Water-in-water pickering emulsions stabilized by talc or kaolinite layered particles

Kaolinite (Kaol) - Al ₂Si ₂O ₅(OH) ₄ and talc - Mg ₃Si ₄O ₁₀(OH) ₂ (Talc) are abundant clay minerals, with layered particles characterized by nanometric thicknesses and few micrometers in length. Such characteristics are interesting attributes when considering the stabilization of emulsions with low interfacial tension, like in water-in-water emulsions. Here, Kaol and Talc layered particles were characterized by several instrumental techniques. Then, we evaluated the effect of Kaol and Talc addition on water-in-water emulsions, formed by aqueous colloidal dispersions of amylopectin (AMP) and xyloglucan (XG) polymers. The emulsions were evaluated macroscopically and by means of droplet size distributions. The apparent contact angle (ACA) of a water droplet in atmospheric air was also measured on Kaol and Talc pressed pellets. Due to a larger droplet size (D50 = 2.01 ± 0.20 μm) when compared to Kaol (D50 = 0.34 ± 0.02 μm), Talc particles did not create complete coverage on the droplet surfaces. The droplets were also dragged down faster, increasing coalescence and the average droplet size after 24 h of preparation. In both cases, the difference in densities between the solids and the aqueous phases led to particle sedimentation, even when adsorbed to the interface of the droplets, generating a concentrated emulsion at the bottom of the flasks. While talc particles sedimented completely after 72 h, Kaol ones remained at the droplets interface, creating Pickering emulsions with enhanced stability.