2 research outputs found
Direct Oil Recovery from Saturated Carbon Nanotube Sponges
Oil
adsorption by porous materials is a major strategy for water purification
and industrial spill cleanup; it is of great interest if the adsorbed
oil can be safely recovered from those porous media. Here, direct
oil recovery from fully saturated bulk carbon nanotube (CNT) sponges
by displacing oil with water in controlled manner is shown. Surfactant-assisted
electrocapillary imbibition is adopted to drive aqueous electrolyte
into the sponge and extrude organic oil out continuously at low potentials
(up to −1.2 V). More than 95 wt % of oil adsorbed within the
sponge can be recovered, via a single electrocapillary process. Recovery
of different oils with a wide range of viscosities is demonstrated,
and the remaining CNT sponge can be reused with similar recovery capacity.
A direct and efficient method is provided to recover oil from CNT
sponges by water imbibition, which has many potential environmental
and energy applications
Symmetric and Asymmetric Meniscus Collapse in Wetting Transition on Submerged Structured Surfaces
The wetting transition from the Cassie–Baxter
to the Wenzel
state is a phenomenon critically pertinent to the functionality of
microstructured superhydrophobic surfaces. This work focuses on the
last stage of the transition, when the liquid–gas interface
touches the bottom of the microstructure, which is also known as the
“collapse” phenomenon. The process was examined <i>in situ</i> on a submerged surface patterned with cylindrical
micropores using confocal microscopy. Both symmetric and asymmetric
collapses were observed. The latter significantly shortens the progression
of the metastable state prior to the collapse when compared with the
former and hence may affect the lifespan of superhydrophobicity. Further
experiments identified that asymmetric collapse were induced by impurities
due to prior use of the structure. The problem is thus of broad relevance,
since endurance through cycles is a practical requirement for these
functional surfaces. Finally, the use of hierarchical structures is
proposed as a remedy. The embedded self-cleaning mechanism serves
to effectively remove the impurities, so as to avoid the triggering
mechanism for asymmetric collapses