The pH-dependent transformation of schwertmannite to goethite at 25°C

At 25 degrees C, synthetic schwertmannite, a common iron compound in acid mine drainage, completely converted in water to a sulphate-containing goethite within similar to 100 days. The rate of transformation doubled as the pH increased from 4.0 to 7.2. In deviation from its normal acicular habit, the goethite appeared as spherical aggregates.