JP6339985B2 - Method for reducing chlorine dioxide concentration in water and water treatment agent for reducing chlorine dioxide concentration in water - Google Patents

Description

  The present invention relates to a method for reducing chlorine dioxide concentration in chlorine dioxide-containing water and a water treatment agent for reducing chlorine dioxide concentration in water. More specifically, the present invention relates to a method for reducing the concentration of chlorine dioxide in chlorine dioxide-containing water, characterized in that the peroxide is added to chlorine dioxide-containing water in the presence of dissolved manganese. The water treatment agent which reduces the chlorine dioxide density | concentration in the chlorine dioxide containing water which comprises.

  Chlorinated chemicals (for example, hypochlorite) are added to pool water, bath water, and hot spring water (especially circulating water) for disinfection and sterilization (for example, sterilization of Legionella). Chlorine chemicals are also used for sewage treatment. However, the treatment with chlorinated chemicals has a problem that trihalomethane, which is an environmental pollutant / carcinogen, can be generated.

In addition, seawater used as cooling water prevents marine organisms (for example, bivalves and hydroworms) from adhering to the cooling water pipeline, and avoids a decrease in cooling efficiency and blockage of the pipeline. Chlorine and peroxide are injected.
Chlorine has a higher biocidal effect as the pH of the water to be treated is higher, and it is difficult to effectively treat it, particularly in the pH range of seawater, so a high concentration needs to be added. On the other hand, since the used seawater is returned to the sea again, it is necessary to manage so that chlorine does not remain to the extent that it affects the seaweed, shellfish and fish in the seawater. Furthermore, there is a problem that trihalomethane is generated as a reaction product of chlorine and organic matter in seawater.
Peroxide has a problem that it requires high concentration injection compared with chlorine, and costs increase. In addition, peroxide remains in the seawater discharge water, which may adversely affect marine organisms.

In order to avoid the above problems, in recent years, chlorine dioxide has been used as a disinfectant / disinfectant / biocide instead of chlorine or peroxide. Since chlorine dioxide has a strong biocidal effect without being affected by pH, it can be effectively treated at a low concentration. Trihalomethane is not generated, and the cost can be further reduced.
Therefore, in the future, chlorine dioxide will not only be used for pool water, bath water, hot spring water, and cooling water, but also as a disinfectant / disinfectant / biocidal agent in many situations (for example, food factories). Use is expected to increase. Further, since chlorine dioxide also has a bleaching action, it is considered that the use of chlorine dioxide as a bleaching agent (for example, at a paper mill) instead of a conventional chlorine-based bleaching agent will increase.

By the way, in consideration of the influence of chlorine dioxide on the environment, water containing chlorine dioxide needs to be managed so that the residual chlorine dioxide concentration becomes a predetermined amount or less when discharged.
To reduce the residual chlorine dioxide concentration, there is a method that uses a reducing agent such as sodium sulfite, but it is expensive because it requires addition of approximately four times the amount of residual chlorine dioxide. There are concerns about the environmental impact of the agent itself.
Therefore, an alternative method with low cost and less environmental impact is desired.

The inventors have found that the chlorine dioxide concentration in water is significantly reduced by peroxide in the presence of dissolved manganese.
Accordingly, the present invention provides a method for reducing the chlorine dioxide concentration in chlorine dioxide-containing water, which comprises adding a peroxide to the chlorine dioxide-containing water in the presence of dissolved manganese. Moreover, this invention provides the water treatment agent which reduces the chlorine dioxide density | concentration in the chlorine dioxide containing water in presence of dissolved manganese which comprises a peroxide.

  According to the present invention, the concentration of residual chlorine dioxide in chlorine dioxide-containing water can be reduced easily and at low cost.

It is a graph which shows the result of having added a peroxide and iron ion, copper ion, or dissolved manganese to the seawater containing chlorine dioxide, and having measured the chlorine dioxide density | concentration in predetermined elapsed time from addition. It is a graph which shows the residual chlorine dioxide density | concentration measured 5 minutes after adding a peroxide and dissolved manganese in various quantity to artificial seawater (sodium carbonate aqueous solution) which injected chlorine dioxide beforehand. It is a graph which shows the residual chlorine concentration measured 5 minutes after adding various amounts of peroxide and dissolved manganese to artificial seawater into which chlorine was previously injected. It is a graph which shows the residual chlorine dioxide density | concentration measured 5 minutes after adding a peroxide and dissolved manganese in various quantity to the seawater which injected chlorine dioxide previously. It is a graph which shows a time-dependent change of the residual chlorine dioxide density | concentration in the seawater which added chlorine dioxide and a peroxide previously. Five minutes after the addition of chlorine dioxide and peroxide, more dissolved manganese was added.

<Method to reduce chlorine dioxide concentration in water>
The chlorine dioxide concentration in the chlorine dioxide-containing water, characterized in that the manganese compound that produces dissolved manganese in the aqueous solution and the peroxide are added to the chlorine dioxide-containing water of the present invention in this order or in the reverse order or simultaneously. This is a method for reducing .
As shown in the examples below, the effect of peroxide reducing the chlorine dioxide concentration in water is enhanced in the presence of dissolved manganese, so according to the method of the present invention, it is used to reduce the chlorine dioxide concentration. Less peroxide is required. Therefore, the method of the present invention can easily reduce the concentration of chlorine dioxide in water at low cost.

  Chlorine dioxide-containing water that is suitable for reducing the chlorine dioxide concentration using the method of the present invention is water that contains chlorine dioxide and that is discharged into the external environment (eg, sea, rivers, lakes, etc.). If it is, it will not be limited, For example, it may be the waste liquid or discharge | emission liquid after using chlorine dioxide as a bleaching agent, disinfectant, disinfection / biocidal agent. The chlorine dioxide-containing water may be fresh water or seawater. Specific examples include waste liquids from food factories and paper mills, effluents from circulating water systems such as pools, bathhouses and hot spring facilities, sewage treated water, and seawater after being used as cooling water. The chlorine dioxide concentration in the chlorine dioxide-containing water before applying the method of the present invention can be, for example, 0.5 mg / L or more.

Dissolved manganese may be contained in the chlorine dioxide-containing water before applying the method of the present invention. Examples of such include seawater pretreated with chlorine dioxide for cooling water. Thus, in one embodiment, the chlorine dioxide containing water is seawater pretreated with chlorine dioxide for cooling water. In one preferred embodiment, the chlorine dioxide containing water is seawater containing dissolved manganese at a concentration of at least 0.01 mg / L. Here, in this invention, the density | concentration about dissolved manganese says manganese conversion amount.
In the method of the present invention, dissolved manganese may be supplied by adding a manganese compound that produces dissolved manganese in an aqueous solution to chlorine dioxide-containing water. Examples of the manganese compound that generates dissolved manganese in an aqueous solution include manganese chloride, manganese sulfate, and manganese nitrate, with manganese sulfate being preferred.
Manganese compounds that produce dissolved manganese in an aqueous solution may be added singly or in combination of two or more.

  Dissolved manganese can be present in the chlorine dioxide-containing water, for example, at a concentration of at least 0.01 mg / L, preferably at a concentration of at least 0.05 mg / L. Although the upper limit of the density | concentration of the dissolved manganese in chlorine dioxide containing water is not specifically limited, From a viewpoint of cost, it may be 1.0 mg / L. In one embodiment, the manganese compound that produces dissolved manganese in an aqueous solution may be added such that the dissolved manganese concentration in the chlorine dioxide-containing water is at least 0.01 mg / L. In one preferred embodiment, the manganese compound can be added such that the dissolved manganese concentration in the chlorine dioxide-containing water is 0.05 to 0.1 mg / L.

Examples of the peroxide include hydrogen peroxide, perborate, perphosphate, persulfate, pernitrate, peracetate, peroxide, and hydrogen peroxide adduct. The salt may be an alkali metal (preferably sodium) salt, an alkaline earth metal (preferably calcium and magnesium) salt or an ammonium salt. One peroxide may be added alone, or two or more peroxides may be added in combination.
Peroxide, chlorine dioxide-containing water, for example, concentration of 0.1 mg / L or more, preferably that could be added in an amount of 0.2 mg / L or more. The upper limit concentration is not particularly limited. In the present invention, the concentration of the peroxide refers to H ₂ O ₂ equivalent amount.

For example, when chlorine dioxide is used as a disinfectant / disinfectant / biocide, from the viewpoint of cost and the influence of peroxide that can remain on the environment when treated water is discharged into the external environment It can be 10 mg / L. In one embodiment, the peroxide may be added such that the concentration in the chlorine dioxide-containing water is 0.1-10 mg / L. In one preferred embodiment, the peroxide may be added such that the concentration in the chlorine dioxide-containing water is 0.2-5 mg / L, more preferably 0.4-2 mg / L. .
By reducing the amount of peroxide used in accordance with the method of the present invention, the peroxide remains at a high concentration in the treated water, adversely affecting the external environment (for example, river water or seawater from which treated water is released). There is no risk of the effect, or it becomes smaller.

  When the chlorine dioxide-containing water is a flowing water system, the addition of the peroxide to the chlorine dioxide-containing water may be continuous or intermittent. In one embodiment, the peroxide and, if necessary, the manganese compound that produces dissolved manganese in an aqueous solution may be added continuously in a predetermined amount. In another embodiment, the peroxide and, if necessary, the manganese compound that produces dissolved manganese in an aqueous solution may be added in an amount depending on the chlorine dioxide concentration measured upstream. In another embodiment, the peroxide and, if necessary, the manganese compound that produces dissolved manganese in an aqueous solution may be added in an amount determined in view of the chlorine dioxide concentration measured downstream. When adding a peroxide and a manganese compound that produces dissolved manganese in an aqueous solution, only one of the amounts may be varied.

  In addition, when it is possible to know the amount of chlorine dioxide previously injected into chlorine dioxide-containing water, the peroxide and the manganese compound that produces dissolved manganese in an aqueous solution, if necessary, are determined based on the chlorine dioxide injection amount. It may be added in the amount. In this case, the amount of peroxide and, if necessary, the manganese compound producing dissolved manganese in the aqueous solution can be determined taking into account the chlorine dioxide concentration measured further downstream.

  One specific embodiment of the present invention is characterized in that a manganese compound and a peroxide that generate dissolved manganese in an aqueous solution are added to chlorine dioxide-containing water in this order or in the reverse order or simultaneously. This is a method for reducing the concentration of chlorine dioxide in chlorine dioxide-containing water. In this embodiment, when the chlorine dioxide-containing water is a flowing water system, one of the manganese compound and peroxide that generate dissolved manganese in the aqueous solution may be added upstream, and the other may be added downstream.

Another specific embodiment of the present invention is a method for reducing the chlorine dioxide concentration in chlorine dioxide-containing seawater, which comprises adding a peroxide to the chlorine dioxide-containing seawater.
In this form, dissolved manganese already exists in the seawater, but if necessary, a manganese compound that generates dissolved manganese in an aqueous solution can be added. By additionally supplying dissolved manganese, the amount of peroxide used can be further reduced.

  When the method of the present invention is applied to cooling water using seawater previously treated with chlorine dioxide in order to prevent adhesion of marine organisms such as shellfish into the flow path, it is finally discharged to the sea. Since the chlorine dioxide concentration in the (used) cooling water can be easily and efficiently reduced by the method of the present invention, the concentration of chlorine dioxide used for seawater treatment can be increased. Therefore, adhesion of marine organisms such as shellfish to the flow path of the cooling water can be prevented more efficiently.

<Water treatment agent and kit for reducing chlorine dioxide concentration in water>
The water treatment agent for reducing the chlorine dioxide concentration in the chlorine dioxide-containing water according to the present invention comprises a peroxide.
The water treatment agent of the present invention may contain one kind of peroxide alone, or may contain two or more kinds of peroxides in combination. Examples of the peroxide include ionic peroxides such as perborate, perphosphate, persulfate, pernitrate, peracetate, peroxide, and hydrogen peroxide adduct. The salt may be an alkali metal salt (preferably sodium salt and potassium salt, more preferably sodium salt), an alkaline earth metal salt (preferably calcium salt and magnesium salt) or an ammonium salt. Specific examples can be sodium perborate, sodium perphosphate, sodium persulfate, sodium percarbonate, calcium peroxide, magnesium peroxide and urea peroxide. The peroxide can be hydrogen peroxide and can be in the form of an aqueous solution (eg, a 20-60% solution).

A kit for reducing the concentration of chlorine dioxide in chlorine dioxide-containing water according to the present invention is characterized by comprising a combination of the above-mentioned water treatment agent and a manganese compound that produces dissolved manganese in an aqueous solution.
The kit of the present invention may contain one kind of manganese compound that generates dissolved manganese in an aqueous solution, or may contain two or more kinds in combination. The manganese compound that produces dissolved manganese in an aqueous solution can be, for example, manganese chloride, manganese sulfate, or manganese nitrate, preferably manganese sulfate.
In using the kit of the present invention, the manganese compound that produces dissolved manganese in the water treatment agent and the aqueous solution may be added separately to the chlorine dioxide-containing water, or may be added after mixing in advance.

Hereinafter, for ease of understanding, the present invention will be specifically described based on examples, but the present invention is not limited thereto.
In the following experiments, chlorine dioxide was analyzed with a chlorine dioxide meter manufactured by HACH (DPD method, lower limit of quantification is 0.04 mg / L or less).

Experiment 1
The effects of different transition metal ions on the reduction of chlorine dioxide concentration by hydrogen peroxide were investigated.
Seawater containing 0.2 mg / L chlorine dioxide, 45% hydrogen peroxide 1 mg / L and iron ions (iron (II) chloride, 0.025 mg / L [as iron]), copper ions (copper chloride (II) , 0.1 mg / L [as copper]) or dissolved manganese (manganese sulfate, 0.025 mg / L and 0.25 mg / L [as manganese]), respectively, 2, 7, 12 and 22 minutes after addition, respectively Chlorine dioxide concentration was measured. Moreover, only 45% hydrogen peroxide 1 mg / L was added, and chlorine dioxide concentrations were measured 2, 6, 11 and 21 minutes after the addition (blank). The results are shown in FIG.
As is clear from FIG. 1, the concentration of chlorine dioxide in seawater was significantly reduced by hydrogen peroxide in the presence of dissolved manganese as compared to the presence of iron ions and copper ions.

  In the following experiments 2 to 5, it was shown that the chlorine dioxide concentration reduction effect by hydrogen peroxide was enhanced in the presence of dissolved manganese. In Experiments 2 and 3, in order to eliminate the influence of chlorine and dissolved manganese contained in seawater, 100 mg / L sodium carbonate aqueous solution (artificial seawater) not containing these was used as chlorine dioxide-containing water. . In Experiments 4 and 5, seawater collected from Tokyo Bay was injected with chlorine dioxide and used as chlorine dioxide-containing water.

Experiment 2
After injecting chlorine dioxide or chlorine into a 100 mg / L aqueous sodium carbonate solution to 1 mg / L, 45% hydrogen peroxide and dissolved manganese were added to a total of 1 mg / L (see Tables 1 and 2). Reference) The residual chlorine dioxide concentration or residual chlorine concentration after 5 minutes was measured. The results are shown in Tables 1 and 2 below. From the data in Tables 1 and 2, the chlorine dioxide removal rate was determined as ([added chlorine dioxide concentration] − [residual chlorine dioxide concentration]) / [added chlorine dioxide concentration] and is shown in FIGS. 2 and 3, the x-axis represents [manganese concentration] / ([hydrogen peroxide concentration] + [manganese concentration]), and the y-axis represents the chlorine dioxide removal rate. Dissolved manganese was added as manganese sulfate.

As is clear from Table 1, dissolved manganese alone did not affect the residual chlorine dioxide concentration after 5 minutes, but hydrogen peroxide alone reduced the residual chlorine dioxide concentration within 5 minutes. .
Similarly, dissolved manganese alone, without influence on the residual chlorine concentration after 5 minutes, hydrogen peroxide alone, within five minutes to reduce residual Tomeshio oxygen concentration (Table 2).
As is apparent from Table 1 and particularly FIG. 2, the effect of reducing the concentration of chlorine dioxide by hydrogen peroxide was enhanced in the presence of dissolved manganese. On the other hand, the chlorine concentration reduction effect by hydrogen peroxide was not enhanced in the presence of dissolved manganese (in Reference Example 2, a decrease in the amount of hydrogen peroxide added (1/2) compared to Reference Example 3). Only a decrease in residual chlorine concentration was observed, corresponding to

Experiment 3
After adding chlorine dioxide to artificial seawater (sodium carbonate aqueous solution 100 mg / L) to 1 mg / L, 45% hydrogen peroxide 0.5-15 mg / L and dissolved manganese 0-0.5 mg / L (See Table 3) and the chlorine dioxide concentration after 5 minutes was measured. The results are shown in Table 3 below.

As Comparative Examples 3 and 4 show, in the absence of dissolved manganese, the concentration of residual chlorine dioxide remains relatively high even when high concentrations of hydrogen peroxide are used. On the other hand, as shown in Examples 7 and 8 , in the presence of a low concentration of dissolved manganese, the effect of reducing the chlorine dioxide concentration of hydrogen peroxide is significantly enhanced. Chlorine dioxide concentration reducing effect of 0.5 mg / L hydrogen peroxide in the presence of 0.5 mg / L dissolved manganese and 2.5 mg / L peroxidation in the presence of 0.05 mg / L dissolved manganese The chlorine dioxide concentration reducing effect of hydrogen is comparable to the chlorine dioxide concentration reducing effect of 15 mg / L hydrogen peroxide in the absence of dissolved manganese. Thus, the presence of dissolved manganese significantly reduces the amount of hydrogen peroxide used to reduce the residual chlorine dioxide concentration (peroxidation in the presence of 0.05 mg / L or 0.5 mg / L of dissolved manganese). The amount of hydrogen used is about 1/30 or about 1/6 in the absence of dissolved manganese, respectively.

Experiment 4:
After injecting chlorine dioxide to seawater collected from Tokyo Bay to 1 mg / L, hydrogen peroxide (45%) and dissolved manganese were added to a total of 1 mg / L (see Table 4). The residual chlorine dioxide concentration after 5 minutes was measured. The results are shown in Table 4.

From the data in Table 4, the chlorine dioxide removal rate was determined as ([added chlorine dioxide concentration] − [residual chlorine dioxide concentration]) / [added chlorine dioxide concentration] and is shown in FIG. The x-axis and y-axis in FIG. 4 are the same as those in FIGS.
As is apparent from Table 4 and FIG. 4, the effect of reducing the concentration of chlorine dioxide by hydrogen peroxide was significantly enhanced in the presence of dissolved manganese.
Since seawater contains dissolved manganese, the residual chlorine dioxide concentration was significantly reduced even when hydrogen peroxide was added alone. Therefore, when the chlorine dioxide-containing water is seawater, the residual chlorine dioxide concentration can be significantly reduced by adding hydrogen peroxide alone.

Experiment 5
Changes in residual chlorine dioxide concentration when adding 1 mg / L of chlorine dioxide and 0.5 mg / L of 45% hydrogen peroxide to seawater in Tokyo Bay, and further adding 0.2 mg / L of dissolved manganese 5 minutes later As shown in FIG.
It is estimated that the chlorine dioxide concentration in seawater gradually decreases immediately after the injection of chlorine dioxide and hydrogen peroxide, and becomes about 1/2 after 5 minutes (from the residual chlorine dioxide concentration after 3 minutes and 10 minutes). Estimated). 2.5 minutes after adding manganese (in addition to the dissolved manganese contained in seawater), the residual chlorine dioxide was below the lower limit of quantification (0.04 mg / L). From this, it can be understood that the presence of dissolved manganese remarkably affects the effect of reducing the concentration of chlorine dioxide by hydrogen peroxide.

Claims (6)

Reducing chlorine dioxide concentration in chlorine dioxide-containing water, characterized by adding manganese compounds and peroxides that produce dissolved manganese in aqueous solution to chlorine dioxide-containing water in this order, in the reverse order, or simultaneously Method. The method of Claim 1 which adjusts the manganese compound which produces | generates a dissolved manganese in aqueous solution so that the dissolved manganese density | concentration in chlorine dioxide containing water may be set to at least 0.01 mg / L. The method of Claim 1 or 2 which adds a peroxide so that the density | concentration in chlorine dioxide containing water may be 0.1-10 mg / L. The method according to claim 1, wherein the chlorine dioxide-containing water is cooling water pretreated with chlorine dioxide for cooling water. The method according to claim 4, wherein the cooling water is seawater. Reducing chlorine dioxide concentration in chlorine dioxide-containing water, characterized by comprising a combination of a water treatment agent characterized by comprising a peroxide and a manganese compound that produces dissolved manganese in an aqueous solution Kit for.

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