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Wyświetlanie 1-3 z 3
Tytuł:
Pyromorphite formation from montmorillonite adsorbed lead
Autorzy:
Bajda, Tomasz
Marchlewski, Tomasz
Manecki, Maciej
Powiązania:
https://bibliotekanauki.pl/articles/2086508.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Mineralogiczne
Tematy:
sorption
desorption
immobilization
crystallization
apatite
smectite
Opis:
The reaction of Pb-adsorbed montmorillonite with aqueous solutions of PO4 and Cl ions results in the decrease in phosphate concentration associated with the formation of a new phase – pyromorphite Pb5(PO4)3Cl. Pyromorphite crystals range in size from hundreds of nm to several tens of μm, depending on the PO4, K, and Ca concentrations in the reacting system. A strong ion-exchange effect of K+ and Ca2+ cations on desorption of Pb2+ from Pb-adsorbed montmorillonite was observed. Also, a high concentration of cations leads to a rapid desorption of Pb and the formation of fine pyromorphite crystals. In contrast, low PO4, K and Ca concentrations result in the formation of relatively large euhedral crystals. Final Pb concentrations are much lower in experimental sets than in control experiments with no phosphate present.
Źródło:
Mineralogia; 2011, 42, 2/3; 75--91
1899-8291
1899-8526
Pojawia się w:
Mineralogia
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis and solubility of brompyromorphite Pb5(PO4)3Br
Autorzy:
Janicka, Urszula
Bajda, Tomasz
Manecki, Maciej
Powiązania:
https://bibliotekanauki.pl/articles/127627.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Mineralogiczne
Tematy:
lead
phosphate
apatite
dissolution
brompyromorphite
solubility product
Opis:
The bromide analogue of pyromorphite Pb5(PO4)3Br was synthesized and characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. The solubility of the brompyromorphite was measured at 25°C and pH values of 2.0, 2.6 and 3.2. For the 3 pH measurements, the average solubility product, log KSP, for the reaction Pb5(PO4)3Br 5Pb2+ + 3PO4 3– + Br– at 25ºC is –77.38 ± 0.70. The free energy of formation, Gf,298, calculated from this measured solubility product is –3724.7 ± 4.3 kJ mol−1. These results confirm that brompyromorphite is more soluble than pyromorphite.
Źródło:
Mineralogia; 2012, 43, 1/2; 129-135
1899-8291
1899-8526
Pojawia się w:
Mineralogia
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Time constraints on experimental studies of lead apatites
Autorzy:
Topolska, Justyna
Bajda, Tomasz
Puzio, Bartosz
Manecki, Maciej
Kozub-Budzyń, Gabriela
Powiązania:
https://bibliotekanauki.pl/articles/2058621.pdf
Data publikacji:
2019
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
pyromorphite
vanadinite
experimental mineralogy
dissolution
solubility synthesis
Opis:
The paper presents the results of experimental studies on the synthesis and thermodynamic stability of selected Pb-apatites in terms of criteria determining termination of the experiments. Based on the case study, we indicate difficulties in analysing the obtained experimental data. Time-resolved sampling of precipitate formed during a dropwise synthesis of pyromorphite was performed and the results were compared to the literature data. It has been concluded that the Ostwald ripening time for synthesized solids depends primarily on the chemical composition of the intended Pb-apatite phase. We presented that heterogeneity of precipitate affects its dissolution in terms of repeatability of the results and equilibrating time. A unique 9-year-long experiment on vanadinite stability at a pH range from 2.0-6.0 revealed that among all tested dissolution conditions only the reactions at the pH = 3.5 can perform as the basis for some thermodynamic calculations. It has been concluded that the rate of phase transitions in the Pb-apatites group can be misleading in terms of determining the equilibrium of the system, and the experimental setup designed particularly to provide reliable controls in this aspect should be involved. Means in this respect have been proposed.
Źródło:
Geological Quarterly; 2019, 63, 4; 721--728
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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