Visual detection method for membrane layer binding force of ultrafiltration membrane

Abstract

The invention discloses a visual detection method for membrane layer binding force of an ultrafiltration membrane. The method comprises the following steps: fixing the ultrafiltration membrane on a stainless steel plate, drawing checks and transverse lines by using a cross-cut knife, pressing by using a hand-push roller after attaching a test adhesive tape, stripping the adhesive tape by using a tensile machine after applying weight pressure, and observing the number of reserved membrane layers in the checks so as to evaluate the binding force. According to the method, simple equipment is adopted, the bonding strength of the membrane layer and the supporting layer is rapidly detected by optimizing parameters, the test result is consistent with the backwashing performance, guidance is provided for preparing the backwashing-resistant ultrafiltration membrane, the research and development period is shortened, and the technical efficiency of the water treatment membrane is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and particularly relates to a visual detection method for the bonding strength of the ultrafiltration membrane layer. Background Art

[0002] In the water treatment industry, ultrafiltration membranes are widely used in the fields of sewage treatment and water resource reuse due to their efficient filtration performance. As a new water treatment technology that combines a membrane separation unit and a biological treatment unit, the Membrane Bio-Reactor (MBR for short) can significantly improve the water treatment efficiency and the quality of the effluent. However, during the long-term operation of the flat membranes used in the MBR system, the filtration ability of the membranes gradually decreases due to pollutant adsorption and membrane pore blockage. To restore the performance of the membranes, it is usually necessary to clean the membranes. In the prior art, the commonly used cleaning method is to disassemble the membrane module from the equipment, perform shutdown cleaning, and cooperate with chemical cleaning agents for treatment. This method has the following problems: First, shutdown cleaning reduces the continuous operation ability of the equipment and affects the treatment efficiency; second, frequent use of chemical cleaning agents increases the operating cost and causes a certain degree of environmental pollution. Therefore, how to reduce the degree of membrane pollution and the cleaning frequency has become a key technical requirement for improving the efficiency of the MBR system.

[0003] To solve the above problems, an online cleaning technology for MBR flat membranes has been developed abroad. This technology flushes away the pollutants blocked in the membrane pores and adhered to the membrane surface by introducing reverse water flow during operation, thereby extending the service life of the membranes and improving the treatment capacity of the MBR membrane module. However, the MBR membrane sheets produced in China generally have the defect that they cannot withstand online backwashing, and the bonding strength between the membrane layer and the support layer is not sufficient to resist the impact of the backwashing water flow, resulting in membrane layer peeling or performance damage. This technical bottleneck significantly restricts the popularization and application of domestic MBR flat membranes. Therefore, developing MBR membrane sheets that can be backwashed online and establishing corresponding performance evaluation methods have become urgent technical problems to be solved in this field.

[0004] Currently, the commonly used method for evaluating the online backwashing ability of MBR membrane sheets is to prepare the membrane sheets into membrane modules and then place them in the actual operating environment for long-term testing, and obtain feedback data by observing the peeling situation of the membrane layer under backwashing conditions. This method has significant deficiencies: First, the testing period is long, and it usually takes several weeks or even months to obtain reliable results, with low efficiency; second, it relies on actual operating data and lacks controllable laboratory testing means, making it difficult to quickly optimize the performance of the membrane sheets during the R & D stage. These defects seriously hinder the R & D progress and industrial application of MBR membrane technology. Therefore, developing a rapid and accurate detection method to evaluate the online backwashing ability of MBR membrane sheets has become an urgent need for the current technological development. Summary of the Invention

[0005] The object of the present invention is to overcome the defects of the prior art and provide a visual detection method for the bonding strength of the ultrafiltration membrane layer.

[0006] The technical solution of the present invention is as follows:

[0007] A visual detection method for the bonding strength of the ultrafiltration membrane layer, comprising the following steps:

[0008] (1) Fix the ultrafiltration membrane to be tested on the first stainless steel plate with the membrane surface facing upwards.

[0009] (2) Use a cross cutter to scratch squares on the surface layer of the ultrafiltration membrane to be tested, ensuring that the blade of the cross cutter penetrates through the membrane layer to the support layer.

[0010] (3) Draw a horizontal line at a certain distance from the squares, also penetrating through the membrane layer to the support layer.

[0011] (4) Attach a 3M test tape to the surface of the ultrafiltration membrane to be tested, covering the scratched area.

[0012] (5) Use a hand-pushed roller to press the 3M test tape firmly to ensure full adhesion between the 3M test tape and the ultrafiltration membrane to be tested.

[0013] (6) Place a second stainless steel plate and a 1 - 2 kg weight on the 3M test tape, apply pressure and start timing.

[0014] (7) After the timing ends, remove the weight and the second stainless steel plate, and use a tensile machine to quickly peel the tape in a 180° peeling manner at a peeling speed of 5 - 20 m / s.

[0015] (8) Observe the remaining quantity of the membrane layer after peeling within the squares to evaluate the bonding strength between the membrane layer and the support layer.

[0016] In a preferred embodiment of the present invention, the cross cutter has 6 teeth with a tooth pitch of 3 ± 0.01 mm.

[0017] In a preferred embodiment of the present invention, the flatness of the first stainless steel plate and the second stainless steel plate is less than or equal to 0.1 mm, the roughness is less than or equal to 0.6 μm, the thickness is 1.5 - 2 mm, and the size is 12 × 6 cm.

[0018] In a preferred embodiment of the present invention, the weight of the hand-pushed roller is 1 kg.

[0019] In a preferred embodiment of the present invention, the test tape is a 3M tape with a width of 20 mm.

[0020] In a preferred embodiment of the present invention, the size of the ultrafiltration membrane to be tested is 6 - 8 × 4 - 6 cm.

[0021] In a preferred embodiment of the present invention, the weight of the weight is 2 kg.

[0022] In a preferred embodiment of the present invention, the peeling speed of the tensile machine is 10 m / s.

[0023] In a preferred embodiment of the present invention, the squares marked in step (2) are 5×5 squares, and the horizontal line is 1 cm away from the squares.

[0024] In a preferred embodiment of the present invention, the pressure application time in step (6) is 30 - 60 s.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. By combining the cross-cutting with a cross-hatch cutter and the tape peeling test, the present invention can complete the detection of the film layer adhesion force in a short time. Compared with the method in the prior art that requires the film sheet to be prepared into a component and then undergoes a running test for several weeks, the evaluation cycle is significantly shortened. This rapid detection ability accelerates the verification process from research and development to application, and improves the efficiency of technology development.

[0027] 2. By optimizing parameters such as the pitch of the cross-hatch cutter teeth, the flatness of the stainless steel plate, the weight of the weight, and the peeling speed of the tensile machine, the present invention simulates the actual stress on the film layer under on-line backwashing conditions. The test results are highly consistent with the performance of the film sheet in the actual backwashing environment, providing a reliable prediction basis for the on-line backwashing ability of the film sheet.

[0028] 3. The equipment used in the present invention includes a cross-hatch cutter, a stainless steel plate, a hand-push roller, a test tape, etc. The structure is simple and easy to obtain, and the test process can be completed without complex instruments or highly skilled operators. This simplicity makes it easy to promote and apply in laboratories and production sites.

[0029] 4. By observing the remaining quantity of the film layer after peeling in the cross-cut area, the present invention provides a quantitative index for the film layer adhesion force. This index can directly guide the optimization of the preparation process of the MBR film sheet, helping R & D personnel quickly screen out the film sheet formulations and process parameters with on-line backwashing ability, thereby improving the quality and production efficiency of the film sheet.

[0030] 5. By accurately evaluating and improving the on-line backwashing ability of the film sheet, the present invention helps to prepare MBR film sheets resistant to backwashing, thereby reducing the cleaning frequency and the usage amount of chemical cleaning agents during operation. This not only reduces the operation cost but also reduces the environmental pollution, meeting the requirements of green and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a side view of the test component in Embodiment 1 of the present invention.

[0032] Figure 2 It is the top view of the test component in Embodiment 1 of the present invention. Specific embodiments

[0033] The technical solution of the present invention will be further described and illustrated below through specific embodiments in conjunction with the accompanying drawings.

[0034] Embodiment 1

[0035] In this embodiment, the ultrafiltration membrane to be tested is tested according to the actual application scenario. During the backwashing process, different backwashing pressures are adjusted. After running for 30 minutes, the bonding condition between the filtration membrane layer and the non-woven fabric support layer in the ultrafiltration membrane to be tested is detected. The specific steps are as follows:

[0036] (1) Fix the ultrafiltration membrane to be tested (membrane) with dimensions of 8×6 cm or 6×4 cm on the first stainless steel plate (steel plate 1), with the membrane surface facing up;

[0037] (2) Use a cross cutter to draw a 5×5 grid on the surface layer of the above-mentioned ultrafiltration membrane to be tested, ensuring that the blade of the cross cutter penetrates the membrane layer to the support layer; the cross cutter has a 6-tooth blade, and the tooth pitch is 3±0.01 mm

[0038] (3) Draw a horizontal line 1 cm away from the above-mentioned 5×5 grid, also penetrating the membrane layer to the support layer;

[0039] (4) Attach a 3M test tape with a width of 20 mm to the surface of the ultrafiltration membrane to be tested, covering the scratched area;

[0040] (5) Use a hand roller with a weight of 1 kg to press the 3M test tape to ensure full adhesion between the 3M test tape and the ultrafiltration membrane to be tested;

[0041] (6) Place a second stainless steel plate (steel plate 2) and a weight of 1-2 kg on the above-mentioned 3M test tape to form a test component as shown in Figure 1 and Figure 2 Apply pressure and time for 30-60 s;

[0042] (7) After the timing ends, remove the weight and the second stainless steel plate, and use a tensile machine to quickly peel the tape in a 180° peeling manner (refer to GB / T 4851 "Test Method for Peel Strength of Adhesive Tape"), and the peeling speed is 10 m / s;

[0043] (8) Observe the remaining quantity of the membrane layer within the above-mentioned 5×5 grid after peeling. The more the remaining quantity, the higher the bonding strength;

[0044] The flatness of the above-mentioned first stainless steel plate and second stainless steel plate is less than or equal to 0.1 mm, the roughness is less than or equal to 0.6 μm, the thickness is 1.5 - 2 mm, and the size is 12×6 cm.

[0045] The results obtained based on the above tests are shown in Tables 1 to 3 below:

[0046] Table 1: 1 kg weight, applying pressure and timing for 30 s

[0047] Number of tape peelings / piece Percentage / % Backwashing pressure / kPa Diaphragm detachment condition Whether the backwashing requirement is met 25 100％ 0 Complete detachment No 20 80％ 5 Complete detachment No 15 60％ 10 Partial detachment No 10 40％ 10 Partial detachment Partially met 5 20％ 12 Not detached Partially met 0 0％ 15 Not detached Met

[0048] Table 2: 1 kg weight, applying pressure and timing for 60 s

[0049] Number of tape peelings / piece Percentage / % Backwashing pressure / kPa Diaphragm detachment condition Whether the backwashing requirement is met 25 100％ 0 Complete detachment No 20 80％ 6 Complete detachment No 15 60％ 7 Partial detachment No 10 40％ 12 Partial detachment Partially met 5 20％ 15 Not detached Partially met 0 0％ 25 Not detached Met

[0050] Table 3: 2 kg weight, applying pressure and timing for 30 s

[0051]

[0052]

[0053] As mentioned above, it is only the preferred embodiment of the present invention, so the scope of implementation of the present invention cannot be limited thereby. That is, equivalent changes and modifications made according to the scope of the present invention patent and the content of the specification should still fall within the scope covered by the present invention.

Claims

1. A visual detection method for the binding force of an ultrafiltration membrane layer, characterized in that: It includes the following steps: (1) Fix the ultrafiltration membrane to be tested on the first stainless steel plate with the membrane surface facing upward; (2) Use a cross cutter to scribe squares on the surface of the ultrafiltration membrane to be tested, ensuring that the blade of the cross cutter penetrates through the membrane layer to the support layer; (3) Draw a horizontal line at a certain distance from the squares, also penetrating through the membrane layer to the support layer; (4) Attach a 3M test tape to the surface of the ultrafiltration membrane to be tested, covering the scratched area; (5) Use a hand roller to press the 3M test tape firmly to ensure full contact between the 3M test tape and the ultrafiltration membrane to be tested; (6) Place a second stainless steel plate and a 1 - 2 kg weight on the 3M test tape, apply pressure and start timing; (7) After the timing ends, remove the weight and the second stainless steel plate, and use a tensile machine to quickly peel the tape in a 180° peeling manner, with a peeling speed of 5 - 20 m / s; (8) Observe the remaining number of the membrane layer after peeling within the squares to evaluate the bonding strength between the membrane layer and the support layer.

2. The visual detection method according to claim 1, characterized in that: The cross cutter has 6 - tooth blades with a tooth pitch of 3 ± 0.01 mm.

3. The visual detection method according to claim 1, wherein: The flatness of the first stainless steel plate and the second stainless steel plate is less than or equal to 0.1 mm, the roughness is less than or equal to 0.6 μm, the thickness is 1.5 - 2 mm, and the size is 12×6 cm.

4. The visual detection method according to claim 1, characterized in that: The weight of the hand roller is 1 kg.

5. The visual inspection method according to claim 1, characterized in that: The test tape is 3M tape with a width of 20 mm.

6. The visual inspection method according to claim 1, characterized in that: The size of the ultrafiltration membrane to be tested is 6 - 8×4 - 6 cm.

7. The visual detection method according to claim 1, characterized in that: The weight of the weight is 2 kg.

8. The visual inspection method according to claim 1, characterized in that: The peeling speed of the tensile machine is 10 m / s.

9. The visual detection method according to claim 1, wherein: The squares scribed in step (2) are 5×5 grids, and the horizontal line is 1 cm away from the squares.

10. The visual detection method according to claim 1, characterized in that: The pressure application time in step (6) is 30 - 60 s.

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