Tailoring the structural and morphological properties of hydroxyapatite materials to enhance the capture efficiency towards copper(II) and lead (II) ions
Articolo
Data di Pubblicazione:
2018
Citazione:
Tailoring the structural and morphological properties of hydroxyapatite materials to enhance the capture efficiency towards copper(II) and lead (II) ions / S. Campisi, C. Castellano, A. Gervasini. - In: NEW JOURNAL OF CHEMISTRY. - ISSN 1144-0546. - 42:6(2018 Mar), pp. 4520-4530. [10.1039/c8nj00468d]
Abstract:
This study deals with the use of calcium hydroxyapatite (HAP) materials as adsorbents for removing heavy metal ions from polluted waters. The synthesis conditions (i.e. P/Ca stoichiometry and nature of the solvent) of HAP samples were properly varied in order to prepare three different samples with tuned properties. Stoichiometric hydroxyapatite, with Ca/P = 1.67 (s-HAP), Ca-deficient hydroxyapatite, with Ca/P < 1.67 (d-HAP), and hydroxyapatite precipitated from hydro-alcoholic solution (a-HAP) were prepared and used as adsorbents for copper and lead ions. Tests were carried out with simulated polluted waters containing single- and binary-metal concentrations of the two ions, with investigation on the selectivity of the metal capture process. The prepared materials were characterized using a suite of methods including FT-IR spectroscopy, X-ray powder diffraction (XRPD), thermogravimetric (TG) analysis, and N2-adsorption/desorption analyses. The results showed that for Pb2+, the removal efficiency maximum (>99%) was independent of the intrinsic properties of the adsorbents, the initial concentration of Pb2+, and the co-presence of Cu2+. Conversely, the removal of Cu2+ was affected by the structural properties of the HAP adsorbents, d-HAP being the most efficient adsorbent for Cu2+ (93%). Immobilization of Pb2+ and Cu2+ onto HAP occurred by two different mechanisms: a dissolution–precipitation mechanism with formation of a Pb10(PO4)6(OH)2 phase was responsible for the Pb2+ uptake, whereas Cu2+ was immobilised by surface complexations involving Ca2+ species with carbonate and hydroxyl groups of HAP. In addition, leaching tests revealed that the confinement of the two metal species on HAP samples was permanent.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
hydroxyapatite; adsorbents; heavy metal removal; Cu2+ions; Pb2+ions; water pollution.
Elenco autori:
S. Campisi, C. Castellano, A. Gervasini
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