Method for removing PFASs through metal ion reinforced ferroelectric flocculation

Abstract

The invention relates to a method for removing PFASs in industrial wastewater through metal ion reinforced ferroelectric flocculation, and belongs to the technical field of electrochemical water treatment. The method comprises the following steps that an iron plate serves as an anode, a stainless steel plate serves as a cathode, one or more metal ions of Co < 2 + >, Ni < 2 + >, Zn < 2 + > and Cu < 2 + > are added, and under the aerobic or anaerobic condition, the initial pH of wastewater is regulated to be 4-7, the metal ion concentration is 0.5-2.0 mM, the electrolysis time is 10-120 min, and the current density is 2.5-30 mA / cm < 2 >. According to the method for treating the PFASs in the industrial wastewater through the metal ion reinforced ferroelectric flocculation, the removal efficiency of the PFASs can be improved, the energy consumption and the iron consumption are reduced, and the metal ions can also be synchronously removed.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater electrochemical treatment, and in particular to a method for removing PFASs by metal ion-enhanced ferroelectric flocculation. Background Art

[0002] Poly- and perfluoroalkyl substances (PFASs) are a class of persistent organic pollutants that persist stably in the environment and readily accumulate in organisms. They pose endocrine, reproductive, developmental, neurological, and immunotoxic risks, posing a threat to aquatic ecosystems. PFASs are known for their high-temperature resistance, corrosion resistance, oleophobicity, and hydrophobicity, and are primarily used in industries such as firefighting, electroplating, textiles, and semiconductor etching. Therefore, developing efficient technologies to remove PFASs from industrial wastewater is crucial for safeguarding aquatic ecosystems and promoting sustainable development.

[0003] Currently, PFASs are commonly removed through methods such as advanced oxidation, reduction, adsorption, ion exchange, and flocculation. Advanced oxidation and reduction technologies have limited defluorination rates for PFASs and are energy-intensive. Adsorption and ion exchange are more suitable for removing lower concentrations of PFASs, but they have limited adsorption capacity and poor regeneration performance. Iron plate anode electrocoagulation can remove PFASs, but its efficiency is low and iron consumption is high. Therefore, it is imperative to develop enhanced ferroelectric flocculation methods for efficient PFAS removal. Summary of the Invention

[0004] Based on the problems existing in the current electrocoagulation technology for removing PFASs, the present invention provides a method for utilizing metal ions to enhance ferroelectric flocculation and improve the removal efficiency of PFASs in industrial wastewater.

[0005] The technical solutions adopted in the present invention are as follows:

[0006] An electrochemical device is provided, comprising a DC power supply, a magnetic stirrer, oxygen / nitrogen, a reactor, an iron plate anode, and a stainless steel plate cathode; an electrolyte salt is added to deionized water in the reactor to form 100 mL of electrolyte, and PFASs and metal ions are added to the electrolyte; an electrode rack is placed above the reactor to fix the distance between the anode and the cathode, and the iron plate anode and the stainless steel plate cathode are immersed in the reaction solution, the anode is connected to the positive electrode of the power supply, and the cathode is connected to the negative electrode of the power supply; a constant current is applied to the DC power supply, and oxygen or nitrogen is introduced.

[0007] In a further technical solution, the electrolyte is prepared by using one or more of NaCl, Na2SO4, and NaHCO3 electrolyte salts, preferably NaCl.

[0008] In a further technical solution, the concentration of the electrolyte salt is 5-200 mM.

[0009] In a further technical solution, the anode and cathode plates have an area of ​​20 cm 2 , with a spacing of 0.5-2.0cm.

[0010] In a further technical solution, the constant current applied by the power supply is 50-600 mA, corresponding to a current density of 2.5-30 mA / cm 2 .

[0011] In a further technical solution, the electrolysis time is 10-120 min, and the amount of metallic iron precipitated from the anode during the electrolysis process is 1.86-224 mM.

[0012] In a further technical solution, the initial concentration of PFOA is 0.001-0.1 mM.

[0013] In a further technical solution, the metal ion Co 2+ 、Ni 2+ 、Cu 2+ 、Zn 2+ One or more of the above, with a concentration of 0.5-2.0mM.

[0014] In a further technical solution, the initial pH of the reaction solution is 4-7.

[0015] In a further technical solution, the magnetic stirring speed is 100-300 r / min.

[0016] In a further technical solution, sufficient oxygen or nitrogen is introduced to maintain aerobic or anaerobic conditions, and the iron flocs are in the form of iron oxyhydroxide or Fe3O4 / green rust respectively; in actual industrial wastewater treatment, air can be provided by aeration and stirring to maintain the aerobic state of the wastewater to produce iron oxyhydroxide, and Fe can be electrochemically generated in situ under no aeration or stirring conditions. 2+ It is easy to deplete the dissolved oxygen in the wastewater, keeping the wastewater in an anaerobic state to produce Fe3O4 / green rust.

[0017] In a further technical solution, the PFASs industrial wastewater is industrial wastewater containing one or more of perfluorobutyric acid (PFBA), 4H-hexafluorobutyric acid (4H-PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), hexafluoropropylene oxide dimer acid (HFPO-DA, GenX), perfluorobutane sulfonic acid (PFBS), perfluoropentane sulfonic acid (PFPeS), perfluorohexane sulfonic acid (PFHxS), perfluoroheptane sulfonic acid (PFHpS), perfluorooctane sulfonic acid (PFOS), perfluorononane sulfonic acid (PFNS), perfluorodecane sulfonic acid (PFDS), and perfluorohexylethyl sulfonic acid (6:2FTS).

[0018] The present invention achieves the following beneficial effects:

[0019] 1. The present invention proposes a method for removing PFASs by using a metal ion-enhanced ferroelectric flocculation method. 2+ 、Ni 2+ 、Cu 2 + 、Zn 2+ Under the presence of one or more of the following conditions, the PFASs removal rate is >90%, which is 20%-50% higher than that without adding metal ions; or when the PFASs removal rate reaches the same level, the power consumption and iron consumption are reduced by 10%-60%.

[0020] 2. The ferroelectric flocculation technology proposed in this invention can effectively remove metal ions, Co 2+ 、Ni 2+ 、Cu 2+ 、Zn 2+ The removal rate is higher than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 PFOA removal efficiency diagram in Examples 1, 2 and Comparative Example 1;

[0022] Figure 2 Figure 2 is a graph of metal removal efficiency in Examples 1 and 2;

[0023] Figure 3 PFOA removal efficiency diagram in Examples 3 and 4 and Comparative Example 2;

[0024] Figure 4 Figure 2 is a graph of metal removal efficiency in Examples 3 and 4; DETAILED DESCRIPTION

[0025] The present invention provides a method for removing PFASs by promoting ferroelectric flocculation with metal ions. To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but this does not limit the scope of protection of the present invention.

[0026] An embodiment of the present invention that has a better effect on removing PFASs includes the following steps:

[0027] An electrochemical device is provided, comprising a direct current power supply, a magnetic stirrer, oxygen / nitrogen, a reactor, an iron plate anode, and a stainless steel plate cathode; an electrolyte salt is added to deionized water in the reactor to prepare 100 mL of an electrolyte, wherein the initial concentration of PFASs is 0.001-0.1 mM; metal ions are added to the electrolyte, wherein the initial concentration is 0.5-2.0 mM; an electrode rack is placed above the reactor to fix the distance between the anode and the cathode, wherein the electrode plates have an area of ​​4 cm×5 cm and a spacing of 0.5-2.0 cm; the iron plate anode and the stainless steel plate cathode are immersed in a reaction solution, wherein the anode is connected to the positive electrode of the power supply, and the cathode is connected to the negative electrode of the power supply; a constant current of 50-600 mA is applied to the direct current power supply, oxygen or nitrogen is introduced to maintain a sufficient oxygen or oxygen-free state, and an initial pH of 4-7; the reaction solution is stirred with the magnetic stirrer at a stirring speed of 100-300 r / min; after electrolysis for 10-120 minutes, a sample is taken and filtered to achieve solid-liquid separation. The concentration of PFASs in the solution was tested using liquid chromatography-mass spectrometry, and the concentration of metal ions in the solution was tested using inductively coupled plasma optical emission spectrometry.

[0028] After treatment, the PFASs removal rate is >90%, and the metal ion removal rate is >90%.

[0029] The following describes this with reference to specific embodiments.

[0030] Example 1

[0031] Simulated wastewater solution (volume 100 mL): 0.01 mM PFOA, 10 mM NaCl, 2 mM Co 2+ , pH=5.

[0032] 1. Provide an electrochemical device with an iron plate as the anode and a stainless steel plate as the cathode. The plates are 4.0 cm × 5.0 cm in size and 1.0 cm apart. The anode is connected to the positive pole of the power supply, and the cathode is connected to the negative pole of the power supply. The reactor volume is 120 mL cylindrical and the material is polypropylene.

[0033] 2. Inject simulated wastewater into the above device.

[0034] 3. Sufficient oxygen is introduced into the simulated wastewater, and the iron produced exists in the form of Fe(III) flocculent ferric oxyhydroxide.

[0035] 4. The DC power supply is powered on, and the current density is 5mA / cm 2 , the stirrer speed is 200r / min.

[0036] Test: Samples were taken after 0, 10, 20, 30, 40, and 60 minutes of power on. After filtration, the PFOA concentration in the solution was tested using a liquid chromatography-mass spectrometer, and the Co concentration in the solution was tested using an inductively coupled plasma emission spectrometer. 2+ Concentration, the results are as follows Figure 1 、 Figure 2 shown.

[0037] Example 2

[0038] The same as Example 1, except that the metal ion was replaced by 2mM Ni 2+ .

[0039] Test: Samples were taken after 0, 10, 20, 30, 40, and 60 minutes of power on. After filtration, the PFOA concentration in the solution was tested using a liquid chromatography-mass spectrometer, and the Ni content in the solution was tested using an inductively coupled plasma emission spectrometer. 2+ Concentration, the results are as follows Figure 1 、 Figure 2 shown.

[0040] Example 3

[0041] 1. Provide an electrochemical device with an iron plate as the anode and a stainless steel plate as the cathode. The plates are 4.0 cm × 5.0 cm in size and 1.0 cm apart. The anode is connected to the positive pole of the power supply, and the cathode is connected to the negative pole of the power supply. The reactor volume is 120 mL cylindrical and the material is polypropylene.

[0042] 2. Inject simulated wastewater into the above device.

[0043] 3. Sufficient nitrogen is introduced into the simulated wastewater, and the iron produced exists in the form of mixed-valent iron particles Fe3O4 / green rust.

[0044] 4. The DC power supply is powered on, and the current density is 5mA / cm 2 , the stirrer speed is 200r / min.

[0045] Test: Samples were taken after 0, 10, 20, 30, 40, and 60 minutes of power on. After filtration, the PFOA concentration in the solution was tested using a liquid chromatography-mass spectrometer, and the Co concentration in the solution was tested using an inductively coupled plasma emission spectrometer. 2+ Concentration, the results are as follows Figure 3 、 Figure 4 shown.

[0046] Example 4

[0047] The same as Example 2, except that the metal ion was replaced by 2.0 mM Ni 2+ .

[0048] Test: Samples were taken after 0, 10, 20, 30, 40, and 60 minutes of power on. After filtration, the PFOA concentration in the solution was tested using a liquid chromatography-mass spectrometer, and the Ni content in the solution was tested using an inductively coupled plasma emission spectrometer. 2+ Concentration, the results are as follows Figure 3 、 Figure 4 shown.

[0049] Example 5

[0050] It is basically the same as Example 1, except that Co 2+ The concentration is 1.0 mM.

[0051] Test: Samples were taken after 0, 10, 20, 30, 40, and 60 minutes of power on. After filtration, the PFOA concentration in the solution was tested using a liquid chromatography-mass spectrometer, and the Co concentration in the solution was tested using an inductively coupled plasma emission spectrometer. 2+ concentration.

[0052] Example 6

[0053] The method is basically the same as Example 1, except that the pH is 7.

[0054] Test: Samples were taken after 0, 10, 20, 30, 40, and 60 minutes of power on. After filtration, the PFOA concentration in the solution was tested using a liquid chromatography-mass spectrometer, and the Co concentration in the solution was tested using an inductively coupled plasma emission spectrometer. 2+ concentration.

[0055] Example 7

[0056] The method is basically the same as Example 1, except that PFOA is replaced by 6:2FTS.

[0057] Test: Samples were taken after 0, 10, 20, 30, 40, and 60 minutes of power on. After filtration, the PFASs concentration in the solution was tested using a liquid chromatography-mass spectrometer, and the Co in the solution was tested using an inductively coupled plasma emission spectrometer. 2+ concentration.

[0058] Comparative Example 1

[0059] Simulated wastewater solution (volume 100 mL): 0.01 mM PFOA, 10 mM NaCl, pH = 5. Other conditions are the same as in Example 1.

[0060] Test: Samples were taken after 0, 10, 20, 30, 40, and 60 minutes of power on. After filtration, the PFOA concentration in the solution was tested using a liquid chromatography-mass spectrometer. The results were as follows: Figure 1 shown.

[0061] Comparative Example 2

[0062] Simulated wastewater solution (volume 100 mL): 0.01 mM PFOA, 10 mM NaCl, pH = 5. Other conditions are the same as in Example 2.

[0063] Test: Samples were taken after 0, 10, 20, 30, 40, and 60 minutes of power on. After filtration, the PFOA concentration in the solution was tested using a liquid chromatography-mass spectrometer. The results were as follows: Figure 2 shown.

[0064] Table 1

[0065]

[0066] Test result analysis

[0067] 1. Comparison of Example 1, Example 2 and Comparative Example 1: When the PFOA removal rate is 50%, in the absence of metal ions, the power consumption and iron consumption are 0.1 Wh and 35 mmol, respectively. 2+ When 2 mM Ni was added, the power consumption and iron consumption were reduced to 50%, 0.05 W h and 17 mmol, respectively. 2+ When the power consumption and iron consumption are reduced to 0.05W h and 17mmol respectively.

[0068] 2. Comparison of Example 1, Example 2 and Comparative Example 1: When the PFOA removal rate was 90%, in the absence of metal ions, the power consumption and iron consumption were 0.35W h and 122 mmol, respectively. 2+ When 2 mM Ni was added, the power consumption and iron consumption were reduced to 50%, 0.18 W h and 61 mmol, respectively. 2+ When the power consumption and iron consumption are reduced to 0.30W h and 104mmol.

[0069] 3. Comparison of Example 3, Example 4 and Comparative Example 2: When the PFOA removal rate was 50%, in the absence of metal ions, the power consumption and iron consumption were greater than 0.15W h and 52 mmol, respectively. 2+ When 2 mM Ni was added, the power consumption and iron consumption were significantly reduced to 0.05 W h and 17 mmol, respectively. 2+ When the power consumption and iron consumption are reduced to 0.10W h and 35mmol respectively.

[0070] 4. Comparison of Example 3, Example 4 and Comparative Example 2: When the PFOA removal rate was 90%, in the absence of metal ions, the power consumption and iron consumption were greater than 0.3W h and 104 mmol, respectively. 2+ When 2 mM Ni was added, the power consumption and iron consumption were significantly reduced to 0.15 W h and 52 mmol, respectively. 2+ When the power consumption and iron consumption are reduced to 0.3W h and 104mmol respectively.

[0071] In summary, the metal ion Co 2+ or Ni 2+ When Co is present, the removal efficiency of PFOA by ferroelectric flocculation is significantly improved under aerobic and anaerobic conditions: under aerobic conditions, the PFOA removal rate is 50% after ferroelectric flocculation for 20 minutes, and the removal rate of PFOA by Co is 50%. 2+ or Ni 2+ In the presence of Co, the PFOA removal rate was 50% after 10 min of ferroelectric flocculation; under aerobic conditions, the PFOA removal rate was 90% after 70 min of ferroelectric flocculation. 2+ When Ni 2+ In the presence of Co, the PFOA removal rate was 90% after 60 min of ferroelectric flocculation; under anaerobic conditions, the PFOA removal rate was 50% after 30 min of ferroelectric flocculation. 2+ When Ni 2+ In the presence of Co, the PFOA removal rate was 50% after 20 min of ferroelectric flocculation; under anaerobic conditions, the PFOA removal rate was 80% after 60 min of ferroelectric flocculation. 2+ When Ni 2+ When Ni is present, the PFOA removal rate is 90% after 60 min of ferroelectric flocculation. Correspondingly, the power consumption and iron consumption are reduced to varying degrees. 2+ ,Co 2+ Under the condition of the presence of Co, the removal efficiency of PFOA by ferroelectric flocculation is more significantly improved, and the power consumption and iron consumption are significantly reduced. 2+ or Ni 2+ The removal rates are all above 90%. Utilizing the metals present in wastewater can enhance ferroelectric flocculation to remove PFASs, reducing energy consumption and iron consumption, and effectively removing metal ions.

[0072] The above description is merely an example of the embodiments of the present invention and is not intended to limit the scope of protection of the present invention. It should be pointed out that for those skilled in the art, omissions, modifications, substitutions, variations, improvements, etc. made within the essential scope of the present invention will be included in the scope of protection of the present invention. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in this application are all within the scope of protection of the claims attached to this application. Therefore, the scope of protection of the patent of this application shall be based on the content of the attached claims, and the description and drawings may be used to interpret the content of the claims.

Claims

1. A method for removing PFASs by metal ion-enhanced ferroelectric flocculation, characterized by: An electrochemical device is provided, comprising a DC power supply, a magnetic stirrer, oxygen / nitrogen, a reactor, an iron plate anode, and a stainless steel plate cathode; an electrolyte salt is added to deionized water in the reactor to form 100 mL of electrolyte, and PFASs and metal ions are added to the electrolyte; an electrode rack is placed above the reactor to fix the distance between the anode and the cathode, and the iron plate anode and the stainless steel plate cathode are immersed in the reaction solution, the anode is connected to the positive electrode of the power supply, and the cathode is connected to the negative electrode of the power supply; a constant current is applied to the DC power supply, and oxygen or nitrogen is introduced.

2. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 1, characterized in that: The electrolyte is prepared by selecting one or more of NaCl, Na2SO4, and NaHCO3 electrolyte salts, preferably NaCl.

3. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 2, characterized in that: The concentration of the electrolyte salt in the electrolyte solution is 5-200 mM.

4. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 1, characterized in that: The anode and cathode plates have an area of ​​20 cm 2 , with a spacing of 0.5-2.0cm.

5. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 1, characterized in that: The constant current applied by the power supply is 50-600 mA.

6. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 5, characterized in that: The electrolysis time is 10-120 minutes, and the amount of metallic iron precipitated from the anode during the electrolysis process is 1.86-224 mM.

7. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 1, characterized in that: The initial concentration of PFASs was 0.001-0.1 mM.

8. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 1, characterized in that: The metal ion is Co 2+ 、Ni 2+ 、Cu 2+ 、Zn 2+ One or more of the .

9. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 8, characterized in that: The metal ion concentration is 0.5-2.0 mM.

10. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 1, characterized in that: The initial pH of the reaction solution is 4-7.

11. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 1, characterized in that: Magnetic stirring was used with a stirring speed of 100-300 r / min.

12. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 1, characterized in that: Adequate oxygen or nitrogen is introduced to maintain aerobic or anaerobic conditions, and the iron flocs are in the form of ferric oxyhydroxide or Fe3O4 / green rust. In actual industrial wastewater treatment, air can be provided by aeration and stirring to keep the wastewater in an aerobic state to produce ferric oxyhydroxide. Under no aeration or stirring conditions, Fe is electrochemically generated in situ. 2+ It is easy to deplete the dissolved oxygen in the wastewater, keeping the wastewater in an anaerobic state to produce Fe3O4 / green rust.

13. The method for removing PFASs by metal ion-enhanced ferroelectric flocculation according to claim 1, characterized in that: PFASs are one or more of perfluorobutyric acid (PFBA), 4H-hexafluorobutyric acid (4H-PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), hexafluoropropylene oxide dimer acid (HFPO-DA, GenX), perfluorobutane sulfonic acid (PFBS), perfluoropentane sulfonic acid (PFPeS), perfluorohexane sulfonic acid (PFHxS), perfluoroheptane sulfonic acid (PFHpS), perfluorooctane sulfonic acid (PFOS), perfluorononane sulfonic acid (PFNS), perfluorodecane sulfonic acid (PFDS), and perfluorohexylethyl sulfonic acid (6:2FTS).

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