Nanoscale Metallic Iron for Environmental Remediation: Prospects and Limitations

TL;DR

This paper critically examines the use of nanoscale metallic iron (nano-Fe0) for groundwater remediation, highlighting its limitations, proposing the roll-front concept as a potential mechanism, and emphasizing the need for further research to establish its efficacy.

Contribution

It provides a comprehensive analysis of nano-Fe0 reactivity, introduces the roll-front mechanism hypothesis, and discusses the limitations and future research directions for nano-Fe0 in environmental remediation.

Findings

Mass transfer limitations hinder nano-Fe0 effectiveness.

The roll-front mechanism could explain successful remediation zones.

Further research is needed for science-based nano-Fe0 application.

Abstract

The amendment of the subsurface with nanoscale metallic iron particles (nano-Fe0) has been discussed in the literature as an efficient in situ technology for groundwater remediation. However, the introduction of this technology was controversial and its efficiency has never been univocally established. This unsatisfying situation has motivated this communication whose objective was a comprehensive discussion of the intrinsic reactivity of nano-Fe0 based on the contemporary knowledge on the mechanism of contaminant removal by Fe0 and a mathematical model. It is showed that due to limitations of the mass transfer of nano-Fe0 to contaminants, available concepts cannot explain the success of nano-Fe0 injection for in situ groundwater remediation. It is recommended to test the possibility of introducing nano-Fe0 to initiate the formation of roll-fronts which propagation would induce the reductive transformation of both dissolved and adsorbed contaminants. Within a roll-front, FeII from nano-Fe0 is the reducing agent for contaminants. FeII is recycled by biotic or abiotic FeIII reduction. While the roll-front concept could explain the success of already implemented reaction zones, more research is needed for a science-based recommendation of nano- Fe0 for subsurface treatment by roll-fronts