Synthesis and Raman spectroscopic study of Mg/Al,Fe hydrotalcites with variable cationic ratios

Abstract

Hydrotalcites of formula Mg 6 (Al,Fe) 2 (OH) 16 (CO 3 )·4H 2 O formed by intercalation with the carbonate anion as a function of divalent/trivalent cationic ratio have been successfully synthesised. The XRD patterns show variation in the d-spacing attributed to the size of the cation. Raman and infrared bands in the OH stretching region are assigned to (1) brucite layer OH stretching vibrations, (2) water stretching bands and (3) water strongly hydrogen bonded to the carbonate anion. Multiple (CO 3 ) 2− symmetric stretching bands suggest that different types of (CO 3 ) 2− exist in the hydrotalcite interlayer. Increasing the cation ratio (Mg/Al,Fe) resulted in an increase in the combined intensity of the two Raman bands at around 3600 cm −1 , attributed to Mg-OH stretching modes, and a shift of the overall band profile to higher wavenumbers. These observations are believed to be a result of the increase in magnesium in the structure. Raman spectroscopy shows a reduction in the symmetry of the carbonate, leading to the conclusion that the anions are bonded to the brucite-like hydroxyl surface and to the water in the interlayer. Water bending modes are identified in the infrared spectra at positions greater than 1630 cm −1 , indicating that water is strongly hydrogen bonded to both interlayer anions and the brucite-like surface.

Combined electron microscopy and vibrational spectroscopy study of corroded Magnox sludge from a legacy spent nuclear fuel storage pond

“…In general, Raman studies of Mg-based minerals are rather limited. Frost and co-workers have carried out several studies and reported Raman spectra for nesquehonite [22], artinite, dypingite [25], synthetic Mg/Al, Fe hydrotalcites [26], natural hydrotalcites with sulphate and carbonate in the interlayer [27] and synthesised hydrotalcites with sulphate, molybdate and chromate ions in the interlayer [28]. Some reference spectra have been made available [29].…”

Recent advances in linear and nonlinear Raman spectroscopy. Part IV

“…The low wavenumber modes of this system are interpreted as arising from a lifting of the degeneracy of the vibrational modes related to Mg, Nb, and Ti sites. Palmer et al [203] describe the synthesis and Raman spectroscopic characterization of Mg/Al,Fe hydrotalcites with variable cationic ratios. Solozhenko et al [204] present the first-and second-order Raman spectra of B 6 O and their dependence on the wavelength of the excitation line from the IR to the DUV.…”

Removal of boron species by layered double hydroxides: A review

“…magnesium [18][19][20][21][22][23][24] and aluminium [25], lithium [26], chromium [27,28], Iron [17,[29][30][31][32][33][34][35][36], calcium [37], zinc [38][39][40][41], gallium [42][43][44][45], nickel [31,40,[46][47][48], indium [43], cobalt [31], manganese [49] and copper [48]. Because of their structure, LDHs are the only clay minerals that exhibit natural anion exchange properties.…”