14
calculated by Brunauer–Emmett–Teller technique, and this can be sourced
from nitrogen adsorption data of 0.05–0.2 relative pressure range. The application of Brunauer–Emmett–Teller equation to isotherms of adsorption–desorption of nitrogen at a temperature of 77 K will also help in revealing the surface
area of activated carbon (Naderi 2015). The process of activating carbon influences its distinct features to the level that the Brunauer–Emmett–Teller surface
area of the activated carbon range from 250 to 2410 m
2
/g, and the pore volume
changes from 0.022 to 91.4 cm
3
/g (Ioannidou and Zabaniotou 2007). Generally,
if no activation process is made on the carbon, the Brunauer–Emmett–Teller
surface areas are usually below 500 m
2
/g (Murzin 2012). The internal surface
area of an activated carbon falls between 500 and 1500 m
2
/g, and this large
internal surface area makes the adsorbent potent (Wigmans 1989).
(ii) Density (g/ml): Pycnometer is used to determine the actual density of activated carbon. The density of activated carbon depends on the starting material,
adopted method of production, process mode of activation, and the final output
of the resulting carbon. For instance, the density of activated carbon from a
wooden source is lower when compared to that from coal (Chiang et al. 1998).
(iii) Porosity (Φ): Porosity with sizes of nanometers or less cannot be exactly
imaged even in sophisticated instruments such as scanning electron microscope. However, an alternative technique has been developed using physical
adsorption of gases, immersion calorimetry, and of small-angle X-rays scattering to characterize porosity (Marsh and Reinoso 2006). Microporosity has the
proportions of molecules and turn to be an indicator showing the relevant
information about the adsorption active site. Hence, there is a binding force
between porosity and adsorption. The industrial functionality of activated carbon relies on its retention capacity, i.e., the time it takes the carbon to retain the
adsorbed species at specific operating conditions without getting desorbed
(Marsh and Reinoso 2006). Thus, molecules of smaller sizes are more porous.
Contrariwise, molecules of larger size experience a closed porosity.
Consequently, closed porosity is at a point when porosity is not accessible to a
specified adsorbate. Closed porosity is not a steady parameter but advances
toward zero (cm
3
/g) but most time never attain zero for activated carbon due to
size decrease in the adsorbate molecule (Marsh and Reinoso 2006).
(iv) Pore volumes and size distribution, V T (cm
3
/g): The surface of activated carbon has a pore size that defines its adsorption capacity, a chemical structure
that stimulates its interaction with adsorbates of polar and nonpolar form, and
active sites which confirm its chemical interactive effects with other molecules
(Ioannidou and Zabaniotou 2007). The pore size distribution of activated carbon can be classified into three which are micropores, mesopores, and macropores. The micropores size of activated carbon is a significant property that
measures its adsorption capacity (Pradhan 2011). Dubinin–Radushkevich
equation is used in ascertaining the micropore volume of activated carbon,
while the mesopore volume and pore size distribution can be estimated using
Barrett–Joyner–Halend adsorption approach and the density functional theory,
respectively (Ahmed and Theydan 2012).
B. Oladipo et al.
calculated by Brunauer–Emmett–Teller technique, and this can be sourced
from nitrogen adsorption data of 0.05–0.2 relative pressure range. The application of Brunauer–Emmett–Teller equation to isotherms of adsorption–desorption of nitrogen at a temperature of 77 K will also help in revealing the surface
area of activated carbon (Naderi 2015). The process of activating carbon influences its distinct features to the level that the Brunauer–Emmett–Teller surface
area of the activated carbon range from 250 to 2410 m
2
/g, and the pore volume
changes from 0.022 to 91.4 cm
3
/g (Ioannidou and Zabaniotou 2007). Generally,
if no activation process is made on the carbon, the Brunauer–Emmett–Teller
surface areas are usually below 500 m
2
/g (Murzin 2012). The internal surface
area of an activated carbon falls between 500 and 1500 m
2
/g, and this large
internal surface area makes the adsorbent potent (Wigmans 1989).
(ii) Density (g/ml): Pycnometer is used to determine the actual density of activated carbon. The density of activated carbon depends on the starting material,
adopted method of production, process mode of activation, and the final output
of the resulting carbon. For instance, the density of activated carbon from a
wooden source is lower when compared to that from coal (Chiang et al. 1998).
(iii) Porosity (Φ): Porosity with sizes of nanometers or less cannot be exactly
imaged even in sophisticated instruments such as scanning electron microscope. However, an alternative technique has been developed using physical
adsorption of gases, immersion calorimetry, and of small-angle X-rays scattering to characterize porosity (Marsh and Reinoso 2006). Microporosity has the
proportions of molecules and turn to be an indicator showing the relevant
information about the adsorption active site. Hence, there is a binding force
between porosity and adsorption. The industrial functionality of activated carbon relies on its retention capacity, i.e., the time it takes the carbon to retain the
adsorbed species at specific operating conditions without getting desorbed
(Marsh and Reinoso 2006). Thus, molecules of smaller sizes are more porous.
Contrariwise, molecules of larger size experience a closed porosity.
Consequently, closed porosity is at a point when porosity is not accessible to a
specified adsorbate. Closed porosity is not a steady parameter but advances
toward zero (cm
3
/g) but most time never attain zero for activated carbon due to
size decrease in the adsorbate molecule (Marsh and Reinoso 2006).
(iv) Pore volumes and size distribution, V T (cm
3
/g): The surface of activated carbon has a pore size that defines its adsorption capacity, a chemical structure
that stimulates its interaction with adsorbates of polar and nonpolar form, and
active sites which confirm its chemical interactive effects with other molecules
(Ioannidou and Zabaniotou 2007). The pore size distribution of activated carbon can be classified into three which are micropores, mesopores, and macropores. The micropores size of activated carbon is a significant property that
measures its adsorption capacity (Pradhan 2011). Dubinin–Radushkevich
equation is used in ascertaining the micropore volume of activated carbon,
while the mesopore volume and pore size distribution can be estimated using
Barrett–Joyner–Halend adsorption approach and the density functional theory,
respectively (Ahmed and Theydan 2012).
B. Oladipo et al.