3.6. Factors influenced the Pb(II) adsorption on the SBA15–0.3NH2
sorbent
In order to elucidate the possible mechanism of Pb(II) removal
from aqueous solutions by adsorption on functionalized siliceous
SBA-15 materials, the effect of initial concentration of Pb(II) ion
adsorption on the most optimized SBA15–0.3NH2 sorbent was
investigated. Initial Pb(II) concentration was adjusted in the ranges
of 100–600 mg/L for adsorption on the functionalized SBA-15 under
natural pH at 30 C for 1 h as shown in Fig. 8. At moderate initial
lead concentration (100–300 ppm) the adsorption of Pb(II) is
high, nearly 90 wt.%), and it remained constant with further increase
in initial lead concentration from 100 to 300 ppm. This result
indicate that the maximum capacity of Pb(II) removal for
functionalized SBA-15 is 90 wt.%, and suggested that the –NH2
groups were readily available and easily accessible probably because
the uniform mesoporous channels of SBA-15-NH2 facilitated
the Pb(II) transportation in the adsorption process. At higher initial
lead concentration (>300 ppm), more Pb(II) was left in solution due
to the saturation of binding site.
Fig. 9 shows the UV–vis adsorption spectra showing the spectral
change upon lead adsorption on SBA15–0.3NH2 from 200 and
400 ppm Pb(II) ions solutions. As seen in this figure, a larger Pb(II)
adsorption on SBA15–0.3NH2 occurs when the water solution contain
a larger Pb(II) ion concentration. The room-temperature electronic
absorption spectra of all sorbents show two bands: an
intense absorption at ca. 210 nm and a less intense feature at ca.
310 nm (Fig. 9) [58]. These transitions contain both ligand-to-metal
charge transfer (N 2p?Pb 6sp) and intra-atomic (Pb 6s2?Pb
6sp) character.
3.6. Factors influenced the Pb(II) adsorption on the SBA15–0.3NH2sorbentIn order to elucidate the possible mechanism of Pb(II) removalfrom aqueous solutions by adsorption on functionalized siliceousSBA-15 materials, the effect of initial concentration of Pb(II) ionadsorption on the most optimized SBA15–0.3NH2 sorbent wasinvestigated. Initial Pb(II) concentration was adjusted in the rangesof 100–600 mg/L for adsorption on the functionalized SBA-15 undernatural pH at 30 C for 1 h as shown in Fig. 8. At moderate initiallead concentration (100–300 ppm) the adsorption of Pb(II) ishigh, nearly 90 wt.%), and it remained constant with further increasein initial lead concentration from 100 to 300 ppm. This resultindicate that the maximum capacity of Pb(II) removal forfunctionalized SBA-15 is 90 wt.%, and suggested that the –NH2groups were readily available and easily accessible probably becausethe uniform mesoporous channels of SBA-15-NH2 facilitatedthe Pb(II) transportation in the adsorption process. At higher initiallead concentration (>300 ppm), more Pb(II) was left in solution dueto the saturation of binding site.Fig. 9 shows the UV–vis adsorption spectra showing the spectralchange upon lead adsorption on SBA15–0.3NH2 from 200 and400 ppm Pb(II) ions solutions. As seen in this figure, a larger Pb(II)adsorption on SBA15–0.3NH2 occurs when the water solution containa larger Pb(II) ion concentration. The room-temperature electronicabsorption spectra of all sorbents show two bands: anintense absorption at ca. 210 nm and a less intense feature at ca.310 nm (Fig. 9) [58]. These transitions contain both ligand-to-metalcharge transfer (N 2p?Pb 6sp) and intra-atomic (Pb 6s2?Pb6sp) character.
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