We present a novel constructed wetland called a vegetable depuration module (VDM) as a pilot test of a bioremediation system (BS) for decontaminating water and soil polluted with heavy metals. The VDM consisted of a pool filled with stones of different granulometry and a substrate top layer composed of a mixture of soil and volcanic ash (50:50, v/v) supplemented with 350 ppm Zn. The BS of sunflower plants colonized by the arbuscular mycorrhizal fungus Rhizophagus intraradices was planted in the VDM. Initially, the substrate registered high concentrations of Zn, Cr, Mn, Cu, and Sr, and had Eh > +500 mV and pH 8.4. Irrigation with a Cu solution by vertical flow was carried out. After 3 months, bioaccumulation factors ranged from 1.00 to 8.90, and translocation rates were >1 for Sr and Cu. Total metals extracted by the BS and percolation were 31%, 34%, 50%, 45%, and 57% for Zn, Cu, Mn, Cr, and Sr, respectively. Only the BS was capable of extracting 94% of Cu and 38% of Zn. VDM allowed us to calibrate the extractive performance of the studied elements in BS. This biotechnological development holds great potential for phytoremediation of polluted areas.

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 (BC_S) and roots (BC_R) 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.

In recent years, critical and secondary raw materials (CRMs and SRMs, respectively) have received great interest within the circular economy model. In this work, the mycorrhizal-assisted phytomining (MAP) system, composed of Helianthus annuus–arbuscular mycorrhizal fungus Rhizophagus intraradices–Zn-volcanic ashes, was applied in bioreactors for the recovery of CRMs (Sr, P) and SRMs (Cr, Zn, Cu, Mn, Rb, Ni) from mining wastes of the Los Cóndores mine (Argentina). Our results showed high bioaccumulation of Sr, P, Mn, and Zn in the aerial tissues, and a high root-to-shoot translocation for Mn (4.02) > Sr > P > Rb > Zn (0.84). Mycorrhization treatment increased the root-to-leaf translocation for Cr and P and prevented translocation towards flower tissues in most elements. The estimated bioextracting potential of the MAP system (290 plants) in a vegetable depuration module (VDM) ranged from 158 mg/m³ P > Zn > Mn > 15.1 mg/m³ Sr. We demonstrated a promising and cost-effective biotechnology applicable in agronomical practices, given the exclusion of toxic elements in flower parts, as well as for the recovery of CRMs and SRMs by hydrometallurgy from plant biomass.

In recent times, the development of innovative processes permits the application of a circular economy approach to the management and exploitation of mining waste with respect to human health and environment, such that society is changing its fundamentally negative perception of the mining sector. This study presents the opportunities and challenges of supplying raw materials from waste using a remote sensing technique, mycorrhizal-assisted phytoremediation, and hydrometallurgical techniques to transform mining waste from a problem to a resource. Soil/mine wastes from the Sierra Pintada mine (Mendoza, Argentina) were mineralogically and chemically analyzed, and then, a mapping of the mining waste was carried out by Sentinel-2A images to identify areas with similar characteristics. The bioaccumulation of HMs by autochthonous shrubs was also determined to select accumulator plant species, and to evaluate their potential for phytoremediation of mine soils at different technological scales, when they were inoculated with arbuscular mycorrhizal fungi originated from a mining-impacted area. RMs were recovered from plant biomass by scaling in bioreactors, the depuration module, and hydrometallurgical techniques. The encouraging results highlight that this multidisciplinary approach can be applied to meet the increasing demand for RMs supply and, at the same time, to protect the environment and public health.

This chapter analyzes the costs-benefits of a particular phytomining methodology named mycorrhizal-assisted phytoremediation (MAP). This MAP system is responsible for phytostabilization and/or phytoextraction of secondary and critical raw materials from contaminated soil or mining wastes. To this aim, we evaluated the application of MAP in a modified constructed wetland, the vegetable depuration module (VDM), which permits the calibration of physical-chemical-biological variables in a contaminated substrate, as well as the partition of chemical elements within the liquid phase due to leaching and solid phases (biomass and soil). This successful methodology allows to scale-up from a Technology Readiness Level (TRL) 6 (demonstration in a relevant environment) toward TRL 7 (demonstration in an operational environment), which implies the transfer to the territory.