A koh-il-rgo membrane for dye wastewater treatment and a preparation method and application thereof

Abstract

The application belongs to the technical field of membrane separation, and provides a KOH-IL-rGO membrane for dye wastewater treatment and a preparation method and application thereof. The graphene-based composite membrane with stable structure is prepared by introducing potassium hydroxide and ionic liquid to perform synergistic modification on reduced graphene oxide. The prepared graphene-based composite membrane is applied to dye wastewater treatment, can keep efficient interception of dye molecules such as methylene blue, realizes the effect of significantly improving water molecule transmission flux, and exhibits excellent stability in long-term operation, and has good application prospect in the field of dye wastewater and the like.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically relating to a KOH-IL-rGO membrane for dye wastewater treatment, its preparation method, and its application. Background Technology

[0002] Dye wastewater is a significant source of industrial wastewater, characterized by its complex composition, high color intensity, and high toxicity, posing a serious threat to aquatic ecosystems and human health. Membrane separation technology, particularly nanofiltration, has shown great potential for advanced treatment and resource reuse of dye wastewater due to its low energy consumption and ease of operation. An ideal nanofiltration membrane needs to possess both high water permeability and high solute selectivity.

[0003] In existing technologies, graphene oxide membranes are widely used in membrane separation technology. However, due to their strong hydrophilicity, graphene oxide membranes are prone to swelling in aqueous environments, leading to structural instability and reduced separation performance. Furthermore, the densely stacked sheet structure of graphene oxide membranes to achieve high rejection rates significantly increases water transport resistance, resulting in generally low water flux. This trade-off between permeability and selectivity severely restricts their practical application.

[0004] Patent document CN107469633A discloses a method for preparing a membrane with enhanced water flux, which involves depositing in-situ synthesized nanoparticles—graphene materials—on the surface of a support to form a film layer using a pressure-driven method. While the graphene membrane prepared by this method exhibits good structural stability, the entire preparation process is time-consuming, and although water flux is improved, it is not possible to simultaneously achieve higher dye rejection and excellent water flux.

[0005] Reduced graphene oxide membranes are composed of partially reduced, stacked graphene nanosheets, with controllable two-dimensional nanochannels forming between the layers, providing an ideal platform for efficient molecular sieving. However, due to its tendency to swell easily in aqueous environments, structural instability, and low water flux, the applicant's prior research patent document CN118543248A discloses a graphene oxide membrane with high-flux desalination performance, its preparation method, and its applications. This method involves introducing ionic liquids into the interlayer channels of reduced graphene oxide to obtain a high-flux desalination membrane, thereby improving the retention rate of metal ions. However, the prior art has not seen the application of this type of ionic liquid-intercalated graphene oxide membrane in dye wastewater, and there are no reports of a technical solution for the synergistic modification of reduced graphene oxide membranes with KOH and ionic liquids for high-flux water flux retention in dye wastewater.

[0006] Currently, developing a modification strategy that can simultaneously enhance the structural stability, water permeability, and dye selectivity of rGO membranes has become an urgent need in this field. Summary of the Invention

[0007] In view of the above problems, the present invention provides a KOH-IL-rGO membrane for dye wastewater treatment with high throughput, high dye rejection rate and excellent structural stability, as well as its preparation method and application; by microscopically modifying two-dimensional graphene oxide nanosheets, a stable and intercalated two-dimensional channel with functional groups is constructed, which can effectively prevent the transport of dye molecules while maintaining rapid water molecule transport.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment includes the following steps:

[0010] (1) Disperse the reducing agent into the graphene oxide (GO) suspension and perform hydrothermal reduction to obtain a reduced graphene oxide (rGO) dispersion;

[0011] (2) Add ionic liquid (IL) and potassium hydroxide (KOH) to the reduced graphene oxide dispersion and disperse evenly to obtain a reduced graphene oxide dispersion synergistically modified by potassium hydroxide and ionic liquid;

[0012] (3) The reduced graphene oxide dispersion modified by potassium hydroxide and ionic liquid obtained in step (2) is assembled on a porous support membrane by vacuum filtration to obtain a reduced graphene oxide membrane based on potassium hydroxide and ionic liquid synergistic modification, denoted as KOH-IL-rGO membrane.

[0013] In step (2), the ionic liquid is a single component or a mixed component of an imidazole ionic liquid, the mass ratio of the ionic liquid to the reduced graphene oxide is (1.0~10.0):1, the mass ratio of the added potassium hydroxide to the reduced graphene oxide is (5.0~220):1, and the mass ratio of potassium hydroxide to the ionic liquid is (1.0~100):1.

[0014] In step (3), the thickness of the KOH-IL-rGO film is 180~220nm.

[0015] The technical solution of this invention utilizes the synergistic effect of hydrothermal reduction, ionic liquid intercalation, and KOH etching, wherein the ionic liquid cations and KOH introduce K... + By inserting cation-π interactions into the interlayer of rGO to act as "molecular bridges" to precisely control and fix the interlayer spacing, and by using KOH to gently etch the rGO carbon skeleton to introduce transport defects, the preparation method of the two-dimensional nanochannel of reduced graphene oxide membrane was precisely controlled, thus successfully constructing a separation membrane with high water flux, high dye rejection rate and excellent stability.

[0016] The present invention is further configured such that the graphene oxide dispersion is composed of a single layer of nanosheets with an average sheet size of 5±1μm.

[0017] The present invention is further configured such that, in step (1), the reducing agent is selected from one or more of potassium hydroxide, sodium hydroxide, or ascorbic acid.

[0018] The present invention is further configured such that the mass concentration of the graphene oxide suspension is 0.1-0.3 mg / mL.

[0019] The present invention is further configured such that the molar concentration of the reducing agent in the graphene oxide suspension is 5.0-30 mmol / L; preferably 7.5-20 mmol / L; more preferably 15±1 mmol / L.

[0020] The present invention is further configured such that, in step (1), the hydrothermal reduction process lasts for 1-4 hours and the processing temperature is 70-90℃.

[0021] The present invention is further configured such that, in step (1), after the reducing agent is added to the graphene oxide suspension, it is uniformly dispersed by mechanical stirring or ultrasonic treatment; in step (2), after the ionic liquid is added to the reduced graphene oxide dispersion, it is also dispersed uniformly by stirring or ultrasonic treatment; wherein the stirring method is magnetic stirring, the speed is set to 600-1200 r / min, and the duration is 0.5-2 hours; the ultrasonic treatment power is 500-800W, and the treatment time is 5-20 minutes.

[0022] The present invention is further configured such that the imidazole ionic liquid is selected from one or more of 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], 1,3-dimethylimidazolium hexafluorophosphate [DMIM][PF6], or 1-butyl-3-methylimidazolium chloride [BMIM][Cl].

[0023] The present invention is further configured such that, in step (2), the mass ratio of ionic liquid to reduced graphene oxide is (1.25~5.0):1, preferably (2.0~3.0):1. An appropriate amount of ionic liquid intercalation helps to enhance the structural stability of graphene nanochannels, while excessive ionic liquid will occupy the effective transport channels, thereby inhibiting the permeability of water molecules.

[0024] The present invention is further configured such that, in step (2), the mass ratio of the added potassium hydroxide to the reduced graphene oxide is (10~210):1, preferably (50~110):1, and more preferably (100~110):1.

[0025] The present invention is further configured such that the concentration of KOH added in step (2) in the reaction system is 0.02~0.5 mol / L, preferably 0.1~0.3 mol / L.

[0026] The present invention is further configured such that, in step (2), the mass concentration of the ionic liquid is 1~3 mg / mL and the solvent is deionized water.

[0027] The present invention is further configured such that, in step (3), the porous support membrane is made of a material selected from mixed cellulose ester, polycarbonate, and polyacrylonitrile, which provides the necessary mechanical strength for the composite membrane.

[0028] The present invention is further configured such that the average pore size of the porous support membrane is 0.1-0.22 μm; when the pore size is too small, it will generate a large mass transfer resistance, while when the pore size is too large, it will affect the orderly stacking of graphene nanosheets, ultimately leading to a decrease in membrane separation performance.

[0029] The present invention is further configured such that, in step (3), the ionic liquid intercalated reduced graphene oxide dispersion obtained in step (2) is appropriately diluted with deionized water, and then uniformly dispersed by ultrasonic treatment, and then loaded onto a porous substrate to prepare the target separation membrane; the ultrasonic power is 500-800W, and the time is 5-20 minutes.

[0030] The present invention is further configured such that, in step (3), the thickness of the KOH-IL-rGO membrane is 180~210nm, for example 180nm, 190nm, 200nm or 210nm.

[0031] In step (3), a vacuum-assisted film formation process is used, and the filtration pressure is 0.1-1.0 bar. Too low a pressure will result in a loose layered structure and insufficient mechanical properties; too high a pressure will result in an overly dense interlayer structure, which is not conducive to the transport of water molecules.

[0032] The present invention also provides a KOH-IL-rGO membrane for dye wastewater treatment prepared by the above preparation method.

[0033] The present invention also provides an application of the above-mentioned KOH-IL-rGO membrane for dye wastewater treatment, for the retention of dye molecules.

[0034] The present invention is further configured such that the dye includes methylene blue, rhodamine, and Congo red.

[0035] The present invention is further configured such that the concentration of the dye is 5-50 mg / L.

[0036] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention constructs a composite membrane with stable two-dimensional nanochannels through the synergistic effect of ionic liquid intercalation and potassium hydroxide modification. The cations in the ionic liquid and the K introduced by potassium hydroxide... + Through cation-π interactions, the interlayer spacing of rGO is precisely regulated and stabilized like a "molecular bridge," effectively suppressing membrane swelling in water and significantly enhancing the membrane's structural stability and mechanical strength.

[0037] (2) The introduction of potassium hydroxide produced a unique and mild etching effect on the rGO carbon skeleton, introducing an appropriate amount of nanoscale defects on the surface and in-plane of the sheets, creating additional channels for rapid transport of water molecules, thereby significantly increasing the water flux while maintaining high selectivity, with the water flux reaching 350~520 L·m -2 ·h -1 ·bar -1 At the same time, the retention rate of dye molecules reaches over 99%.

[0038] (3) The preparation method of the present invention is simple and the conditions are mild. The obtained composite membrane exhibits an ultra-high rejection rate (>99%) and water flux for dye molecules, especially methylene blue, which is far superior to the unmodified rGO membrane and the IL-rGO membrane with only ionic liquid intercalation. It also shows excellent stability in long-term operation and alkaline environment, and has broad application prospects in the field of dye wastewater treatment. Attached Figure Description

[0039] Figure 1 These are images and SEM cross-sectional morphology comparisons of the KOH-IL-rGO membrane prepared in Example 1 and the rGO membrane prepared in Comparative Example 2, where (a) is the rGO membrane and (b) is the KOH-IL-rGO membrane.

[0040] Figure 2 This is a comparison of the infrared spectra of the KOH-IL-rGO membrane prepared in Example 1 and the rGO membrane prepared in Comparative Example 2.

[0041] Figure 3 This is a comparison of Raman spectroscopy results between the KOH-IL-rGO membrane prepared in Example 1 and the rGO membrane prepared in Comparative Example 2.

[0042] Figure 4 This is a comparison chart of the retention performance of the KOH-IL-rGO membrane prepared in Example 1 for different dyes.

[0043] Figure 5 This is a graph showing the dye retention stability of the KOH-IL-rGO membrane prepared in Example 1 under long-term operation.

[0044] Figure 6This is a graph showing the dye retention stability of the rGO membrane prepared in Comparative Example 2 under long-term operation. Detailed Implementation

[0045] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. It should be understood that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of the present invention.

[0046] In this invention, the water flux of the membrane is defined as the volume of water passing through a unit membrane area per unit time, and its calculation formula is as follows:

[0047]

[0048] In the formula Membrane flux (L·m) -2 ·h -1 ·bar -1 ), (L) represents the increase in volume of the permeate during the period. (h) Filtering time Filter area (m) 2 ), (bar) represents the transmembrane pressure.

[0049] The rejection rate is calculated using the following formula:

[0050]

[0051] and These are the dye concentrations in the feed solution and the permeate, respectively. The dye concentrations in the feed solution and the permeate were determined by ultraviolet-visible spectroscopy (UV–Vis).

[0052] The method for preparing a KOH-IL-rGO membrane for dye wastewater treatment proposed in this invention includes the following steps:

[0053] (1) Potassium hydroxide was uniformly dispersed in the graphene oxide suspension system, and after thorough stirring, hydrothermal reduction treatment was carried out to obtain a reduced graphene oxide dispersion.

[0054] (2) Add ionic liquid and potassium hydroxide to the reduced graphene oxide dispersion, and after stirring and ultrasonication to disperse evenly, a reduced graphene oxide (KOH-IL-rGO) dispersion modified by ionic liquid and potassium hydroxide is obtained.

[0055] (3) The modified dispersion obtained above is deposited onto the surface of a porous support membrane by vacuum-assisted filtration to obtain the target composite separation membrane, denoted as KOH-IL-rGO membrane; wherein,

[0056] In step (2), the ionic liquid is a single component or a mixed component of imidazole ionic liquid, the mass ratio of the ionic liquid to the reduced graphene oxide is (1.0~10.0):1, the mass ratio of the added potassium hydroxide to the reduced graphene oxide is (5.0~220):1, and the mass ratio of potassium hydroxide to the ionic liquid is (1.0~100):1; In step (3), the thickness of the KOH-IL-rGO film is 180~220nm; The graphene oxide raw material in step (1) can be obtained commercially or can be prepared independently by referring to the modified Hummers method.

[0057] The modified Hummers process is as follows: Potassium persulfate (2.5 g) and phosphorus pentoxide (2.5 g) are mixed with natural graphite (3.0 g) in concentrated sulfuric acid medium. The reaction temperature is maintained at 78-82℃ and stirred continuously for 4.5 hours to complete the pre-oxidation. After the reaction is terminated, the mixture is cooled, diluted with deionized water to 500 mL, and allowed to stand overnight. The pre-oxidized product is obtained by solid-liquid separation and drying. Subsequently, the above product is mixed with concentrated sulfuric acid at a low temperature of 0-5℃, and potassium permanganate is added to carry out the main oxidation reaction at 34-36℃ for 1.5-2.5 hours. Finally, the reaction is terminated with hydrogen peroxide to achieve the exfoliation of the graphite layers. After repeated washing, filtration, and ultrasonic dispersion, the desired GO suspension is obtained.

[0058] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0059] Example 1

[0060] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment specifically includes the following steps:

[0061] (1) Preparation of reduced graphene oxide dispersion

[0062] Take 100 mL of graphene oxide suspension with a concentration of 0.2 mg / mL, add 1 mL of 1.5 mol / L KOH solution, and magnetically stir at 1000 r / min for 1 hour at room temperature; place the mixture in an environment of 80℃ and heat for 2 hours to complete the hydrothermal reduction, and obtain a reduced graphene oxide dispersion.

[0063] (2) Reduced graphene oxide dispersion synergistically modified by potassium hydroxide and ionic liquid

[0064] Take 4 mL of the reduced graphene oxide dispersion obtained above, with a rGO mass of approximately 0.8 mg, and add 1 mL of 2 mg / mL ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]). The mass ratio of rGO to added [BMIM][PF6] is approximately 1:2.5. Then, add 1 mL of 1.5 mol / L [polymer / liquid] solution. -1 KOH solution. Stirring at 1000 rpm for 1 hour at room temperature until fully mixed, followed by ultrasonication at 700W for 10 minutes to obtain a reduced graphene oxide dispersion synergistically modified by potassium hydroxide and ionic liquid. It should be noted that the mass of the reduced graphene oxide can be directly measured by those skilled in the art.

[0065] (3) Preparation of reduced graphene oxide film (KOH-IL-rGO) synergistically modified by potassium hydroxide and ionic liquid

[0066] The modified dispersion obtained in step (2) was diluted to 20 mL with deionized water, sonicated at 700 W for 10 minutes, and then filtered under a vacuum pressure of 0.1-1.0 bar to a mixed cellulose ester substrate with a pore size of 0.22 μm, thus obtaining the target composite membrane KOH-IL-rGO membrane. The obtained KOH-IL-rGO membrane was characterized, and the results are as follows: Figures 1-3 As shown. Figure 1 The cross-sectional images show that the thickness of the KOH-IL-rGO film is significantly greater than that of rGO, proving the successful intercalation of the ionic liquid. The measured film thickness is approximately 200 ± 10 nm.

[0067] Figure 2 The KOH-IL-rGO membrane was observed at approximately 1167 cm⁻¹. -1 and 1696 cm -1 A new characteristic peak belonging to the CN stretching vibration of the imidazole ring appeared at the point, confirming the successful intercalation of the ionic liquid; Figure 3 The results show that the ID / IG ratio of the KOH-IL-rGO film is significantly increased compared to that of the rGO film, indicating that the degree of defects on the film surface is further increased and the degree of graphitization is reduced, proving the etching effect of KOH on the film surface.

[0068] The dye retention performance of the reduced graphene oxide membrane synergistically modified by potassium hydroxide and ionic liquid was tested: The membrane prepared above, with substrate support, was fixed in a vacuum filtration system. In this experiment, the transmembrane pressure p was 1.0 bar, and the effective membrane area A was 12.34 cm². 2 Use 50 mL of a solution with a concentration of 10 mg / L. -1The separation performance was evaluated using a methylene blue (MB) dye solution. The volume of the permeate was recorded, the dye concentration in the permeate was tested, and the water flux and rejection rate were further calculated. The water flux of the reduced graphene oxide membrane synergistically modified with potassium hydroxide and ionic liquid was determined to be 455.0 L·m⁻¹. -2 ·h -1 ·bar -1 The MB retention rate was 99.68%.

[0069] At the same time, 10 mg L was used respectively -1 The dye retention properties of Congo Red (CR) and Rhodamine B (RB) dye solutions were tested, and the test results are as follows: Figure 4 As shown, the water flux of the KOH-IL-rGO membrane to the CR solution was detected to be 422.9 L·m. -2 ·h -1 ·bar -1 The rejection rate was 95.39%; the water flux to the RB solution was 363.3 L·m⁻¹. -2 ·h -1 ·bar -1 The retention rate was 97.89%.

[0070] Example 2

[0071] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is disclosed, differing from the previous embodiment only in the type of ionic liquid. In this embodiment, the ionic liquid is 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]).

[0072] The composite membrane prepared in this example was tested for methylene blue dye rejection performance under the same dye rejection conditions as in Example 1. The results showed a water flux of 428.7 L·m -2 ·h -1 ·bar -1 The MB retention rate was 99.67%.

[0073] Example 3

[0074] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is disclosed, differing from the previous embodiment only in the type of ionic liquid. In this embodiment, the ionic liquid is 1,3-dimethylimidazolium hexafluorophosphate ([DMIM][PF6]).

[0075] Using the same test conditions as in Example 1, the methylene blue dye rejection performance of the composite membrane prepared in this example was tested. The test results were: water flux of 449.8 L·m -2 ·h -1 ·bar -1The MB retention rate was 99.89%.

[0076] Example 4

[0077] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment differs from the previous example only in the amount of IL added in step (2). In this example, the volume of 2 mg / mL [BMIM][PF6] added is 0.5 mL, i.e., the mass ratio of KOH to IL is 84:1.

[0078] Using the same test conditions as in Example 1, the methylene blue dye rejection performance of the composite membrane prepared in this example was tested. The test results were: water flux of 360.2 L·m -2 ·h -1 ·bar -1 The MB retention rate was 99.24%.

[0079] Example 5

[0080] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment differs from the previous example only in the amount of IL added in step (2). In this example, the volume of 2 mg / mL [BMIM][PF6] added is 2 mL, which means the mass ratio of KOH to IL is 21:1.

[0081] Using the same test conditions as in Example 1, the methylene blue dye rejection performance of the composite membrane prepared in this example was tested. The test results were: water flux of 363.8 L·m -2 ·h -1 ·bar -1 The MB retention rate was 99.04%.

[0082] Example 6

[0083] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is disclosed. The only difference from the previous example is the amount of KOH added in step (2). In this example, 1.5 mol L... -1 The volume of the KOH solution is 0.1 mL.

[0084] Using the same test conditions as in Example 1, the methylene blue dye rejection performance of the composite membrane prepared in this example was tested. The test results were: water flux of 387.3 L·m -2 ·h -1 ·bar -1 The MB retention rate was 99.81%.

[0085] Example 7

[0086] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is disclosed. The only difference from the previous example is the amount of KOH added in step (2). In this example, 1.5 mol L... -1 The volume of the KOH solution is 0.5 mL.

[0087] Using the same test conditions as in Example 1, the methylene blue dye rejection performance of the composite membrane prepared in this example was tested. The test results were: water flux of 412.5 L·m -2 ·h -1 ·bar -1 The MB retention rate was 99.35%.

[0088] Example 8

[0089] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is disclosed. The only difference from the previous example is the amount of KOH added in step (2). In this example, 1.5 mol L... -1 The volume of the KOH solution is 2 mL.

[0090] Using the same test conditions as in Example 1, the methylene blue dye rejection performance of the composite membrane prepared in this example was tested. The test results were: water flux of 366.2 L·m -2 ·h -1 ·bar -1 The MB retention rate was 99.54%.

[0091] Example 9

[0092] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is provided. The preparation steps are the same as in Example 1, except that the concentration of methylene blue (MB) in the dye retention performance test is 5 mg / L. -1 .

[0093] The test results showed that the membrane's water flux was 501.3 L·m. -2 ·h -1 ·bar -1 The MB retention rate was 99.35%.

[0094] Example 10

[0095] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is provided. The preparation steps are the same as in Example 1, except that the concentration of methylene blue (MB) in the dye retention performance test is 25 mg / L. -1 .

[0096] The test results showed that the membrane's water flux was 426.2 L·m. -2 ·h -1 ·bar -1 The MB retention rate was 99.13%.

[0097] Example 11

[0098] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is provided. The preparation steps are the same as in Example 1, except that the concentration of methylene blue (MB) in the dye retention performance test is 50 mg / L. -1 .

[0099] The test results showed that the membrane water flux was 346.9 L·m. -2 ·h -1 ·bar -1 The MB retention rate was 98.65%.

[0100] Example 12

[0101] The retention performance test of Example 1 was used to conduct a long-term filtration test of the KOH-IL-rGO composite membrane prepared in Example 1 with methylene blue solution (10 mg / L). The specific test method was as follows: within the first 2 hours, the test was conducted once at 20-minute intervals, and from 2 to 6 hours, the test was conducted once at 1-hour intervals. The retention stability of the membrane was tested repeatedly.

[0102] The results are as follows Figure 5 As shown, the KOH-IL-rGO membrane exhibited excellent stability, with a water flux decrease of only 1.6% after 360 minutes of continuous operation. Furthermore, the KOH-IL-rGO membrane maintained a retention rate of over 99.5% throughout the entire test, demonstrating its reliable long-term operational performance.

[0103] Comparative Example 1

[0104] A method for preparing a reduced graphene oxide membrane for dye wastewater treatment, compared with Example 1, differs only in that KOH is not added in step (2), only ionic liquid intercalation is performed, and the other steps are the same, to obtain an ionic liquid intercalated reduced graphene oxide membrane (IL-rGO).

[0105] The composite membrane prepared in this example was tested for methylene blue retention performance under the same dye rejection conditions as in Example 1. The test results showed that the water flux of the membrane was 315.7 L·m. -2 ·h -1 ·bar -1The MB rejection rate was 99.69%. Its water flux was significantly lower than that of the KOH-IL-rGO membrane prepared in Example 1, which indicates that the synergistic modification of KOH, especially the additional mass transfer channels introduced by its etching effect, is crucial for achieving ultra-high water flux.

[0106] Comparative Example 2

[0107] A method for preparing a reduced graphene oxide membrane for dye wastewater treatment, compared with Example 1, differs only in that no ionic liquid or KOH is added in step (2). The specific operation is as follows: 4 mL of the reduced graphene oxide dispersion obtained in step (1) of Example 1 is taken, further diluted to 20 mL with deionized water, sonicated at 700 W for 10 min, and then directly filtered onto a mixed cellulose ester substrate with a pore size of 0.22 μm to obtain a reduced graphene oxide membrane (rGO). The obtained composite membrane is characterized, and the results are as follows. Figures 1-3 As shown.

[0108] The composite membrane prepared in this example was tested for methylene blue retention performance under the same dye rejection conditions as in Example 1. The test results showed that the water flux of the membrane was 250.0 L·m. -2 ·h -1 ·bar -1 The MB rejection rate was 99.25%. Its water flux was lower than that of the KOH-IL-rGO membrane prepared in Example 1. Due to the lack of synergistic effect between KOH and the ionic liquid, its interlayer spacing control ability was poor, resulting in a significant reduction in water flux. This indicates that the preparation method in Example 1, through the synergistic modification of ionic liquid and KOH, effectively increased the interlayer spacing of the membrane and introduced mass transfer defects, significantly improving water permeability.

[0109] The rGO composite membrane prepared in the comparative example was subjected to long-term filtration tests with methylene blue solution (10 mg / L). The specific test method was as follows: measurements were taken at 20-minute intervals for the first 2 hours, and at 1-hour intervals for 2-6 hours. The membrane's retention stability was repeatedly tested. The results are as follows... Figure 6 As shown, after 360 minutes of continuous operation, the water flux of the rGO membrane remained stable for the first hour, but then continued to decrease. After 6 hours, the water flux decreased by 42.28%, which was significantly reduced. The stability test results were not as good as those of the KOH-IL-rGO membrane prepared in Example 1.

[0110] Comparative Example 3

[0111] A method for preparing a reduced graphene oxide membrane for dye wastewater treatment, compared with Example 1, differs only in that, in step (2), the supplemented KOH is replaced with the same volume and concentration of NaOH solution, and the other steps are the same, to obtain a reduced graphene oxide membrane NaOH-IL-rGO membrane.

[0112] The composite membrane prepared in this comparative example was tested for methylene blue retention performance under the same dye rejection conditions as in Example 1. The test results showed that the water flux of the membrane was 315.0 L·m⁻¹. -2 ·h -1 ·bar -1 The MB rejection rate was 99.14%. The effect was much worse than in Example 1.

[0113] Comparative Example 4

[0114] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is disclosed. Compared with the previous example, the only difference is that the amount of reduced graphene oxide dispersion taken in step (2) is different, resulting in a different membrane thickness. In this example, the amount of reduced graphene oxide dispersion is 6 mL, and the thickness of the resulting composite membrane is 300 ± 10 nm.

[0115] Using the same test conditions as in Example 1, the methylene blue dye rejection performance of the composite membrane prepared in this example was tested. The test results were: water flux was 180 L·m -2 ·h -1 ·bar -1 The MB retention rate was 98.93%.

[0116] Comparative Example 5

[0117] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is disclosed. Compared with the previous example, the only difference is that the amount of reduced graphene oxide dispersion taken in step (2) is different, resulting in a different membrane thickness. In this example, the amount of reduced graphene oxide dispersion is 8 mL, and the thickness of the resulting composite membrane is 400±10 nm.

[0118] Using the same test conditions as in Example 1, the methylene blue dye rejection performance of the composite membrane prepared in this example was tested. The test results were: water flux of 145 L·m -2 ·h -1 ·bar -1 The MB retention rate was 99.07%.

[0119] Comparative Example 6

[0120] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is disclosed. The only difference from the previous example is the amount of KOH added in step (2). In this example, 1.5 mol L... -1 The volume of the KOH solution is 0.01 mL.

[0121] Using the same test conditions as in Example 1, the methylene blue dye rejection performance of the composite membrane prepared in this example was tested. The test results were: water flux of 322.3 L·m -2 ·h -1 ·bar -1 The MB retention rate was 99.81%.

[0122] Comparative Example 7

[0123] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment is disclosed. The only difference from the previous example is the amount of KOH added in step (2). In this example, 1.5 mol L... -1 The volume of the KOH solution is 3.0 mL.

[0124] Using the same test conditions as in Example 1, the methylene blue dye rejection performance of the composite membrane prepared in this example was tested. The test results were: water flux was 253.7 L·m -2 ·h -1 ·bar -1 The MB retention rate was 99.11%.

[0125] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a KOH-IL-rGO membrane for treating dye wastewater, characterized in that, Includes the following steps: (1) Disperse the reducing agent into the graphene oxide suspension and perform hydrothermal reduction to obtain a reduced graphene oxide dispersion; (2) Add ionic liquid and potassium hydroxide to the reduced graphene oxide dispersion and disperse evenly to obtain a reduced graphene oxide dispersion synergistically modified by KOH and ionic liquid; (3) The synergistically modified reduced graphene oxide dispersion obtained in step (2) is assembled on a porous support membrane by vacuum filtration to obtain a reduced graphene oxide membrane based on the synergistic modification of potassium hydroxide and ionic liquid, denoted as KOH-IL-rGO membrane. In step (2), the ionic liquid is a single component or a mixture of imidazole ionic liquids, the mass ratio of the ionic liquid to the reduced graphene oxide is (1.0~10.0):1, the mass ratio of the added potassium hydroxide to the reduced graphene oxide is (5.0~220):1, and the mass ratio of potassium hydroxide to the ionic liquid is (1.0~100):1; the ionic liquid is selected from one or more of 1-butyl-3-methylimidazolium hexafluorophosphate, 1,3-dimethylimidazolium hexafluorophosphate, or 1-butyl-3-methylimidazolium chloride. In step (3), the thickness of the obtained KOH-IL-rGO membrane is 180~220 nm.

2. The preparation method according to claim 1, characterized in that, In step (1), the reducing agent is selected from one or more of potassium hydroxide, sodium hydroxide, or ascorbic acid; the mass concentration of the graphene oxide suspension is 0.1-0.3 mg / mL, and the concentration of the added reducing agent in the graphene oxide suspension is 5.0-30 mmol / L; the hydrothermal reduction treatment time is 1-4 hours, and the treatment temperature is 70-90℃.

3. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of ionic liquid to reduced graphene oxide is (1.25~5.0):

1.

4. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the added potassium hydroxide to the reduced graphene oxide is (10.0~210):

1.

5. The preparation method according to claim 1, characterized in that, The concentration of KOH added in step (2) in the reaction system is 0.02~0.5 mol / L.

6. The preparation method according to claim 1, characterized in that, In step (3), the porous support membrane is made of a material selected from mixed cellulose ester, polycarbonate, and polyacrylonitrile, with an average pore size of 0.1-0.22 μm.

7. A KOH-IL-rGO membrane for treating dye wastewater, characterized in that, It is prepared by any one of the preparation methods described in claims 1-6.

8. An application of the KOH-IL-rGO membrane for dye wastewater treatment as described in claim 7, characterized in that, Used for the retention of dye molecules.

9. The application according to claim 8, characterized in that, The dyes include methylene blue, rhodamine, and Congo red, and the concentration of the dyes is 5-50 mg / L.

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