JPS61153193A - Treatment of waste water containing boron - Google Patents

Abstract

PURPOSE:To remove efficiently boron by using a water-soluble polymer having a hydroxyl group to form an insoluble deposit in the presence of an Al compd. and a Ca compd. as a pretreatment, and then separating solid from liq. CONSTITUTION:When waste water contg. boron is treated with a resin for adsorbing boron, a water soluble polymer having a hydroxyl group (e.g., water- soluble polyvinyl alcohol) is used to form the insoluble deposit of boron in the boron-contg. waste water in the presence of an Al compd. such as Al sulfate and a Ca compd. such as slaked lime as a pretreatment, and then the deposit is separated from the liq. The separated water having a low content of boron is brought into contact with the resin for adsorbing boron, and the concn. of boron can be reduced to <=1-2mg/l. By this flocculating sedimentation method, the amt. of sludge generated can be reduced to 1/2-1/3 in comparison with the conventional method, and furthermore boron can be efficiently removed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for treating boron-containing wastewater.

(Prior art) (Problem to be solved by the invention) Boron compounds, represented by boric acid and sodium borate, are used in the glass industry as well as nickel plating additives, preservatives, dyes, etc. because they are inexpensive. Boron compounds are widely used in the fields of pigments, cosmetics 9 soaps, photography, etc., and the 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, flue gas desulfurization wastewater, smoke washing wastewater from garbage incinerators, etc. Although boron is considered an essential element for plants, it is difficult to provide it in excess.

It is known that it inhibits its growth, and even within two countries, it is
Some places have extremely strict regulations that determine the permissible concentration in wastewater, which is 2 tag/l or less.

As a method for treating such boron-containing wastewater, ■
There are three methods: adsorption using an anion exchange resin or boron-selective ion exchange resin, removal as an insoluble precipitate using aluminum sulfate or slaked lime, and treatment using a reverse osmosis membrane, all of which are efficient methods. I can't say that. In other words, in the first method, the adsorption capacity for boron is generally small, so when treating waste liquid with a particularly high concentration of boron, it is impossible to treat a small amount of waste liquid, and furthermore, when the resin is regenerated and used, it is difficult to treat the waste liquid. There is a problem in that it is difficult to treat recycled waste liquid. In addition, in the second method, it is almost impossible to clear the above wastewater regulation value due to the characteristics of boron compounds, and if the boron concentration in the treatment liquid is forced to be lowered, a large amount of sludge will be generated. Furthermore, in the third method, the commonly used reverse osmosis membrane has a low removal rate of 50-60% for boron-containing substances, so multi-stage equipment is required to meet wastewater regulation values. However, there are problems such as excessive initial cost.

As a method to deal with these problems, a method has recently been proposed that combines boron removal by coagulation-sedimentation method and boron removal by anion exchange resin (Japanese Patent Laid-Open No. 57-81
, No. 818, and Japanese Patent Application Laid-Open No. 180-180-493).

The methods described in these publications generate a large amount of sludge due to coagulation and sedimentation treatment, and adsorption treatment using anion exchange resin lacks selectivity for boron compounds. has the disadvantage that it cannot be removed.

(Means for solving problems) ゛Therefore, the inventors of the present invention took into consideration the current situation.

Reduces the amount of sludge generated by coagulation and sedimentation treatment,
As a result of intensive research aimed at providing a treatment method for boron-containing wastewater that can efficiently remove boron,
As a pretreatment, an insoluble precipitate is generated in boron-containing wastewater using a water-soluble polymer having a hydroxyl group in the presence of an aluminum compound and a calcium compound, and then solid-liquid separation is performed.

The present invention has been completed based on the discovery that the above object is achieved.

In other words, the present invention involves generating an insoluble precipitate in the boron-containing wastewater by using a water-soluble polymer having a hydroxyl group in the presence of an aluminum compound and a calcium compound as a pretreatment when boron-containing wastewater is treated with a boron-adsorbing resin. This is a method for treating boron-containing wastewater, which is characterized in that it undergoes solid-liquid separation.

To treat boron-containing wastewater according to the present invention, first, a water-soluble polymer having hydroxyl groups is used in the presence of an aluminum compound and a calcium compound to form an insoluble precipitate in the boron-containing wastewater.

The boron-containing wastewater targeted by the present invention includes:

Examples include wastewater discharged from the various processes mentioned above, eluent from resins that have adsorbed boron, and wastewater containing other boron compounds.1 Usually, HsBOs or BO+
Contains boron in the form of -, and the pH is usually 1 to 1.
It is 0. Such boron-containing wastewater ranges in boron concentration from low to high.

B is usually used in a range of 50 to 5+000 mg/1, preferably 100 to 3,000 mg/1, but the present invention is not limited to these boron concentrations.

Examples of the aluminum compound used in the present invention include aluminum sulfate, polyaluminum chloride, etc., and the molar ratio to dissolved boron is 0.3 to 5.
It is sufficient to add twice the amount, preferably 0.5 to 2 times the amount. In addition, examples of calcium compounds include slaked lime, quicklime,
Calcium chloride is mentioned, and the molar ratio is 0.3 to 8 times, preferably 0.5 to 8 times the amount of dissolved boron.
Just add 4 times the amount. Furthermore, examples of water-soluble polymers having hydroxyl groups include water-soluble polyvinyl alcohol.

Starch Soluble starch, carboxymethyl starch,
Natural, semi-synthetic or synthetic polymers such as dextrin, carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, sodium alginate, potassium alginate, propylene glycol alginate, triethanolamine alginate, and ammonium alginate are used, among which water-soluble polyvinyl alcohol is particularly preferred. At this time, the molecular weight of the polyvinyl alcohol used is not particularly limited as long as it is water-soluble, but in consideration of solubility, it is convenient to use one with a relatively low molecular weight of about 300 to 2,000.

In addition, the amount of the polymer having a hydroxyl group added is 1 based on the repeating unit, based on the amount of dissolved boron.
The molar ratio is 0.01 to 3 times, preferably 0.05 to 0.
It is sufficient to use 3 times the amount. If the amount added is less than this, the removal efficiency of the boron-containing compound will decrease, which is undesirable, and if the amount added is more than this, not only will the cost increase, but the subsequent filtration step will be labor-intensive, which is not preferable.

The pH may be adjusted by adding an alkaline agent such as caustic soda or caustic potash as necessary.
It is preferable to adjust H to a range of 6 to 13. When using slaked lime or quicklime as a calcium compound, the specified p) 1 can be achieved without adding a new alkaline agent.
It can range from 6 to 13. Addition of aluminum compounds, addition of calcium compounds, addition of polymers with hydroxyl groups.

And, the order of pH adjustment is not particularly limited in the present invention. When the pH is adjusted to 6 to 13, boron precipitates as an insoluble precipitate, which can be easily separated into solid and liquid.

In the present invention, the water-soluble precipitate produced above is subjected to solid-liquid separation. For this purpose, a known method such as centrifugation may be used.

Next, in the present invention, the separated water with a low boron content obtained from the solid-liquid separation process can be treated to a low concentration of 1 to 2 mg71 by contacting it with a boron adsorption resin.

The boron adsorption resin used in the present invention includes:

Any material that can adsorb boron may be used, but chelate resins represented by the following general formula (1) or (II) are generally preferred.

-CH, -N (1)C
Hz-+CI (OH)3-T-CHtOH (however, +
R1 is a hydrogen atom or an alkyl acid having 1 to 5 carbon atoms, and 7 is 1
~6, represents an integer.

-CH, -N (n)C
(CHtOH)3 (However, RZ represents a hydrogen atom or an alkyl acid having 1 to 5 carbon atoms.

R in the formula (1) is particularly preferably a methyl group or an ethyl group, and n is preferably 4. R2 in the formula (n)
Preferred examples include a hydrogen atom and a methyl group. In addition, as the resin matrix, styrene, divinylbenzene copolymer,
Phenol/formalin resin, epoxy resin, etc. are preferred. Preferred specific examples of these chelate resins include Amberlite IRA-734 (styrene-visinylbenzene copolymer, manufactured by Rohm and Haas), Unicerec tlR, a phenolic chelate resin having a group of formula (I) in the phenol nucleus; -3500 (manufactured by Unitika).

Furthermore, a commercially available anion exchange resin can also be used as the boron adsorption resin, but in this case, a method using a weakly basic ion exchange resin is preferred because of its excellent regeneration efficiency.

Furthermore, in the present invention, Filtrasorb (Filtrasorb)
Activated carbon represented by Trasorb (trade name, manufactured by Calbon Co., Ltd.) may be used as the boron adsorption resin.

These boron-adsorbing resins are usually of an OR type in which the terminal functional group is neutralized with an alkali, and boron can be adsorbed by passing separated water containing boron through the resin layer.

Once the boron adsorption resin is saturated with boron, the resin layer may be backwashed and a regenerant may be passed through it to elute the boron adsorbed on the resin.

As the regenerant, a 1 to 10% by weight aqueous sulfuric acid or hydrochloric acid solution is preferred.

By returning the resulting eluate containing a high concentration of boron to the raw water, the eluate can be treated at the same time. The resin after boron elution is 9 e.g. 4 to 10
It may be reused after being neutralized with an alkaline solution of % by weight.

The water treated in the above adsorption process contains 1 to 100% boron.
It is processed to a level of 2mg/l or less.

It can be discharged directly into rivers, etc.

(Example) Next, the present invention will be specifically explained using examples.

In addition, % in Examples and Comparative Examples represents weight %.

Example 1 Commercially available boric acid was dissolved in ion exchange water, and 500
An aqueous solution (pH 4,0) containing mg/l was prepared.

Aluminum sulfate A for 1000ml of this aqueous solution
lz (SO4)*・tsozo 18.4g (A
#/B = 1.2 (molar ratio)), 6.8g of slaked lime
((Ca/B = 2.0 (molar ratio)) and 2.0 g of a 10% polyvinyl alcohol aqueous solution (0.1 molar ratio to dissolved B based on the repeating unit)
double the amount), the pll becomes 7.0, which increases to 30
After stirring for a minute.

The generated sludge was filtered out using filter paper.

As a result, the boron concentration in one separated water was 50 mg/l,
The boron removal rate was 90%. The amount of sludge generated was 11.0 g-SS/It.

Next, the separated water obtained above was purified using 30 ml of chelate resin Unicelec @ 0R-3500 (manufactured by Unitika) having an aminopolyol group at a water flow rate of 60 w 1 l per hour (SV = 2,0) 1 r-'). When the fluid was passed.

The boron concentration in the treated water is 2 until the water flow rate is 1001#-R.
mβ or less.

Comparative Example 1 Example 1 except that polyvinyl alcohol was not added
It was treated in exactly the same way.

As a result, the boron concentration of the separated water after coagulation and sedimentation treatment was 25
0 mg/l, and the boron removal rate was 50%.

Next, when the separated water obtained above was passed in the same manner as in Example 1, the boron concentration in the treated water was 251/l.
-R was 2 mg7N or less.

Comparative example 2: 6.8% slaked lime without adding polyvinyl alcohol
The treatment was carried out in the same manner as in Example 1 except that the amount of sludge was increased from 17.0 g to 17.0 g. Separated water with the same boron concentration (50 mg/ff1) as in Example 1 was obtained, but the amount of sludge was 27.0 g. .0g-5S/j! 2.5 of Example 1
It was double the amount.

Next, when the separated water obtained above was passed in the same manner as in Example 1, the same results as in Example 1 were obtained.

Example 2 Boron-containing wastewater discharged from a certain Mesoki factory (8940
mg/1. pH 2.1) 5j2 was adjusted to po 9.0 with a 25% aqueous solution of caustic soda.

In this waste liquid, aluminum sulfate All (SO4)31
When 145 g of 8H,0 (to J/B = molar ratio) and 64.5 g of slaked lime (Ca/B = 2.0 molar ratio) and 19.3 g of a 10% polyvinyl alcohol aqueous solution are added, p
H became 10.0, and when it was stirred for 30 minutes and separated into solid and liquid, 9 degrees of Br in the separated water was 160 mg/l.
Met.

This separated water was poured into 30 m
Water flow rate of 301111 per hour (SV=
When the solution was passed through the water at 1.0 Hr-'), B:a in the treated water
Degree high water 138 N/1-R Mateha 1 mg/
1 or less. The amount of sludge generated by coagulation and sedimentation was 30g-5S/N-waste liquid.

Comparative Example 3 Example 2 except that polyvinyl alcohol was not added
The agglomeration process was performed in exactly the same manner as above.

The B concentration in the separated water was 470 rt+g/l.

When this separated water was subjected to adsorption treatment in the same manner as in Example 2, the B concentration in the treated water was 14j per 2 water passes! /I! -R
Until now, it was less than 1 mg#.

Example 3 Flue gas desulfurization wastewater discharged from a certain factory (B 120yag
/ l, Ca 2500 mg/It, 81
300 mg/L, Mg 210mg/Lp■
9.4) For 1(l), sulfuric acid, aluminum
37.0g of SOa)s・181tO (A l /
81.0 (molar ratio)), slaked lime 20.5g (Ca/
B-2,5 (molar ratio)] and 4.8 g of a 10% polyvinyl alcohol aqueous solution were added, stirred for 1 hour, and then solid-liquid separated. The B'a degree in the separated water was 25 rag.
/it was.

This separated water was mixed into a chelate resin resin amberlite IRA-743 (manufactured by Rohm and Haas) 20mj! having an aminopolyol group. When the water was passed at a water flow rate of 100111 per hour (SV = 2.0 Hr-') using a water flow rate of 100111 per hour, the degree of Bfi in the treated water was less than IIIg/l up to a water flow rate of 100 #/f-R.

(Effects of the Invention) According to the present invention, the amount of sludge generated by coagulation-sedimentation treatment can be reduced to 172 to 1/3 compared to the conventional method, and boron can be efficiently removed. Furthermore, according to the present invention, it can be applied to a wide range of wastewater ranging from low to high boron concentrations in raw water, and is particularly effective in treating eluents containing high boron concentrations of 500 mg/l or more. be.

Claims (2)

[Claims] (1) When treating boron-containing wastewater with a boron-adsorbing resin, as a pretreatment, a water-soluble polymer having a hydroxyl group is used in the presence of an aluminum compound and a calcium compound to form an insoluble precipitate in the boron-containing wastewater, and then A method for treating boron-containing wastewater characterized by solid-liquid separation. (2) The treatment method according to claim 1, wherein the water-soluble polymer having hydroxyl groups is water-soluble polyvinyl alcohol.