Environmental Engineering Reference
In-Depth Information
CHAPTER 11
Advances and Challenges
Sushil Raj Kanel and Dhriti Nepal
Micro and mesoporous materials have been a great focus of scientific and
technological interest from almost half of the century. This is due to its large surface
area and extremely high porosity which offers huge potential for its application in a
variety of fields, ranging from materials science to biomedical research. International
Union of Pure and Applied Chemistry (IUPAC) has classified porous materials into 3
groups (Davis, 2002): (a) Microporous materials (MiPMs), having pore diameters less
than 2 nm; (b) mesoporous materials (MePM), having pore diameters ranging from 250
nm; and (c) macroporous materials (MaPM), having pore diameters larger than 50 nm.
The term nanoporous materials (NPM) have been used for those porous materials with
pore diameters of < 100 nm. Hence, the NPM is defined as a material having a pore size
< 100 nm of any solid structural components whether or not the structure itself is nano
size (i.e., < 100 nm). Hence, it covers porous materials lies in MiPMs, MePM and
MaPM. Table 11.1 summarizes the classification of porous materials based on pore size.
The NPM have strong influence on environmental research, especially in the
field of water treatment, due to its extremely good catalytic properties and high
reactivity. This is mainly due to their small pore size and high surface area. Nevertheless,
synthesis of chemical structures with exceptionally high surface areas and controlled
pore sizes is still a great challenge in material research. This rapidly growing field has
made tremendous achievement. For example, until now, the highest surface area has
been obtained for a disordered structure of carbon 2,030 m
2
/g; (Nijkamp et al., 2001),
904 m
2
/g in the case of zeolite Y (Chester et al., 2000) and 4,500 m
2
/g
for
Zn oxide
derivatives (Chae et al., 2004). Recent breakthrough on environmental application of
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