Environmental, Mineralogical, and Genetic Characterization of Ochreous and White Precipitates from Acid Mine Drainages in Taebaeg, Korea

Abstract

X-ray diffraction, energy-dispersive X-ray fluorescence, thermal analysis, scanning electron microscopy, inductively coupled plasma emission spectroscopy, and ion chroma tography were used for the environmental, mineralogical, and genetic characterization of brownish yellow, reddish brown, and white precipitates from acid mine drainage in Taebaeg, Korea. Ferrihydrite+goethite, schwertmannite, and Al-sulfate were precipitated under different chemical environments on the stream bottom of acid mine drainages. The brownish yellow precipitates (Munsell color 9.5YR hues) consist mainly of schwertmannite with traces of quartz, illite, pyrophyllite, goethite, lepidocrocite, and gypsum. The reddish brown precipitates (Munsell color 3.5YR hues) consist mainly of ferrihydrite with small amount of goethite. The white precipitates consist mainly of poorly crystalline Al-sulfate with small amounts of quartz, gypsum, and calcite. Thermal decomposition due to dehydration of ferrihydrite and schwertmannite takes place at approximately 120 °C and 140 °C, respectively. Al-sulfate converts to γ-alumina at 850 °C. SEM study shows that the spheroid and rod-shaped precipitates characteristic of Gallionella consist of iron hydroxide with varying chemical compositions.