KR20120128865A - A single reactor microbial fuel cell using sediment - Google Patents

Abstract

PURPOSE: A single reactor type microbial fuel cell is provided to generate energy without environmental contamination by effectively using deposits of sea bottom. CONSTITUTION: A single reactor type microbial fuel cell comprises deposits of sea bottom, an oxidation electrode in the deposits, seawater poured on the deposits, reduction electrode in the seawater, and an electric wire connected to the oxidation electrode and the reduction electrode. Chitin is added as a substrate into the oxidation electrode. The oxidation electrode is a graphite electrode and can be a consumable electrode. The consumable electrode can be a magnesium electrode.

Description

Single reactor microbial fuel cell using sediment {A SINGLE REACTOR MICROBIAL FUEL CELL USING SEDIMENT}

The present invention relates to a single reactor microbial fuel cell using sediments, and more particularly, to a single reactor microbial fuel cell using subsea deposits, wherein chitin is added as a substrate to the anode.

Fossil fuels have driven industrialization and economic growth in the last few centuries, along with global population growth. In recent years, the depletion of fossil fuels, especially oil and gas, has accelerated the global energy crisis, and no clear solution exists to meet the current and future energy demands. While fossil fuels are a major means of energy production today, they are still difficult to use because of global warming and climate change.

Renewable energy is currently projected as a way to alleviate the global greenhouse crisis. In order to develop new energy sources, the company is working on renewable energy sources other than oil, gas, nuclear power, and natural gas such as solar, bio, wind, hydro, and fuel cells. New generation of electricity from new energy sources without the release of carbon dioxide has been longing for.

Recently, many researches have been conducted on renewable energy technologies that produce electricity and gas using organic materials contained in livestock wastewater, food sewage, and sewage sludge as resources. Among them, the technology using Microbial Fuel Cell (MFC) is a new concept that can convert chemical energy of organic matter contained in sewage water into electric energy by using electroactive microorganism as a catalyst. It caused a notable interest in between. When microbial fuel cells are applied to sewage and wastewater, they are attracting attention as sustainable sewage and wastewater treatment technologies such as direct power recovery, energy saving, and sludge reduction.

Existing researches mainly focus on electricity generation and removal of organic substances using sewage and wastewater, research on microbial community of MFC, and electrode material of MFC. However, MFC's research using submarine sediments is still insufficient.

The present invention has been made to solve the problems of the prior art as described above, the problem to be solved in the present invention is to develop an effective microbial fuel cell using the deposits of the seabed.

In order to solve the above problems,

The present invention provides a single reactor microbial fuel cell comprising a seabed sediment, an oxidizing electrode provided in the seabed sediment, seawater poured on the seabed sediment, a reducing electrode provided in the seawater, and a wire connected to the oxidizing electrode and the reducing electrode. The present invention provides a single reactor microbial fuel cell in which chitin is added as a substrate to the oxidation electrode.

The oxidation electrode may be a graphite electrode.

In addition, the oxidation electrode may be a consumable oxidation electrode.

The consumable oxidation electrode may be a magnesium electrode.

According to the present invention, it is possible to provide a means for producing energy without environmental pollution by efficiently utilizing a large amount of seabed sediment existing on the earth.

1 is a schematic view showing an embodiment of a microbial fuel cell, (a) is a side view, (b) is a view observed from the top,
2 is a graph showing a voltage change over time for each oxide electrode;
3A to 3D are graphs showing the relationship between voltage and current density, current density, and power density in a section in which voltage is constant when magnesium and graphite are used as the anode, and FIG. 3A is November 06, 2010, and 3B. Is a measurement of November 12, 2010, FIG. 3C is November 18, 2010, FIG. 3D is November 22, 2010,
4A to 4D are graphs comparing power generation with and without chitin added to the anode, and FIG. 4A is November 06, 2010, FIG. 4B is November 12, 2010, and FIG. 4C is November 18, 4D is a measurement of November 12, 2010,
5 is a photograph showing the oxidation electrode and chitin before the experiment,
Figure 6 is a photograph showing the physical changes of the anode and chitin after the experiment, (a) is magnesium, (b) is graphite, (c) is magnesium in magnesium + chitin, (d) is chitin in magnesium + chitin (e) shows graphite in graphite + chitin, and (f) shows chitin in graphite + chitin.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention, as described above, includes a seabed sediment, an oxidation electrode provided in the seabed sediment, seawater poured on the seabed sediment, a reduction electrode provided in the seawater and a wire connected to the oxidation electrode and the reducing electrode In a single reactor microbial fuel cell, there is provided a single reactor microbial fuel cell in which chitin is added as a substrate to the oxidation electrode.

The oxidation electrode may be a graphite electrode or a consumable oxide electrode. The consumable oxidation electrode may be a magnesium electrode.

As a result of the power comparison according to the anode in the MFC using the seabed sediment of the present invention, the following conclusions were drawn.

In other words, as a result of comparing the voltage and power generation over time in MFC using sediment, the highest voltage generation was the oxidation electrode of magnesium + chitin, followed by magnesium, graphite + chitin (G + C), and graphite. Appeared. Magnesium was higher than the magnesium + chitin electrode shortly after switching to CCV, but over time the magnesium + chitin electrode generated more voltage. Graphite, which had no voltage at all, generated some voltage over time, and the graphite + chitin electrode generated more voltage than the graphite electrode.

In addition, when comparing the power generation of Mg and G, Mg produced a very large amount of power. However, G showed zero power and zero current, and showed a slight power generation over time. The power density of the consumable anode (Mg) was generally 600 ~ 890 times higher than that of graphite (G), which is used as the anode material of microbial fuel cells, and the current density was 300 ~ 600 times higher.

In addition, the power of chitin added to the two anodes was compared. Mg + C produced the most electricity (P: 31.5 ㎽, I: 125.5 ㎃, Power Density: 1575 ㎽ / ㎡), followed by Mg (P: 22 ㎽, I: 46.9 ㎃, Power Density: 1100 ㎽) / ㎡), G + C (P: 35 ㎼, I: 0.187 ㎃, Power Density: 2 ㎽ / ㎡), G ((P: 0 ㎼, I: 0 ㎃, Power Density: 0 ㎽ / ㎡) You can see that it produced electricity.

In addition, chitin has been shown to bring about an improvement in power with the corrosion of magnesium while slowing the corrosion of the consumable anode. As a result, Mg + C electrodes are expected to be about two times longer than Mg electrodes. According to the present invention, for the long-term use of the MFC using the seabed sediment, the need for substrate injection into the sediment and the possibility of generating sufficient power to manipulate the device available on the seabed using magnesium and chitin were found.

Hereinafter, the present invention will be described in more detail with reference to examples.

< Example >

1. Electric pole

After preparing magnesium (purity 99.99%) and graphite, each of the same shape and size (diameter 5 cm, thickness 1 cm) and two graphite, each titanium wire (0.5 mm diameter) was connected to the electrode, and after 24 hours Finished with non-conductive epoxy.

1 g of chitin was wrapped in a thread using a cloth (16 cm x 16 cm), respectively, for magnesium and graphite electrodes. The other magnesium and graphite electrode did not provide chitin as a control for the experiment. Thus, the configuration of the four electrodes used in this embodiment is as follows: magnesium (Mg), magnesium + chitin (Mg + C), graphite (G), graphite + chitin (G + C).

In the reduction electrode using sediment, the reduction electrode is immersed in water, so dissolved oxygen reacts directly on the platinum, so instead of making PTFE diffusion layer, carbon black (10cm × 10cm) is coated on one side with carbon black and dried for several hours. Later, on the other side, a platinum catalyst solution was added and used.

2. Tank production and operation

Sediments from the Gangneung Namdaecheon Estuary adjacent to Anmok Port in the East Sea were filled in a rectangular tank (450mm × 300mm × 340mm) and filled with artificial seawater (Tetra Marine Salt, United Pet Group Inc. USA) to create an undersea environment in the laboratory. Four anodes (Mg, Mg + C, G, G + C) prepared on a 3 cm deposit were installed and covered again with a deposit to form a total of 6 cm deposit layers. At this time, only the titanium wire connected to the anode was shown on the deposit. A water level of 12 cm was formed by pouring 20 L of artificial seawater solution made by putting sea salt (33 g / L) into the tap water received in advance for more than one day on the sediment (FIG. 1A).

In the tank cover made of styrofoam, a hole was made to enter the titanium wire of the anode, the titanium wire of the cathode, the reference electrode, the thermostat, the thermometer, and the aeration device (Fig. 1b). Then, all of the above were put into the reactor lid, and then the lid was connected to a voltage-current measuring device (Kynel, Korea). Open circuit voltage (OCV) was measured during the first two days, and then the voltage generated by connecting a resistor was measured. The evaporated seawater was replenished by additional supply of brine. The water temperature was maintained at 30 ° C. and aerated at 6 mL / s for dissolved oxygen feed.

3. Calculation

Power density was calculated as the power per unit cathode area (200 cm ² ).

Oxidation and oxygen reduction of magnesium (Mg) are as follows. In MFCs, water or hydrogen peroxide can be produced by oxygen reduction.

Oxidation ^{reaction: Mg → Mg 2 + + 2e} - (1)

(redox potential at pH 7.2, E = -2.105V)

Reduction reaction: O ₂ ^{+ 4H + + 4e - → 2H} 2 O (2)

(redox potential at pH 7, E = 0.805 V)

Overall Cell Voltage = E _cathode -E _anode = 2.91V (3)

4. result

(1) generation of voltage

After the experimental setting, the voltage was measured by OCV for about 50 hours, and then proceeded to a closed circuit voltage (CCV) (FIG. 2). The voltage generation was highest in the anode of magnesium + chitin, followed by magnesium, graphite + chitin, and graphite.

When magnesium is used as the anode, the total cell voltage is 2.91V. As a result, the OCV value of magnesium (Mg) and magnesium + chitin (Mg + C) was measured as 2.25V. The voltage of graphite (G) electrode should be oxidized due to decomposition of organic matter in the sediment, and the reduction reaction should result in total cell voltage of 0.805 V. However, as seen in the result, the effect of internal resistance is also called the effect of internal resistance. I can. Magnesium was higher than the magnesium + chitin electrode shortly after switching to CCV, but over time the magnesium + chitin electrode generated more voltage. Graphite, which had no voltage at all, showed slight voltage generation over time, and graphite + chitin electrode generated more voltage than graphite electrode. In the early stages, the magnesium + chitin electrode produced less voltage than magnesium, suggesting that the corrosion of magnesium may have been slightly delayed because the experiment was conducted by wrapping magnesium with solid chitin. In a closed circuit, the voltage of the magnesium electrode dropped rapidly after about 20 days (500hr) (Fig. 2: about 530hr), which is thought to be caused by the separation of magnesium and titanium electrodes. After that, the voltage increased about 3 days. It was thought that the voltage increased as the corrosion rate of the other part progressed by the separation of the original part and the titanium wire, which accelerated the overall corrosion rate.

(2) Comparison of Power Generation by Anode

After switching to CCV and using magnesium (Mg) and graphite (G) as the anode, the relationship between voltage, current density, current density and power density measured in the section where voltage is constant (Fig. 2: 70 ~ 410hr) 3 is shown.

In the case of Mg and G, the voltage gradually dropped over time. The electric power was also dropped to 11140.05 mW / m 2 and 1.27 mW / m 2 (c in FIG. 3). In the case of G, no power is generated, but it can be seen that power is weakly generated over time.

As shown in Table 1, the power density of the consumable anode (Mg) was generally about 670 to 1000 times higher than that of graphite (G), which is used as the anode material of the microbial fuel cell, and the current density was about 300 to 670. Times higher. However, the external resistance of graphite (G) was significantly higher than that of magnesium (Mg). It is expected that the corrosion of magnesium (Mg) influenced the power increase. Initially, graphite (G) with zero power density does not generate power because no other substrate is injected except organic matter in the sediment. It was found that power was generated over this period. When Mg was used as a power comparison between the consumable anode (Mg) and a commonly used anode (G), it was found that a lot of power was generated and could be used as a power supply source using deposits.

(3) Chitin on the anode chitin Comparison of Power Generation by Addition

4 shows a comparison of power generation with and without the addition of chitin. Comparing the power densities of the two anodes with and without chitin, the highest amount of magnesium (Mg + C) in which chitin was added was 1575.03 mW / m 2 (Fig. 6a), followed by magnesium (Mg) and graphite. Chitin was added to the electrode (G + C), followed by graphite (G). In addition, Mg + C with chitin added showed a power increase of 1 to 8 times that of the electrode using only Mg, and G + C also showed a power increase of 1 to 5 times higher than the electrode using only G (Table 2). Electrodes using only G and G + C generated little power at first, but inadequately generated power over time. Chitin-added graphite electrodes produced higher power than graphite-only electrodes from the outset. It is thought that this acted as substrate as chitin was oxidized.

In the case of Mg in Table 2, it can be seen that the power density suddenly drops, which is thought to affect the Mg electrode next to the sudden increase in the power of Mg + C (Fig. 1b).

(4) Effect of Chitin on Consumable Anodes

After about 40 days of experiments, the voltage of magnesium (Mg) dropped rapidly, whereas the electrode (Mg + C) in which chitin was added to magnesium was continuously generated. This may be due to the end of corrosion of Mg or the disconnection of the titanium wire and the anode, resulting in no voltage.

Table 3 and Figures 5 and 6 are the weight and photograph of the anode before and after the experiment. In order to weigh the correct Mg, calcining was performed for 3 hours in an electric furnace at 550 ° C., and then weighed. The electrode using only Mg did not remain due to the corrosion of all the Mg (FIG. 6 a), but the electrode in which chitin was added to magnesium (Mg + C) had 22.4 g of magnesium in a hard form (FIG. 6 c). Since the weight of the electrode using only Mg could not be measured, it was not possible to compare Mg + C with the corrosion rate. It is thought that chitin may have slowed the corrosion of Mg. And the amount of chitin in Mg and G was 0.98g, respectively, almost unchanged (Table 3).

The electrochemical action of corrosion of magnesium and oxidation of chitin caused the Mg + C electrode to generate higher power than the Mg electrode. Mg + C corroded more slowly than the Mg electrode. It is believed that chitin lowered magnesium consumption. This is shown to require the infusion of substrate into the empty nutrient state of the deposit. In this study, using magnesium and chitin, enough power was generated to manipulate devices available on the sea floor.

Claims (2)

In a single reactor microbial fuel cell comprising a seabed sediment, an oxidation electrode provided in the seabed sediment, seawater poured on the seabed sediment, a reduction electrode provided in the seawater and wires connected to the oxidation electrode and the reducing electrode, A single reactor microbial fuel cell in which chitin is added as a substrate to an anode. The method of claim 1,
Single oxidation tank microbial fuel cell, characterized in that the oxidation electrode is a graphite electrode.

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