A quaternary ammonium modified GA-PVA / PEI-Cl nanofiber and its preparation method and application

Abstract

The present invention relates to the field of nanofiber technology, in particular to a quaternized modified GA-PVA / PEI-Cl nanofiber and a preparation method and application thereof, specifically comprising the following steps: S1. preparing PVA / PEI composite nanofibers: placing polyvinyl alcohol powder and water in an oil bath at 85°C, stirring with a magnetic stirrer for 4 hours to obtain a uniform and transparent spinning solution, namely, solution A; stirring polyethyleneimine with water at room temperature for 4 hours to obtain another uniform and transparent spinning solution, namely, solution B; mixing solution A with solution B to obtain solution C, spinning solution C in an electrostatic spinning machine to obtain PVA / PEI composite nanofibers; S2. preparing GA-PVA / PEI nanofibers; S3. preparing quaternized GA-PVA / PEI-Cl nanofibers. The quaternized modified GA-PVA / PEI-Cl nanofibers prepared by the present invention are mixed with AuCl4 ‑ Through electrostatic interaction, coordination effect and redox interaction, AuCl4 ‑ selective adsorption.

Description

Technical Field

[0001] The present invention relates to the technical field of nanofibers, and in particular to a quaternary ammonium-modified GA-PVA / PEI-Cl nanofiber and a preparation method and application thereof. Background Art

[0002] Gold, with its excellent corrosion resistance, low toxicity, low contact resistance, and superior electrical conductivity, holds unique application value in industries such as electronics, electrical engineering, high-tech, and jewelry. In recent years, with the growing demand for gold in high-tech industries, its price has also risen rapidly. However, natural reserves of high-grade gold are limited, and mining costs continue to rise as resources are depleted. Faced with the challenges of limited gold resources and growing industrial demand for gold, effective measures must be taken to recover gold. Currently, electronic waste and some industrial wastewater contain abundant secondary gold resources. Recycling and reusing these resources can significantly offset the depletion of natural gold resources. Therefore, the secondary recovery and utilization of gold resources is of vital importance to sustainable development strategies.

[0003] Traditional gold recovery technologies suffer from low adsorbent efficiency and poor selectivity. Therefore, there is an urgent need for a potential material that can be used to adsorb and recover gold in wastewater. Summary of the Invention

[0004] Features and advantages of the invention are set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0005] To overcome the problems of the prior art, the present invention provides a method for preparing quaternary ammonium-modified GA-PVA / PEI-Cl nanofibers, which specifically comprises the following steps:

[0006] S1. Preparation of PVA / PEI composite nanofibers: Polyvinyl alcohol powder and water were stirred in an 85°C oil bath with a magnetic stirrer for 4 hours to obtain a homogeneous and transparent spinning solution, referred to as Solution A. Polyethylenimine was stirred with water at room temperature for 4 hours to obtain another homogeneous and transparent spinning solution, referred to as Solution B. Solution A and Solution B were mixed to obtain Solution C, which was spun in an electrospinning machine to produce PVA / PEI composite nanofibers.

[0007] S2. Preparation of GA-PVA / PEI nanofibers: The PVA / PEI composite nanofibers obtained in S1 were cut into 1 x 1 cm pieces. The cut pieces were mixed with glutaraldehyde and then added with anhydrous ethanol. The fibers were cross-linked at 85°C with magnetic stirring for 8 h. After the reaction, the fibers were washed 3-4 times with deionized water and freeze-dried in a vacuum freeze-dryer for 24 h to obtain cross-linked GA-PVA / PEI nanofibers.

[0008] S3. Preparation of quaternized GA-PVA / PEI-Cl nanofibers: The GA-PVA / PEI nanofibers obtained in S2 were cut into small pieces of 1*1 cm. The cut GA-PVA / PEI nanofibers were mixed with propyl chloride, and then anhydrous ethanol was added. The mixture was reacted under magnetic stirring at room temperature for 12 h. After the reaction, the mixture was washed with deionized water 3-4 times and then transferred to a vacuum freeze-drying chamber for freeze-drying for 24 h to obtain the modified GA-PVA / PEI-Cl nanofibers, i.e., quaternized GA-PVA / PEI-Cl nanofibers.

[0009] Preferably, in step S1, the mass ratio of the polyvinyl alcohol powder to the polyethyleneimine is 2-6:1.

[0010] Preferably, the mass percentage of the solute in the solution A and the solution B is 10%-20%.

[0011] Preferably, the mixing mass ratio of the PVA / PEI composite nanofibers to the glutaraldehyde is 1:2.

[0012] Preferably, the mixing mass ratio of the GA-PVA / PEI nanofibers to the n-propyl chloride is 1:10.

[0013] Preferably, in step S1, the parameters of the electrospinning machine are set as follows: voltage of 15.0-18.0 KV, spinning solution flow rate of 11.62 uL / min, drum speed of 300 r / min, receiving distance of 12-15 cm, spinning temperature and humidity of 25 ± 1 ° C and 60 ± 5%, respectively.

[0014] Preferably, the present invention further provides a quaternary ammonium modified GA-PVA / PEI-Cl nanofiber, which is prepared using the above-mentioned method for preparing a quaternary ammonium modified GA-PVA / PEI-Cl nanofiber.

[0015] Preferably, the present invention also provides an application of quaternary ammonium modified GA-PVA / PEI-Cl nanofibers, wherein the quaternary ammonium modified GA-PVA / PEI-Cl nanofibers are applied to AuCl4 - Selective recycling.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are:

[0017] 1. The quaternized GA-PVA / PEI-Cl nanofibers obtained by the present invention are obtained by quaternization modification. The surface of the obtained nanofibers is rich in positive charge, which can realize the reaction of AuCl4 in aqueous solution with negative charge.-- Selective enrichment adsorption.

[0018] 2. The quaternized GA-PVA / PEI-Cl nanofibers obtained by the present invention are reacted with AuCl4 - The adsorption process involves multiple reaction mechanisms such as electrostatic interaction, coordination effect and redox reaction, and therefore has a higher adsorption capacity and better adsorption effect.

[0019] 3. The quaternized GA-PVA / PEI-Cl nanofibers of the present invention exhibit superhydrophilicity, which can reduce the contact energy barrier between them and gold in the solution, and can effectively solve the problem of gold adsorption, recovery and removal in high concentration solutions, and have broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be described in detail below with reference to the accompanying drawings and in combination with examples, and the advantages and implementation modes of the present invention will become more apparent. The contents shown in the accompanying drawings are only used to illustrate the present invention and do not constitute any limitation to the present invention. In the accompanying drawings:

[0021] Figure 1 Schematic diagram of the process of quaternary ammonium modification of GA-PVA / PEI-Cl nanofibers in a specific embodiment of the present invention;

[0022] Figure 2 Schematic diagram of the preparation of quaternary ammonium modified GA-PVA / PEI-Cl nanofibers in a specific embodiment of the present invention;

[0023] Figure 3 Figures 1 and 2 are scanning electron microscope images of nanofibers at various stages obtained in specific embodiment 3 of the present invention, wherein Figure a is a scanning electron microscope image of PVA / PEI composite nanofibers; Figure b is a scanning electron microscope image of GA-PVA / PEI nanofibers; Figure c is a scanning electron microscope image of quaternized GA-PVA / PEI nanofibers; Figure d is a diameter distribution diagram of PVA / PEI composite nanofibers; Figure e is a diameter distribution diagram of GA-PVA / PEI nanofibers; and Figure f is a diameter distribution diagram of quaternized GA-PVA / PEI nanofibers.

[0024] Figure 4 Graphs showing water contact angles of the PVA / PEI composite nanofibers, GA-PVA / PEI nanofibers cross-linked with glutaraldehyde, and GA-PVA / PEI-Cl nanofibers modified with quaternization in Example 3 of the present invention;

[0025] Figure 5 The figure a is the effect of pH on the adsorption process of AuCl4 - Figure a is an analysis diagram of the effect of pH on the adsorption capacity; Figure b is an analysis diagram of the effect of pH on the Zata potential;

[0026] Figure 6 For different AuCl4 in the specific embodiment of the present invention - Analysis diagram of the effect of initial concentration on adsorption process;

[0027] Figure 7 This is an analysis diagram of the influence of different time on the adsorption process in a specific embodiment of the present invention;

[0028] Figure 8 The quaternary ammonium modified GA-PVA / PEI-Cl nanofibers in a complex mixed solution for AuCl4 - Selective impact analysis diagram;

[0029] Figure 9 This is an analysis diagram of the effect of temperature on the adsorption process in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0031] Example 1

[0032] like Figure 1 and Figure 2 As shown, this embodiment provides a method for preparing quaternary ammonium modified GA-PVA / PEI-Cl nanofibers, which specifically includes the following steps:

[0033] S1. Preparation of PVA / PEI composite nanofibers: 2.0 g of polyvinyl alcohol (PVA) powder and 18 g of water were added to a round-bottom flask and stirred in an oil bath at 85°C with a magnetic stirrer for 4 h to obtain a homogeneous, transparent spinning solution (wt=10%), designated as Solution A. 1.0 g of polyethyleneimine (PEI) and 4.0 g of water were added to a beaker and stirred at room temperature for 4 h to obtain a homogeneous, transparent spinning solution (wt=20%), designated as Solution B. Solution A and Solution B were mixed to obtain Solution C, which was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized spinning machine parameters were: voltage 15.0 kV, spinning solution flow rate 11.62 uL / min, drum speed 300 r / min, receiving distance 15 cm, spinning temperature 24°C, and humidity 55%, respectively.

[0034] S2. Preparation of GA-PVA / PEI nanofibers: The PVA / PEI composite nanofibers prepared in step S1 were cut into 1 x 1 cm pieces. 0.310 g of the PVA / PEI composite nanofiber pieces were weighed and placed in a round-bottom flask with 0.620 g of glutaraldehyde (GA). 100 mL of anhydrous ethanol was added as the solvent. The mixture was cross-linked at 85°C with magnetic stirring for 8 h. After the reaction, the nanofibers were washed 3-4 times with deionized water and then freeze-dried in a vacuum freeze-drying oven for 24 h to obtain cross-linked GA-PVA / PEI nanofibers.

[0035] S3. Preparation of quaternized GA-PVA / PEI-Cl nanofibers: Cut the GA-PVA / PEI nanofibers prepared in step S2 into small pieces of 1*1 cm, then weigh 0.20 g of the GA-PVA / PEI nanofiber pieces and place them with 2.0 g of n-propyl chloride in a round-bottom flask, then add 100 mL of anhydrous ethanol as solvent, and react for 12 hours under magnetic stirring at room temperature. After the reaction, the nanofibers are washed with deionized water 3-4 times and then transferred to a vacuum freeze drying oven for freeze drying for 24 hours to obtain quaternized GA-PVA / PEI-Cl nanofibers.

[0036] The obtained quaternized GA-PVA / PEI-Cl nanofibers were used as adsorption materials for the recovery of gold from wastewater.

[0037] Polyethyleneimine (PEI) has good electrospinning properties due to the abundant primary, secondary and tertiary amine groups on its macromolecular chain. However, due to the strong polarity and intermolecular forces of PEI, its electrospinning process is not easy. Therefore, PEI is usually mixed with other polymers to improve its electrospinning performance. Polyvinyl alcohol (PVA) is a water-soluble polymer with many active hydroxyl groups. It has the characteristics of low cost, non-toxicity, good biocompatibility, good mechanical strength and good electrospinnability. The PVA / PEI composite nanofibers prepared by electrospinning can retain the excellent properties of both, are rich in amino groups, and are AuCl4 - active adsorption sites.

[0038] Electrospinning technology can be used to produce nanofibers with a high specific surface area. Surface modification techniques crosslink the nanofiber surface, providing more nitrogen active sites. Quaternization further imparts a high positive charge to the surface. Furthermore, the matrix materials PVA and PEI exhibit a high hydrophilicity due to their numerous hydrophilic groups. This reduces the energy barrier for the adsorbent to contact gold in solution, significantly enhancing adsorption of gold in solution.

[0039] The technical solution adopted in this embodiment is: using polyvinyl alcohol (PVA) and polyethyleneimine (PEI) as matrix materials, using electrospinning technology to prepare composite nanofibers, using glutaraldehyde (GA) for cross-linking modification, and using chlorinated n-propyl chloride as the functional group for quaternization modification to prepare quaternized GA-PVA / PEI-Cl nanofibers. The prepared quaternized GA-PVA / PEI-Cl nanofibers are mixed with AuCl4 - Through electrostatic interaction, coordination effect and redox interaction, AuCl4 - In addition, the quaternized GA-PVA / PEI-Cl nanofibers prepared by the present invention have excellent hydrophilicity, which reduces the energy barrier in the adsorption process and can significantly improve the adsorption rate and adsorption capacity.

[0040] Example 2

[0041] This embodiment provides a method for preparing quaternary ammonium-modified GA-PVA / PEI-Cl nanofibers, which specifically includes the following steps:

[0042] S1. Preparation of PVA / PEI composite nanofibers: 3.0 g of polyvinyl alcohol (PVA) powder and 17 g of water were added to a round-bottom flask and stirred in an oil bath at 85°C with a magnetic stirrer for 4 h to obtain a homogeneous, transparent spinning solution (wt=15%), designated as Solution A. 0.5 g of polyethyleneimine (PEI) and 4.5 g of water were added to a beaker and stirred at room temperature for 4 h to obtain a homogeneous, transparent spinning solution (wt=10%), designated as Solution B. Solution A and Solution B were mixed to obtain Solution C, which was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized spinning machine parameters were: voltage 15.0 kV, spinning solution flow rate 11.62 uL / min, drum speed 300 r / min, receiving distance 15 cm, spinning temperature 24°C, and humidity 55%, respectively.

[0043] S2. Preparation of GA-PVA / PEI nanofibers: The PVA / PEI composite nanofibers prepared in step S1 were cut into 1 x 1 cm pieces. 0.356 g of the PVA / PEI composite nanofiber pieces were weighed and placed in a round-bottom flask with 0.712 g of glutaraldehyde (GA). 100 mL of anhydrous ethanol was added as the solvent. The mixture was cross-linked at 85°C with magnetic stirring for 8 h. After the reaction, the nanofibers were washed 3-4 times with deionized water and then freeze-dried in a vacuum freeze-drying oven for 24 h to obtain cross-linked GA-PVA / PEI nanofibers.

[0044] S3. Preparation of quaternized GA-PVA / PEI-Cl nanofibers: The GA-PVA / PEI nanofibers prepared in step S2 were cut into small pieces of 1*1 cm. 0.357 g of the GA-PVA / PEI nanofiber pieces were weighed and placed in a round-bottom flask with 3.57 g of n-propyl chloride. 100 mL of anhydrous ethanol was added as a solvent. The mixture was reacted under magnetic stirring at room temperature for 12 h. After the reaction, the nanofibers were washed with deionized water 3-4 times and then transferred to a vacuum freeze drying oven for freeze-drying for 24 h to obtain quaternized GA-PVA / PEI-Cl nanofibers.

[0045] The obtained quaternized GA-PVA / PEI-Cl nanofibers were used as adsorption materials for the recovery of gold from wastewater.

[0046] Example 3

[0047] This embodiment provides a method for preparing quaternary ammonium-modified GA-PVA / PEI-Cl nanofibers, which specifically includes the following steps:

[0048] S1. Preparation of PVA / PEI composite nanofibers: 3.5 g of polyvinyl alcohol (PVA) powder and 16.5 g of water were added to a round-bottom flask and stirred in an oil bath at 85°C with a magnetic stirrer for 4 h to obtain a homogeneous, transparent spinning solution (wt=18%), designated as Solution A. 1 g of polyethyleneimine (PEI) and 4 g of water were added to a beaker and stirred at room temperature for 4 h to obtain a homogeneous, transparent spinning solution (wt=20%), designated as Solution B. Solution A and Solution B were mixed to obtain Solution C, which was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized spinning machine parameters were: voltage 15.0 kV, spinning solution flow rate 11.62 uL / min, drum speed 300 r / min, receiving distance 15 cm, spinning temperature 24°C, and humidity 55%, respectively.

[0049] S2. Preparation of GA-PVA / PEI nanofibers: The PVA / PEI composite nanofibers prepared in step S1 were cut into 1 x 1 cm pieces. 0.368 g of the PVA / PEI composite nanofiber pieces were weighed and placed in a round-bottom flask with 0.736 g of glutaraldehyde (GA). 100 mL of anhydrous ethanol was added as the solvent. The mixture was cross-linked at 85°C with magnetic stirring for 8 h. After the reaction, the nanofibers were washed 3-4 times with deionized water and then freeze-dried in a vacuum freeze-drying oven for 24 h to obtain cross-linked GA-PVA / PEI nanofibers.

[0050] S3. Preparation of quaternized GA-PVA / PEI-Cl nanofibers: The GA-PVA / PEI nanofibers prepared in step S2 were cut into small pieces of 1*1 cm. 0.369 g of the GA-PVA / PEI nanofiber pieces were weighed and placed in a round-bottom flask with 3.69 g of n-propyl chloride. 100 mL of anhydrous ethanol was added as a solvent. The mixture was reacted under magnetic stirring at room temperature for 12 h. After the reaction, the nanofibers were washed with deionized water 3-4 times and then transferred to a vacuum freeze drying oven for freeze-drying for 24 h to obtain quaternized GA-PVA / PEI-Cl nanofibers.

[0051] The obtained quaternized GA-PVA / PEI-Cl nanofibers were used as adsorption materials for the recovery of gold from wastewater.

[0052] Example 4

[0053] This embodiment provides a method for preparing quaternary ammonium-modified GA-PVA / PEI-Cl nanofibers, which specifically includes the following steps:

[0054] S1. Preparation of PVA / PEI composite nanofibers: 3.5 g of polyvinyl alcohol (PVA) powder and 16.5 g of water were added to a round-bottom flask and stirred in an oil bath at 85°C with a magnetic stirrer for 4 h to obtain a homogeneous, transparent spinning solution (wt=18%), designated as Solution A. 0.875 g of polyethyleneimine (PEI) and 4.125 g of water were added to a beaker and stirred at room temperature for 4 h to obtain a homogeneous, transparent spinning solution (wt=18%), designated as Solution B. Solution A and Solution B were mixed to obtain Solution C, which was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized spinning machine parameters were: voltage 15.0 kV, spinning solution flow rate 11.62 uL / min, drum speed 300 r / min, receiving distance 15 cm, spinning temperature 24°C, and humidity 55%, respectively.

[0055] S2. Preparation of GA-PVA / PEI nanofibers: The PVA / PEI composite nanofibers prepared in step S1 were cut into 1 x 1 cm pieces. 0.381 g of the PVA / PEI composite nanofiber pieces were weighed and placed in a round-bottom flask with 0.762 g of glutaraldehyde (GA). 100 mL of anhydrous ethanol was added as the solvent. The mixture was cross-linked at 85°C with magnetic stirring for 8 h. After the reaction, the nanofibers were washed 3-4 times with deionized water and then freeze-dried in a vacuum freeze-drying oven for 24 h to obtain cross-linked GA-PVA / PEI nanofibers.

[0056] S3. Preparation of quaternized GA-PVA / PEI-Cl nanofibers: The GA-PVA / PEI nanofibers prepared in step S2 were cut into small pieces of 1*1 cm. 0.315 g of the GA-PVA / PEI nanofiber pieces were weighed and placed in a round-bottom flask with 3.15 g of n-propyl chloride. 100 mL of anhydrous ethanol was added as a solvent. The mixture was reacted under magnetic stirring at room temperature for 12 h. After the reaction, the nanofibers were washed 3-4 times with deionized water and then transferred to a vacuum freeze-drying oven for freeze-drying for 24 h to obtain quaternized GA-PVA / PEI-Cl nanofibers.

[0057] The obtained quaternized GA-PVA / PEI-Cl nanofibers were used as adsorption materials for the recovery of gold from wastewater.

[0058] Example 5

[0059] This embodiment provides a method for preparing quaternary ammonium-modified GA-PVA / PEI-Cl nanofibers, which specifically includes the following steps:

[0060] S1. Preparation of PVA / PEI composite nanofibers: 4.0 g of polyvinyl alcohol (PVA) powder and 16 g of water were added to a round-bottom flask and stirred in an oil bath at 85°C with a magnetic stirrer for 4 h to obtain a homogeneous, transparent spinning solution (wt=20%), designated as Solution A. 0.7 g of polyethyleneimine (PEI) and 4.3 g of water were added to a beaker and stirred at room temperature for 4 h to obtain a homogeneous, transparent spinning solution (wt=14%), designated as Solution B. Solution A and Solution B were mixed to obtain Solution C, which was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized spinning machine parameters were: voltage 15.0 kV, spinning solution flow rate 11.62 uL / min, drum speed 300 r / min, receiving distance 15 cm, spinning temperature 24°C, and humidity 55%, respectively.

[0061] S2. Preparation of GA-PVA / PEI nanofibers: The PVA / PEI composite nanofibers prepared in step S1 were cut into 1 x 1 cm pieces. 0.410 g of the PVA / PEI composite nanofiber pieces were weighed and placed in a round-bottom flask with 0.820 g of glutaraldehyde (GA). 100 mL of anhydrous ethanol was added as the solvent. The mixture was cross-linked at 85°C with magnetic stirring for 8 h. After the reaction, the nanofibers were washed 3-4 times with deionized water and then freeze-dried in a vacuum freeze-drying oven for 24 h to obtain cross-linked GA-PVA / PEI nanofibers.

[0062] S3. Preparation of quaternized GA-PVA / PEI-Cl nanofibers: The GA-PVA / PEI nanofibers prepared in step S2 were cut into small pieces of 1*1 cm. 0.290 g of the GA-PVA / PEI nanofiber pieces were weighed and placed in a round-bottom flask with 2.9 g of n-propyl chloride. 100 mL of anhydrous ethanol was added as a solvent. The mixture was reacted under magnetic stirring at room temperature for 12 h. After the reaction, the nanofibers were washed 3-4 times with deionized water and then transferred to a vacuum freeze-drying oven for freeze-drying for 24 h to obtain modified GA-PVA / PEI-Cl nanofibers.

[0063] The obtained quaternized GA-PVA / PEI-Cl nanofibers were used as adsorption materials for the recovery of gold from wastewater.

[0064] Characterization of samples in this example:

[0065] like Figure 3 As shown in the figure, the surface morphology of the original PVA / PEI composite nanofibers, cross-linked GA-PVA / PEI nanofibers and quaternary ammonium modified GA-PVA / PEI-Cl nanofibers were observed using a scanning electron microscope. It can be clearly observed that the original PVA / PEI composite nanofibers have a uniform diameter and no beading phenomenon, showing a network structure with a diameter mainly distributed around 350 nm. Due to the cross-linking effect, the surface of the GA-PVA / PEI nanofibers cross-linked with glutaraldehyde is obviously rougher than that of the original PVA / PEI composite fibers, and the diameter increases slightly to 370 nm. This change may be due to the cross-linking of the functional groups in PVA and PEI with glutaraldehyde, which increases the quality of the nanofibers. Due to grafting and modification, the quaternary ammonium modified GA-PVA / PEI-Cl nanofibers become thicker after modification compared to the original PVA / PEI composite fibers. On the other hand, as Figure 4 As shown in the figure, the quaternary ammonium modified GA-PVA / PEI-Cl fibers have super hydrophilicity due to the introduction of a large number of hydrophilic groups. In short, the changes in the morphology of the modified fibers show that the quaternary ammonium modification has successfully modified the nanofiber surface and has super hydrophilicity.

[0066] Considering the influence of different factors on the adsorption results, static adsorption was used to investigate the adsorption of AuCl4 by quaternary ammonium modified GA-PVA / PEI-Cl nanofibers under different conditions. - The adsorption capacity of AuCl4 -The initial concentration of the solution (100-600 mg / L), adsorption temperature (25-45℃) and contact time (1-720 min) were determined. The entire adsorption process was carried out in a constant temperature oscillator. The AuCl4 - The concentration is determined by ICP-OES. The theoretical adsorption capacity is calculated according to the following formula:

[0067] ;

[0068] Where: Qe (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.

[0069] like Figure 5 As shown in the figure, the quaternary ammonium modified GA-PVA / PEI-Cl nanofibers showed good ionization performance to AuCl4 in a wide pH range (2-3). - It has a good adsorption effect, with the best adsorption capacity at pH=3. At pH=4, the adsorption capacity drops sharply, and after the pH is greater than 4, the adsorption capacity begins to decrease gradually. The reason for this phenomenon can be explained by the Zeta potential in the figure. It is mainly because when the pH is less than 8.7, the surface of the adsorption material quaternized modified GA-PVA / PEI-Cl nanofiber has a positive charge, which makes it easy to react with the negatively charged AuCl4 - Adsorption occurs between them through electrostatic attraction.

[0070] In order to study the effect of initial concentration on the adsorption capacity of quaternary ammonium modified GA-PVA / PEI-Cl nanofibers, AuCl4 with concentrations of 100-600 mg / L was prepared. - The experiment was carried out at 25℃ and the pH value of the solution was 3. Figure 6 It can be seen that as the concentration increases, the adsorption capacity is positively correlated with the initial concentration, and both are positively correlated with the initial concentration. - When the initial concentration reached 600 mg / L, the adsorption basically reached saturation.

[0071] The effect of contact time on the adsorption process is as follows Figure 7As shown in the figure, the adsorption capacity increased relatively rapidly during the initial 400 min of contact time, which may be due to the fact that the quaternary ammonium modified GA-PVA / PEI-Cl nanofibers have a large number of adsorption sites at this time. After that, the adsorption rate climbed relatively slowly, and the adsorption basically reached equilibrium at 360 min. This result may be related to the fact that the adsorption sites of the quaternary ammonium modified GA-PVA / PEI-Cl nanofibers are largely occupied. On the other hand, a large amount of AuCl4 - Adsorption leads to a decrease in the ion concentration in the solution, thereby weakening the driving force for mass transfer.

[0072] Selectivity experimental verification: 10 mg of quaternary ammonium modified GA-PVA / PEI-Cl nanofibers were added to 20 mL of a mixed solution containing Fe(III), Co(II), Ni(II), Cd(II), Pb(II) and Au(III) at a concentration of 200 mg / L for adsorption. The results are shown in Figure 2. Figure 8 As shown in the figure, the quaternary ammonium modified GA-PVA / PEI-Cl nanofibers have a great influence on the AuCl4 - It showed high adsorption capacity, but had almost no adsorption for other ions. - The modified GA-PVA / PEI-Cl nanofibers have excellent selectivity for AuCl4 - The selectivity of the ion is due to its surface being rich in positive charges, which can easily react with AuCl4 in the form of negative ions. - There is electrostatic interaction between them.

[0073] In addition, it should be noted that, based on the same principle, the selective adsorption effect of the quaternized modified GA-PVA / PEI-Cl nanofibers provided by the present 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 recognition.

[0074] The effect of temperature on the adsorption process was investigated by thermodynamic experiments at different temperatures of 25°C to 45°C (contact time 360 ​​min, pH = 3). The results are as follows: Figure 9 As shown. It can be concluded that within a certain temperature range, as the temperature gradually rises, the adsorption material for AuCl4 - The adsorption capacity of AuCl4 is also expanding, indicating that high temperature conditions are conducive to the adsorption of AuCl4 - This result may be due to the fact that AuCl4 - The spread speed is accelerated.

[0075] From the above experiments, it can be seen that the quaternary ammonium modified GA-PVA / PEI-Cl nanofibers have a strong - It has specific recognition and can quickly and specifically identify and adsorb AuCl4 in wastewater mixed with other metal ions. - , and thus the quaternary ammonium modified GA-PVA / PEI-Cl nanofibers can be used to recover gold in wastewater.

[0076] Example 6

[0077] This embodiment provides a method for preparing GA-PVA / PEI nanofibers that have not been modified by quaternization, which specifically includes the following steps:

[0078] S1. Preparation of PVA / PEI composite nanofibers: 2.0 g of polyvinyl alcohol (PVA) powder and 18 g of water were added to a round-bottom flask and stirred in an oil bath at 85°C with a magnetic stirrer for 4 h to obtain a homogeneous, transparent spinning solution (wt=10%), designated as Solution A. 1.0 g of polyethyleneimine (PEI) and 4.0 g of water were added to a beaker and stirred at room temperature for 4 h to obtain a homogeneous, transparent spinning solution (wt=20%), designated as Solution B. Solution A and Solution B were mixed to obtain Solution C, which was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized spinning machine parameters were: voltage 15.0 kV, spinning solution flow rate 11.62 uL / min, drum speed 300 r / min, receiving distance 15 cm, spinning temperature 24°C, and humidity 55%, respectively.

[0079] S2. Preparation of GA-PVA / PEI nanofibers: The PVA / PEI composite nanofibers prepared in step S1 were cut into 1 x 1 cm pieces. 0.310 g of the PVA / PEI composite nanofiber pieces were weighed and placed in a round-bottom flask with 0.62 g of glutaraldehyde (GA). 100 mL of anhydrous ethanol was added as the solvent. The cross-linking reaction was carried out at 85°C with magnetic stirring for 8 h. After the reaction, the nanofibers were washed 3-4 times with deionized water and then freeze-dried in a vacuum freeze-dryer for 24 h to obtain cross-linked GA-PVA / PEI nanofibers.

[0080] The obtained GA-PVA / PEI nanofibers without quaternary ammonium modification were used as adsorption materials for the recovery of gold from wastewater.

[0081] The nanofibers obtained in Examples 1-6 were used to recover gold from wastewater.

[0082] Adsorption test: 10 mg of each of the quaternized ammonium modified GA-PVA / PEI-Cl nanofibers prepared in Examples 1-5 and the GA-PVA / PEI nanofibers in Example 6 were taken, and a certain volume of wastewater solution was taken from the wastewater pool. The pH value of the wastewater solution was adjusted to pH = 3 using hydrochloric acid. Then, 6 portions of 25 mL of wastewater solution were measured from the acid-adjusted wastewater solution, and the weighed quaternized ammonium modified GA-PVA / PEI-Cl nanofibers and glutaraldehyde cross-linked GA-PVA / PEI nanofibers were placed in the 6 portions of wastewater solution, respectively. The temperature was controlled at 25 ° C. and the solution was shaken at a constant temperature for 15 h before being taken out. The concentrations of each metal ion in the solution before and after adsorption were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The initial concentrations of each ion in the wastewater solution before adsorption were: Au(III) was 166.1 mg / L, Co(II) was 172.1 mg / L, Fe(III) was 159.9 mg / L, Ni(II) is 165.4 mg / L, and Pb(II) is 209.5 mg / L. After the adsorption, the concentration of each metal ion in the wastewater solution was measured, and the adsorption capacity of each nanofiber for each metal in the wastewater was calculated. The above experiment was repeated three times, and the average value was taken. That is, the nanofibers of Examples 1-5 and Example 6 were subjected to three repeated adsorption tests. The adsorption capacity data are shown in Table 1:

[0083] Table 1 Experimental parameters of Examples 1-6 and the adsorption capacity data of each nanofiber for Au(III)

[0084] ;

[0085] As shown in Table 1, the quaternary ammonium modified GA-PVA / PEI-Cl nanofibers have a strong effect on the AuCl4 - The anion adsorption capacity is significantly increased, and the material can be used as an adsorption material for the adsorption of gold in wastewater. At the same time, since PVA and PEI molecules contain a large number of hydrophilic groups, such as hydroxyl and amino groups, they can form hydrogen bonds with water molecules. The PVA / PEI composite nanofibers cross-linked with glutaraldehyde form a stable cross-linked network. This cross-linking increases the number of hydrophilic groups on the surface of the material. Although the PVA / PEI composite nanofibers can improve the hydrophilicity of the material, due to the lack of quaternary ammonium modification, the hydrophilicity of the cross-linked GA-PVA / PEI nanofibers is still relatively poor compared with the quaternary ammonium GA-PVA / PEI-Cl nanofibers. Therefore, when the material is used as an adsorption material for the recovery of gold in wastewater, the adsorption effect is poor.

[0086] While preferred embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art may implement the present invention in a variety of variations without departing from the scope and spirit of the present invention. For example, a feature shown or described as part of one embodiment may be used in another embodiment to yield yet another embodiment. The foregoing are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any equivalent variations made using the present description and accompanying drawings are intended to fall within the scope of the present invention.

Claims

1. A method for preparing quaternary ammonium modified GA-PVA / PEI-Cl nanofibers, characterized in that: The specific steps include: S1. Preparation of PVA / PEI composite nanofibers: Polyvinyl alcohol powder and water were stirred in an 85°C oil bath with a magnetic stirrer for 4 hours to obtain a homogeneous and transparent spinning solution, referred to as Solution A. Polyethylenimine was stirred with water at room temperature for 4 hours to obtain another homogeneous and transparent spinning solution, referred to as Solution B. Solution A and Solution B were mixed to obtain Solution C, which was spun in an electrospinning machine to produce PVA / PEI composite nanofibers. S2. Preparation of GA-PVA / PEI nanofibers: The PVA / PEI composite nanofibers obtained in S1 were cut into 1 x 1 cm pieces. The cut pieces were mixed with glutaraldehyde and then added with anhydrous ethanol. The fibers were cross-linked at 85°C with magnetic stirring for 8 h. After the reaction, the fibers were washed 3-4 times with deionized water and freeze-dried in a vacuum freeze-dryer for 24 h to obtain cross-linked GA-PVA / PEI nanofibers. S3. Preparation of quaternized GA-PVA / PEI-Cl nanofibers: The GA-PVA / PEI nanofibers obtained in S2 were cut into small pieces of 1*1 cm. The cut GA-PVA / PEI nanofibers were mixed with propyl chloride, and then anhydrous ethanol was added. The mixture was reacted under magnetic stirring at room temperature for 12 h. After the reaction, the mixture was washed with deionized water 3-4 times and then transferred to a vacuum freeze-drying oven for freeze-drying for 24 h to obtain the modified GA-PVA / PEI-Cl nanofibers, i.e., quaternized GA-PVA / PEI-Cl nanofibers.

2. The method for preparing quaternary ammonium modified GA-PVA / PEI-Cl nanofibers according to claim 1, wherein: In step S1, the mass ratio of the polyvinyl alcohol powder to the polyethyleneimine is 2-6:

1.

3. The method for preparing quaternary ammonium modified GA-PVA / PEI-Cl nanofibers according to claim 1, wherein: The mass percentage of solute in the solution A and the solution B is 10%-20%.

4. The method for preparing quaternary ammonium modified GA-PVA / PEI-Cl nanofibers according to claim 1, wherein: The mixing mass ratio of the PVA / PEI composite nanofibers to the glutaraldehyde is 1:

2.

5. The method for preparing quaternary ammonium modified GA-PVA / PEI-Cl nanofibers according to claim 1, wherein: The mixing mass ratio of the GA-PVA / PEI nanofibers to the n-propyl chloride is 1:

10.

6. The method for preparing quaternary ammonium modified GA-PVA / PEI-Cl nanofibers according to claim 1, wherein: In step S1, the parameters of the electrospinning machine are set as follows: voltage of 15.0-18.0 KV, spinning solution flow rate of 11.62 uL / min, drum speed of 300 r / min, receiving distance of 12-15 cm, spinning temperature and humidity of 25 ± 1 °C and 60 ± 5%, respectively.

7. A quaternary ammonium modified GA-PVA / PEI-Cl nanofiber, characterized in that: The nanofiber is prepared by the method for preparing quaternary ammonium-modified GA-PVA / PEI-Cl nanofiber according to any one of claims 1 to 6.

8. An application of quaternary ammonium modified GA-PVA / PEI-Cl nanofibers, characterized in that: The quaternized GA-PVA / PEI-Cl nanofibers described in claim 7 are applied to AuCl4 - Selective recycling.

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