JP4058787B2 - Method for treating boron-containing water - Google Patents

Description

[0001]
BACKGROUND 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 by evaporation and ion exchange.
[0002]
[Prior art]
Boron compounds are used in various fields, and some wastewaters generated from these fields or other fields include boron compounds. Since such a compound is considered harmful, a treatment for removing boron from the boron-containing water is performed.
[0003]
As a conventional method for treating boron-containing water, a method of separating and removing boron by coagulation precipitation using an aluminum compound and a calcium compound has been carried out (Japanese Patent Publication Nos. 58-15193 and 59-24876). However, this method has a problem that it is necessary to use a large amount of chemicals, the amount of generated sludge is large, and the treatment is difficult.
[0004]
In addition, a method is also known in which boron is removed by ion exchange of boron-containing water with an anion exchange resin, and the regenerated effluent of the anion exchange resin is evaporated and concentrated (Japanese Patent Publication No. 1-35944). However, in this method, since raw water is directly ion-exchanged, it is necessary to use a large amount of ion-exchange resin, the frequency of regeneration is high, the amount of regenerant used is large, and the treatment of boron in condensed water generated by evaporation and concentration Is not shown.
[0005]
In addition, the boron-containing water is subjected to membrane separation in a reverse osmosis (hereinafter sometimes referred to as RO) membrane device, the concentrated solution is evaporated and concentrated, and the permeated solution of the RO membrane device and the condensed solution obtained by evaporation and concentration are treated with an ion exchange resin. A method is shown (Japanese Patent Laid-Open No. 59-49898). However, in this method, since the boron removal rate of the RO membrane is as low as about 60% at the maximum, a large amount of resin and amount of drug used are required.
[0006]
In this method, the recycled wastewater can be mixed with the raw water and processed. However, when the recycled wastewater is mixed with the raw water and processed by the RO membrane device, the boron concentration of the permeate becomes about 1.5 times the raw water. Therefore, there is a problem that a larger amount of resin and regenerant are required than in the case of direct ion exchange of raw water, and the regeneration frequency is increased.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to obtain a high-quality treated water by efficiently removing boron at a high removal rate without reducing the amount of ion-exchange resin and chemicals used, and without discharging the regeneration drainage of the ion-exchange resin. It is possible to obtain a method for treating boron-containing water that can reduce the amount of sludge generated.
[0008]
[Means for Solving the Problems]
The present invention is the following method for treating boron-containing water.
(1) An evaporative concentration step in which boron-containing water containing 1000 to 10000 mg / l of boron is separated into condensed water and concentrate by evaporative concentration without performing RO membrane treatment ;
An ion exchange step of contacting the condensed water with an ion exchange resin comprising an N-methylglucamine type chelate resin to remove boron;
To regenerate the ion exchange resin with acid, how to process the boron-containing water and a regeneration step of returning the playback drainage in evaporation process.
(2) The method according to (1) above, wherein the regenerated effluent is mixed with raw water, adjusted to a neutral or higher pH, and evaporated and concentrated in an evaporation and concentration step.
[0009]
The boron-containing water to be treated in the present invention is usually water containing boron in the form of orthoboric acid (H ₃ BO ₃ ), but may also contain boron in other forms of borate. Such boron-containing water includes pharmaceutical, cosmetics, soap, and other process wastewaters that use boron compounds, plating wastewater, radioactive wastewater generated from nuclear power plants, geothermal power generation wastewater, flue gas desulfurization wastewater, and waste incineration plants. Smoke drainage and so on. These boron-containing water, which boron is included 1000~10000mg / l is subject to processing.
[0010]
These boron-containing waters may be subjected to the treatment of the present invention as they are, or the treatment of the present invention may be performed after the treatment for removing other components. When the raw water contains solids, other scale components, and corrosive components, these other components are preferably removed by pretreatment such as coagulation precipitation and filtration.
[0011]
The coagulation sedimentation treatment is an operation of adding a coagulant such as an aluminum salt or iron salt and, if necessary, an alkali agent such as calcium hydroxide and coagulating, and separating the solid and other coagulable components by solid-liquid separation. is there. Filtration includes general filtration for solids separation in addition to coagulation filtration.
[0012]
The pretreatment may be performed within the range that removes substances that hinder evaporation and concentration, such as solid matter removal. However, if all components other than boron are removed, boron will be purified in a later step. It can be recovered. In the pretreatment, boron may or may not be removed. Further, as a pretreatment, a concentration operation that reduces the load of the evaporation concentration process may be performed, but in the present invention , the concentration is performed in the evaporation concentration process without performing the RO membrane treatment . In addition to the RO membrane treatment , the concentration can be performed in the evaporative concentration step without performing the concentration operation with incomplete boron separation.
[0013]
In the evaporation and concentration step, the boron-containing water is evaporated together with the regenerated drainage of the ion exchange resin and concentrated to concentrate the boron compound. Although any evaporation apparatus such as heat evaporation, vacuum evaporation, or a combination thereof can be adopted for the evaporation concentration step, heat evaporation is preferable. As the type of each evaporator, any type of evaporator such as a flash type or a film type can be used.
[0014]
Boron-containing water, treated water such as pretreated water, and regenerated drainage of ion exchange resin are introduced into these evaporators to evaporate moisture, condense steam to generate condensed water. Evaporation and concentration can be efficiently performed with a small amount of heat by recovering heat using raw water as cooling water for condensation. Boron compounds and other non-volatile components are concentrated on the liquid side by the evaporation of moisture, and a concentrate is obtained.
[0015]
The concentration factor at this time is determined in consideration of the raw water concentration and the disposal method of the concentrate. The concentrate can be obtained in a solid or liquid state and can be recovered or disposed of as it is, and can also be disposed of after being cured with cement or the like. Further, it can be obtained in the form of a concentrated solution and post-treated by aggregation or the like. In any case, when the boron compound is obtained in a pure form, it can be recovered and used.
[0016]
Since the condensed water obtained in the evaporation and concentration step contains about 1 to 10 mg / l of boron that has been transferred along with the vapor, the condensed water is brought into contact with an ion exchange resin in the ion exchange step to thereby form boron. Remove. Since the boron contained in the condensed water is about 1/100 to 1 / 10,000 of the raw water, the amount of resin and regenerant used here should also be reduced at that rate compared to direct ion exchange of the raw water. Can do.
[0017]
The ion exchange resin used in the ion exchange step uses an anion exchange resin made of an N-methylglucamine type chelate resin to remove boron, but if it is necessary to remove cations, the cation exchange resin is also used. In this case, it is preferable to treat in a mixed bed.
[0018]
Anion exchange resins for removal of boron, a chelate resin having an increased adsorption amount of boron, the use of selective adsorption to N- methylglucamine type resins boron, in addition to removal rate of boron is high, The purity of the recovered boron compound (boric acid) is increased.
[0019]
In the ion exchange step, condensed water is passed through a resin layer filled with an ion exchange resin composed of an N-methylglucamine type chelate resin to perform ion exchange and exchange and adsorb boron. Most of the boron contained in the condensed water is orthoboric acid and is considered to be dissociated in the water according to the equation (1).
[Chemical 1]
H ₃ BO ₃ + H ₂ O = B (OH) ₄ ⁻ + H ⁺ ... (1)
[0020]
The equilibrium in equation (1) varies with pH, and the higher the pH, the more the equilibrium tends to shift to the right. In this case, when the chelate resin is in the SO ₄ form, the treatment is difficult unless the pH is 9 or more, and in the case of the OH form, the treatment can be performed even in the vicinity of neutrality. Therefore, it is preferable.
[0021]
In the ion exchange step, by bringing boron-containing water into contact with the chelate resin, the B (OH) ₄ ⁻ is exchanged and adsorbed on the resin and removed. From the treated water, boron and other anions are removed to obtain treated water with high purity close to pure water, which can be used as it is. When condensed water contains cations, cations can be removed by treatment with a cation exchange resin as described above, and when treating with a resin that also removes other anions as a chelate resin, Pure water can be obtained as treated water.
[0022]
When the chelate resin is saturated with boron, the process proceeds to a regeneration step, the resin layer is back-washed, and a regenerant is passed through to elute the exchanged and adsorbed boron. As the regenerant, general regenerators such as acids and alkalis can be used, but it is particularly preferable to use sulfuric acid, hydrochloric acid or nitric acid. Boron is eluted by passing the regenerant, and a regenerated drainage containing high concentration boron is generated. The resin after the elution of boron can be used for adsorption of boron again after being made into OH form with sodium hydroxide if necessary.
[0023]
The regenerated effluent is directly or after pH adjustment and mixed with raw water to return to the evaporation and concentration step. In the evaporative concentration step, orthoboric acid is more likely to move to the vapor side as the pH is lower. When the raw water is acidic or alkaline and the pH becomes neutral or higher by mixing the regenerated effluent, these may be simply mixed. When these are not mixed and become neutral or more, it is preferable to add an acid or an alkali as a pH adjuster. When acid and alkali are used as the regenerant, they are of course mixed and returned to the evaporation and concentration step.
[0024]
By evaporating and concentrating the water to be treated in which the regenerated effluent is mixed with the raw water in the evaporative concentration step, the concentrated boron and other substances contained in the regenerated effluent are concentrated and recovered or disposed of. Further, the concentration of boron to be treated increases due to the mixing of the regenerated effluent, and the amount of boron transferred to the condensed water side increases accordingly, but these are removed in the ion exchange step.
[0025]
Although it is preferable for the operation of the evaporative concentration process that the quality of the water to be treated supplied to the evaporative concentration process is as stable as possible, for this purpose, the regenerated effluent discharged intermittently is stored in a storage tank and evaporated. It is preferable to return to the concentration step by a certain amount. The evaporative concentration process continues to operate even during regeneration of the ion exchange resin, so the condensed water generated during that time can be stored to homogenize the processing volume, or multiple ion exchange devices can be installed to switch the process continuously. It is preferable to do it automatically.
[0026]
In the above treatment, since boron is concentrated in advance by evaporative concentration and only the condensed water with a low boron content is ion-exchanged, the amount of ion exchange resin and regenerant can be reduced, and the boron removal rate is increased to achieve high water quality. Treated water with a quality close to that of pure water can be obtained. In addition, since the regeneration drainage of the ion exchange resin is returned to the evaporation concentration step and concentrated by evaporation, the regeneration drainage can be easily treated and the amount of generated sludge is reduced.
[0027]
【The invention's effect】
According to the present invention, the boron-containing water containing 1000 to 10000 mg / l of boron is separated into condensed water and concentrate by evaporation and concentration without performing RO membrane treatment, and the condensed water is N -It includes an ion exchange step of removing boron by contacting with an ion exchange resin comprising a methylglucamine type chelate resin, and a regeneration step of regenerating the ion exchange resin with an acid and returning the regenerated effluent to the evaporation and concentration step. , to reduce the amount of ion exchange resin and a drug, regeneration effluent of the ion exchange resins without discharging, it is possible to boron is removed efficiently high removal rate obtain treated water of high quality, sludge The amount can also be reduced.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a system diagram showing a method for treating boron-containing water according to an embodiment of the present invention. In FIG. 1, 1 is an adjustment tank, 2 is an evaporative concentration apparatus, 3 is an ion exchange tank, and 4 is a drainage storage tank.
[0029]
The treatment method of boron-containing water by the above apparatus is as follows. First, the raw water is introduced into the adjustment tank 1 from the raw water channel 5, the regenerated drainage is introduced from the drainage supply channel 6, stirred and mixed by the stirrer 7, and a pH adjuster is injected from the drug injection channel 8 as necessary. Adjust the pH to neutral or higher. The mixed liquid in the adjustment tank 1 is introduced into the evaporative concentration apparatus 2 from the system path 9 as a liquid to be treated.
[0030]
The evaporative concentrator 2 is configured as a heat evaporation type, heats and evaporates the supplied liquid to be processed, condenses the generated vapor to obtain condensed water, and this condensed water is transferred from the system 10 to the ion exchange tank 3. On the other hand, the concentrate is taken out from the concentrate channel 11. Here, boron is concentrated on the concentrate side by evaporation, and a part of the boron moves to the condensate side. Although the steam is cooled by the liquid to be treated and recovered by heat, the detailed illustration is omitted.
[0031]
The ion exchange tank 3 has a resin layer 12 filled with an N-methylglucamine type chelate resin, and boron is exchanged and adsorbed by passing condensed water through the resin layer 12 in the ion exchange step. The treated water is taken out from the treated water channel 13. By providing a plurality of ion exchange tanks 3, continuous processing is performed by switching to the regeneration process when the ion exchange process is completed.
[0032]
The regenerant is injected from the chemical injection path 14 to regenerate the resin layer 12, and the regenerated drainage is sent from the system path 15 to the drainage storage tank 4. The regeneration efficiency can be increased by flowing an acid and an alkali sequentially as the regeneration agent. In this case, these effluents are collected in the effluent storage tank 4 and agitated by the stirrer 16 to neutralize the effluent, and supplied from the effluent supply path 6 to the adjustment tank 1 at a homogenized flow rate.
[0033]
[Example 1]
Examples of the present invention and comparative examples will be described below.
[0034]
Example 1
Raw water of pH 7.0 containing 2500 mg / l of boron was heated to 100 ° C. in an evaporating and concentrating apparatus and evaporated and concentrated at a concentration factor of 15 times to obtain condensed water having a boron concentration of 7.1 mg / l. When this condensed water was passed through a resin layer of N-methylglucamine type boron selective adsorption resin (Diaion CRB-02, trademark, manufactured by Mitsubishi Chemical Corporation) with SV2hr- ¹ , treated water of boron 1 mg / l or less up to 440 BV. was gotten.
[0035]
When the resin layer was regenerated with 100 g / l sulfuric acid, a regenerated drainage solution having a boron concentration of 2450 mg / l was obtained. When this regenerated effluent was mixed with raw water without neutralization, it became pH 3, and when this was concentrated to a concentration factor of 15 in an evaporation concentrator, the boron concentration of the condensed water was 26 mg / l. When this condensed water was passed through the resin layer in the same manner as described above, treated water having a boron concentration of 1 mg / l or less was obtained up to 120 BV.
[0036]
Example 2
In Example 1, sodium hydroxide was added to the regenerated effluent to adjust the pH to 7.0, and the neutralized regenerated effluent was mixed at a ratio of 3 ml to 1 liter of raw water and concentrated by evaporation. The boron concentration of the condensed water at 15 times was 6.9 mg / l. When this condensed water was subjected to an ion exchange treatment in the same manner as in Example 1, treated water having a boron concentration of 1 mg / l or less was obtained up to BV440.
Moreover, the solid substance obtained by drying the concentrate in the said evaporation concentration process was 25g per liter of raw | natural water.
[0037]
Comparative Example 1
When the same waste water as in Example 1 was passed through a boron selective resin with SV2hr ⁻¹ , treated water of 1 mg / l or less was obtained up to 1.5 BV. Further, when the resin adsorbing boron was regenerated with 100 g / l sulfuric acid, a regenerated drainage containing 2480 mg / l of boron was obtained. In this case, the amount of the necessary resin was about 300 times that of Example 1, and the amount of the regenerant and the alkali agent for neutralizing the regenerated drainage was about 300 times that of the Example. For this reason, the amount of the regenerated drainage is almost the same as the amount of the raw water.
[0038]
Comparative Example 2
When the regenerated effluent obtained in Comparative Example 1 was stirred for 30 minutes after addition of sulfuric acid band 45 g / l and slaked lime 150 g / l (pH 12.4), treated water with a boron content of 180 mg / l was obtained. . The amount of solid matter generated at that time was 220 g / l-raw water. On the other hand, the solid matter produced in Example 2 is only 25 g / l-raw water, which is greatly reduced.
[Brief description of the drawings]
FIG. 1 is a system diagram showing a method for treating boron-containing water according to an embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Adjustment tank 2 Evaporation concentration apparatus 3 Ion exchange tank 4 Waste liquid storage tank 5 Raw water path 6 Waste liquid supply path 7, 16 Stirrer 8, 14 Chemical injection path 11 Concentrated liquid path 13 Process water path

Claims (2)

An evaporative concentration step in which boron-containing water containing 1000 to 10,000 mg / l of boron is separated into condensed water and concentrate by evaporative concentration without performing RO membrane treatment ;
An ion exchange step of contacting the condensed water with an ion exchange resin comprising an N-methylglucamine type chelate resin to remove boron;
A method for treating boron-containing water, comprising: a regeneration step of regenerating an ion exchange resin with an acid and returning the regenerated effluent to an evaporation concentration step. The method according to claim 1, wherein the regenerated effluent is mixed with raw water, adjusted to a neutral or higher pH, and evaporated and concentrated in an evaporation and concentration step.

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