Electroacoustic measurements of mixed quartz and iron oxide mineral systems

Surface behavior of the commonly found minerals in nickel laterite ores — quartz, magnetite, hematite and goethite — was investigated using electroacoustic measurements. The goal was to assess the surface potentials as single minerals and in mixed systems to understand possible interactions between particles in laterite slurries. Surface potentials were evaluated according to the electroacoustic theory with the understanding that a direct relationship existed between zeta potential and electroacoustic sonic amplitude (ESA) values. Results were evaluated using Bruinsma's equations. Measured (actual) and calculated ESA values were compared to determine whether the mixed systems remained dispersed or a tendency towards heterocoagulation existed over a range of pHs. For all mixed systems the behavior of the system was affected by the mineral of higher proportion in the mixture. For the fine quartz–magnetite system, no heterocoagulation was observed at all proportions of quartz and magnetite over the entire pH range. In the fine quartz–hematite and fine quartz–goethite systems a tendency towards heterocoagulation was observed with increase in quartz. The effect of the particle size was also investigated using coarse quartz–magnetite mixtures. A higher tendency towards heterocoagulation was observed with coarser quartz. The amount of quartz was found critical for the rheology of laterite slurries, determining the state of dispersion and/or heterocoagulation in the slurry.

Calculated (Bruinsma) vs fitted ESA values for mixed mineral systems of fine and coarse quartz and iron oxide minerals. A deviation from the 1:1 line points to a tendency towards heterocoagulation in the system.Figure optionsDownload as PowerPoint slideHighlights
► ESA measurements were conducted on single and mixed mineral systems.
► ESA values were influenced by the mineral of higher proportion in mixed systems.
► No heterocoagulation was observed in fine quartz–magnetite system.
► Quartz–hematite and quartz–goethite tended to heterocoagulate with increasing quartz.
► Quartz amount determined the state of dispersion or heterocoagulation in the slurry.