摘要：In the present work, beta-calcium pyrophosphate (β-Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub>) was investigated as a potential adsorbent for the removal of heavy metal ions from water. Single-phase β-Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub> powders were synthesized by a simple, scalable and cost-effective wet precipitation method followed by annealing at 800 °C, which was employed for the conversion of as-precipitated brushite (CaHPO<sub>4</sub>∙2H<sub>2</sub>O) to β-Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub>. Physicochemical properties of the sorbent were characterized by means of X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA/DSC), scanning electron microscopy (SEM) and low temperature adsorption–desorption of nitrogen (BET method). The synthesized powders consisted of porous plate-like particles with micrometer dimensions. Specific surface area calculated by the BET method was found to be 7 m<sup>2</sup> g<sup>−1</sup>. For the estimation of sorption properties, the aqueous model solutions containing different metal ions (Al<sup>3+</sup>, Cd<sup>2+</sup>, Co<sup>2+</sup>, Cu<sup>2+</sup>, Fe<sup>2+</sup>, Mn<sup>2+</sup>, Ni<sup>2+</sup>, Pb<sup>2+</sup>, Sn<sup>2+</sup>, Sr<sup>2+</sup> and Zn<sup>2+</sup>) were used. The adsorption test revealed that β-Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub> demonstrates the highest adsorption capacity for Pb<sup>2+</sup> and Sn<sup>2+</sup> ions, while the lowest capacity was observed towards Sr<sup>2+</sup>, Ni<sup>2+</sup> and Co<sup>2+</sup> ions. The optimal pH value for the removal of Pb<sup>2+</sup> ions was determined to be 2, which is also related to the low solubility of β-Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub> at this pH. The adsorption capacity towards Pb<sup>2+</sup> ions was calculated as high as 120 mg g<sup>−1</sup>.
