Separation device and system for separating impurity ions from hypochlorous acid water

Abstract

The present application relates to a separation device or system, which uses a separation membrane as a method for separating impurity ions other than hypochlorous acid from an aqueous solution containing hypochlorous acid as a main component. The present application also provides a solution containing hypochlorous acid as a main component with better storage stability.

Description

Technical Field

[0001] The present disclosure relates to a separation device or system capable of separating impurity ions other than hypochlorous acid from an aqueous solution containing hypochlorous acid as a main component and providing an aqueous solution containing hypochlorous acid as a main component having excellent storage stability. Background Art

[0002] In the past, sodium hypochlorite, a chlorine-based halogenated drug, has been widely used in various fields, including public health, food, and medicine, as a disinfectant with rapid bactericidal power against bacteria at extremely low concentrations and the most reliable effect against viruses such as HIV and HBV. In particular, for viruses without an envelope, such as norovirus, SLV (sapovirus), and Caliciviridae viruses, and rotavirus, alcohol disinfection is not an option, making hypochlorous acid disinfection the preferred method. Specifically, aqueous solutions containing sodium hypochlorite are used in the form of sprays and other methods to disinfect and sterilize various items and environments, including clothing, tableware, glass containers, and plastic containers, in homes and medical settings. Furthermore, powdered forms are also used for disinfection of sewers, swimming pools, and the like. Sodium hypochlorite can also be used for finger disinfection at very low concentrations in the form of an aqueous solution or wet wipes soaked with the aqueous solution. However, the aqueous sodium hypochlorite solution, formed by dissolving sodium hypochlorite salt in water, is strongly alkaline, and even diluted solutions thereof are alkaline. Therefore, if used for finger disinfection, it can cause roughness on the hands (Patent Document 1).

[0003] On the other hand, hypochlorous acid, produced through electrolysis using sodium chloride, has over 80 times the potent bactericidal and antiviral effects of sodium hypochlorite. However, unlike alkaline sodium hypochlorite aqueous solutions, this hypochlorous acid water exhibits acidic properties and is susceptible to corrosion of metals and other materials due to its low pH. Furthermore, under acidic conditions, the increased amount of chloride ions easily generates chlorine and hydrogen chloride gases, causing hypochlorous acid to decompose and quickly drop below its indicated concentration. Furthermore, when hydrogen chloride dissolves in water, it forms hydrochloric acid, making the aqueous solution acidic.

[0004] In contrast, Patent Document 2 describes the use of a two-diaphragm three-chamber electrolytic cell to produce hypochlorous acid water that substantially does not contain impurity ions other than hypochlorous acid. The two-diaphragm three-chamber electrolytic cell is obtained by using diaphragms to separate the anode chamber, the cathode chamber, and the intermediate chamber located between the anode chamber and the cathode chamber and containing an electrolyte.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-229833

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2009-72755 Summary of the Invention

[0009] However, the method of Patent Document 2 has the following problems: When attempting to increase the hypochlorous acid concentration, the pH decreases, resulting in an aqueous solution with a high total chloride ion content, which in turn reduces the hypochlorous acid concentration during storage. Furthermore, when sodium hydroxide, sodium bicarbonate, or the like is used for neutralization to reduce the amount of hydrogen chloride in the aqueous solution, there is the problem of an increase in undecomposed chlorides such as NaCl.

[0010] Therefore, an object of the present disclosure is to provide an aqueous solution containing hypochlorous acid as a main component and having further excellent storage stability.

[0011] The present inventors have studied the above-mentioned problems and found that impurity ions other than hypochlorous acid can be separated from an aqueous solution containing hypochlorous acid as a main component using a separation membrane, thereby providing a more stable aqueous solution containing hypochlorous acid as a main component.

[0012] That is, the present disclosure relates to the following:

[0013] [1] A separation device or system using a separation membrane as a method for separating impurity ions other than hypochlorous acid from an aqueous solution containing hypochlorous acid as a main component.

[0014] [2] The separation device or system according to [1] above, wherein an alkaline substance with a large molecular weight is added to an aqueous solution containing hypochlorous acid as a main component,

[0015] (i) making the molecular weight of the chloride in the aqueous solution greater than that of hypochlorous acid, and / or

[0016] (ii) increasing the size of the hydrate of the ion to be separated by neutralizing the aqueous solution,

[0017] Separation is performed using a separation membrane.

[0018] [3] The separation device or system according to [1] or [2] above, wherein the degree of separation is controlled by using a charged membrane and / or a separation membrane with a predetermined pore size as the separation membrane.

[0019] [4] The separation device or system according to any one of [1] to [3] above, wherein an RO membrane, a NF membrane and / or an UF membrane is used as the separation membrane.

[0020] [5] The separation device or system according to any one of [1] to [4] above, wherein the separation membrane is made of at least one material selected from a polymer, ceramics, and metal.

[0021] [6] The separation device or system as described in [5] above, wherein the high molecular polymer is at least one selected from polysulfone, polyethersulfone, polypropylene, polyethylene, triacetyl cellulose, diacetyl cellulose, nylon polymers and PMMA (polymethyl methacrylate).

[0022] [7] The separation device or system according to any one of [1] to [6] above, wherein the aqueous solution containing hypochlorous acid as a main component is generated by electrolysis or ion exchange.

[0023] [8] A separation device or system as described in any one of [1] to [7] above, wherein an electric field or a magnetic field is used as an auxiliary to separate impurity ions other than hypochlorous acid from an aqueous solution containing hypochlorous acid as a main component.

[0024] [9] The separation device or system as described in any one of [3] to [6] above, wherein the generated chloride is separated from the hypochlorous acid water generated by neutralizing sodium hypochlorite with acid, removing sodium by electrodialysis, or replacing Na ions with H ions by ion exchange.

[0025] According to the present disclosure, in an aqueous solution containing hypochlorous acid as a main component, by reducing impurity ions other than hypochlorous acid in the aqueous solution, an aqueous solution that is less likely to be deactivated and has better storage stability can be obtained, and the formation of rust on metal when the aqueous solution containing hypochlorous acid as a main component is sprayed into space can be suppressed. DETAILED DESCRIPTION

[0026] As used herein, the phrase "containing hypochlorous acid as a main component" means that hypochlorous acid is included as a representative component other than water as a solvent. It does not imply that hypochlorous acid accounts for the majority of the components or that hypochlorous acid is the largest component other than water. In contrast, conventional hypochlorous acid water contains high levels of undecomposed sodium chloride and hydrochloric acid, a pH-regulating component, resulting in a lower proportion of hypochlorous acid than, for example, the solution described later in Embodiment 1 of the present disclosure.

[0027] As used herein, "impurity ions other than hypochlorous acid" refers to ions contained in addition to hypochlorous acid. Specifically, examples of impurity ions other than hypochlorous acid include chloride ions and sodium ions, which are separated from an aqueous solution containing hypochlorous acid as a main component, either in their original form or as other compounds.

[0028] According to Embodiment 1 of the present disclosure, a separation device and system are provided for separating impurity ions other than hypochlorous acid from an aqueous solution containing hypochlorous acid as its primary component using a separation membrane. It is believed that by separating impurity ions other than hypochlorous acid from the aqueous solution, the pH of the aqueous solution can be brought as close to neutral as possible, resulting in an aqueous solution containing hypochlorous acid as its primary component with excellent storage stability. Furthermore, the resulting aqueous solution is less likely to cause metal corrosion or resin degradation.

[0029] In the aqueous solution containing hypochlorous acid as the main component of Embodiment 1, impurity ions other than hypochlorous acid are separated from the aqueous solution using a separation membrane. The pH of the aqueous solution after separation is preferably 4.0 or higher, more preferably 5.0 or higher, and particularly preferably 6.0 or higher. If the aqueous solution contains a large amount of impurity ions, particularly chloride ions, the pH of the aqueous solution decreases, resulting in an acidic aqueous solution. Acidic aqueous solutions tend to increase damage such as irritation and corrosion.

[0030] The water used when preparing the aqueous solution containing hypochlorous acid as the main component for use in the device or system of embodiment 1 is preferably pure water (e.g., RO water), purified water, ion-exchanged water, etc., in order to suppress the mixing of unintended components, such as metal ions or organic matter contained in tap water.

[0031] As the separation membrane used for the separation treatment, for example, a reverse filtration membrane (RO membrane, NF membrane), an ultrafiltration membrane (UF membrane), etc. can be used.

[0032] A hydrophobic membrane with a charged surface is preferably used as the separation membrane. This is because the membrane's charge exerts its influence, making it difficult for charged ionized substances in aqueous solutions to pass through the membrane, thereby improving separation efficiency. In other words, separation is achieved by exploiting the relationship between the charge state of the substance to be separated and the charge state of the membrane used. Alternatively, electric and magnetic fields can be generated to adjust the charge on the membrane surface, thereby increasing the proportion of separated substances.

[0033] Furthermore, by using a separation membrane with a predetermined pore size, substances that pass through the membrane can be selected based on the size of the membrane's pores. While there are no particular limitations on the pore size of the separation membrane, it is preferably 50 nm or less, and more preferably 5 nm or less. Furthermore, it is preferable to use a membrane with a charged surface and a predetermined pore size as the separation membrane. This allows for control over the degree of separation, i.e., the extent of separation, and the selection of substances to be separated.

[0034] The separation membrane may be made of a material comprising a polymer, ceramics, metals or other known materials, either alone or in combination.

[0035] Among the materials constituting the separation membrane, as a high molecular polymer, at least one selected from PSF (polysulfone), PES (polyethersulfone), PP (polypropylene), PE (polyethylene), CTA (cellulose triacetate), CDA (cellulose diacetate), PA (nylon polymer) and PMMA (polymethyl methacrylate) can be used.

[0036] The aqueous solution containing hypochlorous acid as a main component that is applicable to the separation device or system of Embodiment 1 is preferably electrolyzed water. Specifically, it is preferably electrolyzed water containing hypochlorous acid as a main component that is obtained by electrolyzing hydrochloric acid or sodium chloride and potassium chloride as raw materials.

[0037] The pH of the aqueous solution with hypochlorous acid as the main component obtained by the separation device or system of embodiment 1 is preferably 4.0 or more, more preferably 5.0 or more, further preferably 5.5 or more, and particularly preferably 6.0 or more. By making the pH of the aqueous solution with hypochlorous acid as the main component to be 4.0 or more, there is a trend of reduced corrosiveness and being able to be used for various purposes. In particular, when using an aqueous solution with hypochlorous acid as the main component in a humidifier, an air purifier, etc., due to concerns about corrosion or deterioration of the components used in the device, the pH is preferably 5.5 or more. By making the pH to be 5.5 or more, the generation of chlorine (hydrogen chloride gas) can be further suppressed. In addition, it is preferred that the pH of the aqueous solution with hypochlorous acid as the main component be 5.5 or more and 6.5 or less, thereby reducing irritation to the mucous membranes, etc., while meeting the drinking water standard.

[0038] The aqueous solution containing hypochlorous acid as its main component, obtained by the separation device or system of embodiment 1, can be used for various applications due to its characteristics such as a moderately low pH and strong bactericidal and antiviral properties. For example, it can be widely used in various fields such as public health, food, and medicine, including disinfection and sterilization in daily life. It can be applied to disinfection and sterilization / disinfection of various items and environments, such as clothing, tableware, glass containers, and plastic containers, at home or in medical settings. It is particularly suitable for skin cleaning and sterilization, such as finger washing (hand washing disinfection), and sterilization of spaces. In particular, since it does not contain salt and has a low pH, there is no need to worry about corrosion. With tap water, fungi such as mold can sometimes grow in water storage tanks and spread the generated fungi. In addition, because it contains hypochlorous acid with a strong bactericidal effect, it can maintain the hygiene of not only the equipment but also the space. Therefore, it is preferably used in humidifiers, air purifiers, etc. instead of tap water.

[0039] The aqueous solution with hypochlorous acid as the main component suitable for the separation device or system of embodiment 1 can be prepared by various methods. For example, first, in a two-diaphragm three-chamber electrolytic cell, an aqueous sodium chloride solution is used as an electrolyte to perform electrolysis to obtain acidic hypochlorous acid water obtained in the anode chamber. At this time, in the electrolysis using sodium chloride and water, usually, chloride ions migrate to the anode and sodium ions migrate to the cathode. The migrated chloride ions react with water to generate hydrochloric acid (HCl) and hypochlorous acid (HClO), and produce oxygen. In the cathode, the sodium ions react with water to generate sodium hydroxide and produce hydrogen. The reaction of sodium chloride and water is shown in the following formula. Stoichiometrically, the production ratio of hypochlorous acid and hydrochloric acid will not be greater than 1:1, so the production ratio of hypochlorous acid will not exceed that of hydrochloric acid.

[0040] 2NaCl+H2O→2NaOH+HCl+HClO

[0041] The resulting acidic aqueous solution, primarily composed of hypochlorous acid, is then passed through a separation membrane to separate the hydrochloric acid from the aqueous solution, thereby increasing the proportion of hypochlorous acid in the aqueous solution. This treatment, which increases the ratio of hypochlorous acid to hydrochloric acid, simultaneously shifts the pH toward neutral. This treatment can be repeated as many times as necessary to achieve the desired ratio of hypochlorous acid to hydrochloric acid and the desired pH.

[0042] According to a second embodiment of the present disclosure, a separation device or system is provided, which adds a high-molecular-weight alkaline substance to an aqueous solution containing hypochlorous acid as its main component, (i) increases the molecular weight of the chloride in the aqueous solution to be greater than that of hypochlorous acid, and / or (ii) increases the size of the hydrate of the ion to be separated (e.g., sodium ions, chloride ions) by neutralizing the aqueous solution, and then performs separation using a separation membrane. In this second embodiment, a high-molecular-weight alkaline substance is added to a solution containing hypochlorous acid as its main component, and, for example, a solution having a pH of 6.0 to 6.5 is passed through a separation membrane to separate chlorides represented by NaCl. The purpose of performing the neutralization treatment before separation is to neutralize the HCl contained in the aqueous solution containing hypochlorous acid as its main component using an alkaline substance such as NaOH, thereby forming NaCl having a larger molecular weight than HCl, which facilitates separation using the separation membrane. By setting the pH after separation to 6.0 or above, the solution meets the standards for drinking water. In this second embodiment, it is more preferable to set the pH of the aqueous solution containing hypochlorous acid as its main component after separation to 6.0 to 6.8. Here, as the alkaline substance with a large molecular weight, various pH adjusters can be used, specifically, aqueous solutions of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium bicarbonate, potassium bicarbonate, calcium bicarbonate, magnesium bicarbonate, sodium acetate, potassium acetate, calcium acetate, magnesium acetate, sodium citrate, potassium citrate, calcium citrate or magnesium citrate, etc. Among them, an aqueous solution of sodium hydroxide is particularly preferably used.

[0043] The pH of the aqueous solution obtained by the device or system of embodiment 2 is neutral to weakly acidic, ranging from 5.0 to 7.0. Therefore, it is close to the pH of the skin, and the irritation caused by acid and the itching caused by alkali are greatly reduced. In addition, by not tilting to the alkaline side, the generation of trihalomethanes can also be suppressed. When spread indoors, the concentration of hydrogen chloride (HCl) and salt is low, so corrosion, especially the impact on electronic substrates, etc., can be suppressed to a low level. In addition to the uses of the aqueous solution of embodiment 1, it can be used for more purposes, for example, it is particularly suitable for cleaning and sterilizing the skin such as finger washing (hand washing and sterilization), sterilizing spaces, sterilizing instruments, etc., sterilizing bedsores, etc.

[0044] The aqueous solution containing hypochlorous acid as a main component obtained by the separation device or system of embodiments 1-2 of the present disclosure can be used to cleanse, sterilize, or disinfect wounds that have come into contact with blood, such as wounds incurred through surgical or non-surgical means, or can be introduced into the lungs via an inhaler for lung sterilization. Specifically, examples include general surgical procedures, endoscopic procedures, robotic-assisted laparoscopic procedures, oral surgery, bypass surgery, implant surgery, transplant surgery, and other surgical procedures, as well as cauterization, amputation, radiation therapy, chemotherapy, burns, cuts, abrasions, scratches, rashes, ulcers, puncture wounds, bedsores, and combinations thereof. It is preferably used for infection management, scar prevention, and other applications.

[0045] In this specification, matters described in each of the above-mentioned Embodiments 1 and 2 are also applicable to different embodiments unless there is any contradiction.

[0046] Furthermore, the separation devices or systems described in Embodiments 1 and 2 can also perform separation treatment to remove generated chlorides when hypochlorous acid water is generated by methods other than electrolysis as described above, thereby increasing the relative concentration of these chlorides. For example, hypochlorous acid water can be generated by adding acid to sodium hypochlorite for neutralization, removing sodium from sodium hypochlorite through electrodialysis, or replacing Na ions with H ions through ion exchange, and the generated chlorides can be separated using a separation membrane.

[0047] Hereinafter, the present disclosure will be described in detail based on examples, but the present disclosure is not intended to be limited to these examples. It should be noted that the aqueous solution containing hypochlorous acid as a main component obtained in the present disclosure can be stored frozen.

[0048] Example

[0049] Example 1

[0050] Electrolysis is performed using a sodium chloride aqueous solution as the electrolyte in a two-diaphragm, three-chamber electrolytic cell, producing strongly acidic hypochlorous acid water from the anode side. The resulting strongly acidic hypochlorous acid water is passed through an RO membrane (a polyamide RO membrane manufactured by Mitsubishi Chemical AquaSolutions Co., Ltd.) to separate the hydrochloric acid from the aqueous solution, yielding an aqueous solution primarily composed of hypochlorous acid with an increased proportion of hypochlorous acid in the aqueous solution. The hypochlorous acid concentration of the resulting aqueous solution primarily composed of hypochlorous acid is measured using an absorptiophotometer (AQ-102, manufactured by Shibata Chemical Co., Ltd.). The pH is also measured using a multi-function water quality meter (MM-60, manufactured by DKK Toa Co., Ltd.).

[0051] Comparative Example 1

[0052] An aqueous solution containing hypochlorous acid as a main component was obtained in the same manner as in Example 1, except that separation treatment using a separation membrane (RO membrane) was not performed. The concentration of hypochlorous acid and other physical properties of the obtained aqueous solution containing hypochlorous acid as a main component were determined in the same manner as in Example 1. The results are shown in Table 1.

[0053] [Table 1]

[0054]

[0055] As shown in Table 1, after membrane separation in Example 1, the pH increased and the conductivity decreased compared to Comparative Example 1. Therefore, the relative concentration of hypochlorous acid increased, and an aqueous solution containing hypochlorous acid as the main component and having excellent storage stability was obtained.

[0056] Example 2, Comparative Example 2

[0057] As in Example 1 and Comparative Example 1, sodium hydroxide was added to an aqueous solution containing hypochlorous acid as its main component, obtained by electrolysis, to adjust the pH to approximately 5.5. In Example 2, the resulting aqueous solution was subjected to separation using an RO membrane (cellulose membrane manufactured by Toyobo Co., Ltd.) in the same manner as in Example 1 (separation was not performed in Comparative Example 2). Measurements in Example 2 and Comparative Example 2 were performed in the same manner as in Example 1 and Comparative Example 1. The results are shown in Table 2.

[0058] [Table 2]

[0059]

[0060] As can be seen from Table 2, in Example 2, an increase in pH and a decrease in conductivity can be confirmed compared to Comparative Example 2. Therefore, an aqueous solution containing hypochlorous acid as a main component can be obtained, in which the relative concentration of hypochlorous acid is increased, stability is good, and corrosion to metals and the like is suppressed.

Claims

1. A method for producing an aqueous solution containing hypochlorous acid as a main component and having reduced impurity ions using a separation device or system equipped with a separation membrane, the method comprising: (a) Step: Adding a high molecular weight alkaline substance to an aqueous solution containing hypochlorous acid as a main component generated by electrolysis, and thereby (i) making the molecular weight of chloride in the aqueous solution greater than that of hypochlorous acid, and (ii) increasing the size of the hydrate of the ion to be separated by neutralizing the aqueous solution; and (b) a step of separating impurity ions from the aqueous solution containing hypochlorous acid as a main component treated in the step (a) using a separation membrane, and obtaining an aqueous solution containing hypochlorous acid as a main component with reduced impurity ions, The separation membrane is an RO membrane, a NF membrane and / or an UF membrane.

2. The method according to claim 1, wherein The degree of separation is controlled by using a charged membrane and / or using a separation membrane having a predetermined pore size as the separation membrane.

3. The method according to any one of claims 1 to 2, wherein The material of the separation membrane includes at least one selected from polymers, ceramics, and metals.

4. The method according to claim 3, wherein: The high molecular polymer is at least one selected from polysulfone, polyethersulfone, polypropylene, polyethylene, triacetyl cellulose, diacetyl cellulose, nylon polymers and PMMA (polymethyl methacrylate).

5. The method according to any one of claims 1 to 2, wherein As an auxiliary method for separating impurity ions other than hypochlorous acid from an aqueous solution containing hypochlorous acid as a main component, an electric field or a magnetic field is used.

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