facilitate more surface area and a fine porous structure which has a large number of
functional groups.
Some biomaterials like plant and animal tissues require a series of preliminary
processing to make them more available as biosorbents. Properties of adsorbents
depend on the raw material selected and the activation process applied. The physical
and chemical treatments for the activation of adsorbent have effects on the properties
of the adsorbents. Certain biomass has adsorption capacity higher than commercially
available activated carbon, ion exchange resins and zeolites.
The following criteria should be considered while selecting a biosorbent for the
biosorption process:
1. The biosorbent should be less expensive.
2. It should be reusable and the regeneration process should be less tedious.
3. Kinetics of the adsorption should be fast.
2.1 Physical Characteristics
2.1.1 Pore Size and Surface Area
IUPAC has classified the pores into three types based on the pore size, namely,
microporous (<2 nm), mesoporous (2–50 nm) and macroporous (>50 nm) [18]. The
size of the pores has a direct impact on the surface area available for adsorption. The
surface area is defined as the area available on the surface of the adsorbent for the
adsorbate to get adsorbed. It is expressed in m
2 /g. The smaller the pore size, surface
area will be more. As the surface area increases, the amount of adsorbate adsorbed on
to the adsorbent increases.
In the selection of an adsorbent for a process, the size of the adsorbate is taken
into consideration to select appropriate pore size adsorbent. For larger adsorbates,
macroporous and mesoporous adsorbents are used, while for smaller adsorbates,
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K. J. Samuel P N et al.
functional groups.
Some biomaterials like plant and animal tissues require a series of preliminary
processing to make them more available as biosorbents. Properties of adsorbents
depend on the raw material selected and the activation process applied. The physical
and chemical treatments for the activation of adsorbent have effects on the properties
of the adsorbents. Certain biomass has adsorption capacity higher than commercially
available activated carbon, ion exchange resins and zeolites.
The following criteria should be considered while selecting a biosorbent for the
biosorption process:
1. The biosorbent should be less expensive.
2. It should be reusable and the regeneration process should be less tedious.
3. Kinetics of the adsorption should be fast.
2.1 Physical Characteristics
2.1.1 Pore Size and Surface Area
IUPAC has classified the pores into three types based on the pore size, namely,
microporous (<2 nm), mesoporous (2–50 nm) and macroporous (>50 nm) [18]. The
size of the pores has a direct impact on the surface area available for adsorption. The
surface area is defined as the area available on the surface of the adsorbent for the
adsorbate to get adsorbed. It is expressed in m
2 /g. The smaller the pore size, surface
area will be more. As the surface area increases, the amount of adsorbate adsorbed on
to the adsorbent increases.
In the selection of an adsorbent for a process, the size of the adsorbate is taken
into consideration to select appropriate pore size adsorbent. For larger adsorbates,
macroporous and mesoporous adsorbents are used, while for smaller adsorbates,
244
K. J. Samuel P N et al.