RT Journal Article
T1 The role of sulfate groups in controlling CaCO3 polymorphism
A1 Fernández Díaz, María Lourdes
A1 Fernández González, Ángeles
A1 Prieto Rubio, Manuel
AB The nucleation and growth of CaCO3 phases from aqueous solutions with SO4 2-:CO3 2- ratios from 0 to 1.62 and a pH ∼ 10.9 were studied experimentally in batch reactors at 25 ºC. The mineralogy, morphology and composition of the precipitates were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and microanalyses. The solids recovered after short reaction times (5 min to 1 h) consisted of a mixture of calcite and vaterite, with a S content that linearly correlates with the SO4 2-:CO32- ratio in the aqueous solution. The solvent-mediated transformation of vaterite to calcite subsequently occurred. After 24 h of equilibration, calcite was the only phase present in the precipitate for aqueous solutions with SO4 2-:CO3 2- ≤ 1. For SO4 2-:CO3 2- > 1, vaterite persisted as a major phase for a longer time (>250 h for SO4 2-:CO3 2- = 1.62). To study the role of sulfate in stabilizing vaterite, we performed a molecular simulation of the substitution of sulfate for carbonate groups into the crystal structure of vaterite, aragonite and calcite. The results obtained show that the incorporation of small amounts (<3 mole%) of sulfate is energetically favorable in the vaterite structure, unfavorable in calcite and very unfavorable in aragonite. The computer modeling provided thermodynamic information, which, combined with kinetic arguments, allowed us to put forward a plausible explanation for the observed crystallization behavior.
PB Elsevier Science Ltd
SN 0016-7037
YR 2010
FD 2010
LK https://hdl.handle.net/20.500.14352/43359
UL https://hdl.handle.net/20.500.14352/43359
LA eng
NO Spanish Ministry of Science and Innovation,
NO Comunidad de Madrid
DS Docta Complutense
RD 17 abr 2025