Environmental Engineering Reference
In-Depth Information
(a)
(b)
FIGURE 20.10
SEM micrographs for: cellulose-
g
-oxolane-2,5-dione nanoibers (a) and cellulose nanoibers (b).
(a)
(b)
(c)
2 µm*
200 nm*
200 nm*
FIGURE 20.11
SEM micrographs of electrospun chitosan: (a) chitosan/PAM, (b) chitosan/PAM-
g
-furan-2,5-dione, and (c) chi-
tosan/PAM-
g
-furan-2,5-dione nanoibers.
Those of chitosan/PAM were also obtained (Figure 20.11). The average iber diameter
was calculated at 186 nm.
20.4.3 Application of Nanofibers in Trace Metals Removal
The functionalized cellulose and chitosan nanoibers showed enhanced removal of trace
metals in natural water polluted with heavy metals. The grafted functional groups of
oxolane-2,5-dione and furan-2,5-dione have charged sites onto which the divalent metal
cations are exchanged. Undetectable metal ions are adsorbed in these materials and when
eluted with suitable acids like dilute nitric acid can be measured and their levels in the
natural water determined. The desorption of the adsorbed metal ions regenerates the
nanoibers allowing for continuous use up to ive cycles.
20.5 Challenges
Among the properties that make clay a suitable heavy metal adsorbent is the high spe-
ciic surface area. However, this property is suppressed by embedding the clay particles
in a polymer despite the fact that surface area is an important parameter in adsorption
