A biological cathode sensor and its use

Abstract

This invention belongs to the field of environmental monitoring technology, specifically relating to a biocathode sensor and its application. The biocathode sensor provided by this invention includes an electrolytic cell and a three-electrode system. The three-electrode system includes a working electrode, a counter electrode, and a reference electrode. The working electrode includes a modified electrode and an electroautotrophic cathode biofilm loaded on the surface of the modified electrode. The modified electrode includes a base electrode and a modifying material; the modifying material includes riboflavin or iron porphyrin; the electroautotrophic cathode biofilm is a mixed bacterial system mainly composed of Moheibacter. The biocathode sensor provided by this invention can be used to monitor and identify non-toxic organic matter and toxic substances in water bodies.

Description

Technical Field

[0001] This invention belongs to the field of environmental monitoring technology, specifically relating to a biological cathode sensor and its application. Background Technology

[0002] Traditional water pollution detection methods rely on large instruments, resulting in low efficiency and convenience, and making real-time online monitoring of pollutants difficult. Microbial electrochemical technology is a novel biomonitoring technique that can be used to monitor toxic substances and organic matter in water. The monitoring process primarily relies on a unique electron transfer mode between electroactive biofilms and electrodes, known as extracellular electron transfer (EET). When a target pollutant is suddenly present or its concentration changes, the metabolic activity or pattern of electroactive microorganisms is affected, which is then converted into changes in electrical signals by sensors.

[0003] Microbial electrochemical sensing elements are generally classified into anodic and cathodic types. During target analyte monitoring, bioanodic sensors are frequently affected by various water quality parameters. Before monitoring, anaerobic water and carbon sources need to be replenished to ensure a stable baseline signal for the bioanodic sensor. Furthermore, because organic matter is required as an electron donor, the heterotrophic biofilm on the anode may restrict the mass transfer process of the target analyte, thereby reducing the sensor's sensitivity. Compared to bioanodic sensors, biocathode sensors can monitor aerobic water environments without the addition of organic matter, exhibiting lower detection limits and higher sensitivity.

[0004] However, there are currently no biocathode sensors that can be used to monitor and distinguish between organic matter and toxic substances in water. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a biocathode sensor and its application. The biocathode sensor provided by the present invention can be used to monitor and identify organic (non-toxic) and toxic substances in water.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a biocathode sensor, comprising an electrolytic cell and a three-electrode system, wherein the three-electrode system includes a working electrode, a counter electrode, and a reference electrode. The working electrode comprises a modified electrode and a cathode biofilm loaded on the surface of the modified electrode; the modified electrode comprises a base electrode and a modifying material; the modifying material comprises riboflavin or iron porphyrin.

[0008] The cathode biofilm is a mixed bacterial system mainly composed of Moheibacter.

[0009] Preferably, the preparation of the working electrode includes:

[0010] In a three-electrode system with a modified electrode as the working electrode, a stainless steel mesh as the counter electrode, and Ag / AgCl as the reference electrode, an organic carbon source was used as the electrolyte to acclimate the inoculum to an electroheterotrophic anodic biofilm, thereby obtaining an anode loaded with an anodic biofilm.

[0011] The inoculation source is the effluent from MFCs that have been operating stably for more than 3 years.

[0012] After reversing the electrode polarity of the anode of the loaded anode biofilm, the electroautotrophic cathode biofilm is acclimated under the conditions of cathode electrolyte and dissolved oxygen to obtain the working electrode.

[0013] Preferably, the base electrode is a carbon felt electrode, a carbon cloth electrode, or a carbon brush electrode.

[0014] Preferably, the loading of the modifying material on the carbon felt electrode is 5–50 mg / cm³. 2 .

[0015] Preferably, when the modifying material is riboflavin, the method for preparing the modified electrode includes the following steps:

[0016] Under light-protected conditions, the base electrode was immersed in a mixture of sodium alginate and riboflavin to load riboflavin, thus obtaining an electrode loaded with riboflavin and sodium alginate.

[0017] The modified electrode was obtained by immersing the electrode loaded with riboflavin and sodium alginate in an inorganic calcium salt solution for ion exchange.

[0018] Preferably, the crosslinking agent comprises a CaCl2 solution and / or a SrCl2 solution.

[0019] Preferably, when the modifying material is iron porphyrin, the method for preparing the modified electrode includes the following steps:

[0020] Using an iron porphyrin H2SO4 solution as the electrolyte and a basic electrode as the working electrode, a three-electrode system was used for cyclic voltammetry scanning to obtain the modified electrode.

[0021] Preferably, the voltage range of the cyclic voltammetry scan is -1.1 to 2.2V; the number of cyclic voltammetry scans is 4 to 6; and the scan rate of the cyclic voltammetry scan is 50 to 150 mV / s.

[0022] The present invention also provides a method for identifying non-toxic organic matter and toxic substances in water using the aforementioned biocathode sensor, comprising the following steps:

[0023] The water sample to be tested is placed in the biocathode sensor for electrochemical detection to obtain the response current density;

[0024] If the response current of the test result recovers to the baseline current density, then the water sample to be tested contains only non-toxic organic matter.

[0025] If the response current density of the test result recovers, but does not recover to the baseline current density, then the water sample to be tested contains non-toxic organic matter and toxic substances.

[0026] If the response current density of the test result does not recover, then the water sample to be tested contains only toxic substances.

[0027] The present invention also provides a method for detecting the content of non-toxic organic matter and toxic substances in water using the aforementioned biocathode sensor, comprising the following steps:

[0028] The water sample to be tested was placed in the biocathode sensor for electrochemical detection, and the response current density of non-toxic organic matter and the response current density of toxic substances were obtained respectively.

[0029] The content of non-toxic organic matter in the water sample to be tested is obtained based on the response current density of non-toxic organic matter and the predetermined standard curve of non-toxic organic matter.

[0030] The content of non-toxic organic matter in the water sample to be tested is obtained by comparing the response current density of toxic substances with the predetermined standard curve of toxic substances.

[0031] The toxic organic response current density is the difference between the baseline current density and the recovery current density;

[0032] The non-toxic substance response current density is the difference between the recovery current density and the valley current density.

[0033] This invention provides a biocathode sensor, comprising an electrolytic cell and a three-electrode system. The three-electrode system includes a working electrode, a counter electrode, and a reference electrode. The working electrode includes a modified electrode and a cathode biofilm loaded on the surface of the modified electrode. The modified electrode includes a base electrode and a modifying material; the modifying material includes riboflavin or iron porphyrin; the cathode biofilm is a mixed bacterial system dominated by Moheibacter. This invention rapidly enriches the biocathode biofilm dominated by Moheibacter through modified electrodes and polarity reversal, which not only solves the difficulty of biocathode film formation, shortens the sensor start-up time, and improves the sensor's baseline current, but also distinguishes between organic matter and toxins. Attached Figure Description

[0034] Figure 1 The following are the It curves for the start-up of the bioanode in Examples 1-2 and Comparative Example 1;

[0035] Figure 2 The following are the It curves for the start-up of the biocathode in Examples 1-2 and Comparative Example 1;

[0036] Figure 3 The graph shows the change in current density of the biocathode sensor in response to different concentrations of BOD in Application Examples 1-2 and Comparative Application Example 1.

[0037] Figure 4 The graph shows the change in current density of the biocathode sensor in response to different concentrations of formaldehyde in Application Examples 3-4 and Comparative Application Example 2.

[0038] Figure 5 The graph shows the change in current density in response to formaldehyde and sodium acetate using the biocathode sensor in Application Example 3. Detailed Implementation

[0039] This invention provides a biocathode sensor, comprising an electrolytic cell and a three-electrode system. The three-electrode system includes a working electrode, a counter electrode, and a reference electrode. The working electrode includes a modified electrode and a cathode biofilm loaded on the surface of the modified electrode. The modified electrode includes a base electrode and a modifying material. The modifying material includes riboflavin or iron porphyrin. The cathode biofilm is a mixed bacterial system mainly composed of Moheibacter.

[0040] Unless otherwise specified, the present invention does not have special requirements on the source of the raw materials used in the preparation, and commercially available products well known to those skilled in the art can be used.

[0041] The present invention provides a biological cathode sensor, comprising an electrolytic cell and a three-electrode system, wherein the three-electrode system comprises a working electrode, a counter electrode and a reference electrode.

[0042] In this invention, the counter electrode is preferably a stainless steel electrode, and the reference electrode is preferably an Ag / AgCl electrode.

[0043] In this invention, the working electrode includes a modified electrode and a cathode biofilm loaded on the surface of the modified electrode.

[0044] In this invention, the modified electrode includes a base electrode and a modifying material; the modifying material includes riboflavin or iron porphyrin.

[0045] In this invention, the base electrode is preferably a carbon felt electrode, a carbon cloth electrode, or a carbon brush electrode, more preferably a carbon felt electrode; the loading of the modifying material on the base electrode is preferably 5-50 mg / cm³. 2 More preferably 50 mg / cm 2 .

[0046] In this invention, when the modifying material is riboflavin, the method for preparing the modified electrode includes the following steps:

[0047] Under light-protected conditions, the base electrode was immersed in a mixture of sodium alginate and riboflavin to load riboflavin, thus obtaining an electrode loaded with riboflavin and sodium alginate.

[0048] The modified electrode was obtained by immersing the electrode loaded with riboflavin and sodium alginate in an inorganic calcium salt solution for ion exchange.

[0049] In this invention, before modifying the carbon felt electrode, it is preferable to further perform impurity removal and washing on the carbon felt electrode sequentially. In this invention, the impurity removal preferably involves immersing the carbon felt electrode in acetone overnight. In this invention, the washing is preferably performed sequentially by ultrasonic washing with ethanol and ultrasonic washing with deionized water. The number of times the ethanol ultrasonic washing is performed is preferably three, and the number of times the deionized water ultrasonic washing is preferably three, with each washing session preferably lasting 15-20 minutes.

[0050] In this invention, the preparation of the sodium alginate and riboflavin mixture preferably involves mixing a riboflavin solution and a sodium alginate solution to obtain the sodium alginate and riboflavin mixture. In this invention, the concentration of the riboflavin solution is preferably 1–20 mmol / L, more preferably 5–10 mmol / L. In this invention, the mass concentration of the sodium alginate solution is preferably 0.1–2%, more preferably 0.5–1.5%. In this invention, the volume ratio of the sodium alginate solution to the riboflavin solution is preferably 1:2. In this invention, the crosslinking agent preferably includes a CaCl2 solution and / or a SrCl2 solution, more preferably a CaCl2 solution. In this invention, the mass concentration of the inorganic calcium salt solution is preferably 0.4–0.6%, more preferably 0.5%.

[0051] In this invention, the soaking time in the mixture of sodium alginate solution and riboflavin solution is preferably 8-12 hours, more preferably 10 hours. In this invention, the soaking time in the inorganic calcium salt solution is preferably 1.5-2.5 hours, more preferably 2 hours.

[0052] In this invention, after soaking in the inorganic calcium salt solution, the process preferably further includes washing and drying. The washing reagent is preferably deionized water, and the washing is preferably performed until the supernatant is clear. In this invention, the drying temperature is preferably room temperature air drying.

[0053] In this invention, when the modifying material is iron porphyrin, the method for preparing the modified electrode includes the following steps:

[0054] Using an iron porphyrin H2SO4 solution as the electrolyte and a basic electrode as the working electrode, a three-electrode system was used for cyclic voltammetry scanning to obtain the modified electrode.

[0055] In this invention, the iron porphyrin H2SO4 solution comprises iron porphyrin and H2SO4 solution. Preferably, the concentration of the H2SO4 solution is 0.08–0.12 mol·L⁻¹. -1 More preferably 0.1 mol·L -1 In this invention, the concentration of iron porphyrin in the H₂SO₄ solution is preferably 0.01–0.015 mmol·L⁻¹. -1 More preferably, it is 0.013 mmol·L⁻¹. -1 .

[0056] In this invention, the voltage of the cyclic voltammetry scan is preferably -1.1 to 2.2V, more preferably 1 to 2V; the number of cyclic voltammetry scans is preferably 4 to 6, more preferably 5; and the scan rate of the cyclic voltammetry scan is preferably 50 to 150 mV / s, more preferably 100 mV·s. -1 .

[0057] In this invention, the preparation of the working electrode includes:

[0058] In a three-electrode system with a modified electrode as the working electrode, a stainless steel mesh as the counter electrode, and Ag / AgCl as the reference electrode, an organic carbon source was used as the electrolyte to acclimate the inoculum to an electroheterotrophic anodic biofilm, thereby obtaining an anode loaded with an anodic biofilm.

[0059] The inoculation source is the effluent from MFCs that have been operating stably for more than 3 years.

[0060] After reversing the electrode polarity of the anode of the loaded anode biofilm, the electroautotrophic cathode biofilm is acclimated under the conditions of cathode electrolyte and dissolved oxygen to obtain the working electrode.

[0061] In this invention, an anode loaded with an anolyte is obtained by using an organic carbon source as the electrolyte in a three-electrode system with a modified electrode as the working electrode, a stainless steel mesh as the counter electrode, and Ag / AgCl as the reference electrode, and by acclimating the inoculation source to an electroheterotrophic anolyte biofilm.

[0062] In this invention, the inoculum source is preferably the effluent from MFCs that have been operating stably in the laboratory for more than two years, and more preferably the effluent from MFCs that have been operating stably for three years.

[0063] In this invention, the acclimatization conditions of the electroheterotrophic anode biofilm include: the organic carbon source preferably includes a sodium acetate solution, and the concentration of the sodium acetate solution is preferably 1-3 mg / L, more preferably 1 mg / L.

[0064] After obtaining the anodic biofilm, the present invention reverses the electrode polarity of the anode loaded with the anodic biofilm, and then acclimates the electroautotrophic cathode biofilm under the conditions of cathode electrolyte and dissolved oxygen to obtain the working electrode.

[0065] In this invention, the cathode electrolyte preferably comprises a sodium bicarbonate solution, and the mass concentration of the sodium bicarbonate solution is preferably 0.94 to 1 mg / L, more preferably 0.94 mg / L.

[0066] In this invention, the preferred conditions for the acclimatization of the electroautotrophic cathode biofilm include: a dissolved oxygen concentration preferably of 6–8 mg / L, more preferably 8 mg / L, and a voltage preferably of -0.6–0 V, more preferably -0.2 V. In this invention, the acclimatization of the electroautotrophic cathode biofilm is preferably carried out in a constant potential mode.

[0067] The present invention also provides a method for identifying BOD and toxic substances in water using the aforementioned biocathode sensor, comprising the following steps:

[0068] The water sample to be tested is placed in the biocathode sensor for electrochemical detection to obtain the response current;

[0069] If the response current of the test result can recover to the baseline current density, then the water sample to be tested contains only non-toxic organic matter.

[0070] If the response current of the test result can be recovered, but cannot be recovered to the baseline current density, then the water sample to be tested contains non-toxic organic matter and toxic substances.

[0071] If the response current of the test result cannot be recovered, then the water sample to be tested contains only toxic substances.

[0072] In this invention, the recognition mechanism of the non-toxic organic matter is as follows: the electroautotrophic cathode biofilm obtains electrons from the electrode to achieve electroautotrophic growth, and outputs a constant current signal at this time; once organic matter appears in the water, it will change from an electroautotrophic state to a heterotrophic state, which is manifested by a decrease in the current signal. When the organic matter in the water is consumed, the electroautotrophic cathode biofilm will revert to an autotrophic state, and the current will return to the baseline current.

[0073] In this invention, the recognition mechanism of the toxic substance is as follows: the electroautotrophic cathode biofilm obtains electrons from the electrode to achieve electroautotrophic growth, and outputs a constant current signal at this time; once a toxic substance appears in the water, it will poison some of the electroautotrophic cathode biofilm, causing the current signal to drop and become irreversible.

[0074] This invention also provides a method for detecting the content of non-toxic organic matter and toxic substances in water using the biocathode sensor described above, comprising the following steps:

[0075] The water sample to be tested was placed in the biocathode sensor for electrochemical detection, and the response current density of non-toxic organic matter and the response current density of toxic substances were obtained respectively.

[0076] The content of non-toxic organic matter in the water sample to be tested is obtained based on the response current density of non-toxic organic matter and the predetermined standard curve of non-toxic organic matter.

[0077] The content of non-toxic organic matter in the water sample to be tested is obtained by comparing the response current density of toxic substances with the predetermined standard curve of toxic substances.

[0078] The toxic organic response current density is the difference between the baseline current density and the recovery current density;

[0079] The non-toxic substance response current density is the difference between the recovery current density and the valley current density.

[0080] Taking the presence of both non-toxic organic matter and toxic substances in water as an example, this paper explains the determination of the response current of non-toxic organic matter and the response current of toxic substances.

[0081] In this invention, the difference between the baseline current density and the valley current density is the sum of the non-toxic organic response current density and the toxic substance response current density; the difference between the baseline current density and the recovery current density is the toxic response current. Therefore, the non-toxic organic response current density is the difference between the recovery current density and the valley current density.

[0082] In this invention, the method for preparing the predetermined non-toxic organic standard curve preferably includes:

[0083] After the current of the biocathode sensor reached a stable baseline current plateau for 12 hours, the sensor was tested sequentially with BOD5 concentrations of 10 mg / L, 30 mg / L, 50 mg / L, and 70 mg / L for the non-toxic organic compounds to be tested. The current density was fitted with the corresponding BOD5 value to obtain the standard curve of the non-toxic organic compounds to be tested.

[0084] In this invention, the method for preparing the predetermined toxic substance standard curve preferably includes:

[0085] After the current of the biocathode sensor reaches a stable baseline current plateau for 12 hours, a series of toxic substance solutions with concentrations of 10 ppm, 30 ppm, 50 ppm, and 70 ppm are tested using the biocathode sensor. The current density is fitted with the corresponding toxic substance concentration to obtain the standard curve of the toxic substance to be tested.

[0086] In this invention, the toxic substance is preferably formaldehyde.

[0087] In this invention, the output current signal of the biocathode sensor needs to be stable for 12 to 48 hours before the detection.

[0088] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0089] Example 1

[0090] Riboflavin-modified electrode (RF): A 1% sodium alginate solution and a 5mM riboflavin solution were mixed evenly at a volume ratio of 1:2. The carbon felt was then immersed in the solution for 10 hours in a light-protected environment. The electrode was then removed and immersed in a 0.5% CaCl2 solution for 2 hours. After rinsing with deionized water, the electrode was air-dried at room temperature to obtain the riboflavin-modified electrode.

[0091] The riboflavin-modified electrode was used as the anode, a stainless steel mesh as the counter electrode, and an Ag / AgCl electrode as the reference electrode. These three electrodes were connected to a three-electrode single-chamber reactor. The effluent from MFCs that had been stably operating in the laboratory for three years was used as the inoculum. The anolyte was acclimated at 0V. When the current value dropped below 0.5mA, the anolyte was replaced, and this was recorded as one complete acclimation cycle. After five cycles, the anolyte reached maturity.

[0092] After the acclimatization of the anodic biofilm was completed, the electrode polarity was reversed. Then, the three-electrode single-chamber reactor was connected to a multi-channel potentiostat (CHI 1000C). Under the conditions of cathode electrolyte (NaHCO3 solution, concentration of 0.94 mg / L) and dissolved oxygen (concentration of 8 mg / L, provided by an external aeration device), the electroautotrophic cathode biofilm was acclimatized (the voltage during acclimatization was -0.2V) to obtain the biocathode sensor.

[0093] Example 2

[0094] Iron porphyrin modified electrode (FP): containing 0.013 mmol·L⁻¹ -1 0.1 mol·L⁻¹ of iron porphyrin powder -1 Using H2SO4 solution as the electrolyte, the electrolysis proceeds at a voltage of 2.2V and a flow rate of 100mV·s. -1 Cyclic voltammetry was performed at a specific scan rate. After cyclic voltammetry, the electrode was washed with distilled water and then dried in an oven at 60°C to obtain the iron porphyrin-modified electrode.

[0095] Using the above-mentioned iron porphyrin-modified electrode as the anode, a stainless steel mesh as the counter electrode, and an Ag / AgCl electrode as the reference electrode, the three electrodes were connected to a three-electrode single-chamber reactor. The effluent from MFCs that had been running stably in the laboratory for three years was used as the inoculum source to achieve the acclimatization of the anode biofilm at a potential of 0V.

[0096] After the acclimatization of the anodic biofilm was completed, the electrode polarity was reversed. Then, the three-electrode single-chamber reactor was connected to a multi-channel potentiostat (CHI 1000C). Under the conditions of cathode electrolyte (NaHCO3 solution, concentration of 0.94 mg / L) and dissolved oxygen (concentration of 8 mg / L, provided by an external aeration device), the electroautotrophic cathode biofilm was acclimatized (the voltage during acclimatization was -0.2V) to obtain the biocathode sensor.

[0097] Comparative Example 1

[0098] The only difference from Example 1 is that the anode is an unmodified carbon felt electrode.

[0099] Figure 1 The following are the It curves for the start-up of the bioanode in Examples 1-2 and Comparative Example 1, from... Figure 1 It can be seen that during the anode start-up stage, the reactor with the iron porphyrin modification group had the shortest start-up time and the highest peak current density.

[0100] Figure 2 The following are the It curves for the start-up of the biocathode in Examples 1-2 and Comparative Example 1, from... Figure 2 It can be seen that after the conversion from cation to anion, the output current density of the biocathode in the iron porphyrin modified group is the largest.

[0101] Application Example 1

[0102] After the output current signal of the biocathode sensor prepared in Example 1 has been stable for 48 hours, sodium acetate solutions of different concentrations (10 mg / L, 30 mg / L, 50 mg / L, 70 mg / L) are injected into the biocathode sensor in batches for testing. The response of the biocathode sensor to BOD is recorded by time-current curve to test the sensor performance.

[0103] Application Example 2

[0104] After the output current signal of the biocathode sensor prepared in Example 1 has been stable for 48 hours, sodium acetate solutions of different concentrations (10 mg / L, 30 mg / L, 50 mg / L, 70 mg / L) are injected into the biocathode sensor in batches for testing. The response of the biocathode sensor to BOD is recorded by time-current curve to test the sensor performance.

[0105] Comparative Application Example 1

[0106] When the output current signal of the biocathode sensor described in Comparative Example 1 remained stable for 48 hours, sodium acetate solutions of different concentrations (10 mg / L, 30 mg / L, 50 mg / L, 70 mg / L) were injected into the biocathode sensor in batches for testing. The response of the biocathode sensor to BOD was recorded by time-current curves to test the sensor performance.

[0107] Figure 3 To illustrate the current changes in response to different BOD concentrations using the oxygen reduction biocathode sensors in Application Examples 1-2 and Comparative Application Example 1, from... Figure 3 It can be seen that all three groups of biocathode sensors can continuously respond to different concentrations of organic matter, among which the iron porphyrin modified group is the most sensitive to the unit concentration of organic matter.

[0108] Application Example 3

[0109] When the output current signal of the biocathode sensor prepared in Example 1 has been stable for 12 hours, formaldehyde solutions with different concentrations (formaldehyde concentrations in the sensor are 37ppm, 74ppm, 222ppm, 370ppm, and 444ppm, respectively) are injected into the biocathode sensor in batches for testing. The response of the biocathode sensor to toxic substances is recorded by time-current curves to test the sensor performance.

[0110] Application Example 4

[0111] When the output current signal of the biocathode sensor prepared in Example 2 has been stable for 12 hours, formaldehyde solutions with different concentrations (formaldehyde concentrations in the sensor are 37ppm, 74ppm, 222ppm, 370ppm, and 444ppm, respectively) are injected into the biocathode sensor in batches for testing. The response of the biocathode sensor to toxic substances is recorded by time-current curves to test the sensor performance.

[0112] Comparative Application Example 2

[0113] When the output current signal of the biocathode sensor prepared in Comparative Example 1 remained stable for 12 hours, formaldehyde solutions with different concentrations (formaldehyde concentrations in the sensor were 37 ppm, 74 ppm, 222 ppm, 370 ppm, and 444 ppm, respectively) were injected into the biocathode sensor in batches for testing. The response of the biocathode sensor to toxic substances was recorded by time-current curves to test the sensor performance.

[0114] Figure 4 To illustrate the changes in the response current of the oxygen reduction biocathode sensor to different concentrations of formaldehyde in Application Examples 3-4 and Comparative Application Example 2, from... Figure 4It can be seen that when organic matter and toxic substances are present in the water sample, the activity of the biofilm will be inhibited by the toxins, and the output current density of the sensor will recover partially.

[0115] Application Example 4

[0116] The method for preparing the predetermined standard curve of non-toxic organic compounds is as follows:

[0117] After the current of the biocathode sensor reached a stable baseline current plateau for 12 hours, the sensor was tested sequentially with BOD5 concentrations of 10 mg / L, 30 mg / L, 50 mg / L, and 70 mg / L for the non-toxic organic compounds to be tested. The current density was fitted with the corresponding BOD5 value to obtain the standard curve of the non-toxic organic compounds to be tested. The standard curve was: y = 0.0034x + 0.017.

[0118] In this invention, the method for preparing the predetermined toxic substance standard curve preferably includes:

[0119] After the current of the biocathode sensor reaches a stable baseline current plateau for 12 hours, a series of toxic substance solutions with concentrations of 10 ppm, 30 ppm, 50 ppm, and 70 ppm are tested using the biocathode sensor. The current density is fitted with the corresponding toxic substance concentration to obtain the standard curve of the toxic substance to be tested. The standard curve is: y = 0.002x - 0.0014.

[0120] After the output current signal of the biocathode sensor prepared in Example 2 remained stable for 12 hours, a mixed solution containing 74 ppm formaldehyde and 10 mg / L sodium acetate was injected into the biocathode sensor for testing. The response of the biocathode sensor to the toxic / organic mixture was recorded using a time-current curve to test the sensor performance. The test results are shown in […]. Figure 5 The test showed that the corresponding current density for formaldehyde was 0.165 A / m. 2 The corresponding current density for sodium acetate is 0.06 A / m. 2 Substituting the corresponding current densities of formaldehyde and sodium acetate into the corresponding standard curves, the concentrations of formaldehyde and sodium acetate were found to be 82.2 ppm and 12.6 mg / L, respectively.

[0121] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for detecting the content of non-toxic organic matter and toxic substances in water, comprising the following steps: The water sample to be tested was placed in a biocathode sensor for electrochemical detection, and the response current density of non-toxic organic matter and the response current density of toxic substances were obtained respectively. The content of non-toxic organic matter in the water sample to be tested is obtained based on the response current density of non-toxic organic matter and the predetermined standard curve of non-toxic organic matter; the response current density of non-toxic organic matter is the difference between the recovery current density and the valley current density. The content of toxic substances in the water sample to be tested is obtained by comparing the toxic substance response current density with a predetermined toxic substance standard curve; the toxic substance response current density is the difference between the baseline current density and the recovery current density. The biocathode sensor includes an electrolytic cell and a three-electrode system, wherein the three-electrode system includes a working electrode, a counter electrode, and a reference electrode. The working electrode includes a modified electrode and a cathode biofilm loaded on the surface of the modified electrode: the modified electrode includes a base electrode and a modifying material; the modifying material includes riboflavin or iron porphyrin; the cathode biofilm is a mixed bacterial system mainly composed of Moheibacter.

2. The method according to claim 1, characterized in that, The preparation of the working electrode includes: In a three-electrode system with a modified electrode as the working electrode, a stainless steel mesh as the counter electrode, and Ag / AgCl as the reference electrode, an organic carbon source was used as the electrolyte to acclimate the inoculum to an electroheterotrophic anodic biofilm, thereby obtaining an anode loaded with an anodic biofilm. The inoculation source is the effluent from MFCs that have been operating stably for more than 3 years. After reversing the electrode polarity of the anode of the loaded anode biofilm, the electroautotrophic cathode biofilm is acclimated under the conditions of cathode electrolyte and dissolved oxygen to obtain the working electrode; the base electrode is a carbon felt electrode, carbon cloth electrode, or carbon brush electrode; the loading amount of the modifying material on the carbon felt electrode is 5~50 mg / cm³. 2 .

3. The method according to claim 1, characterized in that, When the modifying material is riboflavin, the method for preparing the modified electrode includes the following steps: Under light-protected conditions, the base electrode was immersed in a mixture of sodium alginate and riboflavin to load riboflavin, thus obtaining an electrode loaded with riboflavin and sodium alginate. The modified electrode was obtained by immersing the electrode loaded with riboflavin and sodium alginate in an inorganic calcium salt solution for ion exchange.

4. The method according to claim 1, characterized in that, When the modifying material is iron porphyrin, the method for preparing the modified electrode includes the following steps: Using an iron porphyrin H2SO4 solution as the electrolyte and a basic electrode as the working electrode, a three-electrode system was used for cyclic voltammetry scanning to obtain the modified electrode.

5. The method according to claim 4, characterized in that, The voltage range of the cyclic voltammetry scan is -1.1 to 2.2V; the number of cyclic voltammetry scans is 4 to 6; and the scan rate of the cyclic voltammetry scan is 50 to 150 mV / s.

Images