Synthesis and infrared spectroscopic characterization of selected layered double hydroxides containing divalent Ni and Co

Two new materials based upon layered double hydroxides with nickel and cobalt in the brucite-like layer with and without an anionic surfactant dodecylsulfonate (DS) have been synthesized and characterized by both near-infrared and infrared spectroscopy. This work shows that large anionic surfactants can be incorporated into the interlayer of the LDHs. The presence of the carbonate anions in the interlayer and the hydroxyl surface are readily analyzed by these techniques. The two materials of Ni3 and Co3Al-layered double hydroxides show different behaviour in the near-infrared and FT-IR spectra both in terms of position and band intensity. This is an indirect indication of the incorporation transition metal ions into the brucite-like layers. The nature of the observed reflectance bands in the near-infrared spectral region 12,000–8000 cm−1 is explained in terms of the d–d electronic transitions within the divalent nickel and cobalt brucite layers. The crystal field strengths of octahedral Ni2+ and Co2+ in the synthesized layered double hydroxides are close to but smaller than those in Ni-and Co-bearing carbonate minerals. The analysis of CO32− vibrational modes ν1, ν2, ν3 and ν4 in FT-IR spectra at 1045, 885, 1350 and 760 cm−1 reveals the presence of carbonate ion in the synthetic-layered double hydroxides.