Method for producing ultrapure water

Abstract

The invention relates to a method for producing purified water, said method comprising a step (a) of passing water through a first mixed bed ion exchanger comprising beads having a diameter of between 0.5 and 0.7 mm and a step (b) of passing water through a second mixed bed ion exchanger comprising beads having a diameter of less than 0.5 mm. The invention further relates to a module comprising a first and a second mixed bed ion exchanger and a water treatment system for producing ultrapure water comprising a first and a second mixed bed ion exchanger.

Description

[0001] This invention relates to a method for producing purified water, the method comprising step (a) passing water through a first mixed-bed ion exchanger containing beads with a diameter between 0.5 and 0.7 mm and step (b) passing water through a second mixed-bed ion exchanger containing beads with a diameter less than 0.5 mm. The invention further relates to a module comprising the first and second mixed-bed ion exchangers and a water treatment system comprising the first and second mixed-bed ion exchangers for producing ultrapure water.

[0002] Laboratory ultrapure water is produced from municipal water using a combination of technologies. Typically, activated carbon, reverse osmosis, ion exchange resins, microfiltration / ultrafiltration, UV irradiation, and sterile microfiltration are used alone or in combination to purify water. Ultrapure water purification is the final step in water purification. Milli-Q® (a product of Merck KGaA in Darmstadt, Germany) utilizes ion exchange resins, activated carbon, sterilization and / or photo-oxidation UV lamps, microfiltration, and / or ultrafiltration.

[0003] Ultrapure water (or Type 1 water) is typically characterized by a resistivity greater than 18 MΩ·cm (at 25°C) and a total organic compound (TOC) value of less than 20 parts per billion (ppb). Type 2 water is typically characterized by a resistivity greater than 1.0 MΩ·cm and a TOC value of less than 50 ppb. Type 3 water is the lowest grade of laboratory water, recommended for applications such as glassware rinsing or heating baths, or for supplying Type 1 laboratory water systems. It is characterized by a resistivity greater than 0.05 MΩ·cm and a TOC value of less than 200 ppb.

[0004] In the prior art, the final purification step in ultrapure water production is accomplished by using an ion exchange medium that allows the removal of anions and cations.

[0005] Throughout this invention, ion exchangers, also known as ion exchange resins, are known and proven to be effective in removing ionic impurities from water in the production of pure and ultrapure water. Typically, these are spherically polymerized styrene beads with 0-16% divinylbenzene crosslinking, functionalized by sulfonation (for cation exchange) and amination (for anion exchange), and regenerated, respectively, by strong acid and strong alkali solutions, or other techniques such as electrochemical regeneration. In the following, the term "resin" or "resin beads" refers to the ion exchange material itself (i.e., ion exchange beads), while the term "resin bed" or "resin layer" refers to a resin bed used in a specific arrangement. "Resin" is generally a mixture of both anion and cation exchange resins in a sufficient mixing ratio, resulting in equal capacity for both types of ions or asymmetric capacity for a particular water application. Resins used in the production of pure and ultrapure water require high regeneration rates, such as 95-99%, or even higher. This means that this percentage of ion exchange sites are regenerated to the H form (for cation exchange) and regenerated to the OH form (for anion exchange). For ultrapure water purification, high resin purity is required, meaning very low levels of contaminants and extremely low leaching of total organic carbon. For this reason, the resin is usually further purified.

[0006] In scientific and industrial applications, water deionization for the production of pure and ultrapure water is typically carried out using ion exchange resin beads. The size of the deionization cartridge depends on the expected flow rate, the volume to be treated, and the quality of the water produced. For example, disposable cartridges for small laboratory water systems may contain 1–3 L of resin, while resin bottles for large industrial scale applications typically contain 5–20 L of resin.

[0007] Currently, granular bead-type resins are the only media available in industry and the market. All granular media contain particles with a diameter of approximately 600-700 µm, which is the standard size for industrial use in ion-exchange water deionization. Typically, when municipal water pretreated by RO (conductivity 5-25 µS / cm) is used as feedstock for ultrapure water systems, the cylinder height should be 700-1000 mm to achieve water quality exhibiting a resistivity of 18.2 MΩ·cm. The cylinder diameter is determined to allow sufficient contact time to eliminate ions in a single-pass treatment. For example, the earlier Milli-Q® system (Millipore) with four basins had an inner cylinder diameter of 69 mm and a total resin bed height of 900 mm, reflecting the minimum required resin bed height for achieving ultrapure water quality. Reducing the cylinder height can result in reduced water quality (i.e., failure to achieve ultrapure levels) or reduced cylinder life.

[0008] During the lifespan of an ion exchange cartridge used for water deionization, three zones can be defined, such as in... Figure 8As explained in the text, the minimum resin bed height is called the "ion exchange zone," which is responsible for achieving the desired water quality. This height is a variable that varies with feed water quality, velocity, and target effluent quality. A water treatment tank with only this ion exchange zone is sufficient to achieve the desired water quality, but has zero capacity. As water treatment continues, this zone advances because the resin bed becomes saturated. The height of this zone depends on resin kinetics: faster kinetic resins have shorter zones, and slower kinetic resins have longer zones. The zone upstream of this exchange zone is called the "capacity zone." The longer this zone, the higher the available capacity.

[0009] This means that in existing technology, the size of the cylinder can be reduced simply by decreasing the capacity of the cylinder; however, the ion exchange zone cannot be shortened without compromising water quality. The only way to reduce this zone is by improving resin kinetics. The final zone downstream of the ion exchange zone is called the "trace removal zone," which is specifically used in cylinders used in laboratory ultrapure water systems. This zone ensures that the ultrapure water is free of trace elements that cannot be detected early by water quality indicators such as resistivity meters.

[0010] Attempts have been made to improve the kinetics of such standard ion exchange media in order to provide purification schemes with better performance. Several prior art documents suggest using bead-type ion exchange media to improve their kinetics. In this regard, smaller-sized adsorption media obviously exhibit faster kinetics due to their larger contact surface / bed volume. However, this leads to the disadvantage of higher hydraulic pressure.

[0011] Typically, reducing the diameter of ion exchange resin beads from 550 µm to 250 µm increases the pressure drop by approximately five times. Smaller beads allow for twice the kinetics, but the hydraulic stress is four times greater. Pressure drop is one of the most critical parameters in hydraulic system setups, determining the size of the pump, which is the most energy-consuming component. Theoretically, doubling the pressure requires twice the power and also affects all electrical and mechanical losses. Furthermore, the higher pressure applied to the resin bed column necessitates a more robust hydraulic piping system. Small ultrapure water production systems in laboratories typically operate using booster pumps at approximately 2–3 bar pressure. These systems are usually installed in quiet laboratory environments where the noise from powerful pumps would disturb the user.

[0012] Furthermore, the high pressure applied to the resin bed causes mechanical stress on the resin beads, which can eventually lead to bead breakage. Such particles can contaminate the water, and smaller bead fragments can further increase the pressure drop.

[0013] US 5250187 describes the use of high-kinetic-rate resins for ion exchange applications. The proposed resins are fine-mesh types with small particle diameters. The above flow cytometry uses resins in a fluidized bed to overcome the disadvantages of high hydraulic pressure. This mechanism requires specific design of the resin container. Fluidized beds have the disadvantage of slight leakage of untreated ions. This is tolerable in water softening applications but not suitable for water purification in ultrapure water production.

[0014] The objective of US 2009 / 101586 A1 is to effectively remove radionuclides from water in nuclear-powered plants. In this regard, conventional gel-type resins have certain limitations in terms of radionuclide removal efficiency. Therefore, this document recommends the use of additional layers of small-size macroporous anion exchange resins and / or small-size macroporous chelating resins.

[0015] WO 2013 / 151654 A1 describes the combined use of small-sized particulate adsorbent media and polymeric binders in filtration devices. The combination with the binder allows for reduced pressure drop and enables low-stress filtration.

[0016] EP 1533033 A1 proposes an integral ion exchange medium with a higher contact surface than regular ion exchange resins, as a fast kinetic ion exchange medium without an increase in pressure drop.

[0017] US 4421652 describes a method for treating fluids using beaded resin. The resin bed is loosely packed to avoid high pressure drops.

[0018] Due to the several drawbacks described above, beaded resins have never been used for water deionization or pure / ultrapure water production, despite their advantageous faster kinetics.

[0019] Therefore, there is still a need for schemes that allow the use of fast-dynamic ion exchange media without generating high pressure drops.

[0020] Therefore, the object of the present invention is to provide a scheme for using an advantageous fast-kinetic ion exchange medium in a water purification method without facing the aforementioned disadvantages, such as high pressure drop.

[0021] An unexpected discovery revealed that the combination of standard ion exchange media and bead ion exchange media resulted in excellent performance in water treatment, while simultaneously improving the capacity of the media and the compactness of consumables.

[0022] Therefore, the first embodiment of the present invention is a method for producing purified water, the method comprising step (a) passing water through a first mixed bed ion exchanger containing beads with a diameter between 0.5 and 0.7 mm and step (b) passing water through a second mixed bed ion exchanger containing beads with a diameter less than 0.5 mm.

[0023] According to the present invention, the term purified water refers to type 1, type 2 or type 3 water as defined above, or DI (deionized) water.

[0024] In a preferred embodiment, the purified water is ultrapure water, i.e., type 1 water, characterized by a resistivity greater than 18 MΩ·cm (at 25°C) and a total organic compound (TOC) value of less than 20 parts per billion (ppb).

[0025] In the method of the present invention, steps (a) and (b) can be performed in any order; that is, step (a) can be performed before step (b), or step (b) can be performed before step (a). In a preferred embodiment, step (a) is performed before step (b). In this case, water first passes through a first mixed-bed ion exchanger containing beads with a diameter between 0.5 and 0.7 mm, and then through a second mixed-bed ion exchanger containing beads with a diameter less than 0.5 mm.

[0026] Ion exchangers are typically insoluble matrices in bead form, manufactured from an organic polymer substrate (ion exchange resin). According to the invention, a gel-type ion exchanger is used, comprising a mixture (“mixed bed”) of anion exchange particles and cation exchange particles, respectively in bead form.

[0027] Typically, anion exchange particles facilitate the exchange of hydroxide anions with anions in solution. Cation exchange particles facilitate the exchange of hydrogen ions with cations in solution. Mixtures of anion and cation exchange particles may also include activated carbon particles that adsorb charged or uncharged organic matter that may be present in water. In a preferred embodiment, the mixed-bed ion exchanger consists of a mixture of anion and cation exchange particles.

[0028] The beads of the first mixed-bed ion exchanger have a diameter between 0.5 and 0.7 mm. This resin is also known as "standard resin" or "standard ion exchanger".

[0029] The beads in the second mixed-bed ion exchanger have a diameter of less than 0.5 mm. In a preferred embodiment, the bead diameter is 0.3-0.45 mm. Such resins are also called "bead resins" or "bead ion exchangers".

[0030] Preferably, the ratio of the diameter of beads with a diameter less than 0.5 mm to the diameter of beads with a diameter between 0.5 and 0.7 mm is less than 0.9. More preferably, this ratio is less than 0.8, and most preferably less than 0.7. For example, if the average diameter of the beads in the first mixed-bed ion exchanger is 0.6 mm and the average diameter of the beads in the second mixed-bed ion exchanger is 0.4 mm, then the ratio will be 0.67.

[0031] In this invention, the diameter given represents the diameter of the beads in the regenerated state. The given diameter represents the average particle diameter.

[0032] Preferably, the anion exchange beads and cation exchange beads are monodisperse. The size of the beads can be determined using microscopic imaging instruments, such as Camsizer (Horiba Camsizer XL), Nikon SMZ-2T microscope, or Olympus BX41 microscope (equipped with a DP71 digital CCD camera and Cell imaging software).

[0033] All ion exchange materials known to those skilled in the art can be used in this invention. Typically, ion exchange resins are based on copolymers of styrene and divinylbenzene. The copolymerization of styrene and divinylbenzene results in a cross-linked polymer with a cross-linking degree of 0-16%. After polymerization, ion exchange sites are subsequently introduced. For example, sulfonation allows the production of cation exchange resins with sulfonic acid groups, and chloromethylation followed by amination results in the introduction of quaternary amino functional groups for the production of anion exchange resins. Methods for the manufacture of ion exchange resins are well established, and suitable steps, reagents, and conditions are familiar to those skilled in the art.

[0034] In a preferred embodiment, the first and second mixed-bed ion exchangers are independently based on styrene-divinylbenzene copolymers. More preferably, the mixed-bed ion exchangers are based on sulfonated styrene-divinylbenzene copolymers (cation exchange) and styrene-divinylbenzene copolymers modified with quaternary amino groups (anion exchange).

[0035] Typical capacities for anion exchange resins can be, for example, 1 eq / L, and for cation exchange resins, typically 2 eq / L. However, these figures are not limiting.

[0036] Typically, mixed-bed ion exchangers consist of a mixture of anion and cation exchangers in a ratio that gives them equal capacity for both types of ions.

[0037] Commercially available ion exchange resins with beads of 0.2-0.4 mm in diameter include, for example: - DOW, DOWEX MONOSPHERE 99Ca / 310, 290-317 µm, average 307 µm - DOW, DOWEX MONOSPHERE 99Ca / 320, 302-352 µm, average 317 ±15 µm - DOW, DOWEX MONOSPHERE 99Ca / 350, 317-382 µm, average 347 ±15 µm - DOW, DOWEX fine mesh, 50-100 mesh (300-150 µm), 100-200 mesh (150-74 µm), 200-400 mesh (74-38 µm) - Mitsubishi, Diaion UBK530K (350 µm) - Mitsubishi, Diaion MS01SS (350 µm) Other suitable commercially available ion exchange resins with beads less than 0.5 mm in diameter are listed in the table below: Currently, ion exchange resin manufacturers do not offer ready-to-use, highly regenerable mixed-bed ion exchange resins with smaller bead sizes for pure water production. The resins listed above are typically sold for other applications, such as the purification of sugars and related derivatives from crude sugar juice (cation exchange resins) or the purification of biomolecules for pharmaceutical purposes via chromatography (anion exchange resins).

[0038] Therefore, according to the present invention, such non-regenerated resins or untreated resins used for ultrapure water production must be regenerated and purified before use. Those skilled in the art are fully aware of the necessary steps. For example, the following procedure may be used: The preparative column was packed with resin and rinsed for >15 minutes with a continuous flow of ultrapure water having 18.2 MΩ·cm and <5 ppb TOC at >60 BV / h (BV = bed volume). Then, 2N HCl (for cation exchangers) or 2N NaOH (for anion exchangers) was passed through at 4 BV / h for 1 hour. The column was then rinsed for >15 minutes with a continuous flow of ultrapure water having 18.2 MΩ·cm and <5 ppb TOC at >60 BV / h. The cation and anion exchangers were then mixed in a 1 / 1 equal volume ratio.

[0039] According to the present invention, a commercially available ion exchange resin having beads with a diameter of 0.5-0.7 mm is, for example: Typically, the volume ratio of the first mixed-bed ion exchanger to the second mixed-bed ion exchanger is between 10:1 and 1:5.

[0040] The amount of ion exchanger in the first mixed bed is selected within the linear velocity recommended by the resin supplier for optimal deionization. However, in the context of this invention, a much shorter height than recommended can be selected.

[0041] The amount of the second mixed-bed ion exchange material is selected based on sufficient media depth requirements to completely adsorb ions leaking from the upper resin layer. The dynamic capacity should be close to the total number of ions leaking from the first mixed-bed ion exchange resin during the life of the combined container.

[0042] The diameter and height of the resin bed are determined by the target flow rate for ultrapure water production. For example, a typical mixed-bed ion exchange resin is best suited for operation at a linear velocity of 0.89 cm / s, meaning a 69 mm diameter column is suitable for treating water at a flow rate of 2 L / min. When a 1 MΩ·cm equivalent NaCl solution is fed into the column, with a bed height of 8 cm, a typical resin yields approximately 18 MΩ·cm (at 25°C) of water.

[0043] Beaded resins exhibit superior ion exchange kinetics, for example, twice that of typical mixed-bed ion exchange resins. In this case, beaded resins require only half the bed height to achieve the same ion exchange kinetics compared to conventional resin beds. Therefore, the expected height in use is approximately half.

[0044] Small beads or powdered ion exchange resins with a diameter of less than 0.5 mm offer a large contact surface with the water to be treated, a major reason for the allowable fast ion exchange rates compared to conventionally sized ion exchange resins with an average diameter of 600 µm. However, such very fine adsorption media have significant drawbacks, leading to extremely high pressure drops. Unexpectedly, this combination of both types of media allows for high-performance water purifiers, where conventional resins handle capacity, while fast-kinetic beads handle kinetics and quality. This combination further advantageously results in a more compact water deionization cartridge design, longer lifespan, and higher product water quality.

[0045] In a further embodiment of the invention, the method includes a further step (c) of passing water through an activated carbon bed.

[0046] Activated carbon can remove dissolved organic matter and chlorine.

[0047] Activated carbon is made of porous particles of organic material containing intricate micropores, resulting in a large specific surface area. Organic molecules dissolved in water can enter the pores and bind to their walls through van der Waals forces.

[0048] According to the present invention, either natural or synthetic activated carbon can be used. Natural activated carbon can be produced by processing plant products such as crushed coconut husks carbonized at high temperatures, resulting in irregularly shaped particles and very high mineral extraction. Synthetic activated carbon is produced by the controlled pyrolysis of synthetic spherical beads. Preferably, synthetic activated carbon is used.

[0049] According to the present invention, step (c) may be performed before, between, or within steps (a) and (b).

[0050] Such alternatives are illustrated by the following example: - The water is first passed through an activated carbon bed (step (c)), then through a first mixed bed ion exchanger (step (a)), and then through a second mixed bed ion exchanger (step (b)).

[0051] - The water is first passed through an activated carbon bed (step (c)), then through a second mixed bed ion exchanger (step (b)), and then through a first mixed bed ion exchanger (step (a)).

[0052] - Pass water through a first mixed bed ion exchanger (step (a)), then through an activated carbon bed (step (c)), and then through a second mixed bed ion exchanger (step (b)).

[0053] - Pass water through a second mixed bed ion exchanger (step (b)), then through an activated carbon bed (step (c)), and then through a first mixed bed ion exchanger (step (a)).

[0054] - Water is passed through a first mixed bed ion exchanger (step (a)), then through a first portion of a second mixed bed ion exchanger (step (b)), then through an activated carbon bed (step (c)), and then through a second portion of the second mixed bed ion exchanger (step (b)), i.e., step (c) is performed within step (b).

[0055] - Water is passed through a first mixed-bed ion exchanger mixed with activated carbon (steps (a) and (c)), and then through a second mixed-bed ion exchanger (step (b)).

[0056] - Water is passed through a first portion of a first mixed-bed ion exchanger mixed with activated carbon (steps (a) and (c)), then through a second portion of the first mixed-bed ion exchanger (step (a)), and then through a second mixed-bed ion exchanger (step (b)).

[0057] According to the present invention, the first mixed-bed ion exchanger can therefore be mixed with activated carbon.

[0058] The present invention further relates to a method as defined above, characterized in that the method includes a further step (d) of treating water by reverse osmosis and / or a further step (e) of treating water by electro-deionization, wherein steps (d) and (e) are performed prior to steps (a) and (b).

[0059] Those skilled in the art are familiar with the steps of reverse osmosis and electro-deionization.

[0060] Reverse osmosis (RO) removes many contaminants from water, such as particles, bacteria, and organic matter with a molecular weight >200 Daltons. RO is typically implemented using a semi-permeable membrane that repels these contaminants. Hydraulic pressure is applied to the concentrated solution to counteract the osmotic pressure. The purified water can be collected downstream of the membrane.

[0061] RO membranes are typically made from thin film composites of cellulose acetate or polyamide on a polysulfone substrate.

[0062] Electrodeionization combines electrodialysis and ion exchange processes, resulting in an efficient removal of ions from water, while the ion exchange medium is continuously regenerated by an electric current within the device. Electrodeionization allows for the efficient removal of dissolved inorganic matter, achieving resistivity exceeding 5 MΩ·cm at 25°C (corresponding to a total ion contamination level of approximately 50 ppb). According to the invention, the Elix® module is preferably used for electrodeionization.

[0063] Water purification systems for producing ultrapure water are known and typically consist of: peripheral components such as supports, water quality monitoring resources, pumps, solenoid valves, and transmission units, as well as connecting mechanisms for the releasable mounting of one or two purification cartridges via internal meshing complementary connectors. Due to the depletion of the purification medium and / or membrane clogging over time, timely replacement or replacement based on water consumption is necessary.

[0064] Therefore, media and / or membranes are typically packaged in tubes to facilitate the proper exchange of these consumable media from the corresponding water purification system.

[0065] In a further embodiment, the present invention therefore relates to a module comprising a first mixed-bed ion exchanger and a second mixed-bed ion exchanger, the first mixed-bed ion exchanger comprising beads with a diameter between 0.5 and 0.7 mm, and the second mixed-bed ion exchanger comprising beads with a diameter less than 0.5 mm.

[0066] Such a module can be used in the methods described above.

[0067] Typically, a module is a replaceable cylinder containing the corresponding medium. For example, a module may be in the form of a tube. To establish a connection with a water purification system, the module features a connector capable of a fluid-tight connection between a port on the cylinder and a connector on the system. Suitable connectors are described, for example, in WO 2016 / 128107 A2.

[0068] Within the module, first and second mixed-bed ion exchangers are arranged in series. In this respect, the first mixed-bed ion exchanger may be placed in the upper part of the module, and the second mixed-bed ion exchanger in the lower part, or vice versa. Optionally, a separating mesh or sieve may be used to maintain the medium in the proper position within the module.

[0069] Preferred embodiments of the mixed-bed ion exchange resin in the module are defined above.

[0070] The module according to the invention may further include an activated carbon bed, as defined above. In this case, the activated carbon bed may be located upstream of or between the first and second mixed-bed ion exchangers. In a further embodiment, the activated carbon is mixed with the first mixed-bed ion exchanger.

[0071] The height and diameter of the resin bed in the tube are determined by the water feed, the desired water quality, and the tube capacity, which can be easily determined by those skilled in the art.

[0072] For example, based on the standard resin specifications for UP6150 from Dow / Rohm (as with typical resins mentioned above), a minimum resin bed height of 900 mm is required, while for deionization and ultrapure water purification, the supply flow rate is between 30 and 40 bed volumes per hour (BV / h). A typical laboratory ultrapure water system is designed to dispense 2 L / min. A 3-4 L resin with the required bed height and bed volume to achieve 2 L / min requires a column inner diameter of 65.2 mm to 75.2 mm and a linear velocity (LV) of 1 cm / s to 0.75 cm / s (36 m / h to 27 m / h).

[0073] The same calculations for a given specification of resin Lanxess UP1292 / 1294 with a minimum bed height of 600 mm and a flow rate of 48 BV / h result in an optimal diameter of 73 mm and a linear velocity of 0.8 cm / s (28 m / h).

[0074] Typical laboratory ultrapure water systems such as Milli-Q follow this rule, resulting in a column diameter of 69 mm.

[0075] According to the present invention, the total resin bed height in the cylinder is typically between 10 and 40 cm. Preferably, the total resin bed height is between 10 and 30 cm. In a very preferred embodiment, the total resin bed height is about 25 cm.

[0076] The cartridge is filled with different types of resin. Typically, the resin bed height of the first ion exchange resin in the cartridge is between 5-20 cm, preferably between 5-15 cm. The resin bed height of the second mixed-bed ion exchange resin is typically between 5-20 cm, preferably between 5-15 cm.

[0077] Typically, the cylinder is in the form of a tube with an inner diameter between 65 and 75 mm, preferably about 69 mm.

[0078] Given the prior art, according to the present invention, the combination of standard resin and beaded resin is highly advantageous. From a kinetic point of view, beaded resin requires only a 10 cm resin bed height to achieve 18.2 MΩ·cm from a water feed of 25 µS / cm, while standard resin requires a bed height greater than 20 cm. Since the last 10 cm region of the cylinder plays a kinetic role in determining the dynamic capacity, the type of resin preceding this region has no effect on the capacity. In other words, a cylinder fully filled with beaded resin can exhibit the same capacity as a cylinder filled with a combination of beaded resin and standard resin. In this respect, replacing the 10 cm bottom region of a cylinder filled with standard resin with beaded resin results in a significant effect, reflected in a capacity increase of almost 1000 L. On the other hand, from the viewpoint of hydraulic loss, the combination of standard resin and beaded resin is also advantageous. Compared to a 30 cm beaded resin bed, the 20+10 combination filling exhibits only 2 / 3 of the pressure drop. In other words, compared to a 30 cm standard medium cylinder, the combination filling of a 20 cm standard resin bed and a 10 cm beaded resin bed results in a 30% higher pressure drop, but a 50% increase in capacity. In other words, the 20+10 combination packing exhibits almost the same pressure drop as the 40 cm standard resin bed, but with a 25% reduction in column height and a 20% increase in volume.

[0079] Possible arrangements of resin in the module include, for example: (1) A tube-shaped module with an inner diameter of 69 mm and a total resin bed height of 25 cm contains two resin bed sections: the upper section, with a height of 15 cm, is filled with a first mixed bed ion exchanger; the lower section, with a height of 10 cm, is filled with a second mixed bed ion exchanger.

[0080] (2) A tube-shaped module with an inner diameter of 69 mm and a total resin bed height of 31 cm contains two resin bed sections: the upper section, with a height of 20 cm, contains a first mixed bed resin mixed with activated carbon; the lower section, with a height of 11 cm, is filled with a second mixed bed ion exchanger.

[0081] (3) A tube-shaped module with an inner diameter of 69 mm and a total resin bed height of 30 cm contains two resin bed sections: the upper section, which is 20 cm high, is filled with a first mixed bed ion exchanger or a homogeneous mixture of spherical activated carbon and the first mixed bed ion exchanger; the lower section, which is 10 cm high, is filled with a second mixed bed ion exchanger.

[0082] In a preferred embodiment, arrangement (1) is used.

[0083] The above configuration is suitable, for example, when using feed water with a conductivity of 25 µS / cm (typical for reverse osmosis pretreated water). If more advanced pretreatment systems are used, such as a combination of reverse osmosis and deionization or electro-deionization, or distillation, the conductivity of the feed to the final purification system can be reduced to 1 µS / cm. In this case, even shorter modules can be used, such as: (4) The tube-shaped module with an inner diameter of 69 mm and a total resin bed height of 15 cm contains three resin bed sections: the upper section with a height of 5 cm is filled with activated carbon; the middle section with a height of 5 cm is filled with a first mixed bed ion exchanger; and the lower section with a height of 5 cm is filled with a second mixed bed ion exchanger.

[0084] (5) The tube-shaped module with an inner diameter of 69 mm and a total resin bed height of 15 cm contains three resin bed sections: the upper section with a height of 5 cm is filled with activated carbon; the middle section with a height of 5 cm is filled with a second mixed bed ion exchanger; and the lower section with a height of 5 cm is filled with a first mixed bed ion exchanger.

[0085] (6) A tube-shaped module with an inner diameter of 69 mm and a total resin bed height of 15 cm contains two resin bed sections: the upper section, 10 cm high, contains a first mixed bed resin mixed with activated carbon; the lower section, 5 cm high, is filled with a second mixed bed ion exchanger.

[0086] (7) A tube-shaped module with an inner diameter of 69 mm and a total resin bed height of 10 cm contains two resin bed sections: the upper section with a height of 5 cm contains a first mixed bed ion exchanger; the lower section with a height of 5 cm is filled with a second mixed bed ion exchanger.

[0087] By using a second mixed-bed ion exchanger with a very small bead diameter (e.g., less than 120 µm), the height of the ion exchange zone can be further reduced, resulting in a very high density of the purification cylinder. The reduction in resin bed volume compensates for the increased pressure drop associated with the reduced bead diameter. According to the invention, when using a 1 µS / cm feed and a second mixed-bed ion exchanger with a diameter less than 120 µm, the following modules can be used: (8) A tube-shaped module with an inner diameter of 69 mm and a total resin bed height of 8 cm contains two resin bed sections: the upper section with a height of 5 cm contains a first mixed bed ion exchanger; the lower section with a height of 3 cm is filled with a second mixed bed ion exchanger.

[0088] In a further embodiment, the present invention relates to a water treatment system for producing ultrapure water, the system comprising a first mixed-bed ion exchanger and a second mixed-bed ion exchanger, the first mixed-bed ion exchanger comprising beads with a diameter between 0.5 and 0.7 mm, and the second mixed-bed ion exchanger comprising beads with a diameter less than 0.5 mm.

[0089] Water treatment systems are known in the art. They typically include peripheral components such as supports, water quality monitoring resources, pumps, solenoid valves, and conduction units. When a mixed-bed ion exchanger is provided in a module, a connection mechanism is also required for the releasable mounting of one or more such modules via an internal meshing complementary connector. Connection mechanisms that may be used according to the invention are described, for example, in WO 2016 / 128107 A1.

[0090] Therefore, the present invention also relates to a water treatment system as defined above, wherein first and second mixed-bed ion exchangers are provided in a single module as defined above.

[0091] In an alternative embodiment, first and second mixed-bed ion exchange resins are provided in at least two modules. For example, the first mixed-bed ion exchange resin may be provided in a first cylinder, and the second mixed-bed ion exchange resin may be provided in a second cylinder.

[0092] Modules can be supplied individually or molded together.

[0093] The water treatment system may further include an activated carbon bed, as defined above.

[0094] Similarly, a first mixed-bed ion exchanger, a second mixed-bed ion exchanger, and an activated carbon bed can be provided in a single module as defined above.

[0095] Alternatively, in a preferred embodiment, an activated carbon bed is provided in another module, which comprises an activated carbon bed alone or together with a mixed bed of ion exchangers containing beads with a diameter of less than 0.5 mm.

[0096] For example, in a preferred embodiment, the water purification system may comprise two modules: a first module comprising a first mixed-bed ion exchanger and a second mixed-bed ion exchanger; and a second module located downstream of the first module comprising granular activated carbon and other mixed-bed ion exchangers containing beads with a diameter less than 0.5 mm. A UV photooxidation device is located between the two modules.

[0097] The first module, designed in tube form with an inner diameter of 69 mm and a total resin bed height of 25 cm, deionizes water from pretreated water (such as water pretreated by reverse osmosis, deionization, electro-deionization, distillation, filtration, or a combination of these methods) to ultrapure water up to 18.2 MΩ·cm before photo-oxidative TOC reduction. A combination of standard resin (i.e., the first mixed-bed ion exchange resin) and fast-kinetic resin (i.e., the second mixed-bed ion exchange resin) ensures maximum dynamic capacity. A resistivity unit in the middle after the first tube is used to measure water quality, indicating the end of the first tube's "life," which in turn indicates that the entire paired fill (i.e., both tubes) is nearing the end of its "life." The use of a fast-kinetic zone in the first tube ensures maximum tube capacity for the pair and minimal leakage of trace ions to the second tube. The tube's inner diameter is typically about 69 mm, with the upstream 15 cm section filled with standard ion exchange resin as the capacity zone and the downstream 10 cm section filled with fast-kinetic resin as the ion exchange zone.

[0098] The second chamber also typically has an inner diameter of approximately 69 mm, with its upstream 12.5 cm section filled with activated carbon and its downstream 12.5 cm section filled with fast-kinetic resin. During the nominal operating cycle, the second chamber serves as a trace removal zone or, after the first chamber is saturated, as both an ion exchange zone and a trace removal zone. Separate carbon layers are placed on the upstream (inlet) side of the chamber to remove organic contaminants from the water. Simultaneously, the carbon captures harmful photooxidation byproducts generated by the photooxidation device, such as free radicals and peroxides.

[0099] picture: Figure 1 Experimental setup for dynamic capacity testing as described in Example 1.

[0100] Figure 2A As described in Example 2, the capacity of different media configurations was compared using a synthesized 25 µS / cm NaCl solution as feed water.

[0101] Figure 2B Comparison of hydraulic losses for different media configurations, as described in Example 2.

[0102] Figure 3A The test tube structure is as described in Example 3.

[0103] Figure 3B As described in Example 3, the capacity of different media configurations was compared using a synthesized 25 µS / cm NaCl solution as feed.

[0104] Figure 3C As described in Example 3, a comparison of the capacity of different media configurations using RO water feed.

[0105] Figure 4: Comparison of the capacity of different media configurations using RO water feed, as described in Example 4.

[0106] Figure 5: Comparison of the capacity of different media configurations using a synthesized 25 µS / cm NaCl solution as feed water, as described in Example 5.

[0107] Figure 6: Comparison of capacity of different media configurations using Elix water feed, as described in Example 6.

[0108] Figure 7: Comparison of capacity of different media configurations using Elix water feed, as described in Example 7.

[0109] Figure 8 The three zones of the ion exchange cylinder. Example

[0110] Example 1: The mixed-bed resin used in this example and the experimental setup for simulating different water conditions. The table below summarizes the characteristic parameters of the resin types for bead-mixed bed resin and standard resin: In the following embodiments, beaded mixed-bed ion exchange resin B is used. Beaded mixed-bed ion exchange resin A is also suitable for the purposes of this invention, and its use in the following experiments will lead to similar results.

[0111] Regenerate and purify non-regenerated resins or untreated resins used for ultrapure water production according to the following procedure: The prepared column was packed with resin and rinsed for >15 minutes with a continuous flow of ultrapure water having 18.2 MΩ·cm and <5 ppb TOC at >60 BV / h (BV = bed volume).

[0112] Pass 2N HCl solution (prepared from 25% HCl (EMSURE, Merck KGaA)) (for cation exchangers) or 2N NaOH solution (prepared from 50% NaOH (EMSURE, Merck KGaA)) (for anion exchangers) through the solution at 4 BV / h for 1 hour.

[0113] Rinse the column for >15 minutes with a continuous flow of ultrapure water having 18.2 MΩ·cm and <5 ppb TOC at a rate of >60 BV / h.

[0114] The cation exchanger and anion exchanger are mixed in a 1 / 1 equal capacity ratio.

[0115] Store the mixed resin in heat-sealed plastic bags or tightly closed bottles.

[0116] Dynamic capacity test conditions: To simulate typical water supply conditions in the laboratory, NaCl (Merck EMSURE®) was added to ultrapure water prepared by the Elix® 100 system (Merck KGaA from Darmstadt, Germany), SDS 200 (Merck KGaA from Darmstadt, Germany), and Mill-Q® Reference A+ (Merck KGaA from Darmstadt, Germany) to a conductivity of 25 µS / cm.

[0117] In the test bench, ultrapure water stored in a 10 L PE tank was recirculated through a purification device (Quantum TEX purification cylinder, Merck KGaA from Darmstadt, Germany) and a test column containing an ion exchange resin sample. Upstream of the test column, a salt injection point was positioned where a precise injection pump (ISMATEC MCP-CPF process pump + PMOCKC pump head) added 30 g / L of the prepared concentrated salt solution to a target conductivity of 25 µS / cm. A resistivity sensor (Thornton 770MAX, Mettler Toledo) measured the water resistivity at the inlet and outlet of the test column.

[0118] The test column diameter was 35 mm (as a ¼-scale model) or 69 mm (as a 1 / 1-scale model). The water recirculation flow rate was adjusted to a linear velocity of 0.89 cm / s, which is 0.5 L / min or 2.0 L / min for both column diameters.

[0119] Experimental setup Figure 1 It is displayed in the middle.

[0120] Actual water supply conditions: Typically, ultrapure water for laboratory use is produced from tap water through pretreatment technologies such as RO, RO-DI, RO-EDI, distillation, or combinations thereof, prior to the final purification step using high-quality ion exchange resins. Two categories of feedwater are possible: 1) High ionic charge feed water, typically delivered by a reverse osmosis system with a conductivity of 5-50 µS / cm, including dissolved CO2. The RiOs (Merck KGaA from Darmstadt, Germany) system is used to produce RO water using municipal water feed (Guyancourt, France). The average water quality is 15-25 µS / cm with 15-20 ppm CO2.

[0121] 2) Low-ionic-charge feed water from RO-DI, RO-EDI, or distillation systems containing only up to 1 µS / cm equivalent salt. The Elix® system (Merck KGaA, Darmstadt, Germany) is used to produce this type of water using municipal water feed (Guyancourt, France). The average water quality is 0.1–1 µS / cm with ppm CO2 below the detection limit (<1 ppm).

[0122] The following examples demonstrate the performance of the medium under two conditions.

[0123] Water quality is measured at the column or cylinder outlet using a resistivity sensor and / or a TOC analyzer (A100 / A1000, Anatel).

[0124] Example 2: Capacity of different media A single 30 cm tube (35 mm in diameter) was filled with a mixed-bed resin. The resin bed column was run at 0.5 L / min (equivalent to 0.89 cm / s) using a 25 µS / cm NaCl solution to examine effluent resistivity changes and cylinder capacity. A 10 MΩ·cm setpoint was applied to the capacity endpoint. Additionally, hydraulic losses for each configuration were measured using a differential pressure gauge. The results were normalized to values ​​obtained using a standard 30 cm resin bed.

[0125] Analyze the properties of the following resin bed columns: 1) Standard resin bed, Jetpore: 20 cm high (STD20) 2) Standard resin bed, Jetpore: 30 cm high (STD30) 3) Standard resin bed, Jetpore: 40 cm high (STD40) 4) Combination of a 20 cm standard resin bed (upstream) and a 10 cm bead resin bed (downstream) (STD20+SB10) 5) Small bead resin bed: 30 cm high (SB30) The result is Figure 2A The text appears to be a mix of Chinese characters and symbols, possibly representing a corrupted or incomplete translation. A direct translation wouldn't be meaningful without further context. Column 1, filled with a 20 cm standard resin bed, could not achieve a resistivity of 18 MΩ·cm (at 25°C). Columns 2 and 3, filled with 30 cm and 40 cm standard resin beds, maintained stable levels of ultrapure water quality. The combination of a 20 cm standard resin bed and a 10 cm beaded resin bed (column 4) exhibited a significantly higher capacity than the same height (30 cm) standard resin bed (column 2). Furthermore, the capacity was even better than that of a taller column (40 cm) standard resin bed (column 3). Experiments using column 5, filled with a 100% beaded resin bed, resulted in almost the same curve as the combined column 3, although the amount of fast-kinetic resin bed was much higher.

[0126] Figure 2B The results show the hydraulic loss of the test column. Compared with column 4 (20 cm STD + 10 cm SB), column 3 (40 cm STD) shows almost the same hydraulic loss in terms of pressure drop, while the construction has much less capacity, despite the fact that it has a higher number of resin beds.

[0127] Example 3: Water supply with high ionic charge, Case 1 The commercially available Milli-Q® Direct system from Merck Millipore is an all-in-one system that treats tap water to ultrapure water through activated carbon pretreatment, reverse osmosis, storage tank, UV photo-oxidation, and deionization. In the final DI step, ion exchange resin is used. Typically, tap water ranging from 100 to 2000 µS / cm is purified to 96% to 99% rejection; therefore, the feed ion charge ranges from a few microsiemens to 50 µS / cm. In the prior art, the final purification tube, Q-PAK TEX, has twice the 1.2 L volume of granular purification media (69 mm in diameter, 320 mm in height) and contains 1.2 L of Organex (a homogeneous mixture of spherical activated carbon and standard mixed-bed ion exchange resin) in the first tube and 1.2 L of mixed-bed resin in the second tube. It operates at 2 L / min (linear velocity 0.89 cm / s).

[0128] The following tests were performed in a ¼ scale model, maintaining the linear velocity while reducing the column portion and flow rate to 1 / 4, with a diameter of 35 mm and a flow rate of 0.5 L / min. At the given flow rates, a synthetic 25 µS / cm NaCl solution was used, and in some cases, RO water was used as feed, in continuous flow mode for the test cylinder. The X-axis of the capacity profile is reported for a 69 mm equivalent.

[0129] Test the following constructs: Test constructed in Figure 3A The explanation is as follows.

[0130] The result is Figure 3B (25 µS / cm NaCl solution feed for synthesis) and Figure 3C (RO water feed) shows.

[0131] At 4000 L, the standard filling configuration (1) with a 32 cm Organex resin bed and a 32 cm standard resin bed showed a resistivity decrease of less than 18 MΩ cm (at 25°C).

[0132] The identical construction (2) with a height of only 20 cm for each resin bed resulted in a significant loss of capacity.

[0133] In configuration (3), the 20 cm standard resin bed was replaced with a 10 cm beaded resin bed. Despite the reduction in resin bed volume, this configuration maintained almost the same capacity as the initial configuration (1).

[0134] If the level of organic pollution is not sensitive to the application, structure (4) is a useful alternative to structure (3), providing greater compactness.

[0135] Structure (5) is an extremely compact filling design. This structure, with only half the media volume, can still consistently produce 18.2 MΩ·cm of ultrapure water.

[0136] For comparison, the results of a 30 cm standard resin bed are shown in construction (6).

[0137] Example 4: Water supply with high ionic charge, Case 2 The commercially available Milli-Q® Advantage from Merck Millipore is an ultrapure purification system supplied via pretreatment systems such as RO, RO-DI, RO-EDI, DI, and / or distillation. The system is equipped with the following modules: “Q-GardT1,” a dual-tube module containing a 1.2 L Organex resin bed and a 1.2 L standard mixed-bed resin bed; a 17W photo-oxidation UV reactor; and “Quantum TEX,” a single-tube module containing a 0.5 L Organex resin bed and a 0.5 L mixed-bed resin bed. The packing diameter is 69 mm. The first dual-tube module has a height of 32 cm, and the second single-tube module has a height of 25 cm. The system has a dispensing capacity of 2 L / min.

[0138] The existing technology system is compared with two solutions according to the present invention. Using RO feedwater as described in Example 1, the following configuration was tested: The results are shown in Figure 4: Instead of the three columns in series used in the prior art (Construction 1), the present invention (Construction 3) allows for a much more compact solution.

[0139] Example 5: Compact Ultrapure Water System The commercially available Direct-Q® system from Merck Millipore is an all-in-one system that treats tap water to ultrapure water through activated carbon pretreatment, reverse osmosis, storage tank, UV photo-oxidation, and deionization. Ion exchange resin is used in the final DI step. Typically, tap water ranging from 100 to 2000 µS / cm is purified to 96% to 99% rejection, thus the feed ion charge ranges from a few microsiemens to 50 µS / cm. In the prior art, the final purification tube, Smartpak DQ, has a 1.0 L volume of granular purification media (nominal diameter 69 mm, height 250 mm) and contains 0.5 L of Organex (a homogeneous mixture of spherical activated carbon and standard mixed-bed ion exchange resin) in the upper compartment and 0.5 L of mixed-bed resin in the lower compartment. Due to the lack of ion exchange resin to guarantee operation, the speed is limited to 0.7 L / min (linear velocity 0.31 cm / s).

[0140] The following tests were performed in a 1 / 1 scale model. While prior art cartridges were tested at 0.7 L / min, cartridges according to the invention, using beaded resin, were attempted to operate at 2 L / min. Using RO water feed, cartridges were tested every 2 hours for a 3x 6L dispensing at a given flow rate in intermittent flow mode. 1 (Prior Art) Organex resin bed 12.5 cm Standard resin bed 12.5 cm 2 (This invention) Organex resin bed 15 cm Small bead resin bed 10 cm

[0141] The results are shown in Figure 5: The existing design, using a total resin bed height of 25 cm, produces ultrapure water at 0.7 L / min. Surprisingly, at an increased flow rate of 2 L / min, the design according to the present invention, using a 25 cm resin bed height, achieves the same water quality and cylinder capacity without any performance degradation. Comparing the total amount of ion exchanger in the two designs, the cylinder according to the present invention allows for a higher flow rate with less resin.

[0142] Example 6: Water supply with low ionic charge The commercially available Milli-Q® Integral from Merck Millipore is an all-in-one system that treats tap water to ultrapure water through activated carbon pretreatment, reverse osmosis, electro-deionization, in-line sterilization, storage tank, UV photo-oxidation, and deionization. Ion exchange resins are used in the final DI step. Typically, upstream of the tank, tap water ranging from 100 to 2000 µS / cm is treated to 1 µS / cm and 100 ppb TOC via a purification step. The water in the tank is then passed through UV light and a purifier to obtain ultrapure water on demand. As described in previous examples, a typical column diameter of 69 mm and a packing height of 25 cm are used, containing Organex resin and standard mixed-bed ion exchange resin. The flow rate is 2 L / min (linear velocity 0.89 cm / s).

[0143] As described in Example 1, using Elix water supply, the following tests compare prior art solutions (with a single tube of 69 mm diameter and 25 cm height) with the construction according to the present invention. These constructions use a single tube only 15 cm high and 69 mm in diameter, with combinations of activated carbon and different media layers, as shown in the table below. 1 (Prior Art) Organex resin bed 12.5 cm Standard resin bed 12.5 cm - 2 (This invention) Activated carbon bed 5 cm Standard resin bed 5 cm Small bead resin bed 5 m

[0144] The results are shown in Figure 6: Construction 2, combining a 5cm standard resin bed and a 5cm beaded resin bed, can consistently produce water of 18.2 MΩ·cm quality from Elixir water. An additional 5cm activated carbon layer on top of the ion exchange resin bed ensures a sufficient level of TOC content in the ultrapure water. The height of the ultrapure water purification cylinder according to the invention is approximately half the height of the compared prior art.

[0145] Use the following constructs to perform other tests: 1 (Prior Art) Organex resin bed 12.5 cm Standard resin bed 12.5 cm 2 (This invention) Organex resin bed 10 cm Small bead resin bed 5 cm The results are shown in Figure 7: Instead of separating the activated carbon bed and the ion exchange resin bed, Organex resin, which is a homogeneous mixture of activated carbon and ion exchange resin, is applied to the first medium. Ultrapure water of 18.2 MΩ·cm is obtained by this invention, and similar to the above embodiments, the TOC is also good.

Claims

1. A method for producing purified water, the method comprising step (a) passing water through a first mixed-bed ion exchanger containing beads with a diameter between 0.5 and 0.7 mm and step (b) passing water through a second mixed-bed ion exchanger containing beads with a diameter less than 0.5 mm.

2. The method according to claim 1, characterized in that... The purified water is ultrapure water.

3. The method according to claim 1 or 2, characterized in that... Step (a) is performed before step (b).

4. The method according to one or more of claims 1-3, characterized in that... The first mixed-bed ion exchanger is composed of a mixture of anion exchange particles and cation exchange particles.

5. The method according to one or more of claims 1-4, characterized in that... The second mixed-bed ion exchanger consists of a mixture of anion exchange particles and cation exchange particles.

6. The method according to one or more of claims 1-5, characterized in that... The first mixed-bed ion exchanger is based on a styrene-divinylbenzene copolymer.

7. The method according to one or more of claims 1-6, characterized in that... The second mixed-bed ion exchanger is based on styrene-divinylbenzene copolymer.

8. The method according to one or more of claims 1-7, characterized in that... The volume ratio of the first mixed-bed ion exchanger to the second mixed-bed ion exchanger is between 10:1 and 1:

5.

9. The method according to one or more of claims 1-8, characterized in that... The method includes a further step (c) of passing water through an activated carbon bed.

10. The method according to one or more of claims 1-9, characterized in that... The method includes a further step (d) of treating water by reverse osmosis and / or a further step (e) of treating water by electro-deionization, wherein steps (d) and (e) are performed prior to steps (a) and (b).

11. A module comprising a first mixed-bed ion exchanger and a second mixed-bed ion exchanger, the first mixed-bed ion exchanger comprising beads with a diameter between 0.5 and 0.7 mm, and the second mixed-bed ion exchanger comprising beads with a diameter less than 0.5 mm.

12. The module according to claim 11, characterized in that... The first mixed-bed ion exchanger is based on a styrene-divinylbenzene copolymer.

13. The module according to claim 11 or 12, characterized in that The second mixed-bed ion exchanger is based on styrene-divinylbenzene copolymer.

14. The module according to one or more of claims 11-13, characterized in that... It further includes an activated carbon bed, which is optionally mixed with the first mixed bed ion exchanger.

15. A water treatment system for producing ultrapure water, the system comprising a first mixed-bed ion exchanger and a second mixed-bed ion exchanger, the first mixed-bed ion exchanger comprising beads with a diameter between 0.5 and 0.7 mm, and the second mixed-bed ion exchanger comprising beads with a diameter less than 0.5 mm.

16. The water treatment system according to claim 15, characterized in that... The first and second mixed-bed ion exchangers are provided in a single module according to one or more of claims 11-14.

17. The water treatment system according to claim 15, characterized in that... The first and second mixed-bed ion exchangers are provided in at least two modules.

18. The water treatment system according to one or more of claims 15-17, wherein the system further comprises an activated carbon bed.

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