JPS5815193B2 - How to treat boron-containing water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating boron-containing water, and particularly to a method for efficiently removing boron after concentrating it.

Boron compounds are used for various purposes such as medicine, raw materials for cosmetics, soap industry, and electroplating, and wastewater generated from these manufacturing processes contains boron compounds.

In addition, boron compounds are also contained in radioactive liquid waste generated from nuclear power plants, geothermal power generation wastewater, flue gas desulfurization wastewater, etc.

Methods for treating boron-containing wastewater include adsorption using an ion exchange resin and forming insoluble precipitates using aluminum sulfate, but neither of these methods can be said to be efficient.

This invention removes boron extremely efficiently by concentrating boron-containing water with an ion exchange resin to obtain concentrated boron-containing water, and then forming an insoluble precipitate in the presence of an aluminum compound and a calcium compound. The purpose of this study is to propose a method for treating boron-containing water.

In this invention, boron-containing water is passed through an anion exchange resin layer to concentrate boron in the resin layer, and then a regenerating agent is passed through the resin layer to elute boron, resulting in a recycled waste liquid containing high concentration boron. A method for treating boron-containing water is characterized by forming an insoluble precipitate in the presence of an aluminum compound and a calcium compound and under conditions of pH 9 or higher, and then performing solid-liquid separation.

Boron-containing water is wastewater discharged from the various processes mentioned above and water containing other boron compounds, and is usually BO3-
It contains boron in the form of (in the present invention, boron may also be contained in the form of borofluoride).

It is also possible to directly add aluminum sulfate and calcium hydroxide to such boron-containing water to generate an insoluble precipitate, but as shown in the experimental example below, the boron-containing water is concentrated in advance to increase the concentration of boron compounds. It was found that boron can be removed extremely efficiently by increasing the

That is, the higher the concentration of boron, the greater the amount of boron removed per unit amount of aluminum, and therefore the amount of aluminum added relative to the amount of removed boron may be smaller.

Therefore, in the present invention, prior to the formation of an insoluble precipitate, boron-containing water is concentrated in advance using an anion exchange resin to increase the boron content.

The anion exchange resin may be either weakly basic or strongly basic, but the weakly basic one has better regeneration efficiency.

Additionally, a special resin with increased boron adsorption may be used.

The anion exchange resin is of S04 type or OH type, and boron-containing water is passed through the resin layer to exchange and adsorb boron and concentrate it.

The SO4 type resin can be obtained by regenerating with sulfuric acid or aluminum sulfate, and the OH type resin can be obtained by regenerating with sulfuric acid or aluminum sulfate and then passing sodium hydroxide through the resin.

After the anion exchange resin is saturated with boron, the resin layer is backwashed and a regenerant is passed through to elute the exchanged and adsorbed boron.

As the regenerant, sulfuric acid and/or aluminum sulfate are preferable, and in particular, in order to omit the addition of aluminum ions in the next step, aluminum sulfate or a combination of aluminum sulfate and sulfuric acid is preferable.

As the regenerating agent passes through the system, boron is eluted and a regenerated waste liquid containing a high concentration of boron is generated.

The resin from which boron has been eluted is converted into OH form with sodium hydroxide if necessary, and then boron is concentrated again.

In the next step, the recycled waste liquid is adjusted to pH 9 or higher, preferably pH 9 or higher, in the presence of an aluminum compound and a calcium compound.
An insoluble precipitate is generated by adjusting the pH to 10 or higher, more preferably 12 or higher.

If aluminum ions or calcium ions already exist, there is no need to add them externally, but if they are insufficient, an aluminum compound or calcium compound such as aluminum sulfate or calcium hydroxide is added.

The required amount of aluminum compounds varies depending on the amount of boron in the raw water and treated water, but if B in the raw water is 500 mg/l and B in the treated water is 10 mg/l, the amount of aluminum added is approximately 1500 mg/l, and the amount of B in the raw water is 10 mg/l. is 100mg/l
When B in the treated water is 5 mg/l, the standard amount of aluminum added is about 400 mg/l.

In either case, it can be calculated based on the amount of aluminum added to the amount of removed boron in the experimental examples described later.

The required amount of calcium compound varies depending on the amount of residual aluminum ions in the treated water, but in the above example, the standard amount is about 3% and about 2%, respectively.

The pH is adjusted by adding an alkaline agent if necessary.

When using calcium hydroxide as the calcium agent, it is often not necessary to add a new alkaline agent.

The order of adding the aluminum compound, adding the calcium compound, and adjusting the pH is not particularly limited.

Therefore, calcium hydroxide is added to resin recycling waste liquid to
After making H9 or higher, aluminum sulfate is added, and if p
If H becomes less than 9, calcium hydroxide may be added again, or aluminum sulfate may be added first and then calcium hydroxide may be added to adjust the pH to 9 or higher.

Although the form of the precipitate formed in this way is not clear,
It is insoluble and has good sedimentation properties, and is easily separated into solid and liquid by natural sedimentation and removed in series.

Next, experimental examples and examples showing the effects of the present invention will be described.

Experimental example Dissolve H2BO3 in distilled water and use 10v*’t as B.

A solution containing 50 mg/l and 490 μl/l was prepared, and aluminum sulfate and calcium hydroxide were added to the solution in the prescribed amounts shown in Table 1. After stirring for 30 minutes, it was filtered through No. 5A filter paper.

The results are shown in Table 1 below. From this experimental example, the amount of aluminum sulfate required to remove the amount of boron contained in raw water to a certain level (approximately 5 ppm in this case) is as follows. It can be seen that the addition amount is sufficient.

Therefore, it is advantageous to previously concentrate the boron-containing water using an ion exchange resin.

Moreover, this experimental example shows that even if the boron content is high, when the pH becomes less than 9, the amount of residual aluminum increases, and as a result, the amount of residual boron in the treated water also increases.

Therefore, in the method of the present invention, even if the amount of boron in the raw water is concentrated, the benefits will be reduced if the pH is less than 9 in the subsequent treatment steps.

Example 1 When flue gas desulfurization wastewater (pH 11.7, boron content 42.4 mg/l as B) to which an alkaline agent was added was passed through an SO4 type weakly basic anion exchange resin layer, the boron content in the treated water was 90 Bed. Volume average value is 0.157
It became 7IIi/l.

Then, after stopping the supply of raw water and backwashing the anion exchange resin layer,
Sulfuric acid (100 g/l was passed through SV2.

As a result, a regeneration solution containing 1,460 .mu./l of boron was obtained from this resin layer (boron elution rate: 100%).

Next, add 45,000 mg/l of aluminum sulfate to this waste liquid.
When 1,501 liters of slaked lime slurry was added under stirring, the pH became 12.5.

As a result of solid-liquid separation of the treated solution containing the precipitate in a settling tank, treated water with a boron content of 30 μ/l was obtained.

Example 2 After passing flue gas desulfurization wastewater through an ion exchange resin layer under the same conditions as in Example 1, a mixed solution of sulfuric acid (20 g/l) and aluminum sulfate (50 g/l) was added to this resin layer at SV2. (boron elution rate 95%).

Add 67g of slaked lime slurry while thoroughly stirring the recycled waste liquid.
/l was added.

As a result, the pH was 11.7.

Next, this waste liquid was supplied to a settling tank for solid-liquid separation, and treated water with a boron content of 18 mg/l was obtained.

Example 3 After passing flue gas desulfurization wastewater through an ion exchange resin layer under the same conditions as in Example 1, aluminum sulfate (100%
g/A) was passed through at Sv2 (boron elution rate 80%).
).

Add 104 g/l of stirred slaked lime slurry to the recycled waste liquid,
After adjusting the pH to 12.5, solid-liquid separation was performed in a precipitation tank.

As a result, treated water with a boron content of 3.0 mg/l was obtained.

As is clear from Examples 1 to 3 above, it can be seen that the ion exchange resin adsorbing boron can be sufficiently regenerated in practice using sulfuric acid or aluminum sulfate alone, or a mixture thereof.

Moreover, the boron-containing liquid thus concentrated with the resin is sufficiently treated in the presence of calcium ions and aluminum ions and under conditions of pH 9 or higher, and the amount of residual boron becomes extremely small.

Comparative Example 45% of aluminum sulfate was added to the recycled waste liquid obtained under the same conditions as in Example 1. o00yty' was added, and at the same time sodium hydroxide was added so that the pH was 13.1.
No precipitate formed.

As described above, according to the present invention, after concentrating boron-containing water, an insoluble precipitate is generated by an aluminum compound and a calcium compound, so the amount of boron removed per unit amount of aluminum is increased, and efficient treatment is performed. be able to.

High concentration is possible by using an anion exchange resin for concentration, and by regenerating this with sulfuric acid, aluminum chloride, etc., a highly concentrated boron concentrate can be obtained, and boron can be highly concentrated with simple operations. This has the effect of increasing the boron removal efficiency in the subsequent process.

Claims (1)

[Claims] 1. Boron-containing water is passed through an anion exchange resin layer to concentrate boron in the resin layer, and then a regenerating agent is passed through the resin layer to elute boron, and the high concentration boron produced is 1. A method for treating boron-containing water, which comprises generating an insoluble precipitate from a recycled waste liquid containing an aluminum compound and a calcium compound in the presence of an aluminum compound and a calcium compound at a pH of 9 or more, and then performing solid-liquid separation. 2. The method for treating boron-containing water according to claim 1, wherein the regenerant is sulfuric acid and/or aluminum sulfate. 3. The method for treating boron-containing water according to claim 1 or 2, wherein the aluminum compound is aluminum sulfate. 4. The method for treating boron-containing water according to any one of claims 1 to 3, wherein the calcium compound is calcium hydroxide. 5. The method for treating boron-containing water according to any one of claims 1 to 4, wherein the pH is 12 or more.