Geoscience Reference
In-Depth Information
Fig. 16.6 Effects of pre-
adsorbed Zn(II) versus Zn(II)/
As(III) simultaneous
treatment on As(III)
oxidation kinetics on
birnessite surfaces (pH 4.5,
suspension density = 0.1 g/
L, in 0.01 M NaCl, total
Zn(II) concentration of
100 lM, and N
2
atmosphere).
Percent As(III) depletion,
As(V) release, and total As
adsorption are shown as a
function of time (h). a Initial
As(III) concentrations:
[As(III)]
i
= 100 lM;
b [As(III)]
i
= 300 lM.
Reprinted with permission
from Power et al. (
2005
).
Copyright 2005 American
Chemical Society
was transformed into Pu(VI) by oxidation; but two years later, due to a reduction
process, Pu(VI) was transformed into Pu(IV). Plutonium reduction on the mineral
surface is dependent on both Pu speciation/hydrolysis at the mineral surface as
well as the redox capacity of iron minerals on the surface (Powell et al.
2006
).
Subsurface environments under anoxic conditions may contain high levels of
Fe(II) on the solid phase or dissolved within immobile pore water or groundwater.
The role of Fe(II) species in reductive transformation reactions of organic and
inorganic contaminants in the subsurface was reviewed by Haderlein and Pecher
(
1988
). A major finding of current studies is that Fe(II) associated with solid
phases is much more reactive than Fe(II) present in dissolved forms (e.g., Erbs
et al.
1999
; Hwang and Batchelor
2000
).
Klupinski et al. (
2004
) report a laboratory experiment on the degradation of a
fungicide, pentachloronitrobenzene (C
6
Cl
5
NO
2
), in the presence of goethite and
iron oxide nanoparticles; this study was intended to illustrate the fate of organic
agrochemical contaminants in an iron-rich subsurface. To compare the effects of
iron with and without a mineral presence, experiments were performed using
Fe(II) goethite and Fe(II) with no mineral phase added. The degradation kinetics of
