclear, significantly hindering the structural design of high-performance ODA adsorbents. To elucidate the adsorption mechanism of ODA by TpPa-NO2 COF, molecular dynamics (MD) and density functional theory (DFT) simulations were conducted to reconstruct the process of ODA cation transfer from solution to TpPa-NO2 COF. The MD simulation began by constructing a pre-optimized six-layer COF system, into which 10 chloride anions and 10 ODA cations were randomly introduced. Water was then added to fill the simulation system. Figure 6 (a) MD simulation results show that ODA cations gradually migrate to the COF surface and eventually enter the pores of the COF. Figure 6 (b) For example Figure 6As shown in Figure c, after a 20 ns simulation, approximately 60%–80% of the ODA cations were adsorbed on the surface and within the pores of TpPa-NO2 COF. The microporous structure of TpPa-NO2 COF is key to the efficient capture of ODA cations. This size-matched one-dimensional nanotrap facilitates the interaction between polar functional groups such as carbonyl and nitro groups on the pore walls and ODA. Figure 6 Figure d shows the number density distribution of ODA cations at different times during the simulation. It can be seen that ODA is ultimately stably captured by the microporous structure of TpPa-NO2 COF, confirming the importance of the microporous structure for ODA adsorption by TpPa-NO2 COF. To elucidate the fundamental forces driving ODA capture by TpPa-NO2 COF, the Lennard-Jones (LJ) potential and Coulomb interaction energy were analyzed in detail, such as... Figure 6 As shown in Figure e, throughout the MD simulation, the LJ potential energy and Coulomb interaction energy remained negative and fluctuated within a certain range. This behavior indicates that electrostatic and van der Waals forces play a synergistic role in promoting ODA adsorption. In the initial stage of adsorption, the LJ potential energy decreased sharply relative to the Coulomb interaction energy, exhibiting a more pronounced negative value. This suggests that van der Waals forces play a dominant role in the adsorption process. However, the importance of electrostatic interactions should not be underestimated. Due to the strong electron-withdrawing properties of nitro groups, a locally negatively charged region is provided on the pore surface of COF, thereby enhancing the electrostatic attraction to positively charged ODA cations. The quantification of the Cl in the simulation system... - The mean square displacement (MSD) of ODA cations and water molecules was further investigated to study the hydrophobic interaction between COF and ODA. Figure 6 (f). The results showed that the ODA cation had the lowest MSD, indicating a strong interaction with the COF framework, thus reducing the mobility of ODA molecules. Conversely, water molecules exhibited the highest MSD, due to their relatively weak interaction with the COF framework. When ODA approaches the COF surface, water molecules rapidly displace between them, and the resulting hydrophobic effect significantly enhances the tendency of ODA to be adsorbed by COF.

[0111] DFT calculations are used to reveal other interaction mechanisms between TpPa-NO2 COF and ODA, including polarity, hydrogen bonding, and C-H σ-π interactions. Studies of polar interactions require calculation of the molecular polarity index (MPI) of COF and ODA using Multiwfn software. Due to the strong electronegativity of the nitro and carbonyl groups in the framework, the charge distribution of TpPa-NO2 COF is significantly asymmetric. Figure 7(a) This highlights the inherent strong polarity of nitro-modified COF. Furthermore, the polar surface areas of COF and ODA were quantified (Table 2), defining the region with an absolute surface electrostatic potential (ESP) exceeding 10 kcal / mol as the polar surface. A larger polar surface area relative to the total surface area indicates stronger molecular polarity. By comparing the percentage of polar surface area and MPI, it was found that the polarity of TpPa-NO2 COF is significantly higher than that of ODA, indicating that the polarities of these two substances are complementary. The highly polar carbonyl and nitro functional groups in COF bind to the amino groups of ODA, forming a close contact through polar interactions, thus creating optimal binding sites for capturing ODA. To investigate the hydrogen bonding and C-H σ-π interactions between TpPa-NO2 COF and ODA, a comprehensive Hirshfeld surface analysis was performed on the TpPa-NO2 COF+ODA complex. Figure 7 As shown in Figure b, the red areas on the Hirshfeld surface (marked with red dashed circles) represent hydrogen bonding interactions, particularly the interactions between the nitro, carbonyl, and imine groups of the COF and the amino groups of the ODA. The white areas represent C-H σ-π interactions, occurring between the long alkane chain of the ODA and the aromatic ring of the COF. Figure 7 As shown in Figure c, the fingerprint image details the interactions at the molecular level, the color coding reflects the local density, and the mapping function d norm d is used to measure the intermolecular contact distance in the interaction region. i and d e These correspond to the shortest distances from atoms inside and outside the surface to the current point, respectively. Figure 7 A notable feature of c is the appearance of d. i Value less than d e The sharp peak in the value indicates that ODA acts as a hydrogen bond donor during its interaction with COF. Furthermore, the presence of d in the figure was also observed. i Values ​​exceeding d e Another peak in the value indicates that ODA can also act as a hydrogen bond acceptor when interacting with COF. To quantify the hydrogen bond strength at different interaction sites, we calculated the bond energy using an empirical formula that takes into account the electron density at the bond critical point (Tables 3 and 4). The results show that TpPa-NO2 COF provides a series of sites that can act as hydrogen bond donors or acceptors, which is beneficial for capturing ODA.

[0112] Table 2

[0113]

[0114] Table 3

[0115]

[0116] Table 4

[0117]

[0118] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solutions and inventive concepts of the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an adsorbent for an organic amine flotation agent, characterized in that, Includes the following steps: 2-Nitrophenyl-1,4-diamine is added to a first solvent to form a first solution; 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde is added to a second solvent to form a second solution. The second solution is mixed with glacial acetic acid solution to form a mixed solution. The first solution is heated to 60-100℃, and then the mixed solution is added dropwise to the first solution. After stirring for 1 hour, a large amount of reddish-brown precipitate is formed. Then, the mixture is sealed under vacuum and the reaction is carried out at 120℃ for 24-72 hours to obtain a reddish-brown solid. The solid is collected by centrifugation, washed, and dried to obtain TpPa-NO2 COF. TpPa-NO2 COF is uniformly loaded onto an organic nylon membrane substrate material by vacuum-assisted in-situ deposition to finally prepare a nylon@COF composite membrane.

2. The method for preparing the adsorbent of the organic amine flotation agent according to claim 1, characterized in that, The molar ratio of 2-nitrobenzene-1,4-diamine and 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde is 3:(2-2.5).

3. The method for preparing the adsorbent of the organic amine flotation agent according to claim 1, characterized in that, The first solvent is o-dichlorobenzene or N,N-dimethylformamide; the second solvent is n-butanol or dichloromethane.

4. The method for preparing the adsorbent of the organic amine flotation agent according to claim 1, characterized in that, The concentration of the glacial acetic acid solution is 6-9 M, the volume ratio of the second solvent to the glacial acetic acid solution is (3-10):1, and the molar ratio of 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde to glacial acetic acid is 1:(20-60).

5. The method for preparing the adsorbent of the organic amine flotation agent according to claim 1, characterized in that, The washing refers to washing with dichloromethane for 6-12 hours, washing with anhydrous ethanol for 6-12 hours, and then washing with tetrahydrofuran for 6-12 hours in a Soxhlet extractor; the drying refers to vacuum drying at 60-100°C for 6-12 hours.

6. The method for preparing the adsorbent of the organic amine flotation agent according to claim 1, characterized in that, Using tannic acid as a crosslinking agent, 10 mg TpPa-NO2 COF was uniformly deposited on a nylon substrate with a diameter of 25 mm through a vacuum-assisted in-situ deposition process, and finally a nylon@COF composite membrane was prepared.

7. The adsorbent prepared by the preparation method according to any one of claims 1-6.

8. The application of the adsorbent of claim 7 in the adsorption and removal of organic amine flotation agents in water.

9. The application according to claim 8, characterized in that, The water body is brine from a salt lake, and the organic amine flotation agent is octadecylamine.

10. The application according to claim 9, characterized in that, Adjust the pH to 5-6, the feed concentration of TpPa-NO2 COF to 0.16-0.2 mg / mL, the temperature to room temperature, and the adsorption time to 20 min.

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