1. A method for degrading perfluorooctanoic acid by coupling microbial electro-Fenton with sodium persulfate comprises the following steps:

s1, manufacturing an anode carbon brush and a cathode electrode required by the microbial electro-Fenton system, and preprocessing;

s2, preparing nutrient solution required by the growth of the electrogenesis microorganisms for culturing the electrogenesis microorganisms;

s3, adding anaerobic sludge and nutrient solution into the anode chamber of the reactor, introducing nitrogen into the reactor, and culturing and domesticating the electrogenic microorganisms by using a potassium ferricyanide solution as a cathode chamber;

s4, replacing the cathode solution of the reactor with the perfluorooctanoic acid solution after the anodic electrogenesis microorganism culture, adding sodium persulfate, and applying voltage to obtain the reactor for degrading the perfluorooctanoic acid by electro-Fenton coupling with the sodium persulfate;

s5, maintaining the reactor at a proper temperature, introducing air into the cathode chamber, and degrading the perfluorooctanoic acid under an aerobic condition.

2. The method for degrading perfluorooctanoic acid by coupling microbial electro-fenton reaction with sodium persulfate according to claim 1, wherein the step S1 comprises the following specific steps:

s1-1, processing the carbon fiber wire and the titanium wire with the diameter of 0.8-1.2mm into a carbon fiber brush, wherein the carbon fiber brush has a fixed size;

s1-2, 0.8-1.2 mol.L for the prepared carbon fiber brush^-1Soaking the mixture in NaOH solution for 5.5 to 6.5 hours to remove impurity ions;

s1-3, and further 1 mol. L^-1Soaking in HCl for 5.5-6.5h, and ultrasonically cleaning with deionized water to neutrality;

s1-4, boiling for 2.5-35 h by using deionized water, and replacing water every 30 min;

s1-5, performing heating treatment by using a muffle furnace to obtain an anode carbon brush;

s1-6, cutting the graphite plate into squares of 4cm by 0.5 cm;

s1-7, firstly, soaking the mixture for 4.5 to 5.5 hours by using 1 mol. L-1 NaOH solution to remove impurity ions;

s1-8, soaking the graphite plate in 1 mol. L-1 HCl for 5.5-6.5h, and ultrasonically cleaning the graphite plate with deionized water to be neutral to obtain the graphite plate cathode electrode.

3. The method for degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate according to claim 2, wherein: in the step S1-1, the fixed size refers to that the carbon fiber brush is 6cm long and 4cm in diameter;

preferably, in the step S1-5, the muffle furnace treatment temperature is 480-520 ℃, and the treatment time is 8-12 minutes.

4. The method for degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate according to claim 1, wherein: in step S2, the nutrient solution has a formula containing the following substances per liter of solution: 3mg magnesium sulfate, 0.13mg zinc chloride, 0.005mg zinc sulfate heptahydrate, 1.5mg nitrilotriacetic acid, 0.5mg manganese sulfate monohydrate, 310mg ammonium chloride, 130mg potassium chloride, 0.01mg boric acid, 0.01mg cobalt chloride hexahydrate, 5mg nicotinic acid, 2mg folic acid, 0.01mg copper sulfate pentahydrate, 0.024mg nickel chloride hexahydrate, 0.024mg sodium tungstate dihydrate, 0.1mgB-12, 5mg vitamin B1, 6mg vitamin B2, 10mg vitamin B6, 6mg p-aminobenzoic acid, 2000mg glucose, 2000mg sodium acetate.

5. The method for degrading perfluorooctanoic acid by coupling microbial electro-fenton reaction with sodium persulfate according to claim 1, wherein the step S3 comprises the following specific steps:

s3-1, adopting anaerobic sludge at a concentration tank of a sewage treatment plant as inoculation sludge, settling the taken sludge, and pouring out supernatant;

s3-2, adding the sludge and the prepared nutrient solution into an anode chamber with a carbon fiber brush to form an anolyte;

s3-3, continuously introducing nitrogen into the anode chamber, removing oxygen in the anode chamber, and maintaining a strict anaerobic environment;

s3-4, using potassium ferricyanide solution as catholyte;

s3-5, connecting the reactor and the external resistance in series to form a microbial fuel cell, and culturing and domesticating the electrogenic microbes at a proper temperature.

6. The method for degrading perfluorooctanoic acid by coupling microbial electro-fenton reaction with sodium persulfate according to claim 5, wherein: in step S3-2, the pH of the anolyte is 7-7.5.

Preferably, in the step S3-2, the volume ratio of the sludge to the nutrient solution is 1: 1;

preferably, in the step S3-3, the nitrogen is introduced for 8-12 minutes;

preferably, in the step S3-4, the concentration of the potassium ferricyanide solution is 15-17 g/L;

preferably, in step S3-5, the suitable temperature is 30-37 ℃;

preferably, in step S3-5, the water inlet of the anode chamber is sealed by a rubber plug, and the anode chamber is maintained under anaerobic conditions for culturing;

preferably, in step S3-5, the external resistance in series with the reactor is 1000 Ω.

7. The method for degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate according to claim 1, wherein: step S4 includes the following specific steps:

s4-1, after the anode carbon brush culture is finished, discharging 1/2 of anolyte, and supplementing corresponding nutrient solution;

s4-2, preparing a perfluorooctanoic acid solution for degradation as a catholyte;

s4-3, injecting catholyte into the cathode chamber;

s4-4, connecting the reactor in series with a 10 omega external resistor;

and S4-5, applying a proper voltage to obtain the electro-Fenton coupling sodium persulfate degradation perfluorooctanoic acid reactor.

8. The method for degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate according to claim 7, wherein: in step S4-2, the catholyte includes the following substances per liter: 10-2000mg of perfluorooctanoic acid, 10-200g of sodium persulfate;

preferably, in step S4-5, the suitable voltage is 0-2.0V.

9. The method for degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate according to claim 1, wherein: in step S5, air is introduced into the cathode chamber at a rate of 5 to 50 mL/min.

10. The method for degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate according to claim 1, wherein: in step S5, the suitable temperature is 10-50 deg.C and pH is 1-5.

Background

Perfluorooctanoic acid is a kind of perfluor compound, is an artificially synthesized organic matter, and its molecular formula is CF₃(CF₂)₆COOH. Due to its chemical stability,The perfluorooctanoic acid is commonly used as a polymerization dispersant for producing fluorine-containing compounds such as polytetrafluoroethylene, fluoropolymer and fluororubber since the 50 th 20 th century, is also used as a dispersant for polymerization of tetrafluoroethylene and production of fluororubber as a surfactant, an emulsifier, perfluorooctanoic acid and a sodium salt or ammonium salt thereof, and is also used as a raw material and a beneficiation agent for preparing water and oil increasing agents. The compounds are widely applied to producing articles essential in daily life, such as non-stick coatings, waterproof films, breathable clothes, wire casings, fire-resistant and oil-resistant pipes and the like. Although some countries and factories are beginning to ban the production and use of perfluorooctanoic acid, these fluorine-containing products are still in use, and with the widespread use of fluorine-containing compounds, perfluorooctanoic acid is continuously diffused into the environment, and due to its high stability and difficult degradability, one is beginning to monitor perfluorooctanoic acid in various environmental media and even in human bodies. The perfluoro caprylic acid can enter a human body through the contact of a respiratory tract, a digestive tract and skin, has an elimination half-life period of 3.8 years in the human body, can stay in the human body for a long time, has different degrees of influence on aspects of hormone secretion, an immune system, a female reproductive system, fetal development and the like of the human body, and is also researched and found to be mainly enriched in the liver and blood of the human body, thereby causing great threat to the health of human bodies.

Perfluorooctanoic acid has high stability mainly because all carbon-hydrogen bonds are replaced by fluorocarbon bonds, which have strong bond energy and high energy required for breaking. As humans find perfluorooctanoic acid persistent, bioaccumulating in the environment, and hazardous to humans and other living beings, the control and degradation of perfluorooctanoic acid is becoming a focus of public attention. Currently available methods for removing perfluorooctanoic acid from the environment include physical and chemical methods. Physical methods such as traditional reverse osmosis, activated carbon adsorption and the like can effectively remove perfluorooctanoic acid from water, but the perfluorooctanoic acid is not completely degraded and can be completely removed from the environment only by subsequent treatment. Chemical methods such as thermal decomposition, oxidant oxidation, photocatalytic oxidation, etc. require harsh processing conditions and high costs.

In view of the above, it is desirable to provide a novel perfluorooctanoic acid degradation method, which can effectively degrade perfluorooctanoic acid and improve the degradation efficiency.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for degrading perfluorooctanoic acid by coupling microbial electro-Fenton with sodium persulfate. In the method, microorganism electro-Fenton and sodium persulfate are coupled to form a perfluorooctanoic acid degradation system, and the degradation system can accelerate the degradation speed of perfluorooctanoic acid; the fermentation system can reach 99% of perfluorooctanoic acid degradation rate, the treatment condition is mild, and the perfluorooctanoic acid is degraded thoroughly.

In order to solve the technical problems, the invention adopts the following technical scheme:

a method for degrading perfluorooctanoic acid by coupling microbial electro-Fenton with sodium persulfate comprises the following steps:

s1, manufacturing an anode carbon brush and a cathode electrode required by the microbial electro-Fenton system, and preprocessing;

s2, preparing nutrient solution required by the growth of the electrogenesis microorganisms for culturing the electrogenesis microorganisms;

s3, adding anaerobic sludge and nutrient solution into the anode chamber of the reactor, introducing nitrogen into the reactor, and culturing and domesticating the electrogenic microorganisms by using a potassium ferricyanide solution as a cathode chamber;

s4, replacing the cathode solution of the reactor with the perfluorooctanoic acid solution after the anodic electrogenesis microorganism culture, adding sodium persulfate, and applying voltage to obtain the reactor for degrading the perfluorooctanoic acid by electro-Fenton coupling with the sodium persulfate;

s5, maintaining the reactor at a proper temperature, introducing air into the cathode chamber, and degrading the perfluorooctanoic acid under an aerobic condition.

In the present invention, the term "microbial electro-fenton" is a novel decontamination technology formed by combining fenton technology with microbial fuel cell technology. At the anode of the reactor, the electricity-generating microorganisms degrade organic matters (such as domestic wastewater) to generate electrons and protons, then the electrons and the protons are transferred to the cathode chamber through an external circuit and a proton exchange membrane respectively, and a two-electron oxygen reduction reaction is carried out in the cathode to realize in-situ peroxidationHydrogen production followed by hydrogen peroxide with Fe²⁺The reaction generates hydroxyl free radical, and the hydroxyl free radical with strong oxidizing property can oxidize refractory organic matters.

In the present invention, the term "electrogenic microorganisms" is mainly focused on Proteobacteria and Thelenota phyla, such as Bacillus, Pseudomonas, Rhodococcus, Shewanella, lactococcus, Escherichia coli, etc. The microorganisms generate electrons in the process of metabolizing organic matters and assist electron transfer through an electron transfer chain, and the electricity-generating microorganisms on the anode can be considered as cell mixtures with different functions, and can be used for power generation and proliferation as a power source of the cells.

In the invention, the term "anaerobic sludge" refers to sludge containing anaerobic bacteria community after anaerobic culture in an anaerobic reactor, thereby achieving good organic matter settleability. The method is mainly used for sewage treatment, can degrade various organic pollutants in the original wastewater, and is more economic in cost.

In the present invention, the term "anolyte" refers to a liquid in which the nutrient solution prepared is mixed with sludge in the anode chamber and which is suitable for the growth of electrogenic microorganisms.

As a further improvement of the technical solution, step S1 includes the following specific steps:

s1-1, processing the carbon fiber wire and the titanium wire with the diameter of 0.8-1.2mm into a carbon fiber brush, wherein the carbon fiber brush has a fixed size;

s1-2, 0.8-1.2 mol.L for the prepared carbon fiber brush^-1Soaking the mixture in NaOH solution for 5.5 to 6.5 hours to remove impurity ions;

s1-3, and further 1 mol. L^-1Soaking in HCl for 5.5-6.5h, and ultrasonically cleaning with deionized water to neutrality;

s1-4, boiling for 2.5-35 h by using deionized water, and replacing water every 30 min;

and S1-5, performing heating treatment by using a muffle furnace to obtain the anode carbon brush.

S1-6, cutting the graphite plate into squares of 4cm by 0.5 cm;

s1-7, firstly, soaking the mixture for 4.5 to 5.5 hours by using 1 mol. L-1 NaOH solution to remove impurity ions;

s1-8, soaking the graphite plate in 1 mol. L-1 HCl for 5.5-6.5h, and ultrasonically cleaning the graphite plate with deionized water to be neutral to obtain the graphite plate cathode electrode.

Preferably, in step S1-1, the fixed size refers to a carbon fiber brush length of 6cm and a diameter of 4 cm;

preferably, in the step S1-5, the muffle furnace treatment temperature is 480-520 ℃, and the treatment time is 8-12 minutes.

As a further improvement of the technical solution, in step S2, the nutrient solution has a formula containing the following substances per liter of solution: 3mg magnesium sulfate, 0.13mg zinc chloride, 0.005mg zinc sulfate heptahydrate, 1.5mg nitrilotriacetic acid, 0.5mg manganese sulfate monohydrate, 310mg ammonium chloride, 130mg potassium chloride, 0.01mg boric acid, 0.01mg cobalt chloride hexahydrate, 5mg nicotinic acid, 2mg folic acid, 0.01mg copper sulfate pentahydrate, 0.024mg nickel chloride hexahydrate, 0.024mg sodium tungstate dihydrate, 0.1mgB-12, 5mg vitamin B1, 6mg vitamin B2, 10mg vitamin B6, 6mg p-aminobenzoic acid, 2000mg glucose, 2000mg sodium acetate.

As a further improvement of the technical solution, step S3 includes the following specific steps:

s3-1, adopting anaerobic sludge at a concentration tank of a sewage treatment plant as inoculation sludge, settling the taken sludge, and pouring out supernatant;

s3-2, adding the sludge and the prepared nutrient solution into an anode chamber with a carbon fiber brush to form an anolyte;

s3-3, continuously introducing nitrogen into the anode chamber, removing oxygen in the anode chamber, and maintaining a strict anaerobic environment;

s3-4, using potassium ferricyanide solution (for example, 100mL) as catholyte;

s3-5, connecting the reactor and the external resistance in series to form a microbial fuel cell, and culturing and domesticating the electrogenic microbes at a proper temperature.

Preferably, in step S3-2, the pH of the anolyte is 7-7.5;

preferably, in step S3-2, the volume ratio of the sludge to the nutrient solution is 1:1 (e.g., 50mL each);

preferably, in the step S3-3, the nitrogen is introduced for 8-12 minutes;

preferably, in the step S3-4, the concentration of the potassium ferricyanide solution is 15-17 g/L;

preferably, in step S3-5, the suitable temperature is 30-37 ℃;

preferably, in step S3-5, the water inlet of the anode chamber is sealed by a rubber plug, and the anode chamber is maintained under anaerobic conditions for culturing;

preferably, in step S3-5, the external resistance in series with the reactor is 1000 Ω.

As a further improvement of the technical solution, step S4 includes the following specific steps:

s4-1, after the anode carbon brush culture is finished, discharging 1/2 of anolyte, and supplementing corresponding nutrient solution;

s4-2, preparing a perfluorooctanoic acid solution for degradation as a catholyte;

s4-3, injecting catholyte into the cathode chamber;

s4-4, connecting the reactor in series with a 10 omega external resistor;

and S4-5, applying a proper voltage to obtain the electro-Fenton coupling sodium persulfate degradation perfluorooctanoic acid reactor.

Preferably, in step S4-2, the catholyte includes the following per liter: 10-2000mg of perfluorooctanoic acid, 10-200g of sodium persulfate;

preferably, in step S4-5, the suitable voltage is 0-2.0V.

As a further improvement of the technical proposal, in the step S5, the air is introduced into the cathode chamber at the rate of 5-50 mL/min.

Preferably, in step S5, the suitable temperature is 10-50 deg.C and pH is 1-5.

In step S5 of the present invention, the following reaction may occur in the degradation process of the perfluorooctanoic acid:

2H⁺+O₂+2e^-→H₂O₂

Fe²⁺+H₂O₂+H⁺→Fe³⁺+·OH+H₂O

Fe³⁺+e^-→Fe²⁺

S₂O₈ ^2-→2SO₄ ^-

C₇F₁₅COO^-+SO₄ ^-→C₇F₁₅·+SO₄ ^2-+CO₂

C₇F₁₅·+HO·→C₇F₁₅OH

C₇F₁₅OH→C₆F₁₃COF+HF

C₆F₁₃COF+H₂O→C₆F₁₃COO^-+HF+H⁺

C₆F₁₃COO^-+SO₄ ^-→C₆F₁₃·+SO₄ ^2-+CO₂

C₆F₁₃·+HO·→C₆F₁₃OH

C₆F₁₃OH→C₅F₁₁COF+HF

C₅F₁₁COF+H₂O→C₅F₁₁COO^-+HF+H⁺

C₅F₁₁COO^-+SO₄ ^-→C₅F₁₁·+SO₄ ^2-+CO₂

C₅F₁₁·+HO·→C₅F₁₁OH

C₅F₁₁OH→C₄F₉COF+HF

C₄F₉COF+H₂O→C₄F₉COO^-+HF+H⁺

C₄F₉COO^-+SO₄ ^-→C₄F₉·+SO₄ ^2-+CO₂

C₄F₉·+HO·→C₄F₉OH

C₄F₉OH→C₃F₇COF+HF

C₃F₇COF+H₂O→C₃F₇COO^-+HF+H⁺

C₃F₇COO^-+SO₄ ^-→C₃F₇·+SO₄ ^2-+CO₂

C₃F₇·+HO·→C₃F₇OH

C₃F₇OH→C₂F₅COF+HF

C₂F₅COF+H₂O→C₂F₅COO^-+HF+H⁺

C₂F₅COO^-+SO₄ ^-→C₂F₅·+SO₄ ^2-+CO₂

C₂F₅·+HO·→C₂F₅OH

C₂F₅OH→CF₃COF+HF

CF₃COF+H₂O→CF₃COO^-+HF+H⁺。

any range recited herein is intended to include the endpoints and any number between the endpoints and any subrange subsumed therein or defined therein.

The starting materials of the present invention are commercially available, unless otherwise specified, and the equipment used in the present invention may be any equipment conventionally used in the art or may be any equipment known in the art.

Compared with the prior art, the invention has the following beneficial effects:

1) at present, the removal of perfluorooctanoic acid in a water body by a physical method has the defect of incomplete degradation, while chemical methods such as photocatalytic oxidation, thermal decomposition, electrocatalytic oxidation, oxidant oxidation and the like require harsh implementation conditions and high operation cost, and exercise products generated in the degradation process are incompletely mineralized to cause secondary pollution. The microbial electro-Fenton coupling sodium persulfate system has the advantages of mild reaction conditions, simple equipment structure and capability of efficiently degrading the perfluorooctanoic acid;

2) compared with the common Fenton method, the microbial electro-Fenton system is utilized, and hydrogen peroxide can be spontaneously generated by applying lower voltage without adding a large amount of hydrogen peroxide;

3) compared with the method for treating the perfluorooctanoic acid by using the sodium persulfate as the oxidizing agent, the activation of the sodium persulfate needs high temperature, so the activation cannot be carried out at room temperature, and the required amount of the sodium sulfate is large; the hydroxyl free radical generated by the microbial electro-Fenton system alone cannot degrade the perfluorooctanoic acid. Therefore, the system fuses the two components, sodium persulfate is used as a starter of the degradation reaction of the perfluorooctanoic acid, so that the sodium persulfate loses one electron, the hydroxyl radical can participate in the subsequent degradation reaction, and the synergistic effect of the two components achieves higher degradation efficiency of the perfluorooctanoic acid.

Detailed Description

In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

Example 1

A method for degrading perfluorooctanoic acid by coupling microbial electro-Fenton with sodium persulfate comprises the following steps:

1) processing the purchased carbon fiber wires and titanium wires with the diameter of 1mm into carbon fiber brushes, wherein the length of each carbon fiber brush is 6cm, and the diameter of each carbon fiber brush is 4 cm;

2) 1 mol. L is used for the prepared carbon fiber brush^-1Soaking the mixture in NaOH solution for 6 hours to remove impurity ions;

3) 1 mol. L is used for the carbon brush treated in the step 2)^-1Soaking in HCL for 6h, and ultrasonically cleaning with deionized water to neutrality;

4) boiling the carbon brush treated in the step 3) with deionized water for 3h, and replacing the water every 30 min;

5) heating the carbon brush treated in the step 4) by using a muffle furnace at 500 ℃ for 10 minutes to obtain an experimental carbon brush;

6) cutting the graphite plate into 4cm by 0.5cm squares, first using 1 mol. L^-1Soaking the mixture in NaOH solution for 5 hours to remove impurity ions; with 1 mol. L^-1Soaking the graphite plate in HCL for 6h, and ultrasonically cleaning the graphite plate to be neutral by using deionized water to obtain a graphite plate cathode required by an experiment;

7) anaerobic sludge and nutrient solution are added into the anode chamber of the reactor, nitrogen is introduced into the anode chamber, and the cathode chamber is potassium ferricyanide solution, so that the electrogenic microorganisms are cultured and domesticated. The formula of the nutrient solution is as follows: 3mg magnesium sulfate, 0.13mg zinc chloride, 0.005mg zinc sulfate heptahydrate, 1.5mg nitrilotriacetic acid, 0.5mg manganese sulfate monohydrate, 310mg ammonium chloride, 130mg potassium chloride, 0.01mg boric acid, 0.01mg cobalt chloride hexahydrate, 5mg nicotinic acid, 2mg folic acid, 0.01mg copper sulfate pentahydrate, 0.024mg nickel chloride hexahydrate, 0.024mg sodium tungstate dihydrate, 0.1mg B-12, 5mg vitamin B1, 6mg vitamin B2, 10mg vitamin B6, 6mg p-aminobenzoic acid, 2000mg glucose, 2000mg sodium acetate

8) Replacing the cathode solution of the reactor in which the domestication of the anode electrogenic bacteria is finished in the step 7) with a perfluorooctanoic acid solution, adding sodium persulfate, applying voltage, and introducing air into the cathode to obtain an electro-Fenton coupling sodium persulfate degradation perfluorooctanoic acid reactor;

in the step 8), the concentration of the perfluorooctanoic acid is 50 mg/L;

in the step 8), the voltage is 1.0V, the initial pH of the cathode is 3, and the temperature is 40 ℃; the aeration rate was 15 mL/min.

The analysis results of the intermediate product obtained by degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate and the perfluorooctanoic acid in the embodiment are shown in the following table 1:

table 1: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In the embodiment, the degradation temperature of the microbial electro-Fenton coupling sodium persulfate reactor is 40 ℃, 84% of perfluorooctanoic acid is degraded in 24 hours, the degradation rate is high, and the total degradation rate is 99%. In the degradation process, short-chain intermediate products are generated, including perfluoroheptanoic acid, perfluorohexanoic acid, perfluoropentanoic acid, heptafluorobutyric acid, pentafluoropropionic acid and fluoroacetic acid, and the intermediate products are rapidly degraded. The system can be seen to degrade the perfluorooctanoic acid more thoroughly, and has the advantages of high reaction rate and mild operating conditions.

Example 2

A method for degrading perfluorooctanoic acid by coupling microbial electro-Fenton with sodium persulfate comprises the following steps:

1) processing the purchased carbon fiber wires and titanium wires with the diameter of 1mm into carbon fiber brushes, wherein the length of each carbon fiber brush is 6cm, and the diameter of each carbon fiber brush is 4 cm;

2) 1 mol. L is used for the prepared carbon fiber brush^-1Soaking the mixture in NaOH solution for 6 hours to remove impurity ions;

3) 1 mol. L is used for the carbon brush treated in the step 2)^-1Soaking in HCL for 6h, and ultrasonically cleaning with deionized water to neutrality;

4) boiling the carbon brush treated in the step 3) with deionized water for 3h, and replacing the water every 30 min;

5) heating the carbon brush treated in the step 4) by using a muffle furnace at 500 ℃ for 10 minutes to obtain an experimental carbon brush;

6) cutting the graphite plate into 4cm by 0.5cm squares, first using 1 mol. L^-1Soaking the mixture in NaOH solution for 5 hours to remove impurity ions; with 1 mol. L^-1Soaking the graphite plate in HCL for 6h, and ultrasonically cleaning the graphite plate to be neutral by using deionized water to obtain a graphite plate cathode required by an experiment;

7) anaerobic sludge and nutrient solution are added into the anode chamber of the reactor, nitrogen is introduced into the anode chamber, and the cathode chamber is potassium ferricyanide solution, so that the electrogenic microorganisms are cultured and domesticated. The formula of the nutrient solution is as follows: 3mg magnesium sulfate, 0.13mg zinc chloride, 0.005mg zinc sulfate heptahydrate, 1.5mg nitrilotriacetic acid, 0.5mg manganese sulfate monohydrate, 310mg ammonium chloride, 130mg potassium chloride, 0.01mg boric acid, 0.01mg cobalt chloride hexahydrate, 5mg nicotinic acid, 2mg folic acid, 0.01mg copper sulfate pentahydrate, 0.024mg nickel chloride hexahydrate, 0.024mg sodium tungstate dihydrate, 0.1mgB-12, 5mg vitamin B1, 6mg vitamin B2, 10mg vitamin B6, 6mg p-aminobenzoic acid, 2000mg glucose, 2000mg sodium acetate

8) Replacing the cathode solution of the reactor in which the domestication of the anode electrogenic bacteria is finished in the step 7) with a perfluorooctanoic acid solution, adding sodium persulfate, applying voltage, and introducing air into the cathode to obtain an electro-Fenton coupling sodium persulfate degradation perfluorooctanoic acid reactor;

in the step 8), the concentration of the perfluorooctanoic acid is 50 mg/L;

in the step 8), the voltage is 1.0V, the initial pH of the cathode is 3, and the temperature is 10 ℃. The aeration rate was 15 mL/min.

The analysis results of the intermediate product obtained by degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate and the perfluorooctanoic acid in the embodiment are shown in the following table 2:

table 2: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In the embodiment, the degradation temperature of the microbial electro-Fenton coupling sodium persulfate reactor is 10 ℃, 52% of perfluorooctanoic acid is degraded within 24 hours, the degradation rate is much slower than that of the microbial electro-Fenton coupling sodium persulfate reactor at 40 ℃, and the total degradation rate is only 70%. The reduction in temperature slowed the activity of the electrogenic microorganisms at the anode compared to example 1, and the low temperature was also less favorable for the activation of sodium persulfate, thus resulting in a slower degradation rate.

Example 3

A method for degrading perfluorooctanoic acid by coupling microbial electro-Fenton with sodium persulfate comprises the following steps:

1) processing the purchased carbon fiber wires and titanium wires with the diameter of 1mm into carbon fiber brushes, wherein the length of each carbon fiber brush is 6cm, and the diameter of each carbon fiber brush is 4 cm;

2) 1 mol. L is used for the prepared carbon fiber brush^-1Soaking the mixture in NaOH solution for 6 hours to remove impurity ions;

3) 1 mol. L is used for the carbon brush treated in the step 2)^-1Soaking in HCL for 6h, and ultrasonically cleaning with deionized water to neutrality;

4) boiling the carbon brush treated in the step 3) with deionized water for 3h, and replacing the water every 30 min;

5) heating the carbon brush treated in the step 4) by using a muffle furnace at 500 ℃ for 10 minutes to obtain an experimental carbon brush;

6) cutting the graphite plate into 4cm by 0.5cm squares, first using 1 mol. L^-1Soaking the mixture in NaOH solution for 5 hours to remove impurity ions; with 1 mol. L^-1Soaking the graphite plate in HCL for 6h, and ultrasonically cleaning the graphite plate to be neutral by using deionized water to obtain a graphite plate cathode required by an experiment;

7) anaerobic sludge and nutrient solution are added into the anode chamber of the reactor, nitrogen is introduced into the anode chamber, and the cathode chamber is potassium ferricyanide solution, so that the electrogenic microorganisms are cultured and domesticated. The formula of the nutrient solution is as follows: 3mg magnesium sulfate, 0.13mg zinc chloride, 0.005mg zinc sulfate heptahydrate, 1.5mg nitrilotriacetic acid, 0.5mg manganese sulfate monohydrate, 310mg ammonium chloride, 130mg potassium chloride, 0.01mg boric acid, 0.01mg cobalt chloride hexahydrate, 5mg nicotinic acid, 2mg folic acid, 0.01mg copper sulfate pentahydrate, 0.024mg nickel chloride hexahydrate, 0.024mg sodium tungstate dihydrate, 0.1mgB-12, 5mg vitamin B1, 6mg vitamin B2, 10mg vitamin B6, 6mg p-aminobenzoic acid, 2000mg glucose, 2000mg sodium acetate

8) Replacing the cathode solution of the reactor in which the domestication of the anode electrogenic bacteria is finished in the step 7) with a perfluorooctanoic acid solution, adding sodium persulfate, applying voltage, and introducing air into the cathode to obtain an electro-Fenton coupling sodium persulfate degradation perfluorooctanoic acid reactor;

in the step 8), the concentration of the perfluorooctanoic acid is 50 mg/L;

in the step 8), the voltage is 1.0V, the initial pH of the cathode is 3, and the temperature is 20 ℃. The aeration rate was 15 mL/min.

The analysis results of the intermediate product obtained by degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate and the perfluorooctanoic acid in the present example are shown in table 3 below:

table 3: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In the embodiment, the degradation temperature of the microbial electro-Fenton coupling sodium persulfate reactor is 20 ℃, 61% of perfluorooctanoic acid is degraded within 24 hours, the degradation rate is slower than that at the temperature of 40 ℃, and the total degradation rate is only 78%. The reduction in temperature slowed the activity of the electrogenic microorganisms at the anode, and the lower temperature was also less favorable for the activation of sodium persulfate, compared to example 1, thus resulting in a slower degradation rate.

Example 4

A method for degrading perfluorooctanoic acid by coupling microbial electro-Fenton with sodium persulfate comprises the following steps:

1) processing the purchased carbon fiber wires and titanium wires with the diameter of 1mm into carbon fiber brushes, wherein the length of each carbon fiber brush is 6cm, and the diameter of each carbon fiber brush is 4 cm;

2) 1 mol. L is used for the prepared carbon fiber brush^-1Soaking the mixture in NaOH solution for 6 hours to remove impurity ions;

3) 1 mol. L is used for the carbon brush treated in the step 2)^-1Soaking in HCL for 6h, and ultrasonically cleaning with deionized water to neutrality;

4) boiling the carbon brush treated in the step 3) with deionized water for 3h, and replacing the water every 30 min;

5) heating the carbon brush treated in the step 4) by using a muffle furnace at 500 ℃ for 10 minutes to obtain an experimental carbon brush;

6) cutting the graphite plate into 4cm by 0.5cm squares, first using 1 mol. L^-1Soaking the mixture in NaOH solution for 5 hours to remove impurity ions; with 1 mol. L^-1Soaking the graphite plate in HCL for 6h, and ultrasonically cleaning the graphite plate to be neutral by using deionized water to obtain a graphite plate cathode required by an experiment;

7) anaerobic sludge and nutrient solution are added into the anode chamber of the reactor, nitrogen is introduced into the anode chamber, and the cathode chamber is potassium ferricyanide solution, so that the electrogenic microorganisms are cultured and domesticated. The formula of the nutrient solution is as follows: 3mg magnesium sulfate, 0.13mg zinc chloride, 0.005mg zinc sulfate heptahydrate, 1.5mg nitrilotriacetic acid, 0.5mg manganese sulfate monohydrate, 310mg ammonium chloride, 130mg potassium chloride, 0.01mg boric acid, 0.01mg cobalt chloride hexahydrate, 5mg nicotinic acid, 2mg folic acid, 0.01mg copper sulfate pentahydrate, 0.024mg nickel chloride hexahydrate, 0.024mg sodium tungstate dihydrate, 0.1mgB-12, 5mg vitamin B1, 6mg vitamin B2, 10mg vitamin B6, 6mg p-aminobenzoic acid, 2000mg glucose, 2000mg sodium acetate

8) Replacing the cathode solution of the reactor in which the domestication of the anode electrogenic bacteria is finished in the step 7) with a perfluorooctanoic acid solution, adding sodium persulfate, applying voltage, and introducing air into the cathode to obtain an electro-Fenton coupling sodium persulfate degradation perfluorooctanoic acid reactor;

in the step 8), the concentration of the perfluorooctanoic acid is 50 mg/L;

in the step 8), the voltage is 1.0V, the initial pH of the cathode is 3, and the temperature is 30 ℃. The aeration rate was 15 mL/min.

The analysis results of the intermediate product obtained by degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate and the perfluorooctanoic acid in the present example are shown in table 4 below:

table 4: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In the embodiment, the degradation temperature of the microbial electro-Fenton coupling sodium persulfate reactor is 30 ℃, 66% of perfluorooctanoic acid is degraded within 24 hours, the degradation rate is slower than that of the microbial electro-Fenton coupling sodium persulfate reactor at 40 ℃ and is improved compared with that of the microbial electro-Fenton coupling sodium persulfate reactor at 20 ℃, and the total degradation rate reaches 95%.

Example 5

A method for degrading perfluorooctanoic acid by coupling microbial electro-Fenton with sodium persulfate comprises the following steps:

1) processing the purchased carbon fiber wires and titanium wires with the diameter of 1mm into carbon fiber brushes, wherein the length of each carbon fiber brush is 6cm, and the diameter of each carbon fiber brush is 4 cm;

2) 1 mol. L is used for the prepared carbon fiber brush^-1Soaking the mixture in NaOH solution for 6 hours to remove impurity ions;

3) 1 mol. L is used for the carbon brush treated in the step 2)^-1Soaking in HCL for 6h, and ultrasonically cleaning with deionized water to neutrality;

4) boiling the carbon brush treated in the step 3) with deionized water for 3h, and replacing the water every 30 min;

5) heating the carbon brush treated in the step 4) by using a muffle furnace at 500 ℃ for 10 minutes to obtain an experimental carbon brush;

6) cutting the graphite plate into 4cm by 0.5cm squares, first using 1 mol. L^-1Soaking the mixture in NaOH solution for 5 hours to remove impurity ions; with 1 mol. L^-1Soaking the graphite plate in HCL for 6h, and ultrasonically cleaning the graphite plate to be neutral by using deionized water to obtain a graphite plate cathode required by an experiment;

7) anaerobic sludge and nutrient solution are added into the anode chamber of the reactor, nitrogen is introduced into the anode chamber, and the cathode chamber is potassium ferricyanide solution, so that the electrogenic microorganisms are cultured and domesticated. The formula of the nutrient solution is as follows: 3mg magnesium sulfate, 0.13mg zinc chloride, 0.005mg zinc sulfate heptahydrate, 1.5mg nitrilotriacetic acid, 0.5mg manganese sulfate monohydrate, 310mg ammonium chloride, 130mg potassium chloride, 0.01mg boric acid, 0.01mg cobalt chloride hexahydrate, 5mg nicotinic acid, 2mg folic acid, 0.01mg copper sulfate pentahydrate, 0.024mg nickel chloride hexahydrate, 0.024mg sodium tungstate dihydrate, 0.1mgB-12, 5mg vitamin B1, 6mg vitamin B2, 10mg vitamin B6, 6mg p-aminobenzoic acid, 2000mg glucose, 2000mg sodium acetate

8) Replacing the cathode solution of the reactor in which the domestication of the anode electrogenic bacteria is finished in the step 7) with a perfluorooctanoic acid solution, adding sodium persulfate, applying voltage, and introducing air into the cathode to obtain an electro-Fenton coupling sodium persulfate degradation perfluorooctanoic acid reactor;

in the step 8), the concentration of the perfluorooctanoic acid is 50 mg/L;

in the step 8), the voltage is 1.0V, the initial pH of the cathode is 3, and the temperature is 50 ℃. The aeration rate was 15 mL/min.

The analysis results of the intermediate product obtained by degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate and the perfluorooctanoic acid in the present example are shown in table 5 below:

table 5: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In the embodiment, the degradation temperature of the microbial electro-Fenton coupling sodium persulfate reactor is 50 ℃, 68% of perfluorooctanoic acid is degraded within 24 hours, the degradation rate is slower than that of 40 ℃, and the reason may be that the power generation bacteria die due to overhigh temperature and the hydrogen peroxide production capacity of the system is reduced.

Example 6

A method for degrading perfluorooctanoic acid by coupling microbial electro-Fenton with sodium persulfate comprises the following steps:

1) processing the purchased carbon fiber wires and titanium wires with the diameter of 1mm into carbon fiber brushes, wherein the length of each carbon fiber brush is 6cm, and the diameter of each carbon fiber brush is 4 cm;

2) 1 mol. L is used for the prepared carbon fiber brush^-1Soaking the mixture in NaOH solution for 6 hours to remove impurity ions;

3) 1 mol. L is used for the carbon brush treated in the step 2)^-1Soaking in HCL for 6h, and ultrasonically cleaning with deionized water to neutrality;

4) boiling the carbon brush treated in the step 3) with deionized water for 3h, and replacing the water every 30 min;

5) heating the carbon brush treated in the step 4) by using a muffle furnace at 500 ℃ for 10 minutes to obtain an experimental carbon brush;

6) cutting the graphite plate into 4cm by 0.5cm squares, first using 1 mol. L^-1Soaking the mixture in NaOH solution for 5 hours to remove impurity ions; with 1 mol. L^-1Soaking the graphite plate in HCL for 6h, and ultrasonically cleaning the graphite plate to be neutral by using deionized water to obtain a graphite plate cathode required by an experiment;

7) anaerobic sludge and nutrient solution are added into the anode chamber of the reactor, nitrogen is introduced into the anode chamber, and the cathode chamber is potassium ferricyanide solution, so that the electrogenic microorganisms are cultured and domesticated. The formula of the nutrient solution is as follows: 3mg magnesium sulfate, 0.13mg zinc chloride, 0.005mg zinc sulfate heptahydrate, 1.5mg nitrilotriacetic acid, 0.5mg manganese sulfate monohydrate, 310mg ammonium chloride, 130mg potassium chloride, 0.01mg boric acid, 0.01mg cobalt chloride hexahydrate, 5mg nicotinic acid, 2mg folic acid, 0.01mg copper sulfate pentahydrate, 0.024mg nickel chloride hexahydrate, 0.024mg sodium tungstate dihydrate, 0.1mgB-12, 5mg vitamin B1, 6mg vitamin B2, 10mg vitamin B6, 6mg p-aminobenzoic acid, 2000mg glucose, 2000mg sodium acetate

8) Replacing the cathode solution of the reactor in which the domestication of the anode electrogenic bacteria is finished in the step 7) with a perfluorooctanoic acid solution, adding sodium persulfate, applying voltage, and introducing air into the cathode to obtain an electro-Fenton coupling sodium persulfate degradation perfluorooctanoic acid reactor;

in the step 8), the concentration of the perfluorooctanoic acid is 50 mg/L;

in the step 8), the voltage is 2.0V, the initial pH of the cathode is 3, and the temperature is 40 ℃. The aeration rate was 15 mL/min.

The analysis results of the intermediate product obtained by degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate and the perfluorooctanoic acid in the present example are shown in table 6 below:

table 6: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In the embodiment, the applied voltage of the microbial electro-Fenton coupling sodium persulfate reactor is 2.0V, 60% of perfluorooctanoic acid is degraded within 24 hours, the degradation rate is reduced compared with that when the applied voltage is 1.0V, and the total degradation rate is 77%.

Example 7

Example 1 was repeated with the difference that in step 8) the microbial electro-fenton coupling to the sodium persulfate reactor cathode had an initial pH of 1.

The analysis results of the intermediate product obtained by degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate and the perfluorooctanoic acid in the present example are shown in table 7 below:

table 7: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In this example, the initial cathode pH of the microbial electro-fenton coupled sodium persulfate reactor was 1, 64% of the perfluorooctanoic acid was degraded within 24 hours, the degradation rate was slower than that when the initial cathode pH was 3, and the total degradation rate was 89%.

Example 8

Example 1 was repeated with the difference that in step 8) the microbial electro-fenton coupling was carried out at an initial pH of 5 with the cathode of the sodium persulfate reactor.

The analysis results of the intermediate product obtained by degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate and the perfluorooctanoic acid in the present example are shown in table 8 below:

table 8: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In this example, the initial cathode pH of the microbial electro-fenton coupled sodium persulfate reactor was 5, 66% of the perfluorooctanoic acid was degraded within 24 hours, the degradation rate was slower than that of the case where the initial cathode pH was 3 in example 1, and the total degradation rate was 92%.

Example 9

Example 1 was repeated, with the difference that in step 8) the cathode aeration rate of the microbial electro-fenton coupled sodium persulfate reactor was 5 ml/min.

The analysis results of the intermediate product obtained by degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate and the perfluorooctanoic acid in this example are shown in table 9 below:

table 9: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In the embodiment, the cathode ventilation rate of the microbial electro-Fenton coupling sodium persulfate reactor is 5ml/min, 60% of perfluorooctanoic acid is degraded within 24 hours, the degradation rate is lower than that of the cathode ventilation rate of 15ml/min in the embodiment 1, and the total degradation rate is 81%.

Example 10

Example 1 was repeated with the difference that in step 8) the cathode aeration rate of the microbial electro-fenton coupled sodium persulfate reactor was 25 ml/min. The analysis results of the intermediate product obtained by degrading perfluorooctanoic acid by coupling microbial electro-fenton with sodium persulfate and the perfluorooctanoic acid in this example are shown in table 10 below:

table 10: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In the embodiment, the cathode ventilation rate of the microbial electro-Fenton coupling sodium persulfate reactor is 25ml/min, 65% of perfluorooctanoic acid is degraded within 24 hours, the degradation rate is lower than that of the cathode ventilation rate of 15ml/min in the embodiment 1, and the total degradation rate is 83%.

Comparative example 1

Example 1 was repeated, with the difference that in step 8), no sodium persulfate was added to the catholyte in the microbial electro-fenton reactor.

The intermediate product of the microbial electro-fenton reactor for degrading perfluorooctanoic acid and the analysis results of perfluorooctanoic acid are shown in the following table 11:

table 11: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In this comparative example, the catholyte of the microbial electro-fenton reactor was not added with sodium persulfate, 9% of the perfluorooctanoic acid was degraded within 24 hours, and was hardly degraded after 6 hours, and the degradation rate of the perfluorooctanoic acid was greatly reduced compared to example 1 because the hydroxyl radical was inert to the degradation of the perfluorooctanoic acid.

Comparative example 2

Example 1 was repeated with the difference that in step 8) the applied voltage was 0V, i.e. no applied voltage.

The analysis results of the intermediate product of the microbial electro-fenton coupled sodium persulfate reactor for degrading the perfluorooctanoic acid and the perfluorooctanoic acid in the comparative example are shown in the following table 12:

table 12: analysis results of perfluorooctanoic acid and intermediate products in the reactor

In the comparative example, the microbial electro-Fenton coupling sodium persulfate reactor has no external voltage, 64 percent of perfluorooctanoic acid is degraded within 24 hours, the degradation rate is slower than that of example 1 when the external voltage is 1.0V, and the total degradation rate is 84 percent.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Not all embodiments are exhaustive. All obvious changes and modifications which are obvious to the technical scheme of the invention are covered by the protection scope of the invention.