KR20130117515A - Electrochemical gas permeable membrane type free residual chlorine sensor - Google Patents

Abstract

PURPOSE: An electrochemical gas penetration type residual chlorine sensor is provided to enable the immediate use in a field in a short time due to rapid initial stabilization and rapid sensing speed and to stably measure chlorine remaining in sample solution for a long time. CONSTITUTION: An electrochemical gas penetration type residual chlorine sensor includes a selective residual chlorine penetration film (110), an electrode unit (150), and a cell body unit (160). The selective residual chlorine penetration film penetrates through only free and residual chlorine and no liquid components. The electrode unit is composed of a working electrode (130) causing a current change according to the amount of the residual chlorine penetrated through the selective residual chlorine film; an auxiliary electrode (135); and a reference electrode (140). The selective residual chlorine film, the working electrode, the auxiliary electrode, and the reference electrode are mounted on the cell body unit. The working electrode, the auxiliary electrode, and the reference electrode form three-electrode group structure.

Description

ELECTROCHEMICAL GAS PERMEABLE MEMBRANE TYPE FREE RESIDUAL CHLORINE SENSOR [0001]

One embodiment of the present invention relates to a gas permeable residual chlorine sensor for measuring the concentration of total free chlorine (Cl ₂ , HOCl, OCl ^- ) contained in a sample water by measuring an amount of current input from the outside, The working electrode, the auxiliary electrode, and the reference electrode, which cause a change in current depending on the amount of residual chlorine permeating through the selective residual chlorine permeable membrane permeating the residual chlorine and not permeating the liquid component, and the residual chlorine permeating through the permeable membrane, Permeable residual chlorine sensor assembled with a sensor.

In general, various analytical methods have been developed in order to identify the types and structures of various chemical substances contained in unknown samples and to quantitatively measure the amount of the substances. In recent years, Are being developed for accurate analysis.

In particular, as the need to analyze samples in a short period of time for process automation, quality control, medical analysis, and environmental sample analysis has increased, interest in developing methods and equipment for analyzing chemical substances is increasing.

Electrochemistry is a discipline dealing with the relationship between matter and electricity, such as potential difference, electric charge, and conductivity value change by electrode reaction in solution. The methods used for chemical analysis of materials using this principle are called electrochemical analysis. Potentiometry is a method to quantify a substance by measuring an electrode potential by making an electrochemical cell by immersing an appropriate electrode in a sample solution including an electrolyte, a method of measuring electrical resistance between electrodes is called a conductometry, The coulometry method for measuring the amount of electricity flowing through, and the amperometry method for analyzing the current are called amperometry. In addition, there is a method of measuring and analyzing two electrical properties at the same time. The method of measuring the relationship between current and voltage is the voltammetry, and one of these methods is polarography.

The current-voltage method is a kind of electrochemical analysis method which obtains information about the analytical sample by measuring the change of the current according to the voltage supplied between the working electrode and the auxiliary electrode. It is named as "POLAROGRAPHY" by Heyrovsky, a Czech chemist in the early 1920s Was invented.

Along with the development of instrumentation, polarography has been in its heyday in recent years by measuring trace metals and organic components up to concentrations of 0.5 mg / L or less.

In particular, the electrochemical method is used for the analysis of chemicals. Among them, the current-voltage method measures the change of the current according to the voltage supplied between the working electrode and the auxiliary electrode, and analyzes Method. The current-voltage method is excellent in sensitivity to the analyte and has a fast response time. It is easy to analyze and unlike the optical analysis method of the other, the sample is not affected by the turbidity or color, Is relatively simple. The current-voltage method is comparatively inexpensive and has excellent accuracy and reproducibility, and can be widely applied in almost all fields of analytical chemistry. Such applications are particularly useful not only in water analysis (wastewater, drinking water, river water) and industrial analysis but also in biological fluids such as blood and urine Analysis, food chemistry in fermentation process, process control in industrial chemistry, and environmental analysis.

Currently, most of the domestic water treatment plants are disinfected using chlorine. The water quality of the raw water varies depending on the season and the rainfall. In each water treatment plant, the water quality of the water source is measured to control each treatment process.

In summer, where the rate of microbial growth is highest and the daily rainfall is the largest, continuous monitoring of each treatment process is needed to change the time of the source of the water constantly. In particular, disinfection of microorganisms, which can cause waterborne diseases, The use of an appropriate amount of disinfectant should be used to prevent the use of ineffective chemicals due to the use of excessive disinfectants.

Excessive chlorine injection is also associated with an increase in the carcinogenic trihalomethane (THM), which requires proper chlorine injection and continuous monitoring within the process.

In addition, chlorine disinfection is used for water quality management in public places in terms of public health. In the case of indoor and outdoor swimming pools, chlorine disinfection is currently carried out, but there is no specialist to manage it Quantitative and qualitative drug input and measures have not been implemented.

In order to prevent waterborne infectious diseases using chlorine, it is necessary to maintain a certain amount of residual chlorine in the water supply and drainage. In order to cope with the treatment process for the water resources changing by season and time, the concentration of residual chlorine is continuously monitored . The SNORT method (Stortified Neutral Orthotolyte Method), which is a conventional residual chlorine measuring method, is a method using a slow reaction between orthotolyid and an interfering substance such as binding residual chlorine and iron and nitrite at a neutral pH, The DPD method (N, N-diethyl- p- phenylenediamine) using the colorimetric method was used to measure the SNORT The law and measurement principle are similar, and when the DPD reagent is added to a sample containing free residual chlorine, the reaction occurs immediately and a red color appears. It is possible to determine the concentration of free residual chlorine by measuring the chromaticity of red color developed at neutral pH of 6.2 ~ 6.5. However, both of these methods have long measurement time (about 180 sec) and it is difficult to monitor in real time. Even if it is possible, there is a problem such as the use of a reagent and waste liquid treatment, a considerable skill is required for operation of the apparatus, and even a measuring instrument using a current method other than the use of a reagent requires a high import cost.

At present, various residual chlorine sensors which are dependent on the import of all the available chlorine sensors at the respective water treatment plants are on the market for the above-mentioned purpose. To measure the electrode potential in the sample solution, the potential difference between two points should be measured using two electrodes. The electrode to be measured is referred to as working electrode, and the potential difference should be measured by connecting one electrode according to this. In order to make the cell voltage V equal to the electromotive force E, the condition (equilibrium) of the current i = 0 must be satisfied. For this purpose, an electrode with a stable potential is selected and used as a reference electrode. The potential difference should be measured in an equilibrium state in which the actual current between the working electrode and the reference electrode can be ignored.

The measured potential difference corresponds to the electromotive force (EMF) between the two electrodes. Under this condition i = 0, the voltage drop due to the internal resistance component between the electrodes can be ignored. When an external voltage is applied between the electrodes, a resistance drop (iR drop) occurs between the electrodes, which may cause the reference electrode potential to deviate from the equilibrium value.

An embodiment of the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a three-electrode type electrochemical gas permeation type residual chlorine sensor having excellent sensitivity to an analyte and having excellent electrochemical properties do.

Further, according to an embodiment of the present invention, since the gas permeable membrane, the working electrode, the auxiliary electrode, and the reference electrode are mounted on the cell body and can be assembled with one sensor, The present invention provides a gas permeable residual chlorine sensor.

In addition, one embodiment of the present invention provides an electrochemical gas permeation type residual chlorine sensor capable of producing an inexpensive residual chlorine sensor having an excellent initial stability and response time, excellent stability, a simple structure and easy electrochemical properties, Lt; / RTI >

An electroluminescent type transmission residual chlorine sensor according to an embodiment of the present invention includes a selective residual chlorine permeable membrane which permeates only free residual chlorine and does not permeate a liquid component; An electrode unit comprising an operation electrode, an auxiliary electrode, and a reference electrode which cause a current change according to an amount of residual chlorine permeated through the selective residual chlorine permeable membrane; And a cell body to which the selective residual chlorine permeable membrane, the working electrode, the auxiliary electrode, and the reference electrode are mounted, wherein the working electrode, the auxiliary electrode, and the reference electrode are formed to have a three-electrode structure, A polypropylene resin composition comprising an ethylene-propylene block-polypropylene resin consisting of 75 to 95% by weight of homopolypropylene and 20 to 50% by weight of an ethylene-propylene block copolymer having an ethylene content of 5 to 25% by weight .

Wherein the working electrode and the auxiliary electrode are made of a platinum disk and a platinum wire, the reference electrode is made of an insoluble silver chloride / silver chloride electrode, and the selective residual chlorine permeable membrane is made of a Teflon microporous membrane .

The reference electrode is characterized in that silver chloride containing about 5% by weight of palladium is immersed in an aqueous solution of iron chloride to form a refractory metal layer.

And an application potential of 400 mV is applied to the working electrode based on the reference electrode to electrochemically detect the residual chlorine amount.

The viscosity ratio (dl / g) of the homo polypropylene to ethylene-propylene block copolymer is 0.5 to 2.5, and the melt index (230 ° C., 2.16 kg load) of the ethylene-propylene block-polypropylene resin is 1 to 50 g /. It is characterized by 10 minutes.

The electrochemical gas permeation type residual chlorine sensor according to an embodiment of the present invention can be used immediately in the field in a short time due to the initial stabilization and the quick response time and is excellent in stability and can measure long term residual chlorine in the sample solution It is stable. In addition, it has an excellent reproducibility as compared with the conventional commercialized residual chlorine sensor, and is easy to manufacture, and thus has low analytical cost per sample and easy storage and management of the sensor.

In addition, since there is no use of a reagent, it is stable against the problem of secondary contamination and can be continuously monitored in real time, which is effective for process control.

1 is a side view illustrating an electrolytic gas permeation type residual chlorine sensor according to an embodiment of the present invention in a decomposed state.
FIG. 2 is a graph showing the response curves of 0 to 1 mg / L residual chlorine concentration change of the electroactive type gas permeation type residual chlorine sensor according to an embodiment of the present invention. FIG.
FIG. 3 is a graph showing the response curves of 0 to 5 mg / L residual chlorine concentration change of an electroactive type gas permeation type residual chlorine sensor according to an embodiment of the present invention.
FIG. 4 is a graph showing a correlation curve of 0 to 3 mg / L residual chlorine concentration of an electrochemical gas permeation type residual chlorine sensor and a commercialized residual chlorine sensor according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which those skilled in the art can readily implement the present invention.

FIG. 1 is a side view showing a decomposed state of an electrochemical gas permeation type residual chlorine sensor according to an embodiment of the present invention, and FIG. 2 is a graph showing the electrochemical gas permeation type residual chlorine sensor according to an embodiment of the present invention, FIG. 3 is a graph showing the response curves of residual chlorine concentration of 0-5 mg / L of the electrogalic gas permeation type residual chlorine sensor according to an embodiment of the present invention. FIG. FIG. 4 is a graph showing a correlation curve of 0 to 3 mg / L residual chlorine concentration of an electroactive type gas permeation type residual chlorine sensor and a commercialized residual chlorine sensor according to an embodiment of the present invention.

1, an electroactive gas permeation type residual chlorine sensor according to an embodiment of the present invention includes a gas permeable membrane 110, a working electrode 130, an auxiliary electrode 135, and a reference electrode 140 And the structure is such that the gas permeable membrane 110, the working electrode 130, the auxiliary electrode 135, and the reference electrode 140 are mounted on the cell body 160 and assembled with one sensor. The working electrode 130, the auxiliary electrode 135, and the reference electrode 140 are formed in a three-electrode structure. In the present invention, the working electrode 130, the auxiliary electrode 135, Will be collectively referred to as an electrode unit 150.

In such a gas permeable residual chlorine sensor, the potential of the working electrode 130 changes according to the residual chlorine concentration present in the sample solution, and the reference electrode 140 maintains a constant potential at all times regardless of the conditions of the sample, The residual chlorine concentration in the sample solution can be measured by measuring the current change in the working electrode 130 according to the residual chlorine concentration in the sample solution.

On the other hand, chlorine is the most commonly used bactericide for water treatment and effluent of drinking water. These chlorines are mostly hydrolyzed in water as follows.

Cl ₂ + H ₂ O → HOCl + H ⁺ + Cl ^- (pK ₁ = 4.6)

HOCl ionizes according to the hydrogen ion concentration (pH) of water as follows.

HOCl -> H ⁺ + OCl ^- (pK ₂ = 7.5)

The measurement of the residual chlorine according to the present invention is a measurement of the electron movement (current) flowing by the reduction reaction of hypochlorous acid (HOCl), and the application potential of about 400 mV is applied to induce the reduction reaction of hypochlorous acid do.

At this time, the electrode reaction is as follows.

Working ^{electrodes: HOCl + H + + 2e -} → Cl - + H 2 O

Number of samples: H ₂ O → (1/2) O ₂ + 2H ⁺ + 2e ^-

In addition, the present invention provides a gas permeable residual chlorine sensor for directly using a residual chlorine sensor in an industrial field.

The cell body 160 can be mounted with the gas permeable membrane 110, the working electrode 130, the auxiliary electrode 135, and the reference electrode 140 so that the sample can continuously flow through the electrode, It plays a role in measuring residual chlorine. The gas permeable membrane 110 coupled to one end of the cell body 160 is elastically coupled to the cell body 160 by an O-ring 120.

In addition, the cell body 160 may be formed of a polypropylene resin composition to improve impact resistance. This is to enhance the impact resistance of the cell body 160 to prolong the life of the device. Here, the polypropylene resin composition includes an ethylene-propylene block-polypropylene resin composed of 75 to 95% by weight of homopolypropylene and 5 to 25% by weight of an elastic ethylene-propylene block copolymer having an ethylene content of 20 to 50% by weight .

Here, the viscosity ratio (dl / g) of the homopolypropylene to the ethylene-propylene block copolymer may be 0.5 to 2.5. If the absolute viscosity ratio is less than 0.5, the molecular weight of the polymerized ethylene-propylene block copolymer is lower than that of homopolypropylene, which is a continuous phase, so that it is difficult to absorb the impact. If the absolute viscosity ratio is more than 2.5, The molecular size of the aggregate increases, and the drop impact may be reduced.

The ethylene-propylene block-polypropylene resin may have a melt index (230 ° C, 2.16 kg load) of 1 to 50 g / 10 min. If the melt index is less than 1 g / 10 min, the resin flow characteristics in the extrusion process are lowered, and it is difficult to maintain the absolute viscosity ratio at the optimum condition of 0.5 to 2.5. When the melt index exceeds 50 g / 10 min, The impact resistance may be deteriorated.

The polypropylene resin composition is prepared by charging the components into a stirring-mixing apparatus (e.g. a Hens mixer, a super mixer or a tumbler mixer), stirring the mixture for 1 to 30 minutes and mixing it at a temperature of 180 to 230 ° C in a mill or And the cell body portion 160 of the present residual chlorine sensor can be manufactured by any molding method such as injection molding, extrusion molding or the like by using the polypropylene resin composition thus produced.

In addition, the cell body 160 may have a protective coating layer (not shown) having paint adhesion and excellent impact resistance on its outer surface. The protective coating layer may include (A) a crystalline polypropylene, (B) an ethylene butyl acrylate polymer, (C) a styrene-based hydrogenated block copolymer, and (D) an inorganic filler.

The crystalline polypropylene (A) may comprise at least one selected from a crystalline polypropylene homopolymer and a propylene-alpha olefin crystalline copolymer comprising C2 to C20 (excluding C3) alpha-olefin monomers .

Specific examples of the alpha-olefin monomers may be ethylene, 1-butene, 1-pentene, 1-hexene, 4-methylpentene, 1-heptene, 1-octene and 1-decene and preferably ethylene. The propylene-alpha olefin crystalline copolymer may be, but is not limited to, a block copolymer or a random copolymer.

The content of the polymerization unit of propylene in the propylene-alpha-olefin crystalline copolymer is not particularly limited, but is preferably 50 wt% or more in the copolymer.

The crystalline polypropylene (A) is not particularly limited in terms of stereoregularity, but any crystalline polypropylene that can achieve the object of the present invention can be used without limitation, and more specifically, C-NMR (nuclear magnetic resonance Spectrum) may be from 0.80 to 0.99, and preferably from 0.85 to 0.99.

The melt flow index (MFI, 230 ° C, 2.16 kg load) of the crystalline polypropylene (A) may be 20 to 60 g / 10 min, preferably 20 to 50 g / 10 min.

The crystalline polypropylene (A) may be contained in an amount of 44 to 57% by weight based on the resin composition. If the content of the crystalline polypropylene (A) is less than 44% by weight, the coating adhesion may be deteriorated. If the content of the crystalline polypropylene is more than 57% by weight, the flexural modulus and the coating adhesion may be lowered.

In the ethylene butyl acrylate polymer (B), butyl acrylate may be contained in an amount of 20 to 40% by weight, preferably 25 to 40% by weight, based on the polymerization unit.

The ethylene butyl acrylate polymer (B) may be contained in an amount of 9 to 21% by weight based on the polypropylene resin composition. When the content of the ethylene butyl acrylate polymer (B) is less than 9% by weight, the coating adhesion is poor, and when the content is more than 21% by weight, the flexural modulus may remarkably decrease.

The melt index (190 ° C, 2.16 kg load) of the ethylene butyl acrylate copolymer (B) may be 5 to 250 g / 10 min, preferably 10 to 200 g / 10 min.

The styrene-based hydrogenated block copolymer (C) can further improve paint adhesion and impact resistance to the polypropylene resin composition. The styrene-based hydrogenated block copolymer (C) is preferably a styrene-ethylene-butene-styrene block copolymer (SEBS), a styrene-ethylene-propylene- , Styrene-ethylene-isoprene-styrene block copolymer, acrylonitrile-butylene-styrene block copolymer and the like, preferably styrene-ethylene-butene-styrene block copolymer (SEBS) and Styrene-ethylene-propylene-styrene block copolymer (SEPS).

The styrene-based hydrogenated block copolymer (C) may be contained in an amount of 7 to 21% by weight, preferably 10 to 18% by weight, based on the polypropylene resin composition. When the content of the styrene-based hydrogenated block copolymer (C) is less than 7% by weight, the coating adhesion is decreased. When the content is more than 21% by weight, mechanical properties such as rigidity and coating adhesion may be lowered. The inorganic filler may be used to reinforce the rigidity of the polypropylene resin composition. The inorganic filler may be at least one selected from the group consisting of talc, barium sulfate and calcium carbonate, preferably talc.

The cell body 160 of the residual chlorine sensor according to the present invention can be manufactured by any molding method such as injection molding, extrusion molding, etc., but the present invention is not limited thereto.

The electrochemical gas permeation type residual chlorine sensor according to the present invention will be described in detail as follows.

In the present invention, when an external voltage is applied between the electrodes, a resistance drop (iR drop) occurs between the electrodes and the potential of the reference electrode 140 deviates from the equilibrium value. In order to avoid such an error, System sensor is used.

The potential difference between the working electrode 130 and the reference electrode 140 can be accurately measured regardless of the current value flowing through the electrode reaction.

The potential of the working electrode 130 is adjusted to a potentiostat with reference to the reference electrode 140 so that the current does not flow through the reference electrode 140 and the potential of the reference electrode 140 is maintained at a constant Zero current potential value). Therefore, a current flows between the working electrode 130 and the auxiliary electrode 135. [

On the other hand, when measuring the oxidation-reduction reaction of a specific chemical species dissolved in the electrolytic solution filled through the electrolyte filling port 170, it is necessary to determine which working electrode and the auxiliary electrode are superior to each other. These criteria include a potential window in which the electrode used is suitable for examining the redox reaction of a certain potential region. In the electrode range of this potential window, the electrode almost behaves as a polarization electrode. The potential window varies not only with the electrode but also with the solvent or supporting electrolyte used. (1) hydrogen overvoltage, (2) oxygen overvoltage, (3) dissolution potential of electrode, (4) decomposition of supporting electrolyte, (5) And (6) potential to which impurities react. Such an electrode range varies depending on the hydrogen ion concentration, but the reduction potential of the hydrogen generation may vary depending on the kind of the electrode material. This appears as hydrogen overvoltage, but platinum and gold are the electrode materials with small hydrogen overvoltage. Also, in an aqueous solution, the oxidation reaction zone is limited by the oxygen generating potential. Therefore, the platinum or gold has a very large minimum overvoltage (oxygen overvoltage) for oxygen generation. As a result, platinum (Pt) and gold (Au) have been used as working electrodes and auxiliary electrodes as electrode materials for the electrolytic oxidation of organic compounds and inorganic compounds.

Therefore, in the present invention, platinum or gold is selected as a metal material of the gas permeable residual chlorine sensor operating electrode 130 and the auxiliary electrode 135, and electrochemical properties are investigated to produce an optimal residual chlorine sensor.

The reference electrode 140 may be formed of metal wires such as silver (Ag), palladium (Pd), copper (Cu), and platinum (Pt), or may be formed of a metal layer / Or a soluble metal layer.

In the present invention, a silver / silver chloride (Ag / AgCl) electrode which has good reproducibility of dislocation and is easy to handle and which is most widely used is used. The silver / silver chloride electrode can be used at a high temperature since the silver / silver chloride electrode has a low hysteresis to temperature and a stable potential up to a high temperature. In order to increase the lifetime of the electrode, instead of pure silver, silver containing about 5% Was immersed in a constant aqueous solution of iron chloride for several minutes to several minutes to form a refractory metal layer of a silver chloride layer on the silver metal layer.

The measuring device for measuring the total free chlorine contained in the sample water using the gas permeable residual chlorine sensor as described above comprises a CPU board, an output / power board, and a sensor signal converting circuit by standardizing the case, The output / power board is standardized to be jointly usable in a water quality measuring instrument. The sensor conversion circuit is developed to facilitate measurement range and sensor calibration. The CPU board includes an LCD, a key pad, an LED indicator, The output / power board includes the alarm output, the measured analog output, the power for the CPU, the power for the conversion circuit, and the power for the output circuit. Can be used for both 110 and 220V. In addition, a relay output circuit is added so that a signal such as an alarm can be given to the outside depending on the measured residual chlorine value. To further increase versatility, we add about five solid-state relay (SSR) circuits.

In addition, the converting circuit constitutes a potential adjusting system and a circuit for giving a voltage on the basis of the measured voltage at the reference electrode, which is designed to minimize the influence of external noise by separating the power from the other digital circuit. In addition, a filter circuit for removing external noise and a circuit for measuring temperature and pH are included to provide optimum measurement conditions.

The residual chlorine sensor according to the present invention makes it possible to easily use the residual chlorine sensor directly in the industrial field. The present residual chlorine sensor can be used for various sample conditions up to a wide range of residual chlorine concentration, and the electrochemical properties are the same as or better than those of conventional residual chlorine sensor. The residual chlorine sensor according to the present invention has a simple structure, As a result, it can be usefully used as a residual chlorine sensor for measuring the concentration of residual chlorine in an industrial field instead of a conventional residual chlorine sensor.

Hereinafter, the present invention will be described in more detail with reference to Examples.

However, the following examples illustrate the invention, and the contents of the present invention are not limited by the examples.

< Example >

Fabrication of gas permeable residual chlorine sensor

In the electrochemical type three-electrode system residual chlorine sensor of the present invention, a gas permeable membrane that selectively permeates only residual chlorine generally comprises a Teflon microporous membrane as a working electrode 130, Pt (platinum) Ag or AgCl electrode is used as the reference electrode 140 and a noble metal such as Pt is used as the counter electrode 135 and Au / AgCl electrode is used as the reference electrode 140 Thereby forming a cell body portion as shown in Fig.

To measure electrode potential in a sample water solution, the potential difference between two points should be measured using two electrodes. At this time, the electrode to be measured is called the working electrode 130, and one electrode according to the electrode is connected to measure the potential difference. In order to make the cell voltage V equal to the electromotive force E, the condition (equilibrium) of the current i = 0 must be established. For this purpose, an electrode having a stable potential is selected and used as a reference electrode 140. Therefore, the potential difference should be measured in an equilibrium state in which the actual current between the working electrode 130 and the reference electrode 140 can be ignored. At this time, the measured potential difference corresponds to the electromotive force (EMF) between the two electrodes. Under this condition i = 0, the voltage drop due to the internal resistance component between the electrodes can be ignored.

In addition, when an external voltage is applied between the electrodes, a resistance drop (iR drop) occurs between the electrodes and the potential of the reference electrode 140 deviates from the equilibrium value. To avoid such an error, in the electrochemical measurement, Lt; / RTI &gt; At this time, a cell current flows between the working electrode 130 and the auxiliary electrode 135 and hardly flows between the working electrode 130 and the reference electrode 140. The potential difference between the working electrode 130 and the reference electrode 140 can be accurately measured regardless of the current value flowing through the electrode reaction.

Therefore, in the present invention, since the oxygen overvoltage is generally high, a noble metal such as platinum or gold is selected as the oxidation electrode for the oxidation reaction as the metal material of the working electrode 130 and the auxiliary electrode 135 of the residual chlorine sensor, To obtain an optimal gas permeation type residual chlorine sensor.

< Experimental Example  1>

Of the residual chlorine sensor Sensitivity

The susceptibility of the gas permeable residual chlorine sensor fabricated in the examples to residual chlorine was evaluated.

The residual chlorine sensor was measured and the change of the sensor signal according to the residual chlorine concentration with the concentration of 0 - 5 mg / L was measured.

The residual chlorine sensor is to measure hypochlorous acid (HOCl), which is the most abundant in the total water quality pH, among total free chlorine. Since the free residual chlorine varies depending on the pH, the concentration of hypochlorous acid should be converted into the concentration of hypochlorous acid according to the pH of the sensor signal in order to convert the concentration of total free chlorine by measuring hypochlorous acid.

The signal values converted into the amount of free residual chlorine with respect to the concentration change are shown in FIG. 2 and FIG.

As shown in FIG. 2 and FIG. 3, the conversion sensor signal value according to the change in residual chlorine concentration shows excellent linearity and sensitivity. That is, the linearity from 0 to 1 mg / L is 0.9996 and the linearity from 0 to 5 mg / L is 0.9998.

< Experimental Example  2>

Of the residual chlorine sensor Sensitivity  compare

In order to objectively evaluate the sensitivity to the residual chlorine sensor according to the present invention, a residual chlorine analyzer (Hach's CL17 instrument) commercialized as an automatic measuring instrument using the DPD coloring method was continuously tested under the same conditions by changing the residual chlorine concentration of the sample And the residual chlorine sensitivity correlations were obtained.

Residual chlorine concentrations were measured for each of the same samples with various residual chlorine concentrations using the respective residual chlorine sensors. Fig. 4 shows the correlation curve of the sensitivity of the two residual chlorine sensors calculated from the experiment to the residual chlorine.

As shown in FIG. 4, the gas-permeable residual chlorine sensor according to the present invention has a correlation with a commercialized residual chlorine sensor. Therefore, it was confirmed that the gas permeable residual chlorine sensor and the measuring instrument have comparable residual chlorine measuring ability through a comparative experiment with a commercially available residual chlorine analyzer, which is generally widely used in measurement methods and measurement values.

As described above, the present invention is not limited to the above-described embodiment, but can be applied to a gas permeable residual chlorine sensor according to the present invention, It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

100: protective cap 110: gas permeable membrane
120: O-ring 130: Working electrode
135: auxiliary electrode 140: reference electrode
150: electrode part 160: cell body part
170: Electrolyte filler

Claims (5)

A selective residual chlorine permeable membrane 110 that transmits only free residual chlorine and does not transmit liquid components;
An electrode unit 150 including a working electrode 130, an auxiliary electrode 135, and a reference electrode 140 that cause a current change according to the amount of residual chlorine that has passed through the selective residual chlorine permeable membrane 110; And
Including the cell body portion 160, the selective residual chlorine permeable membrane 110, the working electrode 130, the auxiliary electrode 135 and the reference electrode 140 is mounted,
The working electrode 130, the auxiliary electrode 135, and the reference electrode 140 are formed to have a three-electrode structure,
The cell body 160 includes an ethylene-propylene block-polypropylene resin composed of 75 to 95% by weight homopolypropylene and 5 to 25% by weight of an elastic ethylene-propylene block copolymer having an ethylene content of 20 to 50% by weight. Electrochemical gas permeable residual chlorine sensor, characterized in that molded into a polypropylene resin composition. The method of claim 1,
The working electrode 130 and the auxiliary electrode 135 is composed of a platinum disk and a platinum line,
The reference electrode 140 is made of a poorly soluble silver / silver chloride electrode,
The selective residual chlorine permeable membrane 110 is an electrochemical gas permeable residual chlorine sensor, characterized in that using a microporous membrane made of Teflon material. The method of claim 1,
The reference electrode 140 is an electrochemical gas-permeable residual chlorine sensor, characterized in that the silver chloride is formed by immersing silver containing palladium 5% by weight in an aqueous iron chloride solution to form a poorly soluble metal layer. The method of claim 1,
Wherein an applied potential of 400 mV is applied to the working electrode (130) based on the reference electrode (140) to electrochemically detect the amount of residual chlorine. The method of claim 1,
The viscosity ratio (dl / g) of the homo polypropylene to ethylene-propylene block copolymer is 0.5 to 2.5, and the melt index (230 ° C., 2.16 kg load) of the ethylene-propylene block-polypropylene resin is 1 to 50 g /. Electrochemical gas permeable residual chlorine sensor, characterized in that 10 minutes.

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