A silsesquioxane hybrid fluorescent aerogel, its preparation method and application in recycling gold

Abstract

The application provides a silsesquioxane hybrid fluorescent aerogel, a preparation method thereof and application thereof in recycling gold. The silsesquioxane hybrid fluorescent porous polymer is prepared by using octavinylsilsesquioxane and 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyranyl-4-ylidene)propanedinitrile as raw materials, then the silsesquioxane hybrid fluorescent porous polymer is reacted with thiol-modified chitosan to obtain the silsesquioxane hybrid fluorescent aerogel. The fluorescent aerogel has high specific surface area and large pore volume, good chemical stability and thermal stability, improves the selectivity and adsorption rate of the adsorbent, can directly reduce Au 3+ into gold single element in one step, and gold single element can be extracted by a thiourea solution, and then gold is recycled, and has good application value in recycling of secondary resource precious metals.

Description

Technical Field

[0001] This invention belongs to the field of environmental materials synthesis technology, specifically relating to a silsesquioxane hybrid fluorescent aerogel, its preparation method, and its application in gold recovery. Background Technology

[0002] With the rapid development of the national economy and the continuous improvement of people's living standards, precious metals are increasingly widely used in industrial production and jewelry processing. Due to the limited geological reserves of precious metals, production is difficult and yields are low. However, recycling precious metals from secondary resources is a simple and low-cost process that can turn waste into treasure. Therefore, recycling precious metals not only avoids environmental pollution but also conserves resources, possessing significant environmental and economic value. Thus, from both the perspective of resource continuity and environmental protection, the recycling and utilization of secondary precious metal resources is of paramount importance.

[0003] Currently, methods for recovering gold from wastewater mainly include chemical precipitation, adsorption, ion exchange, and membrane separation. Chemical precipitation involves adding hydroxides or sulfides to react with gold ions to form insoluble metal precipitates. However, this method generates large amounts of sludge, easily causing secondary pollution, and is costly, making it suitable only for high-concentration solutions. Adsorption is a mass transfer process where substances move from a liquid phase to a solid surface, constrained by physical and chemical interactions. The adsorbent is the core of adsorption technology, directly affecting adsorption performance. However, current adsorbents generally suffer from low adsorption kinetics, poor selectivity, low adsorption capacity, and poor chemical stability, making efficient and rapid recovery of gold ions difficult. In ion exchange technology, ion exchange resins exchange cations with metal ions in wastewater without changing the resin's structure. However, suitable reagents are needed to elute and recover the metal. This method is not only costly but also generates secondary pollution. Membrane separation technology is a method of separating particles from a fluid by applying pressure to force the fluid through a porous membrane or filter. Currently, the separation efficiency of metal ions depends on the size of the ions that can be retained and the pore size of the membrane. However, if the pore size of the membrane is too small, it will seriously affect the water flux and make the subsequent metal purification process complicated.

[0004] In summary, all current technologies for recovering gold ions from wastewater have their limitations, and achieving rapid and green recovery of gold ions from wastewater remains extremely challenging. Recently, a photocatalytic reduction method combining adsorption and reduction has been proposed to improve selectivity and recovery efficiency. Among all adsorbents, fluorescent aerogels possess high catalytic activity, excellent adsorption capacity, and ease of synthesis, making them an excellent candidate for photocatalytic reduction materials.

[0005] Therefore, developing a fluorescent aerogel with excellent adsorption capacity, good chemical stability and thermal stability is of great significance for the efficient recovery of gold ions from wastewater. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a silsesquioxane-based hybrid fluorescent aerogel, its preparation method, and its application in gold recovery. This invention uses octavinylsilsesquioxane and 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-yl)malonitrile as raw materials to prepare a silsesquioxane-based hybrid fluorescent porous polymer. This polymer is then reacted with thiol-modified chitosan to obtain the silsesquioxane-based hybrid fluorescent aerogel. The silsesquioxane-based hybrid fluorescent aerogel of this invention possesses a high specific surface area and large pore volume, as well as good chemical and thermal stability. Its structural advantages significantly enhance the interaction between the adsorbent and the adsorbate, improving the selectivity and adsorption rate of the adsorbent. When applied to gold recovery, it can directly remove Au in one step. 3+ It can be reduced to elemental gold, and the elemental gold can be extracted using thiourea solution, thus recovering gold. It has good application value in the recovery of secondary precious metal resources.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing silsesquioxane hybrid fluorescent aerogel includes the following steps:

[0009] (1) Octadecylsilsesquioxane (OVS) and 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-ylidene)malonitrile (CZ-B-DCM) were dissolved in an organic solvent, a catalyst was added, and the mixture was stirred until homogeneous and then heated to carry out the reaction. After the reaction was completed, the reaction system was naturally cooled to room temperature, filtered, and washed to obtain solid I. Solid I was subjected to Soxhlet extraction, and the obtained solid was dried under vacuum to obtain silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM).

[0010] (2) The silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM) obtained in step (1) and the thiol-modified chitosan (Chitosan-SH) were added to water, acetic acid was added, and after stirring evenly, a photoinitiator was added to carry out the reaction. After the reaction was completed, the resulting reaction system was frozen into ice crystals and then freeze-dried to obtain silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan).

[0011] According to a preferred embodiment of the present invention, the molar ratio of octavinylsilsesquioxane (OVS) to 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-ylidene)malonitrile (CZ-B-DCM) in step (1) is (1-6):1, and more preferably (1.5-3):1.

[0012] According to a preferred embodiment of the present invention, the organic solvent in step (1) is 1,2-dichloroethane or o-dichlorobenzene; the mass ratio of the octavinylsilsesquioxane (OVS) to the volume ratio of the organic solvent is 1 g: (35-45) mL.

[0013] According to a preferred embodiment of the present invention, the catalyst in step (1) is anhydrous AlCl3 or anhydrous FeCl3; the molar ratio of the catalyst to octavinylsilsesquioxane (OVS) is (4-5):1.

[0014] According to a preferred embodiment of the present invention, when the organic solvent in step (1) is 1,2-dichloroethane, the reaction temperature is 80-90°C; when the organic solvent is o-dichlorobenzene, the reaction temperature is 190-200°C.

[0015] According to a preferred embodiment of the present invention, the reaction time in step (1) is 12 to 48 hours, and more preferably 20 to 30 hours.

[0016] According to a preferred embodiment of the present invention, the washing step in step (1) is as follows: the solid obtained after filtration is washed 3 to 5 times each with methanol, tetrahydrofuran, chloroform and acetone.

[0017] According to a preferred embodiment of the present invention, the Soxhlet extraction in step (1) is preferably performed by Soxhlet extraction of the obtained solid I in methanol and dichloromethane for 20-30 hours.

[0018] According to the present invention, the vacuum drying temperature in step (1) is 60-100°C, more preferably 70-80°C; and the vacuum drying time is 12-48h, more preferably 20-24h.

[0019] The structural formulas of octavinylsilsesquioxane (OVS) and 2-(2,6-bis((E)-4-(9H-carbazol-9-yl)styryl)-4H-pyran-4-ylidene)malonitrile (CZ-B-DCM) in this invention are shown below:

[0020]

[0021] The raw material octavinylsilsesquioxane (OVS) described in this invention can be prepared according to the literature J. Am. Chem. Soc., 1964, 86, 1120-1125; 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-yl)malononitrile (CZ-B-DCM) can be prepared according to the literature Thin Solid Films 2006, 500, 224-230; other raw materials are common commercial products.

[0022] According to a preferred embodiment of the present invention, the mass ratio of the silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM) to the thiol-modified chitosan (Chitosan-SH) in step (2) is (0.5-4):1, and more preferably (1-2.5):1.

[0023] According to a preferred embodiment of the present invention, the mass ratio of the sesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM) to water in step (2) is 1 g: (20-40) mL.

[0024] According to a preferred embodiment of the present invention, the mass ratio of the thiol-modified chitosan (Chitosan-SH) to the volume ratio of acetic acid in step (2) is 1 g: (0.3-0.8) mL.

[0025] According to a preferred embodiment of the present invention, the photoinitiator in step (2) is α-hydroxyisobutyrylbenzene (HMPP) or 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone; the mass ratio of the photoinitiator to the sesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM) is (0.2 to 1):1.

[0026] According to a preferred embodiment of the present invention, the reaction in step (2) is carried out under ultraviolet light irradiation, the wavelength of which is 295-395 nm; the reaction time is 0.2-2 h, more preferably 0.5-1 h.

[0027] According to a preferred embodiment of the present invention, the freezing temperature in step (2) is -20 to -5°C, and the freezing time is 8 to 24 hours, more preferably 12 to 15 hours; the freezing can be carried out in the freezer compartment of a refrigerator.

[0028] According to a preferred embodiment of the present invention, the freeze-drying temperature in step (2) is -70 to -40°C, more preferably -50°C; and the freeze-drying time is 10 to 38 hours, more preferably 12 to 24 hours.

[0029] The general structural formula of the thiol-modified chitosan (Chitosan-SH) in this invention is shown below:

[0030]

[0031] The thiol-modified chitosan (Chitosan-SH) used in this invention can be prepared according to the literature J. Mater. Chem. A 2019, 7, 4689-4698; the weight average molecular weight of the chitosan raw material used in preparing the thiol-modified chitosan is 25000-35000 Da and the degree of deacetylation is 90-98%.

[0032] The present invention also provides a silsesquioxane-based fluorescent aerogel prepared by the above preparation method.

[0033] According to the present invention, the above-described application based on silsesquioxane hybrid fluorescent aerogel is used to recover gold from wastewater.

[0034] According to a preferred embodiment of the present invention, the specific application method is as follows:

[0035] (a) Add silsesquioxane-based hybrid fluorescent aerogel to wastewater containing gold ions and perform static adsorption under visible light irradiation; or pass wastewater containing gold ions through a glass tube containing silsesquioxane-based hybrid fluorescent aerogel and perform dynamic adsorption under visible light irradiation.

[0036] (b) After adsorption is complete, the silsesquioxane-based fluorescent aerogel that adsorbs gold ions is placed in a 0.5-2 mol / L thiourea solution for desorption, and then Na2S2O5 is added for reduction. After filtration and drying, gold powder is obtained. Borax is then added to the obtained gold powder and melted to obtain elemental gold, thus realizing the recovery of gold ions from wastewater.

[0037] According to a preferred embodiment of the present invention, the concentration of gold ions in the wastewater containing gold ions in step (a) is 50–1000 mg / L; the wastewater containing gold ions also contains Cr. 3+ Cu 2+ Fe 3+ Zn 2+ Mg 2+ Cd 2+ K + Na + One or more of the following, wherein the pH of the wastewater containing gold ions is ≤7.

[0038] According to a preferred embodiment of the present invention, in step (a), the ratio of the mass of the silsesquioxane hybrid fluorescent aerogel to the volume of the wastewater containing gold ions during static adsorption is 1 g:(4000-5000) mL; and the static adsorption time is 5-20 min.

[0039] According to a preferred embodiment of the present invention, in step (a), the flow rate of the wastewater containing gold ions in the dynamic adsorption is 40 to 100 mL / min.

[0040] According to a preferred embodiment of the present invention, the analysis time in step (b) is 20-40 min; the molar ratio of Na2S2O5 to gold ions in wastewater is 2-4:1; the reduction time is 10-20 min; and the drying is performed at 80-100°C for 5-12 h.

[0041] According to a preferred embodiment of the present invention, the mass ratio of borax to gold powder in step (b) is 2 to 4:1; the melting temperature is 1100 to 1400°C, and the melting time is 50 to 90 seconds.

[0042] The technical features and beneficial effects of this invention are as follows:

[0043] 1. This invention uses octavinylsilsesquioxane and 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-yl)malonitrile as raw materials to prepare a silsesquioxane hybrid fluorescent porous polymer. This polymer is then reacted with thiol-modified chitosan to obtain a silsesquioxane-based hybrid fluorescent aerogel. The silsesquioxane hybrid fluorescent porous polymer of this invention is a hybrid porous material with high specific surface area and large pore volume, good chemical and thermal stability. Its structural advantages greatly enhance the interaction between the adsorbent and the adsorbate, significantly improving the adsorption capacity of the silsesquioxane hybrid porous material (PCS-CZ-B-DCM) for gold ions in wastewater. Chitosan, a natural linear polysaccharide, possesses outstanding properties such as non-toxicity, non-irritation, biocompatibility, antibacterial properties, and hydrophilicity, making it an excellent matrix for preparing aerogels. When reacted with porous polymers, the fluorescent groups in the resulting aerogel, along with the amino groups on the chitosan, can directly release Au from the solution under light irradiation. 3+ It is reduced to nano-gold elemental.

[0044] 2. The preparation steps of the hybrid fluorescent porous polymer (PCS-CZ-B-DCM) based on silsesquioxane in the aerogel of this invention are simple, the preparation process conditions are easy to control, and the building unit structure used is novel and has a certain degree of innovation.

[0045] 3. The silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan) obtained by this invention solves the processability problem of insoluble powder polymers and greatly expands the industrial application range of insoluble powder polymers. Attached Figure Description

[0046] Figure 1Example 2 yielded 2-(2,6-bis((E)-4-(9H-carbazol-9-yl)styryl)-4H-pyran-4-ylidene)malononitrile (CZ-B-DCM). 1 H NMR spectrum.

[0047] Figure 2 Example 2 yielded 2-(2,6-bis((E)-4-(9H-carbazol-9-yl)styryl)-4H-pyran-4-ylidene)malononitrile (CZ-B-DCM). 13 C NMR spectrum.

[0048] Figure 3 This is a SEM image of the silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan) prepared in Example 1.

[0049] Figure 4 The images show the infrared spectra of the octavinylsilsesquioxane (OVS), 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-ylidene)malonitrile (CZ-B-DCM), thiol-modified chitosan (Chitosan-SH), the prepared silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM), and the silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan) used in Example 1.

[0050] Figure 5 These are carbon spectra of the octavinylsilsesquioxane (OVS) used in Example 1, the prepared silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM), and the solid-state carbon spectra of the silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan).

[0051] Figure 6 These are the octavinylsilsesquioxane (OVS) used in Example 1, as well as the prepared silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM) and solid silicon spectra based on silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan).

[0052] Figure 7 The X-ray diffraction spectra of the octavinylsilsesquioxane (OVS), 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-ylidene)malonitrile (CZ-B-DCM) used in Example 1, the prepared silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM), and the silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan) are shown.

[0053] Figure 8The thermogravimetric analysis (TGA) curves of the octavinylsilsesquioxane (OVS), 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-ylidene)malonitrile (CZ-B-DCM) used in Example 1, the prepared silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM), and the silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan) are shown.

[0054] Figure 9 This is the N2 adsorption-desorption curve of the silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM) prepared in Example 1.

[0055] Figure 10 This is a pore size distribution diagram of the silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM) prepared in Example 1.

[0056] Figure 11 The PCSs@chitosan aerogel prepared in Example 1 exhibits different Au values ​​under both dark and light conditions. 3+ The adsorption performance is affected by ion concentration.

[0057] Figure 12 The PCSs@chitosan aerogel prepared in Example 1 was tested for its effect on Au at different times under dark and light conditions. 3+ The adsorption performance of ions is affected.

[0058] Figure 13 The PCSs@chitosan aerogel prepared in Example 1 exhibits its activity against Au under both dark and light conditions. 3+ Figure showing the fitting results of the pseudo-second-order reaction kinetics of ion adsorption.

[0059] Figure 14 The PCSs@chitosan aerogel prepared in Example 1 is used in a mixed solution to react with Au. 3+ Selectivity performance diagram of ion adsorption.

[0060] Figure 15 Images show the continuous flow apparatus used to prepare the PCSs@chitosan aerogel in Example 1 and the resulting gold particles.

[0061] Figure 16 The continuous flow device used in Example 1 to process the PCSs@chitosan aerogel at different times affects Au. 3+ Adsorption rate of ions.

[0062] Figure 17 This is a graph showing the cyclic regeneration performance of the continuous flow device for the PCSs@chitosan aerogel prepared in Example 1.

[0063] Figure 18 The adsorption Au of the PCSs@chitosan aerogel prepared in Example 1 3+ XRD patterns before and after. Detailed Implementation

[0064] The invention will be further described below with reference to specific examples and accompanying drawings.

[0065] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0066] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0067] The octavinylsilsesquioxane (OVS), 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-ylidene)malonitrile (CZ-B-DCM), and thiol-modified chitosan (Chitosan-SH) used in the examples were prepared according to Preparation Example 1, Preparation Example 2, and Preparation Example 3, respectively.

[0068] Preparation Example 1

[0069] Preparation of Octadevinylsilsesquioxane (OVS)

[0070] Octadecylsilsesquioxane (OVS) can be prepared according to the literature J. Am. Chem. Soc., 1964, 86, 1120-1125. The specific preparation steps are as follows:

[0071] Add 300 mL of acetone, 60 mL of vinyltrimethoxysilane, and 60 mL of water to a 500 mL single-necked flask. After stirring until homogeneous, add 80 mL of hydrochloric acid dropwise at 0 °C over 30 min. After the addition is complete, stir for 3 min. Once the system is stable, raise the temperature to room temperature and stir at room temperature for 5 days. After the reaction is complete, filter the solid. Wash the solid with acetone until no yellow substance is found. Dry the solid under vacuum at 60 °C for 8 h to obtain a white powder solid, which is octavinylsilsesquioxane (OVS).

[0072] The synthesis route is as follows:

[0073]

[0074] Preparation Example 2

[0075] Preparation of 2-(2,6-bis((E)-4-(9H-carbazol-9-yl)styryl)-4H-pyran-4-ylidene)malononitrile (CZ-B-DCM)

[0076] 2-(2,6-bis((E)-4-(9H-carbazol-9-yl)styryl)-4H-pyran-4-ylidene)malononitrile (CZ-B-DCM) can be prepared according to the literature Thin Solid Films 2006, 500, 224-230. The specific preparation steps are as follows:

[0077] 0.271 g (1 mmol) of 4-(9H-carbazole-9-yl)benzaldehyde and 0.086 g (0.5 mmol) of 2,6-dimethyl-4-pyranylmalonium were placed in a 50 mL single-necked flask, along with 20 mL of acetonitrile and 0.2 mL of piperidine. The mixture was reacted at 88 °C for 24 hours. After the reaction was complete, the mixture was filtered, and the resulting solid was recrystallized in acetonitrile to give 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-yl)malonium (CZ-B-DCM) in 90% yield.

[0078] The data characterization of 2-(2,6-bis((E)-4-(9H-carbazol-9-yl)styryl)-4H-pyran-4-ylidene)malononitrile (CZ-B-DCM) are as follows:

[0079] 1 H NMR (400MHz, (CD2Cl2), δ (ppm): 8.08 (d, J = 8Hz, 4H), 7.81 (d, J = 8Hz, 4H), 7.64 (m, 6H), 7.43 (d,J=8Hz,4H),7.37(t,J=8Hz,4H),7.24(t,J=8Hz,4H),6.86(t,J=16Hz,2H),6.72(s,2H).

[0080] 13 C NMR (100MHz, CD2Cl2), δ (ppm): 60.47, 107.82, 109.93, 115.19, 119.34, 120.48, 120.7 1,123.78,126.28,127.33,129.46,133.69,136.84,139.58,140.56,155.78,158.28.

[0081] 2-(2,6-bis((E)-4-(9H-carbazol-9-yl)styryl)-4H-pyran-4-ylidene)malononitrile (CZ-B-DCM) 1 H NMR spectrum, 13 The C NMR spectra are as follows: Figure 1 and Figure 2 As shown.

[0082] The synthesis route is as follows:

[0083]

[0084] Preparation Example 3

[0085] Preparation of thiol-modified chitosan (Chitosan-SH)

[0086] Thiol-modified chitosan (Chitosan-SH) can be prepared according to the literature J. Mater. Chem. A 2019, 7, 4689-4698. The specific preparation steps are as follows:

[0087] ① Dissolve 0.5g of chitosan (weight average molecular weight of 30000 Da and degree of deacetylation of 95%) in 4mL of 1mol / L HCl solution, and then add deionized water to obtain a chitosan hydrochloride solution with a mass fraction of 1%.

[0088] ②Then 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride was added to bring its concentration to 50 mmol / L;

[0089] ③Then add 500 mg of mercaptopropionic acid and stir at room temperature for 3 hours;

[0090] ④Then add a 1 mol / L sodium hydroxide solution to adjust the pH of the solution to 6.5;

[0091] ⑤ Finally, the solid was obtained by centrifugation, and the solvent was removed by freeze drying (-50℃, 24h) to obtain thiol-modified chitosan (Chitosan-SH).

[0092] Example 1

[0093] A method for preparing silsesquioxane hybrid fluorescent aerogel includes the following steps:

[0094] (1) Synthesis of silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM)

[0095] ① To a dry 50 mL three-necked flask equipped with a magnetic stirrer and a condenser, add 0.285 g (0.45 mmol) of octavinylsilsesquioxane (OVS), 0.204 g (0.3 mmol) of 2-(2,6-bis((E)-4-(9H-carbazol-9-yl)styryl)-4H-pyran-4-ylidene)malonium (CZ-B-DCM), and 11.25 mL of 1,2-dichloroethane. Stir for 15 minutes, then add 0.267 g (2.0 mmol) of anhydrous AlCl3. Stir at room temperature for 30 minutes, then heat to 85 °C and react for 24 h.

[0096] ② After the reaction is complete, the reaction system is naturally cooled to room temperature, filtered, and the obtained solid is washed three times each with methanol, tetrahydrofuran, chloroform, and acetone to obtain solid I.

[0097] ③ The obtained solid I was extracted with methanol and dichloromethane by Soxhlet extraction for 24 h, and the resulting solid was dried under vacuum at 80 °C for 24 h to obtain sesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM).

[0098] (2) Synthesis of silsesquioxane-based fluorescent aerogels (PCSs@chitosan)

[0099] 0.33 g of thiol-modified chitosan (Chitosan-SH) and 0.33 g of the silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM) obtained in step (1) were ground in a mortar for 15 minutes to ensure thorough mixing. The mixture was then added to 10 mL of deionized water. 120 μL of acetic acid was added to dissolve the mixture, and the mixture was stirred for 1 h to ensure thorough mixing. 0.162 g of photoinitiator α-hydroxyisobutyrylbenzene (HMPP) was then added, and a mercaptoene click reaction was carried out under UV light (365 nm) for 0.5 h. After the reaction, the resulting reaction system was transferred to the freezer compartment (-10 °C) and frozen for 12 h to obtain a silsesquioxane hybrid fluorescent hydrogel with ice crystals. The silsesquioxane hybrid fluorescent hydrogel with ice crystals was then freeze-dried at -50 °C for 12 h to obtain a silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan).

[0100] Figure 3 This is a SEM image of the silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan) prepared in this embodiment. Figure 3 It can be seen that the obtained aerogel has an interconnected, well-organized honeycomb structure and pores.

[0101] Figure 4 The infrared spectra of octavinylsilsesquioxane (OVS), 2-(2,6-bis((E)-4-(9H-carbazol-9-yl)styryl)-4H-pyran-4-yl)malononitrile (CZ-B-DCM), thiol-modified chitosan (Chitosan-SH), and the prepared silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM) and silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan) used in this embodiment are provided by [the relevant authority / organism]. Figure 4 The characteristic Si-O-Si peak (1123 cm⁻¹) can be observed in the silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM). -1 ) and the saturated CH bonds produced after the vinyl reaction (2941 cm)-1 The characteristic peaks indicate the successful occurrence of the Fridel-Crafts reaction; based on the Si-O-Si characteristic peaks (1123 cm⁻¹) in the silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan), the reaction is successful. -1 The appearance of ) and the SH key (2570cm) -1 The disappearance of the characteristic peak indicates that the click reaction of mercaptoene occurred smoothly.

[0102] Figure 5 These are the carbon spectra of the octavinylsilsesquioxane (OVS) used in this embodiment, the prepared silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM), and the solid-state carbon spectra of the silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan). The solid-state silicon spectra are shown below. Figure 6 As shown, by Figure 5 It can be seen that the resonance peaks of PCS-CZ-B-DCM from 107.4 to 162.7 ppm correspond to the sp(s) linked to the carbazole amine moiety. 3 nitrogen atom and vinyl sp 2 Carbon atoms on carbon atoms; the resonance signals from 3 to 60 ppm correspond to carbon atoms in the aliphatic regions of Si-CH2-CH2-CZ-B-DCM or Si-CH(CH3)-CZ-B-DCM; PCSs@chitosan exhibits characteristic peaks of chitosan, as well as a new resonance peak corresponding to carbon atoms on the CSC portion at 35.2 ppm, confirming that PCS-CZ-B-DCM has been incorporated into the chitosan backbone. Solid-state silicon spectra of PCS-CZ-B-DCM and PCSs@chitosan show the presence of T3 silicon units [T:CSi-(OSi)3] (-66.8 ppm and -70.2 ppm), indicating that the cage structure of octavinylsilsesquioxane remains intact during preparation without collapse; the signal at -80.6 ppm is attributed to unreacted vinyl groups.

[0103] Figure 7 The X-ray diffraction spectra of the octavinylsilsesquioxane (OVS), 2-(2,6-bis((E)-4-(9H-carbazol-9-yl)styryl)-4H-pyran-4-ylidene)malonitrile (CZ-B-DCM), the prepared silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM), and the silsesquioxane hybrid fluorescent aerogel (PCSs@chitosan) used in this embodiment are shown below. Thermogravimetric analysis curves are also shown. Figure 8 As shown, by Figure 7-8 It can be seen that PCS-CZ-B-DCM and PCSs@chitosan have disordered structures and good heat resistance.

[0104] Figure 9This is the N2 adsorption-desorption curve of the silsesquioxane hybrid fluorescent porous polymer (PCS-CZ-B-DCM) prepared in this embodiment. Figure 10 Its aperture distribution diagram is provided by Figure 9-10 It can be seen that PCS-CZ-B-DCM has a high specific surface area and is a porous material with both mesoporous and microporous structures and a bimodal distribution.

[0105] Application Example 1

[0106] The purpose of this experiment was to investigate the effects of the silsesquioxane hybrid fluorescent aerogel PCSs@chitosan aerogel prepared in Example 1 on different Au values ​​under both dark and light conditions. 3+ The concentration affects the adsorption performance.

[0107] In order to study Au 3+ Effect of concentration on the adsorption capacity of PCSs@chitosan aerogel, in the initial Au concentration range of 50-850 mg / L 3+ Adsorption isotherms were applied at different concentrations. 5 mg of PCSs@chitosan aerogel was placed in a 50 mL beaker equipped with a rotor, and 20 mL of different concentrations of Au-containing solutions were added to each. 3+ An aqueous solution of chloroauric acid was prepared (the pH of the solution was adjusted to 5 with hydrochloric acid after dissolving chloroauric acid in water). Dark environments were created by irradiation with visible light or by wrapping the solution in aluminum foil. The residual Au in the solution was determined using atomic flame absorption spectroscopy. 3+ Ion concentration. The adsorption capacity is calculated using the formula:

[0108]

[0109] In the formula: Q e The adsorption capacity of a unit mass of adsorbent for metal ions is expressed in mg / g.

[0110] C0 is the initial concentration of ions, mg / L;

[0111] C e The concentration of ions in the solution after equilibrium is expressed in mg / L.

[0112] V is the volume of the solution during the adsorption experiment, in L;

[0113] m represents the mass of adsorbent added, in grams.

[0114] The PCSs@chitosan aerogel prepared in Example 1 exhibited different Au values ​​under both dark and light conditions. 3+ The effect of ion concentration on adsorption performance, such as Figure 11 As shown, it was found Figure 11The adsorption isotherm data shown match the Freundlich model instead of the Langmuir model, demonstrating that chemisorption occurs on the material surface. Under illumination, the isotherm model fit yields a saturated adsorption capacity of 3294.61 mg / g; under darkness, the isotherm model fit yields a saturated adsorption capacity of 2230.63 mg / g. These isotherm model fitting results also demonstrate that the aerogel and gold ions exchange electrons on the surface, undergoing a redox reaction.

[0115] Application Example 2

[0116] The purpose of this experiment was to investigate the effects of PCSs@chitosan aerogel on Au at different times under dark and light conditions. 3+ The adsorption performance is affected.

[0117] To investigate the effect of adsorption time on the adsorption capacity of PCSs@chitosan aerogel, the adsorption capacity of PCSs@chitosan aerogel on Au was tested at different times. 3+ The adsorption rate. Take 5 mg of PCSs@chitosan aerogel and place it in a 50 mL beaker equipped with a rotor. Add 20 mL of a solution containing 100 mg / L Au. 3+ An aqueous solution of chloroauric acid was prepared (the solution was dissolved in water and the pH was adjusted to 5 with hydrochloric acid). The solutions were then subjected to either visible light irradiation or to dark environments created by wrapping the solution in aluminum foil. After different reaction times, portions of the solution were collected. The remaining Au in the solution was determined using atomic flame absorption spectroscopy. 3+ Ion concentration. The adsorption capacity is calculated using the formula:

[0118]

[0119] In the formula: Q e The adsorption capacity of a unit mass of adsorbent for metal ions is expressed in mg / g.

[0120] C0 is the initial concentration of ions, mg / L;

[0121] C e The concentration of ions in the solution after equilibrium is expressed in mg / L.

[0122] V is the volume of the solution during the adsorption experiment, in L;

[0123] m represents the mass of adsorbent added, in grams.

[0124] Figure 12 The PCSs@chitosan aerogel prepared in Example 1 was tested for its effect on Au at different times under dark and light conditions. 3+ The adsorption performance of ions is affected. Figure 13The PCSs@chitosan aerogel prepared in Example 1 exhibits its activity against Au under both dark and light conditions. 3+ The results of fitting the pseudo-second-order reaction kinetics of ion adsorption. It was found that... Figure 12 and Figure 13 The adsorption rate data shown match the pseudo-second-order reaction kinetic model, demonstrating that chemisorption dominates the adsorption process.

[0125] Application Example 3

[0126] The purpose of this experiment was to investigate the effects of PCSs@chitosan aerogel on the adsorption of different ions under dark and light conditions.

[0127] Take Na + K + Cu 2+ Mg 2+ Cd 3+ Cr 3+ Fe 3+ Zn 2+ and Au 3+ Taking mixed ions as an example, the reaction of the prepared PCSs@chitosan aerogel with Au was detected. 3+ The adsorption and reduction experiment was conducted. 5 mg of PCSs@chitosan aerogel was placed in a 50 mL beaker equipped with a rotor, and 20 mL of sodium-containing solution was added. + K + Cu 2+ Mg 2+ Cd 3+ Cr 3+ Fe 3+ Zn 2+ and Au 3+ A mixed solution (pH 5) with ion concentrations of 50 mg / L, 50 mg / L, 50 mg / L, 50 mg / L, 50 mg / L, 50 mg / L, 50 mg / L, 50 mg / L, and 100 mg / L was prepared. The concentration of the remaining metal ions in the solution was determined by atomic flame absorption spectroscopy. The adsorption capacity was calculated using the formula:

[0128]

[0129] In the formula: Q e The adsorption capacity of a unit mass of adsorbent for metal ions is expressed in mg / g.

[0130] C0 is the initial concentration of ions, mg / L;

[0131] C e The concentration of ions in the solution after equilibrium is expressed in mg / L.

[0132] V is the volume of the solution during the adsorption experiment, in L;

[0133] m represents the mass of adsorbent added, in grams.

[0134] Figure 14 The PCSs@chitosan aerogel prepared in Example 1 is used in a mixed solution to react with Au. 3+ The selectivity of ion adsorption, such as Figure 14 Experimental results demonstrate that PCSs@chitosan aerogel exhibits good performance in mixed ionic solutions for Au. 3+ The ions exhibit extremely high selectivity.

[0135] Application Example 4

[0136] The purpose of this experiment is to conduct large-scale Au-containing experiments on PCSs@chitosan aerogels. 3+ Waste liquid treatment.

[0137] 20 mg of PCSs@chitosan aerogel was filled into a glass tube. One end of the glass tube was connected to a waste liquid container via a water pipe, and the other end was connected to a peristaltic pump and the waste liquid container in sequence via a water pipe, thus creating a continuous flow device based on PCSs@chitosan aerogel. The leachate obtained from 20 CPUs contained 126.6 mg / L of Au. 3+ Ni 706.9 mg / L 2 + And 2325.2 mg / L of Cu 2+ The volume of the leachate is 300 mL, and the pH is 5. For example... Figure 15 As shown, under visible light irradiation, the leachate passed through the PCSs@chitosan aerogel device at a flow rate of 50 mL / min. Figure 16 As shown, with the increase of device operating time, the Au content in the leachate... 3+ The content continued to decrease, and after running for 7 minutes, more than 99% of the Au content was reduced. 3+ The gold was adsorbed. After adsorption, it was desorbed with 2 mol / L thiourea solution for 30 min, reduced with 1 mol / L Na2S2O5 solution (the molar ratio of Na2S2O5 to gold ions in the leaching solution was 3:1), filtered, and dried at 90℃ for 10 h to obtain black gold powder. Subsequently, 80 mg of borax was placed at the bottom of a crucible, the black gold powder was added into the crucible, compacted, and the crucible was preheated in a furnace at a low temperature of 500℃ for 5 min, then the temperature was increased to 1200℃, and the melting time was 70 s to obtain 37 mg of gold with a purity of 23.8 carats. In addition, the circulation and regeneration capacity of the PCSs@chitosan aerogel device were studied. After desorption with thiourea solution and drying, regeneration experiments were conducted. Figure 17As shown, after five absorption-desorption cycles, the removal efficiency of gold ions by the PCSs@chitosan aerogel device can still reach over 95%.

[0138] Figure 18 The adsorption Au of the PCSs@chitosan aerogel prepared in Example 1 3+ The XRD curves before and after show a very clear signal of gold nanoparticles, indicating that the PCSs@chitosan aerogel can transmit Au. 3+ It is reduced to elemental Au.

[0139] The aerogel adsorbent prepared by the method of this invention has mild preparation conditions, excellent adsorption and selection effects, reduces secondary pollution, and can extract gold from wastewater.

Claims

1. A method for preparing silsesquioxane hybrid fluorescent aerogel, comprising the following steps: (1) Octadecylsilsesquioxane and 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-ylidene)malonitrile were dissolved in an organic solvent, a catalyst was added, and the mixture was stirred until homogeneous and then heated to carry out the reaction. After the reaction was completed, the reaction system was naturally cooled to room temperature, filtered, and washed to obtain solid I. Solid I was subjected to Soxhlet extraction, and the obtained solid was dried under vacuum to obtain silsesquioxane hybrid fluorescent porous polymer. (2) Add the silsesquioxane hybrid fluorescent porous polymer obtained in step (1) and the thiol-modified chitosan to water, add acetic acid, stir evenly, add photoinitiator, and carry out the reaction; after the reaction is completed, freeze the resulting reaction system into ice crystals and freeze dry to obtain silsesquioxane hybrid fluorescent aerogel.

2. The preparation method of silsesquioxane hybrid fluorescent aerogel according to claim 1, characterized in that, The molar ratio of octavinylsilsesquioxane to 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-yl)malonitrile in step (1) is (1~6):1; The organic solvent is 1,2-dichloroethane or o-dichlorobenzene; the mass ratio of the octavinylsilsesquioxane to the volume of the organic solvent is 1 g:(35~45) mL.

3. The preparation method of silsesquioxane hybrid fluorescent aerogel according to claim 1, characterized in that, The molar ratio of octavinylsilsesquioxane to 2-(2,6-bis((E)-4-(9H-carbazole-9-yl)styryl)-4H-pyran-4-yl)malononitrile in step (1) is (1.5~3):

1.

4. The preparation method of silsesquioxane hybrid fluorescent aerogel according to claim 1, characterized in that, The catalyst mentioned in step (1) is anhydrous AlCl3 or anhydrous FeCl3; the molar ratio of the catalyst to octavinylsilsesquioxane is (4~5):

1.

5. The preparation method of silsesquioxane hybrid fluorescent aerogel according to claim 1, characterized in that, When the organic solvent in step (1) is 1,2-dichloroethane, the reaction temperature is 80~90℃; when the organic solvent is o-dichlorobenzene, the reaction temperature is 190~200℃; and the reaction time is 12~48h.

6. The preparation method of silsesquioxane hybrid fluorescent aerogel according to claim 1, characterized in that, The washing step described in step (1) is as follows: the solid obtained after filtration is washed 3 to 5 times each with methanol, tetrahydrofuran, chloroform and acetone; The Soxhlet extraction step is as follows: the obtained solid I is extracted with methanol and dichloromethane for 20-30 h respectively; The vacuum drying temperature is 60~100℃; the vacuum drying time is 12~48h.

7. The preparation method of silsesquioxane hybrid fluorescent aerogel according to claim 1, characterized in that, The mass ratio of the silsesquioxane hybrid fluorescent porous polymer to the thiol-modified chitosan in step (2) is (0.5~4):1; The mass-to-volume ratio of the silsesquioxane hybrid fluorescent porous polymer to water is 1 g:(20~40) mL.

8. The preparation method of silsesquioxane hybrid fluorescent aerogel according to claim 1, characterized in that, The mass ratio of the sesquioxane hybrid fluorescent porous polymer to the thiol-modified chitosan in step (2) is (1~2.5):

1.

9. The preparation method of silsesquioxane hybrid fluorescent aerogel according to claim 1, characterized in that, The mass ratio of the thiol-modified chitosan to the volume ratio of acetic acid in step (2) is 1 g: (0.3~0.8) mL; The photoinitiator is α-hydroxyisobutyrylbenzene or 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone; the mass ratio of the photoinitiator to the sesquioxane hybrid fluorescent porous polymer is (0.2~1):

1.

10. The preparation method of silsesquioxane hybrid fluorescent aerogel according to claim 1, characterized in that, The reaction described in step (2) is carried out under ultraviolet light irradiation with a wavelength of 295~395nm; the reaction time is 0.2~2h. The freezing temperature is -20 to -5°C, and the freezing time is 8 to 24 hours. The freeze-drying temperature is -70 to -40°C; the freeze-drying time is 10 to 38 hours.

11. The preparation method of silsesquioxane hybrid fluorescent aerogel according to claim 1, characterized in that, The reaction time in step (2) is 0.5-1 h; the freezing time is 12-15 h. The freeze-drying temperature is -50℃; the freeze-drying time is 12~24h.

12. A fluorescent aerogel based on silsesquioxane hybrids, characterized in that, It was prepared using the preparation method described in claim 1.

13. The application of the silsesquioxane hybrid fluorescent aerogel according to claim 12 for the recovery of gold from wastewater.

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