Method and apparatus for producing free iodine, and sterilization method.

Abstract

This method produces water containing free iodine, which can be used to suppress slime and fouling, without the use of an oxidizing agent. [Solution] By irradiating water containing iodide, such as an aqueous potassium iodide solution (iodide-containing water), with ultrasonic waves using an ultrasonic transducer 31, free iodine is generated in the iodide-containing water.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for generating free iodine used for suppressing the generation of slime and fouling in various devices through which water flows, and a sterilization method using free iodine.

Background Art

[0002] In various devices through which water flows, such as reverse osmosis membrane devices and electrodialysis (EDI) devices, slime and fouling derived from live bacteria may occur, and clogging of the membranes inside the devices may occur. In order to prevent the generation of slime and fouling, an oxidizing bactericide is added to the water to be treated supplied to those devices. In order to reduce the influence on members such as reverse osmosis membranes, bromine, iodine, etc. are often used as the oxidizing bactericide. However, when using bromine alone or iodine alone, there are problems that its handling is not easy and polyethylene or soft polyvinyl chloride cannot be used for the piping. Therefore, a method is used in which bromide or iodide is added to the water to be treated and then an oxidizing agent such as hypochlorous acid or hypochlorite is also added to liberate bromine or iodine in the water to be treated. Since oxidizing agents such as hypochlorous acid have an adverse effect on members such as reverse osmosis membranes, care must be taken with the amount added.

[0003] Patent Document 1 discloses adding at least one of a chlorine-based oxidizing agent and a bromine-based oxidizing agent to the water to be treated containing iodide ions such that the amount of free chlorine and the amount of free bromine are 1 mol or less per 1 mol of the amount of iodide ions in the water to be treated. According to the technique disclosed in Patent Document 1, since the added chlorine-based oxidizing agent and bromine-based oxidizing agent are consumed to oxidize iodide ions to generate free iodine, the concentrations of the chlorine-based oxidizing agent and the bromine-based oxidizing agent in the water to be treated after free iodine is generated are small, and the generation of slime and fouling can be prevented by free iodine without deteriorating reverse osmosis membranes or the like.

Prior Art Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-135970 [Overview of the project] [Problems that the invention aims to solve]

[0005] When generating free iodine using the method described in Patent Document 1, it is necessary to add an oxidizing agent such as sodium hypochlorite, which requires handling such an oxidizing agent and controlling the amount of oxidizing agent added. Furthermore, since the amount of bromide and iodide to be added is determined while considering the amount of oxidizing agent added, there is a tendency to use excessive amounts of bromide and iodide, which may lead to a greater burden on the environment.

[0006] The object of the present invention is to provide a method and apparatus for producing free iodine that can produce free iodine without using an oxidizing agent, and a sterilization method that applies such a production method. [Means for solving the problem]

[0007] One aspect of the present invention is a method for generating free iodine, which involves irradiating iodide-containing water, with ultrasonic waves to generate free iodine within the iodide-containing water.

[0008] An apparatus for generating free iodine according to one aspect of the present invention comprises an ultrasonic transducer and an oscillation circuit for driving the ultrasonic transducer, and generates free iodine in iodide-containing water, which is water containing iodide, by irradiating it with ultrasonic waves generated by the ultrasonic transducer.

[0009] A sterilization apparatus according to one aspect of the present invention is a method for sterilizing water treatment equipment that treats water to be treated, comprising irradiating iodide-containing water, which is water containing iodide, with ultrasonic waves to generate free iodine in the iodide-containing water, and passing the iodide-containing water containing the generated free iodine through the water treatment equipment. [Effects of the Invention]

[0010] According to the present invention, water containing free iodine, which can be used for purposes such as suppressing slime and fouling, can be produced without the use of an oxidizing agent. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows a free iodine production apparatus according to one embodiment of the present invention. [Figure 2] This figure shows another example of a free iodine production apparatus. [Figure 3] This figure shows yet another example of a free iodine production apparatus. [Figure 4] This figure shows yet another example of a free iodine production apparatus. [Modes for carrying out the invention]

[0012] Next, embodiments for carrying out the present invention will be described with reference to the drawings.

[0013] First, an overview of the method for producing free iodine based on the present invention will be explained. The present invention utilizes the phenomenon in which elemental iodine is released into iodide-containing water (i.e., iodide-containing water) by irradiating the water with ultrasound. According to the findings obtained by the inventors, iodide ions (I - When ultrasound is irradiated onto water containing ), hydrogen radicals (H·) and hydroxyl radicals (OH·) are generated from water (H₂O) as shown in equation (1), and these hydroxyl radicals are converted into iodide ions (I -) reacts with [it] to oxidize iodide ions as shown in formula (2) to generate iodine radicals (I·). When two iodine radicals associate, free iodine (I2) is generated as shown in formula (3). Therefore, the water after ultrasonic irradiation contains free iodine.

[0014] H2O → H· + OH· (1) I - + OH· → I· + OH - (2) 2I· → I2 (3)

[0015] As is well known, in water, an equilibrium as shown in formula (4) is established among free iodine, iodide ions, and triiodide ions (I3 - ).

[0016] I2 + I - ⇔ I3 - (4)

[0017] As the iodide used for the generation of free iodine, water-soluble iodides such as potassium iodide, sodium iodide, etc. can be used. The concentration of iodide in the iodide-containing water before ultrasonic irradiation is not particularly limited as long as it is within the solubility range of iodide in water. Expressed as the concentration of iodide ions, for example, it is preferably 1 mg / L or more and 50 g / L or less, more preferably 1 mg / L or more and 10 g / L or less, and even more preferably 10 mg / L or more and 1 g / L or less.

[0018] In this specification, ultrasound is not limited to sound waves outside the audible range, but refers to ultrasound in the industrial sense, that is, sound waves not intended for listening. In practice, since it is necessary to promote the radical generation reaction described in formula (1), in the present invention, the frequency of the ultrasound is preferably 1 kHz or higher, more preferably 20 kHz or higher, and even more preferably 40 kHz or higher. The upper limit of the usable ultrasound frequency in the present invention is, for example, 1000 kHz. Ultrasound can be generated, for example, by electrically exciting an ultrasonic transducer. Any configuration can be used to irradiate iodide-containing water, which is water containing iodide, with ultrasound. Examples include a submersible type configuration in which the ultrasonic transducer is placed inside a tank that stores the iodide-containing water; a configuration in which the ultrasonic transducer is attached to the outer wall of the tank and ultrasound is irradiated to the iodide-containing water inside the tank via the tank wall; a configuration using a horn-type ultrasonic transducer in which the horn portion of the ultrasonic transducer is immersed in the water inside the tank and ultrasound is irradiated to the iodide-containing water inside the tank; a configuration in which the ultrasonic transducer is attached to the outer surface of a pipe through which the iodide-containing water flows and ultrasound is irradiated to the iodide-containing water inside the pipe via the pipe wall; and a configuration in which the ultrasonic transducer is placed inside the pipe. The irradiation time when irradiating iodide-containing water with ultrasound is not particularly limited, but it is preferable to irradiate for at least 1 minute, more preferably at least 5 minutes, and even more preferably at least 15 minutes.

[0019] Next, the use of the water that has come to contain free iodine by the above production method will be described. In water treatment equipment that performs some kind of water treatment on the water to be treated, such as a reverse osmosis membrane device, an EDI device, a filtration membrane device, or an ion exchange device, by including free iodine in the water to be treated that should be supplied to the water treatment equipment, the inside of the water treatment equipment is sterilized, and the generation of slime and fouling inside the equipment is prevented. When the water treatment equipment includes a membrane such as a reverse osmosis membrane or an ion exchange membrane, the effect of suppressing slime and fouling by free iodine is great. Therefore, in the water to be treated supplied to the water treatment equipment, free iodine generated by the above production method can be included. In this case, an iodide may be added to the water to be treated and then the water to be treated may be irradiated with ultrasonic waves so that free iodine is generated in the water to be treated. Alternatively, the water containing iodide may be irradiated with ultrasonic waves so that the water contains free iodine, and then the water containing free iodine may be mixed with the water to be treated so that the water to be treated contains free iodine.

[0020] Rather than making the water to be treated, which is the water to be processed in the water treatment equipment, contain free iodine, the water used for cleaning or sterilizing the water treatment equipment may contain free iodine. In that case, after irradiating the water containing iodide with ultrasonic waves to generate free iodine, the water may be supplied to the water treatment equipment as cleaning water or the like and passed through. The inside of the water treatment equipment is sterilized by the free iodine contained in the water, and if slime and fouling have occurred, they are removed.

[0021] Figure 1 shows an example of the configuration of a generator that produces free iodine so that the water to be treated supplied to the water treatment equipment contains free iodine. Here, the water treatment equipment is assumed to be a reverse osmosis membrane device 10 equipped with a reverse osmosis membrane 11. A water treatment pipe 12 is provided to supply the water to be treated to the reverse osmosis membrane device 10, and a pump 13 is provided in the water treatment pipe 12 to pressurize the water to be treated toward the reverse osmosis membrane device 10. In the reverse osmosis membrane device 10, reverse osmosis treatment is performed on the water to be treated, and as a result, the reverse osmosis membrane device 10 discharges permeate water that has permeated through the reverse osmosis membrane 11 and concentrated water that has not permeated through the reverse osmosis membrane 11. If the water to be treated contains oxidizing components such as hypochlorous acid, it is preferable to decompose and remove the oxidizing components in advance by adding a reducing agent or the like.

[0022] In the generation apparatus shown in Figure 1, a solution tank 21 is provided for storing an aqueous solution of iodide, specifically potassium iodide, and a solution pipe 22 is provided for discharging the potassium iodide aqueous solution from the solution tank 21. The end of this solution pipe 22 is connected to the water to be treated pipe 12 at point A. Point A is located upstream of the pump 13 in the water to be treated pipe 12. Because the solution pipe 22 is connected to the water to be treated pipe 12, the potassium iodide aqueous solution is added to the water to be treated as iodide-containing water. A submersible ultrasonic transducer 31 is placed inside the solution tank 21, and this ultrasonic transducer 31 is electrically driven by an oscillation circuit 32. As a result, ultrasonic waves are irradiated onto the potassium iodide aqueous solution in the solution tank 21, and free iodine is generated according to the above equations (1) to (3). In the configuration shown in Figure 1, the potassium iodide aqueous solution containing free iodine is mixed with the water to be treated at point A, so the water to be treated supplied to the reverse osmosis membrane apparatus 10 also contains free iodine. Instead of using a submersible ultrasonic transducer 31, the ultrasonic transducer 31 may be attached to the outer wall of the solution tank 21, and ultrasonic waves may be irradiated into the potassium iodide aqueous solution inside the solution tank 21 via the wall of the solution tank 21. The potassium iodide aqueous solution flowing through the solution piping 22 contains free iodine, but as will become clear from the examples described later, its concentration is less than a few mg / L, so polyethylene or flexible polyvinyl chloride can be used for the solution piping 22.

[0023] Figure 2 shows another example of a generating apparatus. The generating apparatus shown in Figure 2 is similar to the generating apparatus shown in Figure 1, but differs from the one shown in Figure 1 in that an ultrasonic transducer 31 is attached to the outer surface of the solution pipe 22, and ultrasonic waves are irradiated onto the potassium iodide aqueous solution flowing through the solution pipe 22 via the pipe wall of the solution pipe 22.

[0024] Figure 3 shows yet another example of the generating apparatus. The generating apparatus shown in Figure 3 is similar to the generating apparatus shown in Figure 1, but differs from the one shown in Figure 1 in that an ultrasonic transducer 31 is attached to the outer surface of the treated water piping 12 at a position between point A and the primary side (i.e., inlet) of the pump 13, and ultrasonic waves are irradiated through the pipe wall of the treated water piping 12 to the treated water to which potassium iodide aqueous solution has been added.

[0025] Figure 4 shows yet another example of the generating apparatus. The generating apparatus shown in Figure 4 is similar to the generating apparatus shown in Figure 1, but differs from the one shown in Figure 1 in that an ultrasonic transducer 31 is attached to the outer surface of the treated water piping 12 at a position between the secondary side (i.e. outlet) of the pump 13 and the inlet of the reverse osmosis membrane apparatus 10, and ultrasonic waves are irradiated through the pipe wall of the treated water piping 12 to the treated water to which potassium iodide aqueous solution has been added. [Examples]

[0026] The present invention will be described in more detail below with reference to examples and comparative examples.

[0027] [Example 1] The generation of free iodine in potassium iodide aqueous solutions by irradiation with ultrasound was investigated. Potassium iodide aqueous solutions with concentrations of 10 mg / L, 100 mg / L, and 1000 mg / L were prepared. An ultrasonic cleaner with a water tank was prepared, a beaker was placed in the water tank of the ultrasonic cleaner, 200 mL of the prepared potassium iodide aqueous solution was poured into the beaker, and the ultrasonic cleaner was operated using the water tank as a water bath to irradiate the potassium iodide aqueous solution in the beaker with ultrasound. The ultrasonic frequency was 40 kHz and the irradiation output was 120 W. In addition, the temperature of the potassium iodide aqueous solution in the beaker was maintained at 25°C by circulating 25°C water in the water tank of the ultrasonic cleaner. The concentration of free iodine (I2) in the potassium iodide aqueous solution in the beaker was measured at predetermined irradiation times. The results are shown in Table 1. The detection limit of the free iodine concentration was 0.07 mg / L.

[0028] [Table 1]

[0029] As shown in Table 1, it was confirmed that free iodine was generated in an aqueous potassium iodide solution with a potassium iodide concentration of 100 mg / L after 8 minutes of ultrasonic irradiation. Higher potassium iodide concentrations resulted in the generation of free iodine with shorter ultrasonic irradiation times, and higher concentrations of free iodine were generated for the same irradiation time.

[0030] [Comparative Example 1] Since iodine is classified as a halogen, we investigated whether free bromine is generated when water containing bromide is irradiated with ultrasound, using bromine, which is also a halogen, as the target. Sodium bromide aqueous solutions with concentrations of 1000 mg / L and 2000 mg / L were prepared. Then, 200 mL of the prepared sodium bromide aqueous solution was poured into a beaker and irradiated with ultrasound for 60 minutes using the same apparatus as in Example 1 and under the same conditions as in Example 1. When the free bromine in the sodium bromide aqueous solution was quantified before, during, and after ultrasound irradiation, the concentration of free bromine was below the detection limit (0.04 mg-Br2 / L) in both the 1000 mg / L and 2000 mg / L sodium bromide concentrations, and no free bromine was detected.

[0031] [Comparative Example 2] Since iodine is classified as a halogen, we investigated whether free chlorine is generated when water containing chloride is irradiated with ultrasound, using chlorine, which is also a halogen, as the target. Sodium chloride aqueous solutions with sodium chloride concentrations of 1000 mg / L and 2000 mg / L were prepared. Then, 200 mL of the prepared sodium chloride aqueous solution was poured into a beaker and irradiated with ultrasound for 45 minutes using the same apparatus as in Example 1 and under the same conditions as in Example 1. When the free chlorine in the sodium chloride aqueous solution was quantified before, during, and after ultrasound irradiation, the concentration of free chlorine was below the detection limit (0.02 mg-Cl2 / L) in both the 1000 mg / L and 2000 mg / L sodium chloride concentrations, and no free chlorine was detected. [Explanation of Symbols]

[0032] 10 Reverse osmosis membrane equipment 11 Reverse osmosis membrane 12. Piping for treated water 13 pumps 21 Solution Tanks 22 Solution piping 31. Ultrasonic transducer 32 Oscillator Circuit

Claims

1. A method for generating free iodine, comprising irradiating iodide-containing water, which is water containing iodide, with ultrasound to generate free iodine in the iodide-containing water.

2. The method for generating iodide according to claim 1, wherein the iodide-containing water is water obtained by adding iodide to water to be treated which is to be supplied to a water treatment device for water treatment, and the water to be treated which contains the generated free iodine is supplied to the water treatment device.

3. The method for generating iodide according to claim 1, comprising adding the iodide-containing water containing the generated free iodine to the water to be treated which is to be supplied to a water treatment device, and then supplying the water to be treated to the water treatment device.

4. The generation method according to any one of claims 1 to 3, wherein the frequency of the ultrasonic waves is 1 kHz or higher.

5. The method for producing according to claim 4, wherein the iodide is potassium iodide, and the concentration of potassium iodide in the iodide-containing water is 10 mg / L or more.

6. Ultrasonic transducer and An oscillation circuit for driving the ultrasonic transducer, Equipped with, A free iodine generation apparatus that generates free iodine in iodide-containing water, which is water containing iodide, by irradiating it with ultrasonic waves generated by the ultrasonic transducer.

7. The generating apparatus according to claim 6, wherein ultrasonic waves are irradiated onto the iodide-containing water in at least one of the tank for storing the iodide-containing water and the piping through which the iodide-containing water flows.

8. A method for sterilizing water treatment equipment that treats water to be treated, Ultrasound is irradiated onto iodide-containing water, which is water containing iodide, to generate free iodine in the iodide-containing water. A sterilization method comprising passing the iodide-containing water, which contains the generated free iodine, through the water treatment equipment.

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