JPS6177752A - Interfacial-potential measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform measurement even in a solid-liquid dispersed system, by applying a specified force to a suspension, attaching fine grains on the surface of a filter, vibrating the filter in the direction along the surface, and measuring an AC signal generated between a pair of electrodes, which are attached to the filter. CONSTITUTION:A suspension to be measured is put in a container 2 so that an upper electrode 108 of a filtering electrode 1 is completely submerged. A motor 6 is driven, and up and down vibrations are imparted to the filtering electrode part 1 by a crank mechanism 5. Then a sucking pump 9 is driven, and a hollow part 104 is made to be a pressure reduced state. The suspension is sucked through a filter 105. Thus grains in the suspension are attached to the surface of the filter 105. The grains are vibrated with respect to the liquid. An AC potential corresponding to the vibration is generated at the electrodes 108 and 109 based on a streaming potential phenomenon. An ammeter 10 is connected between the electrodes 108 and 109. The interfacial potential of the fine grains, which are attached to the filter, is measured baded on the measured value of the AC. Thus the measurement without error can be performed even in the solid-liquid dispersed system.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an apparatus for measuring the amount of charge existing at the interface of a solid-liquid dispersion system.

(B) Prior art In general, in a solid-liquid dispersion system in which solid particles are suspended in a liquid, the amount of charge existing at the interface is expressed as a voltage relative to the potential in the liquid as zero; Potential is usually expressed as an interfacial potential (ζ potential). Methods for measuring ζ potential are broadly divided into electrophoresis, electroosmosis, streaming potential, and sedimentation potential. Among these, electrophoresis is usually used to measure relatively stable dispersion systems with a particle size of 10 μm or less, and also to measure coarse particles such as particles or fibers with a particle size of 1 μm or more, or unstable systems. The streaming potential method is used for measurement.

However, since the electrophoresis method performs measurements by applying electrical energy to the dispersed system to be measured, there are many interfering factors such as electroosmotic flow within the sample, generation of Joule heat, and electrode decomposition reactions, making measurements complicated. Furthermore, among these electrophoresis methods, microelectrophoresis requires that the concentration in the sample suspension be at a level that allows individual particles to be identified, and statistical processing of the migration speed is also performed. It is necessary, but it also involves the complexity of measurement.

On the other hand, the streaming potential method applies mechanical energy to the dispersed system,
This measures the electrical output of the current, so there are few interfering factors, but since the particles are filled in a container etc. that allows only the liquid to pass through, it is necessary to separate the solid and liquid before measurement. For particles of 1 μm or less, deformation of the charged state, that is, overlapping of electric double layers, occurs, resulting in an error in which the measurement result is smaller than the true value.

(C) Purpose The purpose of the present invention is to adopt the streaming potential method, which gives mechanical energy to the dispersed system to be measured and obtains an electrical output.
The object of the present invention is to provide an interfacial potential measuring device that reduces factors that interfere with measurement and is also capable of measuring solid-liquid dispersions of fine particles, which has been difficult to measure due to errors caused by the streaming potential method.

(D) Structure The interfacial potential measuring device of the present invention includes a filter that does not allow the passage of fine particles in a suspension to be measured, and a means for applying a predetermined force to the suspension to be measured to cause the fine particles to adhere to the surface of the filter. and a means for vibrating the filter in a direction along the surface thereof, a pair of electrodes attached to the filter facing each other in a direction corresponding to the direction of vibration, and a means for measuring an alternating current signal generated between the electrodes. It is characterized by being configured so that the interfacial potential of the particles attached to the filter can be determined from the measured value of the AC signal.

(e) Examples Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

In the figure, 1 is a filtration/electrode section which will be described in detail later.

2 is a container for containing the suspension to be measured, and 3 is a magnetic stirrer for stirring the suspension in the container 2. The filtration/electrode unit 1 is connected to a crank mechanism 5 via a shaft 4, and is vibrated in the vertical direction by the rotational drive of a motor 6. Note that 7 is a slide bearing. Further, a suction port 103 provided in the filtration/electrode section 1 is connected to a suction pump 9 via a tube 8. Furthermore, contacts 112 and 113 provided in the filtration/electrode section 1
is connected to a measurement terminal of an ammeter 10, and the output X of the ammeter 10 is input to a synchronous rectifier 11. Note that the ammeter 10 used has an impedance sufficiently smaller than the conductivity of the liquid to be measured. Also,
By detecting the shutter 12 attached to the output shaft of the motor 6 with the photoelectric switch 13, a rectangular wave signal synchronized with the vibration of the filter/electrode section 1 is formed, and this signal y is also input to the synchronous rectifier 11. .

The magnetic stirrer 3 described above, as shown in the front view of the main part in FIG. can be stirred.

FIG. 3 is a central vertical cross-sectional view of the filtration/electrode section 1, and FIG. 4 is an exploded perspective view thereof. The base material 101 is made of an insulating material, and a small hole 1 with a diameter of about 0.5 m to 1 fl is formed on its outer periphery.
A large number of small holes 102 are bored inside the hole 102, and the inside of the small hole 102 is a ring-shaped hole p1oh that communicates with the suction port 103.
It becomes.

A filter 105 is attached to the outside of the small holes 102 so as to cover all the small holes 102. This filter 105
The membrane filter may be of any type as long as it has a mensch size that does not allow particles in the turbid liquid to pass through, but a membrane filter with a constant surface condition and opening is usually used. To attach the filter 105, as shown in FIG. 4, it is wrapped around the base material 101 so as to cover the small hole 102, and a presser 106 is fixed to the screw hole 107 with a screw or the like so as to press the overlapped portion.

Ring-shaped electrodes 10 are provided at both upper and lower ends of the filter 105.
8 and 109 are mounted and connected to the aforementioned contacts 112 and 113 by leads 110 and 111, respectively. Electrodes 108 and 109 are made of gold, platinum, silver-
Use a reversible electrode such as silver chloride.

Next, the effects of the embodiments of the present invention will be described together with the measurement method. As shown in Figure 2, the suspension to be measured is filtered and the electrode section 1
into the container 2 so that the upper electrode 108 is completely submerged,
The motor 6 is driven to apply vertical vibration to the filtration/electrode section 1 by the crank mechanism 5. Next, the suction pump 9 is driven to reduce the pressure in the cavity 104, and the suspension is sucked through the filter 105. As a result, particles in the suspension adhere to the surface of the filter 105 and vibrate against the liquid, so an AC potential corresponding to the vibration is generated at the electrodes 108 and 109 due to the streaming potential phenomenon. do. If an ammeter 10 having an impedance sufficiently smaller than the conductivity of the liquid is connected between the electrodes 108 and 109, an alternating current flows and can be measured. This is because the charge existing at the interface moves relatively due to the relative movement of the solid (filter, particles) and liquid, and the current 7 m flowing here is calculated by the following equation It is related to the potential Vs.

im"'8-r-ω・x o-V S Cosωt-(
1) Here, ε is the dielectric constant of the liquid, r is the filter outer radius of the filtration/electrode section 1 as shown in Fig. 3, ω is the vibration angular velocity, and X
Q is amplitude and t is time. In addition, this formula (11) is applied when the vertical vibration displacement of the filtration/electrode section 1 is configured to approximately become a sine curve (single motion),
This can be achieved by making the arm length of the crank mechanism sufficiently longer than the crank length.

In this case, the output X of the ammeter 10 is expressed by α·cosωt, and its relationship with the output y of the photoelectric switch 13 is as shown in FIG. Note that the output y of the photoelectric switch 13 is shown as an H level when the filtration/electrode section 1 is displaced downward, and as an L level when it is displaced upward, and the shafter 12 shape is selected. In addition, if the charge state of the interface becomes reversed,
The polarity of the output X is reversed as shown by the broken line, and the direction of change shown in 2 below is also reversed.

In the synchronous rectifier 11, the signal X is chopped and synchronously rectified according to the signal y, and is output as a signal 2. An example of the temporal change of this signal 2 is shown in FIG. tl is the time when the vibration of the filtration/electrode section 1 starts, and t2 is the time when the suction starts.

Zf is the interfacial potential of the filter 05. Particles start to accumulate on the surface of the filter 105 when suction starts, and 2 changes accordingly, and when the particles completely cover the filter 05 (time te), it reaches a constant value Zs. Become. This Zs represents the interfacial potential Vs of the particles, and the relationship is shown by the following equation.

Zs=β-t-r-ω・xr3-Vs-=(2)
Here, β is a conversion rate from Lm to 2, and is a value determined as a device constant. Therefore, if Zs is measured, ε, r
, ω+XO are known, so Vs can be found. Vs indicates the amount of charge at the interface, and is the interfacial potential (
zeta potential) is in the relationship of the following equation (3).

ζ where δ is the thickness of the interfacial bilayer. This δ changes depending on the type of ion, ion strength, etc., and cannot be determined theoretically, but if the measurement conditions can be limited, there is no significant change, and therefore Vs is approximately proportional to ζ.

As shown in FIG. 7, V and s obtained by this embodiment of the present invention are the amount of charge on the outermost part (measurement surface) of the particles deposited on the filter 105, and the particles deposited on the lower layer are on the side. Not involved in fixed values. This is because the filter 105 is vibrated in the direction along its surface, that is, the vibration displacement is applied along the surface of the particle deposit layer, and the influence of the overlap of the interfacial double layer as in the conventional streaming potential method is greatly reduced. I never receive it.

In addition, in the above example, an example was shown in which particles were attached to the surface of a cylindrical filter, but if the configuration is not affected by the back surface of the filter, any arbitrary shape may be used. For example, as shown in FIG. 8, an inner dish-shaped filter 105' may be used. In this case, the arrangement positions of the electrodes 108' and 109' and the filter 10
The vibration directions of 5' are shown in the relationship as shown.

Furthermore, the method for depositing particles on the filter is not limited to suction, and methods such as creating a pressure difference in the liquid with the filter in between, or circulating the liquid through the filter can also be considered.

Further, in the above embodiments, the current Lm was measured, but similar results can be obtained by measuring the voltage em generated by vibration. In this case, the relationship between the voltage em and the interfacial dynamic potential is expressed by the following equation <4).

ε・r・ω・xO・β・ζ・ cosωt2π・ (R
2-r') ·λ·δ --- (4) Here, β is the distance between the electrodes, R is the inner radius of the suspension container 2, and λ is the conductivity of the suspension.

In addition, an example was shown in which the vibration of the filtration/electrode section 1 was given a speed change of a sine curve, but since the generated current is proportional to the relative moving speed, any vibration can be given, and there is no need to specify it in particular. .

(f) Effects As explained above, according to the present invention, suspended particles are deposited on the surface of the filter in the suspended liquid to be measured, the filter is vibrated along the surface direction, and the vibration direction is Since the configuration is configured to obtain an alternating current signal correlated to the interfacial potential from a pair of electrodes arranged at Unlike the conventional streaming potential method, it does not cause overlapping of electric double layers (and error-free measurement is possible. Also, because the electrical output is measured by applying mechanical energy (vibration), Osmotic flow, Joule heating.

It is not affected by shadows K due to decomposition, etc. Furthermore, since AC signals are measured, the influence of drift due to the contact potential of the electrodes is extremely small, improving the reliability of the device. Furthermore, in the conventional streaming potential method, solids (particles) are
However, according to the present invention, since measurement is performed while filtering, there is no need to separate solid and liquid in advance, and the procedure is simplified.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of an embodiment of the present invention, Fig. 2 is a front view of the main parts thereof, and Figs. 3 and 4 are respectively a center vertical sectional view and an exploded perspective view of the filtration/electrode section 1 of the embodiment of the present invention. Figure, 5th
The figure shows an ammeter 10 output X and a photoelectric switch 1 according to an embodiment of the present invention.
A graph showing the relationship between the three outputs y, Figure 6 shows the synchronous rectifier 11
A graph showing an example of a temporal change in output 2, FIG. 7 is an explanatory diagram of the operation of an embodiment of the present invention, and FIG. 8 is a diagram showing a filtration/electrode section of another embodiment of the present invention. 1...-Filtration/electrode part 101--Base material 102-Small hole 103--Suction port 104--Cavity
105--Filter 108, lQ9- Electrode 112.113-Contact 2--Container 5--Crank mechanism 9--Suction pump 10--Ammeter 11--Synchronous rectifier 12-Shutter 13--Photoelectric switch

Claims (1)

[Claims] A device for measuring the amount of charge existing at the solid-liquid interface in a solid-liquid dispersion system in which solid particles are suspended in a liquid, the device comprising: a filter that does not allow the particles in the suspension to be measured to pass;
means for applying a predetermined force to the suspension to cause the fine particles to adhere to the surface of the filter; means for vibrating the filter in a direction along the surface; and means facing in a direction corresponding to the vibration direction. The structure includes a pair of electrodes attached to the filter, and means for measuring an alternating current signal generated between the pair of electrodes, and is configured to determine the interfacial potential of particles attached to the filter from the measured value of the alternating current signal. An interfacial potential measuring device characterized by: