566
T. Rasool and W. Baba
Fig. 4 Effect of initial pH
on adsorption capacity Zn(II)
and Ni(II) on ABC
2
3
4
5
6
7
8
0
20
40
60
80
100
Adsorption capacity q (mg/g)
pH
Zn(II)
Ni(II)
explained by relating the effect of pH to the competition between the metal ions and
the hydronium ions onto the working sites of ABC surface. At lower pH of solution,
functional groups get easily protonated due to their association with hydronium ions
(H 3 O
+ ) resulting in the overall positive charge of the surface. Thus, this phenomenon
results in the low uptake of metals at low pH which can be attributed to the repulsive
forces by the composite surface. As the pH increases more functional groups like
carboxylic, amino groups, phosphate groups get exposed which easily facilitate the
binding of metal ions. Again at much higher pH the adsorption of both the metals
began to drop. This happens due to the OH
− species of the solution, which compete
with anion species of divalent Zn(II) and Ni(II) and result in the adsorption of metal
ions.
3.3 Effect of Adsorbent Dosage
The sorption of Zn(II) and Ni(II) on ABC was studied by varying the dosage 0.1
to 0.3 g per 100 ml of solution. The respective results are depicted in Fig. 5. The
results reveal that with an increase in the adsorbent dosage, the adsorption capacity
of the ABC decreases. At the same time the recovery percentage also decreased at
higher dosage for both the metal ions. The maximum adsorption for both the ions
was obtained at 0.1 g of adsorbent dosage. Due to fixed total amount of Zn(II) and
Ni(II) ions available for removal, ion adsorption per mass of adsorbent (adsorption
capacity, q) decreased at higher dosage. The study is in order with some previous
findings (Fourest and Roux 1992; Gong et al. 2005). Moreover, at higher adsorbent
dosage removal efficiency becomes stable showing a low sorption rate increment
per increment of algae bentonite added. The adsorption capacity of Zn(II) and Ni(II)
declined from 69.79 mg/g to 18.64 mg/g and from 85.32 mg/g to 21 mg/g respectively.
T. Rasool and W. Baba
Fig. 4 Effect of initial pH
on adsorption capacity Zn(II)
and Ni(II) on ABC
2
3
4
5
6
7
8
0
20
40
60
80
100
Adsorption capacity q (mg/g)
pH
Zn(II)
Ni(II)
explained by relating the effect of pH to the competition between the metal ions and
the hydronium ions onto the working sites of ABC surface. At lower pH of solution,
functional groups get easily protonated due to their association with hydronium ions
(H 3 O
+ ) resulting in the overall positive charge of the surface. Thus, this phenomenon
results in the low uptake of metals at low pH which can be attributed to the repulsive
forces by the composite surface. As the pH increases more functional groups like
carboxylic, amino groups, phosphate groups get exposed which easily facilitate the
binding of metal ions. Again at much higher pH the adsorption of both the metals
began to drop. This happens due to the OH
− species of the solution, which compete
with anion species of divalent Zn(II) and Ni(II) and result in the adsorption of metal
ions.
3.3 Effect of Adsorbent Dosage
The sorption of Zn(II) and Ni(II) on ABC was studied by varying the dosage 0.1
to 0.3 g per 100 ml of solution. The respective results are depicted in Fig. 5. The
results reveal that with an increase in the adsorbent dosage, the adsorption capacity
of the ABC decreases. At the same time the recovery percentage also decreased at
higher dosage for both the metal ions. The maximum adsorption for both the ions
was obtained at 0.1 g of adsorbent dosage. Due to fixed total amount of Zn(II) and
Ni(II) ions available for removal, ion adsorption per mass of adsorbent (adsorption
capacity, q) decreased at higher dosage. The study is in order with some previous
findings (Fourest and Roux 1992; Gong et al. 2005). Moreover, at higher adsorbent
dosage removal efficiency becomes stable showing a low sorption rate increment
per increment of algae bentonite added. The adsorption capacity of Zn(II) and Ni(II)
declined from 69.79 mg/g to 18.64 mg/g and from 85.32 mg/g to 21 mg/g respectively.