JP5311227B2 - Anion exchanger, its pretreatment method and regeneration method, and purification method and purification apparatus of alkaline aqueous solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anion exchanger whereby metal impurities contained in an aqueous alkali solution thereof can be eliminated rapidly by a simple method, and to provide a method and a device for refining an alkali aqueous solution using the anion exchanger. <P>SOLUTION: The method for refining an alkali aqueous solution includes a pre-treated anion exchanger having been prepared by a process of bringing an anion exchanger into contact with a high concentration alkaline which removes impurities contained in an anion exchanger by making into contact with a high concentration alkali treating liquid being not lower than 5.0 N, and a device 1 for refining an alkali aqueous solution using the anion exchanger 3, and a process of removing metal impurities in an alkali aqueous solution containing the metal impurities by using the anion exchanger. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an anion exchanger capable of removing metal impurities contained in an alkaline aqueous solution to a very low concentration, a pretreatment method and a regeneration method thereof, and a purification method and purification of an alkaline aqueous solution using the anion exchanger. Relates to the device.

  Alkaline aqueous solution is used in the polishing process for the purpose of pH adjustment and buffering together with an abrasive such as colloidal silica, which is used to remove a work-affected layer generated when manufacturing a silicon wafer, and wet after the polishing process. Often used for cleaning. At this time, sodium hydroxide aqueous solution or potassium hydroxide aqueous solution is used for alkali etching, and sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, ammonia, sodium carbonate, sodium hydrogen carbonate, potassium carbonate or hydrogen carbonate is used for polishing process. An aqueous solution of potassium is used, and an aqueous ammonia solution is used for the washing step.

  Alkaline in such an alkaline aqueous solution, for example, sodium hydroxide is produced by electrolysis of sodium chloride, and the produced sodium hydroxide contains various metals on the order of several ppm. Among these metals, for example, copper and nickel penetrate into the silicon wafer and inhibit surface flattening, such as changing electrical characteristics, so an aqueous alkaline solution containing copper or nickel cannot be used as an etchant. . In addition, calcium, magnesium, manganese, iron, cobalt, zinc, aluminum, lead, and other metals remain difficult to diffuse inside the silicon wafer, but remain as residues on the surface. In addition, when it is contained in a chemical solution or polishing solution in a polishing process, it becomes a load in a subsequent cleaning process.

  Note that metals that easily diffuse into the wafer, such as copper and nickel, are difficult to remove and have a greater influence than metals that remain on the wafer surface, such as calcium, magnesium, manganese, iron, cobalt, zinc, aluminum, and lead. For this reason, the concentration of the metal that is easily diffused sometimes has to be reduced to 1/10 to 1/1000 of the concentration of the metal remaining on the surface.

  Therefore, when an alkaline aqueous solution is used for the above-mentioned use, a purification operation is performed in order to reduce metal impurities. As means for purifying the alkaline aqueous solution, there are a recrystallization method, a distillation method, and the like. However, all of them require considerable heat energy, a large apparatus, and complicated operation management.

  On the other hand, as a means to easily purify an alkaline aqueous solution at low cost, for example, a high-concentration sodium hydroxide aqueous solution containing metal impurities is activated after coconut shell activated carbon is treated with nitric acid to adsorb and remove the metal impurities. A method has been proposed (for example, see Patent Document 1). However, since this method requires the preparation of dedicated activated carbon, it causes an increase in cost, and iron can be refined to about 100 ppb, but copper and nickel can be refined to about 100 ppb to meet the required level. Not reached. Moreover, activated carbon elutes metal impurities such as zinc and aluminum contained in the material, and even if activated with nitric acid, it is difficult to reduce these metal impurities. Therefore, it can be used if the requirement for removing metal impurities in the alkaline aqueous solution is limited to iron, but it becomes difficult to use when there are many items such as copper and nickel.

  Furthermore, as a method for reducing metal impurities contained in an aqueous sodium hydroxide solution, a purification method by electrolysis of an aqueous sodium hydroxide solution using a cation exchange membrane is known (for example, see Patent Document 2). According to the above, it is said that the metal impurity in the sodium hydroxide aqueous solution can be 10 ppb or less. However, this method has the disadvantage that the capital investment is high and the apparatus is complicated, so that the refining cost is high and the operation management is difficult.

  In addition, alkaline aqueous solutions using sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, tetramethylammonium hydroxide, ammonia, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, etc. are not used alone. In addition to other chemicals, for example, it is used as an additive for polishing slurry. However, in order to maintain a high-purity alkaline aqueous solution in which metal impurities are reduced to, for example, 100 ppb or less in a high-purity state up to the use location, a transportation means such as an alkaline aqueous solution manufacturing plant or a tank truck is used. Line the parts that come into contact with the alkaline aqueous solution, such as connection / supply piping and drums / tanks, etc., at the wafer manufacturing factory and semiconductor device manufacturing factory with an expensive material such as fluororesin that has little metal elution, or make the material itself from these materials. Have to do.

JP 2004-344715 A JP 2002-317285 A

  As described above, since the conventional alkaline aqueous solution contains metal impurities, it is a general manufacturing method such as an electrolytic method for use in applications such as a silicon wafer etching, polishing process, and cleaning process. Therefore, it is difficult to use it as it is produced, and it is necessary to use recrystallization, distillation, a cation exchange membrane method or the like. However, these methods are not energy efficient, the apparatus is large and complicated, operation management is not easy, and purification costs are high.

  For this reason, development of a simple method for purifying an alkaline aqueous solution in which metal impurities such as calcium, magnesium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, and lead are minimized is desired.

  Further, only the metal impurities must be selectively removed without changing the concentration of the alkaline aqueous solution as the main component. On the other hand, the present applicant has found that the metal impurities in the alkaline aqueous solution can be selectively removed by using an anion exchanger from the opposite idea to the past, and has already filed an application. (International Application No. PCT / JP2007 / 061710), the anion exchanger used here is the same as the anion exchanger conventionally used in other applications, and such anion exchanger is Although the removal performance of metal impurities is sufficiently high, the initial elution of impurities such as metals, organic substances, oil from the anion exchanger, and unreacted components of chemical substances used during synthesis is a problem when the size is increased. Thus, there has been a demand for a pretreatment method for an anion exchanger having a more efficient removal performance.

  Therefore, the present invention has been made to improve the purification efficiency of an alkaline aqueous solution, and is an alkaline aqueous solution used for applications such as a silicon wafer etching, polishing process, and cleaning process, particularly a high concentration of 20% by mass or more. An object of the present invention is to provide an anion exchanger capable of quickly removing the metal impurities contained in an alkaline aqueous solution having a concentration by a simple method, and a method and an apparatus for purifying an alkaline aqueous solution using the anion exchanger. .

  As a result of intensive studies to solve the above problems, the present inventors have reduced the initial problem of impurity elution by performing specific pretreatment on the anion exchanger that has been used so far. The present invention has been completed by discovering that an anion exchanger having an improved ability to remove metal impurities present in the present invention can be obtained.

  The pretreatment method for an anion exchanger according to the present invention comprises a high concentration alkali contact step of removing impurities contained in the anion exchanger by bringing the anion exchanger into contact with a high concentration alkali treatment liquid of 5.0 N or more. It is characterized by having. The anion exchanger of the present invention is obtained by the pretreatment method for an anion exchanger. The impurities contained in the anion exchanger include metals, organic substances, oils, unreacted components of chemical substances used during synthesis, and the like.

  The method for regenerating an anion exchanger according to the present invention comprises an acid contact step in which a used anion exchanger used for removing metal impurities in an alkaline aqueous solution containing metal impurities is brought into contact with an acid treatment solution. To do.

  In addition, the method for purifying an alkaline aqueous solution of the present invention comprises contacting the anion exchanger obtained by the pretreatment method for an anion exchanger of the present invention with an alkaline aqueous solution containing metal impurities, and then adding a metal impurity in the alkaline aqueous solution. The apparatus for purifying an alkaline aqueous solution of the present invention comprises a metal impurity removing step of removing an anion exchanger obtained by the pretreatment method for an anion exchanger of the present invention and / or It has an anion exchanger obtained by the method for regenerating an anion exchanger according to the present invention.

  According to the anion exchanger of the present invention, the metal impurities contained in the alkaline aqueous solution can be quickly removed by a simple operation. According to the alkaline aqueous solution purification method and apparatus of the present invention using this, the above-mentioned Since an anion exchanger is used, metal impurities can be removed from the alkaline aqueous solution by a simple operation, and the alkaline aqueous solution can be purified efficiently.

  Moreover, the pretreatment method of the anion exchanger of the present invention can convert the conventionally used anion exchanger into an anion exchanger excellent in metal impurity removal performance of the present invention. This anion exchanger regeneration method can restore the function so that the metal impurities can be removed again even if the anion exchanger of the present invention is once used for removing metal impurities.

It is the figure which showed schematic structure in 1st Embodiment of the refiner | purifier of the aqueous alkali solution of this invention. It is the figure which showed schematic structure in 2nd Embodiment of the refiner | purifier of the aqueous alkali solution of this invention. It is the figure which showed schematic structure in 3rd Embodiment of the refiner | purifier of the aqueous alkali solution of this invention. It is the figure which showed schematic structure in 4th Embodiment of the refiner | purifier of the aqueous alkali solution of this invention. It is the figure which showed schematic structure in 5th Embodiment of the refiner | purifier of the aqueous alkali solution of this invention. It is the graph which showed the presence state of nickel ion by the pH change in aqueous solution, and a presence rate. It is the graph which showed the existing state and presence ratio of the copper ion by the pH change in aqueous solution. It is the figure which showed the relationship between the density | concentration (normality) of an alkali treatment liquid, and the impurity removal rate from the anion exchanger by the alkali treatment.

[Anion exchanger]
The anion exchanger before the pretreatment used in the present invention is an anion exchanger that has been conventionally used for water treatment and the like, and any of the anion exchangers having primary to quaternary amine groups. Well, not particularly limited. Further, the anion exchange group is bonded to a solid substrate such as a particle or a fiber, and can be used after being processed into a sheet, a filter, a tube, a plate, or the like. These processed anion exchangers are used by being introduced into a container according to the shape.

  Here, the base material is made of materials such as alkali-resistant synthetic resin fibers and synthetic resin particles, and as the base synthetic resin, polyvinyl alcohol, styrene-divinylbenzene copolymer, polysulfone, polyhydroxymethacrylate, polyethylene ( PE), polypropylene (PP), PFA (copolymer of tetrafluoroethylene and perfluoroalkoxyethylene), and synthetic resins such as polytetrafluoroethylene (PTFE) are exemplified, and any of them can be used. From the viewpoint of price, polyethylene, styrene-divinylbenzene copolymer, polysulfone and the like are preferable. These synthetic resins have high resistance to a high-concentration alkaline aqueous solution, for example, a 50 mass% sodium hydroxide aqueous solution. These can be used either alone or in combination.

（式中のＲ^１及びＲ^２は、水素原子、炭素数１〜４のアルキル基、ヒドロキシルエチル基及びヒドロキシプロピル基の中から選択される同一又は異なる１価の基を示す。）及び第４級アンモニウム基

（式中のＲ^３、Ｒ^４及びＲ^５は、水素原子、炭素数１〜４のアルキル基、ヒドロキシルエチル基及びヒドロキシプロピル基の中から選択される同一又は異なる１価の基を示す。）が例示される。 Examples of anion exchange groups bonded to these base materials include primary to tertiary amine groups.

(Wherein R ¹ and R ² represent the same or different monovalent groups selected from a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxylethyl group and a hydroxypropyl group) and the fourth. Secondary ammonium group

(In the formula, R ³ , R ⁴ and R ⁵ represent the same or different monovalent groups selected from a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxylethyl group and a hydroxypropyl group.) Is exemplified.

  Next, an aqueous alkaline solution to be purified in the present invention, particularly an aqueous solution containing sodium hydroxide or the like is essentially used as a regenerant such as a strong basic anion exchanger and a weak basic anion exchanger. Although used, the terminal groups of strong and weakly basic anion exchangers are treated in advance to form OH, so that they exist in various forms as anions in aqueous alkaline solutions. It is possible to remove metallic impurities by an anion exchanger, and the concentration of the alkaline aqueous solution is not changed.

  Strong basic anion exchanger and weak basic anion exchanger processed to OH type are impurities such as silicic acid compounds, carbonate radicals, sulfate radicals, chlorine radicals in addition to many metal impurities present as anions. It is also preferable in that it can be removed. Accordingly, it is possible to remove impurities other than metal impurities by bringing an alkaline aqueous solution containing siliconized impurities, carbonate impurities and metal impurities into contact with the material comprising the anion exchanger of the present invention. is there.

  Although it is possible to remove metal impurities in an alkaline aqueous solution even with a normal anion exchanger before pretreatment as described above, the removal of metal impurities is more efficient by applying the pretreatment of the present invention. It can be an anion exchanger that can be carried out.

  The pretreatment, which is a characteristic part of the present invention, is performed by performing a high concentration alkali contact step in which a conventionally known anion exchanger as described above is brought into contact with a high concentration alkali treatment liquid of 5.0 N or more. is there.

  By this high-concentration alkali contact process, impurities such as metals, organic substances, oils, and unreacted components of chemical substances used in the synthesis that have been present in the anion exchanger before treatment are removed from the high-concentration alkali treatment liquid. It is removed from the anion exchanger by the action of strong osmotic pressure.

After contacting with the high-concentration alkali treatment liquid, the acid treatment liquid penetrates into the anion exchanger by contacting with the acid treatment liquid, and impurities that could not be removed in the high-concentration alkali contact step are removed. Therefore, the anion exchanger can activate ion exchange groups that did not function before the pretreatment to function, and as a result, it can be considered that the removal performance of metal impurities can be improved. It is done.
By such a pretreatment method, for example, in the case of a particulate anion exchanger having a porous structure, shrinkage occurs in contact with high-concentration alkali, expansion occurs in contact with acid, and the interior that could not be removed by a normal cleaning method. It is thought that it was possible to remove even impurities.

  If the anion exchanger brought into contact with the acid treatment liquid as such is brought into contact with the alkaline aqueous solution to be purified as it is, there is a possibility that the liquidity may be changed. It is preferable to contact with a low-concentration alkaline treatment solution in advance so that the functional group is OH type so as not to cause a liquid property change.

  The operation of removing impurities with this acid treatment liquid and further contacting with a low-concentration alkali treatment liquid may be performed before the high-concentration alkali contact step, in which case the impurities contained in the anion exchanger are This is preferable in that it can be removed to some extent before the high-concentration alkali contact step, and the removal of impurities by the high-concentration alkali treatment liquid can be promoted. These operations may be performed at least once, but it is preferable in that the impurities contained in the anion exchanger are removed by repeating twice or more.

  Here, FIG. 8 shows the organic components eluted into the aqueous solution by contacting the anion exchanger before the pretreatment of the present invention with an aqueous sodium hydroxide solution of 0.0 to 20.0 N (normality). The result of measuring the quantity with a spectrophotometer is shown. The removal rate (%) in FIG. 8 was expressed based on the amount of impurities eluted when a saturated aqueous solution of sodium hydroxide was used (100%). The 20.0N sodium hydroxide aqueous solution, which is a saturated aqueous solution, was made into a saturated aqueous solution by adding granular sodium hydroxide to a commercially available 18.0N sodium hydroxide aqueous solution (liquid temperature 25 ° C.). FIG. 8 shows that the removal rate increases as the concentration of the aqueous sodium hydroxide solution increases, that is, a large amount of organic components are eluted. Therefore, in order to remove impurities such as organic components in the anion exchanger, it can be said that it is effective to wash with a higher concentration aqueous alkali solution. In the case of the anion exchanger used in the present invention, it is preferable that the removal rate is 10.0 N or higher from the test results, and it is comparatively easy on the market considering the ease of work that does not require adjustment. It can be seen that 10.0-18.0 N available in

  In addition, the acid treatment liquid used for the acid treatment performed before and after the high-concentration alkali contact step may be an acidic solution, and the type is not particularly limited, but strong acids such as hydrochloric acid, nitric acid, sulfuric acid, etc. A solution using the acid is preferably used. At this time, the concentration of the acid treatment liquid is preferably in the range of 0.1 to 6.0N, and more preferably in the range of 1.0 to 3.0N.

  Moreover, the alkali treatment liquid used for the low concentration alkali treatment may be an alkaline solution, and there is no particular limitation on the kind, but a strong base such as sodium hydroxide, potassium hydroxide, ammonia or the like is used. A solution using a base is preferred. At this time, the concentration of the alkali treatment liquid is lower than the high concentration alkali treatment liquid used in the pretreatment of the present invention, and is preferably in the range of 0.1 to 2.0N.

  Thus, the anion exchanger obtained by pretreatment with a high concentration alkaline treatment solution has higher ability to remove metal impurities in the aqueous alkaline solution than the anion exchanger without pretreatment. The group is activated. In addition, the present pretreatment method is not limited to the purification of high-concentration alkaline aqueous solution, but can also be used for pretreatment of anion exchangers used for purification of pure water, acidic aqueous solution, and organic solvent.

[Purification apparatus and purification method for alkaline aqueous solution]
Next, the purification method and apparatus of the alkaline aqueous solution of the present invention will be described. As shown in FIG. 1, the alkaline aqueous solution purifying apparatus 1 of the present invention includes a tank 2 that contains an alkaline aqueous solution to be purified, and an anion exchanger 3 that removes metal impurities from the alkaline aqueous solution. Is.

  Here, the tank 2 is not particularly limited as long as it can accommodate an alkaline aqueous solution to be purified, and an alkali-resistant material is used.

  As the anion exchanger 3, the anion exchanger of the present invention described above is used, and this anion exchanger is subjected to a specific pretreatment and / or a regeneration treatment described later on a conventionally known anion exchanger. By applying, the ability to remove metal impurities is activated.

  By adopting an apparatus having such a structure, metal impurities can be efficiently removed from an alkali aqueous solution containing metal impurities, and the concentration of the metal aqueous solution can be further reduced as compared with the prior art. It can be a device.

  The purification of the alkaline aqueous solution using this alkaline aqueous solution purification apparatus 1 is that the alkaline aqueous solution accommodated in the tank 2 is sent to the anion exchanger 3 by a pump or the like, and the alkaline aqueous solution is brought into contact with the anion exchanger 3. What is necessary is just to perform by simple operation.

  In order to bring the alkaline aqueous solution into contact with the anion exchanger 3 described above, for example, the anion exchanger 3 is introduced into a column or a column, and the alkaline aqueous solution to be purified is passed therethrough or purified. The anion exchanger 3 may be added to the reaction tank containing the alkaline aqueous solution to be fluidized, and the aqueous alkaline solution to be purified may be fluidized and filtered, and the anion exchanger may be contacted in the form of a cartridge filter. You may let them.

  At this time, the alkaline aqueous solution to be purified in the present invention is not particularly limited as long as it is an alkaline aqueous solution. Examples of the dissolved base include sodium hydroxide, potassium hydroxide, and sodium carbonate. , Potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, ammonia, tetramethylammonium hydroxide and the like, other alkali metal hydroxide solutions such as lithium hydroxide and cesium hydroxide, and alkaline earth metals such as barium hydroxide Examples thereof include metal hydroxide solutions and organic alkaline aqueous solutions such as choline.

  The concentration of the aqueous alkali solution used is 0.01 to 50% by mass for sodium hydroxide, 0.01 to 50% by mass for potassium hydroxide, 0.01 to 23% by mass for sodium carbonate, and 0. 01 to 50% by weight, sodium bicarbonate 0.01 to 8% by weight, potassium bicarbonate 0.01 to 50% by weight, ammonia 0.01 to 30% by weight, tetramethylammonium hydroxide 0.01 to The concentration is preferably 25% by mass and 0.01-50% by mass for choline, 0.1-50% by mass for sodium hydroxide, 0.1-50% by mass for potassium hydroxide, and 0 for sodium carbonate. 0.1-23 wt%, potassium carbonate 0.1-50 wt%, sodium bicarbonate 0.1-50 wt%, potassium bicarbonate 0.01-50 wt% , 0.1 to 30% by weight ammonia, and more preferably in the tetramethylammonium hydroxide at a concentration of 0.1 to 25 mass%. Furthermore, 5-50 mass% for sodium hydroxide, 5-50 mass% for potassium hydroxide, 5-23 mass% for sodium carbonate, 5-50 mass% for potassium carbonate, 5-8 mass% for sodium bicarbonate, Particularly preferred is a high concentration region of 5 to 50% by mass for potassium bicarbonate, 5 to 30% by mass for ammonia, 5 to 25% by mass for tetramethylammonium hydroxide, and 1 to 50% by mass for choline. The present invention is most effective in the area.

  Further, in a high-concentration aqueous solution, such as a saturated aqueous solution, the solubility may change depending on the solution temperature, precipitation may occur, and the viscosity of the solution may change. For example, in a 48 mass% sodium hydroxide aqueous solution, it is preferable to process at 15 degreeC or more, and when it processes below those liquid temperature, it exists in the tendency for performance to fall. Also about other alkaline aqueous solution, the liquid temperature should just be the range which does not exceed the viscosity at the time of a process, and does not reduce process efficiency.

  Examples of the alkaline aqueous solution to be purified include aqueous solutions containing metal impurities such as calcium, magnesium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, and lead. In the present invention, nickel, copper are particularly preferable. Higher removal performance is obtained. Further, it may contain siliconization impurities, carbonic acid impurities, and the like.

  In the removal of metal impurities according to the present invention, for example, an anion exchanger can be used because the metal impurities form negatively charged hydroxide complex ions under a high alkali concentration. This is considered to be due to the selective adsorption and removal of hydroxide complex ions having high affinity with anion exchange groups even in the presence of hydroxide ions, which are anions present in large amounts in an alkaline aqueous solution.

  By using the present invention, for example, nickel and copper, which are metal impurities in an alkaline aqueous solution, can be achieved to 1 ppb or less and, depending on conditions, to 0.1 ppb or less.

  In addition, as an apparatus and a purification method for an alkaline aqueous solution of the present invention, one or more anion exchangers 3 may be used and an anion exchange treatment may be performed once or more for the alkaline aqueous solution to be purified. At this time, the anion exchanger treatment is preferably performed twice or more. Here, the alkaline aqueous solution to be purified, for example, a 48 mass% sodium hydroxide solution rapidly increases in viscosity at less than 15 ° C and freezes at about 10 ° C. It is preferable to maintain. Also about other alkaline aqueous solution, the liquid temperature should just be the range which does not exceed the viscosity at the time of a process, and does not reduce process efficiency.

  In addition, as a method of performing an anion exchanger process twice or more, the method of using the refiner | purifier of the alkaline aqueous solution shown in FIGS. 2-5 is mentioned, for example. FIG. 2 shows an alkaline aqueous solution purification apparatus in which two anion exchangers are connected in series, and FIGS. 3 and 4 show an alkaline aqueous solution purification apparatus in which one of the two anion exchangers can be circulated. FIG. 3 shows the anion exchanger in the latter stage, FIG. 4 shows a purification apparatus for the alkaline aqueous solution in which the circulation treatment is performed with the anion exchanger in the former stage, and FIG. 5 shows both of the two anion exchangers. It is the refiner | purifier of the aqueous alkali solution made to circulate. Although the case where two anion exchangers are used is shown here, three or more anion exchangers may be used.

  In the alkaline aqueous solution purification apparatus 11 of FIG. 2, first, the alkaline aqueous solution to be purified contained in the tank 12 is passed through the first anion exchanger 13 and then accommodated in the primary treatment tank 14, and then 1 The treatment liquid stored in the next treatment tank 14 is passed through the second anion exchanger 15 for treatment. In the alkaline aqueous solution purifying apparatus 21 of FIG. 3, the alkaline aqueous solution to be purified contained in the tank 22 is flowed to the first anion exchanger 23 for treatment, and the treatment liquid is temporarily contained in the primary treatment tank 24. Then, the treatment liquid stored in the primary treatment tank 24 is circulated in the second anion exchanger 25 to obtain a purified alkaline aqueous solution.

  In the alkaline aqueous solution purifying apparatus 31 in FIG. 4, the alkaline aqueous solution to be purified contained in the tank 32 is circulated in the first anion exchanger 33, once it is terminated, and then the second anion. Treat with ion exchanger 34. In the alkaline aqueous solution purification apparatus 41 of FIG. 5, the alkaline aqueous solution to be purified contained in the tank (primary treatment tank) 42 is circulated in the first anion exchanger 43, and this is once completed. Then, the primary treatment alkaline aqueous solution is accommodated in the secondary treatment tank 44, and then the primary treatment alkaline aqueous solution is also circulated in the second anion exchanger 45 to obtain a purified alkaline aqueous solution. It is.

  The first anion exchangers 13, 23, 33, 43 and the second anion exchangers 15, 25, 34, 45 used here all use the anion exchanger of the present invention described above. Usually, an anion exchanger used for water treatment or the like is subjected to a specific pretreatment.

  At this time, the same anion exchanger may be used for the first anion exchangers 13, 23, 33, 43 and the second anion exchangers 15, 25, 34, 45. Different anion exchangers may be used in combination.

A plurality of types of metal impurities existing in the alkaline aqueous solution are known. For example, nickel is in the form of Ni (OH) ₄ ²⁻ , Ni (OH) ₃ ⁻ , Ni (OH) ₂ , and fine particles. However, the abundance ratio thereof varies depending on the pH of the alkaline aqueous solution as shown in the graph of FIG. Moreover, the metal impurity mixed from the outside exists in various forms. This is known to be the same for copper (FIG. 7).

  In the present invention, it is not limited to the apparatus for purifying the alkaline aqueous solution described above, but three or more anion exchangers are used, combined with an anion exchanger not subjected to the pretreatment of the present invention, or an anion exchanger. In addition, a device usually used for water treatment, for example, a filtering device such as a filter (MF, UF, etc.), activated carbon for adsorption of fine particles, synthetic adsorption resin, or the like may be used in combination.

  The anion exchanger of the present invention is found to change the removal efficiency of metal ions by changing its processing speed, and the present inventors utilize this property to improve the efficiency of metal impurities. The present inventors have found a method for purifying an alkaline aqueous solution that can be removed. That is, when the metal impurities in the alkaline aqueous solution are passed and removed using the anion exchanger of the present invention, the treatment speed is in the range where the space velocity SV is 25 / hr or more, preferably 30 / hr or more and 40 / hr or less. When the treatment is performed, among the metal impurities, the form that is relatively easy to remove remains in the anion exchanger, and the form that is difficult to remove passes through without being removed. However, this form which is difficult to remove is also removed by the anion exchanger by performing the treatment so that the space velocity SV is 20 / hr or less, preferably 10 / hr or more and 20 / hr or less.

  Therefore, in order to efficiently remove metal impurities in the alkaline aqueous solution, two or more anion exchangers of the present invention are used, and in the first anion exchanger that first contacts the alkaline aqueous solution, In the second anion exchanger that comes into contact with the aqueous alkaline solution and then passes the liquid so that the treatment speed is slower than that of the first anion exchanger. Different types of metal impurities can be removed separately. This is preferable from the viewpoint of efficiency because the adsorbents of the anion exchanger can be arranged, and this also has a favorable influence on the regeneration operation described later.

  Even when the first and second anion exchangers are used as described above, if the processing speed of the first anion exchanger is low, components that can be easily removed in the first anion exchanger. Both of the components that are difficult to remove and the components that are difficult to remove are removed in a mixed manner, and the effect is reduced both in terms of adsorption amount and regeneration efficiency.

[Regeneration method of anion exchanger]
Next, the method for regenerating an anion exchanger according to the present invention recovers the metal impurity removal ability again with respect to the anion exchanger used for the purification of the alkaline aqueous solution, and the operation is carried out by an anion. The exchanger is brought into contact with the acid treatment liquid and then brought into contact with the alkali treatment liquid. This is a completely different operation from the regeneration of an anion exchanger which is simply brought into contact with a strong basic solution. The anion exchanger used for the purification treatment of the alkaline aqueous solution of the present invention is a strongly basic solution. The ability to remove metal impurities cannot be recovered simply by contacting with an alkali treatment liquid.

その後使用した酸の対イオン型となっている陰イオン交換基を低濃度アルカリ水溶液にてＯＨ型にすることで、再度金属不純物の除去能力が回復する。 This is because the metal removed by the purification of the alkaline aqueous solution of the present invention is mainly in the form of a hydroxide complex ion, and the bond between the hydroxide complex ion and the anion exchange group is strongly basic. This is probably because the contact with the alkaline treatment liquid cannot be sufficiently replaced or regenerated. In the regeneration method of the present invention, first, by contacting with an acid treatment solution, hydroxide complex ions are cationized and metal ions are dissolved in the acid treatment solution as exemplified by the following [Formula 1]. Let

Thereafter, the anion exchange group which is a counter ion type of the acid used is converted to OH type with a low-concentration alkaline aqueous solution, so that the metal impurity removal capability is restored again.

  The acid treatment liquid used for the regeneration can be the same as the acid treatment performed during the pretreatment, and the alkali treatment liquid used for the regeneration is the same as the alkali treatment performed during the pretreatment. Can be used.

If this regeneration method is also adjusted by the above-described method for purifying an alkaline aqueous solution, the number of regenerations and the amount of the acid solution to be used can be reduced.
That is, as a method for purifying an alkaline aqueous solution, two anion exchangers are used, and the first anion exchanger in the previous stage is passed through with a space velocity SV of 25 / hr or more, and the second anion in the subsequent stage. In the exchanger, when the space velocity SV is 20 / hr or less, the acid solution for the first anion exchanger is 1.0 N or more, preferably 1.0 to 3.0 N. For the second anion exchanger, an acid solution of less than 1.0 N, preferably 0.1 to 0.5 N can be used.

  This is because the metal impurities adsorbed on the first anion exchanger are easy to remove, and thus are difficult to remove from the anion exchanger. Therefore, more acid is required for regeneration, and the second anion This is because the metal impurities adsorbed on the exchanger are difficult to remove, so that they can be easily removed from the anion exchanger, so that less acid can be used for regeneration.

  Therefore, an acid solution with an unnecessarily high concentration can be used by selecting and using the acid concentration used for the regeneration operation so that it is sufficient to regenerate due to the nature of the adsorbed metal impurities. This eliminates the need for efficient purification of the aqueous alkali solution and regeneration of the anion exchanger. Furthermore, it is preferable that the number of regeneration, the regeneration time, the amount of acid used during regeneration, and the like can be reduced by removing the metal impurities separately for each anion exchanger as described above.

  As described above, in the case where the treatment with the anion exchanger is not performed in the two-stage treatment with different speeds, the form that is easy to remove can be sufficiently removed by performing only at a high space velocity, but the form that is difficult to remove. Are still contained in the processing solution. On the contrary, if it is performed only at a low space velocity, metal impurities can be sufficiently removed, but various forms of metal impurities are adsorbed in the anion exchanger, and this is regenerated. The regeneration efficiency with respect to the amount of the acid solution used is insufficient, and if it is intended to regenerate properly, the number of regenerations must be increased and the concentration of the acid solution used must be high.

  The present invention configured by combining the above constituent elements can be applied to purification of an alkaline aqueous solution having a low concentration to a high concentration (for example, an alkali concentration of 0.01 to 50% by mass). In particular, the present invention is characterized in that it can be used even if the alkali concentration of the aqueous alkali solution to be purified is 0.1% by mass or higher, particularly 20% by mass or higher.

  Hereinafter, the present invention will be described using examples.

  The measurement of metal impurities was performed with an ICP mass spectrometer (ICP-MS) (manufactured by PerkinElmer, trade name: ELANDRC-II).

  In addition, the processing apparatus and the processing body which were used by the following examples and comparative examples are as follows.

[Processing equipment]
Anion exchanger packed column: Polyvinyl chloride (PVC) column
Diameter 200mm, Height 500mm
Tank material: Polyethylene (PE)
Piping material: PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer)
Pump: Bellows pump (product name: FS-15HT, manufactured by Iwaki Co., Ltd.)

[Used anion exchanger]
(A) Weakly basic anion exchange fiber
Base material: Polyethylene
Functional group: Tertiary amine group
Shape: Diameter 100mm, Height 250mm, Cartridge filter shape
Substrates with iminodiethanol groups introduced as tertiary amine groups into polyethylene fibers by graft polymerization are processed into filters.

[Chemicals used for cleaning]
High concentration alkaline treatment solution:
48 mass% (18N) sodium hydroxide aqueous solution (Asahi Glass Co., Ltd., trade name: Super Alkali)
Low concentration alkaline treatment solution:
A 2.0N (7.4% by mass) sodium hydroxide aqueous solution prepared by adding the 48% by mass sodium hydroxide aqueous solution to ultrapure water.
Acid treatment solution 1:
1.0N (6% by mass) nitric acid prepared by adding 70% by mass (15.7N) nitric acid (manufactured by Kanto Chemical Co., Inc .; grade for electronics industry) to ultrapure water
Acid treatment liquid 2:
1.0N (4% by mass) hydrochloric acid prepared by adding 35% by mass (11.3N) hydrochloric acid (manufactured by Kanto Chemical Co., Ltd .; special grade) to ultrapure water
Acid treatment solution 3:
0.1N (4% by mass) hydrochloric acid prepared by adding 35% by mass hydrochloric acid to ultrapure water

  In the following examples and comparative examples, the anion exchangers used were those having terminal groups of 90% or more OH groups.

  Moreover, 48 mass% sodium hydroxide aqueous solution (Asahi Glass Co., Ltd. make, brand name; super alkali) was used as it was as high concentration alkali aqueous solution of refinement | purification object. This 48 mass% sodium hydroxide aqueous solution contains nickel 50ppb and copper 10ppb from the beginning.

  All of the above processing equipment, PFA piping, PVC column, and pump are immersed in 1.0N nitric acid (concentration: 6% by mass) for 1 hour or more in advance to eliminate metal contamination, and then run with ultrapure water. Washed. An anion exchanger was introduced into this nitric acid-washed PVC column to obtain a test module.

Example 1
Ultra pure water was passed through the test module using the anion exchanger of (A) as an anion exchanger at 0.75 L / min for 12 hours or more, and air was removed and impurities were washed.

12 L of 1.0N hydrochloric acid (concentration: 4% by mass) was injected into this ultrapure water cleaned test module and immersed in it at room temperature for 1 hour for acid treatment. After extracting the solution from the test module, ultrapure water was supplied at 0.75 mL / min and washed with running water until the effluent water reached pH 4-5.
Then, 12 L of 2.0N sodium hydroxide aqueous solution (concentration: 7.4% by mass) was injected and immersed for 20 minutes. After extracting the solution from the test module, 12 L of 2.0N sodium hydroxide aqueous solution was injected again and immersed for 20 minutes at room temperature, and then the solution was extracted from the test module and subjected to low-concentration alkali treatment.

  A 18.0 N (48% by mass) sodium hydroxide aqueous solution is supplied to the low-concentration alkali-treated test module at 0.75 L / min, and the test module is filled with the anion exchanger for 8 hours at room temperature. It was immersed in an aqueous sodium oxide solution and subjected to a high concentration alkali treatment.

  Ultrapure water was supplied to the high-concentration alkali-treated test module at 0.75 L / min and washed with running water until the effluent water had a pH of 9-10.

  Then, the second acid treatment is performed by the same method as the acid treatment, and then the second low concentration alkali treatment is performed by the same method as the low concentration alkali treatment. A treated anion exchanger was produced.

  The obtained test module was installed in the flow path of the alkaline aqueous solution as shown in FIG. The supply amount of 48 mass% sodium hydroxide aqueous solution at a liquid temperature of 25 ° C. was adjusted to 0.5 L / min (SV = 10 / hr), and the solution was passed through the test module to purify the 48 mass% sodium hydroxide aqueous solution. It was.

(Example 2)
Ultra pure water was passed through the test module using the anion exchanger of (A) as an anion exchanger at 0.75 L / min for 12 hours or more, and air was removed and impurities were washed.

  The same pretreatment as in Example 1 was performed, and two obtained test modules (A) were installed in series in the flow path of the alkaline aqueous solution as shown in FIG. The 48 mass% sodium hydroxide aqueous solution supply amount at 25 ° C. to the first anion exchanger (A) and the second anion exchanger (A) is adjusted to 0.5 L / min (SV = 10 / hr). Then, the solution was passed through a test module to purify a 48 mass% sodium hydroxide aqueous solution.

(Example 3)
Ultra pure water was passed through the test module using the anion exchanger of (A) as an anion exchanger at 0.75 L / min for 12 hours or more, and air was removed and impurities were washed.

  The same pretreatment as in Example 1 was performed, and two test modules (A) obtained were used as a first anion exchanger and a second anion exchanger as shown in FIG. It installed and it was set as the purification apparatus of alkaline aqueous solution. The supply amount of 48 mass% sodium hydroxide aqueous solution at 25 ° C. to the first anion exchanger (A) is adjusted to 0.5 L / min (SV = 10 / hr) and the permeate is stored in the primary treatment tank. did. The supply amount of 48 mass% sodium hydroxide aqueous solution at 25 ° C. stored in the primary treatment tank to the second anion exchanger (A) is adjusted to 1.0 L / min (SV = 20 / hr) and circulated. The solution was passed through to purify a 48 mass% sodium hydroxide aqueous solution.

Example 4
Ultra pure water was passed through the test module using the anion exchanger of (A) as an anion exchanger at 0.75 L / min for 12 hours or more, and air was removed and impurities were washed.

  The same pretreatment as in Example 1 was performed, and the two obtained test modules (A) were used as a first anion exchanger and a second anion exchanger as shown in FIG. It installed and it was set as the purification apparatus of alkaline aqueous solution. The supply amount of a 48 mass% sodium hydroxide aqueous solution at 25 ° C. to the first anion exchanger (A) is adjusted to 2.0 L / min (SV = 40 / hr) and circulated through the permeate. Stored in next treatment tank. The 48 mass% sodium hydroxide aqueous solution supply amount stored in the primary treatment tank to the second anion exchanger (A) was adjusted to 0.5 L / min (SV = 10 / hr), and the test module (A ) The solution was passed through to purify a 48 mass% sodium hydroxide aqueous solution.

(Example 5)
Ultra pure water was passed through the test module using the anion exchanger of (A) as an anion exchanger at 0.75 L / min for 12 hours or more, and air was removed and impurities were washed.

  The same pretreatment as in Example 1 was performed, and two test modules (A) obtained were used as a first anion exchanger and a second anion exchanger as shown in FIG. It installed and it was set as the purification apparatus of alkaline aqueous solution. The supply amount of a 48 mass% sodium hydroxide aqueous solution at 25 ° C. to the first anion exchanger (A) was adjusted to 2.0 L / min (SV = 40 / hr) and circulated. The supply amount of a 48 mass% sodium hydroxide aqueous solution at 25 ° C. subjected to circulating liquid treatment to the second anion exchanger (A) was adjusted to 1.0 L / min (SV = 20 / hr). A 48 mass% aqueous sodium hydroxide solution was purified by circulating through the anion exchanger.

(Example 6)
Ultra pure water was passed through the test module using the anion exchanger of (A) as an anion exchanger at 0.75 L / min for 12 hours or more, and air was removed and impurities were washed.

  The same pretreatment as in Example 1 was performed, and the two obtained test modules (A) were used as a first anion exchanger and a second anion exchanger as shown in FIG. It installed and it was set as the purification apparatus of alkaline aqueous solution. The 48 mass% sodium hydroxide aqueous solution supply amount at 25 ° C. to the first anion exchanger was adjusted to 0.5 L / min (SV = 10 / hr), and the permeate was stored in the primary treatment tank. The 48 mass% sodium hydroxide aqueous solution supply amount stored in the primary treatment tank to the second anion exchanger was adjusted to 1.0 L / min (SV = 20 / hr) and passed through to 48 mass%. The aqueous sodium hydroxide solution was purified.

(Comparative Example 1)
Ultra pure water was passed through the test module using the anion exchanger of (A) as an anion exchanger at 0.75 L / min for 12 hours or more, and air was removed and impurities were washed.

  Into this pure water washed test module, 12 L of 2.0N sodium hydroxide aqueous solution was injected and immersed for 20 minutes. After extracting the solution, 12 L of 2.0N sodium hydroxide aqueous solution was injected again and immersed for 20 minutes at room temperature, and then the solution was extracted from the test module and subjected to low-concentration alkali treatment.

  Ultrapure water was supplied to the low-concentration alkali-treated test module at 0.75 L / min, and washed with running water until the effluent water reached pH 9-10.

  Two obtained test modules (A) were placed in series in the flow path of the alkaline aqueous solution as shown in FIG. The supply amount of a 48 mass% sodium hydroxide aqueous solution at 25 ° C. to the first anion exchanger and the second anion exchanger was adjusted to 0.5 L / min (SV = 10 / hr), and passed through the test module. The solution was purified to 48% by weight aqueous sodium hydroxide solution.

(Test Example 1)
The nickel concentration and the copper concentration of each test module effluent obtained by refining the alkaline aqueous solutions of Examples 1 to 6 and Comparative Example 1 were examined by ICP-MS, and the results are shown in Table 1. In addition, the nickel concentration of the aqueous alkali solution before purification was 50 ppb, and the copper concentration was 10 ppb. Further, the adsorption capacity of the anion exchanger used in each of the examples and the comparative examples is 2.5 eq / L in the example in which the pretreatment of the present invention is performed, and 2. in the comparative example in which the conventional pretreatment is performed. It was 0 eq / L.

  From Example 1, it was found that the method for purifying an alkaline aqueous solution of the present invention can sufficiently remove metal impurities such as nickel and copper, and the adsorption capacity is also increased by the pretreatment method of the present invention. The adsorption capacity was measured by passing 1.0N (3.8% by mass) sodium hydroxide through the pre-treated anion exchanger to completely convert the end groups into OH form, and then adding 12 L of 0.1. 1N (0.36% by mass) hydrochloric acid is passed through the anion exchanger, the permeate is collected and quantified, and the permeate after quantification is added with 0.1N (0.4% by mass) aqueous sodium hydroxide solution. And titrated to measure.

  From Example 2, it was found that the metal impurities in the alkaline aqueous solution can be further reduced by performing the anion exchanger contact treatment twice or more.

  However, when the supply amount to the second anion exchanger (A) of the 48 mass% sodium hydroxide aqueous solution treated with the first anion exchanger (A) was increased from Example 6, Even when the anion exchanger treatment was performed twice or more, no change was observed in the metal concentration in the alkaline aqueous solution. From this, it was found that the ability to remove metal impurities is changed by changing the processing speed (the supply amount per unit time here).

  Even if the supply amount of the 48 mass% sodium hydroxide aqueous solution treated with the first anion exchanger (A) to the second anion exchanger (A) is increased from Example 3, the circulating liquid is passed through. It was found that the metal impurities in the alkaline aqueous solution can be further reduced by doing so.

  From Example 4, the amount of the 48 mass% sodium hydroxide aqueous solution supplied to the first anion exchanger was adjusted to 2.0 L / min, and only the metal impurities in a form that can be easily removed by circulating liquids are the first. A 48% by mass aqueous sodium hydroxide solution, which is adsorbed on the anion exchanger (A) and remains in a form that is difficult to remove, is supplied to the second anion exchanger (A), and the second anion exchanger It is considered that metal impurities in a form that is difficult to be removed by adsorption are adsorbed.

  After removing the metal impurities in a form that can be easily removed by the first anion exchanger (A) by performing circulation through each of the first and second anion exchangers (A) from Example 5. By removing metal impurities in a form that is difficult to remove with the second anion exchanger (A), the adsorption capacity of each anion exchanger can be used efficiently. Moreover, rapid purification becomes possible by making each anion exchanger treatment a circulating liquid.

  From Comparative Example 1, even when the anion exchanger treatment was performed twice or more using two anion exchangers (A) subjected to only low-concentration alkali treatment, the metal impurities in the alkaline aqueous solution could be sufficiently removed. There wasn't. It was also confirmed that the adsorption capacity of the anion exchanger was lower than the exchange capacity of the anion exchanger subjected to the pretreatment of the present invention.

  By performing the pretreatment of the present invention, the impurities of the anion exchanger are removed, and the ion exchange groups that did not function before the pretreatment can be activated to function, resulting in metal impurities. It is thought that the removal performance improvement and adsorption capacity increased.

  In addition, by performing the treatment with the anion exchanger subjected to the pretreatment of the present invention twice or more, the contact opportunity between the metal impurity and the anion exchanger in the alkaline aqueous solution is increased, and the metal impurity concentration is further decreased. Conceivable.

  In addition, depending on the form of the metal impurity in the alkaline aqueous solution, the removability changes depending on the amount of the alkaline aqueous solution supplied to the anion exchanger (that is, the processing speed), and the metal impurity in a form that is easy to remove is removed even at high speed processing It is considered that a metal impurity in a form that is difficult to remove cannot be removed unless it is treated slowly. Taking advantage of this characteristic, by removing metal impurities in a form that is easy to remove with the first anion exchanger and metal impurities that are difficult to remove with the second anion exchanger, the adsorption capacity of the anion exchanger is efficient. Now available.

  From the above, one or more anion exchangers of the present invention may be used, and the treatment liquid and the anion exchanger may be contacted one or more times, but using two or more anion exchangers, By subjecting each anion exchanger to circulating liquid treatment, it becomes possible to purify efficiently and quickly.

(Example 7)
The anion exchanger (A) that had been subjected to the purification treatment of the alkaline aqueous solution in Example 1 was a regeneration target. This anion exchanger adsorbs 50 mg of nickel and 10 mg of copper from a 48% by mass aqueous sodium hydroxide solution. Here, the adsorption amounts of nickel and copper in the aqueous solution were calculated as follows. Before purification, 1,050 kg of a 48 mass% sodium hydroxide aqueous solution containing 50 ppb of nickel and 10 ppb of copper was treated by the method of Example 1, and the nickel concentration and the copper concentration in the anion exchanger permeate (purified solution) The amount adsorbed on the anion exchanger was calculated from the concentration of both metals before purification.

  The used test module was removed from the alkaline aqueous solution purifier, and ultrapure water was supplied to the test module at 0.75 L / min, and washed with running water until the effluent became pH 9-10.

  12 L of 1.0N hydrochloric acid as a regenerant was injected into this ultrapure water washed test module and immersed for 1 hour, and then the solution was extracted. Then, 0.75 mL / min of ultrapure water was supplied to the test module, and running water was washed until the effluent reached pH 4-5.

(Comparative Examples 2 and 3)
In Comparative Example 2, a 2.0N sodium hydroxide aqueous solution was used as a regenerant, and in Comparative Example 3, a 2.0N sodium chloride aqueous solution (concentration: 12% by mass) was used. Went.

(Test Example 2)
In Example 7, Comparative Example 2 and Comparative Example 3, the nickel concentration in the regenerant after immersion was analyzed by ICP-MS, and the regeneration rate was calculated. The results are shown in Table 2. The regeneration rate was calculated by setting the nickel amount 50 mg and copper 10 mg adsorbed by the used ion exchanger as 100%, and the nickel amount in the regenerant after immersion was calculated as a percentage. Moreover, when the test similar to Example 1 was done using the test module which performed the reproduction | regeneration processing in Example 7, the same result was obtained.

In the anion exchanger regeneration method of Example 7, it was found that regeneration was performed because nickel and copper were contained in the regeneration agent after immersion in the anion exchanger.
In Comparative Example 2 and Comparative Example 3, it was found that regeneration was not performed because nickel and copper were hardly contained in the regenerant after immersion in the anion exchanger.

  In the conventional anion exchanger regeneration method, the anion exchanger used for the purification of the alkaline aqueous solution of the present invention was not regenerated. This is because the anion exchanger of the present invention and nickel and copper forming a negatively charged hydroxide complex ion are strongly bonded by the action of an ionic bond and a coordinate bond. This is probably because no reproduction is performed in the reproduction process. Similarly, regeneration was not performed by an ion exchange method using sodium chloride.

  In the anion exchanger regeneration method of the present invention, nickel hydroxide complex ions and copper hydroxide captured by the anion exchanger are obtained by performing an acid treatment that has not been used for regeneration of conventional anion exchangers. It became possible to regenerate the complex ions by cationizing them and separating them from the anion exchanger.

(Test Example 3)
The first anion exchanger (A) and the second anion exchanger (A) treated with 1,050 kg of a 48 mass% aqueous sodium hydroxide solution by the method of Example 2 and the method of Example 5 The amount of the regenerant necessary for the regeneration of the first anion exchanger (A) and the second anion exchanger (A) that had been treated with 1,050 kg of a 48 mass% sodium hydroxide aqueous solution was investigated. The amount adsorbed on each anion exchanger was calculated from the nickel concentration and copper concentration in the anion exchanger permeate (purified solution) and the concentrations of both metals before purification.

  4 L of 0.1N hydrochloric acid as a regenerant was injected into the above anion exchanger (4) and immersed for 30 minutes, and then the solution was extracted. Then, 0.75 mL / min of ultrapure water was supplied to the test module, and running water was washed until the effluent reached pH 4-5. Then, the same operation was performed once again.

  4 L of 1.0N hydrochloric acid as a regenerant was injected into the anion exchanger that had been washed with pure water and immersed for 30 minutes, and then the solution was extracted. Then, 0.75 mL / min of ultrapure water was supplied to the test module, and running water was washed until the effluent reached pH 4-5. Thereafter, the same operation was repeated twice.

  The nickel concentration in the regenerant after immersion in each anion exchanger was analyzed by ICP-MS, and the amount of nickel removed from the anion exchanger was calculated. The results are shown in Table 4, and it was found that the regeneration rate exceeded 98%.

  From the results of Test Example 3, it can be seen that in Examples 2 and 5, nickel can be substantially removed from the alkaline aqueous solution by either method, and both are excellent purification methods. However, the method of removing nickel varies greatly depending on the method, and it was also found that the difference affects the difference in regeneration efficiency.

  When each of the first anion exchanger and the second anion exchanger of Examples 2 and 5 was initially processed at a low processing speed as in Example 2, various types of metal impurities were obtained. When a reproduction operation is included, the reproduction operation must be performed many times to remove it. On the other hand, as in the operation of Example 5, the first anion exchanger has a high processing speed, and the second anion exchanger has a low processing speed. It is possible to select whether to remove with an anion exchanger.

  Therefore, even when regenerating those anion exchangers, it is not necessary to use acid solutions (regenerating agents) of various concentrations and once, if the processed anion exchangers are known. By this operation, the metal impurities can be almost completely removed from the anion exchanger, and the regeneration efficiency is extremely good.

  Incidentally, the amount of the acid solution (regeneration agent) necessary for regenerating each anion exchanger can be calculated from the calculation formula shown in Equation 2.

  In Example 2 of Table 4, the first anion exchanger is regenerated twice with 0.1N hydrochloric acid and three times with 1.0N hydrochloric acid, but this is when the concentration of the acid solution is low This was carried out in order to investigate the regeneration efficiency, and in fact, the same regeneration could be performed by performing the regeneration treatment three times with 1.0N hydrochloric acid.

That is, in Example 2, the time and amount of the regenerant necessary for regenerating the anion exchanger are as follows.
[First anion exchanger]
Time required is 30 minutes × 3 times = 1 hour 30 minutes Regenerant amount is 1.0 N × 4 L / time × 3 times ÷ 11.3N = 1.06 L as 70 mass% hydrochloric acid [second anion exchanger]
Time required is 30 minutes x 1 time = 30 minutes Regenerant amount is 0.1 N x 4 L / time x 1 time / 11.3 N = 0.04 L as 70 mass% hydrochloric acid [total]
2 hours, 1.10L

In Example 5, the time and amount of the regenerant required to regenerate the anion exchanger are as follows.
[First anion exchanger]
Time required is 30 minutes x 1 time = 30 minutes Regenerant amount is 1.0 N x 4 L / time x 1 ÷ 11.3 N = 0.35 L as 70 mass% hydrochloric acid [second anion exchanger]
Time required is 30 minutes x 1 time = 30 minutes Regenerant amount is 0.1 N x 4 L / time x 1 time / 11.3 N = 0.04 L as 70 mass% hydrochloric acid [total]
1 hour, 0.39L

  From this result, it was found that, when the anion exchanger of the present invention is used, a method with improved purification and regeneration efficiency can be provided by optimizing the purification conditions and the regeneration conditions.

  DESCRIPTION OF SYMBOLS 1 ... Purification apparatus of aqueous alkali solution, 2 ... Tank, 3 ... Anion exchanger, 11 ... Purification apparatus of aqueous alkali solution, 12 ... Tank, 13 ... 1st anion exchanger, 14 ... Primary treatment tank, 15 ... 2nd anion exchanger, 21 ... purifier for alkaline aqueous solution, 22 ... tank, 23 ... first anion exchanger, 24 ... primary treatment tank, 25 ... second anion exchanger, 31 ... alkali Aqueous solution purifier, 32 ... tank, 33 ... first anion exchanger, 34 ... second anion exchanger, 41 ... alkaline water purifier, 42 ... tank (primary treatment tank), 43 ... first Anion exchanger, 44 ... secondary treatment tank, 45 ... second anion exchanger

Claims (13)

The anion exchanger, have a high concentration alkali contacting step of removing the concentration in contact with more alkali treatment solution 5.0N impurities, after the high-concentration alkaline contacting step, acid treatment the anion exchanger A pretreatment method for an anion exchanger, which is brought into contact with a liquid and further brought into contact with an alkaline treatment liquid having a concentration of 2.0 N or less . The anion exchanger has a high-concentration alkali contact step in which impurities are removed by contacting the anion exchanger with an alkali treatment liquid having a concentration of 5.0 N or more, and the anion exchanger is converted to an acid before the high-concentration alkali contact step. A pretreatment method for an anion exchanger, characterized in that the anion exchanger is brought into contact with a treatment liquid and further brought into contact with an alkaline treatment liquid having a concentration of 2.0 N or less. Claims prior to the high-concentration alkaline contacting step, the contacting with the anion exchanger the acid treatment solution, further concentration and performing at least once contacting the following alkaline processing liquid 2.0N A pretreatment method for an anion exchanger according to 1 .   An anion exchanger obtained by the pretreatment method according to any one of claims 1 to 3.   An impurity removing step of removing metal impurities in the aqueous alkali solution by contacting the anion exchanger obtained by the pretreatment method according to any one of claims 1 to 3 with an aqueous alkali solution containing metal impurities. A method for purifying an alkaline aqueous solution.   In the metal impurity removal step, a first metal impurity removal step in which the alkaline aqueous solution is brought into contact with the first anion exchanger, and the alkaline aqueous solution treated in the first metal impurity removal step is subjected to the second anion exchange. 6. The method for purifying an alkaline aqueous solution according to claim 5, comprising a second step of removing the second metal impurity to be brought into contact with the body.   In the metal impurity removal step, a first metal impurity removal step in which the alkaline aqueous solution is brought into contact with the first anion exchanger, and the alkaline aqueous solution treated in the first metal impurity removal step is subjected to the second anion exchange. A second metal impurity removing step for contacting the body, and the alkaline aqueous solution is treated at different contact speeds in the first metal impurity removing step and the second metal impurity removing step. The method for purifying an alkaline aqueous solution according to claim 6.   The alkaline aqueous solution according to claim 7, wherein a treatment speed SV in the first anion exchanger is 25 / hr or more and a treatment speed SV in the second anion exchanger is 20 / hr or less. Purification method. The anion exchanger obtained by the pretreatment method according to any one of claims 1 to 3, wherein the used anion exchanger is used for removing metal impurities by contacting with an alkaline aqueous solution containing metal impurities. A method for regenerating an anion exchanger, comprising an acid contact step in which metal impurities taken into the anion exchanger are ionized and removed by contacting with an acid treatment solution.   The anion exchanger according to claim 9, wherein the used anion exchanger is in contact with the alkaline aqueous solution, and the acid treatment liquid is 0.1 N or more. Playback method. The used anion exchanger is prepared by sequentially treating the aqueous alkaline solution with the first anion exchanger at a processing speed SV of 25 / hr or more and the second anion exchanger with a processing speed SV of 20 / hr or less. Two kinds of anion exchangers obtained by contact,
The acid contact step is performed using an acid treatment liquid of 1.0 N or more for the first anion exchanger and an acid treatment liquid of less than 1.0 N for the second anion exchanger. The method for regenerating an anion exchanger according to claim 9.   An alkali comprising the anion exchanger obtained by the pretreatment method according to any one of claims 1 to 3 and / or the anion exchanger regenerated by the regeneration method of claim 9. Water purification equipment.   The anion exchanger comprises a first anion exchanger and a second anion exchanger that further removes metal impurities from the aqueous alkaline solution treated with the first anion exchanger. The apparatus for purifying an alkaline aqueous solution according to claim 12.

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