Investigating arsenic forms in tailings from a gold mine

Full text: High concentrations of total arsenic (As) have been measured in soils/tailings of gold mining areas worldwide. Arsenic is a human health concern because it can contribute to skin, bladder, and other cancers. It occurs commonly in the environment in several oxidation states (−3, −1, 0, +3, and +5) and the mobility and toxicity of As are related to its speciation. This work aimed at analyzing mine tailings using X-ray absorption near edge structure (XANES) and the extended X-ray absorption fine structure (EXAFS) spectroscopy to determine the predominant oxidation state of As and to identify the first As neighbors (first shell and second shell) in four tailings (R1, R2, R3 and R4) from the Delita gold mining area (Cuba). The analyses were conducted at the As K-edge (11,867 eV) at the Brazilian Synchrotron Light Laboratory-LNLS (Campinas, Brazil). The spectra were recorded at room temperature using a Si (111) double crystal monochromator with an upstream vertical aperture of 0.5 mm and calibrated with Au L3-edge (11,919 eV). The XANES spectra in each sample confirmed the predominance of pentavalent As (AsV) in all tailings. The EXAFS analysis showed As-O binding at a distance of 1.4A∘ and As-Fe at a distance of 3.0A∘. These findings indicate a pattern very similar to the reference sample of scorodite for all tailings, except in R4, suggesting that another arsenate mineral is associated with this sample. (author)