Degradation method of quinolone antibiotics

Abstract

The invention discloses a method for degrading quinolone antibiotics, and designs a single-needle corona discharge degradation device which realizes energy input by regulating and controlling discharge voltage, so that wet water vapor around a needle tip is ionized to generate high-reaction-activity water free radical cations and clusters thereof; according to the method, the quinolone antibiotics are degraded by utilizing the strong oxidation-reduction property of water free radical cations, the quinolone antibiotics react with target molecules by utilizing the strong oxidation-reduction property of the water free radical cations, and efficient degradation of the antibiotics is realized through a series of chemical processes such as hydroxylation, defluorination and ring opening. The method is simple to operate, has the advantages of high efficiency, no need of a catalyst, low energy consumption and the like, and shows a wide application prospect in the fields of wastewater treatment, environmental restoration and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of water pollution control, and particularly relates to a method for degrading quinolone antibiotics in a water environment by utilizing corona discharge to generate water free radical cations. Background Art

[0002] Quinolones (FQs) are a class of synthetic broad-spectrum antibiotics with high efficacy in treating viral and bacterial infections and have been widely used in recent years. Their high water solubility and environmental persistence make them difficult to effectively degrade in the natural environment, making them an emerging pollutant of global concern. To date, methods for treating quinolone antibiotics in wastewater include chemical reduction and oxidation, activated carbon adsorption, and microbial treatment. Among them, advanced oxidation processes such as electrochemical oxidation, ozone oxidation, Fenton oxidation, and photocatalysis have shown significant advantages in treating refractory organic pollutants due to their ability to generate highly oxidizing hydroxyl radicals. However, these methods still have many limitations in practical application: 1) incomplete mineralization of pollutants, which may produce more toxic intermediates; 2) treatment efficiency is significantly affected by water quality; 3) high energy consumption and high operating costs; and 4) potential for secondary pollution. Therefore, the development of new, efficient, economical, and environmentally friendly FQs degradation technologies has become a critical issue in the current environmental field.

[0003] As a highly active, strongly oxidizing, special reactive species, water dimer radical cations play a vital role in analytical and synthetic chemistry. Water radical cations can not only serve as primary ions in mass spectrometry analysis, significantly improving the sensitivity and selectivity of mass spectrometry detection through charge transfer or proton transfer reactions with target molecules, but also exhibit excellent catalytic properties in chemical reactions. Compared with traditional hydroxyl radicals, water radical cations have a higher oxidation potential, more diverse reaction pathways, and can be generated at room temperature and pressure, avoiding the use of high temperature, high pressure, or strong chemical oxidants, offering significant technical advantages.

[0004] This study designed a corona discharge reactor that precisely controls energy input to ionize water vapor, generating highly active water radical cations and their clusters. These cations then react with antibiotics using their strong oxidizing properties, achieving efficient degradation. Using norfloxacin and ofloxacin, typical quinolone antibiotics, as target pollutants, the degradation effect of water radical cations on these antibiotics and their mechanism of action were systematically investigated. Summary of the Invention

[0005] The present invention aims to provide a method for degrading quinolone antibiotics by reacting water dimer radical cations generated by low-energy corona discharge. By precisely controlling the discharge voltage and the reaction distance between the needle tip and the antibiotic solution, the water vapor moistened around the needle tip is ionized, thereby generating short-lived but highly reactive water radical cations and their clusters. These highly reactive radical cations and their clusters can rapidly react with antibiotic molecules, ultimately decomposing into H2O, CO2, and small molecule compounds, thereby achieving efficient degradation. The present invention does not require the use of a catalyst and can achieve efficient degradation of quinolone antibiotics in a short period of time, thus having considerable application prospects.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for degrading quinolone antibiotics uses a corona discharge reaction device to generate water radical cations and their clusters, which react with the quinolone antibiotics to achieve degradation. The single-needle corona discharge reaction device comprises three parts: a high-voltage power supply, a corona discharge ionization source, and a reaction platform.

[0008] Furthermore, the corona discharge ionization source is a sharp stainless steel discharge needle with a needle tip curvature radius of 30 μm, a needle length of 7 cm, and an outer diameter of 0.16 mm. The discharge needle is fixed on a movable and adjustable iron frame, which can achieve precise adjustment in the horizontal and vertical directions.

[0009] Furthermore, the reaction platform includes a conductive glass plate and an antibiotic solution.

[0010] Furthermore, the conductive glass plate is coated with an ITO transparent conductive film and is located below the corona discharge ionization source for placing the antibiotic solution. The discharge reaction distance, that is, the distance from the discharge needle tip to the antibiotic solution surface, can be controlled by adjusting the iron stand.

[0011] Furthermore, the discharge reaction distance is 5 mm.

[0012] Furthermore, the volume of the antibiotic solution is 30 to 200 μL.

[0013] Furthermore, the corona discharge needle is connected to the positive electrode of the high-voltage power supply, and the conductive glass plate is connected to the negative electrode of the high-voltage power supply. By adjusting the high-voltage power supply, the electric field strength between the discharge needle and the conductive glass plate can be controlled. The tip of the discharge needle generates a stable corona discharge, ionizing water vapor to form highly active water radical cations and their clusters.

[0014] Furthermore, the discharge voltage is controlled between 4.5 and 6.0 kV.

[0015] The present invention has the following beneficial effects: the present invention utilizes corona discharge ionization technology and designs a single-needle degradation reaction device to achieve the preparation of highly active and abundant water radical cations and their clusters under ambient conditions. This technology breaks through the dependence of traditional preparation methods on extreme conditions (such as high vacuum, ultra-low temperature and large-scale reaction devices), reducing equipment costs and energy consumption. The water radical cation clusters have extremely strong oxidizing ability and can directly attack key chemical bonds (such as C—F bonds, C—C bonds and C—N bonds) in quinolone antibiotic molecules, triggering reactions such as defluorination, chain scission and ring opening, and ultimately decomposing quinolone antibiotics into small molecular compounds (such as CO₂, H₂O and inorganic salts), achieving deep mineralization of quinolone antibiotics. No chemical reagents need to be added during the reaction process, which conforms to the principles of green chemistry and is of great significance to environmental protection and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0017] Figure 1 This is a schematic diagram of the structure of the quinolone antibiotic degradation device of the present invention, wherein 1 is a conductive glass plate, 2 is a stainless steel discharge needle, 3 is a reaction distance, and 4 is a high voltage source;

[0018] Figure 2 The UV-visible spectra of norfloxacin before and after degradation and the corresponding concentration changes;

[0019] Figure 3 Mass spectra of norfloxacin before and after degradation;

[0020] Figure 4 Mass spectra of ofloxacin before and after degradation. DETAILED DESCRIPTION

[0021] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it should not be understood as a limitation on the scope of protection of the present invention.

[0022] In the description of the present invention, it should be understood that the descriptions involving directions, such as up, down, front, back, left, right, etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In the description of the present invention, the meaning of "several" is one or more, the meaning of "many" is more than two, and the meanings of "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and the meanings of "above", "below", "within", etc. are understood to include the number itself. If there is a description of first or second, it is only for the purpose of distinguishing technical features, and cannot be understood to indicate or imply relative importance or implicitly indicate the number of the indicated technical features or implicitly indicate the order of the indicated technical features.

[0023] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0024] See also Figures 1-4 The present invention proposes a method for degrading quinolone antibiotics, wherein the degradation device is as follows: Figure 1 As shown, it specifically includes a high-voltage power supply 4, a corona discharge ionization source and a reaction platform.

[0025] The corona discharge ionization source is a sharp stainless steel discharge needle 2, which is fixed on a movable and adjustable iron frame during specific application.

[0026] The tip curvature radius of the stainless steel discharge needle 2 is 30 μm, the needle length is 7 cm, and the outer diameter is 0.16 mm. Precise adjustment in the horizontal and vertical directions can be achieved by controlling the iron stand.

[0027] The reaction platform is fixed below the stainless steel discharge needle 2. Specifically, the reaction platform includes a conductive glass plate 1 and an antibiotic solution. The antibiotic solution to be reacted is placed on the conductive glass plate 1. The stainless steel discharge needle 2 and the antibiotic solution have a certain reaction distance 3. The reaction distance can be adjusted by controlling the iron frame. Preferably, the reaction distance 3 is 5 mm.

[0028] The stainless steel discharge needle 2 is connected to the positive electrode of the high-voltage power supply 4, and the conductive glass plate 1 is connected to the negative electrode of the high-voltage power supply 4. The high-voltage power supply 4 is turned on and applies high voltage to the stainless steel discharge needle 2, causing a stable corona discharge at the tip of the stainless steel discharge needle 2. This ionizes water vapor to form highly active water radical cations and their clusters, which then react with the antibiotic solution. The post-reaction antibiotic solution is collected for subsequent analysis.

[0029] Based on the above device, the specific degradation method of quinolone antibiotics includes:

[0030] Taking typical quinolone antibiotics norfloxacin and ofloxacin as examples, the degradation effect of water radical cations and their clusters on quinolone antibiotics was investigated. A certain volume of antibiotic solution was placed on the conductive glass plate. By adjusting the high-voltage power supply and the discharge distance, the tip of the stainless steel discharge needle 2 generated a discharge and ionized the surrounding water vapor to form water radical cation clusters, which were further exposed to the water radical environment generated by corona discharge to react. The sample solution after the reaction was collected for ultraviolet spectral analysis and mass spectrometry analysis to evaluate the degradation effect and study the reaction mechanism.

[0031] The concentrations of ofloxacin and norfloxacin after degradation were determined using an ultraviolet spectrophotometer. A series of standard solutions of norfloxacin and ofloxacin were prepared at concentrations of 0.5, 1.0, 2.5, 5, and 10 mg / L. UV absorption peaks were recorded. The results showed that norfloxacin and ofloxacin had strong absorption peaks at 293 nm and 277 nm, respectively. Regression equations for the concentration-absorbance standard curves were constructed using the absorbance and concentration of the maximum absorption peak as the ordinate and abscissa, respectively. The linear regression equations for norfloxacin were y = 0.1269x + 0.0249 (R² = 0.9993), and for ofloxacin were y = 0.09x + 0.0154 (R² = 0.9999). The absorbance intensity of the maximum absorption peak was measured using an ultraviolet spectrophotometer and substituted into the standard curve to calculate the corresponding concentration. The degradation rate was then determined based on the change in target compound concentration before and after the reaction. The calculation formula of the degradation rate is: degradation rate = (initial concentration - concentration after reaction) / initial concentration × 100%.

[0032] In specific applications, it was found that the degradation performance of corona discharge is affected by the electric field strength and the sample itself. Based on this, the effects of different solution volumes (30, 50, 100, and 200 μL), discharge voltages (4.5, 5.0, 5.5, and 6.0 kV), and initial solution concentrations (20, 50, 80, and 100 mg / L) on the degradation of quinolone antibiotics were studied. Through exploration and optimization of reaction conditions, the optimal reaction conditions were found to be a solution volume of 30 μL, a discharge voltage of 6.0 kV, and an initial concentration of 20 mg / L.

[0033] The effectiveness of the above-mentioned quinolone antibiotic degradation method is verified by several examples below:

[0034] Example 1

[0035] Taking norfloxacin, a typical quinolone antibiotic, as the target pollutant, the Figure 1The degradation experiment was conducted using the device shown in the figure. The specific steps were as follows: 30 μL of a 20 mg / L norfloxacin solution was added to the conductive glass plate. The discharge voltage was maintained at 4.5 kV and the discharge distance at 5 mm to ensure consistent reaction conditions. Samples were collected after 5, 10, 15, and 20 minutes of discharge reaction.

[0036] The sample solutions after different reaction times in Example 1 were subjected to UV-visible spectroscopy analysis. Figure 2 The changes in the UV-visible absorption spectra of norfloxacin solution before and after the interaction with water dimer radical cations generated by low-energy ambient corona discharge are shown. Figure 2 As can be seen in Figure a, with the increase of reaction time, it can be clearly observed that the peak intensity of norfloxacin at the maximum absorption wavelength gradually decreases, and the solution concentration decreases significantly ( Figure 2 (b) This indicates that the molecular structure of norfloxacin undergoes significant changes during the corona discharge process. After 20 minutes of reaction, the degradation rate of norfloxacin reached 85.5%. These experimental results fully confirm that the water dimer radical cations generated by corona discharge have extremely strong oxidizing ability and can efficiently degrade norfloxacin.

[0037] Example 2

[0038] Taking norfloxacin, a typical quinolone antibiotic, as the target pollutant, the Figure 1 The specific steps are as follows: 30 μL of a 10 mg / L norfloxacin solution was added to a conductive glass plate, the discharge voltage was kept constant at 5.0 kV and the discharge distance was kept constant at 5 mm, and the sample solution was collected after 10 minutes of discharge reaction.

[0039] The sample solution before and after the reaction of Example 2 was diluted 10 times and then subjected to electrospray ionization mass spectrometry analysis. Electrospray ionization mass spectrometry analysis of the norfloxacin solution before and after the reaction of the water radical cation for 10 minutes is as follows: Figure 3As shown, a characteristic ion at m / z 320 was detected in positive ion mode with a signal intensity of approximately 6.83×10³. After 10 minutes of degradation, the signal intensity of this ion decreased significantly, and 15 key reaction products were detected, with distinct characteristic ion peaks at m / z 336, m / z 292, and m / z 318. Tandem mass spectrometry analysis further identified these degradation products, which primarily consisted of replacement of the methyl group on the piperazine ring with a hydroxyl group, decarboxylation of the quinolone, and replacement of the fluorine group on the benzene ring with a hydroxyl group. The newly formed hydroxylated product underwent further oxidation, leading to the opening of the piperazine and quinolone rings, forming a series of intermediates (m / z 334, m / z 350, m / z 324, m / z 294, m / z 292, m / z 251, m / z 296, m / z 270, and m / z 235). These intermediates will be further destroyed by ·OH dissociated from the water dimer radical cations, thereby converting into small molecular compounds (m / z 119 and m / z 147) or even mineralizing into inorganic ions.

[0040] Example 3

[0041] Taking ofloxacin, a typical quinolone antibiotic, as the target pollutant, the Figure 1 The specific steps are as follows: 30 μL of a 10 mg / L norfloxacin solution was added to a conductive glass plate, the discharge voltage was kept constant at 5.0 kV and the discharge distance was kept constant at 5 mm, and the sample solution was collected after 10 minutes of discharge reaction.

[0042] The sample solution before and after the reaction of Example 3 was diluted 10 times and then subjected to electrospray ionization mass spectrometry analysis. Electrospray ionization mass spectrometry analysis of the norfloxacin solution before and after the reaction with the water radical cation for 10 minutes is as follows: Figure 4 As shown in the figure, after 10 minutes of degradation, the signal intensity of the hydrogenation ion of ofloxacin (m / z 362) decreased significantly, and the following characteristic ion peaks were mainly detected: m / z 366, m / z 378, m / z 394, m / z 360, m / z 322, and m / z 338. The degradation products corresponding to these ion peaks indicate that norfloxacin underwent hydroxylation, defluorination, chain scission, and ring opening during the corona discharge process. These unstable intermediates further underwent a series of reactions to form low-molecular-weight organic compounds (m / z 174, m / z 117, and m / z 101), which were ultimately mineralized into CO2 and H2O.

[0043] In summary, this invention, through the design of a single-needle corona discharge device, successfully demonstrates the enormous potential of water radical cations in pollutant degradation. This technology offers the following significant advantages: It is simple to operate and can achieve efficient degradation of quinolone antibiotics without the need for catalysts. This provides an innovative solution to the environmental problems of quinolone antibiotics and other difficult-to-degrade organic pollutants, and exhibits broad application prospects in wastewater treatment, environmental remediation, and other fields.

[0044] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0045] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for degrading quinolone antibiotics, characterized in that: A corona discharge reaction device is used to apply voltage to the corona discharge needle, so that the moist water vapor around the needle tip is ionized to produce water radical cations and their clusters. The highly active water radical cations and their clusters react with quinolone antibiotics to achieve degradation.

2. The method for degrading quinolone antibiotics according to claim 1, wherein: The corona discharge reaction device comprises a high-voltage power supply, a corona discharge ionization source and a reaction platform.

3. The method for degrading quinolone antibiotics according to claim 1, wherein: The voltage is controlled between 4.5 and 6.0 kV.

4. The method for degrading quinolone antibiotics according to claim 1, wherein: The corona discharge ionization source is a stainless steel discharge needle with a tip curvature radius of 30 μm, a needle length of 7 cm, and an outer diameter of 0.16 mm.

5. The method for degrading quinolone antibiotics according to claim 4, wherein: The stainless steel discharge needle is fixed on a movable and adjustable iron frame.

6. The method for degrading quinolone antibiotics according to claim 2, wherein: The reaction platform includes a conductive glass plate and an antibiotic solution located on the conductive glass plate.

7. The method for degrading quinolone antibiotics according to claim 6, wherein: The conductive glass plate is located below the corona discharge ionization source, and the antibiotic solution is placed on the conductive glass plate; there is a certain reaction distance between the discharge needle and the liquid surface of the antibiotic solution.

8. The method for degrading quinolone antibiotics according to claim 7, wherein: The reaction distance is 5 mm.

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