Abstract:

Attapulgite, a clay mineral which possesses the unique one-dimensional nanorod morphology, nanopore structure, natural electronegativity as well as the good water dispersibility, and has attracted extensive attention in the preparation and application of Pickering emulsion. In a few cases, natural attapulgite can directly stabilize the emulsion with a higher aspect ratio or by introducing olive oil containing a large amount of unsaturated fatty acids. In other cases, the hydrophilic natural attapulgite must be modified with the purpose of adjusting its surface wettability in the preparation of stable Pickering emulsion. According to the action mode of modifier and attapulgite, the modification can be divided into non-covalent bond and covalent bond. Non-covalent bond modification was that the modifier acts on the surface of attapulgite through hydrogen bonding, van der Waals force and electrostatic interaction. According to the molecular size of the modifier, non-covalent bond modification can be divided into organic small molecule and organic polymer. Covalent bond modification was the formation of a covalent bond between the silanol group on the surface of the attapulgite and the modifier through chemical reaction. The emulsion stabilized by attapulgite has a wide range of applications, and can be used to fabricate microcapsules or microspheres with sustained drug release, as a template to fabricate porous materials with adsorption, or catalysis, etc. The structural characteristics and physicochemical properties of attapulgite have been introduced, and then the application research progress of attapulgite in the preparation of Pickering emulsion has been summarized. This review provided the useful information for the mechanism analysis and application extension of attapulgite and other clay mineral stabilized Pickering emulsions.

Key words: attapulgite, Pickering emulsion, stabilization mechanism, clay mineral