Quaternary amine modified PPACE-Cl nanofiber, and preparation method and application thereof

Abstract

This invention relates to the field of nanofiber technology, and particularly to a quaternary ammonium-modified PPACE-Cl nanofiber, its preparation method, and its application. S1. Preparation of PAN electrospun nanofibers: Polyacrylonitrile, polyvinylpyrrolidone, and carboxylated multi-walled carbon nanotubes are stirred with N,N-dimethylformamide at room temperature for 6-12 h to obtain a uniform and transparent spinning solution. The resulting spinning solution is then placed in a 10 mL syringe and spun in an electrospinning machine to obtain PAN / PVP / MWCNT-CCOH nanofibers. The obtained nanofibers are then placed in hot water at 60-100°C to remove PVP, yielding PAN / MWCNT-COOH nanofibers. S2. Preparation of nitrogen-enriched modified PPACE nanofibers: The PAN / MWCNT-COOH nanofibers prepared in step S1 are placed in an aqueous solution of polyethyleneimine in a high-pressure reactor to obtain modified PPACE nanofibers. S3. Preparation of quaternary ammonium-modified PPACE-Cl nanofibers. The quaternized PPACE-Cl nanofibers of this invention will prepare nanofibers with a surface rich in positive charge, thereby achieving the effect of AuCl4 exhibiting a negative charge in aqueous solution. ‑ Selective enrichment and adsorption are carried out.

Description

Technical Field

[0001] This invention relates to the field of nanofiber technology, and in particular to a quaternized modified PPACE-Cl nanofiber, its preparation method, and its application. Background Technology

[0002] Gold, as a precious metal, possesses characteristics such as scarcity, durability, ease of processing, and resistance to corrosion, thus imbuing it with high value. The main sources of gold are mining and recycling. Gold recycling is of great significance. Gold mining and refining consume substantial resources and energy; recycling gold can reduce the depletion of natural resources. Gold mining and refining cause environmental pollution, while gold recycling can reduce environmental damage and mitigate the harmful effects of waste on the environment. Recycling gold can reduce production costs and improve resource utilization efficiency. Gold recycling aligns with the principles of a circular economy and contributes to building a resource-saving and environmentally friendly society. Therefore, gold recycling is of great importance for resource conservation, environmental protection, and sustainable development.

[0003] Currently, gold extraction typically consumes large amounts of compounds such as cyanide and aqua regia. However, due to the toxicity of cyanide and the corrosiveness of aqua regia, these processes pose serious threats to the environment and human health. In recent years, researchers have conducted extensive research on environmentally friendly gold extraction technologies, such as leaching processes like chloride, thiosulfate, and thiourea, as well as purification processes like solvent extraction and ion exchange. Traditional hydrometallurgy offers advantages such as low energy consumption and ease of control, but its recovery process is complex, generates large volumes of waste liquid, and suffers from low recovery rates. Furthermore, traditional gold recovery technologies also suffer from low adsorbent efficiency and poor selectivity. Summary of the Invention

[0004] The features and advantages of the present invention are set forth in part in the description which follows, or may be apparent from the description, or may be learned by practicing the invention.

[0005] To overcome the problems of existing technologies, this invention provides a method for preparing quaternized modified PPACE-Cl nanofibers, specifically including the following steps:

[0006] S1. Preparation of PAN electrospun nanofibers: Polyacrylonitrile, polyvinylpyrrolidone, and carboxylated multi-walled carbon nanotubes were stirred with N,N-dimethylformamide at room temperature for 6-12 h to obtain a uniform and transparent spinning solution. The resulting spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine to obtain PAN / PVP / MWCNT-COOH nanofibers. The obtained nanofibers were then placed in hot water at 60-100°C to remove PVP, thus obtaining PAN / MWCNT-COOH nanofibers.

[0007] S2. Preparation of nitrogen-enriched modified PPACE nanofibers: The PAN / MWCNT-COOH nanofibers prepared in step S1 and an aqueous solution of polyethyleneimine were placed in a high-pressure reactor and reacted at 110~140℃ for 12~24h. After the reaction, the nanofibers were washed with pure water more than 3 times and then freeze-dried under vacuum at -50℃ for 12h to obtain modified PPACE nanofibers.

[0008] S3. Preparation of quaternized PPACE-Cl nanofibers: The PPACE nanofibers prepared in step S2 were mixed with chloropropane, and ethanol was added as a solvent. The mixture was refluxed at 80°C with magnetic stirring for 8-12 h. After the reaction was completed, the nanofibers were washed three times with ethanol and then freeze-dried under vacuum at -50°C for 12 h to obtain quaternized modified PPACE-Cl nanofibers.

[0009] Preferably, the mass ratio of polyacrylonitrile, polyvinylpyrrolidone, carboxylated multi-walled carbon nanotubes, and N,N-dimethylformamide is 1:1:1:9-16.

[0010] Preferably, the mass ratio of the PAN / MWCNT-COOH nanofibers to the polyethyleneimine aqueous solution is 1:10.

[0011] Preferably, the mass ratio of the PPACE nanofibers to the chloropropane is 1:0.925-2.775.

[0012] Preferably, the parameters of the electrospinning machine are set as follows: voltage 15.0-18.0KV, spinning solution flow rate 2.0mL / h, roller speed 200 r / min, receiving distance 15 cm, spinning temperature and humidity 25 ± 1 ℃ and 70 ± 5%, respectively.

[0013] The present invention also provides a quaternized modified PPACE-Cl nanofiber, which is prepared by the method described above for preparing quaternized modified PPACE-Cl nanofiber.

[0014] This invention also provides an application of quaternized modified PPACE-Cl nanofibers, in which the quaternized modified PPACE-Cl nanofibers are used as an adsorbent material in AuCl4. - Selective recycling.

[0015] The beneficial effects of this invention are:

[0016] This invention uses polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and carboxylated multi-walled carbon nanotubes (MWCNT-COOH) as matrix materials. Nanofibers are prepared via electrospinning, removing PVP to obtain porous PAN / MWCNT-COOH nanofibers. Polyethyleneimine (PEI) is used as a nitrogen-rich functional group, and quaternization modification with n-propane chloride is then performed to prepare quaternized modified PPACE-Cl nanofibers. These nanofibers are resistant to AuCl4. - The maximum adsorption capacity can reach 808.58 mg / g. The adsorption process conforms to the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model. Moreover, it exhibits good adsorption capacity for AuCl4 in complex, strongly acidic industrial wastewater environments. - Its high selectivity for AuCl4, with a partition coefficient as high as 9482.889 L / g, indicates its high selectivity for AuCl4. - It has a high selective adsorption capacity.

[0017] This invention combines electrospinning and surface grafting techniques to prepare quaternized modified PPACE-Cl nanofiber adsorbents that exhibit superhydrophilicity. The quaternized modified PPACE-Cl nanofibers prepared by this invention possess excellent hydrophilicity, reducing the energy barrier during adsorption and significantly improving the adsorption rate and capacity, thus providing a new technical method for gold recovery from wastewater.

[0018] The quaternized PPACE-Cl nanofibers prepared by this invention have abundant nitrogen-containing groups, which can serve as adsorption sites for AuCl4. - A strong interaction occurs between them, thus affecting AuCl4. - Selective recognition is achieved. Furthermore, due to the excellent hydrophilicity of quaternized PPACE-Cl nanofibers, the contact energy barrier between them and gold in solution can be reduced, allowing AuCl4 to be selectively recognized. - It is reduced to Au(0), thereby promoting the entire adsorption process.

[0019] The quaternized PPACE-Cl nanofibers of this invention employ quaternization modification to impart a positive charge to the surface of the nanofibers, thereby achieving a negative charge on AuCl4 in aqueous solution. - Selective enrichment and adsorption are carried out.

[0020] The quaternized PPACE-Cl nanofibers of the present invention, in combination with AuCl4 - The adsorption process involves multiple reaction mechanisms, including electrostatic interactions, coordination interactions, and redox reactions, which result in high adsorption capacity and good adsorption effect.

[0021] The quaternized PPACE-Cl nanofibers of the present invention exhibit superhydrophilicity, which can reduce the contact energy barrier between them and gold in solution. This can effectively solve the problem of gold adsorption, recovery and removal in high-concentration solutions, and has broad application prospects. Attached Figure Description

[0022] The present invention will be described in detail below with reference to the accompanying drawings and examples. The advantages and implementation methods of the present invention will become more apparent from this description. The accompanying drawings are for illustrative purposes only and do not constitute any limitation on the present invention. In the accompanying drawings:

[0023] Figure 1 This is a schematic diagram of a method for preparing quaternized modified PPACE-Cl nanofibers in a specific embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram illustrating the preparation process of a quaternization-modified PPACE-Cl nanofiber in a specific embodiment of the present invention.

[0025] Figure 3 The images shown are scanning electron microscope (SEM) images of the nanofibers obtained at each stage in Specific Embodiment 3 of the present invention. Figure a is an SEM image of PAN / MWCNT-COOH nanofibers; Figure b is an SEM image of quaternized modified PPACE-Cl nanofibers.

[0026] Figure 4 This is a water contact angle diagram of PPACE nanofibers and quaternized modified PPACE-Cl nanofibers in specific embodiment 3 of the present invention;

[0027] Figure 5 This is a graph showing the effect of pH on the adsorption process in a specific embodiment of the present invention. Figure a shows the effect of pH on AuCl4. - Figure 1 shows the effect of pH on adsorption capacity; Figure 2b shows the effect of pH on Zata potential.

[0028] Figure 6 Different AuCl4 in specific embodiments of the present invention - Figure showing the effect of initial concentration on the adsorption process;

[0029] Figure 7 This is a graph showing the effect of different times on the adsorption process in a specific embodiment of the present invention;

[0030] Figure 8 In a specific embodiment of the present invention, quaternized PPACE-Cl nanofibers react with AuCl4 in a mixed solution. - Selective influence analysis diagram;

[0031] Figure 9This is a diagram illustrating the effect of temperature on the adsorption process in a specific embodiment of the present invention. Detailed Implementation

[0032] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0033] Example 1

[0034] like Figure 1 and Figure 2 As shown, this invention provides a method for preparing quaternized modified PPACE-Cl nanofibers, specifically including the following steps:

[0035] S1. Preparation of PAN electrospun nanofibers: 0.6 g of polyacrylonitrile, polyvinylpyrrolidone, and carboxylated multi-walled carbon nanotubes and 9.6 g of N,N-dimethylformamide (DMF) were added to a beaker. After stirring at room temperature for 6 h, a uniform and transparent spinning solution was obtained. The resulting spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized parameters of the electrospinning machine were set as follows: voltage of 15.0 KV, spinning solution flow rate of 2.0 mL / h, roller speed of 200 r / min, receiving distance of 15 cm, spinning temperature and humidity of 25 ± 1 ℃ and 70 ± 5%, respectively, to obtain PAN / PVP / MWCNT-COOH nanofibers. The obtained PAN / PVP / MWCNT-COOH nanofibers were then placed in 60°C hot water to remove PVP, resulting in PAN / MWCNT-COOH nanofibers.

[0036] S2. Preparation of nitrogen-enriched modified PPACE nanofibers: Weigh 0.2 g of the PAN / MWCNT-COOH nanofibers prepared in step S1, and place them in a high-pressure reactor with 2.0 g of a 10% (w / w) aqueous solution of polyethyleneimine (PEI). React at 110℃ for 12 h. After the reaction, wash the nanofibers with pure water more than 3 times, and freeze-dry them under vacuum at -50℃ for 12 h to obtain modified PPACE nanofibers.

[0037] S3. Preparation of quaternized PPACE-Cl nanofibers: The PPACE nanofibers prepared in step S2 were mixed with chloropropane, and ethanol was added as a solvent. The mixture was refluxed at 80°C with magnetic stirring for 8 hours. After the reaction was completed, the nanofibers were washed with ethanol three times and then freeze-dried under vacuum at -50°C for 12 hours to obtain quaternized modified PPACE-Cl nanofibers.

[0038] The quaternized modified PPACE-Cl nanofibers prepared by the above method were used as adsorbents for gold recovery in wastewater.

[0039] Polyacrylonitrile (PAN) is a commonly used material in electrospinning, possessing good thermal stability and solvent resistance, making it an ideal substrate material for electrospun nanofibers (ENMs). PAN electrospun nanofibers exhibit small pore size, low porosity, high mechanical properties, and stable morphology, and are widely used in the preparation of electrospun fibers. Carbon nanotubes (MWCNT-COOH) show potential in the mass transfer of metal ions in water due to the hydrophilicity and conductivity of their carboxyl groups, as well as their high tensile strength and chemical stability. Polyethyleneimine (PEI) possesses high hydrophilicity and a large number of coordinating groups, enabling it to form complexes with metal anions under acidic conditions.

[0040] Electrospinning technology can prepare nanofibers with high specific surface areas. Surface grafting modification can then be used to functionalize the fiber surface with nitrogen, providing numerous nitrogen-rich active sites. Quaternization modification further imbues the surface with a large number of positive charges. Furthermore, the carboxylated carbon nanotubes introduced by electrospinning and the grafted polyethyleneimine possess numerous hydrophilic groups, exhibiting excellent hydrophilicity. This reduces the adsorbent contact barrier with gold in solution, significantly enhancing the adsorption effect on gold in solution.

[0041] This invention uses polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and carboxylated multi-walled carbon nanotubes (MWCNT-COOH) as matrix materials, and employs electrospinning technology to prepare nanofibers. Polyethyleneimine (PEI) is used as a nitrogen-rich functional group, and quaternized modified PPACE-Cl nanofibers are prepared by quaternization modification with n-propane chloride. The prepared quaternized modified PPACE-Cl nanofibers are then compared with AuCl4. - Solutions interact with each other through electrostatic, coordination, and redox interactions to achieve the desired effect on AuCl4. - Selective adsorption. Furthermore, the quaternized modified PPACE-Cl nanofibers prepared in this invention exhibit excellent hydrophilicity, reducing the energy barrier during adsorption and significantly improving the adsorption rate and capacity.

[0042] Example 2

[0043] This invention provides a method for preparing quaternized modified PPACE-Cl nanofibers, specifically including the following steps:

[0044] S1. Preparation of PAN electrospun nanofibers: 1.0 g of polyacrylonitrile, polyvinylpyrrolidone, and carboxylated multi-walled carbon nanotubes and 9.0 g of N,N-dimethylformamide (DMF) were added to a beaker. After stirring at room temperature for 12 h, a homogeneous and transparent spinning solution was obtained. The resulting spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized parameters of the electrospinning machine were set as follows: voltage of 18.0 KV, spinning solution flow rate of 3.0 mL / h, roller speed of 200 r / min, receiving distance of 15 cm, spinning temperature and humidity of 25 ± 1 ℃ and 70 ± 5%, respectively, to obtain PAN / PVP / MWCNT-COOH nanofibers. The obtained nanofibers were then placed in 100°C hot water to remove PVP, resulting in PAN / MWCNT-COOH nanofibers.

[0045] S2. Preparation of nitrogen-enriched modified PPACE nanofibers: Weigh 0.5 g of the PAN / MWCNT-COOH nanofibers prepared in step S1, and place them in a high-pressure reactor with 5.0 g of a 10% (w / w) aqueous solution of polyethyleneimine (PEI). React at 140℃ for 24 h. After the reaction, wash the nanofibers with pure water more than 3 times, and freeze-dry them under vacuum at -50℃ for 12 h to obtain modified PPACE nanofibers.

[0046] S3. Preparation of quaternized PPACE-Cl nanofibers: Weigh 0.48 g of the PPACE nanofibers prepared in step S2, then weigh 1.332 g of n-chloropropane and place it in a three-necked flask. Add 100 mL of ethanol as a solvent and reflux the reaction at 80 °C with magnetic stirring for 12 h. After the reaction, wash the nanofibers three times with ethanol and freeze-dry them under vacuum at -50 °C for 12 h to obtain quaternized modified PPACE-Cl nanofibers.

[0047] The quaternized modified PPACE-Cl nanofibers prepared by the above method were used as adsorbents for gold recovery in wastewater.

[0048] Example 3

[0049] This invention provides a method for preparing quaternized modified PPACE-Cl nanofibers, specifically including the following steps:

[0050] S1. Preparation of PAN electrospun nanofibers: 0.7 g of polyacrylonitrile, polyvinylpyrrolidone, and carboxylated multi-walled carbon nanotubes and 9.1 g of N,N-dimethylformamide (DMF) were added to a beaker. After stirring at room temperature for 10 h, a homogeneous and transparent spinning solution was obtained. The resulting spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized parameters of the electrospinning machine were set as follows: voltage of 18.0 KV, spinning solution flow rate of 3.0 mL / h, roller speed of 200 r / min, receiving distance of 15 cm, spinning temperature and humidity of 25 ± 1 ℃ and 70 ± 5%, respectively, to obtain PAN / PVP / MWCNT-COOH nanofibers. The obtained nanofibers were then placed in 70°C hot water to remove PVP, resulting in PAN / MWCNT-COOH nanofibers.

[0051] S2. Preparation of nitrogen-enriched modified PPACE nanofibers: Weigh 0.4 g of the PAN / MWCNT-COOH nanofibers prepared in step S1, and place them in a high-pressure reactor with 4.0 g of a 10% (w / w) aqueous solution of polyethyleneimine (PEI). React at 120°C for 15 h. After the reaction, wash the nanofibers with pure water more than 3 times, and freeze-dry them under vacuum at -50°C for 12 h to obtain modified PPACE nanofibers.

[0052] S3. Preparation of quaternized PPACE-Cl nanofibers: Weigh 0.48 g of the PPACE nanofibers prepared in step S2, then weigh 1.128 g of n-chloropropane and place it in a three-necked flask. Add 100 mL of ethanol as a solvent and reflux the reaction at 80 °C with magnetic stirring for 9 h. After the reaction, wash the nanofibers three times with ethanol and freeze-dry them under vacuum at -50 °C for 12 h to obtain quaternized modified PPACE-Cl nanofibers.

[0053] The quaternized modified PPACE-Cl nanofibers prepared by the above method were used as adsorbents for gold recovery in wastewater.

[0054] Example 4

[0055] This invention provides a method for preparing quaternized modified PPACE-Cl nanofibers, specifically including the following steps:

[0056] S1. Preparation of PAN electrospun nanofibers: 0.9 g of polyacrylonitrile, polyvinylpyrrolidone, and carboxylated multi-walled carbon nanotubes and 13.5 g of N,N-dimethylformamide (DMF) were added to a beaker. After stirring at room temperature for 7 h, a homogeneous and transparent spinning solution was obtained. The resulting spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized parameters of the electrospinning machine were set as follows: voltage of 18.0 KV, spinning solution flow rate of 3.0 mL / h, roller speed of 200 r / min, receiving distance of 15 cm, spinning temperature and humidity of 25 ± 1 ℃ and 70 ± 5%, respectively, to obtain PAN / PVP / MWCNT-COOH nanofibers. The obtained nanofibers were then placed in 90°C hot water to remove PVP, resulting in PAN / MWCNT-COOH nanofibers.

[0057] S2. Preparation of nitrogen-enriched modified PPACE nanofibers: Weigh 0.3 g of the PAN / MWCNT-COOH nanofibers prepared in step S1, and place them in a high-pressure reactor with 3.0 g of a 10% (w / w) aqueous solution of polyethyleneimine (PEI). React at 130°C for 15 h. After the reaction, wash the nanofibers with pure water more than 3 times, and freeze-dry them under vacuum at -50°C for 12 h to obtain modified PPACE nanofibers.

[0058] S3. Preparation of quaternized PPACE-Cl nanofibers: Weigh 0.48 g of the PPACE nanofibers prepared in step S2, then weigh 0.648 g of n-propane chloride and place it in a three-necked flask. Add 100 mL of ethanol as a solvent and reflux the reaction at 80 °C with magnetic stirring for 11 h. After the reaction, wash the nanofibers with ethanol at least 3 times and freeze-dry them under vacuum at -50 °C for 12 h to obtain quaternized modified PPACE-Cl nanofibers.

[0059] The quaternized modified PPACE-Cl nanofibers prepared by the above method were used as adsorbents for gold recovery in wastewater.

[0060] Example 5

[0061] This invention provides a method for preparing quaternized modified PPACE-Cl nanofibers, specifically including the following steps:

[0062] S1. Preparation of PAN electrospun nanofibers: 0.8 g of polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and carboxylated multi-walled carbon nanotubes (MWCNT-COOH, abbreviated as CNT) and 9.2 g of N,N-dimethylformamide (DMF) were added to a beaker. After stirring at room temperature for 8 h, a uniform and transparent spinning solution was obtained. The obtained spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized parameters of the electrospinning machine were set as follows: voltage of 18.0 KV, spinning solution flow rate of 2.0 mL / h, roller speed of 200 r / min, receiving distance of 15 cm, spinning temperature and humidity of 25 ± 1℃ and 70 ± 5%, respectively, to obtain PAN / PVP / MWCNT-COOH nanofibers (abbreviated as PAN / PVP / CNT). The obtained nanofibers were then placed in 80°C hot water to remove PVP, resulting in PAN / MWCNT-COOH nanofibers (abbreviated as PPAC).

[0063] S2. Preparation of nitrogen-enriched modified PPACE nanofibers: Weigh 0.5 g of the PAN / MWCNT-COOH nanofibers prepared in step S1, and place them in a high-pressure reactor with 5.0 g of a 10 wt% polyethyleneimine (PEI) aqueous solution. React at 130℃ for 20 h. After the reaction, wash the nanofibers with pure water more than 3 times, and freeze-dry them under vacuum at -50℃ for 12 h to obtain modified PPACE nanofibers.

[0064] S3. Preparation of quaternized PPACE-Cl nanofibers: Weigh 0.48 g of the PPACE nanofibers prepared in step S2, then weigh 0.888 g of n-propane chloride and place it in a three-necked flask. Add 100 mL of ethanol as a solvent and reflux the reaction at 80 °C with magnetic stirring for 10 h. After the reaction, wash the nanofibers three times with ethanol and freeze-dry them under vacuum at -50 °C for 12 h to obtain quaternized modified PPACE-Cl nanofibers.

[0065] The quaternized modified PPACE-Cl nanofibers prepared by the above method were used as adsorbents for gold recovery in wastewater.

[0066] Sample characterization in this embodiment:

[0067] like Figure 3As shown, the surface morphology of the original PAN / MWCNT-COOH nanofibers (wt=8%) and the quaternized ammonium-modified PPACE-Cl nanofibers (wt=8%) was observed using scanning electron microscopy. It can be clearly observed that the original PAN / MWCNT-COOH nanofibers (wt=8%) have a uniform diameter and no beading phenomenon, exhibiting a network structure with a diameter mainly distributed around 600 nm. Due to grafting and modification, the quaternized ammonium-modified PPACE-Cl fibers are thicker than the original PAN / MWCNT-COOH fibers. On the other hand, as... Figure 4 As shown, the quaternized PPACE-Cl fibers exhibit superhydrophilicity due to the introduction of a large number of hydrophilic groups. In summary, the morphological changes of the modified fibers demonstrate the successful modification of the nanofiber surface by quaternization, resulting in superhydrophilicity.

[0068] Considering the influence of different factors on the adsorption results, static adsorption was used to study the adsorption of AuCl4 by PPACE-Cl nanofibers under different conditions. - The adsorption capacity was studied, and the influencing factors mainly included solution pH (1-6), initial Au(III) solution concentration (100-550 mg / L), adsorption temperature (25-45℃), and contact time (1-3000 min). The entire adsorption process was carried out in a constant temperature shaker. The adsorption of AuCl4 before and after adsorption was analyzed. - The concentration was determined by ICP-OES. The theoretical adsorption capacity was calculated using the following formula: The adsorption capacity (mg / g) of the adsorbent was calculated using the following formula (1):

[0069] ;

[0070] In the formula: Q e (mg / g) is the adsorption capacity; C0 (mg / L) is the initial concentration of the solution; C e (mg / L) is the equilibrium concentration of the solution; V (mL) is the volume of the solution; W (g) is the mass of the adsorbent.

[0071] like Figure 5 As shown, PPACE-Cl nanofibers exhibited resistance to AuCl4 over a wide pH range (2-3). - It exhibits good adsorption performance, with the optimal adsorption capacity at pH=2. The adsorption capacity gradually decreases above pH 3. This phenomenon can be explained by the Zeta potential shown in the figure. Specifically, at pH below 7.68, the PPACE-Cl nanofibers carry a positive charge on their surface, making them readily react with AuCl4, which carries a negative charge. - They adhere to each other through electrostatic attraction.

[0072] To investigate the effect of initial concentration on the adsorption capacity of PPACE-Cl nanofibers, AuCl4 solutions with concentrations ranging from 100 to 550 mg / L were prepared. - The experiment was conducted using a solution at 25°C and a pH of 2. Figure 6 It can be seen that the adsorption capacity is positively correlated with the initial concentration as the concentration increases. In AuCl4... - When the initial concentration reaches 400 mg / L, the adsorption is basically saturated.

[0073] The effect of contact time on the adsorption process, such as Figure 7 As shown, the adsorption capacity increases rapidly within the initial 2200 min of contact. This is likely due to the large number of adsorption sites on the PPACE-Cl nanofibers at this stage. Afterward, the adsorption rate increases relatively slowly, reaching near equilibrium at 3000 min. This result may be partly due to the large number of adsorption sites on the PPACE-Cl nanofibers being occupied. In addition, a large amount of Au... 3+ Adsorption leads to a decrease in the concentration of ions in the solution, thereby weakening the driving force of mass transfer.

[0074] The selectivity experiment involved adding 10 mg of PPACE-Cl nanofibers to 25 mL of a mixed solution containing 200 mg / L of Fe(III), Co(II), Ni(II), Cd(II), Pb(II), and Au(III) for adsorption. The results are as follows: Figure 8 As shown, PPACE-Cl nanofibers affect Au 3+ It exhibits high adsorption capacity, while showing almost no adsorption for other ions. This indicates that PPACE-Cl nanofibers have a high adsorption capacity for AuCl4. - PPACE-Cl nanofibers exhibit excellent selectivity for AuCl4. - Its exceptional selectivity is attributed to its surface being rich in positive charges, which readily interacts with AuCl4, which exists as negative ions. - Static electricity is generated between them.

[0075] Furthermore, it should be noted that, based on the same principle, the selective adsorption effect of the quaternized modified PPACE-Cl nanofibers provided by this invention is not limited to AuCl4 in a mixed solution of Fe(III), Co(II), Ni(II), Cd(II), Pb(II) and Au(III). - Specific identification.

[0076] The effect of temperature on the adsorption process was investigated through thermodynamic experiments (contact time 2200 min, pH=2) at different temperatures ranging from 25℃ to 45℃. The results are as follows. Figure 9 As shown, within a certain temperature range, it can be concluded that as the temperature gradually increases, the adsorption of AuCl4 by the adsorbent material... - The adsorption capacity of AuCl4 is also continuously increasing, indicating that high temperature conditions are favorable for AuCl4. - The adsorption of AuCl4 may be due to the high temperature conditions. - The rate of diffusion has accelerated.

[0077] Ten mg of different nanofibers obtained in each step of this embodiment were placed in 25 mL of a solution containing 263.8 mg / L Au(III) for adsorption. The adsorption capacity of each nanofiber is shown in Table 1 below:

[0078] Table 1. Comparison of adsorption capacity of nanofibers obtained at different modification stages

[0079] ;

[0080] As shown in Table 1, the adsorption capacity of PPACE-Cl nanofibers modified by quaternization is greatly improved.

[0081] Comparative Example 1

[0082] This invention provides a method for preparing quaternized modified PPACE-Cl nanofibers, specifically comprising the following steps:

[0083] S1. Preparation of PAN electrospun nanofibers: 0.8 g of polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and 9.2 g of N,N-dimethylformamide (DMF) were added to a beaker. After stirring at room temperature for 8 h, a homogeneous and transparent spinning solution was obtained. The resulting spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized parameters of the electrospinning machine were set as follows: voltage 18.0 KV, spinning solution flow rate 2.0 mL / h, roller speed 200 r / min, receiving distance 15 cm, spinning temperature and humidity 25 ± 1 ℃ and 70 ± 5%, respectively, to obtain PAN / PVP nanofibers. The nanofibers were then placed in 80°C hot water to remove PVP, yielding porous polyacrylonitrile nanofibers.

[0084] S2. Preparation of modified nanofibers: Weigh 0.5 g of the polyacrylonitrile nanofibers prepared in step S1 and place them in a high-pressure reactor with 5.0 g of a 10 wt% polyethyleneimine (PEI) aqueous solution. React at 130℃ for 20 h. After the reaction, wash the nanofibers with pure water more than 3 times and freeze-dry them under vacuum at -50℃ for 12 h to obtain modified nanofibers.

[0085] The modified nanofibers prepared by the above method were placed in wastewater as adsorbent materials.

[0086] Adsorption test: 10 mg of each of the quaternized modified PPACE-Cl nanofibers prepared in Examples 1-5 and the modified nanofibers prepared in Comparative Example 1 were taken. Simultaneously, a certain volume of wastewater solution was taken from the wastewater tank, and the pH of the wastewater solution was adjusted to pH=2 using hydrochloric acid. Six equal volumes of 25 mL wastewater solution were then measured from the acidified wastewater solution. The weighed quaternized modified PPACE-Cl nanofibers and the modified nanofibers were placed in these six wastewater solutions respectively. The temperature was controlled at 25℃ and the solution was shaken at this constant temperature for 8 h. The solutions were then removed, and the concentrations of each metal ion in the solution before and after adsorption were determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The initial concentrations of each ion in the wastewater solution before adsorption were: Au(III) 263.8 mg / L, Co(II) 208.6 mg / L, Fe(III) 201.5 mg / L, Ni(II) 205.3 mg / L, and Pb(II) 210.9 mg / L. After adsorption, the concentration of each metal ion in the wastewater solution was measured to obtain the adsorption capacity of each nanofiber for each metal in the wastewater. The above experiment was repeated three times, and the average value was taken. That is, the nanofibers of each example and comparative example were subjected to three repeated adsorption experiments. The adsorption capacity data are shown in Table 2.

[0087] Table 2. Adsorption capacity of each nanofiber for metal ions obtained using the methods of Examples 1-5 and Comparative Example 1.

[0088] ;

[0089] As shown in Table 2, the AuCl4 quaternized modified PPACE-Cl nanofibers prepared using the method provided in this application are... - It exhibits excellent specific adsorption capacity for AuCl4. - The quaternized PPACE-Cl nanofibers exhibit good affinity and excellent hydrophilicity, reducing the energy barrier during adsorption and significantly improving the adsorption rate and capacity. This makes them suitable for gold recovery from wastewater. Furthermore, the quaternized PPACE-Cl nanofibers in this invention exhibit good affinity for AuCl4. - It exhibits excellent specific adsorption capacity, while adsorbing very little of other heavy metals, which greatly simplifies the subsequent purification process for recovered gold, improves the efficiency of gold recovery, and has high industrial value.

[0090] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings. Those skilled in the art can implement the present invention in various modifications without departing from its scope and spirit. For example, a feature shown or described in one embodiment can be used in another embodiment to obtain yet another embodiment. The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. All equivalent changes made based on the description and drawings of the present invention are included within the scope of the present invention.

Claims

1. A method for preparing quaternized modified PPACE-Cl nanofibers, characterized in that, Specifically, the following steps are included: S1. Preparation of PAN electrospun nanofibers: Polyacrylonitrile, polyvinylpyrrolidone, and carboxylated multi-walled carbon nanotubes were stirred with N,N-dimethylformamide at room temperature for 6-12 h to obtain a uniform and transparent spinning solution. The resulting spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine to obtain PAN / PVP / MWCNT-COOH nanofibers. The obtained nanofibers were then placed in hot water at 60-100°C to remove PVP, thus obtaining PAN / MWCNT-COOH nanofibers. S2. Preparation of nitrogen-enriched modified PPACE nanofibers: The PAN / MWCNT-COOH nanofibers prepared in step S1 were placed in a high-pressure reactor and reacted at 110~140℃ for 12~24h. After the reaction, the nanofibers were washed with pure water more than 3 times and then freeze-dried under vacuum at -50℃ for 12h to obtain modified PPACE nanofibers. S3. Preparation of quaternized PPACE-Cl nanofibers: The PPACE nanofibers prepared in step S2 were mixed with chloropropane, and ethanol was added as a solvent. The mixture was refluxed at 80°C with magnetic stirring for 8-12 h. After the reaction was completed, the nanofibers were washed three times with ethanol and then freeze-dried under vacuum at -50°C for 12 h to obtain quaternized modified PPACE-Cl nanofibers.

2. The method for preparing quaternized modified PPACE-Cl nanofibers according to claim 1, characterized in that, The mass ratio of polyacrylonitrile, polyvinylpyrrolidone, carboxylated multi-walled carbon nanotubes, and N,N-dimethylformamide is 1:1:1:9-16.

3. The method for preparing quaternized modified PPACE-Cl nanofibers according to claim 1, characterized in that, The mass ratio of the PAN / MWCNT-COOH nanofibers to the polyethyleneimine aqueous solution is 1:

10.

4. The method for preparing quaternized modified PPACE-Cl nanofibers according to claim 1, characterized in that, The mass ratio of the PPACE nanofibers to the chloropropane is 1:0.925-2.

775.

5. The method for preparing quaternized modified PPACE-Cl nanofibers according to claim 1, characterized in that, The parameters of the electrospinning machine are set as follows: voltage 15.0-18.0KV, spinning solution flow rate 2.0mL / h, roller speed 200 r / min, receiving distance 15 cm, spinning temperature and humidity 25 ± 1 ℃ and 70 ± 5%, respectively.

6. A quaternized modified PPACE-Cl nanofiber, characterized in that, The quaternized modified PPACE-Cl nanofibers were prepared using the method described in any one of claims 1-5.

7. An application of quaternized modified PPACE-Cl nanofibers, characterized in that, The quaternized modified PPACE-Cl nanofiber of claim 6 was used as an adsorbent in AuCl4. - Selective recycling.

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