JPS63200052A - Interface potential measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a device for measuring the amount of charge (potential difference) present at the interface of a solid-liquid dispersion system.

<Prior art> Generally, 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 relative voltage, with the potential in the liquid being zero. , as a value expressing this, the interfacial potential (zeta potential) is -northmost.

Methods for measuring this zeta potential are broadly classified 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 mainly used.

<Problems to be solved by the invention> Among commonly used measurement methods, the electrophoresis method performs measurements by applying electrical energy to the dispersed system to be measured. There are many interfering factors such as electrode decomposition reactions, making measurements complicated. In addition, among these electrophoresis methods, microelectrophoresis requires that individual particles can be identified in the suspension to be measured, and furthermore, it is necessary to perform statistical processing of the movement speed, which is similar to the electrophoresis method. This is accompanied by the complexity of measurement.

On the other hand, the streaming potential method applies mechanical energy to the dispersed system,
Since the electrical output generated by this is measured, the interfering factors mentioned above are reduced, but since the particles are filled in a container etc. through which only the liquid can pass, it is necessary to separate the solid and liquid before measurement. 1μ
In the case of fine particles smaller than m, there is a problem in that the interfacial double layer overlaps, resulting in an error in the measurement result being smaller than the true value.

Therefore, the present inventor has already deposited suspended particles on the surface of a filter placed in the suspension to be measured, vibrated the filter along the surface direction, and By configuring a pair of electrodes to obtain an alternating current signal that correlates to the interfacial potential, this device is based on the streaming potential method, and it eliminates the need to separate solids and liquids prior to measurement.
Furthermore, they have proposed an interfacial electrodynamic potential measuring device that is less prone to errors due to overlapping interfacial double layers even for microparticles of 1 μm or less (Japanese Patent Application Laid-Open No. 77752/1983).

However, although the device based on this proposal can obtain information proportional to the zeta potential, it is necessary to determine the thickness of the interfacial double layer in order to calculate the absolute value of the zeta potential, which is difficult to measure. There was a problem that.

The present invention has been made in view of the above, and basically adopts the streaming potential method to reduce the above-mentioned interfering factors, and
The object of the present invention is to provide an apparatus that can reduce errors caused by the overlap of interfacial double layers when measuring fine particles, which is a drawback of this streaming potential method, and can also easily determine the absolute value of the zeta potential.

<Means for Solving the Problems> The configuration for achieving the above object will be explained with reference to FIG. 1 corresponding to the embodiment. A flow path C surrounded by a filter made of an insulating material (for example, a sintered compact tube) 1, and a suspension to be measured while maintaining a higher pressure inside the flow path C than the outside of this flow path (gap G). A means for flowing a liquid (for example, a pressure source and a piping system S including a capillary coil R), a means for measuring a potential difference between both ends of a flow path C (for example, a pair of electrodes 7a and 7b and a potential measuring device 8), comprising means (for example, pressure detectors 9a, 9b and pressure measuring device 10) for measuring the pressure difference between both ends of the channel C;
By configuring it so that the interfacial dynamic potential at the solid-liquid interface of the suspension to be measured can be determined from the measured potential difference and pressure difference,
characterized.

<Function> If the liquid to be measured is made to flow while maintaining the pressure inside the flow path C higher than the pressure outside the flow path C, a part of the liquid passes through the filter 1 and flows to the outside, and at this time, particles are absorbed by the filter 1. It is attracted and attached to the inner surface. When the potential difference E between both ends of the flow path C is measured with the entire inner surface of the filter 1 covered with particles, E becomes a value related to the interfacial potential of the particles, and the voltage between both ends of the flow path C at that time is Using the difference P, the zeta potential can be calculated from the Helmholtz-Smolkowski equation.

Here, since the potential difference E is based on the amount of charge on the surface of the deposited layer of particle groups on the inner surface of the filter 1, there is little error due to the overlap of the interfacial double layer.

<Example> Embodiments of the present invention will be described below based on the drawings.

Fig. 1 is a block diagram of an embodiment of the present invention, and Fig. 2 is a thin tube 1 thereof.
FIG. 3 is a partially enlarged sectional view of the tube wall of FIG.

A thin tube 1 formed by sintering insulating particles d...d into a pipe shape
There are many pores communicating with the outside in the tube wall, and the thin tube 1 itself has the function of a filter that partitions the flow path C inside the tube and the gap G outside the tube.

Both ends of the thin tube 1 are removably held in holders 2a and 2b made of an insulating material such as resin, and have appropriate pore diameters depending on the size of particles in the suspension to be measured. It will be installed.

The holder 2a includes a gap G surrounding the thin tube 1, a gap hole 3 and a gap outlet 4 communicating with the lower and upper ends of the gap G, respectively, and the lower end of the channel C inside the thin tube 1. A tubule population 5 is formed that communicates with the . A cell outlet 6 that communicates with the upper end of the channel C in the thin tube 1 is formed in the holder 2b.

A pair of electrodes 7a and 7b made of platinum cotton and facing each other are arranged close to the lower and upper ends of the channel C, respectively, and a potential measuring device 8 is connected between the electrodes 7a and 7b. . Moreover, between the lower end of the flow path C and the thin tube population 5,
Pressure detectors 9a and 9b are disposed between the upper end of the flow path C and the thin tube outlet 6, respectively, and the pressure detector 9a.

The output of 9b is supplied to a pressure measuring device 1o, thereby making it possible to measure the differential pressure between both ends of the channel C.

Void population 3, void outlet 4, capillary population 5 and capillary outlet 6
are led to a closed container 11 or a drainage container 12 containing a suspension to be measured, respectively, by a piping system S as shown. In other words, the tubular population 5 passes through the on-off valve ■1,
The air gap population 3 is connected to the closed container 11 via the on-off valve 2, and the thin tube outlet 1 is connected to the capillary coil R via the capillary coil R.
The air gap outlet 4 is led to a drain container 12 via an on-off valve (2).

Furthermore, the narrow tube outlet 6 and the gap outlet 4 are communicated via an on-off valve 4.

A pressurized region is connected to the closed container 11, and the suspension to be measured in the closed container 11 is controlled by an on-off valve V under a predetermined pressure.
, , V, into the tubular population 5 and the void population 3.

Next, the operation of the embodiment of the present invention will be described together with the measurement procedure.

First, all the on-off valves v1 to {circle around (2)} are opened to drive the pressurized area. As a result, the flow path C and the gap G are filled with the suspension to be measured. When the on-off valve v3 is closed while the pressurized region is still being driven, the suspension in the flow path C and the gap G is discharged through the capillary coil R. Both pressures increase, but in this state, both pressures are the same. From this point on, measurements using the potential measuring device 8 and the pressure measuring device 10 are started. In this state, as shown in FIG. The potential difference E between them is a value related to the interfacial potential between the inner wall surface of the thin tube 1 and the liquid.

Next, close the on-off valves V2 and V4, and open (2). As a result, the gap G is at atmospheric pressure and the flow path C is under pressure, so as shown in FIG. 3(b), part of the liquid in the flow path C is
It flows out to the gap G side through the pores in the wall, but if the pore diameter of the thin tube 1 is made smaller than the particle diameter in the suspension, the flow path C
The particles g, . When particle g300g is sucked and stagnates, particle g0. Since the liquid and the liquid move relative to each other, the potential difference E between the electrodes 7a and 7b includes the charge of the particles. If filtration is performed until the inner wall surface of the thin tube 1 is completely covered with particles g000g, the electrodes 7a, ? The potential difference E between b is particle g, 0
．． The value is related to the interfacial potential of g. That is, the zeta potential ζ of the suspension to be measured can be calculated using the potential difference E at this point and the pressure difference P between both ends of the flow path C, and the Helmholtz-Smolkowski equation below.

4πη λE ζ= □ · □ ε P Here, η is the viscosity coefficient of the liquid, ε is the dielectric constant of the liquid, and λ is the electrical conductivity of the liquid. Here, since the potential difference E is a value based on the amount of charge on the surface of the deposited layer of particles g031g on the inner wall surface of the thin tube 1, there is little error due to the overlap of the interfacial double layer.

In addition, if the flow velocity ■ in the channel C is large, the particles g, 1 g
is peeled off from the wall surface, so the flow velocity (2) needs to be slowed down to some extent, but the capillary coil R also has the function of lowering this flow velocity (V).

In addition, the inner diameter of the thin tube 1, that is, the diameter of the flow path C is usually 1.
Although the diameter is set as follows, it is desirable to set the diameter to an appropriate value in consideration of the length of the flow path C so that the pressure loss when the liquid flows here is increased to some extent.

In the above embodiment, a capillary coil R was provided to make the pressure in the channel C higher than the atmospheric pressure in the gap G in order to suction-filter the particles in the channel C to the wall surface of the thin tube 1. It is also possible to create a configuration in which the coil R is not provided and the pressure inside the gap G is reduced to create a pressure difference with the flow path C.

Further, in the above embodiment, the flow path C was formed by the pipe-shaped thin tube 1 made of a sintered body, but for example, as shown in the exploded perspective view in FIG. The sintered bodies 41a and 41b are placed opposite each other, or the grout plate 42a
, 42b and the filter papers 43a, 43b may be made to face each other to form the flow path C with the gaskets 44a, 44b sandwiched therebetween.

<Effects of the Invention> As explained above, according to the present invention, the suspension to be measured is allowed to flow through the flow path surrounded by a filter while maintaining a higher pressure than the outside. Because the structure is such that the particles in the suspension can be suctioned and adhered to the filter surface to be formed, and the potential difference and pressure difference between both ends of the flow path can be measured.
Using the obtained potential difference and pressure difference, the zeta potential can be immediately calculated from Helmholtz-Smolkowski's 2. Moreover, the measurement principle is based on the streaming potential method, and since no electrical energy is added, there are fewer interfering factors such as osmotic flow, Joule heat, decomposition, etc. As such, there is little error due to overlapping of interfacial double layers in the particle area of 18 m or less, and there is no need for solid-liquid separation prior to measurement.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a partially enlarged sectional view of the tube wall of the thin tube 1, Fig. 3 is an explanatory diagram of its operation, and Fig. 4 is a flowchart of another embodiment of the present invention. It is an explanatory diagram of road C. 1... Thin tube (insulating particle sintered body) 2a,>b... Holder 3... Gap inlet 4... Gap outlet 5... Thin tube inlet 6... Thin tube outlet a, 7b ... Electrode 8 ... Potential measuring device 9a, 9b ... Pressure detector 10 ... Pressure measuring device 11 ... Closed container C ... Channel G ... Gap R ... Capillary coil V, ~■4... On-off valve patent applicant Representative of Shimadzu Corporation
Patent Attorney Nishi 1) New construction 1 diagram 2 (Q) 4b Figure 3 (b)

Claims (1)

[Claims] This is a device that measures 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. an enclosed flow path, means for flowing the suspension to be measured while maintaining a higher pressure within the flow path than the outside of the flow path, and means for measuring a potential difference between both ends of the flow path; A means for measuring the pressure difference between both ends of the flow path is provided, and the solid state of the suspension to be measured is determined based on the measured values of the potential difference and pressure difference.
An interfacial potential measuring device characterized by being configured to be able to determine the interfacial dynamic potential of a liquid interface.