Removal of Ni(II) and Zn(II) from Aqueous Media …
565
Fig. 2 SEM image of a dead algal biomass b ABC
0
2 0
4 0
6 0
-10000
0
10000
20000
30000
40000
Intensity (cps)
2-Theta (Degree)
4.39 nm
13.0 nm
65.2 nm
137.7 nm
39.9 nm
Fig. 3 Diffraction pattern of the ABC
3.2 Effect of Initial pH
The effect of pH on Zn(II) and Ni(II) is shown in Fig. 4. The maximum adsorption
for Zn(II) was observed at pH of 5 while for Ni(II) it was found to fall around the
pH 6. The adsorption of Zn(II) was slightly lower than that of Ni(II). The variation
in the adsorption of both Zn(II) and Ni(II) at different pH values onto ABC may
be attributed to the variation of charges on the surface of adsorbent at different pH
values due to different solute speciation, adsorbent surface and degree of ionization
(Fan et al. 2012). It was observed that the adsorption of metals at extreme basic and
acidic conditions was low. For metal binding functional groups play an important
role and pH significantly effects the functional groups by protonation/deprotonation
which causes varying forces of attraction between sorbate and metal ions (Ullah et al.
2013). At low pH adsorption is not favoured due to competition of metal ions with H
+
ions. As the pH increases, the ligands carrying negative charge increase facilitating
the better binding of positively charged species (Rashid et al. 2016). The adsorption
of both the metals is found to be maximum at pH of about 5–6. Further it may be
565
Fig. 2 SEM image of a dead algal biomass b ABC
0
2 0
4 0
6 0
-10000
0
10000
20000
30000
40000
Intensity (cps)
2-Theta (Degree)
4.39 nm
13.0 nm
65.2 nm
137.7 nm
39.9 nm
Fig. 3 Diffraction pattern of the ABC
3.2 Effect of Initial pH
The effect of pH on Zn(II) and Ni(II) is shown in Fig. 4. The maximum adsorption
for Zn(II) was observed at pH of 5 while for Ni(II) it was found to fall around the
pH 6. The adsorption of Zn(II) was slightly lower than that of Ni(II). The variation
in the adsorption of both Zn(II) and Ni(II) at different pH values onto ABC may
be attributed to the variation of charges on the surface of adsorbent at different pH
values due to different solute speciation, adsorbent surface and degree of ionization
(Fan et al. 2012). It was observed that the adsorption of metals at extreme basic and
acidic conditions was low. For metal binding functional groups play an important
role and pH significantly effects the functional groups by protonation/deprotonation
which causes varying forces of attraction between sorbate and metal ions (Ullah et al.
2013). At low pH adsorption is not favoured due to competition of metal ions with H
+
ions. As the pH increases, the ligands carrying negative charge increase facilitating
the better binding of positively charged species (Rashid et al. 2016). The adsorption
of both the metals is found to be maximum at pH of about 5–6. Further it may be