The molecular structure of the multianion mineral hidalgoite PbAl 3(AsO 4)(SO 4)(OH) 6 - Implications for arsenic removal from soils

The objective of this research is to determine the molecular structure of the mineral hidalgoite PbAl ₃(AsO ₄)(SO ₄)(OH) ₆ using vibrational spectroscopy. The mineral is found in old mine sites. Observed bands are assigned to the stretching and bending vibrations of (SO ₄) ^2- and (AsO ₄) ^3- units, stretching and bending vibrations of hydrogen bonded (OH) ^- ions and Al ³⁺-(O,OH) units. The approximate range of O-H⋯O hydrogen bond lengths is inferred from the Raman and infrared spectra. Values of 2.6989 Å, 2.7682 Å, 2.8659 Å were obtained. The formation of hidalgoite may offer a mechanism for the removal of arsenic from the environment.