A green and environment-friendly novel composite separation membrane and a preparation method thereof

Abstract

The application relates to the technical field of functional materials, analytical chemistry and water treatment environment, in particular to a green and environment-friendly novel composite separation membrane and a preparation method thereof. Biomass polymer material gelatin and graphene oxide are bridged by using natural organic compound tannic acid; tannic acid and gelatin serve as an intercalator and a dispersant, enter into graphene sheet layers, the agglomeration effect between the graphene sheet layers is overcome, the surface oxygen-containing functional groups are reduced, and the available specific surface area is increased. The whole preparation process is green and low in energy consumption; the used materials are rich in sources and low in cost; the membrane has high efficient and accurate separation effect on organic dyes and heavy metal ions in wastewater; and the membrane has good selective separation performance on binary mixed dyes.

Description

Technical Field

[0001] This application relates to the fields of functional materials and analytical chemistry as well as water treatment and environmental technology. More specifically, it relates to a novel green and environmentally friendly composite separation membrane and its preparation method. Background Technology

[0002] In recent years, environmental pollution has become increasingly prominent, with organic dyes and heavy metal pollution attracting widespread global attention. Effectively separating organic dyes and heavy metals from wastewater is a crucial aspect of comprehensive environmental management. The organic dyes referred to in environmental pollution are mainly produced by industrial sectors such as textiles, printing and dyeing, and papermaking. They are characterized by high toxicity, complex composition, stable chemical structure, and poor biodegradability, causing irreversible damage to the ecological environment and human health.

[0003] Heavy metals are mainly generated by anthropogenic factors such as mining, waste gas emissions, and the use of heavy metal products. Lead, copper, chromium, and silver are particularly toxic to environmental organisms, exhibiting carcinogenicity, non-biodegradability, and irreversibility. Therefore, separating organic dyes and heavy metals from aquatic environments and promptly remediating polluted water bodies to reduce the health risks posed by water pollution is an efficient energy-saving and emission-reduction pathway.

[0004] With the development of membrane separation technology, the use of membrane separation technology to treat wastewater pollution has become popular due to its low cost and environmental friendliness. Among them, graphene oxide (GO) membranes are widely used in the field of water purification due to their advantages such as low cost, simple treatment process and chemical resistance, including alcohol-water separation, seawater purification, and dye desalination. In the existing technology, the intercalation materials containing amino groups in previous studies have been derived from petrochemical products such as ethylenediamine, phenylenediamine and ethylenediaminetetraacetic acid (Lu Ying, Preparation and Performance Study of Graphene Oxide-Based Membranes [D], Zhejiang University, 2016.6). From the perspective of green environmental protection, compared with the relatively expensive dopamine, the natural polymer material gelatin can be regarded as a promising dispersant and intercalating agent. Summary of the Invention

[0005] This disclosure provides a novel green and environmentally friendly composite separation membrane and its preparation method. The prepared membrane provides an important reference for the preparation of two-dimensional material membranes with high retention capacity for dyes and heavy metal ions, and can also be used for the precise separation of binary mixed molecules, thereby achieving the successful separation of dyes and heavy metal ions in wastewater.

[0006] In a first aspect, this disclosure provides a novel green and environmentally friendly graphene oxide separation membrane, comprising the natural organic compound tannic acid, the polymer material gelatin, and graphene oxide, wherein the tannic acid and the gelatin serve as an inserter and a dispersant, respectively.

[0007] Preferably, the separation membrane is prepared by directly using vacuum filtration.

[0008] Secondly, this disclosure provides a method for preparing a novel green and environmentally friendly graphene oxide separation membrane. The tannic acid bridges the biomass gelatin and the graphene oxide, with the tannic acid and gelatin acting as intercalating and dispersing agents, respectively, into the interlayer of the graphene oxide sheets. Water is used as the solvent. The mixture is magnetically stirred at room temperature to obtain a well-dispersed blend solution. After low-pressure vacuum filtration, the blend solution is assembled from bottom to top onto a 0.22 μm microporous filter membrane. The membrane is then dried in an oven at 50-60°C for 30-45 minutes to obtain a self-supporting, green and environmentally friendly novel graphene oxide separation membrane.

[0009] Preferably, it includes the following steps:

[0010] (1) Preparation of graphene oxide solution: Weigh the single-layer graphene oxide aqueous dispersion, add deionized water to dilute it into a solution, microwave sonicate for 10-15 min, and then magnetically stir for 30-40 min to prepare the graphene oxide dispersion.

[0011] (2) Prepare gelatin solution: Weigh the gelatin and put it in water. Stir magnetically at 45-50℃ for 15-20 minutes to completely dissolve it and prepare a gelatin solution.

[0012] (3) Preparation of tannic acid (TA) solution: Weigh the tannic acid and put it in water, sonicate it in microwave until it is completely dissolved, and prepare an aqueous solution of tannic acid;

[0013] (4) Preparation of GO-GA-TA composite laminated membrane: The gelatin solvent obtained in step (2) is added to the graphene oxide aqueous solution obtained in step (1), and the mixture is magnetically stirred for 30-40 min until it is completely mixed. Then, TA solution is added and the mixture is magnetically stirred evenly at room temperature for 10-11 h. The mixture is then filtered through a low-pressure vacuum to the surface of a 0.22 μm microporous membrane to obtain a GO-GA-TA membrane. The membrane is then dried in an oven at 50-60℃ for 30-45 min and collected.

[0014] Preferably, in step (1), the mass of the monolayer graphene oxide aqueous dispersion is 0.1-0.5g, and the concentration of the monolayer graphene oxide aqueous dispersion is 10-15mg / g.

[0015] Preferably, in step (2), the mass of the gelatin is 0.01-0.02g.

[0016] Preferably, in step (3), the mass of the tannic acid is 0.01-0.02g.

[0017] Preferably, the thickness of the GO-GA-TA composite laminate is 12.95±10μm.

[0018] Thirdly, this disclosure provides an application of a novel green and environmentally friendly graphene oxide separation membrane, which is used in equipment for preparing water flux or filtration performance.

[0019] Preferably, the green and environmentally friendly novel graphene oxide separation membrane is specifically used to simulate industrial dye wastewater with 20 mg / L of dye and heavy metal ions to test the flux and rejection rate of actual dye and heavy metal ions.

[0020] In summary, this application has the following beneficial effects:

[0021] 1. The entire preparation process of this application uses deionized water and does not use organic solvents. It is green and environmentally friendly. The preparation method is simple and easy to operate, with low equipment requirements, low energy consumption, and high efficiency. It has practical value for industrial-scale production.

[0022] 2. The graphene oxide membrane prepared by the method in this application increases the interlayer spacing due to the addition of tannic acid and gelatin. Under low operating pressure (0.05-0.08MPa), its rejection rate of organic dyes (CV, MB, MG) reaches more than 90%. The membrane material prepared by this method can be applied to the separation of wastewater from industrial dye production.

[0023] 3. The membrane prepared in this application exhibits good adhesion to heavy metal ions (Cr) at relatively low operating pressures (0.05-0.08 MPa). 3+ Cu 2 + Ag + and Pb 2+ The retention rates all reached over 80%;

[0024] 4. This application successfully achieved efficient separation of binary mixed dyes, solving the problem of difficult molecular separation;

[0025] 5. The key advantage of this application lies in the fact that after obtaining the graphene oxide / tannic acid / gelatin composite solution, the GO-GA-TA composite membrane can be directly obtained by vacuum filtration. The entire preparation process is green, pollution-free, and low-energy-consuming. This membrane has excellent filtration performance, with a rejection rate of over 90% for organic dyes (CV, MB, MG) and a good rejection rate for heavy metal ions (Cu). 2+ Ag + and Pb 2+ The rejection rates all reached over 93%. This indicates that the graphene oxide / gelatin / tannic acid composite nanofiltration membrane described in this invention has wide applications in the preparation of equipment for increasing water flux or improving filtration performance.

[0026] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the scope of protection of this disclosure. Attached Figure Description

[0027] Figure 1 These are photographs of the appearance of the self-supporting GO-GA-TA membrane prepared and dried in this application;

[0028] Figure 2 These are photographs of the appearance of the undried GO-GA-TA membranes prepared by vacuum filtration of graphene oxide membranes with different amounts of tannic acid and gelatin according to this application.

[0029] Figure 3 These are photographs of the dried and collected GO membrane, GO-GA membrane, GO-TA membrane, and GO-GA-TA membrane prepared by vacuum filtration of a quantitative graphene oxide membrane, a quantitative tannic acid membrane, and a quantitative gelatin membrane.

[0030] Figure 4 These are comparative infrared images of the GO membrane and the GO-GA-TA membrane in this application;

[0031] Figure 5 These are SEM and EDS images of the GO-GA-TA membrane prepared in this application, wherein (a) is a surface SEM of the GO-GA-TA membrane; (b) is a cross-sectional SEM of the membrane; and (c) is an EDS image of the membrane surface in (a).

[0032] Figure 6 This is a diagram of the water contact angle of the GO-GA-TA membrane in this application;

[0033] Figure 7 The images show the UV-Vis absorption spectrum cutoffs of the GO-GA-TA membrane prepared in this application for crystal violet (CV), methylene blue (MB), malachite blue (MG), and methyl orange (MO), as well as bar graphs of the cutoff rate and flux.

[0034] Figure 8 This is a schematic diagram illustrating the selective separation of binary mixed dyes using the GO-GA-TA membrane prepared in this application;

[0035] Figure 9 This is a bar chart showing the results of heavy metal ion rejection and flux tests on the GO-GA-TA membrane prepared in this application. Detailed Implementation

[0036] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0037] Example

[0038] Example 1

[0039] A novel green and environmentally friendly graphene oxide separation membrane and its preparation method are characterized by comprising the following steps:

[0040] (1) Preparation of graphene oxide solution

[0041] Weigh a certain mass (0.5g) of monolayer graphene oxide aqueous dispersion (10mg / g), add a certain amount of deionized water to dilute it into a solution of a certain concentration, sonicate it in the microwave for 10min, and then stir it magnetically for 30min to prepare a graphene oxide dispersion of a certain concentration.

[0042] (2) Prepare gelatin (GA) solution

[0043] Weigh 0.01g of gelatin and place it in 1mL of water. Stir magnetically at 50℃ for 15min to completely dissolve it and prepare a gelatin solution.

[0044] (3) Prepare tannic acid (TA) solution

[0045] Weigh 0.01g of tannic acid and place it in 1mL of water. Microwave sonicate until completely dissolved to prepare an aqueous solution of tannic acid.

[0046] (4) Preparation of GO-GA-TA composite laminated film

[0047] Gelatin solvent was added to the aqueous solution of graphene oxide and magnetically stirred for 30 min until completely mixed. Then, TA solution was added and magnetically stirred evenly at room temperature for 11 h. The mixture was then filtered through a low-pressure vacuum filter to the surface of a 0.22 μm microporous membrane to obtain a GO-GA-TA membrane. The membrane was dried in an oven at 60 °C for 30 min and collected.

[0048] (5) Using 20 mg / L of dye and heavy metal ions to simulate industrial dye wastewater, the flux and rejection rate of actual dye and heavy metal ions were tested. For example... Figure 1 As shown, the obtained membrane has good integrity.

[0049] like Figure 2 As shown, different amounts of graphene oxide combined with gelatin result in different film formation effects. With increasing amount, the film-forming properties improve, and the film-forming properties are best at a dosage of 0.5g. Therefore, this film was used as the research object to investigate its performance.

[0050] like Figure 3 As shown, the film formation effect after drying is different when a certain amount of graphene oxide is compounded with gelatin or tannic acid. Compared with other films, the GO-GA-TA film has a complete and good independent support film morphology after drying and detachment.

[0051] The membrane was characterized using Fourier transform infrared spectroscopy. Figure 4 As can be seen, by comparing with pure GO membrane, we can find that the infrared absorption peak changed due to the insertion of gelatin and tannic acid, ranging from 3419 to 2925 cm⁻¹. -1 The absorption peak at 1529 cm⁻¹ is broader and sharper, corresponding to the stretching vibration peaks of -OH and NH; -1 With 1684cm -1 The peaks on the left and right correspond to the C=O stretching vibration peak and the NH bending vibration peak in the amide bond (—CONH—), respectively, proving that the introduction of gelatin introduces amino groups into the membrane. At 2925 cm⁻¹ -1 and 2860cm -1 The peaks observed at 2280 cm⁻¹ correspond to the symmetric and antisymmetric stretching vibrations of CH groups on the -CH₂ and -CH₃ groups, respectively. -1 For vibrations of the CH bond. 1442 and 1317 cm⁻¹ -1 The peak at 1183 cm⁻¹ is a characteristic peak for the stretching vibrations of aromatic rings and symmetrical and asymmetric COO- groups. -1 Two strong peaks were observed nearby, corresponding to the characteristic peaks of the ester group's -COC- and -C=O-. This indicates that the carboxyl group of partially reduced GO covalently bonds with the hydroxyl group of TA to form an ester group.

[0052] like Figure 5 As shown, the prepared membrane has a smooth surface and obvious porous structure, with a thickness of approximately 12.95 ± 10 μm. EDS scanning revealed that the C, N, and O elements on the membrane surface are homogeneously distributed, indicating that graphene oxide, gelatin, and tannic acid are uniformly dispersed and stably inserted into the GO membrane, which is beneficial for subsequent application in membrane separation systems.

[0053] The hydrophilicity of the GO-GA-TA membrane surface was analyzed using CA (water contact angle), and the test results are shown below. Figure 6 It can be seen that the contact angle between the membrane surface and water is 58.3±5°, which has good hydrophilic properties and is conducive to attracting water molecules into the water transport channel, which is the key to effective water molecule transport.

[0054] Depend on Figure 7 As shown in a, b, and c, the GO-GA-TA membrane exhibits significant differences in retention rates for different dyes. It achieves retention rates exceeding 95% for MB and MG, and over 87% for CV. However, the retention rate for small molecule MO dyes is only 18.65%, with the lowest flux being 10.59 μm. -2 h -1 bar -1 .

[0055] Figure 8The GO-GA-TA membrane prepared as shown can effectively separate binary mixed dyes (MG / MO).

[0056] The prepared membrane retains Ag + The concentration was then reduced from 20 ppm to 0.03 ppm, achieving a removal efficiency of 99.82%. Simultaneous filtration of other heavy metal ions (10 mL, 20 ppm) clearly showed retention rates all above 80%. Figure 9 The minimum flux was 22.33 Lm. -2 h -1 bar -1 It is important to note that polluted water often contains multiple metallic pollutants, making it crucial for membranes to remove multiple heavy metal ions simultaneously.

[0057] Example 2

[0058] A novel green and environmentally friendly graphene oxide separation membrane and its preparation method are characterized by comprising the following steps:

[0059] (1) Preparation of graphene oxide solution

[0060] Weigh a certain mass (0.5g) of monolayer graphene oxide aqueous dispersion (10mg / g), add a certain amount of deionized water to dilute it into a solution of a certain concentration, sonicate it in the microwave for 10min, and then stir it magnetically for 30min to prepare a graphene oxide dispersion of a certain concentration.

[0061] (2) Preparation of GO laminated films

[0062] The graphene oxide aqueous solution was magnetically stirred at room temperature for 11 hours, and then filtered through a low-pressure vacuum filter to the surface of a 0.22 μm microporous membrane to obtain a GO membrane. The membrane was then dried in an oven at 60 °C for 30 minutes and collected.

[0063] Example 3

[0064] A novel green and environmentally friendly graphene oxide separation membrane and its preparation method are characterized by comprising the following steps:

[0065] (1) Preparation of graphene oxide solution

[0066] Weigh a certain mass (0.5g) of monolayer graphene oxide aqueous dispersion (10mg / g), add a certain amount of deionized water to dilute it into a solution of a certain concentration, sonicate it in the microwave for 10min, and then stir it magnetically for 30min to prepare a graphene oxide dispersion of a certain concentration.

[0067] (2) Prepare gelatin (GA) solution

[0068] Weigh 0.01g of gelatin and place it in 1mL of water. Stir magnetically at 50℃ for 15min to completely dissolve it and prepare a gelatin solution.

[0069] (3) Preparation of GO-GA composite laminated film

[0070] Gelatin solvent was added to the aqueous solution of graphene oxide and magnetically stirred for 30 min until completely mixed. The mixture was then magnetically stirred at room temperature for 11 h until homogeneous. The mixture was then filtered through a low-pressure vacuum filter to the surface of a 0.22 μm microporous membrane to obtain a GO-GA membrane. The membrane was dried in an oven at 60 °C for 30 min and collected.

[0071] Example 4

[0072] A novel green and environmentally friendly graphene oxide separation membrane and its preparation method are characterized by comprising the following steps:

[0073] (1) Preparation of graphene oxide solution

[0074] Weigh a certain mass (0.5g) of monolayer graphene oxide aqueous dispersion (10mg / g), add a certain amount of deionized water to dilute it into a solution of a certain concentration, sonicate it in the microwave for 10min, and then stir it magnetically for 30min to prepare a graphene oxide dispersion of a certain concentration.

[0075] (2) Prepare tannic acid (TA) solution

[0076] Weigh 0.01g of tannic acid and place it in 1mL of water. Microwave sonicate until completely dissolved to prepare an aqueous solution of tannic acid.

[0077] (3) Preparation of GO-TA composite laminated film

[0078] Add the TA solution to the aqueous solution of graphene oxide, stir magnetically for 30 min until completely mixed, stir magnetically for 11 h at room temperature, filter through low-pressure vacuum to the surface of a 0.22 μm microporous membrane to obtain a GO-TA membrane, dry in an oven at 60 °C for 30 min, and collect.

[0079] Comparative Example

[0080] Comparative Example 1:

[0081] A novel green and environmentally friendly composite separation membrane and its preparation method.

[0082] The only difference between this comparative example and Example 2 is that gelatin and tannic acid were not added during the preparation of the membrane. As a result, the GO membrane was not easy to detach from the base membrane and had an uneven surface.

[0083] Comparative Example 2:

[0084] A novel green and environmentally friendly composite separation membrane and its preparation method.

[0085] The only difference between this comparative example and Example 3 is that no tannic acid was added during the preparation of the membrane. The resulting GO-GA membrane had poor integrity, obvious defects at the edges, was not easy to detach from the base membrane, and had an uneven surface.

[0086] Comparative Example 3:

[0087] A novel green and environmentally friendly composite separation membrane and its preparation method.

[0088] The only difference between this comparative example and Example 4 is that no gelatin was added during the preparation of the membrane. The resulting GO-TA membrane had poor integrity, and some membrane material could be detached from the base membrane, but its edges were obviously defective and the surface was uneven.

[0089] The above description is merely an exemplary embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A novel green and environmentally friendly graphene oxide separation membrane, characterized in that, It includes the natural organic compound tannic acid, the polymeric material gelatin, and graphene oxide, wherein the tannic acid and the gelatin serve as an intercalating agent and a dispersing agent, respectively. The separation membrane was prepared by directly using vacuum filtration. The novel green and environmentally friendly graphene oxide separation membrane is prepared by the following steps: tannic acid bridges the gelatin and the graphene oxide, and the tannic acid and gelatin act as intercalating agents and dispersants, entering the interlayer of the graphene oxide sheets. Water is used as the solvent, and the mixture is magnetically stirred at room temperature to obtain a well-dispersed blend solution. After low-pressure vacuum filtration, the blend solution is assembled onto a 0.22 μm microporous filter membrane from bottom to top, and then dried in a 60°C oven for 30 min to obtain a self-supporting novel green and environmentally friendly graphene oxide separation membrane.

2. A method for preparing a novel green and environmentally friendly graphene oxide separation membrane according to claim 1, characterized in that, Includes the following steps: (1) Preparation of graphene oxide solution: Weigh the aqueous dispersion of monolayer graphene oxide, add deionized water to dilute it into a solution, microwave sonicate for 10-15 min, and then magnetically stir for 30-40 min to prepare the graphene oxide dispersion. (2) Preparation of gelatin solution: Weigh the gelatin and put it in water. Stir magnetically at 45-50℃ for 15-20 minutes to completely dissolve it and prepare a gelatin solution. (3) Preparation of tannic acid TA solution: Weigh the tannic acid and put it in water, sonicate it in microwave until it is completely dissolved, and prepare an aqueous solution of tannic acid; (4) Preparation of GO-GA-TA composite laminated membrane: The gelatin solvent obtained in step (2) is added to the graphene oxide dispersion obtained in step (1), and the mixture is magnetically stirred for 30-40 min until it is completely mixed. Then, TA solution is added and the mixture is magnetically stirred at room temperature for 10-11 h. The mixture is then filtered through a low-pressure vacuum to the surface of a 0.22 μm microporous filter membrane to obtain a GO-GA-TA membrane. The membrane is then dried in an oven at 50-60℃ for 30-45 min and collected.

3. The method for preparing the green and environmentally friendly novel graphene oxide separation membrane according to claim 2, characterized in that, In step (1), the mass of the monolayer graphene oxide aqueous dispersion is 0.1-0.5g, and the concentration of the monolayer graphene oxide aqueous dispersion is 10-15mg / g.

4. The method for preparing the green and environmentally friendly novel graphene oxide separation membrane according to claim 2, characterized in that, In step (2), the mass of the gelatin is 0.01-0.02g.

5. The method for preparing the green and environmentally friendly novel graphene oxide separation membrane according to claim 2, characterized in that, In step (3), the mass of the tannic acid is 0.01-0.02g.

6. The method for preparing the green and environmentally friendly novel graphene oxide separation membrane according to claim 2, characterized in that, The thickness of the GO-GA-TA composite laminate is 12.95±10μm.

7. The application of the novel green and environmentally friendly graphene oxide separation membrane according to claim 1, characterized in that, The novel green and environmentally friendly graphene oxide separation membrane is used in the preparation of filtration equipment.

8. The application of the novel green and environmentally friendly graphene oxide separation membrane according to claim 7, characterized in that, The aforementioned green and environmentally friendly novel graphene oxide separation membrane specifically uses 20 mg / L of dye and heavy metal ions to simulate industrial dye wastewater.

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