Chitosan and Chitosan Derivatives as Chelating Agents - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 7

CSMO were regenerated with an efficiency of greater than 84% using 0.01-0.1 methy-
lendiamine tetraacetic acid (EDTA). These results could encourage researchers to use
the cross-linked magnetic CSMO resin in water and wastewater treatment (Monier
et al., 2010b).
metal ion adsorption on Chitosan-Phosphate derivatives
Tri-polyphosphate has been selected as a possible cross-linking agent, which can be
used for the preparation of chitosan gel beads by the coagulation/neutralization effect
(Mi et. al., 1999a, 1999b; Monier et al., 2010b). Chitosan-tripolyphosphate (CTPP)
beads were synthesized, characterized and used for the adsorption of Pb(II) and Cu(II)
ions from aqueous solutions. The experimental data were correlated with the Lang-
muir, Freundlich and Dubinin-Radushkevich isotherm models. The maximum adsorp-
tion capacities of Pb(II) and Cu(II) ions in a single metal system based on the Lang-
muir isotherm model were 57.33 and 26.06 mg/g, respectively. However, the beads
showed higher selectivity towards Cu(II) over Pb(II) ions in the binary metal system.
The kinetic data were evaluated based on the pseudo-first and -second order kinetics
and intraparticle diffusion models and showed that this adsorption obeyed the pseudo-
second order kinetic model, whereby intraparticle diffusion was not the sole rate con-
trolling step. A desorption study was also carried out to show that Pb(II) and Cu(II)
ions adsorbed on the beads can be easily and effectively desorbed using 0.1, 0.01,
and 0.001 M EDTA solution. Infrared spectra were used to elucidate the mechanism
of Pb(II) and Cu(II) ions adsorption onto CTPP beads and revealed that the nitrogen
and oxygen atoms found in the beads were the binding sites for the metal ions. This
new chitosan derived beads might be used to treat wastewaters containing Pb(II) and
Cu(II) ions (Ngah and Fatinathan, 2010). Similarly, Laus R. and his group prepared
chitosan (CTS) cross-linked with both epichlorohydrin (ECH) and triphosphate (TPP),
by covalent and ionic cross-linking, respectively. The new CTS-ECH-TPP adsorbent
was characterized and its adsorption and desorption of Cu(II), Cd(II) and Pb(II) ions in
aqueous solution were investigated. It was discovered that the adsorption is dependent
on the solution pH, and the optimum pH values for the adsorption were 6.0 for Cu(II),
7.0 for Cd(II) and 5.0 for Pb(II). The kinetics study demonstrated that the adsorption
process proceeded according to the pseudo-second order model. The three isotherm
models (Langmuir, Freundlich, and Dubinin-Radushkevich) used in the study men-
tioned above were also employed in the analysis of the adsorption equilibrium data.
The Langmuir model resulted in the best fit and the new adsorbent had maximum
adsorption capacities for Cu(II), Cd(II), and Pb(II) ions of 130.72, 83.75 and 166.94
mgg −1 , respectively. Desorption studies revealed that HNO 3 and HCl were the best
eluents for desorption of Cu(II), Cd(II), and Pb(II) ions from the cross-linked chitosan.
These results suggested that this new adsorbent could be used in the separation, pre
concentration, and Cu(II), Cd(II), or Pb(II) ion uptake from aqueous solutions (Laus
et al., 2010).
metal ion adsorption on edta- and/or dtPa-modified Chitosan derivatives
The adsorption properties of surface modified chitosans with ligands such as ethylene-
diaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA) which