Porosity formation and enhanced solubility of calcium silicate hydrate in hydrothermal synthesis

The objective of this paper was to determine the optimal stirring speed for hydrothermal synthesis of calcium silicate hydrate (CSH) with porous structures. Using Field-emission Scanning Electron Microscopy (FESEM), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and Particle size distributions (PSD), coupled with the Improved of Detached Eddy Simulation (IDDES), porous structure formation mechanisms at different stirring speeds were examined. The CSH formation process was a step-by-step pattern during a complex phase condition; however, CSH with porous structure could be obtained effectively under reasonable stirring speed. The established Avrami Dissolution Dynamics Model indicated that the as-prepared CSH exhibited greatly enhanced Ca2+ and OH− release under proper stirring speed. This was likely due to small particle size, low crystallinity, and large specific surface area (SBET). This porous CSH has potential application in phosphorus removal from wastewater via production of HAP, thus reducing the negative environmental effects of continual natural phosphorus resource depletion.