Precipitation of Ordered Dolomite via Simultaneous Dissolution of Calcite and Magnesite: New Experimental Insights into an Old Precipitation Enigma
In the present study, we demonstrate that ordered dolomite can be precipitated via simultaneous dissolution of calcite and magnesite under hydrothermal conditions (from 100 to 200 degC) The temperature and high carbonate alkalinity have significantly copromoted the dolomite formation. For example, when high purity water was initially used as interacting fluid, only a small proportion of disordered dolomite was identified at 200 degC from XRD patterns and FESEM observations. Conversely, a higher proportion of ordered dolomite, i.e. clear identification of superstructure ordering reflections in XRD patterns, was determined when high carbonate alkalinity solution was initially used in our system at the same durations of reaction. For this latter case, the dolomite formation is favorable therefrom 100 degC and two kinetic steps were identified: (1) protodolomite formation after about 5 days of reaction, characterized by rounded submicrometric particles from FESEM observations and by the absence of superstructure