KR20020007530A - an electro-chemical sensor having cleaning means of using stripping and a cleaning method of the same - Google Patents

Abstract

PURPOSE: An electric chemical sensor having a stripping cleaning element and a method for cleaning thereof are provided to clean working electrodes by oxidating impurities adsorbed to the working electrodes by using cleaning electrodes. CONSTITUTION: An electric chemical sensor having a stripping cleaning element includes first electrodes(2) formed of a plurality of pin type electrodes connected to one another, a second electrode(4) serving as an opposite electrode of the first electrodes in case of measurement, a third electrode(3) serving as an opposite electrode of the first electrodes in case of cleaning, and a main body(1) to which the first to third electrodes are fixed, wherein the third electrode has an exposed area less 1/5 than the second electrode.

Description

An electro-chemical sensor having cleaning means of using stripping and a cleaning method of the same}

The present invention relates to an electrochemical sensor, and more particularly to an electrochemical sensor having cleaning means using a stripping method.

Various types of sensors are used for measuring water quality and analyzing the composition of liquids. For example, in order to measure the residual chlorine concentration, ozone concentration, dissolved oxygen, etc. contained in water, sensors using microorganisms, electrochemical sensors, and the like are used. Among them, the electrochemical sensor is used by dipping the two electrodes of the sensor in a sample and applying a current amount or voltage according to the concentration of residual chlorine or the like contained in the sample when voltage is applied or flows between the two electrodes. It has a form of a composite electrode coupled to this one body.

However, when the electrochemical sensor is used for a long time, impurities are adsorbed to the electrodes constituting the sensor, thereby significantly reducing the sensor's response characteristics. Therefore, it is necessary to periodically clean the sensor, and there are several methods. Typical methods include mechanical cleaning methods, such as a rotary polishing method that continuously scrapes the surface of an electrode, a method of continuously wiping with a ring type brush or silicone rubber, and rotating the electrode in an oval shape in ceramic beads. There is a method of washing. However, the mechanical cleaning method is uneconomical except for places where the quality of the water is not very good or where there is a lot of solid suspended solids because it damages the electrode surface and is expensive to construct the cleaning device. There is also a chemical cleaning method, which removes impurities attached to the electrodes by applying chemicals, which is suitable for sensors used in wastewater treatment plants, but not for use in water purification plants or swimming pools where the water quality is clean. In addition, there are water spraying methods and air spraying methods, but each of them has disadvantages such as freezing risk in winter or expensive equipment.

It is an object of the present invention to provide an electrochemical sensor having a cleaning means using stripping and a cleaning method thereof.

Another technical problem to be solved by the present invention is to provide an electrochemical sensor and a cleaning method thereof that are economical in terms of excellent electrode resilience and maintenance cost.

1 is a perspective view of an electrochemical sensor having cleaning means according to a first embodiment of the present invention,

2 is a perspective view of an electrochemical sensor having cleaning means according to a second embodiment of the invention,

3 is a wiring diagram in a state where the electrochemical sensor of FIG. 2 is connected to a control unit;

4 is a block diagram of a measuring device for using the electrochemical sensor according to an embodiment of the present invention for the measurement of residual chlorine concentration,

5 is a graph comparing the I-V curves of the residual chlorine measurement sensor at the beginning of use and the sensor not cleaned after 5 hours of use.

6 is a graph comparing the I-V curves of the residual chlorine measurement sensor at the beginning of use and the sensor cleaned using the electrochemical cleaning means according to the embodiment of the present invention.

In order to solve this problem, in the present invention, the cleaning electrode is formed separately from the measuring electrode.

Specifically, the first electrode, the second electrode used as the counter electrode of the first electrode at the time of measurement, the third electrode used as the counter electrode of the first electrode at the time of cleaning, and the main body for fixing the first to third electrodes To provide an electrochemical sensor comprising a.

The electrochemical sensor has a first step of applying a reduction potential to the first electrode and maintaining a predetermined time while connecting the first electrode to the second electrode, and a second connecting the first electrode to the third electrode instead of the second electrode. Cleaning using a cleaning method comprising a third step of changing a potential applied to the first electrode.

Next, a sensor for measuring residual chlorine having an electrochemical cleaning means according to an embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a perspective view of an electrochemical sensor having cleaning means using stripping according to an embodiment of the invention.

The main body 1 of the residual chlorine measuring sensor according to the embodiment of the present invention is formed of polyvinyl chloride (PVC), which is durable and easy to process. The working electrode 2 made of platinum Pt is wound in the form of a coil under the main body 1, and the cleaning electrode 3 made of Pt is exposed in the form of dots under the working electrode 2. Under the electrode 3, a reference electrode 4 made of silver / silver chloride (Ag / AgCl) or silver (Ag) or gold (Au) is formed. The main body is connected with a sensor cable 40 connected to a control device (not shown). The working electrode 2, the cleaning electrode 3, and the reference electrode 4 are formed in the sensor cable 40 and are connected to three conductive wires (not shown) which are insulated from each other and are respectively connected to the control device.

2 is a perspective view of an electrochemical sensor having cleaning means according to a second embodiment of the present invention, and FIG. 3 is a wiring diagram in a state where the electrochemical sensor of FIG. 2 is connected to a control device.

On the lower surface of the body 1 made of polyvinyl chloride, a working electrode 2 made of platinum, a cleaning electrode 3, and a reference electrode 4 made of Ag / AgCl or silver (Ag) or gold (Au) Exposed The working electrode 2 has a thin cylinder, that is, an array method in which several pin-shaped electrodes are arranged at regular intervals on one circumference, and these pin-shaped electrodes are connected to each other inside the sensor body 1. It is. The cleaning electrode 3 is composed of one pin-shaped electrode, and the reference electrode 4 is composed of one cylindrical electrode thicker than the working electrode 2 or the cleaning electrode 3. The exposed surfaces of the three electrodes 2, 3 and 4 form a circular cross section. In addition, the three electrodes 2, 3, and 4 are insulated from each other and connected to the control device 30 through three conductors embedded in the sensor cable 40. The control device 30 is provided with a power supply unit 31 and a sensing unit 32, and a switch 33 capable of connecting the working electrode 2 to either the cleaning electrode 3 or the reference electrode 4. ) Is formed.

The pinned shape of the cleaning electrode 3 is made smaller so that the exposed surface is prevented from accumulating more than a predetermined amount of impurities adsorbed in the cleaning process to the impurities adsorbed on the cleaning electrode 3. This is to prevent the sample from being deteriorated by secondary contamination caused by this. Therefore, it is preferable that the exposed area of the cleaning electrode 3 is 1/5 or less compared with the exposed area of the reference electrode 4. In addition, the working electrode 2 is formed by connecting a plurality of pin-shaped electrodes in order to exert a function through the remaining pin-type electrodes even when impurities are adsorbed to some of the pin-type electrodes.

4 is a block diagram of a measuring device for using the electrochemical sensor according to an embodiment of the present invention for the measurement of residual chlorine concentration.

The electrochemical sensor 10 and the temperature sensor 20 are installed in the flow cell 80 according to the embodiment of the present invention, and the electrochemical sensor 10 and the temperature sensor 20 are sensor cables. It is connected to the control device 30 via 40, 50. The inlet pipe 60 and the discharge pipe 70 of the sample are connected to the flow cell 80. Here, the flow cell 80 is a container for temporarily storing a sample so that the electrochemical sensor 10 can measure the residual chlorine concentration or the ozone concentration, and the control device 30 is the temperature sensor 20 and the residual material. The electrical signals received from the chlorine measurement sensor 10 are processed and displayed by the temperature, the concentration of residual chlorine or ozone, and the like, and the measurement operation and the electrode cleaning operation of the electrochemical sensor 10 are controlled.

The operation of the electrochemical sensor having cleaning means using such stripping will be described.

The operation of the electrochemical sensor according to the embodiment of the present invention can be divided into its own functions, such as the measurement of the concentration of residual chlorine and ozone or the amount of dissolved oxygen, and its own electrode cleaning. -A current method (LSASV), a differential pulse bipolar stripping voltage-current method (DPASV), and a square wave (square wave) pulse bipolar stripping voltage-current method.

First, the case of measuring the residual chlorine with respect to the measuring method of the electrochemical sensor according to the embodiment of the present invention will be described as an example.

Dip the two electrodes of the sensor into the sample and measure the residual chlorine. In the measurement, the working electrode 2, which is a Pt wire or array type electrode, is used as the anode and the reference electrode 4 made of Ag / AgCl, Ag, Au, etc. is used as the cathode. In the residual chlorine measurement, the cleaning electrode 3, which is a point electrode made of Pt, is disconnected from the measurement circuit.

When a voltage is applied between the working electrode 2 and the reference electrode 4 for a predetermined time, residual chlorine becomes chlorine gas or hypochlorous acid (HOCl) or hydrochloric acid (HCl) around the working electrode 2, which is an anode by electrolysis. The resulting reaction determines the current flowing between the two electrodes 2, 4. The amount of residual chlorine can be measured by detecting this current. Alternatively, it is also possible to measure the voltage change with residual chlorine concentration.

When the sensor is used for the measurement for a long time in the above manner, impurity ions are adsorbed on the surface of the working electrode 2 which is the anode, and the sensitivity of the sensor is significantly reduced. In this case, the working electrode 2 is cleaned in the following manner to restore the sensitivity.

First, the linear scanning anode stripping voltage-current method will be described by dividing the steps.

First step: A reducing potential of -1.5 V to -1 V is applied to the working electrode 2 to which impurities are adsorbed while the working electrode 2 is connected to the reference electrode 4. It is generally desirable to apply a lower potential as the reduction potential than when measured.

Second step: A state in which a reduction potential is applied to the working electrode 2 is maintained for about 5 minutes so that enough ions are precipitated. While ions are precipitated at the working electrode 2, the sample is prevented from entering the flow cell 80.

Third step: The working electrode 2 is connected to the cleaning electrode 3 using the switch 33.

Fourth Step: The potential of the working electrode 2 is increased linearly towards the positive potential at -1.3V. At this time, the potential finally applied to the working electrode 2 varies depending on the type of the sample or the like.

In this way, the impurities adsorbed on the working electrode 2 reach the respective oxidation potentials and are separated from the working electrode 2 to be dissolved in the sample solution, and some of the impurities are resorbed to the cleaning electrode 4.

Next, the differential pulse anode stripping voltage-current method will be described.

The first to third steps are the same as the linear scan anode stripping voltammetry.

Fourth Step: The potential of the working electrode 2 is increased stepwise at -1.3V toward the positive potential. At this time, the scan rate of the applied voltage is 5 mV / s, and the pulse rate is 0.5 / s.

Finally, the square-wave pulse bipolar stripping voltage-current method is described.

The first to third steps are the same as the linear scan anode stripping voltammetry.

Step 4: Apply a square wave pulse potential in the positive direction to the working electrode 2 which was -1.3V.

The stripping method, which is a cleaning method of the electrochemical sensor, is a method of depositing extremely small amounts of ions in a sample solution on an electrode, oxidizing it into a solution, and then peeling it off. The working electrode 2 is restored to its original state by oxidizing and removing ions, and the sensor can be used semi-permanently if only the cleaning electrode is continuously replaced or pickled.

5 is a graph comparing I-V curves of a residual chlorine measurement sensor at the beginning of use and a sensor not cleaned after 5 hours of use.

As a result of observing the characteristic of the current density appearing in the -1.2V region in the potential section 0, the sensor of the initial use does not change much around 0, whereas the sensor used for a long time has the current density between 0nA / ㎠ and -10nA / ㎠ It can be seen that the oscillation irregularly.

6 is a graph comparing the I-V curves of the residual chlorine measurement sensor at the beginning of use and the sensor cleaned by using a cleaning means using stripping according to an embodiment of the present invention.

The sensor subjected to cleaning using stripping according to the present invention shows almost similar characteristics to the sensor at the beginning of use.

As a result, it can be confirmed that the sensor cleaned according to the present invention exhibits a potential-current characteristic superior to that of the sensor not cleaned.

According to the present invention, the working electrode can be cleaned by oxidizing and peeling away impurities adsorbed on the working electrode using the cleaning electrode. Impurities can be oxidized to a certain potential and dissolved in solution or resorbed to the cleaning electrode. Even if the cleaning electrode is heavily soiled, it does not affect the sensor's response characteristics and can be replaced or cleaned after reuse for a period of time.

Claims (13)

First electrode, A second electrode used as a counter electrode of the first electrode at the time of measurement, A third electrode used as a counter electrode of the first electrode at the time of cleaning, Body to fix the first to third electrodes Electrochemical sensor comprising a. In claim 1, The first electrode is an electrochemical sensor having a form in which a plurality of pin-shaped electrodes are connected to each other. In claim 1, The third electrode is an electrochemical sensor having an area of 1/5 or less exposed than the second electrode. In claim 1, The first electrode and the third electrode of the electrochemical sensor consisting of Pt. In claim 4, The second electrode is an electrochemical sensor consisting of any one of Ag / AgCl, Ag and Au. In claim 1, Cleaning Applying a reduction potential to the first electrode and maintaining the same for a predetermined time while the first electrode is connected to the second electrode; Connecting the first electrode to the third electrode and linearly increasing the potential of the first electrode Electrochemical sensor made through a process comprising a. In claim 1, Applying a reduction potential to the first electrode and maintaining the same for a predetermined time while the first electrode is connected to the second electrode; Connecting the first electrode with the third electrode and increasing the potential of the first electrode stepwise Electrochemical sensor made through a process comprising a. In claim 1, Applying a reduction potential to the first electrode and maintaining it for a predetermined time while the first electrode is connected to the second electrode; Connecting the first electrode to the third electrode and applying a square wave pulse to a potential of the first electrode Electrochemical sensor made through a process comprising a. In the cleaning method of the electrochemical sensor comprising the first to third electrodes, A first step of applying a reduction potential to the first electrode in a state in which the first electrode is connected to the second electrode and maintaining the same for a predetermined time; A second step of connecting the first electrode to the third electrode instead of the second electrode, A third step of changing a potential applied to the first electrode Method of cleaning the electrochemical sensor comprising a. In claim 9, And the third step of linearly increasing the potential of the first electrode. In claim 9, The third step of the cleaning method of the electrochemical sensor, characterized in that for increasing the potential of the first electrode in the step waveform. In claim 9, The third step is a cleaning method of the electrochemical sensor, characterized in that for applying a square wave pulse to the potential of the first electrode. The method according to any one of claims 10 to 12, The reduction potential of the first step is between -1.5V to -1V, the predetermined time of the second step is an electrochemical cleaning method, characterized in that more than 5 minutes.