Chitosan-based Materials in Waste Water Treatment––Recent Developments - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 33

vinyl alcohol foams demonstrated interconnected and open cell structure with large
pore size from tens to hundreds of micrometers and high porosities from 73.6% to
84.3%. Glutaraldehyde was employed to improve the retension of chitosan and copper
adsorption of the chitosan/poly vinyl alcohol foams. While it increased the retension
of chitosan and the adsorption capacities, glutaraldehyde decreased the pore size and
porosity. The macro porous structure of the chitosan/poly vinyl alcohol foams indicate
extensive application prospects in terms of the considerable adsorption of heavy metal
ions (Xiao Wang et al., 2006).
some limitatioNs iN usiNG Natural materials as adsorBeNts
* The adsorption properties of an adsorbent depend on the source of raw materials.
The sorption capacity of chitin and chitosan materials depend on the origin of the
polysaccharide, the degree of N -acetylation, molecular weight and solution properties
and varies with crystallinity, affinity for water, percent deacetylation and amino group
content (Kurita, 2001). These parameters determined by the conditions selected during
the preparation control the swelling and diffusion properties of the polysaccharide and
influence its characteristics (Berger et al., 2004).
*Chitosan-based materials have high affinities for heavy metal ions. Hence chito-
san chelation is a procedure of choice for extraction and concentration techniques in
the removal of heavy metals. However, chitosan has low affinity for basic dyes.
*Pollutant molecules have many different and complicated structures. This is one
of the most important factors influencing adsorption. There is yet little information
in the literature on this topic. Further research is needed to establish the relationship
between pollutant structure and adsorption in order to improve the sorption capacity.
The production of chitosan involves a chemical deacetylation process. Commer-
cial production of chitosan by deacetylation of crustacean chitin with strong alkali
appears to have limited potential for industrial acceptance because of difficulties in
processing particularly with the large amount of waste of concentrated alkaline solu-
tion causing environmental pollution. However, several yeasts and filamentous fungi
have been recently reported containing chitin and chitosan in their cell wall and septa.
They can be readily cultured in simple nutrients and used as a source of chitosan. With
advances in fermentation technology chitosan preparation from fungal cell walls could
become an alternative route for the production of this biopolymer in an ecofriendly
pathway (Crini, 2005).
CoNClusioN
Environmental requirements are becoming of great importance in today's society.
Since, there is an increased interest in the industrial use of renewable resources such
as starch and chitin, considerable efforts are now being made in the research and de-
velopment of polysaccharide derivatives as the basic materials for new applications. In
particular, the increasing cost of conventional adsorbents undoubtedly make chitosan-
based materials one of the most attractive biosorbents for wastewater treatment. Re-
cent and continuing interest in these macro molecules is evident from the number of
papers that appear each year in the literature on this topic.