Environmental Engineering Reference
In-Depth Information
Fig. 6.20 (A) Distribution and (B) adsorption isotherms of copper ions on different magnetic
particles as a function of copper concentration: (a) Fe
3
O
4
coated with silica without templat-
ing, (b) mesoporous-Fe
3
O
4
, (c) Fe
3
O
4
coated with silica without templating but silanized by 3-
APTES, and (d) mesoporous-Fe
3
O
4
silanized with 3-APTES
solution pH. The extractability obtained at pH
<
6 was found to be in the order
Cu
2+
>
Ni
2+
>
Zn
2+
. The distribution coefficient for each metal is relatively low
for pH
<
2. At such a low pH, excess H
+
ions compete with metal ions for binding
with surface amino groups, resulting in a low metal ion loading capacity [48]. From
the results in this figure, a selective loading of copper ions over nickel and zinc is
anticipated. The selective loading was confirmed with loading tests in a solution
containing all three of these types of heavy metal ions. The distribution coefficient
(K
d
) obtained as a function of pH in Fig. 6.21B shows that the extractability of the
