Water treatment device

Abstract

To provide a water treatment device efficiently eliminating metal ions from hard water without using an ion exchange resin.SOLUTION: A water treatment device 1 eliminates metal ions from water to be treated to generate treatment water. The water treatment device includes an electrolysis tank 10 including an anode chamber 15 provided with an anode 12, a cathode chamber 16 provided with a cathode 13 and a film 14 partitioning the anode chamber from the cathode chamber and permeating ions, and generating acidic water and alkaline water from the water to be treated by electrolysis. The water treatment device further includes a control part 100 controlling voltage or current between the anode and the cathode. The acidic water flows in the anode chamber, and the alkaline water flows in the cathode chamber. The control part adjusts at least one of the flow rate of the acidic water in the anode chamber and the flow rate of the alkaline water in the cathode chamber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water treatment device. [Background technology]

[0002] BACKGROUND ART Ion exchange resin water softeners for removing metal ions from hard water have been known (see, for example, Patent Document 1).

[0003] The ion exchange resin water softener of Patent Document 1 removes metal ions (calcium ions and magnesium ions) from hard water using ion exchange resin. Specifically, by passing hard water through a water softener vessel equipped with ion exchange resin with sodium ions attached to its surface, the metal ions in the hard water are replaced with sodium ions, and the metal ions are removed from the hard water. The metal ions present in the hard water are captured on the surface of the ion exchange resin. In this way, the hardness of the hard water is reduced to produce soft water. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-140840 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the ion exchange resin water softener of Patent Document 1 requires a large amount of saltwater to regenerate the ion exchange resin that has captured metal ions, resulting in problems such as time-consuming maintenance. Furthermore, the regeneration process generates wastewater containing a large amount of saltwater, which can lead to soil contamination and increased burdens on sewage treatment. Furthermore, the treated water softened by the ion exchange resin water softener has a high concentration of sodium ions, and in some areas may not be recommended as drinking water. Thus, water treatment devices using ion exchange resins have room for improvement in terms of ease of maintenance and environmental friendliness.

[0006] The present invention has been made in view of the problems inherent in the prior art, and an object of the present invention is to provide a water treatment device that can efficiently remove metal ions from hard water without using an ion exchange resin. [Means for solving the problem]

[0007] In order to solve the above problems, a water treatment device according to one aspect of the present invention is a water treatment device that removes metal ions from water to be treated to produce treated water, and is equipped with an anode chamber having an anode, a cathode chamber having a cathode, and a membrane that separates the anode chamber and the cathode chamber and is permeable to ions, an electrolytic cell that produces acidic water and alkaline water from the water to be treated by electrolysis, and a control unit that controls the voltage or current between the anode and the cathode, wherein the acidic water flows through the anode chamber and the alkaline water flows through the cathode chamber, and the control unit adjusts at least one of the flow rate of the acidic water in the anode chamber and the flow rate of the alkaline water in the cathode chamber. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a water treatment device that can efficiently remove metal ions from hard water without using an ion exchange resin. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating an example of the configuration of a water treatment device according to an embodiment of the present invention. [Figure 2] 3 is a schematic diagram showing the state of migration and insolubilization of metal ions in the electrolytic cell of the water treatment device according to the present embodiment. FIG. [Figure 3] 3 is a schematic diagram showing the state of hydrogen ion migration and neutralization in the electrolytic cell of the water treatment device according to the present embodiment. FIG. [Figure 4] 1 is a graph showing the relationship between the abundance ratio of carbon dioxide (H2CO3), bicarbonate ions (HCO3 -), and carbonate ions (CO3 2-) and pH when carbonate ions are dissolved in water. [Figure 5] 4 is a table for explaining electrolysis control in the water treatment device according to the present embodiment. [Figure 6] This is a graph that schematically shows the relationship between the conductivity of the treated water and the ion migration rate, insolubilization rate, and softening rate of metal ions when only constant current control is performed, when only constant voltage control is performed, and when electrolysis control is performed. [Figure 7] 10 is a graph showing an example of the relationship between the conductivity of the water to be treated and the power consumption when only constant voltage control, only constant current control, and electrolysis control are performed. [Figure 8] 3 is a schematic diagram showing the movement of hydrogen ions in an electrolytic cell of the water treatment device according to the present embodiment. FIG. [Figure 9] 1 is a graph showing the results of calculations using a theoretical model of the relationship between the pH change (vertical axis) of alkaline water in the cathode chamber, the amount of electricity between the electrodes (horizontal axis), and the rate at which H+ crosses the membrane. [Figure 10] 1 is a graph showing the relationship between the pH change of the water in the cathode chamber (vertical axis) and the amount of electricity between the electrodes (horizontal axis), which is derived from equation (19). [Figure 11] 1 is a graph showing an example of the results of measuring the pH of alkaline water in the cathode chamber when the flow rate of acidic water in the anode chamber in a water treatment device is set to 4.6 L / min or 14 L / min. [Figure 12A] 10 is a graph showing a schematic diagram of the relationship between the conductivity and pH of alkaline water and the relationship between the conductivity and pH of acidic water when the flow rates of acidic water and alkaline water are the same under constant voltage control. [Figure 12B] 10 is a graph showing the relationship between the conductivity and pH of alkaline water and the relationship between the conductivity and pH of acidic water when flow rate control is performed in which the flow rate of acidic water is faster than the flow rate of alkaline water under constant voltage control. [Figure 13A] 1 is a graph showing a schematic diagram of the relationship between the conductivity and pH of alkaline water and the relationship between the conductivity and pH of acidic water when the flow rates of acidic water and alkaline water are the same under constant current control. [Figure 13B]1 is a graph showing the relationship between the conductivity and pH of alkaline water and the relationship between the conductivity and pH of acidic water when flow rate control is performed in which the flow rate of acidic water is faster than the flow rate of alkaline water under constant current control. [Figure 14] 1 is a graph showing an example of the relationship between the pH of the water to be treated in the cathode chamber (alkaline water pH) and time. DETAILED DESCRIPTION OF THE INVENTION

[0010] The water treatment device according to the present embodiment will be described in detail below with reference to the drawings. Note that the dimensional proportions in the drawings are exaggerated for the sake of convenience and may differ from the actual proportions.

[0011] The water treatment device of this embodiment is a device that removes and separates metal ions from the water to be treated, thereby reducing the concentration (hardness) of metal ions in the water to a predetermined concentration or less, and producing treated water. 2+ ) and magnesium ions (Mg 2+ ) The definitions of hard water and soft water may be, for example, those of the WHO. That is, soft water may be defined as water with a hardness of less than 120 mg / L, and hard water may be defined as water with a hardness of 120 mg / L or more.

[0012] 1, the water treatment device 1 of this embodiment includes an electrolytic cell 10 that produces acidic water and alkaline water from water to be treated by electrolysis, a first flow path 20 through which the acidic water circulates, and a second flow path 30 through which alkaline water circulates. The water treatment device 1 further includes a water to be treated flow path 40 that supplies the water to be treated, a first outlet flow path 50 through which the treated acidic water flows out from the first flow path 20, and a second outlet flow path 60 through which the treated alkaline water flows out from the second flow path 30.

[0013] 1 and 2, the electrolytic tank 10 includes a solution tank 11, an anode 12, a cathode 13, and an ion-permeable membrane (ion-permeable membrane) 14. The solution tank 11 is a container that holds water to be treated that contains metal ions, and electrolyzes the water to be treated held therein, as described below.

[0014] The anode 12 and the cathode 13 are an electrode pair for electrolyzing the water to be treated in the solution tank 11. The anode 12 is provided in an anode chamber 15, and the cathode 13 is provided in a cathode chamber 16. The anode 12 and the cathode 13 are arranged inside the solution tank 11 so as to face each other with an ion-permeable membrane 14 therebetween. The anode 12 is electrically connected to the positive electrode of a power source 90 for electrolysis, and the cathode 13 is electrically connected to the negative electrode of the power source 90 for electrolysis.

[0015] The ion-permeable membrane 14 is disposed in the solution tank 11 and divides the solution tank 11 into an anode chamber 15 and a cathode chamber 16. That is, the anode chamber 15 is partitioned by a portion of the solution tank 11 and the ion-permeable membrane 14, and the cathode chamber 16 is partitioned by another portion of the solution tank 11 and the ion-permeable membrane 14. The ion-permeable membrane 14 is a member through which metal ions in the water to be treated permeate. Therefore, the ion-permeable membrane 14 is not particularly limited as long as it allows metal ions to permeate, and for example, a porous membrane or a cation exchange membrane can be used. The material of the porous membrane is not particularly limited, and may be, for example, a ceramic material, a resin material, or a metal material.

[0016] A first flow path 20 is connected to the anode chamber 15 of the electrolytic cell 10. That is, the first flow path 20 is connected to the inlet 15a and the outlet 15b of the anode chamber 15, respectively. In the first flow path 20, an acidic water tank 21 for temporarily storing acidic water and a first circulation pump 22 for pumping the acidic water are disposed downstream of the anode chamber 15. Therefore, the acidic water flowing out from the outlet 15b of the anode chamber 15 can pass through the acidic water tank 21 and the first circulation pump 22 and flow into the anode chamber 15 from the inlet 15a of the anode chamber 15.

[0017] Similarly, a second flow path 30 is connected to the cathode chamber 16 of the electrolytic cell 10. That is, the second flow path 30 is connected to the inlet 16a and the outlet 16b of the cathode chamber 16, respectively. In the second flow path 30, an alkaline water tank 31 for temporarily storing alkaline water and a second circulation pump 32 for pumping the alkaline water are disposed downstream of the cathode chamber 16. Therefore, the alkaline water flowing out from the outlet 16b of the cathode chamber 16 can pass through the alkaline water tank 31 and the second circulation pump 32 and flow into the cathode chamber 16 from the inlet 16a of the cathode chamber 16.

[0018] The water to be treated flow path 40 is a flow path that supplies the water to be treated to the electrolytic cell 10. Specifically, the water to be treated flow path 40 branches into two flow paths, which are connected to the first flow path 20 and the second flow path 30. Therefore, the water to be treated is supplied to both the first flow path 20 and the second flow path 30 through the water to be treated flow path 40. The water to be treated flow path 40 is provided with an electromagnetic valve 41 that switches between allowing the water to pass and stopping the water to be passed.

[0019] The first outlet flow path 50 is connected to the downstream side of the first circulation pump 22 via a first electromagnetic valve 51. As will be described later, the first outlet flow path 50 is a flow path for discharging acidic water that has been softened in the electrolytic cell 10. A water valve 52 is provided at the end of the first outlet flow path 50 to switch between allowing and stopping the flow of acidic water that has been softened. The treated water that has been discharged from the first outlet flow path 50 is treated water in which metal ions have been removed or reduced, and can be suitably used.

[0020] The second outlet flow path 60 is connected to the downstream side of the second circulation pump 32 via a second electromagnetic valve 61. As will be described later, the second outlet flow path 60 is a flow path for discharging alkaline water that has been insolubilized in the electrolytic cell 10. The end of the second outlet flow path 60 is connected to a water faucet 52. The water faucet 52 can be used to switch between passing and stopping the alkaline water that has been softened by removing insolubilized matter using the filter 62. The treated water that has been discharged from the second outlet flow path 60 is water in which metal ions have been removed or reduced, and can be used suitably.

[0021] The second outlet flow path 60 is provided with a filter 62 for separating and removing insolubilized matter consisting of metal ions insolubilized in the electrolytic cell 10. The filter 62 is not particularly limited as long as it can remove insolubilized matter, and a cartridge-type filter, a filtration layer using a granular filter medium, a cyclone-type solid-liquid separator, a hollow fiber membrane, etc. can be used.

[0022] 1, a bypass flow path 53 may be connected to the first solenoid valve 51 for sending the softened acidic water to a filter 62. The acidic water that has been softened in the electrolytic cell 10 and circulating through the first flow path 20 has had insolubilized matter sufficiently reduced, but if necessary, the acidic water may be filtered through the filter 62 before being sent to the faucet 52. Furthermore, a bypass flow path 63 may be connected to the second solenoid valve 61 for sending the alkaline water that has been insolubilized in the electrolytic cell 10 directly to the faucet 52 without sending it to the filter 62.

[0023] As shown in FIG. 1 , the water treatment device 1 of this embodiment includes a first conductivity measuring unit 70 that measures the conductivity of water flowing through the anode chamber and a second conductivity measuring unit 80 that measures the conductivity of water flowing through the cathode chamber. In this specification, the water flowing through the anode chamber is also referred to as anode water, and the water flowing through the cathode chamber is also referred to as cathode water. The first conductivity measuring unit 70 is provided on the inlet 15a side of the anode chamber 15 in the first flow path 20, and the second conductivity measuring unit 80 is provided on the inlet 16a side of the cathode chamber 16 in the second flow path 30. However, the location of the first conductivity measuring unit 70 is not particularly limited as long as it can measure the conductivity of the anode water. For example, the first conductivity measuring unit 70 may be provided inside the anode chamber 15 or inside the acidic water tank 21. Similarly, the second conductivity measuring unit 80 may be installed in any location as long as it can measure the conductivity of the cathode water; for example, it may be installed inside the cathode chamber 16 or inside the alkaline water tank 31.

[0024] Conductivity sensors can be used as the first conductivity measuring unit 70 and the second conductivity measuring unit 80. Furthermore, a TDS (total dissolved solids) sensor or a pH sensor can be used as the first conductivity measuring unit 70 and the second conductivity measuring unit 80, as long as the sensors are capable of calculating conductivity.

[0025] The first conductivity measuring unit 70 and the second conductivity measuring unit 80 are electrically connected to the control unit 100 described later, and transmit the numerical values ​​of the conductivity of the anode water and the conductivity of the cathode water measured by the first conductivity measuring unit 70 and the second conductivity measuring unit 80 to the control unit 100.

[0026] The water treatment device 1 further includes an electrolysis power supply 90 and a control unit 100. The electrolysis power supply 90 is electrically connected to the anode 12 and the cathode 13. The electrolysis power supply 90 passes a current between the anode 12 and the cathode 13 and applies a voltage therebetween.

[0027] The control unit 100 is electrically connected to the electrolysis power supply 90 and adjusts the voltage between the anode and the cathode by controlling the electrolysis power supply 90. The control unit 100 is also electrically connected to the solenoid valve 41, first solenoid valve 51, second solenoid valve 61, and water faucet 52 of the water to be treated flow path 40 and controls their opening and closing. The control unit 100 is also electrically connected to the first circulation pump 22 and second circulation pump 32 and controls their operation.

[0028] When the control unit 100 executes operations based on a control program, it may include a storage device such as a ROM (Read Only Memory) or a RAM (Random Access Memory) that stores the control program, and a CPU (Central Processing Unit) that executes the control program. When the control unit 100 executes predetermined operations, it may include a dedicated electronic circuit or the like that realizes the control program in hardware. Furthermore, the control unit 100 may include a timer such as an RTC (Real Time Clock) to measure time.

[0029] The operation of the water treatment device 1 configured as above is premised on the following facts. First, the conductivity of acidic water is proportional to the ion concentration in the acidic water. Therefore, the conductivity of acidic water is proportional to the concentration of metal ions (hardness) contained in the acidic water. Similarly, the conductivity of alkaline water is proportional to the ion concentration in the alkaline water. Therefore, the conductivity of alkaline water is proportional to the concentration of metal ions (hardness) contained in the alkaline water.

[0030] Next, when a voltage is applied to the anode 12 and the cathode 13 with the water to be treated placed in the anode chamber 15 and the cathode chamber 16 of the electrolytic cell 10, the metal ions in the anode chamber 15 permeate the ion-permeable membrane 14 and move to the cathode chamber 16, as shown in Figure 2. In other words, as shown in the electrophoretic velocity equation in Equation 1, the electrophoretic velocity of ions, ν (m / s), is proportional to the ion mobility, μ (m 2The voltage is expressed as the product of the voltage (V / Vs) and the electric field E (V / m). Therefore, the movement of metal ions depends on the magnitude of the voltage (electric field). As shown in FIG. 3, when a voltage is applied to the anode 12 and the cathode 13, the hydrogen ions (H + ) also moves to the cathode chamber 16, and hydroxide ions (OH - ) and neutralizes it.

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[0031] Next, when the water to be treated is placed in the anode chamber 15 and the cathode chamber 16 of the electrolytic cell 10 and electrolyzed, hydrogen ions (H + ) is generated at the cathode 13 by a reduction reaction, and hydroxide ions (OH - ) is produced. Note that this type of water electrolysis depends on the magnitude of the current. [ka]

[0032] The magnesium ions (Mg 2+ ) reacts with the generated hydroxide ions to become magnesium hydroxide (Mg(OH)2), which becomes insoluble. Here, the solubility product K of magnesium hydroxide in water at 25°C is sp is 1.80 x 10 -11 (mol / L) 3 As shown in Equation 2, Mg 2+ and OH - The ionic product of this is the solubility product K sp If the pH is greater than 1, the dissolution equilibrium shifts in favor of the formation of Mg(OH)2, resulting in the formation of an insolubilized product consisting of Mg(OH)2. Therefore, to efficiently insolubilize magnesium ions, it is necessary to increase the pH, i.e., to increase the hydroxide ions.

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[0033] In addition, carbonate ions (CO3 2- ) contained in the treated water. 2+ ) reacts with carbonate ions to become insoluble as calcium carbonate (CaCO3). Here, the solubility product K of calcium carbonate in water at 25°C is sp is 4.96 x 10 -9 (mol / L) 2 Then, as shown in Equation 3, Ca 2+ and CO3 - The ionic product of this is the solubility product K sp When the temperature becomes larger than 100°C, the dissolution equilibrium shifts in the direction of CaCO3 production, resulting in the production of an insolubilized product consisting of CaCO3.

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[0034] In Figure 4, when carbonate ions are dissolved in water, carbonic acid (H2CO3) and bicarbonate ions (HCO3 - ) and carbonate ions (CO3 2- ) and pH. Figure 4 shows that the more alkaline the water pH, the fewer the carbonate and bicarbonate ions and the more carbonate ions there are. Therefore, to efficiently insolubilize calcium ions, it is necessary to increase the pH and increase the carbonate ions.

[0035] Thus, the insolubilization of magnesium ions and calcium ions increases with increasing hydroxide ion concentration. Furthermore, the electrolysis of water depends on the magnitude of the electric current. Therefore, the insolubilization of magnesium ions and calcium ions depends on the magnitude of the electric current.

[0036] Next, the operation of the water treatment device 1 of this embodiment will be described based on the above events. First, the control unit 100 opens the solenoid valve 41 and injects raw water (water to be treated) into the water-to-be-treated flow path 40, the first flow path 20, and the second flow path 30. Then, the water to be treated is injected into the anode chamber 15 and the cathode chamber 16 of the electrolytic cell 10, the acidic water tank 21, and the alkaline water tank 31.

[0037] Next, the control unit 100 measures the conductivity of the anode water and the cathode water using the first conductivity measuring unit 70 and the second conductivity measuring unit 80. Furthermore, the control unit 100 controls the electrolysis power supply 90 to pass a current between the anode 12 and the cathode 13, electrolyzing the water to be treated. The control unit 100 also operates the first circulation pump 22 and the second circulation pump 32 to circulate the water to be treated through the first flow path 20 and the second flow path 30. By performing electrolysis and circulation of the water to be treated for a predetermined time, the water to be treated in the anode chamber 15, the first flow path 20, and the acidic water tank 21 becomes acidic water, and the water to be treated in the cathode chamber 16, the second flow path 30, and the alkaline water tank 31 becomes alkaline water.

[0038] The control unit 100 then measures the conductivity of the anode water (acidic water) and the cathode water (alkaline water) at predetermined time intervals. When almost no metal ions have been removed from the acidic water or alkaline water, both the acidic water and the alkaline water have high conductivity, as shown in "(1) Formation of insolubilized matter" in FIG. 5 . Therefore, the control unit 100 controls the electrolysis power supply 90 to pass a constant current between the anode 12 and the cathode 13. Such constant current control can be achieved by adjusting the current or voltage applied between the anode 12 and the cathode 13.

[0039] As mentioned above, the insolubilization of metal ions is current-dependent, so constant current control promotes the insolubilization of metal ions in alkaline water. As a result, the concentration of metal ions decreases, and the conductivity of alkaline water decreases. However, in acidic water, the insolubilization of metal ions is less likely to occur, so the conductivity remains high.

[0040] Next, if the conductivity measurement shows that the conductivity of the alkaline water has decreased but the conductivity of the acidic water remains high, the control unit 100 controls the electrolysis power supply 90 to apply a constant voltage between the anode 12 and the cathode 13, as shown in "(2) Ion migration" in Figure 5. Note that such constant voltage control can be performed by adjusting the voltage applied between the anode 12 and the cathode 13.

[0041] As described above, electrophoresis, in which metal ions move from the anode chamber 15 to the cathode chamber 16, is voltage-dependent, so when constant voltage control is performed, metal ions in the acidic water in the anode chamber 15 permeate the ion-permeable membrane 14 and move to the cathode chamber 16. As a result, the metal ion concentration in the alkaline water in the cathode chamber 16 increases, and the conductivity of the alkaline water increases. In contrast, the metal ion concentration in the acidic water decreases, and the conductivity of the acidic water decreases.

[0042] Here, as described above, when a constant voltage is applied to the anode 12 and the cathode 13, the hydrogen ions (H + ) also moves to the cathode chamber 16, causing a neutralization reaction and lowering the pH. If the pH of the alkaline water in the cathode chamber 16 drops, the insolubilization of metal ions is suppressed. Therefore, when the control unit 100 measures the conductivity after performing constant current control and finds that the conductivity of the alkaline water has dropped but the conductivity of the acidic water is high, it calculates a voltage value that will maintain the pH of the alkaline water at a high level. For example, the control unit 100 calculates and applies a voltage value that will maintain the pH of the alkaline water at 11 or higher.

[0043] Next, if the conductivity measurement shows that the conductivity of the alkaline water has increased but that of the acidic water has decreased, the control unit 100 controls the electrolysis power supply 90 to pass a constant current between the anode 12 and the cathode 13, as shown in "(3) Formation of insolubilized matter" in Figure 5. Note that such constant current control can be performed by adjusting the current or voltage applied between the anode 12 and the cathode 13.

[0044] As mentioned above, since the insolubilization of metal ions is current-dependent, constant current control promotes the insolubilization of metal ions in alkaline water, which results in a decrease in the concentration of metal ions and a decrease in the conductivity of the alkaline water.

[0045] Next, if the conductivity measurement shows that the conductivity of both the acidic water and the alkaline water has decreased, the control unit 100 determines that softening of both the acidic water and the alkaline water has progressed, as shown in "(4) Softening" in Figure 5.

[0046] In this way, the control unit 100 measures the conductivity of the anode water and the cathode water, and then adjusts the voltage applied between the anode 12 and the cathode 13 to perform electrolysis control that alternates between constant current control and constant voltage control. As a result, metal ions on the acidic water side electrophorese to the alkaline water side, and the metal ions are insolubilized on the alkaline water side, thereby reducing the metal ions in the water to be treated. In this embodiment, the timer of the control unit 100 measures the time during which electrolysis control is performed, and therefore the electrolysis control is performed until a predetermined time has elapsed.

[0047] The control unit 100 then adjusts the first solenoid valve 51 to allow the acidic water in the first flow path 20 to flow into the first outlet flow path 50. The control unit 100 also adjusts the second solenoid valve 61 to allow the alkaline water in the second flow path 30 to flow into the second outlet flow path 60. The alkaline water then passes through a filter 62 provided in the second outlet flow path 60. Because the alkaline water flowing into the second outlet flow path 60 contains insoluble metal ions, the insoluble matter is removed by passing the alkaline water through the filter 62. By opening the water faucet 52, the user can consume the softened acidic water and alkaline water. At this time, the acidic water and alkaline water can be mixed as desired to produce neutral treated water.

[0048] FIG. 6 shows the relationship between the conductivity of the water to be treated and the ion migration rate, insolubilization rate, and water softening rate of metal ions when the control unit 100 only performs constant voltage control, in which a constant voltage is applied to the anode 12 and cathode 13 of the electrolytic cell 10 regardless of the conductivity. FIG. 6 also shows the relationship between the conductivity of the water to be treated and the ion migration rate, insolubilization rate, and water softening rate of metal ions when the control unit 100 only performs constant current control, in which a constant current is applied to the anode 12 and cathode 13 of the electrolytic cell 10 regardless of the conductivity. The "ion migration rate of metal ions" indicates the efficiency at which metal ions migrate from the anode chamber 15 to the cathode chamber 16. The "insolubilization rate of metal ions" indicates the efficiency at which metal ions bind with hydroxide ions and carbonate ions to become insolubilized. The "water softening rate" indicates the efficiency at which metal ions are removed from the water to be treated.

[0049] As described above, because the movement of metal ions depends on the voltage (electric field), when the control unit 100 performs constant voltage control, metal ions move from the anode chamber 15 to the cathode chamber 16 regardless of the conductivity of the water being treated. This means that a high ion migration rate can be maintained. However, because the insolubilization of metal ions depends on the current, constant voltage control improves the insolubilization rate when the conductivity of the water being treated is high, but decreases the insolubilization rate when the conductivity is low. Therefore, if the control unit 100 only performs constant voltage control and not constant current control, the water being treated can be efficiently softened and the water softening rate increased when the conductivity of the water being treated is high, i.e., when the metal ion concentration is high. However, when the conductivity of the water being treated is low, i.e., when the metal ion concentration is low, the insolubilization rate decreases, and therefore the water softening rate also decreases. Thus, when the control unit 100 only performs constant voltage control, the water softening rate is good when the metal ion concentration is high, but the water softening rate deteriorates when the metal ion concentration is low.

[0050] In contrast, because the insolubilization of metal ions depends on the current, when the control unit 100 performs constant current control, metal ions are insolubilized regardless of the conductivity of the water being treated, i.e., a high insolubilization rate can be maintained. However, as described above, because the migration of metal ions depends on the voltage, when constant current control is performed, the ion migration rate improves when the conductivity of the water being treated is low, but decreases when the conductivity is high. Therefore, if the control unit 100 only performs constant current control and not constant voltage control, the water being treated can be efficiently softened and the water softening rate increased when the conductivity of the water being treated is low, i.e., when the metal ion concentration is low. However, when the conductivity of the water being treated is high, i.e., when the metal ion concentration is high, the ion migration rate decreases, and the water softening rate also decreases. Thus, when the control unit 100 only performs constant current control, the water softening rate is good when the metal ion concentration is low, but the water softening rate deteriorates when the metal ion concentration is high.

[0051] In the water treatment device 1 of this embodiment, the voltage applied between the anode 12 and the cathode 13 is adjusted according to the conductivity (hardness) of the anode water and the cathode water, and electrolysis control is performed by repeating constant current control and constant voltage control. This keeps the ion migration rate and insolubilization rate high at all times, and as a result, it becomes possible to obtain a desired water softening rate regardless of the conductivity.

[0052] FIG. 7 shows an example of the relationship between the conductivity of the water to be treated and power consumption when constant voltage control, constant current control, and electrolysis control are performed. Note that symbol C in FIG. 7 shows the relationship between the conductivity and power consumption when only constant voltage control is performed, and symbol D shows the relationship between the conductivity and power consumption when only constant current control is performed. Finally, symbol E shows the relationship between the conductivity and power consumption when electrolysis control according to this embodiment is performed. From FIG. 7, it can be seen that when only constant voltage control is performed, power consumption increases as the conductivity of the water to be treated increases. Furthermore, it can be seen that when only constant current control is performed, power consumption increases as the conductivity of the water to be treated decreases. However, the electrolysis control according to this embodiment switches between constant current control and constant voltage control depending on the conductivity of the water to be treated, and therefore power consumption can be kept low, as shown by symbol E.

[0053] In this embodiment, the range of conductivity of the water to be treated when electrolysis control is performed is preferably a range in which power consumption is lower than when only constant current control or only constant voltage control is performed. In other words, the range of conductivity of the water to be treated (acidic water and alkaline water) to be electrolysis control is preferably within the range indicated by symbol F in Figure 7, specifically, 30 to 8000 μS / cm. This makes it possible to reduce power consumption compared to when only constant current control or only constant voltage control is performed.

[0054] As described above, the conductivity of acidic water is proportional to the concentration (hardness) of metal ions contained in the acidic water, and the conductivity of alkaline water is proportional to the concentration (hardness) of metal ions contained in the alkaline water. However, regardless of the conductivity values ​​of the acidic water and alkaline water, it may be difficult to achieve stable purification performance if the flow rate of the acidic water in the anode chamber 15 and the flow rate of the alkaline water in the cathode chamber 16 are constant. Therefore, in the water treatment device of this embodiment, the control unit 100 is characterized by adjusting at least one of the flow rate of the acidic water in the anode chamber 15 and the flow rate of the alkaline water in the cathode chamber 16.

[0055] As described above, when the water to be treated is placed in the anode chamber 15 and the cathode chamber 16 of the electrolytic cell 10 and electrolyzed, hydrogen ions (H + ) is generated at the cathode 13 by a reduction reaction, and hydroxide ions (OH - ) is generated. When a voltage is applied to the anode 12 and the cathode 13, hydrogen ions (H + ) moves to the cathode chamber 16, and hydroxide ions (OH - ) and neutralizes it, lowering the pH of the alkaline water in the cathode chamber 16. If the pH of the alkaline water in the cathode chamber 16 decreases, the insolubilization of the metal ions may be inhibited.

[0056] To prevent such a decrease in the pH of the alkaline water in the cathode chamber 16, the water treatment device 1 of this embodiment can make the flow rate of the acidic water in the anode chamber 15 faster than the flow rate of the alkaline water in the cathode chamber 16. As a result, even if hydrogen ions generated near the anode 12 attempt to move toward the cathode chamber 16, as shown in FIG. 8 , the hydrogen ions are more likely to move along the flow of the acidic water to the outlet 15b of the anode chamber 15. In other words, the hydrogen ions generated near the anode 12 are more likely to move to the outlet 15b of the anode chamber 15 than to permeate the ion-permeable membrane 14 and move to the cathode chamber 16. The hydrogen ions that have moved to the outlet 15b of the anode chamber 15 then circulate through the first flow path 20 and flow into the anode chamber 15 from the inlet 15a of the anode chamber 15.

[0057] In this way, by increasing the flow rate of the acidic water in the anode chamber 15, the hydrogen ions generated in the anode 12 are more likely to circulate through the anode chamber 15 and the first flow path 20, and are less likely to permeate the ion-permeable membrane 14 and move to the cathode chamber 16. This prevents the pH of the alkaline water in the cathode chamber 16 from decreasing, and promotes the insolubilization of metal ions.

[0058] Even when the flow rate of the acidic water in the anode chamber 15 is increased, constant voltage control allows metal ions in the acidic water in the anode chamber 15 to permeate the ion permeable membrane 14 and migrate to the cathode chamber 16. That is, constant voltage control allows metal ions in the acidic water in the anode chamber 15 that are located near the ion permeable membrane 14 to permeate the ion permeable membrane 14 and migrate to the cathode chamber 16. Furthermore, because the acidic water circulates through the anode chamber 15 and the first flow path 20, constant voltage control allows the metal ions in the acidic water to gradually permeate the ion permeable membrane 14 and migrate to the cathode chamber 16. Therefore, even when the flow rate of the acidic water in the anode chamber 15 is increased, metal ions can efficiently migrate from the anode chamber 15 to the cathode chamber 16.

[0059] In this way, by making the flow rate of the acidic water faster than the flow rate of the alkaline water, the migration of hydrogen ions to the cathode chamber 16 is suppressed, thereby accelerating the increase in pH of the alkaline water. Furthermore, because the migration of hydrogen ions is suppressed, the neutralization point where the hydrogen ions generated at the anode 12 and the hydroxide ions generated at the cathode 13 neutralize is located near the ion-permeable membrane 14. Therefore, the migration of hydrogen ions to the cathode chamber 16 is suppressed, thereby accelerating the increase in pH of the alkaline water. Furthermore, because the migration of hydrogen ions to the cathode chamber 16 is suppressed, acidic water with a low pH can be produced in a short time.

[0060] In the water treatment device 1 of this embodiment, the flow rate of alkaline water in the cathode chamber 16 can also be made faster than the flow rate of acidic water in the anode chamber 15. By making the flow rate of alkaline water faster than the flow rate of acidic water, the number of times the alkaline water circulates through the second flow path 30 increases, thereby increasing the number of times the water to be treated is electrolyzed into alkaline water. Therefore, even if hydroxide ions are consumed to insolubilize the metal ions, the pH of the alkaline water can be made high. As a result, neutral treated water can be easily obtained by mixing the alkaline water and acidic water. Furthermore, by making the flow rate of alkaline water faster than the flow rate of acidic water, the migration of hydroxide ions to the anode chamber 15 is suppressed, allowing alkaline water with a high pH to be produced in a short period of time.

[0061] The method for adjusting the flow rates of the acidic water in the anode chamber 15 and the alkaline water in the cathode chamber 16 is not particularly limited, and can be performed, for example, as follows. As described above, the water treatment device 1 includes a first flow path 20 connected to the anode chamber 15 and through which the acidic water flows, and a second flow path 30 connected to the cathode chamber 16 and through which the alkaline water flows. A first circulation pump 22 and a first solenoid valve 51 are disposed in the first flow path 20 for pumping the acidic water. Similarly, a second circulation pump 32 and a second solenoid valve 61 are disposed in the second flow path 30 for pumping the alkaline water. The first circulation pump 22 and the first solenoid valve 51, as well as the second circulation pump 32 and the second solenoid valve 61, are electrically connected to the control unit 100, and the control unit 100 controls their operation. In this embodiment, the first circulation pump 22 and the first electromagnetic valve 51 constitute a first flow rate adjustment unit, and the second circulation pump 32 and the second electromagnetic valve 61 constitute a second flow rate adjustment unit.

[0062] The flow rate of the acidic water can be controlled by the control unit 100 adjusting the first circulation pump 22 and / or the first solenoid valve 51 of the first flow rate adjustment unit. That is, the flow rate of the acidic water can be increased by increasing the rotation speed of the first circulation pump 22, and the flow rate of the acidic water can be increased by increasing the opening of the first solenoid valve 51. Similarly, the flow rate of the alkaline water can be controlled by the control unit 100 adjusting the second circulation pump 32 and / or the second solenoid valve 61 of the second flow rate adjustment unit.

[0063] In the water treatment device 1, the percentage of hydrogen ions generated in the anode chamber 15 by the electrode reaction that do not migrate across the ion-permeable membrane 14 to the cathode chamber 16 can be calculated using the following formula 4. In other words, the percentage of hydrogen ions that do not migrate from the anode chamber 15 to the cathode chamber 16 can be calculated using the following formula 4.

number

[0064] On the other hand, the percentage (%) of hydrogen ions generated in the electrode reaction that cross the ion-permeable membrane 14 and migrate to the cathode chamber 16 can be calculated using the following formula 5. In other words, the percentage (migration percentage) of hydrogen ions that migrate from the anode chamber 15 to the cathode chamber 16 can be calculated using the following formula 5.

number

[0065] 9, the pH change of the alkaline water in the cathode chamber 16 (vertical axis) and the amount of electricity between the electrodes (horizontal axis) are plotted against the H + The relationship between the rate at which the amount of electricity crosses the membrane and the amount of water passing through the membrane is shown in Figure 9. As shown in Figure 9, as the amount of electricity between the anode 12 and the cathode 13 increases, the pH of the alkaline water increases. + It can be seen that when the proportion of the ions exceeding the ion-permeable membrane 14 is 99.6% or less, the pH of the alkaline water in the cathode chamber 16 is 8.2 or higher.

[0066] Furthermore, from Figure 9, H + It can be seen that as the proportion of H that crosses the ion-permeable membrane 14 decreases, the pH of the alkaline water increases. + It can be seen that when the proportion of H exceeding the ion-permeable membrane 14 is 99% or less, the pH of the alkaline water in the cathode chamber 16 is likely to be 8.2 or higher. + It can be seen that the pH of the alkaline water becomes higher as the proportion of water that exceeds the ion-permeable membrane 14 decreases.

[0067] When the pH of the alkaline water in the cathode chamber 16 is 8.2 or higher, as shown in FIG. 2- ) ratio increases, which can promote the insolubilization of calcium ions. + By increasing the flow rate of the acidic water in the anode chamber 15 so that the proportion of the metal ions that pass through the ion-permeable membrane 14 is 99.6% or less, the insolubilization of the metal ions can be promoted.

[0068] Thus, the proportion of hydrogen ions generated in the anode chamber 15 by the electrode reaction that do not migrate across the ion-permeable membrane 14 to the cathode chamber 16 is preferably 0.4 to 100%. Furthermore, the proportion of hydrogen ions generated in the anode chamber 15 by the electrode reaction that do not migrate across the ion-permeable membrane 14 to the cathode chamber 16 is more preferably 1 to 20%. This configuration promotes the insolubilization of metal ions, thereby reducing the amount of metal ions in the water to be treated.

[0069] The above theoretical model showing the relationship between the pH change of the alkaline water in the cathode chamber 16 and the amount of electricity between the electrodes can be obtained as follows.

[0070] In an electrolysis structure having an ion-permeable membrane 14 that restricts the movement of water between the cathode chamber 16 and the anode chamber 15, Equation 6 can be obtained by considering the ratio α of the amount of protons that move from the anode chamber to the cathode chamber through the ion-permeable membrane to the amount of protons generated by the electrode reaction during water electrolysis.

number

[0071] The derivation process of Equation 6 is shown below. First, the chemical formula for the water electrolysis reaction is given by Equation 2 below. [ka]

[0072] In addition, the chemical equilibrium of carbon dioxide in water is expressed by the following chemical formula 3, and the ratio of carbon dioxide present changes depending on the pH. [ka]

[0073] If the total amount of carbonic acid is a, the molar concentration is C a is expressed by the following equation (1).

number

[0074] Hydroxide ions (OH) produced by electrolysis - and proton H + If the amount of substance is b mol, the molar concentration C b is expressed by the following equation (2).

number

[0075] Here, if the equilibrium constants of carbonate species are K1 and K2, they are expressed by the following equations (3) and (4).

number

[0076] By rearranging the formulas (3) and (4), the following formulas (5) to (7) are obtained.

number

[0077] Furthermore, if the ionic product of water is Kw, the following equations (8) and (9) are derived.

number

[0078] In addition, the total carbon dioxide concentration C a is expressed by the following equation (10).

number

[0079] Substituting equations (6) and (7) into equation (10) and rearranging, we obtain equations (11) to (13).

number

[0080] Substituting equation (13) into equation (7) gives equation (14).

number

number

[0081] Furthermore, the following equation holds true based on the principle of electrical neutrality:

number

[0082] By substituting equations (8), (13), (14), and (15) into equation (16), equation (17) is obtained.

number

[0083] Here, by adding hydroxide ions generated by the electrolysis reaction of water, equations (18) and (19) are obtained.

number

[0084] From equation (19), Figure 10 can be drawn from the pH corresponding to the quantity of electricity. -3 [mol / L], V0=6.0[L].

[0085] Furthermore, when the rate α of the protons generated in the electrolytic reaction in the anode chamber 15 that migrate to the cathode chamber 16 through the ion-permeable membrane 14 is taken into consideration, the following equation (20) is obtained.

number

[0086] In the water treatment device 1, the control unit 100 preferably controls the flow rates of the acidic water and the alkaline water based on the proportion of hydrogen ions generated in the anode chamber 15 by the electrode reaction that do not migrate across the ion-permeable membrane 14 to the cathode chamber 16. In other words, it is preferable to control the flow rates of the acidic water and the alkaline water so that the proportion of hydrogen ions generated in the anode chamber 15 by the electrode reaction that do not migrate across the ion-permeable membrane 14 to the cathode chamber 16 is 0.4 to 100%. By controlling in this manner, it is possible to promote the insolubilization of metal ions in the cathode chamber 16.

[0087] Furthermore, in the water treatment device 1, it is preferable that the control unit 100 controls the flow rate of the acidic water in the anode chamber 15 and the flow rate of the alkaline water in the cathode chamber 16 so that the pH of the alkaline water in the cathode chamber 16 reaches a predetermined value. As described above, when the pH of the alkaline water in the cathode chamber 16 reaches 8.2 or more, carbonate ions (CO 2- ) increases, which can promote the insolubilization of calcium ions. Therefore, it is preferable to control the flow rates of the acidic water in the anode chamber 15 and the alkaline water in the cathode chamber 16 so that the pH of the alkaline water in the cathode chamber 16 reaches, for example, 8.2 or higher. Note that the predetermined value for the pH of the alkaline water is not limited to 8.2 and may be, for example, 10 or 12.

[0088] 11 shows an example of the results of measuring the pH of alkaline water in the cathode chamber 16 when the flow rate of acidic water in the anode chamber 15 in the water treatment device 1 is 4.6 L / min or 14 L / min. The measurement results in FIG. 9 are for a case where the initial conductivity of the water to be treated is 550 μS / cm and electrolysis control is not performed. The measurement results in FIG. 9 are also for a case where the flow rate of alkaline water is the same for both the 4.6 L / min and 14 L / min flow rates of acidic water, and the flow rate of alkaline water is slower than the flow rate of acidic water.

[0089] 11, when the flow rate of the acidic water in the anode chamber 15 is 14 L / min, the pH of the alkaline water increases in a shorter time than when the flow rate is 4.6 L / min. In other words, when the flow rate of the acidic water in the anode chamber 15 is high, the migration of hydrogen ions from the anode chamber 15 to the cathode chamber 16 is suppressed, and the pH of the alkaline water increases in a shorter time.

[0090] As described above, in the water treatment device 1, in order to ensure stable purification performance even for water to be treated with a wide range of conductivity, the control unit 100 is characterized by adjusting at least one of the flow rate of the acidic water in the anode chamber 15 and the flow rate of the alkaline water in the cathode chamber 16. In this case, the control unit 100 may adjust at least one of the flow rate of the acidic water in the anode chamber 15 and the flow rate of the alkaline water in the cathode chamber 16 based on at least one of the conductivity of the acidic water and the conductivity of the alkaline water.

[0091] Specifically, as described above, the water treatment device 1 of this embodiment measures the conductivity of the acidic water and alkaline water, and then adjusts the voltage or current applied between the anode 12 and the cathode 13 to perform electrolysis control that repeats constant current control and constant voltage control.

[0092] 12A shows a schematic diagram of the relationship between the conductivity and pH of alkaline water and the relationship between the conductivity and pH of acidic water when the flow rates of acidic water and alkaline water are the same under constant voltage control. Note that Fig. 12A shows the pH states of acidic water and alkaline water measured upstream of electrolytic cell 10 and measured for the conductivity of acidic water and alkaline water downstream of electrolytic cell 10.

[0093] As shown in Figure 6, with constant voltage control, ions move at a constant speed regardless of conductivity. Meanwhile, the current value is small when the conductivity is low and large when the conductivity is high. In alkaline water, when the conductivity is low, the change in pH is small due to constant voltage control, but with constant voltage control, the amount of hydrogen ions that move to the alkaline water side is large, so the pH of the alkaline water decreases due to neutralization. However, when the conductivity is high, the change in pH is small due to constant voltage control, but the amount of hydrogen ions that move to the alkaline water side is small, so the pH is higher than when the conductivity is low.

[0094] In contrast, in acidic water, when the conductivity is low, the pH change is small due to constant voltage control, but the amount of hydrogen ions that move to the alkaline water side is large under constant voltage control, so the pH of the acidic water is high. Also, when the conductivity is high, the pH change is small due to constant voltage control, but the amount of hydrogen ions that move to the alkaline water side is small, so the pH is lower than when the conductivity is low.

[0095] Figure 12B shows a schematic diagram of the relationship between the conductivity and pH of alkaline water and the relationship between the conductivity and pH of acidic water when flow rate control is performed in which the flow rate of acidic water is faster than the flow rate of alkaline water under constant voltage control.

[0096] As described above, when the conductivity of alkaline water is low, the pH change is small due to constant voltage control. However, when flow rate control is performed, the hydrogen ions migrating to the alkaline water are suppressed, resulting in a higher pH. Furthermore, when the conductivity is high, the pH change is small due to constant voltage control, but the flow rate control suppresses the hydrogen ions migrating to the alkaline water, resulting in a higher pH. In this way, by controlling the flow rate, the overall pH of the alkaline water can be increased regardless of the conductivity of the alkaline water, compared to when the flow rates of the acidic water and the alkaline water are the same.

[0097] In contrast, when the conductivity of acidic water is low, the pH change is small due to constant voltage control, but when flow rate control is performed, the hydrogen ions that move to the alkaline water are suppressed, resulting in a lower pH of the acidic water. Also, when the conductivity is high, the pH change is small due to constant voltage control, but the amount of hydrogen ions that move to the alkaline water due to flow rate control is small, resulting in a lower pH compared to when the conductivity is low. Thus, by controlling the flow rate, the overall pH of the acidic water can be lowered, regardless of the conductivity of the acidic water, compared to when the flow rates of the acidic water and the alkaline water are the same.

[0098] 13A shows a schematic diagram of the relationship between the conductivity and pH of alkaline water and the relationship between the conductivity and pH of acidic water when the flow rates of acidic water and alkaline water are the same under constant current control. Note that Fig. 13A also shows the pH states of acidic water and alkaline water downstream of electrolytic cell 10, measured with the conductivity of the acidic water and alkaline water upstream of electrolytic cell 10.

[0099] As shown in Figure 6, with constant current control, the rate at which hydrogen ions and hydroxide ions are produced by the electrolytic reaction remains constant regardless of the conductivity. Meanwhile, the voltage value is high when the conductivity is low and low when the conductivity is high. In alkaline water, the change in pH remains constant when the conductivity is low, but the amount of hydrogen ions that migrate to the alkaline water is large, so the pH of the alkaline water decreases due to neutralization. However, when the conductivity is high, the change in pH remains constant, but the amount of hydrogen ions that migrate to the alkaline water is small, so the pH is higher than when the conductivity is low.

[0100] In contrast, in acidic water, when the conductivity is low, the pH change is constant, but the amount of hydrogen ions that move to the alkaline water side is large, so the pH of the acidic water is high. Also, when the conductivity is high, the pH change is constant, but the amount of hydrogen ions that move to the alkaline water side is small, so the pH is lower than when the conductivity is low.

[0101] Figure 13B shows a schematic diagram of the relationship between the conductivity and pH of alkaline water and the relationship between the conductivity and pH of acidic water when flow rate control is performed in which the flow rate of acidic water is faster than the flow rate of alkaline water under constant current control.

[0102] As described above, in alkaline water, when the conductivity is low, the change in pH is constant. However, when flow rate control is performed, the hydrogen ions migrating to the alkaline water are suppressed, resulting in a higher pH. Furthermore, when the conductivity is high, the change in pH is constant, but the flow rate control suppresses the hydrogen ions migrating to the alkaline water, resulting in a higher pH. Thus, by controlling the flow rate, the overall pH of the alkaline water can be increased, regardless of the conductivity of the alkaline water, compared to when the flow rates of the acidic water and the alkaline water are the same.

[0103] In contrast, in acidic water, when the conductivity is low, the pH change is constant, but when flow rate control is performed, the hydrogen ions that move to the alkaline water are suppressed, resulting in a lower pH of the acidic water. Also, when the conductivity is high, the pH change is constant, but the amount of hydrogen ions that move to the alkaline water is small due to flow rate control, resulting in a lower pH compared to when the conductivity is low. Thus, by controlling the flow rate, the overall pH of the acidic water can be lowered, regardless of the conductivity of the acidic water, compared to when the flow rates of the acidic water and the alkaline water are the same.

[0104] Thus, in both the constant current control and the constant voltage control, by controlling the flow rate of the acidic water to be faster than that of the alkaline water, the pH of the alkaline water can be increased and the pH of the acidic water can be decreased. Therefore, the flow rate control may be performed by both the constant current control and the constant voltage control, or by either the constant current control or the constant voltage control. In particular, since the constant current control promotes the insolubilization of metal ions, it is preferable to control the flow rate during the constant current control.

[0105] As described above, the water treatment device 1 preferably performs control by repeatedly switching between constant current control and constant voltage control based on the conductivity of acidic water or alkaline water, and further performs flow rate control using at least one of the constant current control and constant voltage control. This configuration makes it possible to achieve stable purification performance for water to be treated with any conductivity.

[0106] Figure 14 is a graph showing the relationship between the pH of alkaline water and time, with and without flow rate control. As shown in Figure 14, by controlling the flow rate so that the flow rate of the acidic water is faster than that of the alkaline water, the pH of the alkaline water rises in a short time, quickly reaching the target pH. The time from when the target pH is reached (the arrival time) to the end time in Figure 14 is the time during which the reaction of insolubilizing metal ions progresses.

[0107] 14, by controlling the flow rate, the arrival time and the end time are reached earlier than when flow rate control is not performed, thereby shortening the electrolysis time and achieving energy savings. Furthermore, by controlling the flow rate, the hydroxide ion concentration and carbonate ion concentration tend to increase, which also makes it possible to shorten the insolubilization reaction time.

[0108] When water to be treated is softened using the water treatment device 1 of this embodiment, inorganic crystals may gradually precipitate on the surfaces of the electrodes. If crystals precipitate on the electrode surfaces, the efficiency of electrolysis of the water to be treated may decrease, and the efficiency of producing acidic water and alkaline water may deteriorate. Therefore, it is preferable that the water treatment device 1 perform electrode purification control after softening a predetermined amount of water to be treated or after using the device for a predetermined period of time.

[0109] Specifically, when purifying the crystals deposited on the surface of at least one of the anode 12 and the cathode 13, first, the water remaining in the water treatment device 1 is discharged and new water is introduced. The newly introduced water may be the water to be treated or may be softened treated water.

[0110] Next, the polarities of the anode 12 and the cathode 13 are switched to each other. That is, the anode 12 is electrically connected to the negative electrode of the power supply 90 for electrolysis, and the cathode 13 is electrically connected to the positive electrode of the power supply 90 for electrolysis. In this state, a current is passed and a voltage is applied, causing the crystals deposited on the surfaces of the electrodes to dissolve in water.

[0111] Here, after the polarities of the anode 12 and the cathode 13 are switched, it is preferable to circulate the water in the anode chamber 15 at least once through the first flow path 20 and circulate the water in the cathode chamber 16 at least once through the second flow path 30. By circulating the water in the anode chamber 15 and the water in the cathode chamber 16 at least once in this manner, crystals on the surfaces of the electrodes can be dissolved, and the electrodes can be purified.

[0112] Thereafter, the polarities of the anode 12 and the cathode 13 are switched to each other. That is, the anode 12 is electrically connected to the positive electrode of the electrolysis power supply 90, and the cathode 13 is electrically connected to the negative electrode of the electrolysis power supply 90. By such control, the electrode surfaces can be purified.

[0113] In the water treatment device 1 of this embodiment, a flow rate measurement unit (flow rate sensor) for measuring the flow rate of acidic water may be provided in the first flow path 20, and a flow rate measurement unit (flow rate sensor) for measuring the flow rate of alkaline water may be provided in the second flow path 30. By providing such flow rate measurement units, the accuracy of flow rate control of acidic water and alkaline water can be improved. However, since the flow rates of acidic water and alkaline water can be estimated by calculation even without the flow rate measurement unit, the flow rate measurement unit is not an essential component in the water treatment device 1 of this embodiment.

[0114] As described above, in the water treatment device 1, the first flow path 20 and the second flow path 30 are circulation flow paths. However, the water treatment device is not limited to this configuration, and the first flow path and the second flow path may be one-pass flow paths that do not circulate water. Furthermore, the first flow path and the second flow path may be a combination of a circulation flow path and a one-pass flow path. Therefore, in this specification, the circulation flow path and the one-pass flow path are collectively referred to as the "first flow path." Similarly, the circulation flow path and the one-pass flow path are collectively referred to as the "second flow path."

[0115] (Addendum) The above description of the embodiments discloses the following techniques.

[0116] (Technology 1) A water treatment device that removes metal ions from water to be treated to produce treated water, an electrolytic cell that includes an anode chamber having an anode, a cathode chamber having a cathode, and a membrane that separates the anode chamber and the cathode chamber and is permeable to ions, and that produces acidic water and alkaline water from the water to be treated by electrolysis; a control unit that controls a voltage or a current between the anode and the cathode; Equipped with The acidic water flows through the anode chamber, and the alkaline water flows through the cathode chamber, The control unit adjusts at least one of the flow rate of the acidic water in the anode chamber and the flow rate of the alkaline water in the cathode chamber.

[0117] In the water treatment device of this embodiment, at least one of the flow rate of the acidic water in the anode chamber 15 and the flow rate of the alkaline water in the cathode chamber 16 is adjusted. As a result, hydrogen ions generated at the anode 12 are less likely to permeate through the ion-permeable membrane 14 and move to the cathode chamber 16. This prevents the pH of the alkaline water in the cathode chamber 16 from decreasing, and promotes the insolubilization of metal ions.

[0118] (Technology 2) The water treatment device according to Technology 1, wherein the control unit controls the flow rate of the acidic water in the anode chamber to be faster than the flow rate of the alkaline water in the cathode chamber, or controls the flow rate of the alkaline water in the cathode chamber to be faster than the flow rate of the acidic water in the anode chamber.

[0119] This configuration makes it difficult for hydrogen ions generated at the anode 12 to pass through the ion-permeable membrane 14 and move to the cathode chamber 16, thereby preventing a decrease in the pH of the alkaline water in the cathode chamber 16 and promoting the insolubilization of metal ions.

[0120] (Technology 3) A first conductivity measuring unit that measures the conductivity of the acidic water flowing through the anode chamber; a second conductivity measuring unit that measures the conductivity of the alkaline water flowing through the cathode chamber; Furthermore, 3. The water treatment device according to claim 1, wherein the control unit adjusts at least one of the flow rate of the acidic water in the anode chamber and the flow rate of the alkaline water in the cathode chamber based on at least one of the conductivity of the acidic water and the conductivity of the alkaline water.

[0121] With this configuration, it is possible to achieve stable purification performance for water to be treated with any conductivity.

[0122] (Technology 4) The water purification system further includes a first flow path connected to the anode chamber and through which the acidic water flows, and a second flow path connected to the cathode chamber and through which the alkaline water flows, a first flow rate adjusting unit for adjusting the flow rate of the acidic water is provided in the first flow path, and a second flow rate adjusting unit for adjusting the flow rate of the alkaline water is provided in the second flow path; 4. The water treatment device according to any one of techniques 1 to 3, wherein the control unit adjusts at least one of a first flow rate adjusting unit and a second flow rate adjusting unit.

[0123] This configuration makes it possible to easily adjust the flow rates of the acidic water and alkaline water, and makes it difficult for hydrogen ions to move from the anode chamber 15 to the cathode chamber 16.

[0124] (Technology 5) The present invention further includes a first flow path connected to the anode chamber and through which water in the anode chamber circulates, and a second flow path connected to the cathode chamber and through which water in the cathode chamber circulates, 5. The water treatment device according to any one of claims 1 to 4, wherein, in order to purify a surface of at least one of the anode and the cathode, the polarities of the anode and the cathode are switched, and then the water in the anode chamber is circulated through the first flow path at least once, and the water in the cathode chamber is circulated through the second flow path at least once.

[0125] With this configuration, the crystals deposited on the surface of the electrode can be dissolved, and the electrode can be purified.

[0126] (Technology 6) The water treatment device according to any one of Technologies 1 to 5, wherein the control unit changes at least one of the voltage and the current between the anode and the cathode.

[0127] This configuration controls the insolubilization of metal ions and the migration of metal ions from the anode chamber to the cathode chamber, thereby enabling efficient removal of metal ions.

[0128] (Technology 7) The water treatment device according to Technology 6, wherein the control unit changes the voltage applied between the anode and the cathode when the conductivity of the water flowing through the anode chamber and the conductivity of the water flowing through the cathode chamber are 30 to 8000 μS / cm.

[0129] In this embodiment, the range of the conductivity of the water to be treated when electrolysis control is performed is preferably set to a range that results in lower power consumption than when only constant current control or only constant voltage control is performed. With this configuration, it is possible to reduce power consumption compared to when only constant current control or only constant voltage control is performed.

[0130] (Technology 8) The water treatment device according to any one of technologies 1 to 7, wherein the control unit switches from one of constant current control and constant voltage control to the other by changing the voltage or current applied between the anode and the cathode.

[0131] This configuration makes it possible to promote the insolubilization of metal ions in the water to be treated, while reducing power consumption compared to the case of constant current control alone or constant voltage control alone.

[0132] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment. [Explanation of symbols]

[0133] 1. Water treatment equipment 10 Electrolytic cell 12 Anode 13 Cathode 14 Membrane (ion-permeable membrane) 15 Anode chamber 16 Cathode Chamber 20 First Channel 30 Second Channel 70 First conductivity measuring unit 80 Second conductivity measuring unit 100 control section

Claims

1. A water treatment device that removes metal ions from water to be treated to produce treated water, an electrolytic cell that includes an anode chamber having an anode, a cathode chamber having a cathode, and a membrane that separates the anode chamber and the cathode chamber and is permeable to ions, and that produces acidic water and alkaline water from the water to be treated by electrolysis; a control unit that controls a voltage or a current between the anode and the cathode; Equipped with The acidic water flows through the anode chamber, and the alkaline water flows through the cathode chamber, The control unit adjusts at least one of the flow rate of the acidic water in the anode chamber and the flow rate of the alkaline water in the cathode chamber.

2. 2. The water treatment device according to claim 1, wherein the control unit controls the flow rate of the acidic water in the anode chamber to be faster than the flow rate of the alkaline water in the cathode chamber, or controls the flow rate of the alkaline water in the cathode chamber to be faster than the flow rate of the acidic water in the anode chamber.

3. a first conductivity measuring unit that measures the conductivity of the acidic water flowing through the anode chamber; a second conductivity measuring unit that measures the conductivity of the alkaline water flowing through the cathode chamber; Furthermore, 3. The water treatment device according to claim 1, wherein the control unit adjusts at least one of the flow rate of the acidic water in the anode chamber and the flow rate of the alkaline water in the cathode chamber based on at least one of the conductivity of the acidic water and the conductivity of the alkaline water.

4. a first flow path connected to the anode chamber and through which the acidic water flows; and a second flow path connected to the cathode chamber and through which the alkaline water flows, a first flow rate adjusting unit for adjusting the flow rate of the acidic water is provided in the first flow path, and a second flow rate adjusting unit for adjusting the flow rate of the alkaline water is provided in the second flow path; The water treatment device according to claim 1 , wherein the control unit adjusts at least one of a first flow rate adjusting unit and a second flow rate adjusting unit.

5. The apparatus further includes a first flow path connected to the anode chamber and through which water in the anode chamber circulates, and a second flow path connected to the cathode chamber and through which water in the cathode chamber circulates, 3. The water treatment device according to claim 1, wherein, in order to purify a surface of at least one of the anode and the cathode, after the polarities of the anode and the cathode are switched, the water in the anode chamber is circulated through the first flow path at least once, and the water in the cathode chamber is circulated through the second flow path at least once.

6. The water treatment device according to claim 1 , wherein the control unit changes at least one of a voltage and a current between the anode and the cathode.

7. 7. The water treatment device according to claim 6, wherein the control unit changes the voltage applied between the anode and the cathode when the conductivity of the water flowing through the anode chamber and the conductivity of the water flowing through the cathode chamber are 30 to 8000 μS / cm.

8. The water treatment device according to claim 1 , wherein the control unit switches between one of constant current control and constant voltage control by changing the voltage or current applied between the anode and the cathode.

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