JPH087175B2 - Rotating electrode and concentration measurement method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rotating electrode and a concentration measuring method, and more particularly to measuring the concentration of a substance to be electrolyzed contained in a slurry, a colloidal solution, a highly viscous solution or the like. The present invention relates to a suitable rotating electrode and a concentration measuring method using the same.

[Prior Art] A rotary electrode is one in which an electrode is connected to a rotary driving device and is rotated in a solution to be measured to generate an electrolytic current of the solution to be measured between a working electrode and a counter electrode. The method of measuring the solute concentration in a solution using a rotating electrode is to obtain a stable electrolytic current (limit diffusion current) that is proportional to the concentration of the substance to be measured by making the thickness of the diffusion layer of the substance to be measured in the solution uniform. Therefore, it occupies an important position in electrochemical analysis.

As this rotating electrode, a rotating wire electrode, a rotating disk electrode, a rotating ring / disk electrode, etc. are known. FIG. 6 is an explanatory view of a conventional quantification method using a rotating electrode, which requires a fixed electrode 21 as a counter electrode in addition to a rotating electrode 20 in which either the cathode or the anode is a single pole (working electrode). is there. For example, as shown in FIG. 6A, the rotating ring / disk electrode has a disk electrode 24 in the center of the rotating electrode 20 and a ring electrode 23 concentrically in the center of the rotating electrode 20 as a working electrode. The electrochemically active substance that flows from the disc pole to the outer ring pole and is electrolytically generated by the disc pole 24 is captured and detected by the ring pole 23.

Ultra-micro electrodes such as micro-comb electrodes are known as electrodes that can obtain a steady diffusion current by diffusing the electrolyte solution into a state close to three dimensions without rotating the electrode or moving the solution. ing.

However, since it is necessary to obtain a uniform diffusion layer of the substance to be measured in the rotating electrode or the ultrafine electrode, it is restricted to the measurement of the sample in which the diffusion layer is easily obtained, and the slurry or the highly viscous solution in which the diffusion layer is difficult to obtain. However, there has been a problem that the concentration of the substance to be measured contained in the colloidal solution or the like cannot be accurately measured.

[Problems to be Solved by the Invention]

An object of the present invention is to solve the above-mentioned problems of the prior art, and to measure the concentration of the substance to be electrolyzed contained in a slurry, a highly viscous solution, a colloidal solution or the like with high accuracy with a simple device, and It is to provide a concentration measuring method using this.

[Means for solving the problem]

The present invention provides a rotating electrode, in which at least one pair of cathode and anode connected to a power source and a measuring unit are provided in parallel to a rotating terminal at intervals of 1 mm or less, and a sample of the rotating electrode. The present invention relates to a concentration measuring method of measuring the concentration of a substance to be electrolyzed in the sample by immersing or contacting with the sample and rotating the sample.

[Action]

By providing the cathode and anode parallel to the rotating terminal at intervals of 1 mm or less, the fixed electrode is not installed in the sample, and the diffusion layer is not restricted to the sample that easily obtains the substance to be electrolyzed in the sample. The concentration of can be measured with high accuracy.

FIG. 1 is a perspective view of a rotary electrode showing an example of the present invention. In the figure, a rotary electrode 3 is a pair of a cathode 1 and an anode 2 provided in parallel at an interval of 1 mm or less, and the cathode 1 and the anode 2 are fixed, and only the tips of these are exposed, and It is composed of an insulating part 3A which is insulated from the constituent parts, a current collecting brush 5 and a power feeding ring 4 which connect the cathode 1 and the anode 2 to a power source and a measuring part, respectively. A noble metal such as platinum is used as a material forming the cathode 1 and the anode 2, and copper, SUS or the like can be used as the cathode. The exposed positions of the cathode 1 and the anode 2 may be the bottom of the rotating electrode 3 or the side thereof as shown in FIG. 1A. For the insulating portion 3A, resins such as epoxy resin, vinyl chloride resin, phenol resin and ceramics can be used.

The cathode 1 and the anode 2 need to be provided in parallel at intervals of 1 mm or less from the viewpoint of measurement accuracy. The closer the electrodes are, the more accurate the measurement will be.However, it will be less affected by dust in the sample and the noise generation rate will increase.
m is preferable, and more preferably about 0.5 mm to 0.3 mm. For a uniform sample with a small amount of contaminants, it is possible to perform measurement with higher accuracy by using electrodes with narrower intervals. There may be at least one pair of cathode and anode, but the cathode and the anode may be alternately arranged and used as a comb-shaped electrode (see FIG. 1B). The greater the number of electrodes, the higher the measurement accuracy. Further, the length of the electrode is preferably shorter from the viewpoint of measurement accuracy, preferably 20 mm to 10 mm or less, and more preferably about 5 mm.

FIG. 2 is a diagram showing an example of a concentration measuring device using the rotating electrode of the present invention.

In the figure, a synchronous motor 9 is provided above the pedestal 12.
Is mounted on the base 13, and a support base 8 is provided on the base 13 via a spring 14 on the lower part thereof, on which a container 7 containing the sample 6 is mounted, and the support shaft 8 is installed on the rotary shaft of the motor 9. The rotating electrode 3 is inserted into the sample 6 in the container 7. After the sample 6 is placed in the container 7 on the support 8, the electrodes 1 and 2 of the rotary electrode 3 are immersed or brought into contact with the sample, and the rotary motor 3 is rotated by the synchronous motor 9. The rotation speed is usually 100 to 3000 rpm. The power supply ring 4 provided on the rotating electrode 3 comes into contact with the current collecting brush 5 connected to the constant voltage power source 10 and the recorder 11, respectively, and supplies a voltage to the electrodes 1 and 2. Electrodes 1, 2 by applying voltage
The electrolysis current generated at is the power supply ring 4 and the current collecting brush 5.
The concentration of the substance to be electrolyzed is calculated from this electrolytic current value based on the calibration curve previously input to the recorder via the. At the time of calculation, it is preferable to perform temperature correction in order to eliminate the influence of temperature and improve the measurement accuracy.

The electrolytic current can also be measured continuously by immersing the rotating electrode 3 in a sample that moves at a relatively constant speed on, for example, a belt conveyor. In this case, since a sample moving at a constant speed is measured, there is almost no deposition of metal or metal hydroxide on the cathode, and continuous measurement is not hindered.

〔Example〕

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

Examples 1 and 2 and Comparative Examples 1 and 2 The water content of the dehydrated sludge was adjusted in four stages, and the water content in this dehydrated sludge was determined by the apparatus of FIG. 2 using the rotary electrode of FIGS. 1 and 1A. Each of the values was measured, and this value was compared with the value measured by the dry weighing method to examine the quantitative property. The rotating electrode is a platinum plate electrode with a thickness of 0.5 mm and a length of 5 mm.
It was rotated at 600 rpm and a voltage of 4 V was applied at room temperature. The results are shown in FIG. 3, but it was found that good quantification was exhibited.

Further, as Comparative Examples 1 and 2, the conventional rotary disk electrode and rotary wire electrode were respectively used to measure the water content of the dehydrated sludge in the same manner as above, but no quantitativeness was observed.

Examples 3 and 4 Vitamin C (reduced form 1-ascorbic acid) was added to the starch slurry, and the concentration of vitamin C was measured by the apparatus of FIG. 2 using the rotating electrode of FIGS. 1 and 1B, respectively. The quantification was examined. The same rotating electrode as in Example 1 was used as the rotating electrode in FIG. 1, and the comb electrode in FIG. 1B was a comb electrode in which 4 rows of cathodes and 3 rows of anodes were alternately arranged in an area of 3 mm × 3 mm. Using. Further, it was rotated at a rotation speed of 1200 rpm and a voltage of 2 V was applied at room temperature. The results are shown in Fig. 4, and it was found that they showed good quantification.

Example 5 The electrolytic current when 100 μl of water was added to 100 ml of isopropanol was continuously measured by the apparatus of FIG. 2 using the rotating electrode of FIG. The results are shown in Fig. 5,
It was found that an electrolytic current proportional to the water content was obtained.

Examples 6 and 7 The rotating electrode of FIG. 1 was prepared with the platinum plate electrodes having lengths of 7 mm and 5 mm, and the water content in the dehydrated sludge on the belt conveyor was continuously changed under the conditions of a rotation speed of 600 rpm and an applied voltage of 4 V. It was measured. The measurement accuracy at this time is 0.5 to 2 with a 7 mm electrode.
%, The range was 0.0 to 1.0% for the 5 mm electrode.

 The measurement accuracy was calculated as follows.

EFFECTS OF THE INVENTION According to the rotating electrode of the present invention, the concentration of the substance to be measured contained in the slurry, the highly viscous solution, the colloidal solution, etc., in which a uniform diffusion tank is difficult to obtain, for example, the water content in the dehydrated sludge can be easily measured by a simple device Can continuously and highly accurately measure.

[Brief description of drawings]

1, 1A and 1B are perspective views of a rotating electrode showing an example of the present invention, and FIG. 2 is a view showing an example of a concentration measuring device using the rotating electrode of the present invention, FIG. Is a diagram showing the relationship between the water content in the dehydrated sludge and the electrolysis current measured using the rotating electrode of the present invention, and FIG. 4 is the content of vitamin C and the electrolysis current measured using the rotating electrode of the present invention. Figure showing the relationship of
FIG. 5 is a diagram showing the relationship between the water content in isopropanol and the electrolysis current measured using the rotating electrode of the present invention, FIG. 6 is an explanatory diagram of a conventional quantification method using a rotating electrode, and FIG. 6A is
It is a figure which shows the structure of a rotating ring disk electrode. 1 ... Cathode, 2 ... Anode, 3 ... Rotating electrode, 3A ... Insulating part, 4 ...
Power feeding ring, 5 ... current collecting brush, 6 ... sample, 7 ... container, 8
… Support, 9… Synchronous motor, 10… Constant voltage power supply,
11 ... Recorder, 20 ... Rotating pole, 21 ... Fixed pole, 22 ... Electrolyte, 23
… Ring pole, 24… disk pole.

Claims (2)

[Claims] 1. A rotating electrode, wherein at least one pair of cathode and anode connected to a power source and a measuring unit, respectively, are provided in parallel to a rotating terminal at intervals of 1 mm or less. 2. A concentration measuring method in which the rotating electrode according to claim (1) is immersed in or brought into contact with a sample and rotated to measure the concentration of a substance to be electrolyzed in the sample.