Adsorbent for binding polyfluorinated organic compounds

Abstract

The invention relates to an adsorbent for binding polyfluorinated organic compounds to a textile carrier material having a finish made of a hydroxy-modified ammonium salt, characterized in that the carrier material is additionally finished with an alkoxy-modified melamine or a polycarboxylic acid, wherein the finish is thermally fixed.

Description

[0001]DTFZ0070 15.05.2025 AK / pd Adsorbent for Binding Polyfluorinated Organic Compounds The invention relates to an adsorbent for binding polyfluorinated organic compounds on a carrier material comprising a hydroxy-modified ammonium salt. Per- and polyfluorinated organic compounds, which include in particular perfluorinated surfactants (PFTs) and perfluorinated carboxylic acids (PFAs) and sulfonic acids (PFSs), were first detected in the environment in the 1970s. Today, they are detectable worldwide in almost all bodies of water, in the atmosphere, in groundwater, and in the tissue and blood of humans and animals. Per- and polyfluorinated organic compounds are persistent and resistant to degradation in the environment. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) are the most widely used worldwide. The European Union's REACH program restricts the manufacture and use of PFOS-related compounds.Furthermore, PFOS was included as a persistent organic pollutant in the Stockholm Convention lists, and the inclusion of PFOA was recommended. The United States Environmental Protection Agency has established a recommended drinking water standard of 70 ng / l for the maximum concentration of PFOA and PFOS. The sale of PFOS has been prohibited since 2020. German patent DE 102020122580 A1 describes an adsorbent system based on cationic amine-containing polyelectrolytes for PFTs. WO 2013 / 050139 A1 and WO 2014 / 161973 A1 describe an adsorbent and a method for removing fluorinated organic compounds from contaminated liquids. The absorbed pollutants are precipitated from the liquid using a second adsorbent. Overall, these pollutants contained in groundwater and wastewater represent a significant problem. There is a need for adsorbents that can reliably remove these pollutants from aqueous environments.The object of the invention is therefore to provide an adsorbent with which these pollutants can be removed from aqueous environments with high efficiency. Accordingly, the invention relates to an adsorbent of the type mentioned above, in which the carrier material is further equipped with a hydroxy-modified melamine or a polycarboxylic acid, the modification being thermally fixed. The polyfluorinated organic compounds are, in particular, perfluorinated and polyfluorinated carboxylic acids and sulfonic acids. Such compounds are widely used in the textile industry, the paper industry, in fire extinguishing agents, and in electroplating, for example as surfactants and for impregnation, and are additives in numerous products. Due to their persistence, they accumulate in the environment, for example on arable land treated with sewage sludge, and in groundwater, and thus enter drinking water and food.The adsorbent according to the invention comprises, firstly, a carrier material, in particular a textile carrier material. This is, for example, a textile fabric, such as cotton, wool, or viscose. Synthetic textile materials can also be used. Secondly, the carrier material is equipped with the actual binding material. This consists of two components that are fixed to the carrier material. Both components are essential for binding the polyfluorinated organic compounds. The first component is a hydroxy-modified ammonium salt, which preferably has two hydroxyethyl groups. The hydroxyethyl groups can be singly or multiply ethoxylated. The ammonium salt further preferably has an alkyl group, in particular a methyl group, as well as a fatty alkyl group or a fatty alkoxypropyl group. Suitable anions include conventional ones, for example, chloride, sulfate, nitrate, or sulfonate.Preferred ammonium salts correspond to formulas I and II, where a and b independently represent 1 to 8, R is an alkyl group with up to 18 carbon atoms, and x- is a conventional anion. The second component is an alkoxy-modified melamine, which may have up to three alkoxy groups. A trimethoxymelamine is preferred. Alternatively, the second component is a polycarboxylic acid with 3 to 6 carboxyl groups on an aliphatic or aromatic backbone. Suitable examples include 1,2,3-propanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, citric acid, and multiply carboxylated benzene. Compounds of formulas III and IV below are particularly preferred. IV, wherein R' is an alkyl group with up to 6 carbon atoms. The ammonium salt, on the one hand, and the alkoxy-modified melamine or the polycarboxylic acid, on the other, are advantageously applied to the support material in a molar ratio of 5:1 to 1:1, preferably in a molar ratio of approximately 2:1. After drying, the support material thus impregnated is subjected to a thermal treatment to fix the treatment. For this purpose, the treated support material is heated to a temperature of 100 to 180°C, preferably 120 to 160°C, for a period of 10 to 30 minutes. Unfixed material is then washed off. The adsorbent according to the invention has proven to be very suitable, in particular for binding PFAs and PFSs from wastewater and groundwater / drinking water. Adsorption rates of more than 90% have been achieved. The invention is further explained by the following examples. The following compounds listed in Table 1 were used in these examples.Table 1: Chemicals Manufacturer Structure. Example 1: A cotton fabric (170 g / cm²) was impregnated with ammonium salt and melamine / polycarboxylic acid according to Table 2. After drying and fixing at 160°C for 15 minutes, the loadings shown in Table 2 were obtained as a percentage of the treated textile material. Example 2: Sections (Table 3) of the textile materials treated according to Example 1 were soaked in 10 ml of water containing 1000 ng / l perfluorooctanecarboxylic acid and shaken for 24 hours. The adsorption by the textile material was then determined. The values ​​shown in Diagram 1 were obtained. Blank Co denotes a blank sample in which the textile material was not treated. Table 2: Sample designation, Molar ratio, Coating, 160°C, Fixed [%] Diagram 1 Example 3: As in Example 2, a sample was treated with 1000 ng / l perfluorooctanesulfonic acid. The data are given in Table 3, the absorbance values ​​in Diagram 2. M4 33.1 mg Diagram 2 Perfluorooctanecarboxylic acid and perfluorooctanesulfonic acid are very common PFTs that regularly enter the environment and are found in wastewater, groundwater, and increasingly also in drinking water and food. Adsorption rates of more than 90% represent a significant improvement over conventional methods. Example 4: As in Example 2, a sample from Example 1 was treated with 517 ng / L perfluorobutanoic acid. The data are given in Table 4, and the absorption values ​​in Diagram 3. T 4 M4 33.2 mg Diagram 3 Example 5: As in Example 2, a sample was treated with 628 ng / l perfluorobutanesulfonic acid. The data are given in Table 5, the absorbance values ​​in Diagram 4. M4 33.2 mg Diagram 4 Diagrams 3 and 4 show the considerable potential of the combinations M1 / M2 for the adsorption of perfluorobutanoic acid and perfluorobutanesulfonic acid.

Claims

Claims 1. Adsorbent for binding polyfluorinated organic compounds to a textile carrier material having a finish of a hydroxy-modified ammonium salt, characterized in that the carrier material is further finished with an alkoxy-modified melamine or a polycarboxylic acid, wherein the finish is thermally fixed.

2. Adsorbent according to claim 1, characterized in that the ammonium salt has two hydroxyethyl groups, which may be multiply ethoxylated.

3. Adsorbent according to claim 2, characterized in that the ammonium salt has an alkyl group, in particular a methyl group.

4. Adsorbent according to any one of the preceding claims, characterized in that the ammonium salt has one of the following formulas I or II: II wherein a and b independently represent 1 to 8, R is a fatty alkyl group with up to 18 carbon atoms, and x- is a conventional anion.

5. Adsorbent according to any one of the preceding claims, characterized in that the alkoxy-modified melamine corresponds to formula III; III wherein R' is an alkyl group with 1 to 6 C atoms.

6. Adsorbent according to any one of claims 1 to 4, characterized in that the polycarboxylic acid is 1,2,3-propanetricarboxylic acid or 1,2,3,4-butanetetracarboxylic acid.

7. Adsorbent according to any one of the preceding claims, characterized in that the hydroxy-modified ammonium salt and the alkoxy-modified melamine or the polycarboxylic acid are applied to the carrier material in a molar ratio of 1:0.2 to 1:1, preferably about 1:0.

5.

8. Adsorbent according to any one of the preceding claims, characterized in that the carrier material is a textile fabric.

9. Adsorbent according to claim 8, characterized in that the carrier material is of natural origin, in particular cotton, wool, or viscose.

10. Use of an adsorbent according to any of the preceding claims for binding per- or polyfluorinated organic compounds, in particular perfluorinated organic carboxylic acids and sulfonic acids from aqueous media, especially wastewater.

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