Nanoscale Porous Materials for Water Treatment: Advances and Challenges - Nanotechnologies for Water Environment Applications - page 324

area (> 200 m 2 /g) porous material. Due to its very high porosity, AA is widely used as
adsorbents for filtering contaminants in drinking water. AA is also used for adsorption
of a wide range of contaminants and catalyst applications. In general, conventional AAs
have ill-defined pore structures, and thus, have low adsorption capacities and act in a
kinetically slow manner. It is well known that an ideal adsorbent should have uniformly
accessible pores, an interlinked pore system, a high surface area, and physical and/or
chemical stability. To meet this requirement, several research groups are actively
developing a variety of techniques to improve AA's porous structure and efficiency.
Table 11.5 summarizes some of the recent development on Alumina-related NPM that
are applied for water treatment.

Contaminants

Hg Cr(III) Cd Ni PNP Actinides TCE - -

1.6

1200

1.4

1000

1.2

800

1.0

600

0.8

0.6

400

Surface Area

0.4

Maximum Adsorption Capacity
(mM-adsobate/g-adsorbant)

200

0.2

SiNPM-1 SiNPM-2 SiNPM-3 SiNPM-4 SiNPM-5 SiNPM-6 SiNPM-7 --

Types of Silica based adsorbents

Figure 11.3 A plot showing different silica based adsorbents with its surface area and its
effect on different contaminants removal. SiNPM-1: mesopores Si functionalized with 3-
mercaptopropyltrimethoxysilane ligands, SiNPM-2: phosphonic acid functional
adsorbent, SiNPM-3: NH2-MCM-41, SiNPM-4: NH2-MCM-41, SiNPM-5:
Cyclodextrin-Silica Nanocomposites (with 0.8% Cyclodextrin), SiNPM-6:
Hydroxypyridinone-mesoporous-Silica, SiNPM-7: Hexagonal (MCM-41) mesoporous
materials.