Impact of carbon, oxygen and sulfur content of microscale zerovalent iron particles on its reactivity towards chlorinated aliphatic hydrocarbons Milica Velimirovic a,b , Per-Olof Larsson c , Queenie Simons a , Leen Bastiaens a,⇑ a Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium b University of Antwerp, Department of Bio-Engineering, Groenenborgerlaan 171, 2020 Antwerp, Belgium c Höganäs AB, Global Development, Bruksgatan 35, 26383 Sweden highlights  Iron composition impacts the disappearance rate of CAHs by mZVI particles.  No correlation between reactivity and specific surface area of the mZVI particles.  The high carbon content induce sorption of the contaminants on the mZVI particles.  Dechlorination of CAHs is generally more rapid by mZVIs containing less oxygen. article info Article history: Received 27 February 2013 Received in revised form 10 July 2013 Accepted 13 July 2013 Available online 17 August 2013 Keywords: Microscale zerovalent iron CAHs disappearance rate Particles composition C, O, S content abstract Zerovalent iron (ZVI) abiotically degrades several chlorinated aliphatic hydrocarbons (CAHs) via reduc- tive dechlorination, which offers perspectives for in situ groundwater remediation applications. The dif- ference in reactivity between ZVI particles is often linked with their specific surface area. However, other parameters may influence the reactivity as well. Earlier, we reported for a set of microscale zerovalent iron (mZVI) particles the disappearance kinetic of different CAHs which were collected under consistent experimental conditions. In the present study, these kinetic data were correlated with the carbon, oxygen and sulfur content of mZVI particles. It was confirmed that not only the specific surface area affects the disappearance kinetic of CAHs, but also the chemical composition of the mZVI particles. The chemical composition, in addition, influences CAHs removal mechanism inducing sorption onto mZVI particles instead of dechlorination. Generally, high disappearance kinetic of CAHs was observed for particles con- taining less oxygen. A high carbon content, on the other hand, induced nonreactive sorption of the con- taminants on the mZVI particles. To obtain efficient remediation of CAHs by mZVI particles, this study suggested that the carbon and oxygen content should not exceed 0.5% and 1% respectively. Finally, the efficiency of the mZVI particles may be improved to some extent by enriching them with sulfur. However, the impact of sulfur content on the reactivity of mZVI particles is less pronounced than that of the carbon and oxygen content. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The use of zerovalent iron (ZVI) for in situ reductive dechlorina- tion of chlorinated aliphatic hydrocarbons (CAHs) has been widely studied and demonstrated in the field as a proven technology (Gill- ham and O’Hannesin, 1994; Matheson and Tratnyek, 1994; Gavas- kar, 1999). Once introduced into the subsurface, ZVI transforms a range of CAHs present in the groundwater into nontoxic com- pounds such as hydrocarbons and chlorides (Matheson and Trat- nyek, 1994). To select cost effective ZVI particles for the cleanup of CAHs contaminated sites, the reactivity of particles is considered crucial for the success of the remediation. Over time, ZVI particles with different properties and from different origin have been studied extensively (Johnson et al., 1996; Su and Puls, 1999; Cheng and Wu, 2000; Barnes et al., 2010). The high specific surface area of the ZVI particles has been identified as an important feature that contributes to the fast degradation of CAHs (Zhang, 2003). How- ever, there are indications that other characteristics of the ZVI par- ticles, such as the source, quality and content of impurities, influence the reactivity as well (Johnson et al., 1996; Burris et al., 1998; Su and Puls, 1999; Wüst et al., 1999; Song and Carraway, 2005; Barnes et al., 2010). For ZVIs produced from different raw 0045-6535/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2013.07.034 ⇑ Corresponding author. Tel.: +32 14 33 5634. E-mail address: leen.bastiaens@vito.be (L. Bastiaens). Chemosphere 93 (2013) 2040–2045 Contents lists available at SciVerse ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere