Study of the Influence of the Crystallographic Orientation of Cassiterite Observed with Colloidal Probe Atomic Force Microscopy and its Implications for Hydrophobization by an Anionic Flotation Collector

In this study, SnO2(110), SnO2(100) as well as SnO2(001) were investigated by using direct force measurements. The high-resolution force spectroscopy measurements were conducted between a silica sphere and sample surfaces in 1 mM KCl between pH 3.1 and 6.2 using colloidal probe atomic force microscopy (cp-AFM- hydrophilic). Dissimilar interactions were detected on different oriented surface. The pH values where the force switched from positive to negative can be clearly distinguished and be ordered as SnO2 (100) < SnO2 (001) ≈SnO2 (110). This observation implies that there is a difference in surface properties between the three orientations. However, no clear interpretation can be made by fitting of the interaction forces in the framework of the Derjaguin-Landau-Verwey-Overbeck (DLVO) theory.1,2
To study the implication of crystallographic orientation to surfactant adsorption, we used Aerosol® 22 (sulfosuccinamate) as anionic collector for cassiterite flotation to functionalize the different samples at pH 3. The contact angle measurements, the topography visualizations by AFM as well as the force measurement using cp-AFM with hydrophobized spheres (cp-AFM-hydrophobized) have shown that the adsorption of Aerosol® 22 followed the range of SnO2(110) > SnO2(100) > SnO2(001) in the concentration from 1x10-6 M to 1x10-4 M.