Ultrasound-induced rapid intercalation of biselenite in layered double hydroxides

The deintercalation of carbonate (CO₃^2-) ions from MgAl-layered double hydroxides (LDHs) (Mg/Al = 2) both in monolayer films and powdered samples under atmospheric conditions in ethanol was investigated. A selenous acid precursor was incorporated into the interlayer gallery. Treatment with 0.5 M selenous acid (H₂SeO₃) for 30 min with powdered LDHs or with 0.1 M H₂SeO₃ for 5 min with the thin film LDHs resulted in carbonate ions being exchanged with biselenite (HSeO ₃^-) ions. Electron microscopy showed that the morphologies of the original LDH particles remained after the reaction, despite the ultrasound being continuously applied for up to 2 h. XRD, FTIR and Raman spectroscopic scattering results strongly suggested that cyclic dimers of biselenite ions were incorporated into the gallery spaces of the LDHs, vertically arranged to the horizontal axes of the MgAl-LDH layers. By using facile ultrasonic treatment in ethanol, carbonate ions in the interlayer spaces of layered double hydroxides can be successfully exchanged with biselenite ions within a few minute.