Method for the reductive degradation of antibiotics containing nitro functional groups by zero-valent iron in the presence of sulfite and ferrous iron

Abstract

The present application relates to the technical field of water pollution control, and particularly relates to a method for reducing and degrading antibiotics containing nitro functional groups by sulfite and ferrous salt reinforced zero-valent iron. The pH value of wastewater containing antibiotics with nitro functional groups is adjusted to 5-9, sulfidation modified zero-valent iron, sulfite and ferrous salt are simultaneously added into the wastewater, and the antibiotics containing nitro functional groups can be reduced and degraded after 3-4 hours of stirring reaction. The method provided by the present application can solve the problem of accumulation of high-toxicity intermediate products in the process of improving the removal rate of antibiotics containing nitro groups, so as to realize efficient and harmless treatment of pharmaceutical wastewater containing antibiotics with nitro functional groups.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water pollution control, and in particular to a method for reducing and degrading antibiotics containing nitro functional groups by zero-valent iron with the assistance of sulfite and ferrous salt. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing the understanding of the general background of the application and does not necessarily constitute an admission or a recognition that the information forms part of the prior art that is already known in any country in the world.

[0003] Nitro group is one of the common and unique functional groups in medicinal chemistry, and can be found in many antibiotic drugs. Currently, widely used antibiotics containing nitro functional groups include nitroimidazoles, nitrofuran and chloramphenicol (CAP) and the like. The nitro functional group can make these antibiotics have good medicinal effect, and its reduction process is also a key step to improve the biodegradability of wastewater containing such antibiotics.

[0004] Micro zero-valent iron is widely used in the reduction and degradation of antibiotics due to its strong reducing property, low cost, easy availability and environmental friendliness. Micro zero-valent iron can reduce nitro group to amino group, and the main process includes that nitro group is first reduced to nitroso group, nitroso group is further reduced to hydroxylamine group, and hydroxylamine group is finally reduced to amino group. However, micro zero-valent iron is easy to form a passivation layer (such as Fe2O3, Fe(OH)3, etc.) during the reaction, which inhibits the rate of reduction of nitro group to nitroso group. At the same time, previous studies have focused on the concentration change of nitro-containing antibiotic parent compounds, and few studies have investigated the distribution of reduction products and the change of ecological toxicity of the system during the reduction process. In the process of reducing nitro group to amino group, the toxicity of nitroso group and the azo group generated by the combination of hydroxylamine group is stronger than that of nitro group. Therefore, it is urgent to construct a reduction and repair system that can not only efficiently remove antibiotic parent compounds, but also reduce the accumulation of high-toxicity intermediates, so as to realize the harmless treatment of wastewater containing nitro-containing antibiotics. SUMMARY

[0005] In order to overcome the above problems, the present application provides a method for reducing and degrading antibiotics containing nitro functional groups by zero-valent iron with the assistance of sulfite and ferrous salt.

[0006] To achieve the above technical purposes, the present application adopts the following technical solutions:

[0007] A method for reducing and degrading antibiotics containing nitro functional groups by zero-valent iron with the assistance of sulfite and ferrous salt, comprising:

[0008] The pH value of the antibiotic wastewater containing nitro functional groups is adjusted to 5-9, and the sulfidation modified zero-valent iron, sulfite and ferrous salt are simultaneously added into the wastewater, and the stirring reaction is carried out for 3-4 h, so that the antibiotic containing nitro functional groups is reduced and degraded.

[0009] In one or more embodiments, the antibiotic containing nitro functional groups includes nitroimidazoles, nitrofuran, nitroquinoline and chloramphenicol, etc.

[0010] In one or more embodiments, the preparation method of the sulfidation modified zero-valent iron includes:

[0011] Nitrogen is introduced into the acetic acid-sodium acetate buffer solution with pH value of 5.5-6.5, so that the dissolved oxygen is reduced to 0, then micron zero-valent iron powder is added, ultrasonic dispersion is carried out, sodium sulfide solution is added, and the reaction is carried out by shaking bed, after the reaction is completed, filtration, washing and freeze-drying are carried out to obtain the sulfidation modified zero-valent iron. The purpose of sulfidation modification is to remove the passivation layer on the surface of the commercially available zero-valent iron and maintain its reaction activity for a certain period of time.

[0012] Preferably, in the sulfidation modified zero-valent iron, the molar ratio of sulfur to iron is 0.05-0.06:1, preferably 0.056:1.

[0013] Further preferably, the dosage of the sulfidation modified zero-valent iron in the wastewater is 50-500 mg / L.

[0014] In one or more embodiments, the sulfite includes K2SO3 or Na2SO3, preferably Na2SO3.

[0015] In one or more embodiments, the dosage of the sulfite in the wastewater is 0.2 mM-10 mM.

[0016] In one or more embodiments, the ferrous salt includes FeSO4, Fe(NO3)2 or FeCl2, preferably FeSO4.

[0017] In one or more embodiments, the dosage of the ferrous salt in the wastewater is 0.5-5 mM.

[0018] In one or more embodiments, the method of the sulfite and ferrous salt for strengthening the zero-valent iron to reduce and degrade the antibiotic containing nitro functional groups can be carried out under anaerobic and aerobic conditions.

[0019] The beneficial effects of the present application are:

[0020] (1) The method for reducing and degrading antibiotics containing nitro functional groups by sulfite and ferrous salt reinforced zero-valent iron provided by the application can solve the problem of accumulation of high-toxicity intermediates in the process of improving the removal rate of antibiotics containing nitro groups, thereby realizing efficient and harmless treatment of pharmaceutical wastewater containing nitro antibiotics. Reason: The addition of ferrous ions can effectively reduce the generation of micron zero-valent iron passivation layer, because the increase of the proportion of Fe(II) in the reaction system can convert the corrosion products into magnetite (Fe3O4) which is beneficial to electron conduction, thereby reducing the formation of Fe(III) passivation layer. Therefore, the addition of ferrous ions can accelerate the reduction rate of nitro to nitroso. At the same time, sulfite can generate active substances that react with nitroso under the catalysis of ferrous salt, and then rapidly reduce them to amino, thereby solving the problem of accumulation of high-toxicity intermediates.

[0021] (2) Sulfite is a common reduced sulfur by-product in tannery, papermaking and other industrial wastewater, and the use of sulfite and ferrous salt reinforced zero-valent iron to reduce and degrade antibiotics containing nitro functional groups conforms to the concept of "waste treatment with waste".

[0022] (3) The method for reducing and degrading antibiotics containing nitro functional groups by sulfite and ferrous salt reinforced zero-valent iron provided by the application has good adaptability and can quickly remove antibiotics containing nitro groups under anaerobic and aerobic conditions without producing high-toxicity intermediates.

[0023] (4) The method for reducing and degrading antibiotics containing nitro functional groups by sulfite and ferrous salt reinforced zero-valent iron provided by the application can advance the dechlorination time point of chloramphenicol when treating chloramphenicol, thereby quickly reducing its ecological toxicity. BRIEF DESCRIPTION OF DRAWINGS

[0024] The drawings accompanying the specification of the application are used to provide a further understanding of the application, and the illustrative embodiments of the application and their descriptions are used to explain the application, and do not constitute an improper limitation on the application.

[0025] Figure 1 The figure is the CAP removal kinetics curve in different systems under anaerobic conditions in Example 1;

[0026] Figure 2 The figure is the CAP removal kinetics curve in different systems under anaerobic conditions in Example 2;

[0027] Figure 3 The figure is the influence of initial pH on the removal of chloramphenicol by the coupling system in Example 3;

[0028] Figure 4 The figure is the influence of sulfite type and concentration on the removal of chloramphenicol by the coupling system in Example 4;

[0029] Figure 5Distribution of CAP degradation products in different systems after 180 min degradation in Example 5;

[0030] Figure 6 Toxicity evaluation results of CAP and its degradation products on Pimephales promelas in Example 6. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0032] It is also important to note that the terms used herein are not intended to limit the particular embodiments of the present application which can be practiced with or without the use of such terms. As used, unless otherwise defined, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It also should be understood that the terms "comprising," "including," and "having," as used herein, are specifically intended to be read as open-ended terms of art.

[0033] Compared with nitroimidazole and nitrofuran antibiotics, chloramphenicol contains not only nitro functional group but also two halogen groups in its structure, which makes it more toxic. Therefore, chloramphenicol is used as a representative of antibiotics containing nitro functional groups in the following examples.

[0034] Preparation of artificial chloramphenicol wastewater: CAP was dissolved in deionized water and stirred to obtain.

[0035] Preparation of sulfidation modified zero-valent iron: 250 mL of HAc-NaAc buffer solution with pH = 6 was prepared in a 250 mL infusion bottle, and then N2 was introduced into the infusion bottle for 30 min. After the N2 was introduced, 1 g of micron zero-valent iron was quickly added, the infusion bottle was sealed and placed in a rolling shaker, and rolled at a speed of 120 r / min for 10 min. After rolling, 1 mL of 1 M Na2S solution was injected using a microsyringe, and immediately placed in a rolling shaker at the same speed for 12 h. The temperature of the rolling shaker was set to 25 C. After rolling, the liquid in the infusion bottle was filtered through a 0.22 μm filter membrane, and the filtered solid was washed with deionized water and anhydrous ethanol three times, respectively. Finally, the solid was freeze-dried to obtain S-ZVI (S / Fe = 0.056).

[0036] Example 1:

[0037] This example verifies the ability of sulfidation modified zero-valent iron-ferrous iron-sulfite coupling system to quickly remove chloramphenicol by comparing the effects of different systems on removing chloramphenicol under anaerobic conditions.

[0038] Five 500 mL beakers were placed in an anaerobic glove box at 25°C, 500 mL of 40 mg / L synthetic chloramphenicol wastewater was added to each of the five beakers, the initial pH of each experimental group solution was adjusted to 6 using 30 mM dilute sulfuric acid, and 200 mg / L of sulfur-modified zero-valent iron (S-ZVI), S-ZVI + ferrous sulfate (FeS04), S-ZVI + sodium sulfite (Na2S03), FeS04+ Na2S03, and S-ZVI + FeS04+ Na2S03 were added to the five beakers, respectively, 2 mM of FeS04 and Na2S03 was added, mechanical stirring at a speed of 350 rpm was used to accelerate the removal of CAP, 2.5 mL was sampled at 0 min, 2 min, 5 min, 10 min, 20 min, 30 min, 60 min, 120 min, and 180 min of the reaction, and the concentration of CAP in the sample was determined by high performance liquid chromatography (C / C0, the concentration of CAP in the system at the sampling time / CAP initial concentration, was used as the ordinate, and the reaction time was used as the abscissa to draw the CAP removal kinetics curve. The results are shown in Figure 1 Within 180 min of reaction time, the S-ZVI + FeS04+ Na2S03 system can remove 99.8% of CAP, while the removal rates of CAP by S-ZVI, S-ZVI + FeS04, S-ZVI + Na2S03, and FeS04+ Na2S03 systems are 23.2%, 48.5%, 14.5%, and 16.8%, respectively. Thus, under anaerobic conditions, the S-ZVI + FeS04+ Na2S03 coupling system has the ability to quickly remove CAP, i.e., sulfite can synergize with ferrous iron to enhance the removal of chloramphenicol by zero-valent iron.

[0039] Example 2:

[0040] This example verifies the applicability of the method of removing chloramphenicol by sulfite synergizing with ferrous iron to enhance zero-valent iron under aerobic conditions by comparing the effects of different systems on the removal of chloramphenicol under aerobic conditions.

[0041] The reaction system was placed in an open environment, and the remaining settings were the same as in Example 1. The results are shown in Figure 2As shown in the table, in the reaction time of 180 min, the S-ZVI+FeSO4+Na2SO3 system can remove 66.4% of CAP, while the removal rates of CAP by the S-ZVI, S-ZVI+FeSO4, S-ZVI+Na2SO3 and FeSO4+Na2SO3 systems are 4.8%, 5.2%, 17.7% and 2.8%, respectively. As can be seen, under aerobic conditions, the removal effect of each system on CAP is reduced, but the S-ZVI+FeSO4+Na2SO3 coupling system also has the ability to quickly remove CAP, that is, the method of removing chloramphenicol by sulfite and ferrous iron-strengthened zero-valent iron is still applicable under aerobic conditions.

[0042] Example 3:

[0043] In this example, by changing the initial pH of the coupling system, the applicability of the method of removing chloramphenicol by sulfite and ferrous iron-strengthened zero-valent iron under different pH conditions is verified.

[0044] The initial pH of the CAP solution in each experimental group was adjusted to 5, 6, 7, 8 and 9 using 30 mM dilute sulfuric acid, and the rest of the settings were the same as in Example 1. The results are shown in Figure 3 As shown in the table, in the reaction time of 180 min, the removal rate of CAP in different experimental groups is greater than 96.7%, and with the change of the initial pH, the degradation curve of CAP does not change significantly. As can be seen, the method of removing chloramphenicol by sulfite and ferrous iron-strengthened zero-valent iron has good pH adaptability.

[0045] Example 4:

[0046] In this example, by changing the concentration and type of sulfite, the important role of sulfite (SO3 2- ) in the S-ZVI+FeSO4+Na2SO3 coupling system is verified.

[0047] Sodium sulfite (Na2SO3) and calcium sulfite (CaSO3) were selected as sulfites, and the dosages of both were set to 0 mM, 0.5 mM, 1 mM, 2 mM and 5 mM, and the rest of the settings were the same as in Example 1. The pseudo-first-order kinetics was used to fit the CAP removal kinetics curves in different experimental groups, and the formula was ln(C / C0)=-kobs·t, where C was the concentration of CAP in the system at the sampling time; C0was the initial concentration of CAP; kobs was the pseudo-first-order kinetic constant of CAP (its value reflected the removal rate of CAP); and t was the reaction time. The results are shown in Figure 4 As shown in the table, with the increase of the concentration of SO3 2- , the removal rate constant of CAP becomes larger, and this trend does not change with the type of sulfite. As can be seen, SO3 2-The S-ZVI+FeSO4+Na2SO3 coupling system plays an important role.

[0048] Example 5

[0049] This example verifies the ability of the S-ZVI+FeSO4+Na2SO3 coupling system to avoid the generation of nitroso-CAP and azo-CAP by comparing the distribution of CAP degradation products at 180 min in different systems.

[0050] The qualitative analysis of the sample components at 180 min in the S-ZVI+Na2SO4 (since S-ZVI cannot quickly remove CAP, the blank control group selects the S-ZVI+Na2SO4 system. According to previous literature reports, Na2SO4 only accelerates electron transfer in the reaction system, and has no other special role), S-ZVI+FeSO4, S-ZVI+Na2SO3 and S-ZVI+FeSO4+Na2SO3 experimental groups was carried out by means of a quadrupole time-of-flight high-resolution mass spectrometer. The results are shown in Figure 5 In the non-coupling system, there are two intermediate products of nitroso-CAP or azo-CAP; and in the coupling system, nitroso-CAP, hydroxylamine-CAP and azo-CAP are not detected. In addition, the degradation products of CAP in the coupling system are mainly amino-CAP, a small amount of dechlorinated products of CAP, and a small amount of new products. Therefore, the method of removing chloramphenicol by sulfite and ferrous iron enhanced zero-valent iron not only has the ability to avoid the generation of nitroso-CAP and azo-CAP, but also can advance the time point of chloramphenicol dechlorination.

[0051] Example 6

[0052] This example verifies the ability of the S-ZVI+FeSO4+Na2SO3 coupling system to avoid the generation of high-toxicity intermediate products by comparing the toxicity evaluation results of different CAP degradation products on blackhead stickleback.

[0053] By means of T.E.S.T toxicity simulation software, blackhead stickleback was selected as the test object, and the logarithm value of the semi-lethal dose (LC 50 ) was selected as the index (the larger the value, the higher the ecological toxicity of the simulated substance to blackhead stickleback), and the toxicity of CAP and its degradation products was simulated. The results are shown in Figure 6 The log(LC 50 ) of CAP is 5.19, and the log(LC 50 ) of nitroso-CAP and azo-CAP is greater than 5.19 (5.25 and 7.18, respectively), and the log(LC 50) are all less than 5.19. Thus, it can be seen that with the reduction of CAP, its ecological toxicity to the blackhead minnow presents a trend of first increasing and then decreasing. In combination with the conclusion of Example 5, it can be known that the method of removing chloramphenicol by synergistic sulfite and ferrous iron fortified zero-valent iron has the ability to avoid the generation of high-toxicity intermediate products.

[0054] The above merely illustrates the preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of sulfite synergized ferrous salt fortified zero-valent iron reduction degradation of antibiotics containing nitro functional groups, characterized in that, The method comprises the following steps: The pH value of antibiotic wastewater containing nitro functional groups is adjusted to 5-9, and sulfidation modified zero-valent iron, sulfite and ferrous salt are simultaneously added into the wastewater, and the reduction degradation of the antibiotic containing nitro functional groups is completed after 3-4 h of stirring reaction; The preparation method of the sulfidation modified zero-valent iron comprises the following steps: Nitrogen is introduced into an acetic acid-sodium acetate buffer solution with a pH value of 5.5-6.5 to reduce the dissolved oxygen to 0, then micron zero-valent iron powder is added, ultrasonic dispersion is carried out, sodium sulfide solution is added, and the reaction is carried out by shaking bed oscillation, after the reaction is completed, the sulfidation modified zero-valent iron is obtained by filtration, washing and freeze-drying; the purpose of sulfidation modification is to remove the passivation layer on the surface of the commercially available zero-valent iron and maintain the reaction activity for a certain period of time.

2. The method of claim 1, wherein, The antibiotic containing nitro functional groups comprises nitroimidazoles, nitrofuran, nitroquinoline and chloramphenicol.

3. The method of claim 1, wherein, In the sulfidation modified zero-valent iron, the molar ratio of sulfur to iron is 0.05-0.06:

1.

4. The method of claim 1, wherein, The dosage of the sulfidation modified zero-valent iron in the wastewater is 50-500 mg / L.

5. The method of claim 1, wherein, The sulfite comprises K2SO3 or Na2SO3.

6. The method of claim 1, wherein, The dosage of the sulfite in the wastewater is 0.2 mM-10 mM.

7. The method of claim 1, wherein, The ferrous salt comprises FeSO4, Fe(NO3)2 or FeCl2.

8. The method of claim 1, wherein, The dosage of the ferrous salt in the wastewater is 0.5-5 mM.

9. The method of claim 1, wherein, The method of sulfite and ferrous salt for strengthening zero-valent iron to reduce and degrade the antibiotic containing nitro functional groups can be carried out under anaerobic and aerobic conditions.

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