INSITU ATR-IR SPECTROSCOPIC STUDY OF XANTHATE ADSORPTION ON MARCASITE

Adsorption of ethyl xanthate, dixanthogen, and monothiocarbonate on freshly ground marcasite from both acidic and basic solutions has been studied. The changes taking place on the surface of the mineral were determined in situ by attenuated total reflection spectroscopy in the infrared (ATR-IR). The sensitivity of the measurement system used made is possible to observe the adsorption products at sub-monolayer coverage. The changes in solution were spectrally determined in the UV. A two-stage adsorption process has been found for ethyl xanthate and dixanthogen. A monolayer form of iron xanthate is formed during the first stage. One of the marcasite samples contained a significant amount of lead; hence a monolayer form of lead xanthate was observed. In the second stage, multilayer coverage of ethyl dixanthogen was observed, independent of impurities in the marcasite. During the xanthate and dixanthogen adsorption on marcasite the products of marcasite oxidation are transferred into the solution. Xanthyl thiosulphide, the reaction product between the xanthate and thiosulphide, has been observed in solution. Reactions of xanthate decomposition catalysed by marcasite take place in solution. The amount of xanthate catalytically decomposed increases with increasing solution pH, with respect to the amount of xanthate adsorbed on the marcasite. At pH 10, when the amount of xanthate adsorbed approaches sub-monolayer coverage, significant amounts of monothiocarbonate, carbon disulphide, and SH- ions are formed in the solution.