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1 A Comprehensive Approach to Heavy Metal Removal by Adsorption …
1.3 Adsorbents
Therefore, the utility of an adsorbent in waste disposal relies on the structure, surface
form of functional groups, degree of polarity, surface area, and hydrophilicity. Adsorbent is a strong material employed in adsorption studies as the adsorbing phase.
Several studies have concentrated on adsorbents which are capable of eradicating
adsorbates at reduced cost. Bailey et al. [28] stated that if an adsorbent needs little
preparation procedure and is available in large quantities, it could be classified a
low-cost material. Hence, cost is therefore a crucial consideration in the choice of an
adsorbing material. A number of adsorbents, including activated carbon, zeolite, peat,
chitin and chitosan, have been used over the years to remove heavy metal ions from
water and wastewater [29]. In this review, these mentioned adsorbents are examined.
1.3.1 Activated Carbon
Activated carbon is among the first adsorbents that have been used in various
processes such as waste management. Watonabe and Ogawa [30] have proposed
the use of activated carbon for the adsorption of heavy metals. A wide surface area
(500–2000 m
2 /g) is still the main significant physical characteristic that enables
gas or vapour to be physically adsorbed. Nevertheless, the significant proportion of
pore spaces offers a greater inner layer to the adsorbent which may be the source
of its significant adsorption capacity. In addition, activated carbon is an important
adsorbent of a variety of contaminant species, such as organic, inorganic, and microbial [31]. Once activated carbon has been depleted owing to metal ion adsorption,
and it may be recovered for another use, but the procedure of recovery leads to
carbon damage and the recovered material will have a significantly reduced adsorption potential relative to virgin activated carbon and this limits its regenerability
property [11, 18, 28, 32]. While activated carbon is a good adsorbent because of its
high potential with organic compounds, its massive cost restricts its usage as an adsorbent in developing countries, particularly on a broad scale. Several research studies
have successful employed activated carbon in removing heavy metals with different
adsorption capacity. Table 1.2 offers the overall recorded adsorption potential of the
activated carbon derived from various materials and their operational parameters.
1.3.2 Zeolite
Zeolite is an adsorbent and can therefore be utilized to eliminate water and wastewater
contaminants. It is a porous aluminosilicate with various structures of the cavities.
1 A Comprehensive Approach to Heavy Metal Removal by Adsorption …
1.3 Adsorbents
Therefore, the utility of an adsorbent in waste disposal relies on the structure, surface
form of functional groups, degree of polarity, surface area, and hydrophilicity. Adsorbent is a strong material employed in adsorption studies as the adsorbing phase.
Several studies have concentrated on adsorbents which are capable of eradicating
adsorbates at reduced cost. Bailey et al. [28] stated that if an adsorbent needs little
preparation procedure and is available in large quantities, it could be classified a
low-cost material. Hence, cost is therefore a crucial consideration in the choice of an
adsorbing material. A number of adsorbents, including activated carbon, zeolite, peat,
chitin and chitosan, have been used over the years to remove heavy metal ions from
water and wastewater [29]. In this review, these mentioned adsorbents are examined.
1.3.1 Activated Carbon
Activated carbon is among the first adsorbents that have been used in various
processes such as waste management. Watonabe and Ogawa [30] have proposed
the use of activated carbon for the adsorption of heavy metals. A wide surface area
(500–2000 m
2 /g) is still the main significant physical characteristic that enables
gas or vapour to be physically adsorbed. Nevertheless, the significant proportion of
pore spaces offers a greater inner layer to the adsorbent which may be the source
of its significant adsorption capacity. In addition, activated carbon is an important
adsorbent of a variety of contaminant species, such as organic, inorganic, and microbial [31]. Once activated carbon has been depleted owing to metal ion adsorption,
and it may be recovered for another use, but the procedure of recovery leads to
carbon damage and the recovered material will have a significantly reduced adsorption potential relative to virgin activated carbon and this limits its regenerability
property [11, 18, 28, 32]. While activated carbon is a good adsorbent because of its
high potential with organic compounds, its massive cost restricts its usage as an adsorbent in developing countries, particularly on a broad scale. Several research studies
have successful employed activated carbon in removing heavy metals with different
adsorption capacity. Table 1.2 offers the overall recorded adsorption potential of the
activated carbon derived from various materials and their operational parameters.
1.3.2 Zeolite
Zeolite is an adsorbent and can therefore be utilized to eliminate water and wastewater
contaminants. It is a porous aluminosilicate with various structures of the cavities.