A method for water disinfection based on synergistic photocatalysis and low-voltage electroporation on metal oxide array

Abstract

This invention discloses a synergistic water disinfection method based on photocatalysis and low-voltage electroporation using a metal oxide array, effectively addressing the problems of high byproduct risk, incomplete disinfection, high energy consumption, and limited applicability of existing water disinfection technologies. The method first prepares a metal oxide nanoarray electrode, wherein the metal oxide is any one or more composites of cuprous oxide, titanium dioxide, zinc oxide, and tungsten trioxide, and the array morphology is at least one of nanowire, nanotube, and nanosheet arrays. This electrode is then placed into the water to be disinfected as the working electrode, and a low-voltage DC electric field is applied. Subsequently, ultraviolet light excitation is performed simultaneously, utilizing the photocatalytic effect of the metal oxide array to generate active oxide species. The enhanced local electric field at the array tip induces electroporation damage to the cell membranes of pathogenic microorganisms, achieving deep water disinfection through the synergistic effect of both. This invention achieves a synergistic effect of physical membrane disruption and deep chemical inactivation.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering and water disinfection technology, specifically relating to a synergistic water disinfection method based on photocatalysis and low-voltage electroporation using a metal oxide array. Background Technology

[0002] With the increasing demand for water environment management and safe water supply, bacteria, viruses, and pathogenic microorganisms are commonly found in water bodies such as medical wastewater, urban sewage effluent, and emergency water supply for sudden situations. Microbial disinfection has become one of the core links in water purification and treatment. Traditional water disinfection technologies mainly include chlorination, ultraviolet disinfection, and ozone disinfection. However, chlorination disinfection easily generates toxic and harmful disinfection byproducts such as chloroform and halogenated organic compounds, posing a risk of secondary water pollution. Ultraviolet disinfection lacks sustained antibacterial ability, has limited effectiveness in inactivating drug-resistant microorganisms, and can only achieve surface disinfection. Ozone disinfection equipment has high investment costs and high energy consumption, making it difficult to apply to small and medium-sized decentralized water disinfection scenarios.

[0003] Electroporation disinfection technology disrupts the cell membrane structure of microorganisms through an electric field, rapidly inactivating them and offering advantages such as fast disinfection speed and no chemical residue. Traditional electroporation technologies often employ high-voltage electric fields, resulting in high energy consumption, stringent equipment insulation requirements, and the potential for water electrolysis to produce byproducts. Existing low-voltage electroporation technologies, when used alone, rely solely on physical electric fields to cause reversible or irreversible damage to the microbial cell membrane, failing to further decompose intracellular substances. This allows damaged microorganisms to potentially repair and revive, leading to insufficient disinfection thoroughness and treatment depth when used alone.

[0004] Metal oxide photocatalytic water disinfection technology has become a research hotspot in novel water disinfection technologies due to its advantages such as being green and requiring no added chemicals, and being able to deeply degrade microorganisms and organic pollutants. Titanium dioxide, zinc oxide, tungsten trioxide, and cuprous oxide are among the most widely used metal oxide photocatalytic materials in the field of aquatic environment. Constructing these materials into array structures such as nanowires, nanotubes, and nanosheets can effectively increase the specific surface area of ​​the materials and optimize the transport path of photogenerated carriers. Compared with powdered catalysts, they are easier to implement and recover, and the reaction interface is superior. However, single photocatalytic disinfection still has inherent shortcomings, such as the fast recombination rate of photogenerated electrons and holes and the limited light energy utilization rate, which makes it difficult to meet the actual needs of rapid and deep disinfection of highly polluted water bodies. Summary of the Invention

[0005] Existing research has attempted to combine photocatalysis and electroporation, but these are mostly simple process superpositions that fail to achieve a substantial synergistic effect, thus failing to balance disinfection efficiency and energy consumption. Addressing the problems of high disinfection byproduct risks, insufficient inactivation efficiency of single photocatalysis, incomplete disinfection via low-voltage electroporation, and lack of substantial synergistic effect in photoelectric co-treatment of existing water disinfection technologies, this invention proposes a synergistic water disinfection method based on photocatalysis and low-voltage electroporation using a metal oxide array. Utilizing a specific metal oxide nanoarray structure, it couples the local enhancement effect of the low-voltage electric field with the generation advantages of photocatalytically active substances, achieving a synergistic effect of physical electroporation membrane disruption and deep inactivation by chemical free radicals. This enables highly efficient and deep disinfection of water microorganisms under low-pressure and low-energy conditions, adaptable to various practical water treatment scenarios.

[0006] Technical solution: A water disinfection method based on photocatalysis and low-voltage electroporation using metal oxide arrays, comprising the following steps:

[0007] Step 1: Prepare metal oxide nanoarray electrodes; the metal oxide is any one or more of cuprous oxide, titanium dioxide, zinc oxide, and tungsten trioxide.

[0008] Step 2: Using the prepared metal oxide nanoarray electrode as the cathode (working electrode) and commercially available copper foam or nickel foam as the anode, place them into the water to be disinfected to construct a low-voltage electroporation reaction system.

[0009] Step 3: Apply a low-voltage DC electric field to the two electrodes and simultaneously excite the water and the surface of the metal oxide nanoarray electrode by light to achieve disinfection of pathogenic microorganisms in the water.

[0010] Furthermore, in step 1, the morphology of the metal oxide nanoarray is at least one of nanowire array, nanotube array, and nanosheet array.

[0011] Furthermore, in step 1, the composite method of multiple metal oxides can be any one of in-situ growth composite, surface loading composite, or heterojunction composite.

[0012] Furthermore, in step 1, the metal oxide nanoarray is a nanoscale structure with an array diameter controlled between 20 and 200 nm and an array growth length controlled between 2 and 20 μm.

[0013] Furthermore, in step 1, the metal oxide nanoarray is a cuprous oxide nanoarray electrode, and the preparation method is as follows:

[0014] Step a: Immerse the copper foam in a dilute hydrochloric acid solution for 10 minutes, turning it over once during the process. Then rinse it three times with deionized water and dry it with cold air. The concentration of the dilute hydrochloric acid solution in step a is 1 mol / L.

[0015] Step b: Place the copper foam in a mixed solution containing NaOH, (NH4)2S2O8, and deionized water, cooled in an ice-water bath, and treat for 20 min, turning it over every 10 min during this period; after removal, rinse three times with deionized water and dry with cold air; in the mixed solution, the concentration of NaOH is 0.7-0.9 g / mL, preferably 0.8 g / mL; the concentration of (NH4)2S2O8 is 0.125-0.3 g / mL, preferably 0.225 g / mL;

[0016] Step c: The dried copper foam is heated at 160-200 °C for 3.5 h under a nitrogen atmosphere to obtain cuprous oxide array electrodes; the preferred temperature is 180 °C.

[0017] Furthermore, in step 2, a low-voltage electroporation reaction system is constructed by inserting a metal oxide array electrode as the cathode and commercially available foamed copper or foamed nickel as the anode into the disinfected water.

[0018] Furthermore, in step 3, the DC low voltage is 0.5 to 5 V, and the distance between the cathode and the anode is 0.1 to 1.5 cm.

[0019] Furthermore, in step 3, ultraviolet light is used as the excitation source, with a wavelength range of 200–420 nm and an illumination intensity controlled between 0.5–2 mW / cm². 2 .

[0020] Furthermore, in step 2, the water body to be disinfected is any one of medical wastewater, urban sewage effluent, or emergency water supply water.

[0021] Beneficial effects:

[0022] (1) This invention utilizes the structural advantages of metal oxide arrays to couple photocatalysis and low-voltage electroporation synergistically. It relies on the enhanced local electric field effect at the array tip to achieve efficient electroporation under low-voltage conditions. At the same time, it utilizes photocatalysis to generate active oxide species, achieving synergy between physical membrane disruption and deep chemical inactivation. This effectively solves the problems of low efficiency of single photocatalytic inactivation and incomplete disinfection by single low-voltage electroporation, significantly improving the inactivation efficiency and treatment depth of microorganisms in water, avoiding the repair and reactivation of damaged microorganisms, and ensuring thorough disinfection.

[0023] (2) The present invention adopts a DC low-voltage electric field, which does not require high-voltage drive, greatly reducing the operating energy consumption and equipment insulation requirements. At the same time, the metal oxide array can be directly used as a photocatalytic active material and an electroporation electrode, without the need to add additional catalysts or independent electrodes, simplifying the reaction system. Moreover, no chemical reagents are added, and no toxic disinfection byproducts such as chloroform are produced, thus achieving green, low-energy consumption and no secondary pollution water disinfection.

[0024] (3) The metal oxide electrode selected in this invention is easy to prepare, has controllable cost, and is suitable for various scenarios such as medical wastewater, urban sewage tailwater, and emergency water supply. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the working principle of a synergistic water disinfection method based on photocatalysis and low-voltage electroporation using a metal oxide array, according to the present invention.

[0026] Figure 2 This is a scanning electron microscope image of the metal oxide (cuprous oxide as an example) array prepared in Example 1 of the present invention;

[0027] Figure 3 The X-ray diffraction pattern of the cuprous oxide array prepared in Example 1 of this invention;

[0028] Figure 4 This is a comparison of the bacterial inactivation efficiency curves of different experimental groups of the cuprous oxide array prepared in Example 1 of the present invention at a peristaltic pump flow rate of 2.0 mL / min and a voltage of 2 V;

[0029] Figure 5 Digital photographs of different bacterial colonies sampled at fixed times under peristaltic pump flow rate of 2.0 mL / min and voltage of 2 V for the cuprous oxide array prepared in Example 1 of this invention. Detailed Implementation

[0030] The technical solution of the present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the embodiments described.

[0031] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0032] The electrode prepared in this embodiment of the invention was subjected to water disinfection testing as follows: The cuprous oxide array synthesized by this invention was modified onto a copper foam conductive substrate. The specific modification process was as follows: the copper foam, after acid washing and alkali oxidation treatment, was placed in an inert atmosphere and pyrolyzed at 180 °C for 3.5 h to allow the cuprous oxide nanowire array to grow uniformly and firmly bond on the surface of the copper foam, thus serving as the cathode; commercially available copper foam or nickel foam was used as the anode, and 150 mL of a 10% concentration was immersed in water. 6A peristaltic pump was used to continuously run a solution of CFU / mL *E. coli* at a flow rate of 2.0 mL / min, applying a low-voltage DC current of 2 V. After continuous operation, samples were plated and incubated at 37 °C for 24 h for counting. The logarithmic inactivation rate was calculated. Four experimental groups were set up: a blank control (no treatment, C0), and four treatment groups: metal oxide array only (C1), metal oxide array + 2 V voltage (C2), metal oxide array + UV irradiation (C3), and metal oxide array + 2 V voltage + UV irradiation (C4). The bactericidal effects of different conditions were compared. The specific UV irradiation conditions were: a 10 W 254 nm UV lamp as the incident light source, with a light intensity of 1 mW / cm². 2 The reaction is continuously irradiated with ultraviolet light.

[0033] Example 1

[0034] This embodiment takes a cuprous oxide array electrode as an example. The specific steps are as follows:

[0035] Copper foam was cut into substrates measuring 2.0 cm × 3.5 cm and immersed in a 1.0 mol / L dilute hydrochloric acid solution prepared with deionized water for 10 min, turning it over once during the immersion process. The substrate was then rinsed three times with deionized water and dried with cold air. Next, it was placed in a mixed solution containing 3.2 g NaOH, 0.9 g (NH4)2S2O8, and 4.0 mL deionized water, cooled in an ice-water bath (NaOH concentration: 0.8 g / mL, (NH4)2S2O8 concentration: 0.225 g / mL), and treated for 20 min, turning it over every 10 min. After removal, it was rinsed three times with deionized water and dried with cold air. Finally, the dried copper foam was heated at 180 ℃ for 3.5 h under a nitrogen atmosphere to obtain a cuprous oxide array electrode. The prepared cuprous oxide array electrode had an array diameter of 170 nm and an array growth length controlled at 14 μm.

[0036] Figure 2 The image shown is a scanning electron microscope image of the cuprous oxide array prepared in Example 1 of this invention. It can be seen that a dense and ordered nanowire array is formed on the copper foam substrate, indicating that the cuprous oxide array electrode was successfully prepared.

[0037] Figure 3 The X-ray diffraction pattern of the cuprous oxide array prepared in Example 1 of the present invention clearly shows the characteristic peaks of cuprous oxide and copper, indicating the successful preparation of the cuprous oxide array electrode.

[0038] Figure 4The graph shows a comparison of the logarithmic inactivation efficiency curves of bacteria in different experimental groups under a peristaltic pump flow rate of 2.0 mL / min and a voltage of 2 V for the cuprous oxide array prepared in Example 1 of this invention. It can be seen that the cuprous oxide array electrode has the highest inactivation efficiency and the fastest growth rate under ultraviolet irradiation, indicating that the cuprous oxide array electrode has good antibacterial properties.

[0039] Figure 5 The image shows digital photographs of different bacterial colonies sampled at fixed times under a peristaltic pump flow rate of 2.0 mL / min and a voltage of 2V on the cuprous oxide array prepared in Example 1 of this invention. As can be seen from the figure, the cuprous oxide array electrode has the fewest bacteria and the best antibacterial effect under ultraviolet irradiation at the same time.

[0040] Example 2

[0041] The difference between this embodiment and Example 1 is that the amount of sodium hydroxide added was adjusted from 3.2 g to 2.8 g (i.e., the concentration of NaOH in the mixed solution is 0.7 g / mL). The rest of the preparation process is the same as in Example 1, and a cuprous oxide array electrode is obtained.

[0042] Example 3

[0043] The difference between this embodiment and Example 1 is that the amount of sodium hydroxide added was adjusted from 3.2 g to 3.6 g (i.e., the concentration of sodium hydroxide in the mixed solution is 0.9 g / mL). The rest of the preparation process is the same as in Example 1, and a cuprous oxide array electrode is obtained.

[0044] The electrodes prepared in the above embodiments were subjected to water disinfection tests, and the results compared with those of Example 1 are shown in Table 1.

[0045] Table 1

[0046]

[0047] As shown in Table 1, adjusting the amount of sodium hydroxide added significantly affects the performance of the cuprous oxide array electrode. Adding 3.6 g of NaOH results in blunted nanoneedle tips and impure crystal phases; adding 2.8 g causes the nanoneedles to be too short and have insufficient density. Based on the results in Table 1, the optimal technical effect is achieved when the amount of sodium hydroxide added in this invention is 3.2 g.

[0048] Example 4

[0049] The difference between this embodiment and Example 1 is that the amount of ammonium persulfate added was adjusted from 0.9 g to 1.2 g (i.e., the concentration of (NH4)2S2O8 in the mixed solution was 0.3 g / mL), while the rest of the preparation process was the same as in Example 1, and cuprous oxide array electrodes were obtained.

[0050] Example 5

[0051] The difference between this embodiment and Example 1 is that the amount of ammonium persulfate added is adjusted from 0.9 g to 0.5 g (i.e., the concentration of (NH4)2S2O8 in the mixed solution is 0.125 g / mL), while the rest of the preparation process is the same as in Example 1, and cuprous oxide array electrodes are obtained.

[0052] The electrodes prepared in the above embodiments were subjected to water disinfection tests, and the comparison results with those of Example 1 are shown in Table 2.

[0053] Table 2

[0054]

[0055] As can be seen from Table 2, adjusting the amount of ammonium persulfate has a significant impact on the performance of the cuprous oxide array electrode. This is because when the amount of ammonium persulfate is 1.2 g, the cuprous oxide array morphology cannot be obtained and the tip electric field effect is lost. When the amount is 0.5 g, the copper source cannot be completely reduced and the crystal phase is impure. According to the results in Table 2, the best technical effect can be obtained when the amount of ammonium persulfate added in this invention is 0.9 g.

[0056] Example 6

[0057] The difference between this embodiment and Embodiment 1 is that the pyrolysis temperature is adjusted from 180 ℃ to 160 ℃, while the rest of the preparation process is the same as in Embodiment 1, to obtain a cuprous oxide array electrode.

[0058] Example 7

[0059] The difference between this embodiment and Example 1 is that the pyrolysis temperature is adjusted from 180 ℃ to 200 ℃, while the rest of the preparation process is the same as in Example 1, to obtain a cuprous oxide array electrode.

[0060] The electrodes prepared in the above embodiments were subjected to water disinfection tests, and the results compared with those of Example 1 are shown in Table 3.

[0061] Table 3

[0062]

[0063] As can be seen from Table 3, adjusting the pyrolysis temperature has a significant impact on the performance of the cuprous oxide array electrode. This is because when the pyrolysis temperature is 160 ℃, the temperature is too low, resulting in insufficient crystallinity of cuprous oxide; when the pyrolysis temperature is 200 ℃, the temperature is too high, causing it to agglomerate. According to the results in Table 3, the best technical effect can be obtained when the pyrolysis temperature in this invention is 180 ℃.

[0064] Comparative Example 1

[0065] Single electroporation sterilization.

[0066] Comparative Example 2

[0067] Single ultraviolet photocatalytic disinfection.

[0068] Comparative Example 3

[0069] This comparative example provides a method for preparing a conventional water disinfection electrode, specifically as follows:

[0070] Equal masses of commercial cuprous oxide powder and activated carbon were mixed at a mass ratio of 1:3. A 5% polyvinyl alcohol aqueous solution was added as a binder. After ultrasonic dispersion for 30 min, the mixture was coated onto a 2.0 cm × 3.5 cm titanium substrate and dried in an oven at 120 ℃ for 2 h. After natural cooling, a conventional cuprous oxide / activated carbon composite sterilization electrode was obtained.

[0071] The electrodes prepared in the above comparative example were subjected to water disinfection tests, and the results compared with those of Example 1 are shown in Table 4.

[0072] Table 4

[0073]

[0074] As shown in the table above, the metal oxide array electrode disclosed in this invention has unique low-voltage electroporation performance compared with conventional water disinfection electrodes, and its efficiency against Escherichia coli under ultraviolet light irradiation is significantly improved, with a logarithmic inactivation efficiency of 5.28 within 300 min.

[0075] The photocatalytic effect of metal oxide nanoarrays is used to generate active oxidants, while relying on the enhanced local electric field effect at the array tip to cause cell membrane electroporation damage to pathogenic microorganisms in water (such as Escherichia coli and drug-resistant Staphylococcus aureus); through the synergistic effect of photocatalysis and low-voltage electroporation, deep disinfection and purification of water is achieved.

[0076] Low-voltage electroporation disrupts the permeability of pathogenic microbial cell membranes, while photocatalytically generated hydroxyl radicals and superoxide radicals invade the microbial cells, achieving deep inactivation. The two work together to create a synergistic disinfection effect, improving the efficiency and depth of microbial inactivation in water.

[0077] In summary, this invention discloses a synergistic water disinfection method based on photocatalysis and low-voltage electroporation using a metal oxide array electrode. This metal oxide array electrode, relying on its one-dimensional tip structure, achieves electroporation inactivation through a local electric field and generates oxidative free radicals through photocatalytic activity. These two elements synergistically construct a highly efficient disinfection system, solving the problems of traditional disinfection materials that rely on additional operations and have low efficiency.

[0078] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for synergistic water disinfection based on photocatalysis and low-voltage electroporation using a metal oxide array, characterized in that, Includes the following steps: Step 1: Prepare metal oxide nanoarray electrodes, wherein the metal oxide is any one or more of cuprous oxide, titanium dioxide, zinc oxide, and tungsten trioxide; Step 2: Using the prepared metal oxide nanoarray electrode as the cathode and commercially available copper foam or nickel foam as the anode, place them into the water to be disinfected to construct a low-voltage electroporation reaction system. Step 3: Apply a low-voltage DC electric field to the two electrodes and simultaneously excite the water and the surface of the metal oxide nanoarray electrode by light to achieve disinfection of pathogenic microorganisms in the water.

2. The disinfection method according to claim 1, characterized in that, In step 1, the morphology of the metal oxide nanoarray is at least one of nanowire array, nanotube array, and nanosheet array.

3. The disinfection method according to claim 1, characterized in that, The composite method of multiple metal oxides can be any one of in-situ growth composite, surface loading composite, or heterojunction composite.

4. The disinfection method according to claim 1, characterized in that, The metal oxide nanoarray is a nanoscale structure with an array diameter controlled between 20 and 200 nm and an array growth length controlled between 2 and 20 μm.

5. The disinfection method according to claim 1, characterized in that, In step 1, the metal oxide nanoarray is a cuprous oxide nanoarray electrode, and the preparation method is as follows: Step a: Immerse the copper foam in dilute hydrochloric acid solution for 10 minutes, turning it over once during the process. Then rinse it three times with deionized water and dry it with cold air. Step b: Place the copper foam in a mixed solution containing NaOH, (NH4)2S2O8 and deionized water and cooled in an ice-water bath for 20 minutes, turning it over every 10 minutes during the process; after removing it, wash it three times with deionized water and dry it with cold air. Step c: The dried copper foam is heated at 160-200 °C for 3.5 h under a nitrogen atmosphere to obtain cuprous oxide array electrodes; the preferred temperature is 180 °C.

6. The disinfection method according to claim 5, characterized in that, In step a, the concentration of the dilute hydrochloric acid solution is 1 mol / L; in the mixed solution of step b, the concentration of NaOH is 0.7–0.9 g / mL, and the concentration of (NH4)2S2O8 is 0.125–0.3 g / mL.

7. The disinfection method according to claim 1, characterized in that, In step 3, the DC low voltage is 0.5 to 5 V, and the distance between the cathode and the anode is 0.1 to 1.5 cm.

8. The disinfection method according to claim 1, characterized in that, In step 3, ultraviolet light is used as the excitation source, with a wavelength range of 200–420 nm and an illumination intensity controlled between 0.5–2 mW / cm². 2 .

9. The disinfection method according to claim 1, characterized in that, In step 2, the water body to be disinfected is any one of medical wastewater, urban sewage effluent, or emergency water supply water.

Images