Sphalerite ZnS

C, b.p. 907"C, d 713. Transition element occurring as zinc blende, sphalerite (Zn,Fe)S calamine or smithsonite (ZnCO j), willemite (Zo2Si04), franklinite (ZnFe204). Extracted by roasting to ZnO and reduction with carbon. The metal is bluish-white (deformed hep) fairly hard and brittle. Burns... 

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. 

Aetivators. These are used to make a mineral surface amenable to collector coating. Copper ion is used, for example, to activate sphalerite (ZnS), rendering the sphalerite surface capable of absorbing a xanthate or dithiophosphate collector. Sodium sulfide is used to coat oxidized copper and lead minerals so that they can be floated by a sulfide mineral collector. 

Zinc occurs most abundantly in tire mineral. Sphalerite, ZnS, which is roasted to produce the oxide before the metal production stage. The products of the roast are then reduced by carbon to yield zinc oxide and CO(g). In the older process, tire Belgian retort process, the metal oxide and carbon are mixed together in a reactor which allows the indirect heating of the charge to produce the gaseous products followed by tire condensation of zinc at a lower temperature in a zone of the reactor which is outside the heating chamber. The carbon monoxide is allowed to escape from the vessel and is immediately burnt in... 

Sulfur is widely distributed as sulfide ores, which include galena, PbS cinnabar, HgS iron pyrite, FeS, and sphalerite, ZnS (Fig. 15.11). Because these ores are so common, sulfur is a by-product of the extraction of a number of metals, especially copper. Sulfur is also found as deposits of the native element (called brimstone), which are formed by bacterial action on H,S. The low melting point of sulfur (115°C) is utilized in the Frasch process, in which superheated water is used to melt solid sulfur underground and compressed air pushes the resulting slurry to the surface. Sulfur is also commonly found in petroleum, and extracting it chemically has been made inexpensive and safe by the use of heterogeneous catalysts, particularly zeolites (see Section 13.14). One method used to remove sulfur in the form of H2S from petroleum and natural gas is the Claus process, in which some of the H2S is first oxidized to sulfur dioxide ... 

In the profiles of the core from the industrial area, mercury displays the highest accumulation. Mercury in this area, close to the industrial district, has probably derived from a large chloralkali plant which has employed mercury cathodes since the fifties. Whereas, at present, very severe measures are taken to prevent mercury spills into the Lagoon, in the past, polluted waters and solid materials were discharged almost untreated. In the most superficial strata a marked decrease in the accumulations is, in fact, recorded. Lead and Cd accumulations are lower here by a factor of 5-10. The presence of cadmium in the sediments of the Lagoon has been referred to sphalerite (ZnS) processing on the basis of a strict concomitant... 

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))...

Activators are those reagents which act in a manner converse to the action of depressants, i.e., they render those minerals floatable which either have been temporarily depressed or would not float without their assistance. They are generally soluble salts which ionize in the aqueous medium. The ions then react with the mineral surface, providing a monomolecular coating and thereby making the mineral surface favourably disposed to the collectors. Sphalerite (ZnS) is essentially not floatable with common collectors. The addition of Cu2+ to the solution, however, alters the mineral surface to CuS, which can adsorb collector. This feature is described elaborately in a later section. 

It is found that the dissolution of zinc sulfides occurs more rapidly when they are in contact with copper sulfide or iron sulfide than when the sulfides of these types are absent. This enhancement is brought about by the formation of a galvanic cell. When two sulfide minerals are in contact, the condition for dissolution in acidic medium of one of the sulfides is that it should be anodic to the other sulfide in contact. This is illustrated schematically in Figure 5.3 (A). Thus, pyrite behaves cathodically towards several other sulfide minerals such as zinc sulfide, lead sulfide and copper sulfide. Consequently, pyrite enhances the dissolution of the other sulfide minerals while these minerals themselves understandably retard the dissolution of pyrite. This explains generally the different leaching behavior of an ore from different locations. The ore may have different mineralogical composition. A particle of sphalerite (ZnS) in contact with a pyrite particle in an aerated acid solution is the right system combination for the sphalerite to dissolve anodically. The situation is presented below ... 

Pb2Sb206(0,0H)), sphalerite (ZnS), and smithsonite (ZnC03) were identified. These minerals are derived from both geogenic and technogenic processes in the Mezica mining district. 

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). 

Both Cu and Zn are base metals. Copper is largely mined from chalcopyrite (CuFeSj), chalcocite (CujS), cuprite (CujO), and malachite (Cu2C03(0H)2). Zinc is essentially produced from sphalerite (ZnS) and smithsonite (ZnCOs). 

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. 

Brion, D. Photoelectron spectroscopic study of the surfaee degradation of pyrite (FeS2), ehaleopyrite (CuFeS2), sphalerite (ZnS), and galena (PbS) in air and water, Appl. Surf. Sci., 1980, Volume 5, 133-52. 

Cadmium was discovered by F. Stromeyer in 1817. In nature, it is mostly found in zinc deposits. The mineral, greenocktite (CdS) is found associated with the zinc ore, sphalerite (ZnS). Similarly zinc carbonate contains otavite (CdCOs) in small amounts. Its abundance in the earth s crust is estimated to he 0.15 mg/kg and in sea water 0.11 irg/L. 

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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