2 research outputs found
Heat-Treated Polyacrylonitrile (PAN) Hollow Fiber Structured Packings in Isopropanol (IPA)/Water Distillation with Improved Thermal and Chemical Stability
In this study, polyacrylonitrile
(PAN) hollow fiber membrane (HFM)
was heat-treated by muffle furnace to strengthen the thermal and chemical
stability. Membrane morphology with different materials was characterized
by scanning electron microscopy (SEM). It has shown that both porosity
and pore size decreased with increasing heat treatment time (<i>t</i> = 0.5, 6, 12 h) and temperature (<i>T</i> =
200, 250, 300, and 350 °C). FTIR was used to explore the change
of chemical bonds and found that dehydrogenation, cyclization, and
cross-linking reactions occurred in thermal treatment. Compared with
original PAN membrane, the hydrophobicity of heat-treated membranes
was obviously improved. The heat-treated membrane PAN-250-6 (PAN–temperature–duration)
was selected and immersed in various boiling solvents for 24 h to
test material stability. PAN-250-6 membrane presented excellent thermal
and chemical stability especially in strong solvent, <i>N</i>,<i>N</i>-dimethylacetamide (166.1 °C), whereas original
PAN membrane was dissolved completely. For comparison, PAN and PAN-250-6
HFMs were further chosen for packing modules, which were used for
the distillation of isopropanol–water solution. During 10 days
of operation, module PAN-250-6 showed high separation efficiency with
comparatively low height of mass transfer unit (HTU) and larger overall
mass transfer coefficients in the ranges of 0.1–0.18 m and
2.5–3.2 cm/s respectively. By analyzing the impact of wetting
condition on mass transfer, it was found that membrane resistance
should be sensitive and attributed more to the change of the overall
resistance. The membrane with better hydrophobicity after heat treatment
was more conducive to distillation with HFMs. With superior thermal
and chemical stability in distillation, this kind of heat-treated
hollow fiber structured packing will be promising in future distillation
applictions
Facile Synthesis of Mesoporous Reduced Graphene Oxide Microspheres with Well-Distributed Fe<sub>2</sub>O<sub>3</sub> Nanoparticles for Photochemical Catalysis
In this study, we report the fabrication of hollow reduced
graphene oxide microspheres with well-distributed Fe<sub>2</sub>O<sub>3</sub> nanoparticles (Fe-rGOS) via a spray-drying methodology. l-Ascorbic acid was employed to reduce graphite oxide (GO) and
improve velocity of electrons transfer. Because of l-ascorbic
acid and the spray-drying procedure, the in situ Fe<sub>2</sub>O<sub>3</sub> nanoparticles with a mean size of 5–10 nm were uniformly
deposited on rGO support and the rGO migrated to the surface of the
drop to form microspheres. The well dispersed nanoparticles not only
generated more active sites and interface contact which was beneficial
to enhance the stability of catalysts but also acted as pillars between
the rGO layers to achieve mesoporous structure. The formed mesoporous
frameworks enhanced mass transfer to a large extent and led to the
much better catalytic efficiency. Therefore, the prepared Fe-rGOS
exhibited a remarkable photocatalytic activity in a wide pH range
and superior recyclability with low leaching of iron ions