Christiansen, B. C.4; Dideriksen, K.4; Katz, A.4; Nedel, S.4; Bovet, N.4; Sørensen, H. O.4; Frandsen, Cathrine1; Gundlach, Carsten5; Andersson, M. P.4; Stipp, S. L. S.4
1 Department of Physics, Technical University of Denmark2 Experimental Surface and Nanomaterials Physics, Department of Physics, Technical University of Denmark3 Neutrons and X-rays for Materials Physics, Department of Physics, Technical University of Denmark4 University of Copenhagen5 Department of Applied Mathematics and Computer Science, Technical University of Denmark
Green rust is a naturally occurring layered mixed-valent ferrous-ferric hydroxide, which can react with a range of redox-active compounds. Sulfate-bearing green rust is generally thought to have interlayers composed of sulfate and water. Here, we provide evidence that the interlayers also contain monovalent cations, using X-ray photoelectron spectroscopy and synchrotron X-ray scattering. For material synthesized with Na+, K+, Rb+, or Cs+, interlayer thickness derived from basal plane spacings correlates with the radius of the monovalent cation. In addition, sequential washing of the materials with water showed that Na+ and K+ were structurally fixed in the interlayer, whereas Rb+ and Cs+ could be removed, resulting in a decrease in the basal layer spacing. The incorporation of cations in the interlayer opens up new possibilities for the use of sulfate green rust for exchange reactions with both anions and cations: e.g., radioactive Cs.
Inorganic Chemistry, 2014, Vol 53, Issue 17, p. 8887-8894