A study on the influence of sodium carbonate concentration on the synthesis of high Mg calcites

Abstract

High Mg calcites in pure phase with controlled magnesium contents were synthesized by using amorphous precursor through a hydrothermal process in the absence of organic additives. It is found that the Mg contents in the high Mg calcites increase with the increase of the molar ratios of carbonate and calcium ions in the mother solutions.

Water: How Does It Influence the CaCO3 Formation?

“…[7,[139][140][141][142][143] Theformation of Mg-ACC is thermodynamically favored over that of pure ACC [144] because the charge density of Mg 2+ is higher than that of Ca 2+ , [145,146] such that the Mg-ACCp hase has stronger interactions with water. [7,[139][140][141][142][143] Theformation of Mg-ACC is thermodynamically favored over that of pure ACC [144] because the charge density of Mg 2+ is higher than that of Ca 2+ , [145,146] such that the Mg-ACCp hase has stronger interactions with water.…”

“…[66,143,144,151] Additives such as Mg 2+ influence the crystallization kinetics of ACCi nt he presence of bulk water. [139,142,143,158,159] Thei ncorporation of Mg 2+ ions into ACCa lso delays its solid-state transformation:T he strong interactions between Mg 2+ and water molecules reduce the mobility of water, [148,154,160] thereby increasing the fraction of rigid water contained in Mg-ACC compared to that contained in ACC. [139,141] By contrast, when the Mg 2+ /Ca 2+ ratio is low,M g-ACC preferentially transforms into Mgcalcite.…”

High‐Magnesium Calcite Mesocrystals: Formation in Aqueous Solution under Ambient Conditions

“…[21] Attempts have also been made to prepare high-Mg calcites in aqueous solutions without organic additives.T he methods were to control the phase transformation of Mg-ACC by limiting the contact between water and Mg-ACCi naconfined space, [22] or by the experimental parameters such as temperature,pH, and the activities of the cations and the carbonate ions. [23][24][25][26][27] While these studies in aqueous solutions have deepened our understanding of the thermodynamic controls on the phase transformation of calcium carbonate,t he biological relevance of these studies awaits further substantiation because biominerals usually have very unique hierarchical levels of structure formation. [28] In particular,t he notion of mesocrystal has been coined to describe the fascinating formation of a" single crystal" through the aggregation of nanocrystals.…”

High‐Magnesium Calcite Mesocrystals: Formation in Aqueous Solution under Ambient Conditions

“…[3] Them ain stream in the synthesis of high-Mg calcites is to exploit additives which are either biomolecules extracted from mineral forming organisms [2,[4][5][6] or synthetic compounds rich in carboxylate groups. [23][24][25][26][27] While these studies in aqueous solutions have deepened our understanding of the thermodynamic controls on the phase transformation of calcium carbonate,t he biological relevance of these studies awaits further substantiation because biominerals usually have very unique hierarchical levels of structure formation. [15] Knowing that ACCc ould be stabilized by al arge variety of additives [16,17] and that ion binding can modulate significantly the nucleation events, [18] the functions of the aforementioned additives upon the Mg-calcite formation are at least two folded.…”

“…First, the additives may bind on the mineral surface to stabilize high-Mg calcites kinetically. [23][24][25][26][27] While these studies in aqueous solutions have deepened our understanding of the thermodynamic controls on the phase transformation of calcium carbonate,t he biological relevance of these studies awaits further substantiation because biominerals usually have very unique hierarchical levels of structure formation. [21] Attempts have also been made to prepare high-Mg calcites in aqueous solutions without organic additives.T he methods were to control the phase transformation of Mg-ACC by limiting the contact between water and Mg-ACCi naconfined space, [22] or by the experimental parameters such as temperature,pH, and the activities of the cations and the carbonate ions.…”