Surface composition of pentlandite under flotation‐related conditions

Abstract

X-ray photoelectron spectroscopy (XPS) and electrochemical techniques have been applied to the investigation of the surface oxidation of pentlandite. Photoelectron spectra indicate that the initial reaction on exposure to air is removal of iron from the pentlandite lattice to form a hydrated iron oxide overlayer and leave a metal-deficient pentlandite in addition to a restructured nickel-iron sulphide. Further oxidation resulted in some nickel being traasferred to the oxide. In dilute acetic acid, the oxide layer was largely soluble. In basic media, the products were the same as in air but the reaction rate was greater. The voltammetric characteristics of pentlandite in solutions of pH 4.6, 9.2 and 13 were consistent with the XPS findings. Pentlandite behaved in a manner similar to that established previously for pyrrhotite, indicating that the iron in pentlandite is preferentially removed on anodic oxidation to leave a metaldeficient sulphide layer. There was evidence for the additional removal of nickel from the sulphide lattice. The formation of sulphate was also indicated on scans to high potentials in basic media.

Self‐induced floatability of sulphide minerals: Examination of recent evidence for elemental sulphur as the hydrophobic entity

“…2(a)) for a galena surface immediately after abrasion in air and the corresponding spectrum for a fresh fracture surface. 13 In particular, no elemental sulphur or any other altered sulphur species was evident from the S 2p or S LMM spectra. This observation was consistent with the absence of peaks from hydrated lead oxide in the Pb 4f or Pb N O 0 spectra, because the formation of a sulphur-rich surface must be preceded by, or concurrent with, the formation of lead-oxygen species.…”

X-ray Photoelectron Spectroscopy in Mineral Processing Studies

“…Buckley and Woods have also found [44][45][46][47][48][49][50][51][52][53][54][55] that oxidation of metal sulfides in atmosphere and aqueous media generally produces surfaces depleted in metal and so enriched in sulfur. The initial oxidation typically yields metal oxides and hydroxide with no oxidized sulfur species, suggesting the formation of "defective metal-deficient" sulfide surfaces.…”

“…Buckley and Woods [44][45][46][47][48][49][50][51][52][53][54][55] have performed a series of studies on the sulfide minerals reacted in air, flotation-and leaching-related aqueous media, and highlighted the existence of metal-deficient surfaces involving S-S bonding and the necessity to cool the samples down to liquid nitrogen (LN) temperatures in order to preserve volatile surface species. In particular, galena crystals oxidized in air or reacted with aqueous solutions and then dried with Ar flushing were cooled to about 180 K during evacuation and measured at LN temperatures [44].…”

Surface and Interface Chemistry in Colloidal Quantum Dots for Solar Applications Studied by X‐Ray Photoelectron Spectroscopy

“…A case in point is the oxidation of PbS, a reaction long‐studied because of its importance in mineral beneficiation using froth flotation, and in the extraction of lead from ore using hydrometallurgical operations such as leaching . The question of whether or not the reaction proceeds congruently (with dissolution of Pb and S in equivalent amounts) has been extensively debated . We have been able to resolve this in studies of nanocrystalline thin films of PbS obtained in a straightforward reaction by precipitation at the interface between toluene (containing a Pb precursor, such as lead diethyldithiocarbamate (Pb(S 2 CNEt 2 ) 2 ) and water (containing Na 2 S) .…”