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Systems Based on Lead Sulfide
Published in Vasyl Tomashyk, 2 Semiconductors, 2022
PbSO4 has a polymorphic transformation at 864°C [at 840°C (Margulis and Kopylov 1964; Tridot et al. 1969)] and melts congruently at 1170°C (Jaeger and Germs 1921). The quenching tests do not allow preserving the high temperature modification (Tridot et al. 1969). This compound exists in a nature as a mineral anglesite, which crystallizes in the orthorhombic structure with the lattice parameters a = 695.802 ± 0.001, b = 848.024 ± 0.003, c = 539.754 ± 0.001 pm (Antao 2012) [a = 845, b = 538, c = 693 pm (James and Wood 1925); a = 695.9 ± 0.2, b = 848.2 ± 0.2, c = 539.8 ± 0.2 pm (Miyake et al. 1978); a = 695.49 ± 0.09, b = 847.23 ± 0.11, c = 539.73 ± 0.8 pm (Jacobsen et al. 1998)].
Lead Toxicity and Flavonoids
Published in Tanmoy Chakraborty, Lalita Ledwani, Research Methodology in Chemical Sciences, 2017
Amrish Chandra, Deepali Saxena
The level of lead in the earth’s crust is about 20 mg/kg. In the environment, it may be derived from either natural or anthropogenic sources. Most of the lead present was buried in subsurface deposits composed of a relatively inert (insoluble) form. As a consequence, humans and other living species have no known use for lead. The amount of lead on the earth’s crust is larger than might be predicted. One reason is that it was concentrated during the earth-forming process and a second is that it is the “sink” for radioactive decay of uranium and thorium. A lead sulfide containing ore found at the surface of the earth’s crust undergoes weathering to the mineral PbSO4 or “anglesite”. Further weathering may result in “cerrusite”, PbCO3. Lead and iron sulfide ore at the interface with unweathered ore, high in clay, is known as “jarosite”. Most lead in ore bodies is in the form of galena or cerrusite, both of which are attractive minerals. Lead has four common isotopes: lead-204, lead-206, lead-207, and lead-208. The last three forms of lead result from the radioactive decay of thorium and two different isotopes of uranium. Lead is found with silver, and due to this reason, it is extensively mined. Lead is also found in conjunction with many other trace elements, especially with antimony.3
Concentrating challenges of the Zarigan complex Pb-Zn-Fe non-sulfide ore
Published in Canadian Metallurgical Quarterly, 2023
Abdolmotaleb Hajati, Faraz Soltani
Zarigan complex oxide-sulfide lead ore contains galena, cerusite, plumbojarosite, plumbogummite, and anglesite lead minerals. The diversity of lead minerals in the sample as well as the different liberation conditions of each mineral has made the concentration methods more challenging. For this reason, in the present paper, various gravity, magnetic, and flotation methods were used for the concentration of lead oxide-sulfide minerals, and finally, a preliminary processing flowsheet was developed. Although considerable studies have been conducted on galena and cerusite, the behaviour of plumbojarosite and plumbogummite minerals from a processing point of view is rarely considered and is one of the innovative aspects of this paper.
First Analytical Study on Second-Century Wall Paintings from Ulpia Traiana Sarmizegetusa: Insights on the Materials and Painting Technique
Published in International Journal of Architectural Heritage, 2020
Ioana Maria Cortea, Luminița Ghervase, Ovidiu Țentea, Anca Constantina Pârău, Roxana Rădvan
The hypothesis that a red lead pigment had been used, was confirmed via the XRD analysis, which showed the presence of minium along with several degradation by-products—such as massicot, plattnerite, galena, plumbous sulfite, and anglesite (Table 4). As shown in previous studies (Aze et al. 2008), red lead alterations during natural ageing can lead to a complex mixture of alteration products that vary depending on the environmental factors, initial pigment properties, or pictorial technique.
Estimating the proportion of bioaccessible lead (BaPb) in household dust wipe samples: a comparison of IVBA and PBET methods
Published in Journal of Environmental Science and Health, Part A, 2023
Chandima Wekumbura, Ganga M. Hettiarachchi, Christina Sobin
Lead in household dust most commonly results from deteriorating lead-based paint, lead-contaminated soil that is tracked indoors, and somewhat less commonly, lead dust carried into the home on work clothes and skin from the adults’ occupational exposures.[6–8] Inhaled Pb is uniquely toxic because it is not believed to be directly influenced by biochemical processes that alter its absorption. In the gut however, ingested lead encounters stomach acids that usually alter its absorption. Thus, the toxicity of ingested lead is associated with its bioaccessibility, defined as the fraction of total lead available for absorption into the blood stream via the gut.[9–11] Dissolved Pb in the form of free ion (Pb2+) is the form that can enter the body and mimic and antagonize the action of calcium (Ca2+) and zinc (Zn2+) ions.[12,13] Ingested lead undergoes a dissolution process in the gastrointestinal tract and the dissolution process varies according to the chemical form of the Pb.[14,15] Materials containing PbCO3 (lead carbonate) or Pb-manganese (Pb–Mn) oxides as the dominant Pb species showed high bioaccessibility (ranging from 60% to 100%) in many in vivo and in vitro studies.[16–24] In addition, many studies reported the low solubility of Pb–phosphate and anglesite, galena, and some Fe–Pb, Pb–O, and Pb sulfate species.[10,25–28] Lead in soil can exist as Pb containing minerals or Pb-bound to other soil minerals. However, the overall solubility and bioaccessibility of soil Pb depend on the relative amounts and reactivity of the different chemical forms (such as crystallinity) and physical forms of Pb and Pb-bound minerals (e.g., accessibility). Most synthetic Pb-associated products contain highly bioaccessible Pb compounds, i.e., leaded paint: PbCrO4 (lead(II) chromate), Pb3O4 (lead(II, IV) oxide), and PbCO3 (lead(II) carbonate), leaded gasoline: Pb(C2H5)4 (tetraethyl and/or tetramethyl lead), and lead arsenate pesticide (PbHAsO4).