Surface segregation of NaBr in mixed NaBr/NaCl crystals precipitated from aqueous solutions containing Br is investigated. Crystals were grown from solutions of a wide range of Br:Cl values and studied using x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive x-ray flourescence (EDX), and atomic force microscopy (AFM). Results indicates that NaBr surface-segregates to cover 4-5% of the surface at the Br:Cl value found in Sea water (1:660). The surface NaBr:NaCl values are ˜ 35 times higher those of the bulk crystals. The surface NaBr forms domains of average size 635 nm x 635 nm x 53 nm. Large areas of the surface contain NaCl with no detectable NaBr. Complete surface segregation of all Br found in sea salt particles is likely to occur, thereby making a greater amount of Br available for surface reactions with gas-phase constituents than would be predicted based on bulk composition.
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)