17
(1) movement of contaminants ion from the solution to the adsorbent surface, (2)
adsorption onto the site of the particle, and (3) movement within the adsorbent particles. The synthesis of carbonaceous materials into activated carbon for remediating contaminants has been extensively described in literature. Agricultural residues
(biowastes) can be utilized as cost-effective adsorption material for heavy metals
ion uptake from polluted areas, thus reducing the environmental pollution with the
approach of “treating waste by waste” (Dai et al. 2018).
Owing to the attraction between the synthesized activated carbon and heavy
metal ions, the ions are bound via a complicated route which are influenced by several mechanisms such as chemisorption, physisorption, membrane diffusion, ion
exchange, particle diffusion, electrostatic attraction, chelation, surface, and internal
complexation (Sud et al. 2008). Biowastes used in synthesis of activated carbon
portrayed a loose, porous arrangement and consist of carboxyl functional groups,
hydroxyl functional groups, and other reactive groups as its main attributes, which
promote their usage as adsorbents. In order to explain the synergy existing among
the functional groups of activated carbon and ions of heavy metals, different modern
techniques have been established to verify the presence of these functional groups,
such methods include the Fourier transform infrared (FT-IR) and the Raman spectroscopy, nuclear magnetic resonance spectroscopy (NMR), electron spin resonance
(ESR) spectroscopy, and X-ray absorption near-edge (XANES) among several others (Iqbal et al. 2009; Memon et al. 2008). Table 1.6 compares adsorption capacity
of adsorbents and mechanisms for some heavy metal ions removal.
Table 1.6 Mechanism of adsorption and maximum adsorption capacity on different biowastes
Heavy
metal ions
(adsorbate)
Biowaste
(adsorbent)
pH
Temperature
(K)
q m
(mg/g) Mechanism
References
Ni(II)
Hemp shive
6.0 293
160.00 Intraparticle
diffusion
Kyzas et al.
(2015)
Cocoa shell
6.0 303
97.59 Intraparticle
diffusion
Kalaivani et al.
(2015)
Mango peel
5.0 298
39.75 Ion exchange
Iqbal et al.
(2009)
Cr(VI)
Teff straw
2.0 298
3.51
Chemisorption
Tadesse et al.
(2015)
Rice husk
1.5 303
11.40 Film diffusion and
intraparticle
diffusion
Singha and Das
(2011)
Zn(II)
Walnut shell
5.0 313
7.48
Ion exchange
Najam and
Andrabi (2016)
Palm oil mill
effluent
5.5 353
68.49 Chemisorption and
intraparticle
diffusion
Adebisi et al.
(2017)
(continued)
1 Synthesis of Activated Carbons for Heavy Metals Removal
(1) movement of contaminants ion from the solution to the adsorbent surface, (2)
adsorption onto the site of the particle, and (3) movement within the adsorbent particles. The synthesis of carbonaceous materials into activated carbon for remediating contaminants has been extensively described in literature. Agricultural residues
(biowastes) can be utilized as cost-effective adsorption material for heavy metals
ion uptake from polluted areas, thus reducing the environmental pollution with the
approach of “treating waste by waste” (Dai et al. 2018).
Owing to the attraction between the synthesized activated carbon and heavy
metal ions, the ions are bound via a complicated route which are influenced by several mechanisms such as chemisorption, physisorption, membrane diffusion, ion
exchange, particle diffusion, electrostatic attraction, chelation, surface, and internal
complexation (Sud et al. 2008). Biowastes used in synthesis of activated carbon
portrayed a loose, porous arrangement and consist of carboxyl functional groups,
hydroxyl functional groups, and other reactive groups as its main attributes, which
promote their usage as adsorbents. In order to explain the synergy existing among
the functional groups of activated carbon and ions of heavy metals, different modern
techniques have been established to verify the presence of these functional groups,
such methods include the Fourier transform infrared (FT-IR) and the Raman spectroscopy, nuclear magnetic resonance spectroscopy (NMR), electron spin resonance
(ESR) spectroscopy, and X-ray absorption near-edge (XANES) among several others (Iqbal et al. 2009; Memon et al. 2008). Table 1.6 compares adsorption capacity
of adsorbents and mechanisms for some heavy metal ions removal.
Table 1.6 Mechanism of adsorption and maximum adsorption capacity on different biowastes
Heavy
metal ions
(adsorbate)
Biowaste
(adsorbent)
pH
Temperature
(K)
q m
(mg/g) Mechanism
References
Ni(II)
Hemp shive
6.0 293
160.00 Intraparticle
diffusion
Kyzas et al.
(2015)
Cocoa shell
6.0 303
97.59 Intraparticle
diffusion
Kalaivani et al.
(2015)
Mango peel
5.0 298
39.75 Ion exchange
Iqbal et al.
(2009)
Cr(VI)
Teff straw
2.0 298
3.51
Chemisorption
Tadesse et al.
(2015)
Rice husk
1.5 303
11.40 Film diffusion and
intraparticle
diffusion
Singha and Das
(2011)
Zn(II)
Walnut shell
5.0 313
7.48
Ion exchange
Najam and
Andrabi (2016)
Palm oil mill
effluent
5.5 353
68.49 Chemisorption and
intraparticle
diffusion
Adebisi et al.
(2017)
(continued)
1 Synthesis of Activated Carbons for Heavy Metals Removal