JPS6015016B2 - Method for measuring the concentration of hypobromite aqueous solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention mainly deals with the treatment of hypobromite (hereinafter abbreviated as MBro) contained in wash water in wet gas treatment equipment using water containing hypobromite as wash water. Concerning a method for measuring the concentration of.

As a secondary method of this type, in principle, a colorimetric method using potassium hydride or a method of measuring redox potential can be considered.

However, although the former is frequently used in the laboratory,
As an industrial measuring instrument, it uses chemicals that are problematic in terms of pollution control, such as potassium iodide and acetic acid, and requires post-treatment of harmful free iodine produced by the reaction between Mold and potassium iodide. There are some problems. Furthermore, free iodine tends to adhere to the saddle liquid of the measuring device, so when measuring free iodine concentration optically, for example, there is not only an error due to loss of iodine adhesion, but also an increase in absorbance due to contamination of the window material. This may cause large measurement errors. In addition, the latter method of measuring redox potential does not provide a satisfactory measurement value because the redox potential of the solution strongly depends on the pH and the coexisting Br concentration, and it only shows a potential change corresponding to the logarithm of the MBr concentration. Scales are difficult. Applying the conventionally known measuring method as described above is not suitable for accurately measuring the M old ro concentration in the gas cleaning water of a wet gas treatment equipment over a long period of time.

This invention was made in order to provide a new and versatile measuring method that essentially does not have the above-mentioned drawbacks. The main purpose of this method is to estimate the concentration of Bro from the absorbance.
After converting most of o into Bro- shape, 290 of Bro-
This is to measure the ultraviolet light absorbance in the range of .

An embodiment of the present invention will be described below. Figure 1 is a system diagram to which the above-mentioned method is applied.
is continuously injected to become a test liquid la whose pH is adjusted to 11 or more, and then introduced into the measurement cell 5 through the filter 4. In this measurement cell 5, ultraviolet rays 7 emitted from a light source 6 pass through an optical filter 8 (preferably a metal film evaporation interference filter with small dispersion), and monochromatic light (for example, 33) It becomes incident as 7a.
While this monochromatic light 7a passes through the measurement cell 5, the test liquid la
It is absorbed by Bm- in the ion beam, and enters the light receiver 9 as transmitted light 7b whose light intensity is reduced in accordance with the ion concentration. The light receiver 9 receives an electric signal 11 having a value corresponding to the intensity of the transmitted light 7b.
The computing unit 10 outputs an MBm concentration signal 1 1 a corresponding to the absorbance signal 11 to a subsequent device (not shown). Next, the principle of this M old ro content measuring method will be explained in detail.

In the figure, the MBro salt in test solution 1 is expressed by the following chemical equation [1}: hypobromite EBro and B
It is in chemical equilibrium with ro-.

HBrkoBro-+H+log(Bro-)/HBr
o) } . ．． ．． '1} = -8.730 pH (260) (where () represents the concentration unit of gram ion/liter or gram mole/liter) From equation m, finding the relationship between the abundance ratio of Bm- and pH, 2
The result is a characteristic curve A shown by a dotted line in the figure.

On the other hand, at 25 qo, the concentration of sodium hypobromite is 1.65 × 3
Using the aqueous solution of 10-yuzu, the abundance ratio of Bro- calculated from the ultraviolet absorption spectrum described below is determined as the characteristic curve B shown by the solid line in FIG. In other words, for both characteristic curves, if the pH is 11, the MBro is 96.
% or more exists as Bro-, which means 3. According to the characteristic curve B in Fig. 2, Bro- has an abundance ratio of about 50% or less at PH Mi9, but in that region, MB
Since ro evaporates into the gas phase as MBr, and its chemical reactivity increases, its concentration becomes unstable.

Therefore, it is not preferable to measure the Mbro concentration at a pH of 9 or lower. Figure 3 shows NaBro 1 at a temperature of 25q0.
．． It is an ultraviolet absorption spectrum diagram of an aqueous solution of fence 12 containing 65×10-3 mo〆/containing, and the effective length of measurement cell 5 is 1
．． 0 enemies.

In the figure, the substance that exhibits maximum absorption at wavelength 33 is B.
It is ro-. Note that the shape of this characteristic curve is
It is almost constant. Figure 4 is a characteristic diagram showing the result of actually measuring the relationship between the NaBro concentration at a temperature of about 260℃ and the absorbance at a wavelength of 33℃, and within the experimental range there is a straight line between the two according to Beer's law below. A relationship was found.

log. /1, = 3.64 x 1 pi CI
...(1) (here loglo/1, is absorbance, lo
is the intensity of the transmitted light 7b when the M old ro concentration is zero, 1, is the intensity of the transmitted light 7b when the M old ro concentration is Cmo / the intensity of the transmitted light 7b at that time, and 1 is the effective length of the measurement cell 5. be. ) As mentioned above, in the example shown in FIG. 1, alkaline solution 3 is added to test solution 1, and - is set to 11 or more to convert almost the entire amount of M old ro in test solution 1 into the Bro- chemical form. After that, the M old RO concentration in the test liquid 1 can be detected by measuring the absorbance within the range from the UV absorption region 290 to 100 m.

The filter 4 is for filtering out hydroxides of metal ions such as iron and calcium, which may be generated when the test liquid 1 is made alkaline, and other coexisting solids. The light source 7 is not particularly limited, and may be a commercially available tungsten lamp or heavy water lamp with a wavelength of 33M.
Any material having an emission band around m may be used.

In addition, the required effective length of the measurement cell 5 is, for example, the measurement wavelength 33
If the lower limit of measurement is when the absorbance due to Bro- is 0.03, then the lower detection limit concentration of MBro is 8.4.
In order to obtain x10-6moso/〆 (1 skin in weight ratio), it is sufficient to use approximately 4.3 skin or more.

Further, the light receiver 14 may be a photomultiplier tube, a silicon photocell, or the like.

In the embodiment described above, the optical filter 8 has a length of 33 meters.
Although we have shown a configuration using an optical device that transmits monochromatic light of It goes without saying that any filter can be used in the same way.

In addition, the pH of the test solution la must be at least 11, and in cases where the measurement accuracy may be rough, the purpose can be achieved by setting the pH to 9.9 or higher. It is something. FIG. 5 shows the above-mentioned ' according to this invention.
In the second embodiment of the method for measuring ro, the reducing liquid 3b fed by the pump 2b is continuously injected into the test liquid la that has passed through the measuring cell 5, and the M old ro in the liquid is continuously injected. Br-
After the sample liquid is reduced to lb, it is introduced into the comparison cell 5b.

On the other hand, the optical path of the monochromatic light 7a is alternately switched at regular intervals by the rotating sector 12, one of which passes through the reflector 13, passes through the sample cell 5, passes through the semi-transparent plate 14, and enters the light receiver 9, and the other passes through the rotating sector 12. 12 to the comparative cell 5b and the reflecting mirror 15.
, enters the light receiver 9 through the semi-transparent plate 14. The absorbance signal 11 output from the light receiver 9 is synchronized with the rotation of the rotating sector 12, and the intensity of the transmitted light 7b of the measurement cell 5 is 1, and the intensity of the light 7b of the comparison cell 5b is
The transmitted light 7c is output as a rectangular wave signal that alternately switches between two values: high and high. If sodium thiosulfate, sodium sulfite, etc., which do not have an absorption band in the ultraviolet region of 290 to 38 valent blood in an aqueous solution, is used as the reducing solution 3b, the sodium sulfate and sodium bromide produced by the reduction reaction will also be in the above-mentioned ultraviolet range. Since it does not have an absorption band, the two values of the above rectangular wave signal are 1,,1
From 2 to the computer 1, calculate the absorbance of the test liquid 1 by log12/1
, and the M old m concentration can be estimated from this absorbance. In this way, it is possible to avoid a measurement error in the MBr concentration due to a decrease in absorbance due to contamination of the test liquid or the like.

Note that if the reducing solution 3b contains an excessive amount of sodium thiosulfate or sodium sulfite compared to the amount of MBm in the test solution la, the oxidation-reduction reaction will occur instantaneously when mixed with the test solution la. The process progresses as follows, reducing M old ro to Br-.

For example, when MBro in the test liquid la is NaBro, the following chemical reaction (D) or (m) proceeds.

9NaBro + Na2S203 12NaOH→ is a2S
04 10 rules aBr 10 days 20... (0) NaBr
o+Na2S03→Na2S04 ten NaBr
・・・・・・(m) The amount of reducing agent added is calculated according to the above reaction formula (
As inferred from 0) and (m), MB in the test solution la
When using sodium thiosulfate, the molar concentration may be 0.2 times or more, and when using sodium sulfite, the molar concentration may be at least 0.2 times.

As described above, according to the present invention, the wavelength of the test liquid is 290~
The purpose of this method is to detect the concentration of MBr from the absorbance of ultraviolet light in blood.
After making the test solution alkaline to pH 9.5 or higher, preferably pHil or higher, it is possible to detect the M old ro concentration by measuring the absorbance.

Compared to the methods deduced in the prior art, the method of the present invention simplifies or eliminates the pretreatment of the test liquid;
Since it is possible to accurately measure the concentration of M and old M in a test liquid quickly and over a long period of time over a wide range, it can be applied to measurements in practical devices with great effect.

[Brief explanation of the drawing]

0 Fig. 1 is a system diagram of an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the relationship between the pH of the solution and the proportion of hypobromite ions, and Fig. 3 is a diagram showing the relationship between the pH of the solution and the proportion of hypobromite ions. 6510-3
Ultraviolet absorption spectrum diagram of an aqueous solution containing Cmo,
Figure 4 shows the concentration of sodium hypobromite aqueous solution and 3
A characteristic diagram showing the relationship with the absorbance of ultraviolet light of 3 Mm, and FIG. 5 is a system diagram of another embodiment of the present invention. In the figure, 1, la, lb are test liquids, 2, 2b are pumps, 3 is alkaline liquid, 3b is reducing liquid, 40 is a filter,
5 is a measurement cell, 5b is a comparison cell, 6 is a light source, 7 is ultraviolet light, 7a is monochromatic light, 7b and 7c are transmitted light, 8 is a filter,
9 is a light receiver, 1 is a calculation unit, 1 is an absorbance signal, 1
1a is an MBro concentration signal, and 12 is a rotating sector. Note that the same reference numerals in the figures indicate the same or corresponding parts. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. The pH of the test liquid is set to 9.5 or higher, and the absorbance of ultraviolet light in the range of 290 to 380 nm by the test liquid is measured,
A method for measuring the concentration of a hypobromite aqueous solution, in which the concentration of hypobromite in the test liquid is estimated from this absorbance. 2. A patent claim in which an excessive amount of a cyclizing agent is added to a test liquid whose absorbance is to be measured, and its absorbance is measured, and the concentration of hypobromite is determined from the difference or ratio between these two absorbances. A method for measuring the concentration of an aqueous hypobromite solution according to item 1. 3. The hypobromite salt according to claim 2, wherein both the reducing agent and the product obtained by adding the reducing agent are substances that have no absorption band for ultraviolet light in the range of 290 to 380 nm. Method for measuring concentration of aqueous solution. 4. The method for measuring the concentration of a hypobromite aqueous solution according to any one of claims 1 to 3, wherein the ultraviolet light for measuring absorbance is monochromatic light having a wavelength of 330 nm as a main component. .