Raman spectroscopic study of the hydrogen and arsenate bonding environment in isostructural synthetic arsenates of the variscite group—M3+ AsO4·2H2O (M3+ = Fe, Al, In and Ga): implications for arsenic release in water

摘要: The Raman spectra of synthetic compounds equivalent to the variscite group: FeAsO4·2H2O AlAsO4·2H2O, GaAsO4·2H2O, and InAsO4·2H2O are reported. In particular, upon comparison it is observed that Type II (weak) H-bond lengths in latter slightly longer, which postulated affect stability (As release) water at pH 5 7. Arsenate stretching bending vibrations were found be distinct terms spectral structure therefore well suited for fingerprinting. calculated AsO bond strengths from existing crystallographic data showed no significant variations. strongest ν1 (AsO43−) stretch was used monitor bonding interactions four AsOM units, where a shift 114 cm−1 order (lowest) < GaAsO4·2H2O AlAsO4·2H2O (highest); this also followed exactly measured arsenic release these phases. This position rationalized stem differences electronegativities M3+ cations. trends mentioned above verified hold isostructural phosphate analogues strengite (FePO4·2H2O) (AlPO4·2H2O) using published data. Therefore, that, as with solution complexes, there may correlation between electronegativity cation phases their or P water. Copyright © 2010 John Wiley & Sons, Ltd.