A modified nanofiber membrane and a method for treating anodizing wastewater from photovoltaic aluminum profiles containing nickel and tin.

Abstract

This invention relates to a modified nanofiber membrane and a method for treating anodizing wastewater from photovoltaic aluminum profiles containing nickel and tin. The preparation method of the modified nanofiber membrane includes the following steps: S1, dispersing polylactic acid in a solvent to obtain a dispersion; S2, adding at least one modifier selected from niobium carbide, vanadium carbide, and molybdenum carbide to the dispersion, stirring evenly to obtain a spinning solution; S3, adding the spinning solution to an electrospinning device, and spinning using the electrospinning device to obtain the modified nanofiber membrane. When the modified nanofiber membrane is installed in a filtration device, it exhibits significant nickel and tin removal effects on anodizing wastewater from photovoltaic aluminum profiles containing nickel and tin, with a nickel removal rate of ≥99% and a tin removal rate of ≥98%, achieving simultaneous removal of nickel and tin. This simplifies the treatment process of anodizing wastewater, reduces treatment costs, and has promising industrial application prospects.

Description

Technical Field

[0001] This invention relates to electrospinning technology and wastewater treatment technology, and in particular to a method for treating wastewater from the anodizing of modified nanofiber membranes and nickel-tin-containing photovoltaic aluminum profiles. Background Technology

[0002] Aluminum profiles used in the photovoltaic field are generally 6-series aluminum alloys, such as 6005, 6061, and 6063. These alloys themselves do not possess special corrosion resistance. Because the environments in which photovoltaic profiles are used place high demands on the surface of aluminum alloys, these 6-series alloys are often anodized to increase their corrosion resistance and extend their service life under certain extreme climates.

[0003] The core of aluminum profile anodizing is to pass electricity through the aluminum profile in a sulfuric acid bath, forming a dense anodic oxide film on the surface. Then, through coloring and sealing baths, the aluminum profile surface acquires a specific color and improved corrosion and weather resistance. Typically, the total nickel ion content in the coloring and sealing baths is 50 g / L, and the tin ion content is 40 g / L. When the mixed chemicals in the baths become ineffective due to repeated use, the bath solution is replaced, resulting in a significant amount of waste liquid.

[0004] The purpose of centralized treatment of the wastewater generated during the anodizing of aluminum profiles in the above process is primarily to remove heavy metals, which can have serious adverse effects on human life and the environment. For example, nickel and tin can enter the human food chain through seepage into groundwater and absorption by plants, causing various health problems, including eczema and allergies, lung cancer and pulmonary fibrosis, chronic bronchitis and sinusitis, heart and liver dysfunction, skin irritation, and headaches. According to relevant requirements, the tin and nickel content in the treated wastewater should meet the "Electroplating Pollutant Discharge Standard" GB21900-2008. Other pollutants, such as total aluminum and phosphate, should also meet the national "Integrated Wastewater Discharge Standard" GB 8978-1996 before discharge.

[0005] Currently, there are many methods for removing heavy metals. For example, chemical precipitation involves adding chemical agents to bring the wastewater containing the same heavy metal ion to the pH value required for precipitation, or adjusting the pH of wastewater containing multiple metal ions in stages to form precipitated sludge, which is then removed by flotation or sedimentation. Coagulation involves adding coagulants to cause heavy metal ions in the wastewater to coagulate or flocculate, forming larger particles that precipitate, thus removing the heavy metals. Adsorption utilizes the structure of adsorbents to remove heavy metal ions, such as activated carbon and silica gel. Ion exchange uses ion exchange resins to separate harmful substances in wastewater; commonly used ion exchange resins include ion exchange resins and zeolites. Membrane separation utilizes the selectivity of polymers to separate substances.

[0006] Among the above methods, membrane separation has advantages such as not introducing new pollution, simple and controllable operation, and reusability. For example, Chinese patent application CN 109107549 A discloses a method for preparing a nanofiber membrane for adsorbing heavy metal nickel ions in wastewater. The prepared nanofiber membrane adsorbs nickel ions and has a good effect on removing nickel from wastewater.

[0007] However, tin and nickel have different properties. The adsorption of nickel by nanofiber membranes is a result of the weak electrostatic interaction between the active groups of nickel and the active groups of the membrane. Tin has different chemical properties than nickel, and tin ions do not possess the same active groups as nickel ions. Therefore, nanofiber membranes, which have a good adsorption effect on nickel, cannot effectively remove tin ions. Research has found that the nanofiber membrane provided in Chinese patent application CN 109107549 A has a tin ion removal rate of only 5-10%, and cannot simultaneously and efficiently remove nickel and tin pollutants from wastewater. Summary of the Invention

[0008] The purpose of this invention is to overcome the problem that existing membrane separation methods cannot simultaneously and efficiently remove nickel and tin pollutants from wastewater, and to provide a modified nanofiber membrane and a method for treating anodizing wastewater from photovoltaic aluminum profiles containing nickel and tin.

[0009] The inventors believe that, considering the need for cost savings and efficiency, removing both nickel and tin ions in a single filtration step is highly practical. Therefore, this application proposes a novel modified nanofiber membrane that can remove not only nickel ions but also tin ions, thus achieving simultaneous removal of nickel and tin from photovoltaic aluminum profile anodizing wastewater.

[0010] To achieve the above objectives, this application chemically modifies polylactic acid electrospun membranes. By introducing modifiers into the spinning solution, the inventors have verified through extensive experiments that three specific modifiers can simultaneously remove nickel and tin. The wastewater purification process based on the modified polylactic acid fiber membrane is simple to operate and saves labor costs, making it valuable for industrial application.

[0011] The specific plan is as follows:

[0012] A method for preparing a modified nanofiber membrane includes the following steps:

[0013] S1. Disperse polylactic acid in a solvent to obtain a dispersion;

[0014] S2. Add at least one modifier selected from niobium carbide, vanadium carbide, and molybdenum carbide to the dispersion, stir evenly, and obtain a spinning solution;

[0015] S3. The spinning solution is added to an electrospinning device, and the electrospinning device is used to spin the fibers to obtain a modified nanofiber membrane.

[0016] Furthermore, the mass concentration of the dispersion is 1-15%, preferably 5-12%, and more preferably 8-10%. By controlling the concentration of the dispersion, the electrospinning process can be controlled, thereby obtaining a dimensionally stable spun product.

[0017] Furthermore, the mass ratio of the modifier added to the polylactic acid in the dispersion is 8-20 parts by weight: 80-92 parts by weight, preferably 10-18 parts by weight: 82-90 parts by weight, and more preferably 12-15 parts by weight: 85-88 parts by weight. This ratio of modifier addition can achieve satisfactory metal ion adsorption while meeting the mechanical performance requirements of the filtration device for using nanofiber membranes as filter media.

[0018] Furthermore, the modifier is preferably vanadium carbide, and more preferably, the mass ratio of vanadium carbide added to polylactic acid in the dispersion is 13-15 parts by weight: 85-87 parts by weight. Different types of carbides have different adsorption effects on metal ions. The inventors have found that compared with manganese carbide, niobium carbide, vanadium carbide, and molybdenum carbide have better nanofiber membrane modification effects. Among them, the mass ratio of vanadium carbide added to polylactic acid in the dispersion is 13-15 parts by weight: 85-87 parts by weight, which can not only efficiently remove tin and nickel from wastewater, but also better maintain the original mechanical strength of polylactic acid nanofiber membranes, avoiding the problem of significant decrease in mechanical properties present with other carbides.

[0019] Furthermore, the solvent is a mixture of dichloromethane and dimethylformamide, with a volume ratio of dichloromethane to dimethylformamide of 2-3:1.

[0020] The present invention also protects the modified nanofiber membrane prepared by the method of preparing the modified nanofiber membrane.

[0021] The present invention also protects a method for treating anodizing wastewater from nickel-tin photovoltaic aluminum profiles, comprising passing the nickel-tin-containing photovoltaic aluminum profile anodizing wastewater through a filtration device, wherein the filtration device is equipped with the modified nanofiber membrane.

[0022] Furthermore, the nickel concentration in the anodizing wastewater of the nickel-tin photovoltaic aluminum profile is 25-100 g / L, the tin concentration is 15-100 g / L, and the pH of the wastewater is 1-6. After treatment with the filtration device at room temperature for 6-12 hours, the nickel concentration in the wastewater does not exceed 0.5 g / L and the tin concentration does not exceed 0.8 g / L.

[0023] Furthermore, the modified nanofiber membrane contains 13-15% vanadium carbide by mass, and has a nickel removal rate of greater than or equal to 99% and a tin removal rate of greater than or equal to 98% in the wastewater.

[0024] Beneficial effects: This invention provides a method for preparing modified nanofiber membranes, which improves the metal ion removal efficiency of polylactic acid nanofiber membranes by modifying them with two-dimensional transition metal carbides.

[0025] Furthermore, the present invention improves the preparation method of modified nanofiber membranes by adding at least one modifier selected from niobium carbide, vanadium carbide, and molybdenum carbide to enhance the simultaneous removal efficiency of nickel and tin.

[0026] Furthermore, by optimizing the vanadium carbide loading of the modified nanofiber membrane and applying it to the treatment method of anodizing wastewater from photovoltaic aluminum profiles containing nickel and tin, the product achieves a nickel removal rate of greater than or equal to 99% and a tin removal rate of greater than or equal to 98% in the wastewater, demonstrating excellent metal ion purification effects and promising prospects for industrial application. Detailed Implementation

[0027] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage.

[0028] The following testing methods are included:

[0029] Nickel and tin ions in water were detected using inductively coupled plasma optical electron spectroscopy (ICP-OES).

[0030] The main reagents used include:

[0031] Commercially available biodegradable polylactic acid (PLA): Glass transition temperature: 65℃, degradation temperature range: 380℃-400℃, density: 1.3g / L, heat distortion temperature: 60℃. Source: NatureWorks PLA4032D (polylactic acid for 3D printing), USA.

[0032] The modifiers are two-dimensional transition metal carbides (2D TMCs): niobium carbide, vanadium carbide, molybdenum carbide, and manganese carbide, all of which are commercially available.

[0033] Solvent: DCM dichloromethane / DMF dimethylformamide, mixed in a volume ratio of 2:1.

[0034] Examples 1-3

[0035] The preparation method of the modified nanofiber membrane, with the amount of each raw material shown in Table 1, includes the following steps:

[0036] S1. Disperse polylactic acid in a solvent to obtain a dispersion;

[0037] S2. Add a modifier to the dispersion and stir until homogeneous to obtain a spinning solution;

[0038] S3. Add the spinning solution to the electrospinning equipment and spin using the electrospinning equipment. The spinning voltage is 12KV, the spray flow rate is 1.0ml / h, the receiving distance is 10cm, and aluminum foil is used as the receiving plate. Dry the prepared nanofiber membrane at 50℃ for 24 hours and take it out to obtain the modified nanofiber membrane.

[0039] Table 1 Raw Material Usage Table / Parts by Weight

[0040]

[0041] Example 4

[0042] Referring to Example 1, the modifier and dosage are different, the raw material dosage is shown in Table 1, and the preparation method is the same as in Example 1.

[0043] Example 5

[0044] Referring to Example 1, the modifier and dosage are different, the raw material dosage is shown in Table 1, and the preparation method is the same as in Example 1.

[0045] Example 6

[0046] Referring to Example 1, the modifier and dosage are different, the raw material dosage is shown in Table 1, and the preparation method is the same as in Example 1.

[0047] Example 7

[0048] Referring to Example 1, the raw material amounts are the same as in Example 1, but the electrospinning process is different. The preparation method is as follows:

[0049] S1. Disperse polylactic acid in a solvent to obtain a dispersion;

[0050] S2. Add a modifier to the dispersion and stir until homogeneous to obtain a spinning solution;

[0051] S3. Add the spinning solution to the electrospinning equipment and spin using the electrospinning equipment. The spinning voltage is 10KV, the spray flow rate is 1.5ml / h, the receiving distance is 10cm, and aluminum foil is used as the receiving plate. Dry the prepared nanofiber membrane at 50℃ for 24 hours and take it out to obtain the modified nanofiber membrane.

[0052] Example 8

[0053] Referring to Example 1, the raw material amounts are the same as in Example 1, but the electrospinning process is different. The preparation method is as follows:

[0054] S1. Disperse polylactic acid in a solvent to obtain a dispersion;

[0055] S2. Add a modifier to the dispersion and stir until homogeneous to obtain a spinning solution;

[0056] S3. Add the spinning solution to the electrospinning equipment and spin using the electrospinning equipment. The spinning voltage is 13KV, the spray flow rate is 1.0ml / h, the receiving distance is 8cm, and aluminum foil is used as the receiving plate. The prepared nanofiber membrane is dried at 50℃ for 24 hours and then taken out to obtain the modified nanofiber membrane.

[0057] Comparative Example 1

[0058] Referring to Example 1, manganese carbide was used as a modifier. The amount of raw materials used is shown in Table 1, and the preparation method is the same as in Example 1.

[0059] Comparative Example 2

[0060] Referring to Example 1, an electrospun membrane was prepared using pure polylactic acid. The amount of raw materials used is shown in Table 1, and the preparation method is the same as in Example 1.

[0061] Nanofiber membrane performance testing

[0062] The tensile strength, Young's modulus, and elongation at break were tested according to ISO 527 standard, using a universal testing machine, model INSTRON 5967. The bending strength was tested according to ISO 178 standard, using a three-point bending tester, model INSTRON 5582. The results are shown in the table below.

[0063] Table 2. Results of Nanofiber Membrane Performance Tests

[0064] Example 1 20MPa 1.5GPa 7％ 35MPa Example 2 20MPa 1.5GPa 7％ 35MPa Example 3 20MPa 1.5GPa 7％ 35MPa Example 4 25MPa 2GPa 6％ 45MPa Example 5 30MPa 2.4 GPa 4％ 50MPa Example 6 33MPa 2.8GPa 3％ 55MPa Example 7 20MPa 1.5GPa 6％ 35MPa Example 8 20MPa 2GPa 4.5％ 43MPa Comparative Example 1 20MPa 1.5GPa 7％ 35MPa Comparative Example 2 5MPa 0.5GPa 10％ 13MPa

[0065] As shown in Table 2, the mechanical properties of the nanofiber membranes were simultaneously improved after adding 8% two-dimensional metal carbide in Examples 1, 2, 3, and Comparative Example 1, because two-dimensional metal carbide materials have high strength, high conductivity, and good dispersibility. In Examples 4, 5, and 6, as the amount of two-dimensional metal carbide added gradually increased from 12% to 15%, the mechanical properties of the nanofiber membranes continued to improve, but the improvement gradually decreased, and even showed a slight decrease, especially in the elongation at break. This is because the two-dimensional metal carbide exhibited interfacial bonding during dispersion, resulting in partial agglomeration. In Examples 7 and 8, the process parameters in Example 1 were changed, affecting the diameter of the electrospinning, the stretching effect, and the uniformity of the membrane. Although other parameters were improved or remained unchanged, the elongation at break decreased. Therefore, the process parameters for preparing electrospun nanofiber membranes need to be adjusted to achieve the best and fixed effect.

[0066] Simulated wastewater treatment experiment

[0067] Wastewater treatment was carried out using the modified nanofiber membranes prepared in the above examples and comparative examples. Simulated wastewater was prepared by adding nickel sulfate and tin sulfate to deionized water and stirring until homogeneous. The nickel ion concentration was 25 g / L and the tin ion concentration was 15 g / L. A small amount of dilute sulfuric acid was added to adjust the pH to 4.

[0068] The prepared modified nanofiber membrane was placed in a filter bag and put into a filter tank. Simulated wastewater was introduced into the filter tank and adsorbed at room temperature for 10 hours. Then the ion concentration of the treated wastewater was measured, as shown in Table 3 below.

[0069] Table 3. Results of the Wastewater Treatment Experiment

[0070] Example 1 0.42g / L 0.40g / L Example 2 0.41g / L 0.39g / L Example 3 0.32g / L 0.30g / L Example 4 0.31g / L 0.30g / L Example 5 0.15g / L 0.10g / L Example 6 0.09g / L 0.08g / L Comparative Example 1 10.90g / L 5.30g / L Comparative Example 2 19.50g / L 11.20g / L

[0071] As shown in Table 3, the polylactic acid nanofiber membrane in Comparative Example 2 has limited adsorption capacity for metal ions and cannot meet the wastewater discharge requirements. In Comparative Example 1, the adsorption performance of polylactic acid modified with manganese carbide was not significantly improved; while niobium carbide, vanadium carbide, and molybdenum carbide showed significant modification effects, exhibiting good nickel and tin adsorption capacity. In Example 3, vanadium carbide modification resulted in better adsorption performance than molybdenum carbide and niobium carbide. The vanadium carbide-modified polylactic acid nanofiber membranes prepared in Examples 5 and 6 achieved nickel removal rates greater than 99% and tin removal rates greater than 98% in wastewater, demonstrating excellent application prospects.

[0072] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0073] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0074] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for treating anodizing wastewater from nickel-tin-containing photovoltaic aluminum profiles, characterized in that: The anodizing wastewater from nickel-tin photovoltaic aluminum profiles is filtered through a filtration device equipped with a modified nanofiber membrane. The nickel concentration in the wastewater is 25-100 g / L, and the tin concentration is 15-100 g / L. After treatment with the filtration device at room temperature for 6-12 hours, the nickel concentration in the wastewater does not exceed 0.5 g / L, and the tin concentration does not exceed 0.8 g / L. The preparation method of the modified nanofiber membrane includes the following steps: S1. Disperse polylactic acid in a solvent to obtain a dispersion; S2. Add vanadium carbide modifier to the dispersion and stir evenly to obtain a spinning solution; the mass ratio of the amount of modifier added to polylactic acid in the dispersion is 13-15 parts by weight: 85-87 parts by weight. S3. The spinning solution is added to an electrospinning device, and the electrospinning device is used to spin the nanofiber to obtain a modified nanofiber membrane. The modified nanofiber membrane has a vanadium carbide mass content of 13-15%, a nickel removal rate of ≥99% and a tin removal rate of ≥98% in the wastewater.

2. The processing method according to claim 1, characterized in that: The mass concentration of the dispersion is 1-15%.

3. The processing method according to claim 2, characterized in that: The mass concentration of the dispersion is 5-12%.

4. The processing method according to claim 3, characterized in that: The mass concentration of the dispersion is 8-10%.

5. The processing method according to any one of claims 1-4, characterized in that: The solvent is a mixture of dichloromethane and dimethylformamide, with a volume ratio of 2-3:1.

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