Method for low-temperature induced photocatalytic degradation of perfluorinated compound

Abstract

The invention discloses a method for low-temperature induced photocatalytic degradation of a perfluorinated compound. The method comprises the following steps: adding a photocatalyst into a solution containing a perfluorinated compound, and uniformly dispersing to obtain a reaction solution; and placing the reaction solution in a low-temperature environment, starting a light source to carry out photocatalytic reaction, and sequentially heating, filtering and detecting after the reaction is finished, thereby obtaining the product. The mass ratio of the perfluorinated compound to the photocatalyst is (1-3): 1; the temperature of the low-temperature environment is-5 to-60 DEG C. According to the method, the catalyst and the perfluorinated compound are concentrated in micron-sized intergranular water in a low-temperature state, so that the reactant concentration is greatly improved, and the perfluorinated compound can be quickly adsorbed on the catalyst and efficiently cracked C-F bonds by hydrated electrons in the low-temperature state, thereby efficiently degrading the perfluorinated compound.

Description

Technical Field

[0001] The present invention relates to a method for degrading perfluorinated compounds, in particular to a method for degrading perfluorinated compounds by low-temperature induction photocatalysis, and belongs to the technical field of water pollution control and sewage treatment. Background Art

[0002] Perfluorinated surfactants (PFASs) are a new class of persistent organic pollutants widely used in manufacturing and industrial production, such as surfactants, flame retardants, and high-temperature lubricants. Large quantities of PFASs are released into the environment with wastewater and waste residues, where they accumulate, posing ecological risks and threatening life and health. PFASs have been incorporated into drinking water standards by various countries and the World Health Organization, making them subject to key regulatory controls.

[0003] Due to the high strength of the C-F bond (450 kJ / mol) and the strong electronegativity of fluorine atoms, PFASs cannot be degraded via traditional advanced oxidation methods. Currently used PFAS treatment technologies primarily include physical adsorption, electrochemical reduction, photocatalysis, and microbial methods. UV-based photochemical technology has emerged as an efficient, green, and sustainable alternative. Traditional photocatalysts, such as nano-ZnS, nano-Ga2O3, and nano-In2O3, have poor electron-hole separation, making the generated electrons and reactive oxygen species difficult to oxidize PFASs, resulting in low degradation efficiency. Currently, research on PFAS photodegradation primarily focuses on improving the catalytic efficiency of existing catalysts through methods such as material modification (BN-TiO2) and functional group heterogeneity (ZnS-[N]). These techniques are complex, and the designed photocatalysts are subject to uncertainty and instability, making it difficult to achieve efficient and stable degradation of PFASs. This inevitably increases the cost of PFAS photodegradation and can easily pollute the environment during the reaction, which is inconsistent with current green energy production concepts.

[0004] Therefore, the existing technology urgently needs an efficient and safe method for degrading perfluorinated compounds to solve or alleviate the current problem of difficult degradation of PFASs, so as to achieve industrial and efficient degradation of perfluorinated compounds. Summary of the Invention

[0005] To address the problems of the prior art, the present invention provides a method for low-temperature induced photocatalytic degradation of perfluorinated compounds. This method significantly increases the concentration of reactants by concentrating the catalyst and perfluorinated compounds in micron-sized intercrystalline water at low temperatures. Furthermore, the perfluorinated compounds can be rapidly adsorbed on the catalyst at low temperatures, efficiently utilizing hydrated electrons to cleave C—F bonds, thereby further degrading the perfluorinated compounds.

[0006] In order to achieve the above technical objectives, the present invention provides a method for low-temperature induced photocatalytic degradation of perfluorinated compounds, comprising: adding a photocatalyst to a solution containing a perfluorinated compound and uniformly dispersing the photocatalyst to obtain a reaction solution; placing the reaction solution in a low-temperature environment, activating a light source to carry out a photocatalytic reaction, and heating, filtering, and detecting the reaction solution after the reaction is completed.

[0007] The mass ratio of the perfluorinated compound to the photocatalyst is 1 to 3:1; and the temperature of the low-temperature environment is -5 to -60°C.

[0008] The method provided by the present invention mainly converts most of the liquid solution into a solid phase under low temperature conditions, thereby confining the catalyst and the perfluorinated compound solution to intercrystalline water with a spatial confinement of micrometer level, thereby greatly increasing the reactant concentration and the effective contact area with the catalyst, thereby effectively increasing the utilization efficiency of hydrated electrons and improving the defluorination and degradation reaction efficiency of the perfluorinated compound.

[0009] As a preferred solution, the concentration of the perfluorinated compound in the reaction solution is 5 to 50 μmol.

[0010] As a preferred solution, the concentration of the photocatalyst in the reaction solution is 0.005 to 0.05 g / L.

[0011] As a preferred solution, the perfluoro compound is at least one of perfluorooctanoic acid, perfluorobutyric acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluorooctane sulfonic acid, perfluorobutane sulfonic acid and perfluorodecane sulfonic acid.

[0012] As a preferred solution, the photocatalyst is any material having a photoelectron effect.

[0013] It should be noted that since the main innovation of the present invention is to spatially confine the perfluorinated compound to the intercrystalline water on the surface of the micron-sized catalyst by freezing, the photocatalytic performance of any substance with a photoelectric effect is significantly improved. This improvement effect is universal, that is, it is applicable to the combination, reconstruction and modification of any perfluorinated compound photocatalyst.

[0014] As a preferred solution, the particle size of the photocatalyst is 20 to 60 nm.

[0015] As a preferred solution, the photocatalyst is a metal oxide and / or a metal sulfide.

[0016] As a preferred solution, the metal oxide is at least one of ZnO, CuO, Fe2O3 and Fe3O4.

[0017] As a preferred solution, the metal sulfide is at least one of zinc sulfide, copper sulfide, iron sulfide, manganese sulfide, molybdenum disulfide and tungsten disulfide.

[0018] As a preferred solution, the conditions for the photocatalytic reaction are: in a closed condition, start the light source, maintain the system temperature at -5 to -60°C, and react for 12 to 48 hours.

[0019] As a preferred solution, the light source is a mercury lamp with a power of 200 to 300 W; the system temperature is -15 to -35°C.

[0020] As a preferred solution, the heating process is: placing the system after the photocatalytic reaction is completed in a warm water bath at 30-38°C, and heating until the system is completely converted into a liquid phase.

[0021] As a preferred solution, the filtration process is: using a 0.22 μm needle filter to obtain a test solution that does not contain insoluble matter.

[0022] As a preferred solution, the detection method is: using LC-MS / MS to detect the concentration of perfluorinated compounds and degradation products, and using ion chromatography to detect the concentration of fluoride ions in the solution.

[0023] The present invention concentrates perfluorinated compounds and catalysts in micron-sized intercrystalline water in a low-temperature environment. Compared with liquid phase solutions, the solute concentration can be increased by several orders of magnitude, which greatly enhances the transmission capacity and utilization efficiency of interfacial electrons. The perfluorinated compounds adsorbed on the catalyst surface can be more absorbed by electrons (e - ), holes (h + )and . O2 - 、 1 Active oxygen such as O2 is utilized to accelerate the breaking of CF bonds and further degrade them.

[0024] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are:

[0025] 1) The method provided by the present invention concentrates the perfluorinated compound and the catalyst in micron-sized intercrystalline water under ultra-low temperature conditions, thereby greatly increasing the concentration of the reactants and significantly improving the degradation amount of the perfluorinated compound per unit mass of the catalyst and per unit time.

[0026] 2) The method provided by the present invention has no strict requirements for the catalyst, and the photocatalytic performance of any substance with a photoelectric effect is significantly improved. This improvement effect is universal, that is, it is applicable to the combination, reconstruction and modification of any perfluorinated compound photodegradable material. Taking metal oxides and metal sulfides as examples, the degradation efficiency of perfluorinated compounds by this method is 75 times the production efficiency of conventional liquid phase reaction systems. In addition, this method has the advantages of simple operation, low equipment cost and environmental friendliness.

[0027] 3) In the technical solution provided by the present invention, due to the spatial confinement effect under freezing conditions, a large amount of reactants are enriched on the catalyst surface, which effectively increases the contact area between the catalyst and the reactants, and realizes the efficient degradation of perfluorinated compounds by photocatalysts at low concentrations. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a graph showing the efficiency of PFOA degradation under light irradiation with low-concentration nano-ZnS in Examples 1 and 2 of the present invention and Comparative Examples 1 and 2 under room temperature and freezing conditions;

[0029] Figure 2 The graph shows the defluorination efficiency of PFOA degradation by low-concentration nano-ZnS under light irradiation at room temperature and freezing conditions in Examples 1 and 2 of the present invention and Comparative Examples 1 and 2;

[0030] Figure 3 The graph shows the efficiency of PFOA degradation under light irradiation with different low concentrations of nano-Fe2O3 and Fe3O4 in Examples 3 and 4 of the present invention and Comparative Examples 3 and 4 under room temperature and different freezing conditions;

[0031] Figure 4 The graph shows the defluorination efficiency of PFOA degradation by light irradiation of different low-concentration nano-Fe2O3 and Fe3O4 under room temperature and different freezing conditions in Examples 3 and 4 of the present invention and Comparative Examples 3 and 4;

[0032] Figure 5 This is a graph showing the efficiency of photodegradation of perfluorinated compounds by nano-Fe3O4 at different low concentrations under room temperature and different freezing conditions in Examples 5 to 9 of the present invention and Comparative Examples 5 to 9. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0034] Moreover, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0036] Unless otherwise defined, all technical and scientific terms used in the present invention are consistent with the prior art knowledge of those skilled in the art and the description of the present invention. The present invention can also be implemented using any methods, equipment and materials in the prior art that are similar or equivalent to the methods, equipment and materials described in the embodiments of the present invention.

[0037] In order to solve or alleviate the current problem of relying solely on modified catalysts or developing new catalysts to improve the degradation efficiency of perfluorinated compounds, a method for efficiently photocatalytically degrading perfluorinated compounds without any modification measures is established. The present invention provides a method for low-temperature degradation of perfluorinated compounds, comprising the following steps:

[0038] Step S1, adding a photocatalytic material to a solution containing a perfluorinated compound, and ultrasonically treating the solution for 10 minutes until the photocatalytic material is completely dispersed to obtain a reaction solution;

[0039] The perfluoro compound solution includes one of perfluorooctanoic acid (PFOA), perfluorobutyric acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluorooctane sulfonic acid (PFOS), and perfluorobutane sulfonic acid (PFBS), and the reaction concentration is 5 to 50 uM.

[0040] The photocatalyst material is any material exhibiting a photoelectric effect. For ease of illustration, the present invention utilizes the most widely used metal oxides and metal sulfides, including but not limited to nano-ZnO, nano-CuO, nano-Fe₂O₃, nano-Fe₃O₄, nano-ZnS, and nano-CuS. These catalysts are unmodified, have a particle size of 20 to 5 nm, and a concentration of 0.005 to 0.05 g / L.

[0041] The ultrasonic treatment power is 200W, the treatment time is 10 minutes, the catalyst is uniformly dispersed in the solution, and the pH of the solution is adjusted to 4-8.

[0042] Step S2, placing the reaction solution in a low-temperature constant temperature bath, turning on the light source to perform a photocatalytic reaction;

[0043] The low-temperature constant-temperature reaction bath uses a solution of water and ethylene glycol (1:1 volume ratio) to control the reaction temperature. The specific reaction temperature is set at 25°C at room temperature and -5 to -60°C at freezing temperature. Of course, to ensure a constant reaction temperature, the ethylene glycol solution in the reaction bath must be replaced promptly to ensure a temperature fluctuation of ±1°C.

[0044] The light source is a 300W mercury lamp with a main wavelength of 365nm ultraviolet light. Specifically, a certain volume of reaction solution is placed in a quartz test tube, marked and sealed, and immediately placed in a reaction bath. At the same time, the light source is turned on and irradiated. This moment is defined as the reaction starting point.

[0045] Step S3: After the reaction, the solid material was filtered using a 0.22 μm filter head, and the filtrate was tested for the concentration of perfluorinated compounds and degradation products using LC-MS / MS. The concentration of F in the solution was detected by ion chromatography (LC). - concentration;

[0046] The reaction time is set to 12 to 48 hours, and a sample is taken out every 2 hours for thawing analysis; the temperature of the water bath is 35±1° C., and the reaction solution is completely thawed.

[0047] Example 1

[0048] This embodiment provides a method for low-temperature degradation of perfluorinated compounds, the process of which is as follows:

[0049] 1. Measure 10 mg of perfluorooctanoic acid (PFOA) in a 500 mL beaker, stir ultrasonically for 20 minutes until completely dissolved, and then transfer to a 1000 mL volumetric flask to obtain a PFOA solution with a concentration of 20 uM.

[0050] 2. Weigh 20 mg of nano zinc sulfide sample with a particle size of about 50 nm, put it into 1000 mL of deionized water solution, and use 200 W ultrasonic treatment for 10 minutes to make it evenly dispersed to prepare a reaction solution with a nano zinc sulfide (ZnS) concentration of 0.02 g / L.

[0051] 3. Measure 100 mL of the 20 μM PFOA solution from step 1 and 100 mL of the 0.02 g / L PFOA solution from step 2 into a 500 mL beaker and stir ultrasonically for 30 min to allow the reaction solution to reach adsorption-desorption equilibrium.

[0052] 4. Adjust the temperature of the low-temperature constant-temperature reaction bath, place the reaction solution in a quartz test tube, and place it in the reaction bath, while turning on a 300W mercury lamp for light irradiation; adjust the temperature of the low-temperature constant-temperature reaction bath to -20°C, measure 10 mL of the reaction solution in step 2 and place them in 6 25 mL quartz test tubes, cover them with stoppers and seal them with sealing film, place them in a low-temperature constant-temperature reaction bath, and illuminate them with a 300W mercury lamp. This moment is defined as the starting point of the reaction, and the reaction time is 12 hours.

[0053] 5. After the reaction is completed, the quartz test tubes under the frozen condition and the room temperature condition are taken out at the same time intervals, and the frozen samples are placed in a water bath at 35±1℃ for thawing. After the solution is completely thawed, the thawed / reacted sample is immediately filtered with a 0.22um filter membrane to remove catalyst particles. The filtrate is tested for the concentration of perfluorinated compounds and degradation products by LC-MS / MS, and the F in the solution is tested by ion chromatography (LC). - concentration.

[0054] Comparative Example 1

[0055] This comparative example is exactly the same as Example 1, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in six 25 mL quartz test tubes, the tubes are stoppered and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, illumination is performed with a 300 W mercury lamp. This moment is defined as the reaction starting point, and the reaction time is 12 hours.

[0056] The results of Example 1 and Comparative Example 1 are as follows Figure 1 、 Figure 2 As shown, nano-ZnS has higher PFOA degradation and defluorination efficiency under freezing conditions compared to room temperature conditions. The PFOA degradation efficiency under freezing conditions was 76.0%, while the degradation efficiency under room temperature was only 3.0%. Nano-ZnS increased the PFOA degradation rate under freezing conditions by 73%. In terms of defluorination rate, the dechlorination rate of PFOA under freezing conditions was 70%, while the defluorination rate of PFOA under room temperature was only 0.2%. Nano-ZnS increased the defluorination rate of PFOA under freezing conditions by 69.8%.

[0057] Example 2

[0058] This example is identical to Example 1, except that 10 mg of a nano-ferric oxide sample having a particle size of approximately 50 nm was weighed and placed in 500 mL of a deionized water solution. 100 mL of a 20 μM PFOA solution and 100 mL of the above-mentioned 0.02 g / L Fe2O3 solution were added to a 500 mL beaker and ultrasonically treated at 200 W for 10 min to uniformly disperse the mixture. To obtain a reaction solution, the nano-ferric oxide (Fe2O3) concentration was 0.01 g / L, and the PFOA concentration was 10 μM.

[0059] Comparative Example 2

[0060] This comparative example is exactly the same as Example 2, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in 6 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 300 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 12 hours.

[0061] The results of Example 2 and Comparative Example 2 are as follows Figure 3 、 Figure 4 As shown, compared to room temperature conditions, nano-Fe2O3 has higher PFOA degradation and defluorination efficiency under frozen conditions. The degradation efficiency of PFOA under frozen conditions is 72.0%, while the degradation efficiency under room temperature is only 2.4%. The degradation rate of PFOA under frozen conditions by nano-Fe2O3 increased by 69.6%. In terms of defluorination rate, the dechlorination rate of PFOA under frozen conditions is 48%, while the defluorination rate of PFOA under room temperature is only 0.2%. The defluorination rate of PFOA under frozen conditions by nano-Fe2O3 increased by 47.8%.

[0062] Example 3

[0063] This example is identical to Example 2, except that: 10 mg of a nano-ferroferric oxide sample with a particle size of approximately 50 nm was weighed and placed in 500 mL of a deionized water solution, 100 mL of a 20 μM PFOA solution and 100 mL of the above-mentioned 0.02 g / L Fe3O4 solution were measured and placed in a 500 mL beaker, and the mixture was ultrasonically treated at 200 W for 10 min to uniformly disperse the mixture, thereby obtaining a reaction solution having a nano-ferroferric oxide (Fe3O4) concentration of 0.01 g / L and a PFOA concentration of 10 μM.

[0064] Comparative Example 3

[0065] This comparative example is exactly the same as Example 3, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in 6 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 300 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 12 hours.

[0066] The results of Example 3 and Comparative Example 3 are as follows Figure 3 、 Figure 4 As shown, compared to room temperature conditions, nano-Fe3O4 has higher PFOA degradation and defluorination efficiency under frozen conditions. The degradation efficiency of PFOA under frozen conditions is 95.0%, while the degradation efficiency under room temperature is only 4.3%. Nano-Fe3O4 improves the PFOA degradation rate under frozen conditions by 91.7%. In terms of defluorination rate, the dechlorination rate of PFOA under frozen conditions is 93%, while the defluorination rate of PFOA under room temperature is only 0.3%. Nano-Fe3O4 improves the defluorination rate of PFOA under frozen conditions by 92.7%.

[0067] Example 4

[0068] This example is identical to Example 3, except that 10 mg of perfluorooctane sulfonic acid (PFOS) was weighed into a 500 mL beaker, ultrasonically stirred for 20 min, and transferred to a 1000 mL volumetric flask until completely dissolved to obtain a PFOS solution with a concentration of 20 uM. 100 mL of the 20 uM PFOS solution and the above-mentioned 100 mL of the 0.02 g / L Fe3O4 solution were measured and placed in a 500 mL beaker. The mixture was ultrasonically treated at 200 W for 10 min to uniformly disperse the mixture to obtain a reaction solution having a nano-ferrous oxide (Fe3O4) concentration of 0.01 g / L and a PFOS concentration of 10 uM.

[0069] Comparative Example 4

[0070] This comparative example is exactly the same as Example 5, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in six 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, illumination is performed with a 300 W mercury lamp. This moment is defined as the reaction starting point, and the reaction time is 12 hours.

[0071] The results of Example 4 and Comparative Example 4 are as follows Figure 5As shown, nano-Fe3O4 has a higher PFOS degradation efficiency under frozen conditions compared to room temperature conditions. The degradation efficiency of PFOS under frozen conditions is 95.0%, while the degradation efficiency under room temperature is only 4.3%. Nano-Fe3O4 improves the PFOS degradation rate under frozen conditions by 91.7%. In terms of defluorination rate, the dechlorination rate of PFOS under frozen conditions is 93%, while the defluorination rate of PFOS under room temperature is only 0.3%. Nano-Fe3O4 improves the defluorination rate of PFOS under frozen conditions by 92.7%.

[0072] Example 5

[0073] This example is exactly the same as Example 4, except that: 10 mg of perfluorobutyric acid (PFBA) was weighed into a 250 mL beaker, ultrasonically stirred for 20 min, and transferred to a 500 mL volumetric flask until completely dissolved to obtain a PFBA solution with a concentration of 20 uM. 100 mL of 20 uM PFBA solution and the above 100 mL of 0.02 g / LFe3O4 solution were measured in a 500 mL beaker and ultrasonically treated at 200 W for 10 min to uniformly disperse them to obtain a reaction solution with a nano-ferrous oxide (Fe3O4) concentration of 0.01 g / L and a PFBA concentration of 10 uM.

[0074] Comparative Example 5

[0075] This comparative example is exactly the same as Example 5, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in six 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, illumination is performed with a 300 W mercury lamp. This moment is defined as the reaction starting point, and the reaction time is 12 hours.

[0076] The results of Example 5 and Comparative Example 5 are as follows Figure 5 As shown in the results, compared with room temperature conditions, nano-Fe3O4 has higher PFBA degradation efficiency and defluorination efficiency under frozen conditions. The degradation efficiency of PFBA under frozen conditions is 63.3%, while the degradation efficiency under room temperature is only 2.4%. The degradation rate of PFBA under frozen conditions by nano-Fe3O4 increased by 60.9%.

[0077] Example 6

[0078] This example is exactly the same as Example 4, except that: 10 mg of perfluoropentanoic acid (PFPeA) was weighed into a 250 mL beaker, ultrasonically stirred for 20 min, and transferred to a 500 mL volumetric flask until completely dissolved to obtain a PFPeA solution with a concentration of 20 uM. 100 mL of 20 uM PFPeA solution and the above 100 mL of 0.02 g / L Fe3O4 solution were measured in a 500 mL beaker and ultrasonically treated at 200 W for 10 min to uniformly disperse them to obtain a reaction solution with a nano-ferrous oxide (Fe3O4) concentration of 0.01 g / L and a PFPeA concentration of 10 uM.

[0079] Comparative Example 6

[0080] This comparative example is exactly the same as Example 5, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in six 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, illumination is performed with a 300 W mercury lamp. This moment is defined as the reaction starting point, and the reaction time is 12 hours.

[0081] The results of Example 6 and Comparative Example 6 are as follows Figure 5 As shown in the results, compared with room temperature conditions, nano-Fe3O4 has a higher PFPeA degradation efficiency under frozen conditions. The degradation efficiency of PFPeA under frozen conditions is 59.6%, while the degradation efficiency of PFPeA under room temperature is only 3.3%. The degradation rate of PFPeA under frozen conditions by nano-Fe3O4 increased by 56.3%.

[0082] Example 7

[0083] This example is exactly the same as Example 4, except that: 15 mg of perfluorohexanoic acid (PFHxA) was weighed into a 250 mL beaker, ultrasonically stirred for 20 min, and transferred to a 500 mL volumetric flask until completely dissolved to obtain a PFHxA solution with a concentration of 20 uM. 100 mL of 20 uM PFHxA solution and the above 100 mL of 0.02 g / L Fe3O4 solution were measured in a 500 mL beaker and ultrasonically treated at 200 W for 10 min to uniformly disperse them to obtain a reaction solution with a nano-ferrous oxide (Fe3O4) concentration of 0.01 g / L and a PFHxA concentration of 10 uM.

[0084] Comparative Example 7

[0085] This comparative example is exactly the same as Example 5, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in six 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, illumination is performed with a 300 W mercury lamp. This moment is defined as the reaction starting point, and the reaction time is 12 hours.

[0086] The results of Example 7 and Comparative Example 7 are as follows Figure 5 As shown in the figure, compared with room temperature conditions, nano-Fe3O4 has a higher PFHxA degradation efficiency under frozen conditions. The degradation efficiency of PFHxA under frozen conditions is 51.6%, while the degradation efficiency of PFHxA under room temperature is only 1.2%. The degradation rate of PFHxA under frozen conditions by nano-Fe3O4 increased by 50.4%.

[0087] Example 8

[0088] This example is identical to Example 2, except that perfluorooctane sulfonic acid (PFOS) was weighed in a 250 mL beaker, ultrasonically stirred for 20 min, and transferred to a 500 mL volumetric flask until completely dissolved to obtain a PFOS solution with a concentration of 20 uM. 100 mL of the 20 uMPOS solution and the above 100 mL of the 0.02 g / LFe3O4 solution were measured and placed in a 500 mL beaker. The mixture was ultrasonically treated at 200 W for 10 min to uniformly disperse the mixture to obtain a reaction solution having a nano-ferrous oxide (Fe3O4) concentration of 0.01 g / L and a PFOS concentration of 10 uM.

[0089] Comparative Example 8

[0090] This comparative example is exactly the same as Example 5, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in six 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, illumination is performed with a 300 W mercury lamp. This moment is defined as the reaction starting point, and the reaction time is 12 hours.

[0091] The results of Example 8 and Comparative Example 8 are as follows Figure 5 As shown in the figure, compared with room temperature conditions, nano-Fe3O4 has a higher PFOS degradation efficiency under frozen conditions. The degradation efficiency of PFOS under frozen conditions is 76.4%, while the degradation efficiency of PFBS under room temperature is only 4.2%. The degradation rate of PFOS by nano-Fe3O4 under frozen conditions increased by 72.2%.

[0092] Example 9

[0093] This example is exactly the same as Example 2, except that: 10 mg of perfluorobutane sulfonic acid (PFBS) was weighed into a 250 mL beaker, ultrasonically stirred for 20 min, and transferred to a 1000 mL volumetric flask until completely dissolved to obtain a PFBS solution with a concentration of 20 uM. 100 mL of 20 uM PFBS solution and the above 100 mL of 0.02 g / L Fe3O4 solution were measured and placed in a 500 mL beaker. The mixture was ultrasonically treated at 200 W for 10 min to uniformly disperse the mixture to obtain a reaction solution having a nano-ferrous oxide (Fe3O4) concentration of 0.01 g / L and a PFBS concentration of 10 uM.

[0094] Comparative Example 9

[0095] This comparative example is exactly the same as Example 5, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in six 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, illumination is performed with a 300 W mercury lamp. This moment is defined as the reaction starting point, and the reaction time is 12 hours.

[0096] The results of Example 9 and Comparative Example 9 are as follows Figure 5 As shown in the figure, compared with room temperature conditions, nano-Fe3O4 has a higher PFBS degradation efficiency under frozen conditions. The degradation efficiency of PFBS under frozen conditions is 69.6%, while the degradation efficiency under room temperature is only 3.9%. The degradation rate of PFBS under frozen conditions by nano-Fe3O4 increased by 65.7%.

[0097] Thus, the described perfluorinated compound degradation method achieves efficient degradation of perfluorinated compounds using conventional semiconductor materials at low concentrations. Specifically, the degradation efficiency of perfluorinated compounds is significantly improved by freezing conditions. The method is simple to operate, inexpensive, environmentally friendly, safe, reliable, and highly applicable.

[0098] In summary, the above technical solutions of the present invention are only preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention's description and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for low-temperature induced photocatalytic degradation of perfluorinated compounds, characterized in that: include: adding a photocatalyst to a solution containing a perfluorinated compound and uniformly dispersing the photocatalyst to obtain a reaction solution; The reaction solution is placed in a low temperature environment, and a light source is started to perform a photocatalytic reaction. After the reaction is completed, the temperature is raised, filtered, and tested in sequence to obtain the product; The mass ratio of the perfluorinated compound to the photocatalyst is 1 to 3:1; and the temperature of the low-temperature environment is -5 to -60°C.

2. The method for low-temperature induced photocatalytic degradation of perfluorinated compounds according to claim 1, characterized in that: The concentration of the perfluorinated compound in the reaction solution is 5-50 μmol; the concentration of the photocatalyst in the reaction solution is 0.005-0.05 g / L.

3. The method for low-temperature induced photocatalytic degradation of perfluorinated compounds according to claim 1, characterized in that: The perfluoro compound is at least one of perfluorooctanoic acid, perfluorobutyric acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluorooctane sulfonic acid, perfluorobutane sulfonic acid and perfluorodecane sulfonic acid.

4. The method for low-temperature induced photocatalytic degradation of perfluorinated compounds according to claim 1, characterized in that: The photocatalyst is any material having a photoelectron effect; the particle size of the photocatalyst is 20-60 nm.

5. The method for low-temperature induced photocatalytic degradation of perfluorinated compounds according to claim 4, characterized in that: The photocatalyst is a metal oxide and / or a metal sulfide; the metal oxide is at least one of ZnO, CuO, Fe2O3 and Fe3O4; the metal sulfide is at least one of zinc sulfide, copper sulfide, iron sulfide, manganese sulfide, molybdenum disulfide and tungsten disulfide.

6. The method for low-temperature induced photocatalytic degradation of perfluorinated compounds according to claim 1, characterized in that: The conditions for the photocatalytic reaction are: in a closed condition, start the light source, maintain the system temperature at -5 to -60°C, and react for 12 to 48 hours.

7. The method for low-temperature induced photocatalytic degradation of perfluorinated compounds according to claim 6, characterized in that: The light source is a mercury lamp with a power of 200-300W; the system temperature is -15--35°C.

8. The method for low-temperature induced photocatalytic degradation of perfluorinated compounds according to claim 1, characterized in that: The heating process is as follows: placing the system after the photocatalytic reaction is completed in a warm water bath at 30-38° C., and heating until the system is completely converted into a liquid phase.

9. The method for low-temperature induced photocatalytic degradation of perfluorinated compounds according to claim 1, characterized in that: The filtering process is as follows: using a 0.22 μm needle filter to obtain a test solution free of insoluble matter.

10. The method for low-temperature induced photocatalytic degradation of perfluorinated compounds according to claim 1, characterized in that: The detection method comprises the following steps: using LC-MS / MS to detect the concentration of perfluorinated compounds and degradation products, and using an ion chromatograph to detect the concentration of fluoride ions in the solution.

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