METHOD FOR PRODUCING A NON-WOVEN MATERIAL SUITABLE FOR THE REMOVAL OF HARMFUL ANIONS FROM AQUEOUS SOLUTION, NON-WOVEN MATERIAL FOR THE REMOVAL OF HARMFUL ANIONS FROM AQUEOUS SOLUTION AND USE OF THE NON-WOVEN MATERIAL

Abstract

The invention relates to a method for producing a nonwoven material suitable for removing harmful anions from aqueous solution by modifying its surface. The method according to the invention comprises the steps: a) providing a nonwoven material selected from the group consisting of polypropylene, polyethylene, viscose, polyamide, polylactide, polyester, polyethersulfone, polysulfone, and polyvinylidene fluoride; b) applying a coating solution to the nonwoven material, wherein the coating solution contains polyallylamine hydrochloride (PAH) and / or polyhexamethylene biguanide (PHMB) as a modifying reagent; c) treating the nonwoven material and the coating solution with electron beam radiation; and d) purifying the modified nonwoven material.

Description

The invention relates to a method for producing a nonwoven material suitable for removing harmful anions from aqueous solution by modifying a surface thereof.Technological BackgroundAs a result of the increasing anthropogenic input of micro-pollutants into water bodies, the effort for obtaining clean drinking water is constantly increasing. In particular, heavily operated agriculture (fertilizing) results in larger quantities of, for example. Nitrate and nitrite ions into the water circuit, so that the limit values of nitrate (50 mg / L) [Drinking wV, 2023, S. 54] and nitrite (0.5 mg / L) [Drinking wV, 2023, S. 57] in water are frequently exceeded. The limits for nitrate / nitrite in drinking water can be met in part only by admixing less contaminated water from other intake areas.If water is to be freed from harmful anions, the prior art offers two possible methods. Firstly, separation is possible via the adsorption of the pollutants on ion exchange resins, and secondly, membrane filtrations with dense polymer membranes can be carried out (nanofiltration, reverse osmosis). However, both methods have problems.The principle of an ion exchange material is based on the fact that ions are bound to a greater extent the greater the charge and, in the case of an identical charge, the greater the ion radius. This makes it possible to significantly reduce the amount of an ion species present in solution and to replace it with another (non-interfering / harmful) ion species. However, the use of ion exchange resins has various disadvantages. Firstly, in ion exchange plants, bacteria are easily colonized, which can lead to an additional water load. In addition, the adsorption on the ion exchange resins takes place non-specifically, so that, in addition to nitrate and nitrite ions, other ions dissolved in the water are also adsorbed. Similarly, adsorption sites are occupied by harmless substances, which results in a more rapid saturation of the material.The use of nanofiltration and reverse osmosis membranes leads to a separation of substances according to the size of the molecule, so that only very small molecules, water and smaller salt ions can pass through the membranes. Due to the necessary small pore size of the membranes, this purification method is associated with high working pressures of up to 40 bar in order to transport the water through the membrane. Accordingly, a very high energy requirement results if drinking water has to be provided in high quantity and quality and application in practice is made more difficult due to the high pressures. Since, as in the method using ion exchange resins, the water to be purified is almost completely desalted, remineralization of the water by addition of important salts is required to obtain drinking water.Various methods for modifying membranes are described in the prior art. DE 10 2009 036 947 A1 relates to a method for modifying polymer membranes, which brings about direct modification of the membrane polymer with low molecular weight compounds using high-energy radiation. DE 10 2009 004 848 B3 describes a method for producing a microporous membrane, on the surface of which a polymer crosslinked by electron radiation is fixed.The object of the invention is therefore to provide an alternative way of removing harmful anions from aqueous solution, the energy requirement of which is as low as possible and in which a reprocessing of the treated water is avoided as far as possible.SUMMARY OF THE INVENTIONThis object is achieved by the process according to the invention for producing a nonwoven material suitable for removing harmful anions from aqueous solution by modifying a surface thereof according to claim 1 and the modified nonwoven material obtained by the process according to claim 7. The production method comprises the steps (in this order) of: a) providing a nonwoven material selected from the group comprising polypropylene, polyethylene, viscose, polyamide, polylactide, polyester, polyethersulfone, polysulfone and polyvinylidene fluoride; b) applying a coating solution to the nonwoven material, wherein the coating solution contains polyallylamine hydrochloride (PAH) and / or polyhexamethylene biguanide (PHMB) as modifying agent; c) treating the nonwoven material and the coating solution with electron radiation; and d) purifying the modified nonwoven material from step c).A further aspect of the invention relates to the use of the modified nonwoven material for removing harmful anions from aqueous solution.Further preferred embodiments of the invention can be found in the dependent claims and the following description.Brief Description of the FigureThe invention is explained in more detail below with reference to several exemplary embodiments and the associated drawing. The single FIGURE shows in a highly schematic manner the method in principle for producing a nonwoven material suitable for removing harmful anions from aqueous solution by modifying a surface thereof.DETAILED DESCRIPTION OF THE INVENTIONFunctions and possible variants of the invention are explained in more detail below with reference to examples. However, the invention is not limited to the specific embodiments.General Aspects of the InventionThe method according to the invention for producing a nonwoven material suitable for removing harmful anions from aqueous solution by modifying a surface thereof comprises the following steps: a) providing a nonwoven material selected from the group comprising polypropylene, polyethylene, viscose, polyamide, polylactide, polyester, polyethersulfone, polysulfone and polyvinylidene fluoride; b) applying a coating solution to the nonwoven material, wherein the coating solution contains polyallylamine hydrochloride (PAH) and / or polyhexamethylene biguanide (PHMB) as modifying agent; and c) treating the nonwoven material and the coating solution with electron radiation; and d) purifying the modified nonwoven material from step c).The invention is based on the finding that, by electron beam immobilization of specific modification reagents, it is possible to produce an adsorber coating on specific nonwoven materials, which permits various anions to be removed from aqueous solution via ionic interactions.The nonwoven materials produced in this way exhibit, inter alia, a surprisingly high adsorption capacity for nitrate and nitrite ions and are therefore particularly suitable for drinking water treatment. The use of the material as a filter fleece also avoids high working pressures, so that the energy costs of the treatment are low.The method for producing a nonwoven material suitable for removing harmful anions from aqueous solution by modifying a surface thereof comprises, in a first step a), providing a nonwoven material suitable for the further method steps. This is a polymer from the group comprising polypropylene, polyethylene, viscose, polyamide, polylactide, polyester, polyethersulfone, polysulfone and polyvinylidene fluoride. A particularly suitable polyester is, in particular, polyethylene terephthalate (PET). The polymers mentioned are particularly suitable for electron beam immobilization, since sufficiently high densities of functionalities are formed during the treatment with the electron beam and a selective reaction with the added reagent is given. In addition, the materials are particularly suitable for the purposes of drinking water treatment, since they are stable with respect to water.The weight per unit area of the nonwoven material used is preferably in the range from 10 to 600 g / m 2, particularly preferably in the range from 20 to 500 g / m 2, in particular in the range from 100 to 300 g / m 2. Below a basis weight of 10 g / m 2 the nonwoven material layer is very thin. This has a disadvantageous effect on the stabilization of the nonwoven material, so that this possibly causes damage due to the mechanical stress when used as a filter nonwoven. Above a basis weight of 600 g / m 2 the nonwoven material layer is unnecessarily thick. Since the penetration depth of the modification is limited at the accelerating voltage used for the electron beam treatment, this represents an unnecessarily high material consumption. In addition, the greater layer thickness of the polymer can adversely affect the flexibility of the filter fleece, so that the filtration capacity of anions is likewise restricted.According to a particularly preferred variant, polyethylene terephthalate (PET) having a basis weight in the range from 100 to 300 g / m 2, for example of 200 g / m 2, is used. This embodiment is particularly suitable for a method for producing a modified nonwoven material for removing harmful anions from aqueous solution, since PET is, on the one hand, a relatively tear-resistant polymer and, on the other hand, absorbs only very little water. With a weight per unit area of 200 g / m 2 of the nonwoven material, particularly suitable mechanical properties with regard to the use as a filter nonwoven result from the layer thickness.In step b) of the method, a coating solution is applied to the nonwoven material, wherein the coating solution contains polyallylamine hydrochloride (PAH) and / or polyhexamethylene biguanide (PHMB) as modifying reagent. In other words, the surface of the nonwoven material to be modified is wetted with the modifying reagent by, for example, dipping the nonwoven into a solution containing the modifying reagent. Alternatively, the solution may be sprayed on. The solvent used can in principle be any solvent which sufficiently dissolves the modifying reagent, does not attack the fleece and does not adversely affect the irradiation. Water is particularly suitable.The modifying reagents used are polyallylamine hydrochloride (PAH; CAS 71550-12-4), polyhexamethylene biguanide (PHMB or polyhexanide; CAS 28757-47-3) or mixtures thereof. The compounds have been found to be suitable for electron beam immobilization. The concentration of the modifying reagent used (optionally total concentration of the modifying reagents used) is preferably in the range from 0.05 to 20% by weight, particularly preferably in the range from 0.1 to 10% by weight, in particular from 0.5 to 2% by weight. A concentration of the modifying reagent less than 0.05 wt % may adversely affect the aqueous solution anion filtration capacity, since at a lower concentration of the modifying reagent after electron beam immobilization, fewer functionalities are also attached to the surface of the nonwoven material. A concentration above 20% by weight may lead to undesired side reactions between the molecules of the modifying reagent when treated with electron radiation. The coating solution can be applied by dipping, spraying and / or painting on the solution.In step c) of the method, the nonwoven material and the coating solution according to b) are treated with electron radiation. As a result, the modifying reagent after b) is immobilized on the nonwoven surface (electron beam immobilization). The radiation dose of the electron radiation is preferably in the range from 20 to 600 kGy, particularly preferably in the range from 100 to 500 kGy, in particular from 200 to 400 kGy. A radiation dose of less than 20 kGy of the electron radiation has disadvantageous effects on the removal of anions from aqueous solution, since below this radiation dose the immobilization of the modifying reagent on the fleece surface takes place only incompletely and consequently fewer molecules of the modifying reagent are bound on the surface. A radiation dose above 600 kGy may lead to undesired side reactions, in particular to chemical decomposition of the modifying reagent. By means of the irradiation, PAH or PHMB are covalently bonded to the polymeric nonwoven material. The reaction with both modifying reagents results in polycationic structures on the surface of the nonwoven material. These polycationic structures have proven to be particularly suitable for the addition of various anions.In step d), the now modified nonwoven material is subsequently purified. The modified nonwoven material is washed and dried. In principle, any liquid can be used as washing agent which sufficiently dissolves the (unreacted) modifying reagent and does not attack the fleece. According to a particularly preferred variant, the modified nonwoven material is washed several times with deionized water and dried at room temperature overnight.The single FIGURE illustrates in a highly schematic manner the process explained above for producing a nonwoven material suitable for removing harmful anions from aqueous solution by modifying a surface thereof. In a step S 1, a nonwoven material selected from the group comprising polypropylene, polyethylene, viscose, polyamide, polylactide, polyester, polyethersulfone, polysulfone and polyvinylidene fluoride is provided. Subsequently, in step S 2, a coating solution is applied to the nonwoven material, wherein the coating solution contains polyallylamine hydrochloride (PAH) and / or polyhexamethylene biguanide (PHMB) as a modifying reagent. After the application, in step S 3, treatment of the nonwoven material and the coating solution with electron radiation is performed. Finally, in step S 4, the modified nonwoven material is purified.Production of Modified Nonwoven MaterialIn the experiments described in more detail below, a nonwoven material made of polyethylene terephthalate (PET) with a basis weight of 200 g / m 2 is provided.In a subsequent process step, a coating solution is applied to the nonwoven material, wherein the coating solution contains polyallylamine hydrochloride (PAH) or polyhexamethylene biguanide (PHMB) as the modifying reagent. The coating solution is applied to the nonwoven material to be modified by immersing the nonwoven material in a coating solution. Water is provided as the solvent of the coating solution. The modifying reagent PAH or PHMB is present in concentrations in a range of 0.5 and 2 wt.%, respectively (see Tables 1 to 4).Immobilization of the modifying reagent on the nonwoven material to be modified is effected by treatment with electron radiation. During the irradiation with electrons, the modifying reagent is bonded to the surface of the nonwoven material. The energy dose of the electron beam is 200 kGy or 400 kGy (see Tables 1 to 4).The modified nonwoven material is obtained after purifying the nonwoven material treated with electron radiation. This purification step comprises a washing process with a liquid and a subsequent drying. Thus, the treated nonwoven material is washed several times with deionized water and dried in air at ambient temperature.Investigation of the Adsorber Effect and Further PropertiesBy way of example, dynamic adsorption experiments for determining the adsorber action of nitrate and nitrite ions are carried out on both the unmodified and the modified nonwoven materials. For this, 10 ml and 50 ml of an aqueous solution containing either 10 ppm nitrate ions or 10 ppm nitrite ions are filtered through a fleece having a surface area of 50 cm 2 at a flow rate of 3 ml / min. The residual concentration of nitrate or nitrite ions is determined spectroscopically in the permeate. The results are summarized for various (unmodified) nonwoven materials in the scope of experimental comparative studies in Tables 1 to 4.The (unmodified nonwoven materials are also investigated with regard to their mechanical properties and functionality. In the course of investigations by means of scanning electron microscopy (SEM), tensile tests and Hg porosimetry, it has been found that the starting materials and modified nonwoven materials do not have a measurable change in the nonwoven morphology, the permeability and the porosity.Comparative Experimental Study 1In Comparative Experimental Study 1, it is examined what effects the concentration of PAH in the coating solution and the energy dose of electron radiation have on the properties of the modified nonwoven material with respect to the removal of nitrate ions from aqueous solution. The remaining amount of nitrate ions in the filtrate is determined in each case according to a volume of 10 ml or 50 ml. Table 1 shows the measurement results for the removal of nitrate ions from aqueous solution using a nonwoven material of polyethylene terephthalate with a PAH-containing coating treated with electron beams of various energy doses. The reference system chosen is a nonwoven material made of PET which has neither been coated with a modifying reagent nor treated with electron radiation. Tab. 1 Tab. 1PET, 200 g / m 2--470PET, 200 g / m 20,52008943PET, 200 g / m 222009148PET, 200 g / m 224008861As can be seen, the nonwoven without modification is not suitable for filtration of nitrate from aqueous solution. Only by the electron beam-induced binding of PAH can nitrate ions be removed to a considerable extent from aqueous solution.In the case of a nonwoven material consisting of PET which has neither been coated with PAH nor treated with electron radiation, the residual amount of nitrate in the permeate is reduced by 47% after filtration of 10 ml of a nitrate-containing aqueous solution. At a volume of 50 ml, the residual amount of nitrate in the permeate is not reduced (0%).The investigations of the modified nonwoven materials show that, at a volume of 10 ml of a nitrate-containing aqueous solution, the reduction of the nitrate ions remaining in the permeate is about 90%, independently of the concentration of PAH in the coating solution and of the energy dose of the electron radiation. This demonstrates, on the one hand, the suitability of these modified nonwoven materials for the removal of nitrate ions from aqueous solution and, on the other hand, that for the filtration of 10 ml of an aqueous nitrate solution, the modified nonwoven materials are already largely optimized, so that both a change in the PAH concentration in the coating solution (0.5 and 2% by weight) and a change in the radiation dose (200 and 400 kGy) influence the filtration capacity only insignificantly.With a volume of 50 ml of a nitrate-containing aqueous solution, the suitability of the modified nonwoven materials for removing nitrate ions from aqueous solution is likewise clear in comparison with the unmodified nonwoven material. Whereas in the latter case the amount of nitrate is not reduced (0%), the amount of nitrate in the respective permeate is reduced by 43 to 61% in the modified nonwoven materials. It is found that as the PAH concentration increases and the energy dose of the electron radiation increases, the filtration capacity of the modified nonwoven material increases. In the course of the investigations, it has been shown that the filter fleece with the greatest filtering capacity of a nitrate-containing aqueous solution comprising 50 mL is a PET fleece material which was treated with a coating solution with 2% by weight of PAH and an electron beam with an energy dose of 400 kGy.Comparative Experimental Study 2In Comparative Experimental Study 2, it is examined what effects the concentration of PAH in the coating solution and the energy dose of electron radiation have on the properties of the modified nonwoven material with respect to the removal of nitrite ions from aqueous solution. The remaining amount of nitrite ions in the filtrate is determined in each case according to a volume of 10 ml or 50 ml. Table 2 shows the measurement results for removing nitrite ions from aqueous solution using a nonwoven material of polyethylene terephthalate having a PAH-containing coating treated with electron beams of various energy doses. The reference system chosen is a nonwoven material made of PET which has neither been coated with a modifying reagent nor treated with electron radiation. Tab. 2 Tab. 2PET, 200 g / m 2--411PET, 200 g / m 20,52008734PET, 200 g / m 222008845PET, 200 g / m 224008868As can be seen, the nonwoven without modification is not suitable for filtration of nitrite from aqueous solution. Only by the electron beam-induced binding of PAH can nitrite ions be removed to a considerable extent from aqueous solution.In the case of a nonwoven material consisting of PET which has neither been coated with PAH nor treated with electron radiation, the residual amount of nitrite in the permeate is reduced by 41% after filtration of 10 ml of a nitrite-containing aqueous solution. At a volume of 50 ml, the residual amount of nitrite in the permeate is only insignificantly reduced (1%).The investigations of the modified nonwoven materials show that, at a volume of 10 ml of a nitrite-containing aqueous solution, the reduction of the nitrite ions remaining in the permeate is about 88%, independently of the concentration of PAH and the energy dose of the electron radiation. This demonstrates, on the one hand, the suitability of these modified nonwoven materials for the removal of nitrite ions from aqueous solution and, on the other hand, that for the filtration of 10 ml of a nitrite-containing aqueous solution, the modified nonwoven materials are already largely optimized, so that both a change in the PAH concentration in the coating solution (0.5 and 2% by weight) and a change in the energy dose (200 and 400 kGy) of the electron radiation influence the filtration capacity of the modified nonwoven material only insignificantly.With a volume of 50 ml of a nitrite-containing aqueous solution, the suitability of the modified nonwoven materials for removing nitrite ions from aqueous solution is likewise clear in comparison with the unmodified nonwoven material. Whereas in the latter case the nitrite quantity is not reduced (0%), in the case of the modified nonwoven materials the nitrite quantity in the respective permeate is reduced by 34 to 68%. It is found that as the PAH concentration increases and the energy dose of the electron radiation increases, the filtration capacity of the modified nonwoven material increases. In the course of the studies, it has been shown that the filter fleece with the greatest filtering capacity of a nitrite-containing aqueous solution comprising 50 ml is a PET fleece material which has been treated with a coating solution with 2% by weight of PAH and an electron beam with an energy dose of 400 kGy.Comparative Experimental Study 3In Comparative Experimental Study 3, it is examined what effects the concentration of PHMB in the coating solution and the energy dose of electron radiation have on the properties of the modified nonwoven material with respect to the removal of nitrate ions from aqueous solution. The remaining amount of nitrate ions in the filtrate is determined in each case according to a volume of 10 ml or 50 ml. Table 3 shows the measurement results for the removal of nitrate ions from aqueous solution using a nonwoven material of polyethylene terephthalate with a PHMB-containing coating treated with electron beams of various energy doses. The reference system chosen is a nonwoven material made of PET which has neither been coated with a modifying reagent nor treated with electron radiation. Tab. 3 Tab. 3PET, 200 g / m 2--470PET, 200 g / m 20,5200893PET, 200 g / m 22200892PET, 200 g / m 22400917As can be seen, the nonwoven without modification is not suitable for filtration of nitrate from aqueous solution. Only by the electron beam-induced binding of PHMB can nitrate ions be removed to a considerable extent from aqueous solution. In the case of a nonwoven material consisting of PET which has neither been coated with PHMB nor treated with electron radiation, the residual amount of nitrate in the permeate is reduced by 47% after filtration of 10 ml of a nitrate-containing aqueous solution. At a volume of 50 ml, the residual amount of nitrate in the permeate is not reduced (0%).The investigations of the modified nonwoven materials show that, at a volume of 10 ml of a nitrate-containing aqueous solution, the reduction of the nitrate ions remaining in the permeate is about 90%, independently of the concentration of PHMB and of the energy dose of the electron radiation. This demonstrates, on the one hand, the suitability of these modified nonwoven materials for the removal of nitrate ions from aqueous solution and, on the other hand, that for the filtration of 10 ml of a nitrate-containing aqueous solution, the modified nonwoven materials are already largely optimized, so that both a change in the PHMB concentration in the coating solution (0.5 and 2% by weight) and a change in the radiation dose (200 and 400 kGy) influence the filtration capacity only insignificantly.At a volume of 50 ml of a nitrate-containing aqueous solution, it is found that the PHMB-coated nonwoven materials are less suitable for removing nitrate ions from aqueous solution than the PAH-coated nonwoven materials (compare Tab. 1 and 3). Whereas in the case of the unmodified nonwoven material the amount of nitrate is not reduced (0%), in the case of the modified nonwoven materials the amount of nitrate in the respective permeate is reduced by 2 to 7%. It is found that increasing the energy dose of the electron radiation brings about a slight improvement in the removal of nitrate ions from aqueous solution.Comparative Experimental Study 4In Comparative Experimental Study 4, it is examined what effects the concentration of PHMB in the coating solution and the energy dose of electron radiation have on the properties of the modified nonwoven material with respect to the removal of nitrite ions from aqueous solution. The remaining amount of nitrite ions in the filtrate is determined in each case according to a volume of 10 ml or 50 ml. Table 4 shows the measurement results for removing nitrite ions from aqueous solution using a nonwoven material of polyethylene terephthalate having a PHMB-containing coating treated with electron beams of various energy doses. The reference system chosen is a nonwoven material made of PET which has neither been coated with a modifying reagent nor treated with electron radiation. Tab. 4 Tab. 4PET, 200 g / m 2--411PET, 200 g / m 20,5200871PET, 200 g / m 22200854PET, 200 g / m 22400865As can be seen, the nonwoven without modification is not suitable for filtration of nitrite from aqueous solution. Only by the electron beam-induced binding of PHMB can nitrite ions be removed to a considerable extent from aqueous solution.In the case of a nonwoven material consisting of PET which has neither been coated with PHMB nor treated with electron radiation, the residual amount of nitrite in the permeate is reduced by 41% after filtration of 10 ml of a nitrite-containing aqueous solution. At a volume of 50 ml, the residual amount of nitrite in the permeate is only insignificantly reduced (1%).The investigations of the modified nonwoven materials show that, at a volume of 10 ml of a nitrite-containing aqueous solution, the reduction of the nitrite ions remaining in the permeate is about 86%, independently of the concentration of PHMB and the energy dose of the electron radiation. This demonstrates, on the one hand, the suitability of these modified nonwoven materials for the removal of nitrite ions from aqueous solution and, on the other hand, that for the filtration of 10 ml of a nitrite-containing aqueous solution, the modified nonwoven materials are already largely optimized, so that a change in the PHMB concentration in the coating solution (0.5 and 2% by weight) and a change in the radiation dose (200 and 400 kGy) influence the filtration capacity only insignificantly.At a volume of 50 ml of a nitrite-containing aqueous solution, it is found that the PHMB-coated nonwoven materials are less suitable for removing nitrite ions from aqueous solution than the PAH-coated nonwoven materials (compare Tab. 1 and 4). Whereas in the case of the unmodified nonwoven material the nitrite quantity is only insignificantly reduced (1%), in the case of the modified nonwoven materials a comparable reduction of the nitrite quantity in the respective permeate takes place (1-5%). It is found that increasing the energy dose of the electron radiation brings about a small improvement in the removal of nitrite ions from aqueous solution.When comparing the described non-woven materials, a non-woven material consisting of PET treated with a 2% by weight PAH solution and electron radiation of an energy dose of 400 kGy (see Tables 1 and 2) shows a clearly improved filtration capacity for nitrate and nitrite ions compared to the unmodified non-woven material.The electron beam-based modification accordingly provides the treated nonwoven material with an adsorber layer for anions. This fleece can be used for separating the stated anions from the drinking water by being used in a filter system, for example installed in the form of a filter pocket. The necessity of such a filter system already arises from the increasing load of the water bodies with nitrate / nitrite entries of anthropogenic origin.The removal of nitrate / nitrite ions from the water to be filtered is effected more efficiently and more specifically than would be the case, for example, with anion exchange resins. At the same time, the non-woven material used represents only a low hydrodynamic resistance, which makes it possible to use low working pressures. The filter system can thus be operated at sufficient line pressure without additional pumps or the like. At the same time, the nonwoven material used gives rise to a lower risk of colonization by microorganisms, such as bacteria, for example, as can occur in the case of anion exchange resins.Regeneration of the Adsorbent MaterialAfter using the modified nonwoven material to remove, for example, nitrate and nitrite ions from aqueous solution, the materials can be purified by rinsing with a diluted saline solution, for example, at a concentration of 0.3% by weight. The adsorbed anions are displaced by the excess of chloride ions, so that the nonwoven material can be used again for removing health-damaging anions from aqueous solution.List of reference charactersS1 Providing a nonwoven material selected from the group comprising polypropylene, polyethylene, viscose, polyamide, polylactide, polyester, polyethersulfone, polysulfone and polyvinylidene fluoride S2 Applying a coating solution to the nonwoven material, wherein the coating solution contains polyallylamine hydrochloride (PAH) and / or polyhexamethylene biguanide (PHMB) as modifying agent S3 Treatment of the nonwoven material and the coating solution with electron radiation S4 Purification of the modified nonwoven material

Claims

A method for producing a nonwoven material suitable for removing harmful anions from aqueous solution by modifying a surface thereof, comprising the steps of: a) providing a nonwoven material selected from the group comprising polypropylene, polyethylene, viscose, polyamide, polylactide, polyester, polyethersulfone, polysulfone and polyvinylidene fluoride; b) applying a coating solution to the nonwoven material, wherein the coating solution contains polyallylamine hydrochloride (PAH) and / or polyhexamethylene biguanide (PHMB) as a modifying agent; c) treating the nonwoven material and the coating solution after step b) with electron beam radiation; and d) purifying the modified nonwoven material of step c).The method of claim 1, wherein the anions to be removed are selected from the group comprising nitrate and nitrite ions.The method of claim 1 or 2, wherein the nonwoven material described in step a) has basis weights in the range of 10 to 600 g / m 2.The method according to any one of the preceding claims, wherein the coating solution described in step b) contains 0.05 to 20 wt.% of the modifying reagent.The method according to any one of the preceding claims, wherein the electron radiation described in step c) has an energy dose in the range of 20 to 500 kGy.The method according to any one of the preceding claims, wherein the purification in step d) provides at least one washing process and a subsequent drying of the modified nonwoven material.A nonwoven material for removing harmful anions from aqueous solution, produced by a process according to claim 1.Use of the nonwoven material according to claim 7 for removing harmful anions from aqueous solution.Use of the nonwoven material of claim 7, wherein the modified nonwoven material is regenerated by rinsing with a saline solution after removal of harmful anions from aqueous solution.