Chitosan and Chitosan Derivatives as Chelating Agents - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 10

Another adsorption study was conducted for the two new chitosan derivatives that
have been prepared from the reaction of cinnamoyl chloride (ChitoCin) and cinnamoyl
isothiocyanate (ChitoThioCin) with chitosan. The modified chitosans were character-
ized to confirm their structures. The metal uptake capacity of the two polymers was
measured at different pH values as well as under competitive and non-competitive
conditions. At pH 5.6, the (ChitoCin and ChitoThioCin) polymers exhibited higher
capacity for Cu(II) (0.461-0.572 mmol/g) than the other metal ions used; the capaci-
ties of the other metal ions are: Fe(III) (0.235-0.341 mmol/g), Cr(III) (0.078-0.099
mmol/g), Co(II) (0.046-0.057 mmol/g) and Ni(II) (0.041-0.053 mmol/g). Two ab-
sorption isotherms were examined for the absorption of metal cations with these two
modified chitosan and it was found that the adsorption mechanism fits the Langmuir
isotherm better than the Freundlich one.
Chitosan sorbents, cross-linked and grafted with amido or carboxyl groups, were
also prepared and their sorption properties for Cu(II) and Cr(VI) uptake were studied
(Kyzas et al., 2009). Equilibrium sorption experiments were carried out at different pH
values and initial ion concentrations. The equilibrium data were successfully fitted to
the Langmuir-Freundlich (L-F) isotherm. The calculated maximum sorption capacity
of the carboxyl grafted sorbent for Cu(II ) was found to be 318 mg/g at pH 6, while
the respective capacity for Cr(VI) uptake onto the amido-grafted sorbent was found to
be 935 mg/g at pH 4.
metal ion adsorption of other Chemically modified Chitosans (Chitosan
derivatives)
The synthesis and chelating properties of chitosan-based polymers has attracted the
attention of several research groups. A number of publications pertaining to the sub-
ject have appeared in the literature. Oshita and coworkers (Oshita et al., 2009) have
prepared cross-linked chitosan resins with catechol, iminodiacetic acid (IDA-type
chitosan), iminodimetylphosphonic acid (IDP-type chitosan), phenylarsonic acid
(phenylarsonic acid-type chitosan), or serine (serine-type chitosan) for the collec-
tion and concentration of uranium(VI). The adsorption behavior of U(VI) and other
ionic species, such as metal ions and oxo-acid ions, on the cross-linked chitosan (base
material) and chitosan resins modified with chelating moieties was investigated us-
ing a column procedure. They discovered that the adsorption ability for U(VI) was
in the order: catechol-type chitosan (type 2) > serine-type chitosan > phenylarson-
ic acid-type chitosan > the others. They concluded that the catechol-type chitosan
was useful for the collection and concentration of uranium(VI). In addition, Katarina
et al. (2009) have synthesized a high-capacity chitosan-based chelating resin, N-(2-hy-
droxyethyl)glycine-type chitosan, using chloromethyloxirane (CMO) as a cross-linker
and as coupling arms and hydroxylethylamine and bromoacetic acid as a synthesizer
for the N-(2-hydroxyethyl)glycine chelating moiety. The CMO could bind with both
of hydroxyl and amino group of the chitosan resin, and then couple with the chelat-
ing moiety. They have found that most transition and rare-earth metals could adsorb
quantitatively on the resin at wide pH ranges and could be separated from alkaline and
alkaline-earth metals. The resin was packed in a mini-column (40 mmlength×2 mm
i.d.) which was installed in a Multi-Auto-Pret system. The Multi-Auto-Pret system