Preparation method for monochloramine, etc.

Abstract

This invention provides a method for preparing monochloramine and / or monobromamine with high stability, even when using water with a higher impurity content compared to pure water. [Solution] A method for preparing monochloramine and / or monobromamine in water, wherein the water has a total organic carbon (TOC) concentration of 1 mg / L or more, a silica concentration of 50 μg / L or more, a chloride ion concentration of 10 μg / L, and a sulfate ion concentration of 10 μg / L or more, and a sodium compound, an ammonium salt, and a halogenated oxidizing agent are mixed with the water, and the concentration of the sodium compound added to the water is 0.3 ppm or more in terms of sodium ion concentration.

Description

Technical Field

[0001] The present invention relates to a method for preparing monochloramine and the like.

Background Art

[0002] Bactericides containing combined halogen such as monochloramine and monobromamine have been conventionally used, for example, added to industrial water such as cooling water in various industries, and used to prevent damage caused by bacteria and fungi.

[0003] For example, Patent Document 1 discloses a method comprising the steps of mixing a solution of a hypochlorite oxidizing agent with a solution of an ammonium salt to produce a biocide, and monitoring a control parameter that indicates when the maximum achievable yield of the biocide is reached without decomposition of the biocide; wherein the control parameter is not pH.

[0004] Further, Patent Document 2 discloses a bactericide to be added to an aqueous system, which is produced by mixing a first composition containing an ammonium salt and an alkaline agent with a halogen-based oxidizing agent.

[0005] Further, Patent Document 3 discloses a method for synthesizing a high-purity chloramine solution, which comprises reacting a sodium hypochlorite solution with a chlorination degree of 100 grade with a combined ammonia mixture at a temperature of -5°C to -20°C.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0007] However, our own investigations have revealed that when preparing monochloramine and monobromamine, if water with a higher impurity content compared to pure water, such as tap water, industrial water, river water, lake water, groundwater, and well water, is used, the stability of the prepared monochloramine and monobromamine deteriorates. The present invention has been made in view of the above, and aims to provide a method for preparing monochloramine and / or monobromamine with high stability even when using water with a higher impurity content compared to pure water. [Means for solving the problem]

[0008] The inventors of this invention conducted diligent research to solve the above problems and, as a result, found that the above problems can be solved by the following configuration example, thus completing the present invention. An example of the configuration of the present invention is as follows.

[0009] [1] A method for preparing monochloramine and / or monobromamine in water, wherein the water has a total organic carbon (TOC) concentration of 1 mg / L or more, a silica concentration of 50 μg / L or more, a chloride ion concentration of 10 μg / L, and a sulfate ion concentration of 10 μg / L or more, and a sodium compound, an ammonium salt, and a halogenated oxidizing agent are mixed with the water, and the concentration of the sodium compound added to the water is 0.3 ppm or more in terms of sodium ion concentration. [2] The preparation method according to [1] above, wherein the sodium compound is mixed with the water such that sodium ions obtained by the sodium compound are present in the water during the reaction of the ammonium salt and the halogenated oxidizing agent. [3] The preparation method according to [1] or [2] above, wherein the sodium compound is at least one selected from the group consisting of sodium chloride, sodium sulfate, and sodium hydroxide. [4] The preparation method according to any one of [1] to [3] above, wherein the ammonium salt is at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium carbamate, ammonium bromide, and ammonium sulfamate. [5] The preparation method according to any one of [1] to [4] above, wherein the halogenated oxidizing agent is at least one selected from the group consisting of hypochlorite, chlorite, chlorate, perchlorate, and chlorine dioxide. [6] The preparation method according to any one of [1] to [5] above, wherein the sodium compound is mixed so that the pH of the water after the addition of the ammonium salt is less than 9. [Effects of the Invention]

[0010] According to the present invention, a method for preparing highly stable monochloramine and / or monobromamine can be provided even when using water with a higher impurity content compared to pure water. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described below, but these embodiments are merely examples of typical embodiments of the present invention and should not be interpreted as narrowing the scope of the invention. Furthermore, the method for preparing monochloramine and the like according to the present invention is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the objectives of the present invention.

[0012] In this disclosure, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively.

[0013] In numerical ranges described stepwise within this disclosure, an upper or lower limit stated in one numerical range may be replaced by an upper or lower limit in another numerical range. In this disclosure, an upper or lower limit stated in one numerical range may be replaced by a value shown in an example.

[0014] The present invention relates to a method for preparing monochloramine and / or monobromamine in water, wherein the water has a total organic carbon (TOC) concentration of 1 mg / L or more, a silica concentration of 50 μg / L or more, a chloride ion concentration of 10 μg / L or more, and a sulfate ion concentration of 10 μg / L or more, and a sodium compound, an ammonium salt, and a halogenated oxidizing agent are mixed with the water, and the concentration of the sodium compound added to the water is 0.3 ppm or more in terms of sodium ion concentration.

[0015] The water used in the preparation method of the present invention has a total organic carbon (TOC) concentration of 1 mg / L or more, a silica concentration of 50 μg / L or more, a chloride ion concentration of 10 μg / L or more, and a sulfate ion concentration of 10 μg / L or more. Water containing these component indicators above the above numerical range can be said to have a higher impurity content compared to pure water. In the preparation of monochloramine and the like, it is known that if impurities in the water used, such as halogen substances like bromide ions, are present in the water at the time of monochloramine production, the possibility of dichloramine (dibromamine) or trichloramine (tribromamine) being produced increases, and the amount of monochloramine (monobromamine) produced decreases. Therefore, it is preferable that the water used in the preparation method of the present invention further contains at least one selected from the group consisting of residual chlorine and total organic halogens (TOX). This is because monochloramine and the like produced using water containing such components are thought to be prone to deterioration in stability.

[0016] The water used in the preparation method of the present invention may have a total organic carbon (TOC) concentration of 0.5 mg / L or higher, preferably 1 mg / L or higher, and more preferably 2 mg / L or higher. This is because such water has a higher impurity content rate compared to pure water. In addition, the total organic carbon (TOC) concentration of the water used in the preparation method of the present invention is preferably 10 mg / L or lower, and more preferably 5 mg / L or lower. In the present disclosure, the total organic carbon (TOC) concentration in water can be measured by a known method.

[0017] The water used in the preparation method of the present invention may have a silica concentration of 50 μg / L or higher, preferably 500 μg / L or higher, more preferably 1 mg / L or higher, even more preferably 10 mg / L or higher, and still more preferably 15 mg / L or higher. This is because such water has a higher impurity content rate compared to pure water. The silica concentration of the water used in the preparation method of the present invention is preferably 200 mg / L or lower, and more preferably 150 mg / L or lower. In the present disclosure, the silica concentration in water is a value obtained by measuring the concentration of ionic silica in water.

[0018] The water used in the preparation method of the present invention may have a chloride ion concentration of 10 μg / L or higher, preferably 100 μg / L or higher, more preferably 500 μg / L or higher, and even more preferably 3 mg / L or higher. This is because such water has a higher impurity content rate compared to pure water. The chloride ion concentration of the water used in the preparation method of the present invention is preferably 50 mg / L or lower, and more preferably 20 mg / L or lower.

[0019] The sulfate ion concentration of water used in the preparation method of the present invention may be 10 μg / L or more, preferably 100 μg / L or more, and more preferably 500 μg / L or more. This is because such water has a higher impurity content rate compared to pure water. The sulfate ion concentration of water used in the preparation method of the present invention is preferably 100 mg / L or less, more preferably 50 mg / L or less.

[0020] The water used in the preparation method of the present invention preferably further has a total hardness of 10.0 mgCaCO₃ / L or more. This is because water with a total hardness of 10.0 mgCaCO₃ / L or more is water containing inorganic substances, and has a higher impurity content rate compared to pure water. The total hardness of the water used in the present invention is more preferably 20.0 mgCaCO₃ / L or more, further preferably 40.0 mgCaCO₃ / L or more, and even more preferably 50.0 mgCaCO₃ / L or more. Further, the total hardness is preferably 500 mgCaCO₃ / L or less, more preferably 300 mgCaCO₃ / L or less.

[0021] The water used in the preparation method of the present invention preferably further has a calcium hardness of 10 mgCaCO₃ / L or more. This is because water with a calcium hardness of 10 mgCaCO₃ / L or more is water containing inorganic substances, and has a higher impurity content rate compared to pure water. The calcium hardness of the water used in the present invention is more preferably 20.0 mgCaCO₃ / L or more, further preferably 40.0 mgCaCO₃ / L or more, and even more preferably 50.0 mgCaCO₃ / L or more. Further, the calcium hardness is preferably 300 mgCaCO₃ / L or less, more preferably 200 mgCaCO₃ / L or less.

[0022] The water used in the preparation method of the present invention preferably has a sodium concentration of 1.0 ppm or higher. This is because such water has a higher impurity content compared to pure water. The water used in the preparation method of the present invention is more preferably 2.0 ppm or higher, and even more preferably 5.0 ppm or higher. Furthermore, the sodium concentration is preferably 200 ppm or less, more preferably 100 ppm or less, and even more preferably 50 ppm or less.

[0023] The water used in the preparation method of the present invention preferably has a total nitrogen concentration of 0.6 mg / L or higher. This is because such water has a higher impurity content compared to pure water. More preferably, the water used in the preparation method of the present invention has a total nitrogen concentration of 0.8 mg / L or higher, and even more preferably 1 mg / L or higher. Furthermore, it is preferable that the total nitrogen concentration be 10 ppm or less.

[0024] In this disclosure, the concentrations of each component in the water described above can be measured by known methods. For example, the total organic carbon (TOC) concentration can be measured by the combustion oxidation-infrared automatic TOC measurement method or the wet oxidation-infrared automatic TOC measurement method (JIS K 0551). The silica concentration can be obtained by measuring the ionic silica concentration by electrothermal atomic absorption spectrometry (JIS K 0555). Chloride ions can be measured using ion chromatography (JIS K 0556). Total hardness can be measured by chelate titration (JIS K 0101). Calcium hardness can be measured by chelate titration (JIS K 0101). Total nitrogen can be measured by summation method (JIS K 0101).

[0025] The water used in the preparation method of the present invention is preferably one or more selected from the group consisting of, for example, tap water, industrial water, river water, lake water, groundwater, and well water. This is because these types of water have a higher impurity content compared to pure water.

[0026] The preparation method of the present invention involves preparing monochloramine and the like by mixing a sodium compound, an ammonium salt, and a halogenated oxidizing agent with the water described above. The order in which the sodium compound, ammonium salt, and halogenated oxidizing agent are mixed with the water is not particularly limited, but it is preferable that the sodium compound is present when the ammonium salt and halogenated oxidizing agent react in the water. That is, the sodium compound may be mixed with the water first, and then the ammonium salt and halogenated oxidizing agent may be mixed with the water. Alternatively, a first composition may be obtained by mixing the sodium compound and the ammonium salt, and then the first composition and the halogenated oxidizing agent may be mixed with the water described above. Alternatively, a second composition may be obtained by mixing the sodium compound and the halogenated oxidizing agent, and then the second composition and the ammonium salt may be mixed with the water described above.

[0027] Monochloramine and monobromamine, which are commonly used as oxidizing agents, are OCl - (Br - )+NH4 + It is a mild oxidizing agent produced by reactions such as NH2Cl(Br) + H2O. For example, monochloramine can be produced by mixing sodium hypochlorite with an ammonium salt. Specifically, examples of ammonium salts include ammonium sulfate, ammonium bromide, ammonium chloride, and ammonium sulfamate, and it is known that these can be used individually or in combination of two or more. It is also known that monochloramine or monobromamine is mixed with an alkaline agent to stabilize monochloramine and monobromamine produced by conventional methods. Furthermore, it is known that monochloramine or monobromamine is added separately to an alkaline agent to adjust the pH of the target to which it is added.

[0028] The inventors noticed that when pure water was used in the preparation of monochloramine and / or monobromamine, the stability of the resulting monochloramine was maintained, whereas when industrial water or well water was used, the stability of the resulting monochloramine deteriorated. Further investigations were conducted. As a result, the inventors discovered that by mixing a sodium compound in the water during the reaction between the ammonium salt and the halogenated oxidizing agent to increase the sodium ions in the water, the stability of the resulting monochloramine was improved, thus completing the present invention. Furthermore, according to the inventors' research, while general well water and industrial water contain sodium ions, even water containing sodium ions has a higher impurity content than pure water if the total organic carbon (TOC) concentration is 1 mg / L or more, the silica concentration is 50 μg / L or more, the chloride ion concentration is 10 μg / L or more, and the sulfate ion concentration is 10 μg / L or more. The inventors found that the presence of sodium ions already present in the water does not contribute to the stability of monochloramine, etc., and that the stability of prepared monochloramine, etc., is improved by adding a sodium compound in addition to ammonium salts and halogenated oxidizing agents.

[0029] In other words, monochloramine and / or monobromamine obtained by the preparation method of the present invention can achieve the same level of stability as monochloramine and / or monobromamine prepared using pure water, even when using water with a higher impurity content compared to pure water.

[0030] In the present invention, it is preferable that the sodium compound is mixed with the water such that sodium ions obtained by the sodium compound are present in the water during the reaction between the ammonium salt and the halogen-based oxidizing agent.

[0031] (Sodium compounds) The sodium compound used in the present invention is not particularly limited as long as it produces sodium ions when dissolved in water. Preferably, the sodium compound is at least one selected from the group consisting of sodium chloride, sodium sulfate, sodium hydroxide, sodium carbonate, sodium bicarbonate, trisodium citrate, monosodium phosphate, disodium phosphate, trisodium phosphate, sodium gluconate, sodium malate, sodium formate, sodium acetate, sodium propionate, sodium butyrate, sodium citrate, sodium succinate, sodium fumarate, sodium lactate, and sodium tartrate. More preferably, the sodium compound used in the present invention is at least one selected from the group consisting of sodium chloride, sodium sulfate, sodium hydroxide, sodium bicarbonate, trisodium citrate, and sodium gluconate, and even more preferably at least one selected from the group consisting of sodium chloride, sodium sulfate, and sodium hydroxide.

[0032] In the preparation method of the present invention, the concentration of the sodium compound added to the water is preferably 0.3 ppm or higher, more preferably 3 ppm or higher, and even more preferably 15 ppm or higher in terms of sodium ion concentration. This is because the amount of monochloramine and / or monobromamine produced by mixing the sodium compound, the ammonium salt, and the halogenated oxidizing agent with the water is improved.

[0033] (Ammonium salt) The ammonium salt used in the present invention is not particularly limited as long as it is an inorganic ammonium salt, which is a reaction product of an inorganic acid and ammonia, or an organic ammonium salt, which is a reaction product of an organic acid and ammonia. The inorganic ammonium salt is preferably at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium carbamate, ammonium bromide, ammonium sulfamate, ammonium carbonate, ammonium bicarbonate, ammonium bicarbonate, ammonium iron(III) sulfate, ammonium persulfate, ammonium tungstate, ammonium metatungstate, ammonium thiocyanate, and ammonium polyphosphate. The organic ammonium salt is preferably at least one selected from the group consisting of ammonium formate, ammonium acetate, ammonium propionate, ammonium butyrate, ammonium citrate, ammonium malate, ammonium succinate, ammonium fumarate, ammonium lactate, and ammonium tartrate. Furthermore, it is even more preferable that the above ammonium salt is at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium carbamate, ammonium bromide, and ammonium sulfamate.

[0034] In the preparation method of the present invention, the pH of the water after adding the ammonium salt to the water is preferably less than 9, more preferably 8.8 or less, and even more preferably 8.5 or less. "After adding the ammonium salt to the water" refers to the water within 15 minutes after adding the ammonium salt. Since the pH of the water changes gradually after mixing the ammonium salt with the water, it is preferable that the pH of the water within 15 minutes after addition is less than 9.

[0035] (Halogenated oxidizing agents) The halogenated oxidizing agent used in the present invention is preferably at least one selected from the group consisting of hypochlorite, chlorite, chlorate, perchlorate, and chlorine dioxide.

[0036] The above hypochlorites include sodium hypochlorite, calcium hypochlorite, potassium hypochlorite, and magnesium hypochlorite. Preferably, the above hypochlorite is at least one selected from the group consisting of sodium hypochlorite, calcium hypochlorite, potassium hypochlorite, and magnesium hypochlorite, and more preferably at least one selected from the group consisting of sodium hypochlorite, calcium hypochlorite, and potassium hypochlorite. Preferably, the above hypochlorite is a low-sodium hypochlorite with a sodium chloride content of 4% or less, and more preferably a low-sodium hypochlorite with a sodium chloride content of 2% or less.

[0037] Examples of the above-mentioned chlorites include sodium chlorite, potassium chlorite, calcium chlorite, and magnesium chlorite. Preferably, the above-mentioned chlorite is at least one selected from the group consisting of sodium chlorite, potassium chlorite, calcium chlorite, and magnesium chlorite.

[0038] Examples of the above-mentioned chlorates include potassium chlorate, sodium chlorate, calcium chlorate, barium chlorate, and magnesium chlorate. Preferably, the above-mentioned chlorate is at least one selected from the group consisting of potassium chlorate, sodium chlorate, calcium chlorate, barium chlorate, and magnesium chlorate.

[0039] Examples of the perchlorates mentioned above include sodium perchlorate, potassium perchlorate, calcium perchlorate, and magnesium perchlorate. Preferably, the perchlorate is at least one selected from the group consisting of sodium perchlorate, potassium perchlorate, calcium perchlorate, and magnesium perchlorate.

[0040] Because the chlorine dioxide mentioned above is an extremely unstable chemical substance, its storage and transportation are very difficult. Therefore, it is preferable to manufacture (generate) chlorine dioxide on-site using a known method and adjust its concentration for use. For example, chlorine dioxide can be produced by the following reaction, and commercially available chlorine dioxide generators (devices) can also be used. (1) Reaction of sodium hypochlorite, hydrochloric acid, and sodium hypochlorite NaOCl+2HCl+2NaClO2→ 2ClO2+3NaCl+H2O (2) Reaction of sodium chlorite with hydrochloric acid 5NaClO2+4HCl → 4ClO2+5NaCl+2H2O (3) Reactions with sodium chlorate, hydrogen peroxide and sulfuric acid 2NaClO3+H2O2+H2SO4→ 2ClO2+Na2SO4+O2+2H2O

[0041] The halogenated oxidizing agent used in the present invention is more preferably a hypochlorite.

[0042] In the present invention, the molar ratio of the halogenated oxidizing agent to the ammonium salt (halogenated oxidizing agent:ammonium salt) is preferably 1:1 to 1:2 as the molar ratio of residual chlorine to nitrogen, more preferably 1:1.1 to 1:2, even more preferably 1:1.2 to 1:2, and particularly preferably 1:1.2 to 1:1.6. Furthermore, in the present invention, it is preferable that the concentration of the halogen-based oxidizing agent is determined such that the dilution ratio is 100 times or less, and more preferably 50 times or less.

[0043] In the present invention, the weight ratio of the first composition to the halogenated oxidizing agent and the weight ratio of the second composition to the ammonium salt are preferably determined such that the molar ratio of the halogenated oxidizing agent to the ammonium salt (halogenated oxidizing agent:ammonium salt) falls within the above range.

[0044] A sterilization method using monochloramine or the like obtained by the preparation method of the present invention is also one embodiment of the present invention. For example, the concentration of monochloramine or the like obtained by the preparation method of the present invention added to the aqueous system to be sterilized is preferably 0.1 to 35 mg / L in terms of total residual chlorine concentration relative to the aqueous water to be sterilized. In this invention, the term "residual chlorine concentration" refers to the "value converted to residual chlorine amount" when the halogenated oxidizing agent is not a chlorine-based oxidizing agent.

[0045] In the preparation method of the present invention, the pH of the water after mixing the sodium compound, the ammonium salt, and the halogen-based oxidizing agent with the water is preferably less than 9, more preferably 8.8 or less, and even more preferably 8.5 or less. Note that "the water after mixing the sodium compound, the ammonium salt, and the halogen-based oxidizing agent with the water" refers to the water within 15 minutes after adding the three agents to the water. Since the pH of the water after mixing the sodium compound, the ammonium salt, and the halogen-based oxidizing agent with the water changes gradually, it is preferable that the pH of the water within 15 minutes after adding the last of the three agents to be mixed with the water is less than 9.

[0046] When the present invention is the sterilization method described above, the timing of adding monochloramine, etc., obtained by the preparation method of the present invention to the aqueous system is not particularly limited, but it is preferable to add it at a step in which the obtained monochloramine, etc., is appropriately mixed with the target aqueous system. For example, if the aqueous system water to be sterilized is the water used in the paper pulp manufacturing process, the monochloramine, etc., obtained by the preparation method of the present invention may be added to a storage tank such as a white water silo or white water pit, or it may be added at any point in the process as long as it can be added to the water used in the paper pulp manufacturing process. Furthermore, the addition of monochloramine and the like obtained by the preparation method of the present invention may be done intermittently or continuously.

[0047] By adding monochloramine, etc., obtained by the preparation method of the present invention described above, to an aqueous system, the occurrence of damage caused by bacteria present in the aqueous system can be effectively suppressed. [Examples]

[0048] The present invention will be described in detail below based on examples, comparative examples, and reference examples, but the present invention is not limited to these examples.

[0049] (Test Example 1: Examples 1-25, Comparative Examples 1-4, Reference Examples 1 and 2) [Preparation of monochloramine] (1) 25 mL of each type of water shown in Table 1 below was dispensed to be used as dilution water. Note that "Osaka City Water (Boiled)" in Table 1 below refers to Osaka City water that was boiled for 10 minutes and then allowed to stand at room temperature. (2) Each sodium compound shown in Table 2 below was mixed with each dilution water so that the sodium ion concentration relative to the dilution water was the concentration shown in Table 2 below, thereby obtaining sodium ion-containing dilution water. (3) The obtained sodium ion-containing dilution water was mixed with low-sodium sodium hypochlorite (13.3% available chlorine, 1.8% sodium chloride, 0.4% sodium hydroxide) so that the theoretical value of the total available chlorine relative to the dilution water was 2600 mg / L. Then, an aqueous ammonium sulfate solution was mixed in so that the concentration of ammonium sulfate added to the dilution water was 6840 mg / L. In Comparative Examples 1 and 2 and Reference Examples 1 and 2, the above step (2) was not performed, and the low-sodium sodium hypochlorite and ammonium sulfate were simply mixed with the dilution water at the same addition concentrations as above. (4) The pH and total chlorine concentration of the water were measured 5 minutes after adding the ammonium sulfate described in (3) above. The method for measuring the total chlorine concentration is as follows. [Method for measuring total chlorine concentration] The total chlorine concentration was measured using the DPD method residual chlorine meter DP-3F (manufactured by Kasahara Chemical Industry Co., Ltd.) by measuring the absorbance photometry based on the color development of DPD reagent. (5) The mixture obtained by adding ammonium sulfate in (3) above was left to stand for 1 hour in an environment of 35°C, and then the total chlorine concentration was measured again. The results obtained are shown in Table 2.

[0050] [Table 1]

[0051] [Table 2]

[0052] From the results in Table 2 above, even when well water 1 was used as the dilution water, when the sodium compound was added at a sodium ion concentration of 0.3 mg / L or higher, the total chlorine retention rate of the resulting monochloramine-containing mixture after standing at 35°C for 1 hour significantly exceeded 60%, confirming that the stability of the generated monochloramine was greatly improved compared to Comparative Example 1, in which no sodium compound was added. In particular, when sodium sulfate was used as the sodium compound, the total chlorine retention rate improved in proportion to the sodium ion concentration generated by the added sodium sulfate, confirming that the stability of monochloramine was improved. The total chlorine retention rate in Reference Example 2, which used boiled water from Osaka City as the dilution water, was approximately 85%, which is close to the total chlorine retention rate of approximately 93% in Reference Example 1, which used pure water as the dilution water. The mechanism by which the stability of monochloramine is improved by using boiled water from Osaka City is unknown, but according to the results shown in Table 2 above, even when water with a higher impurity content than pure water is used, by adding a sodium compound, highly stable monochloramine can be prepared without going through the boiling process of the dilution water. Furthermore, in the test example shown in Example 24, where well water 2 was used as the diluent, it was confirmed that the stability of the generated monochloramine was greatly improved by adding the sodium compound compared to Comparative Example 2, in which the sodium compound was not added. Although this is the only example using well water 2, Example 24 confirmed that it showed a similar trend to well water 1. Furthermore, in the test example using industrial water (Industrial Water 1) as the diluent, as shown in Example 25, it was confirmed that the stability of the generated monochloramine was greatly improved by adding a sodium compound compared to Comparative Example 3, in which no sodium compound was added. This is the only example using industrial water, but Example 25 confirmed that it showed a similar trend to well water 1.

[0053] (Test Example 2: Examples 31-39, Reference Example 1) [Preparation of monochloramine] (1) 25 mL of each of the waters shown in Table 1 above was dispensed to be used as dilution water. The pH of each dilution water was as shown in Table 3 below (Dilution Water (35°C) pH). (2) Each dilution water was mixed with low-sodium sodium hypochlorite (13.3% available chlorine, 1.8% salt, 0.4% sodium hydroxide) so that the theoretical value of total available chlorine relative to the dilution water was 2600 mg / L. (3) Next, the aqueous ammonium sulfate solution was mixed with the sodium compound shown in Table 3 below, and the resulting mixture was mixed so that the concentration of ammonium sulfate added to the dilution water containing low-sodium sodium hypochlorite obtained in (2) above was 380,000 mg / L, and the concentration of sodium ions added to the dilution water was the concentration shown in Table 3 below. The pH of the mixture of the aqueous ammonium sulfate solution and the sodium compound shown in Table 3 below is shown in Table 3 below. (4) The mixture of the ammonium sulfate aqueous solution and the sodium compound described in (3) above was added to the diluted water containing sodium hypochlorite obtained in (2) above, and the pH and total chlorine concentration of the water were measured after 5 minutes. The results obtained are shown in Table 3.

[0054] [Table 3]

[0055] From the results in Table 3 above, it can be confirmed that when the added concentration of the sodium compound is 0.3 mg / L or higher in terms of sodium ion concentration, the amount of monochloramine produced in the mixture is as high as in Reference Example 1, where pure water was used as dilution water.

[0056] (Test Example 3: Examples 41, 42, Reference Example 3) [Preparation of monochloramine] (1) 25 mL of each of the waters shown in Table 1 above was dispensed to be used as dilution water. (2) Each sodium compound shown in Table 2 below was mixed with each dilution water so that the sodium ion concentration relative to the dilution water was the concentration shown in Table 4 below, thereby obtaining sodium ion-containing dilution water. (3) The obtained sodium ion-containing dilution water was mixed with low-sodium sodium hypochlorite (13.3% available chlorine, 1.8% sodium chloride, 0.4% sodium hydroxide) so that the theoretical value of the total available chlorine relative to the dilution water was 4400 mg / L. Then, an aqueous ammonium sulfate solution was mixed in so that the concentration of ammonium sulfate added to the dilution water was 11400 mg / L. In Reference Example 3, the above step (2) was not performed, and the above low-sodium sodium hypochlorite and above ammonium sulfate were simply mixed with the dilution water at the same addition concentrations as above. (4) The pH and total chlorine concentration of the water were measured 5 minutes after adding the ammonium sulfate described in (3) above. The method for measuring the total chlorine concentration is as follows. (5) The mixture obtained by adding ammonium sulfate in (3) above was left to stand for 1 hour in an environment of 35°C, and then the total chlorine concentration was measured again. The results obtained are shown in Table 4.

[0057] [Table 4]

[0058] From the results in Table 4 above, even when the concentration of the agent for monochloramine production was changed and the dilution ratio was set to 30 times, if the added concentration of the sodium compound was 0.3 mg / L or higher in terms of sodium ion concentration, the total chlorine retention rate of the monochloramine-containing mixture remained at 60% or higher even after standing at 35°C for 1 hour, confirming the high stability of the produced monochloramine. Furthermore, in the test example of Example 42, the total chlorine retention rate of the monochloramine-containing mixture after standing at 35°C for 1 hour was approximately 82%, showing stability that significantly exceeded the total chlorine retention rate of 73% when pure water was used as the dilution water. This confirms that, depending on the conditions for monochloramine production, the stability of the produced monochloramine can be greatly improved by adding a sodium compound.

Claims

1. A method for preparing monochloramine and / or monobromamine in water, The water has a total organic carbon (TOC) concentration of 1 mg / L or more, a silica concentration of 50 μg / L or more, a chloride ion concentration of 10 μg / L, and a sulfate ion concentration of 10 μg / L or more. A sodium compound, an ammonium salt, and a halogenated oxidizing agent are mixed with the aforementioned water. A method for preparing monochloramine, etc., wherein the concentration of the sodium compound added to the water is 0.3 ppm or higher in terms of sodium ion concentration.

2. The preparation method according to claim 1, wherein the sodium compound is mixed with the water such that sodium ions obtained by the sodium compound are present in the water during the reaction between the ammonium salt and the halogenated oxidizing agent.

3. The preparation method according to claim 1 or 2, wherein the sodium compound is at least one selected from the group consisting of sodium chloride and sodium sulfate.

4. The preparation method according to claim 1 or 2, wherein the ammonium salt is at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium carbamate, ammonium bromide, and ammonium sulfamate.

5. The preparation method according to claim 1 or 2, wherein the halogenated oxidizing agent is at least one selected from the group consisting of hypochlorite, chlorite, chlorate, perchlorate, and chlorine dioxide.

6. The preparation method according to claim 1 or 2, wherein the sodium compound is mixed such that the pH of the water after the addition of the ammonium salt is less than 9.

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