In this work, we reported a nitrogen-doped
porous carbon (NPC)
that was prepared from waste polyurethane (PU) foams through hydrothermal
carbonization and further activation. The possible reactions occurred
during the hydrothermal carbonation and activation process of waste
PU were proposed based on the results of gas chromatography–mass
spectrometry and thermogravimetric Fourier transform infrared. Hydrothermal
carbonization significantly improved the porous structure and surface
N-containing active groups on carbon. The specific surface area and
the total pore volume were obtained at 1419 m2/g and 0.80
cm3/g, respectively, for porous carbon prepared under 200
°C for 6 h, which were much higher than those without hydrothermal
carbonization (1100 m2/g and 0.66 cm3/g). Moreover,
the nitrogen contents on the porous carbon increased from 1.4 to 2.8
wt % with the majority of pyridinic and pyrrolic N species. The saturated
sulfur capacity of NPC reached as high as 205.06 mg/g, which was almost
2.5 times higher than that without hydrothermal carbonization. The
desulfurization performance could be tightly related to the hierarchical
porous structure and active nitrogen species on the carbon induced
by hydrothermal carbonization/catalysis. Thus, our current efforts
provide a facile strategy for the preparation of porous adsorbent
for H2S removal with the low cost and high efficiency.
Developing a membrane material with
both high CO2 permeability
and high CO2/N2 selectivity is always desired
for CO2 capture, while improving the sustainability of
the membrane preparation process is of equal importance. In the current
work, a nanocellulose crystal (CNC) was blended with hydrophilic Pebax
1657 for CO2 separation application. The CO2/N2 separation performance of Pebax 1657/CNC hybrid membranes
with up to 40 wt % CNC was evaluated by mixed-gas permeation tests
under both dry and humid conditions. The humid test condition simultaneously
increases CO2 permeability and CO2/N2 selectivity of all CNC/Pebax hybrid membranes compared to those
under dry conditions. Introduction of only 5 wt % CNC into Pebax 1657
realizes 42 and 18% increments in CO2 permeability (305.7
Barrer) and CO2/N2 selectivity (41.6), respectively.
However, further increasing the CNC loading increases the tortuosity
of the membrane and results in the self-assembly of CNC in the Pebax
matrix, which is observed by SEM, thus leading to both reduced gas
permeability and CO2/N2 selectivity. The CO2/N2 separation results of 5 wt % CNC/Pebax locate
close to Upper Bound 2008, showing its potential as a CO2/N2 separation membrane material.
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