Method for controlling biological pollution of reverse osmosis membrane through photoelectrochemical filtration pretreatment

Abstract

The invention relates to a method for controlling biological pollution of a reverse osmosis membrane through photoelectrochemical filtration pretreatment. According to the method, a photoelectrochemical reactor is mainly established to inhibit the bacterial biofilm forming ability under ultraviolet illumination and voltage conditions. The photoelectric chemical reactor is composed of a peristaltic pump, a magnetic stirrer, a reactor, an electrochemical filtering assembly, a direct-current power source and an ultraviolet light source and inhibits bacteria added into the reactor from forming a biological membrane. Under the action of voltage, the electrochemical filter assembly inhibits the biofilm forming ability and viability of bacteria by degrading protein and quorum sensing signal molecules in water, and more thoroughly inhibits the biofilm formation through the irradiation of ultraviolet light. Therefore, according to the method disclosed by the invention, the ultraviolet light can be combined with the electrochemical filter assembly to realize effective inhibition of a biological membrane formed by bacteria, the reduction of membrane flux is reduced, and the method has important significance in controlling biological pollution of the reverse osmosis membrane.

Description

Technical Field

[0001] The present invention relates to the technical field of controlling reverse osmosis membrane biofouling by advanced oxidation method, in particular to a method for controlling reverse osmosis membrane biofouling by photoelectrochemical filtration pretreatment. Background Art

[0002] Membrane fouling during reverse osmosis (RO) membrane treatment can reduce water filtration performance and recovery, degrade effluent quality, and increase the frequency of membrane cleaning and replacement. Biofouling caused by bacterial biofilm formation is more difficult to control than inorganic and organic fouling. Therefore, developing effective technologies to control RO membrane biofouling is crucial for improving water treatment efficiency and quality, reducing operating costs, and promoting sustainable development. Current research focuses on controlling RO membrane biofouling by membrane cleaning and pre-membrane treatment. Membrane cleaning primarily involves physical cleaning and chemical cleaning. Physical cleaning primarily relies on mechanical forces to remove loosely adhered filter cake from the membrane surface. However, because some contaminants irreversibly adhere to the membrane material, its cleaning efficiency typically decreases with aging. While the physical cleaning procedure is relatively simple and effective in the early stages of membrane fouling, it has limited flux recovery for severely fouled RO membranes. Chemical cleaning typically uses alkaline cleaning solutions containing various combinations of surfactants, chelating agents, and enzymes, with sodium hypochlorite being particularly effective. Although chemical cleaning is effective in restoring membrane flux, frequent chemical cleaning will still lead to membrane damage and increased operating costs, and its scope of application is still limited. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a method for controlling reverse osmosis membrane biofouling through photoelectrochemical filtration pretreatment. The present invention first screens out materials with strong electrochemical activity, and successfully prepares them into anodes, and constructs them into electrochemical filtration components with stainless steel sheets, which still maintain electrochemical activity under ultraviolet irradiation conditions. The present invention utilizes that the electrochemical filtration component can degrade proteins and quorum sensing signal molecules C8-HSL in water under the action of voltage, interfere with the expression of bacterial quorum sensing genes, effectively inhibit bacterial biofilm formation, and weaken the bacteria's resistance mechanism to ultraviolet light, thereby prompting ultraviolet light to more thoroughly inhibit bacterial biofilm formation and control reverse osmosis membrane biofouling.

[0004] The purpose of the present invention can be achieved by the following solutions:

[0005] The present invention aims to provide an application of a photoelectrochemical reactor in controlling reverse osmosis membrane biofouling, wherein the photoelectrochemical reactor comprises an electrochemical filtration assembly; the electrochemical filtration assembly comprises a metal oxide anode, a stainless steel cathode, and a structure with a cavity in the middle composed of an organic glass frame;

[0006] The metal oxide anode includes a metal base material and a metal oxide supported on the metal base material; the metal oxide includes RuO2 and IrO2.

[0007] In some embodiments of the present invention, the photoelectrochemical reactor further comprises a peristaltic pump, a magnetic stirrer, a reactor, a DC power supply, an ultraviolet lamp, and a reverse osmosis membrane device.

[0008] In some embodiments of the present invention, the reverse osmosis membrane device is composed of a cross-flow reverse osmosis system consisting of three flat-plate reverse osmosis membrane pools.

[0009] In some embodiments of the present invention, the metal oxide anode is prepared by the following method:

[0010] Providing a metal base material;

[0011] Mixing a ruthenium source and an iridium source and dissolving them in a solvent to obtain a coating solution;

[0012] The coating liquid is brushed on the surface of the metal base material, and then heated, sintered and kept warm. After cooling, the coating, drying and sintering are repeated multiple times, and finally sintered at 450-600° C. for 1-4 hours to obtain the metal oxide anode.

[0013] In some embodiments of the present invention, the ruthenium source and the iridium source have an atomic molar ratio of ruthenium to iridium of (4-5): (1-2).

[0014] In some embodiments of the present invention, the heating and sintering temperature is 450-600° C., and the holding time is 15-60 minutes.

[0015] In some embodiments of the present invention, the number of repeated coatings is 10 to 16 times; the loading amount of the metal oxide after repeated coating, drying and sintering is 2.5 to 5 mg / cm 2 .

[0016] In some embodiments of the present invention, the thickness of the organic glass frame is 1-8 cm, and the volume of the cavity is 4-800 cm 3 The effective filtration area of the electrochemical filtration component is 4-100cm 2 .

[0017] In some embodiments of the present invention, the applying comprises the following steps:

[0018] (1) Wastewater pretreatment: adjust the pH value of wastewater to 6-9;

[0019] (2) Electrochemical treatment: The wastewater is transferred to a reactor and stirred at a speed of 200-500 rpm; a UV lamp and an electrochemical filter assembly are placed in the reactor, and the UV irradiation time is 0-6 h, and the applied voltage is 0-6 V;

[0020] (3) Reverse osmosis membrane device treatment: The wastewater pretreated by the photoelectrochemical reactor is added to the reverse osmosis membrane device. The treatment time is 8 days. The rotor flow meter is controlled at 0.4-0.6L / min, the pressure gauge is controlled at 3-4MPa, and the temperature is controlled at 20-30℃.

[0021] In some embodiments of the present invention, the ultraviolet lamp is placed inside the reactor, 2-5 cm away from the electrochemical filter assembly, and the wavelength of the ultraviolet lamp is 365 nm.

[0022] The above technical solution of the present invention has the following advantages over the prior art:

[0023] This method utilizes the electrochemical filtration component's ability to degrade proteins and the signaling molecule C8-HSL in water, interfering with the expression of microbial quorum sensing genes and effectively inhibiting the growth of bacterial biofilms and extracellular polymers. This weakens the bacteria's defense mechanism against ultraviolet light, thereby promoting ultraviolet light-induced bacterial killing and inhibiting the formation of microbial growth films. This method offers the advantages of high efficiency and low processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0025] Figure 1 Scanning electron microscope images of the mixed metal oxide anode of Example 1 of the present invention (a: SEM image of the original titanium plate at a magnification of 500 times; b: SEM image of the original titanium plate at a magnification of 1000 times; c: SEM image of the Ti / RuO2-IrO2 anode at a magnification of 500 times; d: SEM image of the Ti / RuO2-IrO2 anode at a magnification of 1000 times);

[0026] Figure 2 This is the XRD pattern of the mixed metal oxide anode of Example 1 of the present invention;

[0027] Figure 3 This is the pore size analysis diagram of the mixed metal oxide anode of Example 1 of the present invention

[0028] Figure 4 Schematic diagram of the photoelectrochemical reactor of Example 1 of the present invention. The assembly and connection methods of the photoelectrochemical reactor of the present invention are conventional in the art.

[0029] Figure 5 This is a curve showing the membrane flux variation of the reverse osmosis membrane of the photoelectrochemical reactor of Application Example 1 of the present invention under ultraviolet and voltage conditions;

[0030] Figure 6 This is a diagram showing the morphology changes of the reverse osmosis membrane of Application Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0032] Example 1

[0033] This embodiment provides a method for controlling reverse osmosis membrane biofouling through photoelectrochemical filtration pretreatment, as follows:

[0034] (1) Preparation method of mixed metal oxide anode:

[0035] (1) Pretreatment of substrate materials: The substrate pretreatment is divided into two parts: degreasing treatment and acid etching treatment. Using foamed titanium as the substrate material, it is placed in an acetone solution for ultrasonic treatment for 30 minutes to remove surface oil stains. After the degreasing titanium substrate is rinsed with water, it is placed in an oxalic acid solution with a mass concentration of 10%, and etched for 2 hours by heating it to 90°C in a constant temperature water bath. Acid etching can remove the surface oxide film and increase its bonding strength with metal oxides. The titanium substrate that has been ultrasonically cleaned and dried with pure water will show a uniform gray rough surface. If there is a brown-yellow substance (titanium oxalate) attached to part of the surface, use a lower concentration of oxalic acid solution for ultrasonic cleaning, and repeat the previous cleaning and drying steps until the surface shows a gray rough surface.

[0036] (2) Preparation of coating solution: Take appropriate amount of ruthenium trichloride and chloroiridic acid and dissolve them in hydrochloric acid:isopropyl alcohol solution with a volume ratio of 1:1 at a molar ratio of ruthenium to iridium of 8:2, ensuring complete dissolution.

[0037] (3) Coating preparation: The Ti / RuO2-IrO2 anode was prepared by thermal decomposition. Use a brush to dip the coating liquid obtained in step (2) and evenly apply it to the surface of the 3cm×3cm titanium substrate obtained in step (1). Then place the coated material in an oven and dry it at 110℃ for 10 minutes to completely evaporate the solvent. Place the dried substrate in a muffle furnace at 450℃ for 15 minutes. After cooling to room temperature, apply the coating, dry it, and sinter it for the second time. Repeat the coating 15 times until the loading amount reaches 2.5mg / cm 2 Finally, the mixed metal oxides were obtained by sintering at 450 °C for 1 h.

[0038] (2) Characterization of mixed metal oxide anodes:

[0039] (1) Scanning electron microscopy observation of mixed metal oxide anodes: Figure 1 As shown, Figures a and b are SEM images of the titanium plate after etching and cleaning in step (1) of the above step (I) at magnifications of 500 times and 1000 times, respectively. It can be clearly seen that the titanium plate after etching and cleaning is uneven, with particles of various sizes closely connected together, forming an irregular pore structure inside. Figures c and d are SEM images of the anode material obtained after coating the titanium plate with a mixture of ruthenium trichloride and chloroiridic acid and then calcining at high temperature, at magnifications of 500 times and 1000 times, respectively. After coating and high-temperature calcination, metal oxide crystals begin to grow on the surface of the titanium substrate, and the surface of the particles becomes rougher, increasing the specific surface area of the anode; as the metal oxide penetrates into the titanium substrate, the pores of the anode plate are further reduced, which is confirmed by the pore size test results.

[0040] (2) XRD analysis of mixed metal oxide anodes: Figure 2 As shown in the figure, the characteristic peaks of the titanium substrate before coating mainly appear at 35.082°, 38.401°, 40.160°, 52.986°, 62.937°, 70.634°, 74.139°, 76.192°, 77.337°, 82.257°, and 86.733°, which correspond to (100), (002), (101), (102), (110), and (103) of Ti (PDF#89-2762), respectively. , (200), (112), (201), (004), (202) crystal planes; after coating, RuO2 and IrO2 with rutile structure mainly appeared at around 28.017°, 35.084°, and 54.081°, indicating that the metal oxides were successfully loaded on the Ti substrate; after comparison with the standard card, it was found that RuO2 and IrO2 had obvious offset phenomena at (110) and (101) crystal planes, indicating that the coating contained solid solution of Ir and Ru, which enhanced the stability of the anode. Due to Ru 4+ and Ir 4+ The ionic radii of the two elements are very similar, and both are rutile oxides. According to the Hume-Rothery theory, these two elements can form a solid solution. Because X-rays can penetrate the coating, the XRD spectrum contains characteristic peaks of Ti, but no characteristic peaks related to TiO2 appear, indicating that the pyrolytic coating process did not cause oxidation of the titanium substrate.

[0041] (3) Pore size analysis of mixed metal oxide anodes: Figure 3As shown in the figure, before coating, the pores of 4 to 4.5 μm accounted for the largest proportion (20.29%) in the titanium substrate, and after coating, the pores of 0.1 to 5 μm in the anode accounted for 91.08%. The average pore size before and after coating also shrank from 4.3 μm to 1.1 μm, indicating that the metal oxide formed on the titanium substrate can effectively reduce the pore size, which corresponds to the morphological structure results of SEM.

[0042] (III) Construction of photoelectrochemical reactor: Figure 4 As shown, it consists of a peristaltic pump, a magnetic stirrer, a reactor, an electrochemical filtration component, a DC power supply and an ultraviolet light source, wherein the electrochemical filtration component is composed of a mixed metal oxide anode and a stainless steel cathode through a 1.0 cm thick organic glass frame with a cavity in the middle (4 cm 3 ) structure, the effective filtration area is 4cm 2 . Ultraviolet lamp (UV-C, 0.38mW / cm 2 , Shenxing) is placed 2 cm away from the filter component and is selected for use according to experimental conditions. The entire reactor is made of light-proof material.

[0043] Application Example 1

[0044] Specific methods for controlling reverse osmosis membrane biofouling through photoelectrochemical filtration pretreatment:

[0045] (1) Wastewater pretreatment: The pH of the wastewater was adjusted to 7. (2) Electrochemical treatment: The wastewater was pumped into the reactor with a rotor placed at the bottom at a speed of 200 rpm. The UV lamp and the prepared electrochemical filter assembly were placed into the reactor. The UV irradiation time was 0 h and the applied voltage was 3 V. (3) Reverse osmosis membrane device treatment: The wastewater pretreated by the photoelectrochemical reactor was added to the reverse osmosis device for 8 days. The rotor flowmeter was controlled at 0.5 L / min, the pressure gauge was controlled at 3 MPa, and the temperature was controlled at 25°C.

[0046] Comparative Example 1

[0047] This comparative example is the same as Application Example 1, except that the applied voltage is 0V.

[0048] Comparative Example 2

[0049] This comparative example is the same as Application Example 1, except that the ultraviolet irradiation time is 6 hours.

[0050] The wastewater was treated by the apparatus of Comparative Example 1 and Comparative Example 2, and the treated wastewater was transferred to the reverse osmosis membrane apparatus. After 8 days of circulation treatment, the changes in membrane flux and reverse osmosis membrane morphology were compared to understand the biological contamination of the reverse osmosis membrane. Specifically, the same batch of wastewater was added to the reactors of Comparative Example 1 and Comparative Example 2, respectively. The results are shown in FIG. Figure 5 and Figure 6 As shown. Figure 5 It can be seen that the wastewater in comparative example 1 has a faster decline rate in the early stage of membrane flux under the conditions of voltage (3V) and no voltage (0V). At the end of the reaction, the decline of membrane flux under 3V treatment is less than that under 0V. This result shows that under 3V voltage, there is a certain inhibitory effect on the biological fouling of reverse osmosis membrane. In comparative example 2, under the conditions of 3V, the presence or absence of ultraviolet irradiation conditions has a significant effect on the change of membrane flux. The membrane flux declines more slowly under the conditions of 6h ultraviolet irradiation and 3V voltage. Figure 6 As can be seen from the results, the reverse osmosis membrane surface exhibited varying degrees of biofouling. Wastewater pretreated with 0 hours of UV irradiation and 0V voltage produced the most severe membrane fouling, exhibiting a brownish-yellow membrane color and a dense, thick membrane layer. The membrane layer after 0 hours of UV irradiation and 3V pretreatment was relatively loose and easily detached from the membrane. The membrane fouling was least severe after 6 hours of UV irradiation and 3V pretreatment, with a very thin fouling layer and no obvious biofilm layer as seen in the above treatments. These results indicate that under voltage treatment and UV irradiation conditions, pretreatment can inhibit bacterial biofilm formation, reduce membrane flux decline, and effectively control reverse osmosis membrane biofouling.

[0051] In summary, by adding the electrochemical filtration component developed by the present invention to the reactor, under the conditions of applying voltage and ultraviolet irradiation, the biofilm formation ability of bacteria can be significantly inhibited and the decline in membrane flux can be reduced. Figure 5 and Figure 6 As shown, it is of great significance to the control of reverse osmosis membrane biofouling.

[0052] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. Application of a photoelectrochemical reactor in controlling biological fouling of reverse osmosis membranes, characterized in that: The photoelectrochemical reactor includes an electrochemical filtration component; the electrochemical filtration component includes a metal oxide anode, a stainless steel cathode, and a structure with a cavity in the middle composed of an organic glass frame; The metal oxide anode includes a metal base material and a metal oxide supported on the metal base material; the metal oxide includes RuO2 and IrO2.

2. The use according to claim 1, characterized in that The photoelectrochemical reactor further comprises a peristaltic pump, a magnetic stirrer, a reactor, a direct current power supply, an ultraviolet lamp and a reverse osmosis membrane device.

3. The use according to claim 2, characterized in that The reverse osmosis membrane device is composed of a cross-flow reverse osmosis system consisting of three flat reverse osmosis membrane pools.

4. The use according to claim 1, characterized in that The metal oxide anode is prepared by the following method: Providing a metal base material; Mixing a ruthenium source and an iridium source and dissolving them in a solvent to obtain a coating solution; The coating liquid is brushed on the surface of the metal base material, and then heated, sintered and kept warm. After cooling, the coating, drying and sintering are repeated multiple times, and finally sintered at 450-600° C. for 1-4 hours to obtain the metal oxide anode.

5. The use according to claim 4, characterized in that The ruthenium source and the iridium source have a ruthenium to iridium atomic molar ratio of (4-5): (1-2).

6. The use according to claim 4, characterized in that The heating and sintering temperature is 450-600° C., and the holding time is 15-60 minutes.

7. The use according to claim 4, characterized in that The number of repeated coatings is 10 to 16 times; the loading amount of metal oxide after repeated coating, drying and sintering is 2.5-5 mg / cm 2 .

8. The use according to claim 1, characterized in that The thickness of the organic glass frame is 1-8 cm, and the volume of the cavity is 4-800 cm 3 The effective filtration area of the electrochemical filtration component is 4-100cm 2 .

9. The use according to claim 1, characterized in that The application comprises the following steps: (1) Wastewater pretreatment: adjust the pH value of wastewater to 6-9; (2) Electrochemical treatment: The wastewater is transferred to a reactor and stirred at a speed of 200-500 rpm; a UV lamp and an electrochemical filter assembly are placed in the reactor, and the UV irradiation time is 0-6 h, and the applied voltage is 0-6 V; (3) Reverse osmosis membrane device treatment: The wastewater pretreated by the photoelectrochemical reactor is added to the reverse osmosis membrane device. The treatment time is 8 days. The rotor flow meter is controlled at 0.4-0.6L / min, the pressure gauge is controlled at 3-4MPa, and the temperature is controlled at 20-30℃.

10. The use according to claim 1, characterized in that The ultraviolet lamp is placed inside the reactor, 2-5 cm away from the electrochemical filter assembly, and the wavelength of the ultraviolet lamp is 365 nm.

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