A method for eliminating Escherichia coli in water using low-temperature plasma synergistic composite oxides

Abstract

This invention discloses a method for eliminating Escherichia coli in water using a low-temperature plasma synergistic composite oxide, relating to the field of water purification technology. The method includes the following steps: (1) preparation of Cu-Mg-Al (1:2:1) composite oxide; (2) loading the Cu-Mg-Al (1:2:1) composite oxide onto a DBD (dual-medium) medium baffle plate; (3) synergistic treatment of Escherichia coli in water using the Cu-Mg-Al (1:2:1) composite oxide and low-temperature plasma. This invention significantly improves the efficiency of eliminating Escherichia coli in water through the synergistic catalytic effect of low-temperature plasma and composite oxide. The highly active particles generated by the low-temperature plasma (such as ·OH, ·O2−, H2O2, H+, etc.) combine with the composite oxide loaded in the dual-medium DBD reactor, rapidly destroying bacterial cell membranes and achieving a sterilization rate of over 99%, significantly superior to traditional water treatment technologies.

Description

Technical Field

[0001] This invention relates to the field of water purification technology, and more specifically to a method for eliminating Escherichia coli in water using low-temperature plasma synergistic composite oxides. Background Technology

[0002] In recent years, with the aggravation of water pollution, various harmful substances and pathogenic microorganisms (such as Escherichia coli) are present in large quantities in water bodies, seriously affecting the ecological environment and human health. Escherichia coli, as an indicator microorganism, is widely found in sewage, domestic wastewater, and other water bodies, and can cause various diseases. Therefore, how to effectively eliminate E. coli in water bodies has become a key research focus. Traditional water treatment methods (such as chlorination disinfection, ultraviolet irradiation, and ozone oxidation) have good effects in some applications, but they also have drawbacks such as high energy consumption, limited treatment efficiency, and easy generation of harmful byproducts. In particular, they are ineffective in treating low concentrations of pathogens and are prone to drug resistance, prompting the exploration of new, efficient, and safe water treatment technologies.

[0003] With the development of low-temperature plasma technology, some scholars have attempted to use low-temperature plasma to eliminate pathogenic microorganisms in water, and have achieved positive results. Low-temperature plasma generates highly reactive particles (such as O3, ... 1 O2, O2· - Low-temperature plasma (RTP), including ROO·, RO·, and OH·, can effectively destroy the cell structure of microorganisms, thereby eliminating pathogens. However, using low-temperature plasma alone results in high energy consumption during sterilization and may generate numerous byproducts such as ozone and nitrogen oxides, which are detrimental to water safety. Therefore, researchers have proposed low-temperature plasma synergistic catalysis technology to improve treatment efficiency and reduce byproducts. Since plasma-active species cannot selectively excite reactants, all components in water can participate in the plasma reaction, leading to the generation of numerous reaction byproducts. In recent years, plasma catalysis technology has been developed, combining plasma with catalysts to utilize the synergistic effect of high reactivity and high selectivity, thereby improving sterilization efficiency and energy efficiency. In this system, the selection and development of catalysts are crucial. Low-temperature plasma synergistic catalysis technology has shown good application results in waste gas treatment and air sterilization. However, due to the limitations of different phases of target pollutants and purification targets, in aqueous phase reactions, plasma-activated water must first be prepared, followed by the addition of a catalyst. The synergistic elimination of E. coli in water requires two or more steps, reducing the utilization efficiency of plasma and limiting the application of this technology.

[0004] Therefore, providing a highly efficient method for eliminating E. coli in water with fewer reaction steps is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for eliminating Escherichia coli in water using low-temperature plasma synergistic composite oxides.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for eliminating Escherichia coli in water using low-temperature plasma synergistic composite oxides includes the following steps:

[0008] (1) Preparation of Cu-Mg-Al composite oxides

[0009] Take raw materials Cu(NO3)2·3H2O, Mg(NO3)2·6H2O and Al(NO3)3·9H2O, and dissolve them in a mixed aqueous solution;

[0010] Heat to 70℃, ultrasonically react in water bath for 5 hours, and maintain pH between 10 and 11 throughout the process;

[0011] Let stand, skim off the supernatant, filter, and wash repeatedly until neutral to obtain a gel-like product;

[0012] (2) Cu-Mg-Al composite oxide loaded on a dielectric baffle plate under DBD

[0013] The gel-like product prepared in step (2) was evenly coated on the center of the quartz dish. The quartz dish was placed upright in the CVD tube furnace, heated to 150°C, and protected by vacuum and nitrogen gas. The reaction was maintained at 150°C for 4 hours.

[0014] The sample was rapidly heated to 600℃ and calcined for 2 hours to obtain a lower dielectric baffle plate supported on Cu-Mg-Al composite oxide.

[0015] (3) Cu-Mg-Al composite oxides synergistically treat Escherichia coli in water with low-temperature plasma

[0016] The E. coli solution was placed in the lower medium baffle plate prepared in step (2);

[0017] The DBD reactor was started at room temperature with a working power of 20 kHz. The distance between the low-temperature plasma and the liquid surface was 8 mm, i.e., the distance between the upper and lower media was 10 mm. After reacting for 30 min, a certain amount of solution was taken out, and the concentration of Escherichia coli was counted using the plate colony counting method.

[0018] Furthermore,

[0019] The molar ratio of Cu(NO3)2·3H2O:Mg(NO3)2·6H2O:Al(NO3)3·9H2O in step (1) is 1:2:1;

[0020] The ratio of the raw materials to the mixed aqueous solution is 0.6 mmol: 100 mL;

[0021] The mixed aqueous solution comprises 0.60% by mass of urea and 0.01% by mass of NaOH.

[0022] Furthermore, the quartz dish described in step (2) has a thickness of 2 mm and a diameter of 80 mm.

[0023] The area to be coated is 50×50mm.

[0024] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) This invention significantly improves the efficiency of eliminating E. coli in water through the synergistic catalytic effect of low-temperature plasma and composite oxides. The highly reactive particles generated by the low-temperature plasma (such as ·OH, ·O) 2- H2O2, H + The combination of these substances with composite oxides loaded in a dual-media DBD reactor can rapidly destroy bacterial cell membranes, achieving a sterilization rate of over 99%, which is significantly superior to traditional water treatment technologies.

[0026] (2) Traditional plasma water treatment technology usually requires the preparation of plasma-activated water first, and then a two-step operation in combination with the treatment target. However, the present invention uses composite oxides directly loaded in the DBD reactor, which integrates sterilization and catalysis, and can complete the efficient elimination of E. coli in a single step, simplifying the operation process and improving energy utilization efficiency.

[0027] (3) The composite oxide prepared by this invention has excellent antibacterial properties and can interact with the negative charge on the surface of the Escherichia coli cell membrane. In addition, the composite oxide has high stability and can maintain its structure and performance under high voltage discharge conditions, ensuring stable sterilization effect during long-term use.

[0028] (4) Compared with the use of low-temperature plasma technology alone, the present invention optimizes the plasma reaction process. Through the adsorption-catalysis of composite oxides, more active particles are used for sterilization, effectively reducing the generation of harmful byproducts such as ozone and nitrogen oxides, reducing secondary pollution to water quality, and ensuring water safety.

[0029] The composite oxide catalyst of this invention uses hydrotalcite as a precursor, which is inexpensive and has a simple preparation process. It can be used in large-scale water treatment applications and has good economic benefits and broad market prospects. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0031] Figure 1 The image shows the XRD pattern of the Cu-Mg-Al(1:2:1) composite oxide prepared in Example 1.

[0032] Figure 2 These are microscope images of E. coli before and after the experiment in Example 3.

[0033] Figure 3 The images show the bactericidal effect of E. coli in Example 3 and Comparative Examples 1 and 2. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] This invention provides a method for preparing Cu-Mg-Al (1:2:1) composite oxide modified with antibacterial properties, characterized by comprising the following steps:

[0037] (1) Preparation of Cu-Mg-Al(1:2:1) composite oxide

[0038] Dissolve 0.15 mmol of Cu(NO3)2·3H2O, 0.3 mmol of Mg(NO3)2·6H2O and 0.15 mmol of Al(NO3)3·9H2O in 100 mL of a mixed aqueous solution consisting of urea and NaOH (including 0.60% by mass urea and 0.01% by mass NaOH).

[0039] Heat to 70℃, ultrasonically react in water bath for 5 hours, and maintain pH between 10 and 11 throughout the process;

[0040] Let stand, skim off the supernatant, filter, and wash repeatedly until neutral to obtain a gel-like product;

[0041] (2) Cu-Mg-Al (1:2:1) composite oxide loaded on a dielectric baffle plate under DBD

[0042] The gel-like product obtained in step (2) was evenly coated on the center of a quartz dish with a thickness of 2 mm and Φ = 80 mm. The coating area was 50 × 50 mm. The quartz dish was placed in a CVD tube furnace, heated to 150 °C, and protected by vacuum and nitrogen gas. The reaction was maintained at 150 °C for 4 hours.

[0043] The substrate was rapidly heated to 600℃ and calcined for 2 hours to obtain a lower dielectric baffle plate supported on Cu-Mg-Al (1:2:1) composite oxide.

[0044] Crystal structure characterization was performed on supported Cu-Mg-Al (1:2:1) composite oxides, such as... Figure 1 As shown, a broad, diffuse peak packet with relatively weak peak intensity is formed at ~38° and ~61°, indicating that the Fd-3m group structure of the precursor is still retained after Cu doping.

[0045] (3) Cu-Mg-Al (1:2:1) composite oxides synergistically treat Escherichia coli in water with low-temperature plasma.

[0046] Add 10 ml of E. coli solution (10 8 (CFU / mL) was placed in the lower medium baffle plate prepared in step (2);

[0047] The DBD reactor was started at room temperature with a working power of 20 kHz. The distance between the low-temperature plasma and the liquid surface was 8 mm (i.e., the distance between the upper and lower media was 10 mm). After 30 min of reaction, a certain amount of solution was taken out, and the concentration of E. coli was counted using the plate colony counting method.

[0048] To evaluate the bactericidal ability of Cu-Mg-Al (1:2:1) composite oxides in synergy with low-temperature plasma against E. coli.

[0049] Microscopic images of E. coli before and after the experiment are as follows: Figure 2 As shown, Figure 2 A shows E. coli before treatment, indicating a high number of bacteria with a typical rod-shaped structure, suggesting that most of the E. coli were still alive. Figure 2 B shows the state of E. coli bacteria after synergistic low-temperature plasma treatment with Cu-Mg-Al (1:2:1) composite oxides. The bacterial count was significantly reduced and the rod-shaped morphology was difficult to identify, indicating that the bacteria were severely damaged or dead.

[0050] Comparative Example 1: The difference between this comparative example and Example 1 is that the loading process of Cu-Mg-Al(1:2:1) composite oxide in step (2) is removed, and the bactericidal ability of low temperature plasma alone against E. coli is evaluated. The remaining steps are the same as in Example 1.

[0051] Comparative Example 2: The difference between this comparative example and Example 1 is that the DBD reactor startup process in step (3) is removed, and the adsorption and bactericidal ability of Cu-Mg-Al (1:2:1) composite oxide alone against E. coli is evaluated. The remaining steps are the same as in Example 1.

[0052] The synergistic effect of Cu-Mg-Al (1:2:1) composite oxides and low-temperature plasma on the bactericidal effect of E. coli is as follows: Figure 3 As shown, the three treatment methods in Comparative Example 1, Comparative Example 2, and Example 1 are denoted as NTPs, LDOs, and LDOs+NTPs, respectively. With increasing reaction time, all three methods showed some bactericidal effect. After 10 minutes of reaction with NTPs, the E. coli bacterial count decreased from an initial 8 log CFU / mL to approximately 5 log CFU / mL, and approached zero after 20 minutes. LDOs had the weakest bactericidal effect, still showing ~10 CFU / mL after 30 minutes. 3 CFU / mL bacterial survival. When LDOs were used in combination with NTPs, bacteria were almost completely eliminated within 10 minutes, indicating that the synergistic bactericidal effect of LDOs and NTPs was significantly better than that of either method alone.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for eliminating Escherichia coli in water using low-temperature plasma synergistic composite oxides, characterized in that, Includes the following steps: (1) Preparation of Cu-Mg-Al composite oxides Take raw materials Cu(NO3)2·3H2O, Mg(NO3)2·6H2O and Al(NO3)3·9H2O, and dissolve them in a mixed aqueous solution; Heat to 70℃ and react in an ultrasonic water bath for 5 hours, maintaining the pH between 10 and 11 throughout the process. Let stand, skim off the supernatant, filter, and wash repeatedly until neutral to obtain a gel-like product; (2) Cu-Mg-Al composite oxide loaded on a dielectric baffle plate under DBD The gel-like product prepared in step (2) was evenly coated on the center of the quartz dish. The quartz dish was placed upright in the CVD tube furnace, heated to 150°C, and protected by vacuum and nitrogen gas. The reaction was maintained at 150°C for 4 hours. The substrate was rapidly heated to 600℃ and calcined for 2 hours to obtain a lower dielectric baffle plate supported on Cu-Mg-Al composite oxide. (3) Cu-Mg-Al composite oxides synergistically treat Escherichia coli in water with low-temperature plasma The E. coli solution was placed in the lower medium baffle plate prepared in step (2); The DBD reactor was started at room temperature with a working power of 20 kHz. The distance between the low-temperature plasma and the liquid surface was 8 mm, i.e., the distance between the upper and lower media was 10 mm. After reacting for 30 min, a certain amount of solution was taken out, and the concentration of Escherichia coli was counted using the plate colony counting method. The molar ratio of Cu(NO3)2·3H2O:Mg(NO3)2·6H2O:Al(NO3)3·9H2O in step (1) is 1:2:1; The ratio of the raw materials to the mixed aqueous solution is 0.6 mmol: 100 mL; The mixed aqueous solution comprises 0.60% by mass of urea and 0.01% by mass of NaOH; The quartz dish described in step (2) has a thickness of 2 mm and a diameter of 80 mm. The area to be coated is 50×50mm.

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