Environmental Engineering Reference
In-Depth Information
Fig. 1.9
SEM image of
biofilms growing on a
dolomite surface
The feasibility of U(VI) immobilization using SRB biofilms for bioreduction
and the stability of bioreduced U in carbonate-buffered groundwater are still under
discussion, especially for contaminated sites containing carbonate-bearing minerals.
Although the mineral type on which biofilms are grown and the total carbonate
concentration affect U removal efficiency, literature results demonstrate that SRB
biofilms precipitate U and that the precipitated U is stable over a long period of time
S
0
U(IV)
e
-
U(VI)
UO
2
(CO
3
)
2
2-
, UO
2
(CO
3
)
3
4-
U(VI) + CO
3
2-
S
2-
+ H
+
HS
-
+ H
+
U(VI)
U(IV)
U(VI)
U(VI)
SO
4
2-
H
2
S
Fe(II)
e
-
e
-
e
-
Fe(I
I
), Fe(III)
U(VI)
cell
U(IV)
U
(VI)
EPS
e
-
SR
B
B
iofilm
Redox-Sensitive Mineral
U(VI)
cell
: U(VI) adsorbed or intaken by cells; U(VI)
EPS
: U(VI) accumulated in EPS.
Fig. 1.10
Possible mechanisms of U immobilization and remobilization using SRB biofilms
grown on iron-bearing surface. Reprinted (“adapted”) with permission from Marsili et al. [87].
Copyright 2007 American Chemical Society
