Synthesis of β-Ca2P2O7 as an Adsorbent for the Removal of Heavy Metals from Water

• Published in: Sustainability Vol. 13; no. 14; p. 7859
• Main Authors: Griesiute, Diana, Gaidukevic, Justina, Zarkov, Aleksej, Kareiva, Aivaras
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 14.07.2021
• Subjects: Adsorbents; Adsorption; Aluminum; Annealing; Calcium; Calcium phosphates; Carbon dioxide; Cobalt; Crystal structure; Decomposition; Fourier analysis; Fourier transforms; Graphene; Heavy metals; Industrial plant emissions; Infrared analysis; Infrared spectroscopy; Iron; Lead; Low temperature; Manganese; Membrane separation; Metal ions; Metals; Morphology; Nitrates; Nuclear power plants; Physicochemical properties; Pollutants; Porous plates; Scanning electron microscopy; Sorbents; Thermal analysis; Water purification; X-ray diffraction; United States > US
• ISSN: 2071-1050; 2071-1050
• DOI: 10.3390/su13147859

In the present work, beta-calcium pyrophosphate (β-Ca2P2O7) was investigated as a potential adsorbent for the removal of heavy metal ions from water. Single-phase β-Ca2P2O7 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 (CaHPO4∙2H2O) to β-Ca2P2O7. 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 m2 g−1. For the estimation of sorption properties, the aqueous model solutions containing different metal ions (Al3+, Cd2+, Co2+, Cu2+, Fe2+, Mn2+, Ni2+, Pb2+, Sn2+, Sr2+ and Zn2+) were used. The adsorption test revealed that β-Ca2P2O7 demonstrates the highest adsorption capacity for Pb2+ and Sn2+ ions, while the lowest capacity was observed towards Sr2+, Ni2+ and Co2+ ions. The optimal pH value for the removal of Pb2+ ions was determined to be 2, which is also related to the low solubility of β-Ca2P2O7 at this pH. The adsorption capacity towards Pb2+ ions was calculated as high as 120 mg g−1.