Hydrothermal and mechanochemical synthesis of crystalline CaCO₃

Abstract

Mechanochemical and microwave-assisted hydrothermal (MicroWave Treatment [MWT]) procedures were applied to prepare crystalline CaCO3. Mechanochemical process was carried out at different speeds of rotation (500 or 850 rpm/min), different duration times (30 or 60 min) and in the aqueous suspensions or in dry state. MWT synthesis was conducted in a saturated water vapour or under the layer of water. The crystalline and porous structures of the prepared samples as well as their morphology were investigated using N2 adsorption, X-ray diffraction and scanning electron microscopy methods. As a result, the calcium carbonate samples in the form of calcite were obtained. The materials prepared by the mechanochemical route performed in the aqueous suspension are characterized by smaller crystallite sizes as compared to those obtained without the addition of water. The samples obtained hydrothermally have the largest size of crystallites. Powders prepared by energetical milling possess higher values of specific surface area in relation to the parameter for those synthesized hydrothermally. In the process of hydrothermal treatment, macroporous structure of the prepared materials is created. With the increasing specific surface area of the sample, the size of the crystallites decreased.

Solventless Amide Synthesis Catalyzed by Biogenic CaCO3 Materials

“…The pore size and pore volume values would indicate that the incorporation of Ni and Cu carbonates occurs preferentially on the surface of the solid, in agreement with the poor incorporation of these metals as compared with Fe. The isotherm plots of biogenic carbonates in Figure S2 show a typical interparticle macroporosity profile at relative pressures between 0.46 and 0.90, similar to previously reported CaCO 3 . − …”

Biogenic calcium carbonate derived from waste shells for advanced material applications: A review

“…It is interesting to note that all of those structures naturally exist. They can also be synthesized or precipitated with different morphologies or sizes and convert to other polymorphs structures by several techniques such as microwave-assisted (Qi and Zhu, 2006;Qi et al, 2014;Skubiszewska-Zięba et al, 2017), carbonation (Hou and Feng, 2005;Beuvier et al, 2011;Udrea et al, 2012;Lai et al, 2015;Yuan et al, 2015), sonochemical (Zhou et al, 2004;He et al, 2005;Luo et al, 2021), hydrothermal (Zhao et al, 2011;Sulimai et al, 2017) and wet precipitation technique (Brečević et al, 1996). The neat calcium carbonate from eggshells exists in the calcite structure.…”