Preparation method and application of a novel LBL marine biomass hydrogel composite membrane

Abstract

The application discloses a preparation method and application of a novel LBL marine biomass hydrogel composite membrane. The preparation steps of the hydrogel composite membrane are as follows: adding chitosan quaternary ammonium salt into 0.1 M tris-hydrochloric acid solution to obtain chitosan quaternary ammonium salt solution through heating and stirring; adding sodium alginate into tris-hydrochloric acid solution to obtain sodium alginate solution through heating and stirring; taking an ultrafiltration membrane as a base film, spreading the chitosan quaternary ammonium salt solution on the surface of the base film first, pouring away the excessive solution after standing, and then spreading the sodium alginate solution on the chitosan quaternary ammonium salt solution after heat treatment in an oven, pouring away the excessive solution after standing, and heat treating in the oven to obtain a self-assembled hydrogel composite membrane. The layer-by-layer self-assembled hydrogel composite membrane is obtained through repeating the above process for multiple times. The preparation method is simple, the material is green and environment-friendly, the obtained membrane surface has superhydrophilicity, obvious separation efficiency is shown in dye wastewater treatment, and strong anti-pollution performance is shown.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of separation membrane preparation and application, and particularly relates to a preparation method and application of a novel LBL marine biomass hydrogel composite membrane. BACKGROUND

[0002] Traditional treatment processes include flocculation, adsorption, biodegradation, oxidation and other process treatment of textile wastewater. These technologies generally indiscriminately remove pollutants, or degrade macromolecules into small molecules or ions, and it is difficult to truly distinguish "waste".

[0003] In order to improve the dyeing efficiency of target dyes, high-salinity inorganic salts are often contained in textile wastewater, usually up to 5-6wt% of sodium chloride or sodium sulfate. Extracting and recycling valuable components from dye wastewater is an important sustainable production concept. Obviously, water-based dyes and inorganic salts are valuable resources, so their recycling is particularly important. Nanofiltration technology is a low-pressure driven filtration process, which can be used as a sustainable technology to effectively treat textile printing and dyeing wastewater, because it can effectively separate dyes and salts from water. However, nanofiltration membranes can effectively block water-based dye molecules and multivalent salts, so nanofiltration membranes with a molecular weight of 200-1000 Da are generally used. Nanofiltration membranes belong to pressure-driven membranes, which undoubtedly make dye pollution more serious, especially when filtering a mixture of dyes and salts.

[0004] However, conventional interfacial polymerization prepared nanofiltration membranes have a dense separation layer that can effectively hinder the passage of dyes, but at the same time have poor salt permeability, especially for divalent salts. Therefore, the concept of combining loose nanofiltration membranes with tight ultrafiltration membranes is introduced into the separation of dyes and salts, which have larger pore sizes than typical NF membranes. Currently, loose NF membranes and tight UF membranes have been developed to achieve effective separation of dyes and salts. Patents ZL202411078697.4 and ZL201910609824.1 prepared loose nanofiltration membranes on the surface of the base membrane by assembly and interfacial polymerization, which have high dye rejection rate, low inorganic salt rejection rate, and realize efficient separation of dyes and salts.

[0005] Based on this, the application proposes a method of inducing chitosan quaternary ammonium salt (CQAS) and sodium alginate (SA) to assemble into a membrane on the surface of the base membrane by layer-by-layer ionic gelation, to prepare a loose LBL marine biomass hydrogel composite membrane. SUMMARY

[0006] In order to solve the above problems, the purpose of the present application is to provide a preparation method of a novel LBL marine biomass hydrogel composite membrane and its application. It is to use clean ultrafiltration membrane as base film, and to cross-link and gel the tris-hydrochloric acid solution of marine biomass chitosan quaternary ammonium salt and sodium alginate on the surface of the base film through continuous multiple times, and then to obtain a hydrogel composite separation layer formed by layer-by-layer self-assembly on the surface of the base film. The membrane has high retention rate of dyes and low salt ion retention rate.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0008] A preparation method of a novel LBL marine biomass hydrogel composite membrane, comprising the following steps:

[0009] (1) chitosan quaternary ammonium salt is added to 0.1 M tris-hydrochloric acid solution, heated and stirred to obtain a chitosan quaternary ammonium salt solution;

[0010] (2) sodium alginate is added to 0.1 M tris-hydrochloric acid solution, heated and stirred to obtain a sodium alginate solution;

[0011] (3) using ultrafiltration membrane as base film, first spread the chitosan quaternary ammonium salt solution on the surface of the base film, and then heat treat in an oven after standing to obtain a 0.5-layer composite membrane; spread the sodium alginate solution on the surface of the 0.5-layer composite membrane, and then heat treat in an oven after standing for the same time to obtain a layer-by-layer self-assembled hydrogel composite membrane;

[0012] (4) repeat step (3) on the surface of the layer-by-layer self-assembled hydrogel composite membrane obtained in step (3) to obtain a layer-by-layer self-assembled hydrogel composite membrane.

[0013] Further, in step (1), the weight percentage of chitosan quaternary ammonium salt in the chitosan quaternary ammonium salt solution is 1wt%-3wt%, the heating temperature is 60-80℃, the stirring speed is 1000-1500 rpm, and the stirring time is 6-10 h.

[0014] Further, in step (2), the weight percentage of sodium alginate in the sodium alginate solution is 1wt%-3wt%, the heating temperature is 60-80℃, the stirring speed is 1000-1500 rpm, and the stirring time is 6-10 h.

[0015] Further, in step (3), the chitosan quaternary ammonium salt solution is spread on the surface of the base film and left to stand for 5-15 min, the heat treatment temperature is 60-80℃, and the heat treatment time is 10-20 min.

[0016] Further, the time for spreading the sodium alginate solution on the surface of the 0.5-layer composite film in step (3) is 5-15 min, the temperature for heat treatment is 60-80 DEG C, and the time for heat treatment is 10-20 min.

[0017] Further, the number of times for repeating step (3) in step (4) is n, and n is 0-6.

[0018] The novel LBL marine biomass hydrogel composite film obtained by the above preparation method.

[0019] The application of the above novel LBL marine biomass hydrogel composite film in dye wastewater treatment.

[0020] The hydrogel molecular structure contains a large number of hydrophilic groups, which can capture water molecules and form an organic repulsive layer, and the hydrogel layer with strong water binding capacity is introduced on the surface of the separation membrane. Therefore, the membrane can have the performance of anti-dye pollution while ensuring high separation efficiency. The marine biomass material used in the application is green and environmentally friendly, and the gelation on the surface of the base film forms a hydrogel separation layer with a three-dimensional network, which can form a smooth and defect-free separation layer on the surface of the base film through layer-by-layer crosslinking, and can be stably combined with the base film. While effectively separating dyes and salt ions, the hydrogel hydration layer barrier formed can effectively enhance the anti-pollution performance of the membrane.

[0021] The application successfully prepares a surface-uniform, high-efficiency loose LBL hydrogel composite film on the surface of the base film by using the green and biocompatible marine biomass material chitosan quaternary ammonium salt and sodium alginate as the hydrogel base material through the interfacial polyelectrolyte gelation method. The three-dimensional hydrogel layer formed by the layer-by-layer self-assembly on the surface of the composite film can effectively intercept dye molecules, but water molecules and salt ions can pass through, and the charge property of the surface of the composite film can further enhance the interception rate of the same type of dye, and the outermost layer of the nuclear charge can be freely adjusted to achieve the purpose of high-efficiency separation in the aspect of characteristic dye separation. In addition, the super-hydrophilic hydration layer on the surface of the membrane can effectively control the pollution of the membrane surface.

[0022] Compared with the prior art, the application has the following advantages:

[0023] (1) Compared with the traditional hydrogel base material, the marine biomass material chitosan quaternary ammonium salt and sodium alginate is used in the application, and the two materials are green and environmentally friendly, and the introduction of the two materials into the separation membrane preparation field can increase the value-added utilization space.

[0024] (2) The polyelectrolyte gelation process in the application is more gentle, simple and easy to obtain, and can effectively avoid the cost problem caused by the traditional method.

[0025] (3) The present application adopts the interval type layer-by-layer self-assembly preparation method, which can freely determine the surface charge of the membrane while ensuring the flux and retention rate, thereby further enhancing the separation efficiency of the membrane.

[0026] (4) The hydrogel layer on the surface of the composite membrane prepared by the present application endows the membrane with hydrophilicity, which can effectively enhance the anti-fouling performance thereof. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM images of the surface (a, c) and cross-section (b, d) of the LBL hydrogel composite membrane (1.0 and 3.0 layers) of Example 1 and Example 8.

[0028] Figure 2 The surface Zeta potential characterization result graph of the PES-based membrane, Examples 1-8 and Comparative Example 1.

[0029] Figure 3 The surface water contact angle test graph of the PES-based membrane, Examples 1-8 and Comparative Example 1.

[0030] Figure 4 The schematic diagram of the retention rate and flux of the membrane prepared in Example 1 for different ions.

[0031] Figure 5 The flux and retention rate of Example 1 for different dye solutions. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application.

[0033] The preparation steps of the 0.1 M tris-hydrochloric acid solution in the following examples are as follows:

[0034] After adding about 400 mL of deionized water to 7.0 g of 3- (hydroxymethyl) aminomethane powder and fully dissolving it, it was transferred to a 1000 mL volumetric flask, then about 320 mL of 0.1 M HCl aqueous solution was added, then 0.1 M HCl aqueous solution was slowly added to adjust the pH to 7, and finally deionized water was added to constant volume to obtain a 0.1 M tris-hydrochloric acid solution. Example 1

[0035] (1) 1.0 g of chitosan quaternary ammonium salt powder was added to 99.0 g of 0.1 M tris-hydrochloric acid solution in batches, and stirred and heated, the heating temperature was 60℃, the stirring speed was 1000 rpm, and the stirring time was 8 h, to obtain a 1.0 wt% chitosan quaternary ammonium salt solution, which was denoted as solution A.

[0036] (2) 1.0 g sodium alginate powder was added into 99.0 g 0.1 M tris-hydrochloric acid solution in batches under stirring and heating, the heating temperature was 60 °C, the stirring speed was 1000 rpm, and the stirring time was 8 h, to obtain a 1.0 wt% sodium alginate solution, denoted as solution B.

[0037] (3) A clean PES (polyether sulfone) base film was clamped between the grooved polytetrafluoroethylene plate frame, placed on a flat surface, and solution A was spread on the surface for 15 min, then the excess solution on the surface was poured off, and placed in an 80 °C oven for heat treatment for 10 min, to obtain a 0.5-layer composite film.

[0038] (4) Then solution B was spread on the surface of the above-mentioned 0.5-layer composite film, and after standing for 15 min, the excess solution on the surface was poured off, and placed in an 80 °C oven for heat treatment for 10 min, to obtain a 1.0-layer LBL hydrogel composite film. Figure 1 It can be seen that a uniform and continuous hydrogel layer is formed on the surface of the film. Example 2

[0039] (1) 1.5 g chitosan quaternary ammonium salt powder was added into 98.5 g 0.1 M tris-hydrochloric acid solution in batches under stirring and heating, the heating temperature was 70 °C, the stirring speed was 1200 rpm, and the stirring time was 9 h, to obtain a 1.5 wt% chitosan quaternary ammonium salt solution, denoted as solution A.

[0040] (2) 1.5 g sodium alginate powder was added into 98.5 g 0.1 M tris-hydrochloric acid solution in batches under stirring and heating, the heating temperature was 70 °C, the stirring speed was 1200 rpm, and the stirring time was 9 h, to obtain a 1.5 wt% sodium alginate solution B.

[0041] (3) A clean PES base film was clamped between the grooved polytetrafluoroethylene plate frame, placed on a flat surface, and solution A was spread on the surface for 15 min, then the excess solution on the surface was poured off, and placed in an 80 °C oven for heat treatment for 15 min, to obtain a 0.5-layer composite film.

[0042] (4) Then solution B was spread on the surface of the above-mentioned 0.5-layer composite film, and after standing for 15 min, the excess solution on the surface was poured off, and placed in an 80 °C oven for heat treatment for 15 min, to obtain a 1.0-layer LBL hydrogel composite film. Example 3

[0043] (1) 1.0 g of chitosan quaternary ammonium salt powder was added into 99.0 g of 0.1 M tris-hydrochloric acid solution in batches under stirring and heating, the heating temperature was 70°C, the stirring speed was 1200 rpm, and the stirring time was 6 h, to obtain a 1.0 wt% chitosan quaternary ammonium salt solution, which was marked as solution A.

[0044] (2) 1.0 g of sodium alginate powder was added into 99.0 g of 0.1 M tris-hydrochloric acid solution in batches under stirring and heating, the heating temperature was 70°C, the stirring speed was 1200 rpm, and the stirring time was 6 h, to obtain a 1.0 wt% sodium alginate solution, which was marked as solution B.

[0045] (3) A clean PES-based film was clamped between a polytetrafluoroethylene plate frame with grooves, placed on a flat surface, and solution A was spread on the surface and left to stand for 10 min, then the excess solution on the surface was poured off, and placed in an 80°C oven for heat treatment for 10 min, to obtain a 0.5-layer composite film.

[0046] (4) Then solution B was spread on the surface of the above-mentioned 0.5-layer composite film, left to stand for 10 min, then the excess solution on the surface was poured off, and placed in an 80°C oven for heat treatment for 10 min, to obtain a 1.0-layer LBL hydrogel composite film. Example 4

[0047] (1) 1.5 g of chitosan quaternary ammonium salt powder was added into 98.5 g of 0.1 M tris-hydrochloric acid solution in batches under stirring and heating, the heating temperature was 80°C, the stirring speed was 1200 rpm, and the stirring time was 10 h, to obtain a 1.5 wt% chitosan quaternary ammonium salt solution, which was marked as solution A.

[0048] (2) 1.5 g of sodium alginate powder was added into 98.5 g of 0.1 M tris-hydrochloric acid solution in batches under stirring and heating, the heating temperature was 80°C, the stirring speed was 1200 rpm, and the stirring time was 10 h, to obtain a 1.5 wt% sodium alginate solution B.

[0049] (3) A clean PES-based film was clamped between a polytetrafluoroethylene plate frame with grooves, placed on a flat surface, and solution A was spread on the surface and left to stand for 10 min, then the excess solution on the surface was poured off, and placed in a 70°C oven for heat treatment for 15 min, to obtain a 0.5-layer composite film.

[0050] (4) Then solution B was spread on the surface of the above-mentioned 0.5-layer composite film, left to stand for 15 min, then the excess solution on the surface was poured off, and placed in a 70°C oven for heat treatment for 15 min, to obtain a 1.0-layer LBL hydrogel composite film. Example 5

[0051] The procedure of this example is the same as steps (1), (2), (3), and (4) of Example 1. The solution A is spread again on the surface of the above-mentioned 1.0-layer LBL hydrogel composite film, i.e. the procedure of step (3) is repeated, to obtain a 1.5-layer LBL hydrogel composite film. Example 6

[0052] The procedure of this example is the same as steps (1), (2), (3), and (4) of Example 1. The solution A and solution B are spread again on the surface of the above-mentioned 1.0-layer LBL hydrogel composite film, i.e. the procedures of steps (3) and (4) are repeated, to obtain a 2.0-layer LBL hydrogel composite film. Example 7

[0053] The procedure of this example is the same as steps (1), (2), (3), and (4) of Example 1, except for steps (5) and (6).

[0054] (5) The solution A and solution B are spread again on the surface of the above-mentioned 1.0-layer LBL hydrogel composite film, i.e. the procedures of steps (3) and (4) are repeated, to obtain a 2.0-layer LBL hydrogel composite film.

[0055] (6) The solution A is spread again on the surface of the above-mentioned 2.0-layer LBL hydrogel composite film, i.e. the procedure of step (3) is repeated, to obtain a 2.5-layer LBL hydrogel composite film. Example 8

[0056] The procedure of this example is the same as steps (1), (2), (3), and (4) of Example 1, except for steps (5), (6), and (7).

[0057] (5) The solution A and solution B are spread again on the surface of the above-mentioned 1.0-layer LBL hydrogel composite film, i.e. the procedures of steps (3) and (4) are repeated, to obtain a 2.0-layer LBL hydrogel composite film.

[0058] (6) The solution A is spread again on the surface of the above-mentioned 2.0-layer LBL hydrogel composite film, i.e. the procedure of step (3) is repeated, to obtain a 2.5-layer LBL hydrogel composite film.

[0059] (7) The solution B is spread again on the surface of the above-mentioned 2.5-layer LBL hydrogel composite film, i.e. the procedure of step (4) is repeated, to obtain a 3.0-layer LBL hydrogel composite film. Figure 1 It can be seen that a uniform and continuous hydrogel layer is formed on the surface of the film, and the thickness is greater than that of Example 1.

[0060] This comparative example is the same as steps (1), (2), and (3) of Example 1, and there is no other step.

[0061] Zeta potential measurement was performed on PES base membrane, examples 1-8 and comparative example 1, and the results are shown in Figure 2 , indicating that the surface outer layer charge of the membrane can be freely adjusted.

[0062] Surface water contact angle test of PES base membrane, examples 1-8 and comparative example 1 is shown in Figure 3 .

[0063] The LBL hydrogel composite membrane prepared in example 1 was tested, and the results are shown in Figure 4 and Figure 5 : the membrane performance was evaluated by using a cross-flow performance evaluation instrument (laboratory self-made), and the prepared membrane was pre-pressed at 0.2 MPa for 1 h to ensure the stability and effectiveness of the measurement data. Figure 4 , 1000 ppm NaCl (Z+ / Z-: 1), 1000 ppm MgSO4(Z+ / Z-: 1), 1000 ppm MgCl2(Z+ / Z-: 2) as test salt solution, and 200 ppm Congo red dye and various salt ion mixed solution as simulated stock solution, the flux and rejection rate of the membrane were evaluated, and the experimental results showed that the rejection rate of the membrane to salt ions was very low, while the rejection rate to Congo red dye was high, indicating that the LBL hydrogel composite membrane had good separation performance. Figure 5 , the flux and rejection rate of the membrane were tested under 0.2 MPa, and the results showed that the separation performance of the LBL hydrogel composite membrane to these dyes was high. The rejection rate and flux of 200 ppm Congo red of examples 1-8 and comparative example 1 were also compared, and the results are shown in table 1. The formula used in the above test is as follows:

[0064] ;

[0065] F - membrane flux (L·m −2 ·h −1 );

[0066] V - water production volume (L);

[0067] Δt - water production time (h).

[0068] ;

[0069] R - rejection rate (%);

[0070] C p - concentration of permeate;

[0071] C f - concentration of feed liquid.

[0072] Table 1 Retention rate and flux of examples 1-4 and comparative examples 1-5 to 200 ppm congo red

[0073]

[0074] From table 1, the flux and retention rate of the films obtained in examples 1-4 are both high, the film obtained in comparative example 1 has high flux and very low single retention rate, because no self-assembly is performed in comparative example 1. Meanwhile, with the increase of the number of self-assembly layers, it can be seen from examples 5-8 that the retention rate of the film slightly increases, but the flux is lost.

[0075] The above description is only the preferred embodiment of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be covered by the scope of the present application.

Claims

1. A method for preparing a novel LBL marine biomass hydrogel composite membrane, characterized in that: Includes the following steps: (1) Add chitosan quaternary ammonium salt to 0.1 M tris-hydrochloric acid solution, heat and stir to obtain chitosan quaternary ammonium salt solution; (2) Add sodium alginate to 0.1 M tris-hydrochloric acid solution, heat and stir to obtain sodium alginate solution; (3) Using an ultrafiltration membrane as the base membrane, first spread the chitosan quaternary ammonium salt solution on the surface of the base membrane, let it stand, pour off the excess solution, and then heat-treat it in an oven to obtain a 0.5-layer composite membrane; Sodium alginate solution was spread on the surface of a 0.5-layer composite membrane. After standing for the same amount of time, the excess solution was poured off, and the membrane was heat-treated in an oven to obtain a self-assembled hydrogel composite membrane. (4) Repeat step (3) multiple times on the surface of the self-assembled hydrogel composite membrane obtained in step (3) to obtain a layer-by-layer self-assembled hydrogel composite membrane.

2. The method for preparing the novel LBL marine biomass hydrogel composite membrane according to claim 1, characterized in that: In step (1), the chitosan quaternary ammonium salt in the chitosan quaternary ammonium salt solution has a weight percentage of 1wt% to 3wt%, the heating temperature is 60 to 80℃, the stirring speed is 1000 to 1500 rpm, and the stirring time is 6 to 10 h.

3. The method for preparing the novel LBL marine biomass hydrogel composite membrane according to claim 1, characterized in that: In step (2), the sodium alginate solution contains 1 wt% to 3 wt% sodium alginate, the heating temperature is 60 to 80°C, the stirring speed is 1000 to 1500 rpm, and the stirring time is 6 to 10 h.

4. The method for preparing the novel LBL marine biomass hydrogel composite membrane according to claim 1, characterized in that: In step (3), the chitosan quaternary ammonium salt solution is spread on the surface of the base film and left to stand for 5 to 15 minutes. The temperature of the heat treatment is 60 to 80°C and the heat treatment time is 10 to 20 minutes.

5. The method for preparing the novel LBL marine biomass hydrogel composite membrane according to claim 1, characterized in that: In step (3), the sodium alginate solution is spread on the surface of the 0.5-layer composite membrane and left to stand for 5 to 15 minutes. The heat treatment temperature is 60 to 80°C and the heat treatment time is 10 to 20 minutes.

6. The method for preparing a novel LBL marine biomass hydrogel composite membrane according to claim 1, characterized in that: In step (4), step (3) is repeated n times, where n is 0 to 6.

7. A novel LBL marine biomass hydrogel composite membrane is obtained by the preparation method according to any one of claims 1 to 6.

8. The application of the novel LBL marine biomass hydrogel composite membrane as described in claim 7 in the treatment of dye wastewater.

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