Synthesis and thermodynamic data of acetate-containing giorgiosite – a novel hydrated magnesium carbonate
Hoang Nguyen, Ellina Bernard, Frank Winnefeld, Barbara Lothenbach, Päivö Kinnunen
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: [Mg 5 (CO 3 ) 3.25 (OH) 2 (CH 3 COO) 1.5 ·5H 2 O]. In this work, the solubility product (log K s0 ) of this phase was reported for the first time, while we also re-calculated the log K s0 of artinite. This acetate-containing giorgiosite is rather stable at low temperature but artinite [Mg 2 (OH) 2 (CO 3 )(H 2 O) 3 ] and amorphous magnesium carbonates were observed at 20 °C while hydromagnesite [Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O], 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.