JP2003094053A - Method for treating effluent containing boron and sulfate group - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently treating an effluent containing boron and sulfate group and enabling to remove boron until an extent from which the effluent can be discharged. SOLUTION: The method for treating the effluent containing boron removes a salt from the effluent containing boron and the sulfate group by electrodialysis, adjusts pH in the range of 6 to 12 by adding a basic compound into the residue, and treats the obtained solution with a boron selectivity ion- exchange resin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating boron-containing wastewater containing sulfate radicals. According to the present invention, it is possible to efficiently remove boron from boron-containing wastewater containing sulfate radicals up to the discharge standard.

[0002]

2. Description of the Related Art Boron compounds are widely used in plating, glass, pharmaceuticals, dyes, synthetic fiber manufacturing processes, etc.
Boron-containing water is discharged from these manufacturing processes. Boron-containing water is also discharged from the desulfurization process of a thermal (coal) power plant. Conventionally, a method of adsorbing and removing boron with a boron-selective ion exchange resin has been adopted for the treatment of boron-containing water. In addition, the desorbed liquid of boron generated by the regenerating operation of the boron-selective ion exchange resin is concentrated and treated as industrial waste, or solidified with cement or the like to be landfilled.

When boron is present in a certain concentration or more, it may inhibit the growth of plants and may cause nerve damage to animals, so that more strict drainage standards tend to be set. It is desired that the boron-containing water be efficiently treated up to the discharge standard so as not to cause pollution problems.

[0004]

The boron-selective ion-exchange resin used in the above-mentioned conventional method has a considerably small amount of boron adsorbed as compared with the amount of adsorbed ordinary ion-exchange resin and has a boron adsorption performance of There is a problem that the deterioration is likely to occur, and the regeneration operation is often required. Further, when the sulfate group is mixed in the boron-containing water, the adsorption performance of the boron-selective ion exchange resin is further deteriorated.

An object of the present invention is to provide a method capable of efficiently treating a boron-containing wastewater containing a sulfate group using a boron-selective ion exchange resin and removing the boron to the extent that it can be discharged.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies on a method for treating a boron-containing wastewater containing a sulfate group, and as a result, passed the boron-containing wastewater through a boron-selective ion exchange resin to adsorb boron. Upon removal, as a pretreatment thereof, salts are removed from the above boron-containing wastewater containing sulfate by electrodialysis, and a basic compound is added to the obtained residual liquid to adjust the pH to 6 to 12, The present inventors have found that the boron-selective ion-exchange resin can fully exhibit the boron adsorption performance and can effectively treat the boron-containing wastewater, and have reached the present invention.

That is, according to the present invention, the salt is removed from the boron-containing wastewater containing sulfate by electrodialysis, and the pH is adjusted to 6 to 12 by adding a basic compound to the residual solution. The method for treating the boron-containing wastewater is characterized by treating with a boron-selective ion exchange resin.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A method for treating a boron-containing wastewater containing sulfate according to the present invention will be described with reference to FIG. Figure 1
[Fig. 3] is a process schematic diagram for explaining an embodiment of the present invention. In the figure, 1 is a raw water tank, 2 is an electrodialysis device, 3 is a neutralization tank, 4 is a boron adsorption tower filled with a boron-selective ion exchange resin, 5 is a desorbing liquid tank, 6 is a regenerant tank, 7 Is an eluent receiving tank, 8 is a drainage duct, 9 is an acid adsorption tower, 10 is an acid receiving tank, and 11 is a recovered boron receiving tank.

Boron-containing wastewater containing sulfate (strongly acidic)
Is discharged from various manufacturing processes and guided to the raw water tank 1. Boron in water is usually included as boric acid or borate (boron is used herein as a generic term for boric acid and borate). Boron-containing wastewater containing sulfate (hereinafter, this may be abbreviated as raw wastewater) is guided to the electrodialysis device 2 to remove sulfate radicals from the raw wastewater. As the electrodialysis device, it is preferable to use an ion-permeable membrane electrodialysis device from the viewpoint of removing sulfate radicals stably and efficiently. As the anion permeable membrane used in the ion permeable membrane electrodialysis device, it is preferable to use a polyvalent anion permeable membrane particularly in the case of treating synthetic fiber manufacturing wastewater containing a large amount of sulfate radicals. Examples of the polyvalent anion permeable membrane include Selemion (registered trademark) AMV (manufactured by Asahi Glass Industry Co., Ltd.). By this electrodialysis treatment, sulfate radicals in the raw wastewater can be significantly reduced. Depending on the composition of the raw wastewater, for example, in the case of raw wastewater containing 10% by weight of sulfate radicals, the content of sulfate radicals can be reduced to 0.2% by weight. By significantly reducing the sulfate radicals, the boron adsorption performance of the boron-selective ion exchange resin packed in the boron adsorption tower in the subsequent step can be sufficiently exhibited.

The raw waste water from which sulfate radicals have been reduced by the electrodialysis treatment has a weak acidity of about pH 4. In the neutralization tank 3, the basic compound is added to the weakly acidic raw wastewater to adjust its pH to 6-12. When the pH is less than 6, the boron adsorption performance of the boron-selective ion exchange resin in the subsequent step is not sufficiently exhibited due to the remaining sulfate radicals, and when the pH exceeds 12, the boron adsorption by the boron-selective ion exchange resin is performed. Is not done effectively. p
It is preferable to use caustic soda as the basic compound for H adjustment. By such pH adjustment, boron adsorption by the boron-selective ion exchange resin filled in the boron adsorption tower in the subsequent step is effectively performed.

The raw waste water obtained by the above treatment is treated with a boron-selective ion exchange resin. Such processing is
For example, it is preferable to pass the raw wastewater through the boron adsorption tower 4 filled with the boron-selective ion exchange resin at a space velocity (SV) of 1 to 10 / h. By the treatment of the boron-selective ion exchange resin, the boron contained in the raw waste water is adsorbed by the boron-selective ion exchange resin. As a result, the raw wastewater is detoxified to 0 to 1 mg / L, becomes harmless wastewater, and is discharged from the drainage duct 8. The boron-selective ion-exchange resin is not particularly limited as long as it is an ion-exchange resin having a boron-adsorbing performance, but N as an exchange group is used.
Most preferred is a boron adsorbing resin having a methylglucamine group. Examples of the ion exchange resin having an N-methylglucamine group include, for example, Diaion (registered trademark; manufactured by Mitsubishi Chemical Corporation) CRB01 and CRB02, Amberlite (registered trademark; manufactured by Rohm Haas Co., Ltd.) IRA74.
3, Duolite (registered trademark; manufactured by Sumitomo Chemical Co., Ltd.) A368 and the like.

The regeneration treatment of the boron-selective ion exchange resin whose function is deteriorated by adsorbing boron by passing the boron-containing wastewater is carried out as follows. First, the boron adsorbed on the boron-selective ion exchange resin is removed from the desorption liquid tank 5
Space velocity (SV) of boron desorbed liquid from boron to boron adsorption tower 1
It is desorbed by passing the solution at ~ 5 / h. The eluent is stored in the eluent receiving tank 7. A dilute mineral acid aqueous solution is used as the boron desorbing solution. As the diluted mineral acid aqueous solution, for example, it is preferable to use hydrochloric acid or sulfuric acid aqueous solution having a concentration of about 1 to 10% by weight.

Next, a regeneration treatment is carried out by passing a regeneration liquid from the regenerant tank 6 at a space velocity (SV) of 1 to 5 / h through the boron-selective ion exchange resin from which boron has been desorbed. A dilute alkaline aqueous solution is used as the regenerant. As the dilute alkaline aqueous solution, for example, it is preferable to use a dilute caustic soda aqueous solution having a concentration of about 1N.
The boron-selective ion-exchange resin thus regenerated is
It can be reused in the present invention.

The components of the eluent are boron and sulfuric acid, but the concentration of boron is 20 times or more the concentration of boron in the raw waste water, and it is easy to separate and collect.
An eluent consisting of an aqueous solution of boron and sulfuric acid, for example,
According to the method described in Japanese Patent Laid-Open No. 2001-104807, by passing through an acid adsorption column 9 filled with an OH type weakly basic anion exchange resin, fractionation separation is performed into a boron aqueous solution and a sulfuric acid aqueous solution. . The eluent is supplied to the acid adsorption tower 9 at a space velocity (SV) of 1 to 5 / h. First, an aqueous boron solution flows out from the acid adsorption tower 9, and this is led to a recovered boron receiving tank 11, then an aqueous sulfuric acid solution flows out, which is introduced to the acid receiving tank 10, and each of them is fractionated and collected. The obtained boron aqueous solution contains almost no other impurities, and the boron concentration is also about 20 times higher than the boron concentration in the raw wastewater, and for example, it can be reused as a raw material as it is in the fiber manufacturing process. .

[0015]

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

Example 1 Boron-containing wastewater containing sulfate radicals having the composition shown in Table 1 discharged from a synthetic fiber manufacturing process was used to permeate five cation selective permeation membranes and polyanion permeation as anion selective permeation membranes. The membrane [Selemion (registered trademark) AMV] was passed through an ion permeable membrane electrodialysis device (made by Asahi Glass Industry Co., Ltd.) in which four sheets were alternately arranged, and a DC power of voltage 13V and current value 5A was passed through the membrane. A treatment solution with reduced sulfate was obtained. Table 2 shows the composition of the obtained treatment liquid. A 45% aqueous sodium hydroxide solution was added to the treatment liquid to adjust the pH to 8. PH obtained
A boron adsorption tower filled with 250 ml of a boron-selective ion exchange resin [Diaion (registered trademark) CRB02, manufactured by Mitsubishi Chemical Co., Ltd.] regenerated with a caustic soda aqueous solution into a glass tube having an inner diameter of 22 mm and washed with distilled water. To
The liquid was passed at a space velocity (SV) of 8 / h. Boron leaked into the liquid flowing out from the lower part of the boron adsorption tower and its concentration was 1 m.
As a result of examining the amount of liquid passing until it exceeds g / L, it is 30,000
It was ml.

[0017]

[Table 1]

[0018]

[Table 2]

Comparative Example 1 Boron-containing waste water containing sulfate radicals having the composition shown in Table 1 discharged from the synthetic fiber manufacturing process was applied to the boron adsorption tower used in Example 1 in the same space velocity (SV) as in Example 1. ) 8 /
The solution was passed at h. Boron leaked into the liquid flowing out from the lower part of the boron adsorption tower, and the amount of liquid passed until the concentration exceeded 1 mg / L was examined. As a result, it was 1020 ml, and the amount of liquid passed was extremely small.

Comparative Example 2 A boron-containing waste liquid containing sulfate having the composition shown in Table 1 discharged from the synthetic fiber manufacturing step was adjusted to pH 8 with a 45% caustic soda aqueous solution. The obtained pH adjusting liquid,
The boron adsorption tower used in Example 1 was passed through at the same space velocity (SV) 8 / h as in Example 1. Boron leaked into the liquid flowing out from the lower part of the boron adsorption tower, and the concentration was 1 mg / L.
As a result of investigating the amount of liquid passed until it exceeded 7,750 ml, and the amount of liquid passed was small.

[0021]

EFFECTS OF THE INVENTION According to the present invention, boron-containing wastewater containing sulfate can be efficiently treated and boron can be removed to such an extent that it can be discharged. In the present invention, the boron-adsorbing performance of the boron-selective ion exchange resin can be sufficiently exhibited, and the boron-containing wastewater can be effectively treated.

[Brief description of drawings]

FIG. 1 is a schematic process diagram illustrating an embodiment of the present invention.

[Explanation of symbols]

1: Raw water tank, 2: Electrodialysis device, 3: Neutralization tank, 4: Boron adsorption tower, 5: Desorption solution tank, 6: Regenerant tank, 7:
Eluent receiving tank, 8: drainage duct, 9: acid adsorption tower, 10:
Acid receiving tank, 11: Recovered boron receiving tank

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shuichi Yoshikawa             1621 Sakata, Kurashiki City, Okayama Prefecture Kura Co., Ltd.             Within (72) Inventor Hiroyuki Miyawaki             1621 Sakata, Kurashiki City, Okayama Prefecture Kura Co., Ltd.             Within F-term (reference) 4D006 GA17 KA72 KB11 MA13 MA14                       MB07 PA01 PB08 PB28 PC22                       PC41                 4D025 AA09 AB33 BA13 BA16 BA22                       CA03 CA10 DA05 DA06                 4D061 DA08 DB18 EA09 EB04 EB13                       FA08 FA09 FA11

Claims (3)

[Claims] 1. A salt-containing wastewater containing sulfate radicals is electrodialyzed to remove salts, a basic compound is added to the residual liquid to adjust the pH to 6 to 12, and the resulting solution is treated with boron-selective ions. The method for treating the boron-containing wastewater, which comprises treating with an exchange resin. 2. The treatment method according to claim 1, wherein electrodialysis is performed using a polyvalent anion permeable membrane. 3. The basic compound is caustic soda.
The processing method described in.