WO2011065013A1

WO2011065013A1 - Ph adjustment device

Info

Publication number: WO2011065013A1
Application number: PCT/JP2010/006912
Authority: WO
Inventors: 棚橋正和; 棚橋正治; 中野貴徳
Original assignee: 有限会社ターナープロセス
Priority date: 2009-11-27
Filing date: 2010-11-26
Publication date: 2011-06-03
Also published as: JPWO2011065013A1

Abstract

Disclosed is a device that adjusts the pH of a water-containing liquid. Said device is provided with an electrode group (20) that can be inserted into the liquid and a DC power source (11) for applying a voltage to the electrode group (20). The electrode group (20) is provided with: an ion-adsorption electrode (21) that contains a conductive substance (21b) that can reversibly adsorb ions; an opposing electrode (22); and fixed members (a fixed plate (24) and fixed members (25 and 26)). With the conductive substance (21b) and the opposing electrode (22) in contact with the liquid, a voltage is applied such that water is electrolyzed at the opposing electrode (22), thereby changing the quantity of ions adsorbed by the conductive substance (21b) and generating hydrogen ions or hydroxide ions at the opposing electrode (22). As a result the pH of the liquid is changed. In the electrode group (20), the ion-adsorption electrode (21) and the opposing electrode (22) are fixed in place by the fixed members.

Description

pH adjuster

The present invention relates to a pH adjusting device.

Conventionally, various devices for adjusting the pH of a liquid have been proposed. For example, an apparatus has been proposed in which two electrodes are arranged with an ion-permeable diaphragm interposed therebetween, and acid water and alkaline water are prepared by electrolyzing salt water (Japanese Patent Laid-Open No. 7-299457).

In addition, apparatuses for adjusting pH without using a diaphragm have been proposed (Japanese Patent Laid-Open Nos. 4-2884889 and 8-19781). In these apparatuses, a plurality of flat electrodes are arranged at a narrow interval, and water flows in a laminar flow therebetween. By electrolyzing the water flowing between the electrodes, a laminar flow of alkaline water and a laminar flow of acidic water are formed, and alkaline water and acidic water are obtained by taking them out separately. On the other hand, an apparatus that does not use a diaphragm has also been proposed (International Publication WO2006 / 132160A1).

JP-A-7-299457 JP-A-4-284889 Japanese Patent Laid-Open No. 8-19781 International Publication WO2006 / 132160A1

In such a situation, an object of the present invention is to provide an apparatus capable of easily adjusting the pH of a liquid in a place where the liquid exists.

In order to achieve the above object, the pH adjusting device of the present invention is a device for adjusting the pH of a liquid containing water, and includes an electrode group that can be charged into the liquid and a voltage for applying a voltage to the electrode group. Application means, and the electrode group includes an ion adsorption electrode including a conductive material capable of reversibly adsorbing ions, a counter electrode, and a fixing member, and (i) the conductive material and the counter electrode By applying a voltage between the ion-adsorbing electrode and the counter electrode so that water is electrolyzed at the counter electrode while being in contact with a liquid, the amount of ions adsorbed on the conductive substance is reduced. And the step of generating hydrogen ions or hydroxide ions at the counter electrode and, as a result, changing the pH of the liquid is performed. In the electrode group, each of the ion adsorption electrode and the counter electrode is performed. There are fixed by the fixing member.

According to the present invention, the pH of a liquid can be easily adjusted in an environment where the liquid exists. That is, according to the present invention, the pH of the liquid can be easily adjusted in situ.

It is a figure which shows typically the structure of an example of the apparatus of this invention. 2A and 2B are a front view and a cross-sectional view, respectively, of an example of an ion adsorption electrode and a surrounding protective member. It is a front view which shows an example of an ion adsorption electrode. It is a front view which shows an example of a counter electrode and its surrounding protection member. It is a figure which shows the flow of the liquid in an example electrode group. 6A and 6B are schematic views showing an example of pH adjustment using the apparatus of the present invention. 7A and 7B are schematic views showing another example of pH adjustment using the apparatus of the present invention. FIG. 8A is a side view showing an example of an electrode group. FIG. 8B is a cross-sectional view of the electrode group shown in FIG. 8A. FIG. 8C is another side view of the electrode group shown in FIG. 8A. FIG. 8D is another side view of the electrode group shown in FIG. 8A. FIG. 9 shows an average value of current efficiency when an example electrode group is used. FIG. 10 shows an average value of current efficiency when another example electrode group is used.

Hereinafter, embodiments of the present invention will be described. In the following description, embodiments of the present invention will be described by way of examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values and specific materials may be exemplified, but other numerical values and other materials may be applied as long as the effect of the present invention is obtained.

(PH adjuster)
The apparatus of the present invention is an apparatus for adjusting the pH of a liquid containing water. Hereinafter, the liquid containing water may be referred to as “aqueous liquid (A)”. The apparatus of the present invention includes an electrode group that can be charged into the aqueous liquid (A), and a voltage applying means for applying a voltage to the electrode group. The electrode group includes a counter electrode, a fixing member, and an ion-adsorbing electrode including a conductive substance that can adsorb ions reversibly. Hereinafter, the conductive material may be referred to as “conductive material (C)”. The voltage application means is a means for applying a voltage between the ion adsorption electrode and the counter electrode. In the electrode group, each of the ion adsorption electrode and the counter electrode is fixed by a fixing member.

In the pH adjusting device of the present invention, the pH of the aqueous liquid (A) is adjusted by performing step (i) described later. There is no particular limitation on the aqueous liquid (A). The aqueous liquid (A) may contain at least one ion (L) in addition to hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ). Examples of the cation contained in the ion (L) include alkali metal ions (such as sodium ion, potassium ion and lithium ion), alkaline earth metal ions (such as magnesium ion and calcium ion), transition metal ions (such as zinc ion and Cadmium ions), aluminum ions, and the like. Examples of the anion contained in the ion (L) include, for example, chlorine ion, sulfate ion, nitrate ion, organic acid ion, PF ₆ ⁻ , BF ₄ ^{− and the} like.

In the following, cations other than hydrogen ions are referred to as “cations (L ⁺ )” regardless of valence, and anions other than hydroxide ions are referred to as “anions (L ⁻ )” regardless of valence. May be described. The number of ions (L) adsorbed on the conductive material (C) and the ions (L) released from the conductive material (C) may be one or more.

An example of the aqueous liquid (A) is water. As long as the effects of the present invention are obtained, the aqueous liquid (A) may contain a solvent other than water. The aqueous liquid (A) may be an aqueous solution containing a cation (L ⁺ ) and an anion (L ⁻ ). Examples of water-based liquids (A) include water in PET bottles and cups, water in fish tanks, water in bathtubs, hot water, water in pools, water in ponds, etc. Contains liquid.

In step (i), a voltage is applied between the ion adsorption electrode and the counter electrode so that electrolysis of water occurs in the counter electrode while the conductive substance (C) and the counter electrode are in contact with the aqueous liquid (A). To do. By applying this voltage, the amount of ions adsorbed on the conductive substance (C) is changed, and hydrogen ions or hydroxide ions are generated at the counter electrode, thereby changing the pH of the liquid. Below, two examples of process (i) are demonstrated.

(First example)
In the first example, a conductive substance (C) capable of adsorbing a sufficient amount of ions (L) for pH adjustment is used. For example, a conductive substance (C) that does not substantially adsorb ions (L) is used. The aqueous liquid (A) is an aqueous solution containing ions (L).

In this case, when a voltage is applied so that the ion-adsorbing electrode becomes an anode (ie, the counter electrode becomes a cathode), an anion (C) is applied to the conductive substance (C) of the ion-adsorbing electrode. L ⁻ ) is adsorbed, and hydroxide ions and hydrogen gas are generated at the counter electrode. As a result, the pH of the aqueous liquid (A) increases. Conversely, when a voltage is applied so that the ion adsorption electrode becomes a cathode (that is, the counter electrode becomes an anode), the cation (L ⁺ ) is adsorbed on the conductive substance (C) of the ion adsorption electrode, At the counter electrode, hydrogen ions and oxygen gas are generated. As a result, the pH of the aqueous liquid (A) decreases. In the first example, the ion concentration of the aqueous liquid (A) decreases by the amount adsorbed on the conductive substance (C).

By performing the above steps, ions (L) are adsorbed on the conductive substance (C). When the amount of ions (L) adsorbed on the conductive substance (C) increases, the ions (L) are hardly adsorbed. Therefore, when the step (i) is repeated with one electrode group, or when the pH is greatly changed by a small amount of the conductive material (C), the ions (L) adsorbed on the conductive material (C). It is necessary to regenerate the conductive substance (C) by releasing the. For the regeneration of the conductive substance (C), for example, the electrode group may be immersed in a regenerating aqueous liquid (water or aqueous solution) and a voltage applied in the direction opposite to that in step (i). When the conductive substance (C) that adsorbs ions (L) is left in the atmosphere for a long time, the adsorbed ions are released from the adsorbed state by oxygen reduction or resin oxidation. There is. In such a case, it is desirable to wash away the ions whose adsorption state has been released by washing the conductive material (C) before use.

(Second example)
In the second example, a conductive substance (C) in which a sufficient amount of ions (L) for adjusting the pH is adsorbed is used. In the second example, the aqueous liquid (A) may or may not contain ions (L).

Consider a case where cations (L ⁺ ) are adsorbed on the conductive substance (C). In this case, when a voltage is applied so that the ion-adsorbing electrode becomes the anode (that is, the counter electrode becomes the cathode), the cation (L ⁺ ) adsorbed on the conductive substance (C) is converted into the aqueous liquid ( A), and hydroxide ions and hydrogen gas are generated at the counter electrode. As a result, the pH of the aqueous liquid (A) increases.

Next, consider a case where an anion (L ⁻ ) is adsorbed on the conductive substance (C). In this case, when a voltage is applied so that the ion-adsorbing electrode becomes a cathode (that is, the counter electrode becomes an anode), the anions (L ⁻ ) adsorbed on the conductive substance (C) are converted into an aqueous liquid ( A) and hydrogen ions and oxygen gas are generated at the counter electrode. As a result, the pH of the aqueous liquid (A) decreases. In the second example, the ion concentration of the aqueous liquid (A) increases by the amount released from the conductive substance (C).

In the second example, it is necessary to adsorb ions (L) to the conductive substance (C) before performing the step (i). Therefore, in the second example, a step (p) of adsorbing ions (L) to the conductive substance (C) may be performed before the step (i). By reversing the voltage application direction in the step (p) and the voltage application direction in the step (i), the ions (L) adsorbed on the conductive substance (C) in the step (p) are converted into the aqueous liquid (A). Released into.

In an example of the step (p), in the aqueous solution (S) containing ions (L), a voltage is applied between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode becomes an anode (so that the counter electrode becomes a cathode). Apply. By applying this voltage, the negative ions (L ⁻ ) are adsorbed on the conductive substance (C), and water is electrolyzed at the counter electrode. In another example of the step (p), in the aqueous solution (S) containing ions (L), the ion adsorption electrode becomes a cathode (so that the counter electrode becomes an anode) between the ion adsorption electrode and the counter electrode. Apply voltage. By applying this voltage, positive ions (L ⁺ ) are adsorbed on the conductive substance (C), and electrolysis of water occurs at the counter electrode.

By performing step (i) of the second example, the ions (L) adsorbed on the conductive substance (C) are released into the aqueous liquid (A). Therefore, when the step (i) is repeated with one electrode group, or when the pH of the aqueous liquid (A) is greatly changed using a small amount of the conductive material (C), the conductive material ( It is necessary to perform a regeneration treatment for adsorbing ions (L) on C). The regeneration of the conductive substance (C) on which the ions (L) are adsorbed can be performed by the above step (p).

The ions (L) contained in the aqueous solution (S) and adsorbed on the conductive substance (C) may be selected according to the use of the aqueous liquid (A). For example, in the case where the aqueous liquid (A) is water in an aquarium for raising fish, it is preferable to select ions (L) that are less harmful to fish.

According to the apparatus of the present invention, it is possible to adjust the pH of the liquid without using an ion exchange membrane (ion exchange material). However, the apparatus of the present invention may include a separator for preventing a short circuit between the ion adsorption electrode and the counter electrode.

The voltage application in the pH adjusting device of the present invention may be performed by a constant voltage method or a constant current method. By using the constant current method, it is possible to control the pH with a long processing time. The applied voltage is preferably a voltage that causes no or only a little electrolysis of water at the ion adsorption electrode. Usually, the applied voltage is a direct current voltage and the flowing current is a direct current. As long as the effect of the present invention is obtained, a pulse voltage may be applied in the apparatus of the present invention.

In order to cause electrolysis of water at the counter electrode, the potential of the counter electrode needs to be a potential at which electrolysis of water occurs. The potential of the counter electrode is affected by a voltage drop (IR drop) due to liquid resistance between the electrodes. Therefore, in order to realize a fast process, it is preferable that the voltage applied between the counter electrode and the ion adsorption electrode is larger than 2V.

In a typical example, the conductive material (C) is in the form of a sheet. The conductive substance (C) can adsorb ions reversibly. That is, the conductive substance (C) can release the adsorbed ions. As the conductive substance (C), for example, a substance that forms an electric double layer on the surface by adsorbing ions in a solution can be used. When surface charge is present on the surface of the conductive material (C), it is considered that ions having a sign opposite to the surface charge are adsorbed on the surface of the conductive material (C). For example, an anion is adsorbed when the surface charge is a positive charge, and a cation is adsorbed when the surface charge is a negative charge.

As the conductive substance (C), a conductive substance having a large specific surface area can be used. For example, a carbon material can be used. Among the carbon materials, activated carbon is preferably used because of its large specific surface area. For example, the conductive material (C) may be a conductive sheet formed by agglomerating granular activated carbon, or a conductive sheet formed by aggregating granular activated carbon and conductive carbon. Alternatively, it may be an activated carbon block formed by solidifying activated carbon particles, a sheet formed of activated carbon fibers, or a composite of these. Examples of the sheet formed of activated carbon fibers include a cloth formed of activated carbon fibers. Examples of the activated carbon fiber cloth include activated carbon fiber cloths manufactured by Nippon Kainol Co., Ltd. (product numbers such as ACC-5092-15, ACC-5092-20, and ACC-5092-25).

The specific surface area of the conductive substance (C) is, for example, 300 m ² / g or more, and preferably 900 m ² / g or more. The upper limit of the specific surface area is not particularly limited, but may be, for example, 5000 m ² / g or less or 2500 m ² / g or less. In this specification, “specific surface area” is a value measured by the BET method using nitrogen gas.

The amount of the conductive material (C) contained in the electrode group may be determined according to pH adjustment conditions. However, even if the amount of the conductive material (C) is small, the pH can be adjusted by repeating the step (i) and the regeneration treatment of the conductive material (C).

The liquid resistance can be made low and uniform by arranging the ion-adsorbing electrode and the counter electrode in a flat plate shape and arranging them in parallel. The flat ion adsorption electrode may be formed by fixing a conductive material containing granular activated carbon on a metal foil with a binder. The conductive material may include conductive carbon such as acetylene black. Moreover, you may form a flat ion adsorption electrode also by attaching wiring (current collector) to activated carbon fiber cloth. Since the ion adsorption electrode using the activated carbon fiber cloth easily passes ions in the liquid, the ion concentration and pH of the solution can be homogenized. Therefore, the pH can be quickly changed by using such an electrode.

In order to change the pH efficiently and to suppress deterioration of the conductive material (C), it is preferable to prevent excessive gas from being generated on the surface of the conductive material (C). The generation of gas in the substance (C) is likely to occur when the resistance of the conductive substance (C) is large. Therefore, when the resistance of the conductive substance (C) is high, the ion adsorption electrode may include a wiring (current collector) arranged so as to be in contact with the conductive substance (C). For the wiring, for example, a metal wiring can be used, and a metal wiring coated with a metal having high corrosion resistance (for example, a noble metal) may be used. Examples of the metal constituting the wiring include at least one selected from the group consisting of Ti, Ta, and Nb. Examples of the metal that coats the metal include at least one metal (including an alloy) selected from the group consisting of Au, Pt, Pd, and Rh.

For the counter electrode, an electrode that easily generates hydrogen gas or oxygen gas during electrolysis of water is used. For example, an electrode having Pt on the surface is used. Specifically, it is preferable to use an electrode having a metal surface coated with Pt as a counter electrode. For example, an electrode coated with Ti or Nb with Pt may be used as the counter electrode.

In another aspect, the counter electrode may have an actual surface area (surface area measured by a BET method or the like) of 10 times or less (for example, 5 times or less) of its apparent surface area (surface area of the outer shape). Examples of such a counter electrode include a general metal electrode and a graphite electrode. As the surface area of the counter electrode increases, the amount of ions adsorbed on the counter electrode increases. Since the amount of electricity that contributes to the change in pH decreases by the amount of electricity of ions adsorbed on the counter electrode, it is preferable that the surface area of the counter electrode is small. On the other hand, the actual surface area (surface area measured by the BET method or the like) of the conductive substance (C) may be 10 ⁴ times or more the apparent surface area (surface area of the outer shape).

The shape of the counter electrode is not particularly limited. The counter electrode may be a rod-shaped electrode or a sheet-shaped electrode. Further, the counter electrode may be a linear electrode arranged in a stripe shape or a lattice shape. The counter electrode preferably has a shape in which gas generated on the surface of the counter electrode is easily detached from the surface of the counter electrode. For example, a counter electrode in which the total length of the linear electrodes arranged in the vertical direction is 50% or more (for example, 70% or more or 80% or more) of the total length of the linear electrodes constituting the counter electrode is used. As a result, the gas generated on the surface of the counter electrode can be easily discharged upward. Note that “upper”, “lower”, “vertical direction” and “horizontal direction” in the electrode group are respectively the upper direction when the electrode group is disposed in the aqueous liquid (A) in order to perform each step, Means downward, vertical and horizontal.

The fixing member is not particularly limited as long as it can fix the ion-adsorbing electrode and the counter electrode. However, it is preferable to use a material that is resistant in the pH region to be adjusted, and the ion-adsorbing electrode and the counter electrode may be in contact with each other. It is preferred that the part uses at least an insulating material. As the material of the fixing member, for example, a metal material, an inorganic material, a resin material, or a composite material thereof is used.

The fixing member may include a plate (fixing plate) to which at least one selected from the group consisting of the conductive substance (C) and the counter electrode is fixed. The fixing member may include a plate (fixing plate) disposed so as to sandwich at least one selected from the group consisting of a conductive substance and a counter electrode. A through hole may be formed in these fixing members (fixing plates). The aqueous liquid (A) passes through the fixed plate through the through hole.

The through hole formed in the fixing plate may be formed so that the gas generated at the electrode is easily detached from the surface of the electrode. In one example, the upper side surface (and optionally the lower side surface) of the side surfaces of the through hole may be inclined upward from the inner side to the outer side of the electrode group. Further, the through hole may be formed so that gas generated in the electrode is easily discharged to the outside of the electrode group. In one example, the upper side surface (and optionally the lower side surface) of the side surfaces of the through hole may be inclined upward from the inner side to the outer side of the electrode group. According to this configuration, the gas generated on the surface of the electrode is easily discharged to the outside of the electrode group. This gas flow generates a water flow from the inside of the electrode group to the outside of the electrode group. As a result, the probability that hydrogen ions and hydroxide ions generated at the counter electrode are adsorbed to the ion adsorption electrode can be reduced. The through-hole formed in the fixing plate may be long in the vertical direction, and may be, for example, an ellipse long in the vertical direction. Here, “inside” means the center side of the electrode group. The “outside” means the side opposite to the center of the electrode group with the fixing member interposed therebetween.

In one form of the device of the present invention, the counter electrode may be disposed outside the fixed member. In another embodiment of the apparatus of the present invention, the fixing member may include an insulating portion, and the shortest path connecting the ion adsorption electrode and the counter electrode may be blocked by the insulating portion. Note that all of the fixing members may be insulative (the same applies to the following examples). In a preferred embodiment, the counter electrode is disposed outside the fixing member, the fixing member includes an insulating portion, and the shortest path connecting the ion adsorption electrode and the counter electrode is blocked by the insulating portion. In another form of the apparatus of the present invention, the fixing member may include an insulating portion, and the ion-adsorbing electrode and the counter electrode may face each other with the insulating portion interposed therebetween. In these forms, when a voltage is applied between the ion adsorption electrode and the counter electrode, an electric field is applied so as to go around the fixed member. In this case, gas generation is less likely to occur on the surface facing the inner side of the electrode group among the surfaces of the counter electrode. As a result, it is possible to prevent ions (hydrogen ions or hydroxide ions that affect pH) generated on the surface of the counter electrode from moving to the inside of the electrode group. Thereby, it can suppress that the adjustment efficiency of pH falls because hydrogen ion and hydroxide ion are adsorbed by an ion adsorption electrode as an electric double layer. Note that the path between the ion adsorption electrode and the counter electrode is not completely blocked by the fixing member. That is, the ion adsorption electrode and the counter electrode are connected via the aqueous liquid (A).

The electrode group may further include a protective member through which the aqueous liquid (A) can pass. The protective member protects at least one selected from the group consisting of the conductive substance (C) and the counter electrode. The protective member suppresses deformation and breakage of the conductive substance (C) and / or the counter electrode. When a soft material such as activated carbon fiber cloth is used for the conductive material (C), the activated carbon fiber cloth is sandwiched between protective members in order to give rigidity to the activated carbon fiber cloth and form a flat plate. An activated carbon fiber cloth may be fixed on the surface. The electrode group may include a plurality of different protective members. For example, the protective member that protects the conductive substance (C) may be different from the protective member that protects the counter electrode.

The material of the protective member is not particularly limited, but it is preferable to use a material that is resistant in the pH range to be adjusted. Moreover, it is preferable that the part which an ion adsorption electrode or a counter electrode may contact among protective members is formed with an insulating material. As the material of the protective member, for example, a metal material, an inorganic material, a resin material, or a composite material thereof is used. A through hole may be formed in the protective member. Through the through-hole, the aqueous liquid (A) can reach the conductive substance (C). Typically, the protective member is made of an insulating resin.

The protective member may be formed so that the gas generated at the electrode is easily detached from the surface of the electrode. In one example, a through hole is formed in the protective member, and an upper side surface (and optionally a lower side surface) of the side surfaces of the through hole may be inclined upward from the electrode side toward the outside. Further, the protective member may be formed so that gas generated at the electrode is easily discharged to the outside of the electrode group. In one example, a through hole is formed in the protective member, and an upper side surface (and optionally a lower side surface) of the side surfaces of the through hole is inclined upward from the inner side to the outer side of the electrode group. Good. According to this configuration, the gas generated on the surface of the electrode is easily discharged to the outside of the electrode group. This gas flow generates a water flow from the inside of the electrode group to the outside of the electrode group. As a result, the probability that hydrogen ions and hydroxide ions generated at the counter electrode are adsorbed to the ion adsorption electrode can be reduced. The through hole formed in the protective member may be long in the vertical direction, and may be, for example, an ellipse long in the vertical direction.

The electrode group of the present invention may include a member (gas induction member) for inducing gas generated at at least one electrode selected from the group consisting of an ion adsorption electrode and a counter electrode. An example of the gas guiding member has a shape for promoting the separation of the gas generated at the electrode from the electrode. Another example of the gas guiding member has a shape for promoting the gas generated at the electrodes to be discharged to the outside of the electrode group. Examples of the gas guide member include a plate-like member having a through hole formed therein, and examples of the shape of the through hole include the specific shapes described for the through hole of the fixing plate and the through hole of the protective member. It is. Therefore, the fixing plate or the protection member can also serve as the gas induction member. The fixing plate can also serve as a protective member, and can also serve as both the protective member and the gas guiding member. However, the electrode group may further include a protective member and / or a gas guiding member in addition to the fixing plate.

The voltage applying means may be any device that can apply a necessary voltage between the ion adsorption electrode and the counter electrode. For example, the voltage applying means may be an AC / DC converter that converts an AC voltage from an outlet into a DC voltage. The voltage applying means may be a dry battery, a rechargeable battery, or a fuel cell. Further, the voltage application means may be a power generation device, for example, a solar cell or a power generation device using electromagnetic induction.

The apparatus of the present invention may include a pH sensor for monitoring the pH of the aqueous liquid (A) or a timer for measuring a voltage application time. The apparatus of the present invention may include a switch for switching the voltage application direction. Moreover, the apparatus of this invention may be equipped with the stirrer for separating the hydrogen ion and hydroxide ion which were produced | generated on the surface of the counter electrode from the vicinity of an electrode.

The voltage application means can be controlled manually, but may be controlled by a controller. That is, the apparatus of the present invention may include a controller for executing a predetermined process. The apparatus of the present invention may also include an input device for inputting a target pH value and voltage application time to the controller, and a display device for displaying the processing state.

The controller includes an arithmetic processing unit (may include an internal memory), and further includes a storage device such as an external memory or a hard disk drive as necessary. In a storage device (for example, an internal memory, an external memory, or a hard disk drive), a program for executing each process is recorded. The controller is connected to various devices (for example, a power source) and measuring instruments (for example, a pH sensor and a timer). The controller may execute each step by controlling various devices based on the output from the measuring instrument.

In the apparatus of the present invention, it is possible to adjust the pH of the aqueous liquid (A) simply by putting the electrode group into the aqueous liquid (A) and applying a voltage to the electrode group. Therefore, the pH can be adjusted without transferring the aqueous liquid (A) to a special tank. For example, when adjusting the pH of water in a PET bottle, an electrode group may be inserted into the PET bottle and a voltage may be applied to the electrode group. Moreover, when adjusting the pH of the water in the water tank which breeds a fish, an electrode group may be thrown into the water tank and a voltage may be applied to the electrode group. Therefore, the apparatus of the present invention does not require a special tank for pH adjustment.

The electrode group may include a member according to the application. Moreover, it is preferable that an electrode group is made into the shape according to a use. For example, when adjusting the pH of water in a plastic bottle, the electrode group has an elongated shape so that it can be inserted from the mouth of the plastic bottle. In that case, the electrode group may include a member (for example, a lid or a cap) for fixing the electrode group to the mouth of the PET bottle. At this time, in order to release the gas generated at the counter electrode from the inside of the plastic bottle, it is preferable not to seal the mouth of the plastic bottle. For example, a hole that allows the inside and outside of the PET bottle to communicate with each other may be provided in the lid or cap. Further, the electrode group may include a weight so as to be stable in the aqueous liquid (A).

Hereinafter, embodiments of the pH adjusting device of the present invention will be described with reference to the drawings. In the following drawings, the same portions may be denoted by the same reference numerals and redundant description may be omitted. In the following embodiments, an apparatus including one electrode group including one ion adsorption electrode and one or two counter electrodes is shown, but the present invention is not limited to this. For example, the apparatus of the present invention may include a plurality of at least one of an ion adsorption electrode and a counter electrode. The device of the present invention may include a plurality of electrode groups.

(Embodiment 1)
FIG. 1 schematically shows the configuration of the pH adjusting device 10 of the first embodiment. The apparatus 10 includes a DC power supply 11, a pH sensor 12, a controller 13, and an electrode group 20. The pH sensor 12 may be fixed to the electrode group 20. The pH sensor 12 and the controller 13 can be omitted.

The electrode group 20 includes an ion adsorption electrode 21, a counter electrode 22, a protection member 23, a fixing plate (fixing member) 24, and fixing

members

25 and 26. The DC power supply 11 is connected to the ion adsorption electrode 21 and the counter electrode 22. The ion adsorption electrode 21, the protection member 23, and the fixing plate 24 are stacked in the order of fixing plate 24 / protection member 23 / ion adsorption electrode 21 / protection member 23 / fixation plate 24. The counter electrode 22 and the fixed plate 24 are stacked in the order of fixed plate 24 / counter electrode 22 / fixed plate 24. The ion adsorption electrode 21 and the counter electrode 22 are each sandwiched between two fixed plates 24. The upper part of the fixing plate 24 is fixed by a fixing member 25, and the lower part of the fixing plate 24 is fixed by a fixing member 26. The ion adsorption electrode 21 and the counter electrode 22 are fixed by the fixing members (the fixing plate 24, the fixing member 25, and the fixing member 26).

2A is a front view of the ion adsorption electrode 21, the protection member 23, the fixing plate 24, and the fixing

members

25 and 26 as viewed from the outside of the electrode group 20. FIG. A cross-sectional view taken along line IIB-IIB in FIG. 2A is shown in FIG. 2B. Normally, when performing each step, the electrode group 20 is arranged so that the direction of the line IIB-IIB (the vertical direction in FIG. 2A) is the vertical direction.

The protective member 23 is made of a lattice-shaped synthetic resin. That is, the protective member 23 is formed with a plurality of through holes through which liquid passes. The fixing plate 24 and the fixing

members

25 and 26 are made of a plate-shaped synthetic resin. The fixing plate 24 has a plurality of through holes 24h. The configuration of the ion adsorption electrode 21 is schematically shown in FIG. The ion adsorption electrode 21 includes a wiring 21a and an activated carbon fiber cloth 21b. The wiring 21a and the activated carbon fiber cloth 21b are arranged so that they are in sufficient contact with each other and the electrical contact resistance is reduced. The wiring 21a may be sandwiched between a plurality of activated carbon fiber cloths 21b. Moreover, the wiring 21a may be disposed on the outermost surface of one activated carbon fiber cloth 21b or on the outermost surface of a plurality of overlapping activated carbon fiber cloths 21b.

FIG. 4 shows a front view of the counter electrode 22, the fixing plate 24, and the fixing

members

25 and 26 as viewed from the outside of the electrode group 20. The counter electrode 22 has a lattice shape and is sandwiched between two fixing plates 24. The fixing plate 24 has a plurality of through holes 24h.

Of the cross-sections of the through holes 24h, the cross-section parallel to the surface of the fixed plate 24 is an ellipse that is long in the vertical direction. The side surface of the through hole 24 h of the fixing plate 24 is inclined so that the gas generated at the electrode is discharged to the outside of the electrode group 20. Specifically, of the side surfaces of the through-hole 24h, the upper and lower side surfaces are inclined upward from the horizontal toward the outside from the inside of the electrode group 20. By inclining the side surface of the through hole 24h in this way, the gas generated on the surface of the electrode is easily discharged to the outside of the electrode group 20, as shown by the arrows in FIG. Thus, the fixing plate 24 has a function of a gas guiding member. The fixing plate 24 also has a function as a protective member. In addition, although adsorption of ions mainly occurs on the surface of the ion adsorption electrode 21, a slight gas may be generated.

The lower side of the electrode group 20 may be configured so that liquid can easily flow. For example, no electrode may be present in the lower through-hole 24 h on the fixed plate 24. By making the liquid easily flow under the electrode group 20, the liquid can easily circulate in the electrode group 20, and the rate of adsorption and release of ions can be increased.

In the device 10, the protection member 23 may be omitted. Moreover, as long as the ion adsorption electrode 21 and the counter electrode 22 can be fixed in the electrode group 20, one or two of the fixing members (the fixing plate 24, the fixing member 25, and the fixing member 26) may be omitted. Moreover, you may use the protection member and fixing plate of a shape different from the protection member 23 and fixing member (the fixing plate 24, the fixing member 25, and the fixing member 26).

First and second examples in which the pH of the aqueous solution is adjusted using the apparatus 10 will be described below. In the following drawings, the device 10 is schematically shown, and some of the components may be omitted. In the following drawings, liquid hatching is omitted. Further, in the following drawings, the mass conservation law and the charge conservation law may not be considered.

(First example)
A first example will be described with reference to FIGS. 6A and 6B. In the first example, activated carbon fiber cloth 21b (conductive substance (C)) that does not adsorb ions is used. First, the electrode group 20 is thrown into the target aqueous solution 60. In the aqueous solution 60, cations (L ⁺ ) and anions (L ⁻ ) are dissolved.

Next, a DC voltage is applied between the ion adsorption electrode 21 and the counter electrode 22. When raising the pH of the aqueous solution 60, a DC voltage is applied so that the ion adsorption electrode 21 becomes an anode. By this voltage application, as shown in FIG. 6A, the anion (L ⁻ ) is adsorbed to the ion adsorption electrode 21 (activated carbon fiber cloth 21b). In addition, water is electrolyzed on the surface of the counter electrode 22 to generate hydroxide ions and hydrogen gas. As a result, the pH of the aqueous solution 60 increases. On the other hand, when lowering the pH of the aqueous solution 60, a DC voltage is applied so that the ion adsorption electrode 21 becomes a cathode. By applying this voltage, as shown in FIG. 6B, cations (L ⁺ ) are adsorbed to the ion adsorption electrode 21 (activated carbon fiber cloth 21b). Further, water is electrolyzed on the surface of the counter electrode 22 to generate hydrogen ions and oxygen gas. As a result, the pH of the aqueous solution 60 decreases.

(Second example)
A second example will be described with reference to FIGS. 7A and 7B. In the second example, activated carbon fiber cloth 21b (conductive substance (C)) on which ions (L) are adsorbed is used.

When the pH of the target liquid 70 is increased, the cation (L ⁺ ) is adsorbed on the activated carbon fiber cloth 21b by performing the step (p) before the step (i). Specifically, the electrode group 20 is immersed in an aqueous solution 71 containing a cation (L ⁺ ). Next, a DC voltage is applied so that the ion adsorption electrode 21 becomes a cathode. By applying this voltage, as shown in FIG. 7A, cations (L ⁺ ) are adsorbed on the activated carbon fiber cloth 21b.

Next, the electrode group 20 is taken out from the aqueous solution 71 and immersed in the liquid 70. Then, a voltage is applied in the direction opposite to the voltage application direction in the step (p). Specifically, a DC voltage is applied so that the ion adsorption electrode 21 becomes an anode. By applying this voltage, the cation (L ⁺ ) adsorbed on the activated carbon fiber cloth 21 b is released into the liquid 70 as shown in FIG. 7B. In addition, water is electrolyzed on the surface of the counter electrode 22 to generate hydroxide ions and hydrogen gas. As a result, the pH of the liquid 70 increases. In addition, at the time of this voltage application, the anion (L < ^- >) in the aqueous solution 71 can be adsorbed by the activated carbon fiber cloth 21b.

When lowering the pH of the liquid 70, the voltage application direction in the step (p) and the step (i) may be reversed to the voltage application direction in FIGS. 7A and 7B.

In the first and second examples, the pH sensor 12 is introduced into the liquid together with the electrodes. The controller 13 monitors the pH of the liquid with the pH sensor 12, and stops the voltage application when the pH of the liquid reaches a desired value. In addition, when there is no controller 13, what is necessary is just to stop a voltage application, a user watching the output of the pH sensor 12. FIG. In this case, a pH test paper may be used instead of the pH sensor. In addition, voltage application conditions necessary to obtain a target pH value under a specific use condition (amount of liquid or pH value) are obtained in advance, and the user or the controller 13 applies voltage according to the voltage application condition. May be.

Another example of the electrode group is shown in FIG. 8A. The electrode group 80 in FIG. 8A can be used in place of the electrode group 20 described above. A cross-sectional view taken along line VIIIB-VIIIB in FIG. 8A is shown in FIG. 8B. Moreover, the figure which looked at the electrode group 80 from the stationary plate 24a side is shown to FIG. 8C. Moreover, the figure which looked at the electrode group 80 from the counter electrode 22 side is shown to FIG. 8D.

8A to 8D, the electrode group 80 includes an ion adsorption electrode 21, a counter electrode 22, a protection member 23, a fixing plate (fixing member) 24, and fixing members 25 to 27. The fixed plate 24 includes a fixed plate 24a and a fixed plate 24b. A through hole 24h is formed in the fixed plate 24a. The fixed plate 24a and the fixed plate 24b are fixed by fixing members 25 to 27. In the electrode group 80, the protective member 23 may be omitted.

The ion adsorption electrode 21 includes a wiring 21a and an activated carbon fiber cloth 21b. The ion adsorption electrode 21 is sandwiched between two protective members 23. The ion adsorption electrode 21 is fixed to the protection member 23 with a thread (not shown). Further, the ion adsorption electrode 21 is fixed to the fixed plate 24 a via the protective member 23. A lead 21w is connected to the wiring 21a.

The counter electrode 22 includes two electrodes having a linear (rod-like) shape. A lead 22 w is connected to the counter electrode 22. The fixing plate 24b is two insulating resin members having a linear (rod-like) shape. The counter electrode 22 is fixed to the outside of the fixed plate 24b. As shown in FIG. 8B, the shortest path connecting the ion adsorption electrode 21 and the counter electrode 22 is blocked by the fixing plate 24b. More specifically, the shortest path between an arbitrary surface of the counter electrode 22 and the ion adsorption electrode 21 is blocked by the fixing plate 24b. Therefore, when a voltage is applied between the ion adsorption electrode 21 and the counter electrode 22, an electric field is formed so as to go around the fixed plate 24b.

Usually, the electrode group 80 is used in a state where the longitudinal direction of the counter electrode 22 is arranged in the vertical direction. When water is electrolyzed on the surface of the counter electrode 22, gas is generated on the surface of the counter electrode 22, and hydrogen ions or hydroxide ions are generated. Since the counter electrode 22 is disposed outside the fixed plate 24 b, the gas generated on the surface of the counter electrode 22 is difficult to enter the electrode group 80. Therefore, in the electrode group 80, the gas generated on the surface of the counter electrode 22 can be prevented from coming into contact with the ion adsorption electrode 21 or staying inside the electrode group 80. As a result, it is possible to suppress the hydrogen ions and hydroxide ions generated on the surface of the counter electrode 22 from approaching the activated carbon fiber cloth 21 b (conductive substance) of the ion adsorption electrode 21.

Hereinafter, the present invention will be described in more detail by way of examples.

Example 1
In Example 1, an experiment was performed in which the pH of tap water was changed using an electrode group having the same form as the electrode group 20 shown in FIG.

First, the electrode group of the device of the present invention was put into 2 liters of tap water. At this time, an ion adsorption electrode in a state where ions were not adsorbed was used. Then, a DC voltage of 12 volts was applied for 30 minutes between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became an anode (first voltage application). As a result, the pH of tap water changed from 7.81 before voltage application to 9.03 by voltage application for 15 minutes, and to 9.40 by voltage application for 30 minutes. Note that the current flowing between the electrodes changed from 60 mA to 70 mA when the voltage was applied for 15 minutes from the start of voltage application. Further, the current flowing between the electrodes changed from 60 mA to 70 mA when the voltage was applied for 15 to 30 minutes after the start of voltage application. It is considered that anions were adsorbed on the ion adsorption electrode by this initial voltage application.

Next, the electrode group was taken out from the treated tap water, and the taken out electrode group was put into 2 liters of new tap water (pH 7.81). Then, a DC voltage of 12 volts was applied for 45 minutes between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became a cathode (second voltage application). As a result, the pH of tap water changes from 7.81 before voltage application to 6.70 by voltage application for 15 minutes, to 6.38 by voltage application for 30 minutes, and by voltage application for 45 minutes. Changed to 6.12. Note that the current flowing between the electrodes changed from 60 mA to 80 mA when the voltage was applied for 15 minutes from the start of voltage application. Further, the current flowing between the electrodes changed from 50 mA to 80 mA when the voltage was applied for 15 to 30 minutes after the start of voltage application. Further, the current flowing between the electrodes changed from 50 mA to 80 mA when the voltage was applied for 30 to 45 minutes after the start of voltage application. In this second voltage application, it is considered that the anion adsorbed on the ion adsorption electrode in the first voltage application was released and the cation was adsorbed.

Next, the electrode group was taken out from the treated tap water, and the taken out electrode group was put into 2 liters of new tap water (pH 7.81). As described above, it is considered that cations were adsorbed on the ion adsorption electrode of this electrode group. Then, a DC voltage was applied for 15 minutes between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became an anode (third voltage application). At this time, a voltage was applied so that a constant current of 70 mA would flow between the electrodes. As a result, the pH of tap water changed from 7.81 before voltage application to 9.65 by voltage application for 15 minutes. When the voltage was applied, the voltage between the electrodes changed from 12.6 volts to 10.6 volts.

In the first voltage application, the pH of tap water changed from 7.81 to 9.03 by applying the voltage for 15 minutes. In the third voltage application, the pH of tap water changed from 7.81 to 9.65 by the voltage application for 15 minutes. These results indicated that the change in pH was larger when the pH was changed while releasing ions adsorbed on the ion adsorption electrode.

(Example 2)
In Example 2, an experiment for adjusting pH using an electrode group having no fixing member between the ion-adsorbing electrode and the counter electrode and an electrode group having the same form as the electrode group 80 shown in FIG. 8A is performed. went. Hereinafter, an electrode group having no fixing member between the ion adsorption electrode and the counter electrode is referred to as a “first electrode group”, and an electrode group having the same form as the electrode group 80 illustrated in FIG. 8A is referred to as a “second electrode group”. May be referred to as an “electrode group”.

The first electrode group was formed by disposing an ion adsorption electrode and a counter electrode inside a cylindrical insulating resin member in which a plurality of through holes were formed. That is, the ion adsorption electrode and the counter electrode are disposed inside the fixing member. The ion adsorption electrode contained three 170 mm × 13 mm activated carbon fiber cloths. That is, the calculated surface area of the activated carbon fiber cloth was 170 × 13 × 2 × 3 = 13260 mm ² , and the projected area of the ion adsorption electrode was 170 × 13 = 2210 mm ² . The counter electrode was composed of three linear electrodes (diameter 1 mm, length 170 mm) made of titanium coated with platinum. The distance between the ion adsorption electrode and the counter electrode was about 5 mm, and there was no fixing member between them.

The second electrode group was an electrode group having the form shown in FIG. 8A. That is, the counter electrode was disposed outside the fixed member. The ion adsorption electrode of the second electrode group included four 170 mm × 10 mm activated carbon fiber cloths. That is, the calculated surface area of the activated carbon fiber cloth was 170 × 10 × 2 × 4 = 13600 mm ² , and the projected area of the ion adsorption electrode was 170 × 10 = 1700 mm ² . The counter electrode was composed of two linear electrodes (diameter 1 mm, length 170 mm) made of titanium coated with platinum. The distance between the ion-adsorbing electrode and the counter electrode was about 8 mm, and a fixing member made of an insulating resin was present in the shortest path connecting them as shown in FIG. 8A.

An experiment was conducted in which the first electrode group was placed in a PET bottle containing 500 ml of 0.05 wt% KCl aqueous solution, and the pH of the KCl aqueous solution was changed by applying a constant voltage of 12 volts. Specifically, first, in Experiment 1, a voltage was applied between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became an anode. After the end of Experiment 1, Experiment 1 was conducted by immersing the first electrode group used in Experiment 1 in 500 ml of a new 0.05 wt% KCl aqueous solution as it was. In Experiment 2, a voltage was applied between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became a cathode. After the end of Experiment 2, Experiment 1 was performed by immersing the first electrode group used in Experiment 2 in 500 ml of a new 0.05 wt% KCl aqueous solution as it was. In Experiment 3, a voltage was applied between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became an anode. After the end of Experiment 3, Experiment 4 was performed by immersing the first electrode group used in Experiment 3 in 500 ml of a new 0.05 wt% KCl aqueous solution as it was. In Experiment 4, a voltage was applied between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became a cathode.

The experimental results are shown in Table 1. In addition, the average current density in Table 1 is a value of (average current) / (projected area of the ion adsorption electrode).

In addition, an experiment was conducted in which the second electrode group was placed in a PET bottle containing 500 ml of 0.05 wt% KCl aqueous solution, and the pH of the KCl aqueous solution was changed by applying a constant voltage of 12 volts. Specifically, first, in Experiment 5, a voltage was applied between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became an anode. After the end of Experiment 5, Experiment 2 was performed by immersing the second electrode group used in Experiment 5 in 500 ml of a new 0.05 wt% KCl aqueous solution as it was. In Experiment 6, a voltage was applied between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became a cathode. After the end of Experiment 6, Experiment 7 was performed by immersing the second electrode group used in Experiment 6 in 500 ml of a new 0.05 wt% KCl aqueous solution as it was. In Experiment 7, a voltage was applied between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became an anode. After the end of Experiment 7, Experiment 8 was performed by immersing the second electrode group used in Experiment 7 in 500 ml of a new 0.05 wt% KCl aqueous solution as it was. In Experiment 8, a voltage was applied between the ion adsorption electrode and the counter electrode so that the ion adsorption electrode became a cathode. The experimental results are shown in Table 2.

As is clear from Tables 1 and 2, it was possible to change the pH to the same extent with a smaller amount of electricity when the second electrode group was used than when the first electrode group was used. .

The pH of the aqueous KCl solution having a concentration of 0 to 0.10% by weight was changed using the first electrode group and the second electrode group. And the current efficiency was calculated | required about each. The current efficiency (%) was obtained by the following formula.
Current efficiency (%) = (actually measured pH value) × 100 / (theoretical pH value)

Here, “theoretical pH value” means that water is ideally electrolyzed by current (electric quantity) flowing between the electrodes to generate hydrogen ions (or hydroxide ions). It means a pH value calculated from the molar concentration of the generated hydrogen ions (or hydroxide ions).

FIG. 9 shows the average current efficiency when the first electrode group is used. Moreover, the average value of the current efficiency at the time of using a 2nd electrode group is shown in FIG. As is clear from FIGS. 9 and 10, the current efficiency was high when the second electrode group in which the counter electrode was fixed outside the fixing member was used.

The present invention can be used for a pH adjusting device. When the apparatus of the present invention is used, it is possible to adjust the pH of the liquid simply by putting an electrode group into the liquid whose pH is to be adjusted and applying a voltage. Therefore, the pH of the liquid can be easily adjusted. The pH adjusting device of the present invention can be used for pH adjustment of various liquids. For example, it can be used to adjust the pH of water in a fish tank or drinking water in a plastic bottle.

Claims

An apparatus for adjusting the pH of a liquid containing water,
An electrode group that can be put into the liquid, and a voltage applying means for applying a voltage to the electrode group,
The electrode group includes an ion adsorption electrode including a conductive substance capable of reversibly adsorbing ions, a counter electrode, and a fixing member.
(I) by applying a voltage between the ion-adsorbing electrode and the counter electrode so that electrolysis of water occurs in the counter electrode while the conductive substance and the counter electrode are in contact with the liquid; A step of changing the amount of ions adsorbed on the conductive substance and generating hydrogen ions or hydroxide ions at the counter electrode, and as a result, changing the pH of the liquid;
The pH adjusting device in which each of the ion adsorption electrode and the counter electrode is fixed by the fixing member in the electrode group.
The pH adjusting device according to claim 1, wherein the counter electrode is disposed outside the fixing member.
The fixing member includes an insulating portion;
The pH adjusting device according to claim 2, wherein the shortest path connecting the ion-adsorbing electrode and the counter electrode is blocked by the insulating portion.
The fixing member includes a fixing plate to which at least one selected from the group consisting of the conductive material and the counter electrode is fixed;
A through hole is formed in the fixing plate,
The pH adjusting device according to claim 1, wherein an upper side surface of the through holes is inclined upward from the inner side to the outer side of the electrode group.
The electrode group further includes a protective member through which the liquid can pass,
The pH adjusting device according to claim 1, wherein at least one selected from the group consisting of the conductive substance and the counter electrode is protected by the protective member.
The pH adjusting device according to claim 1, wherein the electrode group further includes a member for guiding gas generated at at least one electrode selected from the group consisting of the ion adsorption electrode and the counter electrode.
The pH adjuster according to claim 1, wherein the conductive substance is a sheet formed of activated carbon fibers.