Zn2+ as a Dopant to Stabilize Hydrated Magnesium Carbonates

Abstract

The formation of solid solutions of Mg-carbonates incorporating Zn2+ was investigated. Initially the formation of brucite and nesquehonite was observed in all cases. The presence of Zn retarded the reaction of brucite at the early stages but increased its reaction in the long-term. Nesquehonite [MgCO3۰3H2O] and brucite converted to dypingite [Mg5(CO3)4(OH)2·5H2O] with time, both in the absence and presence of Zn, while dypingite remains stable throughout the duration of the study (1 year). Zn forms a solid solution with dypingite with a maximum Zn/(Mg+Zn) molar ratio of 0.01, which is more stable than pure dypingite. At higher Zn/(Mg+Zn) molar ratios, in addition X-ray amorphous Zn-containing phases with a possible Zn/Mg atomic ratio of 2 formed at early reaction time. The findings reported here confirm the possibility of solid solution formation in HMCs leading to the ability to improve the stability of certain HMCs for safe utilization as construction materials.

Keywords: carbonation, Hydrated magnesium carbonates, Phase stability, Thermodynamic calculations, Solid solution