Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Geology, Geophysics and Environment

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

A Raman spectroscopic study of hydroxyl analogues of pyromorphite-mimetite solid solutions

Giera A., Manecki M., Kwaśniak-Kominek M., Marchlewski T., Borkiewicz O., Rakovan J.

Geology, Geophysics and Environment

2014

Vol. 40, no. 1

86--87

Pyromorphite Pb10(PO4)6Cl2 and mimetite Pb10(AsO4)6Cl2, minerals belonging to apatite group, receive increased attention recently. Induced precipitation of pyromorphite and mimetite in soil pore solutions or waste solutions belongs to the best remediation and reclamation methods (Ma et al. 1995, Maniecki et al. 2009). These phases are the most stable forms of Pb2+ and As5+ in the environment. Deficiency of Cl in the environment can cause formation of their hydroxyl forms: Pb10(PO4)6(OH)2 and Pb10(AsO4)6(OH)2 or their solid solutions. Apatite structure allows for extensive and varied ionic substitutions in all positions. The isomorphic substitutions affect unitcell parameters and chemical properties of these minerals (Botto et al. 1997). Solid solutions of hydroxyl analogues of pyromorphite and mimetite have not been sufficiently characterized to this day. A detailed description of phases from this series is, however, necessary for optimization of the remediation methods. A Raman spectroscopic study of mimetite-pyromorphite series demonstrated a strong correlation between the positions of the vibrational modes and the As/(As+P) ratio (Bajda et al. 2011). Such a correlation may be used to determine the composition of the examined samples of minerals from the series. The current research is based on the assumption that in the case of solid solutions of their hydroxyl analogues similar correlations occur. Therefore, the aim of this study is structural (X-ray diffraction) and spectroscopic (Raman) investigation of the effect of PO4-AsO4 isomorphic substitution on the structure and vibrational spectra. Seven phases were synthesized in computer-controlled chemistate at pH = 11 and 80°C by dropwise mixing of solutions containing Pb2+, PO4 3- and AsO4 3- in stoichiometric proportions. The composition of the final products was Pb10[(PO4)6-x(AsO4)x(OH)2, where x = 0, 1, 2, 3, 4, 5, 6. High-resolution powder X-ray diffraction data was obtained using the diffractometer at beamline 11-BM at the Advanced Photon Source (Argonne National Laboratory, Chicago). A detailed Raman spectroscopy was performed with the use of confocal Raman microscope and OMNIC software (AGH Kraków). The morphology and elemental composition of the samples were characterized by means of Fei Quanta variable pressure SEM/EDS (AGH UST Kraków). Moreover, the chemical composition of synthetic phases was determined by wet chemical analysis. Unit cell parameters increase with substitution of AsO4 for PO4 . Parameter a increases from 449.879 Å to 10.189 Å, while parameter c - from 7.427 Å to 7.516 Å. This is consistent with other solid solution series of lead apatites (Flis et al. 2009). The area under selected Raman effects is also strongly correlated with P and As content. Additionally, systematic shift of the position of Raman effects is observed. The band attributed to the (AsO4)3- ν1 symmetric stretching mode shifts from 808 cm-1 in Pb10(AsO4)6(OH)2 to 814 cm-1 in Pb10[(PO4)5(AsO4)](OH)2. The range of the peak positions for the (PO4)3- ν1 symmetric stretching mode is even wider: from 918 cm-1 in Pb10[(PO4)(AsO4)5](OH)2 to 926 cm-1 in Pb10(PO4)6(OH)2. The observed correlations may be used for semi-quantitative estimation of As and P content using non-destructive Raman spectroscopy.

Geochemical mapping in the area of L’ubietova, Slovak Republic

Giera A.

Geology, Geophysics and Environment

2012

Vol. 38, no. 4

471--472

L’ubietova is a village in the Banska Bystrica Region in the Slovak Republic. There is an old mining spot in its vicinity, where copper was extracted from the Bronze Age to the 19 century. Currently, the region is interesting by mineral collectors due to a p that can be found there, called libethenite. According to the literature (Kodera 1990, Duda & Paulis 2002) there are two areas of copper mineralization near L’ubietova, which differ in the occurrence of copper compounds formed with arsenic and phosphorus. The first deposit (Podlipa) is mainly known for its secondary-mineral paragenesis of copper phosphates, especially libethenite and pseudomalachite. On the second, (the Svatodusna deposit) diverse paragenesis of secondary arsenic minerals developed. The most characteristic of these arsenians are olivenite, euchroite and pharmaco siderite. Many scientific works concern the L’ubietova region (Andras et al. 2009, Rusko et al. 2009), however none of them has yet paid attention to the differentiation and the lateral distribution of copper-phosphorus and copper-arsenic mineralization and to the description of primary and secondary causes of the differentiation and the distribution. The aim of this study was to determine these phenomena and to optimise future analytical procedures, which would allow the local copper mineralization to be examined thoroughly. The project was based on the assumption that surface geochemical mapping will help to establish the range of copper mineralization in two areas distinct from each other if regard to the copper compounds. In order to draw up appropriate methodology, it was necessary to conduct research that included terrain inspection, preliminary sampling and analysis of soil specimens and dump-field material in regard to the content of copper, phosphorus and arsenic. The field study was based on extracting three soil specimens and two dump-field material samples along the profile line. Their chemical composition was later analysed by X-ray Fluorescence (XRF) and their mineral composition was determined by X-ray Diffraction (XRD). The preliminary examination confirmed the existence of lateral differentiation of copper mineralization, which was proved by establishing the differentiation of samples' content of copper, phosphorus and arsenic along the profile line.