JP2006175360A - Method and device for controlling ph of solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for controlling a pH of a solution which can precisely control a pH with a relatively simple device by electrically controlling the number of ions present in the solution. <P>SOLUTION: The pH of the solution is controlled toward a target value by making an electrode charged with a direct-current voltage present in the solution which serves as a target of pH control, continuously controlling an electric potential difference between both electrodes and/or an electric current value, and adsorbing the ion present in the solution to the electrode to control the number of the ions in the solution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention realizes direct control over the solution only by electrical control of the ion concentration, ie, pH, present in the solution, so that the solution pH can be controlled with high accuracy by a relatively simple device. The present invention relates to a pH control method and apparatus.

  Conventionally, solutions having various properties have been used in various industrial fields. Such a solution is used by adjusting the pH so as to have the most appropriate characteristics depending on the application. Such pH control can be performed mainly by controlling the ion concentration.

  As a method for controlling the ion concentration as described above, for example, as shown in Patent Document 1 below, the ion concentration of a solution to be controlled is detected, and a predetermined chemical is replenished so that the ion concentration becomes a target level. What is done by doing is disclosed.

  In addition, as shown in Patent Document 2 below, the solution is permeated through an ion permeable membrane while electrolyzing the solution, and separated into acidic water and alkaline water and introduced into a salt water tank provided with a pH sensor. There has been disclosed a method in which the pH of salt water is controlled to a desired value by adjusting the introduction amount of acidic water and alkaline water based on a detection signal of a pH sensor.

On the other hand, as shown in Patent Documents 3 and 4 below, a technique is disclosed in which a direct current is applied to two electrodes existing in a solution to remove and collect ions in the solution.
JP 2001-103855 A Japanese Patent Laid-Open No. 7-299457 JP-A-6-325983 Japanese National Patent Publication No. 11-505463

  However, in the method as described in Patent Document 1, in addition to the solution tank to be controlled, a replenishing chemical tank and pumps and pipes for replenishing the chemical are required for the number of types of chemicals required. As a result, the equipment becomes large. In the method of Patent Document 2 as well, the acidic water and alkaline water to be introduced are not stored in the tank but are only generated by electrolysis, and the electrolysis is performed in addition to the solution tank (salt water tank) to be controlled. Equipment and piping are required, and the equipment becomes large. For this reason, in any of the above methods, there is a problem that the equipment is complicated and large, and equipment costs and maintenance costs are required. Moreover, since the method of Patent Document 2 requires an ion-permeable membrane, maintenance such as replacement and regeneration is necessary, and it is a fact that a great deal of cost is required to maintain the equipment.

  Further, in any of the methods disclosed in Patent Document 1 and Patent Document 2, the adjustment liquid is merely replenished so that the ion concentration and pH become the target level, and the control target solution itself is not directly controlled. . When such adjustment liquid is replenished, there are problems that variations in the characteristics of the adjustment liquid affect control accuracy, and variations in adjustment accuracy due to excessive replenishment are likely to occur. Also, when trying to finely adjust the ion concentration or pH, a small amount of adjustment liquid is supplied and controlled. However, a small amount of adjustment liquid is mixed well in the tank, and the ion concentration and pH are mixed. Since it is necessary to repeatedly add a small amount of the adjustment liquid again after reflecting in the detected value, there is a problem that the fine adjustment work takes time and labor.

  Furthermore, the methods shown in Patent Documents 3 and 4 are merely methods for removing ionic substances in the solution, and the pH of the solution can be controlled to be an arbitrary target value. Absent.

  The present invention has been made in view of the above circumstances, and is a solution pH control method and apparatus capable of controlling the pH of a solution with high accuracy with a relatively simple device only by direct electrical control over the solution. For the purpose of provision.

  In order to achieve the above object, the pH control method for a solution of the present invention comprises an electrode to which a direct current voltage is applied in a solution to be controlled for pH, and a potential difference and / or current value between the two electrodes is continuously set. The gist is to control the pH of the solution toward the target value by adsorbing ions present in the solution to the electrode and controlling the number of ions in the solution.

  In order to achieve the above object, the pH control apparatus for a solution of the present invention includes a storage tank for storing a solution to be controlled by pH, an electrode that is present in the solution and to which a DC voltage is applied, Control means for continuously controlling the potential difference and / or current value applied between the electrodes, and controlling the potential difference and / or current value applied to both electrodes by the control means, thereby allowing ions present in the solution The gist of the invention is to control the pH of the solution toward the target value by adsorbing to the electrode and controlling the number of ions in the solution.

  That is, the pH control method and apparatus for a solution of the present invention provides an electrode for ions in a solution by continuously controlling a potential difference and / or current value applied to an electrode present in the solution to be pH controlled. The amount of ions in the solution is controlled by controlling the adsorption to the surface. For example, when a positive voltage is applied to the anode in the solution, negative ions in the solution are adsorbed, and when a negative voltage is applied to the cathode, the positive ions are adsorbed and negative ions and positive ions in the solution are reduced. In this way, by controlling the adsorption of ions to the electrode present in the solution, the ion concentration in the solution can be controlled, and the pH of the solution can be controlled to a target value.

  In this way, the electrode is present in the solution to be controlled, and the potential difference and / or current value applied to the electrode is controlled to electrically control the ion concentration present in the solution to be controlled. Only, direct control over the solution can be achieved. Therefore, unlike the conventional case, there is no need for a tank for storing the adjustment liquid, an electrolysis apparatus for producing the adjustment liquid, and complicated piping associated therewith, and the apparatus is greatly simplified and downsized, and the equipment cost and maintenance cost are reduced. Can be saved significantly. Further, since the conventional ion exchange membrane is not required, maintenance of the ion exchange membrane is also unnecessary. Moreover, since the adjustment target liquid is not directly replenished as in the prior art, the control target solution itself is directly controlled, so that variations in the characteristics of the adjustment liquid affect the control accuracy, or variations in adjustment accuracy due to excessive replenishment. The problem of the occurrence of the problem is completely solved. Moreover, even when finely adjusting the pH, it is possible to easily finely adjust the pH by finely adjusting the level of the potential applied to the electrode and finely adjusting the adsorption of ions to the electrode. Compared with the method of replenishing the adjustment solution, highly accurate pH control can be realized in a very short time. As described above, according to the present invention, the pH of a solution can be controlled with high accuracy using a relatively simple device.

In the pH control method for a solution of the present invention, the potential difference and / or current value between the two electrodes is controlled based on a current integrated value obtained by integrating the current value flowing between the two electrodes and the energization time. In the solution pH control apparatus according to the present invention, the control unit includes a current integrating unit that calculates a current integrated value obtained by integrating a current value flowing between both electrodes and an energization time. When controlling the adsorption amount of ions to the electrodes by controlling the potential difference and / or current value between the electrodes based on the calculated current integrated value,
Since the amount of adsorption can be controlled based on a numerical value that is easy to measure, such as an integrated current value, the ion concentration in the solution can be easily controlled.

In the pH control method for a solution of the present invention, when the ion adsorption is controlled to be performed with a potential difference that does not substantially cause electrolysis of the solution, and in the pH control apparatus for the solution of the present invention, the electrode is When the electric potential applied to the electrode is controlled so that the adsorption of the ions is performed in a range that does not substantially cause electrolysis of the solution,
If the solution is electrolyzed, the ion concentration changes by itself, but by performing ion adsorption in a range that does not substantially cause electrolysis of the solution, the pH is controlled only by ion adsorption, and the electrode By reflecting only the control of the potential applied to the pH in the pH and eliminating other factors, it is possible to always realize accurate pH control and ensure the accuracy of pH control.

In the solution pH control apparatus of the present invention, the storage tank is provided with an introduction path for introducing the solution to be controlled by pH and a discharge path for discharging the solution whose pH is controlled. If it is configured to generate automatically,
While introducing the solution to be controlled into the storage tank, the pH is controlled by controlling the adsorption of ions to the electrode in the storage tank, and the pH-controlled solution is continuously discharged from the discharge path. As described above, since the pH of the solution can be controlled while continuously flowing the solution, it is possible to operate with extremely good treatment efficiency.

The solution pH control apparatus of the present invention comprises pH detection means for detecting pH in the solution at or near the discharge path, and the control means is applied to the electrode according to the detection result of the pH of the solution by the pH detection means. When controlling the potential difference and / or current value to be applied,
By controlling the potential difference and / or current value applied to the electrodes in accordance with the pH detection result by the pH detection means, it is possible to control the continuously flowing solution to always have the target pH. In this way, control to the target pH can be continuously performed, and a solution having the target pH can be continuously generated.

In the solution pH control apparatus of the present invention, the introduction path or the discharge path is provided with a flow rate adjusting valve for adjusting the flow rate of the solution introduced or discharged, and the control means controls the pH of the solution by the pH detection means. When controlling the flow control valve according to the detection result,
When controlling the adsorption of ions while continuously flowing the solution, by appropriately controlling the flow rate according to the pH detection result by the pH detection means, the influence of the flow rate on the control accuracy is eliminated, and the target pH is always adjusted. The solution can be produced continuously.

  Next, the best mode for carrying out the present invention will be described.

  FIG. 1 is a diagram showing a first embodiment of a pH control apparatus for a solution of the present invention.

  The pH control device includes a storage tank 1 that stores a solution to be controlled by pH, electrodes 6 and 7 that are present in the solution stored in the storage tank 1 and to which a DC voltage is applied, and the electrodes 6 and 6. 7 and a control circuit 8 for controlling a potential difference and / or a current value applied to 7.

  The electrodes 6 and 7 are connected to a DC power source 4 capable of voltage control and current control, and are composed of an anode 6 to which a positive potential is applied and a cathode 7 to which a negative potential is applied. Reference numeral 5 denotes a switch for switching between a state in which the electrodes 6 and 7 are connected to a DC power source and a DC voltage is applied to the electrodes 6 and 7 and a state in which the electrodes 6 and 7 are short-circuited.

  The storage tank 1 is provided with an introduction path 2 for introducing the solution into the storage tank 1 and a discharge path 3 a for discharging the adjusted solution whose pH is adjusted in the storage tank 1. The discharge path 3a is provided with a pH meter 10 as an ion detection means for detecting the ion concentration of the adjusted solution discharged from the storage tank 1. The introduction path 2 detects the flow rate of the solution introduced into the storage tank 1 at a flow rate adjustment valve 11 that adjusts the flow rate of the solution introduced into the storage tank 1 and the flow rate adjusted by the flow rate adjustment valve 11. A flow meter 9 is provided. The ion concentration detected by the pH meter 10 and the flow rate detected by the flow meter 9 are sent to the control circuit 8. Further, the storage tank 1 is provided with a waste liquid path 3b for discharging the solution in the storage tank 1 as a waste liquid. 24a and 24b are valves provided in the discharge path 3a and the waste liquid path 3b, respectively.

  The control circuit 8 performs switching control of the switch 5 to control the potential applied to the electrodes 6 and 7, thereby adsorbing ions, which are ions in the solution, to the electrodes 6 and 7, and the electrode 6. , 7 to control the release of ions adsorbed into the solution.

  That is, by controlling the potential applied to the electrodes 6 and 7 existing in the solution to be controlled by pH, ions such as ions in the solution are adsorbed to the electrodes 6 and 7 and adsorbed to the electrodes 6 and 7. Control the release of ions into solution.

  When the pH is adjusted by adsorbing ions in the solution to be controlled, the switch 5 is controlled so as to apply a voltage to the electrodes 6 and 7, as shown in FIG. Are adsorbed on the electrodes 6 and 7.

  In this way, by continuously controlling the potential difference and / or current value applied to the electrodes 6 and 7 that are present in the solution to be pH controlled, adsorption of ions in the solution to the electrodes 6 and 7 can be performed. By controlling, the amount of ions in the solution is controlled. For example, when a positive voltage is applied to the anode in the solution, negative ions in the solution are adsorbed, and when a negative voltage is applied to the cathode, the positive ions are adsorbed and negative ions and positive ions in the solution are reduced. In this way, by controlling the adsorption of ions to the electrodes 6 and 7 existing in the solution, the ion concentration in the solution can be controlled and the pH of the solution can be controlled to a target value. It is. Then, the pH-controlled solution is discharged from the discharge path 3a.

  On the other hand, when the amount of ions adsorbed on the electrodes 6 and 7 reaches the limit, as shown in FIG. 1B, the switch 5 is controlled to short-circuit the electrodes 6 and 7 to release the voltage application. Then, the ions 6 and 7 are regenerated by releasing the ions adsorbed on the electrodes 6 and 7 into the solution. The solution from which the ions adsorbed on the electrodes 6 and 7 are released in large quantities is discharged from the waste liquid passage 3b as a waste liquid.

  The voltage applied to the electrodes 6 and 7 is not particularly limited, but is preferably set to about 0.5 to 5V.

  Here, FIG. 1 shows a so-called beaker model schematically showing an example in which the storage tank 1 has one anode 6 and one cathode 7 each, but industrially, as shown in FIG. A cell in which a plurality of collector electrodes (double-sided electrodes) 18a and 18b are arranged can be obtained.

  In this cell, a plurality of (in this example, 12) double-sided electrodes 18a and 18b are disposed between two end plates 16 in a laminated state, and between the double-sided electrodes 18a and 18b and between the double-sided electrodes 18a and 18b, A frame spacer 23 is arranged between the end plates 16. Reference numeral 17 denotes a bolt and nut for fixing the laminated frame spacer 23, the end plate 16, and the double-sided electrodes 18a and 18b.

  One double-sided electrode 18 a is a positive electrode in which the anode 6 is provided on both sides of the separator 12, and the other double-sided electrode 18 b is a negative electrode in which the negative electrode 7 is provided on both sides of the separator 12. Then, the positive electrode 18a and the negative electrode 18b are alternately stacked, so that the anode 6 and the cathode 7 face each other between the adjacent double-sided electrodes 18a and 18b. And the internal space formed by the said double-sided electrodes 18a and 18b, the frame-shaped spacer 23, and the terminal plate 16 is a storage space in which a solution is stored, and the whole cell functions as a storage tank. The storage space is divided into a plurality of (13 in this example) spaces by the double-sided electrodes 18a and 18b.

  Further, an inlet 14 communicating with the introduction path 2 (not shown in FIG. 2) is formed in one end plate 16 (upper side in the figure), and the discharge path 3a and the waste liquid path 3b (see FIG. 2) are formed in the other end plate 16. A discharge port 15 communicating with (not shown in FIG. 2) is formed. Further, in this example, each separator 12 is formed with communication ports 13 in a staggered arrangement so that the solution introduced into the internal storage space flows in a zigzag manner.

  Then, the solution introduced from the introduction port 14 is subjected to adsorption and release of ions and the like to the electrodes 6 and 7 while passing through a plurality of spaces sandwiched between the anode 6 and the cathode 7, and the pH is controlled. Is discharged from the discharge port 15.

  In this way, the electrodes 6 and 7 are present in the solution to be controlled, and the potential difference and / or current value applied to the electrodes 6 and 7 are controlled, whereby the ion concentration present in the solution to be controlled is determined. It is possible to directly control the solution only by electrical control. Therefore, unlike the conventional case, there is no need for a tank for storing the adjustment liquid, an electrolysis apparatus for producing the adjustment liquid, and complicated piping associated therewith, and the apparatus is greatly simplified and downsized, and the equipment cost and maintenance cost are reduced. Can be saved significantly. Further, since the conventional ion exchange membrane is not required, maintenance of the ion exchange membrane is also unnecessary.

  Moreover, since the adjustment target liquid is not directly replenished as in the prior art, the control target solution itself is directly controlled, so that variations in the characteristics of the adjustment liquid affect the control accuracy, or variations in adjustment accuracy due to excessive replenishment. The problem of the occurrence of the problem is completely solved. Moreover, even when the pH is finely adjusted, the pH level is easily adjusted by finely adjusting the level of the potential applied to the electrodes 6 and 7 and finely adjusting the adsorption of ions to the electrodes 6 and 7. As compared with the conventional method of replenishing the adjustment solution, highly accurate pH control can be realized in a very short time. As described above, according to the present invention, the pH of a solution can be controlled with high accuracy using a relatively simple device.

  In the above description, the electrodes 6 and 7 are short-circuited when ions adsorbed on the electrodes 6 and 7 are released into the solution. However, the present invention is not limited to this, and the switch is simply turned off. Application of a DC voltage to the electrodes 6 and 7 may be canceled, or a negative voltage may be applied to the anode 6 and a positive voltage may be applied to the cathode 7 to make a reverse polarity.

  In the above description, an example in which the direct current voltage is applied to the anode 6 and the cathode 7 and the shorted state are switched, and the potential difference between the electrodes 6 and 7 is controlled to control the adsorption and release of ions and the like. As shown, not only on / off of the current between the electrodes 6 and 7 but also control to increase or decrease the potential difference, or control to increase or decrease the value of the current flowing between the electrodes 6 and 7. Adsorption can also be controlled. It is also possible to control adsorption of ions and the like by controlling both the potential difference and the current value to increase or decrease.

  Then, by applying DC voltage to both electrodes 6 and 7 and short-circuiting alternately, reversing the polarity alternately, or continuously controlling the potential difference and current value, positive ions and negative ions Adsorption can be controlled. In this way, the adsorption of ions to the electrodes 6 and 7 existing in the solution is controlled, the concentration and ratio of ions in the solution are controlled to the target value, and the pH of the solution is controlled to the target value. can do.

  The control circuit 8 controls the potential difference and / or current value applied to the electrodes 6 and 7 in accordance with the detection result of ions in the solution by the pH meter 10 as pH detecting means. That is, for example, when the pH of the adjusted solution is different from the target value in the pH meter 10, the switch 5 is switched to apply a voltage to the electrodes 6 and 7, and ions in the solution are adsorbed to the electrodes 6 and 7. Is controlled to become the target value. In addition, as a pH detection means, if the physical quantity corresponding to ion concentration is detected, not only the pH meter 10 but various things can be applied.

  Then, while introducing the solution to be controlled into the storage tank 1 from the introduction path 2, the pH is controlled by controlling the adsorption of ions to the electrodes 6 and 7 in the storage tank 1, and the adjusted solution with controlled pH Are continuously discharged from the discharge path 3a. As described above, since the pH of the solution can be controlled while continuously flowing the solution, it is possible to operate with extremely good treatment efficiency. Further, by controlling the potential difference and / or current value applied to the electrodes 6 and 7 in accordance with the detection result of ions and the like by the pH meter 10, the continuously flowing solution is controlled to always have a target pH. Is possible. In this way, control to the target pH can be continuously performed, and a solution having the target pH can be continuously generated.

  The control circuit 8 controls the flow rate control valve 11 according to the detection result of the pH of the solution by the pH meter 10. That is, when controlling the adsorption of ions while continuously flowing the solution, if the flow rate is too large, the solution is discharged from the discharge path 3a without sufficiently reflecting the pH change of the solution due to the adsorption of ions to the electrodes 6 and 7. On the other hand, if the flow rate is too small, the processing efficiency decreases. Therefore, when controlling the adsorption of ions while continuously flowing the solution, the flow rate is appropriately controlled according to the detection result of the ion concentration by the pH meter 10, thereby eliminating the influence of the flow rate on the control accuracy. A solution having a target pH can be continuously produced.

  Further, the control circuit 8 controls the voltage of the DC power supply 4 to control the potential difference applied to both electrodes 6 and 7, thereby adsorbing ions as ions in the solution to the electrodes 6 and 7. Control the amount. That is, when it is desired to further reduce the ions in the solution to be controlled, the voltage of the DC power supply 4 can be increased so that more ions and the like can be adsorbed to the electrodes 6 and 7. Further, by increasing the voltage of the DC power supply 4, the adsorption speed of ions and the like to the electrodes 6 and 7 is increased, and more sensitive pH control can be performed. Similarly, by controlling the current value applied to both electrodes 6 and 7, the adsorption amount and adsorption speed of ions, which are ions in the solution, to the electrodes 6 and 7 can be controlled.

  Further, the control circuit 8 switches the switch 5 so as to apply a voltage to the electrodes 6 and 7 when the pH of the adjusted solution in the pH meter 10 is different from the target value, so that ions in the solution are applied to the electrodes 6 and 7. In this case, if the target value is not reached even after a predetermined time has elapsed, the flow rate control valve 11 can be controlled so as to reduce the flow rate. In such a case, by reducing the flow rate, the time during which the solution stays in the storage tank 1 becomes longer, and more ions can be adsorbed on the electrodes 6 and 7 to control the pH to the target value. It becomes like this. On the other hand, when the time until the target value is reached is equal to or shorter than a predetermined time set in advance, the flow rate control valve 11 is controlled so that the flow rate becomes larger. In such a case, by increasing the flow rate, the time during which the solution stays in the storage tank 1 is shortened, the pH can be controlled to the target value in a short time, and the processing efficiency can be improved. Become.

  Further, the control circuit 8 switches the switch 5 to apply a voltage to the electrodes 6 and 7 when the pH of the adjusted solution in the pH meter 10 is different from the target value, so that ions in the solution are applied to the electrodes 6 and 7. In this case, if the target value is not reached even after a predetermined time has elapsed, the voltage of the DC power supply 4 can be controlled to be increased. In such a case, by increasing the voltage, it becomes possible to adsorb more ions and the like to the electrodes 6 and 7 and control the pH to the target value. On the contrary, when the time until the target value is reached is equal to or less than a predetermined time set in advance, control is performed so that the voltage of the DC power supply 4 is lowered. In such a case, by reducing the voltage, it is possible to reduce power consumption and improve energy efficiency.

  The control circuit 8 controls the potential difference applied to the electrodes 6 and 7 so that the adsorption of the ions is performed within a range that does not substantially cause electrolysis of the solution. Specifically, it is appropriately set according to the type of solution, but when the solvent is water, it is preferably 2 V or less, and more preferably 1.5 V or less. If the solution is electrolyzed, the pH changes by itself. However, by performing ion adsorption within a range that does not substantially cause electrolysis of the solution, the pH is controlled only by ion adsorption, and the electrode 6 , 7 is reflected only in the control of the potential applied to the pH, and other factors are eliminated, so that accurate pH control can always be realized and the accuracy of pH control can be ensured. Control in such a voltage range is particularly effective when the electrodes 6 and 7 are made of a conductor that is energized with a solution of metal or carbon. In addition, when the electrolysis of the solution occurs, there is a disadvantage that the consumption of the electrode is accelerated and a maintenance cost is required, or a sludge removal facility is required.

  1 and 2 includes a current integration means (not shown) for calculating a current integration value obtained by integrating the current value flowing between the electrodes 6 and 7 and the energization time. By controlling the potential difference and / or current value between the electrodes 6 and 7 based on the calculated integrated current value, the amount of ions adsorbed on the electrodes 6 and 7 can be controlled.

  In this way, the adsorption amount and the release amount can be controlled based on a numerical value that is easy to measure, such as an integrated current value, so that it is easy to control the concentration and existence ratio of ions in the solution.

  In addition, as shown in FIG. 3, two tanks are provided together with the apparatus shown in FIG. 1 and FIG. 2, and the two tank apparatuses are switched and controlled so that suction is performed by the other apparatus when the suction capacity of one is lowered. May be.

  That is, this apparatus has a first storage tank 1a and a second storage tank 1b arranged in parallel. The introduction path 2 for introducing the solution to be controlled is bifurcated and connected to the first storage tank 1a and the second storage tank 1b, respectively, and the first storage tank 1a and the second storage tank are opened and closed by a valve not shown. The solution to be treated can be introduced into any of the tanks 1b.

  On the other hand, the first storage tank 1a and the second storage tank 1b are connected with a discharge path 3a for discharging the treated solution and a waste liquid path 3b for discharging the waste liquid, respectively, and by opening and closing a valve (not shown), The pH adjusted solution is discharged from the discharge path 3a while the pH is controlled by adsorption, and the waste liquid is discharged from the waste liquid path 3b while the electrode is regenerated and the waste liquid is discharged.

  In the above apparatus, first, as shown in FIG. 4A, ions are adsorbed by the first storage tank 1a to adjust the pH of the solution, and the pH adjusted solution is discharged from the discharge path 3a. Thereafter, when the adsorption capacity of the first storage tank 1a decreases, as shown in FIG. 4B, the first storage tank 1a is switched from adsorption to regeneration (the state shown in FIG. 1B), and the first storage tank 1a is stored. The valve is operated so that the solution in the tank 1a is discharged from the waste liquid passage 3b. Further, the control target solution is caused to flow into the second storage tank 1b to start the adsorption in the second storage tank 1b, and the pH adjusted solution is discharged from the second storage tank 1b.

  Thereafter, when the adsorption capacity of the second storage tank 1b decreases, as shown in FIG. 4C, the second storage tank 1b is switched from adsorption to regeneration, and the solution in the second storage tank 1b is discharged from the waste liquid path 3b. Thus, the valve operation is performed, and the adsorption in the first storage tank 1a is started, and the pH-adjusted solution is discharged from the first storage tank 1a.

  By doing so, it is possible to continuously control the pH even during the regeneration of the electrodes 6 and 7 and obtain a solution whose pH has been adjusted continuously.

  As the electrodes 6 and 7, various metal materials such as stainless steel, titanium, nickel, copper, platinum, and gold, and conductive materials such as carbon can be used. The electrodes 6 and 7 are preferably plate-shaped, and the thickness is not particularly limited, but is preferably about 0.1 to 5 mm, and more preferably about 0.5 to 2 mm. Although the space | interval of the anode 6 and the cathode 7 is not specifically limited, About 0.1-5 mm is preferable, More preferably, it is about 0.5-2 mm. It should be noted that the distance between the anode 6 and the cathode 7 does not prevent the distance from being set to 0.1 mm or less unless the solution passes through and prevents adsorption and release of ions.

  When a metal is used as the electrodes 6 and 7, a metal plate that has been subjected to plating or surface modification can be used. For example, the surface layer of a stainless steel plate may be subjected to a low temperature carburizing treatment after a fluorination treatment to form a carbon diffusion permeation layer in which chromium carbide is not substantially precipitated. Moreover, what plated platinum on the titanium plate can also be used. Since these are extremely excellent in corrosion resistance, they are preferably used.

Further, as the electrodes 6, 7, sintered metal powder, plate-like activated carbon, activated carbon nonwoven fabric, conductive ceramics such as silicon carbide, carbon aerogel (pore diameter 2 to BET specific surface area adjusted to 500-2500 m ² / g A porous body such as a 50 nm mesopore-based carbon sheet) can be used. By using such a porous body as the electrodes 6 and 7, the surface area of the electrodes 6 and 7 can be greatly increased, and the amount of adsorption of ions and the like can be remarkably increased.

  The anode 6 and the cathode 7 may be the same type, for example, both are plate-like activated carbon, both are carbon airgel, and both are copper plates. In addition, for example, a combination of a copper plate and a metal plate, a combination of a platinum plate and a stainless steel plate, etc. can be used in combination with different types depending on the type of solution to be controlled for pH and the physical property to be controlled. .

  According to the present invention, for example, the pH was controlled using the KOH aqueous solution as the solution by the apparatus shown in FIG. In this case, the pH of the aqueous KOH solution can be controlled by changing the ion concentration to a predetermined target value.

  Next, examples will be described.

  The pH was controlled by the apparatus shown in FIG. Initially, a voltage was applied to the electrodes 6 and 7 at 1.2 V, the solution was flowed at a flow rate of 50 ml / min, the application of the voltage was canceled after a predetermined time, and the electrical conductivity and pH with the elapsed time were measured. The result of using an aqueous NaOH solution as the solution is shown in FIG. 5, and the result of using an aqueous HCl solution as the solution is shown in FIG. The electrical conductivity at the outlet of the apparatus is shown by a solid line, and the pH is plotted by a black circle.

  As shown in FIG. 5 and FIG. 6, it can be seen that the pH fluctuates due to the application of a voltage and can be controlled to a predetermined target value.

  The test was conducted in a state where water was not passed through the apparatus shown in FIG. 1, targeting a collagen solution (collagen 1.4%) which is an intermediate raw material for cosmetics. The collagen solution is preferably adjusted to the same weak acidity as the bare skin, but is acidic because citric acid is added to dissolve the collagen. This was controlled to be slightly acidic.

The next electrode was immersed in 50 ml of collagen solution and a DC voltage of 1.2 V was applied.
Anode Activated carbon sheet; specific surface area 500 m ² / g / apparent area 27 cm ² ; 1 sheet cathode activated carbon sheet; specific surface area 500 m ² / g • apparent area 27 cm ² ; 1 sheet

As a result, as shown below, it was possible to adjust to a weakly acidic pH range (pH 5.5) preferable for cosmetics.
Voltage application time pH
0 minutes 4.0
15 minutes 4.6
45 minutes 5.5

  The medical medium (culture solution) used for culturing cells is adjusted to an optimum pH for the activity of the cells to be cultured, but the pH is acidic due to the influence of lactic acid generated by the cell activities. And will be outside the optimal cell activity pH range. For this reason, when performing long-term culture, it is necessary to separate the cells from the medium and transfer them to a new medium. Therefore, the pH was controlled for the purpose of reducing the labor and the amount of the medium used.

  The test was performed in the apparatus shown in FIG. A solution prepared by adding acetic acid in advance to a commercially available medium (Introgen Corp .; RPMI1640) to prepare an acid was prepared for the test.

The next electrode was immersed in 50 ml of medium, and a DC voltage of 1.2 V was applied.
Anode Activated carbon sheet; specific surface area 500 m ² / g, apparent area 50 cm ² ; 1 sheet cathode Activated carbon sheet; specific surface area 500 m ² / g, apparent area 50 cm ² ; 1 sheet

As a result, as shown below, it was possible to adjust to a pH range near neutrality preferable as a medium.
Voltage application time pH
0 min 6.5
5 minutes 6.8
15 minutes 6.9

  The hydroponics solution has a weak acidity suitable for the cultivation environment, and the pH was controlled using this as a target value.

  The test was conducted in a state where water passed in the apparatus shown in FIG. As a base solution, as a hydroponics solution, a commercially available solution was dissolved in water and the pH was adjusted to 6.3 (Otsuka House No. 1 made by Otsuka Chemical Co., Ltd. 1500 ppm, Otsuka House No. 2 made 1000 ppm). A solution adjusted to pH 3.6 by adding hydrochloric acid to this base solution was used for the test.

The next electrode was stacked in a 500 ml capacity cell, and a DC voltage of 1.2 V was applied while passing the solution at a flow rate of 50 ml / min.
Anode Activated carbon sheet; specific surface area 500 m ² / g, apparent area 135 cm ² ; 6 sheets Cathode activated carbon sheet; specific surface area 500 m ² / g, apparent area 135 cm ² ; 6 sheets

As a result, as shown below, it was possible to adjust to a neutral to slightly acidic pH range (pH 6.3) preferable as a cultivation environment.
Elapsed time Inlet pH 0 minutes 3.6
Outlet pH 2 minutes 5.4
5 minutes 5.9
10 minutes 6.2
30 minutes 6.3

  Further, the base solution was adjusted to pH 10.3 by adding sodium hydroxide, and the test was performed under the same conditions.

As a result, as shown below, it was able to be adjusted to a neutral to slightly acidic pH range (pH 7.1) preferable as a cultivation environment.
Elapsed time Inlet pH 0 min 10.3
Outlet pH 2 minutes 8.2
5 minutes 7.8
10 minutes 7.2
30 minutes 7.1

  The pH was controlled using the voltage as a parameter. Solutions prepared by adjusting 1000 ppm NaCl solution to pH 3 and pH 10 by adding HCl or NaOH, respectively, were prepared for the test.

With the apparatus shown in FIG. 2, the next electrode was stacked in a 500 ml capacity cell, and a DC voltage was applied while changing the voltage in the range of 0.8 to 2 V while passing the solution at a flow rate of 25 ml / min. .
Anode Activated carbon sheet; specific surface area 500 m ² / g, apparent area 135 cm ² ; 12 sheets Cathode activated carbon sheet; specific surface area 500 m ² / g, apparent area 135 cm ² ; 12 sheets

  FIG. 7 shows the results of the above test, in which the pH of raw water with an inlet pH of 3 was adjusted, the pH of raw water with an inlet pH of 10 was adjusted, and the respective outlet pH values were plotted. As can be seen from the figure, the outlet pH changes by changing the applied voltage, and the pH can be controlled to the target value by adjusting the voltage.

  The present invention, for example, by adjusting the pH of the solution, adjustment of ink color and clarity, adjustment of culture water for hydroponics, adjustment of the activity of lactic acid and yeast in the food production process, etc. It can be applied to various technical fields.

It is a figure which shows schematic structure of the pH control apparatus of 1st Embodiment of this invention. It is a figure which shows the detail of the said pH control apparatus. It is a figure which shows schematic structure of the pH control apparatus of 1st Embodiment of this invention. It is a figure which shows the effect | action of the said pH control apparatus. It is a figure which shows the measurement result of Example 1 of this invention. It is a figure which shows the measurement result of Example 1 of this invention. It is a figure which shows the measurement result of Example 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Storage tank 1a 1st storage tank 1b 2nd storage tank 2 Introductory path 3a Discharge path 3b Waste liquid path 4 DC power supply 5 Switch 6 Electrode (anode)
7 Electrode (cathode)
8 Control Circuit 9 Flow Meter 10 pH Meter 11 Flow Control Valve 12 Separator 13 Communication Port 14 Inlet Port 15 Outlet Port 16 End Plate 17 Bolt Nut 18a Double-sided Electrode (Positive Electrode)
18b Double-sided electrode (negative electrode)
23 Frame-shaped spacer 24a Valve 24b Valve

Claims (9)

  An electrode to which a DC voltage is applied is present in the solution to be controlled by pH, the potential difference and / or current value between the two electrodes is continuously controlled, and the ions present in the solution are adsorbed on the electrode to cause a solution. A pH control method for a solution, wherein the pH of the solution is controlled toward a target value by controlling the number of ions therein.   The amount of ions adsorbed to the electrodes is controlled by controlling the potential difference and / or the current value between the electrodes based on a current integrated value obtained by integrating a current value flowing between the electrodes and a conduction time. The method for controlling the pH of the solution according to 1.   The method for controlling the pH of a solution according to claim 1 or 2, wherein the adsorption of the ions is controlled by a potential difference that does not substantially cause electrolysis of the solution.   A storage tank for storing a solution to be controlled by pH, an electrode that is present in the solution and to which a DC voltage is applied, and a control means that continuously controls a potential difference and / or current value applied between the electrodes. And by controlling the potential difference and / or current value applied to both electrodes by the control means, by adsorbing ions present in the solution to the electrode and controlling the number of ions in the solution, A pH control device for a solution, wherein the pH is controlled toward a target value.   A current integrating means for calculating a current integrated value obtained by integrating the current value flowing between the electrodes and the energization time; and the control means calculates the potential difference and / or current value between the electrodes as the calculated current integrated value. The pH control apparatus according to claim 4, wherein the adsorption amount of ions to the electrode is controlled by controlling based on the above.   The storage tank includes an introduction path for introducing a solution to be controlled by pH and a discharge path for discharging a solution whose pH is controlled, and is configured to continuously generate a solution having a target pH. The pH control apparatus of the solution of Claim 4 or 5.   PH detecting means for detecting the pH in the solution at or near the discharge path is provided, and the control means controls the potential difference and / or current value applied to the electrode according to the detection result of the pH of the solution by the pH detecting means. The apparatus for controlling pH of a solution according to claim 6.   The introduction path or the discharge path is provided with a flow rate adjustment valve for adjusting the flow rate of the solution to be introduced or discharged, and the control means controls the flow rate adjustment valve in accordance with the pH detection result by the pH detection means. The pH control apparatus of the solution of Claim 6 or 7. The electrode is made of a conductor that conducts electricity with the solution, and the control means controls the potential applied to the electrode so that the adsorption of the ions is performed in a range that does not substantially cause electrolysis of the solution. Item 9. The pH controller for the solution according to any one of Items 4 to 8.

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