Synthesis of β-Ca 2 P 2 O 7 as an Adsorbent for the Removal of Heavy Metals from Water

Diana Griesiute, Justina Gaidukevic, Aleksej Zarkov and Aivaras Kareiva
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Diana Griesiute: Institute of Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania
Justina Gaidukevic: Institute of Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania
Aleksej Zarkov: Institute of Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania
Aivaras Kareiva: Institute of Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania

Sustainability, 2021, vol. 13, issue 14, 1-9

Abstract: In the present work, beta-calcium pyrophosphate (β-Ca 2 P 2 O 7 ) was investigated as a potential adsorbent for the removal of heavy metal ions from water. Single-phase β-Ca 2 P 2 O 7 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 4 ∙2H 2 O) to β-Ca 2 P 2 O 7 . 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 2 g −1 . For the estimation of sorption properties, the aqueous model solutions containing different metal ions (Al 3+ , Cd 2+ , Co 2+ , Cu 2+ , Fe 2+ , Mn 2+ , Ni 2+ , Pb 2+ , Sn 2+ , Sr 2+ and Zn 2+ ) were used. The adsorption test revealed that β-Ca 2 P 2 O 7 demonstrates the highest adsorption capacity for Pb 2+ and Sn 2+ ions, while the lowest capacity was observed towards Sr 2+ , Ni 2+ and Co 2+ ions. The optimal pH value for the removal of Pb 2+ ions was determined to be 2, which is also related to the low solubility of β-Ca 2 P 2 O 7 at this pH. The adsorption capacity towards Pb 2+ ions was calculated as high as 120 mg g −1 .

Keywords: calcium pyrophosphate; Ca 2 P 2 O 7; wet precipitation; heavy metals; adsorbent (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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