Infrared Spectroscopic Investigations of the Stability of Xanthate-Mineral Interaction Products

Abstract

The products of the interaction of ethyl xanthate (CH3CH2OCS2−) with copper and chalcocite (Cu2S) electrodes at a controlled potential have been investigated by ex situ infrared spectroscopy. The disappearance of bands assigned to dixanthogen over time indicated that additional reactions were occurring subsequent to the initial interaction. These reactions were also followed by gas-phase infrared photoacoustic spectroscopy (PAS), which suggested the formation of CO2 and COS. The PAS technique was also employed to identify the gas-phase species produced from a variety of powdered minerals [heazlewoodite (Ni3S2), chalcocite (Cu2S), chalcopyrite (CuFeS2), pyrite (FeS2), pyrrhotite (Fe1- xS x), pentlandite ([Fe, Ni]S), galena (PbS), sphalerite ([Zn, Fe]S), and arsenopyrite ([Fe, As]S)] when treated with ethyl and isobutyl xanthates. The main species produced were COS, CO2, and H2O, with CS2 and C2H5OH being observed for ethyl xanthate in certain cases. The results show that the xanthate films decompose over time. The following decomposition pathways could account for the products observed: elimination of the triatomics from metal-xanthate complexes; decomposition of dixanthogen; formation of radicals; and pyrolysis of the xanthate complexes.