WO2023282185A1

WO2023282185A1 - Plasma treatment device and plasma treatment method

Info

Publication number: WO2023282185A1
Application number: PCT/JP2022/026329
Authority: WO
Inventors: 浩孝豊田
Original assignee: 国立大学法人東海国立大学機構
Priority date: 2021-07-08
Filing date: 2022-06-30
Publication date: 2023-01-12
Also published as: JPWO2023282185A1

Abstract

Provided is a plasma treatment device capable of reliably generating plasma. This plasma treatment device is provided with a plasma generation means for generating plasma. The plasma treatment device is provided with an irradiation means for irradiating a first liquid with the generated plasma. The plasma treatment device is provided with a contact means for bringing the first liquid irradiated with the plasma into contact with a second liquid.

Description

Plasma processing apparatus and plasma processing method

This application claims priority based on Japanese Patent Application No. 2021-113787 filed on July 8, 2021. The entire contents of that application are incorporated herein by reference. This specification discloses a technology related to a plasma processing apparatus and a plasma processing method for irradiating a liquid with plasma.

For example, Japanese Patent Application Laid-Open No. 2019-57381 discloses a technique of irradiating a liquid to be processed with microwave plasma.

The components contained in the liquid to be processed may affect the plasma generation part, making it difficult to generate plasma.

This specification discloses a plasma processing apparatus. The plasma processing apparatus includes plasma generating means for generating plasma. The plasma processing apparatus includes irradiation means for irradiating the first liquid with the generated plasma. The plasma processing apparatus includes contact means for bringing the plasma-irradiated first liquid into contact with the second liquid.

There may be various modes of bringing the first liquid into contact with the second liquid. For example, both liquids can be brought into contact by mixing. In the plasma processing apparatus of the present specification, a highly reactive first liquid containing chemically active species and the like can be generated by irradiating the first liquid with plasma. By bringing the first liquid into contact with the second liquid, plasma processing can be performed on the second liquid. Since it is not necessary to irradiate the second liquid with plasma, even if the second liquid contains a component that adversely affects the plasma generating means, the plasma generating means will not be affected by the component.

The plasma generation means may have a plasma generation space for generating plasma. The plasma generation means may include decompression means for depressurizing the plasma generation space.

The decompression means may comprise a first flow path comprising a constricted portion with a narrow cross-sectional area. The first channel may carry the first liquid or the second liquid. The narrowed portion may be connected to the plasma generation space.

The plasma processing apparatus may include a second flow path that merges with the first flow path. The second channel may be connected to the plasma generation space. A second liquid may flow through the first channel. A first liquid may flow through the second channel.

The plasma processing apparatus may include an inner tube and an outer tube that surrounds the inner tube. The plasma-generating space and the second flow path may be arranged in the inner tube. The inner tube and the outer tube may be arranged so that their central axes coincide with each other. A first flow path may be formed between the inner tube and the outer tube, surrounding the outer periphery of the inner tube. The first flow path may have a path extending from one end of the inner tube and the outer tube to the other end, and may include a constricted portion on the path. In the constricted portion, the flow of the second liquid may have a velocity component that swirls around the central axis.

The plasma processing apparatus may further include at least one straightening section arranged on the first flow path up to the throttle section. The rectifying portion may extend in the axial direction of the central axis and be inclined with respect to the axial direction of the central axis.

The straightening section may be formed on at least one of the wall surface of the outer circumference of the inner tube and the wall surface of the inner circumference of the outer tube. The straightening section may have a projection shape protruding from the wall surface or a groove shape recessed from the wall surface.

The plasma processing apparatus may further include a supply section for discharging the second liquid into the first flow path. The direction in which the second liquid is discharged by the supply unit may be inclined with respect to the axial direction of the central axis.

The inner tube may comprise a first tube having a first electrode at a first end and a second tube having a second electrode at a second end. The first tube, the second tube, and the external tube may be arranged so that their central axes are aligned with each other. The first end and the second end may face each other in a non-contact state. A first flow path may be formed between the outer circumferences of the first and second tubes and the inner circumference of the outer tube. A second flow path and a plasma generating space may be formed in regions where the first end and the second end face each other.

The plasma processing apparatus may further include a propagation space configured to allow microwaves to propagate to the plasma generation space.

The first liquid may be a liquid in which no solid solute is dissolved. The second liquid may be a liquid in which a solid solute is dissolved.

One aspect of the plasma processing method disclosed in this specification includes an irradiation step of irradiating the first liquid with plasma. The plasma processing method comprises a contacting step of contacting the first liquid with the second liquid.

In the irradiation process, plasma may be generated in a reduced pressure environment.

In the contacting step, the first liquid may be brought into contact while the second liquid is flowing. In the irradiation step, a reduced pressure environment may be created by the venturi effect provided by the flow of the second liquid.

In the contact process, microwaves may be injected into the space where plasma is generated.

1 is a schematic cross-sectional view of a plasma processing apparatus 100 of Example 1. FIG. 2 is a schematic cross-sectional view of a plasma processing apparatus 200 of a comparative example; FIG. FIG. 3 is a schematic cross-sectional view of a plasma processing apparatus 300 of Example 2; FIG. 11 is a schematic perspective view of a plasma processing apparatus 400 of Example 3; It is a schematic perspective view of the plasma processing apparatus 400a of a modification.

(Configuration of plasma processing apparatus 100)
FIG. 1 is a schematic cross-sectional view of a plasma processing apparatus 100 of Example 1. FIG. The z-direction indicates vertically upward. The plasma processing apparatus 100 includes a first outer conductor 120 , a second outer conductor 130 , an outer tube 140 and an insulating spacer 180 .

The first outer conductor 120 and the second outer conductor 130 have a cylindrical shape sharing the central axis CA. The material of the first outer conductor 120 and the second outer conductor 130 is copper, brass, or other metals. The first outer conductor 120 includes a channel space CH1, a plasma propagation space MP1, and a first electrode 121. As shown in FIG. The channel space CH1 is a space through which a fluid can flow. The channel space CH1 also has a function of cooling the first outer conductor 120 with liquid. The plasma propagation space MP1 is a space for propagating microwaves generated by a microwave generator (not shown). The first electrode 121 is arranged at the first end E<b>1 of the first outer conductor 120 .

The second outer conductor 130 includes a channel space CH2 and a second electrode 131. The channel space CH2 is a space that forms part of the second channel LP2, as will be described later. A plurality of channel spaces CH2 are arranged rotationally symmetrically with respect to the central axis CA. The second electrode 131 is arranged at the second end E2 of the second outer conductor 130 . The second electrode 131 protrudes from the second end E2. The shapes of the first electrode 121 and the second electrode 131 are circular rings having substantially the same diameter.

The first end E1 of the first outer conductor 120 and the second end E2 of the second outer conductor 130 are connected via a ring-shaped insulating spacer 180 . The first outer conductor 120 and the second outer conductor 130 may be fixed by bolts (not shown).

A plasma generation space PG1 is formed in a region where the first end E1 and the second end E2 face each other. The plasma generation space PG1 is an annular space. A first electrode 121 and a second electrode 131 are arranged facing each other in the plasma generation space PG1. A slit S<b>1 is formed between the first electrode 121 and the second electrode 131 . The width of the slit S1 is about 0.05 mm or more and 1 mm or less.

Between the first end E1 and the second end E2, gaps G1 and G2 are formed. The gap G1 is formed inside the insulating spacer 180 and functions as a channel connecting the channel spaces CH1 and CH2. The gap G2 is formed around the outer circumferences of the first outer conductor 120 and the second outer conductor 130, and functions as a flow path connecting the plasma generation space PG1 and the outer circumference space OS1. A second flow path LP2 is formed by the flow path space CH1, the gap G1, the flow path space CH2, and the gap G2, as indicated by the dotted arrow. The second flow path LP2 is a flow path that joins the first flow path LP1 from the flow path space CH1 via the plasma generation space PG1. Since the plasma generation space PG1 is not likely to be immersed in the liquid flowing through the second flow path LP2, plasma can be stably generated.

Also, the gap G2 has a region extending obliquely downward with respect to the horizontal direction (x direction). As a result, gravity can be used to prevent the fluid flowing through the first flow path LP1 from flowing back to the plasma generation space PG1.

The outer tube 140 is arranged outside the first outer conductor 120 and the second outer conductor 130 . The outer tube 140 has a cylindrical shape and shares the central axis CA with the first outer conductor 120 and the second outer conductor 130 . The material of the outer tube 140 is glass, for example.

An outer space OS1 is formed between the outer circumferences of the first outer conductor 120 and the second outer conductor 130 and the inner circumference of the outer tube 140 . The outer space OS1 functions as the first flow path LP1, as indicated by the dotted arrow. The first outer conductor 120 has a first inclined surface 122 protruding toward the outer tube 140 toward the first end E1. The second outer conductor 130 also has a second slanted surface 132 protruding toward the outer tube 140 toward the second end E2. As a result, a narrowed portion RP having a narrow cross-sectional area is formed in the vicinity of the confluence point JP between the first flow path LP1 and the second flow path LP2.

The flow velocity of the liquid flowing through the first flow path LP1 becomes extremely large around the throttle portion RP. The venturi effect can reduce the pressure of the liquid. For example, a liquid under 1 atmosphere can be lowered to about 0.1 atmosphere. Since the plasma generation space PG1 is connected to the throttle portion RP through the gap G2, the plasma generation space PG1 can be decompressed. Since the pressure can be reduced without using a pump or the like, the plasma processing apparatus 100 can be simplified.

(Plasma treatment method)
The plasma processing method according to Example 1 will be described using a case of producing metal nanoparticles as an example. First, a solution containing a metal or metal compound is prepared. In this example, an aqueous solution of silver nitrate was used. The AgNO ₃ concentration was 0.1 mol/L. Then, an aqueous solution of silver nitrate is allowed to flow through the first flow path LP1. Due to the venturi effect, the air pressure around the plasma generation space PG1 is lowered. In this example, the flow rate was set at 55 L/min. Also, the pressure in the plasma generation space PG1 was about 0.2 atm. Also, pure water is allowed to flow through the second flow path LP2. In this example, the flow rate was set at 250 mL/min.

Next, microwaves generated by a microwave generator (not shown) are radiated into the plasma propagation space MP1. The microwave propagates in the direction of the arrow M1 inside the plasma propagation space MP1 and reaches the plasma generation space PG1. In this example, the microwave frequency was 2.45 GHz and the microwave power was 1 kW.

A surface current is then induced in the first outer conductor 120 and the second outer conductor 130 . As a result, a relatively strong electric field is applied between the first electrode 121 and the second electrode 131 . As a result, discharge occurs between the first electrode 121 and the second electrode 131, and plasma is generated in the plasma generation space PG1. The plasma generated in the plasma generation space PG1 irradiates the pure water flowing through the second flow path LP2 with plasma products. Here, plasma products include electrons, positive ions, radicals, and ultraviolet rays. As a result, the pure water flowing through the second flow path LP2 is plasma-treated to generate plasma-treated water containing chemically active species.

The plasma-treated water is immediately introduced to the confluence point JP due to the pressure difference due to the venturi effect, and is mixed with the silver nitrate aqueous solution. That is, the plasma-treated water comes into contact with the silver nitrate aqueous solution. As a result, the chemically active species contained in the plasma-treated water can be chemically reacted with the silver nitrate aqueous solution before the chemically active species are deactivated. Thus, silver nanoparticles can be produced. The silver nanoparticles are aggregates in which silver particles having a particle size of about 20 nm or more and 50 nm or less are aggregated. The silver nitrate aqueous solution flowing through the first flow path LP1 can be continuously plasma-treated in-line. Compared to batch processing, it is possible to increase the production efficiency of silver nanoparticles.

(Challenges and effects)
First, the problem will be described using the plasma processing apparatus 200 of the comparative example shown in FIG. The plasma processing apparatus 200 (FIG. 2) of the comparative example differs from the plasma processing apparatus 100 (FIG. 1) of Example 1 in that the second flow path LP2 is not provided. That is, the plasma processing apparatus 200 of the comparative example is an apparatus that directly irradiates the silver nitrate aqueous solution flowing through the first flow path LP1 with plasma. When the pressure in the plasma generation space PG1 is reduced by the venturi effect, a reverse flow passage LPb may be formed from the confluence point JP toward the plasma generation space PG1. When the silver nitrate aqueous solution flows backward to the plasma generation space PG1, droplets DR of the silver nitrate aqueous solution adhere to the first electrode 121 and the second electrode 131 . Since the silver nitrate aqueous solution is a liquid in which a solid solute is dissolved, the solid solute is solidified and deposits DE are deposited on the first electrode 121 and the second electrode 131 . Discharge stops and plasma processing cannot be performed.

On the other hand, the plasma processing apparatus 100 of Example 1 includes a second flow path LP2 that merges with the first flow path LP1 via the plasma generation space PG1. By irradiating the pure water flowing through the second flow path LP2 with plasma, it is possible to generate highly reactive plasma-treated water containing chemically active species and the like. By mixing the plasma-treated water with the silver nitrate aqueous solution flowing through the first flow path LP1, silver nanoparticles can be generated. That is, the silver nitrate aqueous solution can be plasma-treated through the plasma-treated water. It is possible to completely separate the plasma-treated water generation region and the plasma-treated silver nitrate aqueous solution region. Since it is not necessary to irradiate the silver nitrate aqueous solution with plasma, even if the silver nitrate aqueous solution contains a component that forms the deposit DE, the component does not affect the first electrode 121 and the second electrode 131. . Further, since pure water is a liquid in which solid solutes are not dissolved, deposits DE are not generated. Long-term continuous plasma processing becomes possible.

In the plasma processing apparatus 200 (FIG. 2) of the comparative example, it is conceivable to form an air curtain with gas, for example, in order to prevent the formation of the backflow flow path LPb. However, since gas has a much lower density than liquid, the air curtain cannot sufficiently prevent backflow. In the plasma processing apparatus 100 of the first embodiment, the pure water flowing through the second flow path LP2 can prevent formation of the backflow flow path LPb. Backflow can be reliably prevented by pushing back the backflow liquid with pure water. It becomes possible to prevent the generation of deposits DE.

FIG. 3 is a schematic cross-sectional view of a plasma processing apparatus 300 of Example 2. FIG. The plasma processing apparatus 300 includes a plasma-treated water generator 301 and a tank 302 . The plasma-treated water generating section 301 includes a channel space 310, a plasma generating space PG2, a first electrode 331, a second electrode 332, a microwave introducing section 340, and a dielectric section 350. The channel space 310 functions as a channel LP as indicated by the dotted arrow. In this embodiment, pure water flows through the flow path LP. The flow path space 310 has a constricted portion RP2 at and near the communicating portion with the plasma generating space PG2. The narrowed portion RP2 is a region with a reduced cross-sectional area, and can reduce the pressure of the plasma generation space PG2 by the venturi effect.

The plasma generation space PG2 is a space formed so as to spread outward in the direction perpendicular to the flow path LP. A ring-shaped first electrode 331 and a ring-shaped second electrode 332 are disposed facing each other with a gap in the plasma generation space PG2. The microwave introduction part 340 is a part for propagating microwaves to the plasma generation space PG2. The dielectric portion 350 is a portion that covers the outer periphery of the plasma generation space PG2 to insulate the plasma generation space PG2 from the outside. A tank 302 is a part that holds a liquid 303 to be plasma-processed. In this embodiment, the liquid 303 is an aqueous solution of silver nitrate.

(Plasma treatment method)
The plasma processing method according to Example 2 will be described by taking the case of producing metal nanoparticles as an example. First, the silver nitrate aqueous solution is held in the tank 302 . Then, pure water is allowed to flow through the flow path LP. Due to the venturi effect, the air pressure in the plasma generation space PG2 is lowered. Next, microwaves generated by a microwave generating section (not shown) are radiated into the microwave introducing section 340 .

By applying an electric field between the first electrode 331 and the second electrode 332, plasma is generated in the plasma generation space PG2. The generated plasma irradiates pure water flowing through the flow path LP with plasma products. As a result, the pure water flowing through the flow path LP is plasma-treated to generate plasma-treated water containing chemically active species. The plasma-treated water is discharged downward from the channel space 310, flows into the tank 302, and is mixed with the silver nitrate aqueous solution. Silver nanoparticles are generated by the chemically active species contained in the plasma-treated water reacting with the silver nitrate aqueous solution.

(effect)
Plasma treatment can be applied to the silver nitrate aqueous solution through the plasma-treated water. Since there is no need to irradiate the silver nitrate aqueous solution with plasma, the components contained in the silver nitrate aqueous solution do not affect the first electrode 331 and the second electrode 332 . Long-term continuous plasma processing becomes possible.

(Modification of Example 2)
The liquid 303 to be plasma-treated is not limited to being held in the tank 302 . For example, a second channel for flowing the liquid 303 may be provided. Then, the plasma-treated water flowing through the flow path LP may join the liquid 303 flowing through the second flow path. Since plasma processing can be performed continuously in-line, processing efficiency can be improved compared to batch processing.

(Configuration of plasma processing apparatus 400)
FIG. 4 shows a schematic perspective view of a plasma processing apparatus 400 of Example 3. As shown in FIG. The plasma processing apparatus 400 of Example 3 differs from the plasma processing apparatus 100 (FIG. 1) of Example 1 in that it includes a rectifying section 403 and the like. Parts similar to those of the plasma processing apparatus 100 are denoted by the same reference numerals, and description thereof is omitted. Also, in FIG. 4, the external pipe 140 is indicated by a dashed line, and the supply flow path LP0 and the first flow path LP1 are indicated by dotted lines.

The plasma processing apparatus 400 mainly includes an outer tube 140, an inner tube 401, a pump 402, a plurality of rectifying sections 403, a tank 404, a particle size distribution measuring device 405, and a control device 406. The inner tube 401 has a structure in which the first outer conductor 120 and the second outer conductor 130 are combined. As described in Embodiment 1, the plasma generation space PG1 and the second flow path LP2 are arranged in the region where the first outer conductor 120 and the second outer conductor 130 face each other. The inner tube 401 and the outer tube 140 are arranged so that their central axes CA coincide with each other. A ring-shaped first flow path LP<b>1 surrounding the outer circumference of the inner tube 401 is formed between the inner tube 401 and the outer tube 140 . The first flow path LP1 has a route from the upper end UE of the inner pipe 401 and the outer pipe 140 to the lower end LE. A throttle portion RP is provided on the path of the first flow path LP1.

A ring-shaped first channel inlet LP1E is formed at the upper end UE. A plurality of rectifiers 403 are formed in the vicinity of the upper end UE. That is, the plurality of rectifying portions 403 are arranged on the route to the throttle portion RP of the first flow path LP1. Each of the plurality of rectifying portions 403 is a plate-like member radially connecting the outer circumference of the first outer conductor 120 and the inner circumference of the outer tube 140 . Each of the straightening portions 403 extends in the axial direction (z direction) of the central axis CA and has an inclination A1 with respect to the axial direction (z direction). The magnitude of the slope A1 is not particularly limited. Also, the inclination A1 may be configured to be variable.

The pump 402 is a supply unit that discharges the silver nitrate aqueous solution to the first flow path LP1. The silver nitrate aqueous solution discharged from the pump 402 is supplied to the first channel inlet LP1E via the supply channel LP0. As indicated by the dotted line in FIG. 4, the supply flow path LP0 has an annularly branched flow path so as to supply the entire ring-shaped first flow path inlet LP1E. The flow rate of the silver nitrate aqueous solution supplied from the pump 402 can be adjusted by the rotation speed of the pump 402 . Also, the rotation speed of the pump 402 can be controlled by the controller 406 . The control device 406 is not particularly limited, and may be a PC, for example.

A silver nitrate aqueous solution is introduced vertically downward (-z direction) into the first channel inlet LP1E. The flow direction of the silver nitrate aqueous solution introduced is changed by the rectifying section 403 by the inclination A1. Therefore, the first flow path LP1 output from the rectifying section 403 becomes a swirl flow swirling around the central axis. The first flow path LP1 reaches the throttle portion RP while maintaining the swirling state. Therefore, in the throttle portion RP, the flow of the silver nitrate aqueous solution has a velocity component that swirls around the central axis CA. That is, the flow velocity of the silver nitrate aqueous solution in the constricted portion RP has not only a z-direction velocity component but also x- and y-direction velocity components. The flow velocity of the silver nitrate aqueous solution in the constricted portion RP is not particularly limited, and may be, for example, 10 m/s or more.

A silver nitrate aqueous solution containing silver nanoparticles is discharged from the lower end LE. The discharged silver nitrate aqueous solution passes through the particle size distribution measuring device 405 and is stored in the tank 404 . The particle size distribution measuring device 405 can measure the particle size distribution of the silver nanoparticles in the discharged silver nitrate aqueous solution in real time. The type of particle size distribution measuring device 405 is not particularly limited. A measurement result of the particle size distribution is transmitted to the control device 406 .

The control device 406 feedback-controls the flow rate of the silver nitrate aqueous solution based on the measurement result of the particle size distribution. A specific description will be given. By changing the flow velocity of the aqueous silver nitrate solution, the introduction concentration of the plasma-treated water joining from the second flow path LP2 into the aqueous silver nitrate solution can be controlled. That is, since the flow rate per unit time of the plasma-treated water supplied from the second flow path LP2 and the concentration of chemically active species in the plasma-treated water are constant, the smaller the flow rate of the silver nitrate aqueous solution per unit time, the more silver nitrate The concentration of chemically active species in the aqueous solution can be increased. As the concentration of the chemically active species increases, the amount of chemical reaction can be increased, so the particle size distribution of the silver nanoparticles can be shifted to the larger side. As a result, the particle size distribution of the silver nanoparticles can be controlled within a predetermined range by appropriately feedback-controlling the rotation speed of the pump 402 based on the real-time measurement result of the particle size distribution.

(effect)
As shown in FIG. 1, a second flow path LP2 is formed on the inner side (on the side of the central axis CA) in the vicinity of the narrowed portion RP. The technique of Example 3 can generate a velocity component that revolves around the central axis CA in the flow of the silver nitrate aqueous solution. As a result, a centrifugal force that presses the silver nitrate aqueous solution against the outer tube 140 can be generated at the throttle portion RP. Since the silver nitrate aqueous solution can be kept away from the second flow path LP2, backflow can be reliably prevented. Moreover, even when a swirling flow is used, the venturi effect can be generated at the constricted portion RP, so that the plasma generation space PG1 can be decompressed. In addition, it is preferable that the centrifugal force applied to the silver nitrate aqueous solution in the constricted portion RP is 1 G or more.

(Modification of Example 3)
The structure of the rectifying section is not limited to the example of FIG. 4, and may have various structures. The straightening section can be formed on at least one of the outer wall surface of the inner tube 401 and the inner wall surface of the outer tube 140 . Further, the rectifying portion can have a projection shape protruding from the wall surface or a groove shape recessed from the wall surface. For example, as shown in a modified plasma processing apparatus 400a, the rectifying portion 403a may be a wall-shaped protrusion formed on the outer peripheral wall surface of the first outer conductor 120. FIG. At least a portion of the rectifying portion 403a may be arranged within the range of the region R1 in which the first inclined surface 122 is formed. Note that the illustration of the external tube 140 is omitted in FIG. 5 for ease of viewing.

There may be various modes of discharging the silver nitrate aqueous solution from the pump. For example, as shown in FIG. 5, nozzles 402n that are inclined with respect to the axial direction (z direction) of the central axis CA may be provided. As a result, the silver nitrate aqueous solution in a swirl state having an inclination A2 with respect to the axial direction can be introduced into the first flow path LP1. Alternatively, as shown in FIG. 5, the silver nitrate aqueous solution may be introduced from one point of the ring-shaped first channel inlet LP1E.

Although the embodiments of the present invention have been described in detail above, they are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

(Modification)
The technique of the present specification can be widely applied to various liquids, and can stably form a new chemical reaction field using plasma. As a result, it can be expected to be applied as a new process reaction field for chemical reactions. The field of application of plasma processing herein is not limited to nanoparticle generation, and can be applied to various fields. For example, it can be used for organic matter decomposition treatment and disinfectant water production.

In this specification, the case of generating silver nanoparticles has been described, but it is not limited to this form, and various types of nanoparticles can be generated. For example, when a chloroauric acid aqueous solution is used, gold nanoparticles can be produced.

The liquid to be plasma treated is not limited to pure water, and may be various liquids. For example, it may be a liquid in which no solid solute is dissolved. Since the deposit DE is not deposited, plasma can be continuously generated. Specific examples include alcohols, carboxylic acids, aldehydes, nitric acid, hydrochloric acid, carbonic acid, and aqueous ammonia.

The means for depressurizing the plasma generation spaces PG1 and PG2 is not limited to means using the venturi effect, and various means can be used. For example, the pressure may be reduced using a pump.

The plasma used in the technology of this specification is not limited to low-pressure plasma. Atmospheric plasma may also be used.

Various plasma generating means may be used in the technology of this specification. For example, DC discharge, DC pulse discharge, high-frequency discharge, or the like may be used.

The technical elements described in this specification or drawings demonstrate technical usefulness by themselves or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques exemplified in this specification or drawings can simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

Pure water is an example of the first liquid. A silver nitrate aqueous solution is an example of the second liquid. The second channel LP2 and the channel space 310 are examples of contact means. First outer conductor 120 is an example of a first tube. The second outer conductor 130 is an example of a second tube. Pump 402 is an example of a supply.

Aspects of the present technology are listed below.
[Aspect 1]
a plasma generating means for generating plasma;
irradiation means for irradiating the generated plasma onto the first liquid;
contacting means for bringing the plasma-irradiated first liquid into contact with a second liquid;
A plasma processing apparatus comprising:
[Aspect 2]
The plasma generating means is
a plasma generation space for generating the plasma;
depressurizing means for depressurizing the plasma generating space;
The plasma processing apparatus according to aspect 1, comprising:
[Aspect 3]
The decompression means is a first flow path having a constricted portion with a narrow cross-sectional area, the first flow path through which the first liquid or the second liquid flows,
The plasma processing apparatus according to aspect 2, wherein the constricted portion is connected to the plasma generation space.
[Aspect 4]
A second flow path that merges with the first flow path,
The second flow path is connected to the plasma generation space,
the second liquid flows through the first channel;
The plasma processing apparatus according to aspect 3, wherein the first liquid flows through the second channel.
[Aspect 5]
an inner tube;
an outer tube covering the outer periphery of the inner tube;
with
The plasma generating space and the second flow path are arranged in the inner tube,
The inner tube and the outer tube are arranged so that their central axes are aligned with each other,
the first flow path surrounding the outer circumference of the internal pipe is formed between the internal pipe and the external pipe;
The first flow path has a path extending from one end of the inner tube and the outer tube to the other end, and the narrowed portion is provided on the path,
The plasma processing apparatus according to aspect 4, wherein the flow of the second liquid in the constricted portion has a velocity component that revolves around the central axis.
[Aspect 6]
further comprising at least one straightening section arranged on the first flow path up to the throttle section;
The plasma processing apparatus according to aspect 5, wherein the rectifying section extends in the axial direction of the central axis and is inclined with respect to the axial direction of the central axis.
[Aspect 7]
The straightening section is formed on at least one of an outer peripheral wall surface of the inner tube and an inner peripheral wall surface of the outer tube,
The straightening section has a projection shape protruding from the wall surface or a groove shape recessed from the wall surface,
The plasma processing apparatus according to aspect 6.
[Aspect 8]
further comprising a supply unit for discharging the second liquid into the first flow path,
8. The plasma processing apparatus according to any one of modes 5 to 7, wherein a direction in which the second liquid is discharged by the supply unit is inclined with respect to an axial direction of the central axis.
[Aspect 9]
The inner tube is
a first tube having a first electrode at a first end;
a second tube having a second electrode at a second end;
and
The first tube, the second tube, and the external tube are arranged so that their central axes are aligned with each other,
The first end and the second end face each other in a non-contact state,
The first flow path is formed between the outer peripheries of the first and second tubes and the inner perimeter of the outer tube,
The plasma according to any one of aspects 5 to 8, wherein the second flow path and the plasma generation space are formed in the regions where the first end and the second end face each other. processing equipment.
[Aspect 10]
The plasma processing apparatus according to any one of modes 2 to 9, further comprising a propagation space configured to allow microwaves to propagate to the plasma generation space.
[Aspect 11]
the first liquid is a liquid in which a solid solute is not dissolved;
The plasma processing apparatus according to any one of modes 1 to 10, wherein the second liquid is a liquid in which a solid solute is dissolved.
[Aspect 12]
an irradiation step of irradiating the first liquid with plasma;
a contacting step of contacting the first liquid with a second liquid;
A plasma processing method comprising:
[Aspect 13]
13. The plasma processing method according to aspect 12, wherein in the irradiation step, the plasma is generated in a reduced pressure environment.
[Aspect 14]
In the contacting step, the first liquid is brought into contact while the second liquid is flowing;
14. The plasma processing method according to aspect 13, wherein in the irradiation step, the reduced-pressure environment is generated by a venturi effect obtained by the flow of the second liquid.
[Aspect 15]
15. The plasma processing method according to any one of modes 12 to 14, wherein in the contact step, microwaves are incident on the space for generating the plasma.

100: Plasma processing apparatus 120: First outer conductor 121: First electrode 130: Second outer conductor 131: Second electrode 140: Outer tube JP: Junction point RP: Constriction part LP1: First flow path LP2: Second 2 flow paths PG1: plasma generation space

Claims

a plasma generating means for generating plasma;
irradiation means for irradiating the generated plasma onto the first liquid;
contacting means for bringing the plasma-irradiated first liquid into contact with a second liquid;
A plasma processing apparatus comprising:
The plasma generating means is
a plasma generation space for generating the plasma;
depressurizing means for depressurizing the plasma generating space;
2. The plasma processing apparatus of claim 1, comprising:
The decompression means is a first flow path having a constricted portion with a narrow cross-sectional area, the first flow path through which the first liquid or the second liquid flows,
3. The plasma processing apparatus according to claim 2, wherein said narrowed portion is connected to said plasma generation space.
A second flow path that merges with the first flow path,
The second flow path is connected to the plasma generation space,
the second liquid flows through the first channel;
4. The plasma processing apparatus according to claim 3, wherein said first liquid flows through said second channel.
an inner tube;
an outer tube covering the outer periphery of the inner tube;
with
The plasma generating space and the second flow path are arranged in the inner tube,
The inner tube and the outer tube are arranged so that their central axes are aligned with each other,
the first flow path surrounding the outer circumference of the internal pipe is formed between the internal pipe and the external pipe;
The first flow path has a path extending from one end of the inner tube and the outer tube to the other end, and the narrowed portion is provided on the path,
5. The plasma processing apparatus according to claim 4, wherein the flow of said second liquid in said constricted portion has a velocity component that swirls around said central axis.
further comprising at least one straightening section arranged on the first flow path up to the throttle section;
6. The plasma processing apparatus according to claim 5, wherein said rectifying section extends in the axial direction of said central axis and has an inclination with respect to the axial direction of said central axis.
The straightening section is formed on at least one of an outer peripheral wall surface of the inner tube and an inner peripheral wall surface of the outer tube,
The straightening section has a projection shape protruding from the wall surface or a groove shape recessed from the wall surface,
The plasma processing apparatus according to claim 6.
further comprising a supply unit for discharging the second liquid into the first flow path,
6. The plasma processing apparatus according to claim 5, wherein a direction in which said second liquid is discharged by said supply unit is inclined with respect to an axial direction of said central axis.
The inner tube is
a first tube having a first electrode at a first end;
a second tube having a second electrode at a second end;
and
The first tube, the second tube, and the external tube are arranged so that their central axes are aligned with each other,
The first end and the second end face each other in a non-contact state,
The first flow path is formed between the outer peripheries of the first and second tubes and the inner perimeter of the outer tube,
6. The plasma processing apparatus according to claim 5, wherein said second flow path and said plasma generating space are formed in regions where said first end and said second end face each other.
The plasma processing apparatus according to claim 2, further comprising a propagation space configured to allow microwaves to propagate to said plasma generation space.
the first liquid is a liquid in which a solid solute is not dissolved;
The plasma processing apparatus according to any one of claims 1 to 10, wherein said second liquid is a liquid in which a solid solute is dissolved.
an irradiation step of irradiating the first liquid with plasma;
a contacting step of contacting the first liquid with a second liquid;
A plasma processing method comprising:
The plasma processing method according to claim 12, wherein in said irradiation step, said plasma is generated in a reduced pressure environment.
In the contacting step, the first liquid is brought into contact while the second liquid is flowing;
14. The plasma processing method according to claim 13, wherein in said irradiation step, said reduced-pressure environment is generated by a venturi effect obtained by the flow of said second liquid.
The plasma processing method according to any one of claims 12 to 14, wherein in said contacting step, microwaves are incident on the space for generating said plasma.