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

X-ray diffraction, Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and specific surface area analyses demonstrate that goethite was stable at high temperatures (100 °C) over a wide range in pH (2 to 13). Over the course of 18 h of aging at 100 °C, the crystal morphology and aspect ratio (length/height) of goethite decreased with respect to fresh goethite. Further, the specific surface area also decreased over the course of the experiment, showing approximately 50% reduction at pH 2, 10, and 13. These changes in morphology with aging could influence the adsorption of contaminants in natural settings.