Civil Engineering Reference
In-Depth Information
magnetic separation for the removal and recovery of Cr (VI) from waste-
water. Chang
et al.
(2006) prepared the magnetic chitosan nanoparticles
with an average diameter of 13.5 nm as a magnetic nano-adsorbent. Mag-
netic chitosan nano-adsorbent was shown to be quite effi cient for the fast
removal of Co (II) ions at the pH range of 3-7 and the temperature range
of 20-45°C.
Ngomsik
et al.
(2006) have studied the removal of nickel ions from the
aqueous solution using magnetic alginate microcapsules. Also, magnetic
particles in the microcapsules allowed easy isolation of the microcapsule
beads from aqueous solutions after the sorption process. Mayo
et al.
(2007)
also studied the effect of particle sizes in the adsorption and desorption of
As (III) and As (VI). Different kinds of magnetic nanoparticles were also
employed for the removal of organic pollutants, such as sorption of methy-
lene blue on polycyclic acid-bound iron oxide from an aqueous solution
(Mak and Chen, 2004).
16.5 Synthesis of nanomaterials
There are a number of techniques available to fabricate different nanoma-
terials (Tiwari
et al
., 2008). Nanoparticles can be produced from larger
structures (top-down) by use of ultrafi ne grinders, lasers and vapourization
followed by cooling. For complex particles, nanotechnologists generally
prefer to synthesize nanostructures by a bottom-up approach by arranging
molecules to form complex structures with new and useful properties. The
detailed views on different synthesis routes is beyond the scope of this
chapter and hence they are listed below with references:
layer-by-layer deposition (Philips
et al.
, 2006)
self-assembly (Graveland and Kruif, 2006; Lorenceau
et al.
, 2005)
gas phase synthesis and sol-gel processing (Siegel, 1991, 1994; Uyeda,
1991)
crystallization (Boanini
et al.
, 2006)
microbial synthesis (Bhainsa and Souza, 2006; Bhattacharya and Gupta,
2005)
other methods (sonochemical processing, cavitation processing, micro-
emulsion processing and high-energy ball milling).
16.6 Nanotechnology: health, safety
and environment
Nanotechnology is a potential provider of unprecedented technological
solutions to many environmental problems including climate change, pol-
lution and clean drinking water. It is claimed that it enables economic
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