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Determination of chromium(VI) in phosphorus fertilizers made from recycled materials by DGT

  • Phosphorus (P) fertilizers from secondary resources became increasingly important in the last years. However, these novel P-fertilizer can also contain toxic pollutants e.g. chromium (Cr) in the hexavalent state (Cr(VI)), which is regulated with low limit values in agricultural products (German fertilizer ordinance limit: 2 mg/kg Cr(VI)). The determination of Cr(VI) in these novel fertilizer matrices can be hampered by redox processes that lead to false results with the standard wet chemical extraction method (German norm DIN EN 15192). Therefore, we analyzed Cr(VI) in various P-fertilizers with the DGT technique. DGT devices equipped with a APA (polyacrylamide) diffusion layer and Cr(VI) selective N-methyl-D-glucamine (NMDG) binding layer were used for the study. After a 24 h conditioning period of the fertilizer at 60% of the water holding capacity (WHC), the fertilizers were brought to 100% WHC, transferred onto the DGT devices and deployed for 24 h at 25°C. The extraction of CrPhosphorus (P) fertilizers from secondary resources became increasingly important in the last years. However, these novel P-fertilizer can also contain toxic pollutants e.g. chromium (Cr) in the hexavalent state (Cr(VI)), which is regulated with low limit values in agricultural products (German fertilizer ordinance limit: 2 mg/kg Cr(VI)). The determination of Cr(VI) in these novel fertilizer matrices can be hampered by redox processes that lead to false results with the standard wet chemical extraction method (German norm DIN EN 15192). Therefore, we analyzed Cr(VI) in various P-fertilizers with the DGT technique. DGT devices equipped with a APA (polyacrylamide) diffusion layer and Cr(VI) selective N-methyl-D-glucamine (NMDG) binding layer were used for the study. After a 24 h conditioning period of the fertilizer at 60% of the water holding capacity (WHC), the fertilizers were brought to 100% WHC, transferred onto the DGT devices and deployed for 24 h at 25°C. The extraction of Cr from the DGT binding layer was carried out with 1 M HNO3 for 24 h. The Cr-concentrations of the extract were determined by means of ICP-MS. We found a good correlation between the standard wet chemical extraction and the DGT method for the whole range of P-fertilizers. However, partly soluble Cr(VI) compounds cannot be detected in full extent by the DGT method that is best suited for mobile Cr(VI). Furthermore, Cr K-edge XANES spectroscopy showed that the Cr(VI)-selective DGT binding layer also adsorbs mobile Cr(III) compounds from acid treatment of phosphates which can therefore cause an overestimation of Cr(VI). The DGT method was very sensitive and in most cases selective for the analysis of Cr(VI) in P-fertilizers made from recycled materials. However, the results of certain types of P-fertilizers containing mobile Cr(III) or partly immobile Cr(VI) show that still some optimization of the method is required to avoid over- or underestimation of Cr(VI).zeige mehrzeige weniger

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Metadaten
Autoren/innen:Christian Vogel
Koautoren/innen:O. Krüger, Marie Hoffmann, Christian Adam
Dokumenttyp:Posterpräsentation
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2019
Organisationseinheit der BAM:4 Material und Umwelt
4 Material und Umwelt / 4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Sanitär- und Kommunaltechnik; Umwelttechnik
Freie Schlagwörter:Chromium; Diffusive gradients in thin films (DGT); Fertilzer; Pollutant; XANES spectroscopy
Themenfelder/Aktivitätsfelder der BAM:Umwelt
Umwelt / Umweltschadstoffe
Umwelt / Ressourcenrückgewinnung und Materialverwertung
Analytical Sciences
Analytical Sciences / Strukturanalytik und Materialographie
Veranstaltung:6th Conference on Diffusive Gradients in Thin Films
Veranstaltungsort:Vienna, Austria
Beginndatum der Veranstaltung:17.09.2019
Enddatum der Veranstaltung:20.09.2019
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:23.09.2019
Referierte Publikation:Nein