Controllable preparation method and application of S-COFs nanosheet adsorbent

Abstract

The invention belongs to the technical field of preparation of adsorption separation functional materials, and discloses a controllable preparation method and application of an S-COFs nanosheet adsorbent. According to the method, 2, 5-dimethyl sulfide terephthalaldehyde DMTTPA and 1, 3, 5-tris (4-aminophenyl) benzene TAPB are taken as monomers, cyanobenzene is taken as a reaction solvent, benzoic acid is taken as a catalyst, aniline is taken as a competitor, and the high-crystallinity S-COF adsorbent is controllably prepared under the condition of high temperature by accurately regulating and controlling crystallization time and combining a dialysis purification technology. The method not only realizes controllable morphology, but also greatly improves the adsorption performance. The method has important economic value in the field of precious metal recovery, the problems of precious metal resource waste and environmental pollution in electronic waste can be effectively solved, and meanwhile, a new thought is provided for designing a low-cost high-performance adsorbent.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of adsorption and separation functional materials, and relates to a controllable preparation method of an S-COFs nanosheet adsorbent and application thereof. Background Art

[0002] Innovation in precious metal adsorption and separation technology has core strategic value for resource regeneration and sustainable development, among which the efficient and selective recovery of gold has attracted much attention due to its scarcity and industrial value. Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers formed by connecting two or more organic monomers through dynamic covalent bonds (such as Schiff base bonds, azine bonds, borate bonds, etc.). With its high selectivity of monomers, high specific surface area, adjustable pore structure, good modification ability, and excellent chemical and thermal stability, COFs have become an ideal platform for the study of selective adsorption of metal ions. However, in the existing technology, COFs materials mainly adopt the traditional solvent thermal synthesis method, which has certain limitations in accurately controlling the size and morphology of materials. At the same time, the functionalization strategy of COFs also faces difficulties: although the "top-down" method (such as post-synthesis modification) can introduce functional groups, it is easy to cause pore collapse and a significant reduction in specific surface area; while the "bottom-up" method (through monomer pre-design) helps to maintain the integrity of the pore structure, but it is limited by the difficulty of monomer synthesis and steric hindrance, resulting in difficult synthesis. How to introduce sulfur active sites in a targeted manner into the COFs skeleton while maintaining the high order and high specific surface area of the porous framework has become a key technical issue that urgently needs to be broken through in this field.

[0003] Therefore, we used 2,5-dimethyl sulfide terephthalaldehyde (DMTTPA) and 1,3,5-tri(4-aminophenyl)benzene (TAPB) as functional monomers, utilized the dynamic covalent chemical synthesis strategy under the synergistic effect of solvent-catalyst, and combined it with dialysis purification technology to prepare sulfide-based single crystal covalent organic framework materials (S-COF). By regulating the preparation time of S-COF, we explored its morphology evolution law, and investigated the effects of solution pH, adsorption time, initial solution concentration, temperature and competing ions on the adsorption behavior of gold. This scheme has not been reported yet. Summary of the invention

[0004] To solve the problems of low adsorption capacity, slow adsorption rate, and low site recognition of gold adsorbents in the prior art, the present invention provides a method for controllably preparing S-COFs nanosheet adsorbents based on a solvent-catalyst induction strategy. This method uses 2,5-dimethylthio terephthalaldehyde (DMTTPA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) as functional monomers, benzonitrile as the reaction solvent, benzoic acid as the catalyst, and aniline as the competitor. Under high-temperature conditions, by precisely controlling the crystallization time and combining dialysis purification technology, a highly crystalline and morphology-controllable S-COF material is prepared and applied to efficiently capture gold in electronic waste liquid.

[0005] To achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for controllably preparing S-COFs nanosheet adsorbents, comprising the following steps:

[0007] (1) Dissolve benzoic acid in benzonitrile and heat to temperature T until completely dissolved. Then, successively add a 2,5-dimethylthio terephthalaldehyde stock solution, an aniline-benzonitrile solution, and a 1,3,5-tris(4-aminophenyl)benzene stock solution. Seal the bottle cap and react at reaction temperature T for t1 time;

[0008] (2) After the reaction is completed, cool to room temperature, add an appropriate amount of saturated NaCl aqueous solution and methanol to precipitate the colloid, centrifuge at a set speed r, and repeat the precipitation-centrifugation step twice; place the obtained precipitate in a dialysis bag, dialyze in methanol, then wash it with deionized water and methanol multiple times, and finally vacuum-dry the yellow solid product.

[0009] In step (1), the dosage ratio of benzoic acid, 2,5-dimethylthio terephthalaldehyde, 1,3,5-tris(4-aminophenyl)benzene, and aniline-benzonitrile solution is 5.5 - 16.5 mmol: 0.072 - 0.216 mmol: 0.048 - 0.144 mmol: 0.165 - 0.495 mL.

[0010] In step (1), the reaction temperature T is 60 - 120 °C, and the reaction time t1 is 5 min - 96 h.

[0011] In step (1),

[0012] The dosage ratio of benzoic acid and benzonitrile is 5.5 - 16.5 mmol: 4.835 - 14.505 mL;

[0013] In the 2,5-dimethylthio terephthalaldehyde stock solution, the dosage ratio of 2,5-dimethylthio terephthalaldehyde and benzonitrile is 0.072 - 0.216 mmol: 0.5 - 1.5 mL;

[0014] The preparation of the aniline-benzonitrile solution is to dissolve aniline in benzonitrile, and the concentration of aniline is 0.7 M;

[0015] In the stock solution of 1,3,5-tris(4-aminophenyl)benzene, the dosage ratio of (1,3,5-tris(4-aminophenyl)benzene) to benzonitrile is 0.048 - 0.144 mmol: 0.5 - 1.5 mL;

[0016] In step (2), when precipitating the colloid, the volume ratio of saturated NaCl aqueous solution to methanol is 2:15;

[0017] The centrifugation speed r is 3600 - 10000 rpm, and the centrifugation time is 5 - 15 min;

[0018] The dialysis time is 12 - 24 h;

[0019] The temperature of vacuum drying is 50 °C, and the time is 24 h.

[0020] Use of the S-COFs nanosheet adsorbent prepared by the present invention for selective separation of gold in electronic waste solution.

[0021] The beneficial effects of the present invention are as follows:

[0022] (1) Solved the problems in precious metal recovery: Since the value of precious metal gold in electronic waste is relatively high, the adsorbent of the present invention is designed and prepared for the precious metals in electronic waste. This helps to efficiently recover precious metals in electronic waste and meets the demand for efficient recycling of resources.

[0023] (2) The present invention proposes a solvent-catalyst induction strategy: Using benzonitrile as the reaction solvent and benzoic acid as the catalyst, and combining dialysis purification technology to prepare a highly crystalline and ultra-high specific surface area S-COF adsorbent, thereby significantly improving its adsorption rate and adsorption capacity for gold, showing excellent application prospects.

[0024] (3) Applicable to complex environments and low-concentration precious metals: Traditional adsorption technologies face challenges in the face of low-concentration precious metals, complex competing ions, and extremely acidic environments. Due to the introduction of specific binding sites, the adsorbent provided by the present invention still performs excellently under these conditions, having good stability and adaptability.

[0025] Generally speaking, the present invention has significant economic benefits in the field of precious metal recovery and can effectively address the problems of precious metal resource waste and environmental pollution in electronic waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the morphology of the materials obtained in Example 2 at different reaction times.

[0027] Figure 2 Scanning electron microscope images of the materials prepared at different reaction times in Example 2.

[0028] Figure 3 High-resolution transmission electron microscope image of the material prepared in Example 2 at 96 h.

[0029] Figure 4 X-ray diffraction patterns of the materials prepared at different reaction times in Example 2.

[0030] Figure 5 Effect of pH value on the adsorption capacity of the S-COF adsorbent prepared in Example 1 for gold ions.

[0031] Figure 6 Adsorption kinetics of the S-COF adsorbent prepared in Example 1 for gold ions and its model fitting curves.

[0032] Figure 7 Effect of temperature on the adsorption equilibrium of the S-COF adsorbent prepared in Example 1 for gold ions and its model fitting curves.

[0033] Figure 8 Adsorption selectivity of the S-COF adsorbent prepared in Example 1.

[0034] Figure 9 Adsorption regeneration performance of the S-COF adsorbent prepared in Example 1. Detailed implementation manners

[0035] In the detailed implementation manners of the present invention, the identification performance evaluation is carried out according to the following method:

[0036] It is completed by a static adsorption experiment. The adsorption capacity of 1.0 mg of S-COF for gold ions in the pH range of 1.0 - 6.0 was tested. The content of gold ions after adsorption was determined by an inductively coupled plasma optical emission spectrometer, and the optimal adsorption pH was determined according to the results. Secondly, the effect of adsorption time on the adsorption capacity of S-COF was studied, and the data were fitted and calculated and analyzed by the Pseudo first-order model, Pseudo second-order model, etc. To study the maximum adsorption capacity of S-COF, we carried out adsorption equilibrium experiments in the range of gold ion concentration of 300 - 800 ppm, and the adsorption data were fitted by the Langmuir model and Freundlich model, and the adsorption capacity was calculated according to the results. And printed circuit boards were selected as actual samples to study the selective adsorption performance of S-COF. Finally, its adsorption regeneration performance was tested.

[0037] The present invention will be further described below in conjunction with specific embodiments.

[0038] Example 1:

[0039] Preparation of S-COF

[0040] Add 9.67 mL of benzonitrile to a 40 mL brown glass sample bottle, and then add 11 mmol of benzoic acid (1.35 g). Heat to 90 °C until completely dissolved. After dissolution, successively add the pre-prepared 2,5-dimethylthio terephthalaldehyde stock solution: 2,5-dimethylthio terephthalaldehyde (0.144 mmol, 32.59 mg) dispersed in 1 mL of benzonitrile; 0.33 mL of aniline-benzonitrile solution (aniline dissolved in benzonitrile, concentration 0.7 M) and 1,3,5-tris(4-aminophenyl)benzene stock solution: (1,3,5-tris(4-aminophenyl)benzene (0.096 mmol, 34 mg) dispersed in 1 mL of benzonitrile, ensuring that the total volume of the reaction system is 12.0 mL. Seal the bottle cap and react at 90 °C for 12 h. After the reaction is completed, cool to room temperature until a yellow colloid is formed. Then add 2 mL of saturated NaCl aqueous solution and 15 mL of methanol to precipitate the colloid, centrifuge at 6800 rpm for 10 minutes, and repeat the precipitation-centrifugation step twice. The obtained precipitate is placed in a dialysis bag, dialyzed in methanol for 18 hours, washed repeatedly with deionized water and methanol, and finally the yellow solid product is vacuum dried at 50 °C for 24 h.

[0041] Example 2

[0042] Compared with the technical solution of Example 1, only the reaction time is changed to observe the products at different reaction times.

[0043] Figure 1 The following shows the schematic diagrams of the morphologies of the materials obtained in Example 2 at different reaction times of 5 min, 1 h, and 96 h.

[0044] Figure 2 The following shows the scanning electron microscope images of the materials prepared in Example 2 at different reaction times, corresponding to the reaction times respectively: a: 5 min; b: 15 min; c: 30 min; d: 1 h; e: 4 h; f: 12 h; g: 24 h; h: 48 h; i: 96 h. It can be seen from this that its morphology shows an obvious stage evolution with the reaction time: gradually changing from the initial amorphous aggregates (5 min) to a lychee-like structure with lamellar stacking (1 h), and finally forming regular hexagonal single crystals (96 h).

[0045] Figure 3 The following shows the high-resolution transmission electron microscope image of the material prepared in Example 2 at 96 h. It can be seen from this that the sample shows a regular hexagonal structure with clear boundaries, fully reflecting its high crystallinity.

[0046] Figure 4 The X-ray diffraction patterns of the materials prepared in Example 2 at different reaction times are shown. It can be seen that as the crystallization time extends from 5 minutes to 96 hours, the crystallinity of the sample significantly increases. This may be because a longer reaction time is conducive to crystal growth and defect repair, thus forming a more ordered structure.

[0047] Example 3:

[0048] Preparation of S-COF:

[0049] Add 4.835 mL of benzonitrile to a 40 mL brown glass sample bottle, and then add 5.5 mmol of benzoic acid. Heat to 60 °C until completely dissolved. After dissolution, successively add the pre-prepared 2,5-dimethylthio terephthalaldehyde stock solution: 2,5-dimethylthio terephthalaldehyde (0.072 mmol) dispersed in 0.5 mL of benzonitrile; 0.165 mL of aniline-benzonitrile solution (aniline dissolved in benzonitrile, concentration 0.7 M) and 1,3,5-tris(4-aminophenyl)benzene stock solution: (1,3,5-tris(4-aminophenyl)benzene (0.048 mmol) dispersed in 0.5 mL of benzonitrile. Seal the bottle cap and react at 60 °C for 5 min. After the reaction, cool to room temperature until a yellow colloid is formed. Then add 1 mL of saturated NaCl aqueous solution and 7.5 mL of methanol to precipitate the colloid, centrifuge at 3600 rpm for 5 minutes, and repeat twice. The obtained precipitate is placed in a dialysis bag, dialyzed in methanol for 12 hours, washed repeatedly with deionized water and methanol, and finally the yellow solid product is vacuum dried at 50 °C for 24 h.

[0050] Example 4:

[0051] Preparation of S-COF:

[0052] Add 14.505 mL of benzonitrile to a 40 mL brown glass sample bottle, then add 16.5 mmol of benzoic acid, and heat to 120 °C until completely dissolved. After dissolution, add successively the pre-prepared stock solution of 2,5-dimethylthio terephthalaldehyde: 2,5-dimethylthio terephthalaldehyde (0.216 mmol) dispersed in 1.5 mL of benzonitrile; 0.495 mL of aniline-benzonitrile solution (aniline dissolved in benzonitrile, concentration 0.7 M) and the stock solution of 1,3,5-tris(4-aminophenyl)benzene: (1,3,5-tris(4-aminophenyl)benzene (0.144 mmol) dispersed in 1.5 mL of benzonitrile. Seal the bottle cap and react at 120 °C for 96 h. After the reaction, cool to room temperature until a yellow colloid is formed. Then add 3 mL of saturated NaCl aqueous solution and 22.5 mL of methanol to precipitate the colloid, centrifuge at 10000 rpm for 15 minutes, and repeat twice. The obtained precipitate is placed in a dialysis bag, dialyzed in methanol for 24 hours, washed repeatedly with deionized water and methanol, and finally the yellow solid product is dried in vacuo at 50 °C for 24 h.

[0053] Investigate the effect of pH value on the gold ion adsorption capacity:

[0054] Accurately weigh 6 portions of 1 mg of S-COF prepared under the conditions described in Example 1, and add them to 5 mL of gold ion solutions with pH values of 1, 2, 3, 4, 5, and 6 and a concentration of 500 mg / L respectively. Place them on a shaker at 25 °C for adsorption for 12 h, and collect the supernatant. The remaining gold ion concentration in the solution is detected by an inductively coupled plasma emission spectrometer (ICP), and three parallel experiments are conducted.

[0055] Figure 5 For the effect of pH value on the gold ion adsorption capacity of the S-COF adsorbent prepared in Example 1. It can be seen that the adsorption amount of S-COF is the largest in an environment with pH 5, approximately 1777.55 mg g -1 . Investigate the effect of adsorption time on the gold ion adsorption capacity:

[0056] Accurately weigh 10 portions of 1 mg of S-COF, add them to 5 mL of gold ion solution with a concentration of 500 mg / L and a pH value of 6, and place them on a shaker at 25 °C for adsorption for 5, 10, 15, 30, 60, 90, 120, 240, 480, and 720 min respectively, and collect the supernatant. The remaining gold ion concentration in the solution is detected by an inductively coupled plasma emission spectrometer (ICP), and three parallel experiments are conducted.

[0057] Figure 6The adsorption kinetics of the S-COF adsorbent prepared in Example 1 for gold ions and its model fitting curve. It can be seen that the adsorption equilibrium can be reached within 240 minutes, and its equilibrium adsorption capacity is as high as 1881.55 mg g -1 .

[0058] Investigate the effects of initial concentration and adsorption temperature on the adsorption capacity of gold ions:

[0059] Accurately weigh 6 portions of 1 mg of S-COF, and add them to 5 mL of gold ion solutions with concentrations of 300, 400, 500, 600, 700, and 800 mg / L in turn (pH is 5). Place them on a shaker at 25 °C for 12 h to adsorb, and collect the supernatant; place them on a shaker at 35 °C for 12 h to adsorb, and collect the supernatant; place them on a shaker at 45 °C for 12 h to adsorb, and collect the supernatant. The remaining concentration of gold ions in the solution is detected by an inductively coupled plasma emission spectrometer (ICP), and three parallel experiments are performed.

[0060] Figure 7 The effect of temperature on the adsorption equilibrium of the S-COF adsorbent prepared in Example 1 for gold ions and its model fitting curve. It can be seen that with the increase of the initial concentration and temperature of Au(III), the adsorption capacity increases significantly, and reaches 2520.18 mg·g at 318 K and 800 mg·L -1 . -1 . Through the fitting of the Langmuir and Freundlich models, it is found that the Freundlich model has a higher correlation coefficient, indicating that the adsorption process is mainly dominated by surface heterogeneous multilayer adsorption, which may be related to the porous structure of the material and the heterogeneity of the distribution of recognition sites.

[0061] Investigate the selectivity for metal ions:

[0062] Accurately weigh 3 mg of S-COF prepared under the conditions described in Example 1, add 5 mL of an actual electronic waste liquid containing Au(III), Pd(II), Al(III), Co(II), Cr(III), Cu(II), Na(I), Ni(II), Zn(II), etc. (pH = 3), place it on a shaker at 25 °C for 12 h to adsorb, collect the supernatant, and use an inductively coupled plasma emission spectrometer (ICP) to detect the remaining concentrations of various ions in the solution. Three parallel experiments are performed.

[0063] Figure 8 The adsorption selectivity of the S-COF adsorbent prepared in Example 1. As can be seen from the figure, in the above complex ion system, the removal rate of S-COF for Au(III) reaches 82.07%, indicating that it has excellent selectivity and adsorption efficiency in the separation and recovery of gold.

[0064] Investigation of regeneration performance:

[0065] Accurately weigh 10 mg of S-COF, add it to 10 mL of a gold ion solution with a concentration of 500 mg / L and a pH value of 5, place it on a shaker at 25 °C for 12 h for adsorption, take the supernatant and then remove the solution, wash it with deionized water and then add 10 mL of an eluent prepared from 1 mol / L thiourea and 0.1 mol / L hydrochloric acid, continue to place it on a shaker for 1.5 h for desorption, then centrifuge to collect the adsorbent, remove the solution, wash it with deionized water and dry it. This is one cycle, and a total of six cycles are performed. The remaining gold ion concentration in the solution is detected by an inductively coupled plasma emission spectrometer (ICP), and three parallel experiments are performed.

[0066] Figure 9 It is the adsorption and regeneration performance of the 35-70-COF@DMSA adsorbent prepared in Example 1. As can be seen from the figure, after 6 adsorption-desorption cycles, the adsorption capacity of S-COF for Au(III) still remains above 98% of the initial value.

[0067] Note: The above examples are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above respective examples, those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced; and all technical solutions and their improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A controllable preparation method of an S-COFs nanosheet adsorbent, characterized in that, It includes the following steps: (1) Dissolve benzoic acid in benzonitrile and heat to temperature T until completely dissolved. Then, sequentially add 2,5-dimethylthio terephthalaldehyde stock solution, aniline-benzonitrile solution, and 1,3,5-tris(4-aminophenyl)benzene stock solution. Seal the bottle cap and react at reaction temperature T for t1 hours; (2) After the reaction is completed, cool to room temperature, add an appropriate amount of saturated NaCl aqueous solution and methanol to precipitate the colloid, centrifuge at a set rotation speed r, and repeat the precipitation-centrifugation step twice. Place the obtained precipitate in a dialysis bag, dialyze in methanol, wash it with deionized water and methanol multiple times in sequence, and finally vacuum-dry the yellow solid product.

2. The controllable preparation method of the S-COFs nanosheet adsorbent according to claim 1, characterized in that, In step (1), the dosage ratio of benzoic acid, 2,5-dimethylthio terephthalaldehyde, 1,3,5-tris(4-aminophenyl)benzene, and aniline-benzonitrile solution is 5.5 - 16.5 mmol : 0.072 - 0.216 mmol : 0.048 - 0.144 mmol : 0.165 - 0.495 mL.

3. The controllable preparation method of the S-COFs nanosheet adsorbent according to claim 1, wherein, In step (1), the reaction temperature T is 60 - 120 °C, and the reaction time t1 is 5 min - 96 h.

4. The controllable preparation method of the S-COFs nanosheet adsorbent according to claim 1, wherein, In step (1), the dosage ratio of benzoic acid and benzonitrile is 5.5 - 16.5 mmol : 4.835 - 14.505 mL; in the 2,5-dimethylthio terephthalaldehyde stock solution, the dosage ratio of 2,5-dimethylthio terephthalaldehyde and benzonitrile is 0.072 - 0.216 mmol : 0.5 - 1.5 mL; the preparation of the aniline-benzonitrile solution is to dissolve aniline in benzonitrile, and the concentration of aniline is 0.7 M; in the 1,3,5-tris(4-aminophenyl)benzene stock solution, the dosage ratio of 1,3,5-tris(4-aminophenyl)benzene and benzonitrile is 0.048 - 0.144 mmol : 0.5 - 1.5 mL.

5. The controllable preparation method of the S-COFs nanosheet adsorbent according to claim 1, wherein In step (2), when precipitating the colloid, the volume ratio of saturated NaCl aqueous solution and methanol is 2:

15.

6. The controllable preparation method of the S-COFs nanosheet adsorbent according to claim 1, wherein, In step (2), the centrifugation rotation speed r is 3600 - 10000 rpm, and the centrifugation time is 5 - 15 min.

7. The controllable preparation method of the S-COFs nanosheet adsorbent according to claim 1, characterized in that, In step (2), the dialysis time is 12 - 24 h.

8. The controllable preparation method of the S-COFs nanosheet adsorbent according to claim 1, characterized in that, In step (2), the temperature of vacuum drying is 50 °C, and the time is 24 h.

9. Use of the S-COFs nanosheet adsorbent prepared by the preparation method according to any one of claims 1 to 8 for selectively separating gold in an electronic waste solution.

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