THE ROLE OF CYANIDE IN THE INTERACTION OF ETHYL XANTHATE WITH GALENA

Ultraviolet-visible (UV/Vis) and Fourier transform-infrared (FT-IR) sp ectroscopy were used to examine the kinetics of ethyl xanthate adsorpt ion onto galena at pH 9. In general the rate and extent of ethyl xanth ate adsorption increased with the pulp electrochemical potential (Eh). FT-IR studies using the attenuated total reflectance (ATR) mode confi rmed the presence of lead ethyl xanthate species on galena, with no ev idence of diethyl dixanthogen. The effect of cyanide on the adsorption kinetics of ethyl xanthate on galena depends on the Eh as well as the order of reagent addition. Simultaneous addition of ethyl xanthate an d cyanide results in an increase in the rate and extent of ethyl xanth ate adsorption at Eh values < + 200 mV, whereas at higher Eh values cy anide had little effect on ethyl xanthate adsorption. Furthermore, cya nide addition to galena with preadsorbed ethyl xanthate led to increas ed xanthate adsorption, behaviour which was more pronounced at lower E h values. A possible mechanism for this activation process is proposed , where cyanide interacts with the sulphur moiety of galena, leaving a lead-rich galena surface which is more susceptible to ethyl xanthate interaction. In contrast to pyrite and pyrrhotite surfaces, no competi tive adsorption between cyanide and ethyl xanthate for the galena surf ace was evident. This finding was in agreement with X-ray photoelectro n spectroscopy (XPS) and FT-IR studies which did not detect any surfac e cyano species on galena.