Gold complexes sulfides

Silver is widely distributed throughout the world. It rarely occurs in native form, but is found in ore bodies as silver chloride, or more frequently, as simple and complex sulfides. In former years, simple silver and gold-silver ores were processed by amalgamation or cyanidation processes, The availability of ores amenable to treatment by these means has declined. Most silver is now obtained as a byproduct or coproduct from base metal ores, particularly those of copper, lead, and zinc. Although these ores are different in mineral complexity and grade, processing is similar. 

Gold in complex sulfide ores Gold is impregnated in sulfides of copper, lead or zinc Many deposits, mined for Cu, Pb and Zn are of this type. Gold is an important by-product... 

Key words Amino acids. Catalytic oxidation under ambient conditions, 2-chloroethyl ethyl sulfide, Co-catalysis by copper. Decontamination, Effect of ligands, Gold complexes. Mustard gas, Perfluorinated solvents. Solvent effect. Sulfoxide, Thioether... 

Yuan and coworkers reported the use of HAUCI4 H2O as catalyst for the oxidation of sulfides to sulfoxides by hydrogen peroxide (Scheme 16.37). The corresponding sulfoxides were selectively obtained in the reaction and only small amounts of sulfones were observed in some of the reactions. Different functional groups were tolerated. The authors were able to reuse the gold complex up to six times without significant loss of activity. The reaction performs under mild conditions, in methanol at 25 °C and hydrogen peroxide was used as the oxidant. 

The application area of OSBS process is much wide than the Vanyukov process, which includes lead, antimony and bismuth extraction. Future application of this technology may include refractory gold, complex Cu-Pb-Zn ore processing. Moreover, the process might be used to smelt oxide ore, oxide-sulfide mixed ore, industrial solid waste and living garbage rather than sulfide ore only. 

Corma A, Gonzalez-Arellano C, Iglesias M, Sanchez R Efficient synthesis of vinyl and alkyl sulfides via hydrothiolation of alkynes and electron-deficient olefins using soluble and hetereogeneous gold complexes catalysts. Appl. Catal. A 2010 375 49-54. 

FIGURE 5.3 Luminescent hexanuclear, decanuclear, and dodecanuclear gold(I) sulfide complexes. 

Metals less noble than copper, such as iron, nickel, and lead, dissolve from the anode. The lead precipitates as lead sulfate in the slimes. Other impurities such as arsenic, antimony, and bismuth remain partiy as insoluble compounds in the slimes and partiy as soluble complexes in the electrolyte. Precious metals, such as gold and silver, remain as metals in the anode slimes. The bulk of the slimes consist of particles of copper falling from the anode, and insoluble sulfides, selenides, or teUurides. These slimes are processed further for the recovery of the various constituents. Metals less noble than copper do not deposit but accumulate in solution. This requires periodic purification of the electrolyte to remove nickel sulfate, arsenic, and other impurities. 

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