Nanoscale Porous Materials for Water Treatment: Advances and Challenges - Nanotechnologies for Water Environment Applications - page 320

adsorbed on thiol-functionalized SBA-15 (Aguado et al., 2008) . The mercury
adsorption on the thiol-functionalized mesoporous silicas has been intensively studied
(Mercier and Pinnavaia, 1998; Brown et al., 2000; Nooney et al., 2001; Fryxell et al.,
2005). Yoshitake et al., (2002) reported the formation of almost a monolayer of Si-CH 2 -
CH 2 -CH 2 -SH was followed by bridging of Hg-O-Hg units at sulfur atoms. The
mesoporous silica materials containing functionalized mono-layers were extremely
efficient in removing mercury and other heavy metals. It was also reported that the
mesoporous silica material containing functionalized organic monolayers removes 100
mg mercury per gram of material (Feng et al., 1997; Chen et al., 1999). The self-
assembled monolayers on mesoporous support (SAMMS) has very rapid kinetics and a
high Hg distribution coefficient, K d of 10 5 ml/Kg of removal, which is ~3 orders of
magnitude higher than that of GT-73 resin.
Figure 11.2 (A) Schematic representation of MCM-41 pore-expansion, selective
extraction, and calcination. (B) The corresponding pore size distributions (Sayari et al.,
2005)
Similarly, Thiol- and amino-functionalized SBA-15 silicas with uniform
mesoporosities were prepared and employed for removing heavy metal ions from
wastewater. The thiolated SBA-15 adsorbent exhibited a higher complexation affinity
for Hg(II), while the other metal ions (Cu 2+ , Zn 2+ , Cr 3+ and Ni 2+ ) showed exceptional
binding ability with its aminated analogue (Liu et al., 2000). They also reported that
SBA 15 has higher hydrothermal stability, a higher surface area and a uniform pore size,
and hence, it can be applied for broad application.