HK1041663B - Method of regenerating ion exchange resin - Google Patents

Description

Method for regenerating ion exchange resin

Technical Field

The present invention relates to a method for regenerating ion exchange resins. More particularly, the present invention relates to a method for regenerating ion exchange resins to minimize the residual impurities.

Background

Aqueous hydrogen peroxide is widely used in various fields, for example, as a component of bleaching agents and chemical polishing solutions for paper or pulp. In recent years, aqueous hydrogen peroxide has been increasingly used in the electronics industry, for example as a cleaner for silicon wafers and for semiconductor manufacturing processes. Therefore, it is required to provide an aqueous hydrogen peroxide solution having high purity and high quality by minimizing the content of various impurities therein.

Hydrogen peroxide is currently prepared almost without exception by the anthraquinone process. The anthraquinone process is carried out as follows: first, an anthraquinone derivative (e.g., 2-alkylanthraquinone) is converted to anthrahydroquinone by hydrogenation in a water-insoluble solvent in the presence of a hydrogenation catalyst. Subsequently, the catalyst is removed and the reaction product is oxidized with air, thereby regenerating not only the original 2-alkylanthraquinone but also hydrogen peroxide. The hydrogen peroxide produced is then extracted from the oxidation product with water to obtain an aqueous solution containing hydrogen peroxide. This process is generally referred to as the anthraquinone autoxidation process. The aqueous hydrogen peroxide solution obtained in this way contains inorganic ion/compound impurities such as Al, Fe, Cr, Na and Si from the material of the apparatus. Therefore, the aqueous hydrogen peroxide solution is purified to remove the impurities, so as to achieve high purity meeting the quality requirement of practical application.

In the electronics industry in particular, very high purity aqueous hydrogen peroxide solutions are required. The aqueous hydrogen peroxide solution is required to have an organic impurity content of not more than 10ppm and a metal ion impurity content of not more than 1 ppb. In order to remove impurities from the aqueous hydrogen peroxide solution, ion exchange resins, chelating resins, adsorption resins, and the like are generally used. When such a resin is used to remove impurities on an industrial scale, a continuous liquid-passing manner (column method) is generally employed to ensure high operation efficiency and removal efficiency.

The spent ion exchange resin is typically regenerated with a regenerant. For example, the anion exchange resin is regenerated by filling the anion exchange resin into a column, and then passing the alkali solution, the acid solution, and the alkali solution again through the anion exchange resin column.

However, a disadvantage of the conventional process is that the regenerant can be mixed with the ion exchange resin, rendering it incapable of sufficiently removing ionic impurities from the aqueous hydrogen peroxide feed. Further, another disadvantage of this conventional method is that grooves are formed in the ion exchange resin layer (this phenomenon is called "channeling") and as a result, most of the regenerant passes through these grooves, the contact of the regenerant with the ion exchange resin is not uniform, resulting in failure to uniformly regenerate the ion exchange resin. Furthermore, in the conventional method of regenerating the ion exchange resin in the previous purification column for purifying the crude aqueous hydrogen peroxide solution, the regenerant remains in the purification column and gradually mixes into the purified aqueous peroxide solution. The conventional method has a drawback in that the ion exchange resin column cannot be used for purification in regenerating the ion exchange resin, reducing the production efficiency of the purified aqueous hydrogen peroxide solution.

Under these circumstances, the present inventors have made extensive and intensive studies to solve the above problems. As a result, it was found that the ion exchange resin used was charged into the regeneration column and regenerated by repeating the steps comprising: the aqueous regenerant solution is sprayed from the top nozzle of the regeneration tower downward through the regeneration tower, and then pure water is passed from the bottom of the regeneration tower upward through the regeneration tower, which not only makes it possible to produce regenerated ion exchange resin with minimized impurity residues, but also makes it possible to uniformly perform regeneration of the ion exchange resin. It has also been found that such regeneration avoids mixing of the regenerant into the purification column and enables efficient purification of the aqueous hydrogen peroxide solution without interrupting the purification process for regeneration. The present invention has been completed based on this finding.

Disclosure of Invention

It is an object of the present invention to provide a process for regenerating ion exchange resins which minimizes the content of impurity residues.

The method for regenerating ion exchange resin of the present invention comprises the steps of:

filling the used ion exchange resin into a regeneration tower;

repeating at least twice the steps comprising: the aqueous regenerant solution was passed down through the regeneration column from the top of the regeneration column and pure water was passed up through the regeneration column from the bottom of the regeneration column.

When the ion exchange resin is regenerated by the conventional method, channeling inevitably occurs, and the ion exchange resin cannot be regenerated uniformly, which adversely affects the ion exchange capacity. In contrast, when the ion exchange resin is regenerated by repeating the above-described downward flow of the regenerant and the subsequent upward flow of ultrapure water, convection of the ion exchange resin occurs in the regeneration column, thereby eliminating the occurrence of channeling, and as a result, the ion exchange resin can be efficiently and uniformly regenerated. By repeating the downward and upward flows, the inside of the ion exchange resin can be washed by repeating the contraction-swelling cycle of the ion exchange resin. Further, in the present invention, the ion exchange resin is regenerated without using the purification column, and the ion exchange resin is regenerated using another column (regeneration column). This avoids mixing of the regenerant into the purification column and does not necessitate interruption of the purification of the aqueous hydrogen peroxide solution.

The regenerant is preferably passed downwardly at a space velocity of 1 to 5/hr, and the ultrapure water is preferably passed upwardly at a space velocity of 10 to 30/hr.

In the regeneration column, the portion which contacts with the ion exchange resin, the regenerant and the ultrapure water is preferably composed of a fluororesin, a vinyl chloride resin or a polyolefin resin.

Drawings

FIG. 1 is a schematic diagram of a process for regenerating ion exchange resins according to the present invention;

FIG. 2 is a sectional view of an inlet for introducing ultrapure water used in the method for regenerating an ion exchange resin of the present invention.

Detailed Description

The method for regenerating an ion exchange resin of the present invention is described in detail below.

The invention is characterized in that the used ion exchange resin is regenerated by repeating the steps comprising: the aqueous regenerant solution was passed down through the regeneration column from the top of the regeneration column and pure water was passed up through the regeneration column from the bottom of the regeneration column.

The invention is illustrated with reference to fig. 1. FIG. 1 is a flow diagram of one embodiment of the process for regenerating ion exchange resins of the present invention. In fig. 1, numerals 10 and 11 represent pipes; numeral 12 represents a regeneration column; numeral 13 represents an upper nozzle; numeral 14 represents a bottom strainer; numeral 15 represents a top strainer.

The used ion exchange resin has been purified from aqueous hydrogen peroxide solution, for example by vacuum suction in the form of a slurry drawn from the purification column. The ion exchange resin is fed to the regeneration column 12 in the form of an aqueous suspension through a strainer 14 mounted at the top of the regeneration column. The aqueous regenerant solution is fed to the ion exchange resin through line 10 from an upper nozzle 13. The aqueous regenerant solution that had passed through the ion exchange resin was then discharged from the bottom strainer. On the other hand, ultrapure water is supplied to the ion exchange resin through a pipe 11 via a bottom strainer 14. Ultrapure water which has passed through the ion exchange resin is then discharged from the top strainer 15.

Referring now specifically to FIG. 1, the aqueous regenerant solution was passed downward from the top of the regeneration column at an SV (space velocity) of 1-5/hr and a BV (bed volume, indicating the volume of liquid used per unit volume of ion exchange resin) of 0.5-1L/L-R (this downward flow pass is referred to as downward flow). Then, the downward flow of the regenerant was stopped, and the ultrapure water was passed upward from the bottom of the regeneration column at an SV of 10 to 30/hr and a BV of 0.1 to 0.5L/L-R (this upward flow passage is referred to as an upward flow). In the present invention, this step including the downward flow and the upward flow is repeated at least twice.

Finally, the ion exchange resin was washed with ultrapure water, specifically by repeating 4 to 9 times the downward flow at 10 to 30/hr SV and BV of 3 to 5L/L-R and then the upward flow at 10 to 30/hr SV and BV of 3 to 5L/L-R. This final washing was performed with 30 to 60 times the volume of ultrapure water per unit volume of the resin.

In this regeneration, the ion exchange resin is subjected to repeated contraction-swelling cycles, whereby the inside of the ion exchange resin can be washed. Furthermore, this also eliminates channeling, allowing the ion exchange resin to be regenerated uniformly throughout.

Referring now to FIG. 2, the ultrapure water is preferably introduced through a side port of the bottom strainer 14. Fig. 2 is a cross-sectional view of the bottom strainer. When the bottom strainer having the side holes as shown in fig. 2 is used, not only can the weight of the ion exchange resin be borne, but also the ultra-pure water can uniformly pass through the ion exchange resin layer. And because of the bearing force of the coarse filter to the weight of the ion exchange resin, a large amount of ion exchange resin can be regenerated at one time.

The space velocity of the aqueous regenerant solution is preferably in the range of 1 to 5/hr, more preferably 1 to 4/hr. The space velocity of ultrapure water passing is preferably in the range of 10 to 30/hr, more preferably 10 to 25/hr.

In the regeneration tower of the present invention, the portions (specifically, the liquid feed pipe and the inner wall of the regeneration tower) which come into contact with the ion exchange resin, the regenerant and the ultrapure water are preferably composed of a fluororesin, a vinyl chloride resin or a polyolefin resin. When these portions are made of these resins, impurities derived from these portions can be prevented from being mixed in.

As the fluororesin, a polytetrafluoroethylene resin (PTFE), a tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer resin, a tetrafluoroethylene/hexafluoropropylene copolymer (FEP), a polychlorotrifluoroethylene resin (PCAFE), a tetrafluoroethylene/ethylene copolymer (ETFE), a polyvinylidene fluoride resin (PVDF), a polyvinyl fluoride resin (PVF), and the like are generally used. When a polyolefin resin is used, polyethylene, polypropylene, or the like can be used.

The resin to be regenerated may be an anion exchange resin or a cation exchange resin. Furthermore, the exchange resin in the regeneration column may also be a mixed bed of an anion exchange resin and a cation exchange resin. In the present invention, it is preferred to use a bed of only one exchange resin.

Cation exchange resins useful in the present invention have H⁺Type cation exchange resins, known as strong acid cation exchange resins. Among the strong-acid cation exchange resins, one having a sulfonate group-introduced network molecular structure is generally selected as H⁺Type cation exchange resin. For example, PK216, SK1B and IR-120B can be used as H described above⁺Type strong acid cation exchange resin.

H⁺Type cation exchange resins are regenerated using conventional aqueous solutions of mineral acids such as sulfuric acid and hydrochloric acid. The concentration of the inorganic acid in the aqueous solution of the regenerating agent is preferably in the range of 5 to 15% by weight, more preferably 5 to 12% by weight. The amount of the regenerant is preferably at least 3 times, more preferably 4 to 12 times, the amount (volume) of the cation exchange resin to be treated.

The regenerant is generally passed downward at an SV (space velocity) of 1-5/hr and a BV of 0.5-1L/L-R. The subsequent ultrapure water washing was carried out at an SV of 10-30/hr and at a BV of 0.5-1L/L-R in an upward direction.

After the regenerant was passed and then the ultrapure water was passed, the regenerated ion exchange resin was sufficiently washed, specifically including downward and upward passes of ultrapure water, and this washing cycle was repeated 4 to 9 times. The ultrapure water is preferably flowed upward at an SV of 10 to 30/hr and a BV of 3 to 5L/L-R, and then flowed downward at an SV of 10 to 30/hr and a BV of 3 to 5L/L-R. The resin per unit volume is preferably washed with 30 to 60 times the volume of ultrapure water.

Using a novel cation exchange resin (Na)⁺Type), it is preferable to first perform the adjustment. This adaptation can be accomplished by first regenerating the new cation exchange resin with an aqueous solution of a mineral acid (aqueous regenerant solution), followed by passing the cation exchange resin with 30-60% by weight aqueous hydrogen peroxide at an SV of 5-40/hr and a BV of 50-100L/L-R, and finally regenerating the cation exchange resin with an aqueous solution of a mineral acid (aqueous regenerant solution).

Anion exchange resins useful in the present invention are exchange resins of carbonate ions, bicarbonate ions, hydroxide ions, fluoride ions and other ions.

Among these anion exchange resins, strongly basic resins are generally available, which are prepared by chloromethylating a crosslinked styrene/divinylbenzene copolymer and then aminating the chloromethylated product with trimethylamine or dimethylethanolamine to form a quaternary ammonium salt; weakly basic resins, including crosslinked styrene/dimethylbenzene copolymers having primary or tertiary amines as exchange groups; it is also possible to use crosslinked acrylic polymer resins comprising tertiary amines as exchange groups; alternatively, pyridine anion exchange resins comprising a polymer of unsubstituted or substituted pyridyl groups may be used. Among them, strongly basic anion exchange resins having quaternary amine groups are preferably used. A number of anion exchange resins with quaternary amine groups are commercially available, representative examples include the Diaion (trade name) PA series (e.g., PA316 and PA416) and SA series (e.g., SA10A and SA20A), and Amberlite (trade name) IRA series (e.g., IRA-400, IRA-410, IRA-900, and IRA-904). These resins are generally commercially available in the form of chloride ions.

The regeneration of the anion exchange resin is appropriately selected depending on the type of the target ion. When the anion exchange resin is in the carbonate ion or bicarbonate form, known carbonates or bicarbonates such as sodium carbonate, sodium bicarbonate, potassium carbonate or potassium bicarbonate can be used as the regenerant. When the anion exchange resin is in the hydroxide ion form, a strong base such as sodium hydroxide or potassium hydroxide is used as the regenerant. And when the anionic resin is in the form of fluoride ions, sodium fluoride, potassium fluoride or ammonium fluoride is used as a regenerant.

When the anion exchange resin is in the hydroxide ion form, the aqueous regenerant solution is suitably selected to have a salt concentration in the range of 2 to 10 weight percent, preferably 2 to 8 weight percent; when the anion exchange resin is in the form of carbonate or bicarbonate ions, the salt concentration of the aqueous regenerant solution is from 5 to 15% by weight, preferably from 5 to 12% by weight; when the anion exchange resin is in the form of fluoride ions, the salt concentration of the aqueous regenerant solution is from 1 to 4% by weight, preferably from 2 to 4% by weight. The amount (volume) of the regenerant is preferably at least 3 times, more preferably 4 to 12 times the amount (volume) of the anion exchange resin to be treated.

The regenerant is generally passed downward at an SV (space velocity) of 1-5/hr and a BV of 0.5-1L/L-R. The subsequent ultrapure water washing was carried out at an SV of 10-30/hr and at a BV of 0.5-1L/L-R in an upward direction.

After the regenerant is passed through and then the ultrapure water is passed through, the regenerated ion exchange resin is sufficiently washed, specifically including downward and upward passes of the ultrapure water, and the washing cycle is repeated 4 to 9 times. The ultrapure water is preferably flowed upward at an SV of 10 to 30/hr and a BV of 3 to 5L/L-R, and then flowed downward at an SV of 10 to 30/hr and a BV of 3 to 5L/L-R. The resin per unit volume is preferably washed with 30 to 60 times the volume of ultrapure water.

Using a novel anion exchange resin (Cl)^-Type), it is preferable to first perform the adjustment. This adaptation can be accomplished by first regenerating a new anion exchange resin (Cl) with a strong aqueous base^-Type), then regenerating with carbonate or bicarbonate water solution,a30-60% by weight aqueous hydrogen peroxide solution cooled to 5 ℃ or lower is then passed through the anion exchange resin at an SV of 5-40/hour and a BV of 50-100L/L-R, and then the anion exchange resin is regenerated with an aqueous carbonate solution or an aqueous bicarbonate solution and an aqueous fluoride solution, both of which may be used as an aqueous regenerant solution, depending on the final purpose.

The ion exchange resin subjected to the regeneration treatment is withdrawn by, for example, vacuum suction, and then subjected to a purification column in the form of an aqueous suspension under pressure through a liquid inlet (not shown). Thus, the ion exchange resin can be used for purifying an aqueous hydrogen peroxide solution.

In the present invention, even if a channel is generated in the ion exchange resin layer, the channel can be eliminated, and the ion exchange resin can be efficiently and uniformly regenerated without uneven regeneration. Further, in the present invention, the inside of the ion exchange resin can be washed. The regeneration of the ion exchange resin is carried out by using an ion exchange resin column (regeneration column) other than the purification column. Therefore, the mixing of the regenerant into the purification column can be avoided without interrupting the purification process of the aqueous hydrogen peroxide solution.

Examples

The present invention is further illustrated below with reference to some examples, which are not to be construed as limiting the scope of the invention.

Here, the metal ion impurities were measured by a flameless atomic absorption spectrometry, an ICP-AES method and an ICP-MS method. ppm, ppb and ppt are all based on weight.

Example 1

To a 60.1% by weight aqueous hydrogen peroxide solution (crude aqueous hydrogen peroxide solution) containing metal ion impurities listed in Table 1, sodium acid pyrophosphate was added so that the concentration of sodium acid pyrophosphate was 0.070 g/l. The mixture was allowed to stand for 3 days for aging and then passed through a filter having an average pore size of 0.1 μm. The ratio of the metal atom of aluminum as the metal ion impurity component to the phosphorus atom as the added sodium acid pyrophosphate component (atomic ratio of Al/P) was 0.039.

The filtered aqueous hydrogen peroxide solution was first passed continuously through a packed H at a Space Velocity (SV) of 15/hr⁺First stage column of cation exchange resin type for mixing aqueous hydrogen peroxide solution with H⁺Type cation exchange resin. Subsequently, this treated aqueous hydrogen peroxide solution was continuously passed through a column packed with an anion exchange resin in the form of fluoride ions at a Space Velocity (SV) of 15/hr to contact the aqueous hydrogen peroxide solution with the anion exchange resin in the form of fluoride ions. Thereafter, the aqueous hydrogen peroxide solution thus treated was cooled to-3 ℃ and then continuously passed through an anion exchange resin column packed with the bicarbonate ion form at a Space Velocity (SV) of 15/hr. Finally, the aqueous hydrogen peroxide solution thus treated was passed continuously at a Space Velocity (SV) of 15/hr and packed with H⁺Second stage column of cation exchange resin of type (II) for reacting aqueous hydrogen peroxide with H⁺Type cation exchange resin.

The above-mentioned used ion exchange resin was regenerated in the following manner.

The regeneration of the ion exchange resin is performed using another ion exchange column (regeneration column) other than the aqueous hydrogen peroxide purification column.

Used reproduction of SK1B as H for the first and second stages⁺Type cation exchange resin. The regeneration is carried out using a 10% by weight aqueous hydrochloric acid solution as a regenerant. The regeneration of the cation exchange resin was carried out by repeating 10 times the procedure comprising passing the aqueous regenerant solution downward through the column at an SV of 2.25/hr and a BV of 0.75L/L-R, stopping the passage of the aqueous regenerant solution, and then passing ultrapure water upward through the column at an SV of 13.2/hr and a BV of 0.3L/L-R. Thereafter, a cycle comprising passing ultrapure water downward through the column at SV of 13.2/hr and at BV of 3.3L/L-R and passing the same upward through the column at SV and BV was repeated 6 times, thereby washing the cation exchange resin with ultrapure water. Thus making H go on⁺Regeneration of the type cation exchange resin.

The spent SA20A regenerated product was used as anion exchange resin in the fluoride form. The regeneration was carried out using 3% by weight of aqueous sodium fluoride Solution (SiF)₆The content is as follows: 100ppm or less) as a regenerant. The cation exchange resin regeneration was carried out by repeating 6 times the steps comprising passing the aqueous regenerant solution downward through the column at an SV of 2.25/hr and a BV of 0.75L/L-R, stopping the passage of the regenerant solution, and passing ultrapure water upward through the column at an SV of 13.2/hr and a BV of 0.3L/L-R. Thereafter, the downward passage of ultrapure water through the column at SV of 13.2/hr and BV of 3.3L/L-R and the upward passage through the column at the same SV and BV were repeated 6 times, thus washing the cation exchange resin with ultrapure water. This regenerates the fluoride ion anion exchange resin.

The spent SA20A regenerated product was used as the bicarbonate ion form of the anion exchange resin. Specifically, the used anion exchange resin is first regenerated with sodium hydroxide. As regenerant, 5% by weight aqueous sodium hydroxide solution was used. The regeneration of the anion exchange resin was carried out by repeating 6 times the steps comprising passing the aqueous regenerant solution downward through the column at an SV of 2.25/hr and a BV of 0.75L/L-R, stopping the passage of the aqueous regenerant solution, and passing ultrapure water upward through the column at an SV of 13.2/hr and a BV of 0.3L/L-R. Thereafter, the cycle comprising passing ultrapure water downward through the column at SV of 13.2/hr and at BV of 3.3L/L-R and passing upward through the column at the same SV and BV was repeated 5 times.

Subsequently, the anion exchange resin was regenerated with aqueous sodium bicarbonate. An aqueous solution of 8% by weight of sodium hydrogencarbonate was used as a regenerant. The anion exchange resin regeneration was carried out by repeating 12 times the steps comprising passing the aqueous regenerant solution downward through the column at an SV of 2.25/hr and a BV of 0.75L/L-R, stopping the passage of the aqueous regenerant solution, and passing ultrapure water upward through the column at an SV of 13.2/hr and a BV of 0.3L/L-R. Thereafter, the downward passage of ultrapure water through the column at SV of 13.2/hr and BV of 3.3L/L-R and the upward passage through the column at the same SV and BV were repeated 6 times, thus washing the cation exchange resin with ultrapure water. This concludes the regeneration of the bicarbonate form anion exchange resin.

The ion exchange resins regenerated as described above were filled in the form of slurry into the purification columns.

After the completion of the passage of the aqueous hydrogen peroxide solution through the ion exchange resin column, a sample of a purified aqueous hydrogen peroxide solution from which most of impurities were removed was taken, diluted with ultrapure water, and the concentration of the aqueous hydrogen peroxide solution was adjusted to 31% by weight.

The metal ion impurity concentration of the obtained purified aqueous hydrogen peroxide solution was measured by a flameless atomic spectrometry method and an ICP-MS method. On the other hand, the metal ion impurity concentration of the aqueous hydrogen peroxide feed was measured by a flameless atomic spectrometry method and an ICP-AES method.

The results are shown in Table 2.

TABLE 1

Metal impurity content in aqueous hydrogen peroxide feed

Impurities	Analytical value (ppb)
		Al	770
Cu	0.2
		Fe	4.5
K	132
		Na	15160
Pb	2
		Ca	0.6
Mg	0.6

TABLE 2

The content of metal ion impurities in the prepared purified aqueous hydrogen peroxide solution

	Determination Limit (ppt)	Measured value (ppt)		Determination Limit (ppt)	Measured value (ppt)
						Ag	0.5	ND	Mg	0.2	ND
Al	0.2	0.2	Mn	0.3	ND
						As	2	ND	Mo	0.3	ND
Au	0.2	ND	Na	0.5	ND
						B	4	ND	Nb	0.1	ND
Ba	0.1	ND	Ni	0.7	ND
						Be	5	ND	Pb	0.1	ND
Bi	0.2	ND	Pd	0.3	ND
						Ca	2	ND	Pt	0.2	ND
Cd	0.3	ND	Sb	0.3	ND
						Co	1	ND	Si	50	ND
Cr	1	1	Sn	0.8	ND
						Cu	0.5	ND	Sr	0.05	ND
Fe	0.5	0.7	Ta	0.1	ND
						Ga	0.5	ND	Ti	2	ND
Ge	2	ND	Tl	0.1	ND
						In	0.1	ND	V	1	ND
K	2	ND	Zn	2	ND
						Li	0.02	ND	Zr	0.1	0.1

ND: meaning that the amount of metal impurities is below the limit of the assay.

Comparative example 1

Purification of an aqueous hydrogen peroxide solution was carried out in the same manner as in example 1 except that an ion exchange resin regenerated in the following manner was used. The resulting purified aqueous hydrogen peroxide solution had metal ion impurity concentrations, Na ion, K ion and Al ion concentrations as high as 120ppt, 60ppt and 100ppt, respectively.

Regeneration of ion exchange resins

Used reproduction of SK1B as H for the first and second stages⁺Type cation exchange resin. The regeneration was carried out using 10% by weight of aqueous hydrochloric acid as regenerant. The aqueous regenerant solution was passed downward through the column at an SV of 2.25/hr and a BV of 4L/L-R, and then ultrapure water was passed upward through the column at an SV of 13.2/hr and a BV of 40L/L-R, to conduct ultrapure water washing. Thus obtaining regenerated H⁺Type cation exchange resin.

The spent SA20A regenerated product was used as anion exchange resin in the fluoride form. The regeneration was carried out using 3% by weight of aqueous sodium fluoride Solution (SiF)₆The content is as follows: 100ppm or less) as a regenerant. The aqueous regenerant solution was passed downward through the anion exchange resin at an SV of 2.25/hr and a BV of 4.5L/L-R, and then ultrapure water was passed upward at an SV of 13.2/hr and a BV of 40L/L-R, to conduct ultrapure water washing. Thus, a regenerated anion exchange resin in the form of fluoride ions is obtained.

The spent SA20A regenerated product was used as the anion exchange resin in the bicarbonate ion form. The regeneration was carried out by first using a 5% by weight aqueous solution of sodium hydroxide as a regenerant. The aqueous regenerant solution was passed downward through an anion exchange resin at SV of 2.25/hr and BV of 4.5L/L-R, after which ultrapure water was passed upward at SV of 13.2/hr and BV of 40L/L-R, and washing with ultrapure water was conducted. Subsequently, the anion exchange resin was regenerated with aqueous sodium bicarbonate. The aqueous regenerant solution was passed downward through an anion exchange resin at SV of 2.25/hr and BV of 4.5L/L-R, after which ultrapure water was passed upward at SV of 13.2/hr and BV of 40L/L-R, and washing with ultrapure water was conducted. Thus, a regenerated anion exchange resin in the form of bicarbonate ions is obtained.

The regenerated ion exchange resins are filled into the purification columns as a slurry.

Claims (2)

1. A process for regenerating an ion exchange resin used for purifying a crude aqueous hydrogen peroxide solution, comprising the steps of:

filling the used ion exchange resin in a regeneration tower;

repeating at least twice the following steps: passing the aqueous regenerant solution through the regeneration tower from the top thereof downward, then passing ultrapure water through the regeneration tower from the bottom thereof upward, and then washing the ion exchange resin with water;

wherein the aqueous regenerant solution is passed through the regeneration column from the top thereof downward at a space velocity of 1 to 5/hr and a bed volume of 0.5 to 1L/L-R, and the ultrapure water is passed through the regeneration column from the bottom thereof upward at a space velocity of 10 to 30/hr and a bed volume of 0.1 to 0.5L/L-R.

2. The method according to claim 1 or 2, wherein in the regeneration tower, portions which are in contact with the ion exchange resin, the regenerant and the ultrapure water are each composed of a fluororesin, a vinyl chloride resin or a polyolefin resin.