Online monitoring device and method for concentration of oxidizing agent in galvanic disinfectant of primary battery

Abstract

The invention belongs to the technical field of electrochemistry, and relates to an online monitoring device and method for the concentration of an oxidizing agent in galvanic disinfectant of a primary battery. Comprising a sampling tube, two ends of the sampling tube are respectively provided with a sampling tube inlet and a sampling tube outlet, a primary battery positive electrode and a primary battery negative electrode are arranged in the sampling tube, and the primary battery positive electrode and the primary battery negative electrode pass through an insulating binding post on the tube wall of the sampling tube through a lead to form a loop with a micro galvanometer and a load resistor, and also comprises a timing switch, the micro-galvanometer is connected in parallel with two ends of the load resistor, and the potentiometer is connected in parallel with two ends of the load resistor. The timing switch in the device can preset'short circuit 'and'open circuit' periods to realize periodic dynamic display of the concentration of the oxidizing agent, and compared with an existing method for displaying the concentration through oxidation reduction potential (ORP), the device has the advantages that the response time is fast (lt); and the method can be widely applied to the medical treatment and public health industry, the food industry and the environmental protection industry.

Description

Technical Field

[0001] The invention belongs to the field of electrochemical technology, and in particular relates to a device and method for online monitoring the concentration of a primary battery current-type oxidant. Background Art

[0002] Chlorine-containing disinfectants and ozone water have long been used as disinfectants in industrial fields such as water disinfection, medical and health care, food processing, and sewage treatment. In the above-mentioned disinfection application fields, it is necessary to monitor and control its concentration online to ensure the disinfection effect. Before the present invention, there were different online or offline detection methods. Such as: spectroscopy, mass spectrometry, colorimetry, test paper and other methods, such as: Chinese patents: CN201520734716; CN201921715362; CN201510367332. The above-mentioned detection methods have complex instrument circuits, high costs, and require professional technicians to debug before they can operate normally. In addition, the DPD colorimetric method also requires regular replenishment of consumables such as DPD colorimetric reagents.

[0003] Except for the DPD colorimetric method, all of the above detection methods use the measurement and display of the oxidation-reduction potential (ORP) of the chlorine-containing disinfectant in water as the basic working principle, and the ORP potential value has a display "lag". Due to the characteristic adsorption phenomenon on the electrode surface, when the concentration changes, the adsorption state of the active substance on the working electrode surface cannot be updated in time. The response time is long, and the true concentration of the chlorine-containing agent in the water cannot be displayed immediately and accurately. Summary of the invention

[0004] In order to overcome the above technical deficiencies, the present invention provides a device and method for online monitoring of the concentration of oxidants (such as effective chlorine or ozone) in disinfectant using a primary battery current type.

[0005] According to the Nernst formula:

[0006]

[0007] In formula (1): ——equilibrium electrode potential, ——Standard electrode potential

[0008] a ox ——Activity of oxidized substances, a re ——Activity of reduced substances

[0009] n——the number of electrons gained or lost in the reaction, F——Faraday constant

[0010] when a ox =a re =1, It is called the standard electrode potential.

[0011] If decimal logarithms are used, the above Nernst formula can be written as:

[0012]

[0013] From formula (2), we can know that the activity of a certain oxidized substance (a ox ) and the equilibrium electrode potential of the galvanic cell A semi-logarithmic relationship.

[0014] The present invention adopts the working principle of the galvanic current type device to detect the oxidant in the disinfectant, and takes the effective chlorine as an example to illustrate as follows:

[0015] Electrochemical reaction of positive electrode (also serving as working electrode):

[0016] Negative electrode (also serves as reference electrode) electrochemical reaction:

[0017] Liquid phase reaction:

[0018] The present invention uses a galvanic current type device to detect the working principle of the oxidant in the disinfectant, and takes ozone as an example to illustrate as follows:

[0019] Electrochemical reaction of positive electrode (also serving as working electrode):

[0020] Negative electrode (also serves as reference electrode) electrochemical reaction:

[0021] When the primary cell is working, the oxidized substance is reduced by electrons at the positive electrode (also serving as the working electrode). The reduction current (i) flows through the load resistor (R) and produces a drop (iR). According to Ohm's law (V=iR), the voltage (V) across the load resistor (R) is linearly related to the reduction current (i).

[0022] At this time, the reduction current (i) and the oxidation state activity (a ox ), so the voltage (V) across the load resistor (R) is proportional to the activity (a) of the oxidized substance. ox ) is in direct proportion to each other, which conforms to the Nernst formula.

[0023] From the above working principle, we can know that the potential (V) across the load resistor (R) is the working equilibrium potential of the positive electrode. Value, this The value can be converted into the activity of the oxidized state by the Nernst equation (concentration x activity coefficient).

[0024] The device for online monitoring the concentration of oxidants in a primary battery current type disinfectant of the present invention comprises a sampling tube, wherein two ends of the sampling tube are respectively provided with a sampling tube inlet and a sampling tube outlet, and the sampling tube has a primary battery positive electrode and a primary battery negative electrode inside. The primary battery positive electrode and the primary battery negative electrode pass through insulating terminals on the wall of the sampling tube through leads to form a loop with a microammeter and a load resistor, and also comprises a timing switch, which is connected in parallel with the two ends of the microammeter and the load resistor, and also comprises a potentiometer, which is connected in parallel with the two ends of the load resistor.

[0025] The monitoring device of the present invention sets a load resistor (R) in the external circuit of the primary battery (see attached Figure 1 ) to obtain the restored current (i) signal, and the voltage displayed across the load resistor (R) Pre-calibrated by national standard iodine titration When the concentration of the corresponding oxidized substance is and oxidant concentration. Then, in the actual monitoring process, according to the monitored The concentration of the oxidant in the disinfectant can be known by the calibration curve. As long as the type of oxidant, the positive electrode of the primary battery, the negative electrode of the primary battery, and the load resistance are fixed, the voltage The calibration curve between the concentration of the oxidant and the concentration of the oxidant is fixed. Before the monitoring device of the present invention leaves the factory, the calibration curve can be pre-set, and the device of the present invention can be used to realize the online detection and monitoring of the concentration of the oxidant in the disinfectant.

[0026] In the present invention, a timer switch is provided between the positive and negative electrodes in the external circuit of the primary battery. When the timer switch is "off", the load resistor (R) is displayed at both ends. When the time switch is “closed”, the voltage (V) across the load resistor (R) is displayed as Display potential When the value is “returned to zero”, the concentration of active substances adsorbed on the positive electrode surface approaches zero, and the adsorbed substances in the original double-layer structure of the positive electrode surface are rapidly dissociated, and the adsorption state of the positive electrode surface is updated instantly. According to the preset on / off cycle, the potential value is dynamically displayed. It overcomes the "hysteresis" of conventional detection (ORP) and greatly shortens the "response time". By setting the closing time and opening time of the timing switch, the concentration of the oxidant in the disinfectant can be dynamically and quickly measured.

[0027] In the monitoring device of the present invention, the effective chlorine or ozone water disinfectant to be measured is electronically reduced at the positive electrode, and its reduction current (i) is proportional to the concentration of the disinfectant.

[0028] The primary cell body of the device of the present invention is composed of a positive electrode (also serving as a working electrode), a negative electrode (counter electrode also serving as a reference electrode) and an aqueous solution electrolyte to be tested.

[0029] The positive electrode of the primary cell described in the present invention (also serving as the working electrode) is composed of metal platinum, gold or precious metal oxides (RuO2 / Ti, IrO2 / Ti, TaO2 / Ti) or precious metal mixed oxides.

[0030] The negative electrode of the primary cell described in the present invention (the counter electrode also serves as the reference electrode) is composed of AgCl / Ag or HgCl / Hg.

[0031] The positive electrode and negative electrode of the primary battery of the present invention are respectively arranged in the middle of the injection tube through insulating terminals to contact the detected aqueous solution. The positive electrode of the primary battery is in the shape of a long wire, and the negative electrode of the primary battery is arranged around the anode wire in the shape of a spring coil, and the active surface area of ​​the negative electrode is much larger than the active surface area of ​​the positive electrode.

[0032] The timing switch of the present invention can be controlled to operate in the "open" and "closed" states according to a preset working cycle.

[0033] The microammeter described in the device of the present invention instantly displays the current value (i) of the external circuit loop of the primary battery when it is working, that is, the current value of the electron reduction of the oxidized active substance at the positive electrode.

[0034] The load resistor (R) of the device of the present invention, when the primary battery is discharged, the reduction current (i) on the positive electrode flows through the load resistor (R) through the micro-ammeter, and the potential value (iR value) is displayed dynamically by the potentiometer in real time, and this iR value It can be calibrated by iodine titration and converted into the concentration of effective chlorine oxidant.

[0035] The method for online monitoring of oxidants in disinfectant using the device of the present invention comprises the following steps:

[0036] Step 1: Use iodine titration to determine the The oxidant concentration under Calibration curve with oxidant concentration;

[0037] Step 2: preset the short-circuit time and open-circuit time of the timing switch, connect the sampling tube inlet of the device to the sampling port in the disinfection system, and let the disinfectant flow through the sampling tube and out from the sampling tube outlet;

[0038] Step 3: Start the timing switch and read the voltage across the load resistor during the open circuit time of the timing switch. , according to the calibration curve prepared in step 1, the oxidant concentration at this time is obtained;

[0039] Step 4: As the timing switch is periodically short-circuited and opened, online dynamic monitoring of the oxidant concentration in the disinfectant is achieved.

[0040] Preferably, in step 1, the oxidant is ozone or available chlorine.

[0041] As a preferred embodiment, in the step 2, the short circuit time is set to 10-20 seconds, and the open circuit time is set to 2-5 minutes.

[0042] As a preferred embodiment, in step 3, when the change of the microammeter reading is less than 1% within 10 seconds during the open circuit time, the product of the reduction current (i) and the load resistance (R) is the voltage. .

[0043] The galvanic current type oxidant online monitoring device of the present invention has a short response time (<10 seconds), no "lag" in concentration display, low cost and compact structure. It can be widely used in medical and health, food industry, environmental protection industry, and scientific research and other fields. The online dynamic detection method of the present invention overcomes the deficiency of "lag" in the existing oxidation-reduction potential (ORP) method, greatly shortens the response time and improves the detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Attached Figure 1 Schematic diagram of the structure of a galvanic cell type water oxidant concentration detection device; in the figure, 1 is the sampling tube inlet; 2 is the sampling tube; 3 is the positive electrode of the galvanic cell; 4 is the galvanic cell body; 5 is the negative electrode of the galvanic cell; 6 is the sampling tube outlet; 7 is the time switch; 8 is the microammeter; 9 is the potentiometer; 10 is the load resistor; and 11 is the insulating terminal.

[0045] Figure 2 Schematic diagram of the original battery body structure;

[0046] Figure 3 Dynamic display diagram of time switch time interval and response potential (V);

[0047] Figure 4 Calibration curve of the relationship between effective chlorine concentration (mg / L) and voltage drop on load resistance (iR);

[0048] Figure 5 Calibration curve of the relationship between ozone concentration in water (mg / L) and voltage drop across the load resistor (iR). DETAILED DESCRIPTION

[0049] The method and device of the present invention are further described below in conjunction with embodiments and drawings.

[0050] The on-line monitoring device for the concentration of oxidant in a primary battery current type disinfectant of the present invention comprises a sampling tube 2, wherein the two ends of the sampling tube 2 are respectively provided with a sampling tube inlet 1 and a sampling tube outlet 6, wherein the sampling tube 2 has a primary battery positive electrode 3 and a primary battery negative electrode 5 inside, wherein the primary battery positive electrode and the primary battery negative electrode pass through an insulating terminal 11 on the wall of the sampling tube through a lead wire to form a loop with a microammeter 8 and a load resistor 10, further comprising a timing switch 7, which is connected in parallel with the two ends of the microammeter 8 and the load resistor 10, and further comprising a potentiometer 9, which is connected in parallel with the two ends of the load resistor 10.

[0051] The present invention adopts a specially designed primary battery body 4 core component, and generates a corresponding potential through a load resistor 10 according to the current of the oxidant active substance in water reduced on the primary battery positive electrode 3 Value, real-time online dynamic display of the concentration of effective chlorine in water or the concentration of ozone water in water.

[0052] The positive electrode 3 and the negative electrode 5 of the battery body 4 are arranged in the middle of the sampling tube 1, and the positive electrode 3 and the negative electrode 5 of the battery are exposed in the middle of the aqueous solution to be tested, so that the disinfectant to be tested can be continuously updated to flow through the two electrodes of the battery. The insulating terminal 11 is arranged on the wall of the sampling tube 1 using an insulating material.

[0053] The lead wires of the positive / negative electrodes of the original battery are connected to the dedicated electronic circuit. Figure 1 .

[0054] A micro-ammeter 8 and a load resistor 10 are connected in series between the positive electrode of the primary battery and the upper part of the negative electrode of the primary battery to form an outer loop of the electron circulation. A potentiometer 9 is connected in parallel at both ends of the load resistor 10 to dynamically display iR value.

[0055] A timer switch 7 is connected in parallel at both ends of the positive / negative lead wires outside the primary battery. The timer switch 7 can be pre-set for the time period of the timer switch "short circuit" (closed state) and "open circuit" (disconnected state), see the attached Figure 3 The diagram in the figure shows the dynamic relationship between (iR)V and switching time.

[0056] When the time switch 7 is closed, the primary battery outputs a limiting current. At this time, the oxidant active substance is reduced and exhausted on the positive electrode surface, that is, it is in a "zero" state; when the time switch is disconnected, the current of the oxidant active substance being reduced on the positive electrode flows through the load resistor (R) 10. According to Ohm's law, the iR drop (V) is periodically and dynamically displayed at both ends of the load resistor (R) 10. The iR (V) value is proportional to the reduction current. After being analyzed and calibrated by the national standard "iodine titration method", it can be converted into the concentration of the oxidant substance. See the attached Figure 4 , 5Then, during the test, the concentration of the oxidant in the disinfectant is obtained based on the measured iR and the pre-prepared calibration curve.

[0057] The method for online monitoring of oxidants in disinfectant using the device of the present invention comprises the following steps:

[0058] Step 1: Use iodine titration to determine the The oxidant concentration under Calibration curve with oxidant concentration;

[0059] Step 2: preset the short-circuit time and open-circuit time of the timing switch, connect the sampling tube inlet of the device to the sampling port in the disinfection system, and let the disinfectant flow through the sampling tube and out from the sampling tube outlet;

[0060] Step 3: Start the timing switch and read the voltage across the load resistor during the open circuit time of the timing switch. According to the calibration curve prepared in step 1, the oxidant concentration at this time is obtained;

[0061] Step 4: As the timing switch is periodically short-circuited and opened, online dynamic monitoring of the oxidant concentration in the disinfectant is achieved.

[0062] Preferably, in step 1, the oxidant is ozone or available chlorine.

[0063] Attached Figure 4 It is the calibration curve corresponding to the load resistance of 2MΩ, the positive electrode of the original battery is Au, the negative electrode of the original battery is AgCl / Ag, and the oxidant is available chlorine.

[0064] Attached Figure 5 This is the calibration curve corresponding to the load resistance of 220KΩ, the cathode of the primary battery is AgCl / Ag, and the oxidant is ozone.

[0065] The on-line dynamic detection method of the primary battery current type of the present invention overcomes the deficiency of the existing oxidation reduction potential (ORP) method showing "hysteresis", greatly shortens the response time and improves the measurement accuracy.

[0066] The galvanic current type oxidant online monitoring device of the present invention has a short response time (<10 seconds), no "lag" in concentration display, low cost and compact structure. It can be widely used in the fields of medical health, food industry, environmental protection industry and scientific research.

Claims

1. An online monitoring device for oxidant concentration in a primary battery current type disinfectant, characterized in that: The invention comprises a sampling tube, wherein two ends of the sampling tube are provided with a sampling tube inlet and a sampling tube outlet respectively, and inside the sampling tube are provided with a positive electrode of a primary battery and a negative electrode of the primary battery. The positive electrode of the primary battery and the negative electrode of the primary battery pass through insulating terminals on the wall of the sampling tube through leads to form a loop with a microammeter and a load resistor. The invention also comprises a timing switch, which is connected in parallel with the two ends of the microammeter and the load resistor, and a potentiometer, which is connected in parallel with the two ends of the load resistor.

2. The on-line monitoring device for oxidant concentration in disinfectant according to claim 1, characterized in that: The positive electrode of the primary cell is composed of metal platinum, gold or noble metal oxide or noble metal mixed oxide.

3. The on-line monitoring device for oxidant concentration in disinfectant according to claim 1, characterized in that: The negative electrode of the primary battery is composed of AgCl / Ag or HgCl / Hg.

4. The on-line monitoring device for oxidant concentration in disinfectant according to claim 1, characterized in that: The positive electrode of the original battery is in the shape of a long wire, and the negative electrode of the original battery is in the shape of a spring coil arranged around the positive electrode of the original battery.

5. A method for online monitoring of oxidants in disinfectant using the device of claim 1, characterized in that: The steps include: Step 1: calibrate the device at different φ by iodine titration e The oxidant concentration under e Calibration curve with oxidant concentration; Step 2: preset the short-circuit time and open-circuit time of the timing switch, connect the sampling tube inlet of the device to the sampling port in the disinfection system, and let the disinfectant flow through the sampling tube and out from the sampling tube outlet; Step 3: Start the timing switch and read the voltage φ across the load resistor during the open circuit time of the timing switch. e , according to the calibration curve prepared in step 1, the oxidant concentration at this time is obtained; Step 4: As the timing switch is periodically short-circuited and opened, online dynamic monitoring of the oxidant concentration in the disinfectant is achieved.

6. The method for online monitoring of oxidants in disinfectant according to claim 5, characterized in that: In step 1, the oxidant is ozone or available chlorine.

7. The method for online monitoring of oxidants in disinfectant according to claim 5, characterized in that: In the step 2, the short circuit time is set to 10-20 seconds, and the open circuit time is set to 2-5 minutes.

8. The method for online monitoring of oxidants in disinfectant according to claim 5, characterized in that: In step 3, when the change of the microammeter reading is less than 1% within 10 seconds during the open circuit time, read the microammeter reading i. At this time, φ e =iR.

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