KOH-IL-rGO membrane for dye wastewater treatment as well as preparation method and application of KOH-IL-rGO membrane

Abstract

The invention 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 modified graphene-based composite membrane stable in structure is prepared by introducing potassium hydroxide and ionic liquid to conduct synergistic modification on reduced graphene oxide; the prepared graphene-based composite membrane is applied to dye wastewater treatment, the effect of remarkably improving the water molecule transmission flux can be achieved while dye molecules such as methylene blue are efficiently intercepted, and meanwhile the graphene-based composite membrane shows excellent stability in long-term operation and shows good application prospects in the fields of dye wastewater and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of membrane separation technology, and particularly relates to a KOH-IL-rGO membrane for dye wastewater treatment and a preparation method and application thereof. BACKGROUND

[0002] Dye wastewater is one of the important sources of industrial wastewater, which is complex in composition, high in color and toxic, and poses a serious threat to the water ecosystem and human health. Membrane separation technology, especially nanofiltration technology, has shown great potential in the deep treatment and resource recycling of dye wastewater due to its low energy consumption and simple operation. An ideal nanofiltration membrane needs to have high water permeability and high solute selectivity.

[0003] In the prior art, graphene oxide membranes are widely used in the field of membrane separation technology, but due to the strong hydrophilicity of graphene oxide membranes, they are prone to swelling in aqueous environments, resulting in unstable structure and degradation of separation performance. Moreover, the dense stacked layer structure of graphene oxide membranes for high retention rate will significantly increase the water transport resistance, resulting in generally low water flux. This trade-off between permeability and selectivity seriously restricts its practical application.

[0004] Patent document CN107469633A discloses a method for preparing a membrane with enhanced water flux, which uses in-situ synthesized nanoparticle-graphene material to form a membrane layer on the surface of a support by pressure-driven method. Although the graphene membrane prepared by this method has good structural stability, the entire preparation process is time-consuming, and although the water flux is improved, it cannot simultaneously achieve higher dye retention rate and excellent water flux.

[0005] Reduced graphene oxide membranes are composed of partially reduced and stacked graphene nanosheets, and two-dimensional nanochannels with controllable size can be formed between the layers, providing an ideal platform for efficient molecular sieving. Based on the defects of easy swelling in aqueous environment, unstable structure and low water flux, the prior research results of the applicant, patent document CN118543248A discloses a graphene oxide membrane with high flux desalination performance and a preparation method and application thereof, which is prepared by introducing ionic liquid into the interlayer channel of reduced graphene oxide to obtain a graphene oxide membrane with high flux desalination performance, thereby improving the retention rate of metal ions. However, there is no application of such ionic liquid intercalated graphene oxide membrane in dye wastewater in the prior art, and there is no report on the technology of using KOH and ionic liquid to modify reduced graphene oxide membranes for high water flux retention in dye wastewater.

[0006] At present, it is an urgent need in the field to develop a modification strategy that can simultaneously enhance the structural stability, water permeability and dye selectivity of rGO membranes. SUMMARY

[0007] In view of the above problems, the present application provides a KOH-IL-rGO membrane for dye wastewater treatment with high flux, high dye retention rate and excellent structural stability, and a preparation method and application thereof; by micro-modifying graphene oxide two-dimensional nanosheets, a stable and intercalated two-dimensional channel of functional groups is constructed, which can effectively prevent the transmission of dye molecules while maintaining fast water molecule transmission.

[0008] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0009] A preparation method of a KOH-IL-rGO membrane for dye wastewater treatment, comprising the following steps:

[0010] (1) dispersing a reducing agent into a graphene oxide (GO) suspension, and performing hydrothermal reduction to obtain a reduced graphene oxide (rGO) dispersion;

[0011] (2) adding an ionic liquid (IL) and potassium hydroxide (KOH) into the reduced graphene oxide dispersion, and after uniform dispersion, obtaining a reduced graphene oxide dispersion modified by potassium hydroxide and ionic liquid in cooperation;

[0012] (3) assembling the reduced graphene oxide dispersion modified by potassium hydroxide and ionic liquid in cooperation obtained in step (2) on a porous support membrane by vacuum filtration method, to obtain a reduced graphene oxide membrane based on potassium hydroxide and ionic liquid in cooperation, denoted as KOH-IL-rGO membrane;

[0013] In step (2), the ionic liquid is a single component or a mixed component in 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 ionic liquid is (1.0~100):1;

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

[0015] The technical scheme of the present application realizes the synergistic effect of hydrothermal reduction, ionic liquid intercalation and KOH etching, wherein the ionic liquid cations and K + The cation-π interaction inserts between rGO layers, acts as a "molecular bridge" to accurately regulate and fix the interlayer spacing, and at the same time, KOH produces a mild etching effect on the rGO carbon skeleton, introducing transmission defects, thereby precisely regulating the physical structure and chemical properties of the two-dimensional nanochannel of the reduced graphene oxide membrane, and successfully constructing a separation membrane with high water flux, high dye retention rate and excellent stability.

[0016] The application is further configured that the graphene oxide dispersion is composed of single-layer nanosheets, and the average size of the sheet layer is 5±1 μm.

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

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

[0019] The application is further configured 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; and more preferably 15±1 mmol / L.

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

[0021] The application is further configured that in step (1), the reducing agent is added to the graphene oxide suspension, and mechanical stirring or ultrasonic treatment is used to achieve uniform dispersion; in step (2), the ionic liquid is added to the reduced graphene oxide dispersion, and stirring or ultrasonic treatment is also used to ensure uniform dispersion; the stirring mode is magnetic stirring, the rotation speed is set to 600-1200 r / min, and the duration is 0.5-2 hours; the ultrasonic treatment power is 500-800 W, and the action time is 5-20 minutes.

[0022] The application is further configured 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 application is further configured that in step (2), the mass ratio of the ionic liquid to the reduced graphene oxide is (1.25-5.0):1, preferably (2.0-3.0):1. The appropriate amount of ionic liquid intercalation helps to enhance the structural stability of the graphene nanochannel, and excessive ionic liquid will occupy the effective transmission channel, thereby inhibiting the permeability of water molecules.

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

[0025] The application is further configured that the concentration of the 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 application is further configured that in step (2), the mass concentration of the ionic liquid is 1-3 mg / mL, and the solvent is deionized water.

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

[0028] The application is further configured that the average pore size of the porous support membrane is 0.1-0.22 μm; if the pore size is too small, a large mass transfer resistance will be generated, and if the pore size is too large, the ordered stacking of the graphene nanosheets will be affected, finally leading to the decline of the membrane separation performance.

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

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

[0031] In step (3), a vacuum assisted film forming process is adopted, and the filtration pressure is 0.1-1.0 bar; if the pressure is too low, the layered structure will be loose and the mechanical performance will be insufficient; if the pressure is too high, the interlayer structure will be too dense, which is not conducive to the transmission of water molecules.

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

[0033] The application further provides an application of the above KOH-IL-rGO membrane for dye wastewater treatment, which is used for the interception of dye molecules.

[0034] The application is further configured that the dye includes methylene blue, rhodamine and congo red.

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

[0036] Compared with the prior art, the present application has the following beneficial effects: (1) The present application constructs a composite membrane with stable two-dimensional nanochannels through the synergistic effect of ion liquid intercalation and potassium hydroxide modification. + The cations in the ion liquid and the K

[0037] introduced by potassium hydroxide accurately regulate and stabilize the interlayer spacing of rGO like a "molecular bridge" through common cation-pi interaction, effectively inhibit the swelling of the membrane in water, and significantly enhance the structural stability and mechanical strength of the membrane. -2 -1 -1 (2) The introduction of potassium hydroxide produces a unique mild etching effect on the rGO carbon skeleton, introducing appropriate nanoscale defects on the surface and in the plane of the sheet, creating additional rapid water molecule transport channels, thereby significantly improving the water flux while maintaining high selectivity, with a water flux of 350~520 L·m

[0038] ·h ·bar The rejection rate of dye molecules reaches more than 99%.

[0039] Figure 1 (3) The preparation method of the present application is simple and the conditions are mild, and the obtained composite membrane shows ultra-high rejection rate (>99%) and water flux for dye molecules, especially methylene blue, which is much better than the unmodified rGO membrane and the IL-rGO membrane intercalated only by ion liquid, and exhibits excellent stability in long-term operation and alkaline environment, and has a wide application prospect in the field of dye wastewater treatment.

[0040] Figure 2 is a comparison diagram of membrane images and SEM cross-sectional morphologies of the KOH-IL-rGO membrane prepared in Example 1 and the rGO membrane prepared in Comparative Example 2, wherein (a) is the rGO membrane and (b) is the KOH-IL-rGO membrane.

[0041] Figure 3 is a comparison diagram of infrared spectra of the KOH-IL-rGO membrane prepared in Example 1 and the rGO membrane prepared in Comparative Example 2.

[0042] Figure 4 is a comparison diagram of Raman test of the KOH-IL-rGO membrane prepared in Example 1 and the rGO membrane prepared in Comparative Example 2.

[0043] Figure 5 is a comparison diagram of the rejection performance of the KOH-IL-rGO membrane prepared in Example 1 to different dyes.

[0044] Figure 6 ​is a graph of the retention stability of the dye of the rGO membrane prepared in Comparative Example 2 under long-term operation. DETAILED DESCRIPTION

[0045] The application will be described in detail below with specific examples and in conjunction with the drawings. It should be understood that the described examples are only part of the examples of the application, but not all examples. Based on the examples of the application, all other examples obtained by those skilled in the art without creative labor are within the scope of the application.

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

[0047]

[0048] In the formula, is the membrane flux (L·m -2 ·h -1 ·bar -1 ), is the volume increase of the permeate liquid during the period, is the filtration time (h), is the filtration area (m 2 ), is the transmembrane pressure (bar).

[0049] The retention rate is calculated by the following formula:

[0050]

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

[0052] The preparation method of the KOH-IL-rGO membrane for dye wastewater treatment provided by the application comprises the following steps:

[0053] (1) uniformly disperse potassium hydroxide in a graphene oxide suspension system, and after sufficient stirring, perform hydrothermal reduction treatment to obtain a reduced graphene oxide dispersion liquid;

[0054] (2) add an ionic liquid and potassium hydroxide to the reduced graphene oxide dispersion liquid, and after uniform dispersion by stirring and ultrasonic, obtain a reduced graphene oxide (KOH-IL-rGO) dispersion liquid modified by the ionic liquid and potassium hydroxide in cooperation;

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

[0056] In step (2), the ionic liquid is a single component or a mixed component in 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 ionic liquid is (1.0-100):1; in step (3), the thickness of the KOH-IL-rGO membrane prepared is 180-220 nm; the graphene oxide raw material in step (1) can be obtained by commercial means or can be prepared independently according to a modified Hummers method.

[0057] The specific process of the modified Hummers method is as follows: potassium persulfate (2.5 g) and phosphorus pentoxide (2.5 g) are mixed with natural graphite (3.0 g) in a concentrated sulfuric acid medium, and the pre-oxidation is completed by stirring at a reaction temperature of 78-82°C for 4.5 hours. After the reaction is terminated, cool, dilute with deionized water to 500 mL, and stand overnight. The pre-oxidation product is obtained by solid-liquid separation and drying. Then, the above product is mixed with concentrated sulfuric acid at a low temperature of 0-5°C, and potassium permanganate is added for a main oxidation reaction at 34-36°C for 1.5-2.5 hours. Finally, the reaction is terminated by hydrogen peroxide to achieve intercalation of graphite layers. The desired GO suspension is prepared by repeated washing, filtration, and ultrasonic dispersion treatment.

[0058] The technical solutions of the present application will be further described below in conjunction with specific examples.

[0059] Example 1

[0060] A method for preparing a KOH-IL-rGO membrane for dye wastewater treatment, specifically comprising 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 stir magnetically at a speed of 1000 r / min at room temperature for 1 hour. Heat the mixture to 80°C for 2 hours to complete the hydrothermal reduction, and obtain a reduced graphene oxide dispersion.

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

[0064] Take 4 mL of the above obtained reduced graphene oxide dispersion, the mass of rGO is about 0.8 mg, 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 about 1:2.5, then supplement 1 mL of 1.5 mol / L KOH solution. At room temperature, continue to stir at 1000 r / min for 1 h, mix uniformly, and then obtain the reduced graphene oxide dispersion modified by potassium hydroxide and ionic liquid after 10 min of 700 W ultrasonic treatment. It should be noted that the mass of the reduced graphene oxide can be directly measured by those skilled in the art. -1 KOH solution. At room temperature, continue to stir at 1000 r / min for 1 h, mix uniformly, and then obtain the reduced graphene oxide dispersion modified by potassium hydroxide and ionic liquid after 10 min of 700 W ultrasonic treatment. 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 modified by potassium hydroxide and ionic liquid (KOH-IL-rGO)

[0066] Dilute the modified dispersion obtained in step (2) to 20 mL with deionized water, filter to a mixed cellulose ester substrate with a pore size of 0.22 μm under a vacuum pressure of 0.1-1.0 bar after 10 min of 700 W ultrasonic treatment, and prepare the target composite film KOH-IL-rGO film. Characterize the prepared KOH-IL-rGO film, and the results are shown in Figures 1-3 . Figure 1 The cross-sectional view of the KOH-IL-rGO film shows that the thickness of the KOH-IL-rGO film is obviously larger than that of rGO, proving the successful intercalation of the ionic liquid, and the measured film thickness is about 200±10 nm.

[0067] Figure 2 It is shown that the KOH-IL-rGO film exhibits new characteristic peaks belonging to the C-N stretching vibration of the imidazole ring at about 1167 cm -1 and 1696 cm -1 , confirming the successful intercalation of the ionic liquid; Figure 3 The results show that the ID / IG of the KOH-IL-rGO film is obviously increased compared with that of the rGO film, indicating that the degree of defects on the film surface is further increased, the degree of graphitization is reduced, and the etching effect of KOH on the film surface is proved.

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

[0069] At the same time, 10 mg / L -1 of Congo red (CR) and rhodamine B (RB) dye solutions were used respectively to test the dye rejection performance, and the test results are shown in Figure 4 , it is detected that the water flux of the KOH-IL-rGO membrane to the CR solution is 422.9 L·m -2 ·h -1 ·bar -1 , and the rejection rate is 95.39%; the water flux to the RB solution is 363.3 L·m -2 ·h -1 ·bar -1 , and the rejection rate is 97.89%.

[0070] Example 2

[0071] A preparation method of a KOH-IL-rGO membrane for dye wastewater treatment, compared with the examples, the only difference is that the type of ionic liquid is different. In this embodiment, the ionic liquid is 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]).

[0072] The same dye rejection performance test conditions as in Example 1 were used to test the methylene blue dye rejection performance of the composite membrane prepared in this embodiment, and the test results were: the water flux was 428.7 L·m -2 ·h -1 ·bar -1 , and the MB rejection rate was 99.67%.

[0073] Example 3

[0074] A preparation method of a KOH-IL-rGO membrane for dye wastewater treatment, compared with the examples, the only difference is that the type of ionic liquid is different. In this embodiment, the ionic liquid is 1,3-dimethylimidazolium hexafluorophosphate ([DMIM][PF6]).

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

[0076] Example 4

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

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

[0079] Example 5

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

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

[0082] Example 6

[0083] A preparation method of a KOH-IL-rGO membrane for dye wastewater treatment, which is different from the embodiment only in that the amount of KOH added in step (2) is different. In this embodiment, the volume of 1.5 mol / L KOH solution added is 0.1 mL. -1

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

[0085] Example 7

[0086] ​A preparation method of a KOH-IL-rGO membrane for dye wastewater treatment, compared with the embodiment, the only difference is that in step (2), the amount of KOH added is different. In this embodiment, 1.5 mol L -1 of KOH solution is added.

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

[0088] Example 8

[0089] A preparation method of a KOH-IL-rGO membrane for dye wastewater treatment, compared with the embodiment, the only difference is that in step (2), the amount of KOH added is different. In this embodiment, 1.5 mol L -1 of KOH solution is added.

[0090] The composite membrane prepared in this embodiment was tested for methylene blue dye retention performance under the same test conditions as in Example 1, and the test results were: water flux was 412.5 L·m -2 ·h -1 ·bar -1 , and the MB retention rate was 99.35%.

[0091] Example 9

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

[0093] The test results were: the water flux of the membrane was 501.3 L·m -2 ·h -1 ·bar -1 , and the MB retention rate was 99.35%.

[0094] Example 10

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

[0096] The test results are as follows: the water flux of the membrane is 426.2 L·m -2 ·h -1 ·bar -1 The MB rejection rate is 99.13%.

[0097] Example 11

[0098] A preparation method of a KOH-IL-rGO membrane for dye wastewater treatment, the preparation steps of which are the same as those of Example 1, the only difference being that, in the dye rejection performance test, the concentration of the dye methylene blue (MB) is 50 mg / L -1 .

[0099] The test results are as follows: the water flux of the membrane is 346.9 L·m -2 ·h -1 ·bar -1 The MB rejection rate is 98.65%.

[0100] Example 12

[0101] The KOH-IL-rGO composite membrane prepared in Example 1 is subjected to a long-term filtration test of a methylene blue solution (10 mg / L) by using the rejection performance test experiment of Example 1. The specific test method is as follows: within the first 2 hours, test once every 20 minutes; from 2 hours to 6 hours, test once every hour; and repeat the test of the rejection stability of the membrane.

[0102] The results are shown in Table 1. Figure 5 After continuous operation for 360 minutes, the water flux of the KOH-IL-rGO membrane only decreases by 1.6%, which shows excellent stability. At the same time, the KOH-IL-rGO membrane always maintains a rejection rate of more than 99.5% during the entire test process, proving that it has reliable long-term operation performance.

[0103] Comparative Example 1

[0104] A preparation method of a reduced graphene oxide membrane for dye wastewater treatment, the only difference between which and Example 1 being that, in step (2), no KOH is supplemented, and only ionic liquid intercalation is performed, and the remaining steps are the same, thereby preparing an ionic liquid intercalated reduced graphene oxide membrane (IL-rGO).

[0105] The composite membrane prepared in this example is subjected to a methylene blue rejection performance test by using the same dye rejection performance test conditions as in Example 1. The test results are as follows: the water flux of the membrane is 315.7 L·m -2 ·h -1 ·bar -1, and the MB rejection rate was 99.69%. The water flux of the prepared membrane was significantly lower than that of the KOH-IL-rGO membrane prepared in Example 1, which indicated that the synergistic modification of the KOH and the additional mass transfer channels introduced by the etching effect of the KOH were crucial for achieving the ultra-high water flux.

[0106] Comparative Example 2

[0107] A preparation method of a reduced graphene oxide membrane for dye wastewater treatment, which is different from Example 1 only in that no ionic liquid is added in step (2) and no KOH is supplemented. The specific operation is as follows: 4 mL of the reduced graphene oxide dispersion prepared in step (1) of Example 1 is further diluted to 20 mL with deionized water, and after ultrasonic treatment at 700 W for 10 min, the reduced graphene oxide membrane (rGO) is directly filtered on a mixed cellulose ester substrate with a pore size of 0.22 μm. The prepared composite membrane is characterized, and the results are shown in Figures 1-3 .

[0108] The prepared composite membrane is tested for methylene blue rejection performance under the same dye rejection performance test conditions as in Example 1, and the test results are as follows: the water flux of the membrane is 250.0 L·m -2 ·h -1 ·bar -1 , and the MB rejection rate is 99.25%. The water flux of the prepared membrane is lower than that of the KOH-IL-rGO membrane prepared in Example 1. Due to the lack of the synergistic effect of the KOH and the ionic liquid, the interlayer spacing regulation ability is poor, which greatly reduces the water flux. This indicates that the preparation method of Example 1 effectively increases the interlayer spacing of the membrane and introduces mass transfer defects through the synergistic modification of the ionic liquid and the KOH, which significantly improves the water permeability.

[0109] The rGO composite membrane prepared in this comparative example is tested for long-term filtration of methylene blue solution (10 mg / L), and the specific test method is as follows: the rejection stability of the membrane is tested at intervals of 20 min within the first 2 h, and at intervals of 1 h within 2-6 h. The results are shown in Figure 6 . After continuous operation for 360 min, the water flux of the rGO membrane remains stable for the first hour and then continuously decreases, and the water flux decreases by 42.28% after 6 h. The water flux is greatly reduced, and the stability test effect is not as good as that of the KOH-IL-rGO membrane prepared in Example 1.

[0110] Comparative Example 3

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

[0112] The composite film prepared in this comparative example was tested for methylene blue interception performance under the same test conditions as in Example 1, and the test results were as follows: the water flux of the film was 315.0 L·m -2 ·h -1 ·bar -1 , and the MB interception rate was 99.14%. This was much worse than Example 1.

[0113] Comparative Example 4

[0114] A method for preparing a KOH-IL-rGO film for dye wastewater treatment, which differs from the examples only in that the amount of reduced graphene oxide dispersion solution taken in step (2) is different, and the thickness of the prepared film is different. In this example, the amount of reduced graphene oxide dispersion solution was 6 mL, and the thickness of the prepared composite film was 300±10 nm.

[0115] The composite film prepared in this example was tested for methylene blue dye interception performance under the same test conditions as in Example 1, and the test results were as follows: the water flux was 180 L·m -2 ·h -1 ·bar -1 , and the MB interception rate was 98.93%.

[0116] Comparative Example 5

[0117] A method for preparing a KOH-IL-rGO film for dye wastewater treatment, which differs from the examples only in that the amount of reduced graphene oxide dispersion solution taken in step (2) is different, and the thickness of the prepared film is different. In this example, the amount of reduced graphene oxide dispersion solution was 8 mL, and the thickness of the prepared composite film was 400±10 nm.

[0118] The composite film prepared in this example was tested for methylene blue dye interception performance under the same test conditions as in Example 1, and the test results were as follows: the water flux was 145 L·m -2 ·h -1 ·bar -1 , and the MB interception rate was 99.07 %.

[0119] Comparative Example 6

[0120] A method for preparing a KOH-IL-rGO film for dye wastewater treatment, which differs from the examples only in that the amount of KOH added in step (2) is different. In this example, the volume of 1.5 mol L -1 KOH solution added was 0.01 mL.

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

[0122] Comparative Example 7

[0123] A preparation method of a KOH-IL-rGO membrane for dye wastewater treatment, compared with the examples, the only difference is that in step (2), the amount of KOH added is different. In the example, 1.5 mol L -1 of KOH solution was added.

[0124] The composite membrane prepared in the example was tested for methylene blue dye interception performance under the same test conditions as in Example 1, and the test results were: water flux was 253.7 L·m -2 ·h -1 ·bar -1 , and the MB interception rate was 99. 11%.

[0125] The above embodiments only illustrate the technical concepts and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent transformation or modification made in accordance with the spirit and essence of the present application should be covered within the protection scope of the present application.

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 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. 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, 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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 1-7.

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

10. The application according to claim 9, 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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