Preparation method and application of light-responsive modified polyvinyl chloride nanofiber

Abstract

The present invention discloses a preparation method and application of light-responsive modified polyvinyl chloride nanofibers, and belongs to the technical field of polymer materials. The present invention uses polyvinyl chloride (PVC) as a matrix material, prepares PVC nanofibers by electrospinning technology, and further modifies the PVC nanofibers by an ionic liquid modification method, successfully preparing a modified PVC nanofiber with excellent adsorption properties. The modified nanofiber adsorption material prepared by the present invention by combining electrospinning technology and ionic liquid technology shows good responsiveness to light. By providing visible light irradiation, the adsorption rate and adsorption capacity can be greatly improved. In addition, the light-responsive modified polyvinyl chloride nanofiber prepared by the present invention is applied as an adsorption material to Au 3+ The selective recovery can effectively solve the problem of gold adsorption recovery and removal in high concentration solutions and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a preparation method of light-responsive modified polyvinyl chloride nanofiber and applications thereof. Background Art

[0002] Gold, a common precious metal in our daily lives, is experiencing a surge in consumption not only for jewelry but also due to its favorable physical and chemical properties, is being used in electronics, chemical catalysis, aerospace, and other fields. However, natural high-grade gold reserves are limited, and mining costs are increasing with resource depletion. Existing electronic waste and some industrial wastewater contain abundant secondary gold resources, whose recycling and reuse 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] Polyvinyl chloride (PVC), a common polymer, is frequently used, resulting in the generation of large amounts of PVC-containing waste. PVC waste is typically disposed of by landfill and incineration, but these treatment methods can create new environmental pollution problems. However, PVC contains abundant chlorine-containing side chains, which can serve as reaction sites for modification. Therefore, using PVC as a matrix material for modification can transform environmentally hazardous PVC into a beneficial new material, which is of great significance for environmental and resource recycling.

[0004] Traditional gold recovery technologies suffer from low adsorbent efficiency and poor selectivity. Electrospinning can be used to produce nanofibers with a high specific surface area. Combined with ionic liquid modification, the fiber surface is functionalized with positive charges, providing a large number of nitrogen active sites. Furthermore, the planar conjugated structure of the grafted pyridine ring exhibits excellent light response, significantly enhancing the adsorption of gold from solution under visible light irradiation. Therefore, this type of light-responsive adsorbent material has the potential to be used for the adsorption and recovery of gold from wastewater. Summary of the Invention

[0005] The present invention adopts a simple method to prepare a light-responsive modified polyvinyl chloride nanofiber and uses it to 3+ The present invention uses polyvinyl chloride (PVC) as the matrix material, prepares PVC nanofibers by electrospinning technology, and further modifies the PVC nanofibers by ionic liquid modification to successfully prepare a modified PVC nanofiber with excellent adsorption performance. 3+The maximum adsorption capacity of Au can reach 1243.75 mg / g under the condition of visible light assisted promotion. The adsorption process conforms to the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model, and it shows good adsorption performance for Au in a complex strongly acidic industrial wastewater environment. 3+ The high selectivity of Au is shown in the figure, with a distribution coefficient of 531.08 L / g. 3+ The modified nanofiber adsorption material, prepared by combining electrospinning and ionic liquid technologies, exhibits excellent responsiveness to light. The modified nanofibers prepared by the present invention can significantly increase adsorption rate and capacity by providing visible light irradiation, providing a new technical method for gold recovery in wastewater.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is to use polyvinyl chloride (PVC) as the matrix material, adopt electrospinning technology to prepare nanofibers, and use 4,4-bipyridine as the modified functional group to prepare ionic liquid-modified PVC nanofibers.

[0007] The preparation method of the modified PVC nanofiber is as follows:

[0008] (1) Preparation of PVC electrospinning nanofibers:

[0009] 1.2-1.6 g of polyvinyl chloride (PVC) and 8.4-8.8 g of a mixed solution of DMF and THF (w / w = 1:1) were added to a beaker and stirred at room temperature for 6 hours to obtain a uniform and transparent spinning solution (wt = 12%-16%). The obtained spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized spinning machine parameters were set to: voltage of 15.0 KV, spinning solution flow rate of 1.0 mL / h, drum speed of 400 r / min, receiving distance of 15 cm, spinning temperature and humidity of 25±1°C and 60±5%, respectively.

[0010] (2) Preparation of modified PVC nanofibers: The prepared PVC nanofibers were cut into small pieces of 1*1 cm, and then 0.2 g of the PVC nanofiber pieces were weighed and placed in a three-necked flask with 0.14-0.42 g of 4,4-bipyridine and 0.5-1.5 g of potassium hydroxide. 40 mL of acetonitrile was added as a solvent, and the mixture was reacted at 80°C with magnetic stirring for 1-3 days. After the reaction, the fiber powder was washed with pure water for more than 3 times and then centrifuged. It was vacuum dried at 80°C for 8 hours to obtain modified PVC nanofibers.

[0011] As a preferred spinning solution, the weight content is 12%, the amounts of 4,4-bipyridine and potassium hydroxide are 0.28 g and 1.0 g respectively, and the reaction time is 3 days.

[0012] Another object of the present invention is to use the light-responsive modified polyvinyl chloride nanofibers prepared by the present invention as an adsorption material for Au 3+ Selective recovery of gold from wastewater.

[0013] The modified PVC nanofibers prepared by the present invention have abundant nitrogen-containing groups, which can serve as adsorption sites for Au. 3+ There is a strong interaction between Au and 3+ In addition, because the modified PVC nanofibers have good light response properties, they can promote the electron transfer between them and the gold in the solution under light conditions, and Au 3+ It is reduced to Au(0), thereby promoting the entire adsorption process.

[0014] Compared with the prior art, the advantages and positive effects of the present invention are:

[0015] 1. The modified polyvinyl chloride nanofibers of the present invention are modified by ionic liquid to make the surface of the prepared nanofibers rich in positive charge, so as to realize the reaction of AuCl4 in aqueous solution with negative charge. - Selective enrichment adsorption.

[0016] 2. The modified polyvinyl chloride nanofiber of the present invention is 3+ The adsorption process involves multiple reaction mechanisms such as electrostatic interaction, coordination effect and redox reaction, so it has a higher adsorption capacity and better adsorption effect.

[0017] 3. The modified polyvinyl chloride nanofibers of the present invention show good responsiveness to light and can further enhance the responsiveness to Au under the promotion of visible light. 3+ The adsorption effect can effectively solve the problem of gold adsorption, recovery and removal in high concentration solutions, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0019] Figure 1 FIG1 is a diagram showing the preparation process of the modified polyvinyl chloride nanofiber of the present invention;

[0020] Figure 2 is a scanning electron microscope image of the modified polyvinyl chloride nanofiber of the present invention;

[0021] Figure 3 This is an analysis diagram of the effect of pH on the adsorption process;

[0022] Figure 4 Au under light and no light conditions 3+ Analysis diagram of the effect of initial concentration on adsorption process;

[0023] Figure 5 This is an analysis diagram of the effect of time on the adsorption process under conditions of light and no light;

[0024] Figure 6 To modify the polyvinyl chloride nanofibers to Au in a complex mixed solution 3+ Selective impact analysis diagram;

[0025] Figure 7 This is an analysis diagram of the effect of temperature on the adsorption process;

[0026] Figure 8 This is the light response diagram of modified polyvinyl chloride nanofibers. DETAILED DESCRIPTION

[0027] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] Embodiment 1:

[0030] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is to use polyvinyl chloride (PVC) as the matrix material, adopt electrospinning technology to prepare nanofibers, and use 4,4-bipyridine as the modified functional group to prepare ionic liquid modified PVC nanofibers. 3+ The Au is bonded through electrostatic interaction, coordination interaction and redox interaction. 3+ In addition, light is used to promote the adsorption process to achieve the selective adsorption of Au in water. 3+ Efficient recycling.

[0031] The preparation process of the modified polyvinyl chloride nanofiber in this embodiment is as follows:

[0032] (1) Preparation of PVC electrospinning nanofibers: 1.2 g of polyvinyl chloride (PVC) and 8.8 g of a mixed solution of DMF and THF (w / w = 1:1) were added to a beaker and stirred at room temperature for 6 h to obtain a uniform and transparent spinning solution (wt = 12%). The resulting spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized spinning machine parameters were set as follows: voltage of 15.0 kV, spinning solution flow rate of 1.0 mL / h, drum speed of 400 r / min, receiving distance of 15 cm, spinning temperature of 24 °C and humidity of 55%, respectively.

[0033] (2) Preparation of modified PVC nanofibers: The prepared PVC nanofibers were cut into small pieces of 1*1 cm, 0.2 g of the PVC nanofiber pieces were weighed and placed in a three-necked flask with 0.14 g of 4,4-bipyridine and 0.5 g of potassium hydroxide, and 40 mL of acetonitrile was added as a solvent. The mixture was then reacted at 80°C with magnetic stirring for 3 days. After the reaction, the fiber powder was washed with pure water three times and then centrifuged. It was then vacuum dried at 80°C for 8 hours to obtain light-responsive modified polyvinyl chloride nanofibers.

[0034] Example 2:

[0035] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is to use polyvinyl chloride (PVC) as the matrix material, adopt electrospinning technology to prepare nanofibers, and use 4,4-bipyridine as the modified functional group to prepare ionic liquid modified PVC nanofibers. 3+ The Au is bonded through electrostatic interaction, coordination interaction and redox interaction. 3+ In addition, light is used to promote the adsorption process to achieve the selective adsorption of Au in water. 3+ Efficient recycling.

[0036] The preparation process of the light-responsive modified polyvinyl chloride nanofiber of this embodiment is as follows: Figure 1 As shown, the preparation method is as follows:

[0037] (1) Preparation of PVC electrospinning nanofibers: 1.4 g of polyvinyl chloride (PVC) and 8.6 g of a mixed solution of DMF and THF (w / w = 1:1) were added to a beaker and stirred at room temperature for 6 h to obtain a uniform and transparent spinning solution (wt = 14%). The resulting spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized spinning machine parameters were set as follows: voltage of 15.0 kV, spinning solution flow rate of 1.0 mL / h, drum speed of 400 r / min, receiving distance of 15 cm, spinning temperature of 25 °C and humidity of 60%, respectively.

[0038] (2) Preparation of modified PVC nanofibers: The prepared PVC nanofibers were cut into small pieces of 1*1 cm, 0.2 g of the PVC nanofiber pieces were weighed and placed in a three-necked flask with 0.28 g of 4,4-bipyridine and 1.0 g of potassium hydroxide, and then 40 mL of acetonitrile was added as a solvent. The mixture was reacted at 80°C with magnetic stirring for 3 days. After the reaction, the fiber powder was washed with pure water 3 times and then centrifuged. It was vacuum dried at 80°C for 8 hours to obtain light-responsive modified polyvinyl chloride nanofibers.

[0039] The light-responsive modified polyvinyl chloride nanofibers prepared in this example are used as adsorption materials to recover gold from wastewater.

[0040] Characterization of samples in this example:

[0041] like Figure 2 As shown in the figure, the surface morphology of the original PVC nanofibers (wt=12%-16%) and the modified PVC nanofibers (wt=14%) were observed using a scanning electron microscope. It can be clearly observed that the diameter of the original PVC nanofibers (wt=14%) is uniform and has no beading phenomenon. It shows a network structure with a diameter mainly distributed around 800nm. In addition, the nanofibers with wt% of 12% and 16% have poor morphology and uneven thickness. Due to the action of external force, the modified PVC fibers become shorter than the original PVC fibers after being crushed. At the same time, their diameter becomes thicker than the original fibers and it can be clearly observed that the surface of the modified fibers becomes rough. The reason for this change may be that several fibers of the original PVC fibers are entangled together during the modification process. On the other hand, the holes on the surface of the modified PVC fibers may be caused by the dissolution of the generated potassium salt during the washing process. In short, the changes in the morphology of the modified fibers show that the ionic liquid has been successfully grafted on the surface of the nanofibers.

[0042] Considering the influence of different factors on the adsorption results, static adsorption was used to investigate the adsorption of Au by modified PVC nanofibers under different conditions. 3+ The adsorption capacity of Au(Ⅲ) was studied. The influencing factors mainly included the pH value of the solution (1-9), the initial concentration of Au(Ⅲ) solution (200-1400 mg / L), the adsorption temperature (25-45℃) and the contact time (1-7200 min). The whole adsorption process was carried out in a constant temperature oscillator. 3+ The concentration was determined by ICP-OES. The theoretical adsorption capacity was calculated according to the following formula: The adsorption amount (mg / g) of the adsorbent was calculated according to the following formula (1):

[0043]

[0044] Where: 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.

[0045] like Figure 3 As shown in Figure 2, the modified PVC nanofibers showed good kinetics for Au in a wide pH range (1-3). 3+ It has a good adsorption effect, with the best adsorption capacity at pH = 2. At pH = 4, the adsorption capacity drops sharply, and when 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 3.73, the surface of the modified PVC nanofiber of the adsorption material has a positive charge, which makes it easy to react with the negatively charged AuCl4 - Adsorption occurs between them through electrostatic attraction.

[0046] In order to study the effect of initial concentration on the adsorption capacity of modified PVC nanofibers, Au with a concentration of 200 to 1400 mg / L was prepared. 3+ The experiment was carried out at 25℃ and the pH value of the solution was 2. Figure 4 It can be seen that the adsorption capacity is positively correlated with the initial concentration under the conditions of light and no light. 3+ When the initial concentration reached 800 mg / L, adsorption was essentially saturated. Interestingly, under light conditions, the adsorption capacity nearly doubled compared to the absence of light. These results indicate that light promotes adsorption.

[0047] The effect of contact time on the adsorption process is as follows Figure 5 As shown in the figure, within the initial contact time of 1080 minutes, the adsorption capacity increases relatively rapidly, reaching about 2 / 3 of the maximum adsorption capacity. This may be because the modified PVC nanofibers have a large number of adsorption sites at this time. After this time point, the adsorption rate climbs relatively slowly, and the adsorption basically reaches equilibrium at 3600 minutes. This result may be related to the fact that the adsorption sites of the modified PVC nanofibers are largely occupied. In addition, a large amount of Au 3+ Adsorption leads to a decrease in the ion concentration in the solution, thus weakening the driving force for mass transfer. More interestingly, experiments have found that adsorption capacity under light conditions increases significantly over the same period of time compared to the absence of light. In other words, adsorption under light conditions can reach the same adsorption capacity as in the absence of light in a shorter period of time, greatly improving adsorption efficiency.

[0048] The selective experiment was to add 10 mg of modified PVC nanofibers into 25 mL of 200 mg / L Fe 3+ ,Co 2+ , Ni 2+ , Cd 2+ , Pb 2+ and Au 3+ The results are shown in Figure 2. Figure 6 As shown, the modified PVC nanofibers have a great influence on the Au 3+ It showed high adsorption capacity, while almost no adsorption of other ions. 3+ The modified PVC nanofibers have excellent selectivity for Au 3+ 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.

[0049] In addition, it should be noted that, at present, due to limited experimental conditions, the selective adsorption effect of the light-responsive modified polyvinyl chloride nanofibers provided by the present invention is not limited to Fe 3+ ,Co 2+ , Ni 2+ , Cd 2+ , Pb 2+ and Au 3+ Au in the mixed solution 3+ Specific recognition.

[0050] The effect of temperature on the adsorption process was investigated by thermodynamic experiments at different temperatures of 25°C to 45°C (contact time 1080 min, pH = 2). The results are as follows: Figure 7 As shown. It can be concluded that within a certain temperature range, as the temperature gradually rises, the adsorption material for Au 3+ The adsorption capacity of Au is also expanding, indicating that high temperature conditions are conducive to the adsorption of Au. 3+ This result may be due to the fact that Au 3+ The spread speed is accelerated.

[0051] In order to investigate the mechanism of light promoting the adsorption effect of modified PVC nanofibers, the photocurrent response curve was measured by electrochemical experiments. Figure 8 As shown in the figure, under the irradiation of a xenon lamp light source, the photocurrent response curve of the modified PVC nanofiber was plotted by controlling the conditions of alternating illumination and non-illumination for 50 seconds each. As can be seen from the figure, the current density of the modified PVC nanofiber increased under the conditions of illumination, indicating that illumination promotes charge transfer, which is beneficial to the reduction of Au(III) during the adsorption process and further promotes the adsorption process.

[0052] Example 3:

[0053] The photoresponsive modified polyvinyl chloride nanofiber of this embodiment is prepared as follows:

[0054] (1) Preparation of PVC electrospinning nanofibers: 1.6 g of polyvinyl chloride (PVC) and 8.4 g of a mixed solution of DMF and THF (w / w = 1:1) were added to a beaker and stirred at room temperature for 6 h to obtain a uniform and transparent spinning solution (wt = 16%). The resulting spinning solution was then placed in a 10 mL syringe and spun in an electrospinning machine. The optimized spinning machine parameters were set as follows: voltage of 15.0 kV, spinning solution flow rate of 1.0 mL / h, drum speed of 400 r / min, receiving distance of 15 cm, spinning temperature of 26 °C and humidity of 65%, respectively.

[0055] (2) Preparation of modified PVC nanofibers: The prepared PVC nanofibers were cut into small pieces of 1*1 cm, 0.2 g of the PVC nanofiber pieces were weighed and placed in a three-necked flask with 0.42 g of 4,4-bipyridine and 0.8 g of potassium hydroxide, and 40 mL of acetonitrile was added as a solvent. The mixture was reacted at 80°C with magnetic stirring for 2 days. After the reaction, the fiber powder was washed with pure water three times and then centrifuged. It was vacuum dried at 80°C for 8 hours to obtain light-responsive modified polyvinyl chloride nanofibers.

[0056] The light-responsive modified polyvinyl chloride nanofiber provided by the present invention is used as an adsorption material in the recovery of gold from wastewater.

[0057] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any person skilled in the art may utilize the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes for application in other fields. However, any simple modification, equivalent change, and modification of the above embodiments made in accordance with the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing light-responsive modified polyvinyl chloride nanofibers, characterized in that: Using polyvinyl chloride (PVC) as the matrix material, electrospinning technology was used to prepare nanofibers, and 4,4-bipyridine was used as the modified functional group to prepare ionic liquid-modified PVC nanofibers. The specific preparation steps are as follows: (1) Preparation of PVC electrospinning nanofibers: A mixed solution of 1.2-1.6 g of polyvinyl chloride and 8.4-8.8 g of dimethylformamide (DMF) and tetrahydrofuran (DHF) was added to a beaker and stirred at room temperature for 6 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 PVC nanofibers. (2) Preparation of modified PVC nanofibers: The PVC nanofibers prepared in step (1) were cut into small pieces of 1*1 cm, and then 0.2 g of the PVC nanofiber pieces were weighed and placed in a three-necked flask with 0.14-0.42 g of 4,4-bipyridine and 0.5-1 g of potassium hydroxide. 40 mL of acetonitrile was added as a solvent, and the mixture was reacted at 80°C with magnetic stirring for 1-3 days. After the reaction, the fiber powder was washed with pure water for more than 3 times and then centrifuged. It was vacuum dried at 80°C for 8 hours to obtain modified PVC nanofibers.

2. The method for preparing the light-responsive modified polyvinyl chloride nanofiber according to claim 1, wherein: In step (1), the parameters of the electrospinning machine were set as follows: voltage of 15.0 KV, spinning solution flow rate of 1.0 mL / h, drum speed of 400 r / min, receiving distance of 15 cm, spinning temperature and humidity of 25 ± 1 °C and 60 ± 5%, respectively.

3. The method for preparing the light-responsive modified polyvinyl chloride nanofiber according to claim 1, wherein: In step (1), the mass percentage of DMF and DHF in the mixed solution is 1:1, and the mass percentage of the obtained transparent spinning solution is 12%-16%.

4. The light-responsive modified polyvinyl chloride nanofiber prepared by the method for preparing the light-responsive modified polyvinyl chloride nanofiber according to any one of claims 1 to 3 is applied as an adsorption material to Au 3+ Selective recycling.

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