Use of a sulfur-containing polyimide resin as a silver adsorbent

Abstract

The application discloses application of a sulfur-containing polyimide resin as a silver adsorbent, and the sulfur-containing polyimide resin is a random sulfur-containing polyimide resin or a block sulfur-containing polyimide resin, a structural formula of the random sulfur-containing polyimide resin is shown as formula I, and a structural formula of the block sulfur-containing polyimide resin is shown as formula II. The sulfur-containing polyimide resin particles can also be made into a film type adsorbent, and are convenient to use. In the application, the silver adsorption process is simple, the operation is convenient, the adsorbent has specific adsorption for silver elements, meanwhile, the adsorption process is not interfered by common elements such as potassium, sodium, calcium, magnesium, iron, zinc, copper and cadmium. The adsorbent provided by the application can be normally used in a strong acid, high temperature and high pressure environment, and the resin material can be regenerated through a simple desorption process, and is economic and environment-friendly.

Description

Technical Field

[0001] This invention relates to the application of a sulfur-containing polyimide resin as a silver adsorbent. Background Technology

[0002] Silver, as a precious metal, is a valuable natural resource. It possesses high physical and chemical stability, is easy to cut, and is often used in precious jewelry and currency. In modern industry, due to its excellent ductility, electrical conductivity, corrosion resistance, oxidation resistance, and catalytic activity, it is widely used in chemical, light industry, aerospace, military, pharmaceutical, and environmental protection fields.

[0003] However, silver is extremely rare in the Earth's crust, making it a scarce resource relative to ever-increasing demand. Currently, the precious metals metallurgy industry mainly uses hydrometallurgical processes, which are simple to operate and have low production costs, but suffer from problems such as low concentrations of precious metals in the leachate and a wide variety and high concentrations of impurity metals.

[0004] The main methods for the enrichment and separation of precious metals include metal displacement, activated carbon adsorption, resin adsorption, and extraction. Metal displacement is gradually being replaced by activated carbon due to its high cost. Activated carbon is economical and efficient; however, with the development and advancement of technology, resin methods, which have simple regeneration processes and high selectivity, are gradually replacing activated carbon. Chelating resins have advantages such as large adsorption capacity, easy elution, minimal interference, and good stability. They can be combined with different extraction devices for the enrichment and separation of precious metals and are currently the preferred choice.

[0005] Most commonly used precious metal adsorption and chelating resins are prepared by polymerization reactions on polymer backbones such as polystyrene and polyacrylonitrile, and their temperature resistance is generally limited. Furthermore, they typically employ particulate structures for the enrichment and adsorption of precious metals, making post-processing relatively complex. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by utilizing a polyimide framework structure to prepare a sulfur-containing polyimide resin material that is resistant to high temperatures, organic solvents, and strong acids for the selective adsorption of silver ions, while providing both particulate and film forms. Furthermore, an elution technique is provided to enable the regeneration and reuse of this resin material.

[0007] The technical solution adopted in this invention is:

[0008] An application of a sulfur-containing polyimide resin as a silver adsorbent, wherein the sulfur-containing polyimide resin is a random sulfur-containing polyimide resin or a block sulfur-containing polyimide resin, the structural formula of the random sulfur-containing polyimide resin is shown in Formula I, and the structural formula of the block sulfur-containing polyimide resin is shown in Formula II.

[0009]

[0010] Where m, n, and x are integers from 1 to 1000.

[0011] The sulfur-containing polyimide resin is sulfur-containing polyimide resin particles or sulfur-containing polyimide resin film, wherein the sulfur-containing polyimide resin film is prepared by forming a film from sulfur-containing polyimide resin particles.

[0012] Furthermore, the sulfur-containing polyimide resin film includes random sulfur-containing polyimide resin film or block sulfur-containing polyimide resin film, which are prepared from random sulfur-containing polyimide resin particles or block sulfur-containing polyimide resin particles, respectively.

[0013] Furthermore, the synthesis method of the sulfur-containing polyimide resin particles, i.e., random sulfur-containing polyimide resin particles or block sulfur-containing polyimide resin particles, has been disclosed in Chen, G., Pei, X., Wei, H., Xu, L. and Fang, X. (2015), Synthesis and characterization of sulfonated block copolyimides derived from 4,4'-sulfide-bis(naphthalic anhydride) for proton exchange membranes. J. Appl. Polym. Sci., 132, 41501.

[0014] Specifically, random sulfur-containing polyimide resin particles or block sulfur-containing polyimide resin particles can be prepared by the following method:

[0015] Random sulfur-containing polyimide resin particles were prepared by the following method: Under nitrogen protection, 2,2'-di(sulfonyl)-4,4'-diaminodiphenyl ether, triethylamine and m-cresol were mixed and stirred until 2,2'-di(sulfonyl)-4,4'-diaminodiphenyl ether was completely dissolved. Then, 4,4'-diaminodiphenyl ether, thioether naphthalene dihydric anhydride and benzoic acid were added. This mixture was stirred at room temperature for 30 minutes, then heated to 80°C and reacted for 4 hours, then heated to 180°C and reacted for 18 hours. After cooling to 80°C, the mixture was poured into acetone to obtain fibrous polymer. After washing with acetone, the polymer was extracted with acetone in a Soxhlet extractor for 20 hours and dried in a vacuum oven at 150°C for 24 hours to obtain random sulfur-containing polyimide resin particles. The molar ratio of the sum of the amounts of 2,2'-bis(sulfonic acid)-4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether to the molar ratio of thioether naphthalene dianhydride is 1:1; the molar ratio of the amounts of 2,2'-bis(sulfonic acid)-4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether is 1:0.001 to 1000, preferably 1:0.1 to 10, more preferably 1:0.2 to 4; the molar ratio of the amounts of 2,2'-bis(sulfonic acid)-4,4'-diaminodiphenyl ether and triethylamine is 1:2 to 4; and the molar ratio of the amounts of 4,4'-diaminodiphenyl ether and benzoic acid is 1:3 to 5.

[0016] The reaction equation is shown below:

[0017]

[0018] For the synthesis of 2,2'-bis(sulfonyl)-4,4'-diaminodiphenyl ether, see Fang, J.; Guo, X.; Harada, S.; Watari, T.; Tanaka, K.; Kita, H. Macromolecules, 2002, 35, 9022.

[0019] For the synthesis method of thioether naphthalene dianhydride, see Rusanov, ALPolym Syn Adv Polym Sci, 1994, 111, 115.

[0020] The random polymer was prepared by a one-pot method, in which sulfur-containing diamine monomer, sulfur-free diamine monomer, and dianhydride were dissolved in m-cresol solvent and then directly heated.

[0021] Block-type sulfur-containing polyimide resin particles can be prepared by the following method:

[0022] (1) Under nitrogen protection, 2,2'-di(sulfonyl)-4,4'-diaminodiphenyl ether, triethylamine and m-cresol A were mixed and stirred until 2,2'-di(sulfonyl)-4,4'-diaminodiphenyl ether was completely dissolved. Then, thioether naphthalene dihydride A and benzoic acid A were added. The mixture was stirred at room temperature for 30 minutes, then heated to 80°C and reacted for 4 hours, followed by reaction at 180°C for 18 hours to obtain amino-terminated polyimide oligomers;

[0023] (2) Add thioether naphthalene dihydride B and m-cresol B under nitrogen protection, stir to dissolve, then add 4,4'-diaminodiphenyl ether and benzoic acid B, react at 180°C for 18 h to obtain anhydride-terminated polyimide oligomer.

[0024] (3) When the mixture of steps (1) and (2) is cooled to 80°C, the mixture of step (2) is added to the mixture of step (1), and the reaction solution is reacted at 80°C for 4 hours and at 180°C for 18 hours. When cooled to 80°C, it is poured into acetone to obtain fibrous polymer. After washing with acetone, it is extracted with acetone in a Soxhlet extractor for 20 hours and dried in a vacuum oven at 150°C for 24 hours to obtain block-type sulfur-containing polyimide resin particles.

[0025] The thioether naphthalene dihydride A in step (1) and the thioether naphthalene dihydride B in step (2) are used to distinguish the thioether naphthalene dihydride in different steps. The letters A and B have no chemical meaning.

[0026] Benzoic acid A, benzoic acid B, m-cresol A, and m-cresol B are also used to distinguish raw materials in different steps; the letters A and B have no chemical meaning.

[0027] The ratio of the total amount of the thioether naphthalene dihydride A and thioether naphthalene dihydride B to the total amount of 2,2'-bis(sulfonyl)-4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether is 1:1.

[0028] The molar ratio of the thioether naphthalene dihydride A to 2,2'-bis(sulfonyl)-4,4'-diaminodiphenyl ether is 0.5 to 0.9999:1, preferably 0.9 to 0.99:1;

[0029] The molar ratio of the thioether naphthalene dihydride B to 4,4'-diaminodiphenyl ether is 1.0001 to 1.5:1, preferably 1.01 to 1.1:1;

[0030] The molar ratio of 2,2'-bis(sulfonyl)-4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether is 1:0.001 to 1000, preferably 1:0.1 to 10, and more preferably 1:0.2 to 4.

[0031] The molar ratio of 2,2'-bis(sulfonyl)-4,4'-diaminodiphenyl ether, triethylamine, and benzoic acid A is 1:2 to 4:1.2 to 2, and the molar ratio of 4,4'-diaminodiphenyl ether and benzoic acid B is 1:1.2 to 2.

[0032] The reaction equation is shown below:

[0033]

[0034] The block copolymer was prepared using a two-pot method. In one pot, sulfonated diamine monomer and a portion of dianhydride were reacted to prepare amine-terminated sulfonated blocks. In the other pot, sulfur-free diamine monomer and dianhydride were reacted to prepare anhydride-terminated sulfonated blocks. The two pots were then combined into one pot for imidization to obtain the block copolymer.

[0035] This invention also provides a method for preparing a sulfur-containing polyimide resin film: sulfur-containing polyimide resin particles are dissolved in m-cresol with a solid content of 10% to obtain a homogeneous and viscous solution. This solution is coated onto a clean glass plate and cast into a film. The film is then baked in an oven at 80°C for 12 hours, followed by heating to 120°C and baking for another 12 hours, and then allowed to cool naturally to room temperature. The glass plate is then placed in ethanol to allow it to peel off naturally. The film is then immersed in ethanol for 48 hours, removed, and thoroughly washed with deionized water. It is then immersed in a 2 mol / L hydrochloric acid solution for 72 hours to completely protonate the film. Finally, the film is removed, thoroughly washed with deionized water, and stored in water for later use, thus obtaining a sulfur-containing polyimide resin film. The thickness of the sulfur-containing polyimide resin film is generally 0.05–2 mm, preferably 1 mm.

[0036] Specifically, random sulfur-containing polyimide resin particles are used to prepare random sulfur-containing polyimide resin films, and block sulfur-containing polyimide resin particles are used to prepare block sulfur-containing polyimide resin films.

[0037] This invention provides the application of sulfur-containing polyimide resin as a silver adsorbent, and further, block-type sulfur-containing polyimide resin is preferred as a silver adsorbent. More preferably, block-type sulfur-containing polyimide resin particles or block-type sulfur-containing polyimide resin films are used as silver adsorbents.

[0038] Furthermore, the application method of the silver adsorbent of the present invention is as follows: sulfur-containing polyimide resin particles or sulfur-containing polyimide resin films are added to the solution to be treated containing silver ions, and the solution is shaken on a shaker for 10 minutes to 2 hours or vortexed for 10 to 30 minutes to remove the resin particles or resin films, thereby obtaining the treated solution.

[0039] The amount of sulfur-containing polyimide resin particles or sulfur-containing polyimide resin films added is generally 0.001 to 0.1 g / mL based on the volume of the solution to be treated, preferably 0.01 to 0.05 g / mL.

[0040] After the adsorption treatment is complete, the resin particles are separated from the solution by centrifugation or settling to obtain the treated solution.

[0041] After the adsorption process is complete, the resin film can be directly removed. The operation is simple and convenient, and the loss of resin adsorbent is minimal.

[0042] The silver content in the solution before and after treatment can be determined by inductively coupled plasma mass spectrometry (ICP-MS), and the amount of silver adsorbed by the resin can be calculated.

[0043] In the above adsorption application method, the pH of the silver-containing solution to be treated is ≤7, the resin adsorbent can be used for a long time in a strong acid environment; and the adsorption process can be carried out under high temperature or high pressure conditions, and can also be used normally under pressure at 140℃.

[0044] The sulfur-containing polyimide resin can be desorbed and regenerated after adsorbing silver, and can be recycled.

[0045] The present invention also provides a method for regenerating the above-mentioned sulfur-containing polyimide resin. The process steps and conditions of the method are as follows: the sulfur-containing polyimide resin particles or films adsorbed with silver are placed in a 1 mol / L hydrochloric acid solution containing 10% thiourea by mass, and desorption is performed by ultrasonic vibration or vortex vibration for 10 to 60 minutes. Then, the resin particles are obtained by centrifugation or filtration, or the resin film is directly removed. The obtained particles or films are soaked and washed with a 3 mol / L hydrochloric acid solution, and then dried at 100°C to obtain the regenerated sulfur-containing polyimide resin particles.

[0046] Compared with existing technologies, this invention has the following advantages: the sulfur-containing polyimide resin used is resistant to strong acids and can be used for the adsorption of silver in acidic solutions, such as strongly acidic industrial wastewater. Simultaneously, this material is heat-resistant, exhibiting good thermal stability under normal pressure conditions below 280℃, and can also be used normally under high pressure conditions of 140℃, filling the gap in organic polymer silver adsorption materials for high-temperature, strongly acidic environments.

[0047] The number of sulfur-containing functional groups on the surface of sulfur-containing polyimide resin particles can be adjusted, and the adsorption capacity of the material for metals can be controlled.

[0048] Sulfur-containing polyimide resin is highly hydrophilic and can be uniformly dispersed in the sample solution to be adsorbed, resulting in good adsorption effect.

[0049] The sulfur-containing polyimide resin provided by this invention has a simple and convenient adsorption process for silver, and it has specific adsorption for silver. At the same time, the adsorption process is not affected by elements such as potassium, sodium, calcium, magnesium, iron, zinc, copper, and cadmium. The sulfur-containing polyimide resin has a simple regeneration process, can be recycled, has a long service life, and is green and environmentally friendly. Attached Figure Description

[0050] Figure 1 This is the infrared spectrum of the random sulfur-containing polyimide resin particles prepared in Example 1. (1709 cm⁻¹) -1 and 1668cm -1 The two distinct absorption peaks at 1368 cm⁻¹ represent the asymmetric and symmetric stretching vibrations of the carbonyl group on the imide ring, respectively. -1 The peaks represent the CN stretching vibrations on the imide ring, at 1193 and 1030 cm⁻¹. -1 and 1239, 1085cm -1 The four absorption peaks represent the symmetric and asymmetric stretching vibrations of the sulfonic acid group, respectively.

[0051] Figure 2 This is the NMR spectrum of the random sulfur-containing polyimide resin particles prepared in Example 1. 7.84, 7.45, and 7.03 ppm represent the hydrogens a, b, and c on the benzene ring of 2,2′-bis(sulfonic acid)-4,4′-diaminodiphenyl ether, respectively; 7.45 and 7.24 ppm represent the hydrogens d and e on the benzene ring of 4,4′-diaminodiphenyl ether. Their corresponding integral ratios are consistent with the feed ratio.

[0052] Figure 3 These are TEM images of sulfur-containing polyimide resin films. In the image, (a) is a random sulfur-containing polyimide resin film, and (b) is a block sulfur-containing polyimide resin film. Detailed Implementation

[0053] The following embodiments are given to specifically describe the present invention. However, it should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0054] Example 1

[0055] The molar ratio of sulfur-containing diamine monomer 2,2'-di(sulfonyl)-4,4'-diaminodiphenyl ether (ODADS) and sulfur-free diamine monomer 4,4'-diaminodiphenyl ether (ODA) was set to 6:4 for the reaction. The reaction was carried out according to the preparation method of random sulfur-containing polyimide to obtain random sulfur-containing polyimide resin particles.

[0056] In a nitrogen-protected three-necked flask, 0.6524 g (1.81 mmol) of 2,2'-bis(sulfonyl)-4,4'-diaminodiphenyl ether (ODADS), 0.5390 g (5.33 mmol) of triethylamine, and 8 mL of m-cresol were added. The mixture was stirred until the ODADS was completely dissolved. Then, 0.2417 g (1.21 mmol) of 4,4'-diaminodiphenyl ether (ODA), 1.2866 g (3.02 mmol) of thioether naphthalene dianhydride (SBNTA), and 0.5522 g (4.53 mmol) of benzoic acid were added. The mixture was stirred at room temperature for 30 minutes, then heated to 80 °C for 4 hours and then to 180 °C for 18 hours. After cooling to 80 °C, the mixture was poured into 500 mL of acetone to obtain a fibrous polymer. After washing once with acetone, the product was extracted with acetone in a Soxhlet extractor for 20 h, and then dried in a vacuum oven at 150 °C for 24 h to obtain a triethylamine salt polymer of sulfonated polyimide. The infrared spectrum of the product is shown below. Figure 1 See the nuclear magnetic resonance spectrum. Figure 2 .

[0057] SPI-R (6 / 4): FT-IR (film): 1709cm -1 (v asym C=O), 1668cm -1 (v sym C=O), and 1368cm -1 (v C-N imide), 1239, 1193, 1085, 1030cm -1 (sulfonic acid group stretching).

[0058] Take 2.5g of the resin particles prepared above and add them to 50mL of silver ion solution with a concentration of 2mg / L. Place the solution in a shaker and shake for 30 minutes. Centrifuge to remove the resin particles. The concentration of silver ions in the solution after treatment is 0.274mg / L, and the removal rate of silver ions is 86.3%.

[0059] The resin particles adsorbed with silver ions were placed in 10 mL of 1 mol / L hydrochloric acid solution containing 10% thiourea and desorbed by ultrasonic vibration for 30 minutes. After centrifugation, the supernatant was analyzed, revealing a silver ion desorption rate of 85.5%. The centrifuged resin particles were then washed with 3 mol / L hydrochloric acid and dried at 100°C to complete resin regeneration.

[0060] 2.5 g of the regenerated resin was added to 50 mL of a 2 mg / L silver ion solution, shaken on a shaker for 30 minutes, and centrifuged to remove resin particles. The concentration of silver ions in the treated solution was measured to be 0.281 mg / L, and the silver ion removal rate was 85.95%. The silver adsorption capacity of the regenerated resin was not significantly different from that before regeneration.

[0061] After adsorption and regeneration using the above method for a total of 10 times, the removal rate of silver ions was 80.7%, still exceeding 80%.

[0062] Example 2

[0063] The molar ratio of sulfur-containing diamine monomer to sulfur-free diamine monomer was set to 6:4 for the reaction. The reaction was carried out according to the preparation method of block-type sulfur-containing polyimide resin. The length of the hydrophilic block was controlled to obtain block-type sulfur-containing polyimide resin particles.

[0064] In a nitrogen-protected, nitrogen-protected, three-necked flask, sulfonated diamine ODADS (0.6618 g, 1.84 mmol), triethylamine (0.4467 g, 4.41 mmol), and 8 mL of m-cresol were added. The mixture was stirred until the ODADS was completely dissolved. Then, thioether naphthalene dianhydride (SBNTA) (0.7640 g, 1.79 mmol) and benzoic acid (0.3274 g, 2.68 mmol) were added. The mixture was stirred at room temperature for 30 minutes, then heated to 80 °C for 4 hours and then to 180 °C for 18 hours to obtain amine-terminated polyimide oligomers. In another nitrogen-protected, nitrogen-protected, two-necked flasks, the remaining naphthalene dianhydride (SBNTA) (0.5420 g, 1.27 mmol) and 8 mL of m-cresol were added and stirred until dissolved. Then, unsulfonated diamine ODA (0.2454 g, 1.23 mmol) and benzoic acid (0.2324 g, 1.91 mmol) were added, and the mixture was reacted at 180 °C for 18 h. After the mixture in both flasks cooled to 80 °C, it was transferred to flask 1, and the reaction mixture was reacted at 80 °C for 4 h and then at 180 °C for 18 h. After the mixture in the reaction flasks cooled to 80 °C, it was poured into 500 mL of acetone to obtain a fibrous polymer. After washing once with acetone, it was extracted with acetone in a Soxhlet extractor for 20 h, and then dried in a vacuum oven at 150 °C for 24 h to obtain a triethylamine salt polymer of sulfonated polyimide.

[0065] SPI-B(6 / 4)-40:FT-IR(film):1704cm -1 (v asym C=O), 1656cm -1 (v sym C=O), and 1363cm -1 (v C-Nimide), 1229, 1186, 1081, 1025cm -1 (sulfonic acid group stretching).

[0066] Take 0.5g of the resin particles prepared above and add them to 50mL of silver ion solution with a concentration of 2mg / L. Place the solution in a vortex shaker and shake for 30 minutes. Centrifuge to remove the resin particles. The concentration of silver ions in the solution after treatment is 0.133mg / L, and the removal rate of silver ions is 93.3%.

[0067] The resin particles adsorbed with silver ions were placed in 50 mL of a 1 mol / L hydrochloric acid solution containing 10% thiourea and desorbed by vortexing for 60 minutes. After centrifugation, the supernatant was collected and analyzed, revealing a silver ion desorption rate of 89.1%. The centrifuged resin particles were then washed with 3 mol / L hydrochloric acid and dried at 100°C to complete resin regeneration.

[0068] 0.5 g of the regenerated resin was added to 50 mL of a 2 mg / L silver ion solution, shaken on a shaker for 30 minutes, and centrifuged to remove resin particles. The concentration of silver ions in the treated solution was measured to be 0.139 mg / L, and the silver ion removal rate was 93.05%. The silver adsorption capacity of the regenerated resin was not significantly different from that before regeneration.

[0069] After adsorption and regeneration using the above method for a total of 10 times, the removal rate of silver ions was 88.7%, still exceeding 88%.

[0070] Example 3

[0071] The molar ratio of sulfur-containing diamine monomer to sulfur-free diamine monomer was set to 6:4 for the reaction. The reaction was carried out according to the preparation method of block-type sulfur-containing polyimide resin in Example 2. The length of the hydrophilic block was controlled to obtain block-type sulfur-containing polyimide resin particles.

[0072] Iron, zinc, copper, and cadmium ions were added to a silver ion solution to prepare a multi-element mixed solution containing 2 mg / L of silver ions and 1 mg / L of each of the iron, zinc, copper, and cadmium ions.

[0073] Take 1.0g of the block-type sulfur-containing polyimide resin particles prepared above and add them to 50mL of a multi-element mixed solution containing 2mg / L silver ions and 1mg / L iron, zinc, copper and cadmium ions. Place the solution in a shaker and shake for 30 minutes. Centrifuge and collect the supernatant. The concentration of silver ions in the supernatant was measured to be 0.209mg / L, and the removal rate of silver ions was 89.6%. The concentrations of iron, zinc, copper and cadmium ions remained basically unchanged, proving that the resin particles have basically no adsorption of iron, zinc, copper and cadmium ions.

[0074] Example 4

[0075] The molar ratio of sulfur-containing diamine monomer to sulfur-free diamine monomer was set to 6:4 for the reaction. The reaction was carried out according to the preparation method of block-type sulfur-containing polyimide resin in Example 2. The length of the hydrophilic block was controlled to obtain block-type sulfur-containing polyimide resin particles.

[0076] Potassium, sodium, calcium, and magnesium ions were added to a silver ion solution to prepare a multi-element mixed solution containing 2 mg / L of silver ions and 2 mg / L of each of the potassium, sodium, calcium, and magnesium ions.

[0077] Take 1.0g of the block-type sulfur-containing polyimide resin particles prepared above and add them to 50mL of a multi-element mixed solution containing 2mg / L silver ions and 2mg / L potassium, sodium, calcium and magnesium ions. Place the solution in a shaker and shake for 30 minutes. Centrifuge and collect the supernatant. The concentration of silver ions in the supernatant was measured to be 0.247mg / L, and the removal rate of silver ions was 87.6%. The concentrations of potassium, sodium, calcium and magnesium ions remained basically unchanged, proving that the resin particles have basically no adsorption of potassium, sodium, calcium and magnesium ions.

[0078] Example 5

[0079] The reaction was carried out by setting the molar ratio of sulfur-containing diamine monomer and sulfur-free diamine monomer to 6:4, following the preparation method of block-type sulfur-containing polyimide resin in Example 2. The length of the hydrophilic blocks was controlled to obtain block-type sulfur-containing polyimide resin particles. Then, according to the preparation method of sulfur-containing polyimide film, a block-type sulfur-containing polyimide film was prepared and activated in hydrochloric acid solution.

[0080] The preparation method of block-type sulfur-containing polyimide resin particles is the same as in Example 2.

[0081] The preparation method of the thin film is as follows: Block-type sulfur-containing polyimide resin particles are dissolved in m-cresol with a solid content of 10% to obtain a homogeneous and viscous solution. This solution is coated onto a clean glass plate and cast into a film. The film is then baked in an oven at 80℃ for 12 hours, followed by heating to 120℃ and baking for another 12 hours, and then allowed to cool naturally to room temperature. The glass plate is then placed in ethanol to allow it to peel off naturally. The film is then immersed in ethanol for 48 hours, removed, and thoroughly washed with deionized water. It is then immersed in a 2 mol / L hydrochloric acid solution for 72 hours to ensure complete protonation. Finally, the film is removed, thoroughly washed with deionized water, and stored in water for later use, thus obtaining a block-type sulfur-containing polyimide resin film. The thickness of the block-type sulfur-containing polyimide resin film is 1 mm.

[0082] Alternatively, the block-type sulfur-containing polyimide resin particles were replaced with the random sulfur-containing polyimide resin particles prepared in Example 1 to obtain a random sulfur-containing polyimide resin film. TEM images of both films were measured, as shown below. Figure 3 As shown.

[0083] Figure 3 In the figures, (a) shows a random sulfur-containing polyimide resin film, and (b) shows a block copolymer sulfur-containing polyimide resin film. The determination method is as follows: The sulfur-containing polyimide resin film was placed in a 0.5 mol / L AgNO3 aqueous solution overnight, rinsed with water, and dried at room temperature for 12 hours. The treated film was embedded in epoxy resin, cut into 70 nm thick slices using an ultramicrotome, and then observed under a transmission electron microscope (TEM). In TEM, the darker areas represent hydrophilic phase segments, and the brighter areas represent hydrophobic phase segments. In the random copolymer (a), the ion clusters are relatively small (<10 nm, average 4-5 nm), while in the block copolymer (b), the ion clusters are significantly larger (>40 nm), indicating the formation of microphase separation between a hydrophilic phase (containing sulfonic acid groups) and a hydrophobic phase (without sulfonic acid groups), but no obvious gray band was observed.

[0084] Take 1.5g of the block-type sulfur-containing polyimide film prepared above and add it to 50mL of silver ion solution containing 2mg / L. Place it on a shaker and shake for 30 minutes. Take out the film and measure the concentration of silver ions in the solution to be 0.189mg / L. The removal rate of silver ions is 90.6%.

[0085] The membrane with adsorbed silver ions was placed in 15 mL of 1 mol / L hydrochloric acid solution containing 10% thiourea and desorbed by ultrasonic vibration for 30 minutes. After centrifugation, the supernatant was analyzed, and the desorption rate of silver ions was found to be 89.2%. The centrifuged membrane was then washed with 3 mol / L hydrochloric acid to complete membrane regeneration.

[0086] 1.5 g of the regenerated membrane was added to 50 mL of a 2 mg / L silver ion solution, and the mixture was shaken on a shaker for 30 minutes. The membrane was then removed, and the concentration of silver ions in the treated solution was measured to be 0.196 mg / L, indicating a silver ion removal rate of 90.2%. The silver adsorption capacity of the regenerated resin was not significantly different from that before regeneration.

[0087] After adsorption and regeneration using the above method for a total of 10 times, the removal rate of silver ions is still above 85.5%.

[0088] Example 6

[0089] The sulfur-containing diamine monomer 2,2'-di(sulfonyl)-4,4'-diaminodiphenyl ether (ODADS) and the sulfur-free diamine monomer 4,4'-diaminodiphenyl ether (ODA) were fed into the reaction at a molar ratio of 8:2. The reaction was carried out according to the preparation method of block sulfur-containing polyimide to obtain block sulfur-containing polyimide resin particles.

[0090] In a nitrogen-protected, nitrogen-protected, three-necked flask, sulfonated diamine ODADS (0.9318 g, 2.45 mmol), triethylamine (0.5956 g, 5.88 mmol), and 20 mL of m-cresol were added. The mixture was stirred until the ODADS was completely dissolved. Then, thioether naphthalene dianhydride (SBNTA) (1.0158 g, 2.38 mmol) and benzoic acid (0.4365 g, 3.57 mmol) were added. The mixture was stirred at room temperature for 30 minutes, then heated to 80 °C for 4 hours and then to 180 °C for 18 hours to obtain amine-terminated polyimide oligomers. In another nitrogen-protected, nitrogen-protected, two-necked flasks, the remaining naphthalene dianhydride (SBNTA) (0.2902 g, 0.68 mmol) and 5 mL of m-cresol were added and stirred until dissolved. Then, unsulfonated diamine ODA (0.1217 g, 0.61 mmol) and benzoic acid (0.1155 g, 0.95 mmol) were added, and the mixture was reacted at 180 °C for 18 h. After the mixture in both flasks cooled to 80 °C, it was transferred to flask 1, and the reaction mixture was reacted at 80 °C for 4 h and then at 180 °C for 18 h. After the mixture in the reaction flasks cooled to 80 °C, it was poured into 500 mL of acetone to obtain a fibrous polymer. After washing once with acetone, it was extracted with acetone in a Soxhlet extractor for 20 h, and then dried in a vacuum oven at 150 °C for 24 h to obtain a triethylamine salt polymer of sulfonated polyimide.

[0091] Take 0.5g of the block-type sulfur-containing polyimide resin particles prepared above, add them to 50mL of silver ion solution with a concentration of 2mg / L, place them in a vortex shaker and shake for 30 minutes, centrifuge to remove the resin particles, and measure the concentration of silver ions in the solution after treatment to be 0.143mg / L, with a silver ion removal rate of 92.8%.

[0092] The resin particles adsorbed with silver ions were placed in 50 mL of a 1 mol / L hydrochloric acid solution containing 10% thiourea and desorbed by vortexing for 60 minutes. After centrifugation, the supernatant was analyzed, and the desorption rate of silver ions was found to be 88.2%. The centrifuged resin particles were then washed with 3 mol / L hydrochloric acid and dried at 100°C to complete resin regeneration.

[0093] 0.5 g of the regenerated resin was added to 50 mL of a 2 mg / L silver ion solution, shaken on a shaker for 30 minutes, and centrifuged to remove resin particles. The concentration of silver ions in the treated solution was measured to be 0.149 mg / L, and the silver ion removal rate was 92.5%. The silver adsorption capacity of the regenerated resin was not significantly different from that before regeneration.

[0094] Example 7

[0095] The sulfur-containing diamine monomer 2,2'-di(sulfonyl)-4,4'-diaminodiphenyl ether (ODADS) and the sulfur-free diamine monomer 4,4'-diaminodiphenyl ether (ODA) were fed into the reaction at a molar ratio of 2:8. The reaction was carried out according to the preparation method of block-type sulfur-containing polyimide to obtain block-type sulfur-containing polyimide resin particles.

[0096] In a nitrogen-protected, nitrogen-protected, three-necked flask, sulfonated diamine ODADS (0.2194 g, 0.61 mmol), triethylamine (0.1481 g, 1.46 mmol), and 4 mL of m-cresol were added. The mixture was stirred until the ODADS was completely dissolved. Then, thioether naphthalene dianhydride (SBNTA) (0.2433 g, 0.57 mmol) and benzoic acid (0.1085 g, 0.89 mmol) were added. The mixture was stirred at room temperature for 30 minutes, then heated to 80 °C for 4 hours and then to 180 °C for 18 hours to obtain amine-terminated polyimide oligomers. In another nitrogen-protected, nitrogen-protected, two-necked flasks, the remaining naphthalene dianhydride (SBNTA) (1.0586 g, 2.5 mmol) and 16 mL of m-cresol were added and stirred until dissolved. Then, unsulfonated diamine ODA (0.4908 g, 2.46 mmol) and benzoic acid (0.4648 g, 3.82 mmol) were added, and the mixture was reacted at 180 °C for 18 h. After the mixture in both flasks cooled to 80 °C, it was transferred to flask 1, and the reaction mixture was reacted at 80 °C for 4 h and then at 180 °C for 18 h. After the mixture in the flasks cooled to 80 °C, it was poured into 500 mL of acetone to obtain a fibrous polymer. After washing once with acetone, it was extracted with acetone in a Soxhlet extractor for 20 h, and then dried in a vacuum oven at 150 °C for 24 h to obtain a triethylamine salt polymer of sulfonated polyimide.

[0097] Take 0.5g of the resin particles prepared above and add them to 50mL of silver ion solution with a concentration of 2mg / L. Place the solution in a shaker and shake for 30 minutes. Centrifuge to remove the resin particles. The concentration of silver ions in the solution after treatment is 0.151mg / L, and the removal rate of silver ions is 92.4%.

[0098] The resin particles adsorbed with silver ions were placed in 10 mL of 1 mol / L hydrochloric acid solution containing 10% thiourea and desorbed by ultrasonic vibration for 30 minutes. After centrifugation, the supernatant was analyzed, revealing a silver ion desorption rate of 89.6%. The centrifuged resin particles were then washed with 3 mol / L hydrochloric acid and dried at 100°C to complete resin regeneration.

[0099] 0.5 g of the regenerated resin was added to 50 mL of a 2 mg / L silver ion solution, shaken on a shaker for 30 minutes, and centrifuged to remove resin particles. The concentration of silver ions in the treated solution was measured to be 0.155 mg / L, and the silver ion removal rate was 92.2%. The silver adsorption capacity of the regenerated resin was not significantly different from that before regeneration.

[0100] Example 8

[0101] The molar ratio of sulfur-containing diamine monomer to sulfur-free diamine monomer was set to 6:4 for the reaction. The reaction was carried out according to the preparation method of block-type sulfur-containing polyimide in Example 2 to obtain block-type sulfur-containing polyimide resin particles.

[0102] Take 0.5g of the resin particles prepared above and add them to 50mL of an acidic silver ion solution with a concentration of 2mg / L and pH=1. Shake on a shaker for 30 minutes, then centrifuge to remove the resin particles. The concentration of silver ions in the treated solution is measured to be 0.152mg / L, and the silver ion removal rate is 92.4%. Compared with the data in Example 1, it can be seen that the adsorption performance of the sulfur-containing polyimide resin particles is not affected in the acidic solution.

[0103] Example 9

[0104] The molar ratio of sulfur-containing diamine monomer to sulfur-free diamine monomer was set to 6:4 for the reaction. The reaction was carried out according to the preparation method of block-type sulfur-containing polyimide in Example 2 to obtain block-type sulfur-containing polyimide resin particles.

[0105] Take 0.5g of the resin particles prepared above and add them to 50mL of silver ion solution with a concentration of 2mg / L. Shake the solution in a 95℃ water bath for 30 minutes, then centrifuge to remove the resin particles. The concentration of silver ions in the treated solution is measured to be 0.135mg / L, and the silver ion removal rate is 93.2%. Compared with the data in Example 1, it can be seen that the adsorption performance of sulfur-containing polyimide resin particles is not affected under high temperature conditions.

Claims

1. An application of a sulfur-containing polyimide resin as a silver adsorbent, wherein the sulfur-containing polyimide resin is a random sulfur-containing polyimide resin or a block sulfur-containing polyimide resin, the structural formula of the random sulfur-containing polyimide resin is shown in Formula I, and the structural formula of the block sulfur-containing polyimide resin is shown in Formula II. I II in, m, n, and x are integers from 1 to 1000.

2. The application as described in claim 1, characterized in that... The sulfur-containing polyimide resin is sulfur-containing polyimide resin particles or sulfur-containing polyimide resin film, wherein the sulfur-containing polyimide resin film is prepared by forming a film from sulfur-containing polyimide resin particles.

3. The application as described in claim 2, characterized in that... The sulfur-containing polyimide resin particles are random sulfur-containing polyimide resin particles or block sulfur-containing polyimide resin particles, and the sulfur-containing polyimide resin film includes random sulfur-containing polyimide resin film or block sulfur-containing polyimide resin film, which are respectively prepared from random sulfur-containing polyimide resin particles or block sulfur-containing polyimide resin particles.

4. The application as described in claim 3, characterized in that... The random sulfur-containing polyimide resin particles were prepared by the following method: Under nitrogen protection, 2,2'-di(sulfonyl)-4,4'-diaminodiphenyl ether, triethylamine and m-cresol were mixed and stirred until 2,2'-di(sulfonyl)-4,4'-diaminodiphenyl ether was completely dissolved. Then, 4,4'-diaminodiphenyl ether, thioether naphthalene dihydric anhydride and benzoic acid were added. This mixture was stirred at room temperature for 30 minutes, then heated to 80°C and reacted for 4 hours, then heated to 180°C and reacted for 18 hours. After cooling to 80°C, the mixture was poured into acetone to obtain fibrous polymer. After washing with acetone, the polymer was extracted with acetone in a Soxhlet extractor for 20 hours and dried in a vacuum oven at 150°C for 24 hours to obtain random sulfur-containing polyimide resin particles.

5. The application as described in claim 3, characterized in that... The block-type sulfur-containing polyimide resin particles are prepared by the following method: (1) Under nitrogen protection, 2,2'-bis(sulfonyl)-4,4'-diaminodiphenyl ether, triethylamine and m-cresol A were mixed and stirred until 2,2'-bis(sulfonyl)-4,4'-diaminodiphenyl ether was completely dissolved. Then, thioether naphthalene dihydride A and benzoic acid A were added. The mixture was stirred at room temperature for 30 minutes, then heated to 80°C and reacted for 4 hours, followed by reaction at 180°C for 18 hours to obtain amino-terminated polyimide oligomers; (2) Add thioether naphthalene dihydride B and m-cresol B under nitrogen protection, stir to dissolve, then add 4,4'-diaminodiphenyl ether and benzoic acid B, react at 180°C for 18 h to obtain anhydride-terminated polyimide oligomer. (3) When the mixture of steps (1) and (2) is cooled to 80°C, the mixture of step (2) is added to the mixture of step (1), and the reaction solution is reacted at 80°C for 4 hours and at 180°C for 18 hours. When cooled to 80°C, it is poured into acetone to obtain fibrous polymer. After washing with acetone, it is extracted with acetone in a Soxhlet extractor for 20 hours and dried in a vacuum oven at 150°C for 24 hours to obtain block-type sulfur-containing polyimide resin particles.

6. The application as described in claim 2, characterized in that... The sulfur-containing polyimide resin film was prepared by the following method: sulfur-containing polyimide resin particles were dissolved in m-cresol with a solid content of 10% to obtain a homogeneous and viscous solution. The solution was coated onto a clean glass plate and cast into a film. The film was then baked in an oven at 80°C for 12 hours, and then heated to 120°C for another 12 hours. After natural cooling to room temperature, the glass plate was placed in ethanol to allow it to peel off naturally. The film was then immersed in ethanol for 48 hours. After removal, the film was thoroughly washed with deionized water and then immersed in a 2 mol / L hydrochloric acid solution for 72 hours to completely protonate the film. Finally, the film was removed to obtain the sulfur-containing polyimide resin film. The film was thoroughly washed with deionized water and then stored in water for later use.

7. The application as described in claim 1 or 2, characterized in that... The application of the block-type sulfur-containing polyimide resin as a silver adsorbent.

8. The application as described in claim 1, characterized in that... The method of application is as follows: add sulfur-containing polyimide resin particles or sulfur-containing polyimide resin films to the solution to be treated containing silver ions, shake on a shaker for 10 minutes to 2 hours or vortex for 10 to 30 minutes, remove the resin particles or resin films, and obtain the treated solution.

9. The application as described in claim 8, characterized in that... The sulfur-containing polyimide resin adsorbs silver and is then desorbed and regenerated for reuse.

10. The application as described in claim 9, characterized in that... The regeneration method of the sulfur-containing polyimide resin is as follows: the sulfur-containing polyimide resin particles or films adsorbed with silver are placed in a 1 mol / L hydrochloric acid solution containing 10% thiourea by mass, and desorption is performed by ultrasonic vibration or vortex vibration for 10-60 minutes. Then, the resin particles are obtained by centrifugation or filtration, or the resin film is directly removed. The obtained particles or films are soaked and washed with a 3 mol / L hydrochloric acid solution, and then dried at 100°C to obtain the regenerated sulfur-containing polyimide resin particles or films.

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