Synthesis and thermodynamic data of acetate-containing giorgiosite – a novel hydrated magnesium carbonate

Abstract

Abstract

Organic additives play important roles in enhancing the formation of Mg‑carbonates and reaction kinetics in MgO-based cements. However, little is known about the influences of organics on the formation pathways of carbonate phases and whether organo-modified Mg‑carbonates exist. We found that acetate can be involved in the formation of a new hydrated magnesium carbonate phase containing acetate: [Mg5(CO3)3.25(OH)2(CH3COO)1.5·5H2O]. In this work, the solubility product (log Ks0) of this phase was reported for the first time, while we also re-calculated the log Ks0 of artinite. This acetate-containing giorgiosite is rather stable at low temperature but artinite [Mg2(OH)2(CO3)(H2O)3] and amorphous magnesium carbonates were observed at 20 °C while hydromagnesite [Mg5(CO3)4(OH)2·4H2O], hydrated carbonate brucite (HCB) and amorphous magnesium carbonates were present at 50 and 80 °C. The work enables the potential of using organic additives in steering the reaction and formation of carbonates for better efficacy of carbon utilization and reactions in MgO-based cements.