R4: Mineral sciences of the Earth surface

[R4-06] Aragonite formation from amorphous calcium carbonate (ACC) with addition of n-butylamine

*Hiroyuki KAGI¹, Kensuke Muraoka¹ (1. The University of Tokyo)

Keywords:amorphous calcium carbonate, aragonite, polymorph control

Direct conversion from amorphous calcium carbonate (ACC) to aragonite has been extremely difficult compared to the other two polymorphs, calcite and vaterite. In the present study, aragonite formation with a high polymorph fraction (>97%) was obtained from ACC immersed in n-butylamine under 90% RH (relative humidity) at 30°C for two hours. It is noteworthy that the aragonite with high purity was obtained without the addition of Mg²⁺ ion, which is well known to promote aragonite formation.To understand the effects of hydrophobic and basic properties of n-butylamine, hexane, NH₃ aq., and hexane + NH₃aq. were mixed with ACC and left for two weeks. Aragonite was formed only from the mixture of hexane and NH₃ aq. This result indicates that both hydrophobic and basic properties are required for crystallization from ACC into aragonite.