Browsing by Subject "hydroxylpyromorphite"

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Arsenate substitution in lead hydroxyl apatites: Rietveld refinements and Raman spectroscopic study
(Data obrony: 2014-09-24) Giera, Alicja
Wydział Geologii, Geofizyki i Ochrony Środowiska
This paper focuses on hydroxyl analogues of pyromorphite-mimetite solid solutions, the phases belonging to the apatite supergroup. The aim of the study was their detailed structural analysis and examination of spectroscopic features in regard to the arsenate substitution in lead hydroxyl apatites. Seven synthetic powders were analyzed with the use of synchrotron-based X-ray diffraction, Raman spectroscopy and scanning electron microscopy (SEM-EDS). The structure Rietveld refinements revealed systematic changes of the unit-cell parameters with the isomorphic substitution of phosphates by arsenates. The lowering of hexagonal crystal symmetry to the symmetry of monoclinic crystal system was detected in phases from the OH-analogues of pyromorphite-mimetite series for the first time. The position and intensity of bands on Raman spectra as well as their assignment to the vibrational modes were determined. The linear correlation of the positions of selected bands with the arsenic content was established.
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Eksperymentalny model przemian cerusytu $PbCO_{3}$ w hydroksylpiromorfit $Pb_{5}(PO_{4})_{3}OH$
(Data obrony: 2012-07-16) Stożek, Katarzyna
Wydział Geologii, Geofizyki i Ochrony Środowiska
The objective of this study was characterization of the mechanism of transformation of cerrusite $PbCO_{3}$ into secondary phases in presence of phosphates $PO_{4}{^{3-}}$. The concentration of aqueous $Pb^{2+}$ and formation of secondary phases were monitored during dissolution of cerrusite $PbCO_{3}$ in the presence of $PO_{4}{^{3-}}$ at various pH. XRD and SEM/EDS analyses indicate that in acidic solutions the main product of cerrusite reaction with arsenate ions is phosphoshultenite $PbHPO_{4}$. Hydroksylpyromorphite $Pb_{5}(PO_{4})_{3}OH$ is the only reaction product at alkaline pH. Phospho-shultenite undergoes recrystalization into hydroxylpyromorphite after pH is raised to 9. Simulation of the reaction with PHREEQC model was unsuccessful probably due to poor thermodynamic data and lack of equilibrium in experimental system.