In Situ Investigation of the Adsorption of Styrene Phosphonic Acid on Cassiterite (110) Surface by Molecular Modeling

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, the physicochemical behaviors of the (110), (100), as well as (001) of SnO₂ were investigated by using high-resolution direct force spectroscopy. The measurements were conducted between a silica sphere and sample surfaces in 10 mmol/L KCl between pH 3.1 and 6.2 using colloidal probe atomic force microscopy (cp-AFM-hydrophilic). Dissimilar interactions were detected on different-oriented surfaces. 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). By fitting the force curves in the Derjaguin-Landau-Verwey-Overbeck theory framework, anisotropic surface potentials were computed between the three sample surfaces following a similar trend as force interaction. To study the implication of crystallographic orientation to surfactant adsorption, we used Aerosol 22 (sulfosuccinamate) as an anionic collector for cassiterite flotation to functionalize the different samples at pH 3. The contact angle measurements, the topography visualizations by AFM, and the force measurement using cp-AFM with hydrophobized spheres (cp-AFM-hydrophobized) have shown that Aerosol 22 was adsorbed on the sample surfaces inhomogeneously. The adsorption followed the range of SnO₂(110) > SnO₂(100) > SnO₂(001) in the concentration from 1 × 10^-6 to 1 × 10^-4 mol/L.