title: Synthesis and vibrational spectroscopy of halotrichite and bilinite.
abstract: Near infrared (NIR), infrared (IR) spectroscopy and X-ray diffraction (XRD) have been applied to halotrichites of the formula FeAl(2)(SO(4))(4)·22H(2)O and Fe(2+)Fe(2)(3+)(SO(4))(4)·22H(2)O. Comparison of the halotrichites and their starting materials has been used to give a better understanding of the bonding involved in these types of minerals. The vibrational spectroscopy data has shown that Fe(2+) oxidises during the formation of halotrichite, no preventative measures were implemented to prevent oxidation, and this has been clearly shown by the position and broadness of electronic bands of transition metals in the NIR spectra (12,500-7500 cm(-1)). It is apparent from this region that Fe(3+) substitutes for Al(3+) in the synthesis of halotrichite. Due to the oxidation of Fe(2+) to Fe(3+) the halotrichite sample contains a small portion of bilinite. This has been confirmed by XRD, peaks at 9 and 14° 2θ were observed in the halotrichite sample and are identical to the XRD pattern obtained for bilinite. Substitution of aluminium for Fe(3+) has resulted in significant changes in the overall infrared and NIR spectral profiles. However, the lower wavenumber regions of the NIR spectra have very similar spectral profiles, which indicates a similar structure to halotrichite has formed for bilinite. This work has shown that iron halotrichites can be synthesised and characterised by infrared and NIR spectroscopy.
authors: Chemistry Discipline, Faculty of Science, Queensland University of Technology, Brisbane, Queensland, Australia.
authors: Sara J
authors: SJ
authors: Palmer
authors: B Jagannadha
authors: BJ
authors: Reddy
authors: Ray L
authors: RL
authors: Frost
mesh_terms: D000534:Alum Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D004583:Electrons; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D006878:Hydroxides / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D019265:Spectroscopy, Near-Infrared; D013431:Sulfates / Q000737:chemistry; D028561:Transition Elements / Q000737:chemistry; D014732:Vibration; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D000534:Alum Compounds; D005290:Ferric Compounds; D005296:Ferrous Compounds; D006878:Hydroxides; D013431:Sulfates; D028561:Transition Elements; C510105:halotrichite; D014867:Water; C031356:hydroxide ion