Chitosan-based Materials in Waste Water Treatment––Recent Developments - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 27

acidic solutions. The strong electrostatic attraction between the-NH 3 + of chitosan and
anionic dye can be used to explain the high adsorption capacity (Ming Shen Chiou et al.,
2004). Chitosan bead is a good adsorbent for the removal of Congo red from its aque-
ous solution and 1 g of chitosan in the form of hydro gel beads can remove 93 mg of
the dye at pH 6 (Sandi pan Chatterjee et al., 2007).
Membrane
Membranes and membrane processes were first introduced as an analytical tool in
chemical and biomedical laboratories; they developed very rapidly in to industrial
products and methods with significant technical and commercial impact. Today, mem-
branes are used on a large scale to produce potable water from sea and brackish water,
to clean industrial effluents and recover valuable constituents, purity and to separate
gases, and vapor in petrochemical process (Baker, 2004; Bhattacharya and Misra,
2003).
Muzzarelli reported a decrease in the metal ion sorption efficiency of chitosan
membranes compared to chitosan flakes and attributed this effect to a decrease in
contact surface, despite the thickness of the membrane (Muzzarelli, 1974). Krajewska
prepared chitosan gel membranes and extensively characterized their diffusion proper-
ties (Krajewska, 1996). The permeability of metal ions through these membranes was
measured, Cu < Ni < Zn < Mn < Pb < Co < Cd <Ag (Krajewska, 2001).
Cross-linked chitosan membranes with epichlorohydrin have been proposed to im-
prove pore size, distribution, mechanical resistance, chemical stability, and adsorption
properties (Beppu et al., 2004; Vieira et al., 2006; Wan Ngah et al., 2002). The maxi-
mum Cr adsorption capacity occurred in epichlorohydrin-cross-linked chitosan at pH
6 (Baroni et al., 2007). The removal of divalent metal ions including Cu(II), Co(II),
Ni(II), and Zn(II) from aqueous solutions by chitosan enhanced membrane filtration
was studied. At neutral condition the removal of Cu(II) was more efficient compared
to other metals (Ruey Shin Juang, 1999).
Flakes
Chitosan, a polymer of biological origin has been reported to be an effective adsorbent
for Cr(VI) removal from wastewater (Ramnani, 2006; Rojas, 2005; Schmuhi, 2001).
Cr(VI) removal ratio was optimized by surface response methodology. Accordingly a
maximum of 92.9% Cr(VI) removal was attained at pH 3 with 13 g/l chitosan flakes
from a solution initially concentrated as 30 mg/l (Yasar Andelib Aydin and Nuran
Deveci Aksoy, 2009).
Maruca used chitosan flakes of 0.4-4mm for the removal of Cr(III) from waste-
water. The sorption of arsenate on to chitosan flakes has been studied (Maruca, 1982).
The maximum adsorption capacity occurs at an initial pH 3.5 (Katrina et al., 2009).
Chitosan was chemically modified by introducing xanthate group onto its backbone
using CS 2 under alkaline conditions. The chemically modified chitosan flakes was
used as an adsorbent for the removal of Cd ions from electroplating waste effluent
under laboratory conditions. The maximum uptake of Cd was found to be 357.14 mg/g
at an optimum pH of 8 where as for plain chitosan flakes it was 85.47 mg/g (Divya
Chauhan and Nalini Sankararamakrishnan, 2008).