Saltwater and Sulfide Mineral Flotation: Theoretical and Experimental Perspective

Anna M Nowosielska

In the minerals industry, flotation is a process of separating a valuable mineral from the gangue, based on the differences in hydrophobicity. It involves collisions between solid particles and gas bubbles in an aqueous solution, where the mineral particles will attach to bubbles, and together be carried up and recovered on the surface. Flotation is a complex dynamic interaction govern not only by the properties of particles and bubbles, but also influenced by the solution chemistry. Whilst freshwater is becoming a scarce resource in metallurgical operations, the use of seawater or recycled water is being increasingly recognised in areas with limited freshwater resources. Previous studies demonstrated that the use of saltwater enhances mineral flotation, however, to date, there is no single mechanism to explain the increased flotation efficiency. Earlier investigations proposed three main mechanisms, namely, the destabilization of the hydration layers around the particles, inhibition of bubble coalescence and the compression of the ionic diffuse layers around the particles and bubbles. In view of what has been reported and where further research may be required the aim of this project was to investigate the effects of saltwater on the fundamental particle-particle and particle-bubble interactions during sulfide mineral flotation, using both experimental and theoretical approaches. Galena (PbS) and Sphalerite (Zn, Fe) S were the two main sulfide minerals investigated, with Quartz (SiO2) being the main gangue mineral. Micro-flotation and batch flotation experiments using different NaCl concentrations were carried out and produced encouraging results. Overall, it was found that sulfide mineral recoveries improved with increasing NaCl concentrations. Part of this PhD project focused on developing and applying chemisorption models describing competitive ion adsorption at the galena, sphalerite, quartz and an air bubble surface sites. These models provided a more accurate representation of the electrostatic (ionic) interactions and allowed for the calculation of the “full” total interaction free energy, including charge regulation, for each particle-particle and particle-bubble interaction studied. This work provides a comprehensive account of sulfide mineral flotation in saltwater and highlights the significance of applying both: the theoretical and the experimental procedures for process optimisation.

Saltwater and Sulfide Mineral Flotation: Theoretical and Experimental Perspective

Files and links (1)

Abstract

Details

Metrics