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Journal of Radioanalytical and Nuclear Chemistry, Vol. 267, No.1 (2006) 13–19
0236–5731/USD 20.00 Akadémiai Kiadó, Budapest
©2006 Akadémiai Kiadó, Budapest Springer, Dordrecht
Effect of selected ligands on the U(VI) immobilization by zerovalent iron
C. Noubactep
Centre of Geosciences – Applied Geology, Goldschmidtstrasse 3, D-37077 Göttingen, Germany
(Received December 20, 2004)
The effect of Cl–,CO32–,EDTA, NO2–,NO3–,PO43–,SO42–,and humic substances (HS) on the U(VI) co-precipitation from aqueous solutions by
zerovalent iron (ZVI) was investigated in the neutral pH range. Batch experiments without shaking were conducted for 14 days mostly with five
different ZVI materials (15 g/l), selected ligands (10mM) and an U(VI) solution (20 mg/l, 0.084mM). Apart from Cl–,all tested ligands induced a
decrease of U(VI) coprecipitation. This decrease is attributed to the surface adsorption and complexation of the ligands at the reactive sites on the
surface of ZVI and their corrosion products. The decrease of U(VI) removal was not uniform with the five ZVI materials. Generally, groundwater
with elevated EDTA concentration could not be remediated with the ZVI barrier technology. The response of the system on the pre-treating by two
ZVI materials in 250mM HCl indicated that in situ generated corrosion products favor an irreversible U(VI) uptake. Thus for the long term
performance of ZVI barrier, the iron dissolution should continue in such a way that fresh iron oxide be always available for U(VI) coprecipitation.
Introduction
Uranium contamination of groundwater is
widespread in former mining areas. On some places
contaminated groundwaters have U contents up to
50 mg/l.1,2 The US EPA maximum contaminant level
for U is 30
µg/l. Therefore, efficient, applicable and
affordable techniques are necessary to mitigate the
health risk by eliminating or reducing the removal of U
from the mine water and contaminated groundwater.
Zerovalent iron (ZVI) has been discussed in the
literature as a U removing reagent in permeable reactive
walls.
In the first step of application of ZVI materials for
groundwater remediation, Fe0was considered as
electron donor to chemically reduce the aqueous, mobile
U(VI) species to a less soluble U(IV) precipitate.
Recently, it was demonstrated that under the
experimental conditions mentioned by the cited authors,
U(VI) is almost irreversible entrapped by coprecipitation
in the matrix of in situ generated and aged corrosion
products.6–8 This observation is confirmed by field
speciation data showing that at least 50% of removed
uranium remained in the oxidation state VI.9Therefore,
the long term stability of fixed U(VI) has to be
reconsidered.10 Moreover, it is important to understand
the effect of geochemical variables such as chemical
composition of the plume, pH, and redox potential on
the behavior of the PRB (see Reference 11 and
references therein). It is expected that major ions,
organic and inorganic ligands, will affect the U(VI)
coprecipitation by chemical interactions both with Fe0
and its corrosion products (iron oxides and green rusts)
in a PRB system, which may influence the effectiveness
and longevity of PRB for contaminant removal.
*E-mail: cnoubac@gwdg.de
Based on the uranium geochemistry and the
corrosion properties of iron, four classes of groundwater
constituents can be distinguished:
(1) Electro-active water constituents, which favor
iron corrosion, having higher standard electrode
potentials (Cl–,SO42–,NO3–,...);
(2) Components which readily form complexes with
U(VI) ions (humic substances – HS; CO32–;PO43–);
(3) Other electro-active contaminants, which are
competing with U(VI) in the removal by ZVI (CrO42–,
Pb2+,TcO4–,...);
(4) Metal cations having a standard potential below –
0.44 V (Na+, K+,Mg2+,Ca2+,...). These cations may
not directly affect the fixation by ZVI but compete with
U(VI), e.g., in precipitation reactions, apart from
modifying the ionic strength.
Note that all the materials mentioned interact with
the corrosion products and with the blanc surface of ZVI
materials by sorption of complexation. In the present
study only the materials under 1 and 2 have been
investigated.
The variability of the groundwater composition has
been published12,13 and the effect of groundwater
constituents on the reactivity of Fe0materials14–16 and
their corrosion products at least for some
contaminants,11,17 investigated. The influence of organic
and inorganic ligands on the U(VI) uptake by Fe0has
not been systematically studied. Consequently, this
study deals with the effect of selected organic (EDTA,
HS) and inorganic (Cl–,CO32–,NO2–,NO3–,PO42–,
SO42–)ligands on the coprecipitation of U(VI) by ZVI.
For this purpose, batch experiments without shaken
were performed with a constant amount of well-
characterized ZVI materials (15 g/l) and calculated
amounts (10mM) of selected ligands. Leaching was
made with sodium carbonate (100mM). The initial
uranium concentration was 20 mg/l (0.084mM).
C. NOUBACTEP: EFFECT OF SELECTED LIGANDS ON THE U(VI) IMMOBILIZATION BY ZEROVALENT IRON
14
Experimental
Iron materials
Five iron materials were selected for this study: one
scrap iron from a recycling company (Metallauf-
bereitung Zwickau) termed as “ZVI1”, and four
commercially available Fe0materials for groundwater
remediation termed as “ZVI2”, “ZVI3”, “ZVI4” and
“ZVI5”. ZVI2 is a “Hartgustrahlmittel” from Würth,
ZVI3 is a “Hartgugranulat” from Hermens, ZVI4 is a
“Graugueisengranulat” from G. Maier Metallpulver
GmbH, Rheinfelden, and ZVI5 is a “Eisenschwamm”
from ISPAT GmbH, Hamburg – all of Germany. ZVI5
is a direct reduced iron, all other materials are cast irons
of different geometrical shapes. Apart from ZVI5, the
commercial iron materials were used as obtained. ZVI5
was broken to small pieces and sieved, whereas ZVI1
was only sieved. The experiments were then conducted
with particle sizes between 1.0 and 1.6 mm, mainly
without any chemical pretreatment. Table 1 summarizes
the elemental composition of these materials. The
analyses were made by X-ray fluorescence spectro-
metry. Because of a special manufacturing technology,
the structure of ZVI5 is porous, i.e., it is a direct reduced
iron.
In some experiments, ZVI1 and ZVI2 were pre-
treated with 0.25M HCl for 14 hours to free the iron
surface from corrosion products.
Fixation experiments and analytical method
The fixation, the desorption by 0.1M Na2CO3and
the analytical method used are described elsewhere.8In
all experiments the background (reference) solution was
tap water (TW) of the city of Freiberg (Saxonia,
Germany) having a composition (in mg/l) Cl–:7.5,
NO3–:17.5, SO42–:42, Na+:7.1, K+:1.6, Mg2+:6.8 and
Ca2+:37.1, at pH 7.21.
All experiments were performed in triplicate. Error
bars given in the figures represent the standard deviation
from the triplicate runs.
Results and discussion
The experiments were compared on basis of the
total, the reversible and the irreversible fixations (Ptot,
Prev and Pirrev), defined by:
Ptot = 100% [1–(C/C0)] (1)
Prev.=100% [(C0(V0–V1)/V0(C0–C)] (2)
Pirrev.=100% [1–(C/C0)–(C1V0–C0V1)/C0V0)] (3)
where C0and Care the U concentrations before and
after fixation, respectively. C1is the U concentration
after desorption with 100mM Na2CO3,V0gives the
initial volume, and V1the volume after removing about
13 ml of the solution for U analysis at the end of
fixation.
For the comparison of the efficiency of ZVI
materials for a process iin different systems, the relative
Ufixation (Preli)was defined by:
Preli=100% [Pi/Pi0](4)
where Piand Pi0are the fixation (total or irreversible)
efficiencies of a process in the system irelative to the
reference system i0,respectively.
Experimental conditions
The ligands selected for this study are known for
their interactions with ZVI, iron corrosion products or
U(VI).12,14,18 A humic substance (HS from Aldrich) and
EDTA (disodium salt from Merck) were used as proxies
for organic ligands occurring frequently in soil and
subsurface environments. On the other hand, the tested
inorganic ligands (Cl–,CO32–,NO2–,NO3–,PO43–,
SO42–)are common in most subsurface environments or
can occur in an iron reactive barrier (see Reference 11
and references therein). Consequently, they may
influence the U(VI) coprecipitation by ZVI via
adsorption and complexation with the surface sites of
ZVI and its corrosion products. Elevated ligand
concentrations were used to intensify the expected
interactions with ZVI, U(VI) and the corrosion products.
Apart from CO32–,100mM of inorganic ligands were
used. The concentration of humic substance was
80 mg/l.
Table 1. Elemental composition of iron materials (in percents) used
ZVI C Si Mn P S Cr Mo Ni Fe
ZVI1 3.52 2.12 0.93 n.d. n.d. 0.66 n.d. n.d. n.d.
ZVI2 3.39 0.41 1.10 n.d. 0.105 0.34 n.d. 0.088 n.d.
ZVI3 3.13 0.17 0.42 0.053 0.065 0.16 n.d. 0.23 n.d.
ZVI4 3.13 2.17 0.36 0.022 0.029 0.077 n.d. 0.056 n.d.
ZVI5 1.96 0.12 0.09 0.027 0.14 0.003 n.d. <0.001 n.d.
n.d.: Not determined.
C. NOUBACTEP: EFFECT OF SELECTED LIGANDS ON THE U(VI) IMMOBILIZATION BY ZEROVALENT IRON
15
To avoid high dissolved iron concentrations that are
known to interfere with the U analysis using Arsenazo
III-method (see Reference 19 and references therein), a
preliminary work was conducted to determine the
operative EDTA concentration. Figure 1a shows that for
EDTA concentrations below 14mM, the Fe
concentration was about 100 mg/l. Properly calibrated
Fe(III)–U(VI) solutions enabled the minimization of the
impact of Fe(III) on U analysis.18 An EDTA
concentration of 12.5mM was selected for this study.
For carbonates ions, a similar experiment as for
EDTA was conducted and the results on Fig. 1b show
that for a CO32– concentration higher than 25mM the U
uptake significantly decreased. This is justified by the
known affinity of U(VI) for CO32– ions.12 However, this
decrease was not monotone (Fig. 1b). The non
monotone decrease of the U(VI) removal with
increasing CO32– concentration could be reproduced but
it was not further investigated. It should be pointed out
that, even at 50mM CO32– the U(VI) removal (about
35%) was still higher than at 6mM EDTA (about 22%).
This result shows clearly that, in the presence of
Na2CO3,at concentrations higher as 100mM, the U(VI)
removal still occur. This can be the result of both the
U(VI) fixation onto the newly formed iron carbonate
species20,21 or the U(VI) precipitation, e.g., as uranates,
Na2UO4.22 In all the cases the U(VI) removal was
almost irreversible (Fig. 1b).
This result is interesting because 0.1M Na2CO3
(100mM) is usually used in the literature as U(VI)
desorbing agent. To test the reproducibility, two sets of
experiments were conducted with 50mM CO32– of a
duration up to 75 days. The results in Table 2 show that
the uptake was almost irreversible, and the desorption
has been achieved with 100mM Na2CO3.In fact the
reversible fixation efficiency varies between 1.0 and
6.2%, under the experimental conditions given.
Considering that the irreversibility of U(VI) onto
carbonate species have been determined,20 Na2CO3
cannot be used for testing ZVI materials for U(VI)
remediation. NOUBACTEP et al.22 have proposed the use
of natural CO2-saturated mineral waters, which provide
sufficient amounts of HCO3–for U(VI) complexation at
near neutral pH values.
Fig. 1. Variation of the U(VI) fixation by ZVI1 (scrap iron) as a
function of EDTA (a) and carbonate (b) concentrations. All
experiments have been done in triplicate. Error bars give standard
deviations. The presented lines are not fitting functions, they just joint
the points to facilitate visualization. The values on the curve
in Fig. 1a are the iron concentrations in mg/l
Table 2. Variation of total and reversible fixation of U(VI) by scrap iron (ZVI1) in the presence of 0.05M Na 2CO3
t,
days
Ptot,
%
stot,
%
Prev,
%
srev,
%
t,
days
Ptot,
%
stot,
%
Prev,
%
srev,
%
7 84.8 6.2 4.0 2.1 10 79.3 3.2 1.0 0.5
14 92.0 3.0 7.1 3.6 17 84.4 1.7 1.3 0.9
21 92.5 3.6 6.1 1.0 24 88.7 3.0 1.3 0.4
28 93.7 3.1 6.7 2.0 34 93.4 2.5 0.8 0.7
35 97.4 0.2 4.1 1.1 44 94.4 3.1 1.0 0.7
42 95.7 1.8 5.8 1.8 54 97.6 0.7 1.9 0.7
48 93.3 2.8 7.2 2.1 64 97.1 0.3 1.9 0.7
56 95.3 2.2 5.6 1.4 74 97.0 0.1 2.3 0.4
Two non-parallel experiments were conducted (tvalues). The experiments were conducted in triplicate, si
represents the standard deviation for each triplicate.
C. NOUBACTEP: EFFECT OF SELECTED LIGANDS ON THE U(VI) IMMOBILIZATION BY ZEROVALENT IRON
16
Effect of selected ligands
Figure 2 shows the results of the total, reversible
(Fig. 2a) and irreversible (Fig. 2b) U(VI) fixation by
ZVI1 (scrap iron) for 14 days in the presence of 12.5mM
EDTA, 50mM CO32–,10mM of Cl–,NO2–,NO3–,
PO43– SO42–,and 80 mg/l HS. The equilibration time
was chosen to enable a differentiation of the impact of
the ligands on the U(VI) fixation efficiency, under the
experimental conditions based on preliminary
experiments.18 As reference tap water (TW) was used.
It can be seen in Fig. 2a that the total fixation’s
efficiency diminished on the addition of all the ligands,
except PO43–.The total fixation efficiency varied from
23% for EDTA to 99% for PO43–,in the increasing
order of:
EDTA < CO32–<SO42–<NO3–<NO2–<
<Cl–<HS < TW < PO43–
Figure 2a also shows the variation of the reversible
fixations. For EDTA and CO32– the uptake was
practically irreversible, whereas for other ligands the
extent of the reversibility was very different, varying
from 12% for SO42– to 47% for NO2–.Note that the
reversible fixation (Prev)depended on the mass of fixed
uranium whereas Ptot and Pirrev were relative to the
initial mass of U.
Due to the recovery experiment with 100mM
Na2CO3,the irreversible fixation efficiency varied from
23% for EDTA to 73% for TW (Fig. 2b) in the
increasing order of:
EDTA < NO2–<CO32– < SO42– <
<Cl–<NO3–<PO43– < HS < TW.
Comparing the order of efficiency of various ligands
for the total and irreversible fixation, it becomes clear
that the role of corrosion products in influencing the
U(VI) uptake by individual ligands, is quite
complicated.
PO43– has a particular position as a competitive
complexant for U(VI).12 The observed total fixation is
the result of U(VI) precipitation with PO43–,U(VI)
coprecipitation with in situ generated corrosion
products, sorption onto aged corrosion products and on
the surface of Fe0material. U(VI) precipitation with
PO43– and U(VI) coprecipitation with in situ generated
corrosion products were almost irreversible under the
used experimental conditions.18
EDTA exhibited the lowest fixation efficiency, so it
can be assumed, that the fixed U(VI) amount (23%) is
sufficient to build a U(VI) multi-layer at the available
surface of the ZVI material (15 g/l). QUI et al.23 reported
that these U(VI) layers do not prevent iron to corrode.
This statement is confirmed by the results seen on
Fig. 1a. U(VI) removal remained practically constant
when the iron concentration varied from 45 to more than
700 mg/l.
Humic substances usually form complexes with
U(VI),24,25 whose affinity for corrosion products is
known.26 In the U(VI) analysis, after the addition of
100mM Na2CO3the solution was disturbed by a dark
coloration, therefore, the obtained results for Prev and
Pirrev are only indicative.
Effects of selected ligands on various ZVI
Table 3 summarizes the results of total U(VI)
fixation by scrap iron (ZVI1) and four commercial ZVI
materials (ZVI2, ZVI3, ZVI4 and ZVI5) in the presence
of EDTA, HS, CO32–,Cl–,SO42–,and NO3–.As
reference, tap water (TW) was used.
Fig. 2. Uranium(VI) uptake by ZVI1 (scrap iron) in 12.5mM EDTA,
50mM CO32–,80 mg/l humic substance (HS) and 10mM of Cl–,NO2–,
NO3–,PO43–,SO42–.The reference system contained tap water (TW).
Total and reversible fixation (a), irreversible fixation (b).
The desorption experiments were performed with 100mM Na2CO3.
All experiments have been done in triplicate. Error bars give
standard deviations
C. NOUBACTEP: EFFECT OF SELECTED LIGANDS ON THE U(VI) IMMOBILIZATION BY ZEROVALENT IRON
17
Once again, Ptot decreased on the addition of ligands.
The ZVI materials are listed in the order of increasing
Ptot in tap water, that is: ZVI2 < ZVI3 < ZVI4 < ZVI1 <
ZVI5. The same efficiency order is obtained in the
systems with HS, NO3–and CO32–.Each of the other
systems exhibits different behavior. The most important
consequence of these results is that several materials
should be tested for their reactivity under particular, site
specific conditions of an application and the best should
be retained. For example, if a specific groundwater has a
composition similar to that of the used tap water (TW)
or is rich in organic matter, in NO3–or CO32–,then
ZVI5 is the more reactive material to be considered. If,
on the contrary, the groundwater is rich in chloride (Cl-)
then ZVI4 will be the most indicated. On the other hand,
if the EDTA concentration of a groundwater containing
U(VI) is high, alternative remediation technologies have
to be found.
The current material selection strategy is not
appropriate to address long term reactivity of ZVI
material. Therefore, it is possible, that a material that is
as reactive as porous ZVI5 is, losses its reactivity after
few months. For reactive barriers, however, materials
should be supposed to give satisfying remediation for
several decades.27
Effect of ZVI pre-treatment
To investigate further the reactivity of ZVI materials
for U(VI) uptake under subsurface conditions, two sets
of U(VI) fixation experiments were conducted with
15 g/l ZVI1 and 25 g/l ZVI2 and four ligands (Cl–,
CO32–,EDTA and HS). While not pre-treated ZVI2 had
asmooth surface almost completely covered with a
continuous oxide layer, ZVI1 had a rough surface that
prevented the formation of such an oxide layer at his
surface.
The first set of experiment was identical to the above
described one and the second set consisted in pre-
washing both Fe0materials for 14 hours with a 0.25M
HCl solution. This pre-treatment aimed at a slow and
progressive dissolution of the oxides on ZVI without
strongly affecting the surface structure.28 At the end of
this washing time the surface was optically clean and
had a metallic glaze. It is possible that not all the oxide
was removed from the surface in this manner. However,
it was not the intention of this study to work with totally
clean Fe0material, but rather to evaluate the effect of the
presence of atmospheric corrosion products.
The results for ZVI1 in Table 4 can be summarized
as follows:
Table 3. Variation of total fixation of U(VI) (in percents) for five ZVI materials in
the presence of different ligands
ZVI TW HS Cl–SO42– NO3–EDTA CO32–
ZVI2 81 66 57 43 34 19 0
ZVI3 82 76 55 49 45 10 7
ZVI4 91 84 77 54 65 22 6
ZVI1 95 90 66 71 64 8 26
ZVI5 96 91 71 64 76 26 69
TW: Tap water (reference).
HS: Humic substance.
Table 4. Variation of the relative total and irreversible fixation of U(VI) for untreated and 0.25M
HCl washed ZVI1 and ZVI2 in the presence of selected ligands
ZVI1 (scrap iron) ZVI2 (commercial iron)
Ptot,Pirrev,Preltot,P
relirrev,Ptot,Pirrev,Preltot,Prelirrev,Milieu
%%%%%%%%
[TW] 90 64 100 100 65 33 100 100
[HS] 79 71 88 111 48 37 74 114
[Cl–] 94 62 105 98 63 29 96 89
[EDTA] 17 17 19 27 9 9 14 28
[CO32–] 62 62 69 97 54 54 82 164
TW 93 73 103 115 73 57 113 173
HS 81 77 90 121 38 29 58 88
Cl–90 71 100 112 38 33 58 99
EDTA 22 22 24 34 10 10 16 32
CO32– 48 48 54 75 48 45 74 136
The reference per definition is Prel,the removal efficiency for untreated ZVI1 in tap water (TW).
HS: Humic substance.
The brackets symbolize the coverage of the surface with corrosion products (untreated ZVI).
C. NOUBACTEP: EFFECT OF SELECTED LIGANDS ON THE U(VI) IMMOBILIZATION BY ZEROVALENT IRON
18
(1) With untreated materials, U(VI) total fixation
was slightly accelerated in the system with Cl–
(Preltot =103%). In all other systems the total fixation
decreased, the relative fixation was 88, 69 and 19% for
those with HS, CO32– and HS, respectively.
(2) The acidic pre-treatment of ZVI1 increased the
absolute value of Ptot in all systems, except in that with
50mM CO32–,where Ptot decreased from 62 to 48%.
This suggests that even in the presence of elevated
concentrations of carbonate ions, U(VI) is sorbed onto
iron oxides.
(3) The comparison of the Prel (Preltot and Prelirrev.)
values from the two sets of experiments shows that the
pre-treatment enhanced the U(VI) immobilization
efficiency of the material except in the presence of
CO32–.This is due to the fact that when U(VI) is sorbed
onto aged iron oxides (initially present at the surface), it
is readily desorbed in 100mM Na2CO3.In the
experiment with pre-treated ZVI, U(VI) was
progressively sorbed onto in situ generated corrosion
products and was entrapped in their mass during ageing
(coprecipitation) and was, therefore, not available for
desorption with Na2CO3.8When ZVI was freed from
the corrosion product, only the blanc surface of ZVI
with smaller affinity to U(VI) was available for
sorption.18 Therefore, it is not surprising that pre-
washing diminishes the uptake in the presence of
carbonate ions.
The results with ZVI2 (Table 4) show the same trend
as ZVI1 with the particularity that the effect of the pre-
treatment was more pronounced, yielding to Prelirrev
values higher than 170%. Furthermore, pre-washing
diminished the U(VI) removal in the presence of humic
substances. In the presence of EDTA the U(VI) removal
was not influenced by the acidic treatment. This result
supports the fact that ZVI2 was almost completely
covered with an oxide layer. This oxide layer interacted
with HS or was dissolved in EDTA. Note that if U(VI)
removal were the result of a “reductive precipitation”,
freeing the iron surface from corrosion products would
have increased the uptake efficiency.
This result suggests that for a carbonate rich
groundwater ZVI2 (or generally smooth ZVI) is not
indicated. As discussed above, groundwater with
elevated concentration of EDTA should not be treated
with a reactive ZVI barrier. Humic substances will
slightly lower the efficiency of reactive barriers for
U(VI) remediation whereas Cl–practically has a rather
positive effect on the remediation. This chloride
enhancing iron corrosion property is known and
published.14,29,30 In fact, chloride ions participate
directly in anodic dissolution reactions of metals; thus
their presence tends to increase iron corrosion.
Implications for U(VI) removal barriers
The results of this study show that EDTA and
carbonate ions sensibly affect the efficiency of U(VI)
co-precipitation by ZVI. It is suggested that alternative
to ZVI should be found when elevated EDTA
concentration are present or expected. For carbonate rich
groundwater a rational choice of material can enable a
mitigation effect satisfactorily. However, the long term
behavior of such materials is yet to be addressed.
From the other tested ligands (SO42–,NO3–,NO2–,
Cl–,HS, TW, PO43–)only chloride have shown an
enhancing impact on the co-precipitation by ZVI.
However, even at a chloride rich site, not the most
reactive materials (ZVI1 or ZVI5 in this study) will be
selected for application, but rather those, that are capable
assuring a remediation goal for several decades
satisfactorily. It should be kept in mind, that enhanced
corrosion yields more corrosion products (with volumes
at least 2.3 times larger than that of Fe atom in the ZVI
material) that limit the volume of pore spaces in the
reactive barrier beside potentially inhibiting the
electrochemical dissolution of ZVI.
The U(VI) coprecipitation in the ZVI reactive barrier
is based on the continuously production of fresh and
very reactive corrosion products that incorporate U(VI)
into their structure during aging.7At any specific site,
several materials are to be properly tested for their long
term efficiency for removing the target contaminant.
This study shows that a direct reduced iron (ZVI5) is
capable to remove U(VI) efficiently from aqueous
solutions in the presence of various ligands. The long
term reactivity of the material is yet to be investigated.
For the long term immobilization of U(VI) by ZVI, it is
important that fresh iron oxide should be present in the
barrier zone when the contaminant is transported into
the barrier. In nature, the long term iron corrosion can be
influenced by availability and activity of
microorganisms and/or their metabolites.10 Therefore,
the possible effect of indigenous microorganisms at
specific site are to be considered.
*
The author expresses his gratitude to Dipl. Geol. Manuela
JUNGHANS from the Institute for Mineralogy of the Technical
University, Mining Academy Freiberg (Germany) for remarks and
suggestions, that contributed to improve the quality of this manuscript.
The commercial Fe0samples were kindly provided by Dr. Ralf KÖBER
from the Institute for Earth Geoscience of the University of Kiel. The
scrap iron was kindly purchased by the branch of the MAZ
(Metallaufbereitung Zwickau, Co) in Freiberg. The work was
supported by the German Science Foundation (DFG-GK 272).
C. NOUBACTEP: EFFECT OF SELECTED LIGANDS ON THE U(VI) IMMOBILIZATION BY ZEROVALENT IRON
19
References
1. M. JUNGHANS,C. HELLING,in: Tailings and Mine Waste ‘98,
Balkema, Rotterdam, 1998, p. 117.
2. A. MEINRATH,P. SCHNEIDER,G. MEINRATH,J. Environ.
Radioact., 64 (2003) 175.
3.A. A
BDELOUAS,W. LUTZE,H. E. NUTALL,W. GONG,C. R. Acad.
Sci. Paris, Earth Planet. Sci., 328 (1999) 315.
4. B. GU,L. LIANG,M. J. DICKEY,X. YIN,S. DAI,Environ. Sci.
Technol., 32 (1998) 3366.
5. S. J. MORRISON,R. D. METZLER,E. C. CARPENTER,Environ. Sci.
Technol., 35 (2001) 385.
6. C. NOUBACTEP,G. MEINRATH,B. J. MERKEL,Environ. Chem., 2
(2005) 235.
7. C. NOUBACTEP,G. MEINRATH,P. VOLKE,H.-J. PETER,
P. DIETRICH,B. MERKEL,in: Uranium in the Aquatic
Environment, B. J. MERKEL,B. PLANER-FRIEDRICH,
C. WOLKERSDORFER (Eds), Springer, Berlin, 2002, p. 577.
8. C. NOUBACTEP,G. MEINRATH,P. DIETRICH,B. MERKEL,
Environ. Sci. Technol., 37 (2003) 4304.
9. L. J. MATHESON,W. C. GOLDBERG,W. D. BOSTICK,L. HARRIS,
in: Handbook of Groundwater Remediation Using Permeable
Reactive Barriers: Applications to Radionuclides, Trace Metals,
and Nutrients, D. NAFTZ,S. J. MORRISON,C. C. FULLER and
J. A. DAVIS (Eds), Academic Press, San Diego, Calif., 2002,
p. 343.
10. C. NOUBACTEP,A. SCHÖNER,G. MEINRATH,J. Haz. Mat., (2005),
in press (Available online 4 November 2005).
11. C. SU,R. W. PULS,Environ. Sci. Technol., 38 (2004) 2715.
12. D. LANGMUIR,Aqueous Environmental Geochemistry, Prentice
Hall, Upper Saddle River, NJ, 1997, p. 600.
13. W. STUMM,J. J. MORGAN,Aquatic chemistry, chemical equilibria
and rates, in: Natural Waters, John Wiley & Sons, New York,
1996, p. 1022.
14. G. BOHNSACK,Chlorid und die Korrosion von Eisen und Stahl in
natürlichen Wässer, Vulkan, Essen, 1989, p. 166.
15. N. G. KIRBY,Chem. Eng. Progr., (June 1995) 29.
16. H. KLAS,H. STEINRATH,Die Korrosion des Eisens und ihre
Verhüttung, Stahleisen, Düsseldorf, 1974, p. 632.
17. T. SUGIMOTO,Y. J. WANG,Colloid Interf. Sci., 207 (1998) 137.
18. C. NOUBACTEP,Dissertation, TU Bergakademie Freiberg, Wiss.
Mitt. Inst. für Geologie der TU Bergakademie, Freiberg, 21 (2003)
140.
19. G. MEINRATH,P. VOLKE,C. HELLING,E. G. DUDEL,
B. J. MERKEL,Fresenius J. Anal. Chem., 364 (1999) 191.
20. P. V. BRADY,B. P. SPALDING,K. M. KRUPKA,R. D. WATERS,
P. ZHANG,D. J. BORNS,W. D. BRADY,Sandia Report, SAND99-
0464, 1999, p. 146.
21. P. J. COUGHTREY,M. C. THORNE,D. JACKSON,Radionuclide
Distribution and Transport in Terrestrial and Aquatic Ecosystems:
ACritical Review of Data, A. A. Balkem, 1983, p. 2544.
22. C. NOUBACTEP,J. SONNEFELD,M. SAUTER,Grundwasser, 10
(2005) 35.
23. S. R. QIU,H.-F. LAI,M. J. ROBERSON,M. L. HUNT,C. AMRHEIN,
L. C. GIANCARLO,G. W. FLYNN,J. A. YARMOFF,Langmuir, 16
(2000) 2230.
24. P. CRANÇON,J. VAN DER LEE,Radiochim. Acta, 91 (2003) 673.
25. J. J. LENHART,S. E. CABANISS,P. MACCARTHY,
B. D. HONEYMAN,Radiochim. Acta, 88 (2000) 345.
26. T. ZUYI,C. TAIWEI,D. JINZHOU,D. XIONGXIN,G. YINGJIE,
Appl. Geochem., 15 (2000) 133.
27. C. NOUBACTEP,G. MEINRATH,P. DIETRICH,M. SAUTER,
B. MERKEL,Environ. Chem., 2 (2005) 71.
28. C. NOUBACTEP,P. VOLKE,G. MEINRATH,B. MERKEL,in:
International Conference on Radioactive Waste Management and
Environmental Remediation, 8th.2001 Bruges, Belgium:
American Society of Mechanical Engineers.
29. J. FARRELL,W. D. BOSTICK,R. J. JARABECK,J. N. FIEDOR,
Ground Water, 34 (1999) 618.
30. K.-H. TOSTMANN,Korrosion: Ursachen und Vermeidung, Wiley-
VCH, Weinheim-New York, 2001, p. 331.
31. P. R. ROBERGE,Handbook of Corrosion Engineering, McGraw-
Hill, New York, 1999, p. 1140.
