Ab-initio molecular dynamics simulations evidence the templating role of cations in the green rust sulfate structure

Abstract

The intercalation of sodium into green rust sulfate, a layered double hydroxide (LDH), has been proposed to explain its large interlayer spacing (~11 Å). We compare structures with and without sodium using ab-initio molecular dynamics (AIMD) simulations and conclude that its composition most likely contains sodium: Fe II 6Fe III 3(OH)18Na(SO4)2•nH2O, with 14 ≤ n ≤ 16.With positively charged layers and anions in the interlayer space, Layered Double Hydroxides is are widely used for anionic exchange. However, adsorption of cations using this structure is possible, and can be explained byand an explanation for this is the co-insertion of cations with anions within the interlayer space. 1 The adsorption of cations is often associated with large anions with multiple negative charges, such as EDTA. However, the exchange of small monovalent cations (K + , Na + , Li + ) within sulfate intercalated LDH was experimentally proved in 2018.