X-PEEM, XPS and ToF-SIMS characterisation of xanthate induced chalcopyrite flotation: Effect of pulp potential

Synchrotron-based X-ray photoemission electron microscopy (X-PEEM), X-ray photo-electron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and ultraviolet visible spectroscopy were used to characterize the flotation behaviour of chalcopyrite with xanthate at different processing conditions. The flotation recovery of chalcopyrite decreased from 97% under oxidative conditions (Eh ~ 385 mV SHE, pH 4) to 41% at a reductive potential of - 100 mV SHE (at pH 9). X-PEEM images constructed from the metal L₃ absorption edges were used to produce near-edge X-ray absorption fine structure (NEXAFS) spectra from regions of interest, allowing the variability in mineral surface chemistry of each mineral particle to be analysed, and the effect of pulp potential (Eh) on the flotation of chalcopyrite to be determined. XPS, ToF-SIMS and NEXAFS analyses of chalcopyrite particles at oxidative conditions show that the surface was mildly oxidised and covered with adsorbed molecular CuEX. The Cu 2p XPS and Cu L_2,3 NEXAFS spectra were dominated by Cu^I species attributed to bulk chalcopyrite and adsorbed CuEX. At a reductive potential of - 100 mV SHE, an increase in concentration of Cu^I and Fe^III oxides and hydroxides was observed. X-PEEM analysis was able to show the presence of a low percentage of Cu^II oxides (CuO or Cu(OH)₂) with predominantly Cu^I oxide (Cu₂O) which is not evident in Cu 2p XPS spectra.