JP7638808B2 - How to remove boron - Google Patents

Description

The present invention relates to a method for removing boron from water.

In recent years, ultrapure water with a boron concentration of 1 ng/L or less has been required for silicon cleaning processes and the like during semiconductor manufacturing.
As a method for reducing the boron concentration in water, a method using a boron-selective ion exchange resin has been proposed. For example, Patent Document 1 proposes a method for removing boron by contacting pretreated water with a boron-selective ion exchange resin at a position within a pure water or ultrapure water production facility.

Japanese Patent Application Publication No. 8-84986

However, the inventors' investigations revealed that when attempting to treat boron in water using the boron-selective ion exchange resin described in Patent Document 1, etc., the total organic carbon (TOC) concentration in the treated water tends to increase compared to before treatment.

Further investigation by the present inventors revealed that the increase in the total organic carbon concentration is caused by the elution of hydrocarbons remaining in the ion exchange resin, and that in particular, when an ion exchange resin having glucamine groups is used as the boron-selective ion exchange resin, unreacted glucamine remaining in the ion exchange resin is eluted, which tends to increase the total organic carbon concentration in the treated water.

In this situation, the present invention aims to provide a method for effectively removing boron from the treated water while suppressing an increase in the total organic carbon concentration.

As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that the above-mentioned technical problems could be solved by contacting the water to be treated with a specific boron-selective ion exchange resin having glucamine groups under specific conditions, and completed the present invention based on this finding.

That is, the present invention provides
The present invention provides (1) a method for removing boron, which comprises passing water to be treated having a boron content of 500 μg/L or less through a boron-selective ion exchange resin having glucamine groups and releasing 10 μg/L or less of total organic carbon at a liquid hourly space velocity (SV) of 60 to 700 h ^-1; and (2) the method for removing boron as described in (1) above, in which the boron-selective ion exchange resin has been pretreated by contacting it with an aqueous caustic soda solution.

The present invention provides a method for effectively removing boron from treated water while suppressing an increase in the total organic carbon concentration.

The method for removing boron according to the present invention is characterized in that water to be treated, which has a boron content of 500 μg/L or less, is passed through a boron-selective ion exchange resin having glucamine groups and releasing a total organic carbon amount of 10 μg/L or less, at a liquid hourly space velocity (SV) of 60 to 700 ^h-1 .

In the present invention, the boron content in the water to be treated is 500 μg/L or less, preferably 100 μg/L or less, and more preferably 50 μg/L or less.
Although there is no particular lower limit for the boron content in the water to be treated in the present invention, the boron content in the water to be treated is usually 50 ng/L or more.

In the present invention, by setting the boron content in the treated water to 500 μg/L or less, the boron content in the treated water can be more effectively reduced while suppressing breakthrough of the boron-selective ion exchange resin.

In addition, in this application document, the boron content in the water refers to the value measured using an ICP-MS 8900 manufactured by Agilent Technology.

In the present invention, the water to be treated preferably has a pH of 5-9, more preferably 6-8.
In the present invention, the pH of the water to be treated may be appropriately adjusted before being contacted with the boron-selective ion exchange resin.

In the present invention, examples of the water to be treated include water used for cleaning silicon during semiconductor manufacturing.

In the present invention, the treated water is passed through a boron-selective ion exchange resin that has glucamine groups and releases 10 μg/L or less of total organic carbon.

In the present invention, the boron-selective ion exchange resin having a glucamine group is capable of selectively adsorbing boron by introducing a glucamine group as a chelating group (chelating group) that easily forms a chelate bond with boron, instead of the ion exchange group in the ion exchange resin.

In the present invention, the boron-selective ion exchange resin is not particularly limited as long as it is an ion exchanger having a predetermined total organic carbon release amount in which glucamine groups have been introduced into a resin substrate, and various forms such as powder, beads, and membranes can be used, and it may be either a gel-type ion exchange resin or a porous-type ion exchange resin.

Gel-type ion exchange resins and porous-type ion exchange resins are classified based on the microstructure of the ion exchange resin. Of these, gel-type ion exchange resins are ion exchange resins based on the solvent-free polymerization of styrene and divinylbenzene, and have a non-uniformly cross-linked gel-like structure; they are the most classical type of ion exchange resin.

Porous ion exchange resins refer to ion exchange resins based on resins in which macropores with pore sizes of about 20 nm to 100 nm are formed by using a solvent during polymerization, and include those known as MR types. Porous ion exchange resins can be used in non-aqueous systems because even solvents with low polarity can penetrate into the resin, and since the macropores are not continuous and lack uniformity, they have a lower ion exchange capacity than gel-type resins, but they have high physical strength and excellent resistance to osmotic pressure and mechanical pressure.

In the present invention, the substrate to which the glucamine group, which is the chelating group, is bonded is preferably one or more selected from styrene-based compounds such as cross-linked polystyrene and styrene-divinylbenzene copolymer, condensates of phenols and aldehydes, cross-linked polyacrylic acid, etc., and more preferably cross-linked polystyrene or styrene-divinylbenzene copolymer.

In the present invention, the boron-selective ion exchange resin to which the glucamine group, which is a chelating group, is bonded is preferably an MR type ion exchange resin based on a styrene-divinylbenzene copolymer.

In the present invention, the glucamine group, which is the chelating group, is not particularly limited, but is preferably an N-alkylglucamine group, and more preferably an N-methylglucamine group.

In the present invention, the boron-selective ion exchange resin having glucamine groups has a total organic carbon release rate of 10 μg/L or less, and more preferably 5 μg/L or less.

In this application, the total organic carbon release amount means the amount of total organic carbon (TOC) (μg/L) in the effluent water when test water having a total organic carbon (TOC) of 1.0 μg/L or less is passed through a boron-selective ion exchange resin having glucamine groups at room temperature and a liquid hourly space velocity (SV) of 50 hr ^- 1 for 24 hours.

In addition, in this application document, the total organic carbon (TOC) concentration in water refers to the value measured using a Sievers M9e manufactured by Suez.

In the present invention, by using a specific boron-selective ion exchange resin that has a glucamine group and releases total organic carbon within the above range, boron in the treated water can be effectively removed while suppressing an increase in the total organic carbon concentration.

In the present invention, the boron-selective ion exchange resin having glucamine groups may be pretreated by contacting it with an aqueous solution of caustic soda.
In the present invention, the boron-selective ion exchange resin having glucamine groups is pretreated by contacting it with an aqueous caustic soda solution, so that it is easy to provide one having a desired total organic carbon release amount.

In the present invention, when the boron-selective ion exchange resin having glucamine groups is pretreated by contacting it with an aqueous caustic soda solution, it is preferable to carry out the pretreatment under the following conditions (1) to (3).
(1) 3 to 5 L/LR of 1N NaOH aqueous solution is passed through a boron-selective ion exchange resin at a liquid hourly space velocity (SV) of 4 hr ^-1 .
(A 1N NaOH aqueous solution is passed through the boron-selective ion exchange resin in an amount 3 to 5 times the volume of the boron-selective ion exchange resin so that the ratio of "volume of NaOH aqueous solution passed through per hour/volume of boron-selective ion exchange resin" is 4.)
(2) Next, 1.5 L/LR of ultrapure water or pure water is passed through the boron-selective ion-exchange resin at a liquid hourly space velocity SV=4 hr ⁻¹ to push out the NaOH remaining in the boron-selective ion-exchange resin.
(3) After that, 10 to 20 L/LR of ultrapure water or pure water is passed through the boron-selective ion exchange resin at a liquid hourly space velocity SV=10 hr ⁻¹ to wash it.

In the present invention, when the boron-selective ion exchange resin having glucamine groups is pretreated by contacting it with an aqueous caustic soda solution, it is more preferable to pretreat it under the following conditions (i) to (iii) prior to the pretreatment under the above conditions (1) to (3).
(i) 3 to 5 L/LR of 1N HCl aqueous solution is passed through a boron-selective ion exchange resin at a liquid hourly space velocity, SV, of 4 hr ⁻¹ .
(A 1N HCl aqueous solution in an amount 3 to 5 times the volume of the boron-selective ion exchange resin is passed through so that the ratio of "volume of HCl aqueous solution passed through per hour/volume of boron-selective ion exchange resin" is 4).
(ii) Next, 1.5 L/LR of ultrapure water or pure water is passed through the boron-selective ion-exchange resin at a liquid hourly space velocity SV=4 hr ⁻¹ to push out the HCl remaining in the boron-selective ion-exchange resin.
(iii) Thereafter, 10 to 20 L/LR of ultrapure water or pure water is passed through the boron-selective ion exchange resin at a liquid hourly space velocity SV=10 hr ⁻¹ to wash it.

In this application, pure water means water with an electrical resistivity of 1 to 18 MΩ·cm as measured by a Foxboro in-line resistivity meter, and ultrapure water means water with an electrical resistivity of more than 18.0 MΩ·cm as measured by a Foxboro in-line resistivity meter.

In the present invention, the boron-selective ion exchange resin having glucamine groups and releasing 10 μg/L or less of total organic carbon may be a commercially available product, and an example of such a boron-selective ion exchange resin is ORLITE X-U653J manufactured by Organo Corporation.

In the present invention, the shape of the boron-selective ion exchange resin having glucamine groups is not particularly limited, but for example, if it has a granular shape, the average particle size is preferably 0.2 to 1.0 mm, and more preferably 0.4 to 0.8 mm.

In the present invention, the liquid hourly space velocity SV ("volume of water to be treated passed per hour/volume of boron-selective ion exchange resin") when the water to be treated is passed through the boron-selective ion exchange resin is 60 to 700 hr ^-1 , preferably 75 to 600 hr ^-1 , more preferably 90 to 600 hr ^-1 , and even more preferably 100 to 250 hr ^-1 .

In the present invention, by controlling the liquid hourly space velocity (SV) within the above range when the water to be treated is passed through the boron-selective ion exchange resin, it is possible to effectively remove boron from the water to be treated while suppressing an increase in the total organic carbon concentration.

Conventionally, it has been believed that when water to be treated is passed through a boron-selective ion exchange resin, boron in the water to be treated cannot be sufficiently removed unless the liquid hourly space velocity, SV, is controlled to about 50 hr ^- 1 or less. However, according to the studies of the present inventors, it has been found that when a boron-selective ion exchange resin having glucamine groups and releasing a total organic carbon amount of 10 μg/L or less is used, boron in the water can be sufficiently removed and an increase in the total organic carbon concentration can be controlled even when the liquid hourly space velocity, SV, of the water to be treated is increased to 60 to 700 hr ^-1 , and this has led to the completion of the present invention.

If the liquid hourly space velocity SV when the water to be treated is passed through the boron-selective ion exchange resin is less than 60 hr ^- 1, it is not possible to suppress an increase in the total organic carbon concentration in the treated water. If the liquid hourly space velocity SV when the water to be treated is passed through the boron-selective ion exchange resin is more than 700 hr ^-1 , it becomes difficult to sufficiently suppress the boron content in the treated water.

In the present invention, the boron-selective ion exchange resin that has been passed through a certain amount of treated water can be regenerated by passing a regenerant through it to elute the adsorbed matter, after which the resin is backwashed as necessary. By passing the regenerant through the resin, a regenerated waste liquid containing a high concentration of boron is produced.
The regenerant may include sodium hydroxide.

The present invention provides a method for effectively removing boron from treated water while suppressing an increase in the total organic carbon concentration.

(Example)
The present invention will now be described in more detail with reference to examples, but these are merely illustrative and do not limit the present invention.

Example 1
A boron adsorption column was packed with 500 mL (500 mL-R) of boron-selective ion exchange resin "ORLITE X-U653" (total organic carbon release amount 4 μg/L) manufactured by Organo Corporation, and treated water with a boron concentration of 50 μg/L and a total organic carbon concentration of 2 μg/L was passed through the column for 24 hours at a liquid hourly space velocity SV of 100 hr ^-1 . The boron content (μg/L) and total organic carbon content (μg/L) in the treated water obtained at this time were measured. The results are shown in Table 1.

(Examples 2 to 3, Comparative Examples 1 and 2)
The water to be treated, which had a boron concentration of 50 μg/L and a total organic carbon concentration of 2 μg/L, was passed through the boron adsorption column at a liquid hourly space velocity, SV, of 250 hr ^-1 (Example 2), 500 hr ^-1 (Example 2), 50 hr ^-1 (Comparative Example 1), and 1000 hr ^-1 (Comparative Example 2), respectively, in the same manner as in Example 1. The boron amount (μg/L) and the total organic carbon amount (μg/L) in the treated water were measured. The results are shown in Table 1.

(Comparative Example 3)
The water to be treated, which had a boron concentration of 50 μg/L and a total organic carbon concentration of 2 μg/L, was passed through a boron adsorption column packed with 500 mL (500 mL-R) of boron-selective ion exchange resin "DIAION CRB03" (manufactured by Mitsubishi Chemical Corporation) (total organic carbon release amount of 80 μg/L) for 24 hours at a liquid hourly space velocity (SV) of 50 hr ^-1 .
The boron content (μg/L) and total organic carbon content (μg/L) in the treated water were measured. The results are shown in Table 2.

(Comparative Example 4)
The boron adsorption column was passed through with the water to be treated, which had a boron concentration of 50 μg/L and a total organic carbon concentration of 2 μg/L, at a liquid hourly space velocity (SV) of 100 hr ^-1 , in the same manner as in Example 4. The boron amount (μg/L) and the total organic carbon amount (μg/L) in the treated water were measured. The results are shown in Table 2.

(Comparative Example 5)
(1) Pretreatment of boron-selective ion exchange resin Mitsubishi Chemical Corporation's boron-selective ion exchange resin "DIAION CRB03" (total organic carbon release amount 80 μg/L) was pretreated in advance by contacting with an aqueous caustic soda solution by the following methods (i) to (iii). By the methods (i) to (iii), the total organic carbon release amount of the above-mentioned ion exchange resin became 10 μg/L or less.
(i) 4 L/LR of 1N NaOH aqueous solution was passed through a boron-selective ion exchange resin at a liquid hourly space velocity SV=4 hr ⁻¹ .
(ii) Next, 1.5 L/LR of ultrapure water was passed through the boron-selective ion-exchange resin at a liquid hourly space velocity SV of 4 hr ^-1 to push out the NaOH remaining in the boron-selective ion-exchange resin.
(iii) Thereafter, 15 L/LR of ultrapure water was passed through the boron-selective ion exchange resin at a liquid hourly space velocity SV=10 hr ⁻¹ to wash it.
(2) Treatment of treated water The treated water having a boron concentration of 50 μg/L and a total organic carbon concentration of 2 μg/L was passed through a boron adsorption column packed with 500 mL (500 mL-R) of the boron-selective ion exchange resin obtained by the above pretreatment for 24 hours at a liquid hourly space velocity (SV) of 50 hr ^-1 .
The boron content (μg/L) and total organic carbon content (μg/L) in the treated water were measured. The results are shown in Table 2.

Example 5
The water to be treated, which had a boron concentration of 50 μg/L and a total organic carbon concentration of 2 μg/L, was passed through the boron adsorption column in the same manner as in Comparative Example 5, except that the liquid hourly space velocity, SV, was changed to 100 hr ^-1 , and the amount of boron (μg/L) and the amount of total organic carbon (μg/L) in the treated water were measured. The results are shown in Table 2.

As can be seen from Tables 1 and 2, in Examples 1 to 5, the treated water having a boron content of 500 μg/L or less was passed through a boron-selective ion exchange resin having glucamine groups and a total organic carbon release amount of 10 μg/L or less at a liquid hourly space velocity (SV) of 60 to 700 h ^-1 . This shows that boron in the treated water can be effectively removed while suppressing an increase in the total organic carbon concentration.
Furthermore, from Table 2, it can be seen that in Example 5, the total organic carbon content in the resulting treated water can be more effectively reduced by pretreating the boron-selective ion exchange resin in advance by contacting it with an aqueous caustic soda solution.

On the other hand, from Tables 1 and 2, it can be seen that in Comparative Examples 1 to 3 and 5, the liquid hourly space velocity SV at which the treated water is passed through the boron-selective ion exchange resin is outside the range of 60 to 700 h ^-1 , and therefore the total organic carbon amount in the resulting treated water is high (Comparative Example 1, Comparative Example 3, Comparative Example 5) or the boron amount in the resulting treated water is high (Comparative Example 2).

Furthermore, the results of Comparative Example 3 and Comparative Example 4 show that when a boron-selective ion exchange resin with a high total organic carbon content (μg/L) is used, the effect of reducing the total organic carbon content in the treated liquid is low even when the liquid hourly space velocity, SV, is increased from 50 ^hr (Comparative Example 3) to 100 ^hr (Comparative Example 4) (see Table 2). On the other hand, the results of Comparative Example 5 and Example 5 show that when a boron-selective ion exchange resin with a reduced total organic carbon content (μg/L) in the ion exchange resin by pretreatment is used, the total organic carbon content in the treated liquid can be effectively reduced by controlling the liquid hourly space velocity within a predetermined range (see Table 2).

The present invention provides a method for effectively removing boron from treated water while suppressing an increase in the total organic carbon concentration.

Claims (2)

A method for removing boron, comprising passing treated water having a boron content of 500 μg/L or less through a boron-selective ion exchange resin having a glucamine group and a total organic carbon release amount of 10 μg/L or less at a liquid hourly space velocity (SV) of 60 to 700 h ^-1 . 2. The method for removing boron according to claim 1, wherein the boron-selective ion exchange resin is pretreated by contacting it with an aqueous caustic soda solution.