The development of statistical ToF-SIMS applied to minerals recovery by froth flotation

The role of surface chemistry in recovery of minerals is central to several processes such as froth flotation, leaching, and electrostatic separation. In separation of base metals (eg, Cu, Pb, Zn, and Ni) by froth flotation of their minerals, usually sulphides, the attachment of these mineral particles, after hydrophobic collector addition, to air bubbles is used in operation. The stability of this bubble/particle attachment in both pulp and froth phases is dependent on the hydrophobic/hydrophilic ratio of surface species on individual mineral particle surfaces. The surfaces of individual mineral particles are a complex, distinctly non-uniform array of hydrophobic collector molecules and hydrophilic species (eg, oxidation products, adsorbed ions, fine particles, and precipitates). Hence, this ratio varies widely between different particles of the same mineral. It has been shown to determine whether particles report, correctly or incorrectly, to concentrate or tail (residue). To improve poor flotation recovery or grade, the analysis needed is the variation of this ratio by particle and as a statistical distribution between different mineral phases across a flotation circuit (eg, feed, successive concentrates, and tails). This requires surface analysis of a large number of particles with high spatial resolution and chemical speciation. In this Surface Science Western special issue article, methods to achieve this, using time-of-flight secondary ion mass spectrometry and principal component analysis, developed between the Ian Wark Research Institute and Surface Science Western over 25years are reviewed with applications to flotation. They are equally applicable to interferences in leaching, extraction, and electrostatic separation processes. Copyright (c) 2017 John Wiley & Sons, Ltd.