JP2008237986A - Method for treating boron-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating boron-containing water by which carbonic acid is beforehand economically and efficiently removed, thus boron is efficiently concentrated and separated so as to obtain a concentrated liquid having a high boron concentration and a penetrated liquid having a low boron concentration in a treatment method by which boron-containing water comprising carbonic acid is separated into the boron-concentrated liquid and the penetrated liquid using a reverse osmosis membrane process. <P>SOLUTION: In the treatment method by which boron-containing water comprising carbonic acid is separated into the boron-concentrated liquid and the penetrated liquid using the reverse osmosis membrane process, the method includes: a stage (A) where the pH of the boron-containing water is regulated to 4.5 to 5.5, thereafter, air is blown therein, and the carbonic acid in the boron-containing water is removed as carbon dioxide; and a stage (B) where the pH of the boron-containing water is regulated to 10.5 to 11.5, and thereafter, it is subjected to the reverse osmosis membrane process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for treating boron-containing water, and more specifically, in a treatment method for separating boron-containing water containing carbonic acid into a boron concentrate and a permeate using a reverse osmosis membrane method. The present invention relates to a method for treating boron-containing water, in which carbonic acid is previously removed economically and efficiently, thereby efficiently concentrating and separating boron to obtain a concentrated solution having a high boron concentration and a permeated solution having a low boron concentration.

In recent years, boron-containing water treatment technology has attracted attention in the treatment of mine wastewater discharged from seawater and brine desalination, water purification, factories, mines, and the like.
Boron-containing water is produced as various industrial wastewater. For example, boron compounds represented by boric acid and sodium borate are used as raw materials in various industrial applications such as glass industry, pharmaceuticals, cosmetic raw materials, soap industry, electroplating, dyes, aluminum surface treatment. ing. Therefore, the wastewater generated in these production processes often contains a boron compound. In addition, boron is often contained in wastewater generated from power plants and smoke washing wastewater in garbage incineration plants.

  By the way, boron is an essential trace element for animals and plants, but if it is consumed in excess, it is considered to cause central nervous system damage to animals or growth inhibition to plants. / L, and 10 mg / L outside the sea area, and its separation and removal are attracting attention.

  As a treatment method for boron-containing water, ion-exchange resin or chelate resin is used to adsorb boron in boron-containing water, and then elution treatment is performed with mineral acid to collect high-concentration boron-containing water. Using a coprecipitation agent such as an aluminum compound and a sulfuric acid compound, or an aluminum compound or an iron compound, and fixing boron in water containing boron as sludge; and A method for insolubilization (see, for example, Patent Documents 4 and 5) is disclosed. However, such a treatment method can be applied only in a very limited field. For example, in the adsorption method, since the adsorption capacity of boron is low, addition of a large amount of adsorbent is indispensable. Not practical in economics. In addition, in the immobilization method, since a large amount of coprecipitation agent or the like is added, there is a problem that the amount of operation materials increases and the amount of sludge, which is a boron-containing starch, increases.

  For example, when processing a large amount of boron-containing water having a relatively low concentration, for example, about several tens of ppm, such as mine mine drainage, hot spring water, etc., when applying the above processing method, the time required for the processing The problem is that the amount of sludge becomes enormous, the amount of sludge becomes enormous, and the processing cost becomes very high, which makes it difficult to apply practically.

Furthermore, a method for removing boron by passing boron-containing water through a reverse osmosis membrane is known.
Here, in general, in the method using a reverse osmosis membrane, by adjusting the pH of the boron-containing water to about 10, the concentrated solution having a high boron concentration and the permeate having a low boron concentration can be efficiently recovered from the boron-containing water. It is supposed to be possible. However, since boron-containing water usually contains ions such as carbonic acid in addition to boron, when pH is increased by sodium hydroxide or the like, salts such as carbonate are generated, so that boron is separated by a reverse osmosis membrane. Efficiency is significantly reduced. For example, when calcium, carbonic acid, or the like is contained in addition to boron, when the pH is raised, calcium scale is generated, and the separation efficiency of boron by the reverse osmosis membrane is lowered due to membrane blockage or the like. For this reason, in order to remove calcium, carbonic acid, and the like from boron-containing water that passes through the reverse osmosis membrane, a weakly acidic ion exchange resin and a degassing membrane device are provided in advance, or boron that passes through the reverse osmosis membrane A method of adding a scale inhibitor such as a chelating agent to water (for example, see Patent Document 6) is disclosed.

However, in such a method, as in mine mine drainage, hot spring water, etc., in general, when processing a large amount of water containing carbon dioxide and relatively low concentration of boron, the equipment cost increases, Or, along with problems such as the occurrence of secondary problems due to the scale inhibitor, it was not possible to obtain a concentrated liquid in which boron was concentrated to a level that was practically satisfactory and a permeated liquid having a low boron concentration.
From the above situation, in the reverse osmosis membrane method, there has been a demand for a treatment method that can efficiently obtain a concentrated liquid in which boron is concentrated from boron-containing water containing carbonic acid.

Japanese Patent Laying-Open No. 2005-87825 (first page, second page) JP 2002-173665 A (first page, second page) JP 2001-212455 A (first page, second page) JP 2001-162287 A (first page, second page) Japanese Patent Laid-Open No. 3-38295 (first page) JP-A-11-138165 (first page, second page)

  In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a boron-containing water that is separated from a boron-containing water containing carbonic acid into a boron concentrate and a permeate using a reverse osmosis membrane method. Provides a method for treating boron-containing water, which can remove carbonic acid from wastewater economically and efficiently, thereby efficiently concentrating and separating boron to obtain a concentrated solution having a high boron concentration and a permeated solution having a low boron concentration. There is to do.

  In order to achieve the above object, the inventors of the present invention have used a reverse osmosis membrane method from boron-containing water containing carbonic acid to separate the boron-concentrated liquid and the permeated liquid, and the pH of the boron-containing water. Was adjusted to a specific value, and then subjected to air blowing. Subsequently, after adjusting the pH of the boron-containing water to a specific value and subjected to the reverse osmosis membrane method, carbonic acid was economically produced from the boron-containing water. The present invention was completed by finding that it can be efficiently removed and that boron can be efficiently concentrated and separated.

That is, according to the first invention of the present invention, a process for separating boron-containing water containing carbonic acid into a boron concentrate and a permeate using a reverse osmosis membrane method,
Step (A) of adjusting the pH of the boron-containing water to 4.5 to 5.5 and then subjecting it to air blowing to remove carbonic acid in the boron-containing water as carbon dioxide, followed by the pH of the boron-containing water A process for treating boron-containing water is provided, which comprises the step (B) of adjusting the pH to 10.5 to 11.5 and then subjecting to a reverse osmosis membrane method.

  According to the second invention of the present invention, in the first invention, the air blowing continues the time until the pH of the boron-containing water rises to 7.0 or more. A method for treating water is provided.

  According to a third aspect of the present invention, in the first aspect, the amount of air blown is 0.1 to 0.5 L / min per liter of boron-containing water. A method for treating water is provided.

  According to a fourth aspect of the present invention, there is provided the method for treating boron-containing water according to the first aspect, wherein the carbonic acid concentration after air blowing is 30 mg / L or less.

  According to a fifth aspect of the present invention, there is provided the method for treating boron-containing water according to the first aspect, wherein the alkali used for the pH adjustment is sodium hydroxide.

  According to a sixth invention of the present invention, in any one of the first to fifth inventions, the boron-containing water is mine wastewater containing boron at a concentration of 10 mg / L or more. A method for treating water is provided.

  The method for treating boron-containing water according to the present invention is a method of separating the boron-containing water from a boron-containing water containing carbonic acid into a boron concentrate and a permeate using a reverse osmosis membrane method. By adjusting to the value and subjecting to air blowing and reverse osmosis membrane method, carbonic acid can be removed economically and efficiently from the boron-containing water, and boron is concentrated and separated efficiently, which is practically satisfactory. Since it is possible to obtain a concentrated liquid in which boron is concentrated to a possible level and a permeated liquid having a low boron concentration, its industrial value is extremely high.

Hereinafter, the method for treating boron-containing water of the present invention will be described in detail.
The method for treating boron-containing water according to the present invention is a treatment method in which boron-containing water containing carbonic acid is separated into a boron concentrate and a permeate using a reverse osmosis membrane method, and the pH of the boron-containing water is adjusted. After adjusting to 4.5-5.5, it attach | subjects to air blowing, The process (A) which removes the carbonic acid in this boron containing water as a carbon dioxide gas, Then, pH of boron containing water is 10.5-11. After adjusting to 5, it is characterized by comprising the step (B) of applying to the reverse osmosis membrane method.

In the present invention, when the reverse osmosis membrane method is used to separate the boron concentrate and the permeate, first, the pH of the boron-containing water containing carbonic acid is adjusted to 4.5 to 5.5 for air blowing. It is important to perform the step (A) for removing carbonic acid in advance and the step (B) for adjusting the pH to 10.5 to 11.5 and passing the solution through the reverse osmosis membrane.
That is, in step (A), carbonic acid in boron-containing water can be removed economically and efficiently by blowing air adjusted to a specific pH, and then, during the pH adjustment in step (B), the formation of carbonate Therefore, when the boron is concentrated and separated through the reverse osmosis membrane, the separation efficiency of boron is increased in combination with the action of adjusting to a specific pH, and the concentrated solution and the boron concentration with high boron concentration are increased. Low permeate. The effect of adjusting to a specific pH in these steps will be described in detail in the description of each step.

  The boron-containing water used in the present invention is not particularly limited, and boron containing water at a concentration of 10 mg / L or more and simultaneously containing carbonic acid is used. For example, plating, aluminum surface treatment, glass, Examples include process water in various industries such as dyes, medical treatment, waste water from flue gas desulfurization facilities, waste disposal facilities, mine waste water, hot spring water, and the like.

In the step (A), the pH of the boron-containing water is first adjusted to 4.5 to 5.5. Thus, carbon dioxide in the boron-containing water can be removed as carbon dioxide gas with the blowing of air.
In other words, the carbonic acid contained in the boron-containing water is usually dissolved at a pH of 8 or more in which 96% of the total carbonic acid is dissolved in the form of carbonate ions (CO ₃ ²⁻ ) or bicarbonate ions (HCO ₃ ²⁻ ). Yes. Therefore, it is difficult to remove carbonic acid only by blowing air under these conditions. Here, by adjusting the pH to the range of 4.5 to 5.5, 97% of the total carbonic acid in the boron-containing water takes the form of carbonate ions (CO ₃ ²⁻ ), which can be easily removed by air blowing. Become. If the pH is less than 4.5, the amount of acid added increases, which is economically disadvantageous. On the other hand, if the pH exceeds 5.5, the residual ratio of bicarbonate ions (HCO ₃ ²⁻ ) increases, so that removal is difficult.

  In the said process (A), as a pH adjustment method, it is performed using an acid or an alkali with the pH of the boron containing water which is process raw water. The type and concentration of the acid or alkali are not particularly limited, and sulfuric acid is preferable as the acid.

  In the step (A), the air blowing amount is not particularly limited, and is preferably 0.1 to 0.5 L / min per 1 L of boron-containing water. That is, when the air blowing rate is less than 0.1 L / min per liter, the time required for air blowing becomes very long, and the rate is controlled during operation. On the other hand, if the air blowing rate exceeds 0.5 L / min per liter, mixing with boron-containing water is not efficient and economically disadvantageous.

  The blowing time is not particularly limited, and the pH of the boron-containing water gradually increases from 4.5 to 5.5 as the carbonic acid is removed from the boron-containing water. By measuring the pH, it can be determined that the removal of carbonic acid has been completed when the pH reaches 7.0 or higher. The blowing time is 30 to 60 minutes under normal conditions.

The carbonic acid removal from the boron-containing water accompanying the air blowing will be described in detail with reference to FIG.
Here, 11 L of mine wastewater having a boron concentration of 25 mg / L, a carbonic acid concentration of 550 mg / L, and a pH of 7.4 was used as the boron-containing water. Sulfuric acid was added to the mine wastewater to adjust the initial pH of the boron-containing water to 5.0. Air was blown into the boron-containing water whose pH was adjusted at 2.5 L / min. Thereafter, the carbonic acid concentration at 10 minutes, 30 minutes, 60, 90 minutes and 120 minutes after the start of degassing was measured. FIG. 1 shows the relationship between the deaeration time, the carbonic acid concentration and the pH.
As shown in FIG. 1, the carbonic acid concentration rapidly decreased immediately after the start of degassing, and the carbonic acid concentration in boron-containing water 30 minutes after the start of degassing became 30 mg / L or less, and the carbonic acid concentration thereafter became substantially constant. This shows that the carbonic acid in the treated water can be efficiently separated and removed. Further, the pH of the boron-containing water decreases with a decrease in the carbonic acid concentration, and the pH of the boron-containing water after the carbonic acid concentration becomes 30 mg / L or less is about 7.0, and the pH after that is almost constant. Therefore, the pH of the boron-containing water reflects the transition of the carbonic acid concentration of the boron-containing water, and pH 7.0 can be set as the completion condition for carbonation removal.

  The means for blowing air is not particularly limited, and it is preferable to use a dispersion device such as sinter glass or unglazed plate that can efficiently remove carbon dioxide gas by making air finer. Furthermore, carbon dioxide can be removed in a short time if the reaction efficiency is increased by making the air finer while stirring the solution.

In the said process (B), as pH of boron containing water, it adjusts to 10.5-11.5. Thereby, by passing through the reverse osmosis membrane, a concentrated liquid having a high boron concentration and a permeated liquid having a low boron concentration can be obtained.
That is, boron of boron-containing water is present as B (OH) ₃ or B (OH) ₄ ⁻ , and when the pH is less than 10.5, boric acid in addition to B (OH) ₄ ^— Since OH) ₃ remains, the conventional separation of boron with a reverse osmosis membrane is insufficient when water having a pH of about 10 is used. In the form of B (OH) ₃ , it is difficult to separate boron by a reverse osmosis membrane. On the other hand, when the pH exceeds 11.5, the pH is completely changed to B (OH) ₄ ⁻ as boric acid, so that further increase in pH is unnecessary.

In the step (B), the pH adjustment method is performed using an alkaline aqueous solution. Here, the kind and concentration of the alkali are not particularly limited, and examples thereof include sodium hydroxide and potassium hydroxide, and sodium hydroxide is particularly preferable.
In addition, in the step (A), by removing carbonate ions or bicarbonate ions having a large buffering effect, the amount of alkaline aqueous solution added in pH adjustment is reduced, and the total salt concentration in boron-containing water is reduced. Therefore, the boron separation effect by the reverse osmosis membrane can be improved.

Although it does not specifically limit as a reverse osmosis membrane used by the said process (B), Since a boron containing water with a pH of 10.5-11.5 is passed, it does not deteriorate even if it uses for a long period of time. Thus, an alkali-resistant thing is preferable.
Further, a single-stage or multi-stage reverse osmosis membrane can be installed depending on the target concentrated liquid and the boron concentration of the permeated liquid. For example, when the concentration of boron in the concentrated liquid is increased, a system in which the concentrated liquid in the previous stage is passed through the reverse osmosis membrane in the subsequent stage and the concentrated liquid in the subsequent stage can be recovered. Further, when the boron concentration of the permeate is lowered, a method is adopted in which the permeate in the former stage is passed through the reverse osmosis membrane in the latter stage and the permeate in the latter stage can be collected.

  In the step (B), a concentrated liquid having a boron concentration of 100 mg / L or more and a permeate having a boron concentration of 10 mg / L or less, which are obtained by concentrating boron to a practically satisfactory level, are obtained. The obtained permeate satisfies the drainage standard. Further, the obtained concentrated liquid is further subjected to a concentration operation and then used as a raw material for producing boric acid or the like.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, the analysis method of boron used in the Examples and Comparative Examples was ICP emission analysis, and the analysis method of carbonic acid was the combustion oxidation infrared TOC analysis method.

Example 1
First, as boron-containing water, 100 L of mine wastewater having a boron concentration of 25.5 mg / L, a carbonic acid concentration of 550 mg / L, and a pH of 7.5, sulfuric acid was added to the mine wastewater, and the initial pH of the boron-containing water was adjusted. Adjusted to 5.0. Next, air was blown into the pH-adjusted boron-containing water at 25 L / min. When the pH of the boron-containing water reached 7.0, the air blowing was stopped. Here, the carbonic acid concentration of boron-containing water was 30 mg / L. Subsequently, sodium hydroxide was added to the boron-containing water after air blowing to adjust the pH to 11.0, and boron-containing water 1 was obtained.
Thereafter, the boron-containing water 1 is passed through a reverse osmosis membrane device whose schematic device layout is shown in FIG. 2, and when the amount of permeate extracted from the reverse osmosis membrane device reaches a predetermined amount, the concentrated solution and the permeate Were collected and analyzed for their boron concentration. The results are shown in FIG. FIG. 3 shows the relationship between the permeate withdrawal amount and the boron concentration of the concentrate and permeate.
The outline of the operation method of the reverse osmosis membrane device is shown below.
As the reverse osmosis membrane 5, TFC-SR24 manufactured by Koch was used. The boron-containing water is put into the tank 1 and the pump 2 is operated. The permeate flow meter 7 and the concentrate flow meter 9 are adjusted by the controller 4 and the valve 6 so that the flow rate of the permeate 8 is 3.5 L / min and the flow rate of the concentrate 10 is 35 L / min. The boron-containing water was passed through the reverse osmosis membrane device through the 3 μm filter 3.

(Comparative Example 1)
First, as the boron-containing water, using a mine wastewater having a boron concentration of 25.1 mg / L, a carbonic acid concentration of 550 mg / L, and a pH of 7.4, a sodium hydroxide solution is added to the mine wastewater to adjust the pH to 10. As a result, boron-containing water 2 was obtained.
Thereafter, the boron-containing water 2 is passed through a reverse osmosis membrane device whose schematic device layout is shown in FIG. 2, and when the amount of permeate extracted from the reverse osmosis membrane tester reaches a predetermined amount, Liquids were collected and analyzed for their boron concentration. The results are shown in FIG.

From FIG. 3, in Example 1, after adjusting the pH of boron-containing water containing carbonic acid to a predetermined value, it was subjected to air blowing, and subsequently, the pH of boron-containing water was adjusted to a predetermined value, followed by reverse osmosis. Since it was carried out according to the method of the present invention by subjecting it to a membrane method, carbon dioxide in the treated water was efficiently separated and removed, and when water was passed through the reverse osmosis membrane, the formation of carbonate by pH adjustment was prevented and It can be seen that a combined solution having a high boron concentration and a permeate having a low boron concentration can be obtained in combination with the effect of appropriate pH setting.
On the other hand, in Comparative Example 1, since the removal of carbonic acid and the adjustment of the pH of the boron-containing water passed through the reverse osmosis membrane do not meet these conditions, the concentration of boron in the concentrate and the permeate should be satisfied. It turns out that a result is not obtained.

  More specifically, the boron concentration of the concentrate in the boron-containing water 1 was always higher than the boron concentration of the concentrate of the boron-containing water (b). Regarding the concentrated solution when the permeate withdrawal amount in the boron-containing water 1 is 95 L and the concentrate when the permeate withdrawal amount in the boron-containing water 2 is 91 L, the respective boron concentrations are 131 mg / L and 71 mg / L. Met. Further, the boron concentration of the permeate in the boron-containing water 1 was always lower than the boron concentration of the permeate in the boron-containing water 2. Regarding the permeate when the permeate withdrawal amount in the boron-containing water 1 is 95 L and the permeate when the permeate withdrawal amount in the boron-containing water 2 is 91 L, the respective boron concentrations are 8 mg / L and 15 mg / L. Met.

  As is clear from the above, the method for treating boron-containing water according to the present invention includes carbon dioxide in boron-containing wastewater used in fields such as industrial plants using boric acid, power plants, garbage incineration plants, mines and the like. It is suitable as a method for separating and removing boron from the contained boron-containing water.

It is a figure which shows the relationship between the deaeration time in carbon blowing, a carbonic acid concentration, and pH. It is a figure showing schematic apparatus arrangement | positioning of a reverse osmosis membrane apparatus. It is a figure showing the relationship between the permeate extraction amount of a reverse osmosis membrane apparatus, and the boron concentration of a concentrate and a permeate. (Boron-containing water 1 shows the case of Example 1, and boron-containing water 2 shows the case of Comparative Example 1.)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tank 2 Pump 3 3 micrometer filter 4 Controller 5 Reverse osmosis membrane 6 Valve 7 Permeate flowmeter 8 Permeate 9 Concentrate flowmeter 10 Concentrate

Claims (6)

From the boron-containing water containing carbonic acid, using a reverse osmosis membrane method, a treatment method for separating into a boron concentrate and a permeate,
Step (A) of adjusting the pH of the boron-containing water to 4.5 to 5.5 and then subjecting it to air blowing to remove carbonic acid in the boron-containing water as carbon dioxide, followed by the pH of the boron-containing water A process for treating boron-containing water, which comprises a step (B) of adjusting the pH to 10.5 to 11.5 and then subjecting to a reverse osmosis membrane method.   2. The method for treating boron-containing water according to claim 1, wherein the air blowing continues a time until the pH of the boron-containing water rises to 7.0 or more.   The method for treating boron-containing water according to claim 1, wherein the amount of air blown is 0.1 to 0.5 L / min per liter of boron-containing water.   The method for treating boron-containing water according to claim 1, wherein the carbonic acid concentration after the air blowing is 30 mg / L or less.   The method for treating boron-containing water according to claim 1, wherein the alkali used for pH adjustment is sodium hydroxide.   The method for treating boron-containing water according to any one of claims 1 to 5, wherein the boron-containing water is mine wastewater containing boron at a concentration of 10 mg / L or more.

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