Modified grid and preparation method and application thereof

Abstract

The invention discloses a modified grid and a preparation method and application thereof. The modified grid comprises a substrate layer and a functional layer, amino groups and carboxyl groups are distributed on the functional layer; the substrate layer and the functional layer are combined in a covalent bond mode. The modified grid provided by the invention not only has a good scale inhibition effect, but also has the effects of adsorbing heavy metal ions and inhibiting bacteria.

Description

Technical Field

[0001] The invention specifically relates to a modified grid and a preparation method and application thereof. Background Art

[0002] Reverse osmosis / nanofiltration is an energy-saving, environmentally friendly and efficient water treatment and separation technology, which is widely used in the fields of medicine, food, chemical industry, home appliances, etc. It uses a highly selective reverse osmosis / nanofiltration membrane. When the water to be purified passes through the membrane surface, a part of the water passes through the membrane as purified water, and the salts, bacteria, spores, etc. in the water are retained on the membrane surface and concentrated. As the reverse osmosis / nanofiltration membrane continues to work, more and more bacteria appear on the membrane surface, and the concentration polarization becomes more and more serious, which seriously affects the separation performance and flux of the membrane. Therefore, the separation effect of the reverse osmosis / nanofiltration filter element made of reverse osmosis / nanofiltration membrane becomes worse and worse, and the flow rate becomes lower and lower.

[0003] In order to solve the problem of concentration polarization on the membrane surface, the existing technology generally introduces scale inhibitors before the water flow contacts the membrane surface. The scale inhibitors are slowly released in the water and combine with calcium ions on the membrane surface and are discharged with the wastewater. However, the slow-release concentration of the scale inhibitor is usually uncontrollable, which affects the scale inhibition effect. In addition, the components of the scale inhibitor usually contain phosphorus, so the discharged wastewater is very harmful to the water body.

[0004] In order to solve the problem of bacterial growth on the membrane surface, the membrane is usually modified by mixing in substances with antibacterial and antimicrobial properties, such as silver, zinc, quaternary ammonium salts, etc. However, the membrane surface is easily contaminated by salts, bacteria, spores, colloids, etc. that do not pass through the membrane, which affects the contact between bacteria and the membrane surface, and the effective antibacterial substances are easily lost, resulting in poor antibacterial effects.

[0005] Therefore, how to solve the problem that the scale inhibition effect of the filter membrane is poor and harmful to the water body and that bacteria are easily bred on the surface of the filter membrane is one of the problems that need to be solved urgently in the field of water purification. Summary of the invention

[0006] The present invention mainly aims to overcome the defects of the prior art that the filter membrane surface has poor scale inhibition effect and is harmful to water bodies and breeds bacteria, and provides a modified grid and its preparation method and application. The modified grid provided by the present invention has a good scale inhibition effect and also has the function of adsorbing heavy metal ions and inhibiting bacteria.

[0007] The invention provides a modified grid, which comprises a base layer and a functional layer; the functional layer is distributed with amino groups and carboxyl groups; the base layer and the functional layer are combined in a covalent bond manner.

[0008] In the present invention, the amino groups are evenly distributed on the functional layer.

[0009] In the present invention, the material of the base layer can be a mesh material commonly used in the art, preferably polyester, such as one or more of polymethyl methacrylate, polybutylene terephthalate (PBT) and polyethylene terephthalate (PET).

[0010] In the present invention, the base layer can be commercially available or prepared by a conventional preparation method in the art. For example, the preparation method is to extrude, cool and solidify the raw materials in sequence.

[0011] In the present invention, the source of the amino group can be an amine substance commonly used in the art, and the amine substance is preferably a polyamine, such as one or more of polyethyleneimine (PEI), chitosan, polyvinyl imidazole, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine. In some specific embodiments, the amine substance is polyethyleneimine and chitosan.

[0012] The molecular weight of the amine substance is preferably 7000 g / mol-100000 g / mol, for example 10000 g / mol or 70000 g / mol.

[0013] The mass ratio of the amine substance to the base layer is preferably (1-10):1, such as 1:1, 3:1, 5:1 or 10:1.

[0014] In the present invention, the source of the carboxyl group may be an organic acid, and the organic acid is preferably a macromolecular organic acid, such as one or more of polyacrylic acid, polyaspartic acid, humic acid and hyaluronic acid.

[0015] Wherein, the molecular weight of the organic acid is preferably 10000 g / mol-100000 g / mol.

[0016] Wherein, the molar ratio of the amine substance to the organic acid is preferably 1:(0.1-5), such as 1:0.1, 1:1, 1:2 or 1:5.

[0017] The present invention also provides a method for preparing a modified grid, which comprises the following steps:

[0018] The base layer undergoes a first reaction with an amine substance, and then undergoes a second reaction with an organic acid to form a functional layer on the base layer, thereby obtaining the modified grid.

[0019] In the present invention, the material of the base layer can be a mesh material commonly used in the art, preferably polyester, such as one or more of polymethyl methacrylate, polybutylene terephthalate (PBT) and polyethylene terephthalate (PET).

[0020] In the present invention, the base layer can be commercially available or prepared by a conventional preparation method in the art. For example, the preparation method is to extrude, cool and solidify the raw materials in sequence.

[0021] In the present invention, the amine substance can be an amine substance commonly used in the art, and the amine substance is preferably a polyamine, such as one or more of polyethyleneimine, chitosan, polyvinyl imidazole, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine. Each amine substance molecule contains multiple amino groups, some of which can react chemically with the ester group on the substrate layer to fix it to the substrate layer; some of the amino groups can react with some carboxyl groups to firmly fix the substance containing the carboxyl group, and another part of the amino groups have both antibacterial effect and heavy metal adsorption effect.

[0022] In some specific embodiments, the amine substances are polyethyleneimine and chitosan.

[0023] In the present invention, the molecular weight of the amine substance may be 7000 g / mol-100000 g / mol, for example, 10000 g / mol or 70000 g / mol.

[0024] In the present invention, the organic acid may be a macromolecular organic acid, such as one or more of polyacrylic acid, polyaspartic acid, humic acid and hyaluronic acid.

[0025] In some embodiments, the organic acid is polyacrylic acid and / or polyaspartic acid.

[0026] In the present invention, the molecular weight of the organic acid may be 10000 g / mol-100000 g / mol, for example, 20000 g / mol or 50000 g / mol.

[0027] In the present invention, the mass ratio of the amine substance to the base layer may be (1-10):1, for example, 1:1, 3:1, 5:1 or 10:1;

[0028] In the present invention, the molar ratio of the amine substance to the organic acid may be 1:(0.1-5), for example, 1:0.1, 1:1, 1:2 or 1:5.

[0029] In the present invention, the amine substance can be used for the first reaction in the form of an amine substance aqueous solution.

[0030] Wherein, in the aqueous solution of the amine substance, the concentration of the amine substance may be 1wt.%-10wt.%, for example, 2wt.% or 9wt.%.

[0031] The pH of the aqueous solution of the amine substance is 10-13, preferably 11-13, such as 12.

[0032] The pH can be adjusted by an alkaline solution, preferably a NaOH solution. The method of etching the grid substrate with an amine-alkali co-bath can make the amino group in the amine substance react with the ester group in the substrate material, and introduce the amine substance into the substrate through the action of covalent bonds, thereby increasing the specific surface area and roughness of the grid. Increasing the specific surface area of ​​the grid can increase the number of reaction sites, while increasing the roughness of the grid can synergistically enhance the scale inhibition effect of the grid in the initial stage.

[0033] In the present invention, the temperature of the first reaction may be 60°C-90°C, such as 60°C or 85°C.

[0034] In the present invention, the time of the first reaction can be 2h-10h, such as 3h or 9h.

[0035] In the present invention, the organic acid is used in the form of an organic acid aqueous solution for the second reaction.

[0036] In the present invention, in the organic acid aqueous solution, the concentration of the organic acid may be 1 wt.%-5 wt.%, for example, 1 wt.% or 4 wt.%.

[0037] In the present invention, the temperature of the second reaction may be 50°C-80°C, such as 50°C or 70°C.

[0038] In the present invention, the second reaction time may be 5 h-12 h, such as 5 h or 11 h.

[0039] The present invention also provides a modified grid, which is prepared by the preparation method as described above.

[0040] The present invention also provides a filter element, which comprises the modified grid as described above.

[0041] The present invention also provides the use of the modified grid or the filter element as described above in the field of water treatment.

[0042] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0043] The reagents and raw materials used in the present invention are commercially available.

[0044] The positive and progressive effects of the present invention are:

[0045] In the present invention, the grid in contact with the surface of the membrane is modified to form a functional layer with amino and carboxyl groups distributed therein. The amino group has the functions of adsorbing heavy metals and inhibiting bacteria, and the carboxyl group has the functions of preventing scale and adsorbing heavy metals. Various substances in the functional layer cooperate with each other to enhance the heavy metal adsorption effect. In addition, the functional layer is connected to the base layer by chemical reaction, and the functional layer exists more stably, avoiding the problem of functional active substances falling off and polluting the water body.

[0046] In some preferred embodiments, the modified grid of the present invention can achieve an antibacterial rate of 99.5% against Escherichia coli in the initial state, and reach 99.8% after passing through 8t of water; the antibacterial rate against Staphylococcus aureus can reach 99.7% in the initial state, and reach 99.8% after passing through 8t of water; the flow rate in the initial state reaches 2.5L / min, and after passing through 8t of water, it can be maintained at 2.3L / min, and the heavy metal removal rate is maintained at 99.9%. DETAILED DESCRIPTION

[0047] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0048] Example 1

[0049] (1) placing the PBT substrate in a 2 wt % chitosan (molecular weight 10,000 g / mol) aqueous solution (the pH of the solution was adjusted to 12 with NaOH), with the mass ratio of the amine substance to the substrate being 5:1, and reacting at 60° C. for 9 h. After the reaction was completed, taking out the substrate modified by the amine substance and cleaning it;

[0050] (2) The amine-modified substrate obtained in step (1) is placed in a 1 wt % polyacrylic acid (molecular weight 20,000 g / mol) aqueous solution, with a molar ratio of amine to organic acid of 1:1, and reacted at 50° C. for 11 h. After the reaction is completed, the modified grid is taken out and cleaned, and dried for later use.

[0051] Example 2

[0052] (1) placing the PET substrate in a 9 wt % PEI (molecular weight 70,000 g / mol) aqueous solution (the pH of the solution was adjusted to 12 with NaOH), with the mass ratio of the amine substance to the substrate being 3:1, and reacting at 85° C. for 3 h; after the reaction was completed, taking out the substrate modified by the amine substance and cleaning it;

[0053] (2) placing the amine-modified substrate obtained in step (1) into a 4 wt % polyaspartic acid (molecular weight 50,000 g / mol) aqueous solution, with the ratio of amine to organic acid being 1:2, and reacting at 70° C. for 5 h; after the reaction is completed, taking out the modified grid, cleaning it, and air-drying it for later use.

[0054] Example 3

[0055] (1) placing the PBT substrate in a 2 wt % chitosan (molecular weight 10,000 g / mol) aqueous solution (the pH of the solution was adjusted to 12 with NaOH), with the mass ratio of the amine substance to the substrate being 1:1, and reacting at 60° C. for 9 h. After the reaction was completed, taking out the substrate modified by the amine substance and cleaning it;

[0056] (2) The amine-modified substrate obtained in step (1) is placed in a 1 wt % polyacrylic acid (molecular weight 20,000 g / mol) aqueous solution, with the ratio of amine to organic acid being 1:1, and reacted at 50° C. for 11 h. After the reaction is completed, the modified grid is taken out and cleaned, and dried for later use.

[0057] Example 4

[0058] (1) placing the PBT substrate in a 2 wt % chitosan (molecular weight 10,000 g / mol) aqueous solution (the pH of the solution was adjusted to 12 with NaOH), with the mass ratio of the amine substance to the substrate being 10:1, and reacting at 60° C. for 9 h. After the reaction was completed, taking out the substrate modified by the amine substance and cleaning it;

[0059] (2) The amine-modified substrate obtained in step (1) is placed in a 1 wt % polyacrylic acid (molecular weight 20,000 g / mol) aqueous solution, with the ratio of amine to organic acid being 1:1, and reacted at 50° C. for 11 h. After the reaction is completed, the modified grid is taken out and cleaned, and dried for later use.

[0060] Example 5

[0061] (1) placing the PBT substrate in a 2 wt % chitosan (molecular weight 10,000 g / mol) aqueous solution (the pH of the solution was adjusted to 12 with NaOH), with the mass ratio of the amine substance to the substrate being 1:10, and reacting at 60° C. for 9 h. After the reaction was completed, taking out the substrate modified by the amine substance and cleaning it;

[0062] (2) The amine-modified substrate obtained in step (1) is placed in a 1 wt % polyacrylic acid (molecular weight 20,000 g / mol) aqueous solution, with the ratio of amine to organic acid being 1:1, and reacted at 50° C. for 11 h. After the reaction is completed, the modified grid is taken out and cleaned, and dried for later use.

[0063] Example 6

[0064] (1) placing the PET substrate in a 9 wt % PEI (molecular weight 70,000 g / mol) aqueous solution (the pH of the solution was adjusted to 12 with NaOH), with the mass ratio of the amine substance to the substrate being 3:1, and reacting at 85° C. for 3 h; after the reaction was completed, taking out the substrate modified by the amine substance and cleaning it;

[0065] (2) The amine-modified substrate obtained in step (1) is placed in a 4 wt % polyaspartic acid (molecular weight 50,000 g / mol) aqueous solution, with the ratio of amine to organic acid being 1:5, and reacted at 70° C. for 5 h. After the reaction is completed, the modified grid is taken out and cleaned, and dried for later use.

[0066] Example 7

[0067] (1) placing the PET substrate in a 9 wt % PEI (molecular weight 70,000 g / mol) aqueous solution (the pH of the solution was adjusted to 12 with NaOH), with the mass ratio of the amine substance to the substrate being 3:1, and reacting at 85° C. for 3 h; after the reaction was completed, taking out the substrate modified by the amine substance and cleaning it;

[0068] (2) The amine-modified substrate obtained in step (1) is placed in a 4 wt % polyaspartic acid (molecular weight 50,000 g / mol) aqueous solution, with the ratio of amine to organic acid being 10:1, and reacted at 70° C. for 5 h. After the reaction is completed, the modified grid is taken out and cleaned, and dried for later use.

[0069] Example 8

[0070] (1) placing the PET substrate in a 9 wt % PEI (molecular weight 70,000 g / mol) aqueous solution (the pH of the solution was adjusted to 12 with NaOH), with the mass ratio of the amine substance to the substrate being 3:1, and reacting at 85° C. for 3 h; after the reaction was completed, taking out the substrate modified by the amine substance and cleaning it;

[0071] (2) The amine-modified substrate obtained in step (1) is placed in a 4 wt % polyaspartic acid (molecular weight 50,000 g / mol) aqueous solution, with the ratio of amine to organic acid being 1:10, and reacted at 70° C. for 5 h. After the reaction is completed, the modified grid is taken out and cleaned, and dried for later use.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that only a PBT base layer is included.

[0074] Comparative Example 2

[0075] The difference from Example 2 is that only a PET base layer is included.

[0076] Comparative Example 3

[0077] The PBT substrate layer was placed in a 2wt% chitosan (molecular weight 10000g / mol) aqueous solution (the solution pH was adjusted to 12 with NaOH), the mass ratio of amine substance to substrate layer was 5:1, and the reaction was carried out at 60°C for 9h. After the reaction was completed, the substrate layer modified by the amine substance was taken out, cleaned, and dried for later use.

[0078] Comparative Example 4

[0079] The PBT substrate layer was placed in a 1wt% polyacrylic acid (molecular weight 20000g / mol) aqueous solution, with the mass ratio of organic acid to substrate layer being 1:1, and reacted at 50°C for 11h. After the reaction was completed, the modified grid was taken out and cleaned, and dried for later use.

[0080] Effect Example

[0081] (1) Antibacterial rate test

[0082] Referring to GB21551.2-2010 Special requirements for antibacterial materials with antibacterial, sterilizing and purifying functions for household and similar electrical appliances, the antibacterial performance of the modified grid prepared in the comparative example and the embodiment at the initial stage and after passing through 8t of water was tested by the film pasting method. The test results are shown in Table 1.

[0083] (2) Flow test

[0084] The modified grid prepared in the comparative example and the embodiment was rolled into a nanofiltration filter element with a nanofiltration membrane, a guide cloth, and a central tube, and the net-to-waste ratio was controlled to be 3:1. The filter element flow rate at the beginning and after passing 8 tons of water were tested. The test results are shown in Table 1.

[0085] (3) Heavy metal removal test

[0086] Using 25 ppb cadmium nitrate (Cd(NO3)2) solution as the spike solution, the heavy metal removal rates of the filter elements assembled with modified grids prepared in the comparative example and the example were tested at the initial stage and after 2 tons of the spike solution. The test results are shown in Table 1.

[0087] (4) Effect retention rate

[0088] Effect retention rate = effect after a period of use / initial effect. The results are shown in Table 2.

[0089] Taking the calculation of Escherichia coli antibacterial retention rate as an example, the Escherichia coli antibacterial retention rate = the Escherichia coli antibacterial rate after passing 8t of water / the initial Escherichia coli antibacterial rate.

[0090] Table 1

[0091]

[0092]

[0093] Table 2

[0094]

[0095] The present invention distributes amino and carboxyl groups at the ends of the grid, giving it the performance of scale inhibition, antibacterial and heavy metal adsorption. Combining the data in Table 1 and Table 2, it can be seen that the modified grid provided by the present invention is used in the filter element, and it exhibits excellent antibacterial performance and heavy metal adsorption performance, while also having a high post-rental effect and being able to maintain high stability during use.

[0096] And with the use process, the modified grid of the present invention will even enhance its ability to inhibit bacteria. This may be because the organic acid combines with the calcium ions in the water to form a gel attached to the grid, and the surface roughness of the grid increases, thereby increasing the turbulence on the concentrated water side, and synergistically enhancing the scale inhibition effect of the modified grid during use; it can also synergistically adsorb heavy metals. With the use of the filter element, the organic acid combines with the zinc ions in the water to synergistically enhance the antibacterial effect. With the combination of organic acid substances with calcium ions and zinc ions, it not only affects the surface morphology of the grid, synergistically enhancing the scale inhibition effect, but also synergistically enhances the antibacterial effect of the grid. As the amount of water flowing increases, its antibacterial performance increases instead of decreasing.

[0097] The difference between Comparative Example 1 and Example 1, and between Comparative Example 2 and Example 2 is that the first reaction and the second reaction are not carried out in the comparative example, and the antibacterial, heavy metal adsorption and scale inhibition effects are all exerted by the base material itself. It can be seen from the data in Table 1 that the effects in all aspects are very limited and cannot be directly applied to water treatment.

[0098] Compared with Example 1, Comparative Example 3 differs only in that the second reaction is not performed. Combining the data of Table 1 and Table 2, it can be seen that in the initial state, it has certain antibacterial and heavy metal adsorption capabilities, but after a period of use, for example, after passing through 8t of water, its antibacterial rate against Escherichia coli is only 41.35% of the initial state, and the antibacterial effect on Staphylococcus aureus and the adsorption capacity of heavy metals have also decreased to a certain extent. It can be seen that the combination of the active ingredient and the substrate is not strong enough, and there is a certain degree of loss of active ingredients. This may be because the amine substances in the present invention are all polyamines, and the amino groups provided by them can react chemically with the ester groups on the substrate to fix them to the substrate; on the other hand, they can also react with some carboxyl groups to firmly fix the substances containing carboxyl groups, so that the modified grid has both antibacterial effects and heavy metal adsorption effects, and can also maintain good stability.

[0099] Compared with Example 1, Comparative Example 4 differs only in that the first reaction is not performed. Combining the data in Table 1 and Table 2, it can be seen that the antibacterial effect and heavy metal adsorption capacity in the initial state are already very poor. After a period of use, with the loss of effective ingredients, the antibacterial effect and heavy metal adsorption capacity become worse. In addition, due to the loss of organic acid components, the scale inhibition ability of the modified grid is weakened, causing the pores of the grid to be blocked, resulting in a significant reduction in water flow.

[0100] It can be seen from the data of Example 1 and Examples 3-5 that changing the dosage of amine substances will also have a great impact on the results. Too much or too little amine substances are not conducive to scale inhibition, antibacterial and heavy metal adsorption.

[0101] It can be seen from the data of Examples 2 and 6-8 that the relative amounts of amine substances and organic acids also affect various aspects of the performance of the grid. When the amount of organic acid is too large, it may react chemically with more amino groups, thereby affecting the water treatment effect and the water flow rate.

Claims

1. A modified grid, characterized in that: The invention comprises a base layer and a functional layer; the functional layer is provided with amino groups and carboxyl groups; and the base layer and the functional layer are combined in a covalent bond manner.

2. The modified grid as claimed in claim 1, characterized in that: The material of the base layer is polyester, such as one or more of polymethyl methacrylate, polybutylene terephthalate and polyethylene terephthalate; And / or, the amino groups are uniformly distributed on the functional layer.

3. A method for preparing a modified grid, characterized in that: The method comprises the following steps: a base layer is subjected to a first reaction with an amine substance, and then subjected to a second reaction with an organic acid to form a functional layer on the base layer, thereby obtaining the modified grid.

4. The method for preparing the modified grid as claimed in claim 3, characterized in that: The amine substance is a polyamine, such as one or more of polyethyleneimine, chitosan, polyvinyl imidazole, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine; Preferably, the amine substance is polyethyleneimine and / or chitosan; and / or, the molecular weight of the amine substance is 7000-100000 g / mol, for example 10000 g / mol or 70000 g / mol; and / or, the molecular weight of the organic acid is 10000-100000 g / mol, for example 20000 g / mol or 50000 g / mol; and / or, the organic acid is a macromolecular organic acid, such as one or more of polyacrylic acid, polyaspartic acid, humic acid and hyaluronic acid; Preferably, the organic acid is polyacrylic acid and / or polyaspartic acid.

5. The modified grid as claimed in claim 3, characterized in that: The mass ratio of the amine substance to the base layer is (1-10):1, for example, 1:1, 3:1, 5:1 or 10:1; And / or, the molar ratio of the amine substance to the organic acid is 1:(0.1-5), for example, 1:0.1, 1:1, 1:2 or 1:

5.

6. The method for preparing the modified grid as claimed in claim 3, characterized in that: The amine substance is subjected to the first reaction in the form of an aqueous solution of the amine substance; Preferably, the concentration of the amine substance in the aqueous solution of the amine substance is 1wt.%-10wt.%, for example, 2wt.% or 9wt.%; Preferably, the pH of the aqueous solution of the amine substance is 10-13, preferably 11-13, for example 12; and / or, the organic acid is used in the form of an organic acid aqueous solution for the second reaction; Preferably, the concentration of the organic acid in the organic acid aqueous solution is 1 wt.%-5 wt.%, for example, 1 wt.% or 4 wt.%.

7. The method for preparing the modified grid as claimed in claim 3, characterized in that: The temperature of the first reaction is 60°C-90°C, for example 60°C or 85°C; And / or, the first reaction time is 2h-10h, such as 3h or 9h; and / or, the temperature of the second reaction is 50°C-80°C, such as 50°C or 70°C; And / or, the second reaction time is 5h-12h, such as 5h or 11h.

8. A modified grid, characterized in that: It is prepared by the preparation method described in any one of claims 3 to 7.

9. A filter element, characterized in that: It comprises the modified grid as claimed in any one of claims 1 , 2 and 8 .

10. Use of the modified grid as claimed in any one of claims 1, 2 and 8 or the filter element as claimed in claim 9 in the field of water treatment.

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