CN114441609B

CN114441609B - Substrate-enhanced long-term in-situ bioelectrochemical sensor

Info

Publication number: CN114441609B
Application number: CN202111542529.2A
Authority: CN
Inventors: 孙丹; 谢斌; 李家豪; 陈家旺
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2023-03-28
Anticipated expiration: 2041-12-14
Also published as: CN114441609A

Abstract

The invention discloses a substrate reinforced long-term in-situ bioelectrochemical sensor. The bioelectrochemical sensor is based on the deposit microbial fuel cell principle and comprises an anode chamber, a separator material, a cathode and an external circuit. And adding a macromolecular organic substrate around the anode and placing the substrate inside the anode chamber to form a substrate reinforced anode. The rest space of the anode chamber is filled with bottom mud, the bottom mud provides a strict anaerobic environment and a microorganism inoculation source for the anode, and under the anaerobic decomposition of zymocyte, macromolecular organic matters are slowly and continuously degraded into micromolecular organic matters which can be utilized by electrogenesis microorganisms, so that the continuous supply of substrates required by the electrogenesis of the sensor is ensured, and the normal work of the sensor can be maintained for 6 months in laboratory tests. The invention solves the problem that the general microbial fuel cell is difficult to realize long-term in-situ monitoring as a sensor, and provides a new idea for long-term in-situ low-cost monitoring of natural water environment.

Description

Substrate-enhanced long-term in-situ bioelectrochemical sensor

Technical Field

The invention relates to the field of bioelectrochemical sensors, in particular to a substrate-enhanced long-term in-situ bioelectrochemical sensor.

Background

Microbial Fuel Cells (MFCs) are primary cell devices that convert chemical energy in organic matter into electrical energy using microorganisms as catalysts. At the anode, the electrogenic microorganisms oxidize available small molecule organic substrates (e.g., acetic acid, glucose, etc.) and transfer the generated electrons to the anode. Under the potential difference between the anode and the cathode, the generated electrons are transferred to the cathode through an external circuit, and combine with an electron acceptor (such as oxygen molecules, etc.) and protons to generate water.

The microbial fuel cell can be used as a power supply device and can also be used as various sensors to be applied to natural water bodies. In recent years, BOD (BOD, biochemical oxygen demand) sensors, toxicity sensors, dissolved oxygen sensors, and the like based on microbial fuel cells have been widely studied. Microbial fuel cells have several advantages as sensors. First, it is a primary battery device, meaning that no external power source is required to drive it into continuous operation. And secondly, the microbial fuel cell can operate in water and has no pollution to the environment, so that the microbial fuel cell can be widely applied to various water environments. In addition, the most prominent advantage of microbial fuel cells is low cost. Since MFCs do not require expensive electrodes and catalysts, complex control circuitry, and photoelectric signal converters.

At present, the research of MFC type sensors is still focused on laboratory platforms, and practical application cases, particularly application cases in natural water bodies, are rarely reported. Among them, the most important problem is that MFC cannot continuously obtain electricity-generating fuel in natural water bodies, thereby failing to achieve long-term operation. The microbial fuel cell can maintain normal operation, needs electricity-generating substrates (such as acetic acid, glucose, wastewater and other soluble organic carbon sources) with COD (COD) of more than 200mg/L, but the COD of natural water bodies is generally very low (in national standards, COD of first-class and second-class seawater is less than 15mg/L, COD of first-class and second-class surface water is less than 15mg/L, and COD of fifth-class water is less than 60 mg/L), and the microbial fuel cell can not maintain normal operation. Moreover, continuous addition of exogenous matrix in natural water in either an intermittent or continuous flow mode requires a significant labor cost and is difficult to achieve. Therefore, when natural water monitoring is oriented, the problem of substrate supply of the microbial fuel cell is a key problem for restricting long-term in-situ work of the microbial fuel cell.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a substrate-enhanced long-term in-situ bioelectrochemical sensor.

In order to solve the technical problems, the invention adopts the following technical scheme: a substrate-enhanced long-term in-situ bioelectrochemical sensor comprises an anode chamber, a cathode, a separation material and an external resistor; the anode chamber comprises an anode, macromolecular organic matters and bottom mud; an anode is arranged in the anode chamber, macromolecular organic matters are added around the anode, and the rest space of the anode chamber is filled with bottom mud; a separation material is fixed on the outer side of the anode chamber, and the cathode is fixed on the other side of the separation material; the two ends of the external resistor are respectively connected with the anode and the cathode; the macromolecular organic matter is biodegradable macromolecular organic matter, and is preferably chitin or cellulose; the separating material is used for blocking the seepage of anode chamber bottom mud and simultaneously can not block an ion passage between the cathode and the anode, and is preferably glass fiber, an ion exchange membrane or synthetic fiber cloth.

Further, the material of the anode needs to have good electrical conductivity and be suitable for growth and attachment of microorganisms, and is preferably a carbon material such as carbon cloth, carbon fiber mesh, graphite plate, carbon brush, graphite particles, and carbon paper.

Further, the material of the cathode is preferably a carbon material such as a graphite plate, carbon paper, carbon brush, carbon fiber, or carbon cloth.

Furthermore, the two ends of the external resistor are respectively connected with the anode and the cathode through wires, and the wires are preferably made of corrosion-resistant conductive materials such as titanium wires and stainless steel wires.

Furthermore, the anode chamber and the cathode are positioned in the housing, the housing material needs to have certain mechanical strength and corrosion resistance, and the housing material is preferably high molecular engineering plastics such as glass fiber board and the like.

The invention has the beneficial effects that: the sediment microbial fuel cell based on the substrate strengthening type adopts macromolecular solid organic matters to replace soluble organic matters used by the traditional microbial fuel cell as an anode substrate, adopts bottom mud to construct a strict anaerobic environment of an anode chamber, and prolongs the operation time of the traditional microbial fuel cell as a sensor from days to months. Typical electricity-producing microorganisms cannot or cannot easily directly utilize solid macromolecular organic matters to produce electricity, but in an anaerobic environment constructed by bottom sediment, the fermenting bacteria slowly and continuously decompose the macromolecular organic matters into micromolecular organic matters which can be utilized by the electricity-producing microorganisms, so that the electricity-producing microorganisms can continuously obtain sufficient electricity-producing fuel which is convenient to utilize, and further, the long-term in-situ operation of the microbial fuel cell as a sensor in a natural water body environment is realized.

Drawings

FIG. 1 is a schematic diagram of a substrate-enhanced long-term in situ bioelectrochemical sensor according to the present invention;

FIG. 2 is a schematic view of the structure of a cathode in the present invention;

FIG. 3 is a graph of start-up and long-term operation of a microbial fuel cell as a dissolved oxygen sensor;

FIG. 4 is a graph of the results of 17 response tests of current versus dissolved oxygen concentration in a dissolved oxygen sensor;

FIG. 5 is a schematic diagram of a start-up procedure of a microbial fuel cell as a biosynthesized toxicity sensor;

in the figure, 1-anode, 2-macromolecular organic matter, 3-bottom mud, 4-separation material, 5-cathode, 6-titanium wire, 7-external resistor, 8-shell, 9-bolt and 10-nut.

Detailed Description

The invention is described in further detail below with reference to the drawings.

As shown in FIG. 1, the substrate-enhanced long-term in-situ bioelectrochemical sensor of the present invention is based on the principle of a sediment microbial fuel cell, and comprises an anode chamber, a separation material 4, a cathode 5, a lead 6, an external resistor 7, a housing 8, a bolt 9 and a nut 10; the anode chamber comprises an anode 1, macromolecular organic matters 2 and bottom mud 3; the anode chamber is internally provided with an anode 1, macromolecular organic matters 2 are added around the anode 1, and the rest space of the anode chamber is filled with bottom mud 3 to provide an anaerobic environment and a microorganism inoculation source near the anode. The separation material 4 is fixed outside the anode chamber to prevent the bottom sludge 3 in the anode chamber from losing. Two ends of the external resistor 7 are respectively connected with the anode 1 and the cathode 5 through leads 6; the housing 8 encloses the anode chamber.

The anode 1 is preferably made of carbon materials such as carbon cloth, carbon fiber mesh, graphite plate, carbon brush, graphite particles and carbon paper; the macromolecular solid organic matter 2 is preferably chitin or cellulose; the separating material is preferably glass fiber, an ion exchange membrane or synthetic fiber cloth; the material of the cathode 5 is preferably a carbon material such as a graphite plate, carbon paper, carbon brush, carbon fiber, carbon cloth and the like; the material of the shell 8 is preferably high molecular engineering plastic such as glass fiber board and the like.

Example 1: substrate-enhanced long-term in-situ bioelectrochemical sensor as dissolved oxygen sensor

The invention is designed based on the principle of a sediment microbial fuel cell, and the macromolecular organic matter 2 serving as a slow-release carbon source can provide sufficient micromolecular substrates for anode electrogenesis microbes for a long time, so that the long-term sufficiency of the electrogenesis fuel of the dissolved oxygen sensor is ensured. Cathode reaction of microbial fuel cell: the dissolved oxygen is reacted with the electrons and protons to generate water. Therefore, when the microbial fuel cell is in a cathode-limited state, the cathode reactant (dissolved oxygen concentration) and the reaction rate (current value of the cell) are proportional according to a first order reaction kinetic equation, i.e., the dissolved oxygen concentration can be indicated by measuring the current value of the microbial fuel cell.

The working process of the dissolved oxygen sensor provided by the invention is as follows: the method can not be used for measuring the concentration of the dissolved oxygen in the water body temporarily as the starting period of the dissolved oxygen sensor within 2-3 days after starting. In the starting period, the anode electrogenesis bacteria and the fermentation microorganisms gradually reproduce and grow, the biological community near the anode is continuously changed, macromolecular organic matters are gradually decomposed into micromolecular organic acids by the fermentation microorganisms, the electrogenesis microorganisms utilize decomposition products to generate electricity, and the current of the sensor gradually rises. After 2-3 days, the performance of the anode is stable, the current of the sensor is stable under the same dissolved oxygen concentration, and the sensor is started. After the start-up is completed, the sensor can be used for long-term in-situ monitoring of the concentration of the dissolved oxygen in the water body.

Under the condition that environmental factors such as conductivity, temperature, pH and the like are stable, the current value of the microbial fuel cell and the dissolved oxygen concentration near the cathode present a fixed functional relation, the voltage on the external resistor is measured, the voltage is calculated into current through ohm's law, and the current and the dissolved oxygen concentration are substituted into the functional relation, so that the dissolved oxygen concentration of the water body at the moment can be obtained.

The invention carries out the starting and long-term operation of the dissolved oxygen sensor under the following conditions, and tests on the response of the sensor to different dissolved oxygen concentrations are carried out for 17 times irregularly during the period:

anode: 5cm x 9cm carbon cloth

Cathode: graphite plate with diameter of 3cm and thickness of 0.5cm

Macromolecular organic matter: 6g chitin

Temperature: 30 deg.C

pH：7

Electrolyte solution: naCl solution

Conductivity: 55ms/cm

The operation of the sensor under the above environment is shown in fig. 3, the dissolved oxygen sensor can ensure that the operation current is stabilized at 210 ± 10 μ a within 6 months, and after 6 months, the performance of the sensor gradually decreases due to depletion of chitin. The summary results of 17 tests performed irregularly within 6 months of stable operation of the sensor are shown in fig. 4, the range of the dissolved oxygen sensor is 0-15mg/L, and the current-dissolved oxygen response curve is divided into a linear section (corresponding to a dissolved oxygen concentration of 0-8 mg/L) and a non-linear section (corresponding to a dissolved oxygen concentration of 8-15 mg/L). The current (unit: muA) is represented by x, the dissolved oxygen concentration (unit: mg/L) is represented by y = (x-12.296)/21.388 in the linear section, and the relationship is represented by the non-linear section

In the actual use process, the measured current value x is firstly substituted into a linear relational expression to obtain y, and if the y is within 0-8mg/L, the value of the y is the value of the dissolved oxygen concentration measured by the dissolved oxygen sensor; if y is a negative number, the dissolved oxygen concentration in the water body at this time is considered to be 0. If the calculated y is larger than 8mg/L, substituting x into the nonlinear relational expression to solve y, and if a real number solution exists, taking the real number solution y within the range of 8-15mg/L as the dissolved oxygen concentration value measured by the dissolved oxygen sensor; if no real solution exists, the dissolved oxygen concentration in the water body exceeds the measuring range of the sensor at the moment.

Example 2: substrate-enhanced long-term in-situ bioelectrochemical sensor as biotoxicity sensor

The present invention is designed based on the principles of sediment microbial fuel cells and biocathodes. As in example 1, the anode macromolecular organic substance 2 as a slow-release carbon source can provide sufficient micromolecular substrates for the anode electrogenesis microorganisms for a long time, so that the capability of the anode for outputting electrons for a long time is ensured. Unlike example 1, the cathode has microorganisms growing thereon, which act as a catalyst to accelerate the oxygen reduction reaction at the surface of the cathode. When the cathode is impacted by a biological toxic substance (such as heavy metal ions, organic pollutants and the like), the activity of the microbial catalyst on the surface of the cathode is reduced, so that the current of the sensor is reduced. In the range of bio-lethal concentrations, the greater the impact of toxic substances on the biocathodes, the more the current of the microbial fuel cell is reduced. Therefore, the difference value of the current when the microbial fuel cell has no toxic substance impact and the current after impact can be used for representing the biological comprehensive toxicity of the water body. The working process of the toxicity sensor provided by the invention is as follows: the sensor can not be used for monitoring the comprehensive toxicity of the water organisms temporarily in the starting period of the toxicity sensor within 15 days after starting. During the first 2-3 days of the start-up period, the anodes gradually enriched in microbial communities, the anode performance gradually stabilized, and the current of the sensor first plateaus (fig. 5). During subsequent start-up, autotrophic microorganisms (biocathodes) grow on the cathode by the inoculation, enrichment and cultivation of the substrate sludge, and these microorganisms act as catalysts to accelerate the rate of the cathodic oxygen reduction reaction. In the growth process of the biological cathode, the current of the sensor further rises, when the microbial community on the surface of the cathode grows stably, the current of the sensor reaches stability to form a second platform period (figure 5), and the appearance of the second platform period indicates that the toxicity sensor is started completely, so that the sensor can be used for long-term in-situ monitoring of comprehensive toxicity of water organisms.

When toxic substances appear in the water area monitored by the sensor, the catalytic activity of the biocathode is inhibited, and the current of the sensor is reduced. In this example, the biocathode inhibition ratio is used to reflect the biological comprehensive toxicity of the tested water body, and is calculated by the following formula:

the biocathode current is the current value of the sensor when the biocathode is not impacted by toxicity (the current value corresponding to the platform 2 in fig. 5), the real-time current is the current value of the current sensor, and the blank graphite plate current is the current value when the sensor has no long biocathode (the current value corresponding to the platform 1 in fig. 5). The biocathode inhibition rate reaches 100 percent, which indicates that the biocathode is completely lethal.

The toxicity sensor was tested in the laboratory to be able to run stably for at least 6 months. Toxicity tests were conducted in the laboratory with varying concentrations of copper ions and benzene, and biocathode inhibition was plotted against toxic substance concentration and time as shown in table 1.

Table 1: biocathode inhibition rate under different toxic substances and time

Toxic substances	Concentration of	5min inhibition rate	Inhibition rate of 10min	Inhibition rate for 20min	Inhibition rate of 30min
						Cu ²⁺	4mg/L	38.8％	75.4％	98.7％	100％
Cu ²⁺	8mg/L	88.6％	98.3％	100％	100％
						Benzene (III)	0.005％	10.4％	18.5％	27.8％	30.8％
Benzene and its derivatives	0.025％	20.3％	44.7％	61.6％	70.5％
						Benzene and its derivatives	0.1％	50％	68.1％	94.7％	97.4％

It will be understood by those skilled in the art that the foregoing embodiments are specific examples of the practice of the invention and that various changes in form and detail may be made therein without departing from the spirit and scope of the invention and that the invention may be practiced for other sensors developed based on microbial fuel cells.

Claims

1. The application of the substrate-enhanced long-term in-situ bioelectrochemical sensor is characterized in that the substrate-enhanced long-term in-situ bioelectrochemical sensor comprises an anode chamber, a cathode (5), a separation material (4) and an external resistor (7); an anode (1) is arranged inside the anode chamber, macromolecular organic matters (2) are added around the anode (1), and the rest space of the anode chamber is filled with bottom mud (3); a separation material (4) is fixed on the outer side of the anode chamber, and the cathode (5) is fixed on the other side of the separation material (4); two ends of the external resistor (7) are respectively connected with the anode (1) and the cathode (5); the macromolecular organic matter (2) is chitin or cellulose;

the substrate-enhanced long-term in-situ bioelectrochemical sensor is used as a dissolved oxygen sensor and specifically comprises the following components: macromolecular organic matters are gradually decomposed into micromolecular organic acids by the fermentation microorganisms, the electricity generating microorganisms generate electricity by using decomposed products, a functional relation between the current value of the dissolved oxygen sensor and the dissolved oxygen concentration near the cathode is calibrated, the voltage on the external resistor is measured and calculated into current through an ohm law, and the current and the dissolved oxygen concentration are substituted into the functional relation between the current and the dissolved oxygen concentration, so that the dissolved oxygen concentration of the water body at the moment can be obtained;

and (c) and (d),

the substrate-enhanced long-term in-situ bioelectrochemical sensor is used as a biotoxicity sensor, and specifically comprises the following components: the biological toxicity of the tested water body is reflected by the biological cathode inhibition rate, and the calculation formula is as follows:

。

2. use according to claim 1, wherein the separating material (4) is glass fibre, an ion exchange membrane or synthetic fibre cloth.

3. Use according to claim 1, characterized in that the material of the anode (1) is carbon cloth, carbon fiber mesh, graphite plate, carbon brush, graphite particles or carbon paper.

4. Use according to claim 1, characterized in that the cathode (5) is made of graphite plate, carbon paper, carbon brush, glassy carbon or carbon cloth.

5. The use according to claim 1, characterized in that the two ends of the external resistor (7) are connected to the anode (1) and the cathode (5) respectively by means of wires (6); the lead (6) is a titanium wire or a stainless steel wire.

6. Use according to claim 1, characterized in that the anode chamber and the cathode (5) are located inside a housing (8); the shell (8) is made of high molecular engineering plastics.

7. Use according to claim 6, characterised in that the material of the housing (8) is epoxy glass fibre board.