Method for treating microplastics in water based on combination of pulse electrocoagulation and electrostatic spinning

Abstract

The invention discloses a method for treating micro-plastics in water based on combination of pulse electrocoagulation and electrostatic spinning, which comprises the following steps: treating sewage by using a pulse electrocoagulation method, precipitating the micro-plastics in the sewage into sludge, soaking the flocculated sludge into an organic solution to obtain a polymer solution, and finally treating the polymer solution by using an electrostatic spinning method. The micro-plastic is converted into a commercial film composed of plastic fibers, and the problems that in the prior art, the efficiency of treating the micro-plastic in water is low, the cost is high, and secondary pollution is caused to the treated micro-plastic are solved.

Description

Technical Field

[0001] The present invention belongs to the field of water pollution treatment, and specifically relates to a method for treating microplastics in water based on the combination of pulse electrocoagulation and electrostatic spinning. Background Art

[0002] Microplastics, which are plastic fragments, films, or particles with a size of less than 5 mm, are easily transported through processes such as rainwater runoff and have become a new type of pollutant. Compared with traditional "white pollution" plastics, microplastics pose a higher ecological risk in the natural environment. Not only are they easily ingested by organisms and then accumulated in the body, causing toxic effects, they also easily absorb other toxic substances to form complex pollutants (such as heavy metals and PFAS).

[0003] Current traditional wastewater treatment processes for microplastics in water have significant limitations. Aeration and mechanical agitation during secondary treatment can further fragment microplastics, generating more ultrafine particles and increasing the difficulty and cost of removal. Electrocoagulation offers advantages such as high efficiency and simple operation, making it particularly suitable for treating wastewater with smaller particles and higher concentrations. It is an environmentally friendly and economical wastewater treatment method. More importantly, pulse electrocoagulation technology, through the periodic alternation of anode and cathode, can address issues of electrode passivation and concentration polarization, resulting in lower wastewater treatment power consumption and electrode loss. Furthermore, electrospinning, which utilizes a strong electric field to transform polymer solutions into fibers with diameters ranging from tens to hundreds of nanometers, has practical implications for the treatment and maximization of microplastics in pulse electrocoagulation sludge. The development of a combined pulse electrocoagulation-electrospinning mechanism for microplastic removal in water could effectively address the low efficiency, high cost, and post-treatment secondary contamination of microplastics by conventional treatment processes, and holds significant commercial value.

[0004] Therefore, the development of green, low-cost and efficient microplastic treatment processes is of great practical significance. Summary of the Invention

[0005] In view of the problems of low efficiency and high cost in treating microplastics in water by traditional treatment processes in the prior art, the present invention provides a method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning. The pulse electrocoagulation method is used to treat sewage, and the microplastics in the sewage are precipitated into sludge. The flocculated sludge is then immersed in an organic solution to obtain a polymer solution. Finally, the polymer solution is treated by electrospinning to convert the microplastics into a commercial film composed of plastic fibers, thereby reducing the overall sewage treatment cost while also avoiding the problem of secondary pollution of microplastics after treatment.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning, comprising the following steps:

[0008] S1. Use pulse electrocoagulation method to treat wastewater containing microplastics:

[0009] Add wastewater containing microplastics to an electrolytic cell, insert cathode and anode electrodes, and use a reciprocating machine to control the distance the cathode and anode electrodes are immersed in the wastewater. A 20μm microfiltration membrane is installed at the bottom of the electrolytic cell to collect flocculated sludge. Then, conductive salt is added to control the pH of the solution to 4-9. The power supply uses a CNC dual-pulse power supply with a pulse frequency of 500Hz-5000Hz, an air ratio of 10%-50%, a pulse voltage of ±(2-8)V, and a flocculation reaction of 1h-10h to precipitate the microplastics in the wastewater into flocculated sludge.

[0010] The cathode and anode electrodes are made of one or both of Fe and Al;

[0011] The conductive salt is one or both of NaCl and Na2SO4, and the mixture can be in any proportion;

[0012] S2. Use organic solution to dissolve microplastics in flocculated sludge:

[0013] The flocculated sludge obtained in S1 was dried and then added to the organic solution at a mixing ratio of 1:(0.2-4). The dissolution temperature was controlled at 40°C-80°C and the reaction was carried out for 2h-10h to obtain a polymer solution.

[0014] The organic solution is a mixture of any two of ethanol, acetone, N,N-dimethylformamide, and cyclohexane in any proportion;

[0015] S3. Obtaining plastic film by electrospinning:

[0016] The polymer solution obtained from S2 was reused to dissolve the flocculent sludge multiple times until the plastic mass fraction in the solution was 5%-25%, and then transferred to an electrospinning machine. The applied voltage was regulated to 5kV~30kV (needle) and -2kV~10kV (collector), the scanning speed was 10mm / s-30mm / s, the flow rate was 0.5mL / h-2mL / h, and the spinning time was controlled to 3h-20h to obtain a film composed of plastic fibers. The fiber size of the prepared plastic fiber film was 5μm.

[0017] Furthermore, the control of the distance of the cathode and anode electrodes immersed in sewage by the reciprocating machine described in S1 refers to a telescopic distance of 50 mm and a telescopic rate of 4 mm / s during operation.

[0018] Furthermore, the cathode and anode electrodes described in S1 are made of the same material, the conductive salt is NaCl, and the coagulation reaction time is 2 hours.

[0019] Furthermore, the organic solution described in S2 is acetone and N,N-dimethylformamide, the reaction temperature is 50° C., and the reaction time is 6 h.

[0020] Furthermore, the applied voltages described in S3 were 15 kV (needle) and -7.5 kV (collector), and the scanning speed was 15 mm / s.

[0021] The method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning described in the present invention has a polystyrene (PS) microplastic removal efficiency of ≥94.8% and a polyethylene (PE) microplastic removal efficiency of ≥93.6%. The fiber size of the film composed of the prepared plastic fibers is 5 μm.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention discloses a method for treating microplastics in water based on a combination of pulse electrocoagulation and electrospinning, which uses pulse electrocoagulation to treat wastewater containing microplastics. The process is simple and highly operable.

[0024] 2. The present invention describes a method for treating microplastics in water based on a combination of pulse electrocoagulation and electrospinning. Pulse electrocoagulation is performed using a homemade electrolytic cell. A reciprocating machine is used to control the movement of the electrode to accelerate the formation of floccules. A microfiltration membrane is fixed at the bottom of the electrode to facilitate the collection of flocculent sludge. These changes are of great significance for improving the efficiency of microplastic treatment.

[0025] 3. The present invention describes a method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning, which uses electrospinning to convert microplastics into commercial films composed of plastic fibers, thereby reducing the overall cost of sewage treatment and avoiding the problem of secondary pollution from microplastics after treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0027] Figure 1 is a schematic diagram of an electrolytic cell used in the present invention;

[0028] Figure 2 This is a graph showing the removal efficiency of PS microplastics using a method for treating microplastics in water based on a combination of pulsed electrocoagulation and electrospinning as described in Examples 1, 2, and 3 of the present invention;

[0029] Figure 3This is a graph showing the removal efficiency of PE microplastics using a method for treating microplastics in water based on a combination of pulsed electrocoagulation and electrospinning as described in Examples 1, 2, and 3 of the present invention;

[0030] Figure 4 Macroscopic and microscopic images of plastic films obtained by treating PS microplastics in a method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning as described in Example 1 of the present invention;

[0031] Figure 5 This is a process flow chart of the method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning as described in the present invention. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] Example 1:

[0034] A method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning, such as Figure 5 As shown, the following steps are included:

[0035] S1. Pulse electrocoagulation was used to treat wastewater containing microplastics. Wastewater containing PE and PS microplastics was added to the self-made electrolytic cell ( Figure 1 ), Al electrodes are selected as cathode and anode electrodes, and the distance between the cathode and anode electrodes and the sewage is controlled by a reciprocating machine. The telescopic distance is 50 mm and the telescopic rate is 4 mm / s during operation. A 20 μm microfiltration membrane is installed at the bottom of the electrolytic cell to collect flocculated sludge, and then NaCl conductive salt (0.7 g / L) is added to control the pH of the solution to 6. The power supply uses a CNC dual-pulse power supply with a pulse frequency of 1000 Hz, an air ratio of 20%, a pulse voltage of ±4 V, and a flocculation reaction for 6 hours to precipitate microplastics in the sewage into sludge;

[0036] S2, using organic solution to dissolve microplastics in flocculated sludge, collecting flocculated sludge on the microfiltration membrane, drying it, and then adding it to the mixed organic solution (V N,N-二甲基甲酰胺 :V 丙酮 =4:1), control the dissolution temperature at 50°C, and react for 6 hours to obtain a polymer solution;

[0037] S3. Use electrospinning to obtain plastic film. Reuse the polymer solution obtained in S2 to dissolve the flocculent sludge multiple times until the mass fraction of plastic in the solution is close to 13%. Then transfer it to the electrospinning machine, adjust the applied voltage to 15kV (needle) and -7.5kV (collector), the scanning speed to 15mm / s, the flow rate to 0.8mL / h, and control the spinning time to 8h to obtain a film composed of plastic fibers.

[0038] Figure 1 Schematic diagram of the electrolytic cell used in a method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning in Example 1;

[0039] Figure 2 、 Figure 3 This is a diagram showing the removal efficiency of PS and PE microplastics using a method for treating microplastics in water based on a combination of pulsed electrocoagulation and electrospinning in Example 1; Figure 2 、 Figure 3 As shown, the pulsed electrocoagulation reaction in Example 1 showed good microplastic removal efficiency. After 6 hours of coagulation reaction, the PS microplastic removal efficiency was 96.1%, and the polyethylene (PE) microplastic removal efficiency was 99.2%.

[0040] Figure 4 In Example 1, a method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning was used to treat PS microplastics to obtain macroscopic and microscopic images of the plastic film; Figure 4 As shown, in Example 1, microplastics in flocculated sludge can be effectively converted into a commercial film composed of plastic fibers, reducing the overall sewage treatment cost while also avoiding the problem of secondary pollution from microplastics after treatment.

[0041] Example 2:

[0042] A method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning, comprising the following steps:

[0043] S1. Pulse electrocoagulation was used to treat wastewater containing microplastics. Wastewater containing PE and PS microplastics was added to the self-made electrolytic cell ( Figure 1 ), Fe electrodes are selected as cathode and anode electrodes, and the distance between the cathode and anode electrodes and the sewage is controlled by a reciprocating machine. The telescopic distance is 50 mm and the telescopic rate is 4 mm / s during operation. A 20 μm microfiltration membrane is installed at the bottom of the electrolytic cell to collect flocculated sludge, and then NaCl conductive salt (1 g / L) is added to control the solution pH to 5.8. The power supply adopts a CNC dual-pulse power supply with a pulse frequency of 2000 Hz, an air ratio of 30%, a pulse voltage of ±5 V, and a flocculation reaction of 6 hours to precipitate microplastics in the sewage into sludge;

[0044] S2, using organic solution to dissolve microplastics in flocculated sludge, collecting flocculated sludge on the microfiltration membrane, drying it, and then adding it to the mixed organic solution (V N,N-二甲基甲酰胺 :V 丙酮 =3:1), control the dissolution temperature at 60°C, and react for 8 hours to obtain a polymer solution;

[0045] S3. Use electrospinning to obtain plastic film. Reuse the polymer solution obtained in S2 to dissolve the flocculent sludge multiple times until the mass fraction of plastic in the solution is close to 15%. Then transfer it to the electrospinning machine, adjust the applied voltage to 15kV (needle) and -7.5kV (collector), the scanning speed to 15mm / s, the flow rate to 0.8mL / h, and control the spinning time to 6h to obtain a film composed of plastic fibers.

[0046] See the results Figure 2 、 Figure 3 As shown, the pulsed electrocoagulation reaction in Example 2 showed good microplastic removal efficiency. After 6 hours of coagulation reaction, the PS microplastic removal efficiency was 98.5%, and the polyethylene (PE) microplastic removal efficiency was 93.6%.

[0047] Example 3:

[0048] A method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning, comprising the following steps:

[0049] S1. Pulse electrocoagulation was used to treat wastewater containing microplastics. Wastewater containing PE and PS microplastics was added to the self-made electrolytic cell ( Figure 1 ), Al electrodes are selected as cathode and anode electrodes, and the distance between the cathode and anode electrodes and the sewage is controlled by a reciprocating machine. The telescopic distance is 50 mm and the telescopic rate is 4 mm / s during operation. A 20 μm microfiltration membrane is installed at the bottom of the electrolytic cell to collect flocculated sludge, and then NaCl conductive salt (0.7 g / L) is added to control the solution pH to 6. The power supply adopts a CNC dual-pulse power supply with a pulse frequency of 2000 Hz, an air ratio of 30%, a pulse voltage of ±5 V, and a flocculation reaction for 6 hours to precipitate microplastics in the sewage into sludge;

[0050] S2, using organic solution to dissolve microplastics in flocculated sludge, collecting flocculated sludge on the microfiltration membrane, drying it, and then adding it to the mixed organic solution (V N,N-二甲基甲酰胺 :V 丙酮 =3:1), control the dissolution temperature at 60°C, and react for 4 hours to obtain a polymer solution;

[0051] S3. Use electrospinning to obtain plastic film. Reuse the polymer solution obtained in S2 to dissolve the flocculent sludge multiple times until the mass fraction of plastic in the solution is close to 15%. Then transfer it to the electrospinning machine, adjust the applied voltage to 15kV (needle) and -7.5kV (collector), the scanning speed to 15mm / s, the flow rate to 0.8mL / h, and control the spinning time to 6h to obtain a film composed of plastic fibers.

[0052] See the results Figure 2 、 Figure 3 As shown, the pulsed electrocoagulation reaction in Example 3 showed good microplastic removal efficiency. After 6 hours of coagulation reaction, the PS microplastic removal efficiency was 94.8%, and the polyethylene (PE) microplastic removal efficiency was 97.2%.

[0053] Comparative Example:

[0054] Refer to Example 1, except that S1 uses a DC voltage flocculation method to treat wastewater containing microplastics. The power supply uses a DC power supply with a voltage of 5V and the flocculation reaction is performed for 6 hours to precipitate the microplastics in the wastewater into sludge.

[0055] S2 and S3 are consistent with those in Example 1.

[0056] See the results Figure 2 、 Figure 3 As shown, compared with the pulsed electrocoagulation process in the embodiment, the microplastic removal efficiency of the comparative example is poor. After 6 hours of coagulation reaction, the PS microplastic removal efficiency is only 63.3%, and the polyethylene (PE) microplastic removal efficiency is 56.8%.

[0057] Results and Discussion

[0058] The experimental results obtained by analyzing Example 1, Example 2, Example 3 and the comparative example are as follows. Figure 2 shown.

[0059] Judging from the results, the present invention adopts a pulsed electrocoagulation process, which can improve the efficiency of microplastic treatment and convert microplastics in the flocculated sludge into a commercial film composed of plastic fibers. This has practical significance in solving the problems of low efficiency and high cost in the existing technology of treating microplastics in water and secondary pollution of microplastics after treatment.

[0060] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning, characterized by: The following steps are involved: S1. Use pulse electrocoagulation method to treat wastewater containing microplastics: Add sewage containing microplastics into the electrolytic cell, insert cathode and anode electrodes, and use a reciprocating machine to control the distance of the cathode and anode electrodes immersed in the sewage. Install a 20μm microfiltration membrane at the bottom of the electrolytic cell to collect flocculated sludge. Then add conductive salt to control the pH of the solution to 4-9. Use a CNC dual-pulse power supply with a pulse frequency of 500Hz-5000Hz, an air ratio of 10%-50%, and a pulse voltage of ±(2-8)V. The flocculation reaction lasts for 1h-10h to precipitate the microplastics in the sewage into flocculated sludge. The cathode and anode electrodes are made of one or both of Fe and Al; The conductive salt is one or both of NaCl and Na2SO4, and the mixture can be in any proportion; S2. Use organic solution to dissolve microplastics in flocculated sludge: The flocculated sludge obtained in S1 was dried and then added to the organic solution at a mixing ratio of 1:(0.2-4). The dissolution temperature was controlled at 40°C-80°C and the reaction was carried out for 2h-10h to obtain a polymer solution. The organic solution is a mixture of any two of ethanol, acetone, N,N-dimethylformamide, and cyclohexane in any proportion; S3. Obtaining plastic film by electrospinning: The polymer solution obtained from S2 is reused to dissolve the flocculent sludge multiple times until the plastic mass fraction in the solution is 5%-25%, and then transferred to an electrospinning machine. The applied voltage is regulated to be 5kV-30kV needle and -2kV-10kV collector, the scanning speed is 10mm / s-30mm / s, the flow rate is 0.5mL / h-2mL / h, and the spinning time is controlled to be 3h-20h to obtain a film composed of plastic fibers. The fiber size of the prepared plastic fiber film is 5μm.

2. The method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning according to claim 1, characterized in that: The control of the distance of the cathode and anode electrodes immersed in sewage by the reciprocating machine described in S1 means that the telescopic distance during operation is 50 mm and the telescopic rate is 4 mm / s.

3. The method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning according to claim 1, characterized in that: The cathode and anode electrodes described in S1 are made of the same material, the conductive salt is NaCl, and the flocculation reaction time is 2 h.

4. The method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning according to claim 1, characterized in that: The organic solution described in S2 is acetone and N,N-dimethylformamide, the reaction temperature is 50° C., and the reaction time is 6 h.

5. The method for treating microplastics in water based on the combination of pulse electrocoagulation and electrospinning according to claim 1, characterized in that: The applied voltage as described in S3 was 15 kV needle and -7.5 kV collector, with a scanning speed of 15 mm / s.

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