JPS59213489A - Treatment of water containing boron - Google Patents

Abstract

PURPOSE:To treat efficiently water contg. a boron compd. by adding a chlorine agent to the water contg. boron and other salts and treating the same with a membrane separating stage using a chlorine resistant permeable membrane then treating the water with a permeable membrane having an Nidentical bond. CONSTITUTION:Water contg. a boron compd. is subjected preliminarily to a flocculating treatment to remove coexisting heavy metals such as zinc and nickel and thereafter >=0.1mg/l chlorine agent is added as a residual chlorine to said water. The water contg. boron added with the chlorine agent is supplied to the 1st stage of a membrane separator. A chlorine-resistant semipermeable membrane of cellulose acetate, etc. is required to be used as the permeable membrane in the 1st stage of the membrane separator. Coexisting inorg. and org. salts, Ca, Mg salt, and a part of boron are removed by the 1st stage of the membrane separating process. The water is then supplied to the 2nd stage of a membrane separator using a permeable membrane having an Nidentical bond in the molecule of -CONH-, etc. by which the water is treated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating boron-containing water, and more particularly to a method for treating boron-containing water using a permeable membrane.

In addition to borates, large amounts of inorganic and organic salts are contained in plating industry and flue gas desulfurization wastewater, radioactive wastewater discharged from nuclear power plants, geothermal power generation/Kame wastewater, smoke washing wastewater from Koimi incinerators, etc. It is common that

Conventionally, ion exchange resins have been employed to treat these boron-containing waters. However, if the salt content is low to a certain extent, ion exchange resins can be used, but if it becomes relatively high, efficient separation is no longer possible. In addition, the application of chelate resins has been sidelined, but chelate resins cannot remove coexisting ions and are therefore unsuitable.

On the other hand, a separation method using a cellulose acetate membrane has been proposed for treating boron-containing water. However, cellulose acetate membranes have a fatal drawback of extremely poor removal rates for I)H, alkaline earth metals, and boron (usually 20 to 40%).

Recently, when constructing a new plated pump, there are cases where it is necessary to completely treat the wastewater and recycle the treated water, and conventional treatment methods are not always fully satisfactory. Therefore, efficient countermeasures were required.

The present invention was developed as a result of the above-mentioned efforts to overcome the drawbacks of the prior art, and by using two types of permeable membranes made of different materials, The present invention provides a treatment method that can efficiently treat contained water and has an extremely good water recovery rate.

That is, in this invention, after adding a chlorine agent to water containing boron and other salts, it is treated in a membrane separation process using a chlorine-resistant permeable membrane, dechlorinated if necessary, and then -
This is a method for treating boron-containing water, characterized in that the treatment is performed in a membrane separation step using a permeable membrane having N-bonds.

In this invention, white boron and other salts refer to water containing boron compounds including IJf borates, borofluorides, and other organic and inorganic salts.

The water that is the subject of this invention preferably has a relatively high boron index (M), for example, a boron compound containing 50 to 1,0
00m9/13 (as H3BO3) &, degrees. In addition, boron-containing water usually contains other inorganic and organic chloride metals as well as boron compounds. Contains a large amount of salt.

In the case of this invention, the above salt concentration is 30.000nly
If it exceeds /J3, the negative value of the treated water will gradually worsen, so the target is preferably about 500 to 30,000 m9/l.

Next, this invention will be explained step by step.

First, the boron compound-containing water is sent to the membrane separation process described above, but since the boron compound-containing water usually also coexists with heavy metal salts such as zinc and dichloromethane, it is removed by a coagulation process in advance. is preferable.

In general, many substances exhibit hostile properties, such as water), and they are coagulated using, for example, various iron salts and alkaline agents.

Like this ((, preprocessed (or not preprocessed)
The water containing boron water is sent to the first stage membrane separation process.

Shi, sh, as it is, I! On the +2 side, microorganisms do not propagate, and these adhere to the membrane surface and induce membrane contamination.
Processing efficiency will be completely reduced. In the present invention, first, the entire chlorine agent is added to the boron-containing water.

The chlorine agent is not particularly limited as long as it dissolves in water to generate all available chlorine, and examples include chlorine gas, hypochlorite, and electrolytic chlorine obtained by electrolytically treating salt water.

The amount of the chlorine agent added is 0.1 m978 or more as residual chlorine, preferably about 0.5 to 1 m97 l. If the amount of residual chlorine is less than o, xmyy, e, it may be difficult to prevent the growth of microorganisms.

On the other hand, if it exceeds 11n/13, the effect remains the same, and on the contrary, it becomes necessary to remove residual chlorine in the next process, which becomes uneconomical.

Thus, the boron-containing water containing the chlorine agent is then fed before the first stage separation.

It is necessary to use a salt-resistant semipermeable membrane as the first stage permeable membrane. Examples of such yarns include cellulose acetate yarn, sulfonated polyphenylene oxide yarn, polyacrylonitrile yarn, polyolefin yarn, and sulfonated polysulfone yarn. Regarding the shape of the hatch, any conventional type can be used, such as spiral type, hollow fiber type, pipe conduit type, flat membrane type, etc. However, for water containing a large amount of SS, the sound A flat film type is preferred.

In addition, the first stage is transparent! A can be ultrafiltration power/breath or reverse osmosis membrane, operating pressure is 2 to 75 ky, f/cr
It is about d. However, it is preferable to remove all coexisting salts and microorganisms in the first stage separation process.
It is preferable to use a reverse osmosis membrane, and the operating pressure at that time is IQ ~ 75 kgf/7.

As a result, in the first stage membrane separation step, the AiJ inorganic and organic coexisting salts, scale components lucium, magnesium salts, and some boron compounds are removed from the boron-containing water. In addition, the first stage membrane has 10 membranes that are resistant to free or condensed chlorine, and the residual chlorine in the raw water is O,1rn9/E or more, preferably o,5-
1 mg7 (3) and pressurized treatment (10 to 75 kgf/
cIIX) Then, the residual chlorine in the treated water will be 0.2~Q
, 8 Innoir 6 or so is included. 9 The first stage film is maintained in an almost completely staged state.

Next, this permeated water is supplied to the second stage membrane separator made of a specific material, but a large amount of chlorine agent is added prior to the first stage, so that the amount of residual chlorine is 0, Lmt// (If the amount of chlorine present in the permeated water exceeds 3, it will be inappropriate to feed it as it is to the second stage membrane separation device as it will have an adverse effect on the specific material, so it will be necessary to dechlorinate it in advance. Dechlorination is easily achieved by using physicochemical means using reducing agents such as bisulfite or activated carbon. :, 5・
1. The permeable membrane used in the second stage is limited to membranes having -N- bonds in their molecules. If any other film is used, the boron compound will hardly be removed and the object of the invention cannot be achieved.

A film having -Nh bonds is -C0NH- in the polymer.
and -C,0Ni(NHCO-1 and -CON-co
-i combination'ff: For example, J3-9 (Du
pon wosha), PA-100, PA-300 (UOP
The commercially available membranes are commercially available under the names FT-30 (Intec) and FT-30 (Intec).

The second stage membrane separator has an operating pressure of io~40'kI1.
It is operated at about f/cl.

Membranes with -N- bonds are easily attacked by chlorine MIJ and are susceptible to membrane contamination by microorganisms because chlorine agents cannot be used; however, in the case of this invention,
Since the first stage is sterilized and sterilized using a photospectral chlorine agent, the probability of microorganisms occurring in the second stage membrane Pj11 process is extremely low, and the second stage membrane is stable for a long period of time. You can turn it into a bow and remove all objects. Furthermore, since the concentration of remaining coexisting ions is low, a high water recovery rate can be achieved even at lower pressures. Furthermore, it is known that the removal rate of boron compounds by the -N-bonded film improves as the pH increases (about 9 to 11), and in the case of this invention,
Since scale components have been removed in advance in the first stage membrane separation step, the pH can be raised to the desired value without worrying about scale.

In addition, even if water containing boron compounds is treated with a permeable membrane that has all -N- bonds, the amount of residual chlorine is 0.1 ml; l/8
If it is less than 0.1, microbial contamination will definitely occur;
If it exceeds my/τ, it will have an adverse effect on the membrane and significantly shorten its life, so it is far from practical use.

As mentioned above, in this development, 41 permeable membranes made of 2 different materials are combined in a mechanical manner to treat water containing boron compounds, which has traditionally been difficult to recover and reuse. As a result, the quality of the final treated water obtained is extremely good, and it is possible to use it again just by adding some post-treatment. Of course, it is also possible to leave it outside the thread as it is.

This invention will be further explained below using actual examples.

EXAMPLE This occurrence ψj was observed in plating wastewater discharged from a plating factory.

Sodium hypochlorite was added to the plating wastewater having the quality listed in Table 1 in an amount such that the residual chlorine was 0.7 mq/l.

Next, it was supplied to a reverse osmosis membrane separator fully equipped with a cellulose-based permeable membrane in an vinegar factory, and treated at a pressure of 35 k, yf/crd. As a result, the permeated water shown in Table 1 was obtained (water recovery rate 90%).

Next, sodium bisulfite f 5m9/θ was added to this permeated water to make the residual chlorine fi ”c O,I my/y less than that, and then a membrane containing N Mr@ (FT-31J
, a product of FiJmtec Co., Ltd.)'f:: It was applied to a reverse osmosis membrane separation device equipped with it. The operating pressure at this time is 301cy
It was f/7.

As a result, treated water having the quality shown in Table 1 was obtained.

As you will see, the removal rate of boric acid in the final treated water was 87.5% based on the feed water standard, and the removal rate of conductivity was 98.6%, so the purity was high enough to be recovered and reused. The total water recovery rate was 83.7.

In addition, when an alkaline agent was added to the permeate of the cellulose acetate membrane to adjust the pH to 0.0 (see Table 1, 2nd row, 1 membrane treated water), the removal rate of boric acid improved to 95.8%. Moreover, there was no occurrence of scale at all.

Table 1 Comparison Example In the example, the treatment was carried out under the same conditions as in the example except that a cellulose acetate thread membrane was installed as the second stage membrane separation device.

All results are shown in Table 2.

This result shows that it is almost impossible to remove boron compounds with cellulose acetate-based membranes. Also, the electrical conductivity of the comparative example is one digit higher than that of the example.

Special W “Applicant Kurita Industries Co., Ltd.

Claims (1)

[Claims] 1. After adding a chlorine agent to water containing boron and other salts, it is treated in a membrane separation process using a chlorine-resistant permeable membrane, and if necessary, dechlorinated, and then A method for treating boron-containing water, which comprises treating it in a membrane separation step using a permeable membrane having -N- bonds. 2. The treatment method according to claim 1, wherein the water containing boron and other salts is plating industry smoke wastewater or waste desulfurization wastewater. 3. The treatment method according to claim 1 or 2, wherein the chlorine-resistant permeable membrane is a cellulose acetate membrane. 4. The treatment method according to any one of claims 1 to 3, wherein the membrane separation step is a reverse osmosis membrane separation step.