Calcite-aragonite transformation in an eggshell: a crucial role of organics and assessment of the impact of milling conditions on its extent using Taguchi design
Kenges K. Karafiludis S. Džunda R. Tampubolon I.O. Satybaldiyev B. Emmerling F. Baláž M.
23 August 2024Royal Society of Chemistry
Physical Chemistry Chemical Physics
2024#26Issue 3724279 - 24287 pp.
Phase transformations during high-energy ball milling, a tool of mechanochemistry, are interesting due to the possible production of metastable phases without the need for artificially introducing high temperatures and pressures. In our work, the transformation of calcite to aragonite in an eggshell is studied in detail. The presence of organic material, in either the naturally present eggshell membrane, or artificially supplied l-cysteine, was found to be crucial for the phase transformation to occur, its decomposition leading to a pressure increase necessary for aragonite formation. The presence of sulfur in the organics seems to be crucial, as corroborated by much lower phase transformation extent when utilizing sulfur-free organics for comparison. The degree of the transformation in an eggshell was strongly dependent on the used milling conditions. The optimization was assessed using the Taguchi method, namely using a 44 orthogonal array. The optimized parameters encompassed milling time, sample mass, milling speed and duration of breaks and it was shown that sample mass has a decisive effect on the amount of obtained aragonite. Under the most efficient conditions, 73.7% of aragonite was obtained. Prolonging milling until 4 hours further boosts the transformation, reaching 89.9% of aragonite, but further milling leads to the collapse of the aragonite structure and pure calcite was observed after 5 hours.
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Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, Košice, 04001, Slovakia
Center of Physical-Chemical Methods of Research and Analysis, Al-Farabi Kazakh National University, Tole bi 96A, Almaty, 050012, Kazakhstan
Federal Research Institute for Materials Testing, Richard-Wiltstätter Strasse 11, Berlin, 12489, Germany
Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47, Košice, 04001, Slovakia
Institute of Geotechnics
Center of Physical-Chemical Methods of Research and Analysis
Federal Research Institute for Materials Testing
Institute of Materials Research
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