Mechanisms and Applications of the Synthesized Fusiform Aragonite for the Removal of High Concentration of Phosphate

In the present work, the synthesized calcium carbonate (CaCO 3 ) identified as fusiform aragonite was obtained through the biomimetic mineralization process for possible recovery of high concentration of phosphorus (P) within the wide range of pH. It was characterized before/after phosphate sorption by the combination of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray absorption near-edge structure (XANES) at molecular level. By batch experiments, the sorption isotherms and envelopes of the fusiform aragonite to phosphate were explored. The experimental data showed that the fusiform aragonite at pH ≥6.0 has a steep raising sorption capacity with increasing initial P (>9.0 mM) due to its unique crystalline structure and morphology. The likely mechanism is that the occurrence of fast nucleation growth of Ca-P phases (including amorphous calcium phosphate (ACP), dibasic calcium phosphate (DCP), and hydroxyapatite (HAP)) is triggered upon attainment of the stabilized crystal morphology of aragonite in solution due to phosphate sorption. These features may contribute to the fusiform aragonite as an idea adsorbent for high phosphate removal from wastewater even independent of pH.