JPH09288052A - Fractionating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine particle fractionating apparatus in combination with an ultrasonic wave radiating pressure and electrostatic field having function for suppressing bubbles generated from an electrode. SOLUTION: The fractionating apparatus comprises a tube walls 31, 32 for feeding fluid containing fine particles, ultrasonic vibrators 41, 42 for generating standing waves in the tubes, and two electrode plates 51, 52 of operating electrode and paired electrodes. The solute such as fine particles 15 in liquid is fractionated by the contention of ultrasonic wave radiating pressure and electromagnetic force. The voltage applied to the two plates 51, 52 are controlled by using a potential controller 14 with a reference electrode 7 introduced into the walls 31, 32 as a reference potential, and the potentials of the electrodes 51, 52 are held constant at the highest potential for eliminating the bubbles.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a device for fractionating fine particles in a fluid.

[0002]

2. Description of the Related Art Regarding the radiation pressure applied to fine particles when the radiation pressure of ultrasonic waves is applied to the fine particles, see, for example, John Lube, Journal of Acoustic Society of America, Vol. 89, pages 2140-214.
On page 3 (1991), a diameter of 27
We report successful capture of 0 μm polystyrene spheres. Regarding the principle that fine particles are captured by the radiation pressure of this ultrasonic wave, Yoshioka et al., In Acoustica Vol. 5, pp. 167 to 178, show that the ultrasonic radiation pressure of fine particles in standing waves and traveling waves The size in the fluid is calculated. In addition, regarding a method of fractionating fine particles by antagonizing the radiation pressure of this ultrasonic wave with other external force, for example, RE Upel et al. Journal of the Acoustical Society of America, Volume 71 (1982) 1261
Pp. 1268.

When a potential difference is applied to two electrodes (a working electrode and a counter electrode) introduced into a solution, an oxidation or reduction reaction of ions in the solution occurs on the electrode surface when a certain potential difference is exceeded, and as a result, in the solution. Bubbles are generated in. Since the type of electrode reaction that occurs on the electrode surface is determined by the potential of the electrode, a third electrode called the reference electrode is introduced into the solution, and the potential of the working electrode or the counter electrode is adjusted appropriately based on that potential and kept constant. It is known that it is possible to specify the type of electrode reaction by using, for example, the principle of these is described in Aki Fujishima et al., “Electrochemical measurement method (1)” (Gihodo Publishing Co., Ltd., 1984). Are described in detail. Further, a potentiostat is generally used as a device for keeping the electrode potentials of the working electrode and the counter electrode constant based on the potential of the reference electrode.

In addition, in the hydrogen production reaction on the electrode, the hydrogen overvoltage becomes higher and the electrolysis of water occurs at the reaction electrode where the production process of adsorbed hydrogen atoms (Volmer reaction) is generally controlled. Is known to increase.

[0005]

SUMMARY OF THE INVENTION
As described in No. 241977, the inventors have invented a fine particle fractionation device that fractionally collects fine particles having different particle diameters or fine particles having different materials by combining the radiation pressure of ultrasonic waves and an electrostatic field. No consideration was given to suppressing the generation of bubbles generated by electrolysis from the electrode introduced in. When ultrasonic waves are radiated, even if the initially generated bubbles are small, there is a high possibility that cavitation will occur around the bubbles and grow into large bubbles. When fractionating fine particles in the electrolyte solution, the sound field and the electric field in the solution are disturbed by the bubbles, so that the fine particles cannot be fractionated effectively.

An object of the present invention is to provide a fine particle fractionation device which combines an ultrasonic radiation pressure and an electrostatic field having a function of suppressing bubbles generated from the above electrodes.

[0007]

In order to provide a fine particle fractionation device which combines an ultrasonic radiation pressure having a function of suppressing bubbles generated from electrodes and an electrostatic field, the fractionation device of the present invention is In addition to the two electrodes (working electrode and counter electrode) to be used, a third electrode (reference electrode) is introduced, and a means for adjusting the potential difference between these three electrodes is provided, and a space between the pair of electrodes is provided. It has a means for measuring the magnitude of the flowing current and a means for keeping the potentials of the working electrode and the counter electrode at a potential that does not generate bubbles in the solution. Further, as the electrode material of the cathode, a material such as mercury, zinc, lead, magnesium, tin, etc., whose rate is the generation of adsorbed hydrogen atoms may be used. As the electrode material of the anode, a material having a large oxygen overvoltage such as gold, platinum, cadmium, or silver may be used.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION According to the theoretical analysis on the radiation pressure given by a sound wave described by Yoshioka et al. In Acoustica Vol. 5, pp. 167 to 178, for example, a plane standing wave with a wave number k is used.

[0009]

[Equation 1]

When there is a fine particle at a position at a distance x from the position of the node, the radiation pressure received by this fine particle is

[0011]

[Equation 2]

[0012]

(Equation 3)

Can be set. Here, F is the radiation pressure applied to the particles by the ultrasonic waves, R is the radius of the particles, k
Is the wave number of ultrasonic waves, Eac is the average energy density of ultrasonic waves,
ρ is the density of the fine particles, ρ ′ is the density of the dispersion medium, γ is the compression rate of the fine particles, and γ ′ is the compression rate of the dispersion medium. Then, in the relationship between the fine particles and the solvent, when A is positive, the fine particles try to collect in the node of the standing wave, and when negative, try to collect in the antinode.

Here, when an external electric field is applied, as explained in the previous application,

[0015]

(Equation 4)

A balance equation such as

[0017]

(Equation 5)

Move to the position of. Here, ε is the dielectric constant of the solution, 1 / κ is the thickness of the electric double layer on the surface of the fine particles, Φ ₀ is the ζ potential in the solution of the fine particles, and Ee is the electric field strength.

Here, when a potential difference is applied to the two electrodes (working electrode and counter electrode) introduced into the solution in order to create an electric field, as described in the prior art, when the electrode surface exceeds a certain potential. Ions in the solution are oxidized or reduced on the surface of the electrode, and as a result, bubbles are generated in the solution. Since the type of electrode reaction that occurs on the electrode surface is determined by the potential of the electrode, a third electrode called the reference electrode is introduced into the solution, and the potential of the working electrode or the counter electrode is adjusted appropriately based on that potential and kept constant. It is possible to specify the type of electrode reaction. Therefore, the magnitude of the current flowing between the working electrode and the counter electrode with respect to the potential of the reference electrode is measured, and the potential of the working electrode and the counter electrode is adjusted by controlling the potentials of the working electrode and the counter electrode so that bubbles are not generated by electrolysis. Generation of bubbles can be suppressed.

At this time, when only the working electrode and the counter electrode are used without using the reference electrode, the potential difference between the two electrodes can be measured, but the potential of the two electrodes cannot be measured. Therefore, it is not possible to know what kind of reaction is occurring on the two electrodes, and it is difficult to control it to an appropriate potential that does not cause electrolysis.

By the way, it is considered that the hydrogen production reaction on the electrode proceeds by the following reaction mechanism.

(1) Generation of adsorbed hydrogen atoms (Volmer
reaction)

[0023]

(Equation 6)

(2) Discharge reaction of second proton on adsorbed hydrogen atom (Heyrovsky reaction)

[0025]

(Equation 7)

(3) Hydrogen generation reaction by binding of two adsorbed hydrogen atoms (Tafel reaction)

[0027]

(Equation 8)

First, the reaction (1) occurs on the surface of the cathode electrode, and then the reaction (2) or (3) proceeds to generate hydrogen. At this time, (1) is the rate-determining electrode of mercury, zinc, lead, etc., and (2) is the rate-limiting electrode of silver,
It is known that nickel or the like and platinum (3), palladium, or the like are the rate-determining electrodes. In the electrode reaction in which (1) is rate-determining, the hydrogen overvoltage becomes large, so that the potential at which hydrogen bubbles are first generated on the electrode becomes higher than reactions in which other reactions are rate-limiting. Further, when a material having a large oxygen overvoltage such as gold, platinum, cadmium, or silver is used for the anode, the potential at which oxygen bubbles are generated on the electrode surface of the anode becomes high.

Example FIG. 1 shows a schematic view in the form of a sectional view from the side of a fine particle continuous fractionation apparatus as an example using the present invention. In this device, first, a tube 26 having tube walls 31 and 32 through which a fluid containing fine particles flows (in this embodiment, a section has a rectangular shape).
And ultrasonic transducers 41, 42 for generating standing waves 6 in the tube 26 are attached to the outer walls of the tube walls 31, 32 of the tube 26, and working electrodes are provided on the inner walls of the tube walls 31, 32 of 26. Two electrode plates 51 and 52 are provided as counter electrodes. The solute such as the fine particles 15 in the liquid can be fractionated as shown in (Equation 5) by antagonizing the radiation pressure by the ultrasonic transducers 41, 42 and the electromagnetic force by the electrode plates 51, 52. However, when the fluid is water, the wavelength λ in water is 1.5 mm when the frequency of the ultrasonic waves generated from the ultrasonic transducers 41 and 42 driven by the ultrasonic controller 13 is 1 MHz. The width 2 of the tube walls 31, 32 is λ / 2 or (λ / 2 + n
λ), the standing wave 6 as shown in (Equation 1) is generated in the tube walls 31 and 32. Here, n is an integer. Further, in the concentrating device of this embodiment, when concentrating the fine particles in the tube 26, the fluid in the tube 26 may be stationary or flowing. The voltage applied to the two electrode plates 51 and 52 uses the reference electrode 7 introduced into the tube walls 31 and 32,
This is used as a reference potential and is controlled using the potential control device section 14 to keep the potentials of these two electrodes 51 and 52 constant at the maximum potential at which bubbles are not generated.

As shown in FIG. 2, when the horizontal axis represents voltage and the vertical axis represents current, and changes in current when the potential difference applied between the electrodes is increased, almost no current flows at first. However, when the potential difference is further increased, electrolysis occurs on the electrode surface, and the current suddenly starts to flow. Therefore, in order to maintain the maximum potential at which no bubbles are generated, it is always necessary to adjust the current flowing between the electrodes to be a fixed value or less. That is, when the current increases, the potential difference between the electrodes may be decreased until the current becomes a certain value or less, and when the current value decreases, the maximum voltage may be set at which the current becomes a certain value or less.

In the example of FIG. 2, as shown by the broken line from the point where the current suddenly rises, an asymptotic line is drawn, and the point where it crosses the voltage line is regarded as the voltage at which electrolysis is started. It is preferable to control the current so that the voltage that does not reach this voltage is as large as possible.

It is also possible to obtain the gradient of current change with respect to potential change and estimate the decomposition voltage at which electrolysis occurs based on this. That is, the potentials of the two electrodes are slightly oscillated, the change in the current flowing between the two electrodes at this time is measured by the potential control device unit 14, the slope of the current change is determined, and this slope is below a certain value. The potential control device section 14 may control so as to maintain the maximum potential.

Although this constant value varies depending on the solution conditions,
For example, in the case of 0.5 mol sulfuric acid solution, 1μ on the copper electrode surface
It was A / square cm.

By the way, as can be seen from (Equation 5),
When the potential of the electrode is changed, the ultrasonic energy density Eac is changed according to the change of the potential difference Ee so that the position of balance of fine particles having the same physical properties does not change due to the change of the potential difference Ee. Keep the ratio constant.

Although the reference electrode 7 is placed downstream of the electrodes 51 and 52 in this embodiment, it may be placed upstream of the electrodes.

Next, the recovery of the fractionated fine particles will be described. After fractionating fine particles in a fluid, a movable support rod 8
Moving the thin tube 10 held in the tube walls 31, 32 by 1, 82, 83, 84 in the directions of arrows 91, 92 by the thin tube driving section 32 having a function of monitoring the amount of movement in the tube 26. To move it to an appropriate position in the tube walls 31 and 32, and the fluid flowing into the pipe 26 as shown by the arrow 1 is separated from the flow around the thin tube 10 as shown by the arrows 111 and 112 and separated by the flow shown by the arrow 12. By sucking as described above, it is possible to selectively suck the fine particles 15 separated according to their respective characteristics. Further, the number of the fine particles 15 separated in the tube walls 31, 32 is measured by observing the scattered light by the fine particles 15 or the fluorescence of the fine particles 15 of the light irradiated on the tube walls 31, 32 from a light source (not shown). You can also

Further, as the electrode material on the cathode side of the electrodes 51, 52, by using a material such as mercury, zinc, lead, magnesium, or tin, which rate-controls the production of adsorbed hydrogen atoms, hydrogen by electrolysis at the cathode is used. It is also possible to suppress the generation of bubbles. Furthermore, as the electrode material on the anode side,
By using a material having a large oxygen overvoltage such as gold, platinum, cadmium, or silver, generation of oxygen bubbles due to electrolysis at the anode can be suppressed.

[0038]

By using the present invention, it is possible to effectively fractionate fine particles in a fluid without generating bubbles.

[Brief description of drawings]

FIG. 1 is a schematic view showing a fine particle continuous fractionation device according to an embodiment of the present invention in the form of a cross-sectional view from the side.

FIG. 2 is a graph showing the relationship between voltage and current applied to electrodes.

[Explanation of symbols]

1 ... Solution flow, 2 ... Flow path width, 31, 32 ... Pipe wall, 4
1, 42 ... Ultrasonic transducer, 51, 52 ... Electrode (working electrode and counter electrode), 6 ... Standing wave, 7 ... Reference electrode, 81, 82, 8
3, 84 ... Capillary support rods, 91, 92 ... Movement of support rods, 1
0 ... Capillary tube, 111, 112 ... Flow of solution, 12 ... Flow of fractionated sample, 13 ... Ultrasonic wave controller, 14 ... Potential controller, 15 ... Fine particle.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichiro Umemura 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama Prefectural Institute for Basic Research, Hitachi Ltd.

Claims (3)

[Claims] 1. A container for containing a fluid containing fine particles to be fractionated, one or a plurality of ultrasonic wave generators arranged along the container, and an ultrasonic transducer of the ultrasonic wave generator. Frequency, a specific intensity, an ultrasonic wave of a specific phase difference, or an ultrasonic wave generation control unit for generating a superposition of these, for generating an electric field in the container arranged in the container A pair of two electrodes, a third electrode for measuring the potential of the two electrodes in the container fluid, a means for measuring and adjusting the potential difference between these three electrodes, and a pair of the two electrodes. The means for measuring the magnitude of the electric current flowing between the electrodes, and the means for measuring and adjusting the potential difference between the three electrodes is a potential at which bubbles are unlikely to be generated in the solution. Keep the above and generate the ultrasonic wave Control unit Fractionation apparatus and controls to maintain the ratio of the two constant by changing the ultrasonic energy density in accordance with a change in potential difference between two electrodes forming the pair. 2. An electrode material on the cathode side of the two electrodes forming a pair, wherein the reaction of forming adsorbed hydrogen atoms in the electrolysis reaction of a solution of mercury, zinc, lead, magnesium, tin, etc. is the rate-determining process of electrolysis. The fractionation device according to claim 1, wherein the electrode material is 3. The fractionation device according to claim 1, wherein a material having a large oxygen overvoltage in an electrolysis reaction of a solution of gold, platinum, cadmium, silver or the like is used as an electrode material on the anode side of the pair of two electrodes. .