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Solution-driven processing of calcium sulfate: The mechanism of the reversible transformation of gypsum to bassanite in brines

  • Here, we show that calcium sulfate dihydrate (gypsum) can be directly, rapidly and reversibly converted to calcium sulfate hemihydrate (bassanite) in high salinity solutions (brines). The optimum conditions for the efficient production of bassanite in a short time (<5 min) involve the use of brines with c(NaCl) > 4 M and maintaining a temperature, T > 80 °C. When the solution containing bassanite crystals is cooled down to around room temperature, eventually gypsum is formed. When the temperature is raised again to T > 80 °C, bassanite is rapidly re-precipitated. This contrasts with the better-known behaviour of the bassanite phase in low-salt environments. In low-salinity aqueous solutions, bassanite is considered to be metastable with respect to gypsum and anhydrite, and therefore gypsum-to-bassanite conversion does not occur in pure water. Interestingly, the high-salinity transformation of gypsum-to-bassanite has been reported by many authors and used in practice for severalHere, we show that calcium sulfate dihydrate (gypsum) can be directly, rapidly and reversibly converted to calcium sulfate hemihydrate (bassanite) in high salinity solutions (brines). The optimum conditions for the efficient production of bassanite in a short time (<5 min) involve the use of brines with c(NaCl) > 4 M and maintaining a temperature, T > 80 °C. When the solution containing bassanite crystals is cooled down to around room temperature, eventually gypsum is formed. When the temperature is raised again to T > 80 °C, bassanite is rapidly re-precipitated. This contrasts with the better-known behaviour of the bassanite phase in low-salt environments. In low-salinity aqueous solutions, bassanite is considered to be metastable with respect to gypsum and anhydrite, and therefore gypsum-to-bassanite conversion does not occur in pure water. Interestingly, the high-salinity transformation of gypsum-to-bassanite has been reported by many authors and used in practice for several decades, although its very occurrence actually contradicts numerical thermodynamic predictions regarding solubility of calcium sulfate phases. By following the evolution of crystalline phases with in situ and time-resolved X-ray diffraction/scattering and Raman spectroscopy, we demonstrated that the phase stability in brines at elevated temperatures was inaccurately represented in the thermodynamic databases. Most notably for c(NaCl) > 4 M, and T > 80 °C gypsum becomes readily more soluble than bassanite, which induces the direct precipitation of the latter from gypsum. The fact that these transformations are controlled by the solution provides extensive opportunities for precise manipulation of crystal formation. Our experiments confirmed that bassanite remained the sole crystalline phase for many hours before reverting into gypsum. This property is extremely advantageous for practical processing and efficient crystal extraction in industrial scenarios.zeige mehrzeige weniger

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Autor*innen:Tomasz StawskiORCiD, Stephanos KarafiludisORCiD, Carlos PimentelORCiD, German Montes-HernándezORCiD, Zdravko KochovskiORCiD, Ralf BienertORCiD, Karin WeimannORCiD, Franziska EmmerlingORCiD, Ernesto ScoppolaORCiD, Alexander E.S. Van DriesscheORCiD
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Journal of Cleaner Production
Jahr der Erstveröffentlichung:2024
Organisationseinheit der BAM:4 Material und Umwelt
4 Material und Umwelt / 4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung
6 Materialchemie
6 Materialchemie / 6.3 Strukturanalytik
Veröffentlichende Institution:Bundesanstalt für Materialforschung und -prüfung (BAM)
Verlag:Elsevier B.V.
Jahrgang/Band:440
Aufsatznummer:141012
Erste Seite:1
Letzte Seite:12
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Sanitär- und Kommunaltechnik; Umwelttechnik
Freie Schlagwörter:BESSY; Bassanite; Building and Construction; Calcium sulfate; General Environmental Science; Gypsum; In situ; Industrial and Manufacturing Engineering; MySpot; Raman; Renewable Energy, Sustainability and the Environment; Scattering; Strategy and Management; Synchrotron
Themenfelder/Aktivitätsfelder der BAM:Umwelt
Umwelt / Circular Economy
DOI:10.1016/j.jclepro.2024.141012
URN:urn:nbn:de:kobv:b43-594698
URL:https://www.sciencedirect.com/science/article/pii/S0959652624004591#appsec1
ISSN:0959-6526
Verfügbarkeit des Dokuments:Datei für die Öffentlichkeit verfügbar ("Open Access")
Lizenz (Deutsch):License LogoCreative Commons - CC BY - Namensnennung 4.0 International
Datum der Freischaltung:05.02.2024
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:18.03.2024
Schriftenreihen ohne Nummerierung:Wissenschaftliche Artikel der BAM
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