Preparation of amphiphilic Janus nanoflotation agent and its method for assisting foam flotation in removing perfluorinated compounds from water

Abstract

This invention provides a method for preparing an amphiphilic Janus nanoflotation agent and its application in foam flotation to remove perfluorinated compounds (PFOCs) from water, relating to the technical field of PFOC removal in water. The method for preparing the amphiphilic Janus nanoflotation agent involves grafting hydrophobic and hydrophilic functional groups onto the surface of an SNP (spatial nucleus polymer) to achieve an amphiphilic Janus structure. The introduction of long C-F chains and amino groups respectively yields the hydrophobic and hydrophilic amphiphilic structures, enabling the flotation agent to irreversibly adsorb at the gas-liquid interface and thus exert a highly efficient foam-stabilizing effect. The amphiphilic Janus nanoflotation agent provided by this invention not only generates stable foam during foam flotation but also effectively captures PFCs, thereby achieving the removal of PFOS and PFOA.

Description

Technical Field

[0001] This invention relates to the technical field of removing perfluorinated compounds from water, and in particular to the preparation of an amphiphilic Janus nanoflotation agent and its method for assisting foam flotation in removing perfluorinated compounds from water. Background Technology

[0002] Perfluorinated compounds (PFCs) are a persistent, bioaccumulative, and potentially biotoxic emerging pollutants that have attracted significant attention from the scientific community. Typical PFCs, such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), are widely used in various consumer products and industrial applications due to their unique physicochemical properties, such as hydrophobic / oleophobicity, thermal stability, and acid / alkali resistance. Their large-scale production and use inevitably release them into the aquatic environment, causing unpredictable environmental hazards and ecotoxicity. Conventional water treatment processes such as coagulation, sedimentation, filtration, and disinfection are ineffective in removing PFCs; therefore, developing efficient PFC removal technologies has become a key focus of water environment management.

[0003] Representative patents reported in recent years for PFC removal include: ① A functionally modulated nanofiltration membrane for selectively removing short-chain perfluorinated compounds (CN202311356082.9); ② An adsorption material for removing perfluorinated compounds from water, its preparation method, and its application (CN202211675105.8); ③ A method for removing perfluorinated compounds from groundwater using photoelectrocatalysis synergistic PRB (CN202210809941.4); ④ A system and method for enhancing the removal of perfluorinated compounds from water using constructed wetlands (CN202110466288.1). While the membrane treatment, adsorption, chemical oxidation, and biodegradation methods employed in these patents achieve highly efficient PFC removal, they also suffer from high costs, large investment requirements, and difficulties in industrialization. Foam flotation based on gas-liquid interface adsorption offers engineering advantages such as large throughput, high efficiency, and low energy consumption, making it an important means of enriching / recovering PFCs. However, conventional flotation agents (foaming agents and collectors) that are mainly surfactants have technical defects such as insufficient foam stabilization and poor collection efficiency.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The primary objective of this invention is to provide a method for preparing an amphiphilic Janus nanoflotation agent, which exhibits good foam stability and high collection efficiency for PFCs.

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned amphiphilic Janus nanoflotation agent.

[0007] A third objective of this invention is to provide the application of the aforementioned amphiphilic Janus nanoflotation agent in the removal of perfluorinated compounds from water.

[0008] A fourth objective of this invention is to provide a method for removing perfluorinated compounds from water.

[0009] To achieve the above objectives, the following technical solution is adopted:

[0010] In a first aspect, the present invention provides a method for preparing an amphiphilic Janus nanoflotation agent, comprising the following steps:

[0011] a. Hydrophilic nano-silica (SNP) is wetted with water, then dispersed in an organic solvent, and a fluorosilane coupling agent is added to the organic solvent to carry out the reaction. After the reaction is completed, fluorinated nano-silica is prepared; the mass ratio of the hydrophilic nano-silica to water is 1:1-5:1.

[0012] b. Disperse the fluorinated nano-silica obtained in step a in an organic solvent, then add an aminosilane coupling agent to the organic solvent to carry out the reaction, and after the reaction is completed, prepare the amphiphilic Janus nano-flotation agent.

[0013] As a further technical solution, the organic solvent includes at least one of benzene, toluene, xylene, cyclohexane, or cyclohexanone.

[0014] As a further technical solution, in step a, the concentration of the fluorosilane coupling agent is 0.16-0.83 mmol / L during the reaction.

[0015] As a further technical solution, the fluorosilane coupling agent includes at least one of heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, or nonafluorohexyltrimethoxysilane.

[0016] As a further technical solution, in step b, the concentration of the aminosilane coupling agent is 4.2-20.8 mmol / L during the reaction.

[0017] As a further technical solution, the aminosilane coupling agent includes at least one of 3-aminopropyltrimethoxysilane or 3-(2-aminoethylamino)propyltrimethoxysilane.

[0018] Secondly, the present invention provides an amphiphilic Janus nanoflotation agent, which is prepared by the above-described preparation method.

[0019] Thirdly, the present invention provides the application of the above-mentioned amphiphilic Janus nanoflotation agent in the removal of perfluorinated compounds in water.

[0020] Fourthly, the present invention provides a method for removing perfluorinated compounds from water, which uses foam flotation to remove perfluorinated compounds from water.

[0021] The flotation agent for the foam flotation includes the aforementioned amphiphilic Janus nanoflotation agent.

[0022] As a further technical solution, the following steps are included:

[0023] An aqueous solution containing perfluorinated compounds is mixed with the amphiphilic Janus nano-flotation agent, and the pH is adjusted to 5.0–9.0 before being injected into a foam flotation tower for foam flotation. When the foam can no longer flow out from the top of the foam flotation tower, the aeration is stopped, thus completing the removal of perfluorinated compounds from the aqueous solution.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The preparation method of the amphiphilic Janus nanoflotation agent provided by this invention is simple and convenient. An amphiphilic Janus structure is achieved by grafting hydrophobic and hydrophilic functional groups onto the surface of SNPs. The introduction of long CF chains and amino groups respectively yields hydrophobic and hydrophilic amphiphilic structures, enabling the flotation agent to irreversibly adsorb at the gas-liquid interface and thus exert a highly efficient foam-stabilizing effect. The amino groups drive the migration of anionic PFCs from the aqueous solution to the vicinity of the flotation agent through electrostatic interactions. The CF chains, acting as recognition sites, achieve strong binding with PFCs based on hydrophobic and fluorine-dependent interactions, thereby exerting a selective collection effect.

[0026] The amphiphilic Janus nanoflotation agent provided by this invention can not only be used as a foaming agent, but also as a collector. That is to say, the flotation agent not only generates stable foam during the foam flotation process, but also effectively captures PFCs, making PFOS and PFOA more easily adsorbed on the gas-liquid interface, thereby achieving the purpose of removing PFOS and PFOA.

[0027] 2. This invention provides a foam flotation technology based on the nano flotation agent of this invention, which can be used to remove PFCs from water. Foam flotation has the advantages of simple equipment, low investment, low energy consumption, no pollution and simple operation, and has good prospects for industrialization.

[0028] 3. The use of a foam flotation tower can significantly reduce the volume of defoaming liquid, allowing the amphiphilic Janus nano flotation agent to precipitate naturally, which is beneficial for subsequent desorption and reuse.

[0029] 4. The novel flotation agent and flotation process developed by this invention effectively improve the removal rates of PFOS and PFOA.

[0030] 5. The supernatant after the defoaming solution is settled after froth flotation can be reintroduced into the equalization tank, allowing the remaining PFOS and PFOA to be further processed. The desorbed amphiphilic Janus nanoflotation agent can also be recycled. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the preparation process of the amphiphilic Janus nanoflotation agent in Example 1;

[0033] Figure 2 (a) is a scanning electron microscope (SEM) image of the amphiphilic Janus nanoflotation agent; (b) is a SEM image of the amphiphilic Janus nanoflotation agent after adsorption of gold particles by the hydrophilic amino groups, showing the amphiphilic structure; (c) is an EDS image of the SNP; (d) is an EDS image of the amphiphilic Janus nanoflotation agent; (e) is a contact angle image of the SNP; (f) is a contact angle image of the amphiphilic Janus nanoflotation agent.

[0034] Figure 3 This is a schematic diagram of the flotation process;

[0035] Figure 4 This is a schematic diagram of a flotation device.

[0036] Icons: 1-Air pump; 2-Gas buffer bottle; 3-Gas wetting bottle; 4-Flow regulator; 5-Residual liquid collection tank; 6-Gas distributor; 7-Foam flotation tower; 8-Foam collection tank; 9-Peristaltic pump. Detailed Implementation

[0037] The embodiments and examples of the present invention will be described in detail below. However, those skilled in the art will understand that the following embodiments and examples are for illustrative purposes only and should not be considered as limiting the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0038] In a first aspect, the present invention provides a method for preparing an amphiphilic Janus nanoflotation agent, comprising the following steps:

[0039] a. Hydrophilic nano-silica is wetted with water, then dispersed in an organic solvent, and a fluorosilane coupling agent is added to the organic solvent to carry out the reaction. After the reaction is completed, fluorinated nano-silica is prepared; the mass ratio of the hydrophilic nano-silica to water is 1:1-5:1.

[0040] b. Disperse the fluorinated nano-silica obtained in step a in an organic solvent, then add an aminosilane coupling agent to the organic solvent to carry out the reaction, and after the reaction is completed, prepare the amphiphilic Janus nano-flotation agent.

[0041] This preparation method is simple and convenient. It involves first wetting hydrophilic nano-silica and then dispersing it in an organic solvent to achieve partial surface adsorption of water on the hydrophilic nano-silica, while the other part of the surface is exposed to the organic solvent. The surface of the silica exposed in the organic solvent reacts with a fluorinated silane coupling agent to modify the fluorine group. Then, the prepared fluorinated nano-silica is dispersed in the organic phase, allowing the unmodified surface to react with an aminosilane coupling agent, ultimately achieving an amphiphilic Janus structure. The introduction of long CF chains and amino groups respectively yields amphiphilic structures, allowing the flotation agent to irreversibly adsorb at the gas-liquid interface and thus exert a highly efficient bubble-stabilizing effect. The amino group drives the migration of anionic PFCs from the aqueous solution to the vicinity of the flotation agent through electrostatic interactions, while the CF chain, acting as a recognition site, achieves strong binding with PFCs based on hydrophobic-fluorine interactions, thereby exerting a selective collection effect. In summary, the reagent provided by this invention can be used not only as a foaming agent but also as a collector. That is to say, this reagent not only generates stable foam during the foam flotation process but also effectively captures PFCs, making it easier for PFOS and PFOA to be adsorbed on the gas-liquid interface, thereby achieving the purpose of removing PFOS and PFOA.

[0042] In some alternative embodiments, the organic solvent includes, but is not limited to, at least one of benzene, toluene, xylene, cyclohexane, or cyclohexanone.

[0043] In this invention, in step a, the organic solvent and water are combined to disperse the nano-silica at the liquid-liquid interface of the water and organic phases. Then, a fluorosilane coupling agent is added to the organic phase, so that the nano-silica on one side of the organic phase reacts with the fluorosilane coupling agent.

[0044] In some optional embodiments, in step a, the concentration of the fluorosilane coupling agent is 0.16-0.83 mmol / L, preferably 0.33-0.67 mmol / L, during the reaction.

[0045] In some alternative embodiments, the fluorosilane coupling agent includes, but is not limited to, at least one of heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, or nonafluorohexyltrimethoxysilane, or other fluorosilane coupling agents well known to those skilled in the art.

[0046] In some alternative implementations, the reaction temperature in step a is not specifically limited and can be room temperature, and the reaction time can be, for example, 8-12 hours.

[0047] In some alternative embodiments, step a involves a reaction being carried out under stirring conditions, wherein the stirring speed is 500 to 700 rpm, preferably 650 rpm.

[0048] In some alternative implementations, step a may include washing and drying steps after the reaction is complete.

[0049] In some optional embodiments, in step b, the concentration of the aminosilane coupling agent during the reaction is 4.2-20.8 mmol / L, preferably 8.3-16.6 mmol / L.

[0050] In some alternative embodiments, the aminosilane coupling agent includes, but is not limited to, at least one of 3-aminopropyltrimethoxysilane or 3-(2-aminoethylamino)propyltrimethoxysilane, or other aminosilane coupling agents well known to those skilled in the art.

[0051] In some alternative embodiments, in step a, the hydrophilic nano-silica and the fluorosilane coupling agent react under catalytic conditions;

[0052] The catalyst includes triethylamine.

[0053] The inventors discovered that using triethylamine as a catalyst can accelerate the reaction between hydrophilic nano-silica and fluorosilane coupling agents, shorten the reaction time, and improve the reaction efficiency.

[0054] In some alternative implementations, the reaction temperature in step b is not specifically limited and can be room temperature, and the reaction time can be, for example, 12-20 hours.

[0055] In some alternative implementations, step b, after the reaction is complete, also includes washing and drying steps.

[0056] In some alternative embodiments, the hydrophilic nano-silica is prepared using the Stober method.

[0057] Secondly, the present invention provides an amphiphilic Janus nanoflotation agent, which is prepared by the above-described preparation method.

[0058] The amphiphilic Janus nanoflotation agent provided by this invention can not only be used as a foaming agent, but also as a collector. That is to say, the agent not only generates stable foam during the foam flotation process, but also effectively captures PFCs, making it easier for PFOS and PFOA to be adsorbed on the gas-liquid interface, thereby achieving the purpose of removing PFOS and PFOA.

[0059] In some alternative embodiments, the diameter of the nano-silica is 100-1000 nm.

[0060] Thirdly, the present invention provides the application of the above-mentioned amphiphilic Janus nanoflotation agent in the removal of perfluorinated compounds in water.

[0061] The amphiphilic Janus nanoflotation agent provided by this invention has good foam stability and can effectively capture PFCs, thereby achieving the removal of PFOS and PFOA.

[0062] The perfluorinated compounds include at least one of other long-chain perfluorinated compounds (eight or more carbon chains), such as perfluorooctyl sulfonic acid and perfluorooctanoic acid.

[0063] Fourthly, the present invention provides a method for removing perfluorinated compounds from water, which uses foam flotation to remove perfluorinated compounds from water.

[0064] The flotation agent for the foam flotation includes the aforementioned amphiphilic Janus nanoflotation agent.

[0065] The method provided by this invention can be used to remove PFCs from water bodies. It has the advantages of low investment, low energy consumption, no pollution and simple operation, and has good prospects for industrialization.

[0066] In some alternative implementations, the following steps are included:

[0067] An aqueous solution containing perfluorinated compounds is mixed with the amphiphilic Janus nano-flotation agent, and the pH is adjusted to 5.0–9.0 before being injected into a foam flotation tower for foam flotation. When the foam can no longer flow out from the top of the foam flotation tower, the aeration is stopped, thus completing the removal of perfluorinated compounds from the aqueous solution.

[0068] In some alternative implementations, the process parameters for foam flotation are as follows:

[0069] The dosage of the amphiphilic Janus nanoflotation agent is 500–1200 mg / L, preferably 700–1000 mg / L;

[0070] The gas velocity is 0.3–0.8 L / min, preferably 0.4–0.7 L / min;

[0071] The height of the foam layer is 2 / 5 to 4 / 5 of the height of the foam flotation tower, preferably 3 / 5;

[0072] The defoaming liquid is 1.0% to 10.0% of the feed liquid volume;

[0073] The froth flotation tower is a hollow cylindrical tower with a tower diameter of 30-60 mm and a tower height:to-diameter ratio of 2-4:1.

[0074] In addition, the collected foam is defoamed to obtain defoaming liquid. After centrifugation, the precipitate is collected and the precipitate can be reused after desorption with 50% to 80% ethanol. The inventors have found that the desorbed flotation agent can be re-entered into the equalization tank for flotation, and it can still maintain good results after 2 to 4 times.

[0075] In some alternative implementations, the process flow of froth flotation is as follows: Figure 3 As shown, the process includes: mixing perfluorinated wastewater with the amphiphilic Janus nano-flotation agent provided by this invention, adjusting the pH, and then introducing the mixture into a foam flotation tower for foam flotation. During the flotation process, the foam flowing out from the top of the tower is collected, and the remaining liquid is discharged from the bottom of the tower after flotation. The remaining liquid still contains some perfluorinated compounds, which can be further treated. After the foam at the top of the tower is defoamed, solid-liquid separation is performed. The supernatant is returned to the equalization tank, and the precipitate is desorbed in the desorption tank. The desorbed amphiphilic Janus nano-flotation agent is added to the equalization tank for reuse.

[0076] The present invention will be further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0077] Example 1

[0078] An amphiphilic Janus nanoflotation agent, prepared as in the case example Figure 1 As shown, the preparation method is as follows:

[0079] (1) Adopting the classic Hydrophilic SNPs were prepared by the following method: First, 9 mL of ammonia, 179 mL of ethanol, and 62 mL of deionized water were added to a 500 mL Erlenmeyer flask and mixed thoroughly. Then, 15.9 mL of tetraethyl orthosilicate was added. The mixture was stirred for 2 hours at 120 rpm and 30 °C using a thermostatic magnetic stirrer to form a white product. The precipitate was collected by centrifugation (10,000 rpm, 5 min), redispersed in anhydrous ethanol, washed, and centrifuged again. This process was repeated three times. The final precipitate was dried at 60 °C to obtain the hydrophilic SNPs for later use.

[0080] (2) Grind the SNP obtained in step (1) into a fine and uniform powder. Take 0.5 g and wet it with 0.3 mL of deionized water, then add it to 40 mL of benzene. Disperse it thoroughly using a homogenizer. Add 0.50 mmol / L of tridecafluorooctyltrimethoxysilane to the solution. Stir at room temperature for 10 h (stirring speed is 650 rpm), then centrifuge (10000 rpm, 5 min) to collect the precipitate. Redisperse, wash and centrifuge in anhydrous ethanol. Repeat this step three times. Dry the final precipitate at 60 °C to obtain fluorinated SNP for later use.

[0081] (3) The 0.5 g fluorinated SNP obtained in step (2) was thoroughly dispersed in 50 mL of benzene, and then 12.5 mmol / L of 3-aminopropyltrimethoxysilane was added to the suspension. After reacting for 16 h at room temperature with stirring, the precipitate was collected by centrifugation (10000 rpm, 5 min), redispersed in anhydrous ethanol, washed, and centrifuged again. This step was repeated three times. The final precipitate was dried at 60 °C to obtain the amphiphilic Janus nanoflotation agent.

[0082] The amphiphilic Janus nanoflotation agent prepared in Example 1 was compared with the unmodified nano-silica (including scanning electron microscopy, EDS elemental analysis, and contact angle analysis). The results are as follows: Figure 2 As shown.

[0083] Example 2

[0084] An amphiphilic Janus nanoflotation agent is prepared as follows:

[0085] (1) Adopting the classic Hydrophilic SNPs were prepared by the following method: First, 9 mL of ammonia, 179 mL of ethanol, and 62 mL of deionized water were added to a 500 mL Erlenmeyer flask and mixed thoroughly. Then, 15.9 mL of tetraethyl orthosilicate was added. The mixture was stirred for 2 hours at 120 rpm and 30 °C using a thermostatic magnetic stirrer to form a white product. The precipitate was collected by centrifugation (10,000 rpm, 5 min), redispersed in anhydrous ethanol, washed, and centrifuged again. This process was repeated three times. The final precipitate was dried at 60 °C to obtain the hydrophilic SNPs for later use.

[0086] (2) Grind the SNP obtained in step (1) into a fine and uniform powder. Take 0.5 g and wet it with 0.1 mL of deionized water, then add it to 40 mL of cyclohexane. Disperse it thoroughly using a homogenizer. Add 0.16 mmol / L of heptadecafluorodecyltrimethoxysilane to the solution. Stir at room temperature for 8 h (stirring speed is 700 rpm), then centrifuge (10000 rpm, 5 min) to collect the precipitate. Redisperse, wash, and centrifuge in anhydrous ethanol. Repeat this step three times. Dry the final precipitate at 60 °C to obtain fluorinated SNP for later use.

[0087] (3) The 0.5 g fluorinated SNP obtained in step (2) was thoroughly dispersed in 50 mL of benzene, and then 4.2 mmol / L of 3-(2-aminoethylamino)propyltrimethoxysilane was added to the suspension. After reacting for 12 h with stirring at room temperature, the precipitate was collected by centrifugation (10000 rpm, 5 min), redispersed in anhydrous ethanol, washed, and centrifuged again. This step was repeated three times. The final precipitate was dried at 60 °C to obtain the amphiphilic Janus nanoflotation agent.

[0088] Example 3

[0089] An amphiphilic Janus nanoflotation agent is prepared as follows:

[0090] (1) Adopting the classic Hydrophilic SNPs were prepared by the following method: First, 9 mL of ammonia, 179 mL of ethanol, and 62 mL of deionized water were added to a 500 mL Erlenmeyer flask and mixed thoroughly. Then, 15.9 mL of tetraethyl orthosilicate was added. The mixture was stirred for 2 hours at 120 rpm and 30 °C using a thermostatic magnetic stirrer to form a white product. The precipitate was collected by centrifugation (10,000 rpm, 5 min), redispersed in anhydrous ethanol, washed, and centrifuged again. This process was repeated three times. The final precipitate was dried at 60 °C to obtain the hydrophilic SNPs for later use.

[0091] (2) Grind the SNP obtained in step (1) into a fine and uniform powder. Take 0.5 g and wet it with 0.5 mL of deionized water, then add it to 40 mL of benzene. Disperse it thoroughly using a homogenizer. Add 0.83 mmol / L of nonafluorohexyltrimethoxysilane to the solution. Stir at room temperature for 12 h (stirring speed is 500 rpm), then centrifuge (10000 rpm, 5 min) to collect the precipitate. Redisperse, wash and centrifuge in anhydrous ethanol. Repeat this step three times. Dry the final precipitate at 60 °C to obtain fluorinated SNP for later use.

[0092] (3) The 0.5 g fluorinated SNP obtained in step (2) was thoroughly dispersed in 50 mL of benzene, and then 20.8 mmol / L of 3-aminopropyltrimethoxysilane was added to the suspension. After reacting for 20 h at room temperature with stirring, the precipitate was collected by centrifugation (10000 rpm, 5 min), redispersed in anhydrous ethanol, washed, and centrifuged again. This step was repeated three times. The final precipitate was dried at 60 °C to obtain the amphiphilic Janus nanoflotation agent.

[0093] Comparative Example 1

[0094] An amphiphilic Janus nanoflotation agent, which differs from Example 1 in that it has not been modified with an aminosilane coupling agent.

[0095] Comparative Example 2

[0096] An amphiphilic Janus nanoflotation agent differs from Example 1 in that the hydrophilic SNP is first modified with an aminosilane coupling agent and then modified with a fluorosilane coupling agent.

[0097] Experimental Example 1

[0098] The effect of the amphiphilic Janus nanoflotation agents prepared in Examples 1-3 and Comparative Examples 1-2 on removing perfluorinated compounds was tested using a foam flotation device, and the steps are as follows:

[0099] Foam flotation device such as Figure 4 As shown, it mainly consists of an air pump 1, a gas buffer bottle 2, a gas wetting bottle 3, a flow regulator 4, a residual liquid collection tank 5, a gas distributor 6, a foam flotation tower 7, a foam collection tank 8, and a peristaltic pump 9. The peristaltic pump 9 is connected to the equalization tank and is used to pump the liquid to be separated in the equalization tank to the foam flotation tower 7. The function and connection method of each component are conventional choices in the field and will not be described in detail here.

[0100] The prepared amphiphilic Janus nano-flotation agent was added to an aqueous solution of PFOS and PFOA (total concentration 1000 mg / L, 500 mg / L each) in the equalization tank at a concentration of 800 mg / L. After adjusting the pH to 8.0, the solution was injected into a foam flotation tower (a hollow cylindrical tower with a diameter of 30–60 mm) as feed. Foam flotation was carried out at room temperature with a gas velocity of 0.5 L / min and a foam layer height of 3 / 5 of the height of the foam flotation tower. The foam flowing out of the top of the tower was collected and defoamed. The gas supply was stopped when the foam could no longer flow out of the top of the foam flotation tower. The removal effects of the amphiphilic Janus nano-flotation agent in Examples 1-3 and Comparative Examples 1-2 were statistically analyzed, and the results are shown in Table 1.

[0101] Table 1

[0102]

[0103] The results above show that modification with aminosilane coupling agents can further improve the separation effect of flotation agents on perfluorinated compounds. The modification order of the silane coupling agents in this invention is key. Modification with fluorosilane coupling agents first and then with aminosilane coupling agents can further improve the separation effect of flotation agents on perfluorinated compounds.

[0104] In addition, the inventors prepared two other batches (batch 1 and batch 2, the flotation agent in the above experiment is referred to as batch 1) of flotation agent using the preparation methods of Examples 1-3 and Comparative Examples 1-2 respectively. The experiments were conducted according to the above experimental methods, and it was found that the separation results were basically consistent with those of batch 1 flotation agent.

[0105] Experimental Example 2

[0106] Foam flotation was performed using the flotation agent provided in Example 1 according to the method of Test Example 1, and the following treatment groups were set up:

[0107] Treatment Group 1: The difference from the method in Experimental Example 1 is that the concentration of the amphiphilic Janus nanoflotation agent was set at 1000 mg / L;

[0108] Treatment Group 2: The difference from the method in Experimental Example 1 is that after adding the amphiphilic Janus nanoflotation agent, the pH was adjusted to 7.0;

[0109] Treatment Group 3: The difference from the method in Test Example 1 is that the aminosilane modifier is 3-(2-aminoethylamino)propyltrimethoxysilane;

[0110] Treatment Group 4: The difference from the method in Experimental Example 1 is that the amount of tridecafluorooctyltrimethoxysilane added is set to 0.67 mmol / L.

[0111] The results for each treatment group are shown in Table 2.

[0112] Table 2

[0113]

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an amphiphilic Janus nanoflotation agent, characterized in that, Includes the following steps: a. Hydrophilic nano-silica is wetted with water, then dispersed in an organic solvent, and a fluorosilane coupling agent is added to the organic solvent to carry out the reaction. After the reaction is completed, fluorinated nano-silica is prepared; the mass ratio of the hydrophilic nano-silica to water is 1:1-5:

1. b. Disperse the fluorinated nano-silica obtained in step a in an organic solvent, then add an aminosilane coupling agent to the organic solvent to carry out the reaction, and after the reaction is completed, prepare the amphiphilic Janus nano-flotation agent.

2. The preparation method according to claim 1, characterized in that, The organic solvent includes at least one of benzene, toluene, xylene, cyclohexane, or cyclohexanone.

3. The preparation method according to claim 1, characterized in that, In step a, the concentration of the fluorosilane coupling agent is 0.16-0.83 mmol / L during the reaction.

4. The preparation method according to claim 1, characterized in that, The fluorosilane coupling agent includes at least one of heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, or nonafluorohexyltrimethoxysilane.

5. The preparation method according to claim 1, characterized in that, In step b, the concentration of the aminosilane coupling agent during the reaction is 4.2-20.8 mmol / L.

6. The preparation method according to claim 1, characterized in that, The aminosilane coupling agent includes at least one of 3-aminopropyltrimethoxysilane or 3-(2-aminoethylamino)propyltrimethoxysilane.

7. An amphiphilic Janus nanoflotation agent, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. The application of the amphiphilic Janus nanoflotation agent according to claim 7 in the removal of perfluorinated compounds in water.

9. A method for removing perfluorinated compounds from water, characterized in that, Foam flotation is used to remove perfluorinated compounds from water. The flotation agent for the foam flotation includes the amphiphilic Janus nanoflotation agent as described in claim 7.

10. The method according to claim 9, characterized in that, Includes the following steps: An aqueous solution containing perfluorinated compounds is mixed with the amphiphilic Janus nano-flotation agent, and the pH is adjusted to 5.0–9.0 before being injected into a foam flotation tower for foam flotation. When the foam can no longer flow out from the top of the foam flotation tower, the aeration is stopped, thus completing the removal of perfluorinated compounds from the aqueous solution.

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