CN113740406A - Portable miniaturized COD electrochemical measuring device and measuring method thereof - Google Patents
Portable miniaturized COD electrochemical measuring device and measuring method thereof Download PDFInfo
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- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
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Abstract
The invention relates to a portable miniaturized COD electrochemical measuring device and a measuring method thereof.A software and hardware system for environmental ecology is firstly constructed, the software and hardware system comprises a cylindrical electrochemical experiment pool, a small electrochemical workstation, a circulating pump, an electromagnetic valve, an electric stirrer, an infrared detector, a working electrode, a reference electrode and a counter electrode, and the software system is composed of an artificial intelligence algorithm based on an SVR model. The small-sized electrochemical workstation is based on an electrochemical simulation front end AD5941, a single chip integrates a complete three-electrode-body tether, and the small-sized electrochemical workstation is a novel solution which is high in precision, low in power consumption and capable of being expanded into a multi-parameter measuring system. The working electrode is a BDD electrode, a large amount of hydroxyl radicals with strong oxidizing property can be generated to thoroughly oxidize organic matters in the solution, and the electric quantity passing through the working electrode in the oxidation process is linearly related to the amount of the organic matters in the solution. The main controller calculates a COD value, precision compensation is completed through the SVM model, and data are transmitted to the self-built database through the NB-IoT for a user to check in real time.
Description
Technical Field
The invention relates to a COD electrochemical measurement method, in particular to a portable miniaturized COD on-line measurement device and a method.
Background
Chemical Oxygen Demand (COD) refers to the amount of oxidant consumed under certain conditions to chemically oxidize reducing species (typically oxides) in a treated water sample. COD is an important water quality evaluation comprehensive index, is an important water quality parameter for controlling the total amount of pollution emission in China, and depends on the rapid and efficient detection of COD for the effective control of water pollution. For example, the treatment of high-concentration organic wastewater difficult to degrade relates to a plurality of industrial fields such as pharmacy, printing and dyeing, chemical industry, pesticides, rubber and the like. The waste water has complex components, high organic matter concentration, toxic and difficultly-degraded substances, large treatment difficulty and high investment and operation cost, so that an effective and mature detection technology becomes an important difficult problem to be solved urgently in the field of environmental protection.
The common methods for COD detection mainly comprise a standard chemical oxidation method, an ultraviolet spectroscopy method and an electrochemical advanced oxidation method.
The standard oxidation method is represented by the national standard of dichromate determination of chemical oxygen demand for water quality HJ 828 + 2017, and the test principle is as follows: adding a known amount of potassium dichromate solution into a water sample, taking silver salt as a catalyst under a strong acid medium, boiling and refluxing, taking resorufin as an indicator, titrating unreduced potassium dichromate in the water sample by ammonium ferrous sulfate, and calculating the mass concentration of consumed oxygen according to the amount of the consumed potassium dichromate. On the basis, many scientists continuously seek improvement and provide COD determination technologies which are relatively quick, simple, small in reagent dosage and low in pollution, such as a microwave digestion technology, a spectrophotometry technology, a flow injection technology and the like. The national standard HJ 828-plus 2017 uses a potassium dichromate reflux method to digest samples, and the microwave digestion technology changes the digestion mode, so that the test time is greatly shortened; the COD is determined by spectrophotometry, a spectrophotometer is introduced on the basis of the GB 11914-89 method, the operation is simpler and more convenient, and the analysis speed is higher. The principle is as follows: measuring the absorbance of the redox reaction product Cr (III), calculating the concentration of Cr (III) by utilizing the linear relation between the absorbance and the concentration, and converting the concentration into the COD value of the measured water sample; the introduction of the flow injection technology improves the automation degree and speed, the sample usage amount is less, the technology is based on the spectrophotometry technology and the superposition rapid digestion technology, and the optimization of the detection process is realized by changing the mode that a reagent and a water sample enter a detection system. The standard chemical oxidation method is widely used due to the advantages of high accuracy, high precision, good reproducibility and the like. However, none of these improved techniques have been able to eliminate the problems of the standard methods from the source: a large amount of concentrated sulfuric acid and silver sulfate need to be consumed in the detection process, the waste liquid treatment cost is high, the analysis period is long, the operation is complex, toxic mercury sulfate needs to be added for eliminating the interference of chloride ions in the determination process, and secondary pollution is brought to the environment. Thus limiting the application of standard oxidation processes.
The ultraviolet spectroscopy is a physical method, does not need to consume chemical reagents, has high analysis speed and good detection repeatability, can realize online real-time detection, and is concerned by a plurality of researchers. The basic principle of the ultraviolet spectroscopy online detection is based on ultraviolet absorption of organic matters in sewage, the absorption degrees of different organic matters to light with different wavelengths are different, then a linear relation between an absorption signal and COD is established according to the Lambert-beer law, return light enters a photosensitive tube, and the optical signal is converted into an electric signal and is amplified and collected. However, domestic sewage contains suspended particles and colloids, which are not in the category of COD in terms of analysis, but scatter and interfere with absorption of light passing through a water body, and absorption spectra overlap, so that accurate measurement of COD is affected. Although the ultraviolet absorption spectrometry is usually combined with models such as multiple linear regression, partial least squares regression or neural network to predict the COD value in the water sample, the method adopting the model prediction cannot completely replace the conventional chemical detection method, because the components of the actual water sample, particularly wastewater, are complex, and physicochemical indexes such as the pH value of the sample, inorganic salts and suspended matters affect the absorption spectrum, so that the application of the absorption spectrum in a complex system is limited, and further research on more water samples is required in the future to further expand the application range of the model.
The electrochemical advanced oxidation method is a sewage treatment technology appearing in recent decades, is characterized by generating OH with strong oxidizability, completely oxidizes organic matters difficult to degrade under the condition of electrocatalysis, and calculates the amount of the organic matters in the water body through the current value or the consumption of electric quantity in the oxidation process. The method is an ideal method for treating the waste water containing the organic pollutants difficult to degrade, and generates hydroxyl free radicals (. OH) by anodic oxidation of water, and the hydroxyl free radicals have an oxidation potential as high as 2.8V, so that the organic pollutants difficult to degrade in the waste water can be treatedDegradation of organic oxidation to clean CO2And H2And O. During the period, no oxidant is needed to be added, and no water is needed to be heated and digested. However, this method has not been industrially applied on a large scale due to the limitation of electrode materials. The anode materials commonly used by the electrochemical advanced oxidation method at present mainly comprise a DSA electrode and a BDD electrode. Dsa (dimension stablean) electrodes, also known as dimensionally stable anodes, are electrodes that are coated with a metal oxide coating on a substrate by thermal decomposition, sol-gel, or electroplating. In the field of COD treatment, the DSA electrode substrate material is generally selected from metal titanium with high mechanical strength and good chemical stability, and the coating material is mainly a metal material with high catalytic activity, such as PbO2Iridium tantalum and platinum. Wherein PbO2The DSA electrode of the coating is applied to COD degradation treatment of high organic wastewater in industry due to low cost and high oxidation activity. However, because the DSA electrode has relatively low sensitivity to organic substances and the small-range COD detection limit is low, the method is suitable for large-scale organic matter degradation application, but is not suitable for being used as a COD detection material. In contrast, a boron-doped diamond (BDD) electrode has the excellent characteristics of wide potential window, low background current, good physical and chemical stability and the like, and the formed detection equipment has stable performance and high accuracy and can complete sample detection only in 4-10 min. Most of BDD electrodes are imported in the past and are expensive, but in recent years, domestic science and technology companies have the capability of manufacturing stable BDD electrodes and have been produced in large scale. 30 x 20 x 0.75mm as used in the present invention3The price of the double-sided BDD thin sheet electrode is only 500 yuan RMB, and the cost of the portable miniaturized COD detection device realized by the invention is not higher than 2 thousand yuan.
In conclusion, the traditional standard oxidation method has the problems of long time consumption, complex operation, secondary pollution caused by high-toxicity chemical reagents and the like. The ultraviolet spectroscopy is suitable for simple COD measurement of a treatment system. The electrochemical advanced oxidation method can directly take the electrical parameters caused in the reaction process as analysis signals to quantify the COD value, the COD measurement is completed, meanwhile, the degradation of the COD can be realized, and the detection discharge liquid can be directly discharged into rivers without any secondary pollution. The method has the advantages of simple instrument and device, convenient operation, rapid reaction, short time consumption, environmental protection, easy realization of automation and on-line analysis and monitoring, and is the most promising determination method at present. The BDD electrode greatly reduces the cost of COD measurement by an electrochemical advanced oxidation method in domestic mass production, and the portable low-power-consumption COD detection device greatly promotes domestic water environment treatment by matching with a low-power-consumption and high-integration measurement circuit, and has huge market potential.
Disclosure of Invention
In order to overcome the defects of long detection time, high detection cost, complex operation, difficult realization of on-line measurement, secondary pollution and high requirement on a water sample to be detected in the prior art, the invention provides a portable miniaturized device and a method for measuring COD by using an electrochemical method.
In order to achieve the purpose, the invention adopts the technical scheme that:
the utility model provides a portable miniaturized COD electrochemistry measuring device, is a software and hardware system that is used for ecological environment, includes the hardware system that cylinder electrochemistry experiment pond, small-size electrochemistry workstation, circulating pump, solenoid valve, electric mixer, infrared detector, working electrode, reference electrode, counter electrode and introduction pipeline constitute, and the COD precision compensation software system that is accomplished by artificial intelligence algorithm:
1) the cylindrical electrochemical experimental tank is cylindrical as a whole, the volume is controlled to be 40ml, and the bottom of the cylindrical electrochemical experimental tank is provided with a cylindrical electrochemical experimental tank with the area of 30 x 40mm2The rectangle hole for settle working electrode, working electrode utilize four screws to be fixed in the experiment bottom of the pool through the extrusion of rubber circle, be convenient for and the solution contact that awaits measuring when guaranteeing the leakproofness, cylinder electrochemistry experiment pool left side is sealed with T type rubber buffer, is provided with into appearance hole in the middle of the rubber buffer, and it is provided with reference electrode and counter electrode to advance the appearance hole, cylinder electrochemistry experiment pool upper left side and right downside are provided with injection pipeline and drainage pipe respectively for the interpolation and the discharge of solution await measuring, injection pipeline one end connection instituteThe other end of the cylindrical electrochemical experimental tank is connected with the circulating pump, one end of the drainage pipeline is connected with the right lower side of the cylindrical electrochemical experimental tank, and the other end of the drainage pipeline is connected with the waste liquid barrel;
2) the electric stirrer extends into the cylindrical electrochemical experimental tank from the upper part, the working rotating speed is not higher than 6r/s, and the diameter of the stirring blade is not more than 1 cm;
3) the infrared detector is assembled at the water inlet of the experiment pool and used for detecting whether the liquid to be detected fills the experiment pool or not;
4) one end of the working electrode, one end of the reference electrode and one end of the counter electrode are immersed in the solution to be measured, and the other end of the working electrode, the reference electrode and the counter electrode are connected with the small electrochemical workstation.
5) The working electrode is a boron-doped diamond film (BDD) electrode, the monocrystalline silicon is used as a substrate, the service life is longer, and the area of the upper bottom is not less than 30 x 40mm2The reference electrode is an Ag/AgCl electrode, and the counter electrode is a platinum electrode;
6) the bias voltage of the working electrode is 2.5V, and the oxidation time is 4 min;
furthermore, the small-sized electrochemical workstation comprises an electrochemical simulation front-end chip AD5941, a wireless transmission module and a main controller, wherein the electrochemical simulation front-end single-chip AD5941 integrates all three electrode body tethers and comprises a low-power-consumption high-precision reference voltage generation circuit, a constant potential circuit and a micro current detection circuit, the small-sized electrochemical workstation completes low-power-consumption safe transmission of data by using a narrow-band Internet of things technology, and the main controller controls the narrow-band Internet of things module and the electrochemical simulation front end through a UART (universal asynchronous receiver/transmitter) serial port and an SPI (serial peripheral interface) respectively to realize a portable small-sized COD (chemical oxygen demand) detection circuit.
Furthermore, the drainage pipeline is connected with an electromagnetic valve, the electromagnetic valve is controlled by the main controller to be switched on and off, and the electromagnetic valve is switched on and off to control the solution to be discharged.
Furthermore, the circulating pump is controlled by the main controller, and the opening and closing of the circulating pump controls whether the liquid to be detected enters the experimental tank.
A measuring method of a portable miniaturized COD electrochemical measuring device comprises the following steps: after the system is electrified, the electromagnetic valve is closed, then the circulating pump is started to pump the liquid to be detected from the water quality sampling point into the customized cylindrical electrochemical experiment pool, when the infrared detector detects that the cylindrical electrochemical experiment pool is filled with the liquid to be detected, the circulating pump is closed immediately, and meanwhile, the electric stirrer is started and supplies power to the electrochemical simulation front-end chip AD5941 of the small electrochemical workstation; after the power is supplied to an electrochemical simulation front-end chip AD5941, a timing current method is executed by utilizing a three-electrode-body tether in the chip, data are transmitted to a main controller through an SPI bus interface, the electric quantity flowing at a working electrode within 5min is calculated in the main controller, the content of organic matters in a solution is obtained through a calculation formula, and finally, the detection data are compensated through a trained optimal SVR model; after the timing of 5min is finished, immediately closing the electric stirrer, powering off the electrochemical simulation front-end chip AD5941, simultaneously opening the electromagnetic valve, discharging the solution in the cylindrical electrochemical experiment pool, and finishing the whole COD detection process; and then the main controller sends the COD detection result to a user database through a narrow-band Internet of things. The invention is realized by a COD precision compensation software system.
Furthermore, the COD precision compensation software system completes the COD precision compensation by an artificial intelligence algorithm — SVR model, and the process can be briefly described as follows: establishing an SVR model in MATLAB, carrying out sample data training to obtain an optimal SVR model, then storing the optimal SVR model into a hardware control system, further bringing COD data obtained by real-time measurement into a regression model, and finally obtaining a corresponding accurate value of COD.
The invention has the characteristics and beneficial effects that:
1) electrochemical simulation of the front-end chip AD5941 was used. AD5941 is a high precision, low power consumption Analog Front End (AFE) designed for portable applications requiring high precision, electrochemical-based measurement techniques. The single chip integrates all three-electrode-body tethers such as a low-power-consumption high-precision reference voltage generating circuit, a constant potential circuit and a micro-current detection circuit, and greatly saves the system layout, so that the system has smaller volume and lower power consumption.
2) The SVR model is used as an algorithm model for COD detection data precision compensation, the SVR model is a machine learning algorithm based on a statistical learning theory, and the method has the characteristics of simple structure and strong generalization capability, and has natural superiority on COD measurement data with discreteness and nonuniformity provided by the hardware platform.
3) BDD was used as the working electrode. With the mass production of BDD electrodes in China, the cost of a COD detection device using the BDD electrodes is greatly reduced. The BDD electrode has the excellent characteristics of wide potential window, low background current, good physical and chemical stability and the like, has stronger capability of generating hydroxyl radicals compared with a DSA electrode, has lower BDD loss by using monocrystalline silicon as a substrate, and can continuously work for more than two years.
4) Portability and miniaturization. The invention is matched with a high-performance low-power consumption control circuit, and all components and parts take high integration level and low power consumption as the optimal conditions.
5) The standby time is long. On the premise of low power consumption, the invention is matched with the high-efficiency power supply circuit and the high-efficiency power supply management algorithm, so that the equipment can enter a dormant state in time when not working. If field operation is needed, the solar cell is matched with the rechargeable battery to supply power to the equipment, and theoretically, the standby infinite time can be realized.
6) The cost is low. The BDD electrode is a working electrode, and the BDD electrode is a BDD electrode.
7) And the data transmission is safe and convenient. The data transmission adopts the narrowband internet of things technology, and has lower power consumption and safer transmission environment compared with the wireless transmission technologies such as Bluetooth, 4G, WIFI and the like. Is suitable for field long-time continuous test.
8) Expansibility. The electrochemical simulation front-end chip AD5941 is provided with a plurality of AD/DA and impedance detection ports, and is convenient for the expansion of multi-sensor signal acquisition, such as five items of water quality: turbidity, temperature, dissolved oxygen, conductivity, pH. All water quality parameters are collected in the main controller, and the water quality is comprehensively analyzed, so that the method has a wider application prospect.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a schematic view of the present invention;
in the figure: 1-sampling water quality; 2-a circulating pump; 3-a sample introduction pipeline; 4-an infrared detector; 5-an electric stirrer; 6-cylindrical electrochemical test cell; 7-a working electrode; 8-a control circuit; 9-electrochemical simulation front end; 10-narrowband internet of things; 11-a solenoid valve; 12-drainage pipeline.
FIG. 2 is a block diagram of the system of the present invention.
Detailed Description
Referring to the attached drawings 1 and 2, the portable miniaturized COD electrochemical measuring device provided by the invention is a software and hardware system for ecological environment, and comprises a hardware system consisting of a customized cylindrical electrochemical experiment pool, a small electrochemical workstation, a circulating pump, an electromagnetic valve, an electric stirrer, an infrared detector, a working electrode, a reference electrode, a counter electrode and a sample introduction pipeline, and a COD precision compensation software system completed by an artificial intelligence algorithm:
1) the cylindrical electrochemical experimental tank is cylindrical as a whole, the volume is controlled to be 40ml, and the bottom of the cylindrical electrochemical experimental tank is provided with a cylindrical electrochemical experimental tank with the area of 30 x 40mm2The device comprises a cylindrical electrochemical experimental tank, a rubber ring, a rectangular hole, a sample inlet hole, a reference electrode, a counter electrode, a sample inlet pipeline and a drainage pipeline, wherein the rectangular hole is used for arranging a working electrode, the working electrode is fixed at the bottom of the experimental tank through four screws in an extruding way through the rubber ring, the contact with a solution to be detected is facilitated while the sealing performance is ensured, the left side of the cylindrical electrochemical experimental tank is sealed by the T-shaped rubber plug, the sample inlet hole is formed in the middle of the rubber plug, the reference electrode and the counter electrode are arranged in the sample inlet hole, the sample inlet pipeline and the drainage pipeline are respectively arranged on the upper left side and the lower right side of the cylindrical electrochemical experimental tank and used for adding and discharging the solution to be detected, one end of the sample inlet pipeline is connected with the upper left side of the electrochemical experimental tank, the other end of the sample inlet pipeline is connected with a circulating pump, one end of the drainage pipeline is connected with the lower right side of the electrochemical experimental tank, and the other end of the drainage pipeline is connected with a waste liquid barrel;
2) the electric stirrer extends into the cylindrical electrochemical experimental tank from the upper part, the working rotating speed is not higher than 6r/s, and the diameter of the stirring blade is not more than 1 cm;
3) the infrared detector is assembled at the water inlet of the experiment pool and used for detecting whether the liquid to be detected fills the experiment pool or not;
4) one ends of the working electrode, the reference electrode and the counter electrode are immersed into the solution to be measured, and the other ends of the working electrode, the reference electrode and the counter electrode are connected with the small electrochemical workstation; between the electrodesUnder the drive of potential difference, a large amount of strong oxidizing hydroxyl radicals with 2.8V oxidation potential are generated on the surface of the working electrode and generate oxidation-reduction reaction with organic matters in the solution to be detected to oxidize the organic matters into CO2And H2O, the chemical reaction is accompanied by electrons to pass through the interface between the electrode and the solution to form current, the number of the electrons passing through the interface is represented by total electric quantity Q passing through a circuit, and the electric quantity Q is linearly related to the quantity of organic matters in the solution, so that the COD is detected by an electrochemical method;
5) the working electrode is a boron-doped diamond film (BDD) electrode, the monocrystalline silicon is used as a substrate, the service life is longer, and the area of the upper bottom is not less than 30 x 40mm2The reference electrode is a saturated calomel electrode, and the counter electrode is a platinum electrode;
6) the bias voltage of the working electrode is 2.5V, and the oxidation time is 4 min;
the small-sized electrochemical workstation comprises an electrochemical simulation front-end chip AD5941, a wireless transmission module and a main controller, wherein the electrochemical simulation front-end single chip integrates all three-electrode-body tethers and comprises a low-power-consumption high-precision reference voltage generation circuit, a constant potential circuit and a micro-current detection circuit, the small-sized electrochemical workstation completes low-power-consumption safe transmission of data by using a narrow-band Internet of things technology, and the main controller respectively controls the narrow-band Internet of things module and the electrochemical simulation front end through a UART (universal asynchronous receiver/transmitter) serial port and an SPI (serial peripheral) interface to realize a portable small-sized COD (chemical oxygen demand) detection circuit.
The drainage pipeline is provided with the electromagnetic valve, the solution is discharged by on-off control of the electromagnetic valve, the on-off control of the circulating pump controls whether the solution to be detected enters the experimental tank, and the electromagnetic valve and the circulating pump are controlled by the main controller.
The software system of the invention completes the precision compensation of COD by an artificial intelligence algorithm-SVR model, and the process can be briefly described as follows: establishing an SVR model in MATLAB, carrying out sample data training to obtain an optimal SVR model, then storing the optimal SVR model into a hardware control system, further bringing COD data obtained by real-time measurement into a regression model, and finally obtaining a corresponding accurate value of COD.
The invention discloses a method for detecting COD by using a portable miniaturized COD electrochemical measuring device, which comprises the following steps: the microcontroller controls the system to start once in 30min, executes COD detection, and immediately enters a dormant state after finishing data detection and uploading so as to ensure the ultra-low power consumption operation of the system. After the system is electrified, the electromagnetic valve 11 is closed, then the circulating pump 2 is started to pump the liquid to be detected from the water quality sampling point 1 into the customized cylindrical electrochemical experiment pool 6, and the infrared detector 4 is arranged at the water inlet of the cylindrical electrochemical experiment pool 6. When the infrared detector 4 detects that the cylindrical electrochemical experiment pool 6 is filled with the liquid to be detected, the circulating pump 2 is immediately closed, and the electric stirrer 5 is simultaneously started and supplies power to the electrochemical simulation front-end chip AD5941 of the small electrochemical workstation. The voltage supplied by the electric stirrer 5 is controlled to be stabilized at 1.8V, thereby stabilizing the stirring speed. After the power is supplied to the front-end chip AD5941 by electrochemical simulation, a timing current method is executed by using a three-electrode-body tether in the chip, data are transmitted to a main controller through an SPI bus interface, the electric quantity flowing at a working electrode within 5min is calculated in the main controller, the content of organic matters in a solution is obtained through a calculation formula, and finally, the detection data are compensated through a trained optimal SVR model. And after the timing of 5min is finished, immediately closing the electric stirrer 5, powering off the front end chip AD5941 for electrochemical simulation, simultaneously opening the electromagnetic valve 11, discharging the solution in the cylindrical electrochemical experimental tank 6, and finishing the whole COD detection process. And then the main controller sends the COD detection result to a user database through the narrow-band Internet of things 10. On the basis, the user can access the database data in real time, monitor the COD detection result, and can compare historical detection data to master the COD change condition in the water environment. And when the data is sent into the database, the COD detection process is completely finished, the system enters an ultra-low power consumption sleep mode, and the complete detection process is executed again after timing for 30 min.
The method is realized by a COD precision compensation software system, the COD precision compensation software system completes the precision compensation of COD by an artificial intelligence algorithm-SVR model, and the process comprises the following steps: establishing an SVR model in MATLAB, carrying out sample data training to obtain an optimal SVR model, then storing the optimal SVR model into a hardware control system, further bringing COD data obtained by real-time measurement into a regression model, and finally obtaining a corresponding accurate value of COD.
It should be understood that the above description of the preferred embodiments is given for clarity and not for any purpose of limitation, and that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. The utility model provides a portable miniaturized COD electrochemical measurement device which characterized in that: the system comprises a hardware system consisting of a cylindrical electrochemical experimental tank, a small-sized electrochemical workstation, a circulating pump, an electromagnetic valve, an electric stirrer, an infrared detector, a working electrode, a reference electrode, a counter electrode and a sample introduction pipeline, and a COD precision compensation software system completed by an artificial intelligence algorithm:
1) the cylindrical electrochemical experiment pool is integrally cylindrical, a rectangular hole is formed in the bottom of the cylindrical electrochemical experiment pool and used for accommodating a working electrode, the working electrode is fixed at the bottom of the experiment pool, the left side of the cylindrical electrochemical experiment pool is sealed by a T-shaped rubber plug, a sample inlet hole is formed in the middle of the rubber plug, a reference electrode and a counter electrode are arranged in the sample inlet hole, a sample inlet pipeline and a drainage pipeline are respectively arranged on the upper left side and the lower right side of the cylindrical electrochemical experiment pool and used for adding and discharging a solution to be measured, one end of the sample inlet pipeline is connected with the upper left side of the cylindrical electrochemical experiment pool, the other end of the sample inlet pipeline is connected with a circulating pump, one end of the drainage pipeline is connected with the lower right side of the cylindrical electrochemical experiment pool, and the other end of the drainage pipeline is connected with a waste liquid barrel;
2) the electric stirrer extends into the cylindrical electrochemical experimental tank from the upper part;
3) the infrared detector is assembled at the water inlet of the experiment pool and used for detecting whether the liquid to be detected fills the experiment pool or not;
4) one end of the working electrode, one end of the reference electrode and one end of the counter electrode are immersed in the solution to be measured, and the other end of the working electrode, the reference electrode and the counter electrode are connected with the small electrochemical workstation.
2. The portable miniaturized COD electrochemical measuring device according to 1 characterized in that: the small-sized electrochemical workstation comprises an electrochemical simulation front-end chip AD5941, a wireless transmission module and a main controller, wherein the electrochemical simulation front-end single-chip AD5941 integrates all three electrode body tethers and comprises a low-power-consumption high-precision reference voltage generation circuit, a constant potential circuit and a micro-current detection circuit, the small-sized electrochemical workstation completes low-power-consumption safe transmission of data by using a narrow-band Internet of things technology, and the main controller controls the narrow-band Internet of things module and the electrochemical simulation front end through a UART (universal asynchronous receiver/transmitter) serial port and an SPI (serial peripheral) interface respectively to realize a portable small-sized COD (chemical oxygen demand) detection circuit.
3. The portable miniaturized COD electrochemical measuring device according to 1 characterized in that: the drainage pipeline is provided with an electromagnetic valve, the electromagnetic valve switch is controlled by the main controller in claim 2, and the electromagnetic valve is switched on and off to control the solution to be discharged.
4. The portable miniaturized COD electrochemical measuring device according to 1 characterized in that: the circulating pump is controlled by the main controller in claim 2, and the on-off of the circulating pump controls whether the liquid to be tested enters the experimental tank.
5. The portable miniaturized COD electrochemical measuring device according to 1 characterized in that: the working electrode is a boron-doped diamond film BDD electrode, and monocrystalline silicon is used as a substrate; the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum electrode; the bias voltage of the working electrode is 2.5V, and the oxidation time is 4 min.
6. The portable miniaturized COD electrochemical measuring device according to 1 characterized in that: the volume of the cylindrical electrochemical experimental tank is less than 40ml, the working rotating speed of the electric stirrer is less than 6r/s, and the diameter of the stirring blade is less than 1 cm.
7. A measuring method of the portable miniaturized COD electrochemical measuring device of any one of claims 1 to 4, characterized by comprising the following steps: after the system is electrified, the electromagnetic valve is closed, then the circulating pump is started to pump the liquid to be detected from the water quality sampling point into the customized cylindrical electrochemical experiment pool, when the infrared detector detects that the cylindrical electrochemical experiment pool is filled with the liquid to be detected, the circulating pump is closed immediately, and meanwhile, the electric stirrer is started and supplies power to the electrochemical simulation front-end chip AD5941 of the small electrochemical workstation; after the power is supplied to an electrochemical simulation front-end chip AD5941, a timing current method is executed by utilizing a three-electrode-body tether in the chip, data are transmitted to a main controller through an SPI bus interface, the electric quantity flowing at a working electrode within 5min is calculated in the main controller, the content of organic matters in a solution is obtained through a calculation formula, and finally, the detection data are compensated through a trained optimal SVR model; after the timing of 5min is finished, immediately closing the electric stirrer, powering off the electrochemical simulation front-end chip AD5941, simultaneously opening the electromagnetic valve, discharging the solution in the cylindrical electrochemical experiment pool, and finishing the whole COD detection process; and then the main controller sends the COD detection result to a user database through a narrow-band Internet of things.
8. The measurement method of the portable miniaturized COD electrochemical measurement device according to claim 7, wherein: the method is realized by a COD precision compensation software system.
9. The measurement method of the portable miniaturized COD electrochemical measurement device according to claim 8, wherein: the COD precision compensation software system completes the precision compensation of COD by an artificial intelligence algorithm-SVR model, and the process is as follows: establishing an SVR model in MATLAB, carrying out sample data training to obtain an optimal SVR model, then storing the optimal SVR model into a hardware control system, further bringing COD data obtained by real-time measurement into a regression model, and finally obtaining a corresponding accurate value of COD.
10. The measuring method of the portable miniaturized COD electrochemical measuring device according to claim 5, wherein: the power supply voltage of the electric stirrer is stabilized at 1.8V so as to stabilize the stirring speed.
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