Ultrafiltration membrane assembly as well as preparation method and application thereof

Abstract

The invention provides an ultrafiltration membrane assembly as well as a preparation method and application thereof. The ultrafiltration membrane assembly comprises an ultrafiltration membrane and a floc functional layer loaded on the ultrafiltration membrane. According to the invention, the floc functional layer structure on the ultrafiltration membrane assembly is regulated and controlled by selecting a proper coagulant and adjusting the dosage of the coagulant and the pH value in the coagulation process, so that typical new pollutants are efficiently removed by a low-consumption-short-range water purification process, and the cost of the traditional nanofiltration, reverse osmosis and other enhanced new pollutant removal processes is effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment and membrane pollution control, and relates to an ultrafiltration membrane component, in particular to an ultrafiltration membrane component and a preparation method and application thereof. Background Art

[0002] The extensive use of chemicals has resulted in the continuous detection of a variety of new pollutants such as antibiotics and environmental endocrine disruptors in surface waters and even drinking water sources. Since they are difficult to be effectively removed by conventional processes such as coagulation, they have gradually become the focus of global drinking water treatment. Membrane technology is currently a more advanced water treatment technology. Nanofiltration and reverse osmosis can effectively intercept new pollutants due to their nano and sub-nano structures, but they often face problems such as high energy consumption, high water production costs, low water production rates, and difficulties in concentrated water treatment. The pore size of the ultrafiltration membrane is large, making it difficult to effectively intercept new pollutants. However, the ultrafiltration membrane will inevitably form a filter cake layer during operation. The complex channels and active adsorption sites on it can also effectively adsorb and intercept subsequent pollutants, thereby improving the water quality of the ultrafiltration process. By adjusting the dosage of coagulant or the pH of the coagulation process, the size and characteristics of the flocs can be effectively regulated, thereby affecting the structure of the filter cake layer.

[0003] CN 106861445A discloses a low-pressure membrane water treatment process based on a "sandwich" loose floc protective layer. The process adopts an integrated membrane coagulation reactor. The coagulant is injected into the membrane tank through a coagulant dosing tank, so that the coagulant hydrolyzes the flocs to form a "sandwich" loose protective layer on the membrane surface. The raw water enters the membrane tank and is adsorbed by the floc layer and treated by the membrane before being discharged. The experimental results verify that the loose floc layer can effectively remove smaller molecular humic acid (about 3kDa) and alleviate membrane pollution to a certain extent.

[0004] CN 112960864A discloses an ultrafiltration membrane assembly and its application method in an ultrafiltration system, which is mainly used to remove soluble pollutants in water. The ultrafiltration membrane assembly includes an ultrafiltration membrane and a multifunctional filter cake layer loaded on its surface, wherein the multifunctional filter cake layer contains a biofilm composed of nitrifying bacteria and / or manganese oxidizing bacteria. These biofilms can convert ammonia nitrogen into nitrate nitrogen and convert manganese ions into manganese dioxide. In addition, the adsorption structure can remove heavy metal ions. However, this method has many disadvantages. First, the method is heavily dependent on the activity of the biofilm. The pH, temperature and content of toxic and harmful substances in the influent will affect the activity of the microorganisms, thereby affecting the removal effect of the pollutants. Secondly, the removal efficiency of pollutants in water by the microorganisms in the filter cake layer is limited, and the effect and cost-effectiveness in large-scale water treatment applications need to be verified.

[0005] Therefore, it is necessary to provide a low-cost, low-energy and efficient water purification method. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an ultrafiltration membrane assembly and a preparation method and application thereof. The present invention regulates the structure of the floc functional layer on the ultrafiltration membrane assembly by selecting a suitable coagulant, adjusting the dosage of the coagulant and the pH of the coagulation process, thereby effectively reducing the cost of traditional nanofiltration, reverse osmosis and other enhanced processes for removing new pollutants while achieving a low-cost and short-range water purification process to efficiently remove typical new pollutants.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides an ultrafiltration membrane assembly, comprising an ultrafiltration membrane and a flocculent functional layer supported on the ultrafiltration membrane.

[0009] As a preferred technical solution of the present invention, the raw materials for preparing the flocculent functional layer include humic acid stock solution, kaolin stock solution and iron-containing compounds.

[0010] In the present invention, the humic acid in the floc functional layer simulates the natural organic matter in the water body, the kaolin simulates the turbidity in the water body, and the Fe 3+ The hydroxide formed by hydrolysis and humic acid form a floc mixture, which is then loaded onto the surface of the ultrafiltration membrane to form a floc functional layer. The complex water channels and adsorption sites in the floc functional layer jointly achieve effective removal of new pollutants (such as trimethoprim).

[0011] In a second aspect, the present invention provides a method for preparing the ultrafiltration membrane assembly as described in the first aspect, the preparation method comprising the following steps:

[0012] (1) mixing simulated surface water and a coagulant, and then sequentially performing a first stirring and a second stirring to obtain a mixed solution; the first stirring is accompanied by acid-base adjustment;

[0013] (2) Using the pretreated ultrafiltration membrane to ultrafilter the mixed solution obtained in step (1) to obtain the ultrafiltration membrane assembly.

[0014] In the present invention, the mixed solution obtained by the coagulation process provided in step (1) contains flocs formed by the hydrolysis of the coagulant and humic acid, etc., and then the effective ingredients are retained and loaded through the ultrafiltration process, further improving the ultrafiltration water purification efficiency.

[0015] As a preferred technical solution of the present invention, the turbidity of the simulated surface water in step (1) is 3 to 8 NTU, for example, it can be 3NTU, 3.5NTU, 4NTU, 4.5NTU, 5NTU, 5.5NTU, 6NTU, 6.5NTU, 7NTU, 7.5NTU or 8NTU, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] Preferably, the total organic carbon concentration of the simulated surface water in step (1) is 5 to 10 mg / L, for example, it can be 5 mg / L, 5.5 mg / L, 6 mg / L, 6.5 mg / L, 7 mg / L, 7.5 mg / L, 8 mg / L, 8.5 mg / L, 9 mg / L, 9.5 mg / L or 10 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0017] Preferably, the raw materials for preparing the simulated surface water in step (1) include humic acid solution, kaolin stock solution and ultrapure water.

[0018] Preferably, the concentration of humic acid in the simulated surface water is 0.005-0.03 g / L, for example, it can be 0.01 g / L, 0.015 g / L, 0.02 g / L, 0.025 g / L or 0.03 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the concentration of kaolin in the simulated surface water is 5 to 10 mg / L, for example, it can be 5 mg / L, 5.5 mg / L, 6 mg / L, 6.5 mg / L, 7 mg / L, 7.5 mg / L, 8 mg / L, 8.5 mg / L, 9 mg / L, 9.5 mg / L or 10 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] As a preferred technical solution of the present invention, the coagulant in step (1) includes ferric chloride solution or ferric sulfate solution.

[0021] In the present invention, the humic acid content, kaolin content and coagulant content in the mixed solution of step (2) will affect the formation of the flocculent functional layer in the ultrafiltration membrane assembly and the removal effect of pollutants (such as trimethoprim);

[0022] Among them, the content of humic acid will affect the thickness of the formed floc functional layer; the content of kaolin will affect the turbidity of simulated surface water and the efficiency of floc formation in the coagulation process; the content of coagulant will affect the particle size of the floc and further affect the structure of the floc functional layer.

[0023] Preferably, the dosage ratio of the coagulant to simulated surface water in step (1) is 1 to 15 mg:1L, for example, it can be 1 mg:1L, 3 mg:1L, 5 mg:1L, 7 mg:1L, 9 mg:1L, 11 mg:1L, 13 mg:1L or 15 mg:1L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] As a preferred technical solution of the present invention, the reagent used in the acid-base adjustment in step (1) includes hydrochloric acid or sodium hydroxide.

[0025] Preferably, the pH value of the mixed solution in step (1) is 6 to 7, for example, 6, 6.2, 6.4, 6.6, 6.8 or 7, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] In the present invention, the pH value of the mixed solution will affect the formation of the floc functional layer in the ultrafiltration membrane assembly and the removal effect of pollutants (such as trimethoprim); the pH value will affect the size and characteristics of the flocs formed in the coagulation process: if the pH value is too low, the floc particle size will be smaller, the specific surface area will be larger, the formed floc functional layer will be denser, and the adsorption and retention effect of new pollutants will be enhanced; if the pH value is too high, the floc particle size will be larger, the formed floc functional layer will be looser, and the adsorption and retention effect of new pollutants will be weakened.

[0027] Preferably, the rotation speed of the stirring in step (1) is 150 to 250 r / min, for example, it can be 150 r / min, 170 r / min, 190 r / min, 210 r / min, 230 r / min or 250 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, the stirring time in step (1) is 1.5 to 2.5 min, for example, 1.5 min, 1.7 min, 1.9 min, 2.1 min, 2.3 min or 2.5 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the rotation speed of the secondary stirring in step (1) is 30 to 80 r / min, for example, it can be 30 r / min, 40 r / min, 50 r / min, 60 r / min, 70 r / min or 80 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, the secondary stirring time in step (1) is 12 to 18 minutes, for example, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes or 18 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] In the present invention, the first stirring is rapid stirring, the purpose of which is to make the system mix evenly; the second stirring is slow stirring, the purpose of which is to make the flocs grow gradually. The present invention achieves efficient mixing of the medium in the mixed solution through the two stirring processes, avoiding the influence of the treatment effect of subsequent new pollutants due to the uneven functional layer of the prepared flocs.

[0032] As a preferred technical solution of the present invention, the pretreatment in step (2) includes: soaking the ultrafiltration membrane in ultrapure water and filtering the ultrafiltration membrane in sequence.

[0033] Preferably, the immersion treatment time is 10 to 15 hours, for example, it can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the ultrapure water is replaced 2 to 5 times during the immersion treatment, for example, 2 times, 3 times, 4 times or 5 times.

[0035] Preferably, the amount of ultrapure water used in the filtration treatment is 250-350 mL, for example, 250 mL, 270 mL, 290 mL, 310 mL, 330 mL or 350 mL, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the pore size range of the ultrafiltration membrane is 20 to 50 nm, for example, it can be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] The ultrafiltration membrane used in the preparation process of the ultrafiltration membrane assembly of the present invention is a brand-new polyvinylidene fluoride (PVDF) ultrafiltration membrane. Impurities on the membrane surface can be effectively removed through a soaking treatment process, and the initial flux stability of the ultrafiltration membrane can be ensured through a filtering pretreatment process.

[0038] As a preferred technical solution of the present invention, the amount of the mixed solution in the ultrafiltration treatment in step (2) is 280-320 mL, for example, it can be 280 mL, 285 mL, 290 mL, 295 mL, 300 mL, 305 mL, 310 mL, 315 mL or 320 mL, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Preferably, the environmental pressure of the ultrafiltration treatment in step (2) is 0.005-0.15 MPa, for example, it can be 0.08 MPa, 0.09 MPa, 0.1 MPa, 0.11 MPa, 0.12 MPa, 0.13 MPa, 0.14 MPa or 0.15 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] In the present invention, an inert gas is used to maintain the environmental pressure during the ultrafiltration process; the inert gas includes any one of nitrogen, argon, neon or helium, or a combination of at least two of them; typical but non-limiting combinations include: a combination of nitrogen and argon, a combination of nitrogen and helium, a combination of argon and helium, or a combination of nitrogen, argon and helium.

[0041] As a preferred technical solution of the present invention, the method for preparing an ultrafiltration membrane assembly provided in the second aspect of the present invention comprises the following steps:

[0042] (1) Mix simulated surface water with a turbidity of 3-8 NTU and a total organic carbon concentration of 5-10 mg / L and a coagulant (Fe 3+ Then, the mixture was stirred for 1.5 to 2.5 minutes at a speed of 150 to 250 r / min, and stirred for 12 to 18 minutes at a speed of 30 to 80 r / min to obtain a mixed solution with a pH value of 6 to 7;

[0043] The primary stirring is accompanied by acid-base adjustment using hydrochloric acid or sodium hydroxide;

[0044] The raw materials for preparing the simulated surface water include humic acid solution, kaolin stock solution and ultrapure water; the concentration of humic acid in the simulated surface water is 0.01-0.03 g / L, and the concentration of kaolin is 5-10 mg / L;

[0045] (2) at an ambient pressure of 0.005 to 0.15 MPa, using a pretreated ultrafiltration membrane having a pore size range of 10 to 30 nm to ultrafilter 280 to 320 mL of the mixed solution obtained in step (1) to obtain the ultrafiltration membrane assembly;

[0046] The pretreatment comprises: soaking the ultrafiltration membrane in ultrapure water for 10 to 15 hours; and then filtering 250 to 350 mL of ultrapure water with the ultrafiltration membrane.

[0047] In a third aspect, the present invention provides an application of the ultrafiltration membrane assembly as described in the first aspect, the application comprising: using the ultrafiltration membrane assembly to ultrafiltration purify source water containing new pollutants;

[0048] The new contaminants in the source water include trimethoprim or atenolol.

[0049] More specifically, the application described in the third aspect of the present invention comprises the following steps: at an ambient pressure of 0.08 to 0.15 MPa, ultrafiltration treatment is performed on source water containing new pollutants using the ultrafiltration membrane assembly provided by the first aspect of the present invention.

[0050] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The ultrafiltration membrane assembly provided by the present invention can achieve efficient purification of source water containing new pollutants, and the new pollutant removal rate can reach more than 95%;

[0053] (2) The ultrafiltration membrane assembly provided by the present invention achieves a higher purification efficiency through a lower coagulant dosage, and is expected to replace conventional long-process and high-pressure membrane-enhanced water purification processes such as nanofiltration and reverse osmosis to remove new pollutants;

[0054] (3) The preparation method of the ultrafiltration membrane assembly provided by the present invention is simple, and realizes a low-consumption and short-range water purification process to efficiently remove typical new pollutants while effectively reducing the cost of traditional nanofiltration, reverse osmosis and other enhanced processes for removing new pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a diagram showing the removal effect of trimethoprim by the method provided in Application Examples 1-15 of the present invention;

[0056] Figure 2 This is a diagram showing the removal effect of trimethoprim by the method provided in comparative application example 1 of the present invention under different coagulant dosages or pH conditions;

[0057] Figure 3 This is the removal effect of trimethoprim by the method provided in Comparative Application Example 2 of the present invention under different coagulant dosages or pH conditions. DETAILED DESCRIPTION

[0058] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0059] Example 1

[0060] This embodiment provides an ultrafiltration membrane assembly, which includes an ultrafiltration membrane and a flocculent functional layer supported on the ultrafiltration membrane;

[0061] The raw materials for preparing the flocculent functional layer include humic acid, kaolin stock solution and iron-containing compounds.

[0062] The preparation method of the ultrafiltration membrane assembly comprises the following steps:

[0063] (1) Mixing simulated surface water with a turbidity of 5 NTU and a total organic carbon concentration of 7.5 mg / L and 0.1 mol / L ferric chloride at a ratio of 1 L:2.5 mg, and then stirring for 2 min at 200 r / min and stirring for 15 min at 50 r / min to obtain a mixed solution with a pH value of 6;

[0064] During the stirring, 0.1 mol / L hydrochloric acid and sodium hydroxide are used for acid-base adjustment;

[0065] The raw materials for preparing the simulated surface water include humic acid solution, kaolin stock solution and ultrapure water; the concentration of humic acid in the simulated surface water is 0.02 g / L, and the concentration of kaolin is 7.5 mg / L;

[0066] (2) Under an ambient pressure of 0.1 MPa, 300 mL of the mixed solution obtained in step (1) is ultrafiltered using an ultrafiltration membrane having a pore size range of 10 to 30 nm after pretreatment to obtain the ultrafiltration membrane assembly;

[0067] The pretreatment includes: soaking the ultrafiltration membrane in ultrapure water for 12 hours; and then filtering 300 mL of ultrapure water with the ultrafiltration membrane.

[0068] Example 2-18

[0069] An ultrafiltration membrane assembly, comprising an ultrafiltration membrane and a flocculent functional layer supported on the ultrafiltration membrane;

[0070] The difference between the preparation method of the ultrafiltration membrane assembly and that of Example 1 is that the amount of coagulant added or the pH of the mixed solution is different, as shown in Table 1:

[0071] Table 1

[0072] Coagulant addition amount / mg pH value of mixed solution Example 2 2.5 7 Example 3 2.5 8 Example 4 1 6 Example 5 1 7 Example 6 1 8 Example 7 5 6 Example 8 5 7 Example 9 5 8 Example 10 10 6 Embodiment 11 10 7 Example 12 10 8 Example 13 15 6 Embodiment 14 15 7 Embodiment 15 15 8 Example 16 20 6 Embodiment 17 2.5 5 Embodiment 18 2.5 9

[0073] Embodiment 19

[0074] This embodiment provides an ultrafiltration membrane assembly, which includes an ultrafiltration membrane and a flocculent functional layer supported on the ultrafiltration membrane;

[0075] The difference between the preparation method of the ultrafiltration membrane assembly and that of Example 1 is that:

[0076] In this embodiment, the stirring speed of the first stirring in step (1) is adjusted to 50 r / min and the stirring time is 2 min.

[0077] Embodiment 20

[0078] This embodiment provides an ultrafiltration membrane assembly, which includes an ultrafiltration membrane and a flocculent functional layer supported on the ultrafiltration membrane;

[0079] The difference between the preparation method of the ultrafiltration membrane assembly and that of Example 1 is that:

[0080] In this embodiment, the secondary stirring speed in step (1) is adjusted to 200 r / min for 15 min.

[0081] Embodiment 21

[0082] This embodiment provides an ultrafiltration membrane assembly, which includes an ultrafiltration membrane and a flocculent functional layer supported on the ultrafiltration membrane;

[0083] The difference between the preparation method of the ultrafiltration membrane assembly and that of Example 1 is that:

[0084] In this embodiment, the raw materials for preparing the simulated surface water in step (1) are adjusted to: humic acid solution and ultrapure water, and the concentration of humic acid in the simulated surface water is 0.05 g / L.

[0085] Embodiment 22

[0086] This embodiment provides an ultrafiltration membrane assembly, which includes an ultrafiltration membrane and a flocculent functional layer supported on the ultrafiltration membrane;

[0087] The difference between the preparation method of the ultrafiltration membrane assembly and that of Example 1 is that:

[0088] In this embodiment, the raw materials for preparing the simulated surface water in step (1) are adjusted to: kaolin stock solution and ultrapure water, and the concentration of kaolin in the simulated surface water is 10 mg / L.

[0089] Comparative Example 1

[0090] This comparative example provides an ultrafiltration membrane assembly, which differs from Example 1 only in that:

[0091] The floc functional layer is omitted in this comparative example, that is, this comparative example provides a pre-treated ultrafiltration membrane.

[0092] Comparative Example 2

[0093] This comparative example provides an ultrafiltration membrane assembly, and the preparation method of the ultrafiltration membrane assembly is different from that of Example 1 only in that:

[0094] In this comparative example, the mixed solution in step (1) is adjusted to simulate surface water, that is, the process of mixing the coagulant is omitted in this comparative example.

[0095] Application Example 1

[0096] This application example provides a method for purifying wastewater using the ultrafiltration membrane assembly provided in Example 1, the method comprising the following steps:

[0097] Under an environmental pressure of 0.1 MPa, 300 mL of new pollutant source water was ultrafiltered and purified using the ultrafiltration membrane assembly provided in Example 1; the pollutant in the source water was trimethoprim; and the concentration of the trimethoprim was 1 μg / L.

[0098] Application Example 2-22

[0099] A method for purifying wastewater using the ultrafiltration membrane assembly provided in Example 2-22, the method being the same as that in Application Example 1.

[0100] Comparative application example 1

[0101] This comparative application example provides a method for purifying source water containing new pollutants using the ultrafiltration membrane assembly provided in Comparative Example 1, the method comprising the following steps:

[0102] Mix 1.5 mL of a 200 μg / L trimethoprim stock solution, 300 mL of the simulated surface water provided in Example 1, and ferric chloride, and then stir once at 200 r / min for 2 min, stir twice at 50 r / min for 15 min, let stand for 20 min, and take the supernatant as the effluent from the coagulation process.

[0103] Wherein, during the rapid stirring process, 0.1 mol / L hydrochloric acid or sodium hydroxide is used to adjust the pH value of the coagulation process.

[0104] Comparative Application Example 2

[0105] This comparative application example provides a method for purifying new pollutant source water using the ultrafiltration membrane assembly provided in Comparative Example 1, the method comprising the following steps:

[0106] 1.5 mL of a 200 μg / L trimethoprim stock solution, 300 mL of the simulated surface water and ferric chloride provided in Example 1 were mixed, and then stirred once for 2 min at a speed of 200 r / min, and stirred twice for 15 min at a speed of 50 r / min, and then the solution was ultrafiltered using the ultrafiltration membrane provided in Comparative Example 1 at an ambient pressure of 0.1 MPa.

[0107] Wherein, during the rapid stirring process, 0.1 mol / L hydrochloric acid or sodium hydroxide is used to adjust the pH value of the coagulation process.

[0108] Comparative Application Example 3

[0109] This comparative application example provides a method for purifying new pollutant source water using the ultrafiltration membrane assembly provided in Comparative Example 1, and the method is the same as that in Application Example 1.

[0110] Comparative Application Example 4

[0111] This comparative application example provides a method for purifying new pollutant source water using the ultrafiltration membrane assembly provided in Comparative Example 2, and the method is the same as that in Application Example 1.

[0112] Result analysis:

[0113] (1) The removal effect of trimethoprim by the method provided in Application Example 1-15 is as follows Figure 1 As shown;

[0114] (2) The removal rate of trimethoprim using the methods provided in Application Examples 16-22 and Comparative Application Examples 3-4 is shown in Table 2:

[0115] Table 2

[0116]

[0117]

[0118] (3) The removal effect of trimethoprim by the method provided in Comparative Application Example 1 under different coagulant dosages and / or pH conditions is as follows Figure 2 As shown;

[0119] (4) The removal effect of trimethoprim by the method provided in Comparative Application Example 2 under different coagulant dosages and / or pH conditions is as follows Figure 3 shown.

[0120] By analyzing Figure 1-3 From Table 2, we can see that:

[0121] Under the same conditions, the ultrafiltration membrane assembly provided by the present invention has the best removal capacity for trimethoprim. When the coagulant dosage is 1, 2.5 and 5 mg / L, under weakly acidic (pH=6) and neutral (pH=7) conditions, the ultrafiltration membrane assembly provided by the present invention can achieve a removal effect of more than 95% for trimethoprim;

[0122] From the analysis of application examples 1 and 19-20, it can be seen that the stirring method in the preparation process of the mixed solution affects the formation of the functional layer of the flocs; if slow stirring is used during the preparation process, the system will be unevenly mixed; if fast stirring is used during the preparation process, the flocs will be broken due to shear force and difficult to grow;

[0123] From the analysis of Application Examples 1 and Application Examples 21-22, it can be seen that the composition of the simulated surface water during the mixing process will affect the performance of the floc functional layer. If the simulated surface water does not contain humic acid, the uniformity of the formed floc functional layer will be poor, and the adsorption and interception effects on subsequent pollutants will be weakened; if the simulated surface water does not contain kaolin, but the concentration of corrosive acid is high (such as Application Example 21), after mixing with the coagulant, a large amount of free humic acid will still remain in the solution, which will then be deposited on the membrane, resulting in the formation of a denser and thicker floc functional layer. Although it has excellent removal ability for new pollutants, it will cause the membrane flux of the ultrafiltration membrane to decrease, seriously affecting the service life of the ultrafiltration membrane;

[0124] Analysis of Application Example 1 and Comparative Application Example 4 shows that when the coagulant is not mixed in step (1), humic acid and the like in the simulated water body will be tightly adsorbed on the surface of the ultrafiltration membrane, resulting in excellent removal ability for new pollutants. However, the tight adsorption of humic acid and other components will cause clogging of the ultrafiltration membrane, thereby causing serious membrane pollution, and the reduction of membrane flux will seriously affect the service life of the ultrafiltration membrane.

[0125] In addition, according to Figure 1-3 It can be seen that when the pH value of the mixed solution is too high (such as pH = 8), the purification effect of the ultrafiltration membrane assembly provided by the present invention on new pollutants becomes worse. It can be seen that the regulation of the pH of the system during the preparation process is one of the important factors that determine the purification effect of the ultrafiltration membrane assembly described in the present invention.

[0126] In summary, the present invention regulates the structure of the floc functional layer on the ultrafiltration membrane assembly by selecting a suitable coagulant, adjusting the dosage of the coagulant and the pH of the coagulation process, thereby achieving a low-consumption and short-range water purification process to efficiently remove typical new pollutants while effectively reducing the cost of traditional nanofiltration, reverse osmosis and other enhanced processes for removing new pollutants.

[0127] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. An ultrafiltration membrane assembly, characterized in that: The ultrafiltration membrane assembly comprises an ultrafiltration membrane and a flocculent functional layer loaded on the ultrafiltration membrane.

2. The ultrafiltration membrane assembly according to claim 1, characterized in that: The raw materials for preparing the flocculent functional layer include humic acid stock solution, kaolin stock solution and iron-containing compounds.

3. A method for preparing an ultrafiltration membrane assembly as claimed in claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) mixing simulated surface water and a coagulant, and then sequentially performing a primary stirring and a secondary stirring to obtain a mixed solution; the primary stirring is accompanied by acid-base adjustment; (2) Using the pretreated ultrafiltration membrane to ultrafilter the mixed solution obtained in step (1) to obtain the ultrafiltration membrane assembly.

4. The preparation method according to claim 3, characterized in that: The turbidity of the simulated surface water in step (1) is 3-8 NTU; Preferably, the total organic carbon concentration of the simulated surface water in step (1) is 5 to 10 mg / L; Preferably, the raw materials for preparing the simulated surface water in step (1) include humic acid stock solution, kaolin stock solution and ultrapure water; Preferably, the concentration of humic acid in the simulated surface water is 0.01 to 0.03 g / L; Preferably, the concentration of kaolin in the simulated surface water is 5-10 mg / L, and the turbidity is about 5 NTU.

5. The preparation method according to claim 3 or 4, characterized in that: The coagulant in step (1) comprises ferric chloride solution or ferric sulfate solution; Preferably, the Fe in the coagulant in step (1) 3+ The dosage ratio to simulated surface water is 1-15 mg:1L.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The reagent used in the acid-base adjustment in step (1) includes hydrochloric acid or sodium hydroxide; Preferably, the pH value of the mixed solution in step (1) is 6 to 7; Preferably, the stirring speed in step (1) is 150 to 250 r / min; Preferably, the stirring time in step (1) is 1.5 to 2.5 minutes; Preferably, the rotation speed of the secondary stirring in step (1) is 30 to 70 r / min; Preferably, the secondary stirring time in step (1) is 12 to 18 minutes.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The pretreatment in step (2) comprises: soaking the ultrafiltration membrane in ultrapure water and filtering the ultrafiltration membrane in sequence; Preferably, the soaking time is 10 to 15 hours; Preferably, the ultrapure water is replaced 2 to 5 times during the soaking process; Preferably, the amount of ultrapure water used in the filtration process is 250-350 mL; Preferably, the pore size of the ultrafiltration membrane is in the range of 20 to 50 nm.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The amount of the mixed solution used in the ultrafiltration treatment in step (2) is 280 to 320 mL; Preferably, the environmental pressure of the ultrafiltration treatment in step (2) is 0.05-0.15 MPa.

9. The preparation method according to any one of claims 3 to 8, characterized in that: The preparation method comprises the following steps: (1) Mix simulated surface water with a turbidity of 3-8 NTU and a total organic carbon concentration of 5-10 mg / L and a coagulant (Fe 3+ Then, the mixture was stirred for 1.5 to 2.5 minutes at a speed of 150 to 250 r / min, and stirred for 12 to 18 minutes at a speed of 30 to 80 r / min to obtain a mixed solution with a pH value of 6 to 7; The primary stirring is accompanied by acid-base adjustment using hydrochloric acid or sodium hydroxide; The raw materials for preparing the simulated surface water include humic acid stock solution, kaolin stock solution and ultrapure water; the concentration of humic acid in the simulated surface water is 0.01-0.03 g / L, the concentration of kaolin is 5-10 mg / L, and the turbidity is about 5 NTU; (2) at an ambient pressure of 0.05 to 0.15 MPa, using a pretreated ultrafiltration membrane having a pore size range of 20 to 50 nm to ultrafilter 280 to 320 mL of the mixed solution obtained in step (1) to obtain the ultrafiltration membrane assembly; The pretreatment comprises: soaking the ultrafiltration membrane in ultrapure water for 10 to 15 hours; and then filtering 250 to 350 mL of ultrapure water with the ultrafiltration membrane.

10. An application of the ultrafiltration membrane assembly as claimed in claim 1 or 2, characterized in that: The application includes: using the ultrafiltration membrane assembly to ultrafiltration purify source water containing new pollutants; The new contaminants in the source water include trimethoprim or atenolol.

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