A method for controlling distillation membrane contamination based on in-situ gas generation from micro-interface

Abstract

The present invention relates to a distillation membrane pollution control method based on micro-interface in-situ gas production, comprising: synthesizing nano-scale materials capable of activating hydrogen peroxide; uniformly and stably loading the nano-scale materials on the surface of the distillation membrane to obtain a catalytic distillation membrane; regulating the hydrophilicity and hydrophobicity of the catalytic distillation membrane to obtain an in-situ self-cleaning membrane; when the in-situ self-cleaning membrane is contaminated, adding hydrogen peroxide cleaning liquid for cleaning, activating hydrogen peroxide to generate microbubbles at the membrane distillation micro-interface, forming gas backwashing, and removing membrane pollutants. The method is not only conducive to improving the anti-fouling performance and service life of the membrane, but also easy to implement, low in cost, and energy-saving and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a distillation membrane pollution control method based on micro-interface in-situ gas production. Background Art

[0002] In most parts of the world, increasing water demand and climate anomalies are exacerbating water shortages. Unconventional water sources such as desalinated water will play a key role in resolving the contradiction between water supply and demand, and a major challenge associated with desalination technology is the treatment of the high-salinity wastewater it produces. High-salinity wastewater not only contains high salinity but also may contain organic matter and heavy metal ions. If it is directly discharged without effective treatment, it will cause a series of environmental pollution problems.

[0003] Distillation is the most commonly used method for salt recovery, but it has high operating temperatures and requires high energy consumption. Membrane separation technology has the advantages of low cost, high efficiency, energy saving and environmental protection, simple operation and easy maintenance. However, when the feed solution is highly concentrated or close to saturation, it will be limited by operating pressure and membrane scaling.

[0004] Membrane distillation is a new type of heat-driven membrane separation wastewater treatment technology. In theory, membrane distillation technology can intercept 100% of the macromolecules and ions in the wastewater. The distillation membrane can operate at a lower pressure and is not affected by concentration polarization. It has great potential in the treatment of high-concentration wastewater, especially high-salt wastewater. However, in the process of membrane distillation to treat wastewater with high pollution load, the hydrophobic membrane will be threatened by membrane fouling and membrane wetting to varying degrees, resulting in a significant decrease in membrane performance and greatly shortening the service life of the membrane. Therefore, it is necessary to develop a new membrane cleaning technology to control membrane fouling and membrane wetting problems. Summary of the invention

[0005] The purpose of the present invention is to provide a distillation membrane pollution control method based on micro-interface in-situ gas generation, which is not only conducive to improving the membrane's anti-fouling performance and service life, but also easy to implement, low in cost, energy-saving and environmentally friendly.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a distillation membrane pollution control method based on micro-interface in-situ gas production, comprising:

[0007] synthesizing nanoscale materials capable of activating hydrogen peroxide;

[0008] The nanometer-scale material is loaded evenly and stably on the surface of the distillation membrane to prepare the catalytic distillation membrane;

[0009] The hydrophilicity and hydrophobicity of the catalytic distillation membrane were regulated to obtain an in-situ self-cleaning membrane;

[0010] When the in-situ self-cleaning membrane is contaminated, hydrogen peroxide cleaning solution is added for cleaning. The activated hydrogen peroxide produces microbubbles at the membrane distillation microinterface, forming gas backwash to remove membrane contaminants.

[0011] Furthermore, the nanoscale material is nanoscale manganese dioxide particles.

[0012] Furthermore, the synthesis method of the nano-scale material is: potassium permanganate particles and nitric acid solution are mixed and placed in a hydrothermal kettle, the hydrothermal kettle is placed in an oven, heated at 110-130°C for 18-22 hours, cooled to room temperature, centrifuged and washed with deionized water for 1-3 times, and dried to obtain nano-scale MnO2 particles.

[0013] Furthermore, the catalytic distillation membrane is a polyvinylidene fluoride membrane, namely, a PVDF membrane.

[0014] Furthermore, the method for uniformly and stably loading nano-scale materials on the surface of the distillation membrane to prepare the catalytic distillation membrane is the electrostatic spinning method.

[0015] Furthermore, the modification liquid used to regulate the hydrophilicity and hydrophobicity of the catalytic distillation membrane is 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane solution, namely, FDTS solution.

[0016] Furthermore, the hydrogen peroxide cleaning solution uses 0.001wt% hydrogen peroxide cleaning solution, and each cleaning round lasts for 10 to 15 minutes.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention loads nano-scale material particles stably and evenly on the membrane surface, activates hydrogen peroxide to generate oxygen microbubbles and a large number of oxidative free radicals, forms gas backwash and oxidative free radicals at the membrane distillation micro-interface to degrade pollutants, endows the membrane with in-situ self-cleaning function, and improves the membrane's anti-fouling performance.

[0019] (2) The membrane pollution control method for micro-interface catalytic gas production proposed in the present invention does not require disassembly of the membrane components during the cleaning process. It only needs to replace the feed liquid with a hydrogen peroxide cleaning liquid, thereby solving the membrane pollution problem without hindering normal operation and reducing the cost of use; it causes little damage to the membrane structure and extends the service life of the membrane; it uses less chemical agents and is energy-saving and environmentally friendly.

[0020] (3) The process of the present invention is simple, easy to operate, safe and reliable, and suitable for popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A self-cleaning principle diagram of an in-situ self-cleaning membrane in an embodiment of the present invention;

[0022] Figure 2This is a scanning electron microscope image of the MnO2 / PVDF membrane produced by electrospinning in an embodiment of the present invention;

[0023] Figure 3 Schematic diagram of the water contact angle of the MnO2 / PVDF membrane prepared in the embodiment of the present invention;

[0024] Figure 4 Schematic diagram of the water contact angle of the in-situ self-cleaning membrane prepared in an embodiment of the present invention;

[0025] Figure 5 This is a data diagram of a micro-saturated calcium sulfate pollution experiment on the in-situ self-cleaning membrane prepared in an embodiment of the present invention;

[0026] Figure 6 This is a graph showing the experimental data of a self-cleaning cycle of the in-situ self-cleaning membrane prepared in an embodiment of the present invention using 0.001 wt % hydrogen peroxide as the cleaning liquid. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0028] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] This embodiment provides a distillation membrane contamination control method based on micro-interface in-situ gas generation, comprising the following steps:

[0031] 1) Synthesize nanoscale materials that can activate hydrogen peroxide.

[0032] 2) Through surface loading technologies such as blending and surface coating, nano-scale materials are evenly and stably loaded on the surface of the distillation membrane to produce a catalytic distillation membrane.

[0033] 3) The hydrophilicity and hydrophobicity of the catalytic distillation membrane are regulated to obtain an in-situ self-cleaning membrane with good membrane flux and hydrophobicity.

[0034] 4) When the in-situ self-cleaning membrane is contaminated, hydrogen peroxide cleaning solution is added for cleaning. The activated hydrogen peroxide produces microbubbles at the membrane distillation microinterface, forming gas backwash to remove membrane contaminants.

[0035] The self-cleaning principle of the in-situ self-cleaning membrane prepared by this method is as follows Figure 1 As shown. The present invention applies advanced oxidation technology to the membrane distillation micro-interface, uniformly loads the deoxidizing material that can catalyze hydrogen peroxide decomposition on the membrane surface, forms microbubbles between the surface and the surface sediments, forms gas backwash on the micro-interface, and effectively removes the membrane surface pollution problem; at the same time, the strong oxidizing free radicals generated in the process of activating hydrogen peroxide are used to generate a chain reaction with the pollutants, oxidize and remove the organic pollutants on the membrane surface, and give the surface a strong self-cleaning ability against organic and inorganic pollution, effectively improving the surface anti-fouling performance.

[0036] In step 1), the nanoscale material is nanoscale manganese dioxide particles.

[0037] The synthesis method of the nano-scale material is as follows: potassium permanganate particles and nitric acid solution are mixed and put into a hydrothermal kettle, the hydrothermal kettle is put into an oven, heated at 110-130° C. for 18-22 hours, cooled to room temperature, centrifuged and washed 1-3 times with deionized water, and dried to obtain nano-scale MnO2 particles.

[0038] In step 2), the catalytic distillation membrane is a polyvinylidene fluoride (PVDF) membrane.

[0039] In step 2), the method for uniformly and stably loading the nano-scale material on the surface of the distillation membrane to prepare the catalytic distillation membrane is the electrostatic spinning method.

[0040] In step 3), the modification liquid used to control the hydrophilicity and hydrophobicity of the catalytic distillation membrane is 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane solution, i.e., FDTS solution. The membrane interface can be controlled to be a hydrophilic interface or a hydrophobic interface according to the type of pollutant.

[0041] In step 4), the hydrogen peroxide cleaning solution is a hydrogen peroxide cleaning solution with a mass fraction of less than 0.1 wt%. In this embodiment, a 0.001 wt% hydrogen peroxide cleaning solution is used, and each cleaning round lasts for 10 to 15 minutes.

[0042] Embodiment 1:

[0043] Synthesis of nano-scale MnO2 particles: Mix potassium permanganate particles and nitric acid solution and put them into a hydrothermal kettle, put the hydrothermal kettle into an oven, heat at 120°C for 20 hours, wait for cooling to room temperature, wash with deionized water by centrifugation for 1 to 3 times, and dry to obtain nano-scale MnO2 particles.

[0044] Preparation of in-situ self-cleaning membrane material: 0.75wt% of the nano-scale MnO2 particles obtained in step 1, 12wt% of polyvinylidene fluoride powder and dimethylformamide solution were mixed to prepare a casting solution, and then the casting solution was placed in a magnetic stirrer and incubated in a water bath at 70°C for 3 hours. The casting solution was taken out and cooled to room temperature, and injected into an electrospinning instrument. The positive pressure of the electrospinning instrument was set to 10.5kV, the negative pressure was set to -2kV, the distance from the needle to the roller was 14cm, the needle aperture was φ22, and a mixed mold was obtained under the conditions of controlling the ambient temperature to 40°C and the humidity to 40%. The obtained membrane was recorded as MnO2 / PVDF membrane.

[0045] Modification of in-situ self-cleaning membrane material: Transfer the MnO2 / PVDF membrane obtained in step 2 to 25 ml of ethanol solution and soak it, drop 60 μL of 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane solution, stir it slightly and let it stand for 24 hours, take out the modified membrane, put it in an oven and heat treat it at 100°C for 3 hours, let it stand and cool, and obtain the in-situ self-cleaning modified membrane material.

[0046] Figure 2 This is a scanning electron microscope image of the electrospun MnO2 / PVDF membrane in this example. The small protrusions on the fiber in the image are nano-scale MnO2 particles stably and evenly loaded on the surface of the original PVDF membrane fiber. At the same time, it can be seen that the MnO2 / PVDF membrane pores are not blocked by MnO2 particles, ensuring a good flux of the membrane.

[0047] Figure 3 Schematic diagram of the water contact angle of the MnO2 / PVDF membrane prepared in this example.

[0048] Figure 4 Schematic diagram of the water contact angle of the in-situ self-cleaning membrane prepared in this example. After the MnO2 / PVDF membrane was hydrophobically modified by 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane solution, the water contact angle of the membrane was improved, the hydrophobic property was enhanced, and the membrane reached super hydrophobicity.

[0049] Figure 5 The in-situ self-cleaning membrane prepared in this example has good flux, and the membrane wetting time is delayed by about one time, which has good self-cleaning performance and can effectively extend the service life of the membrane.

[0050] Figure 6 The data of the self-cleaning cycle experiment of the in-situ self-cleaning membrane prepared in this example with a cleaning solution of 0.001wt% hydrogen peroxide is shown in FIG. When a 0.001wt% hydrogen peroxide cleaning solution is selected, the membrane flux decrease rate is low in all operation cycles, and the membrane flux recovery rate after cleaning is high, which effectively delays or inhibits the occurrence of membrane wetting.

[0051] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A distillation membrane pollution control method based on micro-interface in-situ gas generation, characterized in that: include: synthesizing nanoscale materials capable of activating hydrogen peroxide; The nanometer-scale material is loaded evenly and stably on the surface of the distillation membrane to prepare the catalytic distillation membrane; The hydrophilicity and hydrophobicity of the catalytic distillation membrane were regulated to obtain an in-situ self-cleaning membrane; When the in-situ self-cleaning membrane is contaminated, hydrogen peroxide cleaning solution is added for cleaning. The activated hydrogen peroxide generates microbubbles at the membrane distillation microinterface, forming gas backwashing to remove membrane contaminants. The nano-scale material is nano-scale manganese dioxide particles; the synthesis method of the nano-scale material is: potassium permanganate particles and nitric acid solution are mixed and placed in a hydrothermal kettle, the hydrothermal kettle is placed in an oven, heated at 110-130° C. for 18-22 hours, cooled to room temperature, centrifuged and washed 1-3 times with deionized water, and dried to obtain nano-scale MnO2 particles; The catalytic distillation membrane is a polyvinylidene fluoride membrane, i.e., a PVDF membrane; The method of uniformly and stably loading nano-scale materials on the surface of distillation membrane to prepare catalytic distillation membrane is electrospinning; The modification liquid used for regulating the hydrophilicity and hydrophobicity of the catalytic distillation membrane is 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane solution, namely, FDTS solution.

2. The distillation membrane pollution control method based on micro-interface in-situ gas generation according to claim 1 is characterized in that: The hydrogen peroxide cleaning solution is 0.001 wt % hydrogen peroxide cleaning solution, and each cleaning round lasts for 10 to 15 minutes.

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