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Water 2018, 10(5), 651; https://doi.org/10.3390/w10050651

Progress in Understanding the Mechanism of CrVI Removal in Fe0-Based Filtration Systems

Faculty of Industrial Chemistry and Environmental Engineering, Politehnica University Timisoara, Bd. V. Parvan Nr. 6, Timisoara 300223, Romania
Received: 14 April 2018 / Revised: 12 May 2018 / Accepted: 14 May 2018 / Published: 17 May 2018
(This article belongs to the Special Issue Filters in Drinking Water Treatment)
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Abstract

Hexavalent chromium (CrVI) compounds are used in a variety of industrial applications and, as a result, large quantities of CrVI have been released into the environment due to inadequate precautionary measures or accidental releases. CrVI is highly toxic to most living organisms and a known human carcinogen by inhalation route of exposure. Another major issue of concern about CrVI compounds is their high mobility, which easily leads to contamination of surface waters, soil, and ground waters. In recent years, attention has been focused on the use of metallic iron (Fe0) for the abatement of CrVI polluted waters. Despite a great deal of research, the mechanisms behind the efficient aqueous CrVI removal in the presence of Fe0 (Fe0/H2O systems) remain deeply controversial. The introduction of the Fe0-based filtration technology, at the beginning of 1990s, was coupled with the broad consensus that direct reduction of CrVI by Fe0 was followed by co-precipitation of resulted cations (CrIII, FeIII). This view is still the dominant removal mechanism (reductive-precipitation mechanism) within the Fe0 remediation industry. An overview on the literature on the Cr geochemistry suggests that the reductive-precipitation theory should never have been adopted. Moreover, recent investigations recalling that a Fe0/H2O system is an ion-selective one in which electrostatic interactions are of primordial importance is generally overlooked. The present work critically reviews existing knowledge on the Fe0/CrVI/H2O and CrVI/H2O systems, and clearly demonstrates that direct reduction with Fe0 followed by precipitation is not acceptable, under environmental relevant conditions, as the sole/main mechanism of CrVI removal in the presence of Fe0. View Full-Text
Keywords: hexavalent chromium; metallic iron; water treatment; removal mechanism; adsorption; reduction; co-precipitation hexavalent chromium; metallic iron; water treatment; removal mechanism; adsorption; reduction; co-precipitation
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Gheju, M. Progress in Understanding the Mechanism of CrVI Removal in Fe0-Based Filtration Systems. Water 2018, 10, 651.

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