Method for enhancing reactive oxygen generation and antibiotic degradation of paddy field drainage
By constructing a Fe(II)-malic acid complex system in paddy field drainage, the problems of ROS generation and antibiotic degradation in paddy field drainage were solved, achieving efficient and stable ROS generation and antibiotic degradation, improving the degradation efficiency of oxytetracycline, and without causing additional burden on the environment.
Patent Information
- Application Number
- CN202610044252.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-14
- Publication Date
- 2026-02-13
AI Technical Summary
Existing technologies struggle to efficiently and stably generate reactive oxygen species (ROS) in paddy field drainage, and effectively degrade structurally stable antibiotic pollutants with long environmental half-lives, such as oxytetracycline. Furthermore, there is a lack of unified reaction platforms and control methods.
By introducing Fe(II) into a paddy field drainage simulation system to form a complex system with malic acid, optimizing its ratio, and constructing a Fe(II)-malic acid-paddy field drainage reaction system, the efficient generation of ROS was promoted, and its reaction with oxytetracycline was used to degrade antibiotics.
It significantly improved the generation rate and accumulation of ROS in paddy field drainage, and the degradation rate of oxytetracycline reached over 80%. Moreover, it adopted an environmentally friendly method and did not produce secondary pollution.
Smart Images
Figure CN121517005A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of rice paddy organic pollution remediation technology, specifically, it relates to a method for enhancing the generation of active oxygen and antibiotic degradation in rice paddy drainage. Background Technology
[0002] With the widespread application of livestock and poultry manure returning to paddy fields, antibiotic pollution in paddy soil has become increasingly prominent. Among these, oxytetracycline, due to its stable structure, long environmental half-life, and tendency to accumulate in soil-water systems, has become one of the most representative pollutants posing significant ecological risks. Long-term persistence of oxytetracycline in soil can not only affect the structure of microbial communities and soil biological functions but may also be absorbed by crops and enter the food chain, posing potential food safety hazards. Paddy field drainage is a common agricultural practice in rice cultivation. After prolonged flooding, antibiotic pollutants such as oxytetracycline in the soil can enter the water and be discharged into environmental water bodies, causing antibiotic pollution and other problems. Therefore, developing safe, efficient, and applicable antibiotic degradation technologies for paddy field drainage is of significant practical importance.
[0003] Currently, reactive oxygen species (ROS) technology is considered an effective way to degrade various organic pollutants in the environment due to its strong oxidizing capacity. However, traditional advanced oxidation systems still face many limitations in soil environments: on the one hand, catalysts are prone to complexation, passivation, or precipitation in soil solutions, which is not conducive to the continuous generation of ROS; on the other hand, natural soils have a complex composition, and iron is easily affected by mineral structure, organic matter, and other factors, reducing its activity and making it difficult to maintain the ROS generation process. In addition, existing systems have limited effectiveness in degrading oxytetracycline, which has a complex structure and high stability, and lack oxidation technologies with broad-spectrum adaptability.
[0004] Naturally occurring Fe(II), small-molecule organic acids, and dissolved iron components in paddy soil possess the potential to participate in electron transfer, forming a crucial basis for ROS generation. Existing studies have shown that applying small-molecule organic acids to paddy soil undergoing alternating wet and dry conditions can significantly promote the oxidation of ferrous iron by oxygen, thereby generating a large number of ROS free radicals and effectively degrading certain pesticides such as imidacloprid. However, these studies primarily rely on in-situ soil systems, where differences in solid minerals, dissolved organic matter, and microenvironment can interfere with the reaction process, making precise control of free radical generation difficult. Furthermore, existing research has largely focused on pesticide pollutants, with relatively insufficient research on the degradation patterns and promoting mechanisms of antibiotic pollutants.
[0005] Furthermore, there is currently a lack of a unified reaction platform for the efficient and stable generation of ROS in paddy field drainage, which is also easy to regulate and analyze mechanisms. Questions remain unanswered regarding how the synergistic ratio of iron ions and small-molecule organic acids affects ROS yield, whether there is an optimal concentration range, and whether it can effectively degrade typical antibiotics in the environment and has application potential.
[0006] Therefore, there is a need to develop a new method that can efficiently induce ROS generation in a simulated paddy field drainage system, with stable and controllable reactions, and significantly enhance antibiotic degradation capacity. This invention simulates real paddy field drainage conditions using soil extracts, introduces Fe(II) and malic acid to form a complex system, and achieves efficient ROS generation through optimized ratios. The degradation efficiency is verified using oxytetracycline as a representative pollutant, providing a new technical route for the green and sustainable remediation of antibiotic pollution in paddy field drainage. Summary of the Invention
[0007] Given the above shortcomings, a treatment method that can effectively solve the problem of antibiotic pollutants in paddy field drainage, achieve a dual enhancement effect of ROS generation and antibiotic degradation, and at the same time avoid secondary environmental impact is urgently needed in the industry.
[0008] To achieve the above-mentioned technical effects, the present invention employs the following technical means:
[0009] This invention first discloses a method for enhancing the generation of reactive oxygen species and the degradation of antibiotics in paddy field drainage, comprising:
[0010] (1) Select paddy soil without oxytetracycline, air dry it, weigh 30 g and add it to 90 mL of water (soil:water = 1:3), mix well and place it in a 150 mL glass bottle. Shake at 180 r for 30 min at room temperature, then centrifuge at 8000 r for 10 min and take the supernatant to simulate paddy field drainage. Then add oxytetracycline stock solution to make its concentration 5 mg / L, in which the content of the available Fe(II) is less than 20 mg / L.
[0011] (2) In the simulated paddy field drainage obtained in step (1), Fe(II) and malic acid are added to the same reaction system at the same time to construct the Fe(II)-malic acid-paddy field drainage reaction system, wherein: the Fe(II) is added in the form of soluble ferrous salt (FeSO4·7H2O), and the amount added is such that the final concentration of Fe(II) in the reaction system is 0-0.2 g / L; the final concentration of malic acid in the reaction system is 0-1.8 mmol / L; after the addition of Fe(II) and malic acid is completed, the reaction is carried out at room temperature (20-30℃).
[0012] (3) In the Fe(II)-malic acid-paddy field drainage reaction system described in step (2), reactive oxygen species, mainly hydroxyl radicals (·OH), are continuously generated in the system due to the oxidation reaction of Fe(II) under air conditions. To characterize the generation of reactive oxygen species, coumarin is added to the reaction system as a ·OH scavenger, with a final concentration of not less than 0.1 mmol / L. Samples are taken at the set reaction time points, and the reaction system is detected using a three-dimensional fluorescence spectrophotometer to obtain the generation level and cumulative change of ·OH.
[0013] (4) In the Fe(II)-malic acid-paddy field drainage system constructed in step (2), the oxytetracycline present in the paddy field drainage reacts with the generated reactive oxygen species during the reaction process, thereby being continuously degraded. During the reaction process, samples were taken at different time points to determine the residual concentration of oxytetracycline, so as to characterize the degradation rate and degradation efficiency of the antibiotic in the paddy field drainage.
[0014] The effective reaction range of Fe(II) and malic acid was determined by comparing the ·OH generation and oxytetracycline degradation effects under different combinations of Fe(II) concentrations (0-0.2 g / L) and malic acid concentrations (9-1.8 mmol / L). The results showed that when the Fe(II) concentration was 0.1-0.2 g / L and the malic acid concentration was 0.9-1.8 mmol / L, the ·OH generation in the paddy field drainage system was significantly increased, and the degradation rate of oxytetracycline was significantly accelerated. Further experiments were conducted with Fe(II) and malic acid concentrations of 0.1 and 0.2 g / L, and 0.9 and 1.8 mmol / L, respectively.
[0015] Under the above reaction conditions, the formation of ·OH in the paddy field drainage system reaches its highest level when the Fe(II) concentration is 0.2 g / L and the malic acid concentration is 1.8 mmol / L. Under these conditions, the degradation rate of oxytetracycline can reach approximately 80% within 2 hours and approximately 90% within 6 hours. Therefore, the combination of Fe(II) = 0.2 g / L and malic acid = 1.8 mmol / L can be considered as a preferred embodiment of the method of the present invention.
[0016] Under optimized formulation conditions, this system can stably generate high levels of reactive oxygen species at room temperature and under neutral conditions. Validation using oxytetracycline as the target pollutant showed that the system significantly improves its degradation rate and degradation efficiency, outperforming treatment with Fe(II) or malic acid alone, exhibiting a clear synergistic enhancement effect. The malic acid used is an environmentally friendly small-molecule organic acid that does not generate secondary pollution.
[0017] A method is provided to improve the generation of ROS in paddy field drainage and enhance the degradation efficiency of antibiotic pollution.
[0018] Technical solutions: Application of Fe(II) and malic acid complex in improving ROS generation in wastewater. Application of Fe(II) and malic acid complex in enhancing the degradation efficiency of antibiotic pollutants.
[0019] Preferably, the concentrations of Fe(II) and malic acid are 0.9 mmol / L and 1.8 mmol / L, respectively.
[0020] The antibiotic contaminant mentioned above is oxytetracycline (OTC).
[0021] The soil in the above-mentioned farmland is paddy soil with a water-to-soil ratio of 3:1.
[0022] The specific steps are as follows: Fe(II) and malic acid complex are added to the soil-water system during the simulated paddy field drainage period.
[0023] A complex that promotes the degradation of antibiotic pollutants in farmland soil, with Fe(II) and malic acid as its active ingredients.
[0024] Malic acid, acting as a complexing agent, forms a highly reactive Fe(II)-Mal complex with Fe(II), promoting its reaction with O2. As a reducing agent, malic acid efficiently regenerates the reaction byproduct Fe(III) back to Fe(II), thus achieving the continuous and stable generation of ·OH under mild conditions, ensuring the efficient degradation of pollutants. This increases the generation of ROS free radicals in the soil solution and enhances the degradation efficiency of antibiotic pollution.
[0025] Fe(Ⅱ) + Mal → Fe(Ⅱ)-Mal (1)
[0026] Fe(Ⅱ)-Mal + O2→ Fe(Ⅲ)-Mal + O2· - (2)
[0027] 2O2· - + 2H + → H2O2 + O2 (3)
[0028] Fe(Ⅱ)-Mal + H2O2 → Fe(Ⅲ)-Mal + ·OH + OH - (4)
[0029] Fe(Ⅲ)-Mal + Mal → Fe(Ⅱ)-Mal + Mal· +H + (5)
[0030] OTC-(CH3)2N+·OH→OTC-NHCH3+·CH2OH (6)
[0031] C 22 H 24N2O9 (OTC)+~40·OH→22CO2+12H2O+2HNO3 (7)
[0032] The beneficial effects of this invention are as follows:
[0033] (1) This invention adds malic acid to the soil solution system, causing it to complex with Fe(II) to form a highly reactive complexed Fe(II)-Mal structure, which can continuously generate ROS free radicals during air oxidation, thereby significantly promoting the oxidative degradation of antibiotics. Compared with Fe(II) treatment alone, the ROS generation rate in the system of this invention is faster and the accumulation is higher, showing a significant removal effect on oxytetracycline.
[0034] (2) The malic acid used in this invention is a small-molecule organic acid that is naturally found in soil. It is widely available, environmentally friendly, and will not impose an additional burden on the soil ecosystem. Compared with traditional oxidants or chemical fortifiers, this invention has the advantages of high safety, low cost, and suitability for widespread application.
[0035] (3) Malic acid can not only enhance the activation efficiency of Fe(II) and accelerate the generation of free radicals, but also promote the conversion of antibiotics in solution from the adsorbed state to the reactive state, improve the degradability of pollutants, thereby significantly improving the utilization efficiency of ROS and the oxidation rate of pollutants, and achieving the dual enhancement effect of ROS generation and antibiotic degradation. Attached Figure Description
[0036] Figure 1 To add 0.1 g / L Fe(II) ( Figure 1 a) and 0.2 g / L Fe(Ⅱ) ( Figure 1 b) Graph showing the difference in ·OH accumulation after compounding with malic acid of different concentrations;
[0037] Figure 2 To add 0.9 mmol / L malic acid ( Figure 2 a) and 1.8 mmol / L malic acid ( Figure 2 b) Graph showing the difference in ·OH accumulation after compounding with different Fe(II) compounds;
[0038] Figure 3 A comparison of the results after combining Fe(II) and malic acid at different concentrations;
[0039] Figure 4 To add 0.1 g / L Fe(II) ( Figure 4 a) and 0.2 g / L Fe(Ⅱ) ( Figure 4 b) Differences in OTC degradation after compounding with different concentrations of malic acid;
[0040] Figure 5To add 0.9 mmol / L malic acid ( Figure 5 a) and 1.8 mmol / L malic acid ( Figure 5 b) Differences in OTC degradation after compounding with different Fe(II) compounds;
[0041] Figure 6 The graph shows the differences in OTC degradation after combining Fe(II) and malic acid at different concentrations. Detailed Implementation
[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and are therefore only examples, and should not be used to limit the scope of protection of the present invention.
[0043] Example 1
[0044] Construction of a simulated paddy field drainage system and the preliminary effect of Fe(II)-malic acid on ·OH generation.
[0045] A paddy field soil sample with an initial oxytetracycline content of 5 mg / kg was taken, air-dried at room temperature, and then sieved and mixed thoroughly. 30 g of soil was weighed and added to 90 mL of deionized water (soil:water = 1:3), thoroughly shaken and mixed, and allowed to stand for 5 min. The sample was then centrifuged at 8000 r / min for 10 min, and the supernatant was collected as simulated paddy field drainage. The content of available Fe(II) in the simulated paddy field drainage was determined, confirming that it was below 20 mg / L and that the system did not contain exogenous malic acid. The pH of the drainage system was adjusted to 7.0±0.1, and the reaction was conducted at 25±1℃ under air conditions as the basic reaction conditions.
[0046] The simulated paddy field drainage was dispensed into 150 mL glass bottles (each treatment had at least three replicates). Fe(II) was added to the reaction system to a final Fe(II) concentration of 0.10 g / L; subsequently, malic acid was added to final concentrations of 0 mmol / L, 0.9 mmol / L, and 1.8 mmol / L, respectively. A blank control group without Fe(II) and malic acid, and control groups with only malic acid (0.9 mmol / L and 1.8 mmol / L) were also included.
[0047] Coumarin was added to each treatment group as a hydroxyl radical (·OH) scavenger, with a final concentration of 0.1 mmol / L. After the reaction was started, samples were taken at 0, 0.5, 1, 2, 4 and 6 h, and the fluorescence signal of ·OH was measured using a three-dimensional fluorescence spectrophotometer, and the cumulative amount of ·OH was calculated.
[0048] The results showed that in the blank control system without the addition of Fe(II) and malic acid, the accumulation of ·OH remained at a low level, generally below 20 μmol / L within 6 h. The addition of Fe(II) alone (0.10 g / L) increased the accumulation of ·OH, reaching 30-50 μmol / L within 6 h. When malic acid was introduced into the Fe(II) (0.10 g / L) system, the generation of ·OH increased significantly. At a malic acid concentration of 0.9 mmol / L, the accumulation of ·OH increased to 50-70 μmol / L within 6 h; when the malic acid concentration was 1.8 mmol / L, the accumulation of ·OH further increased, reaching 70-90 μmol / L, demonstrating that the Fe(II)-malic acid system had a significant synergistic enhancing effect on reactive oxygen species generation in simulated paddy field drainage. These results are as follows: Figure 1 As shown in a.
[0049] Example 2
[0050] Effect of different malic acid concentrations on ·OH accumulation while keeping Fe(II) = 0.2 g / L constant.
[0051] Based on Example 1, the final concentrations of Fe(II) were fixed at 0.10 g / L and 0.20 g / L, respectively, while maintaining other experimental conditions. Different concentrations of malic acid were added to the simulated paddy field drainage system to achieve final concentrations of 0 mmol / L, 0.9 mmol / L, and 1.8 mmol / L, respectively, with a blank control group (without Fe(II) or malic acid) also included. Coumarin was added to each treatment group as a ·OH scavenger at a final concentration of 0.1 mmol / L, and the cumulative ·OH concentration was measured at regular intervals from 0 to 6 h.
[0052] The results showed that under the condition of Fe(II) = 0.10 g / L, without the addition of malic acid, the cumulative amount of ·OH in the system was generally 30-50 μmol / L within 6 h; when 0.9 mmol / L malic acid was added, the cumulative amount of ·OH increased to 50-70 μmol / L; when the malic acid concentration was 1.8 mmol / L, the cumulative amount of ·OH further increased, reaching 70-90 μmol / L. Under the condition of Fe(II) = 0.20 g / L, the overall level of ·OH formation in the system was higher than that under the 0.10 g / L treatment, with the cumulative amount of ·OH being 40-60 μmol / L without the addition of malic acid; increasing to 70-90 μmol / L after the addition of 0.9 mmol / L malic acid; and reaching 90-120 μmol / L after the addition of 1.8 mmol / L malic acid, showing a more significant enhancing effect. The above results are as follows. Figure 1 a and Figure 1 As shown in b. Furthermore, Figure 2This provides clear kinetic support for the above conclusions: Under both malic acid levels (M0.9 and M1.8), the accumulation of ·OH exhibits a typical characteristic of rapid increase in the initial stage of the reaction (0–1 h), followed by a plateau phase; simultaneously, under the same Fe(II) dosage, the ·OH plateau value of the M1.8 system is consistently higher than that of the M0.9 system, and the F0.2 treatment is higher than that of the F0.1 treatment. Figure 2 a, 2b).
[0053] The results in summary indicate that in the simulated paddy field drainage system, the formation of ·OH is synergistically influenced by both Fe(II) dosage and malic acid concentration. When Fe(II) and a higher concentration of malic acid coexist (e.g., in the F0.2@M1.8 treatment), the accumulation of ·OH reaches its highest level, significantly higher than under single-condition regulation, suggesting that increasing the malic acid concentration amplifies the Fe(II)-induced reactive oxygen species (ROS) generation effect. Therefore, Figure 3 It is clearly shown that in the Fe(II)–malic acid system constructed in this invention, the increase of malic acid concentration can significantly promote the generation of ·OH, and form a synergistic enhancing effect with the amount of Fe(II) added.
[0054] Example 3
[0055] In a simulated paddy field drainage system, the initial concentration of OTC was controlled at approximately 5 mg / L. The final concentrations of Fe(II) were fixed at 0.10 g / L and 0.20 g / L, respectively, and different concentrations of malic acid (0, 0.9, and 1.8 mmol / L) were added to each system. A blank control group was also set up simultaneously. The reaction was carried out at 25±1℃ and pH 7, and samples were taken at 0, 0.5, 1, 2, 4, and 6 h to determine the residual concentration of OTC.
[0056] The results showed that in the control system without added Fe(II) and malic acid, the degradation rate of OTC within 6 h was generally less than 20%. Under the condition of Fe(II) = 0.10 g / L and no malic acid, the degradation rate of OTC increased to 30%-45%; with the addition of 0.9 mmol / L malic acid, the degradation rate of OTC reached 50%-65% within 2 h and increased to 65%-80% within 6 h; when the malic acid concentration was 1.8 mmol / L, the degradation rate of OTC reached 65%-80% within 2 h. Under the condition of Fe(II) = 0.20 g / L, the degradation effect of OTC was further enhanced; with the addition of 1.8 mmol / L malic acid, the degradation rate of OTC reached 70%-85% within 2 h and 85%-95% within 6 h. The above results are as follows: Figure 4 a and Figure 4 As shown in b.
[0057] Under constant Fe(II) concentration, as the malic acid concentration increased from 0 mmol / L to 0.9 mmol / L and 1.8 mmol / L, the C of OTC drugs... t The Ct / C0 value decreased further at all time points, with particularly significant differences in the initial reaction phase (0–2 h), indicating that the addition of malic acid significantly accelerated the initial degradation rate of OTC. Simultaneously, under the same malic acid conditions, the Ct / C0 of the Fe(II) = 0.20 g / L system was generally lower than that of the Fe(II) = 0.10 g / L system, suggesting that increasing the Fe(II) dosage is beneficial for maintaining a higher degradation efficiency. Figure 5 ).
[0058] Example 4
[0059] Based on the results of Examples 1-3, a comparative analysis was conducted on the ·OH generation and OTC degradation effects under different combinations of Fe(II) and malic acid. The results showed that the highest accumulation of ·OH was observed in the simulated paddy field drainage system under the conditions of Fe(II) = 0.20 g / L and malic acid = 1.8 mmol / L, reaching 100-130 μmol / L within 6 hours. Under these conditions, the degradation rate of OTC reached approximately 80% within 2 hours and could further increase to over 90% within 6 hours.
[0060] Compared with other combinations, this Fe(II)-malic acid ratio exhibits the best synergistic effect in terms of ·OH generation efficiency and rapid OTC degradation, and can be considered a preferred embodiment of the present invention. Related results are as follows... Figure 3 and Figure 6 As shown.
[0061] The specification and drawings of this invention are intended to be illustrative rather than restrictive. Based on this invention, those skilled in the art can make substitutions and modifications to some of the technical features without creative effort, and all such modifications are within the scope of protection of this invention.
Claims
1. A method for enhancing the generation of reactive oxygen species and the degradation of antibiotics in paddy field drainage, comprising: (1) Select paddy soil without oxytetracycline, air dry it, add water and shake it, then centrifuge it, take the supernatant as the target solution, add oxytetracycline mother liquor to the target solution, so that the oxytetracycline content in the simulated paddy field drainage solution reaches 5 mg / L and the effective Fe(II) content <20 mg / L, and the simulated paddy field drainage solution is used for later use. (2) Fe(II) and malic acid were added to the simulated paddy field drainage solution to construct the Fe(II)-malic acid-paddy field drainage reaction system; (3) Coumarin was added as an ·OH scavenger to the Fe(II)-malic acid-paddy field drainage reaction system to allow it to react. Samples were taken at the set reaction time points to determine the residual concentration of oxytetracycline in order to characterize the degradation rate and degradation efficiency of antibiotics in paddy field drainage. Samples were taken at the set reaction time points and the reaction system was detected by a three-dimensional fluorescence spectrophotometer to obtain the generation level and cumulative change of ·OH.
2. The method according to claim 1, wherein: The mass-to-volume ratio of paddy soil to water in step (1) is 1 g: 3 mL; The oscillation condition is oscillation at 180 rpm for 30 minutes; The centrifugation conditions were: 8000 rpm for 10 min.
3. The method according to claim 1, wherein: The Fe(II) mentioned in step (2) is FeSO4·7H2O, and its addition amount makes the final concentration of Fe(II) in the Fe(II)-malic acid-paddy field drainage reaction system 0.1-0.2 g / L.
4. The method according to claim 3, wherein: The amount of Fe(II) added is such that the final concentration of Fe(II) in the reaction system is 0.2 g / L.
5. The method according to claim 1, wherein: The final concentration of malic acid in the Fe(II)-malic acid-paddy field drainage reaction system described in step (2) is 0.9-1.8 mmol / L.
6. The method according to claim 5, wherein: The final concentration of malic acid is 1.8 mmol / L.
7. The method according to claim 1, wherein: The reaction temperature in step (3) is 20-30℃.
8. The method according to claim 1, wherein: The final concentration of coumarin in the system in step (3) shall not be less than 0.1 mmol / L.