DEVELOPMENT OF AN INTEGRATED MULTIDISCIPLINARY STRATEGY FOR GALLIUM, IRON AND MANGANESE RECOVERY FROM MINING RESIDUES IN A CONTEXT OF CIRCULAR ECONOMY

Mining and mineral-processing wastes have been giving a lot of concern in recent times. We have evaluated an integrated multidisciplinary strategy for mining residues characterization, as well as for the recovery of secondary (e.g., Fe, Mn) and critical (e.g., Ga) raw materials. After the in situ sampling campaigns in Bichakundi Joda West iron and manganese mine (Keonjhar district, State of Odisha, India), residues have been characterized and the acquired mineralogical, chemical and spectral information have been used to create a map of mining residue deposits by means of the new multispectral satellite Sentinel-2A classification. Furthermore, mycorrhizal-assisted phytoextraction of metals from previously classified soils, based on sunflowers colonized by an AM fungal strain GA5 Rhizophagus intraradices, was carried out in the perspective of subsequent recovery of Ga, Fe and Mn from biomass using hydrometallurgical and electrochemical techniques. The bioconcentration factors in aerial and radicular parts (BCS and BCR, respectively), and translocation factors (TF) followed the order Ga>Mn>Fe for BCS and TF, while for BCR was Ga>Fe>Mn. The results were used to estimate the bioextracting potential by phyto-mycoremediation into a Vegetable Depuration Module (VDM): the highest extraction was estimated for Fe (60 g/VDM), followed by Mn (35 g/VDM) and Ga (1.02 g/VDM), thus confirming a good potential for their subsequent recovery by hydrometallurgical techniques with final purification by selective electrodeposition. Results are encouraging and the application of such multidisciplinary approach can be important to develop a circular model for sustainable exploitation of mining residues.