However, increasing the temperature to 323 K did not improve the removal efficiency, and further increase resulted in a decrease of the removal efficiency. The first
increase to 313 K gave a positive effect to the removal efficiency due to the increase
in active sites and also possible pore opening. On the other hand, increasing
temperature beyond that weakened the adsorbent structure and promoted decomposition process that led to a decrease in the active sites. A similar trend was also
reported in the adsorption of Fe(III) onto the olive stone. The decontamination of Fe
(III) was enhanced as the temperature varied from 278 K to 343 K [48]. Another
work by Albadarin et al. [67] found the increase in removal rate of Cr(VI) using date
pit when the temperature increased from 22
C to 60
C. Adsorption of Zn(II) using
coconut shell biochar attributed to the increase in adsorption capacity of the endothermic diffusion process, where the increase in operating temperature increased
intraparticle diffusion [45].
Table 9.5 Equilibrium time for heavy metal adsorption using agricultural waste-derived
adsorbents
Heavy
metals
Agricultural
wastes
Experimental constants
Equilibrium time
References
As(III) Sugarcane
bagasse
pH ¼ 7, C i ¼ 20 mg/L, adsorbent dosage ¼ 2.5 g/L
120 min
[60]
Cd(II)
Castor leaf
pH ¼ 5, T ¼ 25
C, C i ¼ 25 mg/
L, adsorbent dosage ¼ 0.8 g/L
30 min
[61]
Banana
cellulose
T ¼ 25
C, C i ¼ 50–300 mg/L,
adsorbent dosage ¼ 2 g/L
30 min
[62]
Cu(II)
Pomegranate
peel
pH ¼ 5.8, T ¼ 30
C,
C i ¼ 10–50 mg/L, adsorbent
dosage ¼ 3 g/L
120 min
[63]
Tomato
waste
pH ¼ 8, T ¼ 20–40
C,
C i ¼ 50 mg/L, adsorbent dosage ¼ 4 g/L
60 min
[64]
Cr(VI) Banana skin
pH ¼ 2, C i ¼ 20, 50, 100 mg/L,
adsorbent dosage ¼ 7.5 g/L
30 min (20 mg/L), 1 h
(50 mg/L), 2 h
(100 mg/L)
[65]
Pb(II)
Castor leaf
pH ¼ 5, T ¼ 25
C, C i ¼ 25 mg/
L, adsorbent dosage ¼ 0.8 g/L
30 min
[61]
Fig sawdust
pH ¼ 4, T ¼ 25
C,
C i ¼ 100 mg/L, adsorbent dosage ¼ 1.67 g/L
40 min
[59]
Peanut shell
pH ¼ 5.5 Æ 0.2, T ¼ 20
C,
C i ¼ 100 mg/L, adsorbent dosage ¼ 2 g/L
45 min
[66]
9 Agricultural Waste-Derived Adsorbents for Decontamination of Heavy Metals
381
increase to 313 K gave a positive effect to the removal efficiency due to the increase
in active sites and also possible pore opening. On the other hand, increasing
temperature beyond that weakened the adsorbent structure and promoted decomposition process that led to a decrease in the active sites. A similar trend was also
reported in the adsorption of Fe(III) onto the olive stone. The decontamination of Fe
(III) was enhanced as the temperature varied from 278 K to 343 K [48]. Another
work by Albadarin et al. [67] found the increase in removal rate of Cr(VI) using date
pit when the temperature increased from 22
C to 60
C. Adsorption of Zn(II) using
coconut shell biochar attributed to the increase in adsorption capacity of the endothermic diffusion process, where the increase in operating temperature increased
intraparticle diffusion [45].
Table 9.5 Equilibrium time for heavy metal adsorption using agricultural waste-derived
adsorbents
Heavy
metals
Agricultural
wastes
Experimental constants
Equilibrium time
References
As(III) Sugarcane
bagasse
pH ¼ 7, C i ¼ 20 mg/L, adsorbent dosage ¼ 2.5 g/L
120 min
[60]
Cd(II)
Castor leaf
pH ¼ 5, T ¼ 25
C, C i ¼ 25 mg/
L, adsorbent dosage ¼ 0.8 g/L
30 min
[61]
Banana
cellulose
T ¼ 25
C, C i ¼ 50–300 mg/L,
adsorbent dosage ¼ 2 g/L
30 min
[62]
Cu(II)
Pomegranate
peel
pH ¼ 5.8, T ¼ 30
C,
C i ¼ 10–50 mg/L, adsorbent
dosage ¼ 3 g/L
120 min
[63]
Tomato
waste
pH ¼ 8, T ¼ 20–40
C,
C i ¼ 50 mg/L, adsorbent dosage ¼ 4 g/L
60 min
[64]
Cr(VI) Banana skin
pH ¼ 2, C i ¼ 20, 50, 100 mg/L,
adsorbent dosage ¼ 7.5 g/L
30 min (20 mg/L), 1 h
(50 mg/L), 2 h
(100 mg/L)
[65]
Pb(II)
Castor leaf
pH ¼ 5, T ¼ 25
C, C i ¼ 25 mg/
L, adsorbent dosage ¼ 0.8 g/L
30 min
[61]
Fig sawdust
pH ¼ 4, T ¼ 25
C,
C i ¼ 100 mg/L, adsorbent dosage ¼ 1.67 g/L
40 min
[59]
Peanut shell
pH ¼ 5.5 Æ 0.2, T ¼ 20
C,
C i ¼ 100 mg/L, adsorbent dosage ¼ 2 g/L
45 min
[66]
9 Agricultural Waste-Derived Adsorbents for Decontamination of Heavy Metals
381