Stoppers and Skins on Clay Nanotubes Help Stabilize Oil-in-Water Emulsions and Modulate the Release of Encapsulated Surfactants

Abstract

This work develops the concepts of particle-stabilized emulsions using tubular natural clays known as halloysites to attach to the oil–water interface and stabilize oil-in-water emulsions. Such halloysite nanotubes (HNT) serve as reservoirs for surfactants and can deliver surfactants to the oil–water interface and thus lower the oil–water interfacial tension. This two-step concept of surfactant delivery and droplet stabilization by particles has significant implications to oil spill remediation. However, to deliver surfactant loaded HNTs in a water-based solvent slurry, it is important to stopper the nanotubes to prevent premature release of the surfactant. This work focuses on the use of an environmentally benign two-dimensional metal–organic framework formed by coordinating Fe(III) with a polyphenolic as a stoppering agent. Such metal–phenolic networks (MPN) form a skin around the HNTs, thus providing a way to effectively sequester surfactant cargo for controlled release. Cryo-scanning electron microsco...