Past, present and future global influence and technological applications of iron-bearing metastable nanominerals

Iron-bearing nanominerals such as ferrihydrite, schwertmannite, and green rust behave as metastable precursors leading to the formation of more thermodynamically stable iron mineral phases (e.g., jarosite, goethite, hematite, and magnetite). However, this transformation may last from days to tens or even hundreds of years, making them the most predominant iron-bearing minerals at environmental conditions and at the human time scale. The present review characterizes ferrihydrite, schwertmannite, and green rust nanominerals according to their main physical and chemical properties, and at both nano- and mesoscales. It also presents a comprehensive review of the multiple past and present Earth environments where these nanominerals have played, and still play, a pivotal role in the geochemistry, mineralogy and environmental nanogeosciences of these environments. Finally, the present and future technological applications of these nanominerals as well as their role in the generation of a more sustainable human- Earth relationship is discussed, with a special emphasis on their use in new circular economies and green based technologies.This research was partially supported by Advanced Mining Technology Center (AMTC) from Universidad de Chile; National Agency for Research and Development, ANID, through ANID-PIA Project AFB180004. MAC was financially supported by the Spanish Ministry of Science and Innovation through the Program Ramon y Cajal 2019, Grant RYC2019-026496-I. J.P.H.P. acknowledges the funding from the European Union’s Horizon 2020 Marie Skłodowska-Curie Innovative Training Network (grant no. 675219) and Helmholtz Recruiting Initiative (award no. I-044-16- 01). MPA was financially supported by the Junta de Andalucía through the Emergia Program 2020. Funding for open access charge: Universidad de Huelva / CBUA