On the suitability of admixing sand to metallic iron for water treatment

Chicgoua Noubactep

doi:10.7726/ijeps.2013.1004

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)

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