Preparation method of alpha-NiS / g-C3N4 filament / fiber composite film

Abstract

The application discloses a preparation method of an alpha-NiS / g-C3N4 filament / short fiber composite film, which comprises the following steps: preparing a filament / short fiber composite film, and loading alpha-NiS / g-C3N4 on the filament / short fiber composite film. The preparation of the filament / short fiber composite film refers to loading hydrophilic short fibers and a binder on a filament film. The filament film comprises a hydrophilic filament film. The loading of alpha-NiS / g-C3N4 on the filament / short fiber composite film refers to the following steps: placing the filament / short fiber composite film on a vacuum filtration equipment, adding a suspension liquid containing alpha-NiS / g-C3N4 photocatalysts in the vacuum filtration equipment, performing filtration, then adding PEG-20000 solution and glutaraldehyde solution in the vacuum filtration equipment in sequence, and drying in a vacuum oven after filtration. The alpha-NiS / g-C3N4 photocatalysts are loaded on the filament / short fiber composite film, and the composite film has good mechanical and antibacterial properties, and can be recycled and has a self-cleaning function.

Description

Technical Field

[0001] This invention relates to a method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane, belonging to the field of photocatalytic membrane preparation technology. Background Technology

[0002] In recent years, with the rapid development of global industrial technology, numerous environmental pollution problems have attracted widespread attention. Among these, dyeing and finishing wastewater, containing large amounts of organic pollutants, is widely recognized as one of the major causes of global water pollution and cannot be automatically cleaned up by nature. Therefore, the pollution of the water environment by dyeing and finishing wastewater has always been a major concern. Researchers have been studying the pollution problem of dyeing and finishing wastewater, dedicated to improving the environmental situation. Through unremitting efforts, they have discovered that photocatalysis technology can efficiently solve environmental problems and plays a crucial role in addressing them. With the development of technology, the requirements for the degradation of dye wastewater have evolved from only needing to degrade pollutants with simple structures to also needing to degrade pollutants with more complex structures.

[0003] Faced with these problems, researchers have begun to consider the preparation of photocatalysts for degrading organic pollutants, using this technology to address the pollution of the water environment by dyeing and finishing wastewater, and hoping to improve the efficiency of problem-solving. Compared to other photocatalysts, graphitic carbon nitride (g-C3N4) has a wide range of applications in the field of photocatalysis due to its unique semiconductor band structure and thermal stability. Graphitic carbon nitride photocatalysts have attracted attention for their green and environmentally friendly approach to the degradation of organic pollutants in dyeing and finishing wastewater. However, this type of photocatalyst suffers from problems such as low light absorption efficiency, rapid recombination of photogenerated carriers, and low specific surface area. Therefore, to improve the photocatalytic ability of graphitic carbon nitride, some simple modifications are made to it.

[0004] Membrane separation technology offers the advantage of rapid separation, but in water treatment operations, filter membranes can become fouled and clogged by contaminants, significantly reducing their lifespan. Combining photocatalysis and membrane separation technologies for treating dye wastewater can leverage the advantages of both while overcoming their disadvantages, achieving a synergistic effect greater than the sum of its parts (1+1>2), resulting in energy savings, environmental protection, and cost reduction. For photocatalytic membranes, the substrate membrane needs not only abundant hydrophilic hydroxyl groups on its surface to reduce fouling, but also good stability to allow the photocatalyst to react on the membrane. Furthermore, the membrane itself must possess high UV resistance.

[0005] The problem to be solved is how to prepare a photocatalytic membrane with excellent hydrophilicity, large specific surface area, good antibacterial properties, and good mechanical properties. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane that can combine hydrophilicity and good mechanical properties.

[0007] To solve the above-mentioned technical problems, the objective of this invention is achieved as follows:

[0008] The present invention relates to a method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane, comprising the preparation of the filament / short fiber composite membrane and loading α-NiS / g-C3N4 onto the filament / short fiber composite membrane;

[0009] The preparation of the filament / short fiber composite membrane refers to loading hydrophilic short fibers and a binder onto a filament membrane; the filament membrane includes a hydrophilic filament membrane.

[0010] Loading α-NiS / g-C3N4 onto a filament / short fiber composite membrane refers to placing the filament / short fiber composite membrane on a vacuum filtration device, adding a suspension containing α-NiS / g-C3N4 photocatalyst to the vacuum filtration device, performing filtration, and then sequentially adding PEG-20000 solution and glutaraldehyde solution to the vacuum filtration device. After filtration, the membrane is placed in a vacuum oven for drying.

[0011] The suspension containing α-NiS / g-C3N4 photocatalyst refers to the α-NiS / g-C3N4 photocatalyst added to a dispersant solution;

[0012] The α-NiS / g-C3N4 photocatalyst was prepared by dissolving g-C3N4 in ethanol, adding nickel acetate tetrahydrate, SDS, and thiourea, and stirring continuously; the mixture was then transferred to a reaction vessel and heated and reacted at a set temperature; after the reaction was completed, the reaction vessel was cooled to room temperature, the final product was removed, and washed with deionized water and ethanol respectively, and then dried in a vacuum oven.

[0013] Based on the above scheme and as a preferred embodiment, the preparation of g-C3N4 involves mixing dicyandiamide and ammonium chloride at a ratio of 1:10, grinding them uniformly in a mortar for 1 hour, then transferring the mixture from the mortar to an alumina crucible, covering it, and calcining it in a muffle furnace. The temperature is raised to 550°C after 3 hours, and then calcined at high temperature for 4 hours. Finally, cooling yields g-C3N4 nanosheets.

[0014] Based on the above scheme and as a preferred embodiment of the above scheme: the dispersant is ethanol, propanol or isopropanol; the dispersant solution contains 20-100% dispersant.

[0015] Based on the above scheme and as a preferred embodiment of the above scheme: the hydrophilic short fiber refers to the hydrophilic long filament membrane that has been broken up and has a length of 10-200 micrometers.

[0016] Based on the above scheme and as a preferred embodiment of the above scheme: the filament film further includes a PVDF electrospun film stacked on top of the hydrophilic filament film.

[0017] Based on the above scheme and as a preferred embodiment of the above scheme: the long filament / short fiber composite membrane is made by placing a hydrophilic long filament membrane on a vacuum filtration device, and adding a mixture of hydrophilic short fibers and binder into the vacuum filtration device for filtration.

[0018] Based on the above scheme and as a preferred embodiment of the above scheme: the filament / short fiber composite membrane is made by stacking a hydrophilic filament membrane and a PVDF electrospun membrane, placing them on a vacuum filtration device, and adding a mixture of hydrophilic short fibers and binder into the vacuum filtration device for filtration; the PVDF electrospun membrane is located on the outer side.

[0019] Based on the above scheme and as a preferred embodiment of the above scheme: the filament / short fiber composite membrane is prepared by placing a hydrophilic filament membrane on a vacuum filtration device, adding a mixture of hydrophilic short fibers and binder to the vacuum filtration device for filtration; before complete filtration, a PVDF electrospun membrane is stacked on top of the hydrophilic filament membrane, and then an aqueous binder solution is added to the vacuum filtration device for further filtration. The resulting semi-finished product is then placed in a refrigerator for freezing and then freeze-dried in a freeze dryer.

[0020] Based on the above scheme and as a preferred embodiment of the above scheme: the hydrophilic filament membrane is a blend membrane of cellulose acetate and nitrocellulose.

[0021] Based on the above scheme and as a preferred embodiment of the above scheme: the adhesive is polyurethane.

[0022] The beneficial effects of the present invention are as follows: The preparation method of the α-NiS / g-C3N4 filament / short fiber composite membrane involved in the present invention uses α-NiS / g-C3N4 photocatalyst loaded on the filament / short fiber composite membrane, which has good mechanical and antibacterial properties, and the composite membrane can be recycled and has self-cleaning function. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the preparation process of the α-NiS / g-C3N4 filament / short fiber composite membrane involved in this invention;

[0024] Figure 2 It is the absorbance of a suspension containing α-NiS / g-C3N4 photocatalyst at a wavelength of 332nm;

[0025] Figure 3These are microstructure images of g-C3N4 (a), α-NiS (b), and 15%-α-NiS / g-C3N4 (c).

[0026] Figure 4 XRD patterns (a) of α-NiS, g-C3N4, and α-NiS / g-C3N4 with different mass ratios, and FT-IR patterns (b) of g-C3N4 and 15% α-NiS / g-C3N4;

[0027] Figure 5 This is the XPS full spectrum of g-C3N4 and 15%-α-NiS / g-C3N4;

[0028] Figure 6 XPS spectra of C1s(a), N1s(b), Ni2p(c), and S2p(d) in α-NiS / g-C3N4;

[0029] Figure 7 The UV-vis-DRS plots of α-NiS, g-C3N4, and α-NiS / g-C3N4 with different mass ratios are shown in (a); the Mott-Schottky plot of g-C3N4 is shown in (b).

[0030] Figure 8 The transient photocurrent (a) and electrochemical impedance (EI) plots of different samples are shown in Figure (b).

[0031] Figure 9 These are the TRPL spectra of α-NiS, g-C3N4, and 15%-α-NiS / g-C3N4;

[0032] Figure 10 The graphs show the degradation curves of MB (a) and first-order kinetic curves (b) of different samples, the cyclic photocatalytic degradation curve of methylene blue by 15% α-NiS / g-C3N4 (c), the effect of different scavengers on photocatalytic performance (d), and the degradation curves of DMPO-·OH (e) and DMPO-·O2. - (f) ESR spectrum on 15% α-NiS / g-C3N4 nanocomposite material;

[0033] Figure 11 The surface morphology of WP structure filament / short fiber composite films with PU concentrations of 0 ml (a), 1 ml (b), 2 ml (c), and 3 ml (d) in Examples 1 to 4; the surface morphology (e) and (f) of the WPE structure filament / short fiber composite film involved in Example 5; and the WP structure filament / short fiber composite films with PU concentrations of 1 ml (g) and 2 ml (h) involved in Examples 2 and 3 at high magnification;

[0034] Figure 12These are contact angle test diagrams of filament / short fiber composite films with and without (a) PVDF electrospun film and with (b) PVDF.

[0035] Figure 13 The effects of different structures in Examples 3, 5, and 6 on the mechanical properties of α-NiS / g-C3N4 filament / short fiber composite films;

[0036] Figure 14 The adsorption-desorption curves and pore size distributions of α-NiS / g-C3N4 filament / short fiber composite membranes with different structures in Examples 3, 5, and 6 are shown.

[0037] Figure 15 The images show the original E. coli bacterial suspension diluted 10,000 times (groups 1, 2, and 3) and the E. coli bacterial suspension after antibacterial treatment with α-NiSg-C3N4 filament / short fiber composite membranes of different structures (group 4-WP, group 5-WPE, and group 6-WEP).

[0038] Figure 16 Examples 3, 5, and 6 show the photocatalytic degradation properties of different membranes (a) and (b) their corresponding kinetic linear curves. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0040] Examples 1-4

[0041] This embodiment will be described in detail with reference to the accompanying drawings. The method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane according to this embodiment includes the preparation of the filament / short fiber composite membrane and the loading of α-NiS / g-C3N4 onto the filament / short fiber composite membrane.

[0042] The preparation of the filament / short fiber composite membrane refers to loading hydrophilic short fibers and a binder onto a filament membrane; the filament membrane includes a hydrophilic filament membrane.

[0043] Furthermore, in this embodiment, the hydrophilic filament membrane is a cellulose acetate-nitrocellulose blend membrane. And the hydrophilic short fibers used in this embodiment refer to the hydrophilic filament membrane that has been broken down, with a length of 10-200 micrometers. Specifically, 2.22 grams of the hydrophilic filament membrane are weighed and placed in a blender with 400 ml of deionized water. The blender is run for 5 hours to break down the cellulose acetate-nitrocellulose blend membrane into a soy milk-like solution, which is then poured into a beaker for later use.

[0044] Furthermore, the adhesive is polyurethane. And because it is necessary to bond the hydrophilic short fibers to the filament film, an adhesive needs to be loaded when loading the hydrophilic short fibers, so that the hydrophilic short fibers, α-NiS / g-C3N4 photocatalyst, and the filament film can bond together during the subsequent drying process.

[0045] The filament / short fiber composite membrane is produced by placing a hydrophilic filament membrane on a vacuum filtration device, adding a mixture of hydrophilic short fibers and a binder, and then performing filtration. The α-NiS / g-C3N4 loaded onto the filament / short fiber composite membrane involves placing the filament / short fiber composite membrane on a vacuum filtration device, adding a suspension containing an α-NiS / g-C3N4 photocatalyst, performing filtration, and then sequentially adding a PEG-20000 solution and a glutaraldehyde solution to the vacuum filtration device. After filtration, the membrane is dried in a vacuum oven.

[0046] In this embodiment, the cellulose acetate-nitrocellulose blend membrane is placed on a vacuum filtration device, and 10 ml of a mixture of hydrophilic short fibers and binder is added for filtration. Then, 50 ml of a suspension containing α-NiS / g-C3N4 photocatalyst is added for filtration. Next, 25 ml of a 25% PEG-20000 solution and 25 ml of a 25% glutaraldehyde solution are added sequentially to the vacuum filtration device. After filtration, the membrane is dried in a vacuum oven to obtain the WP structure α-NiS / g-C3N4 filament / short fiber composite membrane.

[0047] The hydrophilic short fiber and binder mixture refers to the mixture formed by adding polyurethane to the above-mentioned solution of cellulose acetate nitrate crushed into a soy milk-like consistency. 0 ml, 1 ml, 2 ml, or 3 ml of polyurethane are added to every 10 ml of the soy milk-like solution formed from crushed cellulose acetate nitrate.

[0048] The suspension containing the α-NiS / g-C3N4 photocatalyst refers to the α-NiS / g-C3N4 photocatalyst added to a dispersant solution. The dispersant solution used is an aqueous solution containing a dispersant, wherein the volume percentage of the dispersant is 20-100%. The dispersant used is ethanol, propanol, or isopropanol; in this embodiment, isopropanol is selected.

[0049] The optimal amount of isopropanol was determined by measuring the absorbance of a suspension containing α-NiS / g-C3N4 photocatalyst at 332 nm. IPA / H2O mixed solutions of different proportions were prepared to determine the uniformly dispersed, high-concentration, and highly stable α-NiS / g-C3N4 suspensions. Isopropanol (IPA) was added at volume ratios of 0%, 20%, 40%, 60%, 80%, and 100%. Dispersion was performed using ultrasound for 2 hours and 4 hours. Since the UV absorption wavelength of graphitic carbon nitride is at 332 nm, the absorbance of the suspension at 332 nm was measured using a UV spectrophotometer. Figure 2 .Depend on Figure 2 It can be seen that the absorbance of the α-NiS / g-C3N4 suspension at 332 nm increases slightly with increasing sonication time. Meanwhile, the absorbance of the α-NiS / g-C3N4 suspension with a 20% isopropanol volume ratio remains the highest during both 2h and 4h sonication. This indicates that a 20% isopropanol volume ratio provides the best dispersibility and the highest photocatalyst concentration in the α-NiS / g-C3N4 suspension. Therefore, a 20% isopropanol aqueous solution can be used as the optimal dispersant ratio.

[0050] The α-NiS / g-C3N4 photocatalyst was prepared by dissolving g-C3N4 in ethanol and sonicating for 40 min, then adding nickel acetate tetrahydrate, SDS, and thiourea, and stirring continuously for 1 h. The resulting mixture was then transferred to a polytetrafluoroethylene (PTFE) reactor and heated at a set temperature of 190°C for 10 h to ensure complete reaction. After the reaction, the PTFE reactor was cooled to room temperature, and the final product was removed and washed three times each with deionized water and ethanol, and then dried in a vacuum oven. In this embodiment, SDS was sodium dodecyl sulfate.

[0051] Nickel acetate tetrahydrate, SDS, and thiourea are reacted in a reactor to generate NiS, which is then loaded onto g-C3N4 nanosheets at a loading rate of 5-25%, where the loading ratio is the mass ratio of g-C3N4 to NiS.

[0052] Furthermore, the preparation of g-C3N4 involves mixing dicyandiamide and ammonium chloride at a ratio of 1:10, grinding them uniformly in a mortar for 1 hour, then transferring the mixture from the mortar to an alumina crucible, covering it, and calcining it in a muffle furnace. The temperature is raised to 550°C after 3 hours, and then calcined at this temperature for 4 hours. Finally, the mixture is cooled to obtain g-C3N4 nanosheets.

[0053] The morphology, structure, optical and photoelectrochemical properties, and photocatalytic degradation performance of the α-NiS / g-C3N4 photocatalyst prepared in this embodiment were tested.

[0054] The microstructure of g-C3N4, α-NiS, and 15%-α-NiS / g-C3N4 was observed using scanning electron microscopy. Figure 3 (a) indicates that g-C3N4 has a sheet-like folded structure. Figure 3 In (b) NiS, the nanoparticles (NPs) are arranged in a stacked state. Figure 3 Image (c) is an electron microscope image of the 15% α-NiS / g-C3N4 nanocomposite material. It can be observed that granular α-NiS is uniformly loaded on the sheet-like stacked g-C3N4, which shows that α-NiS and g-C3N4 are tightly bonded and uniformly loaded together, and the α-NiS / g-C3N4 nanocomposite material was successfully synthesized.

[0055] X-ray diffraction (XRD) was used to characterize α-NiS, g-C3N4, and α-NiS / g-C3N4 photocatalysts with different mass ratios, and the crystal structures of the samples were determined. Figure 4 As shown in (a), the diffraction peaks at 30.3°, 34.8°, 46.0°, and 53.7° in the XRD pattern correspond to the (100), (101), (102), and (110) crystal planes of α-NiS, respectively, consistent with the standard card (PDF No. 02-1280), indicating the successful preparation of α-NiS. Furthermore, the diffraction peak at approximately 27.3° corresponds to the (002) crystal plane, which is caused by reflection from the interlayer stacking of two-dimensional g-C3N4. The diffraction peak corresponding to the (100) crystal plane of 2D g-C3N4 (approximately 13.1°) disappears due to the disappearance of the two-dimensional ultrathin structure of 2D g-C3N4. [74-76] Furthermore, it can be seen that as the mass of α-NiS loading increases, the corresponding peak positions of α-NiS gradually become more pronounced. After the loading mass ratio reaches 10%, the α-NiS / g-C3N4 composite material exhibits typical α-NiS and g-C3N4 peaks. In addition, the diffraction peak positions of α-NiS and g-C3N4 in the α-NiS / g-C3N4 composite material do not shift, indicating that the crystal structure remains unchanged during the synthesis process. Furthermore, the interlayer spacing of the two-dimensional g-C3N4 is approximately 0.335 nm, and the average grain size of α-NiS calculated using the Scherrer equation is 17.5 nm.

[0056] The original g-C3N4 and 15%-α-NiS / g-C3N4 were characterized by FT-IR. Figure 4 As shown in (b), 810 and 878 cm can be observed. -1 The characteristic peaks at 1110-1730 cm⁻¹ belong to triazine and NH units, respectively. -1 The nearby absorption bands are related to the stretching vibration mode of CN heterocycles, and also in the 3000-3500 cm⁻¹ range.-1 The broad peaks between them are due to the tensile vibrations of NH and OH.

[78] Comparing the infrared curves of the original g-C3N4 and 15%-α-NiS / g-C3N4, it is clear that the FT-IR spectrum of the 15%-α-NiS / g-C3N4 nanocomposite is the same as that of the two-dimensional g-C3N4, indicating that the g-C3N4 in 15%-α-NiS / g-C3N4 maintains its chemical structure. The results obtained are consistent with the XRD analysis results.

[0057] The interfacial bond positions between g-C3N4 and 15%-α-NiS / g-C3N4 were analyzed using full-spectrum X-ray photoelectron spectroscopy (XPS). Figure 5 As shown, the full spectrum of g-C3N4 contains three main peaks: C1s, N1s, and O1s, proving that g-C3N4 successfully prepared with its main elements C and N. Since oxygen was not isolated during the high-temperature calcination in the muffle furnace, oxidation occurred, resulting in a small amount of O in the g-C3N4. The full spectrum of 15%-α-NiS / g-C3N4 contains five main peaks: C1s, N1s, O1s, S2p, and Ni2p. The smaller S2p and Ni2p peaks compared to the other three peaks are consistent with a loading mass ratio of only 15%. A comparison of the full spectra of g-C3N4 and 15%-α-NiS / g-C3N4 revealed a significant increase in the two peaks at 164.30 eV and 856.14 eV in the loaded α-NiS / g-C3N4 sample. This is due to the successful loading of α-NiS. Consequently, 15%-α-NiS / g-C3N4 exhibits two additional Ni2p and S2p peaks, indicating the presence of nickel and sulfur elements on the sample surface after loading. This confirms the successful loading of α-NiS onto g-C3N4.

[0058] Further XPS analysis of α-NiS / g-C3N4 yielded the following results: Figure 6 As shown. In Figure 6 In (a), the C1s spectrum of α-NiS / g-C3N4 is deconvolved into three peaks centered at 287.9, 286.5 and 284.8 eV, which correspond to sp2 hybrid carbon (N=CN), non-isostatic carbon cycle π-π* and graphitic carbon (CC), respectively. Figure 6 In (b), the high-resolution XPS spectrum of N1s can be fitted to three peaks centered at 398.5, 400.3, and 404.3 eV. These three peaks originate from sp2 hybridized N (CNC, N2C), triple-coordinated tertiary nitrogen (N–C3, N3C), and charge effects or localization of positive charge in the heterocycle, respectively. The connection between CNC and N-C3 constitutes the tri-s-triazine conjugated framework of g-C3N4. Figure 6Image (c) shows a high-resolution Ni 2p with two spin-orbit doublets and two oscillating satellite peaks. The main peaks at 855.4 and 873.1 eV are consistent with Ni. 2+ The low peaks at 852.6 and 870.0 eV originate from NiS containing a very small amount of positively charged Ni. + Two main oscillatory satellite peaks were observed at 860.7 and 879.3 eV. Figure 6 As shown in (d), the S2p spectrum has two peaks at 162.3 and 161.0 eV, which are related to S2p3 / 2 and S2p1 / 2, respectively.

[0059] The optical properties of NiS, g-C3N4, and α-NiS / g-C3N4 with different loading ratios were studied using a Cary-5000 UV-Vis diffuse reflectance spectrometer. Before testing, vacuum-dried NiS, g-C3N4, and α-NiS / g-C3N4 sample powders with different loading ratios were placed in the sample chamber. The wavelength range for scanning was set to 200-800 nm. The band gap width of α-NiS / g-C3N4 was calculated using formula (1) based on the UV-Vis diffuse reflectance spectra.

[0060]

[0061] The light absorption properties of a photocatalyst directly affect its photocatalytic performance. The UV-vis DRS spectrum of the prepared photocatalyst is as follows: Figure 7 As shown in (a), the absorption edge of the α-NiS / g-C3N4 nanocomposite redshifts with increasing α-NiS content compared to g-C3N4. The light absorption of α-NiS / g-C3N4 is stronger than that of g-C3N4 in the 500-800 nm range, which is attributed to the introduction of NiS, which facilitates the absorption of visible light. The absorption spectra Eg of g-C3N4 and 15% NiS / g-C3N4 were calculated to be 2.76 and 2.52 eV, respectively, according to Equation (1).

[0062] The Mott-Schottky (MS) plot was measured at 1000 Hz in 0.1 M Na₂SO₄ solution to determine the conduction band valence level (CB) of g-C₃N₄. Figure 7 In (b), the positive slope of the Mott-Schottky plot indicates that g-C3N4 is an n-type semiconductor. The flat-band potential (Va) of g-C3N4 at pH 7 was calculated based on the linear potential curve. fb The value is -0.37V vs. NHE. This is different from the V of an n-type semiconductor. fb In comparison, the bottom of CB is -0.1Vg-C3N4 relative to NHE at pH=7. CB It is -0.47V. According to E CB=E VB -Eg, at pH=7, the valence band (VB) edge potential is 2.29V vs. NHE.

[0063] Electrochemical studies were conducted on g-C3N4, 5%-α-NiS / g-C3N4, 10%-NiS / g-C3N4, and 15%-αNiS / g-C3N4, respectively. Figure 8 Figure (a) shows the instantaneous photocurrent-time (It) curves. The results indicate that 15%-α-NiS / g-C3N4 exhibits the highest photocurrent intensity, suggesting that α-NiS loading leads to more efficient electron transfer. Therefore, 15%-α-NiS / g-C3N4 demonstrates the best degradation performance. Electrochemical impedance spectroscopy (EIS) provides further evidence for the charge transfer efficiency of the catalyst. Figure 8 In (b), the 15%-α-NiS / g-C3N4 nanocomposite material exhibits the minimum resistance curve, indicating that the resistance is minimal.

[0064] Time-resolved photoluminescence spectroscopy (TRPL) is a spectroscopic technique generally used to detect the dynamic process of radiative transition spectra of excited states of matter under pulsed monochromatic light irradiation over time. In this experiment, the time-resolved photoluminescence spectrum of the sample was measured using a fluorescence lifetime spectrophotometer, and the average lifetime of photogenerated carriers τ was calculated using the following formula (2).

[0065]

[0066] Where A1 and A2 are the fitting constants for the decay curve; τ1 represents the fast component; and τ2 represents the slow component.

[0067] Figure 9 TRPL spectra of α-NiS, g-C3N4, and 15%-α-NiS / g-C3N4 are shown. The average lifetime of photogenerated carriers τ was determined using Equation (2) below. The average lifetime of carriers in 15%-α-NiS / g-C3N4 (τ = 1.35 ns) is longer than that of pure g-C3N4 (τ = 0.76 ns). Therefore, α-NiS loading on the g-C3N4 surface prolongs the average carrier lifetime, which greatly increases the transfer efficiency of photogenerated carriers required for photocatalytic degradation. The results are consistent with those obtained from electrochemical studies.

[0068] Under simulated sunlight irradiation conditions using a 300W xenon lamp, 30 mg of α-NiS / g-C3N4 photocatalytic powder was dispersed in a 20 mg / L, 50 ml methylene blue (MB) aqueous solution to evaluate the photocatalytic degradation performance of α-NiS / g-C3N4 photocatalytic powder with loading ratios of 5%, 10%, 15%, 20%, and 25% by mass. The results are as follows: Figure 10As shown in (a), the catalyst was dispersed in a methylene blue solution and stirred for 60 min under dark reaction conditions to reach adsorption-desorption equilibrium. The results showed that the adsorption effect on the removal of methylene blue was negligible. Then, a xenon lamp was turned on for photocatalytic reaction. g-C3N4 alone degraded approximately 17% of methylene blue within 120 min. The degradation performance was significantly increased after loading α-NiS. The highest photocatalytic degradation performance, reaching 66% methylene blue degradation rate, was observed after 120 min of photocatalytic reaction at a mass ratio of 15% α-NiS / g-C3N4.

[0069] The above test results indicate that the loading of α-NiS cocatalyst contributes to the improvement of photocatalytic activity. α-NiS-loaded g-C3N4 can attract more photogenerated electrons from the surface of the material, thereby improving the separation efficiency of photogenerated carriers. Furthermore, the degradation kinetics of methylene blue by the α-NiS / g-C3N4 photocatalyst were further evaluated using the pseudo-first-order kinetic equation -ln(C / C0)=kt. The pseudo-first-order kinetic curves of methylene blue degradation by photocatalysts with different mass ratios are shown below. Figure 10 As shown in (b), the 15% α-NiS / g-C3N4 photocatalyst has the highest k value (0.00853 min). -1 ), approximately g-C3N4 (0.00089 min -1 10 times that of ). Figure 10 Image (c) shows the reusability of the prepared 15%-α-NiS / g-C3N4 nanocomposite for the photocatalytic degradation of methylene blue. After four operations, the photocatalytic activity did not decrease significantly, and the photocatalytic activity of 15%-α-NiS / g-C3N4 for methylene blue remained at approximately 66%, with the removal rate decreasing by only 2.2% compared to the initial value. The results indicate that the prepared 15%-α-NiS / g-C3N4 exhibits good reusability and stability in the photocatalytic process.

[0070] Results of free radical capture experiments as follows Figure 10 As shown in (d), isopropanol (IPA), ethylenediaminetetraacetic acid (EDTA), and 1,4-benzoquinone (BQ) inhibit hydroxyl radicals (·OH) and photogenerated holes (h₂O₃), respectively. + ) and superoxide radicals (·O2) - The photocatalytic degradation activity decreased significantly after the addition of IPA and BQ, indicating that the activity of ·OH and ·O2 was significantly reduced. - EDTA plays a dominant role in the photocatalytic degradation of methylene blue. The inhibitory effect of EDTA on TC degradation efficiency is weaker than that of BQ and IPA, indicating that h + Its contribution is less than that of ·OH and ·O2 - Furthermore, electron paramagnetic resonance (ESR) was used to further investigate the active ingredients involved. ESR results showed... Figure 10 In (e) and (f), DMPO-·OH and DMPO-·O2 cannot be detected under dark conditions. - The adducts show obvious signals, but both adducts exhibit signals under light irradiation, with the intensity increasing with irradiation time.

[0071] g-C3N4 was synthesized using a thermal condensation method, and based on this, α-NiS / g-C3N4 nanocomposites were constructed via a hydrothermal method. The photocatalytic performance of x%-α-NiS / g-C3N4 (x = 5, 10, 15, 20, and 25) with different α-NiS loadings was evaluated. A series of characterization tests, including morphology and structure analysis, confirmed the successful preparation of the α-NiS / g-C3N4 photocatalyst, and the following conclusions were drawn:

[0072] (1) XRD tests confirmed that the constructed photocatalyst α-NiS / g-C3N4 nanocomposite contained α-phase NiS, and its chemical structure remained unchanged. EDX mapping showed that α-NiS was uniformly dispersed on g-C3N4. DRS analysis showed that the band gap width of 15%-α-NiS / g-C3N4 was 2.76 eV, which was significantly increased compared to the band gap width of 2.52 eV, indicating that the visible light response capability of 15%-α-NiS / g-C3N4 was significantly enhanced.

[0073] (2) With the increase of α-NiS content, the photocatalytic performance of α-NiS / g-C3N4 nanocomposites first increases and then decreases. Among them, the 15% α-NiS / g-C3N4 nanocomposites exhibit the highest photocatalytic activity and the best methylene blue degradation performance, with a degradation rate of 66%.

[0074] ESR spectroscopy and active substance capture experiments showed that h + ·OH and ·O 2- Both have a promoting effect on the photodegradation of methylene blue. Based on the relative electronic energy level and charge transfer process of α-NiS / g-C3N4 nanocomposite materials, the photocatalytic mechanism of α-NiS / g-C3N4 nanocomposite materials was obtained.

[0075] Example 5

[0076] The method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane in this embodiment differs from that in Embodiment 1 in that the filament membrane further includes a PVDF electrospun membrane stacked on top of the hydrophilic filament membrane.

[0077] The filament / short fiber composite membrane is obtained by stacking a hydrophilic filament membrane and a PVDF electrospun membrane, placing them on a vacuum filtration device, adding 10 ml of a mixture of hydrophilic short fibers and binder, and then filtration. Next, 50 ml of a suspension containing an α-NiS / g-C3N4 photocatalyst is added and filtered again. Then, 25 ml of a 25% PEG-20000 solution and 25 ml of a 25% glutaraldehyde solution are added sequentially to the vacuum filtration device. After filtration, the membrane is dried in a vacuum oven to obtain a WEP-structured α-NiS / g-C3N4 filament / short fiber composite membrane. In this embodiment, the PVDF electrospun membrane is located on the outer side, i.e., the cellulose acetate-nitrocellulose blend membrane is the liquid-facing surface, so that the hydrophilic short fibers are located within the cellulose acetate-nitrocellulose blend membrane. 2 ml of polyurethane is added to every 10 ml of the soy milk-like solution formed by crushing cellulose acetate-nitrocellulose.

[0078] Example 6

[0079] This embodiment describes a method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane, which differs from Embodiment 2 in that: the filament / short fiber composite membrane is prepared by placing a hydrophilic filament membrane on a vacuum filtration device, adding 10 ml of a mixture of hydrophilic short fibers and binder to the vacuum filtration device for filtration; before complete filtration, a PVDF electrospun membrane is stacked on top of the hydrophilic filament membrane, and then a PU aqueous solution (69% solid content) is added to the vacuum filtration device for further filtration for 30 seconds. The resulting sample is then frozen in a refrigerator for 30 minutes, followed by freeze-drying in a freeze dryer for 12 hours. The dried membrane is then placed on a vacuum filtration device, and a pre-prepared suspension (50 ml) is added for filtration. Then, 25 ml of PEG-20000 solution (25%) and 25 ml of 25% glutaraldehyde solution are added sequentially for filtration, followed by drying in a vacuum oven to obtain a WPE-structured α-NiS / g-C3N4 filament-short fiber composite membrane. Add 2 ml of polyurethane to every 10 ml of the soy milk-like solution formed by breaking up the cellulose acetate-nitrocellulose blend membrane.

[0080] The surface morphology of the long filament / short fiber composite membranes in Examples 1 to 6 was analyzed, see... Figure 11 The surface morphology of the filament / short fiber composite film was observed using scanning electron microscopy. Figure 11 a, b, c, and d represent the surface morphology of the WP structure filament / short fiber composite film with PU dosages of 0ml, 1ml, 2ml, and 3ml, respectively, i.e., Examples 1 to 4. Figure 11 Image (a) shows the surface morphology of the cellulose acetate-nitrocellulose blend membrane, which reveals that the cellulose acetate-nitrocellulose blend membrane possesses a dense pore structure. Figure 11As can be seen from (b) and (c), the acetate-nitrocellulose blend membrane solution exhibits a blocky stacking after filtration on the surface of the acetate-nitrocellulose blend membrane, with large pores enclosing small pores. The increase in pore size not only increases the volume but also greatly increases the specific surface area of ​​the composite membrane. Figure 11 (d) shows the surface morphology of the filament / short fiber composite membrane prepared with 3ml PU as a binder. The figure shows that most of the pores are blocked with 3ml PU, making the membrane surface very smooth. Only some parts are still unblocked and some small pores remain. Figure 11 Image (e) shows the surface morphology of the WPE filament / short fiber composite membrane. The spherical surface consists of aggregated PU fibers, while the filamentous surface represents electrospun PVDF filaments. Below these filaments is a loosely packed, sponge-like layer of broken cellulose acetate-nitrocellulose blend membrane sandwiched between the PVDF electrospun membrane and the cellulose acetate-nitrocellulose blend membrane. Figure 11 (f) in the middle. Figure 11 (g) and (h) are electron microscope images of 1 ml and 2 ml PU at higher magnification, respectively. It can be seen from the images that 1 ml PU has more small pores in the same area, while the 2 ml PU sample has a larger connection area between pores on the surface. Based on the experimental results of the surface bonding strength test of the long filament and short fiber composite film, the optimal amount of PU to prepare a composite film with good bonding strength and many pores is 2 ml.

[0081] The effects of adding PVDF electrospun membrane on the filament / short fiber composite membrane were analyzed in Examples 3 and 5, as shown in the figure. Figure 12 The surface properties of the filament / staple fiber composite film before and after the addition of the PVDF electrospun film were tested using a video optical contact angle meter. Figure 12 The changes in contact angle values ​​of the filament / staple fiber composite membranes (a1-a3) without PVDF electrospun film and those with PVDF electrospun film (b1-b3) within 10 seconds after droplet droplet application can be observed. It can be seen that the contact angle of the filament / staple fiber composite membrane without PVDF electrospun film is 74.9° immediately upon droplet application. As the droplet is absorbed over time, the contact angle gradually decreases to 66.5° at 10 seconds. The contact angle of the filament / staple fiber composite membrane with PVDF electrospun film is 94.7° immediately upon droplet application. As the droplet is absorbed over time, the contact angle decreases to 80.2°. This indicates that with the addition of PVDF electrospun film, the contact angle of the filament / staple fiber composite membrane increases. However, the rate of droplet absorption by the filament / staple fiber composite membrane remains approximately the same over time. However, the contact angle of the filament / short fiber composite membrane with added PVDF electrospun film is always greater than that of the filament / short fiber composite membrane without added PVDF electrospun film. This indicates that adding PVDF electrospun film will decrease the hydrophilicity and increase the hydrophobicity of the filament / short fiber composite membrane.

[0082] The mechanical properties of the α-NiS / g-C3N4 filament / short fiber composite film were tested using a universal tensile testing machine. The results are as follows: Figure 13 As shown, the tensile strength of the α-NiS / g-C3N4 filament / short fiber composite membrane increases with the addition of PVDF electrospun membrane, with the WPE structure exhibiting the best tensile strength. This is because the addition of a large amount of PU will clog the pores of the α-NiS / g-C3N4 filament / short fiber composite membrane, thus requiring very high PU dosage. Too much PU will clog the pores and ultimately affect the degradation efficiency, while too little PU will result in weak bonding of the α-NiS / g-C3N4 filament / short fiber composite membrane.

[0083] The specific surface area and porosity of the α-NiS / g-C3N4 supported filament / short fiber composite membrane were analyzed using an automated specific surface area and porosity analyzer via an N2 adsorption-desorption isotherm. Figure 14 As shown. According to IUPAC classification, the α-NiS / g-C3N4 filament / short fiber composite films with WP structure, WEP structure, and WPE structure all exhibit type IV isotherms and type H3 hysteresis loops, indicating that these samples all contain mesoporous structures, and the BET specific surface areas of the samples are 4.226 m². 2 / g, 4.02m 2 / g and 3.65m 2 / g. The water film has small and dense pores, thus the WP structure α-NiS / g-C3N4 filament / short fiber composite membrane has a large specific surface area. The WPE structure α-NiS / g-C3N4 filament / short fiber composite membrane has the second largest specific surface area. The WEP structure α-NiS / g-C3N4 filament / short fiber composite membrane is produced by filtering a broken cellulose acetate-nitrocellulose blend membrane, allowing the cellulose acetate-nitrocellulose blend membrane to enter the large pores of the electrospun membrane, and then loading α-NiS / g-C3N4 photocatalyst powder into the pores, thus significantly reducing its specific surface area.

[0084] The α-NiS / g-C3N4-loaded filament / short fiber composite membranes of Examples 3, 5, and 6 were subjected to photo-irradiation antibacterial tests. The antibacterial effect of the α-NiS / g-C3N4-loaded filament / short fiber composite membranes against *Escherichia coli* was tested using the plate count method, see below. Figure 15 . Figure 15Groups 4, 5, and 6 correspond to Examples 3, 5, and 6, respectively, which are the antibacterial test diagrams of the α-NiS / g-C3N4 filament / short fiber composite membrane with WP structure, the α-NiS / g-C3N4 filament / short fiber composite membrane with WEP structure, and the α-NiS / g-C3N4 filament / short fiber composite membrane with WPE structure. It can be seen that the antibacterial rate reaches 100% in all cases.

[0085] Under 300W xenon lamp irradiation simulating visible light, 50 ml (10 mg) of α-NiS / g-C3N4 was loaded onto long filament / short fiber composite membranes with different structures. After a 60-minute dark reaction to reach adsorption-desorption equilibrium, photocatalytic activity was tested. The test results are as follows: Figure 16 As shown in Figure (a), we can see that all three structures of the α-NiS / g-C3N4 supported filament / short fiber composite membranes conform to the first-order kinetic equation. Among them, the WPE structure of the α-NiS / g-C3N4 filament / short fiber composite membrane exhibits the best degradation performance, with a degradation rate of 68%. This is followed by the WP structure of the α-NiS / g-C3N4 filament / short fiber composite membrane, and finally the WEP structure of the α-NiS / g-C3N4 filament / short fiber composite membrane. The calculated k-values ​​of their pseudo-kinetic equations are shown below. Figure 16 As shown in Figure (b), the k values ​​of the α-NiS / g-C3N4 filament / short fiber composite membranes with WPE structure, WP structure, and WEP structure are respectively 0.00841 min. -1 0.00689min -1 0.00559min -1 .

[0086] The self-cleaning effect of the WPE-structured α-NiS / g-C3N4 filament / short fiber composite membrane prepared in Example 6 was tested. In the cyclic degradation of methylene blue test experiment, after every two cycles, the membrane was removed from the methylene blue solution and immersed in a petri dish containing deionized water. Simultaneously, it was illuminated from a 300W xenon lamp source at a distance of 8 cm to test the self-cleaning ability of the WPE-structured α-NiS / g-C3N4 filament / short fiber composite membrane. The membrane was removed and photographed every hour. Under the irradiation of 300W xenon lamp simulating sunlight, the color at the center of the WPE-structured α-NiS / g-C3N4 filament / short fiber composite membrane had significantly faded after 1 hour. After 2 hours of irradiation, the WPE-structured α-NiS / g-C3N4 filament / short fiber composite membrane had completely degraded the adsorbed methylene blue dye and its color had been completely restored.

[0087] α-NiS / g-C3N4 filament / short fiber composite membranes with different structures were prepared by vacuum filtration and freeze-drying. Based on structural characterization and performance testing, the following conclusions were drawn:

[0088] By exploring the amount of PU used, α-NiS / g-C3N4 filament / short fiber composite films with different structures were prepared without changing the chemical structure of the α-NiS / g-C3N4 photocatalyst and while ensuring uniform loading of the α-NiS / g-C3N4 photocatalyst. Mechanical and antibacterial properties were then tested. The results showed that the WPE-structured α-NiS / g-C3N4 filament / short fiber composite film exhibited the best elongation at break, while the WPE-structured α-NiS / g-C3N4 filament / short fiber composite film showed the best tensile strength. All three structures achieved 100% antibacterial performance.

[0089] The degradation of methylene blue by the α-NiS / g-C3N4 filament / short fiber composite membrane is a first-order kinetic reaction. The optimal structure obtained after degradation testing is the WPE structure of the α-NiS / g-C3N4 filament / short fiber composite membrane. Its photocatalytic performance is approximately the same as that of powdered α-NiS / g-C3N4 photocatalyst, with a degradation rate of 68%, and the amount of photocatalyst used is reduced by 2 / 3.

[0090] Finally, the WPE-structured α-NiS / g-C3N4 filament / short fiber composite membrane was subjected to cycling and self-cleaning tests. The results showed that even after reducing the dosage, it still possessed a significantly higher recycling capacity than powdered photocatalysts. Furthermore, the WPE-structured α-NiS / g-C3N4 filament / short fiber composite membrane, after degradation, could be fully restored after being immersed in deionized water for 2 hours and could be quickly reused.

[0091] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane, characterized in that, This includes the preparation of filament / short fiber composite membranes and the loading of α-NiS / g-C3N4 onto the filament / short fiber composite membranes; The preparation of the filament / short fiber composite membrane refers to loading hydrophilic short fibers and a binder onto a filament membrane; the filament membrane includes a hydrophilic filament membrane; the hydrophilic filament membrane is a blend membrane of cellulose acetate and nitrocellulose; the binder is polyurethane; the hydrophilic short fibers are formed by breaking down the hydrophilic filament membrane, with a length of 10-200 micrometers. Loading α-NiS / g-C3N4 onto a filament / short fiber composite membrane refers to placing the filament / short fiber composite membrane on a vacuum filtration device, adding a suspension containing α-NiS / g-C3N4 photocatalyst to the vacuum filtration device, performing filtration, and then sequentially adding PEG-20000 solution and glutaraldehyde solution to the vacuum filtration device. After filtration, the membrane is placed in a vacuum oven for drying. The suspension containing α-NiS / g-C3N4 photocatalyst refers to the α-NiS / g-C3N4 photocatalyst added to a dispersant solution; The α-NiS / g-C3N4 photocatalyst was prepared by dissolving g-C3N4 in ethanol, adding nickel acetate tetrahydrate, SDS, and thiourea, and stirring continuously. The prepared mixture was transferred to a reaction vessel and heated and reacted at a set temperature. After the reaction was completed, the reaction vessel was cooled to room temperature and the final product was taken out and washed with deionized water and ethanol respectively, and then dried in a vacuum oven.

2. The method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane according to claim 1, characterized in that, The preparation of g-C3N4 involves mixing dicyandiamide and ammonium chloride at a ratio of 1:10, grinding them uniformly in a mortar for 1 hour, transferring them from the mortar to an alumina crucible, covering it, and then calcining it in a muffle furnace. The temperature is raised to 550°C for 3 hours and then calcined at high temperature for 4 hours. Finally, the mixture is cooled to obtain g-C3N4 nanosheets.

3. The method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane according to claim 1, characterized in that, The dispersant is ethanol, propanol, or isopropanol; the dispersant solution contains 20-100% dispersant.

4. The method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane according to claim 1, characterized in that, The filament film also includes a PVDF electrospun film stacked on top of the hydrophilic filament film.

5. The method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane according to claim 1, characterized in that, The filament / short fiber composite membrane is made by placing a hydrophilic filament membrane on a vacuum filtration device, and then adding a mixture of hydrophilic short fibers and binder into the vacuum filtration device for filtration.

6. The method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane according to claim 4, characterized in that, The filament / short fiber composite membrane is made by stacking a hydrophilic filament membrane and a PVDF electrospun membrane, placing them on a vacuum filtration device, and then adding a mixture of hydrophilic short fibers and a binder into the vacuum filtration device for filtration; the cellulose acetate-nitrocellulose blend membrane is the liquid-facing side.

7. The method for preparing an α-NiS / g-C3N4 filament / short fiber composite membrane according to claim 4, characterized in that, The filament / short fiber composite membrane is prepared by placing a hydrophilic filament membrane on a vacuum filtration device, adding a mixture of hydrophilic short fibers and binder to the vacuum filtration device for filtration, and then stacking a PVDF electrospun membrane on top of the hydrophilic filament membrane before complete filtration. The binder aqueous solution is then added to the vacuum filtration device for further filtration. The resulting semi-finished product is then placed in a freezer for freezing and then freeze-dried in a freeze dryer.

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