Chemistry Discipline, Faculty of Science, Queensland University of Technology, Brisbane, Queensland, Australia.
Spectrochim Acta A Mol Biomol Spectrosc. 2011 Jun;79(1):69-73. doi: 10.1016/j.saa.2011.02.001. Epub 2011 Feb 21.
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.
近红外 (NIR)、红外 (IR) 光谱和 X 射线衍射 (XRD) 已应用于化学式为 FeAl(2)(SO(4))(4)·22H(2)O 和 Fe(2+)Fe(2)(3+)(SO(4))(4)·22H(2)O 的卤代三羟。比较卤代三羟及其起始材料有助于更好地了解此类矿物中涉及的键合。振动光谱数据表明，在卤代三羟形成过程中 Fe(2+) 被氧化，没有采取预防措施防止氧化，这在 NIR 光谱中过渡金属的电子带的位置和宽度（12,500-7500 cm(-1)) 清楚地表明。从该区域可以明显看出，在合成卤代三羟时，Fe(3+) 取代了 Al(3+)。由于 Fe(2+) 氧化为 Fe(3+)，卤代三羟样品中含有少量的比尔林石。这已通过 XRD 得到证实，在卤代三羟样品中观察到 9 和 14° 2θ 处的峰，与比尔林石的 XRD 图谱相同。铝取代 Fe(3+) 导致整体红外和近红外光谱谱图发生显著变化。然而，近红外光谱的较低波数区域具有非常相似的光谱谱图，这表明为比尔林石形成的卤代三羟具有相似的结构。这项工作表明，铁卤代三羟可以通过红外和近红外光谱进行合成和表征。
