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Green Synthesis of Magnetic EDTA- and/or DTPA-Cross-Linked Chitosan Adsorbents for Highly Efficient Removal of Metals
The present paper describes a green
and economic approach to explore
EDTA/DTPA-functionalized magnetic chitosan as adsorbents for the removal
of aqueous metal ions, such as CdÂ(II), PbÂ(II), CoÂ(II), and NiÂ(II).
EDTA and DTPA play roles not only as cross-linkers but also as functional
groups in chelating metal ions. The morphology, structure, and property
of the magnetic adsorbents were characterized by SEM, TEM, XRD, EDS,
FT-IR, TGA, and VSM techniques. Their adsorption properties for the
removal of metal ions by varying experimental conditions were also
investigated. The kinetic results revealed that the transportation
of adsorbates from the bulk phase to the exterior surface of adsorbents
was the rate-controlling step. The obtained maximum adsorption capacities
of magnetic adsorbents for the metal ions ranged from 0.878 to 1.561
mmol g<sup>–1</sup>. Bi-Langmuir and Sips isotherm models fitting
well to the experimental data revealed the surface heterogeneity of
the adsorbents. More significantly, the resulting EDTA-/DTPA-cross-linked
magnetic chitosan adsorbents had selectivity to Cu, Pb, Zn, Fe, and
Ni from a practical industrial effluent. Furthermore, their good reusability
and convenient magnetic separation makes them viable alternatives
for real wastewater treatment