Removal and recovery of phosphorus by a long–term stabilized amorphous calcium carbonate

Phosphorus is a non-renewable resource that guarantees food production, while excessive phosphorus discharge leads to water eutrophication. Phosphorus removal/recovery could help improve water quality and ensure food security. In this contribution, silica-stabilized amorphous calcium carbonates (Si-ACC) were prepared and used to remove/recover phosphate in sludge and domestic sewage. The mechanisms were investigated via kinetic and isothermal adsorption studies and XRD, TEM, Raman, and FTIR characterization. The results showed that the homogeneously distributed silica successfully inhibited ACC transformation and helped Si-ACC keep the amorphous feature within 680 d. During phosphorus adsorption, Si-ACC quickly transformed into calcite within 5 min and reacted with phosphorus to generate polycrystalline hydroxylapatite within 60 min. The recovered product possessed a maximum specific surface area (SSA) of 209 m2/g and available phosphorus content of 18.0 %, suggesting that Si-ACC was a promising phosphorus recovery material and the recovered product could be a potential phosphate fertilizer.