title: SEM, EDS and vibrational spectroscopic study of dawsonite NaAl(CO3)(OH)2.
abstract: In this work we have studied the mineral dawsonite by using a combination of scanning electron microscopy with EDS and vibrational spectroscopy. Single crystals show an acicular habitus forming aggregates with a rosette shape. The chemical analysis shows a phase composed of C, Al, and Na. Two distinct Raman bands at 1091 and 1068 cm(-1) are assigned to the CO3(2-) ν1 symmetric stretching mode. Multiple bands are observed in both the Raman and infrared spectra in the antisymmetric stretching and bending regions showing that the symmetry of the carbonate anion is reduced and in all probability the carbonate anions are not equivalent in the dawsonite structure. Multiple OH deformation vibrations centred upon 950 cm(-1) in both the Raman and infrared spectra show that the OH units in the dawsonite structure are non-equivalent. Raman bands observed at 3250, 3283 and 3295 cm(-1) are assigned to OH stretching vibrations. The position of these bands indicates strong hydrogen bonding of the OH units in the dawsonite structure. The formation of the mineral dawsonite has the potential to offer a mechanism for the geosequestration of greenhouse gases.
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia. Electronic address: r.frost@qut.edu.au.
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
authors.forename: Andrés
authors.initials: A
authors.lastname: López
authors.affiliation: Geology Department, School of Mines, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, MG 35,400-00, Brazil.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Scholz
authors.affiliation: NanoLab, REDEMAT, School of Mines, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, MG 35,400-00, Brazil.
authors.forename: Ney Pinheiro
authors.initials: NP
authors.lastname: Sampaio
authors.affiliation: Federal Institute of Minas Gerais, Campus Ouro Preto, Ouro Preto, MG 35,400-000, Brazil.
authors.forename: Fernando A N
authors.initials: FA
authors.lastname: de Oliveira
mesh_terms: D000536:Aluminum Hydroxide / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D013052:Spectrometry, X-Ray Emission; D013059:Spectrum Analysis, Raman; D014732:Vibration
chemical_list: D000536:Aluminum Hydroxide; C016386:dihydroxyaluminum sodium carbonate
keywords: Carbonate; Dawsonite; Hydroxyl; Infrared and Raman spectroscopy