Changes of crystal morphology of aged goethite over a range of pH (2-13) at 100 °C

▶ Spectroscopic, microscopic, and surface area measurements demonstrate that the aspect ratio (length/height) and specific surface area of aged goethite are less than fresh goethite. ▶ The aspect ratio of aged goethite (obtained from AFM images) decreases with increasing pH (pH 2-13) and suggests that improved crystallinity (crystals became smoother and their distribution became more uniform) occur at more alkaline pH. ▶ Specific surface area decreases to ~50% of fresh goethite during the aging process suggesting that the goethite undergoes some re-crystallization.