Raman spectroscopy of hydrotalcites with sulphate, molybdate and chromate in the interlayer

Abstract

Raman microscopy has been used to characterize the interlayer anions in synthesized hydrotalcites of formula Mg 6 Al 2 (OH) 16 (XO 4 )·4H 2 O, where X is S, Mo or Cr. The Raman spectrum shows that both the chromate and molybdate anions are not polymerized in the hydrotalcite interlayer. This lack of polymerization is attributed to the effect of pH during synthesis. A model of bonding is proposed for the interlayer anions based upon the observation of two symmetric stretching modes and symmetry lowering of the chromate, molybdate and sulphate anions. Two types of anions are present, hydrated and hydroxyl surface-bonded.

Thermal analysis of smithsonite and hydrozincite

“…Indeed Raman spectroscopy has proven most useful for the study of diagenetically related minerals such as carbonates and hydroxycarbonate [14][15][16][17][18]. Some previous studies have been undertaken by the authors using Raman spectroscopy to study complex secondary minerals formed by crystallisation from concentrated sulphate solutions [12][13][14][15][16][17][18][19][20][21]. Further hot stage Raman spectroscopy is most useful for the study of the thermal decomposition of minerals [22][23][24][25][26][27].…”

Natural halotrichites—an EDX and Raman spectroscopic study

“…Indeed Raman spectroscopy has proven most useful for the study of diagenetically related minerals such as sulphates, alums and halotrichites [17][18][19][20][21] . Some previous studies have been undertaken by the authors using Raman spectroscopy to study complex secondary minerals formed by crystallisation from concentrated sulphate solutions [15][16][17][18][19][20][21][22][23][24] . In this work we extend this research by using Raman spectroscopy to study four natural halotrichites and compare the spectra with that of the natural minerals.…”

Far infrared and Raman spectroscopy analysis of inorganic pigments

“…is observed, together with three 3 -asymmetrical stretching vibrations at 870 (sh), 897 and 942 cm 1 . 12,13 Lattice vibrations can only be observed in the FIR spectrum as very broad and complex bands with peaks at 150 and 187 cm 1 .…”