Formation of Metastable CaCO₃Polymorphs in the Presence of Oxides and Silicates

Abstract

Carbonate crystallization experiments were carried out in the presence of solid-state oxides and silicates to test the effect of inorganic substrates on the formation of CaCO3 metastable polymorphs. Experimental results unambiguously demonstrate the selective formation of aragonite and vaterite in numerous cases. Further analysis indicates that these metastable phases may be correlated with negatively charged substrate surfaces. This correlation is observed in all cases except for SiO2. We suspect the exception is possibly due to the active dissolution of SiO2 at the experimental pH conditions. Additional results from experiments using pretreated aluminum silicate on which hydrated amorphous silica surface coating is generated by acid leaching support the dissolution hypothesis. These findings suggest that inorganic surface functional groups may have the ability similar to organic ones in selectively inducing metastable carbonate polymorph crystallization.