Process for purifying aqueous hydrogen peroxide solutions

Abstract

The present invention relates to a process for purifying an aqueous hydrogen peroxide solution, comprising at least the following steps: (a) treating the aqueous hydrogen peroxide solution with at least one first reverse osmosis system, (b) treating the obtained hydrogen peroxide solution with at least one first stabilizer, (c) treating the obtained hydrogen peroxide solution with at least one purification device selected from the group consisting of adsorption resins, ion exchange resins and combinations thereof. The present invention also relates to the aqueous hydrogen peroxide solution obtainable thereby, and to its use in microelectronic components and semiconductor manufacturing.

Description

[0001] This application claims priority to European application filed on 6 October 2021 under number 21201296.7, the entire contents of which are incorporated herein by reference for all purposes. Technical Field

[0002] This invention relates to a method for purifying an aqueous solution of hydrogen peroxide, the aqueous solution of hydrogen peroxide obtained by this method, and its use in the manufacture of microelectronic components and semiconductors. Background Technology

[0003] Hydrogen peroxide aqueous solutions are typically prepared via auto-oxidation techniques. Typically, alkyl-substituted anthraquinones undergo cyclic reduction with hydrogen, oxidation in air, and extraction with water to obtain hydrogen peroxide. Many variations of this manufacturing technique are known. After formation, the aqueous hydrogen peroxide can be purified to a certain extent by distillation and stabilized by the addition of various stabilizers. Although these manufacturing techniques differ significantly in their operation, they share a common result: the resulting hydrogen peroxide solution contains significant amounts of residual ionic and nonionic impurities. Typical cationic impurities include (but are not limited to) iron, aluminum, sodium, calcium, zinc, magnesium, and nickel. Typical anionic impurities include nitrate, phosphate, and pyrophosphate. Furthermore, the nature of the auto-oxidation method results in the formation of hydrogen peroxide solutions containing significant organic impurities, typically at concentrations above 50 mg / kg and sometimes as high as 600 mg / kg.

[0004] Aqueous hydrogen peroxide is an important raw material in the semiconductor and microelectronics industries. It is used in many processing steps to produce finished semiconductors or components. The industry requires high purity levels for hydrogen peroxide solutions. Cationic and anionic contamination in semiconductor processes leads to reduced yields and, consequently, higher costs. Furthermore, trace levels of organic contamination are known to affect semiconductor manufacturing processes. Therefore, the contaminant levels present in aqueous hydrogen peroxide produced by auto-oxidation methods are unacceptably high, necessitating further purification to produce semiconductor-grade materials. However, reducing the TOC level in aqueous hydrogen peroxide solutions to below 1 mg / kg is particularly difficult, especially for hydrogen peroxide produced by auto-oxidation methods.

[0005] For many years, reverse osmosis has been a popular technique for purifying hydrogen peroxide solutions intended for electronic applications.

[0006] WO 2005 / 033005 discloses a purification method in which an aqueous solution of hydrogen peroxide initially containing 65 ppm TOC (total organic carbon) is purified by passing it through a reverse osmosis membrane, an adsorption resin column, a cation exchange resin, and an anion exchange resin, thereby reducing the TOC value to 0.49 ppm.

[0007] However, reverse osmosis-based purification methods cannot deliver aqueous hydrogen peroxide with very high purity over time: in particular, an increase (pick-up) of metallic components (mainly iron) is observed in the hydrogen peroxide solution permeate leaving the reverse osmosis membrane. The metallic impurities were found to originate from the reverse osmosis system itself, which is typically partially constructed of stainless steel.

[0008] Currently, it is not possible to easily suppress the generation of such impurities by using reverse osmosis systems made of different materials, because reverse osmosis systems require high operating pressures, and stainless steel is particularly resistant to hydrogen peroxide under such pressures.

[0009] However, the presence of these newly generated metallic impurities is a significant problem: they degrade hydrogen peroxide, forming highly reactive free radicals, which reduce the lifespan of subsequent purification equipment that may be involved in the purification process, thus generating undesirable contaminants in the final purification step, and most importantly, the presence of such metallic impurities implies safety risks.

[0010] The present invention now provides a novel method for purifying aqueous hydrogen peroxide solutions, which provides high-purity aqueous hydrogen peroxide solutions suitable for electronic applications, particularly with TOC levels below 1 mg / kg and / or TN (total nitrogen) levels below 0.05 mg / kg (50 ppb), while avoiding the aforementioned disadvantages. Summary of the Invention

[0011] One aspect of this invention is a method for purifying an aqueous solution of hydrogen peroxide, the method comprising at least the following steps:

[0012] (a) Treating an aqueous hydrogen peroxide solution with at least one first reverse osmosis system.

[0013] (b) The obtained hydrogen peroxide solution was treated with at least one first stabilizer.

[0014] (c) Hydrogen peroxide solution obtained by treatment with at least one adsorption resin.

[0015] (d) Optionally, the obtained hydrogen peroxide solution is treated with at least one ion exchange resin.

[0016] The present invention also relates to an aqueous hydrogen peroxide solution obtained or available according to the method of the invention, the aqueous hydrogen peroxide solution containing less than 1 mg / kg of total organic carbon (TOC), less than 0.05 mg / kg of total nitrogen (TN), and less than 0.00001 mg / kg of iron. In some embodiments performing step (d), the amount of iron is less than 0.000001 mg / kg of the aqueous hydrogen peroxide solution.

[0017] Finally, this invention relates to the use of this aqueous hydrogen peroxide solution in the manufacture of microelectronic components and semiconductors.

[0018] The method according to the invention has one or more of the following advantages:

[0019] - It can maintain the lifespan of one or more purification units downstream of the reverse osmosis system;

[0020] -It improves the safety of the purification method;

[0021] - It is capable of delivering hydrogen peroxide solutions with high purity, especially hydrogen peroxide solutions with very low levels of TOC, TN and iron;

[0022] - It has been found that monitoring TN levels is beneficial for ensuring hydrogen peroxide quality and manufacturing stability.

[0023] - It provides a hydrogen peroxide solution that is essentially free of stabilizers. The aqueous hydrogen peroxide solution of the present invention advantageously exhibits a maximum phosphorus content (in PO4) below 0.001 mg / kg. 3- (indicated) and / or up to 1 mg / kg of dry residue at 105°C.

[0024] These specifications make it particularly suitable for electronic applications. Detailed Implementation

[0025] In this disclosure, the phrase "included between" should be understood as including the limit value.

[0026] This invention first relates to a method for purifying an aqueous solution of hydrogen peroxide, the method comprising at least the following steps:

[0027] (a) Treating an aqueous hydrogen peroxide solution with at least one first reverse osmosis system.

[0028] (b) The obtained hydrogen peroxide solution was treated with at least one first stabilizer.

[0029] (c) Hydrogen peroxide solution obtained by treatment with at least one adsorption resin.

[0030] (d) Optionally, the obtained hydrogen peroxide solution is treated with at least one ion exchange resin.

[0031] The aqueous hydrogen peroxide solution used as a starting material in the method of the present invention can be of industrial or commercial grade. This method is particularly suitable for processing hydrogen peroxide produced from oxygen and hydrogen via an auto-oxidation method or by direct synthesis. The method of the present invention is particularly applicable to processing hydrogen peroxide solutions prepared by an auto-oxidation method. In this case, the hydrogen peroxide solution is preferably subjected to distillation treatment before undergoing the method of the present invention. The hydrogen peroxide solution used in the method of the present invention may also contain stabilizers and / or additives, such as nitrates, phosphates, pyrophosphates, phosphoric acid, nitric acid, or any combination thereof. If desired, the hydrogen peroxide solution can be diluted or concentrated before undergoing a purification process. The concentration of the initial aqueous hydrogen peroxide solution can be, for example, in the range of 5 wt% to 70 wt%, particularly from 30 wt% to 70 wt%, more particularly from 50 wt% to 70 wt%, for example, about 60 wt%.

[0032] The method according to the invention relates to the use of a reverse osmosis system in step (a), hereinafter referred to as a first reverse osmosis system. The first reverse osmosis system includes at least one reverse osmosis membrane. The first reverse osmosis system may include a plurality of reverse osmosis membranes arranged in parallel or in series. According to one embodiment, the first reverse osmosis system includes at least two reverse osmosis membranes connected in parallel. One or more membranes used for reverse osmosis may be made of, for example, polyamide, polypiperazineamide, polyacrylonitrile, and / or polysulfone.

[0033] Reverse osmosis systems typically include a housing made of stainless steel. Stainless steel is currently the material of choice because it can withstand the high pressures applied to the system, which are necessary for the normal operation of reverse osmosis. Therefore, the first reverse osmosis system may contain stainless steel. The pressure applied to the first reverse osmosis system can suitably be in the range of 10 bar to 50 bar, particularly from 20 bar to 40 bar. The flow rate of the hydrogen peroxide aqueous solution fed into the first reverse osmosis system can be from 0.1 m... 3 / h to 5m 3 / h, specifically from 0.4m 3 / h to 1m 3 The temperature of the hydrogen peroxide aqueous solution fed into the first reverse osmosis system can be, for example, in the range of 0°C to 25°C.

[0034] The method of the present invention includes a subsequent treatment step (b), in which the obtained hydrogen peroxide solution (permeate) is further treated with at least one stabilizer (hereinafter referred to as the first stabilizer). Treatment step (b) is advantageous for inhibiting hydrogen peroxide degradation and allowing the at least one adsorption resin downstream of the process to remove metallic impurities (particularly iron present in the hydrogen peroxide solution). Without step (b), metallic impurities, particularly iron, cannot be adequately retained by the adsorption resin, and may thus damage any other possible purification equipment downstream of the adsorption resin; particularly when anion exchange resin is present downstream of the adsorption resin, the loading of metallic impurities, particularly iron, on the anion exchange resin will cause instability, and thus safety issues, and reduce its lifespan. Furthermore, the stability of TOC in the final product can be ensured, and the amount of TN can be controlled at a desired low level. It should be noted that those skilled in the art are reluctant to add supplementary materials to purification methods targeting ultrapure hydrogen peroxide solutions due to concerns that additional materials may lead to contamination by themselves. It has been unexpectedly found that the benefits of treatment with a stabilizer according to the method of the present invention outweigh any such concerns.

[0035] The first stabilizer may be selected, particularly from phosphates, pyrophosphates, phosphoric acid, and combinations thereof, more particularly from pyrophosphates, and even more particularly from pyrophosphoric acid. The amount of stabilizer used to achieve the desired stabilizing effect can be adjusted according to the properties of the stabilizer and the amount of metallic impurities detected upstream in the aqueous hydrogen peroxide stream. For example, the amount of the first stabilizer added to the aqueous hydrogen peroxide solution may range from 0.1 mg / kg to 1 mg / kg. This process can be carried out using any suitable technique. The stabilizer can be added to the aqueous hydrogen peroxide stream manually or automatically. A metering pump system can be used in this regard.

[0036] After step (b) and before step (c), an optional processing step (b') may be performed, wherein the hydrogen peroxide solution obtained from step (b) is further treated with at least one reverse osmosis system (hereinafter referred to as the second reverse osmosis system). This additional processing step (b') is advantageous for improving the purity of the final aqueous hydrogen peroxide solution produced according to the method of the present invention, which is beneficial for demanding electronic applications. It should be noted that the upstream processing step (b) also helps to prevent the second reverse osmosis system of step (b') from undergoing oxidative decomposition by metal-catalyzed reactions such as the Fenton reaction, and thereby improves the lifespan of the second reverse osmosis system. The second reverse osmosis system includes at least one reverse osmosis membrane. The first reverse osmosis system may include a plurality of reverse osmosis membranes arranged in parallel or in series. According to one embodiment, the second reverse osmosis system includes only one reverse osmosis membrane. The one or more membranes used for reverse osmosis may be made of polyamide, polypiperazine amide, polyacrylonitrile, and / or polysulfone. Like the first reverse osmosis system, the second reverse osmosis system may contain stainless steel. Therefore, the first reverse osmosis system and / or the at least one second reverse osmosis system may contain stainless steel.

[0037] The pressure applied to the second reverse osmosis system can suitably be in the range of 10 bar to 50 bar, particularly from 20 bar to 40 bar. The flow rate of the hydrogen peroxide aqueous solution fed into the second reverse osmosis system can be from 0.1 m... 3 / h to 5m 3 / h, specifically from 0.5m 3 / h to 1.3m 3 The temperature of the hydrogen peroxide aqueous solution fed into the second reverse osmosis system can be, for example, in the range of 0°C to 25°C.

[0038] After step (b') and before step (c), an optional treatment step (b”) may be performed, in which the hydrogen peroxide solution obtained from step (b') is further treated with at least one stabilizer (hereinafter referred to as the second stabilizer). The second stabilizer may be the same as or different from the first stabilizer. The second stabilizer is preferably the same as the first stabilizer. Thus, the second stabilizer may be particularly selected from phosphates, pyrophosphates, phosphoric acid, and combinations thereof. Depending on the amount of upstream metal impurities and the nature of the stabilizer, a person skilled in the art knows how much to use to achieve the desired stabilizing effect. For example, the amount of the second stabilizer added to the aqueous hydrogen peroxide solution may be in the range of 0.1 to 1 mg / kg of hydrogen peroxide solution. This treatment can be carried out using any suitable technical means. The stabilizer can be added to the aqueous hydrogen peroxide stream manually or automatically. A metering pump system can be used in this regard.

[0039] The resulting aqueous hydrogen peroxide solution is a stable hydrogen peroxide solution. In other words, it contains a certain amount of stabilizer. When one or more stabilizers are added, one or more phosphate-based stabilizers, the aqueous hydrogen peroxide solution can exhibit a minimum phosphorus content of 0.1 mg / kg (in PO4) at this stage of the purification process. 3- (Represented). Phosphate-based stabilizers are particularly suitable for complex metallic impurities, especially iron, that may be released by one or more upstream reverse osmosis systems. However, the final aqueous hydrogen peroxide solution delivered at the end of the purification method of this invention must be substantially free of impurities and stabilizers in order to be usable in electronic applications.

[0040] Therefore, the method of the present invention includes a processing step (c), wherein the obtained hydrogen peroxide solution is treated with at least one adsorption resin.

[0041] It is recommended to use an adsorption resin with the highest possible surface area. The aim is to adsorb contaminants present in the hydrogen peroxide solution onto the surface of the resin in contact with the solution, ensuring that the hydrogen peroxide solution leaving the contact device is free of adsorbed contaminants. Suitable equipment may be, for example, a column filled with a bed of adsorption resin particles. The adsorption resin can be selected from any polymer product, such as polymer products based on styrene-divinylbenzene copolymers. Commercially available adsorption resins from company DuPont are also mentioned. XAD4 yields good results. The contact time between the hydrogen peroxide solution and the adsorption resin is typically at least 10 minutes, particularly at least 40 minutes. In many cases, it is up to 60 minutes, especially up to 50 minutes. Contact with the adsorption resin is usually carried out at a temperature ranging from 0°C to 25°C, particularly from 5°C to 20°C, with approximately 15°C being suitable.

[0042] The method of the present invention may include an additional processing step (d), wherein the obtained hydrogen peroxide solution is treated with at least one ion exchange resin.

[0043] When an ion exchange resin is used in the method of the present invention, ionic impurities present in the hydrogen peroxide solution are countered by ions such as H+ present in the resin. + or HCO3 - Alternatives. Suitable equipment may be, for example, a column packed with a bed of ion exchange resin particles, or the same resin held within a matrix to form a membrane. Ion exchange resins can be selected from a variety of types. Depending on the impurities to be removed, ion exchange resins may be selected from cation exchange resins, anion exchange resins, or combinations thereof.

[0044] Cation exchange resins can be selected from any polymer product capable of reversibly binding cations. Cation exchange resins can be, for example, based on polystyrene and divinylbenzene copolymers. For optimal removal of cationic components such as sodium and calcium, cation exchange resins of the polystyrene and divinylbenzene copolymer type with sulfate groups are particularly suitable. AmberSep, a commercially available cation exchange resin from DuPont... TM )200 gives good results.

[0045] The contact time between hydrogen peroxide solution and cation exchange resin can range from 10 to 60 minutes, particularly from 15 to 30 minutes. Contact with the ion exchange resin is typically carried out at a temperature ranging from 0°C to 25°C, particularly from 0°C to 15°C, with approximately 5°C being suitable.

[0046] Anion exchange resins can be selected from any polymer product, particularly those capable of reversibly binding anions. Anion exchange resins can be, for example, based on polystyrene and divinylbenzene copolymers. Preferably, anion exchange resins containing quaternary ammonium cation groups can be used. For optimal removal of anionic TOC components, and for safety reasons, anion exchange resins in bicarbonate form are particularly suitable.

[0047] The contact time between hydrogen peroxide solution and anion exchange resin can range from 1 minute to 60 minutes, particularly from 3 minutes to 20 minutes. Contact with the anion exchange resin is typically carried out at temperatures ranging from 0°C to 25°C, particularly from 0°C to 10°C, with approximately 5°C being suitable.

[0048] According to one embodiment, optional step (d) includes treatment with at least one cation exchange resin, followed by treatment with at least one anion exchange resin, and then treatment with at least one cation exchange resin again. This sequence is advantageous because the first cation exchange resin is suitable for capturing some iron and most cationic impurities. The presence of a second cation exchange resin is advantageous because the anion exchange resin may leach out cationic impurities.

[0049] In another embodiment, the first reverse osmosis system and / or the at least one second reverse osmosis system and / or the adsorption resin and / or optionally the ion exchange resin comprises a nitrogen-containing polymer. More particularly, the anion exchange resin may comprise a nitrogen-containing polymer. In this case, the method according to the invention is particularly effective in preventing resin degradation and undesirable nitrogen content in the final product, as well as safety issues.

[0050] The method of the present invention may further include at least one dilution step. In this step, water, preferably ultrapure water, is added to the aqueous hydrogen peroxide solution to reduce its hydrogen peroxide concentration. Typically, the hydrogen peroxide concentration is reduced to a value between 30% and 40% by weight, for example, to a value of about 31% by weight. The dilution step may be performed at any stage of the method, but it may be performed particularly after step (b) or (b') or (b''), and preferably before step (c).

[0051] The method of this invention can produce an aqueous hydrogen peroxide solution with very high purity. Therefore, this invention relates to an aqueous hydrogen peroxide solution obtained or available according to the method of this invention, which particularly contains less than 1 mg / kg of total organic carbon (TOC), less than 0.05 mg / kg of total nitrogen (TN), and preferably less than 0.000001 mg / kg of iron. TOC is measured by combining the catalytic oxidation of organic matter with detection by non-dispersive infrared spectroscopy. For example, total nitrogen (TN) can be measured using a Shimadzu TOC-L TOC / TN analyzer. Iron is measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0052] Advantageously, the aqueous hydrogen peroxide solution of the present invention is substantially free of stabilizers. In particular, the aqueous hydrogen peroxide solution of the present invention advantageously exhibits a phosphorus content (in PO4) of less than 0.001 mg / kg. 3- (This is indicated because it can be measured by ion chromatography).

[0053] In a preferred aspect, the aqueous hydrogen peroxide solution of the present invention exhibits a nitrogen content (expressed as TN) of less than 0.05 mg / kg. This can be measured using a Shimadzu TOC-LTOC / TN analyzer or a similar instrument.

[0054] The hydrogen peroxide aqueous solution of the present invention typically has a dry residue of less than 1 mg / kg at 105°C. The dry residue can be determined by weighing after complete evaporation of the volatile components.

[0055] Hydrogen peroxide aqueous solutions, for example, with a H2O2 concentration of 31 wt%, can exhibit the following impurity distribution:

[0056] Trace metals:

[0057]

[0058]

[0059] Finally, this invention relates to the use of the aqueous hydrogen peroxide solution of this invention in the manufacture of microelectronic components and semiconductors. This invention also relates to a method for manufacturing microelectronic components or semiconductors, the method comprising using the aqueous hydrogen peroxide solution of this invention. Typically, hydrogen peroxide can be used to manufacture semiconductor chips and printed circuit boards. In semiconductor manufacturing, hydrogen peroxide is frequently used in cleaning and etching steps, where hydrogen peroxide is typically applied together with other chemicals such as inorganic acids.

[0060] If any disclosure in any patent, patent application, or publication incorporated herein by reference conflicts with the description of this application to the extent that it may lead to ambiguity in terminology, then this description shall take precedence.

[0061] The invention will now be further described with reference to examples, and is not intended to limit the invention.

[0062] Example

[0063] Example 1 - Purification of H2O2

[0064] The materials were analyzed using the methods described above.

[0065] Membrane purification involved passing a 60% (by weight) aqueous solution of hydrogen peroxide through a polyamide reverse osmosis membrane. The feed pressure was 28 bar gauge pressure and the temperature was 5°C. The TOC value of the feed was 110 mg / kg. The resulting permeate was diluted to a concentration of 31% (TOC level below 0.005 mg / kg) using ultrapure water. The stabilizer SAPP (0.5 mg / kg) was added, and the solution was homogenized and analyzed.

[0066] The adsorption resin allows the stable hydrogen peroxide aqueous solution produced above to pass through at a flow rate of 2.5 BV / h at a temperature of 20°C. XAD4 adsorption resin column.

[0067] Ion exchange was performed by continuously passing the resulting hydrogen peroxide aqueous solution through a cation exchange resin and an anion exchange resin in bicarbonate form at a flow rate of 10 BV / h at 20 °C. The resulting hydrogen peroxide solution had a TOC level of 0.6 mg / kg, a PO4 concentration below the detection limit, and a TN concentration below 0.05 mg / kg.

[0068] Counterexample 1

[0069] Membrane purification involved passing a 60% (by weight) aqueous solution of hydrogen peroxide through a polyamide reverse osmosis membrane. The feed pressure was 28 bar gauge pressure and the temperature was 5°C. The feed TC was 110 mg / kg. The resulting permeate was diluted to a concentration of 31% (TOC level below 0.005 mg / kg) using ultrapure water.

[0070] The adsorption resin allows the hydrogen peroxide aqueous solution generated above to pass through at a flow rate of 2.5 BV / h at a temperature of 20°C. XAD4 adsorption resin column.

[0071] Ion exchange was performed by continuously passing the resulting hydrogen peroxide aqueous solution through a cation exchange resin and an anion exchange resin in bicarbonate form at a flow rate of 10 BV / h at 20 °C. The resulting hydrogen peroxide solution had a TOC level of 0.6 mg / kg, a PO4 concentration below the detection limit, and a TN concentration of 0.065 mg / kg.

[0072] Example 2

[0073] The purification of H2O2 was carried out in a manner substantially similar to that of Example 1, and the iron content after membrane purification was determined to be less than 0.001 mg / kg, and the iron content after the adsorption step was less than 0.000005 mg / kg. After the ion exchange step, the iron content was less than 0.000001 mg / kg. The PO4, TN, and TOC values ​​after the ion exchange step were similar to those in Example 1.

Claims

1. A method for purifying an aqueous solution of hydrogen peroxide, the method comprising at least the following steps: (a) Treating an aqueous hydrogen peroxide solution with at least one first reverse osmosis system. (b) A hydrogen peroxide solution obtained by treatment with at least one first stabilizer, wherein the at least one first stabilizer is selected from phosphates, pyrophosphates, phosphoric acid, and combinations thereof. (c) Hydrogen peroxide solution obtained by treatment with at least one adsorption resin.

2. The method according to claim 1, further comprising a step (d) wherein the obtained hydrogen peroxide solution is treated with at least one ion exchange resin.

3. The method according to claim 2, wherein, Step (d) includes treating the obtained hydrogen peroxide solution with a cation exchange resin, followed by an anion exchange resin, and then with a cation exchange resin again.

4. The method according to any one of claims 1 to 3, wherein, The first reverse osmosis system includes at least two reverse osmosis membranes connected in parallel.

5. The method according to any one of claims 1 to 3, comprising a processing step (b') after step (b) and before step (c), wherein the hydrogen peroxide solution obtained from step (b) is further processed with at least one second reverse osmosis system.

6. The method of claim 5, comprising a processing step (b'') after step (b') and before step (c), wherein the hydrogen peroxide solution obtained from step (b') is further treated with at least one second stabilizer.

7. The method according to claim 6, wherein, The at least one second stabilizer is selected from phosphates, pyrophosphates, phosphoric acid, and combinations thereof.

8. The method according to claim 7, wherein, The at least one second stabilizer is the same as the at least one first stabilizer.

9. The method according to claim 5, wherein, The first reverse osmosis system and / or the at least one second reverse osmosis system comprises stainless steel.

10. The method according to claim 5, wherein, The first reverse osmosis system and / or the at least one second reverse osmosis system and / or the adsorption resin contains a nitrogen-containing polymer.

11. The method according to claim 2, wherein, This ion exchange resin contains a nitrogen-containing polymer.

12. The method according to claim 5, wherein, The first reverse osmosis system and / or the at least one second reverse osmosis system and / or the adsorption resin contains a nitrogen-containing polymer.

13. The method according to claim 3, wherein, This anion exchange resin contains a nitrogen-containing polymer.

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