Method and device for the targeted formation of caco 3 0 ion pairs in calcareous waters

Abstract

The invention relates to a method for stabilising limescale precipitation from drinking or service water in a drinking or service water installation, wherein the drinking or service water comprises dissolved Ca2+ ions and HCO3 - ions, wherein the method comprises the targeted catalytic deprotonation of HCO3 - ions and the continuous formation of CaCO 3 0 - ion pairs in the drinking or service water by contacting the drinking or service water with a polymeric granulate having functional groups, wherein the functional groups of the polymeric granulate comprise carboxylate groups which form cation-binding sites, wherein between 0.01% and 10%, preferably 0.5% to 5%, of the cation-binding sites formed by the carboxylate groups are occupied by at least one di- or trivalent metal cation different from Ca2+, less than 1.5% of the cation-binding sites are occupied by H+ ions, and wherein the remaining cation-binding sites are occupied by Ca2+ ions, with the proviso that the at least one di- or trivalent metal cation different from Ca2+ binds more strongly to the cation-binding sites than Ca2+.

Description

[0001] METHOD AND DEVICE FOR THE TARGETED FORMATION OF CaCO3°

[0002] Ions in calcareous waters

[0003] The present invention relates to a method for stabilizing limescale deposits in drinking and process water installations from drinking or process water containing dissolved calcium. 2+ The invention relates to a device for stabilizing limescale deposits in drinking and process water installations using a polymeric granulate. It further relates to a device for stabilizing limescale deposits in drinking and process water installations for carrying out a method. Finally, the invention relates to the use of a polymeric granulate.

[0004] BACKGROUND OF THE INVENTION

[0005] Calcium carbonate (CaCOrf) – also known as lime – is an important mineral in many types of process and utility water. In drinking water, calcium carbonate is present in dissolved form as Ca 2+ -, HCCE'- and CC '-ions are desirable, since Ca 2+Calcium ions contribute to the supply of calcium to the human body, and bicarbonate / carbonate acts as a pH buffer, making drinking water less corrosive during transport through water pipes. However, if CaCCh precipitates in water pipes or the drinking water installation, this leads to significant technical problems, making regular limescale protection necessary.

[0006] There are various technologies for limescale protection in drinking water installations. Ion exchangers remove the "hardness-causing" minerals (Ca). 2+ - and Mg 2+ - ions) in exchange for other ions. By dosing phosphate- and silicate-containing minerals, limescale precipitation can be prevented, i.e., the formation of limescale deposits is prevented and the limescale remains in the water.

[0007] Since ensuring the quality of drinking water is of the highest priority, the aforementioned technologies have limited applicability. Therefore, for approximately 20 years, processes have been increasingly used in the drinking water sector that form minute calcium carbonate crystals from the hardness-causing minerals in water and release these into the flowing water as seed crystals. Through their growth, the seed crystals in the water stabilize the calcium carbonate precipitation in the downstream drinking water installation. Two process concepts have proven effective for the formation of seed crystals from the hardness-causing minerals present in the water: (a) the catalytic formation of calcium carbonate nuclei on the surfaces of functionalized polymers and (b) the formation of calcium carbonate crystals using electrochemical methods. EP 0 932 583 Bl describes a process for the reduction or...Prevention of stone formation by using two bipolar electrodes to generate tiny lime crystals through the application of electrical voltage and electrolysis, thus providing limescale protection.

[0008] EP 0 957 066 Bl describes a process in which the precipitation of components from solutions is achieved by loading an ion exchange material with counterions. In particular, it describes that the precipitation of CaCOs is successful when the counterions (Ca 2+ The resin arranges ions on the surface of a weakly acidic ion exchange resin in such a way that they form a template for the formation of a calcium carbonate nucleus. The hardness-causing minerals present in calcareous waters consequently adhere to this template and form small calcium carbonate crystals. Once these crystals reach a certain size, they are released into the water and stabilize the calcium carbonate precipitation by crystallizing excess calcium carbonate onto them.

[0009] WO 2010 / 122508 A2 discloses a process for the treatment of water, wherein the water is brought into contact with a catalyst which comprises a water treatment agent bound to a support material, wherein the water treatment agent comprises magnesium ions, aluminium ions, zinc ions, titanium ions and mixtures thereof.

[0010] BRIEF DESCRIPTION OF THE INVENTION

[0011] Currently, there are different approaches to stabilizing limescale deposits in drinking and process water pipes, each with its own advantages and disadvantages:

[0012] • Electrochemical processes – such as those described in EP 0 932 583 Bl – require careful handling when used in drinking water applications to prevent the formation of substances harmful to drinking water during electrolysis (for example, chlorine gas is formed from chloride ions in the water during electrolysis) or to avoid excessively high hydrogen concentrations resulting from water electrolysis. These factors limit the efficiency of limescale nucleation and make scaling up to larger flow rates difficult.

[0013] • The catalytic precipitation of CaCO₃ as calcium carbonate using an ion exchange material as a catalyst – as described, for example, in EP 0 957 066 B 1 – does not have the problems described in EP 0 932 583 Bl. No water-polluting substances are formed, and the process allows for simple scaling via the amount of ion exchange material used. Disadvantages of this process include, firstly, the formation of macroscopic calcium crystal deposits both on the surface of the ion exchange material and within the installations. This can lead to the formation of limescale sludge in drinking water installations. Secondly, only small areas of the surface of the ion exchange material can be activated to act as templates for crystal nucleation. Consequently, large quantities of ion exchange material must be used to achieve the necessary calcium crystal nucleation density for the process to be successful.

[0014] The object of the present invention is therefore to provide a method and a device for limescale protection in drinking water, in which the aforementioned disadvantages are avoided.

[0015] This problem is solved, on the one hand, by a method for stabilizing the limescale precipitate from drinking or process water in a drinking or process water installation, whereby the drinking or process water contains dissolved Ca 2+ -ions and HCOs'-ions, wherein the process comprises the targeted catalytic deprotonation of HCOT ions and the continuous formation of CaCO° ion pairs from the drinking or process water by contacting the drinking or process water with a polymeric granule having active groups, wherein the active groups of the polymeric granule comprise carboxylate groups forming cation binding sites, wherein

[0016] (i) between 0.01% and 10%, preferably 0.5% to 5% of the cation binding sites formed by the carboxylate groups, with at least one of Ca 2+ are proven to be various di- or trivalent metal cations, with the proviso that at least one of Ca 2+ Various di- or trivalent metal cations bind more strongly to the cation binding sites than Ca 2+ ,

[0017] (ii) < 1.5% of the cation binding sites with H + -ions are occupied

[0018] (iii) < 5%, preferably < 2.5% of the cation binding sites with different cations from those in point (i) and from Ca 2+ are documented in various metal cations and

[0019] (iv) where the remaining cation binding sites are filled with Ca 2+ -ions are occupied.

[0020] This problem is solved, on the other hand, by a device for stabilizing limescale deposits in drinking and process water installations, comprising a filter vessel with an inlet for drinking or process water and an outlet, wherein at least one polymeric granulate with active groups is present in the filter vessel, wherein the active groups of the polymeric granulate comprise carboxylate groups that form cation binding sites, wherein

[0021] (i) between 0.01% and 10%, preferably 0.5% to 5% of the cation sites formed by the carboxylate groups, comprising at least one of Ca 2+ are proven to be various di- or trivalent metal cations, with the proviso that at least one of Ca 2+ Various di- or trivalent metal cations bind more strongly to the cation binding sites than Ca 2+>

[0022] (ii) < 1.5% of the cation binding sites with H + -ions are occupied

[0023] (iii) < 5%, preferably < 2.5% of the cation binding sites with different cations from those in point (i) and from Ca 2+ are documented in various metal cations and

[0024] (iv) where the remaining cation binding sites are filled with Ca 2+ -ions are occupied

[0025] Finally, this task is solved by using a polymeric granule with active groups, wherein the active groups of the polymeric granule include carboxylate groups that form cation binding sites, wherein

[0026] (i) between 0.01% and 10%, preferably 0.5% to 5% of the cation sites formed by the carboxylate groups, comprising at least one of Ca 2+ are proven to be various di- or trivalent metal cations, with the proviso that at least one of Ca 2+ Various di- or trivalent metal cations bind more strongly to the cation binding sites than Ca 2+

[0027] (ii) < 1.5% of the cation binding sites with H + -ions are occupied

[0028] (iii) < 5%, preferably < 2.5% of the cation binding sites with different cations from those in point (i) and from Ca 2+ are documented in various metal cations and

[0029] (iv) where the remaining cation binding sites are filled with Ca 2+ -ions are occupied, for the continuous catalytic formation of CaCO^ ion pairs from Ca dissolved in water 2+ - and HCCh' ions.

[0030] The present invention is based on the finding that a specially conditioned polymeric granulate made from calcium ions (Ca) present in flowing water can be used to create a special effect. 2+In a first step, hydrogen carbonate ions (HCOT) are catalytically deprotonated, and in a second step, CaCO₃ ion pairs are generated, which are then immediately released back into the water. This technique differs fundamentally from the prior art, in which the catalytic formation of CaCO₃ ion pairs in drinking and process water is unknown. In EP 0 957 066 Bl, for example, CaCO₃ crystals are directly deposited on the surface of an ion exchange resin in minute areas of highly ordered Ca 2+Carboxylate groups (templates) loaded with calcium ions are formed from the hardness-causing substances in the flowing water. These calcium carbonate crystals are then partially released into the water and act as seed crystals, providing limescale protection. However, a significant proportion of the CaCO₃ crystals remain on the surface of the ion exchange resin, and additional effort is required to prevent limescale buildup on the resin.

[0031] Instead of the formation of calcium carbonate crystals on the surface of the polymeric granules, the invention provides for the formation of CaCO₃ ion pairs in the boundary layer of the polymeric granules. The invention is based on the fact that two ion exchange reactions of water constituents with the granules can occur continuously. In the first reaction, HCO₃⁻ ions dissociate in the boundary layer into CO₃⁻. 2 '- and H + -ions (deprotonation). Two H ions formed in this way +-ions exchange with a Ca 2+ -Ion from the granules. The remaining COs 2 ' -ions form with Ca 2+ CaCO₃ ions from the boundary layer or the water diffuse away from the polymer granules into the flowing water. The second reaction binds Ca₃ again. 2+ -ions from the flowing water in exchange for H + -ions are bound to the granules. For the second reaction, the "reverse reaction," the doping of the granules, which are actually in the calcium form, with specific di- or trivalent metal cations is crucial. Without this doping, the formation of CaCO₃ ion pairs does not proceed continuously. Through the constant formation of CaCO₃ ion pairs from the hardness-causing substances, ions are removed from the calcium carbonate equilibrium, and the water's tendency to deposit limescale is significantly reduced.

[0032] CaCO3 ion pairs were initially considered hypothetical complexes in the description of the calcium carbonate equilibrium. Meanwhile, numerous publications have confirmed the existence and stability of this complex experimentally and computationally. CaCO3 ion pairs remain a subject of ongoing research (see references [1] to [6]). Previously, it was assumed that the formation of CaCO3 ion pairs depended on the concentration of CO3. 2 - (Carbonate) and Ca 2+ The concentration of carbonate ions in water is determined. The carbonic acid equilibrium shows that only at very high pH values ​​(> 10.2) is the carbonate ion concentration greater than the concentration of hydrogen carbonate ions. At a pH of 8.2, the ratio HCO3-7CO3 is... 2 ' = 100 : 1, at a pH of 7 the ratio is HCO37CO3 2' > 1000 : 1. Accordingly, CaCO^ ion pairs are only present in very small concentrations in the water at the typical pH values ​​for drinking water (6.5 - 9.5).

[0033] All details of the invention described below apply equally to the method, apparatus and use.

[0034] The process described here very efficiently catalyzes the formation of CaCO₃ ion pairs. The direct effect on the calcium carbonate equilibrium is that free Ca is released into the water. 2+- and HCOT ions are removed, the pH is lowered, and the equilibrium conditions shift. It is known that for spontaneous (homogeneous) calcium carbonate precipitation from a solution (homogeneous crystal nucleation), a (calculated) 100-fold calcite equilibrium concentration is required to make the formation of calcium carbonate crystal nuclei probable. Therefore, in the supersaturation range below this value, heterogeneous processes are crucial for calcium carbonate crystal nucleation and precipitation. The role of CaCO₃ ion pairs in the interaction with these heterogeneous surfaces is the subject of current research.

[0035] In experimental series where the supersaturation of calcareous solutions is increased by raising the temperature, the samples with CaCO^ ion pairs show no calcium carbonate precipitation for a significantly longer period.

[0036] The formation of such CaCO^ ion pairs with a polymeric granulate and the prevention / reduction of lime precipitation with these ion pairs is currently unknown.

[0037] Further details and embodiments of the method, the apparatus, and the use are described below. For the method, the apparatus, and the use, the di- or trivalent metal cations, preferably selected from the group consisting of Mn, are suitable. 2+ , Fe 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , CD 2+ , Al 3+ , Ga 3+ or combinations thereof, are crucial. All of these metal cations exhibit stronger bonds (bonding constants) with respect to the cation binding sites than Ca. 2+ Particularly preferred are the di- or trivalent metal cations selected from the group consisting of Cu. 2+ , Zn 2+ , Fe2+ , Fe 3+ , Al 3+ or combinations thereof. These metal cations are particularly advantageous for drinking water applications, since Cu 2+ , Zn 2+ , Fe 2+ and Al 3+ These metal cations are less of a health concern and are therefore permitted to be present in higher concentrations in drinking water. Nevertheless, it should be noted that the di- or trivalent metal cations are so strongly bound in the polymer matrix that virtually no release of these metal cations can occur in typical drinking water.

[0038] It is preferably provided that divalent metal cations occupy 0.1% to 10%, preferably 0.5% to 5%, of the cation sites formed by the carboxylate groups. Due to the stronger bonding, it is preferably provided that trivalent metal cations occupy 0.01% to 1% of the cation sites formed by the carboxylate groups.

[0039] Using the reference tests described here (pH / conductivity / [Ca) 2+ ]-ISE with calcium carbonate calculation according to DIN 38404-10) the claimed technical effect is achievable over the entire doping range; the tests are equally applicable to edge areas (see Fig. 6 / 7, evaluation method).

[0040] The di- or trivalent metal cations mentioned in the claims can be fixed in total in the range of 0.01% to 10% of the total capacity at cation binding sites; no relevant release into normal drinking water is to be expected.

[0041] A residual loading of < 1.5% of the cation binding sites with H + -ions (carboxyl groups) serve to adapt to the pH values ​​of the respective drinking and process water.

[0042] It is preferred for the method, apparatus and use that none of the metal ions mentioned in point (iii) are present, so that the feature “< 5%, preferably < 2.5%, particularly preferably 0% of the cation binding sites with ions other than those in point (i) and of Ca 2+ The phrase "are proven to contain various metal cations" can be omitted.

[0043] The highest conversion rates for the formation of CaCO₃ ion pairs were achieved with polymeric granules in which two or more di- or trivalent metal cations are bound to cation-binding sites. In particular, polymeric granules with cation sites occupied as follows were found to be the most catalytically efficient:

[0044] 0.5% - 9% Zn 2+ and 0.05% - 1% Cu 2+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Cu 2+ or

[0045] 0.5% - 9% Zn 2+ and 0.01% - 1% Al 3+ , preferably 0.5% - 5% Zn2+ and 0.05% - 1% Al 3+ or

[0046] 0.5% - 9% Zn 2+ and 0.01% - 1% Fe 3+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Fe 3+ or

[0047] 0.5% - 9% Zn 2+ and 0.05% - 1% Fe 2+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Fe 2+ or

[0048] 0.5% - 8% Zn 2+ and 0.05% - 1% Cu 2+ and 0.01% - 1% Al 3+ , preferably 0.5% - 5% Zn 2+ , 0.05% - 1% Cu 2+ and 0.05% - 1% Al 3+ or 0.05% - 1% Cu 2+ and 0.01% - 1% Al 3+ , with the remaining cation binding sites only occupied by Ca 2+ and H + are occupied.

[0049] These values ​​also apply equally to methods, devices and uses.

[0050] The polymeric granules can be a homopolymer or a copolymer for the process, the apparatus and the use.

[0051] Interestingly, it has been found that polymeric granules, which are a weakly acidic ion exchange resin, are the most suitable base material for the desired process reaction. In particular, ion exchange materials functionalized with carboxyl groups (-COOH) or carboxylate groups (-COO") are suitable. The weakly acidic ion exchange resin is itself a cation exchange material.

[0052] Preferred weakly acidic ion exchange resins include cross-linked polyacrylic acid resins, polymethacrylic acid resins, or resins with iminodiacetic acid as a functional group. Macroporous ion exchangers are preferred due to their superior reaction kinetics. This applies equally to the process, apparatus, and application. The use of weakly acidic ion exchange resins in drinking water treatment is known per se. For example, WO 2018 / 041817 Al describes a process for treating drinking water in which the water hardness is reduced. In this process, drinking water is passed over an ion exchange material partially loaded with zinc ions, which is always also loaded with H + -ions are partially charged. This ion exchange material, conditioned in this way, releases zinc ions into the water and in return accepts Ca 2+ 'Ions. The starting point of WO 2018 / 041817 Al is the provision of drinking water with higher Zn. 2+-salary, as the supply of zinc to the population 2+ which is often insufficient. However, the invention in question is not based on a classic softening ion exchange process, but rather on a catalytic effect.

[0053] Both the method and the apparatus preferably utilize a weakly acidic ion exchange material, which is mainly in its calcium form and has a doping with at least one di- or trivalent metal cation that is comparatively more strongly bound to the carboxylate groups than the calcium. 2+ -ion ​​(higher selectivity). Drinking or brewing water with Ca 2+ Calcium ions and hydrogen carbonate ions are brought into contact with this ion exchange material. In this process, calcium ions and hydrogen carbonate ions from the water are catalytically converted into CaCO₃ ion pairs, ultimately providing limescale protection.

[0054] The carboxylate groups can exist as simple functional groups or more complex functional groups (e.g., iminodiacetate). The cation-binding sites are usually in their initial form, the so-called H-form (-COOH) or Na-form (-COONa). These must be converted to the calcium form ((-COO)₂Ca). For example, patent AT 407 843 B describes a method and apparatus for converting such granules into their calcium form using hydrated lime. The cation exchange material can either be converted from the acid form (H-form) to the Na-form using NaOH and then with Ca 2+ - for example with CaCh - can be converted into the calcium form or directly from the H-form to the calcium form with e.g. hydrated lime or milk of lime (Ca(OH)2).

[0055] If salts of metal cations that are highly soluble even at higher pH values ​​(pH > 7) are used (e.g., CuCh), it is possible to dope with the metal cations only after calcium loading. By stoichiometrically contacting the calcium-form ion exchange material with a salt solution of the transition metal, between 0.01% and 10% of the actual cation binding sites formed by the carboxyl groups of the ion exchange material can be loaded.

[0056] If salts of metal cations are used that lead to the formation of sparingly soluble complexes or to precipitation of the salts at higher pH values, it is advantageous to initially mix the ion exchange resin in the H-form with Ca(OH)2 only between 1% and 90% with Ca 2+Partially load the solution. Then, the dissolved salt of the di- or trivalent metal cation is added to the acidic solution in the planned stoichiometry. If doping with several different metal cations is planned, then one begins with the metal ion that binds most strongly to the polycarboxylates. The metal cations are primarily replaced by ion exchange with Ca 2+ bound to the carboxylate groups.

[0057] In the final step, by adding a corresponding amount of Ca(OH)2, the remaining carboxyl groups in the H-form are combined with Ca 2+ - Loaded with ions.

[0058] The degree of loading can be determined by adding a sample of granules to distilled / deionized water and measuring the pH of the suspension while stirring with a magnetic stirrer. Due to the low ion strength of the solution, it takes some time for the pH to stabilize. The measurement is somewhat faster if the granules are added to a solution containing 1 to 10 mmol / L NaCl; the pH deviation compared to the distillate standard is only slight. The loading is sufficient if the measured pH is between 6.5 (only about 1.5% of the carboxylate groups present are still bound to hydrogen). + loaded) and 9.0 (less than 0.1 per mille are with H + loaded); preferably the pH value is between 7.0 and 8.0. A pH value greater than 8.0 leads to a significant increase in the pH value of the flowing water during the initial run-in phase of the granules and can produce the opposite effect, i.e., increased limescale precipitation.

[0059] Furthermore, it is advantageous to carry out the loading process at temperatures between 40 °C and 80 °C because at higher temperatures the diffusion of ions into and out of the ion exchange material is significantly faster, thus achieving shorter loading times. After the loading process, the granules are rinsed with demineralized water and stirred in an aqueous solution (2 to 10 mmol / L CaCh or Ca(NO3)2) for several hours at a temperature between 60 °C and 80 °C to achieve a uniform distribution of the doped metal ions through diffusion processes within the granules. After another rinse, the finished granules can be dried and packaged for use.

[0060] In this way, between 0.01% and 10% of the actual cation binding sites formed by the carboxylate groups of the ion exchange material can be loaded with specified metal cations.

[0061] The total number of cation binding sites of an ion exchange material per unit volume is called the total capacity (TC). The total capacity of an ion exchange material is determined by titration, and the result is expressed in val / L (eq / L). Since the volume is related to the ionic form of the exchanger, this ionic form must be specified with every measurement. The dry mass capacity (also called weight capacity) is determined after drying. This dry mass capacity measures the concentration of active groups per kilogram of exchanger, without taking moisture into account. It is expressed in val / kg (eq / kg) of dry matter. The ionic form of the ion exchange material must also be specified in this case, as different ions have different masses.

[0062] For weakly acidic resins, the total capacity (TC) corresponds to the number of carboxylate groups (-COO") per volume in the ion exchange material in mol / 1.

[0063] If a polymer or ion exchange material has a total capacity TK in mol / l, then a cation binding site loading of between 1% and 10% or 90% and 99% means that TK* 1 / 100 to TK* 10 / 100 or TK* 90 / 100 to TK* 99 / 100 of the cation binding sites are occupied by the corresponding ions. The charge of the metal cations must be taken into account in this calculation.

[0064] The statement that between 0.01% and 10% of the actual cation binding sites formed by the carboxylate groups in the polymeric granules are occupied by at least one di- or trivalent metal cation means that the sum of all doped metal cations occupies more than 0.01% of the cation binding sites, but the occupancy of the cation binding sites is less than 10%.

[0065] The remaining H +The occupancy (< 1.5%) is primarily determined titrimetrically and related to the number of cation binding sites (total capacity, TK). For this purpose, a defined resin sample (dried or standardized swollen) is equilibrated, and the hydrogen ions transferred into solution are measured. + measured by acid-base titration; the H thus determined + The equivalent fraction is related to the total hydrocarbons (THC) and expressed as a percentage of cation binding sites.

[0066] As a quick test / plausibility check, pH evaluation can be performed according to the Henderson-Hasselbalch G1 calibration (for carboxylate groups pK). s ~ 4.8):

[0067] The activity-based relationship is typically approximated by concentration ratios at a defined ion strength (e.g., measurement in a CCE-poor solution with 1–10 mmol / L NaCl, 20 ± 2 °C, defined resin / water ratio). The pH method does not replace the trimetric primary determination but serves to verify the plausibility of the low H +-Occupancy.

[0068] During operation, as well as during manufacturing / conditioning, alkali-alkaline earth cations (e.g., Na) can form due to ion exchange equilibria. + , K + , Mg 2+ ) are also temporarily bound to carboxylate groups of the active matrix. These exchangeable accompanying cations do not belong to the doping fraction within the meaning of the invention and are not included in the percentage occupancy balance of the cation binding sites. For the purposes of this application, "doping fraction" refers exclusively to the specifically introduced di- or trivalent metal cations M, which together with Ca 2+ Occupy the functional groups of the polymer phase in the product form upon commissioning.

[0069] Typically, the remaining cation binding sites are predominantly occupied by Ca 2+ ; for example, the approx. 2+-Proportion at least ~ 95%, preferably ~ 97%, particularly ~ 98%. In other embodiments, ~ 90% Ca is sufficient. 2+ Provided that the standard test conditions and the success criterion are met, traces of foreign ions that are difficult to avoid (e.g., up to about 5%, preferably up to < 2.5%, based on all available cation binding sites, point iii) in the above explanations) are tolerable without impairing the effect according to the invention. The mere presence or variation of such non-doping accompanying cations—even if they are temporarily bound to active groups—does not constitute a technically relevant deviation from the teaching of the invention. However, the absence of such foreign ions is particularly preferred.

[0070] The catalytic effect for forming calcium carbonate ion pairs can be enhanced by using polymers with different calcium cation loadings and / or different di- or trivalent metal cation loadings. Locally higher and lower concentrations of one or the other ion improve local ion pair formation. This design also makes the device more suitable for varying water qualities. Therefore, it can be provided that a second polymeric granule or further polymeric granules, as previously defined, are included in the filter vessel, with the cation binding sites of the second polymeric granule or further polymeric granules being arranged differently than those of the first polymeric granule.In the other polymeric granules, therefore, between 0.01% and 10% of the actual cation binding sites formed by the carboxylate groups of the polymeric granule with at least one specified metal cation and the remainder of the actual cation binding sites formed by the carboxylate groups of the cation exchange material with Ca. 2+ This is documented. However, the polymeric granules differ in their Ca 2+ and metal cation loadings. Consequently,

[0071] • the ratio of Ca 2+ in the first polymeric granules to Ca 2+ in the second polymeric granule and / or

[0072] • the ratio of di- or trivalent metal cation in the first polymeric granule to metal cation in the second polymeric granule differs.

[0073] The number of CaCO₃ ion pairs formed is also determined by the total surface area of ​​the polymer. The larger the surface area and the shorter the diffusion paths of the reactants, the more effectively the polymer granules form CaCO₃ ion pairs. The starting material, commercially available ion exchange resins, typically has a particle size distribution between 400 pm and 700 pm. A smaller particle size means a larger surface area for the same polymer volume. For optimal catalytic activity, the polymer granules have a particle size distribution between 100 pm and 1200 pm, preferably between 300 pm and 700 pm. Smaller particle sizes, which can be achieved, for example, by milling the cation exchange material, are advantageous for faster ion pair formation. Particle sizes smaller than 100 pm significantly increase the demands placed on the filter elements and also significantly increase pressure losses.

[0074] The polymer granules can be filled into commercially available filter containers (e.g., cartridges for water treatment media such as ion exchange materials, activated carbon, iron removal materials, etc.). The escape of the polymer granules can be prevented by filter elements at the inlet and outlet.

[0075] Preferably, between 0.01% and 10% of the actual cation binding sites formed by the carboxyl groups in the cation exchange material are occupied by at least one corresponding di- or trivalent metal cation. All other cation binding sites formed by the carboxylate groups in the cation exchange material are occupied by Ca 2+ proven.

[0076] Furthermore, a disinfection device for the polymer granules, preferably a thermal disinfection device, can be provided. This prevents the formation of biofilms.

[0077] The device can be installed in a cold water line to an object, in the cold water line to a (central) water heater, in a circulation line around a hot water storage tank, or directly in a hot water storage tank.

[0078] The installation is then carried out either in such a way that the drinking or process water flows through the polymer granules from top to bottom (fixed bed) or from bottom to top (floating bed, upper fixed bed).

[0079] In this process, it is preferably provided that the drinking or process water is allowed to flow through the polymer granules from top to bottom or from bottom to top.

[0080] The process can also include disinfection of the polymer granules after a specific processing time, preferably thermal disinfection. Both the device and the process are preferably intended for use in a drinking or process water pH range of 6.5 to 9.5.

[0081] Unless otherwise specified, the percentage values ​​for the occupancy of the cation binding sites refer to the state at commissioning (before initial contact with tap water). Alternatively, the loading state can also be specified after a defined rinsing phase, e.g., after rinsing through a predetermined number of bed volumes (BV). DETAILED DESCRIPTION OF THE INVENTION

[0082] Crucial for the development of the process was the discovery and proof that an ion exchanger functionalized with carboxylate groups in the Ca form can very efficiently split hydrogen carbonate ions (HCOT) into carbonate ions and protons and bind Ca 2+ When ions attach to the carbonate ions, CaCO₃ ion pairs are generated. These CaCO₃ ion pairs exhibit remarkable stability.

[0083] The process engineering principles and details of the invention are explained below using examples and figures.

[0084] Fig. 1 schematically shows the boundary layer between the polymer in contact with drinking or process water, which contains Ca 2+ - and HCCL' - ions.

[0085] Fig. 2 shows an overview of all reactions in and around the polymer.

[0086] Fig. 3 shows the reaction scheme of the deprotonation of the HCCE' ions and the

[0087] Formation of CaCO° ion pairs.

[0088] Fig. 4 shows the reaction scheme for reloading with Ca 2+ -ions from the water.

[0089] Fig. 5 shows the time course of the pH value and the rate of change of the pH value of storage of special samples in standard water.

[0090] Fig. 6a shows the measurement of the change in conductivity and pH value as a function of time when a granulate according to the invention is brought into contact with a solution containing 8 mmol / 1 NaHCCU.

[0091] Fig. 6b shows, for comparison with Fig. 6a, the calculated values ​​for pH and conductivity as a function of the CaCO₃ ion pairs formed on a granulate according to the invention in an 8 mmol / L NaHCO₃ solution. Fig. 7a shows the results of the measurement of conductivity and free Ca 2+ and the pH value as a function of time for a model tap water (8 mmol / l CaCh and 8 mmol / l NaHCO, mixed in a ratio of 1 : 1) that was brought into contact with a granulate according to the invention.

[0092] Fig. 7b shows, in comparison to Fig. 7a, the results of a calcium carbonate calculation and the dependence on pH value, conductivity, and free Ca. 2+ and the supersaturation of the concentration of CaCO^ ion pairs formed in the model water (8 mmol / l CaCh and 8 mmol / l NaHCCh mixed in a ratio of 1 : 1).

[0093] Fig. 8 shows the result of a miniaturized parallel boiler test run after 4 days: The right illustration shows the boiler without corresponding water treatment; the left illustration shows the boiler with a cartridge containing 10 ml of custom granules in the cold water inlet to the boiler.

[0094] According to the invention, a polymeric granulate is mixed with the tap water to be treated, which contains Ca 2+ and HCO,' and CO, 2 The polymer granules, containing a weakly acidic ion exchanger, are brought into contact with the water. Several reactions occur, leading to the formation of CaCO₃ ion pairs. Some of the charged groups dissociate, leaving behind negatively charged carboxylate groups (-COO⁻), which impart a negative charge to the polymer granule matrix. The resulting electrical potential relative to the water (the "Donnan potential") controls the exchange of ions between the granules and the water.

[0095] This potential attracts positive and consequently negative ions from the water, forming a charged zone as an interface between the granules and the water, the so-called "star layer." This is shown schematically in Fig. 1, where the polymer matrix of the ion exchange material is depicted on the left, containing carboxylate groups (R-COO), carboxyl groups (R-COOH), and carboxylate groups bonded with Ca 2+ The column layer is loaded with ions. Within the stem layer itself, one finds ions originating from the water, particularly Ca. 2+ - and HCO₃⁻ ions. The bubbles around the ions indicate that they are solvated, i.e., that they are surrounded by a shell of water molecules (a "hydration shell"). The ion exchange material interacts differently with the ions present in the tap water.

[0096] The calcium carbonate equilibrium:

[0097] Fundamental to understanding the process is the calcium carbonate equilibrium. The following half-reactions are important for the calcium carbonate equilibrium: (Carbonic acid) (1) (Dissociation of carbonic acid) (2) (Dissociation of hydrogen carbonate) (3) CO2 (Calcium hydrogen carbonate) (4) (Calcium carbonate ion pair) (5) (Autoprotolysis of water) (6)

[0098] The calcium carbonate equilibrium and the equilibrium constants of the partial reactions (and other ions in the water) are described in many literature [7], [8], calculation methods for determining the calcium carbonate equilibrium are standardized, e.g. in [9],

[0099] Reactions in the granules and in the star layer:

[0100] Fig. 2 schematically shows the most important reactions in and around the granules: If reaction (2) (dissociation of hydrogen carbonate) and reaction (6) take place in the stem layer around the granules, then there is a high probability that the released proton (H + ) is attracted by the negative charge of the Donnan barrier and enters the polymeric matrix - ultimately it is an ion exchange - 2 protons from reaction (2) or (6) are exchanged for a Ca 2+ The -ion is exchanged from the granules (“ion exchange 1”). The CCh remaining from reaction (2) 2 ' (Carbonation ions) combine with the Ca present in the star layer or the water to form 2+ CaCO₃ ions form ion pairs (see the reaction scheme in Fig. 3). The overall equation of the reactions is:

[0101] For reaction (7) to proceed continuously, calcium ions from the water must again be bound to the carboxylate groups of the polymer matrix in exchange for protons. The following reaction is the most plausible initial assumption (see reaction scheme Fig. 4):

[0102] No sustainable procedural success with pure Ca 2+ Form:

[0103] However, it turns out that the reloading of the cation exchange resin with Ca 2+ from the flowing water, according to reaction (8), is not permanent without further measures. For example, it is observed that with the pure calcium form of Lewatit® S 8227, a weakly acidic, macroporous cation exchange resin based on polyacrylate, the ion pair formation rate drops by an order of magnitude within 3 weeks in contact with calcareous water.

[0104] This observation can also be formally explained as follows:

[0105] If we write down the law of mass action for reaction (7) and reaction (8),

[0106] _

[0107] K2

[0108] [Ca 2 + ]-[2RCOOH] (10) so in equilibrium of the two reactions, or for the concentration of the CaCO₃ ion pairs formed Equation (12) is the equilibrium for the formation of CaCO₃ ion pairs, known from the calcium carbonate equilibrium. The granules and their loading therefore have no influence on the equilibrium.

[0109] Process optimization:

[0110] To solve this problem, reaction (8) must proceed via a different reaction pathway. If we can assume that, through certain measures, some of the carboxylate groups dissociate more readily, thus making protons more readily available for the reverse reaction, then we can write reaction (8) as follows (R* represents the modification):

[0111] According to the law of mass action, this means:

[0112] And finally

[0113] In the case of equilibrium between reaction (7) and reaction (13), the catalytic state is reached and the following overall reaction results:

[0114] At equilibrium, a decrease in pH value is observed due to the release of protons.

[0115] Note on the mechanistic interpretation: Without being bound to a specific theory, it is assumed that the loading-Z-coverage architecture according to the invention promotes the deprotonation of HCO3 in the stem layer and maintains the continuous formation of neutral (CaCO3)° ion pairs via a proton-coupled ion exchange cycle (see reactions (7)-(8) and overall reaction (17)). The decisive factor is the effect described under the standard test conditions (verification via ISE / EDTA and DIN 38404-10).

[0116] Equation (16) provides the guidelines for optimization: a) The unmodified carboxylate groups ((2 / ?COO-)) should be as completely as possible in the Ca 2+ -form.

[0117] > b) The modified carboxylate groups ((2 / ?*COO-)) should preferably not be associated with Ca 2+ -ions are occupied.

[0118] Condition a) is fulfilled because, when loading the ion exchange material with Ca(OH)2, an equilibrium pH value between 6.5 and 9, preferably between 7 and 8, is targeted. This means that less than 1.5% of all carboxylate groups are undissociated in the hydrogen. + -Form (calculated for a pKs value = 4.8).

[0119] To fulfill condition b), measures must be taken to change the acid character of some of the functional carboxylate groups so that they dissociate more easily.

[0120] Doping with suitable metal cations:

[0121] By selectively doping the ion exchange material in calcium form with suitable metal cations, it is possible to promote the reverse reaction.

[0122] It is known that weakly acidic ion exchangers exhibit very high selectivity for certain metal ions. In reference

[0010] , for example, the selectivity of DVB-crosslinked polyacrylic acids for 21 metal ions was investigated as a function of the pH of the solution. According to this work, the following selectivity is obtained at a pH of 5: Hg 2+ > Fe 3+ > Pb 2+ > Cr 3+ > Cu 2+ > CD 2+ > Al 3+ > Ag + > Zn 2+ > Ni 2+ > Mn 2+ > Co 2+ > Approx 2+ > Sr^ > Ba 2+ > Mg 2+ > K + > Rb + > Cs + > Na + > Li + This scale is not linear: Hg 2+For example, it is bound a million times more strongly than the alkali metal cations.

[0123] In reference

[0011] , a macroporous, DVB-crosslinked, weakly acidic ion exchanger based on polyacrylate (Lewatit® CNP 80) was tested for its suitability to absorb heavy metals from aqueous solutions. This ion exchanger is exceptionally well suited for absorbing heavy metals. The selectivity of this ion exchanger for heavy metal ions is given as follows:

[0124] Ni 2+ > Cu 2+ > CD 2+ > Zn 2+ > Pb 2+ For the present invention, those metal cations are important which are bound significantly more strongly to the functional groups of the ion exchange resin than the calcium ions. 2+ - and Mg 2+-ions, the main divalent cations in common drinking and process waters. The binding of the metal cations to the carboxylate groups occurs partly electrostatically, partly covalently, and partly through ligand bonding.

[0125] Table 1: Ion radii (r) in pm (1 picometer = 10⁻¹⁰) 12 m), electronegativities (%) and the electron configuration of the most important ions for this invention (references

[0012] ,

[0013] ): KZ stands for the coordination number

[0126] The doping of suitable metal ions causes in the calcium 2+ -ion-loaded resin matrix undergoes some changes at the doping site: a) Table 1 shows that all listed metal ions have a smaller ion radius than Ca 2+ (100 pm: 1 pm = 1 picometer = 10' 12 m). The electrostatic interactions of these ions with neighboring bound Ca 2+-ions lead to local stresses. b) Metal ions with incomplete t / -orbitals (e.g., Co) 2+ , Ni 2+ , Cu 2+ ) tend to bind to ligands and form strong local complexes

[0014] , c) In the case of metal cations with fully occupied t / -orbitals such as Zn 2+ , CD 2+ and Ga 3+ (Pseudo-noble gas configuration) no ^ / -electrons are available for complex formation; electrostatic bonding to the functional groups and the difference in electronegativity between the bonding partners become the decisive factor. Since these ions are more electronegative than the Ca 2+ -ions have a stronger effect on the bonding electrons in the resin matrix than the Ca 2+ -ions. In the vicinity of the doped transition element ions, charge shifts of the electrons towards the doped metal cations occur

[0014] , d) Al 3+-ions have a noble gas configuration and are strongly electrostatically bound to up to three functional groups. e) The consequence is that in the vicinity of the doped metal cations, the bonds of the carboxylate groups to Ca 2+ -ions and H + -ions are weakened. f) Assuming that the doped metal cations are uniformly distributed in the polymeric matrix of the ion exchange material and considering models of the influence of doping on the neighborhood, it can be considered that between 0.5% and 10% of the total carboxylate groups should be doped with metal cations. g) Al 3+ -ions bind very strongly to the carboxylate groups, and experiments have shown that they hardly diffuse into the resin matrix, instead remaining fixed in the outer edge region of the ion exchanger. In the case of Al 3+Therefore, doping concentrations of 0.01% (based on the total capacitance) also show significant effects for hydrogen ions, while doping concentrations above 1% offer no advantage. h) The effect of doping with metal cations is comparable to n- and p-doping in semiconductors. In semiconductors, the doped foreign atoms create sites to provide additional electrons for electron conduction (n-type) or to remove electrons (p-type; "hole conduction"). Doping with metal cations in the calcium form of the weakly acidic ion exchange material creates free sites in the vicinity of the metal cations for the easier diffusion of hydrogen. + - and Ca 2+ -ions through the polymeric matrix. i) For trivalent cations, low doping levels (0.01–1% TK) are preferred, while divalent cations can have TK levels of 0.5–5%; this optimizes the long-term stability of the matrix. In particular, Al 3+It remains predominantly in the outer edge of the granules; > 1% provides no additional benefit. For Cu 2+ / Fe 2+ / Fe 3+ For long-term stability reasons, matrix values ​​< 1% are preferred.

[0127] The doped metal cations must be strongly bound within the polymer matrix to prevent them from being leached or exchanged from the matrix via various reactions, particularly in drinking water applications. Furthermore, the release of these doped ions must not result in concentrations in the drinking water that pose a health risk. The binding characteristics, the selectivity of the ion exchange material, and the toxicity of the ions in drinking water applications determine the choice of metal cations to be doped.

[0128] The bonds of the metal cations in the resin matrix are different depending on the pH value

[0010] ,

[0011] , Even though the use in the drinking water sector is limited to pH values ​​between 6.5 and 9.5, it is useful to combine different metal cations in order to create suitable reaction sites for different water qualities.

[0129] If no data are available, selectivity coefficients can be determined operationally by a batch equilibrium test (displacement test): Carboxylate resin in Ca form is contacted at pH ~5, 25 °C and defined ion strength with a solution containing Ca 2+ and the test cation M n+ contains. After equilibrium is reached, the selectivity coefficient is calculated according to the IUP AC definition, e.g.

[0130] Does k apply M / Ca > 1, becomes M n+ as "stronger than Ca 2+“Understood. Equivalent established equilibrium methods can be used. (Selectivity series according to Ref.

[0010] serve for material selection). Depending on the salt used, the loading with metal cations takes place either after the conversion of the weakly acidic ion exchange material from the H-form to its Ca-form, or the weakly acidic ion exchange material is first only partially loaded (1% - 90%) with Ca 2+ and adds a dissolved salt containing the corresponding metal cation to the acidic solution.

[0131] The loading with Al 3+ - or Fe 3+ -Ion exchange must take place in an acidic solution (pH less than 4) to avoid precipitation of the salts (it is advisable to first load the ion exchange material with less than 5% Ca 2+If the matrix is ​​to be doped with multiple ions, one starts with the ion exhibiting the highest selectivity. Finally, all remaining carboxyl groups (-COOH) are removed by adding Ca(OH)₂ with Ca 2+ -ions are loaded. To accelerate the loading process and to achieve a homogeneous distribution of all metal ions in the polymer matrix, it is advantageous to carry this out at higher temperatures (40°C to 80°C).

[0132] If an optimized catalyst is desired for use in drinking water applications, then the incorporation of Zn is necessary. 2+ -, Cu 2+ -, Fe 2+ -, and / or Al 3+ -ions are preferred because the drinking water regulations are most tolerant with regard to these ions (limit values ​​for Cu). 2+ : 2 mg / l; for Zn 2+ The Drinking Water Ordinance does not specify a limit value; the WHO gives a guideline value of 3 mg / l; for Fe 2+ Ions and Al 3+-ions are given an indicator value of 0.2 mg / l). An ion exchange Ca 2+ Antioxidation against these metal cations practically does not occur in the pH range of drinking water from 6.5 to 9.5.

[0133] Another point to consider is the influence of the doped metal cations on the stability of the resin matrix. Cu 2+ -ions have a strong influence on the bond strength of the surrounding carboxylate groups and promote the dissociation of bound H + - or gallons. However, Cu 2+ -ions also react with components of the resin matrix and oxidize them; Cu 2+ becomes Cu in the process + reduced. Cu 2+ -ions and similarly Fe 2+ - and Fe 3+ For this reason, copper ions pose a problem for the stability of the polymer matrix and can lead to dewetting of the matrix. Therefore, doping with Cu should be avoided. 2+ - , Fe 2+ - or Fe 3+-ions only occur to a small extent (less than 1% of the total capacity).

[0134] Experimental findings: i) Identifying suitable metal cation dopings: To determine suitable metal cations, metal cation combinations, and metal cation concentrations, the following screening experiment was devised and carried out:

[0135] Lewatit® S8227 from Lanxess was used for the experiments. Lewatit® S8227 is a macroporous, DVB-crosslinked, weakly acidic ion exchanger based on polyacrylate. Its capacity is specified by the manufacturer as 4.3 val / l, corresponding to 4.3 mol of carboxyl groups in one liter of granules (dry). The ion exchanger is available in its H + -Form supplied.

[0136] Samples were prepared by first adding the H + -Form of the granules to 25% of the total capacity with Ca 2+The granules were loaded by the appropriate addition of Ca(OH)2 at 60°C. Subsequently, various metal salts in different concentrations were added to the acidic solution (pH value was always less than 4) to further load the granules with Cu. 2+ -, Fe 2+ -, Ni 2+ -, Fe 3+ - or Al 3+ - to load ions and combinations thereof (CuCh, Fe(II) chloride, Fe(III) chloride, aluminum sulfate tetradecahydrate, NiCh). It is shown that under acidic conditions, the metal cations of the salts preferentially react with the Ca 2+ Ions are exchanged in the resin. If the granules are additionally loaded with several metal cations, one starts with the metal cation with the higher selectivity:

[0137] Fe 3+ > Cu 2+ > Al 3+ > Zn 2+ > Ni 2+ .

[0138] The samples produced in this way are still 75% in the H +-form and react as weakly acidic ion exchangers with aqueous solutions.

[0139] A solution containing 10 mmol / L CaCh and 2 mmol / L NaHCCl was prepared as a test water standard. One gram of a moist resin sample was added to 100 ml of the test water standard, and the change in pH over time was measured at 20 °C with continuous stirring using a magnetic stirrer. 2+ The -ion from the solution is converted to 2 H + -ions from the resin sample were exchanged. The exchanged H +Hydrogen ions react with HCCL' ions in the solution. The hydrogen carbonate serves several purposes: firstly, to enable defined pH measurements through its buffering effect, secondly, to slow down the ion exchange over time, and thirdly, to act as a titration reference. The rate of change of pH is calculated numerically from the measurement curves and plotted against the measured pH value. Figure 5 shows the results of the experiments for two samples: The reference sample contains only 25% Ca 2+ was loaded; the second sample was loaded with 25% Ca after loading. 2+ with 1% Zn 2+ and 0.5% Al 3+The inlay shows the change in pH over time for the two samples; the "25% Ca-1% Zn-0.5% Al" sample exhibits a significantly faster decrease in pH than the "25% Ca" sample. The main diagram shows the rate of change of pH plotted against the pH value. The diagram shows two maxima for each curve: one maximum in the pH range between 7 and 8, where the pKa value of bicarbonate is 7.48 (bicarbonate accepts a proton and reacts to form CO₂ and H₂O - see equations (1) and (2)). A second maximum is found in the pH range between 4 and 5. The carboxylate groups in typical weakly acidic ion exchangers have a pKa value of around 4.8. Loading with different ions shifts the maxima and alters the exchange kinetics. The evaluation considers the relative changes compared to the 25% Ca sample – if the rate is higher, then the exchange kinetics are also faster, i.e., H₂ is present more quickly. +-ions for ion exchange with Ca 2+ available because the doped metal cations weaken the bond strength of the carboxyl groups in their environment; the maxima in the pH range between 4 and 5 shift relative to smaller PKA values.

[0140] Different combinations and concentrations of metal cations were tested in this way. The best results were shown with samples containing Al 3+ -, Cu 2+ - and Zn 2+ - ions and combinations of these ions have been doped. ii) Detection of the formation of CaCO₃ ion pairs:

[0141] Lewatit® S8227 from Lanxess was used again for the experiments. A granulate according to the invention was produced by first mixing the H +The product form of the granules was loaded with Ca(OH)₂ to 80% of its total capacity at 60 °C. After rinsing the granules with distillate, a ZnCl₂ solution corresponding to 4% of the total capacity of the granules was added and held in contact with the granules at 60 °C for approximately 6 hours. After another rinse, Ca(OH)₂ was added again to increase the loading to 100% of the total capacity. The final step was carried out at 60 °C for 24 hours to distribute all metal ions as evenly as possible within the granules. After rinsing with the distillate, the product form exhibited an equilibrium pH of 9.0 in the distillate. The product form can be described as a weakly acidic ion exchanger in the Ca 2+ -Form describes the form that uses Zn with 4% of the total capacity 2+-ions are doped. Figure 6a shows the measurement results of the following experiment. To distinguish the formation of CaCO₃ ion pairs from calcium carbonate precipitation in a solution, the following experiment was designed: A solution containing 8 mmol / L NaHCCl is used as model water – this solution contains no calcium ions. One gram of the product form described above is added to 100 ml of this solution. The suspension is continuously stirred with a magnetic stirrer; the experimental temperature is 20 °C. After a short settling time, both the pH value and the conductivity of the solution increase.

[0142] Fig. 6b shows the results of a calcium carbonate calculation according to DIN 38404-10191, in which it is assumed that two hydrogen carbonate ions of the solution react in a reaction according to reaction (1) to form a CaCO₃ ion pair and a free CO₃ 2The '-ion is formed. The calculation shows that both the pH increase and the increase in conductivity can be explained by the formation of CaCO₃ ion pairs. At the end of the measurement, the total hardness of the solution was measured by complexometric titration with EDTA – EDTA is a very strong complexing agent that dissolves existing CaCO₃ ion pairs – and the determined total hardness value of 4 mg / L agrees very well with the calculation. The measured calcium originates from the granules used.

[0143] Gebauer et al.

[0015] have used a similar method (titrating CaCh into a NaHCOs buffer) to show the formation of CaCO° ion pairs and subsequently of (CaCO3)n clusters as a precursor to calcium carbonate precipitation.

[0144] Figure 7a shows the measurement results of the following experiment. A CaCh solution with 8 mmol / L (prepared from demineralized water and CaCh of Pa quality) was mixed 1:1 with a NaHCCh solution with 8 mmol / L (demineralized water and NaHCCh of Pa quality) as model tap water. 5 g (moist) of the product form described above, with a slightly lower loading (equilibrium pH in the distillate = 7.8), were added to 100 ml of this model water. The experiment was carried out at 20 °C and the solution was stirred with a magnetic stirrer.

[0145] The pH value and the free Ca were measured. 2+ Ion centration with an ion-selective electrode and the conductivity. The settling-in of the measuring electrodes is noticeable in the first 200 s. The addition of the ion exchange material caused the conductivity and the concentration of free Ca to change. 2+The number of ions in the solution decreased (conversion into CaCO2 ion pairs); the pH of the solution dropped – reaction (7) and reaction (8) are in equilibrium (“catalytic state”). After approximately 5000 s, the pH stops decreasing, reaches a minimum, and then rises slightly again. The conductivity and the concentration of free Ca 2+ However, the concentration of calcium ions continues to decrease. In approximately 10,000 seconds, the concentration of free calcium decreases. 2+ -ions decrease by approximately 30 mg / l in the solution - this corresponds to approximately 0.75 mmol / l CaCO2 ion pairs (without correction for total calcium concentration; the exact quantification is described further below).

[0146] The resulting pH minimum depends on the degree of loading of the granules with gallons and the concentration of Ca 2+ -ions in water. At pH minimum, no gallons can be extracted from the water to replace H + Ions are exchanged from the granules. The further decrease in Ca 2+The presence of hydrogen ions in the solution can be explained by the continued dissociation of HCO₃⁻ ions in the boundary layer of the granules; the carbonate ions immediately react with calcium ions to form CaCO₂ ion pairs. The released hydrogen + Hydrogen ions must react in a pH-neutral manner via a different pathway. One possibility is the reverse of reactions (1) and (2) – a proton reacts with another hydrogen carbonate ion to form water and CO2: so that the following overall reaction results:

[0147] 2 ■ HCO2+ Ca 2+ CaCO2 + H2O + CO2 (19)

[0148] Ca is also effectively transferred via the reaction channel (19). 2+- and HCOT ions are removed from the calcium carbonate equilibrium. However, reaction pathway (17) has a greater influence on the calcium carbonate equilibrium, and the process is preferably operated in this range. The reduction of the degree of supersaturation can be adjusted by the contact time of the water with the granules (defined by the ratio of granule quantity / flow rate). The degree of Ca loading of the granules 2+The concentration of calcium ions is crucial in determining the pH minimum. For optimal process success, the equilibrium pH of the product in the distillate should be lower than the pH of the drinking and process water being treated; preferably, this value lies between 7.0 and 8.0. The process can be optimized for different water qualities by mixing similar granules with different equilibrium pH values ​​of the product form. For example, product form A has an equilibrium pH of 7.0, and product form B has an equilibrium pH of 8.0. Figure 7b shows the results of a calcium carbonate calculation according to DIN 38404-10 191 using the model water, in which it is assumed that CaCO₃ ion pairs are constantly formed by reaction (17). The conductivity and the free Ca 2+ The decrease in supersaturation decreases with the formation of ion pairs. Figure 3 shows the decrease in supersaturation, defined by S = j. erCalcite saturation). If the parameter S reaches the value 1, then The water is in calcium carbonate equilibrium – in the model water used, this value is reached at 0.4 mmol / L of CaCO₃ ion pairs formed. The data in Fig. 6a show that saturation was reached after approximately 3000 s. If S < 1, then the water is undersaturated.

[0149] To unambiguously quantify the neutral (CaCO3)° ion pairs formed in solution, a biaxial mass balance is additionally used as proof: Parallel to the determination of free Ca 2+Using an ion-selective electrode (ISE), the total calcium is determined complexometrically (EDTA) before and after the experiment (EDTA also dissolves calcium carbonate ion pairs). Alternatively, to dissolve the complexes, a small amount of hydrochloric acid can first be added to the solution, and only then can the calcium ion content of the solution be determined complexometrically. Assuming that calcium carbonate precipitation is excluded (e.g., by checking the turbidity), the following applies:

[0150] Formed ion pair concentration:

[0151] [CaCO3°] = | AtCa - A[Ca 2+ ] | with

[0152] AtCa = tCa a - tCa e , where tCa denotes the total calcium concentration determined by EDTA (t stands for total, a and e stand for beginning and end).

[0153] A[Ca 2+ ] = [Ca 2+ ] a - [Ca 2+ ] e , where [Ca 2+] the free calcium concentration determined by ISE (a and e represent the concentration at the beginning and end of the measurement). t a = Beginning of the time interval; t e = End of the time interval.

[0154] For example, in the experiment with the model tap water (see description of Figures 7a and 7b), the total calcium content of the solution was additionally determined by complexometric titration with EDTA at the beginning and end (after approximately 10,000 s in the pH saturation range) of the measurement. The free calcium ion concentration at the beginning and end can be seen in Figure 7a.

[0155] Complexometric with

[0156] EDTA: AtCa = 0.45 mmol / 1 ion-selective

[0157] Calcium electrode. A[Ca 2+ ] = 0.65 mmol / l corresponding to 26 mg / l

[0158] [CaCO3°] = 0.20 mmol / 1

[0159] The measured values ​​obtained in this way (including the measured value trend) are additionally confirmed by a calcium carbonate calculation according to DIN 38404-10; the comparisons of measured and calculated values ​​are shown in Fig. 7a / 7b.

[0160] For further validation, a granule sample with at least 10,000 bed volumes is preferably rinsed with the model water over a period of 24 hours. The batch experiment is then repeated with the model water and the results compared.

[0161] Hi) Limescale protection with CaCO₃ ion pairs:

[0162] CaCO₃ ion pairs play an important role in the formation of precursors of calcium carbonate crystal nuclei during calcium carbonate precipitation (see references [1] to [6]). The formation of CaCO₃ ion pairs has a direct effect on the calcium carbonate equilibrium, in which this Ca 2+ -ions and HCO3 — Ions are removed and the pH value is also lowered.

[0163] Figure 7b shows the calculated effect of ion pair formation in model water on the calcium carbonate equilibrium. The degree of supersaturation and the saturation index are significantly reduced. In the previously described experiment (Figure 7a), calcium carbonate saturation is reached after approximately 3000 s.

[0164] To determine the influence of CaCO₃ ion pairs on the stabilization of limescale precipitation in domestic hot water heaters, a miniaturized boiler test rig based on DVGW Worksheet W512 was constructed and operated. Glass test tubes with a diameter of 3 cm and a length of 15 cm were used as boilers; a stainless steel tube (6 mm outer diameter, 4 mm inner diameter) was inserted close to the bottom of the test tube via a double-hole rubber stopper; this tube served as the cold water inlet. The heated water could drain out through the second hole of the rubber stopper. The effective filling volume of the boiler defined in this way is approximately 80 ml. The miniaturized glass boilers were suspended in a water bath thermostatically controlled at 80 °C. The model water described above was used as the test water (8 mmol / L CaCh₃ and 8 mmol / L NaHCO₃ mixed in a 1:1 ratio).This model water meets the requirements of DVGW Worksheet W512: total hardness > 3.5 mmol / L; limescale precipitation potential at 15 °C > 30 mg / L as CaCCL. The model water has a (calculated) limescale precipitation potential of 46.2 mg / L at 15 °C and a limescale precipitation potential of 86.6 mg / L at 80 °C. Two boilers were operated in parallel; 10 ml of the product described above (Lewatit S8227 in CaCCL) was added to the inlet of one boiler in a small filter cartridge. 2+ -Form doped with 4% of the total capacity with Zn 2+-ions). A peristaltic pump was switched on for one minute every 30 minutes, pumping 50 ml / min of model water through each section. Over four days, approximately 9.6 liters of water were flushed and heated per boiler in this way. Weighing the boilers (using glass test tubes) after drying in the oven showed a limescale deposit of 185 mg in the boiler without water treatment in the inlet; no limescale deposits could be detected in the boiler with the granules in the inlet during this period – see also Fig. 8. The process success according to the DVGW regulations can therefore be stated as 100%. The test setup and procedure defined in this way represents a 100-fold reduction compared to the test setup and procedure described in the regulations. Conversely, 1000 ml of these granules are sufficient to achieve a process success of 100% in the original test run. The test run was repeated after the granules in the filter cartridge (10 ml) had been exposed to approximately 48 h of water.The system was rinsed at 200 ml / min with Zirler tap water (total hardness: 14.9 °dH, pH = 8.0) (approx. 550 liters of water, corresponding to approx. 55,000 bed volumes). The subsequent test run with the model water still showed no limescale deposits after 4 days.

[0165] Installation and design of the devices for limescale protection:

[0166] The polymer-containing containers can be installed in the main cold water line to treat all the water in a building; alternatively, they can be installed only in the cold water inlet to central water heaters. A special variant involves installing the devices in the circulation line of central water heaters or around a hot water storage tank. This method proves particularly effective at high water temperatures because higher temperatures weaken the OH bond of the carboxylate group, allowing it to dissociate more easily. Integrating a cartridge directly into the water heater, as described, for example, in patents AT 409 261 B and AT 409 624 B, is another viable option.

[0167] When using devices in cold water systems, regular disinfection of the polymer is necessary for hygienic and procedural reasons. The large organic surfaces of the polymer can be colonized by biofilms, which can then become a source of persistent bacterial contamination in the drinking water system. Biofilms also impede the transport of ions / substances at the polymer / water interface and must be prevented. Regular disinfection of the polymer, preferably thermal disinfection, is therefore advisable. Studies with drinking and process water that is chlorinated for hygienic reasons (chlorine content < 0.3 mg / L) show that no further disinfection of the devices is necessary in these cases.

[0168] Influence of the capacity of the base granulate:

[0169] An initial screening of ion exchange materials as a basis for the polymer showed that, with otherwise identical procedures for the production of the modified polymer, polymers that have high-capacity ion exchange resins as a base exhibit significantly better catalytic activity.

[0170] Influence of the polymer grain size:

[0171] The reaction kinetics are determined by the surface area of ​​the polymer. The larger the surface area and the shorter the diffusion paths of the reactants, the more effective the polymer. The base material, commercially available ion exchange resins, typically has a particle size distribution between 200 pm and 700 pm. A smaller particle size means a larger surface area for the same polymer volume. The produced polymers can be easily dried; in their dry form, they are hard enough to be milled. In this way, finer-grained polymers with a very large effective surface area can be produced. The necessary finer filters and the higher pressure drops across the polymer bed can be addressed through design considerations. Unlike conventional ion exchangers, which require regular regeneration of the ion exchange material, regeneration—which involves handling chemicals—is not necessary according to the invention.

[0172] Both the process and the device can be used in a wide temperature range. Temperatures between 10 °C and 80 °C have been successfully tested. The use of the polymer at higher temperatures (>50 °C) shows significantly improved catalytic activity. Temperatures between 5 °C and 70 °C are advantageous for a longer polymer lifespan.

[0173] REFERENCES

[0174] [1] Damiano Genovese et al., Role of CaCO3° Neutral Pair in Calcium Carbonate

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Claims

1. REQUIREMENTS 1. Method for stabilizing limescale deposits from drinking or process water in a drinking or process water installation, wherein the drinking or process water contains dissolved Ca 2+ -ions and HCOT ions, wherein the process comprises the targeted catalytic deprotonation of HCOT ions and the continuous formation of CaCO^ ion pairs from the drinking or process water by contacting the drinking or process water with a polymeric granule having active groups, wherein the active groups of the polymeric granule comprise carboxylate groups forming cation binding sites, wherein (i) between 0.01% and 10%, preferably 0.5% to 5% of the cation binding sites formed by the carboxylate groups, with at least one of Ca 2+ are proven to be various di- or trivalent metal cations, with the proviso that at least one of Ca 2+Various di- or trivalent metal cations bind more strongly to the cation binding sites than Ca 2+ (ii) < 1.5% of the cation binding sites with H + -ions are occupied (iii) < 5%, preferably < 2.5%, particularly preferably 0% of the cation binding sites with different from those in point (i) and from Ca 2+ are documented in various metal cations and (iv) where the remaining cation binding sites are filled with Ca 2+ -ions are occupied.

2. The method according to claim 1, characterized in that the di- or trivalent metal cations are selected from the group consisting of Mn 2+ , Fe 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , CD 2+ , Al 3+ , Ga 3+ or combinations thereof, preferably the di- or trivalent metal cations are selected from the group consisting of Cu 2+ , Zn 2+ , Fe 2+, Fe 3+ , Al 3+ or combinations thereof.

3. A method according to claim 1 or claim 2, characterized in that at least two di- or trivalent metal cations are bound to cation binding sites, wherein the cation binding sites are connected with 0.5% - 9% Zn 2+ and 0.05% - 1% Cu 2+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Cu 2+ or • 0.5% - 9% Zn 2+ and 0.01% - 1% Al 3+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Al 3+ or • 0.5% - 9% Zn 2+ and 0.01% - 1% Fe 3+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Fe 3+ or • 0.5% - 9% Zn 2+ and 0.05% - 1% Fe 2+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Fe 2+ or • 0.5% - 8% Zn 2+ , 0.05% - 1% Cu 2+ and 0.01% - 1% Al 3+ , preferably 0.5% - 5% Zn 2+, 0.05% - 1% Cu 2+ and 0.05% - 1% Al 3+ or • 0.05% - 1% Cu 2+ and 0.01% - 1% Al 3+ are occupied.

4. Device for stabilizing limescale deposits in drinking and process water installations for carrying out a method according to one of claims 1 to 3, comprising a filter vessel with an inlet for drinking or process water and an outlet, wherein at least one polymeric granulate with active groups is present in the filter vessel, wherein the active groups of the polymeric granulate comprise carboxylate groups that form cation binding sites, wherein (i) between 0.01% and 10%, preferably 0.5% to 5% of the cation binding sites formed by the carboxylate groups, with at least one of Ca 2+ are proven to be various di- or trivalent metal cations, with the proviso that at least one of Ca 2+Various di- or trivalent metal cations bind more strongly to the cation binding sites than Ca 2+ , (ii) < 1.5% of the cation binding sites with H + -ions are occupied (iii) < 5%, preferably < 2.5%, particularly preferably 0% of the cation binding sites with different from those in point (i) and from Ca 2+ are documented in various metal cations and (iv) where the remaining cation binding sites are filled with Ca 2+ -ions are occupied.

5. Device according to claim 4, characterized in that the di- or trivalent metal cations are selected from the group consisting of Mn 2+ , Fe 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , CD 2+ , Al 3+ , Ga 3+ or combinations thereof, preferably the di- or trivalent metal cations are selected from the group consisting of Cu 2+ , Zn 2+ , Fe 2+, Fe 3+ , Al 3+ or combinations thereof.

6. Device according to claim 4 or claim 5, characterized in that at least two di- or trivalent metal cations are bound to cation binding sites, wherein the cation binding sites are connected with • 0.5% - 9% Zn 2+ and 0.05% - 1% Cu 2+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Cu 2+ or • 0.5% - 9% Zn 2+ and 0.01% - 1% Al 3+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Al 3+ or • 0.5% - 9% Zn 2+ and 0.01% - 1% Fe 3+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Fe 3+ or • 0.5% - 9% Zn 2+ and 0.05% - 1% Fe 2+ , preferably 0.5% - 5% Zn 2+ and 0.05% - 1% Fe 2+ or • 0.5% - 9% Zn 2+ , 0.05% - 1% Cu 2+ and 0.01% - 1% Al 3+ , preferably 0.5% - 3% Zn 2+, 0.05% - 1% Cu 2+ and 0.05% - 1% Al 3+ or • 0.05% - 1% Cu 2+ and 0.01% - 1% Al 3+ are occupied.

7. Device according to one of claims 4 to 6, characterized by a disinfection device for the granules, preferably a thermal disinfection device.

8. Device according to one of claims 4 to 7, characterized in that the polymer is a weakly acidic ion exchange resin, preferably based on polyacrylic acids, polymethacrylic acids or iminodiacetic acid groups.

9. Device according to one of claims 4 to 8, characterized in that at least two different polymeric granules with active groups are present in the filter container.

10. Use of a polymeric granule with active groups, wherein the active groups of the polymeric granule comprise carboxylate groups forming cation binding sites, wherein (i) between 0.01% and 10%, preferably 0.5% to 5% of the cation binding sites formed by the carboxylate groups, with at least one of Ca 2+ various di- or trivalent metal cations are proven, provided that at least one of them Approx 2+ Various di- or trivalent metal cations bind more strongly to the cation binding sites than Ca 2+ , (ii) < 1.5% of the cation binding sites with H + -ions are occupied (iii) < 5%, preferably < 2.5%, particularly preferably 0% of the cation binding sites with different from those in point (i) and from Ca 2+ are documented in various metal cations and (iv) where the remaining cation binding sites are filled with Ca 2+ -ions are occupied, for the continuous catalytic formation of CaCO^ ion pairs from Ca dissolved in water 2+ - and HCCh' ions.

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