Wet oxidation catalyst, its preparation method and application in the treatment of pyraclostrobin production wastewater

Abstract

The present invention discloses a wet oxidation catalyst, a preparation method thereof, and an application thereof in the treatment of pyraclostrobin production wastewater. The wet oxidation catalyst comprises a rice straw biochar carrier and active metals and / or their alloys loaded on the surface and pores thereof, and the active metals are Cu, Fe, and Cr. The preparation method includes adding rice straw biochar and active metal salts into deionized water, impregnating and stirring, ultrasonicating, and drying, then mixing the obtained dried sample with a nitrogen source, and performing staged calcination under an inert gas condition, and performing acid immersion treatment and drying on the obtained calcined sample to obtain the wet oxidation catalyst. The catalyst has simple and easily available raw materials, is easy to separate and recover from wastewater, can treat high-concentration pyraclostrobin production wastewater, has high COD and TOC removal rates, and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic material preparation, and particularly relates to a wet oxidation catalyst, a preparation method thereof, and an application thereof in the treatment of pyraclostrobin production wastewater. Background Art

[0002] Pyraclostrobin has the advantages of high efficiency, low toxicity, environmental friendliness, etc., and is widely used in the prevention and control of crop diseases such as cucumber powdery mildew, downy mildew, and banana scab, and has a broad market prospect. The synthetic wastewater of pyraclostrobin mainly contains organic characteristic pollutants such as toluene, methanol, tetrahydrofuran, p-chlorophenylhydrazine and its derivatives, p-chloroaniline, n-hexane, methyl acrylate, etc., with a COD exceeding 40,000 mg / L, and has the characteristics of complex composition, high toxicity, high COD, and high salt content, belonging to high-concentration and difficult-to-degrade organic chemical wastewater. Therefore, researching and exploring an efficient pretreatment technology for pyraclostrobin production wastewater has become a current difficulty.

[0003] Catalytic wet oxidation technology is an advanced oxidation technology for efficiently degrading organic pollutants in high-concentration organic wastewater, and it has good COD removal effects on high-concentration organic wastewater generated in industries such as petrochemical, dye, pesticide, printing and dyeing, and leather. In this process, the presence of a catalyst can effectively reduce the harsh conditions of the reaction, make the catalytic wet oxidation process more safe, environmentally friendly, and have stronger operability. Therefore, the research and development of catalysts is of great significance for catalytic wet oxidation. However, most catalytic materials have the disadvantages of difficult development, high cost, and difficult preparation, and cannot fully meet the requirements of wastewater treatment. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a wet oxidation catalyst that can treat high-concentration organic wastewater, has high COD and TOC removal rates for wastewater, is simple to prepare, has strong operability, and has strong application value, a preparation method thereof, and an application thereof in the treatment of pyraclostrobin production wastewater.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions.

[0006] A wet oxidation catalyst, wherein the wet oxidation catalyst includes a rice straw biochar carrier, and the surface and pores of the rice straw biochar carrier are loaded with active metals and / or their alloys, and the active metals are Cu, Fe, and Cr.

[0007] As a general technical concept, the present invention also provides a preparation method of a wet oxidation catalyst, including the following steps:

[0008] (1) Immerse rice straw biochar and active metal salts in deionized water, stir, and then perform ultrasonic treatment. The active metal salts include metal Cu salts, metal Fe salts, and metal Cr salts. After drying, a dried sample is obtained;

[0009] (2) Mix the obtained dried sample with a nitrogen source and perform staged calcination under non-reactive gas conditions. First, perform one-stage calcination at 400°C to 500°C, and then perform two-stage calcination at 600°C to 800°C to obtain a calcined sample; wherein, the non-reactive gas is at least one of nitrogen and inert gas;

[0010] (3) Perform acid soaking treatment on the obtained calcined sample, and after drying, a wet oxidation catalyst is obtained.

[0011] For the above method for preparing a wet oxidation catalyst, preferably, in step (1), the metal Cu salt is CuCl2, the metal Fe salt is FeCl3, the metal Cr salt is CrCl3, and the mass ratio of the rice straw biochar, metal Cu salt, metal Fe salt, and metal Cr salt is 4 to 6:0.5 to 2:0.5 to 1:0.2 to 0.5. The mass ratio of the rice straw biochar to the volume of water is 0.5 g to 4.0 g:25 mL to 100 mL.

[0012] For the above method for preparing a wet oxidation catalyst, preferably, in step (1), the ultrasonic treatment time is 20 min to 30 min, the drying is vacuum drying, and the conditions for vacuum drying are: vacuum degree 0.05 MPa to 0.1 MPa, vacuum drying temperature 50°C to 100°C, and vacuum drying time 12 h to 24 h.

[0013] For the above method for preparing a wet oxidation catalyst, preferably, in step (1), the preparation process of the rice straw biochar is: uniformly mix rice straw powder and solid base, and under non-reactive gas conditions, calcine at 500°C to 600°C for 4 h to 5 h to obtain rice straw biochar, wherein the mass ratio of the rice straw powder to the solid base is 1 to 1.5:0.5 to 0.7, and the non-reactive gas is at least one of nitrogen and inert gas.

[0014] For the above method for preparing a wet oxidation catalyst, preferably, in step (2), the nitrogen source is one of urea and dicyandiamide powder; the one-stage calcination time is 2 h to 4 h, and the two-stage calcination time is 2 h to 3 h.

[0015] In the above method for preparing a wet oxidation catalyst, preferably, in step (3), in the acid soaking treatment, the acid includes one of hydrochloric acid and sulfuric acid, the concentration of the acid is 2.5 mol / L to 4 mol / L, the temperature of the acid soaking treatment is room temperature, and the time of the acid soaking treatment is 180 min to 360 min.

[0016] As a general technical concept, the present invention also provides an application of the above wet oxidation catalyst or a wet oxidation catalyst prepared by the above preparation method in the treatment of pyraclostrobin production wastewater.

[0017] In the above application, preferably, the application includes the following steps: mixing pyraclostrobin production wastewater with a wet oxidation catalyst, and performing a catalytic wet oxidation reaction under the conditions of a reaction temperature of 200 °C to 270 °C and a reaction pressure of 2.5 MPa to 7.5 MPa to decompose the organic matter in the wastewater and achieve the treatment of the wastewater.

[0018] In the above application, preferably, the reaction oxygen charge is 1.5 times to 3 times the theoretical oxygen demand, the reaction time is 1.0 h to 3.0 h, and the dosage of the wet oxidation catalyst is 0.5 g / L wastewater to 2.0 g / L wastewater.

[0019] In the above application, preferably, the basic characteristics of the pyraclostrobin production wastewater are: pH value 3 to 5, COD 45000 mg / L to 60000 mg / L, TN 850 mg / L to 950 mg / L, TOC 60773 mg / L to 61335 mg / L, and the biodegradability index B / C of the wastewater is 0.15 to 0.17.

[0020] In the present invention, the pyraclostrobin production wastewater is contacted with the catalyst, and under high temperature and high pressure conditions, the decomposition and reaction of the organic matter are accelerated, so that the organic matter is decomposed into small molecule substances such as CO2 and N2, thereby achieving the purpose of removing the organic matter and improving the biodegradability.

[0021] In the present invention, the pyraclostrobin production wastewater is the mixed wastewater collected from each section in the industrial production process of synthesizing pyraclostrobin.

[0022] The carrier material used in the catalyst preparation of the present invention is rice straw. After washing with water to remove the adhesion substances on the straw surface, it is naturally air-dried, placed in a muffle furnace and dried at 105 °C for 6 - 12 h until the material is of constant weight, then crushed, soaked in distilled water for 12 - 24 h to remove soluble substances and suspended solids, then placed in a constant temperature oven at 70 °C for drying, put into a dry plastic sealed bag for sealing, and placed in a desiccator for storage as the raw material for preparing biochar, that is, rice straw powder.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] (1) The wet oxidation catalyst of the present invention has excellent catalytic activity and can efficiently treat high-concentration organic wastewater. Under suitable conditions, the COD removal rate of the pyraclostrobin production wastewater can reach more than 90%, and the TOC removal rate can reach more than 80%.

[0025] (2) The wet oxidation catalyst of the present invention has the advantages of low cost, excellent dispersion, stability and catalytic performance. This catalyst can resourcefully utilize waste rice straw, reduce the pollution caused by agricultural and sideline product waste, and the density of the catalyst material is relatively small (such as 331 kg / m 3 ). After the reaction is completed and statically treated, the catalyst material can naturally float on the surface of the wastewater, making solid-liquid separation easy.

[0026] (3) The wet oxidation catalyst of the present invention can be applied to the catalytic wet oxidation treatment of high-concentration pyraclostrobin production wastewater. By adding the catalyst, the refractory pollutants in the pyraclostrobin production wastewater can be adsorbed on the surface of the catalyst, increasing the contact area between the active metal or its alloy and the organic pollutants in the wastewater, promoting the oxidation and decomposition of the organic pollutants in the wastewater into small molecular compounds, improving the wet oxidation effect, providing an important guarantee for the subsequent oxidation catalytic effect and efficiency, and having important significance for improving the pretreatment effect of pyraclostrobin production wastewater, reducing production costs and protecting the environment. It can be seen that the catalytic material of the present invention has excellent catalytic effect in the treatment of high-concentration pyraclostrobin production wastewater and is worthy of popularization and application. Description of the Drawings

[0027] Figure 1 It is the scanning electron micrograph of the rice straw biochar in Example 1 of the present invention.

[0028] Figure 2 It is the scanning electron micrograph of the wet oxidation catalyst in Example 1 of the present invention.

[0029] Figure 3 It is the external view of the wet oxidation catalyst in Example 1 of the present invention. Detailed Embodiments

[0030] The present invention will be further described below in conjunction with the drawings in the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0031] The water quality of the pyraclostrobin production wastewater, which is the pretreatment object in the following embodiments, is as follows: the pH value is about 3 - 5, the COD is 45000 - 60000 mg / L, the TN is 850 - 950 mg / L, the TOC concentration is 60773 - 61335 mg / L, and the biodegradability index B / C of the wastewater is 0.15 - 0.17.

[0032] Weigh 20 g of rice straw powder into a sealed crucible, mix it evenly with 10 g of potassium hydroxide, place it in a tubular furnace, heat it to 500 - 600 °C, and carbonize the biomass straw for 4 - 5 h under the condition of an inert atmosphere. Slowly lower the temperature to 50 - 100 °C, take it out, and cool it to room temperature under drying conditions to obtain rice straw biochar, the morphology of which is as Figure 1 shown.

[0033] Example 1

[0034] A preparation method of a wet oxidation catalyst of the present invention includes the following steps:

[0035] (1) Weigh 4 g of rice straw biochar, 0.5 g of CuCl2, 0.5 g of FeCl3, and 0.2 g of CrCl3, add 50 mL of deionized water for impregnation, stir evenly, then ultrasonicate for 30 min, and dry at a vacuum degree of 0.07 MPa and 50 °C for 24 h. After drying, a dried sample is obtained.

[0036] (2) Mix the dried sample with 6 g of urea, and calcine it at 400 °C for 3 h under nitrogen conditions to reduce Cu 2+ , Fe 3+ and Cr 3+ to obtain elemental Cu, Fe, and Cr; further increase the temperature and calcine at 800 °C for 2 h to obtain a calcined sample.

[0037] (3) Immerse the prepared calcined sample in a 3 mol / L sulfuric acid solution at room temperature for 240 min to remove the surface Cu, Fe, and Cr. After drying, a wet oxidation catalyst is obtained, and the material density is 331 kg / m 3 , and the appearance is as Figure 3 shown.

[0038] As Figure 2 shown, the wet oxidation catalyst prepared in this example includes a modified straw biochar carrier. The carrier has a rich pore structure with a pore size range of 10 - 50 nm. A large amount of active metals or their alloys are adsorbed inside and outside the carrier, and the active metals are Cu, Fe, and Cr.

[0039] An application of the wet oxidation catalyst of this example in the treatment of pyraclostrobin production wastewater includes the following steps:

[0040] Add 500 mL of pyraclostrobin production wastewater to a 1.0 L permanent magnet rotary stirring high-pressure reactor, and add the wet oxidation catalyst prepared in this example. The dosage of the wet oxidation catalyst is 0.5 g / L to 2.0 g / L of wastewater. Seal it and carry out the catalytic wet oxidation reaction at 240°C - 270°C and a pressure of 3.0 - 7.5 MPa. During the reaction process, continuously stir and cool with circulating condensed water. After the reaction, cool with circulating condensed water. Take the solution after the reaction to measure the chemical oxygen demand (COD) and total organic carbon (TOC), and compare the effects with the wet oxidation reaction without adding a catalyst. The results are shown in Table 1.

[0041] Table 1 Treatment effect of catalytic wet oxidation on pyraclostrobin production wastewater under different reaction conditions

[0042]

[0043]

[0044] It can be seen from Table 1 that compared with the treatment effect of catalytic wet oxidation without adding a catalyst, the catalytic wet oxidation system with added catalyst can greatly improve the treatment effect of pyraclostrobin production wastewater, and the removal rates of its COD and TOC are significantly improved. For example, when the reaction temperature is 240°C, the catalyst dosage is 1.0 g / L, and the reaction time is 2 h, the removal rates of COD and TOC of the catalytic wet oxidation system for organic wastewater are 71.8% and 66.7% respectively, which are more than 17% and 15% higher than the removal rates of COD and TOC without adding a catalyst. When the catalyst dosage increases, the treatment effect of catalytic wet oxidation on pollutants is further improved. For example, when the catalyst dosage is 1.5 g / L, the removal effect of catalytic wet oxidation on pollutants is significantly higher than that when the catalyst is 1.0 g / L. In addition, the reaction temperature can further improve the removal effect of organic pollutants. When the reaction temperature is 270°C, the catalyst dosage is 1.5 g / L, and the reaction time is 2.5 h, the removal rates of COD and TOC by catalytic wet oxidation are as high as 90.1% and 88.2% respectively.

[0045] Example 2

[0046] A preparation method of the wet oxidation catalyst of the present invention includes the following steps:

[0047] (1) Weigh 4.5 g of rice straw biochar, 1.0 g of CuCl2, 0.5 g of FeCl3, and 0.2 g of CrCl3, add 50 mL of deionized water for impregnation. After stirring evenly, ultrasonicate for 30 min, and dry at a vacuum of 0.07 MPa and 50°C for 24 h. After drying, obtain a dried sample.

[0048] (2) Mix the dried sample with 6 g of urea and calcine it at 400 °C for 3 h under nitrogen conditions to reduce Cu 2+ , Fe 3+ and Cr 3+ , obtaining elemental Cu, Fe, and Cr; further increase the temperature and calcine it at 800 °C for 2 h to obtain a calcined sample.

[0049] (3) Acid soak the prepared calcined sample with a 2.5 mol / L sulfuric acid solution at room temperature for 240 min to remove the surface Cu, Fe, and Cr. After drying, a wet oxidation catalyst is obtained, and the material density is 329 kg / m 3 .

[0050] An application of the wet oxidation catalyst of this embodiment in the treatment of pyraclostrobin production wastewater includes the following steps:

[0051] Add 500 mL of pyraclostrobin production wastewater to a 1.0 L permanent magnet rotating stirring high-pressure reactor, and add the wet oxidation catalyst prepared in this embodiment. The dosage of the wet oxidation catalyst is 0.5 g / L to 2.0 g / L of wastewater. Seal it and carry out a catalytic wet oxidation reaction at 220 °C - 240 °C and a pressure of 2.5 - 3.5 MPa. During the reaction process, continuously stir and cool it with circulating condensed water. After the reaction, cool it with circulating condensed water, take the reaction solution to measure the chemical oxygen demand (COD) and total organic carbon (TOC), and compare the effects with the wet oxidation reaction without adding a catalyst. The results are shown in Table 2.

[0052] Table 2 Treatment effect of catalytic wet oxidation on organic wastewater under different reaction conditions

[0053]

[0054] As can be seen from Table 2, the catalytic wet oxidation system with a catalyst can significantly improve the treatment effect of pyraclostrobin production wastewater compared with the wet oxidation system without a catalyst. When the reaction temperature is 220 °C, the catalyst dosage is 1.0 g / L, and the reaction time is 2 h, the removal rates of COD and TOC of the organic wastewater by the catalytic wet oxidation system are 55.1% and 49.7% respectively, which are more than 15% and 13% higher than the COD and TOC removal rates without adding a catalyst. Under the condition that other conditions are the same, when the wet oxidation temperature rises to 240 °C, the removal rates of COD and TOC increase by 19% and 23% respectively compared with those at 220 °C.

[0055] Example 3

[0056] A preparation method of the wet oxidation catalyst of the present invention includes the following steps:

[0057] (1) Weigh 4.5 g of rice straw biochar, 1.0 g of CuCl2, 0.5 g of FeCl3, and 0.2 g of CrCl3, add 50 mL of deionized water for impregnation. After stirring evenly, ultrasonic for 30 min, and dry at a vacuum degree of 0.07 MPa and 50 °C for 24 h. After drying, a dried sample is obtained.

[0058] (2) Mix the dried sample with 6 g of urea, and calcine at 400 °C for 3 h under nitrogen conditions to reduce Cu 2+ , Fe 3+ and Cr 3+ to obtain elemental Cu, Fe, and Cr; further increase the temperature and calcine at 800 °C for 2 h to obtain a calcined sample.

[0059] (3) Acid soak the prepared calcined sample with a 2.5 mol / L sulfuric acid solution at room temperature for 240 min to remove the surface Cu, Fe, and Cr. After drying, a wet oxidation catalyst is obtained, and the material density is 333 kg / m 3 ,.

[0060] An application of the wet oxidation catalyst of this example in the treatment of pyraclostrobin production wastewater includes the following steps:

[0061] Add 500 mL of pyraclostrobin production wastewater to a 1.0 L permanent magnet rotating stirring high-pressure reactor, and add the wet oxidation catalyst prepared in this example. The dosage of the wet oxidation catalyst is 0.5 g / L to 2.0 g / L of wastewater. Seal it and carry out a catalytic wet oxidation reaction at 235 °C - 265 °C and a pressure of 3.0 - 5.5 MPa. During the reaction process, continuously stir and cool with circulating condensed water. After the reaction, cool with circulating condensed water, take the solution after the reaction to measure the chemical oxygen demand (COD) and total organic carbon (TOC), and compare the effects with the wet oxidation reaction without adding a catalyst. The results are shown in Table 3.

[0062] Table 3 Treatment effects of catalytic wet oxidation on organic wastewater under different reaction conditions

[0063]

[0064] As can be seen from Table 3, the catalytic wet oxidation system with the addition of a catalyst can significantly improve the treatment effect of pyraclostrobin wastewater compared to the wet oxidation system without a catalyst, which is manifested as a substantial increase in the removal rates of COD and TOC. When the reaction temperature is 235 °C, the catalyst dosage is 1.0 g / L, and the reaction time is 2 h, the removal rates of COD and TOC of the catalytic wet oxidation system for organic wastewater are 69.4% and 65.1% respectively, which are more than 18% and 17% higher than the removal rates of COD and TOC without the addition of a catalyst.

[0065] As described above, it is only the preferred embodiment of the present invention, and there is no any form of limitation to the present invention. Although the present invention has been disclosed as above with the preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of the protection of the technical solution of the present invention.

Claims

1. Application of a wet oxidation catalyst in the treatment of pyraclostrobin production wastewater, characterized in that, It includes the following steps: Mix the pyraclostrobin production wastewater with the wet oxidation catalyst, and carry out catalytic wet oxidation reaction under the conditions of reaction temperature of 200°C to 270°C and reaction pressure of 2.5 MPa to 7.5 MPa to decompose the organic matter in the wastewater and achieve the treatment of the wastewater; The wet oxidation catalyst includes a rice straw biochar carrier, and the surface and pores of the rice straw biochar carrier are loaded with active metals and / or their alloys, and the active metals are Cu, Fe, and Cr; The preparation method of the wet oxidation catalyst includes the following steps: (1) Immerse and stir rice straw biochar and active metal salts in deionized water, and then perform ultrasonic treatment. The active metal salts include metal Cu salts, metal Fe salts, and metal Cr salts. After drying, a dried sample is obtained; the mass ratio of the rice straw biochar, metal Cu salt, metal Fe salt, and metal Cr salt is 4 to 6:0.5 to 2:0.5 to 1:0.2 to 0.5; (2) Mix the obtained dried sample with a nitrogen source, and perform staged calcination under non-active gas conditions. First, perform one-stage calcination at 400°C to 500°C, and then perform two-stage calcination at 600°C to 800°C to obtain a calcined sample; wherein, the non-active gas is at least one of nitrogen and inert gas; (3) Perform acid soaking treatment on the obtained calcined sample, and after drying, obtain the wet oxidation catalyst; In step (1), the preparation process of the rice straw biochar is as follows: Mix rice straw powder and solid base evenly, and calcine at 500°C to 600°C for 4 h to 5 h under non-active gas conditions to obtain rice straw biochar, wherein the mass ratio of the rice straw powder to the solid base is 1 to 1.5:0.5 to 0.7, and the non-active gas is at least one of nitrogen and inert gas.

2. The application according to claim 1, characterized in that In step (1), the metal Cu salt is CuCl2, the metal Fe salt is FeCl3, the metal Cr salt is CrCl3, and the mass of the rice straw biochar to the volume of water is 0.5 g to 4.0 g:25 mL to 100 mL.

3. The application according to claim 1, wherein In step (1), the ultrasonic treatment time is 20 min to 30 min, the drying is vacuum drying, and the conditions of the vacuum drying are: vacuum degree of 0.05 MPa to 0.1 MPa, vacuum drying temperature of 50°C to 100°C, and vacuum drying time of 12 h to 24 h.

4. The application according to any one of claims 1 to 3, characterized in that, In step (2), the nitrogen source is one of urea and dicyandiamide powder; the one-stage calcination time is 2 h to 4 h, and the two-stage calcination time is 2 h to 3 h.

5. The application according to any one of claims 1 to 3, characterized in that, In step (3), in the acid soaking treatment, the acid includes one of hydrochloric acid and sulfuric acid, the concentration of the acid is 2.5 mol / L to 4 mol / L, the temperature of the acid soaking treatment is room temperature, and the time of the acid soaking treatment is 180 min to 360 min.

6. The application according to any one of claims 1 to 3, characterized in that The reaction oxygen charge is 1.5 times to 3 times the theoretical oxygen demand, the reaction time is 1.0 h to 3.0 h, and the dosage of the wet oxidation catalyst is 0.5 g / L wastewater to 2.0 g / L wastewater; And / or, the basic characteristics of the pyraclostrobin production wastewater are as follows: pH value is 3 - 5, COD is 45000 mg / L - 60000 mg / L, TN is 850 mg / L - 950 mg / L, TOC is 60773 mg / L - 61335 mg / L, and the biodegradability index B / C of the wastewater is 0.15 - 0.17.

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