Water remediation by metallic iron: Much ado about nothing –  1 
As profitless as water in a sieve? 2 
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Chicgoua Noubactep *(1,2,3)
 (1) Angewandte Geologie, Universität Göttingen, Goldschmidtstraße 3, D - 37077 Göttingen, 
Germany; 
(2) Kultur und Nachhaltige Entwicklung CDD e.V., Postfach 1502, D - 37073 Göttingen, 
Germany; 
(3) Comité Afro-européen - Avenue Léopold II, 41 - 5000 Namur, Belgium; 
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Running title: Interdisciplinary approach gone astray? Save the peer-review system. 12 
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*Correspondance address:  
PD Dr. Chicgoua Noubactep 
Geologie, Universität Göttingen, Goldschmidtstraße 3, D - 37077 Göttingen, Germany 
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e-mail: cnoubac@gwdg.de
Tel. +49 551 39 33191 
Fax: +49 551 399379 
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Keywords: Interdisciplinary approach, Peer-review system, Permeable reactive barrier, Water 
treatment, Zero-valent iron. 
 
 
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Water remediation by metallic iron: Much ado about nothing - As profitless as water in 
a sieve? 
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Chicgoua Noubactep 
Angewandte Geologie, Universität Göttingen, Goldschmidtstraße 3, D-37077, Göttingen, Germany. 
Kultur und Nachhaltige Entwicklung CDD e.V., Postfach 1502, D-37005 Göttingen, Germany. 
Comité Afro-européen - Avenue Léopold II, 41 - 5000 Namur, Belgium. 
e-mail: cnoubac@gwdg.de; Tel. +49 551 39 3191, Fax: +49 551 399379. 
 
There has been much ado about water treatment with metallic iron (Fe0) since the early 1990s. 
Thousands of articles, books, papers and technical reports have been written (i) describing 
laboratory feasibility tests, pilot plant performances and field implementations from around 
the world, (ii) outlining fundamental causes of failure (if applicable), and (iii) suggesting 
changes for more efficient Fe0 systems [1,2]. However, crucial knowledge about the operating 
mode of Fe0-based systems is still lacking. In other words, fundamental knowledge necessary 
for the proper design of more efficient Fe0 remediation systems is still largely ignored [3].  
To fill this knowledge gap and exploit the huge potential of Fe0 for water treatment, it is 
urgent to use a scientifically-based, truly interdisciplinary approach. Such a comprehensive, 
holistic and inclusive approach will unify a sound community in the quest of more efficient 
Fe0 remediation systems. This argumentation is not new as the funding policy of several 
agencies is based on ‘interdisciplinary approach’. In other words, an interdisciplinary 
approach is already largely followed. Yet still severe crises are encountered, in particular 
concerning the mechanism of contaminant removal in Fe0/H2O systems or even, concerning 
the intrinsic nature of Fe0. Is Fe0 a stand-alone reducing agent or a parent of (adsorbing, 
enmeshing and) reducing agents? The discussion on the nature of Fe0 is now lasting more 
than 6 years [4] but is still largely profitless. It seems, there is a lack of willingness to test new 
ideas even though the comfortable one is obviously not efficient.  
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The technology of treating water with Fe0 was born with the spurious perception, that Fe0 is a 
reducing agent [5]. This illusive view would have challenged almost a 200-years-old 
knowledge on the electrochemical nature of aqueous corrosion [6,7] and almost 100 years 
expertise from intensive research on aqueous iron corrosion [8]. In 1923, Ulick Richardson 
Evans (1889-1980) has provided a modern understanding of the corrosion process based on 
the electrochemical theory. Fortunately, the pioneers of the technology have not explicitly 
challenged the electrochemical theory of aqueous iron corrosion. They have simply ignored it 
and built a self-satisfactorily ‘knowledge system’ regarding Fe
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0 as a reducing agent. This 
knowledge system can not explain why chemical species without any redox properties have 
been quantitatively removed in Fe0/H2O systems. Moreover, for Fe0 to act as a reducing 
agent, electrons from the metal body should be relayed to the species of concern (including 
contaminants) by electronic conductive phases [5]. However, neither the multi-layer oxide 
scale on iron is conductive nor natural organic materials have been (univocally) positively 
tested as ‘electron shuttles’ [9-13]. In fact, the model of oxide scale generation and evolution 
sustaining the ‘reductive transformation’ concept [9] was proven inconsistent by 
Odziemkowski and colleagues [10-12]. Moreover, although magnetite films (Fe3O4) are 
electronic conductive in nature, the whole oxide scale on Fe0 is always made of several layers 
including layers of FeIII-species [14-16]. This evidence makes quantitative electron transfer 
from the metal body to species adsorbed at the outer surface of the oxide scale unlikely. In 
other words, all ‘crutches’ that have supported the introduction of the illusive concept have 
been proven false, but the concept is still miraculously alive. 
A cursory look at the literature on remediation with Fe0 reveals a vast scholarship originating 
from diverse disciplines and using Fe0 of various types and sizes for multiple goals (e.g. 
environmental remediation, drinking water production, soil cleaning, wastewater treatment) 
[17-19]. The acronym “zero-valent iron” is used to designate elemental/metallic iron. That is 
iron in the oxidation state zero (Fe0). The term ‘valence’ in “zero-valent iron” is wrongly 
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used. This misleading acronym is anterior to the Fe0 remediation technology. However, Fe0 is 
(still almost) univocally used as electron source for contaminant reductive transformation. 
Current and past researches aim to improve the understanding of interactions within the 
Fe
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0/H2O system, such that more efficient systems could be designed. It is obvious that no real 
improvement is possible when the intrinsic nature of Fe0 is not established/recognized [20]. 
The intrinsic nature of aqueous metal corrosion is summarized in a paper by Sato [21] in the 
following terms: “Metallic corrosion produces a layer of corrosion precipitates on the metal 
surface in aqueous solutions. The interfacial layer thus produced influences the corrosion of 
underlying metals depending on its ionic and electronic properties. The presence of a gel-like 
or porous precipitate layer of insoluble rusts such as hydrous metal salts or oxides causes 
either accelerated metallic corrosion or passivation”. This text recalls that iron is corroded by 
water and that the Fe0 surface is covered by oxide layers. These layers are non conductive as a 
rule. Accordingly, regardless from the background of any active researcher, his primary work 
should consist on elucidating how such a system will behave in the presence of target species, 
including the contaminants. If such an approach was adopted, a false concept would have not 
been introduced in the 1990s. Moreover, an alternative view would have not remain 7 years 
mostly untested. 
Arguments against the alternative view are numerous and include the following: (i) the 
prevailing concept is well accepted, (ii) it is not worth to look nearly into the matter, (iii) the 
author has not presented experimental results, (iv) the author has already published this 
argument in other forums, (v) no better support of old arguments are given, and (vi) related 
articles appeared in ‘low impact journal’. Taken together this argumentation is not based on 
scientific facts and has even not really addressed the crucial point: the reductive 
transformation concept is simply false. The best pseudo-scientific argument will not correct 
this mistake. A more scientific attitude recommends that the inherently wrong concept is 
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abandoned and the alternative, already positively tested by few researchers [20,22-24] is 
considered as the new compass in exploring the Fe
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0/H2O universe. 
There is indeed much ado about the operating mode of Fe0/H2O systems, as there should be. 
The critical issue of this discussion is the mechanism of contaminant removal. This issue is 
elegantly solved by simply properly considering the iron corrosion literature [14-16]. 
Alternatively, the thermodynamics of iron oxidative dissolution and the subsequent 
precipitation of iron phases can be considered. Instead of arguing with examples, scientists 
should have trusted the expertise of their colleagues who are closer in their academic 
background to electrochemistry [25,26]. Thus, it is argued that the operating mode of Fe0/H2O 
systems must be addressed comprehensively through sound interdisciplinary studies. In this 
effort, expertise of individual scientists should be respected. If individual expertise is not 
respected, the vast array of ‘scientific’ studies may just seep though the sieve of intellectual 
selfishness. This intellectual selfishness is as profitless as water in a sieve [27,28].  
To conclude, the German thinker, Johann Wolfgang von Goethe (28.08.1749 - 22.03.1832) 
will be quoted: “In the sciences, people quickly come to regard as their own personal 
property that which they have learned and had passed on to them at the universities and 
academies. If someone else comes along with new ideas that contradict the Credo and in fact 
even threaten to overturn it, then all passions are raised against this threat and no method is 
left untried to suppress it. People resist it in every way possible: pretending not to have heard 
about it; speaking disparagingly of it, as if it were not even worth the effort of looking into the 
matter. And so a new truth can have a long wait before finally being accepted." It is amazing, 
perhaps also surprising, to realize that this observation is valid even for an evidence resulting 
from a falsification of the mainstream corrosion science. It seems that the primordial 
motivation for scientific publication is no more the scientific content but some common 
‘urgencies’ ("publish or perish"). Relevant ‘urgencies’ include patents, promotions, proposal 
success or salary increments [29]. "Publish or perish" is an excellent threatening reminder of 
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the importance of the publication of scientific achievements. However, despite simplified 
accessibility to scientific articles (e.g. SciFinder
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®, Scopus®, Web of Sciences®) dealing with 
Fe0, individual articles must be critically and impartially evaluated. In other words, the ‘‘So 
what?’’ question [30] should always be in the mind of each author, if scientific progress is 
sought. 
Acknowledgements 
Thanks are due to Sabine Caré (Laboratoire Navier (ENPC/IFSTTAR/CNRS) Paris/France) 
for fruitful collaboration on the consideration of the expansive nature of iron corrosion. The 
manuscript was improved by the insightful comments of anonymous reviewers from CLEAN 
Soil, Air, Water. 
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