5
1.2.3 Extruded Activated Carbon
Extruded activated carbon is a blend of powdered activated carbon (anthracite or
coal) and binder, which are extruded at high pressure into a cylindrical-shaped pellets with diameters varying from 0.8 to 130 mm. Activated catalysts, like potassium
hydroxide, are mixed prior to extrusion to achieve a specific pore structure (Gupta
2017). Extruded activated carbon creates minimal dust, gives a low-pressure drop-in
system, and has high mechanical strength which is an essential factor in the gas–
phase applications.
1.3 Methods of Preparation of Activated Carbon
Activated carbon is an amorphous form of carbon which has been subjected to specific treatments in order to acquire a sophisticated internal pore structure, large specific surface area, good surface reactivity, and appropriate physical forms (Dias
et al. 2007; Yahya et al. 2015). As a result of these features, activated carbon is
widely used as adsorbent for pollution control in a host of environmental applications including the removal of heavy metals, volatile organic compounds, nitrates,
and color from wastewater and industrial effluents (Akpen et al. 2011; GonzálezGarcía 2018; Onyeji and Aboje 2011). Widespread applications of activated carbon,
availability of feedstock, increasing awareness, and stringent regulations regarding
environmental pollution are among the driving forces for research in this area
(Roman et al. 2013). The forms, precursors, features, and applications of AC are
shown in Table 1.1.
1.3.1 Feedstock for Activated Carbon Production
Coconut shell, coal, and wood are the most commonly used feedstocks for activated
carbon production. However, attention has recently shifted to agricultural residues
(biowastes) as cheaper and readily available alternatives due to their high carbon
contents, low ash and inorganic contents, relative rigidity, and the need for their
proper disposal as wastes. While some studies focus on agricultural waste materials
of substantial rigidity such as shells and stones of fruits that include oil palm, olives,
dates, cherries, and coconuts, others consider residues and processing wastes such
as olive cakes, sawdust, rice husks, cotton stalk, coffee husks, spent grains, sugarcane, and sugar beet bagasse. Table 1.2 shows the typical feedstock for the production of activated carbon. High carbon, high volatile solids, and low ash contents are
necessary for high yield of activated carbon with good pore volume and surface area
(Lua et al. 2006).
1 Synthesis of Activated Carbons for Heavy Metals Removal
1.2.3 Extruded Activated Carbon
Extruded activated carbon is a blend of powdered activated carbon (anthracite or
coal) and binder, which are extruded at high pressure into a cylindrical-shaped pellets with diameters varying from 0.8 to 130 mm. Activated catalysts, like potassium
hydroxide, are mixed prior to extrusion to achieve a specific pore structure (Gupta
2017). Extruded activated carbon creates minimal dust, gives a low-pressure drop-in
system, and has high mechanical strength which is an essential factor in the gas–
phase applications.
1.3 Methods of Preparation of Activated Carbon
Activated carbon is an amorphous form of carbon which has been subjected to specific treatments in order to acquire a sophisticated internal pore structure, large specific surface area, good surface reactivity, and appropriate physical forms (Dias
et al. 2007; Yahya et al. 2015). As a result of these features, activated carbon is
widely used as adsorbent for pollution control in a host of environmental applications including the removal of heavy metals, volatile organic compounds, nitrates,
and color from wastewater and industrial effluents (Akpen et al. 2011; GonzálezGarcía 2018; Onyeji and Aboje 2011). Widespread applications of activated carbon,
availability of feedstock, increasing awareness, and stringent regulations regarding
environmental pollution are among the driving forces for research in this area
(Roman et al. 2013). The forms, precursors, features, and applications of AC are
shown in Table 1.1.
1.3.1 Feedstock for Activated Carbon Production
Coconut shell, coal, and wood are the most commonly used feedstocks for activated
carbon production. However, attention has recently shifted to agricultural residues
(biowastes) as cheaper and readily available alternatives due to their high carbon
contents, low ash and inorganic contents, relative rigidity, and the need for their
proper disposal as wastes. While some studies focus on agricultural waste materials
of substantial rigidity such as shells and stones of fruits that include oil palm, olives,
dates, cherries, and coconuts, others consider residues and processing wastes such
as olive cakes, sawdust, rice husks, cotton stalk, coffee husks, spent grains, sugarcane, and sugar beet bagasse. Table 1.2 shows the typical feedstock for the production of activated carbon. High carbon, high volatile solids, and low ash contents are
necessary for high yield of activated carbon with good pore volume and surface area
(Lua et al. 2006).
1 Synthesis of Activated Carbons for Heavy Metals Removal