JP2532952B2 - Chemical oxygen demand measuring method and measuring reagent - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for measuring a chemical oxygen demand and a reagent used therefor, which can quickly and simply measure the chemical oxygen demand of a test water. It is a thing.

Conventional technology The method of measuring chemical oxygen demand (hereinafter referred to as COD) is described in Japanese Industrial Standards (JIS) K0101 and K0102.
Oxygen consumption by potassium permanganate (COD _Mn ) at 100 ℃, oxygen consumption by potassium permanganate (COD _Mn20 ) at 20 ℃, oxygen consumption by alkaline potassium permanganate (COD _OH ), potassium dichromate It is measured as oxygen consumption (COD _cr ). Further, Japanese Patent Laid-Open No. 186147/1988 proposes a method of shortening the measurement time by carrying out a thermal oxidation reaction using a high frequency dielectric heating means.

Problems to be Solved by the Invention Since the COD measurement method specified in JIS requires complicated operations such as heating and titration, it is necessary to quickly perform the measurement at the management site such as an outdoor water treatment device or a septic tank. It was difficult to adapt to the request to know the water quality condition.

Further, the method described in Japanese Patent Laid-Open No. 63-186147 also requires a power source and a high frequency dielectric heating device, and it is a very difficult method to carry out at the outdoor water quality control site.

Means for Solving the Problems The present inventors have repeated various tests in order to solve such problems, potassium permanganate, a water-soluble basic substance and diphenylamine-4-sulfonic acid or 2, The intended purpose was achieved by adding a reagent containing 4-diaminodiphenylamine as an essential component to the test water and comparing the colored state of the test water.

The potassium permanganate used in the practice of the present invention is commercially available as a special grade or primary grade, and its form may be solid powder or aqueous solution.

Water-soluble basic substances suitable for carrying out the present invention are water-soluble alkali metal hydroxides (earth metals), alkali metal phosphates, alkali metal borates, alkali metal carbonates, etc. Of the compounds shown, representative ones are sodium hydroxide, potassium hydroxide, calcium hydroxide, trisodium phosphate, tripotassium phosphate,
Examples include sodium carbonate and potassium carbonate.

The diphenylamine-4-sulfonic acid or 2,4-diaminodiphenylamine used in the practice of the present invention is preferably a commercially available special grade or primary grade,
The form may be solid, powder or aqueous solution.

In carrying out the present invention, potassium permanganate, a water-soluble basic substance and diphenylamine-4-, which are essential components, are used.
The means for adding the reagent containing sulfonic acid or 2,4-diaminodiphenylamine to the test water is a method of adding it in a powder mixture in advance, a method of adding it in an aqueous solution of the mixture in advance, a method of adding each component individually in powder, Although any method such as a method of individually adding the components in an aqueous solution may be used, a method of preparing an aqueous solution of the mixture in advance is particularly suitable.

COD from the test water colored according to the practice of the invention
As a method of measuring, it is desirable to compare the coloring state of the test water using a standard hue plate having a continuous hue change, especially in order to withstand outdoor use, a colorant is added to the colorless acrylic resin. A synthetic resin reference hue plate formed by molding is suitable.

It is already known that, when potassium permanganate is reduced under alkaline conditions, its hue changes with the reduction of potassium permanganate. However, the change in the hue was very slow, and it was difficult to predict the COD value from the change.

The present invention makes this dull hue change sharp to make the difference in hue clear, and enables stable and accurate measurement.

That is, by adding diphenylamine-4-sulfonic acid or 2,4-diaminodiphenylamine to potassium permanganate or a basic substance, an effect of changing a gradual change in hue into a sharp difference in hue is caused, which is quick and simple. Various colorimetric measurements are possible.

Diphenylamine-4-sulfonic acid or 2,4-
Diaminodiphenylamine is a substance used as an indicator for redox titration in ordinary chemical analysis,
The redox potential at the color change point is +0.70 V or +0.80 V, both of which show red in the oxidized form and colorless in the reduced form. Therefore, it is considered that discoloration near the equivalence point potential of + 0.57V of the redox reaction of potassium permanganate in alkaline is sensitive and interacts with the discoloration of potassium permanganate to cause a sharp difference in hue. To be

Example 1 As a COD source substance, a mixture of glucose, polypeptone, and meat extract in a weight ratio of 50:30:20 (hereinafter referred to as artificial sewage COD source) was dissolved in water to give a COD _Mn concentration of 2,
5,10,15,20,25,30,40,50 ppm sample water was prepared respectively. Then, 10 ml each of the test water was sampled, 0.62 mg of permanganese, 8 mg of sodium hydroxide and 0.04 mg of 2,4-diaminodiphenylamine were added as 0.2 ml of an aqueous solution of the mixture, and the mixture was allowed to stand at room temperature (25 ° C.) for 4 minutes, When the coloring state of each test water at that time was observed, it was as shown in Table 1.

Nine reference hue plates made of a translucent synthetic resin were prepared by using the hue of this test water as a standard, and as shown in the drawing, circular reference hue plates were made by arranging these continuously. (Refer to the drawing) Next, COD _Mn unknown artificial sewage COD source aqueous solution is used as a test water
10 ml of the sample was sampled, the same reagent as above was added thereto, and the sample was colored under the same conditions. As a result, a purple color was obtained, and the COD _Mn of this sample water was judged to be 10 ppm from the reference hue plate. On the other hand this artificial wastewater
When the COD source aqueous solution was measured by the method described in JIS K0102, COD _Mn was 9.8 ppm, which was almost the same as the measured value of the present invention.

Examples 2 to 7 In Example 1, a mixture of the compounds shown in Table 2 in a predetermined ratio was used as a reagent, and the same operation was repeated. The same color change as in 1 was observed, confirming that it can be used as a reagent for measuring COD.

Comparative Example 1 The same operation as in Example 1 was performed except that the reagent except 2,4-diaminodiphenylamine was used as the reagent in Example 1, and the color condition of each test water was observed. It was as shown in.

As a result of this test, in the COD _Mn value range of 2 to 25 ppm, there was no difference in the hue of the test water, and it was recognized that COD _Mn during this period could not be measured.

Example 8 Small septic tank treated water was used as a sample containing a COD source, diluted with water, and COD _Mn was set to 5,10,15,20,30,40,50,60,
80 ppm test water was adjusted respectively. 10 ml of each test water
0.62 mg of potassium permanganate, trisodium phosphate 64
mg, 2,4-diaminodiphenylamine (0.04 mg) was added, the mixture was allowed to stand at room temperature (25 ° C.) for 4 minutes, and the coloring state of each test water at that time is as shown in Table 4.

Nine reference hue plates made of a transparent synthetic resin were prepared on the basis of the hue of this test water, and the reference hue plates were circular.

Next, COD _Mn unknown small septic tank treated water was used as test water, and each reagent was added to it in the same manner as above, and room temperature (25 ° C)
When left for 4 minutes, the test water exhibited bluish purple, and the COD _Mn of the test water was judged to be 30 ppm from the standard hue plate. On the other hand, JIS K01
When the COD _Mn of this sample water was measured by the method described in 02, it was 33 ppm, and both were almost the same.

Comparative Example 2 The coloring state of the test water was observed by treating under the same conditions as in Example 8 except that 2,4-diaminodiphenylamine was removed as a reagent in Example 8, and the results are shown in Table 5. there were.

As a result, it was found that in the range of COD _Mn 5-40 ppm, there was no difference in the hue of coloring, and COD _Mn during this period could not be measured.

Example 9 Using treated water (COD _Mn 50 ppm) of a wastewater treatment facility of a confectionery manufacturer that manufactures a cake as a sample containing a COD source, it was diluted with water to obtain COD _Mn of 5,10,15,20,30, 40,50pp
The water samples of m were adjusted respectively.

0.62 mg of potassium permanganate in 10 ml of each test water,
Add 64 mg of trisodium phosphate and 0.04 mg of 2,4-diaminodiphenylamine, leave at room temperature (23 ° C) for 4 minutes,
The coloring state of each test water at that time is as shown in Table 6, and the relationship between the COD _Mn value obtained in Example 8 and the hue of the test water was exactly the same.

Therefore, the circular reference hue plate prepared in Example 8 was also used in this example.

Next, the treated wastewater of this confectionery manufacturer unknown to COD _Mn was used as test water, and each reagent was added to this as described above, and it was left at room temperature (23 ° C) for 4 minutes. The COD _Mn of this test water was determined to be 40 ppm from the reference hue plate. On the other hand, when the COD _Mn of this sample water was measured by the method described in JIS K0102, it was 38 ppm, and both were almost the same.

EFFECTS OF THE INVENTION According to the present invention, the chemical oxygen demand of the test water can be measured by a quick and simple operation, and it can be immediately used even in a place where the operation such as heating or titration cannot be performed outdoors, such as in a river. Practical effects such as measurement can be significant.

[Brief description of drawings]

The drawing is a plan view showing an example of the reference hue plate in the present invention.

Claims (3)

(57) [Claims] 1. Potassium permanganate, a water-soluble basic substance and diphenylamine-4-sulfonic acid or 2,4.
A method for measuring a chemical oxygen demand, which comprises adding a reagent containing diaminodiphenylamine as an essential component to test water and comparing the colored state of the test water. 2. The method according to claim 1, wherein the coloring state of the test water is compared by using a reference hue plate having a continuous hue change. 3. Potassium permanganate, water-soluble basic substance and diphenylamine-4-sulfonic acid or 2,4
-A reagent for measuring chemical oxygen demand, which comprises diaminodiphenylamine as an essential component.