Insights into the mild-hydrothermal hydration mechanisms and material properties of Dololimes and Mg-lime

Understanding and controlling the hydration of the CaO-MgO system is essential for tailoring its reactivity, surface properties, and performance across industrial applications, particularly where fully converted and high-surface-area hydroxides are required. This work investigates the hydration behavior and microstructural evolution of four oxide materials (three dololimes and one Mg-based lime) obtained by calcining selected dolostones (1050-1250 °C) and a magnesite (750 °C). Hydration was carried out under mild hydrothermal conditions (80-140 °C, 0-0.3 MPa) using two protocols: water only (T1) and water with 2 wt% triethanolamine (TEA; T2). Phase composition and crystallite size were quantified by XRPD with Rietveld refinement, while textural and morphological features were assessed through helium pycnometry, N₂ adsorption, scanning electron microscopy, and laser diffraction. Lower calcination temperature promoted periclase reactivity, enabling nearly complete conversion to brucite (<1 wt% MgO). TEA addition refined portlandite and brucite crystallites (13-16 nm), enhanced structural homogeneity, and increased surface area (51-59 m^2/g) and pore volume (0.20–0.27 cm^3/g). The results highlight the role of TEA in controlling nucleation and growth during hydration, providing insights into phase evolution mechanisms relevant to reactive Ca-Mg oxide systems. Moreover, these findings are particularly relevant for industrial applications such as flue gas desulfurization (FGD) and the design of high-reactivity lime-based materials.