Organo-Bentonite-Coated Interfaces: Interfacial Properties and Cyclic Response

The accumulation of amphiphilic molecules,nanoparticles, or microorganismsat interfaces has important implications for multiphase flow in porousmedia. We optimize the composition of stable organo-bentonite suspensionsto enhance particle adsorption onto the oil-water interface.Then, we use the pendant drop method to explore time-dependent effectson surface tension and the consequences of contraction-expansioncycles. Brownian motion brings organo-bentonite particles to the oil-waterinterface where they adsorb and accumulate to reduce the apparentinterfacial tension in time. The adsorption energy of platy organo-bentoniteparticles is significantly higher than the adsorption energy of sphericalnanoparticles of the same volume. Then, a shell-like interface developsafter particle jamming during droplet contraction, and further contractionleads to shell buckling and wrinkle formation (rather than desorption).The shell-like interface experiences an anisotropic stress field andcannot be described by the Young-Laplace equation. The evolutionof interfacial tension during contraction and expansion shows stronghysteresis; furthermore, the results suggest that the number of adsorbedparticles at the interface increases with the number of cycles. Naturalclay nanoparticles can facilitate the development of cost-effectiveand environmentally friendly alternatives for field-scale applications.

Automated summary

The accumulation of amphiphilic molecules, nanoparticles, or microorganisms at interfaces has significant effects on multiphase flow in porous media. By optimizing the composition of stable organo-bentonite suspensions, we enhance particle adsorption onto the oil-water interface. We investigate the time-dependent effects on surface tension and observe the development of a shell-like interface during droplet contraction, which experiences buckling and wrinkle formation.