Method for killing escherichia coli in water through cooperation of low-temperature plasma and composite oxide

Abstract

The invention discloses a method for killing escherichia coli in water through cooperation of low-temperature plasma and composite oxide, and relates to the technical field of water purification. Comprising the following steps: (1) preparing a Cu-Mg-Al (1: 2: 1) composite oxide; (2) loading a Cu-Mg-Al (1: 2: 1) composite oxide on the DBD lower dielectric baffle plate; and (3) the Cu-Mg-Al (1: 2: 1) composite oxide cooperates with the low-temperature plasma to treat the escherichia coli in the water body. Through the synergistic catalysis of the low-temperature plasma and the composite oxide, the efficiency of killing the escherichia coli in the water is greatly improved. High-activity particles (such as. OH,. O2-, H2O2, H < + > and the like) generated by the low-temperature plasma are combined with the composite oxide loaded in the double-medium DBD reactor, bacterial cell membranes can be rapidly destroyed, the sterilization rate reaches 99% or above, and the method is remarkably superior to a traditional water treatment technology.

Description

Technical Field

[0001] The invention relates to the technical field of water purification, and more particularly to a method for killing Escherichia coli in water using low-temperature plasma in conjunction with composite oxides. Background Art

[0002] In recent years, with the aggravation of water pollution, various harmful substances and pathogenic microorganisms (such as Escherichia coli, etc.) exist in water bodies in large quantities, seriously affecting the ecological environment and human health. As an indicator microorganism, Escherichia coli is widely present in water bodies such as sewage and domestic wastewater, and can cause a variety of diseases. Therefore, how to effectively eliminate Escherichia coli in water bodies has become a research focus. Traditional water treatment methods (such as chlorination disinfection, ultraviolet irradiation, ozone oxidation, etc.) have good effects in some applications, but they also have defects such as high energy consumption, limited treatment efficiency, and easy production of harmful by-products. In particular, the treatment effect on low-concentration pathogens is poor, and it is easy to produce drug resistance problems, which has prompted people to explore new efficient and safe water treatment technologies.

[0003] With the development of low-temperature plasma technology, some scholars have tried to use low-temperature plasma to kill pathogenic microorganisms in water and have achieved positive results. Low-temperature plasma produces highly active particles (such as O3, 1 O2, O2 - , ROO·, RO·, OH·, etc.) can effectively destroy the cell structure of microorganisms and eliminate pathogens. However, the single use of low-temperature plasma technology consumes high energy in the sterilization process, and may produce more by-products such as ozone and nitrogen oxides, which is not conducive to water safety. Therefore, the researchers further proposed low-temperature plasma synergistic catalytic technology to improve the treatment effect and reduce by-products. Since plasma active species cannot selectively excite reactants, all components in water can participate in plasma reactions, resulting in a large number of reaction by-products. In recent years, plasma catalytic technology has been developed to combine plasma with catalysts, and utilize the synergistic effect of high reactivity and high selectivity to improve sterilization efficiency and energy efficiency. In this system, the selection and development of catalysts are crucial. Low-temperature plasma synergistic catalytic technology has been applied well in waste gas treatment and air sterilization. However, due to the limitations of different phases of target pollutants and purification targets, in the water phase reaction, plasma-activated water is first prepared, and then the catalyst is added. The two synergistically kill Escherichia coli in water. It takes two steps or more to operate, which reduces the utilization efficiency of plasma and limits the application of this technology.

[0004] Therefore, providing a method for eliminating Escherichia coli in water with high utilization rate and few reaction steps is an urgent problem 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 killing Escherichia coli in water by using low-temperature plasma in conjunction with composite oxides.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for killing Escherichia coli in water by using low-temperature plasma in conjunction with composite oxides comprises the following steps:

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

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

[0010] Heat to 70°C and react in an ultrasonic water bath for 5 hours, maintaining the pH between 10-11 during the whole process;

[0011] Let it stand, remove the supernatant, filter, and wash repeatedly until it becomes neutral to obtain a gelatinous product;

[0012] (2) Cu-Mg-Al composite oxide loaded on the DBD lower dielectric baffle

[0013] The colloidal product prepared in step (2) was evenly applied to the center of a quartz dish, and the quartz dish was placed upright in a CVD tube furnace, and the temperature was raised to 150°C, and nitrogen was passed through the furnace for protection under vacuum, and the temperature was maintained at 150°C for 4 hours;

[0014] Rapidly heating to 600°C and calcining for 2 hours to obtain a lower dielectric baffle plate loaded with Cu-Mg-Al composite oxide;

[0015] (3) Treatment of Escherichia coli in water by Cu-Mg-Al composite oxides and low-temperature plasma

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

[0017] The DBD reactor was started at room temperature with an operating power of 20 kHz. The distance between the low-temperature plasma and the liquid surface was 8 mm, that is, the distance between the upper and lower media was 10 mm. After reacting for 30 minutes, a certain amount of solution was taken out and the Escherichia coli concentration 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 material: mixed aqueous solution is 0.6mmol:100mL;

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

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

[0023] The coating area is 50×50 mm.

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

[0025] (1) The present invention greatly improves the efficiency of killing Escherichia coli in water through the synergistic catalytic effect of low-temperature plasma and composite oxide. The high-activity particles (such as ·OH, ·O 2- , H2O2, H + The combination of the composite oxides loaded in the dual-medium DBD reactor can quickly destroy the bacterial cell membrane, with a sterilization rate of more than 99%, which is significantly better than traditional water treatment technology.

[0026] (2) Conventional 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 to be directly loaded in the DBD reactor, integrating sterilization and catalysis, and can complete the efficient elimination of Escherichia coli in a single-step operation, simplifying the operation process and improving energy utilization efficiency.

[0027] (3) The composite oxide prepared by the present invention has excellent antibacterial properties and can interact with the negative charges on the surface of the Escherichia coli cell membrane. In addition, the composite oxide has high stability and can still maintain its structure and performance under high voltage discharge conditions, ensuring a 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-catalytic effect of the composite oxide, more active particles are used for sterilization, effectively reducing the generation of harmful by-products such as ozone and nitrogen oxides, reducing secondary pollution to water quality, and ensuring water safety.

[0029] The composite oxide catalyst of the present invention uses hydrotalcite as a precursor, has low material cost, simple preparation process, can be used for large-scale water treatment applications, and has good economic benefits and broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

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

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

[0033] Figure 3 The E.Coli sterilization effect diagram of Example 3 and Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

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

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

[0038] 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 were dissolved in 100 mL of a mixed aqueous solution consisting of urea and NaOH (including 0.60% by mass of urea and 0.01% by mass of NaOH);

[0039] Heat to 70°C and react in an ultrasonic water bath for 5 hours, maintaining the pH between 10-11 during the whole process;

[0040] Let it stand, remove the supernatant, filter, and wash repeatedly until it becomes neutral to obtain a gelatinous product;

[0041] (2) Cu-Mg-Al (1:2:1) composite oxide loaded on the DBD lower dielectric baffle

[0042] The colloidal product obtained in step (2) was evenly applied to the center of a quartz dish with a thickness of 2 mm and Φ=80 mm, with an application area of ​​50×50 mm. The quartz dish was placed in a CVD tube furnace, heated to 150° C., evacuated and nitrogen was passed for protection, and the reaction temperature was maintained at 150° C. for 4 hours;

[0043] Rapidly heating to 600°C and calcining for 2 hours to obtain a lower dielectric baffle plate loaded with Cu-Mg-Al (1:2:1) composite oxide;

[0044] The crystal structure of the loaded Cu-Mg-Al (1:2:1) composite oxide was characterized. Figure 1 As shown, broad diffuse peak packets with weaker peak intensity are formed at ~38° and ~61°, indicating that the Fd-3m group structure of the precursor is still retained after Cu doping.

[0045] (3) Treatment of Escherichia coli in water by Cu-Mg-Al (1:2:1) composite oxide synergistic with low-temperature plasma

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

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

[0048] The bactericidal ability of Cu-Mg-Al (1:2:1) composite oxide synergistic with low-temperature plasma against E. coli was evaluated.

[0049] Microscope photos of E.Coli before and after the experiment are shown below. Figure 2 As shown, Figure 2 A is E. coli before treatment, showing a large number of bacteria with a typical rod-shaped structure, indicating that most of the E. coli are alive. Figure 2 B shows the status of E. Coli bacteria after Cu-Mg-Al (1:2:1) composite oxide synergistic low-temperature plasma treatment. The number of bacteria is significantly reduced and the rod-shaped morphology is difficult to identify, indicating that the bacteria are severely damaged or dead.

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

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

[0052] The bactericidal effect of Cu-Mg-Al (1:2:1) composite oxide and low-temperature plasma on E.Coli Figure 3 As shown, the three treatment methods of Comparative Example 1, Comparative Example 2 and Example 1 are recorded as NTPs, LDOs and LDOs+NTPs respectively. As the reaction time increases, the three methods have a certain bactericidal effect. After 10 minutes of NTPs reaction, the amount of E. Coli bacteria decreased from the initial 8log to about 5log CFU / mL, and was close to 0 after 20 minutes. The bactericidal effect of LDOs was the weakest, and there was still ~10 after 30 minutes. 3 CFU / mL bacterial retention. When LDOs and NTPs were used in combination, the 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 one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for killing Escherichia coli in water by using low-temperature plasma in combination with composite oxides, characterized in that: The following steps are involved: (1) Preparation of Cu-Mg-Al composite oxide Take the raw materials Cu(NO3)2·3H2O, Mg(NO3)2·6H2O and Al(NO3)3·9H2O and dissolve them into the mixed aqueous solution; Heat to 70°C and react in an ultrasonic water bath for 5 hours, maintaining the pH between 10-11 during the whole process; Let it stand, remove the supernatant, filter, and wash repeatedly until it becomes neutral to obtain a gelatinous product; (2) Cu-Mg-Al composite oxide loaded on the DBD lower dielectric baffle The colloidal product prepared in step (2) was evenly applied to the center of a quartz dish, and the quartz dish was placed upright in a CVD tube furnace, and the temperature was raised to 150°C, and nitrogen was passed through the furnace for protection under vacuum, and the temperature was maintained at 150°C for 4 hours; Rapidly heating to 600°C and calcining for 2 hours to obtain a lower dielectric baffle plate loaded with Cu-Mg-Al composite oxide; (3) Treatment of Escherichia coli in water by Cu-Mg-Al composite oxides and low-temperature plasma Placing the E. coli solution in the lower medium baffle plate prepared in step (2); The DBD reactor was started at room temperature with an operating power of 20 kHz. The distance between the low-temperature plasma and the liquid surface was 8 mm, that is, the distance between the upper and lower media was 10 mm. After reacting for 30 minutes, a certain amount of solution was taken out and the Escherichia coli concentration was counted using the plate colony counting method.

2. The method according to claim 1, characterized in that 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 material: mixed aqueous solution is 0.6mmol:100mL; The mixed aqueous solution includes 0.60% by mass of urea and 0.01% by mass of NaOH.

3. The method according to claim 1, characterized in that The quartz dish in step (2) has a thickness of 2 mm and a diameter of 80 mm. The coating area is 50×50 mm.

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