Preparation of an iron-based microwave catalytic material and its application in the treatment of sulfonamides and hexavalent chromium

Abstract

The invention discloses a method for preparing an iron-based microwave catalytic material and a method for degrading sulfonamides and reducing hexavalent chromium. The method comprises the following steps: mixing iron salt, zinc salt, biochar, boric acid, and citric acid in deionized water in a certain proportion, stirring in a 60-80°C water bath, and drying the gel-like substance at 400-600°C to obtain a microwave catalyst after drying. The synthesized microwave catalyst is added to sulfonamides and hexavalent chromium-contaminated wastewater, degrading sulfonamides by oxidation reaction in a microwave field, and reducing hexavalent chromium by reduction reaction. Experiments show that the degradation rate of sulfonamides and the reduction rate of hexavalent chromium can reach 100% within 10 minutes. The microwave catalyst of the present invention can quickly and efficiently oxidize and degrade sulfonamide antibiotics and reduce hexavalent chromium without adding additional oxidants or reducing agents, and has the advantages of high efficiency, wide pH application range, environmental friendliness, and low processing cost.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing functional materials for catalytic oxidation-reduction treatment of environmental pollutants, and specifically relates to a method for preparing an iron-based microwave catalytic material and a method for degrading sulfonamide drugs and reducing hexavalent chromium. Background Art

[0002] Sulfonamides are a class of drugs that contain aminosulfonamides. Sulfamethoxazole (SMX), as a typical representative of sulfonamides, is widely used in the biopharmaceutical industry and is used in large quantities. However, the abuse of sulfonamide antibiotics and their secondary metabolites will inhibit the activity of microorganisms in aquatic ecosystems and directly threaten human health through enrichment in the food chain. What's more serious is that SMX is also included in the World Health Organization's list of Class III carcinogens. In the metallurgical, electroplating and other industries, the large-scale discharge of chromium-containing industrial wastewater has caused a large amount of Cr(VI) to exist in natural water bodies and sewage treatment plants. Cr(VI) is highly soluble in water and has high mobility in soil and water bodies. It is one of the three internationally recognized carcinogenic metal compounds and poses a serious threat to ecosystems and human health. In sewage treatment plants, there is a situation of combined pollution of Cr(VI) and SMX. Therefore, it is urgent to develop a method to efficiently treat these pollutants.

[0003] There have been many studies on the remediation technologies for these two water pollutants. The main treatment methods for common SMX wastewater include biodegradation, physical adsorption, traditional chemical methods and advanced oxidation methods; the commonly used remediation technologies for Cr(VI) polluted wastewater mainly include biodegradation, precipitation, ion exchange, physical adsorption and zero-valent iron reduction. These methods have shown good treatment effects on SMX and Cr(VI), but there are still many problems and shortcomings. The Chinese patent "A method for catalytic degradation of sulfonamide drugs in water using chelating agent modified Fe3O4 material, application number 201811063334.8" discloses a method for catalytic degradation of sulfonamide drugs in water using chelating agent modified Fe3O4 material. The method prepares a chelating agent modified Fe3O4 catalyst to catalyze the oxidation degradation of sulfamethoxazole in water by persulfate (PMS). Although the method has a short treatment time (20-40min), the degradation efficiency is low (<70%) and the price of the added chemical oxidant PMS is high. The Chinese patent "A composite material for efficiently treating hexavalent chromium pollution in the environment, its preparation method and application, application number 202211329027.6" discloses a composite material for efficiently treating hexavalent chromium pollution in the environment, its preparation method and application. The method prepares nano-carbon sulfide loaded biochar material by coprecipitation method, and uses it as an adsorbent to adsorb Cr(VI) in water. Although this method has high removal efficiency of Cr(VI) in water, it has a long treatment time, and there is a large amount of Cr(VI) on the adsorbed material, which requires secondary treatment of the adsorbent. The Chinese patent "Microbial combination and method for repairing polycyclic aromatic hydrocarbons and hexavalent chromium composite contaminated soil, application number 202211428273.7" discloses a method for repairing polycyclic aromatic hydrocarbons and hexavalent chromium composite contaminated soil. The method uses a combination of multiple microorganisms to achieve the purpose of simultaneously repairing polycyclic aromatic hydrocarbons and Cr(VI) in the soil. Although this method can simultaneously repair and degrade organic matter and reduce Cr(VI), it has the problems of long repair time (30-60d) and low repair efficiency (<80%). Designing an efficient, pollution-free technology for simultaneously treating SMX and Cr(VI) in wastewater is of great significance in the field of water pollution treatment. Summary of the invention

[0004] In view of the above problems, the present invention focuses on the preparation of green environmentally friendly materials and the design of efficient environmental remediation technology. Iron salt, zinc salt, biochar, boric acid and citric acid are used as raw materials to prepare boron-doped zinc ferrite loaded biochar microwave catalyst by a one-step pyrolysis method. Under microwave radiation, electrons (e - )-hole (h + ) pairs and separate quickly. These electrons and holes can directly participate in redox reactions, or they can generate other active substances to indirectly participate in the degradation of pollutants. For example, electrons can react with oxygen to produce superoxide radicals. (See Formula 1), the holes can react with water to produce hydroxyl radicals (·OH) (see Formula 2), which will further degrade and mineralize pollutants in the water.

[0005]

[0006] H2O+h + → OH+H + (2)

[0007] The present invention realizes the degradation of SMX and the reduction of Cr(VI) by the following principle: after adding a microwave catalyst to a water body contaminated with SMX and Cr(VI), the catalyst first adsorbs SMX and Cr(VI) in the water body, and under microwave radiation, the electrons generated on the catalyst surface will reduce the adsorbed Cr(VI), while the holes and other active substances generated on the catalyst surface will oxidize the adsorbed SMX. While the SMX and Cr(VI) adsorbed on the catalyst surface are degraded and reduced respectively, the catalyst will continue to adsorb SMX and Cr(VI) from the water body, and the cycle will continue until all the SMX in the water body is degraded and all the Cr(VI) is reduced. The advantage of the present invention is that sulfonamides can be oxidized and degraded quickly and efficiently and hexavalent chromium can be reduced without the need for an external oxidant, and the processing cost is low.

[0008] To achieve the above object, the present invention provides a method for preparing an iron-based microwave catalytic material, comprising the following steps:

[0009] S1: iron salt, zinc salt, biochar, and boric acid are mixed in deionized water, and a certain amount of citric acid is added to form a mixture;

[0010] S2: stirring the mixture obtained in step S1 for 2-4 hours under water bath heating, and then drying in an oven to obtain a gel;

[0011] S3: heating the gel-like substance obtained in step S2 to 400-600° C. at a heating rate of 2-5° C. / min and calcining for 1-3 h, and then washing with deionized water for 3-5 times to obtain an iron-based microwave catalytic material;

[0012] According to some embodiments of the present invention, the iron salt in step S1 is at least one of ferric nitrate and ferric chloride.

[0013] According to some embodiments of the present invention, the zinc salt in step S1 is at least one of zinc nitrate and zinc chloride.

[0014] According to some embodiments of the present invention, the biochar in step S1 is a carbon material formed by pyrolysis of woody construction waste.

[0015] According to some embodiments of the present invention, the molar ratio of the iron salt, zinc salt, biochar, boric acid and citric acid in step S1 is 2:1:(0.1-0.2):(0.05-0.2):(1-1.2). Preferably, the molar ratio of the iron salt, zinc salt, biochar, boric acid and citric acid in step S1 is 2:1:0.1:0.1:1.

[0016] According to some embodiments of the present invention, the water bath temperature in step S2 is 60-80° C., and the water bath time is 2-4 h.

[0017] According to some embodiments of the present invention, the drying temperature in step S2 is 60-80° C., and the drying time is 6-12 hours.

[0018] According to some embodiments of the present invention, the heating rate in step S3 is 2-5° C. / min.

[0019] The present invention further provides an application method of the above catalyst, namely, a method for degrading sulfonamide drugs and reducing hexavalent chromium, characterized in that the iron-based microwave catalyst prepared above is added to sulfonamide drugs and hexavalent chromium wastewater in a certain proportion, reacts in a microwave field, and simultaneously oxidizes and degrades sulfonamide drugs and reduces hexavalent chromium.

[0020] According to some embodiments of the present invention, it is characterized in that the pH of the reaction system is 3-11; the usage amount of the iron-based microwave catalyst is 0.5-2 g / L; and the microwave power is 240-800W.

[0021] The microwave catalyst of the present invention utilizes a specific principle and cooperates with the processing of the preparation method to achieve rapid and efficient oxidation degradation of sulfonamide antibiotics and reduction of hexavalent chromium without adding additional oxidants or reducing agents. It has the advantages of high efficiency, wide pH application range, environmental friendliness and low processing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope photograph of the microwave catalyst prepared by the present invention.

[0023] Figure 2 This is the effect diagram of Example 1. Experimental conditions: [SMX] = 10 mg·L -1 , [Cr 6+ ]=30mg·L -1 , [FZBC] = 2 g·L -1 , [MW power] = 240W.

[0024] Figure 3 This is the effect diagram of Example 2. Experimental conditions: [SMX] = 10 mg·L -1 , [Cr 6+]=30mg·L -1 , [FZBC] = 0.5 g·L -1 , [MW power] = 800W.

[0025] Figure 4 This is the effect diagram of Example 3. Experimental conditions: [SMX] = 10 mg·L -1 , [Cr 6+ ]=30mg·L -1 , [FZBC] = 0.5 g·L -1 , [MW power] = 400W.

[0026] Figure 5 This is the effect diagram of Example 4. Experimental conditions: [SMX] = 10 mg·L -1 , [Cr 6+ ]=30mg·L -1 , [FZBC] = 0.5 g·L -1 , [MW power] = 800W. DETAILED DESCRIPTION

[0027] The content of the present invention is further described below in conjunction with specific examples, but it should not be construed as limiting the present invention. If not specifically indicated, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0028] Example 1

[0029] 1. At room temperature, iron nitrate, zinc nitrate, biochar, boric acid, and citric acid were added to 50 mL of deionized water in a molar ratio of 2:1:0.1:0.05:1, magnetically stirred in a 60 °C water bath for 4 h, and then dried in a 60 °C oven for 12 h to form a black gel.

[0030] 2. The black gel in step 1 was heated to 400°C in a tube furnace at a heating rate of 2°C / min and kept warm for 3 hours. After cooling, it was washed with deionized water and dried to obtain FZBC microwave catalyst.

[0031] 3. 0.1 g of the FZBC catalyst obtained in step 2 was added to 50 mL of SMX and Cr(VI) wastewater, respectively, and reacted in a microwave reactor with a power of 240 W. Samples were taken at 2, 5, 10, 15, and 20 min, and the concentrations of SMX and Cr(VI) in the samples were detected by high performance liquid chromatography and ultraviolet spectrophotometer, respectively. The results are shown in Figure 2. Figure 2As shown in the data, in the absence of microwave radiation, FZBC has a certain adsorption effect on SMX and Cr(VI); in the microwave field, SMX and Cr(VI) are completely removed within 10 minutes, indicating that the microwave catalyst can simultaneously and quickly and efficiently oxidize and degrade SMX and reduce Cr(VI) in the microwave field.

[0032] Example 2

[0033] 1. At room temperature, iron nitrate, zinc nitrate, biochar, boric acid, and citric acid were added to 50 mL of deionized water in a molar ratio of 2:1:0.2:0.2:1.2, magnetically stirred in an 80 °C water bath for 2 h, and then dried in an 80 °C oven for 6 h to form a black gel.

[0034] 2. The black gel in step 1 was heated to 600°C in a tube furnace at a heating rate of 5°C / min and kept warm for 1 hour. After cooling, it was washed with deionized water and dried to obtain FZBC microwave catalyst.

[0035] 3. 0.025 g of the FZBC catalyst obtained in step 2 was added to 50 mL of SMX and Cr(VI) wastewater, respectively, and reacted in a microwave reactor with a power of 800 W. Samples were taken at 2, 5, 10, 15, and 20 min, and the concentrations of SMX and Cr(VI) in the samples were detected by high performance liquid chromatography and ultraviolet spectrophotometer, respectively. The results are shown in Figure 2. Figure 3 As shown, in the microwave field, SMX and Cr(VI) were completely removed within 10 min.

[0036] Example 3

[0037] 1. At room temperature, iron nitrate, zinc nitrate, biochar, boric acid, and citric acid were added to 50 mL of deionized water in a molar ratio of 2:1:0.2:0.2:1.2, magnetically stirred in a 70 °C water bath for 4 h, and then dried in an oven at 80 °C for 6 h to form a black gel.

[0038] 2. The black gel in step 1 was heated to 500°C in a tube furnace at a heating rate of 5°C / min and kept warm for 2 hours. After cooling, it was washed with deionized water and dried to obtain FZBC microwave catalyst.

[0039] 3. 0.025 g of the FZBC catalyst obtained in step 2 was added to 50 mL of SMX and Cr(VI) wastewater, respectively, and the pH was adjusted to 3, 5, 7, 9, and 11 with H2SO4 or NaOH, respectively, and the reaction was carried out in a microwave reactor with a power of 400 W. Samples were taken at 2, 5, 10, 15, and 20 min, and the concentrations of SMX and Cr(VI) in the samples were detected by high performance liquid chromatography and ultraviolet spectrophotometer, respectively. The results are shown in FIG. Figure 4As shown, when the pH is between 3-11, SMX can be completely degraded within 10 minutes; the degradation effect of Cr(VI) is more obvious under acidic conditions, but overall it can also be completely degraded within 10 minutes, indicating that the microwave catalyst of the present invention has a wide range of applications.

[0040] Example 4

[0041] The reaction solution of Example 2 was allowed to stand, solid-liquid separation was performed using an ordinary magnet, the supernatant was poured out, the FZBC after the reaction was recovered, and the recovered FZBC was used as a catalyst to treat SMX and Cr(VI) wastewater respectively. The remaining operations were the same as those of Example 2. The results are shown in FIG. Figure 5 When reused for the fourth time, both SMX and Cr(VI) can be completely removed within 20 min, indicating that the microwave catalyst of the present invention has good reuse performance.

[0042] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for degrading sulfonamides and / or reducing hexavalent chromium, It is characterized in that The iron-based microwave catalytic material is added to the sulfonamides and hexavalent chromium wastewater in proportion to form a reaction system, and the reaction is carried out in the microwave field to oxidatively degrade the sulfonamides and reduce the hexavalent chromium; The preparation of the iron-based microwave catalytic material comprises the following steps: S1: iron salt, zinc salt, biochar, and boric acid are mixed in deionized water, and citric acid is added to form a mixture; S2: stirring the mixture obtained in step S1 under heating in a water bath, and then drying in an oven to obtain a gel-like substance; S3: heating the gel-like substance obtained in step S2 to 400-600° C. at a heating rate of 1-6° C. / min and calcining for 1-3 h, and then washing with deionized water to obtain an iron-based microwave catalytic material; The iron salt is at least one of ferric nitrate and ferric chloride; The zinc salt is at least one of zinc nitrate and zinc chloride; The molar ratio of the iron salt, zinc salt, biochar, boric acid and citric acid in step S1 is 2:1: (0.1-0.2): (0.05-0.2): (1-1.2); In step S2, the water bath temperature is 60-80°C, and the water bath time is 2-4 hours; the drying temperature is 60-80°C, and the drying time is 6-12 hours.

2. The method according to claim 1, It is characterized in that The biochar described in step S1 is a carbon material formed by pyrolysis of woody construction waste.

3. The method according to claim 1, It is characterized in that The molar ratio of the iron salt, zinc salt, biochar, boric acid and citric acid in step S1 is 2: 1: 0.1: 0.1:

1.

4. The method according to claim 1, It is characterized in that The heating rate in step S3 is 2-5°C / min.

5. The method according to claim 1, It is characterized in that The pH of the reaction system is 3-11.

6. The method according to claim 1, It is characterized in that The usage amount of the iron-based microwave catalytic material is 0.5-2 g / L.

7. The method according to claim 1, It is characterized in that The microwave power in the microwave field is 240-800W.

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