Sponge-like xanthate-modified chitosan
with a three-dimensional
network macroporous structure was prepared using a facile one-pot
approach. The as-prepared adsorbent possessed remarkable adsorption
capacity and excellent mechanical property as well as rapid and intact
separation performance. Adsorption properties of Pb(II), Cd(II), Ni(II),
and Zn(II) on xanthate-modified chitosan sponge (XCTS) were systematically
investigated in single and multiple systems. The experimental data
for each heavy metal adsorption well fitted to the pseudo-second-order
kinetic model and Langmuir isotherm model. The maximum adsorption
capacities of Pb(II), Cd(II), Ni(II), and Zn(II) were 216.45, 92.85,
45.46, and 41.88 mg/g, respectively. The mutual interference effects
of heavy metals in multiple systems were investigated using the inhibitory
effect and equilibrium adsorption capacity ratios. The results indicated
that the coexisting metal ions had a synergistic promoting effect
on Pb(II) adsorption. The competitive adsorption behaviors of Pb(II)
in multiple systems were successfully described by the Langmuir and
Langmuir competitive models. The adsorption capacity of Pb(II) in
multiple systems was higher than that in single system while those
of Cd(II), Ni(II), and Zn(II) had a significant decrease in multiple
systems, especially for Ni(II) and Zn(II). It turned out that Pb(II)
could be effectively removed from an aqueous solution in the presence
of Cd(II), Ni(II), and Zn(II), whereas the removal of Cd(II), Ni(II),
and Zn(II) would be restrained by the presence of Pb(II). The high
selective factor and physicochemical properties of these studied heavy
metals revealed the selective adsorption sequence: Pb(II) > Cd(II)
> Ni(II) > Zn(II). The characteristic analyses showed sulfur
and nitrogen
atoms participated in the heavy metal adsorption. The interaction
mechanism between Pb(II) and coexisting metal ions could be attributed
mainly to the direct displacement effect
