4
It is predominantly used as colloid dispersion medium in polluted phase and also
in the removal of contaminants from aqueous, gaseous, and even solid environment.
Due to its small particle size and tendency to form dust, powdered activated carbon
is used directly as an add-on to other process units rather than being used singly.
However, powdered activated carbon is not an ideal choice for applications that use
considerable amount of activated carbon as it is not regenerated because of the challenges linked with recycling the carbon.
Powdered activated carbon finds typical applications in aqueous environments.
Heavy metals ions such as Hg can be adsorbed using powdered activated carbon
prepared from Casuarina equisetifolia leaves with varying particle size from 45 to
75 μm (Ranganathan 2003). Powdered activated carbon has been extensively used
to remove various gaseous pollutants discharged into the atmosphere through flue
gases. Example of such pollutants includes zero valent metals (e.g., Hg and Pb),
polycyclic aromatic hydrocarbons, and organic compounds (e.g., polychlorobenzenes, furans, dioxins). Bais et al. (2008) successfully applied powdered activated
carbon for separation of organic pollutants such as fluoranthene and hexachlorobenzene from gas stream.
1.2.2 Granular Activated Carbon
Granular activated carbon exists in granular or extruded form of coal. It may also be
developed through the granulation of pulverized powders using high-temperature
binders such as coal tar pitch. In both fixed and moving systems, smaller granular
activated carbon is particularly suited to liquid phase applications, while larger
granular activated carbon is better for vapors and gases.
Granular activated carbon has an average particle size of 1–5 mm which is relatively large and has a proportionately smaller external surface area than powdered
activated carbon. In addition, not less than 90% of its weight is held back on a standard mesh sieve size of 180 μm (80 mesh). Its reusability, ease of handling, regenerative properties, and offer of lower pressure drop make granular activated carbon
advantageous over powdered activated carbon.
Typical environmental applications of granular activated carbon are in the
removal of heavy metals. Toxic pollutants such as Pb is released into the environment as part of the end product of lead acid batteries, refineries operations, fuel
combustion, and fertilizers made from phosphate, mining activities, and emissions
from vehicles. It has been reported that Pb has significant impact on human health
and the environment (Dwivedi et al. 2008). Literature study shows that granular
activated carbon packed bed and batch system have been used to remove Pb effectively (Chelme-Ayala et al. 2009). Granular activated carbon can also be employed
in the removal of pesticides (Chelme-Ayala et al. 2009), insecticides (Daneshvar
et al. 2007), and volatile organic compounds (Bansode et al. 2003) from contaminated groundwater and soils.
B. Oladipo et al.
It is predominantly used as colloid dispersion medium in polluted phase and also
in the removal of contaminants from aqueous, gaseous, and even solid environment.
Due to its small particle size and tendency to form dust, powdered activated carbon
is used directly as an add-on to other process units rather than being used singly.
However, powdered activated carbon is not an ideal choice for applications that use
considerable amount of activated carbon as it is not regenerated because of the challenges linked with recycling the carbon.
Powdered activated carbon finds typical applications in aqueous environments.
Heavy metals ions such as Hg can be adsorbed using powdered activated carbon
prepared from Casuarina equisetifolia leaves with varying particle size from 45 to
75 μm (Ranganathan 2003). Powdered activated carbon has been extensively used
to remove various gaseous pollutants discharged into the atmosphere through flue
gases. Example of such pollutants includes zero valent metals (e.g., Hg and Pb),
polycyclic aromatic hydrocarbons, and organic compounds (e.g., polychlorobenzenes, furans, dioxins). Bais et al. (2008) successfully applied powdered activated
carbon for separation of organic pollutants such as fluoranthene and hexachlorobenzene from gas stream.
1.2.2 Granular Activated Carbon
Granular activated carbon exists in granular or extruded form of coal. It may also be
developed through the granulation of pulverized powders using high-temperature
binders such as coal tar pitch. In both fixed and moving systems, smaller granular
activated carbon is particularly suited to liquid phase applications, while larger
granular activated carbon is better for vapors and gases.
Granular activated carbon has an average particle size of 1–5 mm which is relatively large and has a proportionately smaller external surface area than powdered
activated carbon. In addition, not less than 90% of its weight is held back on a standard mesh sieve size of 180 μm (80 mesh). Its reusability, ease of handling, regenerative properties, and offer of lower pressure drop make granular activated carbon
advantageous over powdered activated carbon.
Typical environmental applications of granular activated carbon are in the
removal of heavy metals. Toxic pollutants such as Pb is released into the environment as part of the end product of lead acid batteries, refineries operations, fuel
combustion, and fertilizers made from phosphate, mining activities, and emissions
from vehicles. It has been reported that Pb has significant impact on human health
and the environment (Dwivedi et al. 2008). Literature study shows that granular
activated carbon packed bed and batch system have been used to remove Pb effectively (Chelme-Ayala et al. 2009). Granular activated carbon can also be employed
in the removal of pesticides (Chelme-Ayala et al. 2009), insecticides (Daneshvar
et al. 2007), and volatile organic compounds (Bansode et al. 2003) from contaminated groundwater and soils.
B. Oladipo et al.