42
W. Stumm and H. Bilinski
Adsorbability o/Pb(C0 3 ) on Si0 2 -Surface
While Pb.aq
2+ is not sorbed (A: [PbJTOT = 2.3 x 10~
6 M,
[Pb] T O T = 9.3 x 10"
7 M, [C0 3
2 ~]
concentration = 22 m amorphous S1O2 per liter.
pH = 4.62) the carbonato complex (B:
—4
4 x 1 0 M) is strongly sorbed on silica surfaces. Surface area
100
o
UJ
o
ω
~
/
& —
B
A
A
1 . .
[
p
b]ioT20
40
60
TIME (MIN)
-0.60
-0.50
-0.40
E (V)
-0.30
- 0 2 0
>
Q.
UJ
<
Log [C0§""
Fig. 3. Anodic Stripping Voltammetry of Lead (PbTOT
= 2.3 X 10
6 M). The shift in peak potential
2—
observed with increasing [CO3 ] indicates the formation of carbonato complexes. An evaluation of
this potential shift (see Figure below) shows that the predominant species formed under these
conditions is Pb(C0 3 )2
2 . The plot gives a stability constant for the reaction Pb + 2 C 0 3
2 ~ =
Pb(C0 3 ) 2
2 " is log & = 10.7. (25°C, I = 0.1, KN0 3 ).
W. Stumm and H. Bilinski
Adsorbability o/Pb(C0 3 ) on Si0 2 -Surface
While Pb.aq
2+ is not sorbed (A: [PbJTOT = 2.3 x 10~
6 M,
[Pb] T O T = 9.3 x 10"
7 M, [C0 3
2 ~]
concentration = 22 m amorphous S1O2 per liter.
pH = 4.62) the carbonato complex (B:
—4
4 x 1 0 M) is strongly sorbed on silica surfaces. Surface area
100
o
UJ
o
ω
~
/
& —
B
A
A
1 . .
[
p
b]ioT20
40
60
TIME (MIN)
-0.60
-0.50
-0.40
E (V)
-0.30
- 0 2 0
>
Q.
UJ
<
Log [C0§""
Fig. 3. Anodic Stripping Voltammetry of Lead (PbTOT
= 2.3 X 10
6 M). The shift in peak potential
2—
observed with increasing [CO3 ] indicates the formation of carbonato complexes. An evaluation of
this potential shift (see Figure below) shows that the predominant species formed under these
conditions is Pb(C0 3 )2
2 . The plot gives a stability constant for the reaction Pb + 2 C 0 3
2 ~ =
Pb(C0 3 ) 2
2 " is log & = 10.7. (25°C, I = 0.1, KN0 3 ).