ABSTRACT
The recent advances in modern instrumentation have propelled the research in surface force measurements by surface force apparatus (SFA) and atomic force microscope (AFM) [5]. The non-DLVO (Derjaguin-Landau-Verwey-Overbeek) colloidal forces, such as the hydration force, hydrophobic force, undulation force, protrusion forces, ion correlation forces, steric forces, and structural forces in nonaqueous systems, have been either experimentally confirmed or newly discovered [6]. For mineral processing applications, the colloidal forces involved have been measured for a range of mineral systems, such as silica-mica [7], silica-iron oxide [8], silica-alumina [9], silica-covellite [10], silica-zinc sulfide [11], zinc sulfide-zinc sulfide [12], and silica-air bubbles [13-15], to name a few. In the measurement of the colloidal forces between a silica particle and a synthetic zinc sulfide particle in aqueous supporting electrolyte solutions [11], the objective was to determine whether asymmetric oxide-sulfide interactions could be predicted from the knowledge of the symmetric systems. The limited data showed a monotonic repulsive force profile with no adhesion on separation in a 0.2 mmol KC1 aqueous solution at pH 5.8. In this paper, we report the detailed force measurement with a fractured mineral sphalerite and a silica sphere in the context of selective sphalerite flotation. This work stems from the observed contamination of sphalerite concentrate by silica, if floated from a neutral pH slurry, but not from an alkaline slurry.
