Electrospun membrane for reducing content of ni / bi in electronic grade sulfuric acid and preparation method thereof

Abstract

The application discloses a kind of electrospinning membrane materials for reducing the content of Ni / Bi in electronic grade sulfuric acid and preparation method, the electrospinning membrane material uses N,N-dimethylformamide as solvent, polyvinylidene fluoride as polymer, graphene oxide as chemical adsorption complexing agent, which is configured into stable film liquid with suitable viscosity for electrospinning, and the PVDF / GO electrospinning membrane material is obtained by spinning.The application can effectively solve the problem of high content of specific metal ion impurities in the purification of existing high-purity sulfuric acid, especially for the high removal capacity of Ni and Bi metal ions.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electronic chemical products, and in particular to an electrospun membrane material for reducing the content of Ni / Bi in electronic-grade sulfuric acid and a preparation method thereof. BACKGROUND

[0002] Electronic-grade sulfuric acid, also known as ultrapure sulfuric acid, high-purity sulfuric acid, etc., is widely used in the integrated circuit (IC), semiconductor and other microelectronic industries as a chemical reagent. In the wafer production process, electronic-grade sulfuric acid is mainly responsible for photoetching, cleaning, etching, etc. of wafers, which can effectively remove inorganic residues, impurity particles and carbon deposits on the wafers, thereby ensuring the quality and performance of the wafers. In addition, electronic-grade sulfuric acid can also be used as a solution, which is mainly used to produce electrolyte for lithium batteries and other rechargeable batteries.

[0003] There are mainly two methods for preparing electronic-grade sulfuric acid at present: industrial sulfuric acid rectification method, which uses industrial sulfuric acid as raw material and adds a strong oxidizing agent to prepare the product by rectification, and can be used for small-scale production; and sulfur trioxide gas absorption method, which uses ultrapure water to directly absorb clean sulfur trioxide gas to prepare the product, and can be used for large-scale production. The rectification method has high energy consumption and cost, some impurities are difficult to remove, the generated waste gas and acid mist are harmful to the human body and are not conducive to environmental protection, and is only suitable for small-scale production. The sulfur trioxide gas absorption method can effectively avoid the above-mentioned shortcomings of the rectification method, but the existing gas absorption method cannot effectively remove sulfur dioxide gas, so that the prepared sulfuric acid contains a certain amount of trace sulfur dioxide impurities, which affects the performance of the sulfuric acid.

[0004] With the rapid development of the integrated circuit, semiconductor and lithium battery markets in China, the technology is continuously improving, and the precision of components is continuously increasing. Electronic-grade sulfuric acid plays a crucial role in the manufacturing process of integrated circuits, semiconductors and lithium batteries, especially in the cleaning and etching process of silicon wafers. The presence of heavy metal impurities has a significant impact on the performance of electronic-grade sulfuric acid:

[0005] 1. Affecting the performance of integrated circuits: heavy metal impurities such as Bi and Cr, when attached to the surface of silicon wafers, can reduce the P-N junction voltage and affect the electrical performance of integrated circuits (ICs).

[0006] 2. Reducing IC yield: During the processing of silicon wafers, insoluble solid particles or metal ions may conduct electricity between the fine circuits, causing short circuits. A few metal ions or dust can cause ICs with small line widths to be scrapped, resulting in a decrease in IC yield of about 50%.

[0007] 3. Reducing the insulation voltage: Alkali metal impurities such as Ni, Na and Ca can melt into the oxide film, resulting in a decrease in the insulation voltage.

[0008] 4, the diffusion effect of the diffusion agent: impurity ions such as Be, Au, etc. can affect the diffusion effect of the diffusion agent.

[0009] 5, photoetching defects and uneven oxidation layer: dust particles can cause photoetching defects and uneven oxidation layer, affecting the quality of the mask and the plasma etching process.

[0010] Therefore, in order to obtain high-quality and high-yield integrated circuit chips, very pure electronic-grade sulfuric acid must be used to clean the silicon wafer to remove various contaminants and reduce the influence of heavy metal impurities. Therefore, it is necessary to develop an electronic-grade sulfuric acid with extremely low content of heavy metals to solve the problem of high content of specific metal ion impurities in the existing electronic-grade sulfuric acid purification process, so as to meet the high-purity requirements of various industries for electronic-grade sulfuric acid and the sharp increase in demand for high-purity sulfuric acid. SUMMARY

[0011] In order to overcome the shortcomings of the prior art, one of the purposes of the present application is to provide an electrospun membrane material for reducing the content of Ni / Bi in electronic-grade sulfuric acid.

[0012] The second purpose of the present application is to provide a preparation method of an electrospun membrane material for reducing the content of Ni / Bi in electronic-grade sulfuric acid.

[0013] One of the purposes of the present application is achieved by the following technical scheme: an electrospun membrane material for reducing the content of Ni / Bi in electronic-grade sulfuric acid, wherein N,N-dimethylformamide is used as a solvent, polyvinylidene fluoride is used as a polymer, and graphene oxide is used as a chemical adsorption complexing agent. The membrane liquid with suitable viscosity for electrospinning and stability is configured, and then spinning is performed to obtain a PVDF / GO electrospun membrane material.

[0014] Optionally, the mass ratio of N,N-dimethylformamide to polyvinylidene fluoride is 85-95:5-15, and the amount of graphene oxide is 0.01-6% of the total mass of N,N-dimethylformamide and polyvinylidene fluoride.

[0015] Optionally, the mass ratio of carbon to oxygen in the graphene oxide is 6:4.

[0016] The second purpose of the present application is achieved by the following technical scheme: a preparation method of an electrospun membrane material for reducing the content of Ni / Bi in electronic-grade sulfuric acid, comprising the following steps:

[0017] (1) configuring a basic membrane liquid: weighing N,N-dimethylformamide with a mass percentage of 85-95% and polyvinylidene fluoride with a mass percentage of 5-15%, the sum of the mass percentages of the two components being 100%, mixing the above components with each other, stirring with a stirrer for 1-3h, and then vacuum defoaming for 5-30min to obtain a basic membrane liquid;

[0018] (2) Configuration of electrospinning membrane liquid: take 0.01% to 6% of the total weight of the base membrane liquid of graphene oxide, mix graphene oxide with the base membrane liquid obtained in step (1), stir for 1 to 3 hours, and defoam under vacuum for 5 to 30 minutes to obtain an electrospinning membrane liquid;

[0019] (3) Electrospinning: pour the electrospinning membrane liquid obtained in step (2) into an electrospinning machine, and use the electrospinning machine to spin a film on tin paper, with a spinning time of 2 to 8 hours to obtain a spinning film;

[0020] (4) Drying: dry the spinning film obtained in step (3) for 0.5 to 2 hours, then peel the spinning film from the tin paper to obtain a PVDF / GO electrospinning membrane material.

[0021] Optionally, in step (1), the mass percentage of N,N-dimethylformamide is 88% to 92%, and the mass percentage of polyvinylidene fluoride is 8% to 12%, and the sum of the mass percentages of the two components is 100%.

[0022] Optionally, in step (2), the amount of graphene oxide is 2% to 4% of the total weight of the base membrane liquid.

[0023] Optionally, in step (3), the spinning conditions are as follows: spinning voltage 8 to 16 kV, and push-in speed 0.6 to 1.4 mL / h.

[0024] Optionally, the molecular weight of the polyvinylidene fluoride is 300-400 thousand.

[0025] Optionally, the mass ratio of carbon to oxygen in the graphene oxide is 6:4.

[0026] Optionally, the preparation method of the graphene oxide is as follows:

[0027] (21) At room temperature, add graphite powder and sodium nitrate to the reactor, add rotor; pour in 300 ml of concentrated sulfuric acid and stir with magnetic stirrer; the amount ratio of graphite powder, sodium nitrate and concentrated sulfuric acid is 3-5 g: 2-3 g: 100 ml;

[0028] (22) Slowly add potassium permanganate to the reactor under ice bath, cover with plastic wrap, and react at room temperature for 4 days, with stirring 2 to 3 times a day to release heat; the mass ratio of potassium permanganate to graphite powder is 3-5:1;

[0029] (23) After 4 days of reaction, slowly add 500-1000 ml of deionized water, stir and release heat; add 50-100 ml of hydrogen peroxide, stir multiple times, and the reaction is a golden sand-like graphene oxide dispersion liquid, which is cooled to room temperature;

[0030] (24) The golden sand-like graphene oxide dispersion was centrifuged for the first time at 4500-5500 rpm for 5 min. After centrifugation, the upper layer was discarded, deionized water was added to disperse the gel-like graphene oxide, and the mixture was stirred. The dispersion was then centrifuged for the second time at 4500-5500 rpm. After centrifugation, the upper layer was discarded to remove sulfuric acid.

[0031] (25) Add deionized water, shake well, sonicate in an ice bath for 3-5 minutes, centrifuge for the third time at 1500-2500 rpm for 3-5 minutes, repeat this step until the upper liquid is no longer viscous, collect the lower liquid, freeze dry the lower liquid to obtain graphene oxide.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] This application utilizes a novel super-adsorption material—PVDF / GO electrospun membrane—to effectively address the problem of high content of specific metal ion impurities in existing high-purity sulfuric acid purification processes, particularly demonstrating high removal capacity for Ni and Bi metal ions.

[0034] By placing the PVDF / GO electrospun membrane material of this invention after the four-stage distillation column, the adsorption and removal of specific metal ions in electronic-grade sulfuric acid are enhanced. Its porous structure can effectively remove impurities such as organic macromolecules, bacteria, viruses, and anionic impurities from electronic-grade sulfuric acid, as well as effectively remove Ni and Bi metal ion impurities, thus meeting the high purity requirements of various industries for electronic-grade sulfuric acid and the rapid increase in demand for high-purity sulfuric acid. Attached Figure Description

[0035] Figure 1 The scanning electron microscope (SEM) image (10 μm) of the PVDF / GO electrospun film material of the preferred embodiment 2 of the present invention is shown.

[0036] Figure 2 The scanning electron microscope (SEM) image (1 μm) of the PVDF / GO electrospun film material of the preferred embodiment 2 of the present invention is shown.

[0037] Figure 3 The scanning electron microscope (SEM) and EDS images (10 μm) of the graphene oxide (GO) used in the preferred embodiment 2 of the present invention are shown.

[0038] Figure 4 To obtain Figure 3 Distribution of carbon and oxygen elements in EDS tests at points ① and ② in the SEM image;

[0039] Figure 5 To obtain Figure 3 The carbon and oxygen content at point ① in the SEM image obtained from EDS testing;

[0040] Figure 6 SEM image of the graphene oxide GO used in the preferred embodiment 2 at ②; Figure 3 EDS test of carbon and oxygen element content graph at ② in the SEM image;

[0041] Figure 7 SEM and EDS test graph (10 μm) of another place of the graphene oxide GO used in the preferred embodiment 2;

[0042] Figure 8 SEM image of the graphene oxide GO used in the preferred embodiment 2 at ③, ④, ⑤; Figure 7 EDS test of carbon and oxygen element distribution graph at ③, ④, ⑤ in the SEM image;

[0043] Figure 9 EDS test of carbon and oxygen element content graph at ③ in the SEM image; Figure 7

[0044] EDS test of carbon and oxygen element content graph at ④ in the SEM image; Figure 10 Figure 7 EDS test of carbon and oxygen element content graph at ⑤ in the SEM image;

[0045] Figure 11 Figure 7 EDS test of carbon and oxygen element content graph at ⑤ in the SEM image;

[0046] Figure 12 Data graph of PVDF / GO electrospinning membrane material of the preferred embodiment 2 of the present application removing Ni metal ions from high-purity sulfuric acid;

[0047] Figure 13 Data graph of PVDF / GO electrospinning membrane material of the preferred embodiment 2 of the present application removing Bi metal ions from high-purity sulfuric acid. DETAILED DESCRIPTION

[0048] Hereinafter, the present application will be further described in conjunction with the accompanying drawings and specific embodiments, and it should be noted that the following described embodiments or technical features can be combined in any manner to form new embodiments without conflict.

[0049] In the present application, unless specified, all the parts and percentages are weight units, and the equipment and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following examples are conventional methods in the art, unless otherwise specified.

[0050] ​​The application provides a kind of electrospun membrane material for reducing the content of Ni / Bi in electronic grade sulfuric acid, which uses N,N-dimethylformamide (DMF) as solvent, polyvinylidene fluoride (PVDF) as polymer and graphene oxide (GO) as chemical adsorption complexing agent, and is configured into a stable membrane liquid with suitable viscosity for electrospinning.

[0051] As a further embodiment, the mass ratio of N,N-dimethylformamide (DMF) to polyvinylidene fluoride (PVDF) is 85-95:5-15, and the amount of graphene oxide is 0.01-6% of the total mass of N,N-dimethylformamide (DMF) and polyvinylidene fluoride (PVDF).

[0052] As a further embodiment, the mass ratio of carbon to oxygen in the graphene oxide (GO) is 6:4, and the atomic ratio of carbon to oxygen is 2:1.

[0053] The application also provides a preparation method of the electrospun membrane material for reducing the content of Ni / Bi in electronic grade sulfuric acid, which comprises the following steps:

[0054] (1) configuring a basic membrane liquid: weighing N,N-dimethylformamide (DMF) with a mass percentage of 85-95% and polyvinylidene fluoride (PVDF) with a mass percentage of 5-15%, the sum of the mass percentages of the two components being 100%, mixing the above components with each other, stirring with a stirrer for 1-3 hours, and vacuum defoaming for 5-30 minutes to obtain a basic membrane liquid;

[0055] (2) configuring an electrospun membrane liquid: weighing graphene oxide (GO) with an amount of 0.01%-6% of the total weight of the basic membrane liquid, mixing the graphene oxide (GO) with the basic membrane liquid obtained in step (1) with each other, stirring with a stirrer for 1-3 hours, and vacuum defoaming for 5-30 minutes to obtain an electrospun membrane liquid;

[0056] (3) electrospinning: pouring the electrospun membrane liquid obtained in step (2) into an electrospinning machine, and spinning into a film on tin paper using the electrospinning machine, the spinning time being 2-8 hours to obtain a spinning film;

[0057] (4) drying: drying the spinning film obtained in step (3) for 0.5-2 hours, and then peeling the spinning film from the tin paper to obtain a PVDF / GO electrospun membrane material.

[0058] As a further embodiment, in step (1), the mass percentage of N,N-dimethylformamide (DMF) is 88-92%, the mass percentage of polyvinylidene fluoride (PVDF) is 8-12%, and the sum of the mass percentages of the two components is 100%.

[0059] As a further implementation, in step (2), the amount of graphene oxide is 2-4% of the total weight of the base film solution.

[0060] As a further implementation, in step (3), the spinning conditions are as follows: spinning voltage 8-16 kV, push-in speed 0.6-1.4 mL / h.

[0061] As a further implementation, the molecular weight of the polyvinylidene fluoride (PVDF) is 200-500 thousand.

[0062] As a further implementation, the mass ratio of carbon to oxygen in the graphene oxide is 6:4.

[0063] As a further implementation, the preparation method of the graphene oxide is as follows:

[0064] (21) At room temperature, graphite powder, sodium nitrate are added to the reactor, and the rotor is added; 300 ml of concentrated sulfuric acid is poured, and magnetic stirring is performed; the amount ratio of the graphite powder, sodium nitrate, and concentrated sulfuric acid is 3-5 g: 2-3 g: 100 ml;

[0065] (22) Under ice bath, potassium permanganate is slowly added to the reactor, covered with plastic wrap, and reacted at room temperature for 4 days, with stirring 2-3 times a day to release heat; the mass ratio of potassium permanganate to graphite powder is 3-5:1;

[0066] (23) After 4 days of reaction, 500-1000 ml of deionized water is slowly and repeatedly added, stirred, and heat is released; 50-100 ml of hydrogen peroxide is added, stirred repeatedly, and the reaction presents a golden sand-like graphene oxide dispersion liquid, which is cooled to room temperature;

[0067] (24) The golden sand-like graphene oxide dispersion liquid is subjected to a first centrifugation at 4500-5500 rpm for 5 min, and after centrifugation, the upper layer is discarded, deionized water is added to disperse the gel-like graphene oxide, and a second centrifugation is performed at 4500-5500 rpm, after which the upper layer is discarded to remove sulfuric acid;

[0068] (25) Deionized water is added and shaken, ice bath ultrasonic is performed for 3-5 min, and a third centrifugation is performed at 1500-2500 rpm for 3-5 min, and the operation is repeated until the upper layer is not thick, the lower layer is collected, and the lower layer is freeze-dried to obtain graphene oxide.

[0069] The following are specific embodiments of the present application, and in the following examples, the raw materials, equipment, etc. used can be obtained by purchase unless otherwise specified.

[0070] Example 1

[0071] A PVDF / GO electrostatic spinning membrane material is prepared by the following steps:

[0072] (1) 85% by mass of DMF and 15% by mass of PVDF are weighed and mixed to prepare a base membrane liquid, and stirred for 1 h, and then defoamed under vacuum for 15 min; wherein the PVDF is selected from PVDF with a model number of Solef6010 from Sinopec Solutia Company, USA, and has a molecular weight of 400,000.

[0073] (2) 0.01% of GO by mass of the total weight of the base membrane liquid is weighed and mixed with the base membrane liquid to prepare an electrostatic spinning membrane liquid, and stirred for 1 h, and then defoamed under vacuum for 15 min;

[0074] (3) The electrostatic spinning machine is used to spin a membrane on a tin paper, and the spinning conditions are as follows: a spinning voltage of 8 kV, a push injection speed of 0.6 mL / h, and a spinning time of 2 h;

[0075] (4) The membrane is peeled off from the tin paper after being dried for 2 h to obtain a PVDF / GO electrostatic spinning membrane material.

[0076] Example 2

[0077] A PVDF / GO electrostatic spinning membrane material is prepared by the following steps:

[0078] (1) 88% by mass of DMF and 12% by mass of PVDF are weighed and mixed to prepare a base membrane liquid, and stirred for 1 h, and then defoamed under vacuum for 15 min; wherein the PVDF is selected from PVDF with a model number of Solef6010 from Sinopec Solutia Company, USA, and has a molecular weight of 400,000.

[0079] (2) 3% of GO by mass of the total weight of the base membrane liquid is weighed and mixed with the base membrane liquid to prepare an electrostatic spinning membrane liquid, and stirred for 1 h, and then defoamed under vacuum for 15 min;

[0080] (3) The electrostatic spinning machine is used to spin a membrane on a tin paper, and the spinning conditions are as follows: a spinning voltage of 12 kV, a push injection speed of 1 mL / h, and a spinning time of 6 h;

[0081] (4) The membrane is peeled off from the tin paper after being dried for 2 h to obtain a PVDF / GO electrostatic spinning membrane material.

[0082] Example 3

[0083] A PVDF / GO electrostatic spinning membrane material is prepared by the following steps:

[0084] (1) Take 95% by mass of DMF and 5% by mass of PVDF, mix to configure the base membrane liquid, stir for 1 h, and then vacuum defoam for 15 min; wherein the PVDF is selected from the PVDF with a model number of Solef6010 from Sino-American, and the molecular weight thereof is 400,000.

[0085] (2) Take 6% by mass of GO based on the total weight of the base membrane liquid, mix with the base membrane liquid to configure the electrospinning membrane liquid, stir for 1 h, and then vacuum defoam for 15 min;

[0086] (3) Use the electrospinning machine to spin the membrane on the tin paper, and the spinning conditions are as follows: the spinning voltage is 16 kV, the injection speed is 1.4 mL / h, and the spinning time is 8 h;

[0087] (4) After drying for 2 h, the membrane is peeled off from the tin paper to obtain the PVDF / GO electrospinning membrane material.

[0088] The graphene oxide GO of Examples 1-3 is prepared by the following steps:

[0089] (21) At room temperature, 10 g of graphite powder and 7.5 g of sodium nitrate are added to the reactor, and the rotor is added; 300 ml of concentrated sulfuric acid is poured, and magnetic stirring is performed;

[0090] (22) Under ice bath, 40 g of potassium permanganate is slowly added to the reactor, and the fresh-keeping film is covered, and the reaction is performed at room temperature for 4 days, and the heat is removed by stirring 2-3 times a day;

[0091] (23) After 4 days of reaction, 800 ml of deionized water is slowly and repeatedly added, stirred, and the heat is removed; 60 ml of hydrogen peroxide is added, and the reaction is stirred to obtain a golden sand-shaped graphene oxide dispersion liquid, which is cooled to room temperature;

[0092] (24) The golden sand-shaped graphene oxide dispersion liquid is centrifuged at 5000 rpm for the first time, centrifuged for 5 min, and the upper layer is discarded after centrifugation, and the deionized water is added to disperse the gel-like graphene oxide, and the second centrifugation is performed at 5000 rpm, and the upper layer is discarded after centrifugation to remove sulfuric acid;

[0093] (25) Deionized water is added and shaken, and ultrasonic treatment is performed for 5 min in an ice bath, and the third centrifugation is performed at 2000 rpm for 5 min, and the operation is repeated until the upper liquid is not viscous, and the lower liquid is collected and freeze-dried to obtain the graphene oxide GO.

[0094] Comparative Example 1

[0095] The difference between Comparative Example 1 and Example 2 is that the concentration of the base membrane liquid in step (1) is too high, specifically, 82% by mass of DMF and 18% by mass of PVDF are weighed and mixed to configure the base membrane liquid; the rest of the conditions are the same as those in Example 2.

[0096] Comparative Example 2

[0097] The difference between Comparative Example 2 and Example 2 is that the concentration of the base membrane liquid in step (1) is too low, specifically, 96% by mass of DMF and 4% by mass of PVDF are weighed and mixed to configure the base membrane liquid; the rest of the conditions are the same as those in Example 2.

[0098] Comparative Example 3

[0099] The difference between Comparative Example 3 and Example 2 is that the polyvinylidene fluoride PVDF in step (1) is selected from PVDF of type Solef 1015 from Solvay, USA, with a molecular weight of 1 million; the rest of the conditions are the same as those in Example 2.

[0100] Comparative Example 4

[0101] The difference between Comparative Example 4 and Example 2 is that the spinning conditions in step (3) are different, specifically, the spinning voltage is 7 kV, the push-in speed is 0.5 mL / h, and the spinning time is 8 h; the rest of the conditions are the same as those in Example 2.

[0102] Comparative Example 5

[0103] The difference between Comparative Example 5 and Example 2 is that the spinning conditions in step (3) are different, specifically, the spinning voltage is 17 kV, the push-in speed is 1.5 mL / h, and the spinning time is 8 h; the rest of the conditions are the same as those in Example 2.

[0104] Comparative Example 6

[0105] The difference between Comparative Example 6 and Example 2 is that the graphene oxide GO used in step (2) is purchased from the graphene oxide of type S926168 from the company Mclane; the rest of the conditions are the same as those in Example 2.

[0106] Comparative Example 7

[0107] The difference between Comparative Example 7 and Example 2 is that the mass ratio of potassium permanganate to graphite powder in the preparation of graphene oxide GO in step (2) is different, specifically, the ratio of the amount of potassium permanganate to the amount of graphite powder is 2:1; the rest of the conditions are the same as those in Example 2.

[0108] Comparative Example 8

[0109] Compared with Example 2, the difference of Comparative Example 8 is that the mass ratio of potassium permanganate and graphite powder is different in step (2) of the graphene oxide (GO) preparation method. Specifically, the ratio of potassium permanganate to graphite powder is 6:1, and the other conditions are the same as in Example 2.

[0110] Effect evaluation and performance testing

[0111] The performance of the electrospun membranes in Examples 1-3 and each comparative example in removing specific metal ions was tested. The test items and results are shown in Table 1.

[0112] 1. Cross-flow filtration experiment

[0113] The electrospun membranes prepared in Examples 1-3 and various comparative examples were tested using a cross-flow filtration integrated device. First, the electrospun membranes prepared in Examples 1-3 and various comparative examples were tested. The membrane was assembled into a cross-flow filtration integrated device, and then the same batch of electronic-grade sulfuric acid was introduced into the inlet. During cross-flow filtration, the flow of electronic-grade sulfuric acid generated two components of force on the membrane surface: a normal force perpendicular to the membrane surface, allowing the electronic-grade sulfuric acid to pass through the membrane surface; and a tangential force parallel to the membrane surface, flushing away the retained substances (including metal ions) on the membrane surface. Each filtration of electronic-grade sulfuric acid lasted 3 minutes, and 1 ml of the final electronic-grade sulfuric acid was collected at the outlet; this experiment was repeated 3 times, and the electronic-grade sulfuric acid filtrate was obtained from 3 separate tests.

[0114] 2. ICP-MS Experiment

[0115] Trace metal ion tests were performed on sulfuric acid stock solution and electronic grade sulfuric acid filtrate using an ICP-MS device in a Class 100 cleanroom. Specifically, trace metal ion tests were conducted on (1) high-purity sulfuric acid stock solution, (2) first-pass sulfuric acid filtrate, (3) second-pass sulfuric acid filtrate, and (4) third-pass sulfuric acid filtrate. ① ICP-MS stands for Inductively Coupled Plasma-Mass Spectrometry. The ICP acts as an ion source. It utilizes a high-power, high-frequency radio frequency signal applied to an inductive coil to form a high-temperature plasma inside the coil. Gas propulsion ensures the balance and continuous ionization of the plasma. The sample being analyzed is pumped into an atomizer by a peristaltic pump to form an aerosol, which is then carried into the central region of the plasma torch by a carrier gas, where it evaporates, decomposes, is excited, and ionizes. The high-temperature plasma causes most elements in the sample to ionize, releasing an electron and forming a monovalent positive ion. ② Ions in the plasma are effectively transferred to the mass spectrometer via the ICP-MS interface; ③ Mass spectrometry is a mass screening and analysis instrument that detects the intensity of a certain ion by selecting ions with different mass-to-nucleus ratios (m / z) to pass through, and then analyzes and calculates the trace amount of a certain element. The test results are used to explain the filtration effect of this membrane material on specific metal ions by selecting the trace amount changes of specific metal ions.

[0116] Table 1 is the test results of the removal of specific metal ions of the electrospun membrane material of each embodiment

[0117]

[0118] The metal ion removal rate (%) refers to the percentage of the concentration of a certain metal ion in the filtered high-purity sulfuric acid to the concentration of the same metal ion in the high-purity sulfuric acid stock solution before filtration.

[0119] Table 2 is Figure 3 , 8 The test results of the carbon-oxygen mass ratio of graphene oxide GO in five places in the SEM image shown in Table 2

[0120] Wt% ① ② ③ ④ ⑤ Carbon atoms 59.5 57.5 62.6 60.3 62.1 Oxygen atoms 40.5 42.5 37.4 39.7 37.9

[0121] Figures 1-2 The SEM test image of the PVDF / GO electrospun membrane material of the preferred embodiment 2 of the present application is shown in the figure. The fibers in the PVDF / GO electrospun membrane material prepared by the present application exhibit a smooth non-bead morphology, and the fiber diameter (about 500 nm) is relatively uniform, which can be used for the PVDF / GO electrospun membrane material suitable for filtering electronic-grade sulfuric acid.

[0122] Figures 3-11 The SEM and EDS test images of the graphene oxide GO prepared by the present application are shown in the figure. The graphene oxide GO prepared by the present application is in a sheet shape, with a thickness of about 0.8-1.2 nm and an average radial size of 40-60 μm. The mass ratio of C and O in the graphene oxide GO prepared by the present application is about 6:4.

[0123] As shown in the above table and Figures 12-13 By preparing a new type of superabsorbent material, PVDF / GO electrospun membrane material, the content of specific metal ions such as Ni and Bi in electronic-grade sulfuric acid can be effectively reduced, and the problem of high content of specific metal ion impurities in existing high-purity sulfuric acid purification can be effectively solved.

[0124] In addition, in Comparative Example 1-2, the concentration of the base membrane solution is too high or too low, which leads to the failure of silk-like film formation, and therefore the trace amounts of metal ions cannot be filtered.

[0125] In Comparative Example 3, the PVDF with a molecular weight of 1 million has poor film-forming effect, and the membrane material contains less GO, and the filtering effect is not as good as the membrane material prepared by the present application.

[0126] In Comparative Examples 4-5, the spinning conditions are insufficient or too high, which also affects the quality of the spinning, leading to the failure of silk-like film formation, and therefore the trace amounts of metal ions cannot be filtered, and the filtration capacity of the membrane material cannot be tested.

[0127] The comparative example 6 uses the purchased GO, and since the purchased GO has many impurities, more metal ion impurities are introduced in the filtering process, so the percentage exceeds 100%.

[0128] In the comparative examples 7-8, the ratio of the amount of potassium permanganate to the amount of graphite powder, the amount of potassium permanganate is too small, so that the oxidation degree of graphene is low, and the adsorption capacity of GO is poor. The amount of potassium permanganate is too high, so that the oxidation degree of graphene reaches the threshold value, and the adsorption effect cannot be further improved. In addition, the impurities introduced by potassium permanganate are not completely removed, and the filtering and removing effect is not as good as that of the present application.

[0129] The above embodiments are only preferred embodiments of the present application, and cannot be used to limit the scope of protection of the present application. Any non-essential changes and substitutions made by those skilled in the art on the basis of the present application shall fall within the scope of protection of the present application.

Claims

1. An electrospun film material for reducing the Ni / Bi content in electronic-grade sulfuric acid, characterized in that, The electrospun membrane material uses N,N-dimethylformamide as a solvent, polyvinylidene fluoride as a polymer, and graphene oxide as a chemical adsorption complexing agent to prepare a membrane solution with suitable viscosity for electrospinning and stability. After spinning, a PVDF / GO electrospun membrane material is obtained. The mass ratio of N,N-dimethylformamide to polyvinylidene fluoride is 85~95:5~15, and the molecular weight of polyvinylidene fluoride is 300,000-500,000. The amount of graphene oxide used is 0.01~6% of the total mass of N,N-dimethylformamide and polyvinylidene fluoride; the mass ratio of carbon to oxygen in the graphene oxide is 6:

4.

2. A method for preparing an electrospun film material with reduced Ni / Bi content in electronic-grade sulfuric acid as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of basic membrane solution: Weigh 85-95% N,N-dimethylformamide and 5-15% polyvinylidene fluoride. The sum of the mass percentages of the two components is 100%. Mix the above components together and stir in a mixer for 1-3 hours. Then, defoam under vacuum for 5-30 minutes to obtain the basic membrane solution. (2) Prepare electrospinning membrane solution: Weigh 0.01~6% of the total weight of the base membrane solution and mix the graphene oxide with the base membrane solution obtained in step (1). Stir for 1~3 hours and then defoam under vacuum for 5~30 minutes to obtain the electrospinning membrane solution. (3) Electrospinning: Pour the electrospinning film solution obtained in step (2) into the electrospinning machine, and use the electrospinning machine to spin the film on the tin foil. The spinning time is 2~8h to obtain the spun film. (4) Drying: Dry the spun film obtained in step (3) for 0.5 to 2 hours. Then peel the spun film off the tin foil to obtain PVDF / GO electrospun film material.

3. The method for preparing electrospun film material with reduced Ni / Bi content in electronic-grade sulfuric acid as described in claim 2, characterized in that, In step (1), the mass percentage of N,N-dimethylformamide is 88-92%, the mass percentage of polyvinylidene fluoride is 8-12%, and the sum of the mass percentages of the two components is 100%.

4. The method for preparing an electrospun film material with reduced Ni / Bi content in electronic-grade sulfuric acid as described in claim 2, characterized in that, In step (2), the amount of graphene oxide used is 2 to 4% of the total weight of the base film liquid.

5. The method for preparing an electrospun film material with reduced Ni / Bi content in electronic-grade sulfuric acid as described in claim 2, characterized in that, In step (3), the spinning conditions are as follows: spinning voltage 8~16kV, injection speed 0.6~1.4mL / h.

6. The method for preparing an electrospun film material with reduced Ni / Bi content in electronic-grade sulfuric acid as described in claim 2, characterized in that, The preparation method of the graphene oxide is as follows: (21) At room temperature, add graphite powder and sodium nitrate into the reactor and add a rotor; pour in 300 ml of concentrated sulfuric acid and stir magnetically; the ratio of graphite powder, sodium nitrate and concentrated sulfuric acid is 3~5 g: 2~3 g: 100 ml; (22) Potassium permanganate was slowly added to the reactor under ice bath conditions, covered with plastic wrap, and reacted at room temperature for 4 days, stirring 2 to 3 times a day to exothermic the reaction; the mass ratio of potassium permanganate to graphite powder was 3 to 5:

1. (23) After 4 days of reaction, slowly add 500-1000 ml of deionized water multiple times, stir, and exothermic; add 50-100 ml of hydrogen peroxide, stir multiple times, and the reaction will form a golden sand-like graphite oxide dispersion. Cool to room temperature. (24) The golden sand-like graphene oxide dispersion was centrifuged for the first time at 4500~5500 rpm for 5 min. After centrifugation, the upper layer was discarded, deionized water was added to disperse the gel-like graphene oxide, and the mixture was stirred. The dispersion was then centrifuged for the second time at 4500~5500 rpm. After centrifugation, the upper layer was discarded to remove sulfuric acid. (25) Add deionized water, shake well, sonicate in an ice bath for 3-5 minutes, centrifuge for the third time at 1500-2500 rpm for 3-5 minutes, repeat this step until the upper liquid is no longer viscous, collect the lower liquid, freeze dry the lower liquid to obtain graphene oxide.

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