In order to evaluate the possible use of natural fluor-hydroxyapatite (FOHAp) crystals as soil additive for the in situ remediation of heavy-metal contaminated soils, the crystal structure of FOHAp crystals, used in batch experiments at 22°C with pH within the range 4.8-9.5 and in presence of Zn2+ ions, was determined. Crystal structures (space group P63/m) converged to R = 0.026 for untreated FOHAp and to R =0.028 (Experiment 1) and R= 0.032 (Experiment 2) for Zn2+-treated FOHAp crystals. The site occupancy ratios [(Zn-Ca)2/(Zn-Ca)1] obtained from the refinement of electron density is = 1.500 for natural FOHAp, 1.500 (Experiment 1) and 1.520 (Experiment 2) in Zn2+-treated crystals. The value deriving from experiment 2 agrees with small changes in Ca2 site occupancy. Ca2O6X polyhedron distortions may be related both to a slight preference of Zn for Ca2 and to OH for F substitution during the overall reaction sequence.
Reactions of Zn2+ aqueous solutions with fluor-hydroxyapatite: a crystallographic evidence / Brigatti, Maria Franca; Benincasa, Emanuele; Malferrari, Daniele; Medici, L.; Poppi, Luciano. - In: NEUES JAHRBUCH FUR MINERALOGIE MONATSHEFTE. - ISSN 0028-3649. - STAMPA. - 3:3(2002), pp. 129-137. [10.1127/0028-3649/2002/2002-0129]
Reactions of Zn2+ aqueous solutions with fluor-hydroxyapatite: a crystallographic evidence
BRIGATTI, Maria Franca;BENINCASA, Emanuele;MALFERRARI, Daniele;POPPI, Luciano
2002
Abstract
In order to evaluate the possible use of natural fluor-hydroxyapatite (FOHAp) crystals as soil additive for the in situ remediation of heavy-metal contaminated soils, the crystal structure of FOHAp crystals, used in batch experiments at 22°C with pH within the range 4.8-9.5 and in presence of Zn2+ ions, was determined. Crystal structures (space group P63/m) converged to R = 0.026 for untreated FOHAp and to R =0.028 (Experiment 1) and R= 0.032 (Experiment 2) for Zn2+-treated FOHAp crystals. The site occupancy ratios [(Zn-Ca)2/(Zn-Ca)1] obtained from the refinement of electron density is = 1.500 for natural FOHAp, 1.500 (Experiment 1) and 1.520 (Experiment 2) in Zn2+-treated crystals. The value deriving from experiment 2 agrees with small changes in Ca2 site occupancy. Ca2O6X polyhedron distortions may be related both to a slight preference of Zn for Ca2 and to OH for F substitution during the overall reaction sequence.
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