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Evidence for liquid-liquid phase separation during the early stages of Mg-struvite formation

  • The precipitation of struvite, a magnesium ammonium phosphate hexahydrate (MgNH₄PO₄ · 6H₂O) mineral, from wastewater is a promising method for recovering phosphorous. While this process is commonly used in engineered environments, our understanding of the underlying mechanisms responsible for the formation of struvite crystals remains limited. Specifically, indirect evidence suggests the involvement of an amorphous precursor and the occurrence of multi-step processes in struvite formation, which would indicate non-classical paths of nucleation and crystallization. In this study, we use synchrotron-based in situ x-ray scattering complemented by cryogenic transmission electron microscopy to obtain new insights from the earliest stages of struvite formation. The holistic scattering data captured the structure of an entire assembly in a time-resolved manner. The structural features comprise the aqueous medium, the growing struvite crystals, and any potential heterogeneities or complexThe precipitation of struvite, a magnesium ammonium phosphate hexahydrate (MgNH₄PO₄ · 6H₂O) mineral, from wastewater is a promising method for recovering phosphorous. While this process is commonly used in engineered environments, our understanding of the underlying mechanisms responsible for the formation of struvite crystals remains limited. Specifically, indirect evidence suggests the involvement of an amorphous precursor and the occurrence of multi-step processes in struvite formation, which would indicate non-classical paths of nucleation and crystallization. In this study, we use synchrotron-based in situ x-ray scattering complemented by cryogenic transmission electron microscopy to obtain new insights from the earliest stages of struvite formation. The holistic scattering data captured the structure of an entire assembly in a time-resolved manner. The structural features comprise the aqueous medium, the growing struvite crystals, and any potential heterogeneities or complex entities. By analysing the scattering data, we found that the onset of crystallization causes a perturbation in the structure of the surrounding aqueous medium. This perturbation is characterized by the occurrence and evolution of Ornstein-Zernike fluctuations on a scale of about 1 nm, suggesting a non-classical nature of the system. We interpret this phenomenon as a liquid-liquid phase separation, which gives rise to the formation of the amorphous precursor phase preceding actual crystal growth of struvite. Our microscopy results confirm that the formation of Mg-struvite includes a short-lived amorphous phase, lasting >10 s.zeige mehrzeige weniger

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Metadaten
Autor*innen:Stephanos KarafiludisORCiD, E. ScoppolaORCiD, S.E. WolfORCiD, Z. KochovskiORCiD, D. Matzdorff, A. E. S. Van DriesscheORCiD, J. HövelmannORCiD, Franziska EmmerlingORCiD, Tomasz M. StawskiORCiD
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):The Journal of Chemical Physics
Jahr der Erstveröffentlichung:2023
Organisationseinheit der BAM:6 Materialchemie
6 Materialchemie / 6.3 Strukturanalytik
Veröffentlichende Institution:Bundesanstalt für Materialforschung und -prüfung (BAM)
Verlag:AIP Publishing
Verlagsort:Woodbury, NY
Jahrgang/Band:159
Ausgabe/Heft:13
Aufsatznummer:134503
Erste Seite:1
Letzte Seite:12
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Crystallization; In-situ scattering; Liquid-liquid-phase-separation; Non-classical crystallization; Nucleation; Physical and theoretical chemistry; Struvite
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Materialdesign
Material / Nano
DOI:10.1063/5.0166278
URN:urn:nbn:de:kobv:b43-584766
ISSN:1089-7690
Verfügbarkeit des Dokuments:Datei für die Öffentlichkeit verfügbar ("Open Access")
Lizenz (Deutsch):License LogoCreative Commons - CC BY - Namensnennung 4.0 International
Datum der Freischaltung:04.10.2023
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:09.10.2023
Schriftenreihen ohne Nummerierung:Wissenschaftliche Artikel der BAM
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