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Metal–Crucible Interactions
Published in Nagaiyar Krishnamurthy, Metal–Crucible Interactions, 2023
The crucible has an interesting function in the ancient process known as cupellation. Native silver exists but is not commonly seen. It is usually found in nature combined with other metals, e.g. in the lead minerals galena (lead sulphide) or cerussite (lead carbonate). Silver is produced primarily by smelting and then cupellation of argentiferous lead ores. Smelting yields silver and lead combined. Lead melts at 327°C, lead oxide at 888°C and silver at 960°C. To separate the silver, the alloy is melted in an oxidizing environment at 960°C to 1000°C. The lead oxidizes to lead monoxide, known as litharge. The liquid lead oxide is removed or absorbed by capillary action into the hearth linings. The base of the hearth was made in the form of a saucepan and covered with an inert and porous material rich in calcium or magnesium, such as shells, lime or bone ash (Bayley and Eckstein 2006). A calcareous lining is essential because lead reacts with silica (clay) to form lead silicate. Lead silicate is viscous and impedes the absorption of litharge. Lead does not react with the calcareous materials. It is captured by the materials purely by the physical phenomena of absorption. Some of the litharge may evaporate, but the rest is absorbed by the porous earth lining to form ‘litharge cakes'. The litharge could be reduced back to lead separately.
Influence of drinking water quality on the formation of corrosion scales in lead-bearing drinking water distribution systems
Published in Journal of Environmental Science and Health, Part A, 2021
Previous work[4] reported the results obtained using XRD on the P3 sample. In brief: the outermost layer, L1, displayed a very noisy XRD pattern in which hydrocerussite was the only identifiable crystalline phase. The presence of PbO2 was proposed in light of Raman results, but could not be confirmed by XRD. Similarly, the XRD patterns obtained for the outermost layer of the samples for Municipalities B and C (B5-L1, result not shown, and C1-L1 in Figure 1a) were poorly resolved, though characteristic peaks for hydrocerussite can be discerned. This indicates the presence of amorphous phases together with crystalline hydrocerussite on these samples. Hydrocerussite was identified as the main lead carbonate phase in both the inner layer of the samples collected from Municipalities B and C (B5-L2 and C1-L2) and their corresponding innermost layer (B5-L3 and C1-L3). A minor contribution from PbO can be also observed. In comparison with the XRD results obtained for surface layer samples P3-L1, B5-L1, and C1-L1, the result obtained for sample D1-L1 (Figure 1b), collected from Municipality D, revealed a distinct XRD pattern that suggests hydrocerussite is the main lead carbonate phase, with minor contributions from cerussite and PbO2. Furthermore, this result indicates that the outermost layer sample obtained from Municipality D (D1-L1) contained the least amorphous phases amongst all tested outermost layer samples. For the case of the D1-L2 sample, the XRD indicates hydrocerussite as dominant lead carbonate phase, with some cerussite contribution.
Potential of Equisetum ramosissimum Desf. for remediation of antimony flotation tailings: a case study
Published in International Journal of Phytoremediation, 2019
Dragana Ranđelović, Nevena Mihailović, Slobodan Jovanović
The conducted petrological analysis of FT showed the presence of quartz, limestone (calcite and dolomite), and fragments of vulcanite rocks (Figure 2a and b). X-ray diffraction analysis on selected flotation tailing samples showed that the dominant crystal phase was quartz, followed by dolomite, and calcite. The smallest participation in the sample belonged to the clay minerals (kaolinite) and plagioclase (Figure S1). Our SEM analysis (Figures 2c and d, Tables S1 and S2) revealed the presence of small fragments of ore minerals (barite, cerussite), as well as coatings on coarser lithic grains (quartz). Carbonates possess high buffering capacity that can neutralize acid inputs produced by diverse oxidative processes (e.g., oxidation of sulfide minerals) or by precipitation of hydroxides and the dissolution of minerals (Sherlock et al. 1995).
Mineral characterisation of the non-sulphide Zn mineralisation of the Florida Canyon deposit, Bongará District, Northern Peru
Published in Applied Earth Science, 2019
Saulo Batista de Oliveira, Caetano Juliani, Lena Virgínia Soares Monteiro
The mineral characterisation of the Florida Canyon zinc and lead deposit showed that the ore minerals comprise both sulphides–sphalerite, galena and pyrite-, and non-sulphide–smithsonite (mainly), hemimorphite, cerussite, and goethite-, which are hosted by carbonate rocks composed of dolomite, calcite, and quartz.The genesis of Florida Canyon non-sulphide mineralisation is associated with fault structures reaching up to hundreds of meters in depths. This supergene assemblage is a paleo-climatic guide, suggesting tropical climatic conditions for its generation. By analogy to the Cristal non-sulphide Zn deposit, also located in the Bongará District, a late Miocene age is assumed for the Florida Canyon supergene Zn mineralisation.The ore minerals (sulphide and non-sulphide) occur in different proportions in the four sectors of the Florida Canyon deposit. Therefore, a concentration plant with different routes for the different ore types should be considered in the economic evaluation of the deposit.