207
adsorbent itself. Moreover, it occurs at lower temperature, which is in general
near the critical temperature of material to be adsorbed.
• Chemisorption (chemical adsorption): It occurs due to the interaction of adsorbed
surface and the solid. This process is irretrievable and is of great concern in
catalysis. Therefore, the energy of the process of chemisorption is considered
similar to that of any chemical reaction, i.e., it may be either exothermic or endothermic of variable magnitude varying from negligible to huge. The elementary
steps of the process are often highly endothermic processes (requiring high
adsorption energy) (Andreev et al. 2019).
8.3.10 Adsorbent Properties
In order for commercial applications, the sorbent is supposed to have the following
qualities:
• It should be highly selective, enabling sharp separations.
• The adsorbent capacity should be high, hence utilizing least amount of sorbent.
• Kinetically favorable.
• Transport properties enabling speedy sorption.
• Thermal stability, i.e., stable at extreme temperatures.
• Chemical stability, i.e., inertness toward contacting fluids, preserving not only
the amount but also the chemical integrity of the sorbent.
• Mechanical strength and its hardness increasing its life.
• Lacking the tendency to enhance or reinforce any chemical reactions.
• The ability of regeneration when applied for commercial purposes (Singh and
Gupta 2016).
8.3.11 Factors Affecting Adsorption
Various factors that influence adsorption procedure are given below:
• The composition of an adsorbent also plays major role in its adsorption capacity.
Adsorbents with specific functional groups can adsorb anions and cations from
solution. The degree of adsorption relates to kinds and density of the adsorption
sites available.
• Surface area is a major factor affecting adsorption behavior of filter media; it is
directly related to adsorption capacity of an adsorbent. Nanostructured adsorbents showed more adsorption capacity compared to micro and macro one due to
large surface area.
• Adsorption is affected by many other several physicochemical characteristics of
an adsorbate, such as the size of adsorbate molecule, solubility, surface charge,
8 Agricultural Waste Absorbents for Heavy Metal Removal
adsorbent itself. Moreover, it occurs at lower temperature, which is in general
near the critical temperature of material to be adsorbed.
• Chemisorption (chemical adsorption): It occurs due to the interaction of adsorbed
surface and the solid. This process is irretrievable and is of great concern in
catalysis. Therefore, the energy of the process of chemisorption is considered
similar to that of any chemical reaction, i.e., it may be either exothermic or endothermic of variable magnitude varying from negligible to huge. The elementary
steps of the process are often highly endothermic processes (requiring high
adsorption energy) (Andreev et al. 2019).
8.3.10 Adsorbent Properties
In order for commercial applications, the sorbent is supposed to have the following
qualities:
• It should be highly selective, enabling sharp separations.
• The adsorbent capacity should be high, hence utilizing least amount of sorbent.
• Kinetically favorable.
• Transport properties enabling speedy sorption.
• Thermal stability, i.e., stable at extreme temperatures.
• Chemical stability, i.e., inertness toward contacting fluids, preserving not only
the amount but also the chemical integrity of the sorbent.
• Mechanical strength and its hardness increasing its life.
• Lacking the tendency to enhance or reinforce any chemical reactions.
• The ability of regeneration when applied for commercial purposes (Singh and
Gupta 2016).
8.3.11 Factors Affecting Adsorption
Various factors that influence adsorption procedure are given below:
• The composition of an adsorbent also plays major role in its adsorption capacity.
Adsorbents with specific functional groups can adsorb anions and cations from
solution. The degree of adsorption relates to kinds and density of the adsorption
sites available.
• Surface area is a major factor affecting adsorption behavior of filter media; it is
directly related to adsorption capacity of an adsorbent. Nanostructured adsorbents showed more adsorption capacity compared to micro and macro one due to
large surface area.
• Adsorption is affected by many other several physicochemical characteristics of
an adsorbate, such as the size of adsorbate molecule, solubility, surface charge,
8 Agricultural Waste Absorbents for Heavy Metal Removal