(59c) Aspects of Wettability Heterogeneities in Flotation - Investigations with Inverse Gas Chromatography and Colloidal Probe Atomic Force Microscopy

In flotation for the separation of fine particles (approx. 5 µm < x < 200 µm), the main particle property of separation is a differing wettability of the constituents. This most crucial property in the economically important process of flotation is often only and incompletely, quantitatively described in terms of static contact angles of water. A water contact angle larger than 90° is referred to as hydrophobic and hydrophilic vice versa. Looking at Young’s equation shows that it is actually the interacting phases’ surface energies split in disperse and polar components which describes whether there will be hydrophobic/hydrophilic hydration interactions leading to attraction or repulsion. This, we have previously published for various more or less hydrophobic minerals in correlation to their flotability (c.f. Rudolph & Hartmann, Coll.Surf.A 513, 380-388). In the same paper we also discussed the heterogeneity of wettabilities as assessed with the novel method of inverse gas chromatography. Furthermore we have also reported on hydrophobic force distributions as assessed with atomic force microscopy which are as well due to wettability heterogeneities (c.f. Fritzsche et al., Coll.Surf.A 459, 166-171).

In this paper we present wettability distributions of different substrates and particles with various surface roughnesses/shapes and degrees of hydrophobization as assessed with inverse Gas Chromatography iGC, colloidal probe atomic force microscopy CP-AFM and dynamic sessile drop analyses. We are putting the results in context in unifying models and present methodologies helpful to make use of the fundamental information and their impact on the actual industrial separation process in fundamental process models. Besides froth flotation we also emphasize the impact on selective hydrophobic flocculation process.