Characterizing the reactivity of metallic iron in Fe0/EDTA/H2O systems 
with column experiments 
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Noubactep C. 
Angewandte Geologie, Universität Göttingen, Goldschmidtstraße 3, D - 37077 Göttingen, Germany. 
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e-mail: cnoubac@gwdg.de; Tel. +49 551 39 3191, Fax: +49 551 399379 
Abstract 
Characterizing the intrinsic reactivity of iron materials for environmental remediation has 
received relative little interest. Available results are mostly based on the removal extent of 
selected contaminants in batch systems. Under static conditions however, contaminant 
removal depends on the properties of the oxide-film. The present study was performed to 
investigate the chemical reactivity of nine Fe0 materials under conditions that minimize the 
formation of an oxide-film on the metal surface. Ethylenediaminetetraacetate (EDTA) was 
used to sustain Fe0 dissolution during column testing for two months. The results confirm Fe0 
dissolution rate in 2 mM EDTA as a good tool for comparative reactivity characterization. 
Moreover, long-term column studies with 2 mM EDTA enable: (i) the evidence of increased 
powdered Fe0 reactivity relative to granular materials, and (ii) a clear differentiation among 
granular materials which exhibited very closed extents of iron dissolution under static 
conditions. Future works comparing Fe0 intrinsic reactivity should ideally characterize 
material behaviour in an oxide-free system and compare the results to those obtained under 
relevant experimental conditions. 
Key words: Column study; EDTA; Electrochemical reactivity; Water Remediation; 
Zerovalent iron. 
1. Introduction 
Iron-based permeable reactive barriers (iron walls) have been successfully used as an efficient 
in situ remediation technology for groundwaters contaminated with various organic and 
inorganic compounds over the past 15 years [1-5]. The real mechanism of contaminant 
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removal is yet to be elucidated. Despite a broad consensus on reductive transformations [1], 
quantitative contaminant removal by other mechanisms has been reported. Currently, it is 
assumed that Fe
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0/H2O systems may remove chlorinated organics by reductive degradation, 
whereas metals, metalloids and radionuclides may be removed via reductive precipitation, 
surface adsorption or complexation, or co-precipitation with the Fe oxyhydroxides that are 
generated in the system [2-4]. The validity of this concept is progressively questioned [6-12]. 
In fact, some of the enumerated processes must be fundamental and valid for all possible 
pollutants while others will be valid only in particular situations (e.g., the contaminant is 
reducible). In addition to the diversity of successfully removed contaminants in Fe0/H2O 
systems, there is diversity among Fe0 sources (intrinsic properties) and thus diversity in the 
chemical reactivity of used materials. 
Over the past 20 years Fe0 materials used in laboratory and field Fe0/H2O systems was 
available from a variety of commercial sources including [13-15]: (i) chemical reagents (e.g. 
Merck, Across, Aldrich), (ii) untreated scrap iron and by-products [15, 16], and (iii) Fe0 
materials manufactured for environmental remediation (e.g. Connelly-GPM Inc., G. Maier 
GmbH, ISPAT GmbH, Peerless Metal Powders & Abrasive). The results of experiments 
using such different materials have been compared to each other with little care on the 
intrinsic material reactivity (see next section). To date there is no standard parameter to 
evaluate the intrinsic reactivity of Fe0 materials [17]. However, it is well known that, the 
metal type and method of manufacture are as important as the environment (solution 
corrosiveness) for corrosion processes [18]. Clearly, the presence and amount of alloying and 
other foreign elements, the size of the material, and whether the metal is cast, forged, wrought 
or welded are critical to material intrinsic reactivity (corrodibility). A further problem with the 
majority of commercially available Fe0 is that the materials are produced from scrap iron and 
steel obtained from a number of primary industries using iron in the production of automotive 
and related industrial parts [13]. Therefore, the “feedstock” for commercially available Fe0 is 
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a mixture including scrap iron and steel. The mixture is heated at 700 to 1200°C in rotary 
kilns to burn off the non-metallic materials, especially the cutting oils [13]. Accordingly, the 
real manufacturing history of commercially available Fe
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0 is not traceable. This is the major 
reason why materials should be characterized “as received”. 
Factors affecting Fe0 reactivity in laboratory experiments can be divided into three subgroups: 
(i) material-dependent factors (intrinsic reactivity - mostly not directly accessible to 
researchers), (ii) environment-dependent factors (investigable at individual relevant sites), and 
(iii) operational experimental parameters (should be designated to mimic environment-
dependent factors). Environment-dependent factors and operational experimental parameters 
are not addressed in the present work. As concerning material-dependent factors, they 
include: Fe0 manufacturing history, Fe0 elemental composition, Fe0 particle size (nm, μm, 
mm), Fe0 surface area and surface property (also of generated oxides). A decade of 
investigations on Fe0 have not clarified the relative importance of the individual factors of this 
subgroup [15, 19, 20]. However, an unjustified importance was attributed to one of these 
parameters: the surface area [19, 21] and kinetic rate constant (kobs) are usually normalized to 
the surface area [22, 23]. To characterize the Fe0 intrinsic reactivity, most of the tested 
materials were used without any pre-treatment (“as received”). Only one material was crushed 
and sieved to yield particle size relevant for field applications (≤ 2 mm). Their chemical 
reactivity is evaluated as the extent of iron dissolution in the presence of 
Ethylenediaminetetraacetate (EDTA available as Na2-EDTA). 
The ability of EDTA to sustain iron oxidative dissolution is well documented in the corrosion 
science [24-26] and has been used to avoid the formation of oxide-film on Fe0 in experiments 
investigating contaminant removal in Fe0/H2O systems [27-29]. A comprehensive discussion 
on the chemistry of the Fe0/EDTA/H2O system is given by Pierce et al. [30]. Previous works 
characterizing the reactivity of Fe0 in the presence of EDTA (2 mM) showed that the kinetic 
rate constant of iron dissolution (termed kEDTA) is a useful parameter to differentiate the 
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reactivity of Fe0 materials in batch systems [15]. To further characterize the reactivity of Fe0 
in batch experiments, a parameter τ
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EDTA was introduced [31, 32]. Per definition, τEDTA is the 
time necessary to reach aqueous Fe saturation under given experimental condition assuming 
1:1 Fe/EDTA complexation ([Fe] = 2 mM or 112 mg/L). 
The objective of the present work was to investigate the feasibility of using EDTA to 
characterize the reactivity of Fe0 materials in column studies. For this purpose a series of nine 
pre-selected Fe0 materials are used. Their chemical reactivity in a 2 mM EDTA solution is 
comparatively examined. The extent of iron dissolution in individual columns is used to 
assess Fe0 reactivity. For the sake of clarity the definition of chemical reactivity will be 
recalled. 
2. Electrochemical reactivity of Fe0
In discussing the suitability of Fe0 for environmental remediation one has to properly 
distinguish between the corrodibility of Fe0 and the corrosiveness of the aqueous 
environment. Fe0 corrodibility is the material's susceptibility to corrosion or the material’s 
intrinsic chemical reactivity. Because iron corrosion is primarily an electrochemical process, 
Fe0 intrinsic reactivity can be regarded as Fe0 electrochemical reactivity. The corrosiveness of 
the environment refers to the aggressiveness of the aqueous solution toward Fe0 oxidative 
dissolution. Consequently, Fe0 corrodibility and solution corrosiveness are not objective 
parameters but subjective tendencies. Accordingly, the Fe0 electrochemical reactivity is its 
tendency to undergo an oxidative dissolution. Similarly, the corrosiveness of a contaminant 
for a given Fe0 material is its ability to induce oxidative dissolution of the material. Efforts to 
characterize electrochemical reactivity of Fe0 in neutral and close-to-neutral solutions are 
complicated by two major parameters: (i) the formation of oxide layers on Fe0, and (ii) the 
interactions of dissolved species within the oxide layers. Therefore, efforts has been made to 
characterize iron-corrosion-related processes in the absence of oxide layers [15, 26, 30, 31]. 
One of these efforts is used in this study. It consists in using EDTA as chelating agent to 
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avoid the formation of oxide layers on Fe0 and thus, to sustain Fe0 oxidative dissolution by 
molecular O
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2 (and H2O). 
The presentation above shows clearly that each Fe0 material is characterized by its 
electrochemical reactivity and each contaminant by its corrosiveness for a given Fe0. More 
precisely, a given concentration of a contaminant (in a given solution – ionic strength, pH 
value) exhibits a certain corrosiveness for a given Fe0. The difficulty arises when one has to 
compare data obtained by various investigators under different experimental conditions even 
when the experiments would have used the same mass loading of a given Fe0 material [32]. 
To take these weaknesses into account, the present study comparatively investigates the 
kinetics and the extent of Fe0 oxidative dissolution by molecular O2 (and H2O) in the presence 
of EDTA for nine materials in column experiments. 
3.  Materials and Methods 
3.1 Solutions 
Based on previous works, a working EDTA-solution of 0.002 M was used [15, 31, 32]. 
Working EDTA solutions (0.02 M or 2 mM) was obtained by a one step dilution (1:20) of a 
stock solution prepared from an analytical grade chemical (ethylenediaminetetraacetic acid di-
sodium salt - ACROS Organics). A standard iron solution (1000 mg/L) from Baker JT® was 
used to calibrate the Spectrophotometer. The reducing reagent for FeIII-EDTA was ascorbic 
acid. The ascorbic buffer was used to keep the pH <4.0. 1,10 orthophenanthroline (ACROS 
Organics) was used as reagent for FeII complexation. Used L(+)-ascorbic acid and L-ascorbic 
acid sodium salt were of analytical grade. All solutions were prepared using deionised water. 
3.2 Fe0 materials 
One laboratory grade iron powder (ACROS Organics - ZVI9), one scrap iron (ZVI7), and 
seven commercially available iron materials have been tested. Table 1 summarizes the main 
characteristics of these materials together with their iron content. Before used ZVI3 was 
crushed and sieved; the size fraction 1.0-2.0 mm was used without any further pretreatment. 
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The specific surface area of the materials varies between 0.043 and 1.8 m2 g-1. These data 
were compiled from the literature (Tab. 1). The objective of this study is to compare the 
materials in the form in which they could be used in field applications. Accordingly, the  
materials were compared mostly on the basis of the extent of iron dissolution from the same 
initial mass of Fe
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0 (1.0 g) by the same volume of 2 mM EDTA. Apart from ZVI3, all other 
materials were used as obtained. Crushing and sieving ZVI3 aimed at working with materials 
of particle size relevant for field applications. The materials differ regarding their 
characteristics such as iron content, nature and proportion of alloying elements, and shape. No 
information about the manufacture process (e.g. raw material, heat treatment) was available. 
A survey of the elemental composition (Table 1) shows that the tested materials primarily 
differ in their carbon (and silicon) contents. Thereafter the tested materials can be divided into 
three classes: (i) ZVI1, ZVI2, ZVI4, ZVI5, ZVI6 and ZVI7 containing more than 3% carbon 
(cast irons), (ii) ZVI8 and ZVI9 containing less than 3% C are mild steels, and (iii) ZVI3, 
direct reduced iron, containing 1.96 % C belongs to the third class because of the particularity 
of his manufacturing technology, yielding to porous materials. 
Apart from ZVI5 with a regular spherical shape, homogeneous size (d = 1.2 mm) and smooth 
surface [34], all other materials were irregular in shape (filings and shavings) with a rough 
surface. ZVI3 was of very rough surface and even porous. ZVI1, ZVI4, ZVI5, ZVI6 and ZVI9 
were visibly covered with rust whereas all other samples retained their metallic glaze. 
The nine used materials were selected from eighteen Fe0 materials after characterization in 
batch experiments using the EDTA-test [15]. The results are presented elsewhere [32]. The 
results suggested that the batch EDTA-test may not be suitable for characterizing powdered 
Fe0 and Fe0 filings with high proportion of fines [32]. To test the validity of this assumption 
one powdered material (from six tested in [32]) was incorporated in this study together with 
eight materials representative for the variability of the reactivity obtained for the twelve other 
granular materials (chips, filings, shavings). 
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3.3 Iron dissolution studies 157 
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Laboratory scale glass columns were operated in up-flow mode. Nine glass columns (40 cm 
long, 2.6 cm inner diameter) were used. The columns were packed with sand. Each column 
contains 1.0 g of a different Fe0 material in its most upper part. The effective length, the bulk 
density and the porosity of the packed columns were not characterized as they were not 
necessary for the discussion of the results. The kinetics and the extent of iron oxidative 
dissolution by EDTA were the sole targets. The influent solution contained 2 mM EDTA and 
was pumped upwards from PE bottles using a peristaltic pump (Ismatec, ICP 24). Tygon 
tubes were used to connect inlet reservoir, pump, column and outlet. The experiment was 
performed at room temperature (21-25 °C). A stable flow rate of about 11.0 mLh-1 was 
maintained throughout the experiment. Samples for analysis were collected in flow through 
bottles at periodic intervals. The experiments were stopped after 62 days. 
3.4 Analytical methods 
The aqueous iron concentration was determined with a Varian Cary 50 UV-VIS 
spectrophotometer, using a wavelength of 510 nm for iron determination and following the 
1,10 orthophenanthroline method [38, 39]. The instrument was calibrated for iron 
concentration ≤ 10 mg.L-1. The pH value was measured by combined glass electrodes (WTW 
Co., Germany). Electrodes were calibrated with five standards following a multi-point 
calibration protocol in agreement with the current IUPAC recommendation [40]. 
4. Results and discussion 
4.1 Expression of experimental results 
The amounts of Fe dissolved during 62 d are expressed as a percentage, on a mass basis, of 
the total mass (1 g) of the used materials and summarized in Table 2. Although the Fe content 
of individual materials was available, the leaching percentage was referenced to the initial 
mass of material (1.0 g). This choice is justified by the fact that materials are characterized on 
the weight basis for their capacity to be used for contaminant removal. Regardless from the 
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actual removal mechanism, the extent of contaminant mitigation is necessarily coupled with 
the extent of Fe dissolution. Therefore, not the total Fe content is essential, but rather the 
reactive proportion (leaching extent) and the kinetics of the leaching process. The changes in 
pH was not recorded. The kinetics of Fe dissolution is expressed as variation of aqueous Fe 
concentration with the cumulative volume which is directly proportional to the elapsed time. 
The experiment was stopped after that 16.0 to 16.8 L of EDTA has flowed through the 
columns. Potentially, 16 L of EDTA (2 mM) can dissolved 1.8 g Fe. Depending on the 
electrochemical reactivity of the individual materials, the amount of leached Fe during the test 
varies from 27 to 73 % of the initial weight of Fe
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0 material (1.0 g). 
4.2 Kinetics of Fe0 oxidative dissolution 
Figure 1a shows that two from the nine tested materials exhibited markedly increased 
dissolution kinetics after the half time of the experiment (1 month corresponding to the date 
where 8 L of EDTA has flowed through the columns): ZVI3 (direct reduced iron) and ZVI8 
(powder). After 1 month all materials exhibited very similar dissolution kinetics (Fig 1a). The 
powdered material exhibited the most rapid kinetic of iron dissolution with 77 % of the total 
leached amount of Fe (729 mg after 62 d, Table 2) been leached after 1 month. The extent of 
iron leaching after 1 month for all other materials, relative to the total leached amount at the 
end of the experiment, varies between 54 and 66 %. The order of reactivity of the material 
deduced from the extent of leached iron after 1 month (31 d) is the following:  
ZVI5 < ZVI7 < ZVI2 < ZVI9 < ZVI4 < ZVI6 < ZVI3 < ZVI1 < ZVI8. 
The order of reactivity derived from the total amount of leached iron at the end of the 
experiment (62 d) is the following:  
ZVI5 < ZVI4 < ZVI6 < ZVI9 < ZVI11 < ZVI2 < ZVI7 < ZVI3 < ZVI8 
Either Fe0 material used in this study (including powdered ZVI8) might be suitable for use in 
field reactive wall applications unless it is not affordable. The different reactivity for 
dissolution in 2 mM EDTA would certainly influence the choice of Fe0 with regard of site 
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specific conditions. It is interesting to notice that ZVI9 with one of the largest surface area 
(1.8 m
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2 g-1) is one of the poorest reactive materials. Also ZVI5 and ZVI6 with the largest 
carbon content are among the less reactive materials. Given the similarities in surface area of 
used materials due to similarity in the particle size (except for powdered ZVI8 and porous 
ZVI3), it is definitively clear that Fe0 manufacture history causes the observed differences in 
reactivity. Due to lack of information on these two aspects, their importance can not be 
accurately accessed or discussed in the remainder of the paper. Although discussing the 
effects of Fe0 manufacture history is over the scope of this work, a brief discussion on the 
impact of iron content and surface area will be given bellow. 
Figure 2 summarises the extent of iron dissolution from tested materials as function of 
specific surface area (Fig. 2a) and the iron content (Fig. 2b) of the materials. It is obvious that 
neither the iron content nor the SSA correlated with the extent of Fe leaching by EDTA. From 
Fig. 2a the material with the highest surface area exhibited one of the lowest Fe leaching 
efficiency and from Fig. 2b the material with the lowest iron content exhibited the highest Fe 
leaching efficiency.  
Figure 1b summarises the kinetics of iron dissolution from the seven granular materials 
(filings, chips) with similar reactivity in fig 1a. Due to a change in the scale on the 
concentration axe (≤ 50 mg/L) a certain reactivity differentiation can be made graphically. For 
example it can be seen that ZVI5 (cast iron having the least surface area) is the least reactive 
material whereas ZVI1, ZVI2 and ZVI7 exhibit an increased initial dissolution kinetic. After 
about one month ZVI7 (and to some extent ZVI2) was the sole material exhibiting an 
increased dissolution kinetics. These results indicated that systems containing powdered and 
granulated materials will loss their efficiency sometimes after their field implementation. For 
systems with powdered materials the loss of efficiency is due to depletion of readily reactive 
site at the surface. Efficiency loss for granular material is due to intrinsic properties. Note that 
no passivation due to hydroxide/oxide precipitation is expected under flowing conditions in 
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EDTA. Considering intrinsic reactivity loss in material selection will certainly reduce the 
probability of barrier failure. For example, Morrison et al. [41], reported on a Fe
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that showed sooner breakthrough than expected for molybdenum and uranium. Performance 
failure was attributed to: (i) the continual build-up of mineral precipitates on the Fe0 surface, 
(ii) the loss of pore space, (iii) the development of preferential flow paths, and (iv) the 
complete bypass of the Fe0/H2O system resulting in the loss of hydraulic control. The results 
of the present study suggest that a non purposeful material selection could have been an 
important factor as well. 
4.3 Extent of Fe0 oxidative dissolution 
Figure 3 summarises the evolution of the cumulative mass of leached iron as function of the 
volume passed through the columns. As for the kinetics, a net difference is observed for ZVI8 
and ZVI3 (Fig. 3a). All other seven materials exhibited very similar dissolution behaviour in 
the initial phase of the experiment (4 L of EDTA passed or 2 weeks) and a clearer reactivity 
differentiation with increasing experimental duration. Most of available experiments are 
performed in batch systems (iron precipitation after saturation) and the experimental durations 
are rarely greater than 2 days. In such experiments only the initial reactivity of Fe0 materials 
are tested. Even though tested materials are often those used for field Fe0/H2O systems, 
accurate long-term data are very difficult to obtain, particularly when service life in the range 
of decades are needed. This study shows that long-term column experiments (together with 
purposeful modelling efforts) can help to bridge the gap between field and laboratory. 
4.4 Discussion 
The results of Fe0 oxidative dissolution by molecular O2 in 2 mM from this study are 
compared with that obtained by the same materials for methylene blue (MB) discoloration 
[42] and 2 mM EDTA Fe0 dissolution in batch systems [32]. The order of reactivity of 
material for column studies for 1 month (initial dissolution) and 2 months (long term 
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dissolution) are given separately above. The order of reactivity for the other systems are the 
following: 
EDTA: ZVI5 < ZVI2 < ZVI9 < ZVI4 < ZVI6 < ZVI7 < ZVI3 < ZVI1 < ZVI8 
MB:   ZVI5 < ZVI2 < ZVI7 < ZVI3 < ZVI6 < ZVI9 < ZVI4 < ZVI1 < ZVI8 
The comparison of the initial kinetics of Fe0 dissolution in batch (kEDTA) and column (31 d) 
studies reveals that ZVI5 and ZVI2 are the least reactive materials whereas ZVI3, ZVI1 and 
ZVI8 are the most reactive ones. However, ZVI1, ZVI2 and ZVI5 are all cast irons whereas 
ZVI3 is direct reduced iron. Therefore, the relative Fe0 reactivity can not be predicted from 
the elemental chemical composition. Only direct reduced iron could confirm the foreseeable 
effect of increased reactivity due to porosity or increased surface area.  
The relative reactivity of the four other materials do not show also a net trend. This is 
certainly due to the fact that 1 month is a too long time to be considered as time of initial 
dissolution. Therefore, the order of reactivity considering the initial dissolution is the 
following obtained in batch experiments: 
ZVI5 < ZVI2 < ZVI9 < ZVI4 < ZVI6 < ZVI7 < ZVI3 < ZVI1 < ZVI8. 
The order of dissolution deduced from the total mass of Fe leached after 62 days was the 
following: 
ZVI5 < ZVI4 < ZVI6 < ZVI9 < ZVI1 < ZVI2 < ZVI7 < ZVI3 < ZVI8. 
It is very interesting to observe that only ZVI5 and ZVI8 conserved their ranking in both 
classifications. However, it can be emphasized that for longer experimental duration ZVI8 
(powder) will be depleted. Therefore, the selection of a material should take into account its 
reactivity, the relative the flux of contaminant in the ground water and the volume of water to 
be treated. In some cases it could be advantageous to work with a less reactive material like 
ZVI5 which is reactive in the long-term. Some applications will need powdered and even 
nano-sized Fe0 for short-time rapid contaminant removal. Next to the iron intrinsic reactivity 
yielding Fe0 dissolution, the relationship between Fe0 reactivity and contaminant removal 
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depends on the oxide-films formed as result of iron corrosion. To take this important aspect 
into account the relative reactivity of used materials as accessed by the extent of methylene 
blue (initial concentration 20 mg/L) discoloration for 1 month [42] was compared to the data 
on iron dissolution in 2 mM EDTA. The results of MB removal were more comparable to that 
of iron dissolution in batch systems than to that of columns systems. The slight differences 
can be attributed to the surface state (roughness, oxidation state) of individual materials. 
5. Concluding remarks 
EDTA has been used for the characterization of the reactivity of Fe0 materials mostly of 
similar particle size (comparable available surface area). The observed great differences in the 
chemical reactivity could not be correlated with the surface area. This suggests that surface 
area plays a secondary role in controlling Fe0 electrochemical reactivity. The carbon contain 
of the materials was not also determinant for electrochemical reactivity. Because intrinsic 
factors determining the chemical reactivity of Fe0 materials are of limited accessibility, 
available materials should be tested in a systematic holistic approach to identify trends in their 
general reactivity. In this effort, beside batch and column study with chelating agents (e.g. 
EDTA), long-term batch and column experiment with various contaminants are needed. 
Given the large spectrum of contaminants that have been successfully removed in Fe0/H2O 
systems, this ambitious work can not be achieved by individuals or isolated research groups. 
The challenge should be to move from studies proving the viability of Fe0 technology to 
investigations incorporated within a broad-based understanding of process occurring in 
Fe0/H2O systems [43]. In this effort the proper characterization of used materials is a 
fundamental issue. 
Acknowledgments 
For providing the materials investigated in this study the author would like to express his 
gratitude to the branch of the MAZ (Metallaufbereitung Zwickau, Co) in Freiberg (Germany), 
Gotthart Maier Metallpulver GmbH (Rheinfelden, Germany), Connelly GPM Inc. (USA), Dr. 
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Ralf. Köber from the Institute Earth Science of the University of Kiel and Dr. Vera Biermann 
from the Federal Institute for Materials Research and Testing (Berlin, Germany). Emin 
Özdem (student research assistant) is acknowledged for technical support. The work was 
granted by the Deutsche Forschungsgemeinschaft (DFG-No 626/2-2). 
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 17
Table 1: Origin, name and main characteristics of tested Fe0 materials. 429 
430  
 origin original denotation  code  form ∅ 
(μm) (a)
MAZ, mbH Sorte 69(b) ZVI6  filings 80-4000 
G. Maier GmbH FG 0300/2000 ZVI1  filings 200-2000 
G. Maier GmbH FG 1000/3000 ZVI4  filings 1000-3000 
Würth Hartgußstrahlmittel ZVI5  spherical 1200 
Hermens Hartgußgranulat ZVI2  granular 1500 
G. Maier GmbH Graugußgranulat ZVI7 chips 350-1200 
ISPAT GmbH Schwammeisen ZVI3 filings 9000 
Connelly-GPM ETC-CC-1004 ZVI9 filings 500-1000 
ACROS Fe, powder, 99% ZVI8  powder 45 
(a) Average values from material supplier; (b) Scrap iron material. 431 
432 
433 
 
 18
Table 2. Elemental composition and specific surface area (SSA) of iron materials used in this 
study. n.a. = not available and n.d. = not determined. 
433 
434 
435  
ZVI Elemental (%) SSA 
 C Si Mn Cr Mo Ni Fe (m2/g) 
ZVI1(a) 3.2 1.95 n.a. 0.023 n.a. 0.02 92.00 0.048(b)
ZVI2 3.13 0.17 0.42 0.16 n.d. 0.23 96.7 0.50(c)
ZVI3 1.96 0.12 0.09 0.003 n.d. <0.001 86.3 0.63(d)
ZVI4(a) 3.2 1.95 n.a. 0.023 n.a. 0.02 92.00 0.048(b)
ZVI5 3.39 0.41 1.10 0.34 n.d. 0.088 91.5 0.043(c)
ZVI6 3.52 2.12 0.93 0.66 n.d. n.d. 99.8 0.29(e)
ZVI7(a) 3.13 2.17 0.36 0.077 n.d. 0.056 96.7 0.50(f)
ZVI8 n.a. n.a. n.a. n.a. n.a. n.a. 99.0 n.a. 
ZVI9(a) 2.85 1.85 0.60 0.10 0.15 0.13 89.82 1.8(g)
(a) Data of elemental composition from supplier, (b) ref. [33], (c) ref. [34], (d) Data from supplier, 436 
437 
438 
439 
440 
(e) ref. [35]; (f) ref. [36], (g) ref. [37]. 
 
 
 19
Table 3: Extent of Fe dissolution in column studies for the nine tested Fe0 materials. ‘VT’ is 
the total volume of EDTA (2 mM) that has flowed into the individual columns. 
‘m
440 
441 
442 
443 
444 
445 
T’ is the total mass of leached Fe from individual materials and P (%) is the 
corresponding percentage relative to the initial mass of 1.0 g (or 1000 mg). As a 
rule, the more reactive a material the bigger the mT and P values. General 
conditions: pH0 = 5.2, [EDTA]0 = 2 mM, T = 23 ± 2 °C. 
Fe0 form VT mT P 
  (L) (mg) (%) 
ZVI5 spherical 16.6 272 27.2 
ZVI4 filings 16.6 295 29.5 
ZVI6 filings 16.6 298 29.8 
ZVI9 filings 16.3 332 33.2 
ZVI1 filings 16.6 340 34.0 
ZVI2 granular 16.2 376 37.6 
ZVI7 chips 16.0 430 43.0 
ZVI3 filings 16.8 513 51.3 
ZVI8 powder 16.5 729 72.9 
446 
447 
448 
 
 
 20
448 
449 
Figure 1 
 
0 4 8 12 16
0
30
60
90
120
(a)
 ZVI1
 ZVI2
 ZVI3
 ZVI4
 ZVI5
 ZVI6
 ZVI7
 ZVI8
 ZVI9
iro
n 
/ [
m
g/
L]
Σ volume / [L]
 450 
451 
452 
 
 
0 4 8 12 16
0
10
20
30
40
50
(b)  ZVI1
 ZVI2
 ZVI4
 ZVI5
 ZVI6
 ZVI7
 ZVI9
iro
n 
/ [
m
g/
L]
Σ volume / [L]
 453 
454 
 21
Figure 2 454 
455  
0 25 50 75 100 125 150 175
250
300
350
400
450
500 (a) SSA
Fe
 / 
[m
g]
SSA / [dm2/g]
 456 
457  
88 92 96 100 104
250
300
350
400
450
500
550
(b) iron content
Fe
 / 
[m
g]
Fe content / [%]
 458 
459 
460 
461 
 
 
 22
461 
462 
Figure 2 
 
0 4 8 12 16
0
100
200
300
400
500
600
700 (a)
 ZVI1
 ZVI2
 ZVI3
 ZVI4
 ZVI5
 ZVI6
 ZVI6
 ZVI8
 ZVI9Σ i
ro
n 
/ [
m
g]
Σ volume / [L]
 463 
464  
0 4 8 12 16
0
75
150
225
300
375
450
(b) ZVI1
 ZVI2
 ZVI4
 ZVI6
 ZVI6
 ZVI6
 ZVI9
Σ i
ro
n 
/ [
m
g]
Σ volume / [L]
 465 
466 
 23
Figure Captions 466 
467 
468 
469 
470 
471 
472 
473 
474 
475 
476 
477 
478 
479 
480 
481 
Figure 1: 
Iron release (mg/L) from the Fe0 materials by 2 mM EDTA for 62 days in column 
experiments: (a) all tested Fe0 materials and (b) the seven Fe0 materials exhibiting similar 
reactivity. The lines are not fitting functions, they simply connect points to facilitate 
visualization. 
Figure 2: 
Cumulative iron release (mg) from the Fe0 materials as function of (a) material specific 
surface area (SSA), and (b) material iron content. It is interesting to see that both parameters 
play a secondary role in controlling Fe electrochemical reactivity. 
Figure 3: 
Cumulative iron release (mg) from the Fe0 materials as function of the total volume of 2 mM 
EDTA passed through the columns: (a) for all tested Fe0 materials and (b) for the seven Fe0 
materials exhibiting similar reactivity. The lines are not fitting functions, they simply connect 
points to facilitate visualization. 
 
 24