JPS5836605B2 - Dehydration method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a dehydration method by electroosmosis.

Conventional dehydration by electro-osmosis often uses a filter material and separates water through electric current at the same time as normal filtration. 46-10600) is common, and the action of electric current is used supplementarily.

In contrast, the present invention deals exclusively with gel-like substances and paste-like substances for which ordinary filtration is almost impossible, and generally does not perform ordinary filtration using pressure or the like at the same time.

For this reason, it is necessary that the electrically drawn water does not return back, but in the case of gel, the water drawn out almost never returns, and in the case of paste, the ion exchange membrane prevents the water from returning due to the properties described below. do.

When energized, the ion exchange membrane has selective permeability for positive or negative ions, but has the property of allowing water to permeate in the same direction as the ions.

The magnitude of this phenomenon of electrophoresis in membranes varies greatly depending on the structure of the membrane, the concentration of the liquid, etc., but in general, the higher the water content of the membrane is, and the lower the ion concentration in the liquid, the greater the electrophoresis. According to these conditions, the electrical permeation in the membrane can be made very large.

Ion exchange membranes are generally made of a dense material, and there is almost no permeation of water due to pressure, and the movement of water due to diffusion is usually extremely slow.

The ion exchange membrane is also a type of gel that has an electric charge, but because it has a dense crosslinked structure inside, it does not contract even though water passes through it when electricity is applied.

From the properties of ion exchange membranes as described above, it can be concluded that ion exchange membranes are the most suitable diaphragms to use when dehydration is carried out exclusively by electrical action.

Dehydration from the gel can also be achieved by bringing both electrode plates into direct contact with the gel without using a membrane.

However, in this case, the reaction at the electrode, especially the oxidation reaction at the anode, causes a chemical change in the object, which is generally not preferred.

Especially when the target object is food, etc., chemical changes must be avoided.

This chemical change can be prevented by separating the electrode and the object with an ion exchange membrane.

By using a membrane, an electrode chamber is formed and filled with an aqueous solution, but due to the aforementioned properties of the membrane, almost no movement of water towards the object occurs.

Ordinary ion exchange membranes are susceptible to oxidizing effects such as chlorine, so
If the gel etc. contains chlorine ions and generates chlorine at the anode, choose an oxidation-resistant anion exchange membrane, or install an oxidation-resistant semipermeable membrane between the anode and anion exchange membrane. It is desirable for people to do so.

In addition, since ordinary anion exchange membranes are clogged with organic matter and cause an increase in electrical resistance, it is desirable to use a membrane that is resistant to organic contamination if there is such a possibility.

The configuration of the apparatus used in the present invention will be explained with reference to FIG.

What each symbol represents in the figure is as follows.

1 Anode 2 Cathode 3 Anion exchange membrane 4 Neutral diaphragm or cation exchange membrane 5 Object to be dehydrated 6 Anode chamber 7 Cathode chamber 8 Oxidation-resistant diaphragm When the body of the object to be dehydrated is a gel with a negative charge, between the negative and anode poles When energized, the main body components are drawn toward the anion exchange membrane, and water is drawn toward the neutral diaphragm or cation exchange membrane, and if a cation exchange membrane is present, a large portion of the water is drawn into the cathode chamber. It is pulled in and some of it drips to the bottom, but
In the case of a neutral diaphragm, most of it is not drawn in and drips out.

When a slight pressure is applied from both sides of the bipolar chamber, as the water content decreases, the amount of gel etc. decreases, and the distance between the negative and positive ion exchange membranes gradually decreases, thus achieving the purpose of dehydration.

Gels or pastes are generally electrically charged, or tend to become electrically charged, and are affected by the electric current in the manner described above.

The gel or paste tends to become electrically charged when it has a weak acid or weak base group. This means that by adding such an acid, the weak acid or weak basic group, respectively, dissociates and becomes electrically charged.

In this way, adjusting the pH and imparting a charge has a very large effect in the present invention.

When the object is a gel, the part 5 in Figure 1 may be the gel itself or the gel placed in a cloth bag, and generally there is no need to constitute a chamber, but in the case of a paste, this part is It is necessary to put the paste in it as one chamber.

In the case of a paste, it is desirable to use a structure that uses both negative and positive ion exchange membranes, but when using a neutral diaphragm, it is preferably a semipermeable membrane that can block water.

When the target substance is cation exchangeable (has a negative charge)
can be configured without using a cation exchange membrane.

This is because the target substance acts similar to a cation exchange membrane.

Further, a configuration without using an anion exchange membrane is also possible, but this is outside the scope of the present application.

When the object has no electric charge, the mechanism may be different, but it is possible to incorporate an appropriate amount of soluble inorganic salts into the object and draw out water along with ions by utilizing only the electroosmotic properties of the ion exchange membrane. is possible.

Although the present invention is applicable to inorganic substances such as dehydration of china clay, it is particularly useful for dehydration of gels or pastes of organic substances.

For example, dehydration of tokoroten (agar production), dehydration of protein gel or soluble protein paste, etc.

Example 1 In the apparatus shown in Fig. 1, the cation exchange membrane was a sulfonated copolymer of vinyl acetate and ethylene (exchange capacity 3.1 meq/gr, water content 42%, thickness 0). As the anion exchange membrane, a styrene-divinylbenzene-based strongly basic anion exchange membrane (exchange capacity 1.8 meq/gr, water content 35%, thickness 0.1 mm) was used.

The effective area and tilt are sxsc4.

Diaphragm 8 was not used. A nickel plate was used for each electrode, and a 5% aqueous sodium sulfate solution was used for both electrode chamber solutions.

Gel-like soy protein (88% moisture, 0.3% salt, thickness 12 mm) was sandwiched between the membranes, and a current of 0.25 amperes (11
~13 volts) for 25 minutes.

A slight pressure was applied to the gel during energization by lightly tightening the entire structure, including both electrode chambers, with a thin rubber ring.

After electricity was applied, the thickness of the gel became four peaks.

Example 2 A polyethylene microporous membrane (thickness 0) was used instead of a cation exchange membrane.
．． The same apparatus as in Example 1 was used except that a 1 mm ) gel was used, and agar gel was inserted instead of soybean protein gel.

(Dimensions are 5X5X1.4CrIL, dry agar or 1%,
A small amount of ammonia was added to bring the pH of the gel to about 9.

) 0.40 ampere (12-15 volts) current 15
Power was applied for a minute.

After energization, the thickness of the gel was approximately 7.0 mm.

Example 3 The same apparatus as in Example 1 was used, except that the section 5 in FIG. 1 was made into one chamber with a thickness of 5 mm and a Teflon porous membrane was used as the diaphragm 8.

Chamber 5 was filled with a 20% aqueous solution of soluble fish protein (2% salt).

A current of 0.5 ampere (65-9 volts) was passed through this, and the 20% soluble protein solution described above was added as the liquid in chamber 5 decreased.

After 100 minutes, the protein concentration in chamber 5 became 50%.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of an apparatus used in the present invention.

Claims (1)

[Scope of Claims] 1. A dehydration method characterized by arranging an anion exchange membrane on the anode side when dehydrating a gel or paste-like material by electroosmosis. 2. A dehydration method characterized by arranging an anion exchange membrane on the anode side and a cation exchange membrane on the cathode side when dehydrating a gel or paste-like material by electroosmosis. 3. A dehydration method characterized by arranging an oxidation-resistant diaphragm between the anode and the anion exchange membrane when dehydrating a gel or paste-like material by electroosmosis using an anion exchange membrane on the anode side.