Method for producing water containing permanganate ions

Abstract

The present invention addresses the problem of providing a novel method for producing, without using an organic iron compound as a production material, a water in which permanganate ions persist stably for a long period of time. The solution to the problem involves dissolving a divalent inorganic iron compound and a divalent manganese compound in a water having a pH lower than 3.5, and supplying ozone micro-bubbles in the water.

Description

[Technical field]

[0001] The present invention relates to a method for producing water containing permanganate ions. [Background technology]

[0002] Permanganate ion (MnO4 - It is well known that permanganate ions are used as oxidizing agents in various oxidation reactions. Permanganate ions are also known to be used as disinfectants and deodorants. However, when permanganate ions are prepared by dissolving a permanganate compound such as potassium permanganate in water, there is a problem that the permanganate ions are reduced and disappear within a short period of time. In order to solve this problem, the present inventors have been engaged in research into a method for producing water in which permanganate ions are stable for a long period of time, and as a result, have developed a method for producing water in which permanganate ions are stable for a long period of time, and have obtained a method for producing water in which the concentration is 1 to 300 g / Nm 3 Patent Document 1 reports a method for producing water containing permanganate ions by dissolving 0.1 μM to 1 mM of a divalent manganese compound, 0.1 μM to 1 mM of an organic iron compound, and 1 to 300 mM of an inorganic salt in water in which ozone microbubbles have been generated using ozone gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 017820 Summary of the Invention [Problem to be solved by the invention]

[0004] The method for producing water containing permanganate ions reported by the present inventor in Patent Document 1 is highly regarded by those skilled in the art because it allows permanganate ions to be stably present in water for a long period of time. However, as described in Patent Document 1, when water containing permanganate ions is produced by this method, precipitates are generated in the water, but it was later discovered that the amount of precipitates generated is large and it takes several days for the generation of precipitates to subside, which is inconvenient because it takes a long time to filter the generated precipitates and ship them as a product. It was speculated that the reason why such precipitates occur over several days is because an organic iron compound is used as a production raw material.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a novel method for producing water in which permanganate ions are stably present for a long period of time without using an organic iron compound as a raw material. [Means for solving the problem]

[0006] In view of the above, the method for producing water containing permanganate ions of the present invention comprises dissolving a divalent inorganic iron compound and a divalent manganese compound in water having a pH of less than 3.5, and then supplying ozone microbubbles into the water, as described in claim 1. The manufacturing method according to claim 2 is the manufacturing method according to claim 1, wherein the divalent inorganic iron compound is at least one selected from iron chloride (II), iron sulfate (II), and iron nitrate (II). The manufacturing method according to claim 3 is the manufacturing method according to claim 1, in which a divalent inorganic iron compound is dissolved so that the concentration of divalent iron ions is 1 to 100 ppb. The manufacturing method according to claim 4 is the manufacturing method according to claim 1, wherein the divalent manganese compound is at least one selected from manganese(II) chloride, manganese(II) sulfate, and manganese(II) nitrate. In addition, the manufacturing method according to claim 5 is the manufacturing method according to claim 1, in which the divalent manganese compound is dissolved so that the concentration of the divalent manganese ion is 0.1 μM to 1 mM. The production method according to claim 6 is the production method according to claim 1, in which no inorganic salt is further dissolved. The manufacturing method according to claim 7 is the manufacturing method according to claim 1, in which the pH of the water is adjusted to 5.0 to 9.0 after ozone microbubbles are supplied into the water. Effect of the Invention

[0007] According to the present invention, it is possible to provide a novel method for producing water in which permanganate ions are stably present for a long period of time without using an organic iron compound as a production raw material. BEST MODE FOR CARRYING OUT THEINVENTION

[0008] The method for producing water containing permanganate ions of the present invention involves dissolving a divalent inorganic iron compound and a divalent manganese compound in water having a pH of less than 3.5, and then supplying ozone microbubbles into the water.

[0009] In the method for producing water containing permanganate ions of the present invention, first, a divalent inorganic iron compound and a divalent manganese compound are dissolved in water with a pH of less than 3.5. The reason for dissolving the divalent inorganic iron compound and the divalent manganese compound in water with a pH of less than 3.5 is that if a divalent inorganic iron compound is dissolved in water with a pH of 3.5 or more, when ozone microbubbles are later supplied to the water, trivalent iron oxide (Fe2O3) is generated from the divalent iron ions and precipitates, and there is a risk that permanganate ions cannot be generated sufficiently. In addition, if a divalent manganese compound is dissolved in water with a pH of 3.5 or more, when ozone microbubbles are later supplied to the water, trivalent manganese oxide (Mn2O3) or tetravalent manganese oxide (manganese dioxide: MnO2) is generated from the divalent manganese ions and precipitates, and there is a risk that permanganate ions cannot be generated sufficiently. The pH of the water in which the divalent inorganic iron compounds and divalent manganese compounds are dissolved is preferably less than 3.0.

[0010] The water may be, for example, water having an electrical conductivity of less than 300 μS / cm. Pure water having an electrical conductivity of 3 μS / cm or less can be suitably used, but tap water or groundwater may also be used.

[0011] As the acid for adjusting the pH of the water to less than 3.5, it is preferable to use an inorganic acid such as hydrochloric acid, sulfuric acid, or sulfuric acid.

[0012] Examples of divalent inorganic iron compounds that dissolve in water with a pH of less than 3.5 include iron chloride (II), iron sulfate (II), and iron nitrate (II). It is preferable to dissolve the divalent inorganic iron compound so that the concentration of divalent iron ions is 1 to 100 ppb. If the concentration of divalent iron ions is less than 1 ppb, there is a risk that permanganate ions cannot be generated sufficiently. On the other hand, if the concentration of divalent iron ions exceeds 100 ppb, there is a risk that trivalent iron oxide (Fe2O3) is generated from the divalent iron ions and easily precipitates when ozone microbubbles are later supplied to the water.

[0013] As the divalent manganese compound that dissolves in water with a pH of less than 3.5, manganese chloride (II), manganese sulfate (II), manganese nitrate (II), etc. can be used. It is preferable that the divalent manganese compound is dissolved so that the concentration of the divalent manganese ion is 0.1 μM to 1 mM. If the concentration of the divalent manganese ion is less than 0.1 μM, there is a risk that permanganate ions cannot be generated sufficiently. On the other hand, if the concentration of the divalent manganese ion exceeds 1 mM, there is a risk that trivalent manganese oxide (Mn2O3) or tetravalent manganese oxide (manganese dioxide: MnO2) is generated from the divalent manganese ion when ozone microbubbles are later supplied to the water, and precipitation is likely to occur. It is more preferable that the divalent manganese compound is dissolved so that the concentration of the divalent manganese ion is 1 to 100 μM.

[0014] The order in which the divalent inorganic iron compound and the divalent manganese compound are dissolved in water having a pH of less than 3.5 is not particularly limited, and they may be dissolved simultaneously or in a stepwise manner.

[0015] In the method for producing water containing permanganate ions of the present invention, it is not necessary to further dissolve inorganic salts such as sodium chloride, potassium chloride, magnesium chloride, magnesium sulfate, etc., as in the method for producing water containing permanganate ions described in Patent Document 1. Although further dissolving inorganic salts does not adversely affect the production of water containing permanganate ions by the method of the present invention, it is preferable not to further dissolve inorganic salts, since this may restrict the applications of the produced water containing permanganate ions (water with a high salt concentration is not desirable for use in, for example, electrical equipment).

[0016] Next, ozone microbubbles are supplied for a predetermined time, for example, 1 minute to 24 hours, into water having a pH of less than 3.5 in which a divalent inorganic iron compound and a divalent manganese compound are dissolved. The method of supplying ozone microbubbles into water may be a method known per se, and can be performed using a microbubble generator using a two-phase flow swirling method or a pressurized dissolution method that can generate microbubbles with a particle size of 5 to 50 μm. When the two-phase flow swirling method is adopted, a vortex with a radius of 10 cm or less is forcibly generated using a rotor or the like, and a gas-liquid mixture containing ozone to be contained inside the microbubbles is struck against an obstacle such as a wall surface or a fluid with a different relative speed, thereby dispersing the gas components acquired in the vortex as the vortex disappears, thereby generating the desired ozone microbubbles. In addition, when the pressurized dissolution method is adopted, ozone to be contained inside the microbubbles is dissolved in water under a high pressure of 2 atmospheres or more, and then the solution is released to atmospheric pressure, whereby ozone microbubbles can be generated from the supersaturated condition of the dissolved gas generated. In this case, a large number of vortices with a radius of 1 mm or less are generated at the pressure release site by using the water flow and obstacles, and a large number of gas phase nuclei (bubble nuclei) are formed due to the molecular vibration of water in the central region of the vortex flow, and the gas components in the water are diffused toward these bubble nuclei under supersaturated conditions, and the bubble nuclei grow, so that a large amount of desired ozone microbubbles can be generated. Note that the ozone microbubbles generated by these methods have a particle size of 50 μm or less, and have a particle size peak at 10 to 15 μm when measured with a liquid particle counter using a laser light blocking method (for example, LiQuilaz-E20 manufactured by SPM Co., Ltd.), and the number of microbubbles in the peak region is 1000 pieces / mL or more (see JP-A-2000-51107 and JP-A-2003-265938, etc., if necessary). The ozone gas used to supply ozone microbubbles into water is, for example, 1 to 300 g / Nm using a commercially available oxygen source ozone generator. 3 The concentration is 1g / Nm 3 If ozone gas with a concentration of less than 300 g / Nm is used, it may not be possible to efficiently supply a large amount of ozone microbubbles into the water.3 It is difficult to prepare an ozone gas that exceeds this concentration. The ozone gas may contain oxygen, nitrogen, and the like in addition to ozone.

[0017] The above steps can produce water in which permanganate ions are stable for a long period of time, but the pH of the produced water containing permanganate ions is less than 3.5. Therefore, in order to make the produced water containing permanganate ions weakly acidic to weakly alkaline, which is versatile for the use of permanganate ions such as oxidizers, disinfectants, and deodorants, it is preferable to adjust the pH to 5.0 to 9.0 after supplying ozone microbubbles to the water for a predetermined period of time. As the alkali for adjusting the pH of the water to 5.0 to 9.0, it is preferable to use an inorganic alkali such as sodium hydroxide or potassium hydroxide.

[0018] The water containing permanganate ions produced in this way has a pH of 5.0 to 9.0, and is versatile in terms of the use of permanganate ions. Like the water containing permanganate ions produced by the production method described in Patent Document 1, permanganate ions are present stably in water for a long period of time at a concentration of 0.1 μM to 1 mM, typically 1 to 100 μM, and its half-life is, for example, 3 months or more when filled in a sealed container under atmospheric pressure and stored at a temperature of 40°C. The salt concentration is preferably 0.3% or less, more preferably 0.1% or less. In addition, when the pH of the water containing permanganate ions is adjusted to 5.0 to 9.0, precipitates are generated in the water, but the amount of precipitates generated is small and the generation subsides within a short period of time. Therefore, for example, the day after the pH of the water containing permanganate ions is adjusted to 5.0 to 9.0, the generated precipitates can be filtered and shipped as a product. EXAMPLES

[0019] The present invention will be described in detail below with reference to examples, but the present invention should not be construed as being limited to the following description.

[0020] Example 1: A 15-L glass container was filled with 10 L of ultrapure water with an electrical conductivity of 0.06 μS / cm, and hydrochloric acid was added to adjust the pH to 2.8. Iron (II) chloride was then dissolved therein to give a divalent iron ion concentration of approximately 25 ppb, and manganese (II) chloride was then dissolved therein to give a divalent manganese ion concentration of 50 μM. Ozone microbubbles with a particle size of 15 to 50 μm were generated in this liquid using a pressurized dissolution type microbubble generator and supplied for 10 minutes. The device was operated while circulating the water inside. An oxygen source ozone generator was used for the microbubble generator, and approximately 50 g / Nm 3 Ozone gas prepared at a concentration of was supplied at about 1 L / min. After 10 minutes, the water turned a pale pink color, suggesting the generation of permanganate ions in the water. After stopping the operation of the microbubble generator, sodium hydroxide was added to adjust the pH to 7.0, and the water was left to stand naturally for a day and night in an indoor environment, after which a small amount of precipitate that had formed in the water when the pH was adjusted to 7.0 was removed by filtration using a 1.2 μm membrane filter (no further generation of precipitates was observed after that). When the obtained filtrate was measured with an ultraviolet-visible-near infrared spectrophotometer, a group of peaks of permanganate ions was present in the vicinity of 500-600 nm (it was confirmed that a group of peaks of the same shape was present in the same place by measuring water containing permanganate ions produced by dissolving sodium chloride in distilled water to make the salt concentration 0.25% and then dissolving potassium permanganate under the same conditions).

[0021] The permanganate ion concentration of the water containing permanganate ions produced in this way was about 10 μM (concentration calculated by comparing the height of the peak group of permanganate ions measured with an ultraviolet-visible-near infrared spectrophotometer with the height of the peak group of water containing permanganate ions at a concentration of 20 μM produced using potassium permanganate as a standard solution), and the salinity was measured with a salinity meter and found to be about 0.05%. When this water containing permanganate ions was filled into a PET bottle as a sealed container under atmospheric pressure and stored at a temperature of 40°C, the half-life of the permanganate ions was investigated and found to be more than three months (more than half of the permanganate ions remained after three months had passed). In addition, 1 mL of the water containing permanganate ions was sampled, and ethylenediaminetetraacetic acid (EDTA) was added to the sample to a concentration of 20 mM, followed by 5,5-dimethyl-1-pyrroline N-oxide (DMPO) to a concentration of 200 mM, and then hydrochloric acid was added to a concentration of 500 mM. The resulting mixture was then drawn into a quartz cell and measured with an electron spin resonance (ESR) device, whereupon a prominent DMPO-OH signal with a 1:2:2:1 peak pattern was confirmed. In addition, the water containing permanganate ions was stored in a plastic bottle in a cool, dark place, and the same measurement was performed three months later. A signal with a 1:2:2:1 peak pattern was confirmed, and the peak length was more than 90% of the peak length immediately after production.

[0022] Example 2: Water containing permanganate ions was produced in the same manner as in Example 1, except that, instead of the operation of adjusting the pH of the water to 7.0 by adding sodium hydroxide in Example 1, the amount of sodium hydroxide added was reduced to adjust the pH to 5.5. The permanganate ion concentration of the water containing permanganate ions produced in this manner was about 10 μM, and the salt concentration was about 0.03%. The half-life of the permanganate ions in this water containing permanganate ions and the results of measurement using an electron spin resonance device were the same as those of the water containing permanganate ions produced in Example 1.

[0023] Example 3: Water containing permanganate ions was produced in the same manner as in Example 1, except that iron sulfate (II) was added instead of iron chloride (II). The permanganate ion concentration of the water containing permanganate ions produced in this manner was about 10 μM, and the salt concentration was about 0.05%. The half-life of the permanganate ions in this water containing permanganate ions and the results of measurement using an electron spin resonance device were the same as those of the water containing permanganate ions produced in Example 1.

[0024] Example 4: Water containing permanganate ions was produced in the same manner as in Example 1, except that manganese sulfate (II) was added instead of manganese chloride (II). The permanganate ion concentration of the water containing permanganate ions produced in this manner was about 10 μM, and the salt concentration was about 0.05%. The half-life of the permanganate ions in this water containing permanganate ions and the results of measurement using an electron spin resonance device were the same as those of the water containing permanganate ions produced in Example 1.

[0025] Example 5: When the bactericidal effect of the water containing permanganate ions produced in Example 1 against the pathogen Salmonella Enteritidis was examined, an excellent bactericidal effect was observed.

[0026] Example 6: The water containing permanganate ions produced in Example 1 was orally administered to day-old chicks hatched from SPF eggs of Line-M chickens to examine toxicity, and no toxicity was observed.

[0027] Example 7: When the cytotoxicity of the water containing permanganate ions produced in Example 1 to chicken embryo fibroblasts (CEF cells) was examined, no cytotoxicity was observed. [Industrial Applicability]

[0028] INDUSTRIAL APPLICABILITY The present invention has industrial applicability in that it provides a novel method for producing water in which permanganate ions are stably present for a long period of time without using an organic iron compound as a production raw material.

Claims

1. A method for producing water containing permanganate ions by dissolving a divalent inorganic iron compound and a divalent manganese compound in water having a pH of less than 3.5, and then supplying ozone microbubbles into the water.

2. 2. The method according to claim 1, wherein the divalent inorganic iron compound is at least one selected from the group consisting of iron(II) chloride, iron(II) sulfate, and iron(II) nitrate.

3. 2. The method according to claim 1, wherein the divalent inorganic iron compound is dissolved so that the concentration of divalent iron ions is 1 to 100 ppb.

4. 2. The method according to claim 1, wherein the divalent manganese compound is at least one selected from the group consisting of manganese(II) chloride, manganese(II) sulfate, and manganese(II) nitrate.

5. 2. The method according to claim 1, wherein the divalent manganese compound is dissolved so that the concentration of divalent manganese ions is 0.1 μM to 1 mM.

6. The method according to claim 1, further comprising dissolving no inorganic salt.

7. The method according to claim 1, wherein the pH of the water is adjusted to 5.0 to 9.0 after the ozone microbubbles are supplied into the water.