JP3015486B2 - Waste liquid treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating and recovering an alkaline waste solution of sulfate. More specifically, the present invention regenerates and recovers alkali and sulfuric acid from a sulfate alkaline waste liquid such as a waste liquid containing Na ₂ SO ₄ and NaOH discharged in a production process and the like, for example, in the production of iron hydroxide. And a method for treating an alkaline waste liquid of sulfate.

[0002]

Generation of the Prior Art Generally in iron hydroxide adding alkali to the food, such as iron (II) sulfate and, Na ₂ SO _4, alkaline waste liquid such as sulfates waste liquid, including NaOH discharged in the manufacturing process or the like Is generally neutralized, that is, the waste liquid is neutralized by adding an acid, and the resulting neutralized aqueous solution is discharged into public waters. Also, a technique of separating various salt solutions such as sodium sulfate into acid and alkali by an ion exchange membrane electrodialysis apparatus using a bipolar membrane has been known for a long time, as shown in, for example, Japanese Patent Publication No. 32-3962. ing.

[0003]

However, the above-described conventional neutralization method not only requires a large amount of acid to neutralize the waste liquid, but also releases the neutralized aqueous solution which harms the environment. is there. In the method of separating an acid and an alkali by an electrodialysis device of an ion exchange membrane using a bipolar membrane, when the alkaline waste liquid to be treated is supplied as it is, not only does the anion exchange membrane deteriorate quickly,
Since the current efficiency was extremely poor, there was a problem that it was difficult to implement.

[0004]

Means for Solving the Problems The present inventors have solved the problems of the prior art in treating the above-mentioned alkaline waste solution of sulfate, and at the same time, recycle and recover recyclable alkali and acid from the waste solution. The purpose of the present invention is to provide a processing method which is excellent in resource saving and economic efficiency.

That is, according to the present invention, an alkaline effluent of sulfate is treated in an ion exchange membrane electrodialyzer (A) comprising a cation exchange membrane and an alkali-resistant monovalent anion selective permeable membrane. And then dealkalized, and then an ion exchange membrane electrodialyzer (B) comprising a combination of a cation exchange membrane, a bipolar membrane and an anion exchange membrane in that order.
And a method for treating a waste liquid characterized in that the dealuated sulfate waste liquid is treated to separate and recover the acid and alkali.

According to the present invention, it is necessary to first treat an alkaline waste solution of sulfate to remove alkalinity in an ion exchange membrane electrodialyzer (A). In this method, the acid and alkali can be separated and recovered well without treating the waste liquid, particularly without damaging the anion exchange membrane.

The configuration of the ion exchange membrane electrodialyzer (A) and the dialysis method thereof according to the present invention are not particularly limited in accordance with the prior art, but the alkali ion-resistant monovalent anion is selected as the anion exchange membrane. It is important to use a permeable membrane. Such an alkali-resistant monovalent anion-selective permeable membrane has a particle size of 10 μm or less in a mixture mainly composed of a monomer having a functional group compatible with the introduction of an anion exchange group, a crosslinking agent and a polymerization initiator. After the paste-like material containing the spherical polyethylene fine powder is attached to a polyethylene cloth-like substrate and polymerized, a functional group capable of introducing an anion exchange group on at least one surface of the film is a strong base. An anion exchange membrane obtained by introducing a quaternary base type ion exchange group into the inside after converting so that the anion exchange group cannot be introduced is particularly preferable. Of course, it is preferable to use a general alkali-resistant cation exchange membrane as the cation exchange membrane.

A typical embodiment of the ion exchange membrane electrodialysis apparatus (A) of the present invention is schematically shown in FIG. 1 together with the flow of electrodialysis. That is, in FIG. 1, a cation exchange membrane 1 and an alkali-resistant monovalent anion selective permeable membrane 2 are formed between an anode 3 and a cathode 4 to form a chamber 5.
An alkaline (NaOH) aqueous solution of a sulfate (Na ₂ SO ₄ ) was supplied to the mixture, and the mixture was subjected to electrodialysis.
a ₂ S0 ₄ aqueous solution to obtain a NaOH aqueous solution from the chamber 6.

Next, as the ion exchange membrane electrodialyzer (B) for treating the waste liquid of dealkalized sulfate, for example, a known technique as described in Japanese Patent Publication No. 32-3962 described above is employed. . The cation exchange membrane, bipolar membrane, and anion exchange membrane used in such an ion exchange membrane electrodialysis device (B) are each known and are not particularly limited. Generally, as the cation exchange membrane, an alkali-resistant cation exchange membrane which is stable against a liquid having a particularly high pH is preferably used. For example, Neosepta CMH (trade name, manufactured by Tokuyama Soda Co., Ltd.) is applied. In addition, as an anion exchange membrane,
An ultra-low diffusive anion exchange membrane for acid concentration having low hydrogen ion diffusivity, for example, Neosepta ACM (trade name, manufactured by Tokuyama Soda Co., Ltd.) or the like is applied. Furthermore, as a bipolar membrane, for example, the cover film is partially covered, and the surface of the cover film that is not in contact is sulfonated to introduce a cation exchange group, and then the cover film is peeled off. Bipolar membranes into which anion exchange groups have been introduced (JP-A-55-86821, JP-A-55-99927)
), The interface between the anion exchange membrane and the cation exchange membrane is treated with an inorganic compound, and the two membranes are joined together (JP-A-59-47235). The anion exchange membrane is formed by reacting an amine with partially chloromethylated polystyrene. And a cation exchange resin in the form of fine particles, and a bipolar membrane (Japanese Patent Laid-Open No. 1-502673) in which a cation exchange membrane is formed on a partially sulfonated polystyrene and a hydrogenated butadiene block copolymer. Alternatively, a bipolar membrane in which an anion exchange membrane (layer) is formed on the surface of a cation exchange membrane in which heavy metal ions are present in the membrane can be suitably used because water can be decomposed at a low voltage.

[0010] A typical embodiment of the ion exchange membrane electrodialysis apparatus (B) of the present invention is schematically shown in Fig. 2 together with an acid and alkali generation flow. In FIG. 1, the combination of the bipolar membrane 10, the cation exchange membrane 11, and the anion exchange membrane 12 between the anode 16 and the cathode 17 is one unit. Sulfate waste liquid (Na ₂ SO ₄ ) is supplied to a chamber 14 formed between the cation exchange membrane 11 and the anion exchange membrane 12, and is formed between the bipolar membrane 10 and the anion exchange membrane 12. A thin aqueous sulfuric acid solution (H ₂ SO ₄ ) is also supplied to the chamber 13, and a thin aqueous alkali hydroxide solution (NaOH) is supplied to a chamber 15 formed between the bipolar membrane 10 and the cation exchange membrane 11. The acid (H ₂ SO ₄ ) generated from the chamber 13 and the chamber 15 by the multi-chamber electrodialysis as described above.
To obtain an alkali (NaOH).

[0011]

According to the present invention, it is possible to satisfactorily separate and recover an acid and an alkali from a waste liquid without discarding the alkaline waste liquid. That is, in the present invention,
In order to remove alkali from sulfate alkaline wastewater in advance by an ion exchange membrane electrodialyzer using an alkali-resistant anion exchange membrane, a conventional ion exchange membrane electrodialysis apparatus using a bipolar membrane is used. The acid and the alkali can be separated and recovered from the waste liquid without deterioration of the ion exchange membrane. Of course, the resulting acid and alkali can each be reused. Therefore, the present invention is extremely useful industrially as a method for treating an alkaline waste solution of sulfate, such as environmental conservation, energy saving sources, and economic efficiency.

[0012]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

The alkali-resistant monovalent anion selective permeable membrane used in this example was obtained by the following production method. That is, 70 parts by weight of chloromethylstyrene, 15 parts by weight of divinylbenzene, 2 parts by weight of benzyl peroxide,
Melting point 110 ° C in 2 parts by weight of NBR rubber, average particle size 7
μm spherical low-density polyethylene fine powder (trade name:
70 parts by weight of Flow Beads LE-1080) were added to obtain a paste. Next, the paste was applied to a 100-density plain woven cloth (trade name: nip strong net) made of high-density polyethylene as a reinforcing agent, and coated with a Tetron film as a release agent. Polymerized. Further, the tetron film was peeled off from the film polymer obtained by the polymerization, and immediately immersed in an aqueous solution of 10% by weight of trimethylamine and 20% by weight of acetone for 15 hours.

Example 1 Production of iron hydroxide and Na ₂ SO discharged from the production process
₄ An aqueous waste solution having a composition of 142 g / l and 80 g / l of NaOH was used for the following method (1) according to the method of the present invention.
And the processing of (2). (1) First, using an ion-exchange membrane electrodialysis apparatus having 10 cells each having a set of an alkali-resistant monovalent anion-selective anion exchange membrane and cation exchange membrane and having an effective membrane area of 10 dm ^2. Processed. The operating conditions are as follows:
0 ° C., current density 5 A / dm ² , membrane surface circulation flow rate 6 cm / s
ec. As a result, 2
100% of NaOH at 100 g / l could be recovered. The current efficiency was 90%. (2) The neutral Na ₂ SO ₄ aqueous solution obtained by decomposing the alkali in the above (1) was subjected to the following treatment. That is, the effective membrane area of a cell comprising a bipolar membrane, an anion exchange membrane and a cation exchange membrane as a set of 5 cells is 10 dm ^2.
The treatment was performed using an ion exchange membrane electrodialyzer. The operating conditions are a solution temperature of 30 ° C. and a current density of 10 A / d.
m ² , the membrane surface circulation flow rate was 6 cm / sec, and the NaOH regenerated in the alkali line was transferred to the alkali tank.
H ₂ SO ₄ regenerated in the acid line was recovered in the acid tank. As a result, 40 g / l of Na
50 g / l of H ₂ SO ₄ could be recovered from the OH and acid lines. The current efficiency was 80%.

[0015]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a method for treating waste liquid using an ion exchange membrane electrodialysis apparatus (A) of the present invention.

FIG. 2 is a schematic diagram showing a method for treating waste liquid using the ion exchange membrane electrodialysis apparatus (B) of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cation exchange membrane 2 Alkali-resistant monovalent anion selective permeable membrane 3 Anode 4 Cathode 5 Waste liquid supply chamber → discharge line 6 Alkaline recovery chamber, recovery line 10 Bipolar membrane 11 Cation exchange membrane 12 Anion exchange membrane 13 Acid recovery room, recovery line 14 Supply room for dealkalized waste liquid 15 Alkaline recovery room, recovery line 16 Anode 17 Cathode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 61/44 500 B01D 61/58 C02F 1/469

Claims (1)

(57) [Claims] In an ion exchange membrane electrodialyzer (A) comprising a combination of a cation exchange membrane and an alkali-resistant monovalent anion selective permeable membrane, an alkaline waste solution of sulfate is treated and dealkalized. Then, in the ion exchange membrane electrodialyzer (B) in which a cation exchange membrane, a bipolar membrane, and an anion exchange membrane are sequentially combined, the dealkalized sulfate waste liquid is treated to separate it into acid and alkali. And a method for treating a waste liquid.