Porous COF adsorbent for efficiently enriching palladium as well as preparation method and application of porous COF adsorbent

Abstract

The invention relates to a porous COF adsorbent for efficiently enriching palladium as well as a preparation method and application of the porous COF adsorbent, and belongs to the technical field of composite materials. The porous COF adsorbent capable of efficiently enriching palladium is marked as COF-BcTd and is generated through an acylation reaction of 1, 3, 5-benzoyl chloride and 1, 3, 4-thiadiazole-2, 5 diamine, the structural formula of the porous COF adsorbent capable of efficiently enriching palladium is # imgabs0, and the porous COF adsorbent capable of efficiently enriching palladium can be used for efficiently and selectively adsorbing and enriching palladium ions from a solution and has high cyclic regeneration capacity.

Description

Technical Field

[0001] The invention relates to a porous COF adsorbent for efficiently enriching palladium and a preparation method and application thereof, belonging to the technical field of composite materials. Background Art

[0002] Palladium belongs to the platinum group metals, has similar chemical properties to metals such as platinum and rhodium, and has a wide range of uses. For example, in the electronics industry, palladium is widely used to manufacture electronic components such as multilayer ceramic capacitors; in the automotive industry, palladium is a key component in automobile exhaust catalytic converters. With the continuous development of the science and technology industry, the demand for palladium in various industries continues to increase. If we rely too much on the supply of primary palladium ore, the palladium supply chain will suffer a serious impact. By recycling secondary resources containing palladium, it can not only effectively alleviate the pressure of primary ore mining, but also ensure the continuous acquisition of palladium resources by various industries. Therefore, the recovery of palladium from secondary resources such as palladium-containing waste / waste liquid has important economic benefits and strategic significance.

[0003] At present, direct reduction is usually used to treat high-concentration palladium-containing solutions, but this method is not suitable for low-concentration palladium-containing solutions. The adsorption method is used for the separation and enrichment of low-concentration precious metals due to its high efficiency. Common adsorption materials such as resins, silica gel, and biomass have disadvantages such as low adsorption capacity, poor selectivity, high cost, and complicated processes.

[0004] Existing covalent organic frameworks (COFs) have a large number of active groups distributed on their surfaces, with excellent adsorption performance and easy regulation and modification. However, existing COFs materials for adsorbing palladium metal still have a series of technical problems, such as high synthesis costs due to the high prices of some monomers used to synthesize COFs; insufficient structural stability due to changes in the structure of COFs in strong acid or strong base solutions; and poor adsorption selectivity due to competitive adsorption in actual solutions. Summary of the invention

[0005] In view of the problem that the existing covalent organic framework (COFs) adsorbent materials have poor adsorption performance for low-concentration palladium ions, the present invention proposes a porous COF adsorbent with high efficiency for enriching palladium, and a preparation method and application thereof. The porous COF adsorbent with high efficiency for enriching palladium is produced by the acylation reaction of 1,3,5-benzenetricarboxylic acid chloride and 1,3,4-thiadiazole-2,5-diamine. The porous COF adsorbent with high efficiency for enriching palladium can be used for high-efficiency and selective adsorption of low-content palladium ions from a solution, and has a strong recycling and regeneration capability.

[0006] A porous COF adsorbent for efficiently enriching palladium, the adsorbent is generated by acylation reaction of 1,3,5-benzenetricarboxylic acid chloride and 1,3,4-thiadiazole-2,5-diamine, denoted as adsorbent COF-BcTd, and its structural formula is:

[0007]

[0008] The preparation method of the porous COF adsorbent with high efficiency of enriching palladium comprises the following specific steps:

[0009] (1) stirring and dissolving 1,3,5-benzenetricarboxylic acid chloride and 1,3,4-thiadiazole-2,5-diamine in N,N-dimethylformamide solvent to obtain a 1,3,5-benzenetricarboxylic acid chloride solution and a 1,3,4-thiadiazole-2,5-diamine solution, respectively, and mixing equal volumes of the 1,3,5-benzenetricarboxylic acid chloride solution and the 1,3,4-thiadiazole-2,5-diamine solution to obtain a mixed solution;

[0010] (2) placing the mixed solution in a reaction vessel, stirring the reaction at a temperature of 60 to 80° C. for 12 to 36 hours, cooling to room temperature, separating the solid and the liquid, washing the solid with N,N-dimethylformamide and ethanol in turn, and vacuum drying to obtain a porous COF adsorbent with high efficiency in enriching palladium.

[0011] Preferably, the solid-to-liquid ratio g:mL of 1,3,5-benzenetricarboxylic acid chloride to N,N-dimethylformamide in the 1,3,5-benzenetricarboxylic acid chloride solution in step (1) is 1:60-70.

[0012] Preferably, the solid-to-liquid ratio g:mL of 1,3,4-thiadiazole-2,5-diamine to N,N-dimethylformamide in the 1,3,4-thiadiazole-2,5-diamine solution in step (1) is 1:90 to 110.

[0013] Preferably, the reaction temperature in step (2) is 60-80°C.

[0014] Preferably, the reaction time of step (2) is 12 to 36 hours.

[0015] The porous COF adsorbent with high efficiency in enriching palladium is used in selectively adsorbing palladium ions in a solution.

[0016] Preferably, the palladium ion content in the solution is 30-60 mg / L.

[0017] The cyclic regeneration method of the porous COF adsorbent with high efficiency of enriching palladium: the COF-BcTd after adsorbing palladium is eluted with a desorption solution (40 mL) consisting of 1% concentrated hydrochloric acid and 10% thiourea for 20 hours, then washed with deionized water for 3-4 times and dried.

[0018] The principle of the selective adsorption of low-concentration palladium ions by the porous COF adsorbent for efficiently enriching palladium of the present invention is that Pd(II) in the solution chelates with the amide group of the adsorbent COF-BcTd, and at the same time, Pd(II) produces strong electrostatic adsorption and weak electrostatic adsorption with the C=S group and CN bond of COF-BcTd. Under the dual effects of chelation and electrostatics, the adsorbent COF-BcTd achieves adsorption enrichment of 50 mg / L palladium solution.

[0019] The beneficial effects of the present invention are:

[0020] (1) The porous COF adsorbent for efficiently enriching palladium of the present invention has functional groups such as amide groups, C=S groups, and CN bonds, so that it has abundant adsorption sites, can efficiently and selectively adsorb low-concentration palladium ions in the solution, and has strong recycling and regeneration capabilities;

[0021] (2) The porous COF adsorbent of the present invention which efficiently enriches palladium uses a covalent organic framework adsorption material prepared from organic matter with abundant adsorption sites, and has a larger pore volume and specific surface area and adsorption material stability;

[0022] (3) The porous COF adsorbent of the present invention that efficiently enriches palladium can achieve an adsorption rate of 93.13% for a 50 mg / L palladium solution. After repeating four times, the adsorption rate of palladium can also reach 88.70%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a SEM image of the porous COF adsorbent for efficient palladium enrichment in Example 1;

[0024] Figure 2 This is the EDS image of the porous COF adsorbent for efficient palladium enrichment in Example 1;

[0025] Figure 3 This is the FT-IR image of the porous COF adsorbent for efficient palladium enrichment in Example 1;

[0026] Figure 4 This is an XPS graph of the porous COF adsorbent for efficiently enriching palladium in Example 1 before and after the adsorption of palladium ions;

[0027] Figure 5 This is a SEM image of the porous COF adsorbent for efficient palladium enrichment in Example 1 after adsorbing palladium ions;

[0028] Figure 6 This is the EDS graph of the porous COF adsorbent for efficiently enriching palladium in Example 1 after adsorbing palladium ions. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0030] Example 1: A method for preparing a porous COF adsorbent for efficient enrichment of palladium, the specific steps are as follows:

[0031] (1) stirring and dissolving 1,3,5-benzenetricarboxylic acid chloride and 1,3,4-thiadiazole-2,5-diamine in N,N-dimethylformamide solvent respectively to obtain a 1,3,5-benzenetricarboxylic acid chloride solution and a 1,3,4-thiadiazole-2,5-diamine solution, and mixing the 1,3,5-benzenetricarboxylic acid chloride solution and the 1,3,4-thiadiazole-2,5-diamine solution in equal volumes to obtain a mixed solution; the solid-liquid ratio g:mL of 1,3,5-benzenetricarboxylic acid chloride to N,N-dimethylformamide in the 1,3,5-benzenetricarboxylic acid chloride solution is 1:65, and the solid-liquid ratio g:mL of 1,3,4-thiadiazole-2,5-diamine to N,N-dimethylformamide in the 1,3,4-thiadiazole-2,5-diamine solution is 1:100;

[0032] (2) The mixed solution was placed in a reaction vessel, stirred and reacted at a temperature of 70° C. for 24 h, cooled to room temperature, and then the solid and liquid were separated. The solid was washed with N,N-dimethylformamide and ethanol in turn, and vacuum dried to obtain a porous COF adsorbent with high efficiency of enriching palladium, which was recorded as adsorbent COF-BcTd; the reaction formula is:

[0033]

[0034] The SEM, EDS, FT-IR and XPS images of the adsorbent COF-BcTd of this example are shown in Figures 1 to 4 The adsorbent is mainly composed of elements C, N, O and S. The weight percentages of C, N, O and S are 59.66%, 20.22%, 10.71% and 9.41% respectively. In the FT-IR image, 1098cm -1 The energy band at 1382 cm corresponds to the CS-stretching vibration. -1 The energy band at 1662 cm corresponds to the CN-stretching vibration. -1 The band at 1577 cm is related to the stretching vibration of C=O of amide group CONH-. -1 The spectral band at is related to the deformation vibration of the amine group, indicating that 1,3,5-benzenetricarboxylic acid chloride and 1,3,4-thiadiazole-2,5-diamine have successfully undergone acylation reaction; XPS analysis shows that the peaks in the spectrum of COF-BcTd mainly come from C1s, N 1s, O 1s and S2p;

[0035] The selective adsorption performance of palladium ions by the porous COF adsorbent COF-BcTd for efficient palladium enrichment in this example is measured:

[0036] At room temperature, the adsorbent COF-BcTd (40 mg) and the solution to be adsorbed (pH = 2.5, 10 mL) were added to a 15 mL centrifuge tube, wherein the solution to be adsorbed contained 50.57 mg / L of Pd(II), 47.34 mg / L of Li(I), 1.26 g / L of Mg(II), 2.48 mg / L of K(I), 7.08 g / L of Na(I), 1.41 g / L of Al(III), and 41.96 mg / L of Ga(III); the mixture was shaken at a shaking speed of 200 rpm for 20 h on an oscillator; the adsorbent was separated by centrifugation and the supernatant was obtained, and the residual concentration of the remaining metal ions in the supernatant was determined by ICP-OES;

[0037] The removal rates of Pd(II) were calculated to be 71.19%, Li(I) to be 0.02%, Mg(II) to be 0%, K(I) to be 0.02%, Na(I) to be 0.01%, Al(III) to be 0.01%, and Ga(III) to be 0.06%.

[0038] It can be seen that the porous COF adsorbent COF-BcTd for efficient palladium enrichment in the product of this embodiment has a strong selectivity for palladium ions;

[0039] The performance of the adsorbent COF-BcTd in this example in adsorbing palladium ions is measured:

[0040] Add the adsorbent COF-BcTd (40 mg) and Pd(II) solution (pH=2.5, 10 mL, 50 mg / L) into a 15 mL centrifuge tube at room temperature and shake at 200 rpm for 20 h in a shaker; centrifuge to separate the adsorbent and obtain the supernatant;

[0041] The adsorbent COF-BcTd after adsorption of palladium ions was analyzed by SEM, EDS, and XPS. Figures 4 to 6 , Figure 4 The characteristic peak of Pd was found in XPS. Figure 5 It can be seen that the distribution state of Pd on the adsorbent is uniform; Figure 6 It can be concluded that the content of Pd reaches 33.43%;

[0042] ICP-OES determined that the residual palladium ion concentration in the supernatant was 3.09 mg / L, the adsorption capacity of the adsorbent COF-BcTd for Pd(II) was 41.95 mg / g, and the adsorption efficiency was 93.13%; after adsorbing palladium ions, COF-BcTd was eluted with a desorption solution (40 mL) composed of 1% concentrated hydrochloric acid and 10% thiourea for 20 hours; after centrifugation, the adsorbent was washed with distilled water until the solution was neutral to complete the regeneration of the adsorbent COF-BcTd; after 4 repeated experiments, the adsorption rate of the fourth adsorption of Pd(II) was 88.70%.

[0043] Example 2: A method for preparing a porous COF adsorbent that efficiently enriches palladium, the specific steps are as follows:

[0044] (1) stirring and dissolving 1,3,5-benzenetricarboxylic acid chloride and 1,3,4-thiadiazole-2,5-diamine in N,N-dimethylformamide solvent to obtain a 1,3,5-benzenetricarboxylic acid chloride solution and a 1,3,4-thiadiazole-2,5-diamine solution, and mixing the 1,3,5-benzenetricarboxylic acid chloride solution and the 1,3,4-thiadiazole-2,5-diamine solution in equal volumes to obtain a mixed solution; the solid-liquid ratio of 1,3,5-benzenetricarboxylic acid chloride to N,N-dimethylformamide in the 1,3,5-benzenetricarboxylic acid chloride solution g:mL is 1:60, and the solid-liquid ratio of 1,3,4-thiadiazole-2,5-diamine to N,N-dimethylformamide in the 1,3,4-thiadiazole-2,5-diamine solution g:mL is 1:90;

[0045] (2) The mixed solution was placed in a reaction vessel, stirred and reacted at a temperature of 60° C. for 12 h, cooled to room temperature, and then the solid and liquid were separated. The solid was washed with N,N-dimethylformamide and ethanol in turn, and vacuum dried to obtain a porous COF adsorbent with high efficiency of enriching palladium, which was recorded as adsorbent COF-BcTd; the reaction formula is:

[0046] The selective adsorption performance of palladium ions by the porous COF adsorbent COF-BcTd for efficient palladium enrichment in this example is measured:

[0047] At room temperature, the adsorbent COF-BcTd (40 mg) and the solution to be adsorbed (pH = 2.5, 10 mL) were added to a 15 mL centrifuge tube, wherein the solution to be adsorbed contained 50.57 mg / L of Pd(II), 47.34 mg / L of Li(I), 1.26 g / L of Mg(II), 2.48 mg / L of K(I), 7.08 g / L of Na(I), 1.41 g / L of Al(III), and 41.96 mg / L of Ga(III); the mixture was shaken at a shaking speed of 200 rpm for 20 h on an oscillator; the adsorbent was separated by centrifugation and the supernatant was obtained, and the residual concentration of the remaining metal ions in the supernatant was determined by ICP-OES;

[0048] The removal rates of Pd(II) were calculated to be 71.05%, Li(I) to be 0.02%, Mg(II) to be 0%, K(I) to be 0.02%, Na(I) to be 0.01%, Al(III) to be 0.02%, and Ga(III) to be 0.07%.

[0049] It can be seen that the porous COF adsorbent COF-BcTd for efficient palladium enrichment in the product of this embodiment has a strong selectivity for palladium ions;

[0050] The performance of the adsorbent COF-BcTd in this example in adsorbing palladium ions is measured:

[0051] Add the adsorbent COF-BcTd (40 mg) and Pd(II) solution (pH=2.5, 10 mL, 50 mg / L) into a 15 mL centrifuge tube at room temperature and shake at 200 rpm for 20 h in a shaker; centrifuge to separate the adsorbent and obtain the supernatant;

[0052] The residual palladium ion concentration in the supernatant was determined by ICP-OES to be 4.29 mg / L, the adsorption capacity of the adsorbent COF-BcTd for Pd(II) was 45.75 mg / g, and the adsorption efficiency was 90.47%; the COF-BcTd after adsorbing palladium ions was eluted with a desorption solution (40 mL) composed of 1% concentrated hydrochloric acid and 10% thiourea for 20 h; after centrifugation, the adsorbent was washed with distilled water until the solution was neutral to complete the regeneration of the adsorbent COF-BcTd; after 4 repeated experiments, the adsorption rate of Pd(II in the fourth adsorption was 87.13%.

[0053] Example 3: A method for preparing a porous COF adsorbent that efficiently enriches palladium, the specific steps are as follows:

[0054] (1) stirring and dissolving 1,3,5-benzenetricarboxylic acid chloride and 1,3,4-thiadiazole-2,5-diamine in N,N-dimethylformamide solvent respectively to obtain a 1,3,5-benzenetricarboxylic acid chloride solution and a 1,3,4-thiadiazole-2,5-diamine solution, and mixing the 1,3,5-benzenetricarboxylic acid chloride solution and the 1,3,4-thiadiazole-2,5-diamine solution in equal volumes to obtain a mixed solution; the solid-liquid ratio g:mL of 1,3,5-benzenetricarboxylic acid chloride to N,N-dimethylformamide in the 1,3,5-benzenetricarboxylic acid chloride solution is 1:70, and the solid-liquid ratio g:mL of 1,3,4-thiadiazole-2,5-diamine to N,N-dimethylformamide in the 1,3,4-thiadiazole-2,5-diamine solution is 1:110;

[0055] (2) The mixed solution was placed in a reaction vessel, stirred and reacted at a temperature of 80° C. for 36 hours, cooled to room temperature, and then the solid and liquid were separated. The solid was washed with N,N-dimethylformamide and ethanol in turn, and vacuum dried to obtain a porous COF adsorbent with high efficiency of enriching palladium, which was recorded as adsorbent COF-BcTd; the reaction formula is:

[0056] The selective adsorption performance of palladium ions by the porous COF adsorbent COF-BcTd for efficient palladium enrichment in this example is measured:

[0057] At room temperature, the adsorbent COF-BcTd (40 mg) and the solution to be adsorbed (pH = 2.5, 10 mL) were added to a 15 mL centrifuge tube, wherein the solution to be adsorbed contained 50.57 mg / L of Pd(II), 47.34 mg / L of Li(I), 1.26 g / L of Mg(II), 2.48 mg / L of K(I), 7.08 g / L of Na(I), 1.41 g / L of Al(III), and 41.96 mg / L of Ga(III); the mixture was shaken at a shaking speed of 200 rpm for 20 h on an oscillator; the adsorbent was separated by centrifugation and the supernatant was obtained, and the residual concentration of the remaining metal ions in the supernatant was determined by ICP-OES;

[0058] The removal rates of Pd(II) were calculated to be 71.01%, Li(I) to be 0.03%, Mg(II) to be 0.01%, K(I) to be 0.02%, Na(I) to be 0.01%, Al(III) to be 0.01%, and Ga(III) to be 0.08%.

[0059] It can be seen that the porous COF adsorbent BPD-POP for efficiently enriching palladium in the product of this embodiment has extremely strong selectivity for palladium ions;

[0060] The performance of the adsorbent COF-BcTd in this example in adsorbing palladium ions is measured:

[0061] Add the adsorbent COF-BcTd (40 mg) and Pd(II) solution (pH=2.5, 10 mL, 50 mg / L) into a 15 mL centrifuge tube at room temperature and shake at 200 rpm for 20 h in a shaker; centrifuge to separate the adsorbent and obtain the supernatant;

[0062] The residual palladium ion concentration in the supernatant was determined by ICP-OES to be 3.23 mg / L, the adsorption capacity of the adsorbent COF-BcTd for Pd(II) was 41.81 mg / g, and the adsorption efficiency was 92.83%; the COF-BcTd after adsorbing palladium ions was eluted with a desorption solution (40 mL) composed of 1% concentrated hydrochloric acid and 10% thiourea for 20 h; after centrifugation, the adsorbent was washed with distilled water until the solution was neutral to complete the regeneration of the adsorbent COF-BcTd; after 4 repeated experiments, the adsorption rate of Pd(II in the fourth adsorption was 85.23%.

[0063] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A porous COF adsorbent for efficient palladium enrichment, characterized in that: The adsorbent is generated by acylation reaction of 1,3,5-benzenetricarboxylic acid chloride and 1,3,4-thiadiazole-2,5-diamine, and is recorded as adsorbent COF-BcTd, and its structural formula is:

2. The method for preparing the porous COF adsorbent for efficient palladium enrichment according to claim 1, characterized in that: The specific steps are as follows: (1) stirring and dissolving 1,3,5-benzenetricarboxylic acid chloride and 1,3,4-thiadiazole-2,5-diamine in N,N-dimethylformamide solvent to obtain a 1,3,5-benzenetricarboxylic acid chloride solution and a 1,3,4-thiadiazole-2,5-diamine solution, respectively, and mixing equal volumes of the 1,3,5-benzenetricarboxylic acid chloride solution and the 1,3,4-thiadiazole-2,5-diamine solution to obtain a mixed solution; (2) placing the mixed solution in a reaction vessel, stirring the reaction at a temperature of 60 to 80° C. for 12 to 36 hours, cooling to room temperature, separating the solid and the liquid, washing the solid with N,N-dimethylformamide and ethanol in turn, and vacuum drying to obtain a porous COF adsorbent with high efficiency in enriching palladium.

3. The method for preparing a porous COF adsorbent for efficient palladium enrichment according to claim 2, characterized in that: Step (1) The solid-to-liquid ratio of 1,3,5-benzenetricarboxylic acid chloride to N,N-dimethylformamide in the 1,3,5-benzenetricarboxylic acid chloride solution is 1:60-70.

4. The method for preparing a porous COF adsorbent for efficient palladium enrichment according to claim 2, characterized in that: Step (1) The solid-to-liquid ratio of 1,3,4-thiadiazole-2,5-diamine to N,N-dimethylformamide in the 1,3,4-thiadiazole-2,5-diamine solution is 1:90 to 110.

5. The method for preparing a porous COF adsorbent for efficient palladium enrichment according to claim 2, characterized in that: The reaction temperature of step (2) is 60-80°C.

6. The method for preparing a porous COF adsorbent for efficient palladium enrichment according to claim 2, characterized in that: The reaction time of step (2) is 12 to 36 hours.

7. Use of the porous COF adsorbent for efficiently enriching palladium according to claim 1 in selectively adsorbing palladium ions in a solution.

8. According to the use of claim 7, the palladium ion content in the solution is 30-60 mg / L.

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