Abstract
In this work, mycorrhizal-assisted phytoextraction (MAP, Helianthus annuus–arbuscular mycorrhizal fungus Rhizophagus intraradices–Zn-volcanic ashes) was applied for the recovery of secondary and critical raw materials (SRMs and CRMs, respectively) from Joda West (Odisha, India) mine residues, within a novel multidisciplinary management strategy. Mine residues were preliminarily characterized by using advanced analytical techniques, and subsequently mapped, classified and selected using multispectral satellite Sentinel-2A images and cluster analysis. Selected mine residues were treated by MAP at laboratory scale, and the fate of several SRMs (e.g., Zn, Cr, As, Ni, Cu, Ca, Al, K, S, Rb, Fe, Mn) and CRMs (such as Ga, Ti, P, Ba and Sr) was investigated. Bioconcentration factors in shoots (BCS) and roots (BCR) and translocation factors (TF) were: 5.34(P) > BCS > 0.00(Al); 15.0(S) > BCR > 0.038(Ba); 9.28(Rb) > TF > 0.02(Ti). Results were used to predict MAP performance at larger scale, simulating a Vegetable Depuration Module (VDM) containing mine residues (1 m3). Estimated bio-extracting potential (BP) was in the range 2417 g/m3 (K) > BP> 0.14 g/m3 (As), suggesting the eventual subsequent recovery of SRMs and CRMs by hydrometallurgical techniques, with final purification by selective electrodeposition, as a viable and cost-effective option. The results are promising for MAP application at larger scale, within a circular economy-based approach.
Highlights
The arbuscular mycorrhizal (AM) fungus Rhizophagus intraradices strain GA5 colonized sunflower roots in both MA+ and B+ treatments after 133 days with typical AM fungal structures, whilst no root colonization was found in the noninoculated plants in control treatments (B− and MA− ), as expected (Figure 6B)
The average concentrations of SRMs (Fe, Mn, Zn, Cr, As, Ni, Cu, Rb, Al, K, S and Ca) and CRMs (Ba, Ga, P, Ti and Sr) in soil samples taken from each pot of the contaminated and blank treatments, as well as in sunflower plant biomass after 133 days of growth are reported in Tables 1 and 2
The present work confirmed that it is possible to apply the mycorrhizal-assisted phytoextraction (MAP) system in contaminated soils from mining areas classified by remote sensing as Class 2 and 4, and to carry out the bio-extraction of all the elements studied
Summary
The aim is to promote the transition to a more circular model that can strongly contribute, with products, processes and business models that are designed, to maximize the value and utility of resources while at the same time reducing adverse health and environmental impacts (Figure 1) This multidisciplinary strategy combines: New sensitive technologies (such as remote sensing technologies) for mapping and classification of mining wastes containing minerals and metals; New solutions for chemical, physical and morphological characterization; An eco-innovative methodology for converting mining waste into resource: mycorrhizal-assisted phytoextraction (MAP) of mining wastes, and the consequent accumulation of secondary and critical raw materials (SRMs and CRMs, respectively) in biomass tissues; Recovery of SRMs and CRMs from biomass through hydrometallurgy and/or electrochemical methods. The metals are purified to a high degree of purity by electrochemical methods
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