Enhanced Vaterite And Aragonite Crystallization At Controlled Ethylene Glycol Concentrations

Abstract

Calcium carbonate (CaCO3) has three distinct anhydrous polymorphs, namely vaterite, aragonite and calcite. Although there is a high demand for aragonite and vaterite polymorphs for biomedical use, their unstable nature makes it challenging to synthesize them compared to calcite, which is the most stable form of CaCO3. Despite the remarkable effort on stabilizing vaterite and aragonite polymorphs in aqueous solutions, phase-pure vaterite and aragonite polymorphs have not been synthesized yet, without referring to the use of additives, surfactants or elevated temperatures. Herein, the effect of ethylene glycol (EG) concentration and temperature on the formation of vaterite and aragonite particles were investigated at 25 °C and 70 °C. Results showed that 60% EG containing precursor solution-without any other additive-can prevent vaterite/aragonite-to-calcite transformation regardless of the synthesis temperature. Furthermore, the size of CaCO3 particles decreased as EG concentration increased and it reached its minimum average values at 80% EG. The results of this study revealed the potential use of the proposed synthesis route to stabilize vaterite and aragonite polymorphs, tailor their content, morphology and size without using any additives, surfactants and elevated temperatures.

Aragonite and Its Composites: Preparations, Properties and Applications

“…The metathesis reaction for the production of aragonite whiskers involves the spontaneous precipitation of Ca 2 + -CO 3 2À -H 2 O system derived from the soluble carbonates and calcium salts. In this method, CaCl 2 is commonly used as calcium salt, while Na 2 CO 3 , [36,[55][56][57] NaHCO 3 , [58] NH 4 HCO 3 , [59] and K 2 CO 3 [60] are employed as the carbonate source. The reaction mechanism of this synthesis method can be described as below:…”

“…(Ref. [58] Copyright 2019 The Authors and dergipark.org), (Ref. [49] Copyright 2013 Balaban Desalination Publications), (Ref.…”

“…Urchin-like aragonite particles were formed through the growth of needle-like or rod-like aragonite whiskers around the center nucleus, which was a common secondary structure observed in aragonite precipitation (Figure 3D1). [58] At a reaction temperature of 70 °C in the Ca(Ac) 2 -NaHCO 3 -H 2 O system, semi-urchinlike aragonite precipitates were obtained when the ethylene glycol (EG) content was 40 %. This can be attributed to an increased nucleation rate at the growth front due to EG incorporation.…”

“…(Copyright 2015,The Royal Society of Chemistry). (D1-D6): Urchin-like aragonite particles precipitated with different additives (D1, D2)[58,73] , reaction temperature (D3, D4)[49] and reactant concentration (D5, D6)[74] . (Ref [58].…”

“…(D1-D6): Urchin-like aragonite particles precipitated with different additives (D1, D2)[58,73] , reaction temperature (D3, D4)[49] and reactant concentration (D5, D6)[74] . (Ref [58]. Copyright 2019 The Authors and dergipark.org), (Ref [49].…”