JPS5926322B2 - Method for treating solutions containing acids or alkalis and/or salts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating a solution containing acid or alkali and/or salt using a semipermeable membrane.

Aqueous solutions containing acids or alkalis and/or salts are discharged in large quantities from manufacturing, treatment or processing processes in various industries.

Examples include wastewater from starch production, caustic soda-containing wastewater from rayon production, acid-containing solutions from nonferrous metal processing processes, black paddle-containing solutions from plating wastewater, and sulfuric acid-containing solutions from wood saccharification liquors.

In recent years, there has been a particular demand for recovering and reusing various active ingredients, including acids, alkalis, and salts, from these waste liquids.

It is widely practiced to concentrate and recover solutions containing various active ingredients, acids, and alkalis using reverse osmosis membranes and ultrafiltration membranes.

However, there are some practical problems, and in many cases it is not possible to recover it efficiently.

That is, in general, reverse osmosis membranes and ultrafiltration membranes have few acid- and alkali-resistant membranes, and usually have a pH of 4 to 8, preferably I).
It is often required to use H7.

Therefore, a neutralization step is required as a pretreatment, and the salt generated by neutralization increases the load on the reverse osmosis membrane, making it virtually unusable or unable to increase the concentration ratio. arise.

The present invention improves these drawbacks by placing a solution containing an acid or alkali and/or a salt in opposition to a dialysate via a diffusion dialysis membrane, and passing the acid or alkali and/or salt in the solution through the membrane. The remaining solution from which acids or alkalis and/or salts have been removed is then concentrated using a reverse osmosis membrane or an ultrafiltration membrane to obtain the desired concentrated solution; This is a method for treating a solution containing an acid or alkali and/or a salt, characterized in that water obtained by a filtration membrane is used as a dialysate for the diffusion dialysis, if necessary.

According to the present invention, most of the acid or alkali and/or salt in the liquid to be treated can be recovered in a state containing almost no impurities through diffusion dialysis in the first step.
Satisfies the pn limitations of the process reverse osmosis or ultrafiltration membrane,
In addition, especially for reverse osmosis membranes, salt etc. are removed, so
Since the osmotic pressure of the solution is reduced, the pressure load is significantly reduced and a concentrated solution containing the desired active ingredient can be obtained with high efficiency, and at the same time, the active ingredient can be obtained as a highly purified product with low salt or ash content. .

Furthermore, water obtained by reverse osmosis or ultrafiltration can be used as a dialysate in the first step, diffusion dialysis.

Diffusion dialysis membrane devices used in the present invention include flat membrane types, tube types, spiral types, and hollow fiber membrane types. This is preferable because it can be done.

As the hollow fiber membrane type, a heat exchange type as shown in FIG. 1, in which a plurality of hollow fibers are arranged substantially parallel to each other in a diffusion dialysis container, is preferable.

The outer diameter of the hollow fiber is preferably 5000μ or less, preferably 2
It is 0 to 2000μ, more preferably 40 to 1000μ.

The smaller the outer diameter of the hollow fibers, the more compact the device can be, and the better the mechanical strength and pressure resistance, so the film thickness can be reduced.

The thickness of the hollow fiber membrane is preferably from 5 to 100 microns, preferably from 10 to 80 microns, from the viewpoint of dialysis properties.

The materials for the diffusion dialysis membrane include various organic synthetic resins such as hydrophobic resins (vinyl chloride, polyester, acrylic resins such as polyacrylonitrile, polyolefins such as polyethylene, etc.), hydrophilic resins (polyvinyl alcohol (
(hereinafter referred to as PVA), cellulose, polyhydroxyethyl methacrylate (HEMA), etc. Among these, hydrophilic resins and PVA-based resins are particularly stable over a wide pH range, and are also dialyzable. It is preferable because it is also excellent.

Here, PVA-based resin refers to PVA1, which is normally used in vinylon, as well as monomers that can be copolymerized with vinyl alcohol, such as vinyl alcohol, vinyl pyrrolidone, vinyl chloride, methyl methacrylate, acrylonitrile, and itaconic acid. copolymers, etc.

The PVA-based membrane used in the present invention has a swelling degree of 1.01 to 1.
80 times, more preferably 1.01 to 1.40 times.

PVA-based membranes have hydrophilic properties as a characteristic of PVA, and can be made into membranes with any degree of swelling.However, in order to improve the dialysis properties that are the objective of the present invention, the degree of swelling should be 1.01 to 1.01.
It is desirable that it be 1.80 times.

The degree of swelling is a factor that indicates the density of the structure of the PVA membrane.
From the relationship between the structure of the membrane and the substance to be separated, it is considered that a degree of swelling within the above range is highly effective.

Here, the degree of swelling is a value expressed as the ratio of the cross-sectional thickness or outer diameter of a flat membrane, hollow fiber, etc. to the dry membrane.

Measurement of dry thickness or outer diameter at room temperature 20℃, RH 60
% after being left for one day and night.For wet measurements, the sample was kept at 25℃.
This is done after leaving it in water for one day and night.

Water obtained by the reverse osmosis membrane or ultrafiltration membrane in the second step is used as part of the dialysate, but clean water such as industrial water may also be used as appropriate.

In the diffusion dialysis membrane of the first step, most of the acids, alkalis, and/or salts in the raw wave treatment liquid are transferred to the dialysate side, and the acids, alkalis, and salts can be recovered in substantially pure form.

Next, reverse osmosis membranes or ultrafiltration membrane devices that process the remaining solution after removing acids, alkalis, and salts include flat membrane types, tube types, spiral types, and hollow fiber types, similar to diffusion dialysis membranes. It will be done.

Materials for reverse osmosis membranes or ultrafiltration membranes include cellulose (cellulose acetate, cellulose 2-3 acetate), polyamide (aromatic polyamide, piperazine polyamide,
polyfumaramide), heterocyclic polymer systems (polybenzimidazole, polyimidazopyrrolone), polyacrylic systems (polyacrylic acid, polyno-idoxyethyl methacrylate, polymethyl methacrylate, acrylonitrile), graft polymer systems (polyethylene, polypropylene), Examples include vinyl-based materials (PVA, polyvinylpyrrolidone) and inorganic materials (porous glass), among which cellulose-based materials (such as cellulose acetate) and polyamide-based materials are preferred because they are thin, durable, and exhibit high permeability.

This reverse osmosis membrane or ultrafiltration membrane allows the desired concentrated liquid to be obtained, and the resulting concentrated liquid is of high quality and contains almost no acid or alkali and/or salt, or almost no acid or alkali and/or salt. On the other hand, the water obtained by reverse osmosis or ultrafiltration membrane is used as a dialysate in the first step, diffusion dialysis, if necessary.

Whether to use a reverse osmosis membrane or an ultrafiltration membrane is determined by the type of liquid to be treated.

In some cases, a reverse osmosis membrane and an ultrafiltration membrane can be used together.

In the present invention, a solution containing an acid or alkali and/or a salt is an aqueous solution containing an active ingredient such as an organic substance or an inorganic substance in addition to an acid or alkali and/or a salt. Processing waste liquid from starch raw materials such as sweet potatoes, corn, wheat, and rice), processing waste liquid from sugar manufacturing (beet sugar, sucrose), protein foods (
Examples include wastewater from processing soybeans, fish paste products, seafood, and livestock foods, wastewater from rayon manufacturing, and wastewater from wood saccharification solutions.

From these waste liquids, active ingredients such as acids, alkalis, and salts as well as monosaccharides to polysaccharides such as starch and glycose, proteins, polypeptides, and amino acids such as amino acids can be obtained as a desired concentrated liquid. On the other hand, the acid or alkali obtained by dialysis can be reused for further manufacturing purposes, and the concentrated solution of the active ingredient can be effectively used as feed, fertilizer, food, or other raw materials.

Next, the present invention will be further explained with reference to the drawings.

FIG. 1 shows an example of a hollow fiber membrane type diffusion dialysis apparatus, in which a liquid to be treated is introduced from an inlet 5, passes through a plurality of hollow fibers 2 made of a semipermeable membrane, and is taken out from an outlet lower.

On the other hand, during the passage through the hollow fibers, permeated components such as acids, alkalis, and salts pass through the hollow fiber membranes to the dialysate side and are taken out from the outlet 3.

On the other hand, the dialysate is introduced from the inlet 4, flows outside the hollow fibers, and is taken out from the outlet 3 in a state containing acids, alkalis, and salts.

The dialysate taken out from step 3 contains acid, 7/lz potash, and salt in almost pure form, so it can be reused as is.

Note that in FIG. 1, 1 is a casing.

FIG. 2 shows an example of a hollow fiber membrane type reverse osmosis membrane device, in which a solution containing almost no acid or alkali and/or salt taken out from the outlet lower in FIG. It passes through a plurality of hollow fibers 9 made of a permeable membrane and is taken out from an outlet 11 as a concentrated liquid having a desired concentration.

On the other hand, during the passage of the solution through the hollow fibers, permeated components such as water pass through the hollow fiber membranes, migrate to the outside of the hollow fibers, and are taken out from the outlet 10.

The water taken out from the outlet 10 is circulated to the dialysate inlet 4 shown in FIG.

Note that 8 in FIG. 2 is a casing.

FIG. 3 shows a flow sheet in which the diffusion dialysis membrane device A shown in FIG. 1 and the reverse osmosis membrane device B shown in FIG. 2 are combined.

FIG. 4 shows a flow sheet when the liquid to be treated flows outside the hollow fibers of the diffusion dialysis membrane device A and the reverse osmosis device B.

Note that 13 indicates the introduction of a new dialysate. The present invention will be further explained below with reference to Examples.

Example 1 To produce potato starch, potatoes are ground to make grinding holes. When the resulting liquid is centrifuged, starchy milk that is insoluble in water, such as starch, and water-soluble components, such as protein, are separated. Goodbye to potato juice.

Starch milk goes through a refining process to produce starch, but potato juice is usually discarded.

Potato juice contains approximately 5% solids, with 1-1.2% protein and 0.8-1% non-protein nitrogen components.
It is a highly concentrated wastewater with a sugar content of 1.5%, an ash content of 1.5%, and a BOD of 30,000 to 40,000 ppm.

To prevent pollution, this wastewater is concentrated by vacuum evaporation and further dried to obtain a protein-containing powder, but due to the quality of the product, it could not be used 100% as animal feed.

That is, the powder (dry product) contains 20 to 24% protein, 16 to 20% non-protein nitrogen, 30% carbohydrates, and 30% ash, and the particularly high ash content deteriorates the product quality.

Furthermore, when this liquid is concentrated using a reverse osmosis device, the ash content is high, so the osmotic pressure is high and it is not possible to concentrate it to a high concentration.

When this liquid is first treated with a dialysis membrane, the ash content is approximately 60%.
was removed, and the quality of the resulting dry powder was improved.

In other words, potato juice is processed using a hollow fiber type dialysis device (outer diameter 6
00μ, film thickness 40μ, swelling degree 1.25 made by Clan PVA
The treatment was carried out by pouring the dialysate on the outside of the hollow fibers (hollow fibers), and flowing the dialysate inside the hollow fibers.

The dialysate (water) was used in an amount three times that of potato juice, and treated in a countercurrent one-pass method.

As a result, the composition of the liquid before and after was as follows.

This treatment liquid was transferred to a tubular reverse osmosis device (As-19 manufactured by Abcor).
7).

As a result, it was possible to concentrate to a much higher concentration than when the above treatment was not performed.

The operating conditions of the reverse osmosis device are liquid temperature 35℃ and inlet pressure 56kg.
/cm, and the outlet pressure was 30 kg/crA.

The results are shown below.

In addition, the analysis values of the powder dried after being concentrated using a reverse osmosis device were 31% protein, 16% non-protein nitrogen, 37% carbohydrates, and 1 ash.
It was 6%.

This result indicates that the osmotic pressure, which reduces the driving force of reverse osmosis, was reduced by partially removing the ash in the treatment solution.

The permeate from the reverse osmosis device had a BOD of 100 ppm or less, and could be used as a dialysate.

Example 2 The pulp press liquid used in the rayon manufacturing process contains hemicellulose in highly concentrated caustic soda.

Since caustic soda is a liquid with a high concentration of about 5 Mot/l, neutralizing it and disposing of it will result in a large economic loss.

Moreover, the coexisting hemicellulose has special uses.

Therefore, an attempt was made to continuously separate and recover caustic soda and hemicellulose by dialysis and ultrafiltration of the squeezed fluid.

For dialysis, a hollow fiber type dialysis device was used as in Example 1, the squeezed liquid was poured on the outside of the hollow fibers, and the squeezed liquid was poured inside the hollow fibers.
Double the amount of water (one part permeated water) was flowed countercurrently and treated in one pass.

The dialysis results are as follows.

Liquid to be treated Caustic soda 5.5Mol/1 Hemicellulose table 23 g/l Treatment after dialysis Caustic soda 0.2Mol/1 Physical liquid hemicellulose 17 g/1 Recovered caustic soda Caustic soda 1.95Mol/l-
Da solution...The treated solution after reuse dialysis contains 0.2 Mol/l of caustic soda, so the pH is around 13.3. To treat this solution, a membrane that can withstand that pH is used. Alternatively, partial neutralization must be performed to bring the pH to a level that can be tolerated by the membrane used.

In this case, use the HFM membrane manufactured by Abcor (pH range 0.5 to 1).
3.5), ultrafiltration was carried out without any particular neutralization treatment.

The following composition was obtained by increasing the volume concentration factor by 10 times.

Concentrate Caustic soda 0.2Mol/1 Hemicellulose 170 g/l Permeate Caustic soda 0.2Mol/A...
...The water was used for dialysis, that is, the alkali was recovered and the pH was adjusted by dialysis, and hemicellulose was continuously concentrated using an ultrafiltration membrane.

Example 3 Naturally flavored liquids are obtained by decomposing extracts of marine products and plants with hydrochloric acid to obtain liquids with appropriate tastes.

In that case, if the acid is decomposed and then neutralized, the neutralization will produce salt, which will remove the taste from the salt.

Additionally, agents such as caustic soda are required for neutralization, which also increases osmotic pressure.

Therefore, the solution after hydrochloric acid decomposition is collected by dialysis as in Example 2, and at the same time, the pH is automatically increased to a pH that can be concentrated using a reverse osmosis membrane, and the osmotic pressure is also lowered, making it possible to concentrate to a high concentration. .

That is, a hollow fiber dialysis device was used as in Example 2,
The solution to be treated was flowed inside the hollow fibers, and the dialysate was flowed to the outside of the hollow fibers for treatment, and the following results were obtained.Liquid to be treated Hydrochloric acid 100'i? /l amino nitrogen 12
〃 Post-dialysis treatment liquid Hydrochloric acid 5 〃Amino nitrogen 11 〃 Recovered hydrochloric acid solution Hydrochloric acid 35 〃 ・・−・・
・Reuse This liquid is concentrated using a tubular reverse osmosis device as in Example 1, but the treated liquid after dialysis has a pH of about 1, and there are currently no reverse osmosis membranes on the market that are resistant to this.

Therefore, in Komata, the solution was neutralized with caustic soda to a pH of 7, and then concentrated.

The amount of caustic agent required for this operation was within 5% compared to the case where the stock solution was N-neutralized, so there were no problems from an economical or osmotic point of view.

33P/J to 38 as amino nitrogen concentration? /l of concentrated liquid was obtained.

[Brief explanation of the drawing]

Fig. 1 shows an example of a hollow fiber membrane type diffusion dialysis membrane device, Fig. 2 shows an example of a hollow fiber membrane type reverse osmosis membrane device, and Fig. 3 shows the diffusion dialysis membrane device shown in Fig. 1 and the reverse osmosis membrane device shown in Fig. 2. FIG. 4 shows a flow sheet in which the liquid to be treated flows outside the hollow fibers of a diffusion dialysis membrane device and a reverse osmosis membrane device.

Claims (1)

[Scope of Claims] 1. A solution containing an acid or alkali and/or a salt is placed opposite the dialysate via a diffusion dialysis membrane, and the acid or alkali and/or salt in the solution is transferred to the dialysate through the membrane. The remaining solution from which the acid or alkali and/or salt has been removed is then concentrated using a reverse osmosis membrane or an ultrafiltration membrane to obtain the desired concentrated solution; A method for treating a solution containing acid or alkali and/or salt, characterized in that water is circulated as a dialysate in the diffusion dialysis as necessary. 2. The method according to the first claim, wherein the diffusion dialysis membrane is a polyvinyl alcohol resin membrane. 3. The method according to the first claim, wherein the diffusion dialysis membrane is a polyvinyl alcohol resin hollow fiber membrane.