Cross-linked polystyrene-vinylpyridine copolymers and their preparation and application in metal-catalyzed organic reactions

Abstract

A cross-linked polystyrene-vinylpyridine copolymer, its preparation, and application in metal-catalyzed organic reactions. The copolymer is synthesized in a one-step process using styrene and 4-vinylpyridine as monomers, divinylbenzene as a cross-linking agent, potassium persulfate (K2S2O8) as an initiator, and water as a solvent. The copolymer is inexpensive and easy to prepare, and can quickly and effectively adsorb noble metal ions from complex solutions as a solid-phase adsorbent. Furthermore, the adsorbent can be desorbed by a solvent, and the noble metal-loaded adsorbent can also be directly used in organic catalytic reactions, achieving secondary utilization of the noble metal.

Description

Technical Field

[0001] The present invention relates to the technical field of materials and organic chemical synthesis, and in particular to a cross-linked polystyrene-vinylpyridine copolymer (PS-r-P4VP) capable of efficiently recovering precious metals, as well as its preparation and application in metal-catalyzed organic reactions. Background Art

[0002] Precious metals (gold, silver, and platinum group metals) and their compounds have excellent chemical stability, leading to their widespread application in the electronics industry, energy conversion, organic catalysis, biomedicine, and other fields. The natural abundance of platinum group elements such as platinum, palladium, ruthenium, rhodium, and iridium is far lower than that of gold and silver. With the rapid upgrading of products in various fields, the demand for platinum group precious metals is outstripping supply. However, the natural reserves of precious metals are very limited, leading to increasing attention on how to recover platinum group precious metals from discarded secondary resources. Industrial electronic waste and spent catalysts account for a significant proportion of secondary precious metal resources. Currently, commonly used methods for precious metal recovery include solution leaching, redox methods, and solid-phase adsorption. Solid-phase adsorption does not require large amounts of organic solvents and other chemicals and is considered the most environmentally friendly, efficient, and economical method for precious metal recovery. The most studied solid-phase adsorbents include porous metal-organic frameworks (MOFs), polymers and their composites, biosorbents, and porous hydrogels. These adsorbents have common characteristics: large specific surface area, stable chemical properties, and nitrogen- or sulfur-containing functional groups that interact with precious metal compounds.

[0003] Despite the complexity and diversity of solid-phase adsorption technologies for precious metals, desorption of adsorbed precious metal ions from solid-phase adsorbents to achieve direct recovery and reuse remains a significant concern. Literature research indicates that commonly used desorption solvents include thiourea in hydrochloric acid, mixed solutions of nitric acid and hydrochloric acid, or hydrochloric acid solutions of Na₂S₂O₃ or KSCN. Desorption of solid-phase adsorbents requires strong acid solutions and the introduction of large amounts of chemicals such as thiourea and KSCN, which hinders the true recovery and reuse of precious metal ions.

[0004] Pyridine is a six-membered heterocyclic compound containing a nitrogen heteroatom. The lone pair of electrons on the pyridine nitrogen atom and the π electrons on the six-membered ring determine the ability of the pyridine compound to coordinate with metals. In organic synthetic chemistry, pyridine compounds are often used as ligands to coordinate with metal catalysts to catalyze organic reactions. Weakly basic pyridine compounds can be protonated under acidic conditions, making the pyridine ring positively charged. Palladium chloride (PdCl2) can be protonated in hydrochloric acid solution, usually as PdCl3 - and PdCl4 2-Therefore, compounds containing pyridine groups can interact with Pd(II) in hydrochloric acid solution through coordination and ion exchange to form pyridine metal complexes, which can achieve the adsorption and recovery of Pd(II).

[0005] Existing methods for preparing precious metal adsorbents such as MOFs have problems such as poor stability. For example, patent publication number CN113663648A discloses "A post-synthesis modified MOF material adsorbent, preparation method and application thereof". The MOF adsorbent material that can adsorb and recover palladium ions is obtained through post-synthesis modification. The preparation process is relatively complex and the production cost is high, which is not conducive to large-scale production. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a cross-linked polystyrene-vinylpyridine copolymer (PS-r-P4VP) that can efficiently recover precious metals, as well as its preparation and application in metal-catalyzed organic reactions. The copolymer uses styrene and 4-vinylpyridine as monomers, divinylbenzene as a cross-linking agent, potassium persulfate (K2S2O8) as an initiator, and water as a solvent. It is synthesized in a one-step process and has the characteristics of being cheap and easy to prepare. It is a solid-phase adsorbent that can quickly and effectively adsorb precious metal ions from complex solutions. This adsorbent can not only be desorbed by solvent, but the adsorbent loaded with precious metals can also be directly used in organic catalytic reactions, thereby realizing the secondary utilization of precious metals.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] Cross-linked polystyrene-vinylpyridine copolymer, its general chemical formula is: PS-r-P4VP; structural formula is:

[0009]

[0010] The preparation method of a cross-linked polystyrene-vinylpyridine copolymer comprises the following steps: using a precipitation polymerization method, styrene and 4-vinylpyridine as monomers, divinylbenzene as a cross-linking agent, potassium persulfate (K2S2O8) as an initiator, and water as a solvent, to synthesize a polymer styrene-4-vinylpyridine (PS-r-P4VP) copolymer in a one-step process, and the reaction formula is as follows:

[0011]

[0012] The molar ratio of styrene to 4-vinylpyridine is 1:(2-5).

[0013] The application of cross-linked polystyrene-vinylpyridine copolymer in metal-catalyzed organic reactions can effectively adsorb and recover precious metal ions in acidic solutions.

[0014] Cross-linked polystyrene-vinylpyridine copolymers are able to selectively capture noble metal ions in the presence of other interfering metal ions.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The PS-r-P4VP copolymer prepared by the present invention has excellent solvent resistance, acid and alkali resistance, and thermal stability, and the preparation method is simple to operate, has high preparation efficiency, and low production cost; the polymer adsorbent with a PS to P4VP molar ratio of 1: (2-5) has a high adsorption capacity for platinum group precious metals, can quickly reach adsorption equilibrium at room temperature, and responds quickly to precious metals.

[0017] (2) The polymer adsorbent for recovering precious metals of the present invention can be directly applied to precious metal-catalyzed organic reactions without desorption, such as palladium-catalyzed Suzuki coupling reaction, Sonogashira reaction, Heck reaction, Kumada coupling reaction, Buchwald-Hartwig coupling, Hiyama coupling, hydrogenation reaction, etc.; the polymer adsorbent adsorbed with precious metals can realize the reuse of the catalyst and still maintain catalytic activity, which can maximize the utilization rate of precious metal catalysts and solve the problem of recycling and reuse of precious metal catalysts in industry.

[0018] (3) The PS-r-P4VP copolymer designed and prepared in the present invention can selectively capture platinum group noble metals such as Au(III), Rh(II), Ru(II) and Pd(II) in a multi-metal mixed system. The adsorption mechanism involves ion exchange, coordination and redox. Therefore, it has the characteristics of selectively capturing noble metal ions.

[0019] In summary, compared with the prior art, the present invention uses styrene and 4-vinylpyridine as monomers and is synthesized in a one-step process. It is cheap and easy to prepare, and can quickly and effectively adsorb precious metal ions from complex solutions. It can also selectively capture precious metal ions in the presence of other interfering metal ions. Moreover, this adsorbent can not only be desorbed by solvent, but the adsorbent loaded with precious metals can also be directly used in organic catalytic reactions, realizing the secondary utilization of precious metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Flow chart of the adsorption of Pd(II) by PS-r-P4VP copolymer and its direct catalytic organic reaction.

[0021] Figure 2 The optimization of the optimal adsorption conditions of Pd(II) by PS-r-P4VP is shown in Figure 2. Figure 2(a) The effect of the ratio of pyridine groups in the adsorbent on the adsorption of Pd(II) was verified (pH = 1, adsorption time 2 h, adsorption temperature at room temperature); Figure 2 (b) The effect of solution pH on Pd(II) adsorption was verified (adsorption time 2 h, room temperature, PS:P4VP=1:3, adsorbent dosage 50 mg); Figure 2 (c) Effect of adsorption time (pH = 1, room temperature, PS:P4VP = 1:3, adsorbent dosage 50 mg); Figure 2 (d) is the temperature (pH = 1, adsorption time is 2 hours, PS:P4VP = 1:3); the above Pd (II) solutions are all 25 mL, with a concentration of 1 mg / mL.

[0022] Figure 3 is the adsorption efficiency of Pd(II) after five repeated adsorptions of PS-r-P4VP copolymer after desorption.

[0023] Figure 4 shows that PS-r-P4VP copolymer adsorbs Pd(II) and acts as a palladium catalyst to catalyze organic reactions.

[0024] Figure 5 20 Suzuki coupling reactions of PS-r-P4VP copolymer oxidized by potassium persulfate (K2S2O8) and supported on Pd(II) catalyst.

[0025] Figure 6 The adsorption of RuCl3 by PS-r-P4VP copolymer.

[0026] Figure 7 The adsorption of Rh2(CH3COO)4 by PS-r-P4VP copolymer.

[0027] Figure 8 The adsorption of HAuCl4 by PS-r-P4VP copolymer.

[0028] Figure 9 The PS-r-P4VP copolymer exhibits selective adsorption of Rh(II), Ru(II) and Pd(II). DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the embodiments.

[0030] Example 1

[0031] Preparation of cross-linked polystyrene-4-vinylpyridine copolymer (PS:P4VP=1:3) by the following specific steps:

[0032] 440 mg (1.6 mmol) of K₂S₂O₈ and 80 mg of hydroxyethyl cellulose were weighed into a 250 mL three-necked flask. 160 mL of deionized water was sparged with nitrogen to remove dissolved oxygen. The sparged 160 mL of deionized water was then added to the 250 mL three-necked flask, and nitrogen was continued to be purged to remove oxygen. The mixture was stirred at room temperature for 30 minutes to ensure complete dissolution of the K₂S₂O₈ and hydroxyethyl cellulose. 2.08 g (20 mmol) of styrene, 6.31 g (60 mmol) of 4-vinylpyridine, and 1.04 g (8 mmol) of divinylbenzene were weighed and added to the three-necked flask. The mixture was then reacted at 80°C under nitrogen for 24 hours. After the reaction, a white solid was observed in the three-necked flask. After cooling to room temperature, the solid was filtered and washed with a large amount of deionized water and anhydrous ethanol to remove unreacted monomers and other impurities. Finally, the solid was dried in a vacuum drying oven at 80°C and ground to obtain 8.9 g of cross-linked polystyrene-4-vinylpyridine copolymer powder with a yield of 94%.

[0033] The synthesis method of copolymers with other ratios can be achieved by simply changing the feed ratio of different monomers, that is, adjusting the molar ratio of styrene to 4-vinylpyridine to between 1:(2-5).

[0034] Example 2

[0035] Based on the product obtained in Example 1, the effect of adsorption conditions on the adsorption effect of precious metal palladium was tested. The specific steps are as follows:

[0036] 1. Effect of pH value on adsorption effect: In a 40mL centrifuge tube, prepare 25mL of hydrochloric acid aqueous solution with different pH values, add 25mg PdCl2 to the centrifuge tube to obtain 1.0mg / mL PdCl2 hydrochloric acid solution with different pH values. Add 100mg PS-r-P4VP (PS:P4VP=1:3) polymer adsorbent to verify the effect of different pH values ​​on the adsorption effect of PS-r-P4VP adsorbent. The adsorption experiment was carried out in a constant temperature oscillator and oscillated at room temperature for 3 hours. After complete adsorption, the adsorbent was separated by centrifugation. Take the supernatant, remove the residual solids with a filter membrane with a pore size of 0.22μm, and test the absorbance of the supernatant with a UV-visible absorption spectrometer. The value represents the change in the metal ion content in the acidic solution. The experimental results are as follows. Figure 2 (b) shown.

[0037] 2. Effects of pyridine group content, adsorbent dosage, adsorption time and temperature on adsorption effect: PdCl2 solution with pH 1 and concentration of 1.0 mg / mL was prepared to verify the adsorption effect of different pyridine group contents and different adsorbent dosages ( Figure 2 (a)), adsorption time ( Figure 2 (c)) and adsorption temperature ( Figure 2(d) The effect of the adsorption performance of the PS-r-P4VP adsorbent. Adsorption experiments were conducted in a thermostatic oscillator at room temperature for 3 hours. After complete adsorption, the adsorbent was separated by centrifugation. The supernatant was filtered through a 0.22 μm pore size membrane to remove residual solids, and the absorbance of the supernatant was measured using a UV-visible absorption spectrometer. The absorbance value represents the change in the metal ion content in the acidic solution.

[0038] Based on the above experimental results, it was concluded that the PS-r-P4VP (PS:P4VP=1:3) polymer adsorbent can rapidly adsorb Pd(II) from acid solution at pH=1 within 30 minutes at room temperature, with an adsorption capacity of 622 mg / g.

[0039] The experimental steps of the palladium chloride desorption experiment (PS:P4VP=1:3) are as follows: prepare 25mL of PdCl2 hydrochloric acid solution with a pH=1 and a concentration of 1.0mg / mL, and add 50mg of PS-r-P4VP (PS:P4VP=1:3) polymer microsphere adsorbent. The adsorption experiment was carried out in a constant temperature oscillator at room temperature and a rotation speed of 150rpm. After 3 hours of adsorption, all PdCl2 in the solution was adsorbed by the adsorbent. After the adsorption was completed, 76mg of thiourea was added to the centrifuge tube to form a 0.04M thiourea-0.1M hydrochloric acid aqueous solution for desorption. Continue shaking on the constant temperature shaking flask for 12 hours. After desorption, the solution was centrifuged and filtered, and the obtained adsorbent was washed three times with a 0.04M thiourea-0.1M hydrochloric acid aqueous solution, and then washed three times with anhydrous ethanol to remove any residual thiourea. After drying for 6 hours, the obtained adsorbent was subjected to the next PdCl2 adsorption test, and five cycles were repeated. The experimental results are as follows. Figure 3 shown.

[0040] In summary, the polymer adsorbent with a molar ratio of PS to P4VP of 1:(2-5) has a high adsorption capacity for precious metal palladium, can quickly reach adsorption equilibrium within 30 minutes at room temperature, responds quickly to precious metals, and has simple preparation methods, high preparation efficiency, and low production costs. The polymer adsorbent can be desorbed and recycled, realizing the green concept of maximizing economic utilization and sustainable development.

[0041] Precious metals are often used as catalysts in organic reactions. However, their natural abundance is very limited, making efficient recovery and secondary utilization of precious metals a hot research topic. This invention directly applies recovered precious metals to organic reaction catalysis, enabling the realization of multiple precious metal-catalyzed organic reactions.

[0042] The application of cross-linked polystyrene-vinylpyridine copolymer in metal-catalyzed organic reaction specifically comprises the following steps:

[0043] Aqueous hydrochloric acid solutions of various precious metals with specific pH values, concentrations, and volumes were prepared, and a PS-r-P4VP polymer adsorbent was added to recover the precious metals from the acid solution. Adsorption experiments were conducted in a thermostatic oscillator, oscillating at room temperature for 3 hours. After complete adsorption, the adsorbent was centrifuged. The supernatant was collected, and residual solids were removed using a 0.22 μm pore size filter membrane. The absorbance of the supernatant was measured using a UV-Vis absorption spectrometer, and the absorbance value indicated the change in metal ion content in the acid solution. The precious metal-loaded adsorbent obtained by centrifugation was filtered, washed, and dried to obtain a precious metal catalyst, which can be directly used as a catalyst for organic reactions such as Heck, Sonogashira, Buchwald-Hartwig, Kumada coupling, and Miyaura boronesterification reactions. According to embodiments of the present invention, palladium-catalyzed Suzuki coupling reactions produce a large amount of palladium black after completion, significantly reducing catalytic activity. The present invention uses potassium persulfate (K2S2O8) as an oxidant, which can reoxidize the palladium black to divalent palladium in the acid solution, which can continue to catalyze organic reactions, enabling catalyst reuse.

[0044] Test of the catalytic performance of PS-r-P4VP-Pd(II) in organic reactions

[0045] Heck reaction: 94.5 mg of PS-r-P4VP-PdCl2 powder (containing 18.0 mg of PdCl2, 0.1 mmol) and 52.4 mg of PPh3 were added to a 25 mL two-necked flask, followed by 10 mL of DMF as solvent. Subsequently, 314.0 mg (2.0 mmol) of bromobenzene, 313 mg (3.0 mmol) of styrene, and 450 mg (4.0 mmol) of NaHCO3 were added in sequence, and the mixture was reacted at 135°C under nitrogen for 12 hours. After completion of the reaction, the catalyst was recovered by filtration, the filtrate was extracted with DCM, and the organic phase was dried over anhydrous Na2SO4. The product was concentrated and separated by column chromatography, with petroleum ether as the eluent. The yield was 56%. The reaction equation is shown in Figure 4(a).

[0046] Sonogashira reaction: 18.7 mg of PS-r-P4VP-PdCl2 powder (containing 3.55 mg of PdCl2, 0.02 mmol) was added to a 10 mL sealed tube. Then, under a nitrogen atmosphere, 2.5 mL of deionized water was added as the solvent. Then, 408 mg (2.0 mmol) of iodobenzene, 245 mg (2.4 mmol) of phenylacetylene, and 0.83 mL (10 mmol) of tetrahydropyrrole were added in sequence, and the reaction was allowed to proceed at room temperature for 24 hours. After completion of the reaction, the catalyst was recovered by filtration, the filtrate was extracted with dichloromethane, and the organic phase was dried over anhydrous Na2SO4. The concentrated product was separated by column chromatography, and the eluent was petroleum ether. The yield was 81%. The reaction equation is shown in Figure 4(b).

[0047] Suzuki coupling reaction: 20 mg of PS-r-P4VP-PdCl2 powder (containing 3.6 mg of PdCl2, 0.02 mmol) and 11 mg of PPh3 were added to a 25 mL single-necked flask, followed by 5.0 mL of toluene as solvent. 204 mg (1.0 mmol) of iodobenzene, 204 mg (1.5 mmol) of o-methylphenylboronic acid, and 276 mg (2.0 mmol) of K2CO3 were then added in sequence. The mixture was reacted at 85°C in an air atmosphere for 12 hours. After completion of the reaction, the catalyst was recovered by filtration, dried, and reused. The filtrate was evaporated to remove anhydrous ethanol, extracted with dimethyl methyl ether, and the organic phase was dried over anhydrous Na2SO4. The concentrated product was separated by column chromatography, with petroleum ether as the eluent, yielding 98%. The reaction equation is shown in Figure 4(c).

[0048] Buchwald-Hartwig coupling reaction: Weigh 190 mg (1.12 mmol) of diphenylamine, 21.2 mg of PS-r-P4VP-PdCl2 (containing 3.97 mg of PdCl2, 0.0224 mmol), and 12.5 mg (0.0448 mmol) of tricyclohexylphosphine into a 10 mL sealed tube. Purge the system three times to remove oxygen. Dissolve 212 mg (1.68 mmol) of p-chlorotoluene in 1 mL of toluene and quickly add to the sealed tube. Weigh 215 mg (2.24 mmol) of sodium tert-butoxide in 4 mL of toluene and slowly add dropwise to the sealed tube at room temperature. After the addition is complete, heat to 120°C and maintain for 12 hours. After the reaction, filter and recover the catalyst. The filtrate is extracted with DCM, and the organic phase is dried over anhydrous Na2SO4. The concentrated product was separated by chromatographic column, and the eluent was petroleum ether, with a yield of 54%. The reaction equation is shown in Figure 4(d).

[0049] Kumada coupling reaction: PS-r-P4VP-PdCl2 (containing 8.9 mg PdCl2, 0.05 mmol) and 28 mg (0.1 mmol) of tricyclohexylphosphine in diethyl ether were added to a solution of 4-phenyl-gem-difluorostyrene (1 mmol). A THF solution (5.0 mmol) of Grignard reagent was added dropwise under N2 atmosphere at room temperature. The mixture was reacted at reflux temperature for 12 hours. After completion of the reaction, the reaction mixture was quenched with saturated aqueous NH4Cl solution (5 mL) and extracted with ethyl acetate (3×10 mL). The combined organic layers were washed with water and brine, then dried over anhydrous Na2SO4, filtered, and concentrated in vacuo. The crude residue was then purified by silica gel column chromatography using n-hexane as the eluent to obtain the pure target compound in 60% yield. The reaction equation is shown in Figure 4(e).

[0050] Miyaura boronate esterification: To a solution of 2-bromonaphthalene (1 mmol) in DMSO (10 mL) were added 19 mg of PS-r-P4VP-PdCl2 (containing 3.55 mg of PdCl2, 0.02 mmol), 19 mg (0.04 mmol) of 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (Xphos), and 216 mg (2.2 mmol) of anhydrous potassium acetate. The mixture was reacted at 80°C under a nitrogen atmosphere for 12 hours. After completion of the reaction, the solids were removed by filtration, and the reaction mixture was extracted with ethyl acetate (3 × 15 mL). The organic layer was washed with water and saturated brine, then dried over anhydrous Na2SO4, filtered, and concentrated in vacuo. Purification by silica gel column chromatography using a mixture of petroleum ether and ethyl acetate (40:1) as the eluent afforded the pure target compound in a 77% yield. The reaction equation is shown in Figure 4(f).

[0051] Suzuki coupling reaction catalyst recovery experiment: 176 mg of PS-r-P4VP-PdCl2 powder (containing 32 mg of PdCl2, 0.18 mmol) and 100 mg of PPh3 (0.36 mmol) were added to a 100 mL single-necked flask, followed by the addition of 30 mL of anhydrous ethanol as solvent. Subsequently, 1.57 g (9.0 mmol) of 4-bromofluorobenzene, 1.65 g (13.5 mmol) of phenylboronic acid, and 3.8 g (18.0 mmol) of K3PO4 were added in sequence. The reaction was allowed to proceed in air at 60°C for 4 hours. After completion of the reaction, the catalyst was recovered by filtration, dried, and reused. The filtrate was evaporated to remove the anhydrous ethanol, extracted with dichloromethane, and the organic phase dried over anhydrous Na2SO4. The product was concentrated and separated by column chromatography, with petroleum ether as the eluent. The recovered polymer catalyst (containing 0.18 mmol of Pd) was filtered, washed, and dried, and added to 90 mL of pH 1 hydrochloric acid solution and ultrasonically dispersed. 180 mg (0.67 mmol) of K2S2O8 was added to the hydrochloric acid solution as an oxidant, stirred at room temperature for 3 hours, filtered and dried to obtain the treated catalyst. The recovered catalyst was subjected to scale-down experiments according to the corresponding recovery rate ratio, and the Suzuki coupling reaction was repeatedly catalyzed under the same experimental conditions to verify the sustainable utilization of the catalyst. The results of the palladium catalyst reuse experiment are as follows: Figure 5 shown.

[0052] In summary, according to the results of Example 2, the polymer adsorbent for recovering precious metals of the present invention can be directly applied to precious metal-catalyzed organic reactions, without the need for desorption, such as palladium-catalyzed Suzuki coupling reactions, Sonogashira reactions, Heck reactions, Kumada coupling reactions, Buchwald-Hartwig coupling reactions, Hiyama coupling reactions, and hydrogenation reactions. The polymer adsorbent that has adsorbed precious metals can be oxidized to enable the reuse of the catalyst while still maintaining catalytic activity. This work can maximize the utilization rate of precious metal catalysts and solve the problem of precious metal catalyst recovery and reuse in industry.

[0053] Example 3

[0054] Universality of adsorption to other precious metals

[0055] Adsorption of ruthenium chloride (RuCl3) (such as Figure 6 shown).

[0056] In a 40 mL centrifuge tube, prepare 25 mL of RuCl₃ hydrochloric acid solution with a pH of 0 and a concentration of 0.1 mg / mL. Add the polymer adsorbent PS-r-P4VP (PS:P-4VP = 1:3) to verify the effect of different adsorbent dosages on RuCl₃ adsorption. The adsorption experiment was performed in a constant temperature, constant speed oscillator at 150 rpm for 12 hours at room temperature. After adsorption, the mixture was centrifuged at 15,000 rpm for 15 minutes. The supernatant was aspirated and filtered through a 0.22 μm pore size membrane to remove solids. The absorbance of the supernatant was measured using a UV-visible absorption spectrometer, representing the change in metal ion concentration in the acid.

[0057] Adsorption of hydrogen tetrachloroaurate (HAuCl4) (e.g. Figure 7 shown).

[0058] In a 40 mL centrifuge tube, prepare 25 mL of a 1.0 mg / mL HAuCl₄ hydrochloric acid solution at pH 1. PS-r-P4VP (PS:P4VP = 1:3) was added to verify the effect of varying adsorbent dosages on HAuCl₄ adsorption. Adsorption experiments were performed in a constant-temperature, constant-speed oscillator at 150 rpm for 12 hours at room temperature. After adsorption, the mixture was centrifuged at 15,000 rpm for 15 minutes. The supernatant was aspirated and filtered through a 0.22 μm pore size filter to remove solids. The absorbance of the supernatant, representing the change in metal ion content in the acid, was measured using a UV-Vis spectrometer.

[0059] Adsorption of rhodium acetate dimer (Rh2(CH3COO)4) (e.g. Figure 8 shown).

[0060] In a 40 mL centrifuge tube, 25 mL of a 2 mg / mL Rh2(CH3COO)4 hydrochloric acid solution with a pH of 1 was prepared. PS-r-P4VP (PS:P4VP = 1:3) was added to test the effect of different adsorbent dosages on Rh2(CH3COO)4 adsorption. Adsorption experiments were conducted in a thermostatic shaker at 150 rpm for 12 hours at room temperature. After adsorption, the mixture was centrifuged at 15,000 rpm for 15 minutes. The supernatant was aspirated and filtered through a 0.22 μm pore size membrane to remove solids. The absorbance of the supernatant, representing the change in metal ion content in the acid, was measured using a UV-visible absorption spectrometer.

[0061] Selective adsorption experiments of metal ions (such as Figure 9 shown).

[0062] A 60 mL mixed solution of 14 metal ions (FeCl₃, CuCl₂, CeCl₃, ZnCl₂, CoCl₂, CaCl₂, ZrCl₄, BaCl₂, MgCl₂, NiCl₂, CdCl₂, PdCl₂, RuCl₃, and Rh₂(CH₃COO)₄) was prepared at a pH of 1 and a concentration of 0.5 mg / mL. 10 mL of the mixed solution was reserved for analysis, and 300 mg of PS-r-P4VP (PS:P4VP = 1:3) polymer adsorbent was added to the remaining 50 mL of the mixed solution. Adsorption experiments were performed in a thermostatic oscillator at 150 rpm for 12 hours at room temperature. After adsorption, the solution was centrifuged at 15,000 rpm for 15 minutes. The supernatant was aspirated and filtered through a 0.22 μm pore size filter to remove solids. The concentrations of the various metal ions before and after adsorption were analyzed using inductively coupled plasma mass spectrometry (ICP-MS).

[0063] In summary, according to the results of Example 3, the PS-r-P4VP copolymer designed and prepared in the present invention can selectively recover platinum group precious metals such as Au(III), Rh(II), Ru(II) and Pd(II) in a multi-metal mixed system, and can maintain the dual advantages of efficient adsorption and selective adsorption under the interference of metal ions such as iron, copper and nickel.

Claims

1. Application of cross-linked polystyrene-vinylpyridine copolymer in adsorption of platinum group noble metal ions, characterized in that: Ability to selectively capture noble metal ions in acidic solutions in the presence of other interfering metal ions; The chemical formula of cross-linked polystyrene-vinylpyridine copolymer is: PS-r-P4VP; the structural formula is: The preparation method of the cross-linked polystyrene-vinylpyridine copolymer comprises the following steps: using precipitation polymerization, styrene and 4-vinylpyridine as monomers, divinylbenzene as a cross-linking agent, potassium persulfate K2S2O8 as an initiator, and water as a solvent, to synthesize the polymer styrene-4-vinylpyridine (PS-r - P4VP) copolymer, the reaction formula is as follows: The molar ratio of styrene to 4-vinylpyridine is 1:(2-5).

Images