Fate of Cyanide in Gold Ores Containing Reduced Sulphur Minerals
The chemistry of aqueous cyanide containing species in the presence of reduced sulfur sources was investigated. Reactions were studied as a function of time and tracked using novel analytical techniques developed for the analysis of the species of interest in the sample matrix. Species of interest in this work were free cyanide, thiocyanate, cyanate, metallo-complexed cyanide, and various sulfur and sulfur-oxygen species. The studies were conducted under constant temperature conditions at pH values above 10.5 and in the absence of light in order to eliminate photochemically induced cyanide reaction effects. The reaction products of cyanide when in contact with pure sulfur, pyrite, pyrrhotite, sphalerite, and cinnabar are reported. These data combined with data for copper, arsenic and lead sulfides, which have been previously published, are used to predict the fate of cyanides in refractory gold ores containing sulfides. A mass balance on the cyanide reaction products was completed for all experiments.From these studies insight into the chemical relationships of cyanide, the specific metal sulfide,thiocyanate and cyanate have been gained. When looking at the results of the experiments, it was immediately apparent that even though the overall conversions of cyanide to thiocyanate were different, most of the samples exhibited a similar pattern of reactions. The recovery of cyanide in these experiments was better than we expected, averaging in most experiments to be over 90 percent.Based on this research, the formation of cyanate was probably the main route of loss. The pathway choice for the various minerals was also elucidated in these experiments. The competitive oxidation pathways that cyanide can take have been tracked for sufficient time to determine the final fate of cyanide in a process.Initially, it was thought that the cyanate may be involved in a hydrolysis reaction to form ammonia and carbonate ion, but upon further inspection of the data, there was not the drop-off in total cyanide recovery that would manifest itself were this to happen. On the other hand, the hydrolysis of thiocyanate to cyanate and sulfate would require oxidizing conditions which did not exist in solution at the beginning of the experiment. If the solutions were to be sufficiently oxidizing in nature for this to happen, the initial amount of cyanide would have been converted to cyanate quickly. The data support premise that the hydrolysis of thiocyanate to cyanate and sulfate occurs to some extent in the experiments conducted. Knowledge gained from the experiments with pure metal sulfides helped interpret the results of experiments with refractory ores found in the State of Nevada.
Gold hydrometallurgy Cyanide chemistry Thiocyanate chemistry
J. C. Wilmot E.B. Milosavljevic L. Solujic J.L. Hendrix
Freeport-McMoRan Mining Co., Phoenix, USA University of Nebraska-Lincoln, Lincoln, USA
国际会议
XXIV International Mineral Processing Congress(第24届国际矿物加工大会)
北京
英文
2958-2964
2008-09-24（万方平台首次上网日期，不代表论文的发表时间）