3 research outputs found
Processing–Structure–Property Correlations of Polyethersulfone/Perfluorosulfonic Acid Nanofibers Fabricated via Electrospinning from Polymer–Nanoparticle Suspensions
Polyethersulfone (PES)/perfluorosulfonic acid (PFSA)
nanofiber
membranes were successfully fabricated via electrospinning method
from polymer solutions containing dispersed calcium carbonate (CaCO<sub>3</sub>) nanoparticles. ATR-FTIR spectra indicated that the nanoparticles
mainly existed on the external surface of the nanofibers and could
be removed completely by acid treatment. Surface roughness of both
the nanofibers and the nanofiber membranes increased with the CaCO<sub>3</sub> loading. Although FTIR spectra showed no special interaction
between sulfonic acid (−SO<sub>3</sub>) groups and CaCO<sub>3</sub> nanoparticles, XPS measurement demonstrated that the content
of −SO<sub>3</sub> groups on external surface of the acid-treated
nanofibers was enhanced by increasing CaCO<sub>3</sub> loading in
solution. Besides, the acid-treated nanofiber membranes were performed
in esterification reactions, and exhibited acceptable catalytic performance
due to the activity of −SO<sub>3</sub>H groups on the nanofiber
surface. More importantly, this type of membrane was very easy to
separate and recover, which made it a potential substitution for traditional
liquid acid catalysts
Preparation and Characterization of High-Performance Perfluorosulfonic Acid/SiO<sub>2</sub> Nanofibers with Catalytic Property via Electrospinning
Polymer nanofiber-supported perfluorosulfonic acid (PFSA)/SiO<sub>2</sub> catalysts are successfully fabricated by electrospinning
method from polymer/nanoparticle suspensions. This kind of catalyst
has a large number of active acid sites and high specific surface
area up to 85.6 m<sup>2</sup>/g. Scanning electron microscope images
reveal that the catalysts present high porosity and inner-connected
porous structure which varies much with SiO<sub>2</sub> loading. Nitrogen
adsorption–desorption measurements demonstrate a wide distribution
of pore sizes inside the composites. Catalysts of different compositions
are evaluated in esterification in a batch reactor under various conditions,
and the results indicate that those of 20 wt % PFSA loading have the
best activity of unit PFSA. Supporting PFSA by a nanofibrous matrix
enhances liquid holdups inside the catalysts and offers accessibility
of the acid sites, and therefore improves the activity of the catalysts.
Moreover, these catalysts allow recovery at high percentages and regeneration
with high activity
FAS Grafted Electrospun Poly(vinyl alcohol) Nanofiber Membranes with Robust Superhydrophobicity for Membrane Distillation
This
study develops a novel type of electrospun nanofiber membranes
(ENMs) with high permeability and robust superhydrophobicity for membrane
distillation (MD) process by mimicking the unique unitary microstructures
of ramee leaves. The superhydrophobic ENMs were fabricated by the
eletrospinning of polyÂ(vinyl alcohol) (PVA), followed by chemical
cross-linking with glutaraldehyde and surface modification via low
surface energy fluoroalkylsilane (FAS). The resultant FAS grafted
PVA (F-PVA) nanofiber membranes were endowed with self-cleaning properties
with water contact angles of 158° and sliding angles of 4°
via the modification process, while retaining their high porosities
and interconnected open structures. For the first time, the robust
superhydrophobicity of the ENMs for MD was confirmed by testing the
F-PVA nanofiber membranes under violent ultrasonic treatment and harsh
chemical conditions. Furthermore, vacuum membrane distillation experiments
illustrated that the F-PVA membranes presented a high and stable permeate
flux of 25.2 kg/m<sup>2</sup>h, 70% higher than those of the commercial
PTFE membranes, with satisfied permeate conductivity (<5 μm/cm)
during a continuous test of 16 h (3.5 wt % NaCl as the feed solution,
and feed temperature and permeate pressure were set as 333 K and 9
kPa, respectively), suggesting their great potentials in myriad MD
processes such as high salinity water desalination and volatile organiccompounds
removal