36
2 Thermodynamics, Kinetics and Desorption Studies …
2
3
4
5
6
7
8
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90
20
30
40
50
60
70
80
90
100
25 30 35 40 45 50 55
50
60
70
80
90
100
Removal efficiency (%)
pH
pb(II)
Cu(II)
Ni(II)
Zn(II)
Cd(II)
(a)
Removal efficeincy (%)
Contact time (min)
pb(II)
Cu(II)
Ni(II)
Zn(II)
Cd(II)
(b)
pb(II)
Cu(II)
Ni(II)
Zn(II)
Cd(II)
Removal efficiency (%)
Temperature (
o C)
(c)
Fig. 2.7 Plot of physicochemical parameters showing the effect of a pH, b contact time and
c temperature (initial concentration; = 40 mg/L, agitation speed of 150 rpm)
on their time of contact with the adsorbent in the medium. The variation of metal
ion adsorption onto the G/CR-CS surface with contact time is presented in Fig. 2.7b.
As illustrated, the adsorption capacity increased rapidly until equilibrium is reached
at an optimal contact time of 45 min for Pb(II) and Cu(II) and 60 min for Ni(II)
and Zn(II). The rapid adsorption at the initial stage may be because all active sites
on the adsorbent surface were vacant; hence, increasing contact time between the
adsorbate and the adsorbent results in the rapid uptake until adsorption equilibrium.
However, at equilibrium the adsorption sites are all covered with metal ions which
cause repulsion with increase in time.
2.5.3 Effect of Temperature
Temperature is one of the most important experimental parameters for heavy metal
ion removal from aqueous solution. As a measure of the average kinetic energy of
metal ions, temperature decrease or increase, changes the amount of heavy metal
ion being removed or retained by the adsorbent. Hence, the temperature effect on
metal ions adsorption was studied at a pH of 5, agitation speed of 150 rpm, and
equilibrium time of 1 h, adsorbent initial concentration dose of 40 mg/L (modified
2 Thermodynamics, Kinetics and Desorption Studies …
2
3
4
5
6
7
8
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90
20
30
40
50
60
70
80
90
100
25 30 35 40 45 50 55
50
60
70
80
90
100
Removal efficiency (%)
pH
pb(II)
Cu(II)
Ni(II)
Zn(II)
Cd(II)
(a)
Removal efficeincy (%)
Contact time (min)
pb(II)
Cu(II)
Ni(II)
Zn(II)
Cd(II)
(b)
pb(II)
Cu(II)
Ni(II)
Zn(II)
Cd(II)
Removal efficiency (%)
Temperature (
o C)
(c)
Fig. 2.7 Plot of physicochemical parameters showing the effect of a pH, b contact time and
c temperature (initial concentration; = 40 mg/L, agitation speed of 150 rpm)
on their time of contact with the adsorbent in the medium. The variation of metal
ion adsorption onto the G/CR-CS surface with contact time is presented in Fig. 2.7b.
As illustrated, the adsorption capacity increased rapidly until equilibrium is reached
at an optimal contact time of 45 min for Pb(II) and Cu(II) and 60 min for Ni(II)
and Zn(II). The rapid adsorption at the initial stage may be because all active sites
on the adsorbent surface were vacant; hence, increasing contact time between the
adsorbate and the adsorbent results in the rapid uptake until adsorption equilibrium.
However, at equilibrium the adsorption sites are all covered with metal ions which
cause repulsion with increase in time.
2.5.3 Effect of Temperature
Temperature is one of the most important experimental parameters for heavy metal
ion removal from aqueous solution. As a measure of the average kinetic energy of
metal ions, temperature decrease or increase, changes the amount of heavy metal
ion being removed or retained by the adsorbent. Hence, the temperature effect on
metal ions adsorption was studied at a pH of 5, agitation speed of 150 rpm, and
equilibrium time of 1 h, adsorbent initial concentration dose of 40 mg/L (modified