JP2013027859A - Method for sterilizing seawater and sterilizing component generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for sterilizing seawater capable of effectively sterilizing seawater by electrolyzing the seawater so that a peak top of an ultraviolet spectrum after electrolyzing is generated in a specified range and by generating sterilizing components such as ozone in the seawater.SOLUTION: In the method for sterilizing the seawater, the seawater is electrolyzed so that a first peak top of an ultraviolet absorption spectrum of the seawater after electrolyzing is generated in a wavelength of 245-275 nm and a second peak top is generated in a wavelength of 310-340 nm, and thus, the sterilizing component such as ozone is generated in the seawater. The seawater is preferably electrolyzed so that a third peak top of the ultraviolet absorption spectrum of the seawater after electrolyzing is generated in the wavelength of 280-305 nm, and that absorbance in the third peak top is lower than the absorbance in the first peak top and the second peak top.

Description

  The present invention relates to a seawater sterilization method for generating a sterilizing component such as ozone in seawater, and a sterilizing component generator.

  Conventionally, seawater has been used in large quantities in food and drink raw materials, processing water, washing water, storage / transportation water, aquaculture water, etc., and most of them use the collected seawater as it is. However, seawater generally contains various germs such as various pathogens. In particular, when ballast water is loaded to stabilize a ship by a cargo ship, aquatic organisms contained in the ballast water affect the ecosystem when discharged to the outside of the ship.

  Non-Patent Document 1 describes the trend of conventions on ballast water sterilization in various countries and companies, and describes that heat treatment, filtration, physical separation, ultraviolet irradiation, etc. can be applied to ballast water. Has been. Non-Patent Document 2 describes a ballast water purification system that combines agglomeration technology and magnetic separation technology. Further, Non-Patent Document 3 describes a mechanism for sterilizing seawater using an ultraviolet irradiation device.

  However, sterilization of ballast water by filtration, physical flocculation, and ultraviolet light irradiation has the advantage that post-treatment of filtered seawater is not necessary, but facilities for performing these treatments are large-scale. The problem that the weight also increases arises.

  Further, as a seawater sterilization method, for example, a method of generating hypochlorous acid by electrolysis of seawater and using effective chlorine contained in hypochlorous acid is known. Seawater is usually weakly alkaline, and in the weakly alkaline region, the residual rate of effective chlorine ions, which are effective sterilizing species in hypochlorous acid, decreases, so high concentration hypochlorous acid of about 100 to 1000 ppm is generated. Without effective sterilization.

  Therefore, when seawater such as ballast water is sterilized, there is a problem that the ecological environment is changed by hypochlorous acid having strong alkalinity. In order to prevent changes in the ecological environment, a large amount of ballast water neutralizer and neutralizer are necessary, which is economically burdensome.

  Non-Patent Documents 4 and 5 describe techniques for electrolyzing seawater using electrodes to sterilize.

When a disinfectant such as sodium hypochlorite (NaClO) or hydrogen peroxide (H ₂ O ₂ ) is used, these disinfectants are expensive, which is an economic burden. Moreover, since the said disinfectant may not be allowed to flow into the environment as it is, it becomes necessary to perform post-treatment. Even if seawater is directly sterilized by electrolysis, the sterilized seawater must be treated as it is because hypochlorous acid is generated. Furthermore, relatively large electric power is required to sterilize seawater, and an economic effect cannot be obtained.

K. Yasui, “Development Trend of Ballast Water Treatment Technology Using Active Substances”, MBRIJ Ann. Rep. 2007, p.76-82. Mitsubishi Heavy Industries website, “Agglomeration magnetic separation method“ Hitachi ballast water purification system ”has received IMO basic approval and has started onboard testing”, Internet <URL: http://www.mhi.co.jp/news/story/ 080407.html> "Application example of medium-scale UV sterilizer", Internet <URL: http://www.senlights.co.jp/jirei/sakkinjirei.htm> Jong-Chul Park et al., Applied Environmental Microbiology, Apr. 2003, 2003, p.2405-2408 "6th Research Meeting on Slightly Acidic Electrolyzed Water", Abstracts of Lectures, p6

  The present invention has been made in view of such a problem, and electrolyzes seawater so that the peak top of the ultraviolet spectrum after electrolysis occurs in a specific range, and efficiently generates seawater by generating sterilizing components in the seawater. Is to provide a method for reforming seawater that can be sterilized.

  In order to solve the above-mentioned problems, the present inventors have intensively studied a sterilization method in seawater, particularly in ballast water. As a result, it was found that seawater can be effectively sterilized by bringing seawater into contact with the electrode and electrolyzing the seawater so that the peak top of the ultraviolet spectrum after electrolysis occurs in a specific range of wavelengths, thereby completing the present invention. It was.

  That is, the first subject of the present invention is that the first peak top of the ultraviolet absorption spectrum of seawater after electrolysis occurs between wavelengths 245 to 275 nm and the second peak top occurs between wavelengths 310 to 340 nm. This is a seawater sterilization method characterized in that a sterilizing component is generated in seawater by electrolyzing seawater.

  According to such a configuration, the sterilizing component generated by the electrode is dissolved in seawater, and the number of viable bacteria present in the seawater can be easily reduced by the strong oxidizing power of the sterilizing component. In addition, the sterilization method of the present invention can suppress the generation of hypochlorous acid that may change the ecological environment, and can perform sterilization more efficiently at a low voltage.

  Further, in the seawater sterilization method, the third peak top of the ultraviolet absorption spectrum of the seawater after electrolysis occurs between wavelengths 280 to 305 nm, and the absorbance at the third peak top is the first peak top and the second peak absorbance. It is preferable to electrolyze the seawater so that the absorbance is lower than the respective absorbances at the peak top.

  According to such a configuration, it can be said that the sterilizing component is surely generated by electrolysis, and seawater in which the number of viable bacteria is reduced by the strong oxidizing power of the sterilizing component can be obtained.

  According to such a configuration, the number of viable bacteria in seawater can be more safely reduced without generating hypochlorite ions in seawater.

  In the seawater sterilization method, it is preferable that at least one of the anode and the cathode is boron-doped diamond.

  According to such a configuration, the electrode is hardly consumed by elution by electrolysis, and more sterilizing components can be generated.

  In the sterilizing component generator, it is preferable that the electrode is any one selected from the group consisting of platinum, iridium, palladium, osmium, rhodium, and ruthenium, at least one of the anode and the cathode.

  According to such a configuration, the number of viable bacteria present in the seawater can be easily reduced by the sterilizing components generated by these electrodes and dissolved in the seawater.

  Further, the second subject of the present invention is that the first peak top of the ultraviolet absorption spectrum of seawater after electrolysis occurs between wavelengths 245 to 275 nm and the second peak top occurs between wavelengths 310 to 340 nm. A sterilizing component generator is characterized in that a sterilizing component is generated in seawater by electrolyzing seawater.

  According to such a sterilizing component generator, the sterilizing component generated by the diamond electrode and dissolved in the seawater has a strong oxidizing power, so that the number of viable bacteria existing in the seawater is easily reduced. be able to. In addition, the sterilizing component generator of the present invention can be significantly reduced in voltage and size as compared with conventional seawater sterilizers. Although the first peak top occurs between wavelengths 245 to 275 nm and the second peak top is unknown as a bactericidal component occurring between wavelengths 310 to 340 nm, the first peak top is an ultraviolet absorption spectrum of ozone. It is inferred that it is a bactericidal component that contains or is associated with ozone.

  According to the present invention, the electrolysis of seawater so that the peak top of the ultraviolet spectrum after electrolysis occurs in a specific range of wavelengths, and the sterilizing component is generated in the seawater by electrolysis. Bacteria present in seawater can be sterilized easily and efficiently. Moreover, generation | occurrence | production of the hypochlorous acid which has a bad influence on an ecological environment can be suppressed, and it can disinfect preferentially by the oxidizing power of a disinfection component. And since the sterilization component generator of this invention can sterilize with a low voltage, it can achieve size reduction.

It is a schematic diagram of the sterilization component generator of seawater concerning this embodiment. It is a figure which shows the pH measured value at the time of electrolyzing a 3.5 wt% NaCl aqueous solution and artificial seawater using the electrode concerning this embodiment. It is an IV characteristic at the time of using a conductive diamond electrode for electrolysis of artificial seawater. It is a figure which shows the ultraviolet absorption spectrum at the time of electrolyzing artificial seawater and soft water using the electrode concerning this embodiment. It is a figure which shows the ultraviolet absorption spectrum of the sodium hypochlorite solution measured using the ultraviolet-ray-absorption-spectrum measuring apparatus concerning this embodiment. It is a figure which shows the ultraviolet absorption spectrum at the time of electrolyzing a NaCl solution using the electrode concerning this embodiment. It is a figure which shows the ultraviolet absorption spectrum in the initial stage at the time of electrolyzing artificial seawater using the electrode concerning this embodiment. It is a figure which shows the ultraviolet absorption spectrum in the initial stage at the time of electrolyzing artificial seawater using the platinum electrode concerning this embodiment. It is a figure which shows the ultraviolet absorption spectrum for every time at the time of electrolyzing artificial seawater using the electrode concerning this embodiment. It is a figure which shows the light absorbency change for every time in 255 nm and 290 nm at the time of electrolyzing artificial seawater using the electrode concerning this embodiment.

  In the seawater sterilization method according to the present embodiment, the first peak top of the ultraviolet absorption spectrum of seawater after electrolysis occurs between wavelengths 245 to 275 nm, and the second peak top occurs between wavelengths 310 to 340 nm. It is characterized in that a sterilizing component is generated in seawater by electrolyzing seawater.

  Conductive diamond is known for its wide potential window. For example, it has been found that when cyclic voltammetry is measured using a standard calomel electrode, it has a relatively wide potential window of −2 to 2V. In this way, conductive diamond has a wide potential window, is covalent, and the atoms on the outermost surface of the electrode are firmly bonded to the electrode base material, so it does not react with components in the solution. . Therefore, if the electrode material is diamond, it is suitable as an electrode material used for sterilization because it can efficiently generate sterilizing components such as ozone and the electrode wear is small.

When fresh water is electrolyzed using this diamond electrode as an anode, oxygen (O ₂ ) and ozone (O ₃ ) are generated. Since active oxygen and ozone immediately after generation have strong oxidizing power, bacteria are oxidized and sterilized by oxygen and ozone.

On the other hand, even when seawater is electrolyzed, since the first ultraviolet absorption peak wavelength is close to 260 nm, which is the absorption wavelength of ozone water in fresh water, and has a bactericidal effect, there is a high possibility that ozone is generated. However, it differs from fresh water electrolysis in that there is a second ultraviolet absorption band between wavelengths 310-340 nm. It should be noted that oxygen (O ₂ ) and ozone (O ₃ ) are not necessarily stable because there are more types of ions in seawater than fresh water. For example, it is conceivable that halogens and sulfate ions such as chlorine, bromine and iodine react by electrolysis to generate new sterilizing components. It is also conceivable that the ozone generated and these combine to produce a new sterilizing component.

  In any case, it is clear from the experimental results that the number of bacteria after electrolysis has been drastically reduced. Further, according to the present invention, since there is almost no absorption by hypochlorite ions in the ultraviolet absorption spectrum, it is considered that almost no hypochlorite ions are generated.

  Further, it is known that ozone obtained by electrolyzing fresh water and dissolved in the fresh water selectively oxidizes organic substances contained in the fresh water. Ozone dissolved in fresh water decomposes and disappears by oxidizing organic substances. Furthermore, even if ozone is left as it is for a certain time, it is decomposed into harmless oxygen.

  In addition, ozone can be actively decomposed into oxygen by contacting with a catalyst such as activated carbon. By doing in this way, safety can be secured by a simple method. If the seawater electrolysis product is ozone, it is considered that it has an organic substance oxidation function and can ensure safety.

  Furthermore, when seawater is electrolyzed, sodium chloride (NaCl) contained in seawater is decomposed. As a result, hypochlorite ions are generated, and the hypochlorite ions have the same sterilizing power as ozone, so that the sterilizing effect of seawater can be increased synergistically. However, hypochlorite ions are weakly alkaline, so when chlorine ions change to hypochlorite ions, the balance between sodium ions and chlorine ions in seawater is lost, and weak acids are weak against sodium ions, which are strong alkalis. Since the hypochlorite ion is balanced, the entire solution shows alkalinity, which adversely affects the ecological environment.

  Therefore, the present inventors have intensively studied the correlation between the voltage applied to the conductive diamond electrode brought into contact with seawater and the generation of hypochlorite ions. As a result, when electrolysis of seawater is performed with a conductive diamond electrode, hypochlorite ions are hardly generated if applied at a value near the voltage at which electrolysis starts, and has a peak top in the same ultraviolet absorption vector as ozone. It was found that bactericidal components were generated.

  In other words, when sterilization is performed on normal soft water using a conductive diamond electrode, the electrolysis starting voltage of soft water is about 5 V, so that a potential of 5 V or more is applied to an electrode having conductive diamond as an anode. Electrolytic ozone water is generated. Similarly, since the electrolysis start voltage of artificial seawater is about 3 V, in artificial seawater, a sterilizing component that is considered to be ozone is generated in seawater by applying a potential of 3 V or more to an electrode having conductive diamond as an anode. Can be made.

  In addition, the above-described sterilizing effect of seawater is not limited to the conductive diamond, and can be obtained in the same manner even with a metal having a relatively wide potential window due to a platinum group element.

  Then, the inventors set the seawater so that the first peak top of the ultraviolet absorption spectrum of the seawater after electrolysis occurs between wavelengths 245 to 275 nm and the second peak top occurs between wavelengths 310 to 340 nm. It was found that when electrolyzed, seawater can be sterilized by a sterilizing component that is considered to be ozone generated effectively without generating a large amount of sodium hypochlorite. If seawater is electrolyzed so that the absorbance at the peak top in the vicinity of 290 nm derived from hypochlorite ions is higher than the absorbance at the peak top, a large amount of hypochlorite ions are generated. That is bad for the ecological environment.

  Further, the third peak top of the ultraviolet absorption spectrum of seawater after electrolysis occurs between wavelengths 280 to 305 nm, and the absorbance at the third peak top is greater than the absorbance at the first peak top and the second peak top. More preferably, the seawater is electrolyzed so as to be low. If seawater is electrolyzed under the above conditions, generation of hypochlorite ions can be further suppressed.

  Moreover, it is preferable that the 3rd peak top of the ultraviolet absorption spectrum of the said seawater exists between wavelengths 280-305 nm, and the light absorbency in a 3rd peak top is lower than the light absorbency in a 1st peak top and a 2nd peak top. . The third peak top is an absorption peak derived from hypochlorite ions. If the third peak top is lower than the first and second peak tops, almost no hypochlorite ions are generated. It can be said.

  Thus, the sterilization component considered to be ozone is preferentially generated by electrolyzing seawater so that the peak top of the ultraviolet spectrum after electrolysis occurs in a specific range. And since the hypochlorite ion produced | generated from the chlorine ion contained in seawater hardly generate | occur | produces, the sterilization method excellent in the environmental aspect can be provided.

  The seawater is preferably ballast water. Ballast water is water used as a bottom load of a ship or as a heavy stone loaded on the ship bottom. This ballast water is discharged out of the ship instead of loading luggage at each port. At that time, there is a problem that aquatic organisms contained therein affect the ecosystem as an alien species. If the sterilization method of this invention is used, ballast water can be more effectively sterilized by the effect mentioned above.

  In the ozone generator according to the present embodiment, the first peak top of the ultraviolet absorption spectrum of seawater after electrolysis occurs between wavelengths 245 to 275 nm, and the second peak top occurs between wavelengths 310 to 340 nm. It is a device that generates sterilizing components in seawater by electrolyzing seawater.

  An embodiment of the present invention will be described below with reference to FIG.

  The sterilizing component generator of the present invention has a sterilizing tank 1 for storing seawater containing bacteria. The sterilization tank 1 may be provided with a stirring device that stirs seawater. Moreover, the sterilization tank 1 may be provided with a heater and a cooler.

  Furthermore, an RO membrane pump 3 is connected to the sterilization tank 1. An electrode 2 is provided at the other end of the RO membrane pump 3 through a filter 4. The electrode 2 may be housed in a branch pipe, and a plurality of the electrodes 2 may be arranged to process a large flow rate. Furthermore, an RO membrane (filter) 4 is connected to the other end of the electrode 2.

  That is, the raw water of seawater is separated by the RO membrane (filter) 4 and brought into contact with the electrode 2 while flowing the separated seawater to obtain electrolyzed seawater. Seawater brought into contact with the electrode 2 is transported to the sterilization layer 5 by the RO membrane pump 3.

  The RO membrane filter 4 may be a coarse filter according to the concentration of solid substances in seawater. Further, the sterilizing layer 5 may be the same as the sterilizing layer 1. The seawater brought into contact with the electrode 2 may be discharged after further mixing with an appropriate amount of untreated seawater in the sterilization layer 5, or may be discharged into the sea as it is without passing through the sterilization layer 5. .

  Although the installation location of the electrode 2 is not particularly limited, it is preferable that the electrode 2 be installed in the vicinity of the seawater flow path to sterilize the seawater. This is because the electrolysis efficiency increases in the vicinity of the electrode and at a location where the flow velocity is large.

  The seawater containing the sterilizing component considered to be ozone generated efficiently in this way is transported to the sterilizing layer 5 by the RO membrane pump 3, and the transported seawater is seawater by the sterilizing component such as ozone remaining in the sterilizing layer 5. Sterilization of continues.

  The electrode 2 is energized by a DC power source. As described above, when electrolysis is performed such that the first peak top of the ultraviolet absorption spectrum of seawater after electrolysis occurs between wavelengths 245 to 275 nm and the second peak top occurs between wavelengths 310 to 340 nm, It is possible to provide an environmentally superior sterilization method without generating more hypochlorous acid generated from chlorine contained in seawater.

  The electrode 2 is preferably composed of boron-doped diamond, at least one of the anode and the cathode, but more preferably composed of boron-doped diamond for both the anode and the cathode. This is because if the electrode material is a diamond electrode, it is possible to efficiently generate sterilizing components such as ozone, and the wear of the electrode is small.

  Such a boron-doped diamond electrode is obtained, for example, by using a semiconductor material such as a silicon wafer as a base material and forming a boron-doped diamond thin film on the surface of the wafer base material. As the boron-doped diamond electrode, it is possible to use a melted wafer or self-standing type conductive polycrystalline diamond deposited and synthesized in a plate shape without using a base material. Moreover, what was laminated | stacked on metal substrates, such as Nb, W, and Ti, can also be utilized.

  The boron-doped diamond thin film is provided with conductivity by doping a predetermined amount of boron during synthesis of the diamond thin film. In addition, it is preferable that the quantity of dope is 50-20,000 ppm with respect to the carbon content of a diamond thin film. If it is less than 50 ppm, ozone cannot be generated efficiently, and if it exceeds 20,000 ppm, the doping effect is saturated.

  The electrode 2 is preferably at least one of an anode or a cathode selected from the group consisting of platinum, iridium, palladium, osmium, rhodium, and ruthenium. When these platinum groups are used for electrodes, ozone can be generated preferentially. However, when these platinum groups are used, elution due to electrolysis may be caused and the electrode may be consumed.

  As the electrode according to the present invention, a plate-shaped electrode is usually used, but a plate having a network structure can be used. For example, it is possible to arrange a wire-like cathode with a diamond electrode on a flat plate with an electrolytic membrane therebetween, or a mesh-like cathode with a membrane electrode separated from a diamond electrode on a flat plate. Further, the number of electrodes is not particularly limited.

  Moreover, it is preferable that the temperature of the seawater sterilized is -4 to 35 degreeC, and it is more preferable that it is 0 to 25 degreeC. If it exceeds 35 ° C., for example, the solubility of ozone will decrease, the release of ozone into the air will increase, the ozone concentration will decrease, and the sterilization efficiency will decrease.

  On the other hand, if the temperature falls below the above temperature range, it becomes ice and cannot be fed. Seawater sterilized by the ozone generator of the present invention can be brought to an appropriate temperature by appropriate heating means and cooling means. Although it does not specifically limit as a heating means, The heater etc. which utilized heat exchange with a heater, hot water, steam, etc. are mentioned. The cooling means is not particularly limited, and a cooler such as air cooling or water cooling can be used.

  Moreover, it is also possible to perform heat exchange between the seawater introduced into the sterilizing component generator and the seawater delivered from the sterilizing component generator using heat exchange means. Seawater introduced into the ozone generator is cooled by the heat exchange, and seawater sent from the sterilizing component generator is heated.

  In the sterilizing component generator of the present invention, seawater can be passed by separating the anode and the cathode provided in the device with a diaphragm. The material of the diaphragm is not particularly limited as long as it can pass protons and does not inhibit the electrolysis in the electrolytic reaction apparatus, and a fluorine-based resin is particularly preferable.

  Moreover, the sterilization component generator of this invention can be set as the apparatus which can sterilize a large flow rate seawater by storing an electrode in a branch pipe and arranging multiple electrodes. In addition, the proton permeable membrane can be recovered by pausing the electrode and stopping the flow of seawater into the pipe as appropriate.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples.

[Examination of electrolysis start voltage]
Using a 3.5 wt% NaCl aqueous solution in which 14 g of Japanese Pharmacopoeia NaCl is dissolved in 400 ml of pure water, and artificial seawater, artificial seawater in which 333 g is dissolved in 10 L of Red Sea Salt (manufactured by Red Sea Fish Pharm). Then, each of the conductive diamond electrode formed on the φ3 mm titanium rod and the platinum electrode of φ1 mm was arranged in parallel by 60 mm apart by about 6 mm.

  Electrolysis was carried out at an electrode voltage of 6 V and an electric current of 500 mA. The electrolysis was stirred with a magnetic stirrer, and the pH value was measured using a pH meter Model PH81 manufactured by Yokogawa Electric Corporation. Results are shown.

  Looking at the 3.5 wt% NaCl solution in FIG. 2, it shows weak acidity at the beginning of electrolysis, but neutralized sodium ions, which are strong alkalis, due to weakly alkaline hypochlorite ions that appear with the start of electrolysis. In order to reduce the strongly acidic chlorine ions, it was found that the hydrogen ion exponent was unbalanced and suddenly changed to alkaline. On the other hand, artificial seawater contains many inorganic components, and since it is alkaline from the beginning, it does not show a significant pH change with the electrolysis time, but the pH value gradually shifts to alkaline. As a result, it is considered that hypochlorite ions and other negative ions are increased from the state of being weakly alkaline and stable as salt in artificial seawater, resulting in pH change.

  Next, FIG. 3 shows the IV characteristics of electrolysis when the above electrode is used for artificial seawater. From FIG. 3, it was found that electrolysis was started from about 3 V, and hypochlorite ions were hardly generated below 3 V.

  In the figure, the IV curve fluctuates with the number of experiments. This is due to the fact that deposits are generated near the electrode due to excess of hypochlorite ions generated by electrolysis, and the counter electrode. This is probably because platinum chloride was formed on the platinum surface. The electrolysis start voltage does not change even if the IV characteristic varies, and depends on the physical properties of the solution as long as the electrode material is the same.

[Study by UV absorption spectrum]
The inventor examined in detail by the ultraviolet absorption spectrum of the process until hypochlorous acid was generated.

  Using soft water, artificial seawater, Red Sea Salt (manufactured by Red Sea Fish Pharm), on a diamond electrode with boron-doped diamond film formed on a titanium rod of φ2 mm x 80 mm, around a SUS304 wire of φ0.5 mm A cathode in which a proton permeable membrane (Nafion 117, manufactured by DuPont) is wound around the entire circumference is further wound around a diamond electrode, and a diamond electrode having a diameter of 2 mm and a platinum electrode having a diameter of 1 mm are arranged in parallel at a distance of about 6 mm. And measured.

  The electrolysis conditions were an electrode voltage of 3.95 V, a current of 50 mA, and the ultraviolet absorption spectrum of the artificial seawater was measured before starting electrolysis, 2 minutes after starting electrolysis, and 8 minutes after starting electrolysis in a 400 ml ultraviolet absorption spectrum measuring cell. Moreover, the ultraviolet spectrum of the soft water before the electrolysis start and 2 minutes after the electrolysis start was also measured under the same electrolysis conditions. Here, a deuterium lamp was used as the light source, and the ratio of the ultraviolet intensity at each wavelength to the ultraviolet light absorption spectrum of pure water, that is, the absorbance (absorbance) (arbitrary unit) was taken as the vertical axis. FIG. 4 shows the result.

  From the results of FIG. 4, when neither artificial seawater nor soft water was electrolyzed, an absorption peak near 260 nm which is an absorption peak derived from ozone and an absorption peak near 290 nm which is a peak derived from hypochlorite ion are observed. Was not.

  In soft water, ozone was generated during electrolysis and an ozone absorption peak was observed. In artificial seawater, a large absorption peak of hypochlorite ions is observed in the ultraviolet absorption spectrum 8 minutes after electrolysis, and an absorption band having the same peak wavelength as ozone is observed in the ultraviolet absorption spectrum 2 minutes after electrolysis. It was done.

  Next, 1 μl of sodium hypochlorite (manufactured by Wako Pure Chemical Industries, Ltd.) having an effective chlorine concentration of 6% was dissolved in 300 ml of pure water, and the ultraviolet light absorption spectrum was measured with the same ultraviolet light absorption spectrometer as described above. . The result is shown in FIG.

  From the result of FIG. 5, when electrolyzing a sodium hypochlorite aqueous solution, the same absorption spectrum as ozone was not observed unlike the case where the seawater was electrolyzed. From this, it was speculated that in the electrolysis of seawater, ozone is preferentially generated in the early stage of electrolysis, and the generation of hypochlorite ions is promoted as electrolysis proceeds.

  Next, using a 3.5 wt% NaCl aqueous solution in which 350 g of Japanese Pharmacopoeia NaCl is dissolved in 10 l of pure water, the Na electrode is made of SUS304 by placing a diamond of φ2 mm in a SUS304 tube of φ1 / 4 inch. Electrolysis was carried out at a flow rate of 0.4 LM using a SUS304 tube having a diameter of ¼ inch as a cathode using an electrode insulated from the tube and forming a one-way flow path. FIG. 6 shows the ultraviolet absorption spectrum for each electrode potential and current.

  From the results shown in FIG. 6, it was observed that hypochlorite ions were generated from the beginning of electrolysis.

  Next, using artificial seawater, Red Sea Salt (manufactured by Red Sea Fish Farm), the Na electrode was insulated from the SUS304 tube by placing a diamond electrode of φ2 mm in the SUS304 tube of φ1 / 4 inch. Electrolysis was carried out at a flow rate of 0.4 LM by forming a one-way flow path using an electrode and a SUS304 tube of φ1 / 4 inch as a cathode. FIG. 7 shows the ultraviolet absorption spectrum for each electrode potential and current.

  As is clear from the results of FIG. 7, when artificial seawater was used, an absorption band appeared in the vicinity of a wavelength of 260 nm at the initial stage of electrolysis. Further, when the electrolysis potential was increased, a peak top considered to be derived from ozone at a wavelength of 245 to 275 nm and an unknown peak top of a wavelength of 310 to 340 nm were observed. In addition, although it is unclear what the unknown peak top is derived from, it may be some sterilizing component.

  In addition, when electrolysis proceeds, a peak attributed to hypochlorite ions at a wavelength of 280 to 305 nm, which was not initially observed, is observed. However, under the conditions of the present invention, the same absorption peak as ozone is more hypochlorite ions. It has a greater intensity than the absorption peak and could not be observed in this experiment.

  Next, FIG. 8 shows an ultraviolet absorption spectrum when artificial seawater similar to that described above is used and a platinum electrode of φ2 mm is used as the anode instead of the diamond electrode.

  From the result of FIG. 8, the tendency is not so remarkable as the diamond electrode and the intensity is small, but a peak similar to ozone is observed, and the intensity of the same peak as ozone is dominant. No peak was observed.

  Next, the channel was closed and the 3L beaker was filled with artificial seawater and circulated. The solution was transferred to a 400 ml quartz beaker, and the ultraviolet absorption spectrum after each fixed time was measured after electrolysis. The flow rate at this time is 0.4 LM as in the one-way experiment, and the electrolytic electrode is an electrode in which the diamond electrode of φ2 mm and the platinum electrode of φ1 mm are arranged approximately 6 mm apart in parallel, and the electrolysis conditions are 3.8 V, It was 47 mA. The result of the ultraviolet absorption spectrum after each time is shown in FIG.

  As is apparent from the results of FIG. 9, the same absorption peak intensity as ozone is larger until 30 minutes after electrolysis, the absorption peak intensity at wavelengths of 310 to 340 nm becomes larger after 35 minutes, and finally the wavelength of 280 to 800 It was absorbed by the peak of hypochlorous acid near 305 nm, and it was found that hypochlorite ions were predominantly generated. When sterilizing seawater using the electrode of the present invention, it has become clear that it is preferable to carry out at the initial stage of electrolysis.

  FIG. 10 shows a graph showing changes in absorbance at 255 nm and a graph showing changes in absorbance at 290 nm. When each spectral peak is observed, the peak near 325 nm increases monotonously with time, the peak at 255 nm increases rapidly in the initial stage, and the rate of increase thereafter changes. It is considered that this is because the peaks around 325 nm broadly affect the ozone peak, and as the electrolysis proceeds, the peaks are added together. Therefore, it has been clarified that the component considered to be ozone is selectively generated in the artificial seawater in the region where the peak of the ultraviolet absorption spectrum at the initial stage of electrolysis shows a double peak.

[Examination of sterilization]
First, a Teflon (registered trademark) tube having an inner diameter of φ1 / 4 inch was connected to a diaphragm pump having a flow rate of 1.5 L / min, and a proton permeable membrane (Nafion 117) was placed on the inlet of the φ2 mm titanium rod. ), A conductive diamond electrode coated with conductive diamond as an anode and a stainless steel electrode as a cathode were arranged. The flow rate at the time of measurement was 400 ml / min.

<Sample 1>
Next, the seawater is stored in the sterilization tank of the sterilizing component generator of the present invention, and after applying a voltage of 3.95 V and a current of 45 mA to the electrode, it waits for about 1 minute until the water in the apparatus is sufficiently replaced. Sample 1 was collected in a sterile container and refrigerated. Further, an ultraviolet absorption ozone concentration meter (UV OZONE MONITOR model-500, manufactured by Sugawara Jitsugyo Co., Ltd.) was installed in the pump part of the sterilizing component generator of the present invention and measured. As a result, a display of 0.7 ppm was shown. In addition, since this ozone concentration meter is for fresh water, there is a possibility that ozone concentration is not correctly shown in seawater. In addition, during the application of electrolysis, the ultraviolet light absorption ozone concentration meter was turned off so as not to sterilize the bacteria in the seawater by ultraviolet rays generated from the ultraviolet light absorption ozone concentration meter.

<Sample 2>
Sample 2 was seawater that was not sterilized by the sterilizing component generator of the present invention and collected in a sterile container and refrigerated.

<Sample 3>
It is the same as Sample 1 except that the medium stored in the sterilization tank of the sterilization component generator is pure water left in the atmosphere for 2 weeks.

<Sample 4>
Sample 4 was obtained by collecting pure water left in the atmosphere for 2 weeks without sterilization using the sterilizing component generator of the present invention and collecting it in an aseptic container and refrigerated.

  Table 1 below shows the results of transporting the above samples 1 to 4 to the Japan Food Analysis Center and measuring the number of bacteria per 1 ml.

  From the results in Table 1, it was found that the number of sterilized seawater as well as pure water can be significantly reduced by using the sterilizing component generator and the sterilizing method of the present invention.

Subsequently, 8.6 × 10 ⁶ cells / ml seawater was prepared to identify the bacteria that survived in the artificial seawater, and enterococcus faecalis NBRC 12964 (standard strain) was entered into the artificial seawater. A sample in which 6 × 10 ⁶ particles / ml were dispersed was prepared. Then, bring the sterilizing component generator of the present invention downsized so that it can be carried to the Japan Food Analysis Center, pass the above sample through the sterilizing component generator, and perform electrolysis of 3.9 V and 45 mA, which is about the electrolysis start voltage of seawater. Electrolysis was performed under the conditions. (Power source: P4K36-1, manufactured by Matsusada Precision Co., Ltd.). The seawater container subjected to the electrolysis was sealed, and the number of viable bacteria was measured within 10 minutes which is the lifetime of ozone. As a result of sterilization by the sterilizing component generator of the present invention, it was confirmed that the number of viable bacteria decreased to 10 cells / ml or less.

1, 5 Sterilization tank 2 Electrode 3 RO membrane pump 4 RO membrane (filter)

Claims (7)

  By electrolyzing seawater so that the first peak top of the ultraviolet absorption spectrum of seawater after electrolysis occurs between wavelengths 245 to 275 nm and the second peak top occurs between wavelengths 310 to 340 nm, A seawater sterilization method characterized by generating a sterilizing component. A third peak top of the ultraviolet absorption spectrum of seawater after electrolysis occurs between wavelengths 280-305 nm,
The seawater sterilization method according to claim 1, wherein seawater is electrolyzed so that the absorbance at the third peak top is lower than the absorbance at the first peak top and the second peak top.   The seawater sterilization method according to claim 1 or 2, wherein at least one of the electrode and the anode is boron-doped diamond.   At least one of the anode or the cathode used for electrolysis of seawater is any one selected from the group consisting of platinum, iridium, palladium, osmium, rhodium, and ruthenium. The method for sterilizing seawater as described in 1.   5. The seawater sterilization method according to any one of claims 1 to 4, wherein the seawater after electrolysis contains either ozone or a bromine compound.   Disinfection in seawater by electrolyzing seawater so that the first peak top of the ultraviolet absorption spectrum of seawater after electrolysis occurs between wavelengths 245 and 275 nm and the second peak top occurs between wavelengths 310 and 340 nm A sterilizing component generator characterized by generating components.   The sterilizing component generator according to claim 6, wherein the seawater after electrolysis contains either ozone or a bromine compound.

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