A method for removing organic pollutants in water by activating sulfite with Fe-N-C

Abstract

The present invention relates to a method for removing organic pollutants in water by activating sulfite with Fe-N-C, belonging to the technical fields of new catalyst materials and environmental purification technologies. An iron salt and a carbon-nitrogen precursor are added to an organic solvent, and the iron salt and the carbon-nitrogen precursor form a complex. Then, the organic solvent is removed to obtain a dry powder. The dry powder is calcined under a protective atmosphere, and after carbonization, an Fe-N-C catalyst is obtained. The present invention solves the bottleneck problem of low efficiency in traditional heterogeneous sulfite activation technology due to few reactive sites and slow oxygen mass transfer by constructing carbon-based metal active sites with oxygen-rich properties. This catalytic oxidation method has high treatment efficiency and simple operation, has a wide pH application range, strong anti-ion interference ability, and high reusability, and has broad application prospects in the field of actual industrial wastewater treatment.

Description

Technical Field

[0001] The present invention belongs to the technical fields of new catalyst materials and environmental purification technologies, and more specifically, relates to a method for removing organic pollutants in water by activating sulfite using Fe-N-C. Background Art

[0002] The bacterial drug resistance caused by the residue, migration, and accumulation of antibiotics in environmental media has become one of the greatest threats to global public health. China is the largest producer and user of antibiotics in the world. The long-term overuse of antibiotics in industries such as the pharmaceutical industry and animal husbandry has led to serious water environmental pollution, posing a serious threat to the ecological environment and human health.

[0003] Sulfite is one of the typical pollutants in industrial wastewaters such as flue gas desulfurization, mining, and papermaking. In the carcinogen list published by the International Agency for Research on Cancer of the World Health Organization in 2017, sulfite was classified as a Group 3 carcinogen. Research has found that sulfite can be activated by transition metals to generate reactive free radicals such as sulfate radicals (SO4 ·- ), which can oxidize and remove co-existing pollutants, achieving the simultaneous detoxification and comprehensive treatment of sulfite and co-existing pollutants. Therefore, using sulfite activation technology to achieve the removal of antibiotics has important practical significance for the ecological environment and sustainable development.

[0004] However, in the process of forming SO4 ·- free radicals, dissolved oxygen plays a crucial role. The currently developed heterogeneous sulfite activators have limited oxygen adsorption capacity and few active sites, resulting in low activation efficiency. Therefore, constructing active sites for oxygen adsorption to solve the bottleneck problem of low efficiency caused by slow oxygen mass transfer and few reaction active sites in traditional heterogeneous sulfite activation systems can further promote the practical application of sulfite activation technology in the remediation of antibiotic-contaminated water. In recent years, iron-nitrogen-carbon (Fe-N-C) materials have been widely used in the electrochemical oxygen reduction reaction (ORR). The research team led by Academician Baoxin He found that Fe-N-C has excellent O2 enrichment performance and abundant Fe catalytic active sites (Science Advance, 2015, 1: e1500462). However, most of the current preparation processes of Fe-N-C materials require the use of templating agents, with complex processes and high costs, severely restricting their practical applications. Summary of the Invention

[0005] Aiming at the above defects or improvement requirements of the prior art, the present invention provides an Fe-N-C catalyst, a preparation method, and the application of this Fe-N-C in activating sulfite to remove antibiotic organic pollutants in water, aiming to construct FeN x(X is 3, 4 or 5) The active site is used to activate sulfite. On the one hand, it is expected to fundamentally solve the problem of slow oxygen mass transfer. On the other hand, highly dispersed metals and carbon-based catalysts with strong conductivity can be obtained, thereby solving the technical problems such as few reactive sites of sulfite activators, slow oxygen mass transfer, and low oxidation efficiency in the prior art.

[0006] According to the first aspect of the present invention, a preparation method of an Fe-N-C catalyst is provided, including the following steps:

[0007] (1) Add an iron salt and a carbon-nitrogen precursor to an organic solvent. The iron salt and the carbon-nitrogen precursor form a complex, and then remove the organic solvent to obtain a dry powder;

[0008] (2) Calcinate the dry powder obtained in step (1) under a protective atmosphere, and the Fe-N-C catalyst is obtained after carbonization.

[0009] Preferably, the carbon-nitrogen precursor is o-phenanthroline or dicyandiamide.

[0010] Preferably, the mass ratio of the iron salt to the carbon-nitrogen precursor is 0.25 - 1.00.

[0011] Preferably, the calcination temperature is 700 - 1000 °C, and the calcination time is 1 - 3 h.

[0012] According to another aspect of the present invention, an Fe-N-C catalyst prepared by any one of the methods is provided.

[0013] According to another aspect of the present invention, an application of the described Fe-N-C catalyst for activating sulfite to remove organic pollutants in water bodies is provided.

[0014] Preferably, the pH of the water body is 4.0 - 10.0;

[0015] Preferably, the pH of the water body is 7.0 - 10.0.

[0016] Preferably, the organic pollutant is at least one of tetracycline hydrochloride, ciprofloxacin, and sulfamethoxazole;

[0017] Preferably, the concentration of organic pollutants in the water body is 5 - 20 mg / L.

[0018] Preferably, the mass ratio of the Fe-N-C catalyst to the amount of substance of sulfite is 0.2 g / mmol - 1.0 g / mmol.

[0019] Preferably, the sulfite is at least one of sodium sulfite, sodium bisulfite, calcium sulfite, calcium bisulfite, and magnesium sulfite.

[0020] Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention mainly have the following technical advantages:

[0021] (1) The catalyst prepared by the present invention has excellent oxygen enrichment ability, highly dispersed Fe active sites and strong electrical conductivity.

[0022] (2) The Fe-N-C activated sulfite system of the present invention has a significant effect on reducing antibiotic pollution in water. At present, the few reactive sites and slow oxygen mass transfer rate severely limit the oxidation efficiency of the sulfite activation system. By constructing FeN x (X is 3, 4 or 5) sites on the carbon substrate material, the surface active sites of the catalyst can be greatly enriched. At the same time, the introduction of FeN x (X is 3, 4 or 5) sites significantly enhances the oxygen enrichment ability, thus greatly accelerating the generation rate of sulfate radicals and improving the oxidation efficiency of the sulfite activation technology. In addition, the high electrical conductivity of the carbon substrate can further promote the electron transfer reaction during the sulfite activation process.

[0023] (3) The sulfite activation system is generally limited to acidic or near-neutral conditions, and the iron-based catalyst is greatly affected by pH and has poor activity under alkaline conditions. Due to the abundant catalytic active sites, strong electrical conductivity and excellent oxygen enrichment ability of the catalyst in the present invention, the activation of sulfite and the conversion of oxygen-sulfur radicals can be quickly achieved, so as to efficiently generate SO4 ·- radicals. Therefore, the efficient removal of antibiotic pollutants can be achieved within a wide pH range (pH = 4.0–10.0). This makes up for the shortcoming of poor activity of traditional sulfite activation technology under alkaline conditions and has strong adaptability to actual wastewater.

[0024] (4) The organic pollutant treatment technology based on Fe-N-C activated sulfite provided by the present invention has important industrial significance in the efficient comprehensive treatment of sulfite and antibiotic pollution. When the Fe-N-C catalyst is added to the polluted water containing organic matter and mixed evenly, sulfite is added to form a multiphase coexistence system, and the generated strongly oxidizing sulfate radicals oxidize and remove organic matter under the condition of normal temperature stirring. Due to the high concentration of sulfate radicals generated by the technical system, it is not only applicable to the treatment of industrial antibiotic wastewater, but also can be applied to other fields, such as the wastewater of the actual printing and dyeing industry.

[0025] (5) By utilizing the strong adsorption performance of the carbon substrate, the present invention can significantly promote the adsorption and enrichment of pollutants by the catalyst and promote the removal process of pollutants. At the same time, the stability of the carbon substrate enables the catalyst to have good reusability. Through simple solid-liquid separation, without drying or calcination, the catalyst can be recycled. And the iron dissolution concentration is extremely low, which will not cause secondary pollution.

[0026] (6) Compared with the prior art, in the present invention, no templating agent is required in the catalyst preparation process, the process is simple and easy to operate, suitable for mass production, and has broad application prospects.

[0027] (7) The carbon source and iron source required for the preparation of the catalyst of the present invention are widely sourced and inexpensive, and the preparation method is simple. In addition, sulfite is a pollutant in industrial wastewater such as flue gas desulfurization, mining, and papermaking. Using sulfite as an oxidant conforms to the green environmental protection strategy of "treating waste with waste".

[0028] (8) The antibiotic wastewater treatment method provided by the present invention has rapid reaction, simple process, strong operability, is easy to promote and utilize, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 X-ray diffraction patterns of Fe-N-C and control materials N-C, Fe x O y and O.

[0030] Figure 2 High-resolution transmission electron microscopy image (left) and selected area diffraction pattern (right) of Fe-N-C.

[0031] Figure 3 Oxygen temperature-programmed desorption experiments of Fe-N-C and control materials N-C, Fe2O3.

[0032] Figure 4 Degradation effects of Fe-N-C / Na2SO3 and different control material systems on tetracycline hydrochloride.

[0033] Figure 5 Effect of initial pH of solution on degradation of tetracycline hydrochloride by Fe-N-C / Na2SO3 system.

[0034] Figure 6 Effect of common coexisting anions on degradation of tetracycline hydrochloride by Fe-N-C / Na2SO3 system.

[0035] Figure 7 Recycling experiment of Fe-N-C. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Example 1

[0038] This example provides a method for removing organic pollutants in water by activating sulfite with Fe-N-C, which specifically includes the following steps:

[0039] (1) Dissolve ferric nitrate and phenanthroline in an ethanol solvent at a mass ratio of 1:2.

[0040] (2) Remove the ethanol solvent by evaporation; calcine the obtained dry powder at 800 °C for 2 h under a nitrogen atmosphere; finally, remove unstable metal species from the carbonized sample by pickling. After washing with water and drying, an Fe-N-C catalyst is obtained.

[0041] (3) Add the Fe-N-C catalyst and sodium sulfite at a ratio of 0.5 g / mmol to tetracycline hydrochloride with an initial concentration of 5 mg / L, adjust the initial pH of the solution to 4.0, and stir to make them react.

[0042] Results and analysis:

[0043] Characterize the Fe-N-C catalyst prepared in this example and the control materials N-C (without iron salt) and Fe x O y (without phenanthroline), and explore the efficiency and stability of Fe-N-C-activated sulfite in degrading organic pollutants.

[0044] Figure 1 For the X-ray diffraction patterns of the Fe-N-C catalyst and the N-C and Fe x O y control materials. It can be found that characteristic diffraction peaks appear at 24.0° and 43.3° in the patterns of Fe-N-C and N-C, which belong to the (0 0 2) and (1 0 0) crystal planes of graphitic carbon, respectively. In addition, a characteristic peak attributed to Fe3C appears at 44.7°, indicating that in addition to Fe and N being anchored on the carbon skeleton (FeN x , X = 3, 4, 5), the excess Fe agglomerates and forms Fe3C nanoparticles with the carbon skeleton. The diffraction peaks of the control material Fe x O y are consistent with the standard spectrum of Fe2O3. In addition, compared with the N-C material, the (1 0 0) peak in the pattern of Fe-N-C is sharper, indicating better graphitization degree and stronger conductivity.

[0045] Figure 2High-resolution transmission electron microscopy image (left) and selected area diffraction pattern (right) of Fe-N-C. Fe-N-C exhibits a graphite-like flaky structure with Fe3C encapsulated in the graphite carbon layer. The 0.34 nm fringe spacing corresponds to the graphite layer, indicating that the main structure of Fe-N-C is graphite carbon, and the 0.24 nm fringe spacing corresponds to Fe3C. The clear diffraction rings in the selected area diffraction pattern (right) further prove the coexistence of Fe3C and the carbon skeleton. That is, the main components of the Fe-N-C catalyst are FeN X and Fe3C.

[0046] Figure 3 Oxygen temperature-programmed desorption experiments of Fe-N-C and control materials N-C and Fe2O3 are shown. It was found that no obvious oxygen desorption was observed for Fe2O3, a weak oxygen adsorption peak appeared in the N-C graph, while obvious oxygen desorption peaks appeared at 250 - 300 °C, 400 - 420 °C, and 650 - 680 °C for Fe-N-C, corresponding to physical oxygen adsorption, superoxide species adsorption, and lattice oxygen desorption, respectively. This result confirms that Fe-N-C has excellent oxygen adsorption performance.

[0047] Figure 4 The degradation effects of different catalysts activating the Na2SO3 system on tetracycline hydrochloride are given. The results show that within 60 min, the removal rates of tetracycline hydrochloride by pure Na2SO3 / Fe2O3 and Na2SO3 / N-C are only 17.7% and 29.8% respectively. When Na2SO3 coexists with Fe-N-C, the removal rate of tetracycline hydrochloride is as high as 100%, and the reaction rates are 41.7 and 25 times those of the Fe2O3 and N-C systems respectively, which is mainly attributed to the oxygen-rich property of the Fe-N-C catalyst, the high dispersion of metallic Fe, and the strong electrical conductivity.

[0048] Figure 5 The influence of the initial pH of the solution on the degradation of tetracycline hydrochloride by the Fe-N-C / Na2SO3 system is shown. The results show that this technical system can achieve efficient removal of tetracycline hydrochloride in a wide pH range (pH = 4.0 - 10.0). This makes up for the shortcoming of poor activity under alkaline conditions of traditional sulfite activation technology and has strong adaptability to actual wastewater.

[0049] Figure 6 The influence of common coexisting anions on the degradation of tetracycline hydrochloride by the Fe-N-C / Na2SO3 system is shown. Various inorganic anions widely exist in natural waters and actual wastewaters and may affect the degradation process of target pollutants. As Figure 6 can be seen, the common anions CO3 2- 、SO4 2- 、Cl - and NO3 -It has little effect on the degradation of tetracycline hydrochloride, indicating that the Fe-N-C / Na2SO3 system has strong adaptability to coexisting anions.

[0050] Figure 7 This is the recycling experiment of the Fe-N-C catalyst. After the reaction, the catalyst can be recycled by simple solid-liquid separation without any treatment. The catalyst was recycled 4 times, and the degradation rate of TC was still not less than 80%. And the iron dissolution concentration was extremely low during the whole reaction process, indicating that the prepared catalyst has good recycling stability.

[0051] Through the above analysis, it can be seen that the method in this example obtains an Fe-N-C catalyst with highly dispersed active sites, excellent oxygen enrichment ability and good conductivity, realizing the effective activation and utilization of sulfite and the efficient and rapid degradation of antibiotic pollutants. In addition, this method can still maintain high oxidation performance in a wide pH range and in the presence of coexisting anions. The catalyst has good recycling stability and no secondary pollution. Moreover, the raw materials are easily available, inexpensive, and the preparation method is simple, so this method has high practical value and broad application prospects.

[0052] Example 2

[0053] (1) Dissolve ferric chloride and phenanthroline in an ethanol solvent at a mass ratio of 1:2.

[0054] (2) Remove the ethanol solvent by evaporation; calcine the obtained dry powder at 800 °C for 2 h under a nitrogen atmosphere; finally, remove the unstable metal species from the carbonized sample by pickling. After washing with water and drying, the Fe-N-C catalyst is obtained.

[0055] (3) Add the Fe-N-C catalyst and sodium sulfite at a ratio of 0.5 g / mmol to tetracycline hydrochloride with an initial concentration of 5 mg / L, adjust the initial pH of the solution to 4.0, and stir to make it react. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride is as high as 100%.

[0056] Example 3

[0057] (1) Dissolve ferric nitrate and phenanthroline in an ethanol solvent at a mass ratio of 1:1.

[0058] (2) Remove the ethanol solvent by evaporation; calcine the obtained dry powder at 800 °C for 2 h under a nitrogen atmosphere; finally, remove the unstable metal species from the carbonized sample by pickling. After washing with water and drying, the Fe-N-C catalyst is obtained.

[0059] (3) The Fe-N-C catalyst and sodium sulfite were added to tetracycline hydrochloride with an initial concentration of 5 mg / L at a ratio of 0.5 g / mmol. The initial pH of the solution was adjusted to 4.0, and stirring was carried out to make it react. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride was as high as 100%.

[0060] Example 4

[0061] (1) Ferric nitrate and phenanthroline were dissolved in an ethanol solvent at a mass ratio of 1:4.

[0062] (2) The ethanol solvent was removed by evaporation; the obtained dry powder was calcined at 800 °C for 2 h in a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by pickling. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0063] (3) The Fe-N-C catalyst and sodium sulfite were added to tetracycline hydrochloride with an initial concentration of 5 mg / L at a ratio of 0.5 g / mmol. The initial pH of the solution was adjusted to 4.0, and stirring was carried out to make it react. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride was as high as 95%.

[0064] Example 5

[0065] (1) Ferric nitrate and phenanthroline were dissolved in an ethanol solvent at a mass ratio of 1:2.

[0066] (2) The ethanol solvent was removed by evaporation; the obtained dry powder was calcined at 1000 °C for 1 h in a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by pickling. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0067] (3) The Fe-N-C catalyst and sodium sulfite were added to tetracycline hydrochloride with an initial concentration of 5 mg / L at a ratio of 0.5 g / mmol. The initial pH of the solution was adjusted to 4.0, and stirring was carried out to make it react. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride was as high as 100%.

[0068] Example 6

[0069] (1) Ferric nitrate and phenanthroline were dissolved in an ethanol solvent at a mass ratio of 1:2.

[0070] (2) The ethanol solvent was removed by evaporation; the obtained dry powder was calcined at 700 °C for 3 h in a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by pickling. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0071] (3) The Fe-N-C catalyst and sodium sulfite were added to tetracycline hydrochloride with an initial concentration of 5 mg / L at a ratio of 0.5 g / mmol, and the initial pH of the solution was adjusted to 4.0. Stir to make them react. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride was as high as 92%.

[0072] Example 7

[0073] (1) Ferric nitrate and phenanthroline were dissolved in an ethanol solvent at a mass ratio of 1:2.

[0074] (2) The ethanol solvent was removed by evaporation; the obtained dry powder was calcined at 800 °C for 2 h in a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by pickling. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0075] (3) The Fe-N-C catalyst and sodium sulfite were respectively added to ciprofloxacin and sulfamethoxazole with an initial concentration of 5 mg / L at a ratio of 0.5 g / mmol, and the initial pH of the solution was adjusted to 4.0. Stir to make them react. After 60 min of heterogeneous reaction, the degradation rates of ciprofloxacin and sulfamethoxazole were 98% and 85% respectively.

[0076] Example 8

[0077] (1) Ferric nitrate and phenanthroline were dissolved in an ethanol solvent at a mass ratio of 1:2.

[0078] (2) The ethanol solvent was removed by evaporation; the obtained dry powder was calcined at 800 °C for 2 h in a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by pickling. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0079] (3) The Fe-N-C catalyst and sodium sulfite were added to tetracycline hydrochloride with an initial concentration of 20 mg / L at a ratio of 1.0 g / mmol, and the initial pH of the solution was adjusted to 4.0. Stir to make them react. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride reached 82%.

[0080] Example 9

[0081] (1) Ferric nitrate and phenanthroline were dissolved in an ethanol solvent at a mass ratio of 1:2.

[0082] (2) The ethanol solvent was removed by evaporation; the obtained dry powder was calcined at 800 °C for 2 h in a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by pickling. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0083] (3) The Fe-N-C catalyst and sodium sulfite were added to tetracycline hydrochloride with an initial concentration of 5 mg / L at a ratio of 0.2 g / mmol, and the initial pH of the solution was adjusted to 4.0, followed by stirring to initiate the reaction. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride was 70%.

[0084] Example 10

[0085] (1) Ferric nitrate and o-phenanthroline were dissolved in an ethanol solvent at a mass ratio of 1:2.

[0086] (2) The ethanol solvent was removed by evaporation; the resulting dry powder was calcined at 800 °C for 2 h under a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by acid washing. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0087] (3) The Fe-N-C catalyst and calcium sulfite were added to tetracycline hydrochloride with an initial concentration of 5 mg / L at a ratio of 0.5 g / mmol, and the initial pH of the solution was adjusted to 4.0, followed by stirring to initiate the reaction. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride was 100%.

[0088] Example 11

[0089] (1) Ferric nitrate and o-phenanthroline were dissolved in an ethanol solvent at a mass ratio of 1:2.

[0090] (2) The ethanol solvent was removed by evaporation; the resulting dry powder was calcined at 800 °C for 2 h under a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by acid washing. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0091] (3) The Fe-N-C catalyst and magnesium sulfite were added to tetracycline hydrochloride with an initial concentration of 5 mg / L at a ratio of 0.5 g / mmol, and the initial pH of the solution was adjusted to 4.0, followed by stirring to initiate the reaction. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride was 72%.

[0092] Example 12

[0093] (1) Ferric nitrate and o-phenanthroline were dissolved in an ethanol solvent at a mass ratio of 1:2.

[0094] (2) The ethanol solvent was removed by evaporation; the resulting dry powder was calcined at 800 °C for 2 h under a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by acid washing. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0095] (3) The Fe-N-C catalyst and sodium sulfite were added to tetracycline hydrochloride with an initial concentration of 5 mg / L at a ratio of 0.5 g / mmol, and the initial pH of the solution was adjusted to 7.92. Stir to make them react. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride was 93.7%.

[0096] Example 13

[0097] (1) Ferric nitrate and o-phenanthroline were dissolved in an ethanol solvent at a mass ratio of 1:2.

[0098] (2) The ethanol solvent was removed by evaporation; the obtained dry powder was calcined at 800 °C for 2 h under a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by pickling. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0099] (3) The Fe-N-C catalyst and sodium sulfite were added to tetracycline hydrochloride with an initial concentration of 5 mg / L at a ratio of 0.5 g / mmol, and the initial pH of the solution was adjusted to 10.0. Stir to make them react. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride was 82%.

[0100] Example 14

[0101] (1) Ferric nitrate and dicyandiamide were dissolved in an ethanol solvent at a mass ratio of 1:2.

[0102] (2) The ethanol solvent was removed by evaporation; the obtained dry powder was calcined at 800 °C for 2 h under a nitrogen atmosphere; finally, the unstable metal species in the carbonized sample were removed by pickling. After washing with water and drying, the Fe-N-C catalyst was obtained.

[0103] (3) The Fe-N-C catalyst and sodium sulfite were added to tetracycline hydrochloride with an initial concentration of 5 mg / L at a ratio of 0.5 g / mmol, and the initial pH of the solution was adjusted to 10.0. Stir to make them react. After 60 min of heterogeneous reaction, the degradation rate of tetracycline hydrochloride was 100%.

[0104] Comparative Example 1 Removal of tetracycline hydrochloride by simple sulfite

[0105] 0.4 mmol of sodium sulfite was directly added to a tetracycline hydrochloride solution with an initial concentration of 5 mg / L, and the pH of the solution was adjusted to 4.0. It was found that after 60 min of reaction, tetracycline hydrochloride was hardly removed. This shows that in the Fe-N-C / sulfite system, the degradation of tetracycline hydrochloride mainly comes from the activation of Fe-N-C. Further illustrates the high efficiency of Fe-N-C.

[0106] Comparative Example 2 Removal of tetracycline hydrochloride by homogeneous iron salt-activated sulfite

[0107] The iron content in Fe-N-C was measured to be 4.97% by inductively coupled plasma optical emission spectrometer. Assuming that all iron was dissolved, the calculated iron concentration was 9.9 mg / L. 9.9 mg / L of ferric nitrate and 0.4 mmol of sodium sulfite were added to the tetracycline hydrochloride solution with an initial concentration of 5 mg / L, and the pH of the solution was adjusted to 4.0. It was found that after 60 min of reaction, the degradation rate of tetracycline hydrochloride was only 71.52%, which was much lower than that of the present invention (100%). This was mainly attributed to the excellent oxygen-rich performance of the catalyst and highly dispersed iron active sites. This further demonstrated the advancement and high efficiency of the present invention method. In addition, the present invention method can overcome the problems of narrow pH application range in traditional homogeneous systems, inability to recycle catalytic active components, and easy generation of secondary pollution, and has broad application prospects.

[0108] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Application of Fe-N-C catalyst in activating sulfite to remove organic pollutants in water body, characterized in that, The Fe-N-C catalyst is prepared by the following steps: (1) Add an iron salt and a carbon-nitrogen precursor to an organic solvent. The iron salt and the carbon-nitrogen precursor form a complex, and then remove the organic solvent to obtain a dry powder. The carbon-nitrogen precursor is phenanthroline or dicyandiamide; (2) Calcinate the dry powder obtained in step (1) under a protective atmosphere. The calcination temperature is 700-1000 °C, and the calcination time is 1-3 h. After carbonization, the Fe-N-C catalyst is obtained.

2. The application according to claim 1, characterized in that The pH of the water body is 4.0-10.

0.

3. The application according to claim 2, wherein The pH of the water body is 7.0-10.

0.

4. The application according to any one of claims 1-3, characterized in that, The organic pollutant is at least one of tetracycline hydrochloride, ciprofloxacin, and sulfamethoxazole.

5. The application according to claim 4, wherein The concentration of the organic pollutant in the water body is 5-20 mg / L.

6. The application according to claim 1, characterized in that, The mass ratio of the Fe-N-C catalyst to the amount of substance of sulfite is 0.2 g / mmol - 1.0 g / mmol.

7. The application according to claim 1, characterized in that The sulfite is at least one of sodium sulfite, sodium bisulfite, calcium sulfite, calcium bisulfite, and magnesium sulfite.

8. The application according to claim 1, characterized in that The mass ratio of the iron salt to the carbon-nitrogen precursor is 0.25-1.00.

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