A cof adsorbent for pb ions and preparation and application thereof

Abstract

The application relates to a COF adsorbent for efficiently and selectively recovering Pb (II) and application thereof, and belongs to the field of high-efficiency adsorbents for adsorbing heavy metals and high-sensitivity electrochemical sensors. A Schiff base reaction occurs between benzene [1,2-b:3,4-b':5,6-b'] trithiophene-2,5,8-trialdehyde (BTT) and 3,3'-dihydroxybenzidine (DHBD) to obtain BTT-DHBD-COF, which has excellent adsorption performance on Pd (II), and the adsorption capacity can reach 570.7 mg / g after 10 min of adsorption; the detection limit of BTT-DHBD-COF / GCE on Pb (II) is 3*10 ‑12 mol L ‑1 .

Description

Technical Field

[0001] This invention relates to a COF adsorbent for highly efficient selective adsorption and high-sensitivity detection of Pb(II), its preparation and application, belonging to the field of highly efficient adsorbents for heavy metal adsorption and high-sensitivity electrochemical sensors. Background Technology

[0002] Heavy metal water pollution has drawn significant attention from industrialists and scientists, and is considered a global environmental problem. Heavy metal ions produced by industrialization and mining operations are not only harmful to the environment and non-biodegradable, but can also accumulate in the human body through the food chain. This can have serious impacts on ecosystems and public health. Lead ions (Pb(II)) are considered one of the most harmful heavy metal ions to human health. Long-term consumption of drinking water contaminated with Pb(II) can lead to anemia, kidney damage, central nervous system dysfunction, and even death.

[0003] Currently, the most common technologies for removing heavy metals from wastewater are precipitation, electrolysis, solvent extraction, biological treatment, and adsorption. Among these methods, precipitation and electrolysis have relatively poor selective removal capabilities for heavy metal ions. Solvent extraction and biological treatment methods cannot be reused, and the treated water quality does not meet requirements. Due to its simplicity, flexibility, lack of toxic byproducts, environmental friendliness, multifunctionality, and ease of regeneration, adsorption has become an important technology for capturing harmful metal ions from aqueous solutions. The selection of adsorbent is a fundamental component of adsorption. Traditional adsorbents (such as activated carbon and nanoparticle adsorbents) suffer from poor selectivity and low adsorption performance. Porous adsorbents (COFs) have become candidate materials for effective removal of heavy metal ions due to their advantages such as high specific surface area, abundant functional groups, accessible pore structure, adjustable pore size, and ease of modification. To date, no research has been reported on the highly efficient selective adsorption and high-sensitivity detection of Pb(II) using the BTT-DHBD-COF adsorbent. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a COF adsorbent for highly efficient selective adsorption and high-sensitivity detection of Pb(II) and its application. This invention synthesizes BTT-DHBD-COF by reacting a carbonyl-containing BTT monomer with a hydroxyl-containing DHBD monomer via a solvothermal method using a Schiff base reaction, achieving highly efficient selective adsorption and high-sensitivity detection of Pb(II) in water.

[0005] This invention discloses a COF adsorbent for Pb ions, wherein the adsorbent is synthesized by a Schiff base reaction of benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-trialdehyde (BTT) and 3,3'-dihydroxybenzidine (DHBD). The resulting adsorbent exhibits high COF at 1624 cm⁻¹. -1A C=N peak was generated at that point.

[0006] This invention discloses a COF adsorbent for Pb ions, at 1438 cm⁻¹. -1 A COH peak was generated at 1255 cm⁻¹. -1 A CS peak was generated at that location.

[0007] The benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-trialdehyde (BTT) contains a carbonyl group and an S group.

[0008] The 3,3'-dihydroxybenzidine (DHBD) contains amino and hydroxy groups.

[0009] The present invention discloses a COF adsorbent for Pb ions, wherein the XRD pattern shows a diffraction peak with an intensity greater than 1000 au at 2.73º.

[0010] This invention discloses a method for preparing a COF adsorbent for Pb ions, comprising the following steps:

[0011] (1) Dissolve BTT and DHBD in a mixture of o-dichlorobenzene (o-DCB) and n-butanol (n-BuOH) and stir until homogeneous to obtain a ready solution;

[0012] (2) Add acetic acid (HAc) to the prepared solution;

[0013] (3) Use a liquid nitrogen bath (77 K) for rapid freezing and perform N freezing pump-thawing cycles to remove oxygen, and heat at 115~125°C, where N is greater than or equal to 2.

[0014] (4) After the reaction is complete, the sample is centrifuged, washed once with furan, and dried under vacuum to obtain BTT-DHBD-COF.

[0015] Optionally, in step (1), the molar ratio of BTT to DHBD is 1:1.5.

[0016] Optionally, in step (1), the volume ratio of o-dichlorobenzene (o-DCB) to n-butanol (n-BuOH) is 1:1~2.

[0017] Optionally, the volume ratio of the sum of the volumes of o-dichlorobenzene (o-DCB) and n-butanol (n-BuOH) to 6M acetic acid (HAc) is 20:0.8~1.2, preferably 20:1.

[0018] Optionally, in step (3), the heating temperature is 120 °C and the reaction time is 70~74 h.

[0019] Optionally, in step (4), the vacuum drying temperature is 80~120 ℃ and the time is 12~24 h.

[0020] Furthermore, the microstructure of the obtained COF adsorbent is rod-shaped.

[0021] The COF adsorbent designed and prepared in this invention can be used to adsorb lead ions, preferably divalent lead ions. The COF adsorbent designed and prepared in this invention can also be used to adsorb other heavy metal ions.

[0022] The COF adsorbent designed and prepared in this invention, when coated on an electrochemical sensor, can be used to detect the concentration of divalent lead ions in a liquid.

[0023] The COF adsorbent designed and prepared in this invention can achieve a maximum adsorption capacity of 570.7 mg / g for divalent lead ions under the current technological limitations.

[0024] Given the limitations of current technology, the COF adsorbent designed and prepared in this invention, when coated onto an electrochemical sensor, exhibits a high sensitivity detection limit, such as 3 × 10⁻⁶, when detecting divalent lead ions in solution. -12 mol L -1 .

[0025] The beneficial effects of this invention are:

[0026] 1. The BTT-DHBD-COF prepared by this invention has novel morphology, structure and composition, and the preparation process is simple and convenient.

[0027] 2. Through adjustments to the technical solution in this invention, the obtained BTT-DHBD-COF adsorbent is used for highly efficient selective adsorption and high-sensitivity detection of Pb(II), exhibiting excellent selective adsorption performance (maximum adsorption capacity up to 570.7 mg / g) and a high sensitivity detection limit (3*10). -12 mol L -1 ). Attached Figure Description

[0028] Figure 1 The XRD pattern of BTT-DHBD-COF prepared in Example 3 of this invention.

[0029] Figure 2 The image shows the scanning electron microscope (SEM) pattern of BTT-DHBD-COF prepared in Example 3 of this invention.

[0030] Figure 3 The image shows the FT-IR spectrum of the BTT-DHBD-COF material prepared in Example 3 of this invention.

[0031] Figure 4 The effect of initial concentration on the adsorption performance of Pb(II) is shown.

[0032] Figure 5 Example 3 of this invention studies the adsorption mechanism of Pb(II).

[0033] Figure 6 The electrochemical sensing performance of the COF material prepared in Example 3 is shown.

[0034] Figure 7 DPASV plots of BTT-DHBD-COF / GCE electrodes prepared with slurries of different concentrations in 0.0001 μM Pb(II) solution.

[0035] Figure 8 The FT-IR spectrum of the BTT-DHBD-COF material obtained in Example 1;

[0036] Figure 9 The image shows the FT-IR spectrum of the BTT-DHBD-COF material obtained in Example 2. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0038] Example 1

[0039] This embodiment presents the preparation and application of a COF adsorbent for highly efficient selective adsorption and high-sensitivity detection of Pb(II), specifically including the following steps:

[0040] (1) Add BTT (33 mg, 0.1 mmol) and DHBD (32.25 mg, 0.15 mmol) sequentially to a mixed solution of o-dichlorobenzene (o-DCB) and n-butanol (v / v = 2:1) and sonicate for 10 min.

[0041] (2) After ultrasonic treatment, add 0.15 mL of 6 M HAc.

[0042] (3) Rapid freezing was performed using a liquid nitrogen bath (77 K), followed by three freeze pump-thaw cycles to remove oxygen, and heating at 120°C for 72 hours.

[0043] (4) After the reaction is complete, the sample is centrifuged, thoroughly washed several times with THF, and vacuum dried at 80°C for 12 hours to obtain BTT-DHBD-COF.

[0044] Example 2

[0045] This embodiment presents the preparation and application of a COF adsorbent for highly efficient selective adsorption and high-sensitivity detection of Pb(II), specifically including the following steps:

[0046] (1) Add BTT (33 mg, 0.1 mmol) and DHBD (32.25 mg, 0.15 mmol) sequentially to a mixed solution of o-dichlorobenzene (o-DCB) and n-butanol (v / v = 1:2) and sonicate for 10 min.

[0047] (2) After ultrasonic treatment, add 0.15 mL of 6 M HAc.

[0048] (3) Rapid freezing was performed using a liquid nitrogen bath (77 K), followed by three freeze pump-thaw cycles to remove oxygen, and heating at 120°C for 72 hours.

[0049] (4) After the reaction is complete, the sample is centrifuged, thoroughly washed several times with THF, and vacuum dried at 80°C for 12 hours to obtain BTT-DHBD-COF.

[0050] Example 3

[0051] This embodiment presents the preparation and application of a COF adsorbent for highly efficient selective adsorption and high-sensitivity detection of Pb(II), specifically including the following steps:

[0052] (1) Add BTT (33 mg, 0.1 mmol) and DHBD (32.25 mg, 0.15 mmol) sequentially to a mixed solution of o-dichlorobenzene (o-DCB) and n-butanol (v / v = 1:1) and sonicate for 10 min.

[0053] (2) After ultrasonic treatment, add 0.15 mL of 6 M HAc.

[0054] (3) Rapid freezing was performed using a liquid nitrogen bath (77 K), followed by three freeze pump-thaw cycles to remove oxygen, and heating at 120°C for 72 hours.

[0055] (4) After the reaction is complete, the sample is centrifuged, thoroughly washed several times with THF, and vacuum dried at 80°C for 12 hours to obtain BTT-DHBD-COF.

[0056] Figure 1 The image shows the XRD pattern of the COF material prepared in Example 3. The results show that a COF diffraction peak (intensity of about 1345 au) appeared at 2.73º in the composite material, indicating that the COF material was successfully prepared.

[0057] Figure 2 The image shows a SEM of the COF material prepared in Example 3. It can be seen that the COF is a rod-shaped structure with a length of 0.5-3 μm and a diameter of 460 nm.

[0058] Figure 3 The image shown is the FT-IR spectrum of the COF material prepared in Example 3. After synthesizing BTT-DHBD-COF, BTT is 1680 cm⁻¹. -1 The C=O peak and DHBD at 3382 cm⁻¹ -1 and 3307 cm -1 The -NH2 peak disappears at 1624 cm⁻¹ due to the amine-aldehyde condensation reaction. -1 The presence of a C=N peak at the point indicates that BTT-DHBD-COF was successfully prepared.

[0059] Adsorption experiment: BTT-DHBD-COF of Example 3 was added to a wastewater solution containing Pb(II) for adsorption. Figure 4 The adsorption performance of the COF material prepared in the examples is shown, with a maximum adsorption capacity of 570.7 mg / g for Pb(II). This is higher than most reported adsorbents, indicating that BTT-DHBD-COF has excellent adsorption performance for Pb(II).

[0060] Adsorption mechanism study: Five possible adsorption models were constructed for BTT-DHBD-COF and Pb(II). Optimization results and binding energies (ΔE) are shown below. Figure 5 As shown, these results indicate that N, O, and S atoms in BTT-DHBD-COF can capture Pb(II) through coordination.

[0061] Electrochemical sensing performance: The BTT-DHBD-COF of this embodiment was used to prepare the electrode BTT-DHBD-COF / GCE, and different concentrations of Pb(II) were detected in PBS buffer solution (pH 5). Figure 6 The electrochemical sensing performance of the COF material prepared in Example 3 shows a detection limit of 3.0 × 10⁻⁶ for Pb(II). -12 mol L -1 μM. This is higher than most reported electrode materials, indicating that BTT-DHBD-COF has excellent electrochemical sensing performance for Pb(II).

[0062] Furthermore, during the technology development process, experiments were conducted on the DPASV of BTT-DHBD-COF / GCE electrodes prepared with slurries of different concentrations (1.5 mg BTT-DHBD-COF added to 1 mL, 0.7 mL, 0.5 mL, and 0.3 mL of a mixture of water and ethanol (v / v = 3:1)). Figure 7The results showed that the DPASV electrochemical signal of the BTT-DHBD-COF / GCE electrode prepared by adding 1.5 mg of BTT-DHBD-COF to 0.3 mL of a mixture of water and ethanol (v / v=3:1) was more obvious.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An application of a COF adsorbent for Pb ions, characterized in that: The adsorbent was synthesized by a Schiff base reaction of benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-trialdehyde with 3,3'-dihydroxybenzidine. The resulting adsorbent was subjected to a Schiff base reaction at 1624 cm⁻¹. -1 A C=N peak was generated at this location; The COF adsorbent for Pb ions is prepared by the following steps: (1) Dissolve BTT and DHBD in a mixture of o-DCB and n-BuOH and mix thoroughly to obtain a standby solution; in step (1), the molar ratio of BTT to DHBD is 1:1.5; in step (1), the volume ratio of o-DCB to n-BuOH is 1:1~2. (2) Add acetic acid to the prepared solution; the volume ratio of the sum of the volumes of o-DCB and n-BuOH used to the volume of 6M acetic acid is 20:0.8~1.2; (3) Use liquid nitrogen bath for freezing and perform N freezing pump-thawing cycles to remove oxygen, and heat at 120°C for 70~74h, where N is greater than or equal to 2; (4) After the reaction is complete, the sample is centrifuged, washed with furan, and dried under vacuum to obtain BTT-DHBD-COF; in step (4), the temperature of vacuum drying is 80~120 ℃ and the time is 12~24 h. According to the specified ratio, 1.5 mg of BTT-DHBD-COF was added to 0.3 mL of a mixture of water and ethanol to prepare a slurry. The slurry was coated onto an electrochemical sensor to prepare a BTT-DHBD-COF / GCE electrode, which was used to detect the concentration of divalent lead ions in the liquid. The volume ratio of water to ethanol in the mixture was 3:

1. When the obtained COF adsorbent was coated onto an electrochemical sensor, its detection limit for divalent lead ions in solution was 3 × 10⁻⁶. -12 mol L -1 .

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