Speciation of surface gold in pressure oxidized carbonaceous gold ores by TOF-SIMS and TOF-LIMS

To the best of our knowledge, this is the first attempt ever to speciate gold preg-robbed by carbonaceous matter using a surface sensitive microbeam technique. This approach enables the direct determination of gold species sorbed on carbonaceous particulates thus providing a new tool in understanding the chemistry of gold sorption on carbon. The reasoning behind this effort was to study the detrimental effect chloride ions have on gold recovery by pressure oxidation of carbonaceous sulfide ores, a technology largely used by the mining industry. The characterization of the sorbed gold species involved three surface sensitive microbeam analytical techniques (TOF-SIMS, TOF-LIMS and XPS) providing confirmatory results for better accuracy. Optimum conditions for detection of gold compounds with minimum fragmentation by TOF-SIMS and TOF-LIMS mass spectrometers have been determined. A reference library of 16 major gold complexes with halogen, thiosulfate, cyanide and thiocyanate groups relevant to the gold recovery processes has been established. The most suitable of the microbeam techniques tested was found to be negative (-ve) ion TOF-LIMS, offering best sensitivity and a small analytical spot size. (C) 2002 Elsevier Science B.V. All rights reserved.