JP2001219163A - Treatment method of boron-containing water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating boron-containing water, which is capable of removing boron by using a general anion exchange resin alone, and in which the regeneration step is simple and can be performed at low cost. obtain. SOLUTION: Boron-containing water 11 is pretreated in a pretreatment device 1 and introduced into an ion exchange device 3, and an anion exchange resin 4 is introduced.
After the ion exchange step of exchanging and adsorbing boron by passing through, the pure water 21 is heated to 40 to 60 ° C. and introduced into the ion exchange device 3 to perform pre-cleaning of the anion exchange resin layer 4, and then alkali The aqueous solution 23 is heated to 40 to 60 ° C. and introduced into the ion exchange device to regenerate the anion exchange resin layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating boron-containing water by treating boron-containing water by ion exchange.

[0002]

2. Description of the Related Art Boron compounds are used in various fields, and some wastewaters generated from these fields and those discharged from other fields contain those containing boron compounds.
Since such compounds are considered harmful, treatments have been performed to remove boron from boron-containing water.

As a method for treating boron-containing water, there is a treatment method by ion exchange (JP-A-57-81881).
issue). In this method, boron is adsorbed by bringing boron-containing water into contact with an anion exchange resin, the anion exchange resin is regenerated with a regenerant, and the removal of boron is repeated. As the anion exchange resin used in such a method, besides a general anion exchange resin widely used for ion exchange, a boron selective adsorption resin which is a chelate resin having enhanced selectivity for boron adsorption is used. I have.

In a general treatment method using an anion exchange resin, when an adsorbed anion exchange resin is regenerated, when an aqueous alkali solution is used as a regenerant, the hardness component in the resin becomes insoluble material such as magnesium hydroxide. Therefore, there is a problem that water flow resistance in the next ion exchange step is increased, and water flow is impossible. For this reason, it is necessary to remove the hardness component with a cation exchange resin before the treatment with the anion exchange resin, and there is a problem that boron cannot be removed by the anion exchange resin alone.

[0005] On the other hand, treatment with a boron selective adsorption resin does not have such a problem and can remove boron at a high removal rate. However, since it is a special resin, it is necessary to use an expensive resin. In addition, regeneration is regeneration with sulfuric acid,
The two-stage regeneration of the alkali is required, and the process is complicated, and there are problems such as a high chemical and other costs.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems by removing boron by using a general anion exchange resin alone, and by a simple and low-regeneration process. An object of the present invention is to provide a method for treating boron-containing water that can be treated at a low cost.

[0007]

The present invention relates to the following method for treating boron-containing water. (1) an ion exchange step of exchanging and adsorbing boron by bringing boron-containing water into contact with an anion exchange resin, a precleaning step of precontacting the anion exchange resin having exchanged and adsorbed boron with pure water, and a precleaning step. A regeneration step of regenerating the anion exchange resin by bringing the anion exchange resin into contact with an aqueous alkali solution. (2) The method according to the above (1), wherein the pure water in the pre-cleaning step is 40 to 60 ° C. (3) The aqueous alkali solution in the regeneration step is 40 to 60.
(1) or (2) above.

[0008] In the present invention, the boron-containing water to be treated is usually water containing boron in the form of orthoboric acid (H ₃ BO ₃ ), but may be borate or other forms containing boron. Examples of such boron-containing water include pharmaceutical, cosmetic, soap, metal, semiconductor, and other wastewater from manufacturing processes, plating wastewater, radioactive wastewater from nuclear power plants, and flue gas desulfurization from coal-fired power plants. Drainage, geothermal power generation drainage, smoke incineration drainage, etc.

These boron-containing waters may have different boron contents depending on the generation source, generation time, and the like. For example, in a surface treatment step of a metal or semiconductor using boric acid, high-concentration boron-containing water is generated during the surface treatment, and low-concentration boron-containing water is generated in a subsequent washing step. In addition, different sources produce different concentrations of boron-containing water. These boron-containing water can also be treated by mixing different kinds of water,
It can also be processed separately.

[0010] These boron-containing waters may contain other components. When the boron-containing water contains other components, the contamination of the resin in the ion exchange step can be prevented by removing turbidity and other components by pretreatment such as coagulation separation, filtration, and membrane separation. It is preferred.

In the present invention, such boron-containing water is brought into contact with an anion exchange resin in an ion exchange step to exchange and adsorb boron to the resin. As the anion exchange resin, a strongly basic anion exchange resin used for general ion exchange is preferable. Such anion exchange resins are preferably used in the OH form.

The boron-containing water in the ion exchange step;
The method of contacting the anion exchange resin is not particularly limited, and may be a method such as immersion. However, the resin is packed in a column to form a resin layer, and boron-containing water is passed through the resin layer to exchange and adsorb boron. A column water flow method is preferred. In this case, the flow direction may be an upward flow or a downward flow. The conditions for passing water are SV0
It can be 120 hr ^-1 , preferably 5 to 20 hr ^-1 . By bringing the boron-containing water into contact with the anion exchange resin, the boron in the boron-containing water is exchange-adsorbed and removed by the anion exchange resin. Although boron in the boron-containing water has a BO ₃ ^3- in pH8 less, at pH9 or B (OH) ₄ ^- is assumed that a, both exchange groups anion exchange resin - and ^(OH) Be exchanged.

It is preferred that the effluent is not returned to the ion exchange step in the ion exchange step. After removing boron, the boron-containing water can be used for various purposes such as washing by using the treated water as recovered water by simple treatment such as desalination.
At this time, if the use of the recovered water is interrupted, for example, if the flow of water through the resin layer is interrupted each time, it is difficult to restart the flow of water. However, it is not preferable to continue passing water while returning the treated water to the raw water tank, because the efficiency of removing boron decreases. The reason is that, when the anion is removed by ion exchange and the water having an increased OH ^- ion concentration is passed through the resin layer again, a part of the boron trapped by the resin is eluted. Guessed. In other words, it is presumed that passing water through the resin layer while returning the treated water to the raw water tank is equivalent to simultaneously removing boron and regenerating the resin (desorption of boron).

After the completion of the ion exchange step, a pre-cleaning step is performed before moving to the regeneration step. In this case, the ion exchange is stopped at the stage where the anion exchange resin exchanges and adsorbs boron with the progress of ion exchange and reaches saturation, and the process proceeds to the pre-cleaning step. The end point of the ion exchange step is the point in time when the boron concentration in the treated water exceeds the set value, and this point can be detected to start the pre-cleaning step.

The pre-cleaning step is performed by contacting with pure water. The purpose of the prewash is to replace the raw water present around the resin with pure water. Since a hard component such as magnesium contained in the raw water reacts with the alkali to produce an insoluble substance, it is present around the resin in the pre-cleaning step prior to the regeneration. In order to remove such a hardness component, replacement is performed with pure water. In the case of passing water through the column, washing is performed by passing pure water of 1 BV or more, preferably 1 to 5 BV. The flow rate of the pure water in the pre-cleaning is SV ⁰ to 50 hr ^-1 , preferably 5 to ¹ hr.
0 hr ^-1 . In this case, after draining, pure water may be introduced and pre-cleaning may be performed, or pure water may be directly introduced and pre-cleaning may be performed. When heating regeneration is performed in the next regeneration step, 40 to 60 ° C, preferably 45 to 5
It is preferable to heat the resin by performing pre-washing with pure water heated to 5 ° C.

After completion of the pre-cleaning step, the process proceeds to a regeneration step, in which the anion exchange resin is brought into contact with an aqueous alkali solution to perform regeneration. As the alkaline aqueous solution, an aqueous solution of an alkali hydroxide such as sodium hydroxide or potassium hydroxide of 7 to 10% by weight which has been conventionally used as a regenerant for an anion exchange resin is preferable, but another alkaline aqueous solution may be used. The conditions for the regeneration are the same as in the conventional regeneration of the anion exchange resin. In the case of column water flow, after chemical injection with an alkaline aqueous solution, extrusion with the same amount of pure water is performed, and further washing with pure water is performed. The amount of alkaline aqueous solution used is NaOH
It is preferably 10 to 200 g, preferably 40 to 80 g, per liter of resin in conversion. The flow rate during chemical injection and extrusion is SV ⁰ to 50 hr ^-1 , preferably 3 to 10 h.
r ^-1 , the flow rate during washing is 0 to 50 hr ^-1 , preferably 3 to 50 hr ^-1 .
It can be 10 hr ^-1 .

Regeneration is carried out at 40-60 ° C., preferably 45-5 ° C.
It is preferable to use an alkaline aqueous solution heated to 5 ° C. Elution of boron is sufficiently performed by regeneration at room temperature,
Elution of silica (SiO ₂ ), which is exchange-adsorbed to an anion exchange resin together with boron, proceeds efficiently under heating. If silica remains in the resin even when boron is completely eluted by regeneration, the ion exchange capacity of the anion exchange resin will not be completely restored, and the boron removal rate in the next ion exchange step will decrease. In order to prevent this, silica is efficiently eluted by regenerating with the alkaline aqueous solution heated as described above, whereby the regenerating efficiency is increased and the ion exchange capacity of the resin can be increased.

It is preferable that the heating and regeneration be performed from the beginning of the regeneration. For this purpose, it is preferable to heat the resin by performing the pre-cleaning in the previous step with heated pure water. Since the extrusion of the chemical injection liquid has a strong nature of the continuation of the chemical injection, it is preferable to perform the extrusion with similarly heated pure water,
Subsequent washing does not require heating because of the strong nature of washing away the eluted components. When the amount of boron and other components in the washing wastewater becomes equal to or less than the set value, the flow of the washing water is stopped, the regeneration step is terminated, and the process returns to the ion exchange step to treat the boron-containing water, and this is repeated.

By pre-washing the anion exchange resin with pure water prior to regeneration as described above, the raw water present around the resin can be replaced with pure water. This eliminates the hardness component, so that even if a high-concentration aqueous alkaline solution is passed through to regenerate the resin, no insoluble substances such as magnesium hydroxide are precipitated in the resin layer. Therefore, the pressure loss does not increase in the next ion exchange step, and the treatment of the boron-containing water can be continued for a long time.

As described above, since there is no precipitation of magnesium hydroxide or the like, it is not necessary to remove the hardness component with the cation exchange resin prior to the treatment with the anion exchange resin. Therefore, boron can be removed with the anion exchange resin alone. , Makes the process easier. Moreover, there is no need to use an expensive boron-selective adsorption resin as the anion exchange resin, a general-purpose anion exchange resin can be used, and the regeneration can be performed at a low cost because the single-stage regeneration with an alkaline aqueous solution is possible. it can.

Further, by performing regeneration of the anion exchange resin under heating, the silica can be efficiently eluted and the regeneration efficiency can be increased. By performing pre-washing under heating, the regeneration efficiency can be further improved. In addition, the boron removal rate in the next ion exchange step can be increased. Further, by removing boron in the ion exchange step without returning the effluent to the ion exchange step, the boron removal rate can be increased.

[0022]

As described above, according to the present invention, a pre-cleaning step with pure water is provided before the regeneration step, so that boron can be removed by using a general anion exchange resin alone. The regeneration step is simple and can be performed at low cost.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing a method for removing boron-containing water according to the embodiment. In FIG. 1, reference numeral 1 denotes a pretreatment device, which uses an MF membrane separation device or a UF membrane separation device. Reference numeral 2 denotes a pretreatment water tank, and reference numeral 3 denotes an ion exchange device on which an anion exchange resin layer 4 is formed. 5 is a treated water tank, 6 is a desalination device, and a reverse osmosis membrane separation device is used. 8 and 9 are heaters.

The method for treating boron-containing water according to the embodiment is performed as follows. First, raw water 11 consisting of boron-containing water
Is introduced into the pretreatment device 1 to perform membrane separation using an MF membrane or a UF membrane to remove impurities such as turbidity and high molecular organic matter into the concentrated solution 1.
After being concentrated to the second side and discharged, the permeated liquid 13 is stored in the pretreatment water tank 2. In the ion exchange step, the pretreated water 14 in the pretreated water tank 2 is introduced into the ion exchange device 3, passed through the anion exchange resin layer 4 to exchange and adsorb boron, and the treated water 15 is stored in the treated water tank 5. The treated water 16 in the treated water tank 5 is introduced into the desalination device 6 and subjected to membrane separation by a reverse osmosis membrane to be desalted.
The concentrate 17 containing salt and other impurities is discharged. The desalinated water 18 desalinated by the desalination device 6 is stored in the pure water tank 7 as pure water. The pure water 19 in the pure water tank 7 is sent to the use point as recovered water.

When the anion exchange resin layer 4 is saturated with boron, the supply of the pretreatment water 14 is stopped, the ion exchange step is completed, and the process proceeds to the precleaning step. During this time, the raw water 11 may be stopped, or the pretreatment water may be stored in the pretreatment water tank 2 by continuing the liquid supply. Further, the treated water in the treated water tank 5 may be sent to the desalination device 6 to continue the desalination. In the pre-cleaning step, after draining the ion exchange device 3, or without performing it, pure water 21 in the pure water tank 7 is sent as pre-cleaning water, and if necessary, heated to 40 to 60 ° C. by the heater 8 to perform ion exchange. The raw water in the ion exchange device 3 is introduced into the device 3, and the raw water in the ion exchange device 3 is replaced with pure water, which is pre-cleaning water. When heating is performed by the heater 8, the anion exchange resin layer 4 is also heated.

After stopping the supply of the pre-cleaning water and completing the pre-cleaning step, the process proceeds to the regeneration step. In the regeneration step, an alkaline aqueous solution 23 is supplied, and if necessary, the mixture is heated to 40 to 60 ° C. by the heater 9 and introduced into the ion exchange device 3, passed through the anion exchange resin layer 4, and exchange-adsorbed boron and other anions. And the drainage liquid 22 is discharged. Thereby, the anion exchange resin layer 4 is regenerated to the OH form. When heating is performed by the heater 9, the silica is eluted efficiently and the regeneration efficiency is increased. After the chemical injection with the alkaline aqueous solution 23, the extruding is performed by feeding the pure water 21 at the same flow rate as in the case of the chemical injection, and then the cleaning is performed by increasing the flow rate.

After the end of the regeneration step, the ion exchange step of the ion exchange device 3 is restarted. In this case, since the pre-washing step replaces the raw water present around the resin of the anion exchange resin layer 4 with pure water and has no hardness component, even if the regeneration is performed with an aqueous alkali solution, an insoluble substance such as magnesium hydroxide is used. No precipitation and no increase in pressure loss. For this reason, ion exchange after restart is also performed efficiently, and boron is removed at a high removal rate. Further, when heating is performed in the washing and regeneration steps, silica is eluted and the regeneration efficiency is high, so that the boron removal rate is high. In the ion exchange step, by performing the treatment without returning the treated water 15 or 16 of the ion exchange device 3 to the pretreatment water tank 2, the boron removal rate can be maintained high.

In the above method, as the pretreatment device 1, an impurity removing means such as a coagulation separation device or a filtration device can be adopted instead of the membrane separation device. Desalination device 6
Also, an ion exchange device and other desalting means can be employed.

[0029]

EXAMPLES Examples of the present invention and comparative examples will be described below. In the following Examples and Comparative Examples, treatment was performed using the water-containing boron-containing water shown in Table 1.

[0030]

[Table 1]

Example 1 In the ion exchange step, raw water having a quality shown in Table 1 (boron-containing water) was applied to the OH type anion exchange resin layer by SV7.5 hr.
^Water was passed at ^-1 to exchange and adsorb boron. At the stage when the anion exchange resin is saturated with boron, the ion exchange process is completed and the process is shifted to the washing process, and pure water at 50 ° C. is added at SV 7.5 hr ⁻¹ for 2 hours.
Washing was performed by passing water for 0 minutes. Then move on to the regeneration process,
A 4% aqueous solution of sodium hydroxide at 50 ° C. was passed through the system at SV 3 hr ⁻¹ for 20 minutes to perform chemical injection, and then pure water at 50 ° C. was added to the SV.
Perform extrusion was 20 minutes through the water at 3 hr ^-1, to complete the regeneration process was washed further with pure water at room temperature for 20 minutes through the water at SV6hr ^-1. Thereafter, the ion exchange step was restarted and the raw water was supplied to remove boron. FIG. 2 shows a change in the pressure loss (Δp) of the treated water at this time, and FIG. 3 shows a change in the boron concentration.

Comparative Example 1 FIG. 2 shows changes in pressure loss (Δp) when regeneration was performed without performing pre-cleaning in Example 1.

Example 2 FIG. 3 shows a change in the concentration of boron in treated water when ion-exchange is performed by circulating all of the treated water in the ion exchange device in Example 1.

Example 3 FIG. 3 shows the change in the concentration of treated water boron when the pre-cleaning water was not heated in Example 2.

From the results shown in FIG. 2, it can be seen that in the case of regenerating without pre-cleaning (Comparative Example 1), the increase in pressure loss is so great that it is difficult to continue ion exchange. Example 1) shows no increase in pressure loss, indicating that ion exchange can be continued. Further, from the results of FIG. 3, the increase in the boron concentration is higher in the case where the treated water is not returned (Example 1) than in the case where the treated water in the ion exchange step is returned to the ion exchange step (Examples 2 and 3). Less,
Also, it can be seen that the increase in the boron concentration is smaller when heating is performed (Example 2) than when heating is not performed in the pre-cleaning (Example 3).

[Brief description of the drawings]

FIG. 1 is a flowchart of a processing method according to an embodiment.

FIG. 2 is a graph showing a change in Δp in an example and a comparative example.

FIG. 3 is a graph showing a change in boron concentration in an example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pretreatment device 2 pretreatment water tank 3 ion exchange device 4 anion exchange resin layer 5 treatment water tank 6 desalination device 7 pure water tank 8, 9 heater

Claims (3)

[Claims] An ion exchange step of exchanging and adsorbing boron by bringing boron-containing water into contact with an anion exchange resin; a pre-washing step of pre-washing the anion exchange resin having adsorbed and adsorbed boron with pure water; A regenerating step of regenerating the washed anion exchange resin by bringing the anion exchange resin into contact with an aqueous alkali solution, the method comprising the steps of: 2. The temperature of pure water in the pre-cleaning step is 40 to 60 ° C.
The method of claim 1, wherein 3. The method according to claim 1, wherein the alkaline aqueous solution in the regeneration step
The method according to claim 1 or 2, wherein the temperature is -60 ° C.