Data/hora: 09/06/2024 12:35:09

Biblioteca(s): | Embrapa Solos.
Data corrente: | 19/10/2021
Data da última atualização: | 19/10/2021
Autoria: | MAVROPOULOS, E.; ROSSI, A. M.; COSTA, A. M.; PEREZ, C. A. C.; MOREIRA, J. C.; SALDANHA, M. F. C.
Afiliação: | ELENA MAVROPOULOS, CBPF; ALEXANDRE MALTA ROSSI, CBPF; ANDRÉA M. COSTA, CBPF; CARLOS ANDRÉ C. PEREZ, NUCAT; JOSINO C. MOREIRA, FIOCRUZ; MARCELO FRANCISCO COSTA SALDANHA, CNPS.
Título: | Studies on the mechanisms of lead immobilization by hydroxyapatite.
Ano de publicação: | 2002
Fonte/Imprenta: | Environmental Science and Technology, v. 36, n. 7, p. 1625-1629, 2002.
DOI: | https://doi.org/10.1021/es0155938
Idioma: | Inglês
Notas: | Na publicação: Marcelo Saldanha.
Conteúdo: | The sorption of lead by synthetic hydroxyapatite (HA) from solutions containing Pb2+ initial concentrations up to 1770 mg L-1 was studied. X-ray diffractometry (XRD) associated with Rietveld methodology for refining the spectra pattern was used in order to characterize the mechanisms of lead uptake. It is shown that the dissolution of hydroxyapatite is followed by the formation of a solid solution, Pb(10-x)Cax(PO4)6(OH)2, with Pb ions mostly occupying Ca(II) sites. The Ca/Pb molar ratio of this solid solution decreases continuously until it reaches the structure of a pure hydroxypyromorphite. The cell parameters and the crystallite mean size behavior of both mineral phases reinforce the hypothesis that hydroxypyromorphite, PbHA, formation is the end of a process in which Pb(10-x)Cax(PO4)6(OH)2 crystallites are continuously dissolved and recrystallized producing crystals with lower calcium content. Combination of Inductively Coupled Plasma spectrometry (ICP), chemical analysis, and XRD results permitted the conclusion that lead ions are not completely immobilized by precipitating Pb(10-x)Cax(PO4)6(OH)2. Additional surface mechanisms also contribute to Pb2+ uptake. During Pb2+ sorption process, pH variations of the solution phase showed a more complex pattern than previously reported. Contribution of surface mechanisms, in addition to the hydroxyapatite dissolution, could explain this behavior.
Palavras-Chave: | Dissolution; Physical and chemical processes.
Thesaurus Nal: | Hydroxyapatite; Metals; Sorption.
Categoria do assunto: | P Recursos Naturais, Ciências Ambientais e da Terra
Registro original: | Embrapa Solos (CNPS)
Exemplares: | CNPS - (20864-1) - UPC - AP - DD -  -  -  - DIS