A method for degrading perfluorinated compounds in sludge

Abstract

The present invention discloses a method for degrading perfluorinated compounds in sludge, comprising the following steps: adding an indole polymer solution to a sludge extract containing perfluorinated compounds, and performing a degradation reaction on the perfluorinated compounds under light; the structure of the indole polymer is shown below: #imgabs0# Compared with small molecule indole derivatives containing long-chain alkyl groups and positively charged amine groups, the indole polymer provided by the present invention has higher stability, can sustainably and stably generate hydrated electrons and efficiently degrade PFOA; compared with polyindole, it can effectively capture PFCs in polluted water bodies, form self-assembled inclusions with them, thereby improving the degradation effect and reducing the amount of raw materials used.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental treatment, in particular to a method for degrading perfluorinated compounds in sludge. Background Art

[0002] Among various environmental pollutants, perfluorinated compounds (PFCs) are widely used in textiles, printing and dyeing, fire protection and other fields. However, perfluorinated compounds are new types of persistent organic pollutants. The large-scale production and use of perfluorinated compounds have caused increasingly serious water and soil environmental pollution, and have attracted widespread attention from researchers at home and abroad.

[0003] Perfluorooctanoic acid (PFOA) is one of the most representative perfluorinated compounds. Due to their antimicrobial, hydrophobic, and highly stable properties, perfluorinated compounds pose a serious threat to water, soil, and ecosystems. Therefore, PFC degradation technology has become a major challenge in environmental governance.

[0004] Currently, the commonly used methods for degrading PFCs include advanced oxidation processes, electrochemical oxidation, photocatalytic degradation, ultrasonic degradation, thermal cracking, and hydrated electron reduction defluorination. Photoinduced hydrated electron reduction defluorination is the most efficient of the existing PFC degradation technologies due to its simple reaction setup, rapid and thorough degradation, and low energy consumption.

[0005] Among them, the use of indole derivatives to generate hydrated electrons through light is a key research focus for future PFC degradation technologies. However, existing technologies using small-molecule indole derivatives or polyindole suffer from the drawbacks of high raw material usage and poor degradation performance, which to some extent limits the development of PFC degradation technologies. Therefore, developing new technologies based on this foundation for more efficient PFC pollution control is a hot topic and key research topic in this field. Summary of the Invention

[0006] The present invention aims to overcome the defects and shortcomings of the prior art and provide a method for degrading perfluorinated compounds in sludge. The indole polymer used to degrade perfluorinated compounds in the present invention contains a long-chain alkyl group and a positively charged quaternary ammonium salt in its molecular structure, can effectively capture PFCs in polluted water, form self-assembled inclusions with PFOA, continuously and stably generate hydrated electrons, and efficiently degrade PFOA.

[0007] The object of the present invention is to provide a method for degrading perfluorinated compounds in sludge, comprising the following steps:

[0008] Adding an indole polymer solution to a sludge extract containing perfluorinated compounds, and subjecting it to light-induced reaction to degrade the perfluorinated compounds;

[0009] The structure of the indole polymer is shown below:

[0010]

[0011] Wherein, R1, R2, R3 and R4 are independently selected from H or , R5 is selected from a linear alkyl group having 14 to 22 carbon atoms, and R1, R2, R3 and R4 are not H at the same time; the number average molecular weight of the indole polymer is 3000 to 8000 g / mol.

[0012] In some embodiments of the present invention, the structure of the indole polymer is as follows:

[0013] 、 or .

[0014] The number average molecular weight of the indole polymer is 3000-8000 g / mol.

[0015] In some embodiments of the present invention, the mass ratio of the perfluorinated compound to the indole polymer is 1:10-40.

[0016] In some embodiments of the present invention, the pH value of the sludge extract containing perfluorinated compounds is 4.0-7.0.

[0017] In some embodiments of the present invention, the temperature of the light irradiation reaction is 25±2° C., and the time is 4 to 8 hours.

[0018] In some embodiments of the present invention, the light source of the illumination reaction is a low-pressure mercury lamp.

[0019] In some embodiments of the present invention, the content of perfluorinated compounds in the perfluorinated compound-containing sludge extract is 3.02×10 -3 mg / L, and the content of the indole polymer in the indole polymer solution is 0.6-1 mg / L.

[0020] Another object of the present invention is to provide a method for degrading perfluorinated compounds in sludge, wherein the method for preparing the indole polymer comprises the following steps:

[0021] S1. Chlorinating indolecarboxylic acid and reacting with alkylhydroxyethylammonium chloride to obtain an indole derivative;

[0022] S2. The indole derivative is dissolved in acetonitrile to form an acetonitrile solution of the indole derivative, the acetonitrile solution of the indole derivative is added dropwise to an acetonitrile solution of ferric chloride, the reaction is stirred, and purified to obtain an indole polymer;

[0023] In some embodiments of the present invention, the indolecarboxylic acid is selected from at least one of indole-4-carboxylic acid, indole-5-carboxylic acid, indole-6-carboxylic acid, and indole-7-carboxylic acid;

[0024] In some embodiments of the present invention, the alkyl hydroxyethyl ammonium chloride is selected from at least one of tetradecyl dimethyl hydroxyethyl ammonium chloride, octadecyl dimethyl hydroxyethyl ammonium chloride, and behenyl dimethyl hydroxyethyl ammonium chloride.

[0025] In some embodiments of the present invention, in S1, the chlorination reagent is selected from SOCl2.

[0026] In some embodiments of the present invention, in S1, the temperature of the chlorination is 80-100° C., and the time is 15-25 hours.

[0027] In some embodiments of the present invention, in S1, the mass ratio of the indolecarboxylic acid to the alkylhydroxyethylammonium chloride is 1.1-1.5:1.

[0028] In some embodiments of the present invention, in S1, the mass ratio of the indolecarboxylic acid to the chlorination reagent is 1:1.1-1.5.

[0029] In some embodiments of the present invention, in S1, the reaction temperature is 110-130° C., and the reaction time is 10-20 hours.

[0030] In some embodiments of the present invention, in S2, the mass ratio of the indole derivative to ferric chloride is 1:2-4.

[0031] In some embodiments of the present invention, in S2, the stirring reaction is carried out at room temperature for 8 to 16 hours.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) Compared with small molecule indole derivatives containing long-chain alkyl groups and positively charged amine groups, the indole polymers of the present invention are more stable, can continuously and stably generate hydrated electrons and efficiently degrade PFOA.

[0034] (2) Compared with polybenzazole, the indole polymer of the present invention contains long-chain alkyl groups and positively charged quaternary ammonium salts in its molecular structure, which can effectively capture PFCs in sludge and form self-assembled inclusions with PFOA, significantly improving the degradation effect and reducing the amount of raw materials used, thereby reducing energy consumption and costs.

[0035] (3) The present invention uses an indole polymer with a moderate molecular weight to effectively improve the degradation effect of PFOA. If the molecular weight of the indole polymer is too large, it cannot form self-assembled inclusions with PFOA. If the molecular weight of the indole polymer is too small, it cannot continuously and stably generate hydrated electrons and efficiently degrade PFOA.

[0036] (4) The indole polymer provided by the present invention has stable properties and its degradation effect on PFCs is not significantly affected under complex environmental conditions. Therefore, the method for degrading PFCs in sludge provided by the present invention has a wide range of applications. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the concept of the present invention and the technical effects produced in conjunction with the embodiments, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. The test methods used in the embodiments are all conventional methods unless otherwise specified; the materials, reagents, etc. used, unless otherwise specified, can all be reagents and materials obtained from commercial channels.

[0038] Example 1

[0039] This embodiment provides an indole polymer, and the preparation method thereof comprises the following steps:

[0040] S1. 10 parts by mass of indole-4-carboxylic acid and 11 parts by mass of SOCl2 were added to a reaction flask, 40 parts by mass of N,N-dimethylformamide was added, and the mixture was reacted at 100°C for 15 hours. Then, 9.1 parts by mass of tetradecyldimethylhydroxyethylammonium chloride was added, and the mixture was stirred for 1 hour. 1 mL of triethylamine was added, and the mixture was reacted at 120°C for 15 hours. The crude product after the reaction was filtered, rotary evaporated to dryness, and separated and purified by silica gel column to obtain an indole derivative.

[0041] S2. 10 parts by mass of the above indole derivatives were dissolved in 50 mL of acetonitrile to form an acetonitrile solution of the indole derivatives. The acetonitrile solution of the indole derivatives was added dropwise to a 50 mL acetonitrile solution containing 20 parts by mass of ferric chloride. The reaction was stirred at room temperature for 10 hours. The product was repeatedly washed with methanol and dried to obtain an indole polymer with a number average molecular weight of 8000 g / mol. The structural formula of the indole polymer is as follows:

[0042] .

[0043] Example 2

[0044] This embodiment provides an indole polymer, and the preparation method thereof comprises the following steps:

[0045] S1. 10 parts by mass of indole-4-carboxylic acid and 15 parts by mass of SOCl2 were added to a reaction flask, 40 parts by mass of N,N-dimethylformamide was added, and the mixture was reacted at 90°C for 20 h. Then, 8.3 parts by mass of dioctyldimethylhydroxyethylammonium chloride was added, and the mixture was stirred for 1 hour. 1 mL of triethylamine was added, and the mixture was reacted at 110°C for 18 hours. The crude product after the reaction was filtered, rotary evaporated to dryness, and separated and purified by silica gel column to obtain an indole derivative.

[0046] S2. 10 parts by mass of the above indole derivatives were dissolved in 50 mL of acetonitrile to form an acetonitrile solution of the indole derivatives. The acetonitrile solution of the indole derivatives was added dropwise to a 50 mL acetonitrile solution containing 25 parts by mass of ferric chloride. The reaction was stirred at room temperature for 12 hours. The product was repeatedly washed with methanol and dried to obtain an indole polymer with a number average molecular weight of 7260 g / mol. The structural formula of the indole polymer is as follows:

[0047] .

[0048] Example 3

[0049] This embodiment provides an indole polymer, and the preparation method thereof comprises the following steps:

[0050] S1. 10 parts by mass of indole-5-carboxylic acid and 14 parts by mass of SOCl2 were added to a reaction flask respectively, 40 parts by mass of N,N-dimethylformamide was added, and the mixture was reacted at 100°C for 12 hours. Then, 7.1 parts by mass of octadecyldimethylhydroxyethylammonium chloride was added, and the mixture was stirred for 1 hour. 1 mL of triethylamine was added, and the mixture was reacted at 130°C for 10 hours. The crude product after the reaction was filtered, rotary evaporated to dryness, and separated and purified by silica gel column to obtain an indole derivative.

[0051] S2. 10 parts by mass of the above indole derivatives were dissolved in 50 mL of acetonitrile to form an acetonitrile solution of the indole derivatives. The acetonitrile solution of the indole derivatives was added dropwise to a 50 mL acetonitrile solution containing 40 parts by mass of ferric chloride. The reaction was stirred at room temperature for 16 hours. The product was repeatedly washed with methanol and dried to obtain an indole polymer having a number average molecular weight of 3000 g / mol. The structural formula of the indole polymer is as follows:

[0052] .

[0053] Example 4

[0054] This embodiment provides a method for degrading perfluorinated compounds in sludge, which specifically includes the following steps:

[0055] The content of perfluorinated compounds in the sludge extract containing 1 part by mass of PFOA is 3.02×10 -3 mg / L, 10 parts by mass of the indole polymer solution prepared in Example 1 was dispersed in the sludge extract, the indole polymer content in the indole polymer solution being 0.6 mg / L, and the pH of the solution was adjusted to 6.0 using 0.1M NaOH and HCl. The prepared reaction solution was magnetically stirred for 1 hour and then transferred to a quartz glass reactor for photodegradation under the irradiation of a 36W low-pressure mercury lamp. The temperature of the photodegradation reaction was controlled at 25±2°C, and the reaction time was 6 hours. 2 mL of the sample was sampled every 30 minutes, extracted with 200 mL of methanol, and the remaining PFOA content was detected by high-performance liquid chromatography-mass spectrometry (HPLC-MS / MS) to calculate the PFOA degradation rate.

[0056] Example 5

[0057] This embodiment provides a method for degrading perfluorinated compounds in sludge, which specifically includes the following steps:

[0058] The content of perfluorinated compounds in the sludge extract containing 1 part by mass of PFOA is 3.02×10 -3 mg / L, 18 parts by mass of the indole polymer solution prepared in Example 2 was dispersed in the sludge extract, the indole polymer content in the indole polymer solution being 1 mg / L, and the pH of the solution was adjusted to 5.0 using 0.1M NaOH and HCl. The prepared reaction solution was magnetically stirred for 1 hour and then transferred to a quartz glass reactor for photodegradation under the irradiation of a 36W low-pressure mercury lamp. The temperature of the photodegradation reaction was controlled at 25±2°C, and the reaction time was 5 hours. 2 mL of the sample was sampled every 30 minutes, extracted with 200 mL of methanol, and the remaining PFOA content was detected by high-performance liquid chromatography-mass spectrometry (HPLC-MS / MS) to calculate the PFOA degradation rate.

[0059] Example 6

[0060] This embodiment provides a method for degrading perfluorinated compounds in sludge, which specifically includes the following steps:

[0061] The content of perfluorinated compounds in the sludge extract containing 1 part by mass of PFOA is 3.02×10 -3mg / L, 30 parts by mass of the indole polymer solution prepared in Example 3 was dispersed in the sludge extract, the indole polymer content in the indole polymer solution being 0.7 mg / L, and the pH of the solution was adjusted to 4.0 using 0.1M NaOH and HCl. The prepared reaction solution was magnetically stirred for 1 hour and then transferred to a quartz glass reactor for photodegradation under the irradiation of a 36W low-pressure mercury lamp. The temperature of the photodegradation reaction was controlled at 25±2°C, and the reaction time was 4 hours. 2 mL of the sample was sampled every 30 minutes, extracted with 200 mL of methanol, and the remaining PFOA content was detected by high-performance liquid chromatography-mass spectrometry (HPLC-MS / MS) to calculate the PFOA degradation rate.

[0062] Comparative Example 1

[0063] This comparative example provides a polybenzazole, the preparation method of which comprises the following steps:

[0064] 50 mL of acetonitrile was placed in a three-necked flask, followed by the slow addition of 0.04 mol of ferric chloride, which was stirred thoroughly to dissolve. Subsequently, 30 mL of acetonitrile containing 0.01 mol of indole was added dropwise under a nitrogen atmosphere. The mixed solution was shaken at 300 rpm for 15 hours. The shaken solution was filtered through a 0.22 μm organic filter membrane by vacuum filtration, retaining polybenzazole particles on the membrane. The polybenzazole particles were repeatedly washed with methanol and 60°C hot water to remove impurities. The mixture was then vacuum dried at 70°C for 10 hours. Finally, the polybenzazole was ground using an agate mortar and pestle and passed through a 100-mesh sieve to obtain polybenzazole.

[0065] Comparative Example 2

[0066] This comparative example provides a method for degrading perfluorinated compounds in sludge, which specifically comprises the following steps:

[0067] The content of perfluorinated compounds in the sludge extract containing 1 part by mass of PFOA is 3.02×10 -3 mg / L, 10 parts by mass of the polybenzazole solution prepared in Comparative Example 1 was dispersed in the sludge extract, the polybenzazole content in the polybenzazole solution was 0.6 mg / L, and the pH of the solution was adjusted to 6.0 using 0.1M NaOH and HCl. The prepared reaction solution was magnetically stirred for 1 hour and then transferred to a cylindrical quartz glass reactor for photodegradation under the irradiation of a 36W low-pressure mercury lamp. The temperature of the photodegradation reaction was controlled at 25±2°C and the reaction time was 6 hours. 2 mL was sampled every 30 minutes, extracted with 200 mL of methanol, and the remaining PFOA content was detected by high-performance liquid chromatography-mass spectrometry (HPLC-MS / MS) to calculate the degradation rate of PFOA.

[0068] Comparative Example 3

[0069] This comparative example provides a method for degrading perfluorinated compounds in sludge, which specifically comprises the following steps:

[0070] The content of perfluorinated compounds in the sludge extract containing 1 part by mass of PFOA is 3.02×10 -3 mg / L, 10 parts by mass of the indole derivative solution prepared in step S1 of Example 1 was dispersed in the sludge extract to a concentration of 0.6 mg / L. The pH of the solution was adjusted to 7.0 using 0.1 M NaOH and HCl. The prepared reaction solution was magnetically stirred for 1 hour and then transferred to a cylindrical quartz glass reactor for photodegradation under irradiation with a 36 W low-pressure mercury lamp. The photodegradation reaction temperature was controlled at 25 ± 2°C, and the reaction time was 5 hours. 2 mL of the sample was sampled every 30 minutes, extracted with 200 mL of methanol, and the remaining PFOA content was determined by high-performance liquid chromatography-mass spectrometry (HPLC-MS / MS) to calculate the PFOA degradation rate.

[0071] Comparative Example 4

[0072] This comparative example provides a method for degrading perfluorinated compounds in sludge, which specifically comprises the following steps:

[0073] The content of perfluorinated compounds in the sludge extract containing 1 part by mass of PFOA is 3.02×10 -3 mg / L, 18 parts by mass of the indole derivative solution prepared in step S1 of Example 2 was dispersed in the sludge extract to a concentration of 1 mg / L. The pH of the solution was adjusted to 5.0 using 0.1M NaOH and HCl. The prepared reaction solution was magnetically stirred for 1 hour and then transferred to a quartz glass reactor for photodegradation under irradiation with a 36W low-pressure mercury lamp. The photodegradation reaction temperature was controlled at 25±2°C, and the reaction time was 4 hours. 2 mL of the sample was sampled every 30 minutes, extracted with 200 mL of methanol, and the remaining PFOA content was determined by high-performance liquid chromatography-mass spectrometry (HPLC-MS / MS) to calculate the PFOA degradation rate.

[0074] Comparative Example 5

[0075] This comparative example provides a method for degrading perfluorinated compounds in sludge, which specifically comprises the following steps:

[0076] The content of perfluorinated compounds in the sludge extract containing 1 part by mass of PFOA is 3.02×10 -3mg / L, 40 parts by mass of the indole derivative solution prepared in step S1 of Example 3 was dispersed in the sludge extract to a concentration of 0.7 mg / L. The pH of the solution was adjusted to 6.0 using 0.1 M NaOH and HCl. The prepared reaction solution was magnetically stirred for 1 hour and then transferred to a quartz glass reactor for photodegradation under irradiation with a 36 W low-pressure mercury lamp. The photodegradation reaction temperature was controlled at 25 ± 2°C, and the reaction time was 8 hours. 2 mL of the sample was sampled every 30 minutes, extracted with 200 mL of methanol, and the remaining PFOA content was determined by high-performance liquid chromatography-mass spectrometry (HPLC-MS / MS) to calculate the PFOA degradation rate.

[0077] The degradation rates of PFOA in Examples 4 to 6 and Comparative Examples 2 to 5 are shown in Table 1:

[0078] Table 1. Degradation rates of PFOA in Examples 4-6 and Comparative Examples 2-5.

[0079]

[0080] The stability test of the present invention is mainly carried out by repeating Examples 4 to 6 and Comparative Examples 2 to 5 for 10 times to degrade PFOA, and then testing the degradation effect of Examples 4 to 6 and Comparative Examples 2 to 5 on PFOA again. The specific results are shown in Table 2:

[0081] Table 2. Stability tests of Examples 4-6 and Comparative Examples 2-5.

[0082]

[0083] As shown in Tables 1-2, the indole polymers provided in Examples 1-3 are more effective than polyindole and small molecule indole derivatives in degrading perfluorinated compounds. In addition, the indole polymers provided by the present invention are stable. After being used to degrade PFOA 10 times, the photodegradation reaction of PFOA still has a high degradation rate, and the degradation effect does not change significantly.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for degrading perfluorinated compounds in sludge, characterized in that: include The steps are as follows: Adding an indole polymer solution to a sludge extract containing perfluorinated compounds, and subjecting it to light-induced reaction to degrade the perfluorinated compounds; The preparation method of the indole polymer comprises the following steps: S1. Chlorinating indolecarboxylic acid and reacting with alkylhydroxyethylammonium chloride to obtain an indole derivative; S2. The indole derivative is dissolved in acetonitrile to form an acetonitrile solution of the indole derivative, the acetonitrile solution of the indole derivative is added dropwise to an acetonitrile solution of ferric chloride, the reaction is stirred, and purified to obtain an indole polymer; The indolecarboxylic acid is selected from at least one of indole-4-carboxylic acid, indole-5-carboxylic acid, indole-6-carboxylic acid, and indole-7-carboxylic acid; The alkyl hydroxyethyl ammonium chloride is selected from at least one of tetradecyl dimethyl hydroxyethyl ammonium chloride, octadecyl dimethyl hydroxyethyl ammonium chloride, and behenyl dimethyl hydroxyethyl ammonium chloride; The structure of the indole polymer is shown below: Wherein, R1, R2, R3 and R4 are independently selected from H or , R5 is selected from a linear alkyl group having 14 to 22 carbon atoms, and R1, R2, R3 and R4 are not H at the same time, and the number average molecular weight of the indole polymer is 3000 to 8000 g / mol.

2. The method for degrading perfluorinated compounds in sludge according to claim 1, characterized in that: The structure of the indole polymer is shown below: 、 or .

3. The method for degrading perfluorinated compounds in sludge according to claim 1, characterized in that: The mass ratio of the perfluorinated compound to the indole polymer is 1:10-40.

4. The method for degrading perfluorinated compounds in sludge according to claim 1, characterized in that: The pH value of the sludge extract containing perfluorinated compounds is 4.0-7.

0.

5. The method for degrading perfluorinated compounds in sludge according to claim 1, characterized in that: The temperature of the light reaction is 25±2°C and the time is 4 to 8 hours.

6. The method for degrading perfluorinated compounds in sludge according to claim 1, characterized in that: The light source of the illumination reaction is a low-pressure mercury lamp.

7. The method for degrading perfluorinated compounds in sludge according to claim 1, characterized in that: The content of perfluorinated compounds in the perfluorinated sludge extract is 3.02×10 -3 mg / L, and the content of the indole polymer in the indole polymer solution is 0.6-1 mg / L.

8. The method for degrading perfluorinated compounds in sludge according to claim 1, characterized in that: In S1, the chlorination reagent is selected from SOCl2.

9. The method for degrading perfluorinated compounds in sludge according to claim 1, characterized in that: In S1, the mass ratio of the indolecarboxylic acid to the alkylhydroxyethylammonium chloride is 1.1-1.5:

1.

10. The method for degrading perfluorinated compounds in sludge according to claim 1, characterized in that: In S2, the mass ratio of the indole derivative to ferric chloride is 1:2-4; The stirring reaction is carried out at room temperature for 8 to 16 hours.

Images