SIMS study of adsorption of collectors on pyrite

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Adsorption of sulfide collectors such as xanthate on pyrite has been studied extensively over several decades using a wide variety of techniques. In spite of this, there are unanswered questions as to the identity of adsorbed species on pyrite surfaces—dixanthogen vs. iron xanthate complexes. Far less is known in non-xanthate collector systems. We have used Secondary Ion Mass Spectroscopy (SIMS) successfully in the past to obtain direct evidence for the identity of the adsorbed collector species on copper sulfides, galena and Cu-activated quartz. The present study is an extension of the SIMS analysis to investigate the adsorption of xanthate, dithiophosphate, dithiocarbamate, and modified thionocarbamates and thioureas on pyrite. Adsorption of these collectors on chalcocite was also studied for comparison. An attempt was also made to obtain SIMS spectra for pure dixanthogens at room temperature. The collector molecular ion was detected for pure amyl dixanthogen, but only dixanthogen fragments were observed for the isobutyl and ethyl homologues. Only in the case of dithiocarbamate (DTC) was there direct evidence for the presence of not only the collector dimer, but also iron–DTC complexes. On chalcocite, only the copper–DTC complexes were detected (no dimer). In the case of xanthate, the collector molecular ion and its S adduct—which are possible fragments from dixanthogen—were detected on pyrite, along with a fragment peak suggesting Fe 2X. For dithiophosphate, the collector molecular ion and Fe(DTP)(OH) complex were detected (no dimer). For modified thionocarbamate and thiourea, adsorption on pyrite was negligible. SIMS results obtained in this study imply that one cannot subscribe only to collector dimers as the predominant species on pyrite under practical flotation conditions and rule out the formation of Fe-collector complexes for the adsorption of collectors on pyrite.