Effect of sodium dodecul sulfate on stability of gibbsite platelet stabilized emulsion foams

Amphiphilic molecules of anionic sodium dodecul sulfate (SDS) were used to modify the hydrophobicity of cationic gibbsite platelets in aqueous foams prepared by mechanical frothing. Contact-angle (θ) measurements revealed that the originally hydrophilic particles with an apparent θ of ∼30° become partially hydrophobic, θ > 50°, as the SDS concentration increased above ∼1 mM. Stable foams with up to 20 h duration were rendered with the preferential adsorption of the partially hydrophobized platelet particles (SDS ≥ 2.9 mM, solids concentration of 10 vol.%) at the water–air interface so that coalescence and disproportionation (i.e., Ostwald ripening) of the air-in-water (a/w) bubbles are suppressed. Macroporous alumina foams consisting of both open and closed pore structure, a mean cell diameter of about 300 μm, a sharp cell wall, and a relative porosity of 90% were produced by firing the dried gibbsite foams to 1500 °C in air atmosphere.