JP3208122B2 - Molded body for measuring pH of pore water in soil and pH measuring method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring the pH of pore water in soil, which is difficult to measure with a pH electrode or a pH test paper.
A new and improved pH measurement method .

[0002]

2. Description of the Related Art As a method for measuring the pH of a solution, a pH meter comprising a glass electrode and a reference electrode is immersed in a measuring solution, and a pH value is obtained by measuring an electromotive force between the electrodes. A method of immersing the measurement solution in a pH test paper that has been immersed in a filter paper and dried with a pH indicator that changes color with a change in pH, and comparing the color of the test paper with a standard color tone table to read the pH, It has been widely used in the past.

[0003]

SUMMARY OF THE INVENTION However, sludge
In wastewater containing a large amount of dirt and suspended solids, and in high-temperature and high-humidity conditions, p
It is difficult to apply the H measurement method.

[0004] In particular, when geological disposal of high-level radioactive waste is required, it is necessary to measure the pH of soil with a high consolidation density in an underground environment, or the interface between the soil and a structure or the like. Even if the amount of pore water existing in the soil or boundary is extremely small and the pore water can be squeezed out using a centrifuge, the pH can be measured using a conventional pH meter or pH test paper. It is extremely difficult to do.

Accordingly, the present invention measures the pH of a small amount of pore water in soil having a high compaction density, which is difficult to measure by a conventional method using a pH meter or pH test paper, or at the interface between soil and a structure. The purpose of the present invention is to provide a new and improved method for measuring pH.

[0006]

[0007]

That is, the method of measuring pH in soil according to the present invention comprises adsorbing a pH indicator to adsorbent particles.
The sensitized colored particles are placed tightly in a protective sheet consisting of a dialysis membrane.
After inserting the sealed molded body for pH measurement into the soil and leaving it to stand for a predetermined time, the coloring particles in the protective sheet are taken out, and the pH value is obtained from a change in the color of the coloring particles. It is.

Is pH measurement target object [0008] pH measurements molded articles
And soil, while inserted into the interface between the soil and the structure left to stand predetermined time, only the solution during pore water to penetrate inside the molded body through a protective sheet made of dialysis membrane of the molding , Gap
Suspended particles such as sludge in water are prevented from penetrating by the protective sheet. The solution that has permeated the protective sheet comes into contact with the colored particles inside the molded article, and changes the color of the pH indicator adsorbed on the colored particles according to the pH of the solution. The color-developed particles thus discolored are taken out of the protective sheet, and the pH value can be determined from the color change of the color-developed particles.

For the change in the color of the coloring particles, a method of reading the pH by comparing the color tone of the coloring particles with a standard color tone table prepared in advance can be adopted. It is preferable to adopt a method in which a change in the color of the color-forming particles is measured as a reflectance by a colorimeter and a pH value corresponding to the reflectance is obtained.

The molded body can be formed into various shapes such as a tube, a flat bag, a capsule, etc., so that the molded body for pH measurement can be easily inserted into the object for pH measurement.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The molded body for pH measurement used in the present invention can be produced by the following method. The pH indicator may be selected from the indicators shown in Table 1 in consideration of the discoloration range. The selected pH indicator is
Dissolve in ethyl alcohol to make it supersaturated and p
Prepare H indicator solution.

[0012]

[Table 1]

[0013] On the other hand, the selection of the adsorbent selects a pH indicator that is well adsorbed, has high chemical resistance, and maintains good adsorption performance in the operating temperature range. Examples of such adsorbents include molecular sieves and Amberlite X
Synthetic adsorbents such as the AD series and ion exchange resins such as the Dowex and Amberlite IR series can be preferably used. After selecting the adsorbent, the adsorbent is washed with ethyl alcohol to remove impurities such as dust.

Next, the pH indicator solution prepared above and the washed adsorbent particles are mixed, and the pH indicator solution is impregnated in the adsorbent and adsorbed. The impregnation time may be a time sufficient for the pH indicator to adsorb to the adsorbent particles, and is generally 12 hours or more. Thereafter, the operation of replacing the supernatant liquid with distilled water is performed 10 times or more to completely replace ethyl alcohol with distilled water. The coloring particles thus obtained are stored in distilled water.

The coloring particles are then taken out of distilled water for storage and sealed in a protective sheet while the surface is still wet to form a molded article. The protective sheet has the function of protecting the colored particles from sludge and suspended matter in the pH measurement target, preventing the passage of these particles in the measurement target, and forming only the solution in the measurement target. It passes through the body and comes into contact with the coloring particles. As the protective sheet having such a function, a dialysis membrane such as a semipermeable membrane can be used. For example, a membrane made of a cellulose derivative, a membrane filter such as a Millipore filter, or the like can be preferably used.

The shape of the protective sheet may be an insertion easy shape during pH measurement object, for example to tubing shape and capsules shaped body is easy to use, the interface or cracks surface of soil and concrete In such a case, a flat molded body is easily inserted.

After leaving the molded body in the pH measurement object for a time sufficient for the solution in the pH measurement object to permeate through the protective sheet formed of the dialysis membrane of the molded body, the protective sheet is not damaged. After carefully removing the molded product from the object of pH measurement using plastic tweezers or the like, a change in color of the coloring particles inside the protective sheet is examined.

The color change of the color-forming particles is determined by comparing the color tone with a standard color tone table prepared in advance in the same manner as measuring the color change of a conventional pH test paper, and determining the pH value corresponding to this color tone. Although the pH value can be obtained, the pH value can be measured with higher accuracy by measuring the change in color of the color-forming particles using a colorimeter. The colorimeter is a device for converting a color into a numerical value, and is capable of measuring a reflectance (%) for light of each wavelength in a range of, for example, 400 to 700 nm. Using this colorimeter, the change in color of the coloring particles that have been brought into contact with a solution having a known pH is measured as a reflectance, and the relationship between the pH value and the reflectance is created as a calibration curve. Then p
H. Take out the colored particles inside the protective sheet from the molded body after being left in the object to be measured, measure the change in color of the colored particles as a reflectance using a colorimeter in the same manner, and correspond to the measured reflectance. The pH value to be determined can be determined using a calibration curve created in advance.

The creation of a calibration curve (a graph showing the relationship between the pH value and the reflectance) using a colorimeter will be described in further detail.
First, the coloring particles in distilled water are brought into contact with a known pH solution,
The change in color of the coloring particles at this time is measured as a reflectance using a colorimeter. FIG. 1 shows the change in color of the coloring particles when the coloring particles obtained by adsorbing the pH indicator bromoxylenol blue to the adsorbent Amberlite XAD-4 are brought into contact with a known pH solution having a pH of 6.5 to 10.0. Shows the relationship between the wavelength and the reflectance when measured as the reflectance of light whose wavelength is changed in the wavelength range of 400 to 700 nm using a colorimeter.

In the graph of FIG. 1, the change width of the reflectance with respect to each pH at the wavelength of 620 nm is most remarkable. Therefore, a calibration curve as shown in FIG. 2 can be created by plotting the relationship between the pH value and the reflectance with the wavelength of 620 nm as the wavelength for preparing the calibration curve. In FIG.
Calibration curves for other pH indicators obtained in the same manner are also shown. Using such a calibration curve, pH
Take out the colored particles from the inside of the molded body for pH measurement placed in the object to be measured, measure the change in color as a reflectance with a colorimeter, and determine the pH value corresponding to the measured reflectance. Can be.

The optimum wavelength for preparing a calibration curve was 620 nm in the case of bromoxylenol blue.
This optimum wavelength differs depending on the pH indicator. FIG.
Table 2 shows the optimum wavelength for preparing a calibration curve for the pH indicators shown in Table 1. For other pH indicators, a calibration curve can be created from the optimum wavelength by the same method.

[0022]

[Table 2]

It is also possible to create a mathematical expression based on polynomial approximation corresponding to the calibration curve without preparing a graph of the calibration curve, and calculate the pH value using this mathematical expression.

[0024]

EXAMPLE Bromoxylenol blue was used as a pH indicator and dissolved in ethyl alcohol so as to be supersaturated to prepare a pH indicator solution. Amberlite XAD-4 (particle size: 400-700 μm, manufactured by Organo Co., Ltd.) was used as an adsorbent, washed with ethyl alcohol, and impregnated with the above pH indicator solution for 12 hours.
The pH indicator solution was adsorbed on the adsorbent particles. Then
Prepare the coloring particles by completely replacing the supernatant with distilled water,
Stored in distilled water.

The colored particles are taken out of the distilled water for storage, and the cellulose tube for dialysis (dialysis membrane U) is washed in advance with 1 liter of distilled water for 24 hours while keeping the surface wet.
C20-32-100, manufactured by VISKASE SALES CORP.), Filled in a protective sheet, tightly sealed both ends of the tube with a thread, and formed into a tube-shaped molded body for pH measurement (length 10 m).
m, diameter 5 mm). The dialysis cellulose used here is regenerated cellulose regenerated from a chemically treated natural cellulose by a viscose method, that is, α-cellulose as a main component.

After the molded body for pH measurement prepared as described above was placed in sludge to be subjected to pH measurement and allowed to stand for one week, the colored particles inside the molded body were taken out, and a spectrophotometer (CM-20) was used.
22, manufactured by Minolta Co., Ltd.).
The reflectance at a wavelength of m was measured. The relationship between the wavelength and the reflectance at this time is shown in the graph of FIG.

The curve shown in the graph of FIG. 3 and the wavelength 620 n for preparing a calibration curve of bromoxylenol blue as a pH indicator.
From the intersection with m, a reflectance of 10% is determined. Based on the value of the reflectance, a pH value of 8.5 corresponding to the reflectance of 10% can be read from the calibration curve of bromoxylenol blue in FIG.

[0028]

Effects of the Invention According to the present invention As can be seen from the above, it is possible to perform the measure pH traces pore water in the soil which has been difficult heretofore simply and effectively.

[Brief description of the drawings]

FIG. 1 shows a case where a change in color of a color-forming particle obtained by contacting a color-forming particle obtained by adsorbing a pH indicator bromoxylenol blue to an adsorbent particle with a known pH solution is measured as a reflectance using a colorimeter. 4 is a graph showing the relationship between wavelength and reflectance.

FIG. 2 is a wavelength (620 nm) for preparing a calibration curve in FIG.
5 is a graph showing a calibration curve in which the relationship between the pH value and the reflectance in FIG. Calibration curves obtained in the same manner for various pH indicators are also shown.

FIG. 3 is a graph showing the relationship between wavelength and reflectance when the change in color of the coloring particles used in the examples is measured as reflectance using a colorimeter.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takeshi Isogai 33, Muramatsu, Oji, Tokai-mura, Naka-gun, Ibaraki Pref. , A) JP-A-50-67188 (JP, A) JP-A-63-206653 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 31/22 123 G01N 21/80

Claims (2)

(57) [Claims] 1. A molded article for measuring pH, which is obtained by adsorbing a coloring agent having a pH indicator adsorbed on adsorbent particles in a protective sheet made of a dialysis membrane , is inserted into soil and left for a predetermined time.
After squeezing, take out the coloring particles in the protective sheet and form
It is characterized by calculating pH value from color change of color particles
A method for measuring the pH of pore water in soil. 2. A colorimeter for measuring the change in color of the color-forming particles.
Measure as reflectivity, and calculate the pH value corresponding to this reflectivity.
The pore water in the soil according to claim 1, wherein
pH measurement method.