Ultrafine bubble liquid and method for producing ultrafine bubble liquid

Abstract

To provide an ultrafine bubble liquid that is suitable for use in any field and enables long-term storage, and a method for producing the ultrafine bubble liquid.SOLUTION: An ultrafine bubble liquid U disclosed herein contains, in a solvent, ultrafine bubbles and a surfactant. The surfactant has a concentration of 20 μmol / L to 70 μmol / L. The surfactant is a cationic surfactant of an ammonium salt. The cationic surfactant is benzalkonium chloride.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an ultra-fine bubble liquid and a method for producing an ultra-fine bubble liquid. [Background technology]

[0002] Fine bubbles, which are microscopic bubbles with a diameter of 100 μm or less, have cleaning, catalytic, sterilizing and disinfecting effects, deodorizing, microparticle adsorption, bioactivation, and friction reduction effects, and are used in many fields by utilizing these effects. Among fine bubbles, ultrafine bubbles with a diameter of less than 1 μm are called ultrafine bubbles according to the International Organization for Standardization (ISO) standard. Unlike microbubbles with a diameter of 1 μm or more, ultrafine bubbles are characterized by staying in water for a long period of time. In addition, since ultrafine bubbles are electrically charged, they have a high cleaning power without the use of cleaning or chemicals. In addition, due to the highly functional catalytic effect and sterilizing and disinfecting effect of ultrafine bubbles, they are expected to be used in the medical and pharmaceutical fields, as well as in the food and drinking water fields.

[0003] For example, a cleaning solution described in JP 2020-94088 A (Patent Document 1 below) is known as an ultrafine bubble used in the cleaning field. This cleaning solution contains ultrafine bubbles and a surfactant, and is characterized in that the particle diameter of the ultrafine bubbles is 50 nm or more and 200 nm or less, the concentration is 108 particles / mL or more, the concentration of the surfactant is 1 / 10 times or more and less than 1 times the critical micelle concentration, and the surface of the ultrafine bubbles is covered with the surfactant. A surfactant is an amphiphilic chemical substance that has both hydrophilic and hydrophobic groups in its molecule. In general, during cleaning, it first wets and penetrates contaminants to promote their removal, solubilizes and emulsifies (removes) the contaminants with self-organized bodies called micelles, and then acts as a dispersant to prevent the contaminants from reattaching. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-94088 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above cleaning solution, the surfactant concentration is more than 1 / 10 and less than 1 times the critical micelle concentration, and it is assumed that it will be used in the cleaning field, so it is thought that it cannot be used in other fields. In particular, in the medical field, it is preferable to add less surfactant, and further consideration is required for use in fields other than cleaning. On the other hand, if the surfactant concentration is too low, the stability of the ultra-fine bubbles decreases, which is disadvantageous in terms of long-term storage.

[0006] The present disclosure has been completed based on the above-mentioned circumstances, and aims to provide an ultra-fine bubble liquid that can be used in any field and can be stored for a long period of time, and a method for producing an ultra-fine bubble liquid. [Means for solving the problem]

[0007] The ultra-fine bubble liquid of the present disclosure is an ultra-fine bubble liquid containing ultra-fine bubbles and a surfactant in a solvent, wherein the concentration of the surfactant is 20 μmol / L to 70 μmol / L, the surfactant is a cationic surfactant of an ammonium salt, and the cationic surfactant is benzalkonium chloride. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide an ultra-fine bubble liquid that can be used in any field and can be stored for a long period of time, and a method for producing an ultra-fine bubble liquid. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram showing an ultra-fine bubble liquid generating device. [Diagram 2] FIG. 2 is a graph showing the change over time in the amount of change in UFB concentration due to differences in the types of surfactants. [Diagram 3] FIG. 3 is a graph showing the change over time in the amount of change in UFB concentration due to differences in cationic surfactants. [Figure 4] FIG. 4 is a graph showing the change over time in the amount of high-concentration UFB concentration due to differences in the amount of benzalkonium chloride added. [Diagram 5] FIG. 5 is a graph showing the change over time in the amount of change in low-concentration UFB concentration due to differences in the amount of benzalkonium chloride added. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. (1) The ultra-fine bubble liquid of the present disclosure is an ultra-fine bubble liquid containing ultra-fine bubbles and a surfactant in a solvent, wherein the concentration of the surfactant is 20 μmol / L to 70 μmol / L, the surfactant is a cationic surfactant of an ammonium salt, and the cationic surfactant is benzalkonium chloride.

[0011] Ultrafine bubbles are known to disperse in liquids for a long period of time, but gradually decrease over time due to aggregation and other factors. Even if they are commercialized and distributed in liquid form, there is an issue that the quality at the time of manufacture cannot be guaranteed due to the decrease over time. Ultrafine bubbles are known to be colloidal particles with a zeta potential, and since they have an electric charge of approximately -5 to -50 mV, they are capable of adsorbing surfactants due to the electric charge. Therefore, by covering the surface of ultrafine bubbles with a surfactant, the hydrophobic surface of the ultrafine bubbles becomes hydrophilic, which is thought to improve the stability of the ultrafine bubbles.

[0012] After studying this issue, the inventors of the present application produced a liquid containing ultra-fine bubbles and discovered that adding benzalkonium chloride, a cationic surfactant, to the liquid at a concentration of 20 μmol / L to 70 μmol / L allowed the ultra-fine bubbles to be preserved for a long period of time. Specifically, they discovered that the ultra-fine bubble concentration, which normally decreases to 10% or less in one week, remains at 90% or more even after three months by using benzalkonium chloride. The reasons for this are believed to be as follows. 1. A cationic surfactant with a positive functional group selectively adsorbed onto ultrafine bubbles, which have a negative zeta potential. 2. As a result of the adsorption of the surfactant, the unstable gas / liquid interface becomes gas / solid / liquid, and a shell-like structure is formed by the surfactant, making it more difficult for the ultrafine bubbles to aggregate together. 3. The surfactant is in the form of a chain, with the other end of the positive functional group dangling in the water. This surfactant acts as a physical barrier, preventing contact between ultrafine bubbles and inhibiting their aggregation. 4. If there is an excess of surfactant that is not completely adsorbed to ultra-fine bubbles (free surfactant), it will induce further adsorption and promote the aggregation of ultra-fine bubbles. By minimizing the amount of surfactant added, this phenomenon can be suppressed.

[0013] In the method of adding a surfactant as described above, there is a risk of increasing the amount of surfactant added in fields such as environmental protection, medicine, and health care, where contamination with foreign matter is undesirable. In this regard, the inventors of the present application have discovered that ultra-fine bubbles can be preserved for a long period of time with a minimum amount of benzalkonium chloride added, at a concentration of 20 μmol / L to 70 μmol / L. This reduces the risk of contamination in the fields of environmental protection, medicine, and health care, and provides an ultra-fine bubble liquid that can be used in any field and can be preserved for a long period of time.

[0014] (2) The method for producing ultra-fine bubble liquid of the present disclosure includes the steps of generating ultra-fine bubbles in a solvent to produce an ultra-fine bubble-containing liquid, and adding a surfactant to the ultra-fine bubble-containing liquid so that the surfactant concentration is 20 μmol / L to 70 μmol / L to produce an ultra-fine bubble liquid, wherein the surfactant is a cationic surfactant of an ammonium salt, and the cationic surfactant is benzalkonium chloride.

[0015] [Details of the embodiment of the present disclosure] The embodiments of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0016] (1) Overall structure An embodiment of the present disclosure will be described with reference to Fig. 1. The ultra-fine bubble liquid generating device 1 is a device that generates ultra-fine bubbles in a liquid (for example, water such as pure water) to generate ultra-fine bubble liquid.

[0017] As shown in FIG. 1, the ultra-fine bubble liquid generating device 1 has a porous element 33 having a large number of pores, and is equipped with a first tank 3 arranged on one side of the element 33, a second tank 5 arranged on the other side of the element 33, a gas supply unit 9 that supplies gas (e.g., nitrogen gas) to the first tank 3, and a liquid supply unit 11 that supplies liquid to the first tank 3.

[0018] <First Tank> The first tank 3 is configured to store liquid and gas and to be able to pressurize the inside. In other words, it has an airtight structure that prevents liquid and gas from flowing out, except for the parts for supplying and outflowing liquid and for inflowing gas, which will be described later. A first pressure sensor 29 is disposed in the first tank 3 to detect the internal pressure (atmospheric pressure).

[0019] A gas inlet 17 is provided on a side wall 15 of the first tank 3 for introducing gas supplied from the gas supply unit 9 into the inside. A liquid inlet 21 is provided on an upper portion 19 of the first tank 3 for introducing liquid supplied from the liquid supply unit 11 into the inside. When liquid is placed in the first tank 3, the gas inlet 17 is located at a position above the liquid level.

[0020] <Gas supply section> The gas supply unit 9 includes a gas cylinder 43 filled with gas, a first pipe 45 connecting the gas cylinder 43 and the gas inlet 17, a first opening / closing valve 47 for opening and closing the flow path of the first pipe 45, and a third pressure sensor 49 for detecting the pressure inside the gas cylinder 43. Examples of gases that can be supplied from the gas supply unit 9 to the first tank 3 include air, water vapor, hydrogen (H2, D2, T2), rare gases (He, Ne, Kr, Xe, Rn, Ar), oxygen, ozone, carbon monoxide, carbon dioxide, nitrogen, ammonia, chlorine, hydrogen chloride gas, dicyan, sulfur dioxide, hydrogen iodide, phosphine, nitrogen oxides (NO, NO2, NO3, N2O, N2O2, N2O3, N2O4, N2O5, N2O6), hydrocarbons (alkanes and paraffins such as methane and ethane; ethylene, propylene, etc.), and the like. One or more of the following gases can be used: alkenes such as ethylene; alkynes such as acetylene; fluorine gases (F2, HF, CF4, C2F6, C3F8, C4F8, CHF3, SF6, NF3, SiF4), chloride gases (Cl2O, C2H5Cl, HCl, NOCl, CH2Cl, COCl2), bromide gases (Br2, HBr), alcohols, amines, aldehydes, esters, ethers, ketones, terpenes, lactones, thiols, fragrances, and essential oils.

[0021] <Liquid supply section> The liquid supply unit 11 includes a second pipe 51 connected to the liquid inlet 21 to supply the liquid to the first tank 3, and a second on-off valve 53 to open and close the flow path of the second pipe 51. Although not shown, a tank or the like for storing the liquid is disposed upstream of the second pipe 51. The liquid supplied from the liquid supply unit 11 to the first tank 3 may be at least one or more liquids selected from the group consisting of water (pure water, ultrapure water, purified water, tap water), alcohol such as ethanol, or hydrogen peroxide.

[0022] <Communicating pipe, injection valve> A cylindrical stainless steel communication pipe 27 is provided at the bottom 23 of the first tank 3, extending vertically downward via a liquid supply port 25. The liquid in the first tank 3 is supplied to the second tank 5 through the communication pipe 27. An injection valve 31 is provided in the communication pipe 27, and the flow rates of the liquid and gas passing through the communication pipe 27 can be adjusted. A cylindrical element 33 is connected to the lower end of the communication pipe 27. Hereinafter, the region formed by the first tank 3, the communication pipe 27, and the element 33 will be referred to as a first region 70.

[0023] <element> The element 33 is cylindrical with a closed lower end (tip). The upper end of the element 33 is fitted onto the communicating pipe 27 and joined by a glass seal (not shown) so as to be in close contact with the communicating pipe 27 without any gaps. The element 33 is a porous sintered body whose main component is ceramic (e.g., alumina), and a large number of pores (communicating holes through which liquid can pass) are formed throughout the sintered body. The sintered body has a single-layer structure (i.e., a symmetrical structure) in which a large number of pores exist in a similar state (e.g., a similar average pore diameter). The ceramic constituting the element 33 is, for example, a sintered body obtained by sintering one or more materials selected from the group consisting of alumina, aluminum nitride, silicon oxide (silicon monoxide, silicon dioxide (silica)), silicon nitride, boron nitride, zirconia, titania, mullite, magnesia, ceria, doped ceria, alumina cement, calcium phosphate, glass, barium titanate, ferrite, steatite, forsterite, silicon carbide, zeolite, silica glass, silicate glass, and shirasu glass. Among these, the ceramic is preferably a sintered body obtained by sintering alumina.

[0024] <Second Tank> The second tank 5 is configured to be able to store liquid. A second pressure sensor 41 is disposed in the second tank 5 to detect the internal pressure (atmospheric pressure). In addition, the second tank 5 is provided at the lower part of its side wall 37 with a liquid outlet 39 for taking out the liquid from the second tank 5 to the outside.

[0025] <Liquid extraction part> Liquid outlet 39 is connected to liquid outlet 13. Liquid outlet 13 includes a third pipe 55 for taking out the liquid to the outside, and a third on-off valve 57 for opening and closing the flow path of third pipe 55.

[0026] <Differential pressure application section> The differential pressure applying part 10 is composed of an airtight first tank 3, a gas supply part 9, a liquid supply part 11, and an injection valve 31. The differential pressure applying part 10 applies a differential pressure between one side (the first tank 3 side) and the other side (the second tank 5 side) of the element 33.

[0027] <Control Unit> The ultra-fine bubble liquid generator 1 includes a control unit 60, and is configured so that the differential pressure imparting unit 10 is controlled by a computer or the like. Specifically, based on the measured values ​​of the supply amount and flow rate of the liquid supplied to the first tank 3, the pressure inside the first tank 3, etc., the control unit 60 performs the opening and closing operations of the first on-off valve 47, the second on-off valve 53, the injection valve 31, etc., and controls the supply amount of the liquid and the pressure inside the first tank 3 to be preset values.

[0028] (2) Manufacturing method of ultra-fine bubble liquid U In the generation process for generating the ultra-fine bubble liquid U, first, gas is supplied from the gas supply unit 9 to the first tank 3 to fill the insides of the first tank 3 and the second tank 5 with the gas. Then, after closing the second on-off valve 53, the first on-off valve 47, and the injection valve 31, the second on-off valve 53 is opened to supply liquid (solvent) to the first tank 3. Thereafter, the second on-off valve 53 is closed and the first on-off valve 47 is opened to supply gas to the first tank 3. At this time, the gas is supplied so that the pressure inside the first tank 3 becomes a pressure (for example, 0.5 MPa) higher than atmospheric pressure by adjusting the opening and closing of the first on-off valve 47. As a result, the gas and liquid are pressurized and stored inside the first tank 3. Meanwhile, the pressure inside the second tank 5 is adjusted to be lower than the pressure inside the first tank 3 after pressurization.

[0029] When the injection valve 31 is opened in this state, the gas and liquid stored in the first tank 3 flow through the communication pipe 27 into the element 33 and are sprayed from the inside of the element 33 to the outside. At this time, the gas and liquid that flowed into the element 33 pass through the multiple pores of the element 33 and are sprayed to the outside of the element 33, and are stored in the second tank 5 as ultra-fine bubble-containing liquid U1 in which the gas-containing bubbles and the liquid are mixed. The ultra-fine bubble-containing liquid U1 can be taken out of the second tank 5 from the outlet 13 provided in the second tank 5 into the container C. After this, the surfactant S is added to the ultra-fine bubble-containing liquid U1 with a micropipette MP so that the concentration of the surfactant is 20 μmol / L to 70 μmol / L, to produce the ultra-fine bubble liquid U (see FIG. 1). When the surfactant S is a cationic surfactant of an ammonium salt, the cationic surfactant may be benzalkonium chloride. As a result, the surface of the ultra-fine bubbles is covered with the surfactant S, making it possible to store the ultra-fine bubbles for a long period of time.

[0030] The ultra-fine bubble liquid U contains bubbles with diameters on the order of nanometers (ultra-fine bubbles). The order of nanometers refers to a value in the range of 1 nm to 999 nm. The diameter of such bubbles can be adjusted, for example, by changing the pore size of the element 33. The pore size of the element 33 can be adjusted, for example, by changing the particle size of the ceramic material that constitutes the element 33 (for example, the particle size of alumina).

[0031] The ultrafine bubbles can be contained in various products, etc., in addition to at least one or more liquids selected from the group consisting of the above-mentioned water (pure water, ultrapure water, purified water, tap water), alcohol such as ethanol, and hydrogen peroxide solution. Examples of such products include cosmetics such as beauty essence, lotion, beauty pack, milky lotion, hair growth agent, hair growth agent, hair care product, body cleanser (cleansing, face wash, shampoo, body soap, etc.), perfume, fragrance, etc.; beverages, alcoholic beverages, seasonings, soups, retort foods (liquid foods, etc.), and foods such as supplements; water for injection, physiological saline, extracellular fluid replacement fluid, artificial colloid, artificial blood, blood transfusion, blood preparations, and buffer solutions (acetate buffer, phosphate buffer, citrate buffer, citrate phosphate buffer (McIlvaine buffer), borate buffer, tartrate buffer, Tris buffer, phosphate buffered saline, etc.). Examples of such products include medical supplies such as body washes (eye washes, nose washes, stomach washes, lung washes, intestinal washes, etc.), contact lens washes, eye drops, injection preparations, injections (DDS preparations, vaccines, low molecular weight drugs, medium molecular weight drugs, high molecular weight drugs, genetic drugs), nebulizer liquids, and liquids for liquid breathing; bio-products such as culture fluids (glucose-containing culture fluids, albumin-containing culture fluids, antibody-containing liquid culture fluids, vitamin-containing culture fluids, serum-containing culture fluids, plasma-containing culture fluids, etc.); and other products such as alcohols, organic solvents (hexane, acetone, gasoline, kerosene, diesel, and other hydrocarbons), and heavy water. Ultra-fine bubbles can be applied to such products by, for example, adding the ultra-fine bubble liquid U generated by the generation device 1 to the above-mentioned products, or by using the liquid supplied from the liquid supply unit 11 as the above-mentioned products. In the present disclosure, the ultra-fine bubble liquid U may refer to the liquid that is one of the above-mentioned products and contains ultra-fine bubbles.

[0032] (3) Evaluation method A method for measuring the concentration of ultra-fine bubble liquid will be described below. 1. Pure water (2 ml) is pressurized with gas (0.5 MPa) into the micropores of a ceramic porous body to generate microbubbles to obtain a solution (UFB water). 2. UFB water was placed in a beaker and sterilized by UV irradiation to prevent an increase in particle concentration due to bacterial growth. 3. 35 ml of the above UFB water was placed in a glass vial, and a surfactant was added using a micropipette. 4. After the addition, the mixture was stirred at 60 rpm for 1 minute and then allowed to stand for 1 hour in an environment at room temperature of 25°C and humidity of 50%. 5. UFB concentration was measured using NanoSight®. 6. The sample was left to stand in an environment with a room temperature of 25°C and a humidity of 50%, and the nanosites were measured after a given period of time.

[0033] (Equipment used) NanoSight: NanoSight NS-300 Purpose: A device to detect the particle size and particle concentration of nanoparticles in liquid Principle: A device that detects the concentration and diameter of nanoparticles in liquid using nanoparticle tracking analysis that applies laser diffraction. Measurement conditions: Frequency: 405 nm, Camera Level: 15, Number of captures: 5, Capture duration: 60, Detection Threshold: 4

[0034] (How to generate ultra-fine bubbles) Porous ceramic body (material: alumina, silica) Pore diameter of porous body: 1500 nm, porosity: 31% Generates 2-5ml of pure water per pass. Gas pressure applied: 0.5MPa -Microscopic bubbles were generated by pressurizing gas and water through the micropores.

[0035] (Glass vial) Violamo screw cap vial Capacity: 30ml (full: 40ml) Glass: Borosilicate glass-1 (JR-1), thickness: 1.3 mm (bottom thickness: 1.7 mm) Cap: PP (top thickness: 2mm) Packing: PP high sheet (PP, PE), thickness 1mm Glass outer diameter: 32mm, inner diameter: 29.4mm

[0036] (Micropipette) ·Micropipette (smart) Capacity: (μL): 100~1000 Minimum variable volume (μL): 0.1 (UV sterilization (sterilizer)) Model number: FV-209B

[0037] (4) Surfactant selection: evaluation of functional groups (Overview / Purpose) In order to verify the types of surfactants that can be applied to UFB, various surfactants were added to UFB water and the change in UFB concentration over time was evaluated. The results are shown in Table 1. [Table 1] According to Table 1, it was found that only cationic lauryl trimethyl ammonium chloride could be retained for more than five times longer than other surfactants. In Comparative Examples 2 to 11 in Table 1, surfactants were added by weight, and the weights actually added are shown in Table 2. In the early stage of the change over time, UFBs below the lower limit of measurement of the analyzer may associate and the number density may increase. [Table 2] Figure 2 is a graph showing the results of Table 1. Figure 2 shows that Comparative Examples 10 and 11 show higher retention rates than the other Comparative Examples.

[0038] (5) Evaluation of cationic surfactants (Overview / Purpose) When applying surfactants to UFB, in order to verify the optimal type of cationic surfactant, various surfactants were added to UFB water and the change in UFB concentration over time was evaluated. As a result, as shown in Table 3, it was confirmed that lauryltrimethylammonium chloride, cetyltrimethylammonium chloride, and benzalkonium chloride were able to retain more than 50% of UFB even after three months. Among these, it was confirmed that when 40 μmol / L (represented as μM in Table 3) of benzalkonium chloride was added, more than 90% of the UFB concentration was retained. [Table 3] In addition, benzethonium chloride is a solid, and there is concern that it may have poor dispersibility. It is expected that lauryltrimethylamine chloride and cetyltrimethylammonium chloride will reach extreme values ​​when the amount added is further increased, but increasing the amount added is a negative factor.

[0039] (6) Verification of UFB concentration and surfactant addition amount (Overview / Purpose) When applying surfactants to UFB, we found that benzalkonium chloride is optimal for producing an effect with a small amount. It is generally said that the amount of surfactant added depends on the total surface area of ​​the dispersion target. Therefore, we conducted verification with surfactants of different concentrations. As a result, as shown in Table 4, when benzalkonium chloride was added at 20.0 to 70.0 μmol / L (represented as μM in Table 4), it was confirmed that more than 50% of the UFB could be retained even after 3 months. Among them, when 40.0 μmol / L of benzalkonium chloride was added, it was confirmed that more than 90% of the UFB concentration was retained. In addition, since the UFB concentration did not increase rapidly even in low UFB concentration samples, it was found that benzalkonium chloride was not mismeasured due to aggregation or micelle formation. In Table 4, it was confirmed that the UFB concentration was maintained by setting the benzalkonium chloride concentration to 20 μmol / L to 70 μmol / L, but the lower limit concentration of benzalkonium chloride may be 30 μmol / L, and the upper limit concentration of benzalkonium chloride may be 60 μmol / L or 50 μmol / L. [Table 4] Figure 4 is a graph showing Example 2 in Table 4, and Figure 5 is a graph showing Example 3. Note that the low concentration range is at the lower limit of Nanosite's reliability range (1E+08 or less), so the measurement variability increases. In this case, it can be determined that there is a significant difference between 10 μM and other conditions, but the significant difference between 20 to 70 μM cannot be discussed (it cannot be determined which condition is the extreme value).

[0040] (7) Effects In past cases, the amount of additive was not stated or was added in large amounts, but in Examples 1 to 3, it was found that the addition of a very small amount was effective in improving UFB retention. This makes it possible to apply this to fields such as pharmaceuticals, where foreign matter is undesirable.

[0041] In addition, benzalkonium chloride, which was used in Examples 1 to 3, is a surfactant that is sometimes used in pharmaceuticals and is known to be safe in vivo. It was confirmed that benzalkonium chloride is effective regardless of the UFB concentration when the amount added is 20 μM or more.

[0042] Because the highly safe surfactant can be effective even with only minute additions, this technology can be applied in any field, expanding the possibilities for various UFB products.

[0043] (Other embodiments) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0044] In the above embodiment, pure water is used as the solvent, but ultrapure water, purified water, tap water, or other water may be used, and alcohol or the like may be used instead of water.

[0045] The ultra-fine bubble liquid generating device and generating method are not limited to the above embodiment, and various generating devices and generating methods can be adopted. [Explanation of symbols]

[0046] 1: Ultra-fine bubble liquid generator 3: First tank 5: Second tank 9: Gas supply section 10: Differential pressure application section 11: Liquid supply section 13: Liquid outlet section 15: Side wall 17: Gas inlet 19: Upper section 21: Liquid inlet 23: Bottom section 25: Liquid supply port 27: Connecting pipe 29: First pressure sensor 31: Injection valve 33: Element 37: Side wall 39: Liquid outlet 41: Second pressure sensor 43: Gas cylinder 45: First pipe 47: First on-off valve 49: Third pressure sensor 51: Second pipe 53: Second on-off valve 55: Third pipe 57: Third on-off valve 60: Control section 70: First region

Claims

1. An ultra-fine bubble liquid containing ultra-fine bubbles and a surfactant in a solvent, The concentration of the surfactant is 20 μmol / L to 70 μmol / L; The surfactant is an ammonium salt cationic surfactant, The ultra-fine bubble liquid, wherein the cationic surfactant is benzalkonium chloride.

2. A step of producing an ultra-fine bubble-containing liquid by generating ultra-fine bubbles in a solvent; and adding the surfactant to the ultra-fine bubble-containing liquid so that the surfactant concentration becomes 20 μmol / L to 70 μmol / L to produce an ultra-fine bubble liquid, The surfactant is an ammonium salt cationic surfactant, The method for producing ultra-fine bubble liquid, wherein the cationic surfactant is benzalkonium chloride.

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