Device for photocatalytic degradation of polychlorinated naphthalene in soil and degradation method

Abstract

The invention belongs to the technical field of remediation of contaminated soil, and particularly relates to a device for degrading polychlorinated naphthalene in soil through photocatalysis and a degradation method. The device mainly comprises a base, a metal support frame, a reaction glass tank body, a rotating cutter matched with the tank body, a driving motor, a transmission gear, a supporting gear and an adjusting nut, and all the units are mutually supported and run in a transmission mode. The light source matched with the device can be an LED lamp or natural sunlight. According to the photocatalytic device, the S-doped g-C3N4 / MIL-101 (Fe) photocatalyst is adopted, so that the photocatalytic device is high in photocatalytic capacity, stable and non-toxic in a soil environment and capable of effectively improving the degradation efficiency of octachloronaphthalene. The treatment method for removing the soil polluted by the polychlorinated naphthalene is simple, low in device cost, capable of utilizing solar energy, high in efficiency and free of secondary pollution, and is a method friendly to the soil environment.

Description

Technical Field

[0001] The invention belongs to the technical field of contaminated soil restoration, and in particular relates to a device and a degradation method for photocatalytically degrading polychlorinated naphthalenes in soil. Background Art

[0002] Polychlorinated naphthalenes (PCNs) are a class of persistent organic pollutants widely present in the natural environment. They are a series of compounds formed by different links of 1 to 8 chlorine atoms on naphthalene, with a total of 75 PCNs homologues. PCNs have high chemical and thermal stability, good insulation and low flammability, and are widely used in various industrial products, such as temperature regulating fluids, cable insulation, wood preservatives, engine oil additives, etc. With the widespread application of PCNs, PCNs have entered the natural environment. Since PCNs have similar structures and properties to dioxins and polychlorinated biphenyls, they can cause "dioxin" toxic effects, including embryotoxicity, hepatotoxicity, immunotoxicity, skin lesions, teratogenicity and carcinogenicity, causing harm to organisms and the environment. Octachloronaphthalene (CN-75), also known as octachloronaphthalene, has a higher degree of chlorination, so its migration and transformation in the environment is more stable and its degradation time is longer. Therefore, octachloronaphthalene can migrate in the environment for a longer time, especially in the soil environment, where it is more stable.

[0003] At present, the main methods for PCNs degradation include mechanochemistry, biodegradation, high-temperature melting and ultrasonic degradation. Although the biodegradation treatment of PCNs has a good treatment effect, it has disadvantages such as a cyclic process, high environmental requirements, and difficult to control conditions. As for other physical and chemical methods, there are disadvantages such as high cost and incomplete treatment that can easily cause secondary pollution. Photodegradation is one of the important ways for organic matter to be transformed and generated in the environment. Since most of the sunlight reaching the earth's surface is ultraviolet light and visible light, the photodegradation or transformation of organic matter under ultraviolet light and visible light has always attracted much attention.

[0004] Graphitic carbon nitride (g-C3N4) is a common non-metallic photocatalyst with the advantages of wide band gap (about 2.7eV), low cost, wide source of raw materials, and stable physical and chemical properties. However, the disadvantages of g-C3N4 are also obvious. The absorption efficiency of visible light is weak, the recombination of photogenerated electrons and holes is serious, and the photocatalytic performance is weak. These disadvantages seriously limit its application in environmental remediation. Therefore, it is a feasible way to modify g-C3N4 with metals or elements to increase the photocatalytic ability of g-C3N4. Metal-organic framework materials (MOFs) are new porous coordination polymers that have attracted much attention in recent years. MOFs can use a variety of metal ions as connectors, and can also choose a variety of organic ligands as connectors. Fe-based MOFs have the advantages of low cost, environmental protection, high specific surface area, semiconductor and photosensitivity, and have been applied in adsorption, sensing, catalysis and batteries. Summary of the invention

[0005] The object of the present invention is to provide a device and method for photocatalytically degrading polychlorinated naphthalenes in soil with low cost and simple operation.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A device for photocatalytically degrading polychlorinated naphthalenes in soil comprises a base, a metal support frame, a reaction glass tank body and a driving motor, and is characterized in that the base carries the metal support frame; the four corners of the metal support frame are respectively provided with adjusting nuts I, II, III and IV; four gears, namely, a transmission gear I, III, a supporting gear I and II, are installed on the metal support frame, and the four gears support a detachable reaction glass tank body; the driving motor is loaded on the side of the tail of the metal support frame, and the driving motor is connected to the transmission gear I; and a tank body matching rotary cutter is arranged inside the reaction glass tank body.

[0008] Furthermore, in the above-mentioned device for photocatalytic degradation of polychlorinated naphthalenes in soil, the adjusting nut III and the adjusting nut IV are located at the tail end of the metal support frame, and the adjusting nut I and the adjusting nut II are located near the mouth of the reaction glass tank body, and the adjusting nut I and the adjusting nut II can slide on the reserved track of the metal support frame.

[0009] Furthermore, in the above-mentioned device for photocatalytic degradation of polychlorinated naphthalenes in soil, the support gear I and the support gear II are located near the mouth of the reaction glass tank body; the transmission gear II is installed at the tail of the reaction glass tank body, and the transmission gear II is respectively connected to the transmission gear I and the transmission gear III in a meshing manner.

[0010] Furthermore, in the above-mentioned device for photocatalytic degradation of polychlorinated naphthalenes in soil, the rotating blades supporting the tank body include three rotating blades made of polytetrafluoro material, and the three rotating blades are adhered to the inner wall of the tank body of the reaction glass tank body and are distributed at intervals.

[0011] Furthermore, in the above-mentioned device for photocatalytic degradation of polychlorinated naphthalenes in soil, the transmission gear III is detachable.

[0012] The method for photocatalytically degrading polychlorinated naphthalenes in soil using the device for photocatalytically degrading polychlorinated naphthalenes in soil described in any one of the above items is as follows: polychlorinated naphthalene contaminated soil and S-doped g-C3N4 / MIL-101 (Fe) photocatalyst are placed in a reaction glass tank body of the device for photocatalytically degrading polychlorinated naphthalenes in soil, a driving motor is started to rotate the reaction glass tank body, and stirring is performed in the dark until fully mixed; subsequently, under the irradiation of a visible light source, the angle of the reaction glass tank body is adjusted by adjusting the adjusting nut I and the adjusting nut II, so that the mixed soil sample in the reaction glass tank body is fully irradiated by the light source, and the rotation speed of the reaction glass tank body is controlled by the driving motor, and the rotating blade of the tank body continuously flips the mixed soil sample in the tank when the reaction glass tank body rotates, so as to catalytically degrade polychlorinated naphthalenes in soil.

[0013] Furthermore, in the above-mentioned method for photocatalytic degradation of polychlorinated naphthalenes in soil, the mass ratio of S-doped g-C3N4 / MIL-101(Fe) photocatalyst to polychlorinated naphthalenes contaminated soil is 5:95; and the concentration of polychlorinated naphthalenes contaminated soil is 5-10 mg / kg.

[0014] Furthermore, in the above-mentioned method for photocatalytic degradation of polychlorinated naphthalenes in soil, the visible light source is an external LED light source or natural sunlight.

[0015] Preferably, the wavelength of the external LED light source is λ≥420nm, the light source is 50cm away from the soil, and the light intensity is 12.5W / m 2 .

[0016] Furthermore, in the above-mentioned method for photocatalytic degradation of polychlorinated naphthalenes in soil, the preparation method of the S-doped g-C3N4 / MIL-101 (Fe) photocatalyst comprises the following steps:

[0017] 1) Melamine, urea and ethylamine thiourea in a mass ratio of 3:2:1.5 were fully mixed by ball milling, and then the mixture was placed in a ceramic crucible with a lid, stabilized at 550°C for 2 hours, and cooled to obtain S-doped g-C3N4;

[0018] 2) FeCl3.6H2O was stirred in DMF, and then S-doped g-C3N4 and H2BDC were added in sequence. The molar ratio of S-doped g-C3N4, FeCl3.6H2O and H2BDC was 2:1:2. After stirring, the above mixture was transferred into a hydrothermal reactor and reacted at 150°C for 24h to obtain S-doped g-C3N4 / MIL-101(Fe) photocatalyst.

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

[0020] 1. The device and method of the present invention have high efficiency in removing octachloronaphthalene. Polychlorinated naphthalene, as a persistent organic pollutant, can migrate in the environment for hundreds of days or even several years before being completely mineralized. The degradation cycle of octachloronaphthalene by this method can be controlled within 20 days.

[0021] 2. The present invention uses S-doped g-C3N4 / MIL-101 (Fe) as a photocatalyst, which is stable in the soil environment and has no soil toxicity and biotoxicity, and no secondary pollution will be generated during the treatment process.

[0022] 3. The device of the present invention can be applied to a variety of environments, not only for small-scale indoor simulation research, but also for photocatalytic degradation research under natural environment conditions.

[0023] 4. The device of the present invention is easy to operate, and the stirring speed can be adjusted by controlling the rotation speed of the tank body. At the same time, the angle of the tank body can also be controlled to control the incidence and irradiation of light. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the main structure of the device of the present invention.

[0025] Figure 2 It is a left-side structural schematic diagram of the device of the present invention.

[0026] Figure 3 It is a schematic diagram of the right side structure of the device of the present invention.

[0027] In the figure: 1. base, 2. metal support frame, 3. reaction glass tank body, 4. tank body supporting rotary cutter, 5. driving motor, 6. transmission gear Ⅰ, 7. transmission gear Ⅱ, 8. transmission gear Ⅲ, 9. support gear Ⅰ, 10. support gear Ⅱ, 11. adjusting nut Ⅰ, 12. adjusting nut Ⅱ, 13. adjusting nut Ⅲ, 14. adjusting nut Ⅳ. DETAILED DESCRIPTION

[0028] The following is further explanation in conjunction with specific implementation measures.

[0029] Example 1 Device for photocatalytic degradation of polychlorinated naphthalenes in soil

[0030] A device for photocatalytically degrading polychlorinated naphthalenes in soil comprises a base 1, a metal support frame 2, a reaction glass tank body 3, a rotating cutter 4 matching the tank body, a driving motor 5, a transmission gear I6, a transmission gear II7, a transmission gear III8, a supporting gear I9, a supporting gear II10, an adjusting nut I11, an adjusting nut II12, an adjusting nut III13, and an adjusting nut IV14.

[0031] The base 1 of the device carries a metal support frame 2, and the four corners of the metal support frame 2 are respectively provided with adjusting nuts I11, II12, III13 and IV14, and the adjusting nuts III13 and IV14 are located at the tail end of the metal support frame 2, and the adjusting nuts I11 and II12 are located near the mouth of the reaction glass tank body 3. The angle between the metal support frame 2 and the base 1 is adjusted by sliding the adjusting nuts I11 and II12 on the reserved track of the metal support frame 2, thereby adjusting the angle of the reaction glass tank body 3, so that the mouth of the reaction glass tank body 3 can be tilted and raised by 0-35°.

[0032] Four gears, namely, transmission gear I6, transmission gear III8, support gear I9 and support gear II10, are installed on the metal support frame 2, wherein the transmission gear III8 is a detachable component; the above four gears support the detachable reaction glass tank body 3, and the reaction glass tank body 3 can be disassembled after the transmission gear III8 is disassembled and separated from the metal support frame 2; the support gear I9 and the support gear II10 are located near the mouth of the reaction glass tank body 3 to support the mouth of the reaction glass tank body 3; a transmission gear II7 is installed at the tail of the reaction glass tank body 3, and the transmission gear II7 is respectively connected to the transmission gear I6 and the transmission gear III8 in a meshing manner; a drive motor 5 is loaded on the side of the tail of the metal support frame 2, and the drive motor 5 is connected to the transmission gear I6. The driving motor 5 provides power for the entire device. When the driving motor 5 is turned on, the driving motor 5 drives the transmission gear I6, the transmission gear I6 drives the transmission gear II7, the transmission gear II7 drives the operation of the reaction glass tank body 3 and the transmission gear III8, and at the same time, the support gear I9 and the support gear II10 support the tank body to ensure the smooth rotation of the reaction glass tank body 3. At the same time, the driving motor 5 is also used to control the rotation speed of the reaction glass tank body 3.

[0033] The reaction glass tank body 3 is provided with a tank body supporting rotary cutter 4, which includes three rotary cutters made of polytetrafluoroethylene material, which are adhered to the inner wall of the tank body and distributed at intervals. When the reaction glass tank body 3 rotates, the tank body supporting rotary cutter 4 will continuously turn the soil sample in the tank to achieve the purpose of uniform illumination.

[0034] Example 2 Preparation method of S-doped g-C3N4 / MIL-101 (Fe) photocatalyst

[0035] 1) Melamine, urea and ethylamine thiourea in a mass ratio of 3:2:1.5 were fully mixed by ball milling, and then the mixture was placed in a ceramic crucible with a lid, stabilized at 550°C for 2 hours, and cooled to obtain S-doped g-C3N4.

[0036] 2) FeCl3.6H2O was weighed and stirred in DMF, and then S-doped g-C3N4 was added, followed by H2BDC, S-doped g-C3N4:FeCl3.6H2O:H2BDC=2:1:2 (molar ratio), and the mixture was stirred. The mixture was transferred into a hydrothermal reactor and reacted at 150°C for 24h to obtain S-doped g-C3N4 / MIL-101(Fe).

[0037] Example 3 Photocatalytic degradation method for octachloronaphthalene in soil

[0038] Octachloronaphthalene was selected as the representative of PCNs homologues.

[0039] 1) Take 1.0 kg of soil, dry it naturally in the shade, grind it, sterilize it by intermittent high pressure for 3 times, and air dry it for later use.

[0040] 2) Preparation of soil contaminated with octachloronaphthalene: Add the sterilized soil sample prepared in step 1) to a n-hexane solution dissolved in octachloronaphthalene (5 mg octachloronaphthalene per 1000 mL n-hexane) at a ratio of mass: volume = 1 g: 1 mL. Then place the soil sample in a ventilated place for 12 hours to obtain soil contaminated with octachloronaphthalene at a concentration of 5 mg / kg.

[0041] 3) Weigh 190 g of octachloronaphthalene contaminated soil and mix them in a mass ratio of 5:95 between S-doped g-C3N4 / MIL-101(Fe) and octachloronaphthalene contaminated soil, i.e., 10 g of S-doped g-C3N4 / MIL-101(Fe) mixed with 190 g of soil, i.e., 200 g of mixed soil sample.

[0042] 4) Place 200 g of the mixed soil sample in the reaction glass tank of the device in Example 1, start the drive motor to rotate the reaction glass tank, and stir until fully mixed in the dark. Then, under the irradiation of LED tissue culture light source (the wavelength of the LED light λ≥420nm, the mixed soil sample is 50cm away from the light source, and the light intensity is 12.5W / m 2 , temperature is 25±0.1℃, humidity is 70±0.1%), the angle of the reaction glass tank is adjusted by adjusting nut Ⅰ and adjusting nut Ⅱ, so that the mixed soil sample in the reaction glass tank can be fully irradiated by the light source, and the rotation speed of the reaction glass tank is controlled by the driving motor. The rotating knife of the tank body continuously turns over the mixed soil sample in the tank when the reaction glass tank body rotates, and the light is exposed for 20 days.

[0043] 5) Take 5 g of mixed soil sample every two days and put it into a 15 mL centrifuge tube. Use a mixed solution of n-hexane containing 5% acetone, 5 mL at a time, water bath ultrasonic extraction for 15 min, centrifuge at 3000 r / min for 10 min, extract three times, combine, and the total solution volume is 15 mL. Determine the octachloronaphthalene content in the combined mixed solution.

[0044] Treatment effect: After 2 days and 20 days of irradiation, the degradation rates of octachloronaphthalene in the soil reached 15.57% and 92.54%, respectively.

[0045] Example 4 Photocatalytic degradation method for octachloronaphthalene in soil

[0046] 1) Take 1.0 kg of soil, dry it naturally in the shade, grind it, sterilize it by intermittent high pressure for 3 times, and air dry it for later use.

[0047] 2) Preparation of soil contaminated with octachloronaphthalene: Add the sterilized soil sample prepared in step 1) to a n-hexane solution dissolved in octachloronaphthalene (10 mg of octachloronaphthalene per 1000 mL of n-hexane) at a ratio of mass: volume = 1 g: 1 mL. Then place the soil sample in a ventilated place for 12 hours to obtain soil contaminated with octachloronaphthalene at a concentration of 10 mg / kg.

[0048] 3) Weigh 190 g of octachloronaphthalene contaminated soil and mix them in a mass ratio of 5:95 between S-doped g-C3N4 / MIL-101(Fe) and octachloronaphthalene contaminated soil, i.e., 10 g of S-doped g-C3N4 / MIL-101(Fe) mixed with 190 g of soil, i.e., 200 g of mixed soil sample.

[0049] 4) Place 200g of the mixed soil sample in the reaction glass tank of the device in Example 1, start the drive motor to rotate the reaction glass tank, and stir until fully mixed in the dark. Then, place the mixture under natural sunlight (the intensity of natural sunlight is 150-175W / m 2 , average temperature is 27±0.1℃, average humidity is 65±0.1%), the angle of the reaction glass tank is adjusted by adjusting nut Ⅰ and adjusting nut Ⅱ, so that the mixed soil sample in the reaction glass tank can be fully irradiated by the light source, and the rotation speed of the reaction glass tank is controlled by the driving motor. The rotating knife of the tank body continuously turns over the mixed soil sample in the tank when the reaction glass tank body rotates, and the light is exposed for 20 days.

[0050] 5) Take 5 g of mixed soil sample every two days and put it into a 15 mL centrifuge tube. Use a mixed solution of n-hexane containing 5% acetone, 5 mL at a time, water bath ultrasonic extraction for 15 min, centrifuge at 3000 r / min for 10 min, extract three times, combine, and the total solution volume is 15 mL. Determine the octachloronaphthalene content in the combined mixed solution.

[0051] Treatment effect: After 2 days and 20 days of irradiation, the degradation rates of octachloronaphthalene in the soil reached 16.21% and 96.22%, respectively.

Claims

1. A device for photocatalytically degrading polychlorinated naphthalenes in soil, comprising a base (1), a metal support frame (2), a reaction glass tank (3), and a drive motor (5), characterized in that: The base (1) carries a metal support frame (2); the four corners of the metal support frame (2) are respectively provided with an adjusting nut I (11), an adjusting nut II (12), an adjusting nut III (13) and an adjusting nut IV (14); four gears, namely a transmission gear I (6), a transmission gear III (8), a support gear I (9) and a support gear II (10), are installed on the metal support frame (2), and the four gears support a detachable reaction glass tank body (3); a driving motor (5) is mounted on the side of the rear end of the metal support frame (2), and the driving motor (5) is connected to the transmission gear I (6); and a tank body matching rotary cutter (4) is provided inside the reaction glass tank body (3).

2. The device for photocatalytic degradation of polychlorinated naphthalenes in soil according to claim 1, characterized in that: The adjusting nut III (13) and the adjusting nut IV (14) are located at the rear end of the metal support frame (2), and the adjusting nut I (11) and the adjusting nut II (12) are located near the mouth of the reaction glass tank body (3). The adjusting nut I (11) and the adjusting nut II (12) can slide on the reserved track of the metal support frame (2).

3. The device for photocatalytic degradation of polychlorinated naphthalenes in soil according to claim 1, characterized in that: The supporting gear I (9) and the supporting gear II (10) are located near the mouth of the reaction glass tank body (3); a transmission gear II (7) is installed at the rear of the reaction glass tank body (3), and the transmission gear II (7) is respectively connected to the transmission gear I (6) and the transmission gear III (8) in a meshing manner.

4. The device for photocatalytic degradation of polychlorinated naphthalenes in soil according to claim 1, characterized in that: The tank body supporting rotary cutters (4) include three rotary cutters made of polytetrafluoroethylene material, and the three rotary cutters are adhered to the inner wall of the reaction glass tank body (3) and are distributed at intervals.

5. The device for photocatalytic degradation of polychlorinated naphthalenes in soil according to claim 1, characterized in that: The transmission gear III (8) is detachable.

6. A method for photocatalytically degrading polychlorinated naphthalenes in soil using the device for photocatalytically degrading polychlorinated naphthalenes in soil according to any one of claims 1 to 5, characterized in that: The method is as follows: placing polychlorinated naphthalene contaminated soil and S-doped g-C3N4 / MIL-101 (Fe) photocatalyst in a reaction glass tank (3) of a device for photocatalytically degrading polychlorinated naphthalene in soil, starting a driving motor (5) to rotate the reaction glass tank (3), and stirring in the dark until fully mixed; subsequently, under the irradiation of a visible light source, adjusting the angle of the reaction glass tank (3) by adjusting an adjusting nut I (11) and an adjusting nut II (12) so that the mixed soil sample in the reaction glass tank (3) is fully irradiated by the light source, and at the same time, the rotation speed of the reaction glass tank (3) is controlled by the driving motor (5), and a rotating blade (4) of the tank body continuously turns over the mixed soil sample in the tank when the reaction glass tank (3) rotates, so as to catalytically degrade the polychlorinated naphthalene in the soil.

7. The method for photocatalytic degradation of polychlorinated naphthalenes in soil according to claim 6, characterized in that: The mass ratio of S-doped g-C3N4 / MIL-101(Fe) photocatalyst to PCN-contaminated soil is 5:95; the concentration of PCN-contaminated soil is 5-10 mg / kg.

8. The method for photocatalytic degradation of polychlorinated naphthalenes in soil according to claim 6, characterized in that: The visible light source is an external LED light source or natural sunlight.

9. The method for photocatalytic degradation of polychlorinated naphthalenes in soil according to claim 8, characterized in that: The wavelength of the external LED light source is λ≥420nm, the light source is 50cm away from the soil, and the light intensity is 12.5W / m 2 .

10. The method for photocatalytic degradation of polychlorinated naphthalenes in soil according to claim 6, characterized in that: The preparation method of the S-doped g-C3N4 / MIL-101 (Fe) photocatalyst comprises the following steps: 1) Melamine, urea and ethylamine thiourea in a mass ratio of 3:2:1.5 were fully mixed by ball milling, and then the mixture was placed in a ceramic crucible with a lid, stabilized at 550°C for 2 hours, and cooled to obtain S-doped g-C3N4; 2) FeCl3.6H2O was stirred in DMF, and then S-doped g-C3N4 and H2BDC were added in sequence. The molar ratio of S-doped g-C3N4, FeCl3.6H2O and H2BDC was 2:1:

2. After stirring, the above mixture was transferred into a hydrothermal reactor and reacted at 150°C for 24h to obtain S-doped g-C3N4 / MIL-101(Fe) photocatalyst.

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