Transformation process of amorphous magnesium carbonate in aqueous solution

Abstract

Amorphous magnesium carbonate (AMC) is an important phase in the early formation stage of magnesium carbonate. In this study, precipitation experiments were conducted to clarify the formation and transformation process of AMC in aqueous solution. Fine AMC particles precipitated, immediately after mixing of Na₂CO₃ and MgCl₂ solutions. Chemical composition of the AMC was determined to be approximately MgCO₃·2H₂O although two hydration states were expected to exist for AMCs. Subsequently, the AMC transformed in aqueous solutions into needle–like crystals of nesquehonite (MgCO₃·3H₂O), eventually to tiny polycrystalline particles of dypingite [Mg₅(CO₃)₄(OH)₂·5H₂O] via a solvent–mediated processes.