Abstract

This communication clarifies the relationships between sand addition and the sustainability of iron/water systems for environmental remediation. It is shown that any enhanced contaminant removal in an iron/sand/water relative to an iron/water system is related to the avoidance/delay of particle cementation by virtue of the inert nature of sand. The argument that sand dissolution produces protons (H+) to sustain iron corrosion is disproved by the very low dissolution kinetics solubility of SiO2-bearing minerals under environmental conditions. This demonstration corroborates the concept that aqueous contaminant removal in iron/water systems is not a process mediated by electrons from Fe0.

Highlights

  • IntroductionThe use of metallic iron (Fe0) has become an established technology for environmental remediation and water treatment in recent years (OHannesin and Gillham, 1998; Odziemkowski and Simpraga, 2004; Bartzas et al, 2006; Li et al, 2006; Henderson and Demond, 2007; Hussam and Munir, 2007; Hussam, 2009; Noubactep et al 2009a; O et al., 2009; Bartzas and Komnitsas, 2010; Li and Benson, 2010; Comba et al, 2011; Gheju, 2011; Gunawardana et al, 2011; Jeen et al, 2011; Allred, 2012; Ingram et al, 2012; Jeen et al., 2012; Huang et al, 2012; Noubactep et al, 2012a; Ruhl et al, 2012a; Ruhl et al, 2012b; Ruhl et al, 2012c)

  • Reported studies are focused on ways to enhance the Fe0 reactivity such as using nano-sized particles and bimetallic systems (Ghauch et al, 2011; Crane and Scott, 2012; Noubactep et al, 2012a), using other reactive metallic elements (e.g. Al0, Ti0, Zn0) (Bojic et al, 2007; Sarathy et al, 2010; Guo et al, 2012; Lee et al, 2012; Salter-Blanc et al, 2012) or using hybridized systems like Fe0/Fe3O4/FeII (Huang et al, 2012; Huang et al, 2013a; Huang et al, 2013b)

  • The validity of the current paradigm has been seriously questioned as the relevance of direct reduction for observed efficiency of Fe0/H2O systems was challenged (Lavine et al, 2001; Noubactep, 2007; Noubactep, 2008; Jiao et al, 2009; Ghauch et al, 2010; Noubactep, 2010a; Noubactep, 2010b; Ghauch et al, 2011; Gheju and Balcu 2011; Noubactep, 2011a; Noubactep, 2011b; Noubactep, 2012a; Liu et al, 2013)

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Summary

Introduction

The use of metallic iron (Fe0) has become an established technology for environmental remediation and water treatment in recent years (OHannesin and Gillham, 1998; Odziemkowski and Simpraga, 2004; Bartzas et al, 2006; Li et al, 2006; Henderson and Demond, 2007; Hussam and Munir, 2007; Hussam, 2009; Noubactep et al 2009a; O et al., 2009; Bartzas and Komnitsas, 2010; Li and Benson, 2010; Comba et al, 2011; Gheju, 2011; Gunawardana et al, 2011; Jeen et al, 2011; Allred, 2012; Ingram et al, 2012; Jeen et al., 2012; Huang et al, 2012; Noubactep et al, 2012a; Ruhl et al, 2012a; Ruhl et al, 2012b; Ruhl et al, 2012c). The idea that sand/quartz (SiO2) admixture enhances the extent/efficiency of contaminant removal in Fe0/H2O systems has significant support in the literature (Powell et al, 1995; Kaplan and Gilmore, 2004; Song et al, 2005; Wu et al, 2005; Guo et al, 2011). The observed enhanced efficiency (Song et al, 2005; Bi et al, 2009; Gottinger et al, 2010) should be explained by other processes

Descriptive aspects
Findings
Sand as dispersant
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