Environmental Engineering Reference
In-Depth Information
with alginate and CNTs can be overcome by formation of calcium alginate/multi-
walled carbon nanotubes (CA/MWCNTs) composite fiber. As defined in our labo-
ratory, CA/MWCNT composite fiber was prepared using CaCl
2
as cross-linking
agent by wet spinning. The composite fiber not only makes full use of the heavy
metals and dyes adsorption properties of alginate and MWCNTs, but also pre-
vent MWCNTs from breaking off the composites to cause second micro pollution
to water. Such technique is also a practical approach to overcome the high cost
difficulty encountered in the use of CNTs for environmental remediation. Inre-
cent work, the adsorption properties for methylene blue (MB) and methyl orange
(MO) organic dyes on CA/MWCNT composite fiber were characterized by using
batch adsorption method. For preparation of SA/MWCNT dispersions, usually
SA was dissolved in distilled water to produce a viscous solution with the con-
centration of 3 wt.% SA after mechanical agitation for 4 h at ambient temperature
and continue stirring for30 min at 50°C. Then different amount of MWCNTs were
added into SA solution under constant stirring for 30 min at room temperature and
then ultrasonic 15 min to achieve homogeneous dispersion. Preparation of CA/
MWCNT composite fibers Spinning dope was prepared for different concentra-
tions of nanotube and SA. A narrow jet of spinning solution was injected through
a 0.5 mm diameter needle into a coagulation bath containing a 5 wt.% aqueous
solution of CaCl
2
, and then collected on a spindle outside the bath, which was
rotated. The coagulated fibers were then washed several times with deionized
water and then dried in air under tension. The CA/MWCNT biocomposite fibers
obtained had a linear-density of about 50 dtex. A novel material, the CA/MW-
CNTs composite fiber as an effective bio adsorbent for ionic dyes removal has
been prepared. The adsorbent toward ionic dyes has higher adsorption capacity
due to the introduction of MWCNTs and the large specific area of fiber form of
the composite. Batch adsorption experiments showed that the adsorption process
followed second-order kinetic model. The results suggested that the initial pH
value is one of the most important factors that affect the adsorption capacity of the
dyes onto CA/MWCNTs. The desorption experiments showed the percentage of
the desorption were found to be 79.7% and 80.2% for MB at pH2.0 and MO at pH
13.0, respectively, which were corresponding to the adsorption experiments. The
CA/MWCNT composite fiber can be used as environment friendly bio adsorbent
for the removal of ionic dyes from aqueous solution due to the efficient and fast
adsorption process.
One effective method to resolve the second pollution caused by CNTs is to
search for suitable supporters to immobilize CNTs for preparing macroscopic
CNTs composites in order to make full use of the current microsized CNTs. Al-
ginate, the salt of alginic acid, has hydrophilicity, biocompatiblity, non-toxicity,
exceptional formability and is a linear chain structure of guluronic acid (G) resi-
dues arranged in a block wise fashion. It has a high affinity and binding capacity
for metal ions and has already been widely used as heavy metal adsorbent
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