Preparation and phosphorus recovery performance of porous calcium-silicate-hydrate

Porous calcium-silicate-hydrate was synthesized and used to recover phosphorus from wastewater. The principal objective of this study was to explore the phosphorus recovery performance of porous calcium-silicate-hydrate prepared by different Ca/Si molar ratios. Phosphorus recovery mechanism was also investigated via Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectrum (EDS), Brunauer-Emmett-Teller (BET) and X-ray Diffraction (XRD). The law of Ca2+ release was the key of phosphorus recovery performance. Different Ca/Si molar ratios resulted in the changes of pore structures. The increase of specific surface area and the increase in concentration of Ca2+ release were well agreement together. The Ca/Si molar ratio of 1.6 for porous calcium-silicate-hydrate is more proper to recover phosphorus. The pore structure of porous calcium silicate hydrate provided a local condition to maintain a high concentration of Ca2+ release. Porous calcium-silicate-hydrate could release a proper concentration of Ca2+ and OH- to maintain the pH values at 8.5-9.5. This condition was beneficial to the formation of hydroxyapatite. Phosphorus content of porous calcium-silicate-hydrate reached 18.64% after phosphorus recovery. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.