Enhanced adsorption of arsenic onto maghemites nanoparticles: As(III) as a probe of the surface structure and heterogeneity.

Published

Journal Article

When normalized per unit of surface area, the quantity of arsenic adsorbed at the maghemite surface remains constant for particles between 300 and 20 nm. However, nanoparticles smaller than 20 nm exhibit enhanced adsorption capacity. The origin of this observed size-dependence for adsorption or "nano effect" is unclear. Arsenic was chosen as a probe of the surface structure to explore adsorption mechanisms occurring at the surface of maghemite nanoparticles (6 nm). Two factors contributing to the enhanced reactivity of nanoscale maghemites were determined. The first is related to a size-dependent structural modification of the surface of particles and the decrease of the occupancy of the tetrahedral site that leaves vacant, highly reactive adsorption sites. In particular, there is a site localized in a six-membered iron octahedral ring. This site is the only one for which an oxidation of As(III) occurs. The second factor relates to the thermodynamics of a decrease of the surface free energy. The high density of As adsorbed at the saturation of the surface can be related to crystal growth.

Full Text

Duke Authors

Cited Authors

  • Auffan, M; Rose, J; Proux, O; Borschneck, D; Masion, A; Chaurand, P; Hazemann, J-L; Chaneac, C; Jolivet, J-P; Wiesner, MR; Geen, AV; Bottero, J-Y

Published Date

  • April 2008

Published In

Volume / Issue

  • 24 / 7

Start / End Page

  • 3215 - 3222

PubMed ID

  • 18266393

Pubmed Central ID

  • 18266393

Electronic International Standard Serial Number (EISSN)

  • 1520-5827

International Standard Serial Number (ISSN)

  • 0743-7463

Digital Object Identifier (DOI)

  • 10.1021/la702998x

Language

  • eng