Ecotoxicity of iron oxide nanocatalysts, produced from acid mine drainage, when submitted to the action of ozone in aqueous medium

Iron oxides recovered from acid mine drainage represent a potential raw material for the low-cost production of nanogoethite or nanohematite, with a degree of purity suitable for its use as a catalyst in processes for treating liquid effluents with ozone. Thus, the toxicity of iron nanoparticles needs to be determined to predict their impact on the environment, before and after they have been used in these processes. In this context, the objective of this study was to evaluate the toxicity of nanogoethite and nanohematite produced from acid mine drainage as well as to compare the results with high-purity synthetic hematite. Nanogoethite was obtained from acid mine drainage and, after its heat treatment at 450 degrees C, produced nanoparticles of hematite. The materials were characterized by X-ray diffraction, transmission electron microscopy, and determination of the specific surface area and porosity based on N-2 adsorption/desorption isotherms. Ecotoxicity tests were carried out using standardized protocols for bioluminescence with Vibrio fischeri, lethality of Artemia sp, germination of Lactuca sativa L (lettuce) seeds, and growth of Allium cepa L (onion) roots. The toxicity results indicated stability of the nanoparticles, which are not significantly altered by the action of ozone in aqueous medium. For all samples, the values indicated low or no toxicity under the conditions of the experiments. These results provide an indication that the iron nanoparticles recovered from the waste industry can be used as catalysts without adverse effects on the environment.