An application of near-infrared and mid-infrared spectroscopy to the study of natural halotrichites : halotrichite, apjohnite and wupatkiite


Autoria(s): Frost, Ray L.; Reddy, B. Jagannadha; Keeffe, Eloise C.
Data(s)

01/07/2010

Resumo

Near-infrared (NIR) and Fourier transform infrared (FTIR) spectroscopy have been used to determine the mineralogical character of isomorphic substitutions for Mg2+ by divalent transition metals Fe, Mn, Co and Ni in natural halotrichite series. The minerals are characterised by d-d transitions in NIR region 12000-7500 cm-1. NIR spectrum of halotrichite reveals broad feature from 12000 to 7500 cm-1 with a splitting of two bands resulting from ferrous ion transition 5T2g ® 5Eg. The presence of overtones of OH- fundamentals near 7000 cm-1 confirms molecular water in the mineral structure of the halotrichite series. The appearance of the most intense peak at around 5132 cm-1 is a common feature in the three minerals and is derived from combination of OH- vibrations of water molecules and 2 water bending modes. The influence of cations like Mg2+, Fe2+, Mn2+, Co2+, Ni2+ shows on the spectra of halotrichites. Especially wupatkiite-OH stretching vibrations in which bands are distorted conspicuously to low wave numbers at 3270, 2904 and 2454 cm-1. The observation of high frequency 2 mode in the infrared spectrum at 1640 cm-1 indicates coordination of water molecules is strongly hydrogen bonded in natural halotrichites. The splittings of bands in 3 and 4 (SO4)2- stretching regions may be attributed to the reduction of symmetry from Td to C2v for sulphate ion. This work has shown the usefulness of NIR spectroscopy for the rapid identification and classification of the halotrichite minerals.

Formato

application/pdf

Identificador

http://eprints.qut.edu.au/33161/

Publicador

NIR Publications (imprint of IM Publications)

Relação

http://eprints.qut.edu.au/33161/1/c33161.pdf

DOI:10.1255/jnirs.877

Frost, Ray L., Reddy, B. Jagannadha, & Keeffe, Eloise C. (2010) An application of near-infrared and mid-infrared spectroscopy to the study of natural halotrichites : halotrichite, apjohnite and wupatkiite. Journal of Near Infrared Spectroscopy, 18(3), pp. 177-189.

Direitos

Copyright 2010 IM publications

Fonte

Chemistry; Faculty of Science and Technology

Palavras-Chave #030600 PHYSICAL CHEMISTRY (INCL. STRUCTURAL) #030606 Structural Chemistry and Spectroscopy #halotrichite, apjohnite, wupatkiite, Near-IR and Mid-infrared
Tipo

Journal Article