Thermal behaviour of natural and synthetic iron precipitates from mine drainage

• Published in: Journal of thermal analysis and calorimetry 2014-05, Vol.116 (2), p.625-632
• Main Authors: Pulišová, P., Máša, B., Michalková, E., Večerníková, E., Maříková, M., Bezdička, P., Murafa, N., Šubrt, J.
• Format: Article
• Language: English
• Subjects: Acid mine drainage; Adits; Analysis; Analytical Chemistry; Calorimetry; Chemistry; Chemistry and Materials Science; Heating; Hematite; Inorganic Chemistry; Iron; Measurement Science and Instrumentation; Physical Chemistry; Polymer Sciences; Precipitates; Precipitation; Rain and rainfall; Scanning electron microscopy; Urea; Ureas
• ISSN: 1388-6150; 1588-2926; 1572-8943
• DOI: 10.1007/s10973-014-3759-6

TG–DTA, MS detections and XRD were used to characterize thermal behaviour of iron precipitates from acid mine drainage prepared by precipitation with urea and natural iron precipitates sampled from sludge bed (settling pit Sedem žien and old abandoned adit Hodruša , mining area Banská Štiavnica, Slovakia). The high-resolution transmission electron microscopy and scanning electron microscopy (SEM) techniques were used to characterize the surface microstructure and shape of the synthesized and sampled iron precipitates. The SEM micrographs of the iron precipitates (natural and precipitated with urea) show that the samples had formed into agglomerates, probably due to attractive forces of quite large surface area. During heating of the all samples up to 200 °C, physically adsorbed water was removed. On further heating in the range from 250 to 350 °C in natural iron precipitates, the less stable forms (goethite, ferrihydrite, and schwertmannite) transform to more stable forms like hematite. In case of synthetic samples, the transformation runs in two steps: first in the range from 250 to 350 °C, and second in the range from 600 to 750 °C.