Ethanol-micro-nano bubble synergistic penetration reinforced membrane cleaning method

Abstract

The application discloses an ethanol-micro-nano bubble synergistic penetration reinforced membrane cleaning method, and belongs to the technical field of membrane cleaning. The method comprises the following steps: (1) washing the contaminated membrane with water, completely immersing the washed contaminated membrane in an ethanol aqueous solution for 10-120 min, so that the membrane pollution layer is softened, swelled and loosened, and the stubborn pollutants are loosened; (2) blowing micro-nano bubbles into the ethanol aqueous solution in step (1), and removing the membrane pollutants by utilizing the micro-jet and shearing force generated by the bubble rising and breaking, and synergizing with ethanol; (3) stopping the micro-nano bubble supply, washing the membrane surface treated in step (2) with water in a forward cross flow until the washing liquid is free of ethanol residue, and the cleaning is completed. The method can realize efficient, deep and green cleaning of the contaminated membrane, and overcomes the double defects that the traditional physical cleaning is not complete and the chemical cleaning damages the membrane and the wastewater is difficult to treat.

Description

Technical Field

[0001] This invention belongs to the field of membrane cleaning technology, specifically relating to a membrane cleaning method that enhances permeation through ethanol-micro-nano bubbles. Background Technology

[0002] Membrane separation technology, with its advantages of high efficiency, energy saving, environmental friendliness, and high separation precision, has become one of the key technologies in the fields of material separation and water treatment, and is widely used in many industries such as municipal sewage treatment, industrial wastewater treatment, biomedicine, and food processing. However, during long-term continuous operation of membrane modules, impurities such as suspended particulate matter, colloidal substances, organic pollutants, and microorganisms in the water can easily adhere to and deposit on the membrane surface, or deeply block the membrane pores, leading to a series of problems such as membrane flux decline, separation performance degradation, and increased system energy consumption, significantly reducing the service life of the membrane elements. Therefore, efficient and green membrane cleaning technology is crucial to ensuring the long-term stable operation of membrane separation systems.

[0003] Currently, mainstream membrane cleaning methods are divided into two categories: physical cleaning and chemical cleaning. Conventional physical cleaning includes backwashing, air-water scrubbing, and ultrasonic cleaning, which have advantages such as simple operation, no chemical residue, and environmental friendliness. However, their mechanism of action is singular, and their ability to remove stubborn complex pollutants such as biofilms and sticky organic scale layers is insufficient, resulting in limited cleaning efficiency. Traditional acid-base chemical cleaning, while having strong decontamination capabilities and rapid cleaning results, relies on large amounts of acids, alkalis, oxidants, and other chemical agents. This not only increases the cost of cleaning consumables but also generates complex chemical-containing cleaning wastewater, significantly increasing the difficulty and cost of downstream wastewater treatment. At the same time, highly corrosive chemical agents can easily erode the membrane material's structure, causing irreversible damage to membrane performance and accelerating the aging and scrapping of membrane elements.

[0004] Micro-nano bubble technology, as a novel green physical cleaning method, has been gradually researched and applied in the field of membrane cleaning due to its unique advantages such as large specific surface area, high mass transfer efficiency, long residence time, and strong interfacial activity. For example, Chinese patent document CN118874225A discloses a method for online cleaning of MBR hollow fiber membranes using ozone micro-nano bubbles. This method uses ozone micro-nano bubbles with a dissolved ozone concentration of 0.1-1 mg / L for online maintenance cleaning, solving the problems of decreased activated sludge activity, membrane structure damage, and low ozone utilization in practical engineering applications caused by traditional online chemical cleaning of MBRs. Chinese patent document CN112537823A discloses a method for enhancing chemical cleaning and controlling ultrafiltration membrane aging using micro-nano bubble technology. This invention uses physical bubbles to assist the action of chemical cleaning liquid, alleviating excessive damage to the ultrafiltration membrane caused by high-concentration chemical agents and delaying membrane aging. However, existing micro-nano bubble composite cleaning technologies still have significant limitations: most technical solutions still require the use of acid and alkali chemical agents, failing to break free from chemical agent dependence and fundamentally solve problems such as the disposal of chemical-containing waste liquid, secondary pollution, and membrane corrosion.

[0005] Therefore, there is an urgent need to develop a new type of green membrane cleaning process that requires no acid or alkali chemical cleaning agents, has a short cleaning cycle, strong penetration and decontamination capabilities, thoroughly removes pollutants, has low operating costs, and does not damage the membrane substrate, so as to provide solutions for efficient operation and maintenance of membrane modules and resource-based regeneration of decommissioned membranes. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a membrane cleaning method that utilizes ethanol-micro-nano bubble synergistic permeation enhancement. This method enables efficient, deep, and green cleaning of fouled membranes, overcoming the dual drawbacks of incomplete physical cleaning and membrane damage and wastewater treatment issues associated with traditional cleaning methods.

[0007] The specific technical solution adopted is as follows: A membrane cleaning method with ethanol-micro / nano bubble synergistic permeation enhancement includes the following steps: (1) Rinse the fouled membrane with water, and then immerse the rinsed fouled membrane completely in an ethanol aqueous solution for 10-120 min at a temperature of 15-25℃ to soften, swell, and loosen the stubborn contaminants in the membrane fouling layer; the volume fraction of ethanol in the ethanol aqueous solution is 5%-30%; (2) Inject micro-nano bubbles into the ethanol aqueous solution of step (1) and use the micro-jet and shear force generated by the rising and breaking of the bubbles to remove membrane contaminants in conjunction with ethanol. (3) Stop the supply of micro-nano bubbles and rinse the membrane surface after step (2) with water in a forward cross-flow until there is no ethanol residue in the rinsing solution, and the cleaning is completed.

[0008] This invention utilizes the strong penetration, deep swelling, and gentle loosening properties of ethanol to pre-soak the fouled membrane in an aqueous ethanol solution, opening the membrane pores and softening organic pollutants and biofilm. Then, the localized micro-jet flow and high-energy shear force generated by the rising and rupture of micro-nano bubbles in the liquid phase thoroughly remove the loosened pollutants from the membrane surface and pores. This method, employing the synergistic penetration and enhanced cleaning effect of ethanol and micro-nano bubbles, achieves efficient, deep, and environmentally friendly cleaning of fouled membranes without the need for any highly corrosive cleaning agents such as acids, alkalis, or oxidants.

[0009] Furthermore, the fouling membrane can be a microfiltration membrane, ultrafiltration membrane, nanofiltration membrane, or reverse osmosis membrane. The cleaning method of this invention can efficiently remove contaminants deposited on these membranes during operation. This cleaning method is widely applicable to fouling membranes with different pore sizes and retention characteristics, exhibiting good versatility and meeting the membrane cleaning needs of various water treatment and separation scenarios.

[0010] Furthermore, in step (1), the water rinsing time is 10-30 min and the rinsing flow rate is 0.1-1.5 m / s.

[0011] Further, in step (2), the micro-nano bubbles are generated by a micro-nano bubble generator. One end of the micro-nano bubble generator is connected to a pipeline, which is placed at the bottom of the ethanol-water solution for gas distribution. The gas distribution time is 5-60 min. The operating pressure of the micro-nano bubble generator is 2-4 bar, and the gas intake is 0.1-2 m³ / s. 3 / h.

[0012] Preferably, in step (2), the gas in the micro-nano bubbles is nitrogen, and the size of the micro-nano bubbles is 20-1000 nm, more preferably 20-500 nm. Under the above process parameters, the cleaning effect is better.

[0013] Furthermore, in step (3), the water forward cross-flow rinsing time is 10-60 min, and the rinsing flow rate is 0.1-1.5 m / s.

[0014] The present invention also provides a regenerated membrane obtained by the ethanol-micro / nano bubble synergistic permeation enhancement membrane cleaning method.

[0015] Preferably, the flux recovery rate of the regenerated membrane is between 98% and 100%.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The cleaning method of the present invention constructs a time-sequential synergistic system of ethanol penetration swelling and micro-nano bubble micro-jet stripping. It is not a simple superposition of ethanol cleaning and micro-nano bubble technology, but forms a progressive synergistic mechanism of penetration-loosening-stripping, resulting in excellent cleaning effect.

[0017] (2) The cleaning method of the present invention first rinses the loose contaminants on the membrane surface with water to remove floating dust, suspended particles and other easily detachable contaminants, reducing the subsequent cleaning load. Then, the strong penetrability of ethanol is used to enter the contaminant layer, soften, swell and loosen the stubborn contaminants. Finally, the local micro-jet and high-energy shear force generated by the rise and rupture of micro-nano bubbles in the liquid phase completely peel off the loosened contaminants from the membrane surface and pores. The method of the present invention does not require any acid, alkali, oxidant or other strong corrosive cleaning agents, thus avoiding membrane corrosion and aging from the source, and is green and environmentally friendly.

[0018] (3) The method of the present invention can efficiently remove deep pollutants on the membrane surface and inside the membrane pores, and the flux recovery rate is close to 100%. Attached Figure Description

[0019] Figure 1 This describes a membrane cleaning process that utilizes the synergistic permeation enhancement of ethanol and micro / nano bubbles. Detailed Implementation

[0020] To make the objectives, features, and advantages of this invention more apparent and understandable, a detailed description is provided below through specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Technical features in various embodiments of the invention can be combined appropriately without mutual conflict.

[0021] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification are prior art known to those skilled in the art. Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0022] Example 1 In this embodiment, the membrane cleaning method with ethanol-micro / nano bubble synergistic permeation enhancement includes the following steps: (1) Membrane pretreatment: Take the contaminated ultrafiltration membrane and rinse it with pure water for 20 min at a flow rate of 1.0 m / s to remove surface dust and loose sludge; (2) Ethanol soaking and penetration: The contaminated membrane after rinsing in step (1) is completely immersed in an ethanol aqueous solution at a temperature of 20°C for 30 min. The volume fraction of ethanol in the ethanol aqueous solution is 5%. The strong permeability of ethanol is used to penetrate the contaminated layer, soften, swell and loosen the stubborn contaminants. (3) Ethanol and micro / nano bubble coupled synergistic cleaning: Turn on the micro / nano bubble generator. The micro / nano bubble generator distributes gas through the gas distribution tube placed at the bottom of the ethanol aqueous solution. The gas in the micro / nano bubbles is nitrogen. The size of the micro / nano bubbles is 100-500 nm. Bubble cleaning for 5 min; using the micro-jet and shear force generated by the rising and breaking of bubbles, the ethanol synergistically removes the contaminants from the membrane surface and pores. (4) Pure water rinsing: Stop the supply of micro-nano bubbles, rinse the membrane surface with pure water in a forward cross-flow for 20 min at a flow rate of 1.0 m / s, until the rinsing solution is clear and has no ethanol smell, and the cleaning is completed.

[0023] Example 2 In this embodiment, the membrane cleaning method with ethanol-micro / nano bubble synergistic permeation enhancement includes the following steps: (1) Membrane pretreatment: Take the contaminated nanofiltration membrane and rinse it with pure water for 25 min at a flow rate of 0.5 m / s to remove surface dust and loose sludge; (2) Ethanol soaking and penetration: The contaminated membrane after rinsing in step (1) is completely immersed in an ethanol aqueous solution at a temperature of 20°C for 60 min. The volume fraction of ethanol in the ethanol aqueous solution is 10%. The strong permeability of ethanol is used to penetrate the contaminated layer, soften, swell and loosen the stubborn contaminants. (3) Coupling and synergistic cleaning of ethanol and micro-nano bubbles: Turn on the micro-nano bubble generator. The micro-nano bubble generator distributes gas through the gas distribution tube placed at the bottom of the ethanol aqueous solution. The gas in the micro-nano bubbles is nitrogen. The size of the micro-nano bubbles is 50-300 nm. Bubble cleaning for 30 min; using the micro-jet and shear force generated by the rising and breaking of bubbles, the ethanol will completely remove the contaminants from the membrane surface and pores. (4) Pure water rinsing: Stop the supply of micro-nano bubbles, rinse the membrane surface with pure water in a forward cross-flow for 30 min at a flow rate of 1.0 m / s, until the rinsing solution is clear and has no ethanol smell, and the cleaning is completed.

[0024] Example 3 In this embodiment, the membrane cleaning method with ethanol-micro / nano bubble synergistic permeation enhancement includes the following steps: (1) Membrane pretreatment: Take the fouled reverse osmosis membrane and rinse it with pure water for 30 min at a flow rate of 0.5 m / s to remove surface dust and loose sludge; (2) Ethanol soaking and penetration: The contaminated membrane after rinsing in step (1) is completely immersed in an ethanol aqueous solution at a temperature of 20°C for 90 min. The volume fraction of ethanol in the ethanol aqueous solution is 15%. The strong permeability of ethanol is used to penetrate the contaminated layer, soften, swell and loosen stubborn contaminants. (3) Coupling and synergistic cleaning of ethanol and micro-nano bubbles: Turn on the micro-nano bubble generator. The micro-nano bubble generator distributes gas through the gas distribution tube placed at the bottom of the ethanol aqueous solution. The gas in the micro-nano bubbles is nitrogen. The size of the micro-nano bubbles is 20-200 nm. Bubble cleaning for 40 min; using the micro-jet and shear force generated by the rising and breaking of bubbles, the ethanol will completely remove the contaminants from the membrane surface and pores. (4) Pure water rinsing: Stop the supply of micro-nano bubbles, rinse the membrane surface with pure water in a forward cross-flow for 45 min at a flow rate of 1.5 m / s, until the rinsing solution is clear and has no ethanol smell, and the cleaning is completed.

[0025] Example 4 In this embodiment, the membrane cleaning method with ethanol-micro / nano bubble synergistic permeation enhancement includes the following steps: (1) Membrane pretreatment: Take the contaminated microfiltration membrane and rinse it with pure water for 30 min at a flow rate of 1.5 m / s to remove surface dust and loose sludge; (2) Ethanol soaking and penetration: The contaminated membrane after rinsing in step (1) is completely immersed in an ethanol aqueous solution at a temperature of 20°C for 120 min. The volume fraction of ethanol in the ethanol aqueous solution is 30%. The strong permeability of ethanol is used to penetrate the contaminated layer, soften, swell and loosen the stubborn contaminants. (3) Coupling and synergistic cleaning of ethanol and micro / nano bubbles: Turn on the micro / nano bubble generator. The micro / nano bubble generator distributes gas through the gas distribution tube placed at the bottom of the ethanol aqueous solution. The gas in the micro / nano bubbles is nitrogen. The size of the micro / nano bubbles is 500-1000 nm. Bubble cleaning for 60 min; using the micro-jet and shear force generated by the rising and breaking of bubbles, the ethanol will completely remove the contaminants from the membrane surface and pores. (4) Pure water rinsing: Stop the supply of micro-nano bubbles, rinse the membrane surface with pure water in a forward cross-flow for 60 min at a flow rate of 1.5 m / s, until the rinsing solution is clear and has no ethanol smell, and the cleaning is completed.

[0026] Comparative Example 1 The only difference between this comparative example and Example 3 is that, in step (3), a micro-nano bubble generator is not used for bubbling cleaning; all other processes and procedures are the same as in Example 3.

[0027] Comparative Example 2 The only difference between this comparative example and Example 3 is that in steps (2) and (3), the aqueous ethanol solution is replaced with pure water, while the other processes and procedures are the same as in Example 3.

[0028] Comparative Example 3 The only difference between this comparative example and Example 3 is that in steps (2) and (3), the aqueous ethanol solution is replaced with a 0.1% NaOH solution. All other processes and procedures are the same as in Example 3.

[0029] Comparative Example 4 The only difference between this comparative example and Example 3 is that in steps (2) and (3), the aqueous ethanol solution is replaced with a 0.1% sodium hypochlorite solution. All other processes and procedures are the same as in Example 3.

[0030] Comparative Example 5 The only difference between this comparative example and Example 3 is that in steps (2) and (3), the aqueous ethanol solution is replaced with a 0.025% sodium dodecylbenzenesulfonate SDBS solution. All other processes and procedures are the same as in Example 3.

[0031] Sample Analysis Flux tests were performed on the regenerated membranes obtained after cleaning in Examples 1-4 and Comparative Examples 1-5. The test medium for nanofiltration membranes was 2000 ppm sodium sulfate solution, the test medium for reverse osmosis membranes was 2000 ppm sodium chloride solution, and the test medium for microfiltration and ultrafiltration membranes was pure water.

[0032] Table 1 Performance test results of the regenerated membrane after cleaning

[0033] The flux recovery rate is calculated by multiplying the ratio of the regenerated membrane flux after cleaning to the initial membrane flux by 100%. It can be seen that the cleaning method of the present invention can effectively restore the flux of the fouled membrane. The synergistic cleaning effect of ethanol-micro-nano bubble coupling is stronger than its individual effect, and the membrane flux does not significantly exceed that of the original membrane, indicating that the membrane is not significantly damaged.

[0034] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A membrane cleaning method with ethanol-micro / nanobubble synergistic permeation enhancement, characterized in that, Includes the following steps: (1) Rinse the fouled membrane with water, and then immerse the rinsed fouled membrane completely in an ethanol aqueous solution for 10-120 min at a temperature of 15-25℃ to soften, swell, and loosen the stubborn contaminants in the membrane fouling layer; the volume fraction of ethanol in the ethanol aqueous solution is 5%-30%; (2) Inject micro-nano bubbles into the ethanol aqueous solution of step (1) and use the micro-jet and shear force generated by the rising and breaking of the bubbles to remove membrane contaminants in conjunction with ethanol. (3) Stop the supply of micro-nano bubbles and rinse the membrane surface after step (2) with water in a forward cross-flow until there is no ethanol residue in the rinsing solution, and the cleaning is completed.

2. The membrane cleaning method with ethanol-micro / nano bubble synergistic permeation enhancement according to claim 1, characterized in that, The types of fouling membranes include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, or reverse osmosis membranes.

3. The membrane cleaning method with ethanol-micro / nano bubble synergistic permeation enhancement according to claim 1, characterized in that, In step (1), the water rinsing time is 10-30 min and the rinsing flow rate is 0.1-1.5 m / s.

4. The membrane cleaning method with ethanol-micro / nanobubble synergistic permeation enhancement according to claim 1, characterized in that, In step (2), micro-nano bubbles are generated by a micro-nano bubble generator. One end of the micro-nano bubble generator is connected to a pipeline, which is placed at the bottom of the ethanol aqueous solution for gas distribution. The gas distribution time is 5-60 min.

5. The membrane cleaning method with ethanol-micro / nano bubble synergistic permeation enhancement according to claim 1, characterized in that, In step (2), the gas in the micro-nano bubbles is nitrogen.

6. The membrane cleaning method with ethanol-micro / nanobubble synergistic permeation enhancement according to claim 1, characterized in that, In step (2), the size of the micro-nano bubbles is 20-1000 nm.

7. The membrane cleaning method with ethanol-micro / nano bubble synergistic permeation enhancement according to claim 1, characterized in that, In step (3), the forward cross-flow rinsing time is 10-60 min and the rinsing flow rate is 0.1-1.5 m / s.

8. The regenerated membrane obtained by the membrane cleaning method with ethanol-micro / nano bubble synergistic permeation enhancement according to any one of claims 1-7.

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