Environmental Engineering Reference
In-Depth Information
TABLE 21.3 (continued)
Possible.Reactions.of.Adsorption.of.As(III).and.As(V).by.Ferrihydrite
Fe OH)
|(
]
−
1
+
H AsO
−
→
Fe O As OH
|
(
)]
0
2
2
4
2
2
Fe OH)
|(
]
−
1
+
H AsO
−
→
Fe O As O)(OH
|
(
)]
−
1
2
2
4
2
As.(V).at.pH.9.2
Fe OH
−
]
−
1 2
/
+
HAsO
2
−
→ −
Fe OAs O OH
(
) (
)]
−
3 2
/
4
2
Fe OH
−
]
−
1 2
/
+
HAsO
2
−
→ −
Fe OAs O
(
) ]
−
5 2
/
4
3
Fe (OH)
|
]
−
1
+
HAsO
2
−
→
Fe O As O OH
|
(
)(
)]
−
1
2
4
2
Fe (OH)
|
]
−
1
+
HAsO
2
−
→
Fe O As O
|
(
)]
−
2
2
4
2
2
Source:
.
Jain,.A..et.al.,.
Environ. Sci. Technol
.,.33(8),.1179,.1999.
phase.in.mine.tailings.and.play.a.signiicant.role.in.limiting.the.release.of.
As.from.tailings.to.the.environment.(Langmuir.et.al..2006)..In.the.work.of.
Langmuir. et. al.,. the. solubility. product. of. scorodite. was. established. with.
regard.to.the.As.and.Fe.concentrations.(Figure.21.4)..The.decreasing.solubil-
ity.product.of.scorodite.with.increasing.pH.and.Fe/As.ratio.can.increase.the.
fraction.of.As.released.into.water.
1000
100
C
A
Scorodite (cr)
10
B
1
Region 4
Region 3
0.1
Region 1
Region 2
FO
0.01
0.001
0
1
2
3
4
5
6
7
8
pH
FIGURE 21.4
The. solubility. of. scorodite. in. terms. of. As. (upper. solid. line). and. Fe. (lower. solid. line).. (From.
Langmuir,.D..et.al.,.
Geochim. Cosmochim. Acta
,.70(12),.2942,.2006.)
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