A novel method for surface wettability modification of talc through thermal treatment

Silica tetrahedron (also called siloxane) is an important structure of clay minerals, the percentage of which influences the hydrophobicity, polarity and other surface properties on clay mineral surfaces. In this study, a novel method for surface wettability modification of talc through thermal treatment has been put forward. In this method, the symmetrical siloxane structures on talc basal surfaces were broken by transforming the non-polar siloxane structure into a polar structure during the thermal treatment process, thus to decrease the hydrophobic components on talc surfaces, and therefore achieve the goal of surface wettability modification. This study was performed through the measurements of thermosgravimetric analysis and differential scanning calorimetry (TG-DSC), contact angle and wetting heat measurements, fourier transform infrared spectroscopy (FTIR), and Si-29-nuclear magnetic resonance spectroscopy (Si-29 NMR) as well as molecular dynamic simulations (MDs). The results indicate that the thermal treatment at 960 degrees C for only a very short time could greatly decrease the contact angle of water on talc surfaces. The mechanism could be attributed to that the thermal treatment leads to the disorder of some of the Si-O bond length and O-Si-O bond angle in talc silica tetrahedron structure, which finally results in the disorder of the symmetrical siloxane structure and the formation of the amorphous silica phase. And the decrease of hydrophobic siloxane structures on talc surface gives rise to the relatively strong hydrophilicity on talc surfaces. This current method improves the wettability of talc without any addition of modifiers, which would be helpful of many applications of clay minerals, such as clay-polymer composites, filler materials, clay mineral dispersion in aqueous suspensions or mineral processing, etc.