CN105217800A - Graphene/polypyrrole bioelectrode and preparation method and application thereof - Google Patents

Abstract

The invention discloses a preparation method of a graphene/polypyrrole bioelectrode, comprising the following steps: (1) dispersing graphene oxide in water, adding polypyrrole, stirring evenly, adding an oxidant, and reacting to obtain graphene oxide/polypyrrole solution, then filtered and dried to obtain graphene oxide/polypyrrole powder; (2) adding graphene oxide/polypyrrole powder into the medium of dissimilar metal-reducing bacteria, immersing the carbon cloth electrode in it, and then inoculating it with dissimilar metal-reducing bacteria , stirring and reacting for 3 to 4 days, repeating the above steps twice to obtain a graphene/polypyrrole bioelectrode. The invention also discloses the application of using the graphene/polypyrrole bioelectrode as a cathode of a biobattery to reduce hexavalent chromium in electrolyte. The invention constructs a biocathode with high catalytic efficiency and strong tolerance, improves the biocatalysis activity and electron transfer rate of the cathode, and strengthens the ability of bioelectrochemical removal of hexavalent chromium in water.

Description

A kind of graphene/polypyrrole bioelectrode and its preparation method and application

technical field

The invention belongs to the technical field of electrode materials, and in particular relates to the preparation of a biological electrode and its application in removing hexavalent chromium in groundwater.

Background technique

Chromium and its compounds are important basic raw materials in the fields of chemical industry, light industry, and alloy materials. They are widely used in petroleum refining, electroplating, chromium production, battery manufacturing, and metallurgy. During this process, a large amount of chromium-rich wastewater will be produced. , into the soil through discharge, which further causes serious environmental pollution in groundwater. Chromium generally exists in the form of trivalent chromium and hexavalent chromium in groundwater, and hexavalent chromium is a carcinogen, its toxicity is much higher than that of trivalent chromium, and because of its high solubility and mobility in the environment, it is easy to pass through ingestion , Inhalation or skin contact invades the human body, causing a large number of diseases and diseases, such as damage to the psychological or central nervous function, damage to the lungs, kidneys, liver and other vital organs of the human body. Therefore, hexavalent chromium is identified as the first category of pollutants in my country's industrial wastewater discharge standards, and the US Environmental Protection Agency (EPA) also lists it as a highly dangerous toxic substance. Therefore, the development of effective technologies to remove Cr(VI) from groundwater is necessary for public health and ecosystem safety.

Usually, the treatment method of chromium in groundwater is to reduce hexavalent chromium to non-toxic trivalent chromium by chemical method or electrolytic method, and the solubility of trivalent chromium in water is very low, and it is easy to form precipitation, so as to achieve the purpose of removal. The chemical method to treat chromium-containing wastewater is to use a reducing agent to reduce hexavalent chromium to trivalent chromium precipitation under acidic conditions. These reactions are required to be carried out under acidic conditions, which may easily cause secondary pollution of the water body, and the cost of the reducing agent is high and cannot be reused. The electrolytic treatment of chromium-containing wastewater is generally carried out under acidic conditions. It uses the electrons generated by the electrolysis of water at the anode to transfer to the cathode to reduce hexavalent chromium, but the electrolysis of the anode water requires a high oxidation-reduction potential, which will consume a lot of energy. . Other treatment methods such as ion exchange, membrane separation, and biosorption have also been used to remove Cr(VI) from water. Although these methods have certain effects on the removal of hexavalent chromium, they require additional chemical consumption or high energy input, and even produce certain secondary pollution, which limits the wide application of these technologies.

In recent years, bioelectrochemical technology (BES, bioelectrochemical systems), formed by the intersection of environmental microbiology and electrochemistry, has broad application prospects in environmental governance and waste resource utilization. BES usually divides the reactor into an anode chamber and a cathode chamber by a proton exchange membrane. The metal oxide can be used as the final electron acceptor of respiration (reduction process), and the electrons generated during the oxidation of the substrate (organic matter) can be transferred to the anode, and then reach the cathode through an external circuit, and react with electron acceptors such as oxygen , so as to complete the entire chemical redox reaction and generate current in the external circuit. Recent studies have found that hexavalent chromium ions can also be used as cathode electron acceptors in bioelectrochemical systems, thereby being reduced to non-toxic trivalent chromium. Compared with existing chromium-containing wastewater treatment technologies, it does not require additional investment. Adding a reducing agent or additional energy input, but using the electrons provided by the organic matter in the anodic oxidation wastewater to reduce the hexavalent chromium in the cathode, while treating the organic matter in the wastewater, the hexavalent chromium is also reduced, and it is possible to treat waste with waste. Researchers pay attention. However, in the current bioelectrochemical system to reduce hexavalent chromium, the chemical cathode is only under acidic conditions to achieve a high hexavalent chromium removal effect, and it needs to consume a large amount of alkaline solution to adjust it to neutral to meet the standard. , limiting its further application.

Contents of the invention

The technical problem to be solved by the present invention is to provide a graphene/polypyrrole bioelectrode.

The technical problem to be solved by the present invention is to provide the preparation method of the above-mentioned graphene/polypyrrole bioelectrode.

The final technical problem to be solved by the present invention is to provide the application of the above-mentioned graphene/polypyrrole bioelectrode in removing hexavalent chromium in groundwater.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A kind of preparation method of graphene/polypyrrole bioelectrode, comprises the steps:

(1) disperse graphene oxide in water, add polypyrrole, stir evenly, add oxidizing agent, react to obtain graphene oxide/polypyrrole solution, then filter, dry to obtain graphene oxide/polypyrrole powder, described drying is in Dry at 50°C for 16 hours under vacuum;

(2) Add the graphene oxide/polypyrrole powder obtained in step (1) into the dissimilatory metal-reducing bacteria culture medium, immerse the carbon cloth electrode in it, then inoculate the dissimilatory metal-reducing bacteria into it, and react for 3 to 4 days under stirring conditions , the stirring reaction, the stirring speed is 200rpm, the reaction temperature is 25 ° C, the carbon cloth electrode is taken out, and the above steps are repeated twice, and the obtained carbon cloth electrode is a graphene/polypyrrole bioelectrode.

In step (1), the concentration of graphene oxide in water is 2 to 5 mg/ml, the mass ratio of polypyrrole to graphene oxide is 1 to 4:1, the oxidant is FeCl ₃ , and the amount of oxidant added is 50 ~100 mg/ml, preferably 75 mg/ml.

In step (2), the dissimilating metal-reducing bacteria is one or a mixture of Pseudomonas, Geobacter, and iron-reducing bacteria, and the Pseudomonas is preferably Pseudomonas AeruginosaATCC39324, and the ground The bacillus is preferably GeobactersulfurreducensATCC51573, and the iron-reducing bacteria is preferably RhodoferaxferrireducensATCCBAA-621; the inoculation amount of the dissimilating metal-reducing bacteria is 1%-10% of the volume of the dissimilating metal-reducing bacteria culture medium.

Above-mentioned Pseudomonas, Geobacter, iron-reducing bacteria are cultured as follows:

Take glucose 0.5~1g/L, NH ₄ Cl 0.1~0.4g/L, NaH ₂ PO ₄ 1~5g/L, Na ₂ HPO ₄ 2~5g/L, KCl 0.1~0.3g/L, pH= 6.5～7.5, the solvent is water, after mixing evenly, it is sterilized by autoclave to obtain the culture medium; The desired Pseudomonas, Geobacter, and iron-reducing bacteria were obtained after culturing for 48 hours under the condition of 1 min.

In step (2), the concentration of the graphene oxide/polypyrrole powder in the dissimilatory metal-reducing bacteria medium is 0.1-1 mg/ml.

The graphene/polypyrrole bioelectrode prepared by the above method for preparing the graphene/polypyrrole bioelectrode falls within the protection scope of the present invention.

The application of the above-mentioned graphene/polypyrrole bioelectrode in electrode removal of hexavalent chromium in water is within the protection scope of the present invention.

Preferably, the graphene/polypyrrole bioelectrode is used as the cathode of the biobattery to reduce hexavalent chromium in the catholyte.

Further, the microbial electrochemical device is constructed by the following method:

A proton exchange membrane is used to separate the reactor into a cathode chamber and an anode chamber. The graphene/polypyrrole _bioelectrode is used as the cathode, and the carbon cloth is used as the anode. The reactor is connected to a resistor. The electrolyte in the anode chamber contains a Shewanella, carbon source, 50 mM phosphate buffer at pH 7.0. It is also possible to replace the carbon source with industrial organic wastewater, which can achieve the purpose of treating waste with waste; the Shewanella bacterium is Shewanella MR-1, ATCC700550.

The carbon source is 5-20 mmol/l sodium lactate.

Beneficial effect:

1) The self-assembly of graphene/polypyrrole bioelectrode by using dissimilatory metal-reducing bacteria simplifies the problem of modification on the electrode.

2) Combining graphene/polypyrrole with strong electronic conductivity, good biocompatibility and the function of capturing microorganisms during the reduction of graphene oxide to construct a biocathode with high catalytic efficiency and strong tolerance, which is helpful for improving the biocatalytic activity of the cathode And electron transfer rate, enhanced bioelectrochemical removal of hexavalent chromium in water will have a positive effect.

3) Propose a set of bio-technology for efficient removal of hexavalent chromium in water, which uses electrons generated by organic matter in water during anodic oxidation and transfers them to the biocathode to achieve the purpose of quickly removing hexavalent chromium in groundwater.

Description of drawings

Figure 1 is a schematic diagram of the structure of a graphene/polypyrrole bioelectrode.

Figure 2 is a schematic diagram of the graphene/polypyrrole bioelectrode used as a cathode to remove hexavalent chromium in groundwater in a bioelectrochemical device; the marks in the figure are as follows: 1, resistance, 2 anode chamber, 3 cathode chamber, 4 anode, 5 cathode , 6 proton exchange membrane.

Fig. 3 is an output power diagram of the graphene/polypyrrole bioelectrodes of Examples 1-3 of the present invention and unmodified carbon cloth (comparison group).

Fig. 4 shows the effect of removing hexavalent chromium in water by the graphene/polypyrrole bioelectrodes and unmodified carbon cloth (comparison group) of Examples 1-3 of the present invention.

detailed description

The present invention can be better understood from the following examples. However, those skilled in the art can easily understand that the content described in the embodiments is only for illustrating the present invention, and should not and will not limit the present invention described in the claims.

The dissimilating metal-reducing bacteria used in the following examples are Pseudomonas Aeruginosa (ATCC39324), Geobacter sulfurreducens (ATCC51573), and Iron-reducing bacteria (Rhodoferax ferrireducens, ATCC BAA-621).

The cultivation method of dissimilatory metal-reducing bacteria is as follows: take glucose 0.5~1g/L, NH ₄ Cl 0.1~0.4g/L, NaH ₂ PO ₄ 1~5g/L, Na ₂ HPO ₄ 2~5g/L, KCl0. 1～0.3g/L, pH=6.5～7.5, the solvent is water, after mixing evenly, it is sterilized by autoclave to obtain the culture medium; The desired dissimilatory metal-reducing bacteria were obtained after culturing at a temperature of 37°C and a rotational speed of 250r/min for 48 hours.

The Shewanella used in the following examples is (ShewanellaMR-1, ATCC700550), and the cultivation method of Shewanella is as follows:

Take 10mM sodium lactate, 50mM phosphate buffer solution, pH7.0, the solvent is water, mix well, and then sterilize in an autoclave to obtain the culture medium; The required Shewanella bacteria were obtained after culturing for 48 hours at a temperature of 37° C. and a rotational speed of 250 r/min.

Example 1:

A kind of preparation method of graphene/polypyrrole bioelectrode, concrete preparation steps are as follows:

(1) Take the graphene oxide powder and disperse it with deionized water to prepare a graphene oxide solution with a concentration of 2 mg/ml, and then put the dispersion into an ultrasonic cleaning machine for ultrasonic treatment for 30 min. Then polypyrrole was added to the graphene oxide dispersion at a mass ratio of 1:1 to graphene oxide, then stirred for 2 h, then 5 g of FeCl was added as an oxidant, and further stirred for ₃ h. The final product was filtered, washed three times with deionized water, and dried under vacuum at 50° C. for 16 h to obtain graphene oxide/polypyrrole powder.

(2) Take graphene oxide/polypyrrole powder and add it to the culture medium of dissimilatory metal-reducing bacteria to obtain a graphene oxide/polypyrrole dispersion with a concentration of 0.2 mg/ml, and then completely immerse the carbon cloth electrode in the dispersion , and the dissimilatory metal-reducing bacteria were inserted into the solution according to the volume ratio of the solution at 1%, and stirred at 25°C and 200rpm for 4 days, the electrode and the solution turned black, and the carbon cloth electrode was taken out, and the above steps were repeated twice, Finally, a graphene/polypyrrole bioelectrode is obtained.

Example 2:

A kind of preparation method of graphene/polypyrrole bioelectrode, concrete preparation steps are as follows:

(1) Take the graphene oxide powder and disperse it with deionized water to prepare a graphene oxide solution with a concentration of 3 mg/ml, and then put the dispersion into an ultrasonic cleaner for ultrasonic treatment for 30 min. Then polypyrrole was added to the graphene oxide dispersion at a mass ratio of 2:1 to graphene oxide, then stirred for 2 h, and then ₅ g of FeCl was added as an oxidant, and further stirred for 4 h. The final product was filtered, washed three times with deionized water, and dried under vacuum at 50° C. for 16 h to obtain graphene oxide/polypyrrole powder.

(2) Get the graphene oxide/polypyrrole powder and add it to the dissimilatory metal-reducing bacteria culture medium to obtain a graphene oxide polypyrrole dispersion with a concentration of 0.8mg/ml, and then completely immerse the carbon cloth electrode in the dispersion, And the inoculum containing dissimilatory metal-reducing bacteria is inserted into the solution according to the volume ratio of the solution at 8%, and stirred for 3 days, the electrode and the solution both turn black, and the solution is replaced with the dissimilatory metal-reducing bacteria culture medium for reaction 4 Days, repeated two cycles, and finally obtained a graphene/polypyrrole bioelectrode.

Example 3:

A kind of preparation method of graphene/polypyrrole bioelectrode, concrete preparation steps are as follows:

(1) Take the graphene oxide powder and disperse it with deionized water to prepare a graphene oxide solution with a concentration of 4 mg/ml, and then put the dispersion into an ultrasonic cleaner for ultrasonic treatment for 30 min. Then polypyrrole and graphene oxide mass ratio are (3:1) join in graphene oxide dispersion liquid, then stir 4h, then add 5g of FeCl ₃ as oxidant again, and further stir 3h. The final product was filtered, washed three times with deionized water, and dried under vacuum at 50° C. for 16 h to obtain graphene oxide/polypyrrole powder.

(2) Add the graphene oxide/polypyrrole powder into the dissimilatory metal-reducing bacteria medium to obtain a graphene oxide polypyrrole dispersion with a concentration of 0.5 mg/ml, and then completely immerse the carbon cloth electrode in the dispersion, And the inoculum containing dissimilatory metal-reducing bacteria is inserted into the solution at a volume ratio of 5%, and stirred for 4 days, and both the electrode and the solution turn black, and the solution is replaced with the dissimilatory metal-reducing bacteria culture medium for reaction 4 Days, repeated two cycles, and finally obtained a graphene/polypyrrole bioelectrode.

The formation process and structure of the graphene/polypyrrole bioelectrode in Examples 1 to 3 are shown in Figure 1, and its effect evaluation when used as a cathode material of a bioelectrochemical device for removal of hexavalent chromium in groundwater is as follows:

The schematic diagram of bioelectrochemical device is as shown in Figure 2, and wherein, 1 is resistance, 2 is anode chamber, 3 is cathode chamber, 4 is carbon cloth anode, 5 is the graphene/polypyrrole biocathode prepared by the present invention, 6 is proton exchange membrane.

The specific assembly steps and operation of the bioelectrochemical device are as follows:

(1) Put the carbon cloth anode and the prepared graphene/polypyrrole biocathode into the anode chamber and the cathode chamber respectively.

(2) Add Shewanella bacteria and 10 mmol/l sodium lactate phosphate buffer solution into the anode chamber to adjust the pH to 7.

The cathode compartment is filled with a simulated groundwater solution containing hexavalent chromium with a concentration of 40 mg/l and a pH of 7.

Connect the above bioelectrochemical device to a 1000 ohm resistor and run the bioelectrochemical system. Then samples were taken regularly to measure the removal changes of hexavalent chromium.

The graphene/polypyrrole biocathode prepared by 1～3 in the embodiment is compared with the unmodified carbon cloth (contrast group), and its output power result is as shown in Figure 3, thus it can be seen that, by the embodiment 1～3 The maximum power of the prepared graphene/polypyrrole bioelectrode is 1.06mW/m ³ , 1.61mW/m ³ , 1.89mW/m ³ , and the maximum power of the unmodified carbon cloth electrode is only 0.35mW/m ³ , Example 1 ～3 The maximum power of graphene/polypyrrole bioelectrode prepared is 3.0 times, 4.6 times and 5.4 times that of unmodified carbon cloth electrode. The removal effect of the four kinds of electrodes on the removal of hexavalent chromium in water was further analyzed. It can be seen from Figure 4 that the removal rate of the unmodified carbon cloth electrode was only 15% after 48 hours of reaction, while the graphene/polypyrrole bioelectrode effect The removal rates of hexavalent chromium were significantly enhanced. After 48 hours of reaction, the removal rates of hexavalent chromium of the graphene/polypyrrole bioelectrodes prepared in Examples 1-3 reached 70%, 85%, and 95%, respectively. It can be seen that the graphene/polypyrrole bioelectrode not only improves the electricity production of the bioelectrochemical device, but also improves the reduction rate of the electrode for hexavalent chromium under neutral conditions.

Example 4:

Use the electrons generated by anodizing the actual wastewater to remove the hexavalent chromium in the cathode. The specific method is as follows:

The preparation of the graphene/polypyrrole bioelectrode is the same as in Example 3, and the assembly of the bioelectrochemical device is shown in FIG. 2 . The specific assembly steps and operation of the bioelectrochemical device are as follows:

(1) Put the carbon cloth anode and the prepared graphene/polypyrrole biocathode into the anode chamber and the cathode chamber respectively.

(2) Add Shewanella bacteria and actual domestic sewage (COD at 1000mg/l) into the anode chamber, and adjust the pH to 7.

The cathode compartment is filled with a simulated groundwater solution containing hexavalent chromium with a concentration of 40 mg/l and a pH of 7.

Connect the above bioelectrochemical device to a 1000 ohm resistor and run the bioelectrochemical system. Then samples were taken regularly to measure the removal changes of hexavalent chromium. After 48 hours of reaction, the COD removal rate of the wastewater in the anode reached 80%, the generated output power was 1.4mW/m ³ , and the removal rate of hexavalent chromium reached 82%. It shows that hexavalent chromium can be reduced while treating the organic matter in wastewater, and the effect of treating waste with waste can be achieved.

Claims (10)

1. a preparation method for Graphene/polypyrrole bioelectrode, is characterized in that, comprise the steps:

(1) graphene oxide is dispersed in water, adds polypyrrole, stir, add oxygenant, be obtained by reacting graphene oxide/polypyrrole solution, refilter, drying obtains graphene oxide/polypyrrole powder;

(2) graphene oxide/polypyrrole powder that step (1) obtains is added in alienation metallic reducing bacterium culture medium, by carbon cloth electrode submergence wherein, then inoculate alienation metal reducing miroorganisms wherein, stirring reaction 3 ~ 4 days; Take out carbon cloth electrode, repeat above step twice, the carbon cloth electrode obtained is Graphene/polypyrrole bioelectrode.

2. the preparation method of Graphene according to claim 1/polypyrrole bioelectrode, it is characterized in that, in step (1), the concentration of graphene oxide in water is 2 ~ 5mg/ml, polypyrrole is by being 1 ~ 4:1 with graphene oxide mass ratio, and described oxygenant is FeCl ₃, the add-on of oxygenant is 50 ~ 100mg/ml.

3. the preparation method of Graphene according to claim 1/polypyrrole bioelectrode, is characterized in that, in step (2), described alienation metal reducing miroorganisms be pseudomonas, the mixture of one or more in bacillus, iron-reducing bacterium.

4. the preparation method of Graphene according to claim 1/polypyrrole bioelectrode, is characterized in that, in step (2), the concentration of graphene oxide/polypyrrole powder in alienation metallic reducing bacterium culture medium is 0.1 ~ 1mg/ml.

5. the preparation method of Graphene according to claim 1/polypyrrole bioelectrode, is characterized in that, in step (2), the formula of alienation metallic reducing bacterium culture medium is as follows: glucose 0.5 ~ 1g/L, NH ₄cl0.1 ~ 0.4g/L, NaH ₂pO ₄1 ~ 5g/L, Na ₂hPO ₄2 ~ 5g/L, KCl0.1 ~ 0.3g/L, pH=6.5 ~ 7.5, solvent is water.

6. Graphene/polypyrrole bioelectrode that the preparation method of the Graphene described in any one of Claims 1 to 5/polypyrrole bioelectrode prepares.

7. the application of Graphene according to claim 6/polypyrrole bioelectrode in electrode removal water in sexavalent chrome.

8. application according to claim 7, is characterized in that, using the negative electrode of Graphene/polypyrrole bioelectrode as biofuel cell, and the sexavalent chrome in reduction catholyte.

9. application according to claim 8, is characterized in that, builds microorganism electrochemical device by the following method:

Utilize proton exchange membrane that reactor is separated into cathode compartment and anolyte compartment, using Graphene/polypyrrole bioelectrode as negative electrode, reactor, as anode, is connected with resistance by carbon cloth, containing OD in the electrolytic solution of anolyte compartment ₆₀₀it is the phosphoric acid buffer of the Shewanella of 0.4, carbon source, 50mMpH7.0.

10. application according to claim 9, is characterized in that, described carbon source is 5 ~ 20mmol/l Sodium.alpha.-hydroxypropionate.