Reply to the Comment on “Reduction of chromate by granular iron in the presence of dissolved CaCO3” by C. Noubactep

Gui, Lai; Jeen, Sung‐Wook; Blowes, David W.; Gillham, Robert W.; Yang, YanQi

doi:10.1016/j.apgeochem.2009.08.006

Cited by 3 publications

(2 citation statements)

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“…Researchers and practitioners have long recognized the limits of the reductive transformation concept [11][12][13][14]. However, the view that contaminants are primarily adsorbed and coprecipitated with iron corrosion products [29,30,33] has partly faced with very sceptic views [45,46] or is just degraded to an ''alternative hypothesis to be considered'' [47]. Fortunately, sceptic views are based on the large acceptability of the concept of reductive transformation which was a consen- sus [4] and not the results of hard experimental facts.…”

Section: Discussionmentioning

confidence: 97%

The suitability of metallic iron for environmental remediation

Noubactep¹

2010

Env Prog and Sustain Energy

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Aqueous contaminant removal in the presence of metallic iron is often regarded as a reductive transformation mediated by the Fe 0 surface. However, successful removal of theoretically nonreducible contaminants has been largely reported. This article presents a rebuttal of the concept of contaminant reductive transformation. It is argued through a careful examination of the evolution of the volume and adsorptive properties of iron and its corrosion products that contaminants are primarily adsorbed and coprecipitated with iron corrosion products. One may wonder how the Fe 0 technology will develop with the new concept.

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Section: Discussionmentioning

confidence: 97%

The suitability of metallic iron for environmental remediation

Noubactep¹

2010

Env Prog and Sustain Energy

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“…Moreover, removed contaminants and their potential reaction products are progressively enmeshed in the matrix of ageing corrosion products and are very stable under natural conditions. Accordingly, instead of maintaining an inconsistent concept [33,34,53,54], the scientific community should focus his attention on ways to sustain the corrosion process rather to try to free the Fe 0 from spontaneously generated corrosion products. It should be observed that operational tools presently used to sustain Fe 0 reactivity such as: (i) using smaller particle size of Fe 0 (including nano-scale Fe 0 ), (ii) mixing experimental systems or (iii) using bimetallic systems all result in increased corrosion products generation.…”

Section: Discussionmentioning

confidence: 98%

Elemental metals for environmental remediation: Learning from cementation process

Noubactep¹

2010

Journal of Hazardous Materials

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The further development of Fe(0)-based remediation technology depends on the profound understanding of the mechanisms involved in the process of aqueous contaminant removal. The view that adsorption and co-precipitation are the fundamental contaminant removal mechanisms is currently facing a harsh scepticism. Results from electrochemical cementation are used to bring new insights in the process of contaminant removal in Fe(0)/H(2)O systems. The common feature of hydrometallurgical cementation and metal-based remediation is the heterogeneous nature of the processes which inevitably occurs in the presence of a surface scale. The major difference between both processes is that the surface of remediation metals is covered by layers of own oxide(s) while the surface of the reducing metal in covered by porous layers of the cemented metal. The porous cemented metal is necessarily electronic conductive and favours further dissolution of the reducing metal. For the remediation metal, neither a porous layer nor a conductive layer could be warrant. Therefore, the continuation of the remediation process depends on the long-term porosity of oxide scales on the metal surfaces. These considerations rationalized the superiority of Fe(0) as remediation agent compared to thermodynamically more favourable Al(0) and Zn(0). The validity of the adsorption/co-precipitation concept is corroborated.

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