金瓜石黃金瀑布酸性礦山排水沉澱物之礦物學研究

Ochreous iron-oxyhydroxide precipitates occur at the bedrock surface of Golden Falls as a result of the long-term discharge of acid mine drainage (AMD) produced by chemical weathering of the Chinkuashih gold-copper deposits and tailings. X-ray diffraction, SEM, TEM, FTIR, ICP, and TG-DTA data indicated that the ocher precipiates were dominated by schwertmannite with an average chemical formula of Fe₁₆O₁₆(OH)₁₁(SO₄)_2.5·16H₂O. The schwertmannite occurred as nanometric fibrous crystallites that had an radiating arrangement forming spheroidal aggregates with hedgehog-like surface microstructures and a specific surface area of 76 m²/g. The ICP analysis further suggested that the schwertmannite contained 2,794 ppm As, 439 ppm Al, 115 ppm Cu, and 23 ppm Cr on average. The result implies that the environmental impacts of the Golden Falls AMD may have been deferred and/or reduced by the precipitation of schwertmannite and the sorption of As and metals thereon.