CN105762372A - Method for preparing microbial fuel cell anode electrodes from agricultural wastes - Google Patents

Abstract

The invention relates to the technical field of microbial fuel cells, in particular to a method for preparing anode electrodes of microbial fuel cells from agricultural waste; the samples are dried and reacted for 30 minutes in a nitrogen atmosphere with a heating rate of 10°C/min and 400°C. The nitrogen flow rate was controlled at 600Ml/min to carbonize the sample, and then it was taken out and ground to 60 mesh, soaked in 5wt% HCl for 6h, and washed until neutral. Soak in 3wt% HF for 6h, wash until neutral, and dry. Mix and grind the sample with KOH to 100 mesh, move it to a nickel crucible, and set the activation conditions as follows: temperature setting 700-900°C, temperature 1-2h, ratio 1:2-1:6; Biomass porous carbon electrodes are prepared from agricultural waste bean dregs to prepare high-quality electrodes with high specific surface area, high capacitance, and good microbial biomass enrichment effect; Strong, green products and other advantages.

Description

A method for preparing microbial fuel cell anode electrodes from agricultural waste

technical field

The invention relates to the technical field of microbial fuel cells, in particular to a method for preparing anode electrodes of microbial fuel cells from agricultural waste.

Background technique

In recent years, with the depletion of fossil energy and the harm caused to the environment by the combustion of coal, oil and other fossil fuels, it has become an urgent task to find a resource-saving and environment-friendly new energy.

According to reports, in 2014, China's soybean production was about 12.35 million tons, the import volume was 71.404 million tons, the export volume was 2.07 million tons, and the domestic soybean apparent consumption was 83.547 million tons. China is one of the main countries that process soybeans in the world. As the largest by-product in the soybean processing industry (accounting for about 15% to 20% of the dry weight of whole beans), okara produces about 16 million tons of wet okara per year. In the current recycling Among them, it is mostly recycled as feed and other agricultural and sideline products. However, generally bean dregs contain 85% moisture, 3.0% protein, 0.5% fat, and 8.0% carbohydrates (cellulose, polysaccharides, etc.), and their nutritional value is low. Okara is treated as agricultural waste by burning, which has a certain degree of impact on the environment. How to recycle it reasonably has become a hot spot worthy of attention.

A microbial fuel cell is a device that uses microorganisms to directly convert chemical energy in organic matter into electrical energy. Its basic working principle is: in the anaerobic environment of the anode chamber, the organic matter decomposes under the action of microorganisms and releases electrons and protons. The circuit is transmitted to the cathode to form a current, and the protons are transmitted to the cathode through the proton exchange membrane. The oxidant (usually oxygen) gets electrons at the cathode and is reduced and combined with protons to form water, which has the characteristics of high power generation efficiency and less environmental pollution.

In traditional microbial fuel cells, activated carbon fiber felt is used as the electrode material, and it is closely attached to the inner wall of the reactor. It has a high specific surface area (effective area 2513cm ² ) and good electricity generation effect (patent name: a suitable A three-dimensional electrode biofilm system for treating wastewater with low carbon-to-nitrogen ratio and high ammonia-nitrogen ratio, patent application number: 201110373581X). It has also been reported that a graphite carbon plate wound with activated carbon fibers is used as an electrode material to support metal copper and palladium (patent name: electrochemical-biofilm synergistic reactor and its application in nitrogen-containing organic wastewater, patent application number: 2013101777107). The electrodes prepared by these methods have better performance, but it is not difficult to find through analysis that the cost of their preparation and raw materials is relatively high. However, if the prepared microbial fuel cell electrodes are used to solve the energy problem, and at the same time, the agricultural waste materials can be used as resources, this technology is more meaningful for promotion.

In recent years, how to turn waste bean dregs and other agricultural wastes into treasures has become a hot spot and has attracted close attention from all countries. In order to form porous structures in raw materials, there are currently two main methods. One is the template method, which uses templates to effectively control the pore structure, thereby preparing materials with ordered structures and uniform pore sizes. (Patent name: A method for constructing nanoporous membrane electrodes for direct methanol fuel cells based on the sacrificial template method, patent application number: 2013105249177) However, this method involves the use and removal of template agents, and the steps are complicated, and the specific surface area is difficult to improve. promote. The present invention adopts the carbonization-activation method, which is a traditional method for preparing porous carbon electrodes. The process is mature, and the carbon material is activated by alkali at low cost, and an electrode with high specific surface area, high capacitance, and good biocompatibility is prepared. Material.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing microbial fuel cell anode electrodes from agricultural waste. The electrode material prepared by the method has the characteristics of high specific surface area, high capacitance and good biocompatibility. In the anode of the microbial fuel cell, the effect of battery power generation and environmental restoration is good.

In order to solve the problems of the technologies described above, the technical scheme adopted in the present invention is as follows:

A method for preparing microbial fuel cell anode electrodes with agricultural waste, comprising the steps of:

(1) Carbonize the waste bean dregs sample to obtain a porous carbon material. The carbonization conditions are: raise the temperature to 400°C in a nitrogen atmosphere and continue to react at this temperature for 30 minutes. The heating rate is 10°C/min, and the nitrogen flow rate is controlled at 600ml/min. ;

(2) Grinding the carbonized material in step (1) to 60 mesh, soaking in dilute hydrochloric acid for 6 hours, and washing to neutrality;

(3) Soak the material treated in step (2) with hydrofluoric acid for 6 hours, wash until neutral, and dry;

(4) Mix and grind the material treated in step (3) with potassium hydroxide to 100 mesh, move it to a nickel crucible, and activate it under a nitrogen atmosphere. The activation condition is: react at 700-900°C for 1-2h, The mass ratio of material to KOH is 1:2-1:6;

(5) Soak the material obtained in step (4) with dilute hydrochloric acid for 12 hours, wash to neutral, and dry; prepare a porous carbon electrode material with strong electrochemical properties;

(6) Cut foam nickel;

(7) putting the material obtained in step (6) into dilute sulfuric acid and ultrasonically for 15min;

(8) putting the material obtained in step (7) into distilled water and ultrasonically for 15min;

(9) putting the material obtained in step (8) into 0.5mol/L sodium hydroxide solution and ultrasonically for 15min;

(10) putting the material obtained in step (9) into distilled water for ultrasonication, washing to neutrality, and drying at 50° C. to obtain pretreated nickel foam;

(11) The porous carbon electrode material obtained in step (5) is mixed with acetylene black and polytetrafluoroethylene in proportion, and a small amount of dehydrated alcohol is added, evenly applied to the foamed nickel obtained in step (10), and maintained at 10MPa 3min, make the electrode of the fuel cell.

Further, in the step (4) under nitrogen atmosphere, the activation conditions are: react at 800° C. for 1 h, and the mass ratio of material to KOH is 1:3.

Further, in step 4, under nitrogen atmosphere, the activation conditions are: react at 800° C. for 1 h, and the mass ratio of material to KOH is 1:4.

Further, in the step 4, under a nitrogen atmosphere, the activation conditions are: react at 800° C. for 1.5 h, and the mass ratio of material to KOH is 1:4.

Further, the mass percent of dilute hydrochloric acid in the step (2) and step (5) is 5%.

Further, the mass percentage of hydrofluoric acid in the step (3) is 3%.

Further, the concentration of dilute sulfuric acid in the step (7) is 0.5mol/L.

Further, the mass ratio of porous carbon electrode material, acetylene black and polytetrafluoroethylene in the step (11) is 8:1:1.

Further, the mass percentage of the polytetrafluoroethylene is 15%.

The beneficial effects of adopting the technical solution of the present invention are:

1. The present invention uses agricultural waste bean dregs to prepare biomass porous carbon electrodes, and prepares high-quality electrodes with high specific surface area, high capacitance, and good microbial biomass enrichment effect;

2. The present invention can utilize waste resources as resources, and has the advantages of high raw material utilization rate, strong functionality, and environmentally friendly products.

Description of drawings

Fig. 1 Cyclic voltammograms of porous carbon materials at different scan rates;

The galvanostatic charge-discharge curve of Fig. 2 porous carbon material;

The Nyquist diagram of Fig. 3 porous carbon material;

The scanning electron microscope picture of Fig. 4 porous carbon material;

Figure 5 The buried depth position of the porous carbon electrode material;

Figure 6 Soil remediation effect of microbial fuel cell.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

Dry the sample, and react for 30 minutes in a nitrogen atmosphere with a heating rate of 10°C/min and 400°C, and control the nitrogen flow rate at 600Ml/min to carbonize the sample, then take it out and grind it to 60 mesh, and soak it in 5wt% HCl for 6h , wash to neutral. Soak in 3wt% HF for 6h, wash until neutral, and dry; mix and grind the sample with KOH to 100 mesh, move it to a nickel crucible, and set the activation conditions as follows: temperature setting 700°C, temperature 1h, ratio 1:4, the obtained activated porous carbon material is marked as D-700-4-1.

Example 2

Dry the sample, and react for 30 minutes in a nitrogen atmosphere with a heating rate of 10°C/min and 400°C, and control the nitrogen flow rate at 600Ml/min to carbonize the sample, then take it out and grind it to 60 mesh, and soak it in 5wt% HCl for 6h , wash to neutral. Soak in 3wt% HF for 6h, wash until neutral, and dry; mix and grind the sample with KOH to 100 mesh, move to a nickel crucible, and set the activation conditions as follows: temperature setting 800°C, temperature 1h, ratio 1:2, the activated porous carbon material was obtained, marked as D-800-2-1.

Example 3

Dry the sample, and react for 30 minutes in a nitrogen atmosphere with a heating rate of 10°C/min and 400°C, and control the nitrogen flow rate at 600Ml/min to carbonize the sample, then take it out and grind it to 60 mesh, and soak it in 5wt% HCl for 6h , wash to neutral. Soak in 3wt% HF for 6h, wash until neutral, and dry. Mix and grind the sample with KOH to 100 mesh, move it to a nickel crucible, and set the activation conditions as follows: temperature setting 800°C, temperature 1h, ratio 1:3, and the activated porous carbon material is obtained, marked as D -800-3-1.

Example 4

Dry the sample, and react for 30 minutes in a nitrogen atmosphere with a heating rate of 10°C/min and 400°C, and control the nitrogen flow rate at 600Ml/min to carbonize the sample, then take it out and grind it to 60 mesh, and soak it in 5wt% HCl for 6h , wash to neutral. Soak in 3wt% HF for 6h, wash until neutral, and dry; mix and grind the sample with KOH to 100 mesh, move to a nickel crucible, and set the activation conditions as follows: temperature setting 800°C, temperature 1h, ratio 1:4, the activated porous carbon material was obtained, marked as D-800-4-1.

Example 5

Dry the sample, and react for 30 minutes in a nitrogen atmosphere with a heating rate of 10°C/min and 400°C, and control the nitrogen flow rate at 600Ml/min to carbonize the sample, then take it out and grind it to 60 mesh, and soak it in 5wt% HCl for 6h , wash to neutral. Soak in 3wt% HF for 6h, wash until neutral, and dry; mix and grind the sample with KOH to 100 mesh, move to a nickel crucible, and set the activation conditions as follows: temperature setting 800°C, temperature 1h, ratio 1:5, the activated porous carbon material was obtained, marked as D-800-5-1.

Example 6

Dry the sample, and react for 30 minutes in a nitrogen atmosphere with a heating rate of 10°C/min and 400°C, and control the nitrogen flow rate at 600Ml/min to carbonize the sample, then take it out and grind it to 60 mesh, and soak it in 5wt% HCl for 6h , wash to neutral. Soak in 3wt% HF for 6h, wash until neutral, and dry; mix and grind the sample with KOH to 100 mesh, move to a nickel crucible, and set the activation conditions as follows: temperature setting 800°C, temperature 1h, ratio 1:6, the activated porous carbon material was obtained, marked as D-800-6-1.

Example 7

Dry the sample, and react for 30 minutes in a nitrogen atmosphere with a heating rate of 10°C/min and 400°C, and control the nitrogen flow rate at 600Ml/min to carbonize the sample, then take it out and grind it to 60 mesh, and soak it in 5wt% HCl for 6h , wash to neutral. Soak in 3wt% HF for 6h, wash until neutral, and dry; mix and grind the sample with KOH to 100 mesh, move it to a nickel crucible, and set the activation conditions as follows in a nitrogen atmosphere: temperature setting 800°C, temperature 1.5h, The ratio is 1:4, and the activated porous carbon material is obtained, which is marked as D-800-4-1.5.

Example 8

Dry the sample, and react for 30 minutes in a nitrogen atmosphere with a heating rate of 10°C/min and 400°C, and control the nitrogen flow rate at 600Ml/min to carbonize the sample, then take it out and grind it to 60 mesh, and soak it in 5wt% HCl for 6h , wash to neutral. Soak in 3wt% HF for 6h, wash until neutral, and dry. Mix and grind the sample with KOH to 100 mesh, move it to a nickel crucible, and set the activation conditions as follows: temperature setting 800°C, temperature 2h, ratio 1:4, marked as D-800-4-2.

Example 9

Dry the sample, and react for 30 minutes in a nitrogen atmosphere with a heating rate of 10°C/min and 400°C, and control the nitrogen flow rate at 600Ml/min to carbonize the sample, then take it out and grind it to 60 mesh, and soak it in 5wt% HCl for 6h , wash to neutral. Soak in 3wt% HF for 6h, wash until neutral, and dry; mix and grind the sample with KOH to 100 mesh, move it to a nickel crucible, and set the activation conditions as follows: temperature setting 900°C, temperature 1h, ratio 1:4, the activated porous carbon material was obtained, marked as D-900-4-1.

The performance parameters of the porous carbon material prepared by the above method are shown in Table 1. The activation time is 800°C, the time is 1h, and the effect is the best when the ratio is 3:1.

Table 1 Pore structure parameters and specific capacitance of porous carbon carbon

Table 1 shows the pore structure parameters and specific capacitance of porous carbon. It can be seen that the porous carbon material prepared with an activation temperature of 800 °C, an activation time of 1 h, and an activation ratio of 1:3 has the best specific surface area and pore volume. Figure 1 shows the cyclic voltammograms of porous carbon materials with an activation temperature of 800°C, an activation time of 1 h, and an activation ratio of 1:3 at scan rates of 50 mV/s, 100 mV/s, and 150 mV/s. It can be seen from Figure 1 that the as-prepared porous carbon materials exhibit quasi-rectangular shapes at three scan rates, and a good rectangular shape means fast charge-discharge performance. Figure 2 shows the galvanostatic charge-discharge curve of the porous carbon material prepared under the above conditions at a current density of 0.5A/g, the curve is a relatively symmetrical isosceles triangle, indicating that the prepared porous carbon material has good Coulombic efficiency and good double-layer capacitance performance. Figure 3 is the electrochemical impedance spectroscopy (EIS) at room temperature, the frequency range from 0.01Hz to 100kHz, tested in 1MH2SO4. The prepared porous carbon Nyquist plot consists of a concave semicircle in the high frequency range and a sloped line in the low frequency range, respectively. From the diameter of the semicircle shown in this curve, it can be seen that the material has the lowest charge transfer resistance and the best electron conductivity. Figure 4 is a scanning electron microscope image of the prepared porous carbon, it can be seen that it has a rich mesoporous structure.

Example 10

The obtained porous carbon was prepared by activating at 800° C. for 1 hour at a ratio of 3:1, soaking in 5 wt% HCl for 12 hours, washing until neutral, and drying. Put the cut foam nickel into 0.5mol/L sulfuric acid (H2SO4), distilled water, and 0.5mol/L sodium hydroxide (NaOH) solution for 15 minutes, then wash until neutral, and dry at 50°C , to get primary treated foamed nickel. Porous carbon electrode material and acetylene black, the polytetrafluoroethylene of 15wt% are mixed uniformly by the mass ratio of 8:1:1, add a small amount of dehydrated alcohol, smear evenly on the nickel foam of step ten (10) gained (positive and negative All coated), maintained at 10MPa for 3min to make an electrode for a fuel cell.

For the construction of sediment-type microbial fuel cells, real river sludge and natural surface water are used to build batteries, and the overlying water of 2-4cm is always maintained. The buried depth position of the electrode material made of the above-mentioned porous carbon as the anode is shown in Figure 5, and the cathode is nickel foam placed between the overlying water and the sediment.

Figure 6 shows the remediation effect of microbial fuel cells on contaminated soil. We measure the current once a day and compare it with the uncontaminated current. It can be seen that the current in the contaminated soil increased significantly after 14 days, and the soil remediation rate reached 32%.

Although the above-mentioned embodiments have described the technical solution of the present invention in detail, the technical solution of the present invention is not limited to the above embodiments. Any modification will fall within the scope defined by the claims of the present invention.

Claims (9)

1. A method for preparing microbial fuel cell anode electrode with agricultural waste, is characterized in that, comprises the steps: (1) Carbonize the waste bean dregs sample to obtain a porous carbon material. The carbonization conditions are: raise the temperature to 400°C in a nitrogen atmosphere and continue to react at this temperature for 30 minutes. The heating rate is 10°C/min, and the nitrogen flow rate is controlled at 600ml/min. ; (2) Grinding the carbonized material in step (1) to 60 mesh, soaking in dilute hydrochloric acid for 6 hours, and washing to neutrality; (3) Soak the material treated in step (2) with hydrofluoric acid for 6 hours, wash until neutral, and dry; (4) Mix and grind the material treated in step (3) with potassium hydroxide to 100 mesh, move it to a nickel crucible, and activate it under a nitrogen atmosphere. The activation condition is: react at 700-900°C for 1-2h, The mass ratio of material to KOH is 1:2-1:6; (5) Soak the material obtained in step (4) with dilute hydrochloric acid for 12 hours, wash to neutral, and dry; prepare a porous carbon electrode material with strong electrochemical properties; (6) Cut foam nickel; (7) putting the material obtained in step (6) into dilute sulfuric acid and ultrasonically for 15min; (8) putting the material obtained in step (7) into distilled water and ultrasonically for 15min; (9) putting the material obtained in step (8) into 0.5mol/L sodium hydroxide solution and ultrasonically for 15min; (10) putting the material obtained in step (9) into distilled water for ultrasonication, washing to neutrality, and drying at 50° C. to obtain pretreated nickel foam; (11) The porous carbon electrode material obtained in step (5) is mixed with acetylene black and polytetrafluoroethylene in proportion, and a small amount of dehydrated alcohol is added, evenly applied to the foamed nickel obtained in step (10), and maintained at 10MPa 3min, make the electrode of the fuel cell. 2. A method for preparing microbial fuel cell anode electrodes from agricultural waste according to claim 1, characterized in that: in the step (4), under a nitrogen atmosphere, the activation condition is: react at 800° C. for 1 h , the mass ratio of material to KOH is 1:3. 3. A method for preparing microbial fuel cell anode electrodes from agricultural waste according to claim 1, characterized in that: in step 4, under a nitrogen atmosphere, the activation conditions are: react at 800 ° C for 1 h, and the material The mass ratio to KOH is 1:4. 4. A method for preparing microbial fuel cell anode electrodes from agricultural wastes according to claim 1, characterized in that: in step 4, under a nitrogen atmosphere, the activation conditions are: react at 800°C for 1.5h, The mass ratio of material to KOH is 1:4. 5. A method for preparing microbial fuel cell anode electrodes from agricultural waste according to claim 1, characterized in that: the mass percent of dilute hydrochloric acid in the step (2) and step (5) is 5%. 6. A method for preparing microbial fuel cell anode electrodes from agricultural wastes according to claim 1, characterized in that: the mass percentage of hydrofluoric acid in the step (3) is 3%. 7. A method for preparing microbial fuel cell anode electrodes from agricultural wastes according to claim 1, characterized in that: the concentration of dilute sulfuric acid in the step (7) is 0.5mol/L. 8. a kind of method preparing microbial fuel cell anode electrode with agricultural waste according to claim 1, is characterized in that: in described step (11), porous carbon electrode material, acetylene black and polytetrafluoroethylene mass ratio are 8:1:1. 9. A method for preparing microbial fuel cell anode electrodes from agricultural wastes according to claim 1, characterized in that: the mass percentage of polytetrafluoroethylene is 15%.