15
(v) Iodine number (mg/g): Iodine number is recognized as a crucial factor used
in characterizing the efficiency of activated carbon as it measures the activity
level in carbon. High iodine number indicates a high degree of carbon activation (Pradhan 2011). Activated carbon adsorbs iodine at a spontaneous rate,
and this makes iodine number a signal of the total surface area of the activated
carbon. It is usually measured using ASTM D28 standard method.
(vi) Moisture content: This emanates from the polar functional groups on the surface of the activated carbon which gives information regarding the active site
for water adsorption. Commercially, activated carbon has been reported to be
transported when provision is made available for contact with the atmospheric
condition. Therefore, atmospheric moisture needs to be considered when
transporting activated carbon (Zhou et al. 2001). The weight difference of the
carbon before and after adsorption signifies the water content present in the
sample. The constant dry weight method is used in determining the moisture
content and its effects on activated carbon.
1.6.2 Chemical Characteristics of Activated Carbon
(i) Chemical structure and surface morphology: Adsorption isotherm structure
gives necessary information on the process of adsorption and magnitude of the
surface area reachable to the adsorbate. London dispersion or van der Waals is
usually the binding force associated with activated carbon (Crini and Lichtfouse
2018). Activated carbon does not have strong affinity to certain chemical compounds such as alcohols, hard acid and bases, metals, and most inorganic compounds. The pore structure and the internal surface area can be analyzed with
mercury porosimetry or physical adsorption measurements (Figueiredo and
Moulijn 2012). The bonding element in water (H, O) together with all other
atoms has a significant influence on adsorption. Boehm (1966) method shows
how the oxygen bound surface functional groups could be measured in adsorption. This titration method put forward by Boehm is usually used in identifying
the acidic groups with different strengths on activated carbons. As a surface
phenomenon, the adsorption frequency and the degree of activated carbon to a
given adsorbate rely on its surface chemistry and pore texture (Guo and
Rockstraw 2007). Hence, the surface chemistry and structural appearances of
carbon will define the diffusion of adsorption surface sites and their accessibility during synthesis (Zhang et al. 2005). The surface morphology of the carbonated and activated product can be analyzed using scanning electron
microscope, but for the characterization of its functional group, Fourier transform infrared spectroscopy will be better for the analysis (Maulina and
Iriansyah 2018).
(ii) Ash content (%): Ash content is the inorganic remains after oxidation. The
composition of the ash and their distribution cause the activated carbon to have
strong catalytic effects and affinity for water (Chiang et al. 1998). The characteristics of any type of activated carbon are affected by the content of the ash it
1 Synthesis of Activated Carbons for Heavy Metals Removal
(v) Iodine number (mg/g): Iodine number is recognized as a crucial factor used
in characterizing the efficiency of activated carbon as it measures the activity
level in carbon. High iodine number indicates a high degree of carbon activation (Pradhan 2011). Activated carbon adsorbs iodine at a spontaneous rate,
and this makes iodine number a signal of the total surface area of the activated
carbon. It is usually measured using ASTM D28 standard method.
(vi) Moisture content: This emanates from the polar functional groups on the surface of the activated carbon which gives information regarding the active site
for water adsorption. Commercially, activated carbon has been reported to be
transported when provision is made available for contact with the atmospheric
condition. Therefore, atmospheric moisture needs to be considered when
transporting activated carbon (Zhou et al. 2001). The weight difference of the
carbon before and after adsorption signifies the water content present in the
sample. The constant dry weight method is used in determining the moisture
content and its effects on activated carbon.
1.6.2 Chemical Characteristics of Activated Carbon
(i) Chemical structure and surface morphology: Adsorption isotherm structure
gives necessary information on the process of adsorption and magnitude of the
surface area reachable to the adsorbate. London dispersion or van der Waals is
usually the binding force associated with activated carbon (Crini and Lichtfouse
2018). Activated carbon does not have strong affinity to certain chemical compounds such as alcohols, hard acid and bases, metals, and most inorganic compounds. The pore structure and the internal surface area can be analyzed with
mercury porosimetry or physical adsorption measurements (Figueiredo and
Moulijn 2012). The bonding element in water (H, O) together with all other
atoms has a significant influence on adsorption. Boehm (1966) method shows
how the oxygen bound surface functional groups could be measured in adsorption. This titration method put forward by Boehm is usually used in identifying
the acidic groups with different strengths on activated carbons. As a surface
phenomenon, the adsorption frequency and the degree of activated carbon to a
given adsorbate rely on its surface chemistry and pore texture (Guo and
Rockstraw 2007). Hence, the surface chemistry and structural appearances of
carbon will define the diffusion of adsorption surface sites and their accessibility during synthesis (Zhang et al. 2005). The surface morphology of the carbonated and activated product can be analyzed using scanning electron
microscope, but for the characterization of its functional group, Fourier transform infrared spectroscopy will be better for the analysis (Maulina and
Iriansyah 2018).
(ii) Ash content (%): Ash content is the inorganic remains after oxidation. The
composition of the ash and their distribution cause the activated carbon to have
strong catalytic effects and affinity for water (Chiang et al. 1998). The characteristics of any type of activated carbon are affected by the content of the ash it
1 Synthesis of Activated Carbons for Heavy Metals Removal