Minerals galena, PbS

Why does the solubility of a salt of a basic anion increase with decreasing pH Write chemical reactions for the minerals galena (PbS) and cerussite (PbC03) to explain how acid rain mobilizes traces of metal from relatively inert forms into the environment, where the metals can be taken up by plants and animals. 

The most important Pb ore is the heavy black mineral galena (PbS), while other ore minerals are anglesite (PbS04), cerussite (PbC03) and pyromorphite (Pb5(P04)3Cl). 

Lead, like tin, is a metal with which the ancient world was familiar. The rather simple pyrometallurgy permitted easy recovery of lead from the mineral galena, PbS. 

Lead is obtained from the sulfide mineral galena, PbS. First the mineral is roasted to the oxide, which is then reduced with carbon in a blast furnace. Write chemical equations for this process. 

Lead is obtained chiefly from galena (PbS) by a roasting process. Anglesite, cerussite, and minim are other common lead minerals. 

Activators enhance the adsorption of collectors, eg, Ca " in the fatty acid flotation of siUcates at high pH or Cu " in the flotation of sphalerite, ZnS, by sulfohydryl collectors. Depressants, on the other hand, have the opposite effect they hinder the flotation of certain minerals, thus improving selectivity. For example, high pH as well as high sulfide ion concentrations can hinder the flotation of sulfide minerals such as galena (PbS) in the presence of xanthates (ROCSS ). Hence, for a given fixed collector concentration there is a fixed critical pH that defines the transition between flotation and no flotation. This is the basis of the Barsky relationship which can be expressed as [X ]j[OH ] = constant, where [A ] is the xanthate ion concentration in the pulp and [Oi/ ] is the hydroxyl ion concentration indicated by the pH. Similar relationships can be written for sulfide ion, cyanide, or thiocyanate, which act as typical depressants in sulfide flotation systems. 

Lead The production of lead from lead sulphide minerals, principally galena, PbS, is considerably more complicated than the production of zinc because tire roasting of the sulphide to prepare the oxide for reduction produces PbO which is a relatively volatile oxide, and therefore the temperature of roasting is limited. The products of roasting also contain unoxidized galena as well as die oxide, some lead basic sulphate, and impurities such as zinc, iron, arsenic and antimony. 

Indium (0.24 ppm) is similar in abundance to Sb and Cd, whereas T1 (0.7 ppm) is close to Tm and somewhat less abundant than Mo, W and Tb (1.2 ppm). Both elements are chalcophiles (p. 648), indium tending to associate with the similarly sized Zn in its sulfide minerals whilst the larger T1 tends to replace Pb in galena, PbS. Thallium(I) has a similar radius to Rb and so also concentrates with this element in the late magmatic potassium minerals such as feldspars and micas. 

Sulfide minerals and K. Sulfides are among the least soluble ionic compounds. Their AQ, values are often smaller than 10-25. For this reason, many sulfides are found as minerals, for example (clockwise from the left), iron pyrite (FeS2), yellow orpiment (AS2S3). and black galena (PbS). 

Fig. 1.2 Crystal structures of the major sulfides (metal atoms are shown as smaller or black spheres) (A) galena (PbS) structure (rock salt) (B) sphalerite (ZnS) structure (zinc blende) (C) wurtzite (ZnS) strucmre (D) pyrite structure and the linkage of metal-sulfur octahedra along the c-axis direction in (/) pyrite (FeSa) and (//) marcasite (FeSa) (E) niccolite (NiAs) structure (F) coveUite (CuS) structure (layered). (Adapted from Vaughan DJ (2005) Sulphides. In Selley RC, Robin L, Cocks M, Plimer IR (eds.) Encyclopedia of Geology, MINERALS, Elsevier p 574 (doi 10.1016/B0-12-369396-9/00276-8))...

Lead(II) sulfide occurs widely as the black opaque mineral galena, which is the principal ore of lead. The bulk material has a band gap of 0.41 eV, and it is used as a Pb " ion-selective sensor and IR detector. PbS may become suitable for optoelectronic applications upon tailoring its band gap by alloying with II-VI compounds like ZnS or CdS. Importantly, PbS allows strong size-quantization effects due to a high dielectric constant and small effective mass of electrons and holes. It is considered that its band gap energy should be easily modulated from the bulk value to a few electron volts, solely by changing the material s dimensionality. 

In sediments of the Mezica mining and smelting area, mineral phases such as cerussite (PbC03), galena (PbS) (Fig. 2), pyromorphite (Pb5(P04)3CI), descloizite (PbZn(V04)(0H)), bindheimite... 

Silver items, however, are also relatively rare in the archaeological record. The most common metal found is either copper, usually alloyed with either tin (bronze) or, in the later periods, zinc (brass), or iron. The latter contains very little lead and, because of severe corrosion problems, its survival rate is often low (but see Degryse et al., 2007). Fortunately, copper can also be characterized from its lead isotope signature, since the primary ore of copper is chalcopyrite (CuFeS2), which often co-occurs with galena (PbS) and sphalerite (ZnS). Even if the ore used is a secondary mineral formed by the oxidation of the primary deposit, the copper smelted from such a deposit would normally be expected to... 

Occurrence. The principal mineral is sphalerite (ZnS), the most important impurity of which is FeS sphalerite commonly occurs with galena (PbS). Other minerals are wurtzite (the hexagonal modification of ZnS) and smithsonite or calamina (ZnC03). 

Occurrence. It is by far the most abundant of the heavy elements. The most important ore is galena PbS. Other minerals are anglesite PbS04, cerrusite PbCO. ... 

Sulfur is an element found in many common minerals, such as galena (PbS), pyrite (fool s gold, FeSj), sphalerite (ZnS), cinnabar (HgS), and celestite (SrSO ), among others. About 1/4 of all sulfur procured today is recovered from petroleum production. The majority of sulfur is the result of or a by-product of mining other minerals from the ores containing sulfur. 

Lead is produced commercially from its principal ore, galena (PbS). The ore is associated with sulfides of several metals including iron, copper, zinc, silver, bismuth, arsenic, antimony and tin. The ore is crushed and ground. It then is selectively separated from gangue and other valuable minerals by one or more processes that include gravity separation and flotation. Selective... 

These minerals have never been mentioned as potential targets for luminescent sorting because of the absence of natural emission even under laser excitation. LIBS may be an excellent opportunity, because all those elements have strong and characteristic lines. Figure 8.17 present examples of malachite (Cu), galena (Pb), and sphalerite (Zn) breakdown spectra. 

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