Water treatment device

Abstract

A water treatment device (1) removes metal ions from water to be treated to generate treated water, the water treatment device having an electrolytic cell (10) having an anode chamber (15) having an anode (12), a cathode chamber (16) having a cathode (13), and a membrane (14) separating the anode chamber and the cathode chamber and capable of allowing ions to pass through, the electrolytic cell (10) generating acidic water and basic water from the water to be treated by electrolysis. The water treatment device further has a control unit (100) that controls the voltage or current between the anode and the cathode. The acidic water circulates in the anode chamber, and the basic water circulates in the cathode chamber, and the control unit controls the flow rate of the acidic water in the anode chamber and the flow rate of the basic water in the cathode chamber in a manner satisfying formula 1.

Description

Technical Field

[0001] This disclosure relates to a water treatment apparatus. Background Technology

[0002] Previously, ion exchange resin water softeners for removing metal ions from hard water were known (see, for example, Patent Document 1).

[0003] Patent Document 1 describes an ion exchange resin water softener that removes metal ions (calcium and magnesium ions) from hard water using ion exchange resin. Specifically, by flowing hard water through a water softener container equipped with ion exchange resin whose surface is coated with sodium ions, the metal ions in the hard water are replaced with sodium ions, thereby removing the metal ions from the hard water. Furthermore, the metal ions present in the hard water are captured by the surface of the ion exchange resin. This reduces the hardness of the hard water, producing soft water.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-140840 Summary of the Invention

[0007] However, the ion exchange resin water softener in Patent Document 1 has the following problems: A large amount of brine is required to regenerate the ion exchange resin that has captured metal ions, making maintenance time-consuming and labor-intensive. Furthermore, regeneration generates regeneration wastewater containing large amounts of brine, increasing soil pollution and the burden on wastewater treatment. Additionally, the treated water softened by the ion exchange resin water softener has a high sodium ion concentration, making it unsuitable for drinking water depending on the region. Therefore, there is room for improvement in water treatment devices using ion exchange resins from both a maintenance and environmental perspective.

[0008] This disclosure was made in view of the problems existing in the prior art. Moreover, the object of this disclosure is to provide a water treatment apparatus that can efficiently remove metal ions from hard water even without the use of ion exchange resins.

[0009] To address the aforementioned issues, the water treatment apparatus disclosed herein is a water treatment apparatus that removes metal ions from treated water to generate treated water. It comprises: an electrolytic cell having an anode chamber with an anode, a cathode chamber with a cathode, and a membrane separating the anode chamber and the cathode chamber and allowing ions to permeate; the electrolytic cell generates acidic water and alkaline water from the treated water through electrolysis; and a control unit that controls the voltage or current between the anode and the cathode, wherein the acidic water flows in the anode chamber, and the alkaline water flows in the cathode chamber, and the control unit controls the flow rate of the acidic water in the anode chamber and the flow rate of the alkaline water in the cathode chamber in a manner satisfying Formula 1.

[0010] [Number 1]

[0011] Attached Figure Description

[0012] Figure 1 This is a schematic diagram illustrating an example of the structure of the water treatment apparatus according to this embodiment.

[0013] Figure 2 This is a schematic diagram showing the migration and insolubility of metal ions in the electrolytic cell of the water treatment apparatus according to this embodiment.

[0014] Figure 3 This is a schematic diagram showing the migration and neutralization of hydrogen ions in the electrolyzer of the water treatment apparatus according to this embodiment.

[0015] Figure 4 This shows the carbonic acid (H₂CO₃) and bicarbonate ions (HCO₃⁻) when carbonate ions are dissolved in water. - ) and carbonate ions (CO3) 2- A graph showing the relationship between the presence of ( ) and pH.

[0016] Figure 5 This is a table used to explain the electrolysis control in the water treatment apparatus involved in this embodiment.

[0017] Figure 6 It is a graph that summarizes the relationship between the conductivity of the treated water and the ion mobility, insolubility and softening rate of metal ions in the cases of constant flow control only, constant pressure control only, and electrolysis control.

[0018] Figure 7 This is a graph illustrating an example of the relationship between the conductivity of the water being treated and the power consumption when only constant pressure control, only constant current control, and electrolysis control are performed.

[0019] Figure 8This is a schematic diagram illustrating the migration of hydrogen ions in the electrolyzer of the water treatment apparatus according to this embodiment.

[0020] Figure 9 This is a graph showing the results obtained by using a theoretical model to calculate the relationship between the pH change (vertical axis) of the alkaline water in the cathode chamber and the charge between the electrodes (horizontal axis) and the proportion of H+ crossing the membrane.

[0021] Figure 10 This is a graph showing the relationship between the pH change of the water in the cathode chamber (vertical axis) and the electrical charge between the electrodes (horizontal axis) derived from equation (19).

[0022] Figure 11 This is a graph showing an example of the results obtained by measuring the pH of alkaline water in the cathode chamber when the flow rate of acidic water in the anode chamber is set to 4.6 L / min or 14 L / min in a water treatment device.

[0023] Figure 12 This is a flowchart illustrating an example of a method for controlling the flow rate of acidic water in the anode chamber based on the pH of alkaline water measured by a pH measuring unit.

[0024] Figure 13 This is a graph illustrating an example of the relationship between the pH (alkaline side pH) of the treated water in the cathode chamber and time. Detailed Implementation

[0025] The water treatment apparatus according to this embodiment will now be described in detail using the accompanying drawings. Furthermore, the scale of the drawings has been exaggerated for ease of explanation and may sometimes differ from the actual scale.

[0026] This embodiment of the water treatment apparatus produces treated water by removing and separating metal ions from the water to reduce the concentration (hardness) of metal ions in the water to below a specified concentration. The metal ions include calcium ions (Ca). 2+ ) and magnesium ions (Mg 2+ Furthermore, the WHO definition can be used as a standard for defining hard and soft water. That is, water with a hardness less than 120 mg / L can be defined as soft water, and water with a hardness greater than 120 mg / L can be defined as hard water.

[0027] like Figure 1As shown, the water treatment apparatus 1 of this embodiment includes: an electrolytic cell 10, which generates acidic water and alkaline water from the water to be treated by electrolysis; a first flow path 20, in which acidic water is circulated; and a second flow path 30, in which alkaline water is circulated. The water treatment apparatus 1 also includes a treated water flow path 40 for supplying the water to be treated, a first outflow flow path 50 for discharging the treated acidic water from the first flow path 20, and a second outflow flow path 60 for discharging the treated alkaline water from the second flow path 30.

[0028] like Figure 1 and Figure 2 As shown, the electrolytic cell 10 includes a solution tank 11, an anode 12, a cathode 13, and a membrane (ion-permeable membrane) 14 that allows ions to pass through. The solution tank 11 is a container for holding water to be treated containing metal ions, and as described later, the water to be treated held inside is electrolyzed.

[0029] Anode 12 and cathode 13 are electrode pairs used for electrolyzing the water to be treated in the solution tank 11. Anode 12 is disposed in anode chamber 15, and cathode 13 is disposed in cathode chamber 16. Anode 12 and cathode 13 are arranged opposite each other inside the solution tank 11, separated by an ion-permeable membrane 14. Furthermore, anode 12 is electrically connected to the positive terminal of the electrolysis power supply 90, and cathode 13 is electrically connected to the negative terminal of the electrolysis power supply 90.

[0030] An ion-permeable membrane 14 is disposed within a solution tank 11, dividing the solution tank 11 into an anode chamber 15 and a cathode chamber 16. Specifically, the anode chamber 15 is separated by a portion of the solution tank 11 and the ion-permeable membrane 14, while the cathode chamber 16 is separated by the remaining portion of the solution tank 11 and the ion-permeable membrane 14. Furthermore, the ion-permeable membrane 14 is a component that allows metal ions in the treated water to pass through. Therefore, the ion-permeable membrane 14 is not particularly limited as long as it allows metal ions to pass through; for example, a porous membrane or a cation exchange membrane can be used. Additionally, the material of the porous membrane can be, for example, ceramic materials, resin materials, or metal materials, but is not particularly limited.

[0031] The anode chamber 15 of the electrolytic cell 10 is connected to the first flow path 20. That is, the inlet 15a and outlet 15b of the anode chamber 15 are respectively connected to the first flow path 20. Moreover, in the first flow path 20, an acidic water tank 21 for temporarily storing acidic water and a first circulation pump 22 for pressurizing and pumping acidic water are arranged downstream of the anode chamber 15. Therefore, the acidic water flowing out of the outlet 15b of the anode chamber 15 can flow into the interior of the anode chamber 15 from the inlet 15a through the acidic water tank 21 and the first circulation pump 22.

[0032] Similarly, the cathode chamber 16 of the electrolytic cell 10 is connected to the second flow path 30. That is, the inlet 16a and outlet 16b of the cathode chamber 16 are respectively connected to the second flow path 30. Moreover, in the second flow path 30, an alkaline water tank 31 for temporarily storing alkaline water and a second circulation pump 32 for pressurizing alkaline water are arranged downstream of the cathode chamber 16. Therefore, alkaline water flowing out of the outlet 16b of the cathode chamber 16 can flow into the interior of the cathode chamber 16 from the inlet 16a through the alkaline water tank 31 and the second circulation pump 32.

[0033] The treated water flow path 40 is the flow path that supplies the treated water to the electrolytic cell 10. Specifically, the treated water flow path 40 branches into two flow paths and connects to the first flow path 20 and the second flow path 30. Therefore, the treated water is supplied to both the first flow path 20 and the second flow path 30 through the treated water flow path 40. In addition, a solenoid valve 41 is provided in the treated water flow path 40 to switch the flow and stop of the treated water.

[0034] The first outflow path 50 is connected to the downstream side of the first circulating pump 22 via a first solenoid valve 51. As described later, the first outflow path 50 is a path for the acidic water that has undergone softening treatment in the electrolytic cell 10 to flow out. Furthermore, a tap 52 is provided at the end of the first outflow path 50 to switch the flow and stop of the softened acidic water. The treated water flowing out of the first outflow path 50 is treated water with removed or reduced metal ions, and can be appropriately utilized.

[0035] The second outflow path 60 is connected to the downstream side of the second circulation pump 32 via the second solenoid valve 61. As described later, the second outflow path 60 is the path through which alkaline water that has undergone insoluble treatment in the electrolytic cell 10 flows out. Furthermore, the end of the second outflow path 60 is connected to a faucet 52. The faucet 52 allows for switching the flow of water through and off the alkaline water that has been softened by the filter 62 after the removal of insoluble substances. The treated water flowing out of the second outflow path 60 is water with removed or reduced metal ions, and can be appropriately utilized.

[0036] A filter 62 is provided in the second outflow path 60. The filter 62 is used to separate and remove the insoluble matter composed of metal ions after it has been dissolved in the electrolytic cell 10. The filter 62 is not particularly limited as long as it can remove the insoluble matter. It can be a cylindrical filter, a filter layer using granular filter material, a cyclone solid-liquid separator, a hollow fiber membrane, etc.

[0037] In addition, it can also be like Figure 1As shown, the first solenoid valve 51 is connected to a bypass flow path 53 for conveying softened acidic water to the filter 62. The insoluble matter in the acidic water that has been softened in the electrolyzer 10 and circulates in the first flow path 20 is sufficiently reduced, but the acidic water can also be filtered by the filter 62 before being supplied to the faucet 52, if necessary. Alternatively, the second solenoid valve 61 can be connected to a bypass flow path 63, which is used to directly supply alkaline water that has been treated in the electrolyzer 10 without conveying it to the filter 62, to the faucet 52.

[0038] like Figure 1 As shown, the water treatment apparatus 1 of this embodiment includes a first conductivity measuring unit 70 for measuring the conductivity of water flowing in the anode chamber and a second conductivity measuring unit 80 for measuring the conductivity of water flowing in the cathode chamber. Furthermore, in this specification, the water flowing in the anode chamber is also referred to as anolyte water, and the water flowing in the cathode chamber is also referred to as catholyte water. The first conductivity measuring unit 70 is located in the first flow path 20 near the inlet 15a of the anode chamber 15, and the second conductivity measuring unit 80 is located in the second flow path 30 near the inlet 16a of the cathode chamber 16. However, the location of the first conductivity measuring unit 70 is not particularly limited as long as it can measure the conductivity of the anolyte water; for example, it can be located inside the anode chamber 15 or inside the acidic water tank 21. Similarly, the location of the second conductivity measuring unit 80 is not particularly limited as long as it can measure the conductivity of the catholyte water; for example, it can be located inside the cathode chamber 16 or inside the alkaline water tank 31.

[0039] Conductivity sensors can be used as the first conductivity measuring unit 70 and the second conductivity measuring unit 80. Furthermore, as long as the conductivity can be calculated, 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.

[0040] The first conductivity measuring unit 70 and the second conductivity measuring unit 80 are connected to the control unit 100 (described later) and send the values ​​of the conductivity of the anolyte 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.

[0041] like Figure 1As shown, the water treatment apparatus 1 includes a first pH measuring unit 15c for measuring the pH of water flowing in the anode chamber 15 and a second pH measuring unit 16c for measuring the pH of water flowing in the cathode chamber 16. In this embodiment, the first pH measuring unit 15c is disposed inside the anode chamber 15, and the second pH measuring unit 16c is disposed inside the cathode chamber 16. Furthermore, the location of the first pH measuring unit 15c is not particularly limited as long as it can measure the pH of the anolyte water; for example, it can be disposed in the first flow path 20 or inside the acidic water tank 21. Similarly, the location of the second pH measuring unit 16c is not particularly limited as long as it can measure the pH of the cathode water; for example, it can be disposed in the second flow path 30 or inside the alkaline water tank 31.

[0042] The first pH measuring unit 15c and the second pH measuring unit 16c are electrically connected to the control unit 100, and send the pH values ​​of the anolyte and the cathode water measured by the first pH measuring unit 15c and the second pH measuring unit 16c to the control unit 100.

[0043] The water treatment apparatus 1 also 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. Furthermore, the electrolysis power supply 90 flows current and applies voltage between itself and the anode 12 and the cathode 13.

[0044] The control unit 100 is electrically connected to the electrolysis power supply 90, and adjusts the voltage between the anode and cathode by controlling the electrolysis power supply 90. Additionally, the control unit 100 is electrically connected to the solenoid valve 41, the first solenoid valve 51, the second solenoid valve 61, and the faucet 52 of the water flow path 40, and controls their opening and closing. Furthermore, the control unit 100 is electrically connected to the first circulation pump 22 and the second circulation pump 32, and controls their operation.

[0045] Furthermore, when executing actions based on the control program, the control unit 100 may also include storage devices such as ROM (Read Only Memory) and RAM (Random Access Memory) for storing the control program, as well as a CPU (Central Processing Unit) for executing the control program. Additionally, the control unit 100 may also include dedicated electronic circuitry for implementing the control program in hardware when executing predetermined actions. The control unit 100 may also include a timing unit such as an RTC (Real Time Clock) for measuring time.

[0046] When the water treatment device 1 with this structure operates, the following phenomena are predicated on the following: First, the conductivity of acidic water is proportional to the concentration of ions in the acidic water. Therefore, the conductivity of acidic water is proportional to the concentration (hardness) of metal ions contained in the acidic water. Similarly, the conductivity of alkaline water is proportional to the concentration of ions in the alkaline water. Therefore, the conductivity of alkaline water is proportional to the concentration (hardness) of metal ions contained in the alkaline water.

[0047] Next, with the water to be treated added to the anode chamber 15 and cathode chamber 16 of the electrolytic cell 10, and a voltage applied to the anode 12 and cathode 13, as follows: Figure 2 As shown, metal ions in the anode chamber 15 migrate to the cathode chamber 16 after passing through the ion permeation membrane 14. That is, as shown in Equation 2, the electrophoretic velocity ν (m / s) of the ions is determined by the ion mobility μ (m / s). 2 The migration of metal ions is expressed as the product of voltage (V / m) and electric field E (V / m). Therefore, the migration of metal ions depends on the magnitude of the voltage (electric field). Furthermore, as... Figure 3 As shown, when a voltage is applied to the anode 12 and the cathode 13, hydrogen ions (H+) present in the anode chamber 15... + It also migrates into cathode chamber 16, reacting with hydroxide ions (OH-). - It reacts and neutralizes.

[0048] [Number 2]

[0049]

[0050] Next, when water to be treated is added to the anode chamber 15 and cathode chamber 16 of the electrolytic cell 10 for electrolysis, as follows: Figure 3 As shown in chemical formula 1, hydrogen ions (H+) are generated in anode 12 through an oxidation reaction. + In cathode 13, hydroxide ions (OH-) are generated through a reduction reaction. - Furthermore, the electrolysis of such water depends on the magnitude of the current.

[0051] [Chemistry 1]

[0052]

[0053] Moreover, the magnesium ions (Mg) contained in the treated water 2+ It reacts with the generated hydroxide ions to form magnesium hydroxide (Mg(OH)₂), thus becoming insoluble. Here, the solubility product K of magnesium hydroxide in water at 25°C is... sp 1.80×10 -11 (mol / L) 3 Moreover, as shown in Equation 3, when Mg becomes 2+ With OH- The ion product is greater than the solubility product K. sp Under these conditions, the dissolution equilibrium shifts towards the formation of Mg(OH)₂, thus generating an insoluble compound composed of Mg(OH)₂. Therefore, to efficiently insolubleize magnesium ions, the pH needs to be increased, i.e., the amount of hydroxide ions needs to be increased.

[0054] [Number 3]

[0055]

[0056] Additionally, carbonate ions (CO3-) can be released into the treated water through the dissolution of carbonates from minerals or the dissolution of carbon dioxide from the air. 2- Furthermore, the calcium ions (Ca) contained in the treated water... 2+ It reacts with carbonate ions to form calcium carbonate (CaCO3), thus becoming insoluble. Here, the solubility product K of calcium carbonate in water at 25°C is... sp It is 4.96×10 -9 (mol / L) 2 Moreover, as shown in Equation 4, when Ca becomes 2+ With CO3 - The ion product is greater than the solubility product K. sp In this case, the dissolution equilibrium shifts towards the formation of CaCO3, thus generating an insoluble compound composed of CaCO3.

[0057] [Number 4]

[0058]

[0059] Here, in Figure 4 The diagram shows the carbonic acid (H₂CO₃) and bicarbonate ions (HCO₃⁻) in water when carbonate ions are dissolved. - ) and carbonate ions (CO3) 2- The presence of ) is related to pH. Figure 4 It is known that when water is alkaline, the levels of carbonate and bicarbonate ions decrease, while the level of carbonate ions increases. Therefore, to efficiently prevent calcium ions from dissolving, it is necessary to increase the pH to increase the carbonate ion concentration.

[0060] Thus, as the concentration of hydroxide ions increases, the insolubility of magnesium and calcium ions also increases. Furthermore, the electrolysis of water depends on the magnitude of the current. Therefore, the insolubility of magnesium and calcium ions depends on the magnitude of the current.

[0061] Next, based on the above phenomena, the operation of the water treatment apparatus 1 of this embodiment will be explained. First, the control unit 100 sets the solenoid valve 41 to the open state, and injects the water to be treated, which is the raw water, into the water to be treated flow path 40, the first flow path 20, and the second flow path 30. Furthermore, the water to be treated is injected into the anode chamber 15 and cathode chamber 16 of the electrolytic cell 10, as well as the acidic water tank 21 and the alkaline water tank 31.

[0062] Next, the control unit 100 measures the conductivity of the anolyte 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 allow current to flow between the anode 12 and the cathode 13, electrolyzing the water to be treated. Additionally, the control unit 100 operates the first circulation pump 22 and the second circulation pump 32 to circulate the water to be treated in the first flow path 20 and the second flow path 30. Through electrolysis and circulation of the water to be treated for a predetermined time, the water in the anode chamber 15, the first flow path 20, and the acidic water tank 21 becomes acidic water, and the water in the cathode chamber 16, the second flow path 30, and the alkaline water tank 31 becomes alkaline water.

[0063] Then, the control unit 100 measures the conductivity of the anolyte (acidic water) and the catholyte (alkaline water) at predetermined intervals. Here, under the condition that almost no metal ions are removed from the acidic and alkaline water, such as... Figure 5 As shown in "(1) Formation of insoluble substances", both acidic and alkaline water become states with high conductivity. Therefore, the control unit 100 controls the electrolysis power supply 90 to flow a constant current between the anode 12 and the cathode 13. Furthermore, such constant current control can be achieved by adjusting the current or voltage applied between the anode 12 and the cathode 13.

[0064] As mentioned above, the insolubility of metal ions depends on the current; therefore, under constant current control, the insolubility of metal ions is promoted in alkaline water. As a result, the concentration of metal ions decreases, and thus the conductivity of alkaline water decreases. However, in acidic water, the insolubility of metal ions is difficult to achieve, and therefore the conductivity remains high.

[0065] Next, when the conductivity measurement results show that the conductivity of alkaline water decreases while maintaining the high conductivity of acidic water, such as... Figure 5 As shown in “(2) Ion Migration”, the control unit 100 controls the electrolysis power supply 90 to apply a constant voltage between the anode 12 and the cathode 13. Furthermore, such constant voltage control can be achieved by adjusting the voltage applied between the anode 12 and the cathode 13.

[0066] As described above, the electrophoretic migration of metal ions from the anode chamber 15 to the cathode chamber 16 depends on the voltage. Therefore, under constant voltage control, metal ions in the acidic water of the anode chamber 15 migrate to the cathode chamber 16 after passing through the ion-permeable membrane 14. As a result, the concentration of metal ions in the alkaline water of the cathode chamber 16 increases, thus increasing the conductivity of the alkaline water. Conversely, the concentration of metal ions in the acidic water decreases, thus decreasing the conductivity of the acidic water.

[0067] Here, as described above, when a constant voltage is applied to the anode 12 and the cathode 13, hydrogen ions (H+) present in the anode chamber 15... + The alkaline water in the cathode chamber 16 also migrates to the cathode chamber 16, thus undergoing a neutralization reaction and lowering the pH. With the pH of the alkaline water in the cathode chamber 16 decreasing, the insolubility of metal ions is suppressed. Therefore, the control unit 100, after performing constant current control and measuring conductivity, calculates the voltage value required to maintain the pH of the alkaline water at a high level when the conductivity of the alkaline water decreases but the conductivity of the acidic water remains high. For example, the control unit 100 calculates and applies a voltage value that maintains the pH of the alkaline water at 11 or higher.

[0068] Next, in cases where the conductivity measurement results show that the conductivity of alkaline water increases while the conductivity of acidic water decreases, such as... Figure 5 As shown in “(3) Formation of insoluble substances”, the control unit 100 controls the electrolysis power supply 90 to flow a constant current between the anode 12 and the cathode 13. Furthermore, such constant current control can be achieved by adjusting the current or voltage applied between the anode 12 and the cathode 13.

[0069] As mentioned above, the insolubility of metal ions depends on the current; therefore, under constant current control, the insolubility of metal ions is promoted in alkaline water. As a result, the concentration of metal ions decreases, and thus the conductivity of the alkaline water decreases.

[0070] Next, the conductivity was measured, and the results showed that the conductivity decreased in both acidic and alkaline water. Figure 5 As shown in “(4) Softening”, the control unit 100 determined that both acidic and alkaline water had been softened.

[0071] In this way, after measuring the conductivity of the anolyte and cathode water, the control unit 100 adjusts the voltage applied between the anode 12 and the cathode 13 to perform electrolysis control by repeatedly applying constant current and constant voltage control. As a result, metal ions migrate from the acidic water side to the alkaline water side, where they remain insoluble, thus reducing the amount of metal ions in the treated water. Furthermore, in this embodiment, the electrolysis control time is measured by the timing unit of the control unit 100, and this electrolysis control continues until a predetermined time has elapsed.

[0072] Then, the control unit 100 adjusts the first solenoid valve 51 to direct the acidic water in the first flow path 20 to the first outflow path 50. Simultaneously, the control unit 100 adjusts the second solenoid valve 61 to direct the alkaline water in the second flow path 30 to the second outflow path 60. This alkaline water then passes through a filter 62 installed in the second outflow path 60. Since the alkaline water flowing into the second outflow path 60 contains insoluble metal ions, these insoluble substances are removed by the filter 62. Furthermore, by keeping the faucet 52 open, the user can use both softened acidic and alkaline water. At this time, by arbitrarily mixing the acidic and alkaline water, neutral treated water can be used.

[0073] Here, in Figure 6 The diagram illustrates the relationship between the conductivity of the treated water and the ion mobility, insolubility, and softening rate of metal ions, under the condition that the control unit 100 performs constant voltage control by applying a constant voltage to the anode 12 and cathode 13 of the electrolytic cell 10 regardless of conductivity. Furthermore, in... Figure 6 The diagram also illustrates the relationship between the conductivity of the treated water and the ion mobility, insolubility, and softening rate of metal ions, under the condition that the control unit 100 performs constant current control by flowing a constant current through the anode 12 and cathode 13 of the electrolytic cell 10 regardless of conductivity. Furthermore, "metal ion mobility" represents the efficiency of metal ions migrating from the anode chamber 15 to the cathode chamber 16. "Metal ion insolubility" represents the efficiency with which metal ions bind with hydroxide ions and carbonate ions and remain insoluble. "Softening rate" represents the efficiency of removing metal ions from the treated water.

[0074] As described above, the migration of metal ions depends on voltage (electric field). Therefore, when the control unit 100 performs constant pressure control, metal ions migrate from the anode chamber 15 to the cathode chamber 16 regardless of the conductivity of the water being treated, thus maintaining a high ion mobility. However, since the insolubility of metal ions depends on current, under constant pressure control, the insolubility increases when the conductivity of the water being treated is high, but decreases when the conductivity is low. Therefore, assuming that the control unit 100 performs only constant pressure control and not constant current control, water softening can be performed efficiently when the conductivity of the water being treated is high, i.e., when the concentration of metal ions is high, thereby improving the water softening rate. However, when the conductivity of the water being treated is low, i.e., when the concentration of metal ions is low, the insolubility decreases, and therefore the water softening rate also decreases. Thus, when the control unit 100 performs only constant pressure control, the water softening rate is good when the concentration of metal ions is high, but deteriorates when the concentration of metal ions is low.

[0075] In contrast, the insolubility of metal ions depends on the current. Therefore, when the control unit 100 performs constant current control, metal ions are insoluble regardless of the conductivity of the treated water, i.e., the insolubility rate can be maintained at a high level. However, as mentioned above, the migration of metal ions depends on the voltage. Therefore, when constant current control is performed, the ion migration rate increases when the conductivity of the treated water is low, but decreases when the conductivity is high. Therefore, assuming that the control unit 100 only performs constant current control and not constant voltage control, water softening can be performed efficiently when the conductivity of the treated water is low, i.e., when the concentration of metal ions is low, thereby improving the water softening rate. However, when the conductivity of the treated water is high, i.e., when the concentration of metal ions is high, the ion migration rate decreases, and therefore 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 concentration of metal ions is low, but deteriorates when the concentration of metal ions is high.

[0076] In the water treatment apparatus 1 of this embodiment, the voltage applied between the anode 12 and the cathode 13 is adjusted according to the conductivity (hardness) of the anolyte and cathode water to perform electrolysis control by repeatedly applying constant current and constant voltage control. Therefore, by maintaining high ion mobility and insolubility, the desired softening rate can be obtained regardless of the conductivity.

[0077] Here, in Figure 7 The image shows an example of the relationship between the conductivity of the treated water and the power consumption during constant pressure control, constant current control, and electrolysis control. Furthermore, Figure 7 Reference numeral C in the accompanying drawings indicates the relationship between conductivity and power consumption when only constant voltage control is performed, and reference numeral D indicates the relationship between conductivity and power consumption when only constant current control is performed. Furthermore, reference numeral E indicates the relationship between conductivity and power consumption when electrolysis control according to this embodiment is performed. Figure 7 It is known that when only constant pressure control is performed, power consumption increases as the conductivity of the treated water increases. Furthermore, it is known that when only constant current control is performed, power consumption increases as the conductivity of the treated water decreases. However, in this embodiment, the electrolysis control switches between constant current control and constant pressure control based on the conductivity of the treated water, thus, as indicated by reference numeral E in the attached figure, power consumption can be kept relatively low.

[0078] Furthermore, in this embodiment, the conductivity range of the water being treated during electrolysis control is preferably a range that consumes less power compared to the cases of constant current control only and constant voltage control only. That is, the conductivity range of the water being treated (acidic and alkaline water) under electrolysis control is preferably... Figure 7Within the range of reference numeral F shown in the attached figures, specifically preferably 30 μS / cm to 8000 μS / cm. Therefore, compared to the cases of constant current control only and constant voltage control only, power consumption can be suppressed.

[0079] Here, as described above, when water to be treated is added to the anode chamber 15 and cathode chamber 16 of the electrolytic cell 10 for electrolysis, hydrogen ions (H+) are generated in the anode 12 through an oxidation reaction. + In cathode 13, hydroxide ions (OH-) are generated through a reduction reaction. - Moreover, such as Figure 3 As shown, when a voltage is applied to the anode 12 and the cathode 13, hydrogen ions (H+) present in the anode chamber 15... + ) migrates into cathode chamber 16 and reacts with hydroxide ions (OH-) - The reaction neutralizes the alkaline water in cathode chamber 16, thus lowering the pH. This lower pH can potentially inhibit the insolubility of metal ions.

[0080] To suppress the decrease in pH of the alkaline water in the cathode chamber 16, the water treatment apparatus 1 of this embodiment is structured such that the flow rate of the acidic water in the anode chamber 15 is faster than the flow rate of the alkaline water in the cathode chamber 16. Therefore, as... Figure 8 As shown, even if hydrogen ions generated near the anode 12 migrate towards the cathode chamber 16, they readily migrate along the flow of acidic water towards the outlet 15b of the anode chamber 15. That is, hydrogen ions generated near the anode 12 migrate towards the outlet 15b of the anode chamber 15 more readily than those that migrate towards the cathode chamber 16 after passing through the ion permeation membrane 14. Then, the hydrogen ions that have migrated to the outlet 15b of the anode chamber 15 circulate in the first flow path 20 and flow into the anode chamber 15 from the inlet 15a.

[0081] In this way, by increasing the flow rate of the acidic water in the anode chamber 15, the hydrogen ions generated at the anode 12 can easily circulate in the anode chamber 15 and the first flow path 20, making it difficult for them to migrate to the cathode chamber 16 after passing through the permeate membrane 14. Therefore, the decrease in pH of the alkaline water in the cathode chamber 16 can be suppressed, thereby promoting the insolubility of metal ions.

[0082] Furthermore, even when the flow rate of the acidic water in the anode chamber 15 is increased, constant pressure control can be applied to allow metal ions in the acidic water of the anode chamber 15 to migrate through the ion-permeable membrane 14 and then to the cathode chamber 16. That is, constant pressure control can be applied to allow metal ions in the acidic water of the anode chamber 15 located near the ion-permeable membrane 14 to migrate through the ion-permeable membrane 14 and then to the cathode chamber 16. Additionally, since the acidic water circulates in the anode chamber 15 and the first flow path 20, constant pressure control can be applied to allow metal ions in the acidic water to gradually migrate through the ion-permeable membrane 14 and then 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 migrate efficiently from the anode chamber 15 to the cathode chamber 16.

[0083] The method for adjusting the flow rate of acidic water in the anode chamber 15 and the flow rate of alkaline water in the cathode chamber 16 is not particularly limited, and can be performed as follows, for example. As described above, the water treatment apparatus 1 includes: a first flow path 20 connected to the anode chamber 15, through which acidic water flows; and a second flow path 30 connected to the cathode chamber 16, through which alkaline water flows. A first circulation pump 22 and a first solenoid valve 51 for pressurizing acidic water are disposed in the first flow path 20. Similarly, a second circulation pump 32 and a second solenoid valve 61 for pressurizing alkaline water are disposed in the second flow path 30. 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 a control unit 100, which controls their operation. Moreover, in this embodiment, the first circulation pump 22 and the first solenoid valve 51 constitute a first flow rate adjustment unit, and the second circulation pump 32 and the second solenoid valve 61 constitute a second flow rate adjustment unit.

[0084] Furthermore, the flow rate of acidic water can be controlled by adjusting the first circulation pump 22 and / or the first solenoid valve 51 of the first flow rate adjustment unit via the control unit 100. That is, the flow rate of acidic water can be increased by increasing the rotational speed of the first circulation pump 22, and the flow rate of acidic water can be increased by increasing the opening degree of the first solenoid valve 51. Similarly, the flow rate of alkaline water can be controlled by adjusting the second circulation pump 32 and / or the second solenoid valve 61 of the second flow rate adjustment unit via the control unit 100.

[0085] In the water treatment apparatus 1, the percentage (%) of hydrogen ions generated in the anode chamber 15 through the electrode reaction that do not migrate to the cathode chamber 16 after crossing the ion permeation membrane 14 can be determined by the following formula 5. That is, the percentage (%) of hydrogen ions that do not migrate from the anode chamber 15 to the cathode chamber 16 can be determined by the following formula 5.

[0086] [Number 5]

[0087]

[0088] In Equation 5, the electrode distance W (m) is the shortest distance between the anode 12 and the cathode 13, the flow velocity (m / s) in the electrolytic cell is the flow velocity of the acidic water in the anode chamber 15, and the electrode length L (m) is the length of the anode 12 in the direction of the acidic water flow. Hydrogen ion mobility μ (m) 2 / Vs) represents the ion mobility μ of hydrogen ions, which is 36.2 × 10⁻⁶. -8 (m 2 / Vs). In addition, the solution potential V(V) of the acid is the voltage applied to the acidic water from the electrolysis power supply 90 via the anode 12 in the form of a control voltage.

[0089] Similarly, in the water treatment apparatus 1, the percentage (%) of hydroxide ions generated in the cathode chamber 16 through the electrode reaction that do not migrate to the anode chamber 15 after crossing the ion permeation membrane 14 can be determined by the following formula 6. That is, the percentage (%) of hydroxide ions that do not migrate from the cathode chamber 16 to the anode chamber 15 can be determined by the following formula 6.

[0090] [Number 6]

[0091]

[0092] In Equation 6, the electrode distance W (m) is the shortest distance between the anode 12 and the cathode 13, the flow velocity (m / s) in the electrolytic cell is the flow velocity of the alkaline water in the cathode chamber 16, and the electrode length L (m) is the length of the cathode 13 in the direction of alkaline water flow. Hydroxide ion mobility μ (m) 2 / Vs) represents the ion mobility μ of hydroxide ions, which is 20.55 × 10⁻⁶. -8 (m 2 / Vs). In addition, the solution potential V(V) of the alkali is the voltage applied to the alkaline water from the electrolysis power supply 90 via the cathode 13 in the form of a control voltage.

[0093] Here, in the water treatment apparatus 1, the condition under which the neutralization point of the hydrogen ions generated at the anode 12 and the hydroxide ions generated at the cathode 13 becomes the ion-permeable membrane 14 is [H + The proportion that does not cross the membrane] = [OH] - [The proportion that does not cross the membrane]. Therefore, according to equations 5 and 6 and this condition, when the flow rates of acidic water and alkaline water are controlled by the control unit 100 in a manner that satisfies equation 7, the hydrogen ions generated at the anode 12 are less likely to migrate to the cathode chamber 16 after passing through the ion permeation membrane 14. As a result, the decrease in pH of the alkaline water in the cathode chamber 16 can be suppressed, thereby promoting the insolubility of metal ions.

[0094] [Number 7]

[0095]

[0096] Furthermore, regarding the water treatment apparatus 1, more preferably, the control unit 100 controls the flow rate of acidic water in the anode chamber 15 and the flow rate of alkaline water in the cathode chamber 16 in a manner satisfying formula 8. With such control, hydrogen ions are less likely to migrate into the cathode chamber 16. Therefore, the decrease in pH of the alkaline water in the cathode chamber 16 can be further suppressed, thereby promoting the insolubility of metal ions.

[0097] [Number 8]

[0098]

[0099] Here, the proportion (%) of hydrogen ions generated by the electrode reaction that migrate through the ion permeation membrane 14 to the cathode chamber 16 can be calculated using the following formula 9. That is, the proportion (transfer ratio) of hydrogen ions that migrate from the anode chamber 15 to the cathode chamber 16 can be calculated using the following formula 9.

[0100] [Number 9]

[0101]

[0102] exist Figure 9 The figure shows the pH change (vertical axis) and the electrical charge between electrodes (horizontal axis) of the alkaline water in cathode chamber 16 calculated using a theoretical model, as well as the relationship between pH and H2. + The results obtained from the relationship between the proportions crossing the membrane. Figure 9 H is also shown in the middle. + The flow rate of acidic water in the anode chamber when the proportion of water passing through the membrane is at a specified value. That is, H... + With 99.60% of the water passing through the membrane, the flow rate of acidic water in the anode chamber is 0.185 L / min. + With 67% of the water passing through the membrane, the flow rate of acidic water in the anode chamber is 15 L / min.

[0103] like Figure 9 As shown, the pH increases with increasing charge between the anode 12 and the cathode 13. Furthermore, it can be seen that in H... + When the proportion of ion permeate passing through ion-permeable membrane 14 is less than 99.6%, the pH of the alkaline water in cathode chamber 16 is 8.2. Furthermore, due to... Figure 9 It can be seen that, with H + As the proportion of water passing through ion-permeable membrane 14 decreases, the pH of alkaline water increases.

[0104] Furthermore, when the pH of the alkaline water in cathode chamber 16 is above 8.2, such as Figure 4 As shown, carbonate ions (CO3) 2-The increased proportion of H+ ions promotes the insolubility of calcium ions. Therefore, by increasing the proportion of H+ ions... + Increasing the flow rate of acidic water in the anode chamber 15 by allowing the proportion of water passing through the ion-permeable membrane 14 to be less than 99.6% can promote the insolubility of metal ions.

[0105] Thus, the proportion of hydrogen ions generated in the anode chamber 15 by the electrode reaction that do not migrate to the cathode chamber 16 after crossing the ion-permeable membrane 14 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 to the cathode chamber 16 after crossing the ion-permeable membrane 14 is more preferably 1% to 20%. This structure promotes the insolubility of metal ions, thereby reducing the amount of metal ions in the treated water.

[0106] Furthermore, the theoretical model described above, which represents the relationship between the pH change of the alkaline water in the cathode chamber 16 and the electrical charge between the electrodes, can be derived as follows.

[0107] In an electrolysis structure having an ion-permeable membrane 14 that suppresses the flow of water between a cathode chamber 16 and an anode chamber 15, if the ratio α of the amount of protons migrating from the anode chamber to the cathode chamber via the ion-permeable membrane to the amount of protons generated by the electrode reaction based on water electrolysis is taken into account, Equation 10 can be obtained.

[0108] [Number 10]

[0109]

[0110] Here, each symbol represents the following.

[0111] i: current [A]

[0112] t: Time (seconds)

[0113] F: Faraday constant [C / mol]

[0114] V0: Water volume [L]

[0115] K w : Ion product of water [mol] 2 / L 2 ]

[0116] K1: Equilibrium constant of carbonic acid and bicarbonate ions [mol] 2 / L 2 ]

[0117] K2: Equilibrium constant between bicarbonate ions and carbonate ions [mol] 2 / L 2 ]

[0118] [H +Molar concentration of protons [mol / L]

[0119] C a Total molar concentration of carbonic acid [mol / L]

[0120] α: The proportion of protons generated by the electrolysis reaction that migrate towards the cathode side [-]

[0121] The following shows the derivation process of Equation 10. First, the chemical formula for the electrolysis reaction of water is given by the following chemical formula 2.

[0122] [Chemistry 2]

[0123]

[0124] In addition, the chemical equilibrium of carbonic acid in water is represented by the following chemical formula 3, and the ratio of carbonic acid present varies with pH.

[0125] [Chemistry 3]

[0126]

[0127] If the total amount of carbonic acid is denoted as a, then the molar concentration C a It is represented by the following formula (1).

[0128] [Number 11]

[0129]

[0130] If the hydroxide ions based on electrolysis are OH - and proton H + Let the amount of substance be b mol, then the molar concentration C b It is represented by the following formula (2).

[0131] [Number 12]

[0132]

[0133] Here, if the equilibrium constants of the carbonate species are set as K1 and K2, they are represented by the following equations (3) and (4).

[0134] [Number 13]

[0135]

[0136] If we rearrange equations (3) and (4), we get the following equations (5) to (7).

[0137] [Number 14]

[0138]

[0139] In addition, if the ion product of water is set as Kw, then the following equations (8) and (9) are derived.

[0140] [Number 15]

[0141]

[0142] In addition, the total carbonic acid concentration C a It is represented by the following equation (10).

[0143] [Number 16]

[0144]

[0145] If we substitute equations (6) and (7) into equation (10) and rearrange them, we get equations (11) to (13).

[0146] [Number 17]

[0147]

[0148] Substituting equation (13) into equation (7) yields equation (14).

[0149] [Number 18]

[0150]

[0151] Substituting equation (13) into equation (6) yields the following equation.

[0152] [Number 19]

[0153]

[0154] Furthermore, according to the principle of electrical neutrality, the following equation holds true.

[0155] [Number 20]

[0156]

[0157] If we substitute equations (8), (13), (14), and (15) into equation (16), we get equation (17).

[0158] [Number 21]

[0159]

[0160] Here, by adding hydroxide ions generated through the electrolysis of water, we obtain formulas (18) and (19).

[0161] [Number 22]

[0162]

[0163] According to equation (19), it is possible to describe the pH value corresponding to the charge. Figure 10 .also, Figure 10 In the example, using Ca = 2.66 × 10 -3 Calculations were performed using [mol / L] and V0 = 6.0 [L].

[0164] Furthermore, if we consider the proportion α of protons generated in the electrolysis reaction of the anode chamber 15 after migrating to the cathode chamber 16 via the ion permeation membrane 14, we obtain equation (20).

[0165] [Number 23]

[0166]

[0167] The pH curve when the value of α changes is as follows Figure 9 .exist Figure 9 The value in the middle indicates that as protons migrate into the cathode chamber 16, the rise in pH of the cathode chamber 16 is suppressed, i.e., neutralized.

[0168] In the water treatment apparatus 1, the control unit 100 preferably controls the flow rates of acidic water and alkaline water based on the proportion of hydrogen ions generated in the anode chamber 15 through the electrode reaction that do not migrate to the cathode chamber 16 after crossing the ion-permeable membrane 14. That is, it is preferable to control the flow rates of acidic water and alkaline water such that the proportion of hydrogen ions generated in the anode chamber 15 through the electrode reaction that do not migrate to the cathode chamber 16 after crossing the ion-permeable membrane 14 is 0.4% to 100%. By controlling it in this way, the insolubility of metal ions can be promoted in the cathode chamber 16.

[0169] Furthermore, in the water treatment apparatus 1, it is preferable that the control unit 100 controls the flow rate of acidic water in the anode chamber 15 and the flow rate of 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, by making the pH of the alkaline water in the cathode chamber 16 8.2 or higher, carbonate ions (CO3) are reduced. 2- The increased proportion of [acidic water] promotes the insolubility of calcium ions. Therefore, it is preferable to control the flow rate of acidic water in the anode chamber 15 and the flow rate of alkaline water in the cathode chamber 16 such that the pH of the alkaline water in the cathode chamber 16 reaches, for example, 8.2 or higher. Furthermore, this specified value for the pH of the alkaline water is not limited to 8.2; for example, it can be 10 or 12.

[0170] exist Figure 11 The image shows an example of the results obtained by measuring the pH of alkaline water in cathode chamber 16 when the flow rate of acidic water in anode chamber 15 is set to 4.6 L / min or 14 L / min in water treatment apparatus 1. Furthermore, Figure 11The measurement results were obtained under conditions where the initial conductivity of the treated water was 550 μS / cm, without electrolysis control. Additionally, Figure 11 The test results were obtained under the condition that the flow rate of alkaline water was the same when the flow rate of acidic water was either 4.6 L / min or 14 L / min, and the flow rate of alkaline water was slower than that of acidic water.

[0171] like Figure 11 As shown, when the flow rate of acidic water in anode chamber 15 is 14 L / min, compared to when the flow rate is 4.6 L / min, the pH of alkaline water increases rapidly in a short time. That is, when the flow rate of acidic water in anode chamber 15 is high, the migration of hydrogen ions from anode chamber 15 to cathode chamber 16 is inhibited, and the pH of alkaline water increases rapidly.

[0172] Table 1 shows examples of the ion mobility, insolubility, and softening rate of metal ions when the flow rate of acidic water in the anode chamber 15 is set to 4.6 L / min and 14 L / min in the water treatment apparatus 1. As shown in Table 1, it can be seen that by setting the flow rate of acidic water from 4.6 L / min to 14 L / min, the insolubility (the efficiency of metal ions binding with hydroxide and carbonate ions and remaining insoluble) and softening rate (the efficiency of removing metal ions from the treated water) are increased. That is, it can be seen that when the flow rate of 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 short time, thus increasing the insolubility and softening rate. However, the ion mobility (the efficiency of metal ions migrating from the anode chamber 15 to the cathode chamber 16) does not change, therefore it can be seen that even with an increased flow rate of acidic water, metal ions can still migrate efficiently from the anode chamber 15 to the cathode chamber 16.

[0173] [Table 1]

[0174]

[0175] As described above, the water treatment apparatus 1 of this embodiment includes a first pH measuring unit 15c for measuring the pH of water flowing in the anode chamber 15 and a second pH measuring unit 16c for measuring the pH of water flowing in the cathode chamber 16. Furthermore, the control unit 100 preferably controls the flow rate of acidic water in the anode chamber 15 based on the pH of the alkaline water measured by the pH measuring unit.

[0176] Figure 12 This is a flowchart illustrating an example of a method for controlling the flow rate of acidic water in the anode chamber 15 based on the pH of alkaline water measured by the second pH measuring unit 16c. Figure 13This is a graph illustrating an example of the relationship between the pH (alkaline side pH) of the treated water in the anode chamber 15 and time.

[0177] In the water treatment apparatus 1, firstly, the control unit 100 injects the water to be treated into the treated water flow path 40, the first flow path 20 and the second flow path 30, the anode chamber 15 and the cathode chamber 16 of the electrolytic cell 10, and the acidic water tank 21 and the alkaline water tank 31. Next, the control unit 100 controls the electrolysis power supply 90 to allow current to flow between the anode 12 and the cathode 13, thus electrolyzing the water to be treated. Additionally, the control unit 100 operates the first circulation pump 22 and the second circulation pump 32 to circulate the treated water in the first flow path 20 and the second flow path 30. Through electrolysis and circulation of the treated water for a predetermined time, the treated water in the anode chamber 15, the first flow path 20, and the acidic water tank 21 becomes acidic water, and the treated water in the cathode chamber 16, the second flow path 30, and the alkaline water tank 31 becomes alkaline water.

[0178] Here, control unit 100 begins to follow... Figure 12 The control unit 100 controls the flow chart. In step S1, the control unit 100 measures the pH of the treated water (alkaline water) in the cathode chamber 16. Next, in step S2, if the result obtained by measuring the pH of the alkaline water in the cathode chamber 16 is that the pH of the alkaline water is lower than the target, i.e., if... Figure 13 If the pH of the alkaline water is lower than the target pH curve as indicated by the attached figure (1), proceed to step S3.

[0179] In step S3, the control unit 100 increases the flow rate of acidic water by adjusting the first circulation pump 22 and / or the first solenoid valve 51 of the first flow rate adjustment unit. Specifically, the flow rate of acidic water is increased by increasing the rotational speed of the first circulation pump 22 and increasing the opening of the first solenoid valve 51.

[0180] After the processing in step S3, in step S1 again, the control unit 100 measures the pH of the alkaline water in the cathode chamber 16. Next, in step S2, the control unit 100 measures the pH of the alkaline water in the cathode chamber 16, and the result is as follows... Figure 13 If the pH of the alkaline water is above the target value as indicated by the attached diagram (2), proceed to step S4.

[0181] In step S4, if the pH of the alkaline water in the cathode chamber 16 is above the target pH curve and reaches the target pH, it is determined whether the water treatment end time has been reached. Furthermore, Figure 13 The period from the time it takes to reach the target pH (reach time) to the end time is the time during which the reaction that renders the metal ions insoluble takes place. Then, when the pH of the alkaline water is above the target pH curve and the water treatment end time has been reached, the flow rate control of both acidic and alkaline water is terminated.

[0182] Furthermore, in step S4, if the water treatment end time has not been reached, the pH of the alkaline water in the cathode chamber 16 is measured again to determine whether the pH of the alkaline water is above the target pH curve. If the pH of the alkaline water has not reached the target pH curve, the difference between the pH of the alkaline water and the target pH curve is calculated, and the flow rate of the acidic water is increased to bring the pH of the alkaline water to the target pH curve.

[0183] In this way, the control unit 100 controls the flow rate of acidic water in the anode chamber 15 based on the pH of the alkaline water measured by the pH measuring unit, thereby making it easier for the alkaline water to reach the target pH. Therefore, it is possible to further promote the insolubility of metal ions.

[0184] Furthermore, in the water treatment apparatus 1 of this embodiment, a flow rate measuring unit (flow rate sensor) for measuring the flow rate of acidic water can be provided in the first flow path 20, and a flow rate measuring unit (flow rate sensor) for measuring the flow rate of alkaline water can be provided in the second flow path 30. By providing such a flow rate measuring unit, the accuracy of the flow rate control of acidic and alkaline water can be improved. However, even without a flow rate measuring unit, the flow rates of acidic and alkaline water can be estimated by calculation; therefore, in the water treatment apparatus 1 of this embodiment, a flow rate measuring unit is not an essential structure.

[0185] As described above, in the water treatment apparatus 1, the first flow path 20 and the second flow path 30 are configured as circulating flow paths. However, the water treatment apparatus is not limited to this configuration; single-flow flow paths that do not circulate water can also be used as the first and second flow paths. Furthermore, circulating flow paths and single-flow flow paths can be combined as the first and second flow paths. Therefore, in this specification, circulating flow paths and single-flow flow paths are collectively referred to as the "first flow path." Similarly, circulating flow paths and single-flow flow paths are collectively referred to as the "second flow path."

[0186] (Postscript)

[0187] Based on the description of the above embodiments, the following technology is disclosed.

[0188] (Technology 1) A water treatment apparatus for removing metal ions from water to be treated to generate treated water, the water treatment apparatus comprising: an electrolytic cell having an anode chamber having an anode, a cathode chamber having a cathode, and a membrane separating the anode chamber and the cathode chamber and allowing ions to permeate, the electrolytic cell generating 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 in the anode chamber and the alkaline water flows in the cathode chamber, the control unit controlling the flow rate of the acidic water in the anode chamber and the flow rate of the alkaline water in the cathode chamber in a manner satisfying the following formula 24.

[0189] [Number 24]

[0190]

[0191] In the water treatment apparatus of this embodiment, by increasing the flow rate of acidic water in the anode chamber 15 in a manner that satisfies Equation 24, hydrogen ions generated at the anode 12 are less likely to migrate to the cathode chamber 16 after passing through the ion permeation membrane 14. Therefore, the decrease in pH of the alkaline water in the cathode chamber 16 can be suppressed, thereby promoting the insolubility of metal ions.

[0192] (Technology 2) The water treatment apparatus according to Technology 1 further includes a pH measuring unit, which measures at least one of the pH of acidic water flowing in the anode chamber and the pH of alkaline water flowing in the cathode chamber.

[0193] With this configuration, the flow rate of acidic water in the anode chamber and the flow rate of alkaline water in the cathode chamber can be controlled based on the pH measured by the pH measuring unit. Therefore, the decrease in pH of the alkaline water in the cathode chamber 16 can be suppressed, thereby promoting the insolubility of metal ions.

[0194] (Technology 3) The water treatment apparatus according to Technology 2, wherein the control unit controls the flow rate of the acidic water in the anode chamber based on the pH of the alkaline water measured by the pH measuring unit.

[0195] This structure can suppress the decrease in pH of the alkaline water in the cathode chamber 16, thereby promoting the insolubility of metal ions.

[0196] (Technology 4) The water treatment apparatus according to any one of technologies 1 to 3, wherein the pH of the alkaline water in the cathode chamber is 8.2 or higher.

[0197] Based on this structure, the insolubility of metal ions can be promoted, thereby reducing the metal ions in the treated water.

[0198] (Technology 5) A water treatment apparatus according to any one of technologies 1 to 4, wherein the control unit causes at least one of the voltage and current between the anode and the cathode to change.

[0199] This structure controls the insolubility of metal ions and their migration from the anode chamber to the cathode chamber, thus enabling efficient removal of metal ions.

[0200] (Technology 6) According to the water treatment apparatus of Technology 5, when the conductivity of the water flowing in the anode chamber and the conductivity of the water flowing in the cathode chamber are 30 μS / cm to 8000 μS / cm, the control unit causes a change in the voltage applied between the anode and the cathode.

[0201] In this embodiment, the conductivity range of the water being treated during electrolysis control is preferably set to a range that consumes less power compared to the cases of constant current control only and constant pressure control only. With this structure, power consumption can be reduced compared to the cases of constant current control only and constant pressure control only.

[0202] (Technology 7) A water treatment apparatus according to any one of technologies 1 to 6, wherein the control unit switches from constant current control to constant voltage control by changing the voltage or current applied between the anode and the cathode.

[0203] According to this structure, it is possible to promote the insolubility of metal ions in the treated water, and compared with the cases of constant flow control only and constant pressure control only, it is possible to suppress power consumption.

[0204] The above describes this embodiment, but this embodiment is not limited thereto, and various modifications can be made within the scope of the main idea of ​​this embodiment.

[0205] The entire contents of Japanese Special Appeal No. 2024-052088 (application date: March 27, 2024) are incorporated herein by reference.

[0206] Industrial availability

[0207] According to this disclosure, a water treatment apparatus can be provided that can efficiently remove metal ions from hard water even without using ion exchange resins.

[0208] Explanation of reference numerals in the attached figures

[0209] 1: Water treatment equipment

[0210] 10: Electrolytic cell

[0211] 12: Anode

[0212] 13: Cathode

[0213] 14: Membrane (ion-permeable membrane)

[0214] 15: Anode Chamber

[0215] 15c: First pH Measurement Section

[0216] 16: Cathode Chamber

[0217] 16c: Second pH measuring section

[0218] 100: Control Department

Claims

1. A water treatment apparatus for removing metal ions from water to be treated to generate treated water. The water treatment device includes: An electrolytic cell comprising an anode chamber having an anode, a cathode chamber having a cathode, and a membrane separating the anode chamber and the cathode chamber and allowing ions to permeate, the electrolytic cell generating acidic water and alkaline water from the water being treated by electrolysis; and The control unit controls the voltage or current between the anode and the cathode. in, The acidic water flows through the anode chamber, and the alkaline water flows through the cathode chamber. The control unit controls the flow rate of the acidic water in the anode chamber and the flow rate of the alkaline water in the cathode chamber in a manner that satisfies Formula 1. [Number 1] 。 2. The water treatment apparatus according to claim 1, wherein, It also includes a pH measuring unit that measures at least one of the pH of acidic water flowing in the anode chamber and the pH of alkaline water flowing in the cathode chamber.

3. The water treatment apparatus according to claim 2, wherein, The control unit controls the flow rate of the acidic water in the anode chamber based on the pH of the alkaline water measured by the pH measuring unit.

4. The water treatment apparatus according to any one of claims 1 to 3, wherein, The pH of the alkaline water in the cathode chamber is above 8.

2.

5. The water treatment apparatus according to any one of claims 1 to 4, wherein, The control unit causes a change in at least one of the voltage and current between the anode and the cathode.

6. The water treatment apparatus according to claim 5, wherein, When the conductivity of the water flowing in the anode chamber and the conductivity of the water flowing in the cathode chamber are 30 μS / cm to 8000 μS / cm, the control unit causes a change in the voltage applied between the anode and the cathode.

7. The water treatment apparatus according to any one of claims 1 to 6, wherein, The control unit switches between constant current control and constant voltage control by changing the voltage or current applied between the anode and the cathode.

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