XPS and FTIR study of the influence of electrode potential on activation of pyrite by copper or lead

Activation of pyrite by either copper or lead ions and subsequent xanthate adsorption on activated surfaces were studied in aqueous solutions of pH 5, 6.5 and 9 under different electrochemical conditions using X-ray Photoelec tron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). At pH 5, the copper concentration on the surface of pyrite increased stron gly when the electrode potential was changed towards cathodic direction. At low activation potentials (E-h less than or equal to + 100 mV), a change i n the chemical state of sulfur on the surface was observed by XPS proposing formation of a copper-containing surface sulfide phase. In electrochemical ly-controlled xanthate adsorption, the behavior of copper-activated pyrite resembled that of chalcopyrite (CuFeS2). The results indicate that activati on of pyrite by copper at pH 5 can be controlled by the potential of the mi neral. At pH 9. the copper content on the surface was independent of the po tential of pyrite and no changes were observed in chemical state of sulfur if compared to unactivated pyrite in the potential region - 100 to + 400 mV (SHE). In the case of pyrite activation by lead, no changes were observed in sulfur spectra at either pH 5 or 9 at different electrode potentials. Th e concentration of lead on the surface increased at pH 5 when potential was changed towards cathodic direction. All lead present at the surface of pyr ite was concluded to be in the form of lead(II)-oxygen species and no evide nce of exchange between lead and iron was found. Both adsorbed xanthate and dixanthogen were observed on the surface of Cu-activated pyrite after acti vation at cathodic potentials (- 100 to + 50 mV) and subsequent treatment i n either ethyl or amyl xanthate solution of pH 5 or 6.5 at potential region + 350 to 550 mV (standard hydrogen electrode, SHE). In a similar experimen ts with Pb-activated pyrite, only a faint indication of the adsorbed collec tor species was found proposing that lead rather depresses than activates p yrite. (C) 1999 Elsevier Science B.V. All rights reserved.