Biomedical Engineering Reference
In-Depth Information
make chitosan one of the most attractive materials for wastewater treatment (Babel
and Kurniawan, 2003).
Chitosan can easily be modified by chemical or physical processes to prepare chi-
tosan derivatives. These processes may be used for controlling the reactivity of the
polymer (improving the affinity of the sorbent for the metal, changing the selectiv-
ity series for sorption, changing the pH range for optimum sorption) or enhancing
sorption kinetics (controlling diffusion properties, for example) (Guibal, 2004). Eric
Guibal et. al. (2006b) has published a review on the use of chitosan for the removal of
particulate and dissolved contaminants and concluded that chitosan was very efficient
at removing particulate and dissolved contaminants through coagulation-flocculation
processes involving several mechanisms such as charge neutralization, precipitative
coagulation, bridging, and electrostatic patch. Combining these processes (as a func-
tion, for example, of pH conditions) enables the design of competitive procedures
for the treatment of wastewaters or pre-treatment of potable water. They have also
concluded that chitosan offers a promising alternative to the use of mineral reagents
(alum salts, ferric salts) or synthetic polymers. The use of a polymer of biological
origin, coming from a renewable resource, biodegradable, and thus less aggressive for
final discharge in the environment (sludge landfill, dispersion in the aqueous phase
of residues) is an important criterion for future developments. Its attractiveness as an
analytical reagent arises from the fact that it can offer simple and inexpensive deter-
minations of various organic and inorganic substances (Cimerman et al., 1997). The
insertion of functional groups in the chitosan matrix may improve their capacity for
interaction with metallic ions by complexation, thereby increasing their adsorption
properties (Hall and Yalpani, 1980; Krishnapriya and Kandaswamy, 2010; Rodrigues
et al., 1998). Also, according to Pearson's hard and soft acid-base theory, polymers
containing functional groups with N or S donor atoms should be promising as sorbents
of precious metal ions; some published research papers have demonstrated this view-
point (Aydin et al., 2008; Fujiwara et al., 2007; Hubicki et al., 2007; KaƂedkowski and
Trochimczuk, 2006).
Heavy metal is a general collective term that applies to the group of metals and
metalloids with an atomic density greater than 4 g/cm 3 . Heavy metals include lead,
cadmium, zinc, mercury, arsenic, silver, chromium, copper, iron, and the platinum
group elements (Negm and Ali, 2010). Contamination of aquatic media by heavy
metals is a serious environmental problem, mainly due to discard of industrial waste
(Prasad et al., 2002; Reddad et al., 2002). Heavy metals are highly toxic at low con-
centrations and can accumulate in living organisms, causing several disorders and
diseases (Bailey et al., 1999; Gotoh et al., 2004; Sag and Aktay, 2002). Environmental
pollution is defined as the presence of a pollutant in the environment (air, water, and
soil) that may be poisonous or toxic and will cause harm to living things in the polluted
environment (Kotrba and Ruml, 2000). Environmental pollution by heavy metals is
very prominent in areas of mining and at old mine sites, and pollution decreases with
increasing distance away from the mining sites (Peplow, 1999).
 
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