Water security caused by heavy metals
poses a deleterious hazard
to public health and the ecological system. The construction of adsorbents
by polyamidoamine (PAMAM) dendrimers for efficient removal of metal
ions has attracted considerable interest. However, the general method
for the fabrication of these adsorbents was achieved by the surface
chemical modification of the substrates with PAMAM dendrimer, which
usually causes the defects of low density and uneven distribution
of the dendrimer, the blocking of pores, and reducing the adsorption
performance. Hence, the development of a new method for preparation
of PAMAM dendrimer-based adsorbent to realize the efficient and enhanced
adsorption of metal ions is still a challenge. Herein, methylisothiocyanate
decorated PAMAM dendrimer/mesoporous silica composites (G0-S-1/x, G1.0-S-1/x, G2.0-S-1/x, x = 2, 4, 6, 8, 10) were synthesized by the direct
sol–gel reaction of alkoxysilyl-containing functional PAMAM
dendrimer. The adsorbents display enhanced adsorption property for
Hg(II) and Cd(II) as compared with the same adsorbents which were
prepared by traditional chemical modification method. Take G2.0-S-1/2
as an example, the maximum adsorption capacities are 2.41 and 0.87
mmol·g–1 for Hg(II) and Cd(II), respectively
. Moreover, the adsorbents show excellent selective adsorption and
regeneration property. G2.0-S-1/2 displays distinct selectivity for
Hg(II) with the presence of Co(II), Pb(II), Cd(II), and Cu(II). The
regeneration percentage still maintains 95.2% after five adsorption–desorption
cycles. The adsorption mechanism is also certified by the experimental
method and theoretical calculation.
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