SPP2045 - Multidimensional separation of ultrafine particles using a mechanical flotation cell combined with froth fractionation - MultiDimFlot

Froth flotation is one of the most important techniques in the mining industry to efficiently separate particles with sizes between 10 μm and 200 μm. The particles are separated according to their difference in wettability, as hydrophobic particles attach to gas bubbles and are recovered in a froth, whereas hydrophilic particles tend to stay in the pulp. Although, the wettability is the most prominent separation feature, other particle properties, such as size, morphology, surface energy or the dispersion state also affect the separation process since it includes a number of complex micro processes with specific particle-bubble interactions that occur in the pulp and in the froth phase. Low ore grades and very fine composite particles in electronic devices are forcing the industry to adapt and improve existing flotation techniques to the processing of ultrafine particles (< 10 μm), as the material needs to be milled down to finer size fractions to obtain sufficient liberation of the valuable minerals. For that reason, the project “MultiDimFlot”, which is part of the German research foundation priority programme DFG-SPP 2045 “MehrDimPart”, investigates the separation of ultrafine particles (< 10 μm) based on multiple particle properties. A novel separation apparatus is used that combines the advantages of a mechanical flotation cell that comes with a high particle-bubble collision rate (thus a high recovery) with those from a flotation column with a fractionating effect due to its deep froth (thus a high grade). A well-characterised model particle system, consisting of glass spheres and glass fragments as the floatable fraction and magnetite as the non-floatable fraction is used for the separation tests. These investigations will help to further understand the behaviour of ultrafine particles during flotation and how certain particle properties affect the separation process. Furthermore, the possibilities and limitations of different analysis techniques, e.g. coupled SEM-EDX, flow cytometry or inverse gas chromatography are investigated for their use in ultrafine particle characterization.