Method for removing residual antibiotics in wastewater by utilizing catechin enhanced Fenton system

Abstract

The invention relates to the technical field of water treatment, provides a catechin-reinforced Fenton system and a method for removing residual antibiotics in wastewater by using the catechin-reinforced Fenton system, and relates to a method for removing organic pollutants in water by using an advanced oxidation technology. The method comprises the following steps: adjusting the pH value of an antibiotic solution to be treated to 6 by using acid and alkali, sequentially adding catechin (CAT) and ferrous sulfate heptahydrate (FeSO4. 7H2O), then adding hydrogen peroxide (H2O2), and reacting and oxidizing to remove antibiotics. And the concentrations of Fe (II) and H2O2 are controlled according to the concentration of organic matters in the wastewater, and the addition amount of CAT is determined, so that the Fenton reaction efficiency is improved to the maximum extent, and medicaments are effectively saved. According to the method, an environment-friendly natural substance CAT is introduced as a complexing reducing agent, Fe (III) in a Fenton system is reduced, Fe (III) / Fe (II) circulation in the system is promoted, the concentration of soluble Fe (II) is increased, iron mud is reduced, the utilization rate of a medicament is increased, the generation capacity of hydroxyl free radicals (. OH) in the Fenton reaction system is enhanced, and the efficiency of removing antibiotics in water is improved.

Description

Technical Field

[0001] The present invention belongs to the water treatment technology field of the environmental treatment technology field, and relates to a wastewater treatment method for promoting the Fenton oxidation effect, specifically to a Fenton system strengthened by catechins and a method for removing residual antibiotics in wastewater by using the same. Background Art

[0002] Antibiotics are widely used in livestock and poultry breeding to prevent diseases and promote growth. However, a large amount of antibiotics (about 75%) cannot be completely metabolized by animals and enter the environment in the form of the original drug through feces and urine. These residual antibiotics enter water bodies and soil through livestock and poultry wastewater and finally enter the human body through the food chain, resulting in an increase in microbial drug resistance. At the same time, due to the high treatment cost and the lack of effective processes, it is difficult to remove the antibiotic residues in livestock and poultry manure, further exacerbating the treatment difficulty and threatening public health. According to the national pollution source census data and research, livestock and poultry breeding has become one of the main sources of agricultural non-point source pollution in China. Among them, antibiotic residues are key pollutants with great harm, difficult to remove, and slow to degrade, which has attracted wide social attention.

[0003] Tylosin (TYL) is a macrolide antibiotic, which is commonly used to treat respiratory and digestive tract diseases of livestock and poultry and is used as a feed additive to promote animal growth. Its usage is also large, and after metabolism in livestock and poultry, a considerable proportion of the residues are still excreted with feces. Due to its extensive use and abuse, it accumulates continuously in the environment. The TYL remaining in the environment can induce the generation of drug-resistant bacteria, thereby increasing the treatment difficulty and cost. When the detection rate and concentration of TYL in natural water bodies reach a certain level, it will damage the aquatic ecosystem and affect the balance of the microbial community, and will also accumulate through the food chain and threaten human health.

[0004] Most antibiotic pollutants have poor biodegradability and are difficult to be degraded by conventional sewage treatment processes. Advanced oxidation technologies can utilize strongly oxidizing species to deeply oxidize organic pollutants. Among them, Fenton oxidation is the most widely applied technology. This technology uses ferrous ions to activate hydrogen peroxide to generate hydroxyl radicals (·OH) to degrade organic pollutants. The ·OH generated in the system has strong oxidizing properties and can oxidize and remove organic pollutants in water without selectivity. However, the Fenton reaction system has problems such as the low-efficiency cycle of Fe(Ⅲ) to Fe(Ⅱ) and the easy precipitation of iron under the condition of pH > 4.0.

[0005] To improve the iron cycle in the Fenton oxidation process, a variety of reducing agents have been used in combination with Fenton reagents. Among them, homogeneous reducing agents (such as hydroxylamine hydrochloride, ascorbic acid, sodium bisulfite, etc.) have a strong ability to reduce Fe(III), but it is difficult to separate them from water bodies, and some of them are toxic themselves, which limits their large-scale application; heterogeneous reducing agents (such as tungsten sulfide, molybdenum sulfide, molybdenum oxide, etc.) are prone to leaching toxic metal ions during the Fenton oxidation process, resulting in secondary pollution.

[0006] To solve the above problems, the present invention has developed the use of a natural phenolic substance, catechin (CAT). As a complexing reducing agent, CAT accelerates the regeneration of Fe(II) in the Fenton system, promotes the generation of ·OH in the reaction system, and at the same time maintains the solubility of iron in the solution, enhancing the efficiency of Fenton oxidation of refractory organic compounds in a green and efficient manner. Summary of the Invention

[0007] The present invention solves the problems of the Fe(III) / Fe(II) cycle hindrance and the easy precipitation of Fe(III) existing in the traditional Fenton reaction system, and also improves the problems such as the difficulty in separating the reducing agents added in the enhanced Fenton reaction, the easy leaching of toxic metal ions, and the biological toxicity. It provides a Fenton system enhanced by catechin and a method for removing residual antibiotics in wastewater. In this method, catechin is used as a complexing reducing agent to reduce Fe(III) to Fe(II), activate the generation of increased ·OH, and maintain the solubility of iron, thereby achieving an increase in the degradation rate of the substrate in the Fenton system. This method not only effectively avoids problems such as slow iron cycle and easy precipitation of iron ions in the Fenton system, but also solves the problem of secondary pollution existing in homogeneous / heterogeneous reducing agents, making the Fenton system more advantageous in the treatment of antibiotic wastewater.

[0008] To achieve the object of the present invention, there is provided a Fenton system enhanced by catechin and a method for removing residual antibiotics in wastewater. Catechin (CAT), ferrous sulfate heptahydrate (FeSO4·7H2O) are sequentially added to an aqueous solution containing antibiotics, and then hydrogen peroxide (H2O2) is added to remove the antibiotic solution through an oxidation reaction.

[0009] Among them, the antibiotic tylosin, which is a kind of macrolide antibiotic, has a concentration of 10 mg / L.

[0010] Among them, in the whole reaction system, the concentration range of the dosage of H2O2 is 0.25 - 4 mM. Preferably, the system concentration of the dosage of H2O2 is 0.5 mM; the concentration range of the dosage of FeSO4·7H2O is 12.5 - 200 μM. Preferably, the system concentration of the dosage of FeSO4·7H2O is 0.025 mM.

[0011] In this reaction system, the dosage concentration range of CAT (catalyst or complexing agent) is 6.25 - 100 μM, and the preferred concentration is 12.5 μM. By adding CAT as a complexing reducing agent to the system, it can form a stable complex with iron, keep it in a soluble state, and accelerate the Fe(Ⅲ) / Fe(Ⅱ) cycle. This significantly improves the efficiency of the system in removing antibiotics. In addition, after introducing CAT, the applicable range of the effective pH of the system is broadened, and a high removal efficiency of TYL (target pollutant) can be maintained under the conditions of pH 3.0 - 9.0.

[0012] The present invention determines the optimal dosage of reagents in the catechin-enhanced Fenton system, which not only ensures a high removal rate of TYL but also avoids the problem of secondary pollution caused by excessive dosing of reagents.

[0013] Generally speaking, compared with the prior art, the technical advantages of the present invention are as follows: (1) The method of the present invention can improve the removal efficiency of tylosin, especially achieve high-efficiency removal of the target substance in a short time, can achieve a high TYL removal efficiency, and is significantly superior to the traditional Fenton process. (2) The system of the present invention can achieve good removal of TYL in drinking water within the range of the initial solution pH from 3 to 9. When pH ≤ 6, the method of the present invention can basically achieve complete removal of TYL in water. Even when pH = 9.0, the removal rate of TYL can still reach %, indicating that the method of the present invention has a wide applicable range of pH. (3) The method of the present invention is strengthened by enhancing the oxidation performance of the catechin-enhanced Fenton system, significantly improving the utilization rate of H2O2, and thus reducing the treatment cost of the catechin-enhanced Fenton system for removing antibiotics. (4) As a complexing reducing agent, CAT can effectively promote the Fe(Ⅲ) / Fe(Ⅱ) cycle, increase the dissolved iron concentration, and increase the generation of ·OH in the system, thereby improving the degradation rate of antibiotics in the reaction system. (5) Under the conditions of the presence of common inorganic anions (Cl - , NO3 - ) and natural organic matter (humic acid, FA) with different concentrations, the method of the present invention can achieve efficient removal of TYL in water. The following further illustrates the catechin-enhanced Fenton system of the present invention and its method for removing residual antibiotics in wastewater with reference to the accompanying drawings. Brief Description of the Drawings

[0014] Figure 1 For the removal rates of TYL in the experimental system (Embodiment 1) and the control system (Embodiment 2).

[0015] Figure 2For the influence of the dosage of Fe(Ⅱ) on the efficiency of TYL removal in Embodiment 3.

[0016] Figure 3 For the influence of the dosage of H2O2 on the efficiency of TYL removal in Embodiment 4.

[0017] Figure 4 For the influence of the dosage of CAT on the efficiency of TYL removal in Embodiment 5.

[0018] Figure 5 For the influence of the initial solution pH on the efficiency of TYL removal in Embodiment 6.

[0019] Figure 6 For the degree of H2O2 utilization in the system and the control system in Embodiments 1 and 2.

[0020] Figure 7 For the influence of different chloride ion concentrations on the efficiency of TYL removal in the system in Embodiment 7.

[0021] Figure 8 For the influence of different nitrate ion concentrations on the efficiency of TYL removal in the system in Embodiment 8.

[0022] Figure 9 For the influence of different humic acid concentrations on the efficiency of TYL removal in the system in Embodiment 9.

[0023] Figure 10 For the detection of the generation of hydroxyl radicals in Embodiment 10. Specific Embodiments

[0024] The materials and devices used in the following experiments are as follows.

[0025] Experimental materials: tylosin (TYL), catechin (CAT), ferrous sulfate heptahydrate (FeSO4·7H2O), 30% hydrogen peroxide (H2O2), sulfuric acid (H2SO4), sodium hydroxide (NaOH), sodium chloride (NaCl), sodium nitrate (NaNO3), fulvic acid (FA), 5,5-dimethyl-1-pyrroline-N-oxide, all chemical reagents are of analytical grade; methanol (HPLC grade) and ultrapure water.

[0026] Embodiment 1

[0027] All the experiments were carried out in a 1000 mL beaker. 500 mL of an antibiotic solution with a concentration of 10 mg / L was placed in the beaker, and the pH value was adjusted to the initial pH of the solution reaction, pH = 6, with H2SO4 or NaOH solution. 1 mL of FeSO4·7H2O solution and 1 mL of catechin solution were added. The beaker was placed in a thermostatic magnetic stirrer, and a certain concentration of H2O2 solution was added, and the reaction timing started from this moment. Samples were taken at the set time intervals (0.5, 5, 10, 20, 30, 40, 50, 60, 70, 80 min). Immediately after sampling, an excessive amount of methanol was added to stop the reaction. After filtration through a 0.45 μm filter membrane, the residual antibiotic concentration was measured by HPLC.

[0028] Embodiment 2

[0029] Similar to the steps of Embodiment 1, the reaction systems were respectively CAT / Fe(Ⅱ) / H2O2, Fe(Ⅱ) / H2O 2、 CAT / Fe((Ⅲ) / H2O2, Fe(Ⅲ) / H2O2. It can be seen from the results that the degradation of TYL was improved under the action of CAT, and CAT promoted the iron cycle.

[0030] Embodiment 3

[0031] 500 mL of an antibiotic solution with a concentration of 10 mg / L was placed in a beaker. After the pH value of the aqueous solution was adjusted with dilute sulfuric acid and alkali, the initial pH of the system was 6. An initial concentration of 10 mg / L of TYL antibiotic solution was added to a 1 L beaker, and different concentrations of FeSO4·7H2O were added: 12.5, 25, 50, 100, 200 μmol / L, and then 25 μmol / L of CAT solution and 0.5 mmol / L of H2O2 solution were added. The results showed that as the concentration of Fe(II) increased, the degradation effect of TYL gradually enhanced. Almost complete degradation of TYL occurred at 50 μmol / L. When the concentration of Fe(II) further increased, the degradation rate hardly increased significantly, showing a gradually stabilizing phenomenon.

[0032] Embodiment 4

[0033] In the experiment, a TYL antibiotic solution with an initial concentration of 10 mg / L was added to a 1-L beaker. The initial pH of the solution was adjusted to 6 with dilute sulfuric acid and sodium hydroxide. Subsequently, 50 μmol / L FeSO4·7H2O and 25 μmol / L CAT solution were added. Finally, different ratios of H2O2 / Fe(II): 5:1, 10:1, 20:1, 40:1, 80:1 with concentrations of 0.25, 0.5, 2, 4 mmol / L were added respectively. The results showed that the degradation effect of TYL was good at different concentrations. Especially at 10:1, it was almost completely degraded. From 10:1 to 80:1, the degradation of TYL continued to increase, but the effect was very slight.

[0034] Embodiment 5

[0035] Add 1-L beaker with 10 mg / L of TYL simulated wastewater with an initial concentration. Adjust the initial pH value of the aqueous solution to 6 with dilute sulfuric acid and sodium hydroxide. Fix the concentration of FeSO4·7H2O at 50 μmol / L, and according to different CAT / Fe(II) molar ratios (2:1, 1:1, 1:2, 1:4, 1:8), the concentration of CAT increases from 6.25 μmol / L to 100 μmol / L. Finally, add H2O2 solution according to the ratio of H2O2 / Fe(II) = 10:1. The results show that as the CAT / Fe(II) molar ratio increases from 1:8 to 2:1, the degradation rate of TYL first increases and then is inhibited. Appropriate amount of CAT can significantly accelerate the degradation of TYL, and excessive CAT will act as a quencher to quench hydroxyl radicals.

[0036] Embodiment 6

[0037] In the experiment, add 1-L beaker with 10 mg / L of TYL simulated wastewater with an initial concentration. Adjust the solution to different initial pH values of 3, 4, 5, 6, 7, 8, 9 with dilute sulfuric acid and sodium hydroxide, and then add 50 μmol / L FeSO4·7H2O, 25 μmol / L CAT solution and H2O2 solution with H2O2 / Fe(II) = 10:1. The results show that the degradation rate of TYL gradually decreases with the increase of pH value, but the degradation effect is good, and pH has little limitation on this system.

[0038] Embodiment 7

[0039] Place 500 mL of an antibiotic solution with a concentration of 10 mg / L in four beakers. Add sodium chloride to each beaker to prepare antibiotic solutions containing 0, 1, 5, and 10 mmol / L of sodium chloride respectively. After adjusting the pH value with dilute sulfuric acid and base, the initial pH of the system is 6. Add a TYL antibiotic solution with an initial concentration of 10 mg / L to a 1-L beaker, and add 50 μmol / L FeSO4·7H2O, 25 μmol / L CAT solution, and an H2O2 solution with a ratio of H2O2 / Fe(II) = 10:1. Cl - and ·OH react to form Cl· with relatively low oxidation ability, thereby consuming ·OH in the system and affecting the degradation of TYL in the system. However, in the degradation reaction of TYL, the degradation rate slightly decreases, but this difference can be ignored.

[0040] Embodiment Eight

[0041] Add simulated TYL wastewater with an initial concentration of 10 mg / L to a 1-L beaker. Add sodium nitrate to four beakers to prepare antibiotic solutions containing 0, 1, 5, and 10 mmol / L of sodium nitrate respectively. Adjust the initial pH value of the aqueous solution to 6 with dilute sulfuric acid and sodium hydroxide. Add 50 μmol / L FeSO4·7H2O and 25 μmol / L CAT solution, and finally add an H2O2 solution in a ratio of H2O2 / Fe(II) = 10:1. NO3 - has a slight inhibitory effect on the degradation of TYL. This is because it will react with ·OH to form NO3 - ·, which also plays a certain role in the degradation of TYL, so the influence is relatively low.

[0042] Embodiment Nine

[0043] In the experiment, add a TYL antibiotic solution with an initial concentration of 10 mg / L to a 1-L beaker. Add fulvic acid to four beakers to prepare antibiotic solutions containing 0, 10, 50, and 100 mg / L of humic acid respectively. Adjust the initial pH of the solution to 6 with dilute sulfuric acid and sodium hydroxide. Then add 50 μmol / L FeSO4·7H2O and 25 μmol / L CAT solution, and finally add H2O2 with a ratio of H2O2 / Fe(II):10:1 at a concentration of 0.5 mmol / L. As the FA concentration increases, the removal rate of TYL gradually decreases. This is because FA can compete for active free radicals in the system to generate other products, thereby inhibiting the removal rate of TYL.

[0044] Embodiment Ten

[0045] Sampling was carried out on the basis of Embodiment 1, and an electron paramagnetic resonance spectrometer was used to detect the generation of hydroxyl radicals. In this experiment, 100 mmol / L of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was selected as a spin trap to capture hydroxyl radicals in the reaction system. The signal intensity of the DMPO-OH adduct was detected to qualitatively determine the presence of hydroxyl radicals in the aqueous solution. The results showed that hydroxyl radicals (·OH) were generated, and the EPR signal peak appeared in a ratio of 1:2:2:1, with a g-factor of 2.0065.

Claims

1. A method for removing residual antibiotics in wastewater by using a Fenton system enhanced by catechins and the like, characterized in that: Catechins are added to the Fenton reaction system; Fe(II) in the Fenton reaction system reacts with H2O2 to generate hydroxyl radicals, and in this process, Fe(II) is oxidized to Fe(III); the catechins are used to reduce the Fe(III) generated in the system to Fe(II), thereby maintaining the solubility of iron in the solution, thereby allowing Fe(II) in the system to react with H2O2 to generate more hydroxyl radicals.

2. A method for removing residual antibiotics in wastewater by using a catechin-enhanced Fenton system and the method, characterized in that The method is implemented according to the following steps: catechin (CAT) and ferrous sulfate heptahydrate (FeSO4·7H2O) are sequentially added to an aqueous solution containing antibiotics, and then hydrogen peroxide (H2O2) is added to remove the antibiotics in drinking water through an oxidation reaction.

3. The method for removing residual antibiotics in wastewater by using the Fenton system enhanced by catechins according to claim 2, characterized in that: in, The stirring method is magnetic stirring, and the rotation speed is 500-700r / min.

4. The method for removing residual antibiotics in wastewater by using the Fenton system enhanced by catechins according to claim 2, characterized in that: In the whole reaction system, the concentration range of H2O2 is 0.25-4 mmol / L, the concentration range of FeSO4·7H2O is 12.5-200 μmol / L, and the concentration range of CAT is 6.25-100 μmol / L.

5. The method for removing residual antibiotics in wastewater by using the Fenton system enhanced by catechins according to claim 2, characterized in that The water to be treated was stirred evenly for 80 minutes under the conditions of an initial pH of 6 and a temperature of 20±5°C.

6. The method for removing residual antibiotics in wastewater by using the Fenton system enhanced by catechins as claimed in claim 1, characterized in that: The hydroxyl radicals are used to oxidize the antibiotic.

7. The method for removing residual antibiotics in wastewater by using the Fenton system enhanced by catechins according to claim 2, characterized in that: in, The antibiotic is tylosin, a macrolide antibiotic, with a concentration of 10 mg / L.

8. The method for removing residual antibiotics in wastewater by using the Fenton system enhanced by catechins according to claim 2, characterized in that: in, The antibiotic aqueous solution may contain one or more types of inorganic anions and humus.

9. The method for removing residual antibiotics in wastewater by using the Fenton system enhanced by catechins according to claim 10, characterized in that: The inorganic anion is selected from one of chloride ion and nitrate ion, and the humus is selected from one of humic acid.

10. The method for removing residual antibiotics in wastewater by using the Fenton system enhanced by catechins according to claim 1, characterized in that: In the CAT-Fenton system, organic pollutants in the water to be treated can be effectively oxidized and degraded by enhancing the generation of active free radicals without the need for additional aeration, heating, ultraviolet irradiation, microwave irradiation, ultrasonic cavitation or external electromagnetic field.

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