Environmental Engineering Reference
In-Depth Information
(a)
(b)
12
7
Crosslinked PA A/PVA without MWCNTs
Crosslinked PA A/PVA with MWCNTs
ZVI NP-immobilized PAA/PVA mat without MWCNTs
ZVI NP-immobilized PAA/PVA mat with MWCNTs
6
10
5
8
4
6
3
4
2
2
1
0
0
0
10
20
30
Strain (%)
40
50
60
0
10
20
30
Strain (%)
40
50
60
figure 6.4
Typical stress-strain curves of nanofibrous mats. (a) Cross-linked PAA/PVA nanofibrous mats with and without MWCNTs;
(b) ZVI NP-immobilized nanofibrous mats with and without MWCNTs. reproduced with permission from ref. [13]. © royal Society
of Chemistry.
ZVI NPs according to the procedures described earlier [14]. Typical stress-strain curves (Figure 6.4) show that the mechanical
properties of the electrospun nanofibrous mats with and without ZVI NP immobilization were significantly enhanced even with
only 1.0 wt% MWCNTs incorporated within the nanofibers [13, 19].
6.4.2
bimetallic iron-based Nps
due to the metastability and easy oxidation of ZVI NPs, their capability to remediate environmental pollutants is limited.
Therefore, synthesis of iron-based bimetallic NPs could be an effective way to maintain the reactivity of ZVI NPs. In our
recent work, we investigated the feasibility of using electrospun PAA/PVA nanofibers as a nanoreactor to prepare bimetallic
Fe/Pd NP-immobilized composite nanofibers [69]. In our approach, the cross-linked PAA/PVA nanofibrous mats were dipped
in an aqueous ferric trichloride solution to allow Fe
3+
to complex with available free carboxyl groups of PAA through ionic
exchange, followed by reduction via NabH
4
to form ZVI NPs. These ZVI NP-containing nanofibrous mats were then immersed
into a solution of palladium chloride. Then, bimetallic Fe/Pd NPs were finally formed by a replacement reaction due to the
high metal activity of Fe than that of Pd. The mean diameter of the Fe/Pd NPs was estimated to be 2.8 ± 0.92 nm. Elemental
analysis of the Fe/Pd NP-immobilized nanofibers demonstrated that the Fe and Pd loading percentages were 19.44 and
2.44 wt%, respectively.
6.4.3
other Metal Nps
besides the immobilization of metal iron-based NPs within and/or on the surface of polymer nanofibers, other noble metal NPs
are also capable of being immobilized. recently, we reported the formation and immobilization of Au NPs into electrospun
nanofibers through in situ reduction [70, 71]. In brief, freshly prepared polyethyleneimine (PEI)/PVA nanofibrous mats were
cross-linked under glutaraldehyde (gA) vapor to render them water-stable. Then, the cross-linked PEI/PVA nanofibrous mats
were immersed into an aqueous solution of HAuCl
4
to allow AuCl
4
-
ions to complex with the free amine groups of PEI via ionic
exchange, and the Au NPs were finally formed by reducing the complexed AuCl
4
−
with NabH
4
. SEM morphology observation
shows that the Au NP-immobilized nanofibrous mats retain a uniform and porous structure, similar to the cross-linked electro-
spun PEI/PVA nanofibers without Au NPs. Cross-sectional TEM images show that the Au NP-immobilized PEI/PVA nanofi-
bers have round-shaped patterns of Au NPs that are uniformly distributed within the cross section of the fibers with a mean
diameter of 11.8 ± 3.3 nm. Energy-dispersive spectroscopy and Fourier transform infrared spectroscopy characterization further
demonstrated the successful immobilization of Au NPs within the nanofibers.
