Magnesium-Mediated Nanocrystalline Mosaics of Calcite

Abstract

Magnesium ions are widely found in calcium-based biominerals as an accessory component. In this report, the influence of magnesium ions on the crystal growth of CaCO 3 was investigated on the basis of the nanostructure. The morphology of calcite grown in a supersaturated solution was drastically changed from a regular rhombohedron into a spherical architecture consisting of nanocrystalline mosaics in the presence of a large number of magnesium ions. While magnesium ions were substituted for ca. 6% of calcium ions in the crystal lattice at a maximum, an excess amount of magnesium produced an amorphous phase leading to the nanostructure with modulation of the crystal growth of calcite.

Orientation and morphology of calcite nucleated under floating monolayers: A magnesium-ion-enhanced nucleation study

“…At the opposite end from the (0 0 1) face, the crystals terminate either in small {10.4} planes or in larger crystals, in small irregular pitted or incomplete faces. The expression of these faces has been shown before in bulk growth and also in growth at SnO 2 surfaces [6,13].…”

“…At Mg/Ca¼10 the crystals are now nearly hemispherical, no longer displaying any regular surface features seen in the previous crystals except for the nucleating face. [10,13,15]. However, growth under alcohol Langmuir monolayers has shown fairly poor orientation and there is no in situ X-ray data showing oriented growth [15,19].…”

“…A large number of studies made use of solid supports such as gold/silver coated alkanethiols [10,11], silica supported polymerized 1-,12-pentacosadiyonic acid [12], or even inorganic (SnO 2 coated glass) surfaces [13]. Solid-substrate-supported templates have been very successful in nucleating CaCO 3 in many different orientations, depending upon variables such as the chain length, functional group, and underlying substrate.…”

Artificial weathering pools of calcium-rich industrial waste for CO2 sequestration

“…6, bottom, wheat-sheaf-like bundles of calcium carbonate can be seen. It has been reported that the precipitation of the calcium carbonate in these morphologies is caused by the presence of impurities of Mg [29,30]. The existing impurities of Mg among others in our system (Table 1) cause the precipitation of the calcite into these morphologies of bundles.…”

Calcium promotes cadmium elimination as vaterite grains by tobacco trichomes

“…The transformation of vaterite into calcite may be poisoned also by substitutional impurities, such as Mn 2+ (Nassrallah-Aboukais et al, 1998a), Cu 2+ (NassrallahAboukais et al, 1998b) and Mg 2+ (Kitamura, 2001;Nishino et al, 2009), but is hastened by Cd 2+ and Pb 2+ (Brecevic et al, 1996;Brecevic, 1999, 2000). This explanation apparently does not apply to biogenic carbonates, because the calcite crystals produced by tobacco generally hold more trace metals than vaterite (Table 1), and vaterite has more cadmium.…”