The phosphate removal mechanisms of Calcite were investigated with the tests of Xray diffraction (XRD) analysis

transmission electron microscope (TEM) measurement

fourier transform infrared spectroscopy (FTIR) analysis

specific surface area by BrunauerEmmettTeller(BET) method and pole size distribution by BarrettJoynerHalenda(BJH) method. The main influencing factors on phosphate removal were investigated and the removal mechanism was approved. It was shown that phosphate removal efficiency was significantly influenced by reaction time

temperature

pH value and dosage of calcite. And with BET

BJH and TEM tests

no porous materials

less than 16.0 m2/g for the specific surface area and below 0.085 cm3/g for total pore volume

were found during the reaction process so as to prove that absorption was not the main way of phosphate removal. And based on XRD and FTIR tests

it was found that chemical precipitation was the main way of phosphate removal which contained two steps: the formation of CaHPO4·2H2O(DCPD) and its transformation to ACP

and the controlling step was DCPD’s transformation to ACP.