Leaching of sulfides

Leaching of sulfide sulfur from subaerial young (Miocene-Pliocene) volcanic rocks (Shikazono, 1987b). 

Possibility (1) was proposed by Shikazono (1987b) who considered that the lower values of sulfide sulfur than base-metal vein-type deposits and Kuroko deposits can be explained by the leaching of sulfide sulfur from volcanic rocks with lower values (0%o to -t-5%o) (Uyeda and Sakai, 1984). 

Dutrizac, J. E. The leaching of sulfide minerals in chloride media. Hydrometallurgy 1992, 29, I 45. 

Tuovinen, O.H. and Kelly, D.P., 1972. Biology of Thiobacillus ferrooxidans in relation to the microbiological leaching of sulfide ores. Z. Allg. Mikrobiol., 12 311—346. 

Wadsworth, M.E., 1972. Second Tutorial Symposium on Extractive Metallurgy, Leaching of Low and High Grade Ores, Dump Deposits and Concentrates, Part III, Advances in the leaching of sulfide and oxide minerals. University of Utah. 

Nonoxidalive leaching of sulfide minerals generally is not favored thermodynamically. Back-reaction with H2S limits the extent of reaction. An exception is galena (PbS), which dissolves sonoxidatively in chloride solutions, according to the reaciion... 

A.cidSolutions. DHute sulfuric acid is the most important solvent for oxide ore and for dead roasted sulfide concentrates. For instance, the leaching of zinc oxide, described by the foHowing equation, can be written as foHows ... 

Oxidi ng Solutions. In many leaching processes the mineral must be oxidized, as for instance, in the leaching of copper sulfides by ferric sulfate or ferric chloride solutions. 

Another important example is the leaching of nickel sulfide under ammonia and oxygen pressure to form hexaammine nickel (Sherritt-Gordon process). 

The filtered sodium thioantimonate solution obtained from the leaching of stibnite with sodium sulfide may also be reduced directly to metal by elemental sodium (17). Yields ia excess of 95% of 99.5 pure antimony are claimed (18). 

Microbiological leaching of copper and uranium has been commercially developed and research has iadicated that microorganisms may be used to oxidize complex antimony sulfide minerals (22,23). If this technology is developed commercially, it may aHow for the exploitation of many low grade antimony deposits. 

Hydrometallurigcal Processes. In hydrometaHurgical processes, metal values and by-products are recovered from aqueous solution by chemical or electrolytic processes. Values are solubilized by treating waste, ore, or concentrates. Leaching of copper ores in place by rain or natural streams and the subsequent recovery of copper from mnoff mine water as impure cement copper have been practiced since Roman times. Most hydrometaHurgical treatments have been appHed to ores or overburden in which the copper was present as oxide, mixed oxide—sulfide, or native copper. PyrometaHurgical and hydrometaHurgical processes are compared in Reference 34. 

The metallic or semi-metallic character of many common sulfides implies the significance of electrochemical factors in the study of their oxidation, which is relevant to environmental, energy, and metallurgical issues, e.g., in connection with the direct electrochemical conversion of sulfide ores to metals, the pressure leaching of ore materials, or flotation processes. 

Fig. 2.43. Graphical illustration of sulfur isotope values of HiS (left axis and. solid line) produced during basalt-seawater interaction at various water/rock ratios. Calculations assume that seawater sulfate is mostly removed as anhydrite, that any residual sulfate is reduced by iron oxidation in reacting basalt, and that there is quantitative leaching of basaltic sulfide and homogeneous mixing of both sulfides. Dashed line...

The reaction presented above is utilized to leach lead sulfate obtained by thermal oxidation of a mixture of sulfide minerals. The rate of dissolution chemically with a reagent in an... 

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