Bioreduction of iron (hydr)oxides from mine Tailings under marine conditions
- Autores: Robert Benaiges Fernandez
- Directores de la Tesis: Jordi Urmeneta Maso (dir. tes.), Jordi Cama Robert (dir. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2021
- Idioma: inglés
- Tribunal Calificador de la Tesis: Ricardo Amils Pibernat (presid.), Joaquín Vila Grajales (secret.), Mercè Corbella i Cordomí (voc.)
- Programa de doctorado: Programa de Doctorado en Biotecnología por la Universidad de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TESEO
- Resumen
Mining industry faces environmental problems concerning waste management. Given the environmental issues associated with storage of mine wastes on land, one disposal option that has gained attraction is submarine tailings disposal (STD). This practice involves disposal of mine tailings under seawater through underwater pipelines. Discharged mine wastes may be geochemically altered by microbial communities that living in the seabed have an ecophysiology that is compatible with the mine tailings. These communities (e.g., Shewanella, Geobacter) would be able to reduce the structural Fe(III) of oxides and oxyhydroxides (henceforth referred to as (hydr)oxides) of iron contained in the tailings, leading to a release of Fe(II) and Trace Elements (TEs) into the marine environment. The present study aimed at understanding the reaction of bioreduction of iron (hydr)oxides that are contained in mine tailings and assessing the environmental impact of STD. For this purpose, different samples of iron (hydr)oxides and mine tailings were reacted in batch and column experiments in the presence of Shewanella loihica, a dissimilatory iron reducing bacteria. The release of Fe(II) and TE was monitored throughout the experiments, and the surface of the reacted oxides were examined. Geochemical simulations of the experimental data were used to quantify the extent of the overall reductive dissolution reaction. Furthermore, to understand the influence of aqueous iron in the ocean’s nitrogen cycle, a series of experiments were carried out with Fe(II) released from bioreduced iron oxides in the presence of nitrite. Results showed that Shewanella loihica bioreduces Fe(III) from the iron (hydr)oxides contained in the mine tailings under marine conditions. The dissolution process leads to a release of Fe(II) and TEs, which are harmful for the marine environment. It was deduced that the reactive surface area of the iron (hydr)oxides is a key factor in the bioreduction process as it provides available Fe(III) and available surface, on which Shewanella loihica attach for electron transferring. However, adsorption of some of released Fe(II) onto the surface leads to a decrease in the reactive surface area, which lowers the total available Fe(III), and to a transformation of the former oxide to a new biogenic phase containing Fe2+/Fe3+ (i.e. magnetite). Moreover, it was demonstrated that the Fe(II) released promotes a nitrite removal, interfering thus with the nitrogen cycle of the ocean. The nitrite removal was characterized using chemical and isotopic analyses, which allowed a better understanding of the mechanisms controlling the Fe(II)-N interaction and an identification of the source of nitrite reduction in the sea. From the results, it is inferred that STD can become a major environmental concern because (1) the Fe(II) released may lead to fertilization and eutrophication of disposal sites, resulting in an oxygen depletion and an expansion of the oxygen minimum zone and (2) the TEs released bioaccumulate in the environment and trophic webs, ultimately affecting human health and social economic development.
