New Paper: Effects of Organic Coatings on Reactivity of Zerovalent Metals

[PGT]

This chapter combines new results with review of prior results to provide a fairly complete and balanced perspective on the role that organic coatings plays in determining the reactivity of zerovalent metals in aquatic media. The focus is mainly on nano-scale zerovalent iron (nZVI) and organic polyelectrolytes like carboxymethylcellulose (CMC) and natural organic matter (NOM). The introduction of this chapter also gives a very broad perspective on the relevance of zerovalent metals in environmental science.

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Tratnyek, P. G., A. J. Salter-Blanc, J. T. Nurmi, J. E. Amonette, J. Liu, C. Wang, A. Dohnalkova, and D. R. Baer. 2011. Reactivity of zerovalent metals in aquatic media: Effects of organic surface coatings. In: P. G. Tratnyek, T. J. Grundl , and S. B. Haderlein (ed.), Aquatic Redox Chemistry. ACS Symposium Series, American Chemical Society, Washington, DC, Vol. 1071, Ch. 18, pp 381-406.

Granular, reactive zerovalent metals (ZVMs)--especially iron (ZVI)--form the basis for model systems that have been used in fundamental and applied studies of a wide variety of environmental processes. This has resulted in notable advances in many areas, including the kinetics and mechanisms of contaminant reduction reactions, theory of filtration and transport of colloids in porous media, and modeling of complex reactive-transport scenarios. Recent emphasis on nano-sized ZVI has created a new opportunity: to advance the understanding of how coatings of organic polyelectrolytes--like natural organic matter (NOM)--influence the reactivity of environmental surfaces. Depending on many factors, organic coatings can be activating or passivating with respect to redox reactions at particle-solution interfaces. In this study, we show the effects of organic coatings on nZVI vary with a number of factors including: (i) time (i.e., "aging" is evident not only in the structure and composition of the nZVI but also in the interactions between nZVI and NOM) and (ii) the type of organic matter (i.e., suspensions of nZVI are stabilized by NOM and the model polyelectrolyte carboxymethylcellulose (CMC), but NOM stimulates redox reactions involving nZVI while CMC inhibits them).

DOI: http://dx.doi.org/10.1021/bk-2011-1071.ch018