Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Froth flotation is an efficient separation process for particles with sizes between 10 μm and 200 μm, which is based on differences in the particle wettabilities, or more precisely dewettingability. Therefore, a fundamental understanding of the interfacial properties is required. Within the project MultiDimFlot, which is part of the priority programme SPP2045, funded by the German research foundation (DFG), the selective separation of ultrafine particles (< 10 μm) according to multiple particle properties (e.g. wettability, shape, size) by flotation is investigated. For this purpose, two ultrafine glass particle fractions with different shapes are used, i.e. glass spheres and fragments, and their wettability is modified via an esterification reaction using alcohols, where the wettability of the esterified particles is controlled by the length of the alkyl chain.
In order to investigate the influence of wetting heterogeneities on the separation via flotation, glass slides with the same chemical composition as the glass particles and that were esterified in the same way, were analysed via atomic force microscopy (AFM). By applying colloidal probe AFM in dry and liquid mode, information on the hydrophobic interactions on the surface of the glass slides with different levels of wettability are obtained. Furthermore, the esterified glass slides are analysed by measuring static and dynamic contact angles against water using the sessile drop method. This information is set into context with the surface energy results of the glass particles, obtained via inverse gas chromatography as well as results obtained by liquid-liquid extraction of particles, which is used to study the behaviour of the particles at the interface.
The correlation of the various methods shed light on the (de)wetting(ability) heterogeneities, how these are changed through esterification and how these results can be transferred to flotation.