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.

Raw materials are essential for all sectors of the economy as well as for all innovative technologies. Currently, industry is largely dependent on imports and consumption of these materials, and in the future, following the global energy transition, this trend will drastically increase. For this reason, it is necessary to develop new strategies to meet the supply–demand of raw materials by strategic sectors and technologies. To this end, mining residues are turning into viable raw materials sources as they represent reliable access to valuable resource supply. This work aims to validate a methodology providing more in-depth quali-quantitative information about 100 samples of mining residues collected in the Joda West mine (India) by multidisciplinary strategy in order to valorize and promote efficient resource use. In this paper, physicochemical and mineralogical characterization and hyperspectral signatures have been integrated with satellite Sentinel-2A data. In particular, the X-ray powder diffraction (XRPD), X-ray fluorescence (XRF), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) analyses indicated the presence of mining residues samples rich in raw materials that were possible to spectrally distinguish in order to use them as input for the object-oriented classification of a satellite image. The satellite resulting map highlighted four different classes of mining residues with mean concentrations of around 36% for hematite, 23.5% for quartz, 9% for kaolinite and 5% for pyrolusite. These results represent the possibility of transforming an environmental problem (mining residues) into a resource potentially exploitable by industries knowing their composition and position in the study area. Moreover, by doing so, it will be possible to ensure sustainable consumption of the raw materials and to build resilient economies and societies, minimizing environmental degradation.

Rare earth elements (REEs), independently by the economic value, have a strategic importance and are involved, as critical materials, in the competition for their supply. An innovative process with the introduction of a preliminary physicochemical treatment was proposed. The mechanical activation of waste of fluorescent powders was performed by a vibratory disc mill at different experimental conditions to optimize the process. The mechanical forces induced to the powders cause crystal structure defects with a consequent increase of rare earths leachability. Factorial experimentations and analysis of variance were studied to determine the significant effects of the investigated factors (mechanical activation time, sulfuric acid concentration, pulp density and leaching temperature), especially for terbium dissolution. The preliminary activation allows to increase terbium dissolution of 35%. Then, according to the best conditions the subsequent operations of precipitation and calcination were performed obtaining a purity of 98.3% as rare earth oxides. Based on the experimental results, the flowsheet for rare earths recovery has been proposed and implemented by SuperPro Designer, a simulation software for process analysis and mass-energy balances. Finally, this paper reports a comparison between the present process with the mechanical pre-treatment and the alternative method based on thermal pre-treatment.

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.

The quantification of asbestos in ophiolitic rocks is of particular importance in the management of soil and rock excavated in civil works and materials from quarry exploitation. In Italy, a well-described quantitative method is currently available taking advantage of the high resolution of scanning electron microscopy (SEM) and the mineral discrimination provided by energy dispersion spectroscopy (EDS) (Italian Ministerial Decree of 06/09/1994). The method provides a limit of detection of ca. 4-10 ppm and delivers quantitative results for asbestos content higher than 100 ppm. Conversely, a guide for on-field sampling and laboratory sample milling / preparation is still required, to correctly define the quantities of materials of variable geometric dimensions and weight to be sampled following a representative approach. The development of a proper sampling protocol will define the minimum volume of material that is required to correctly represent an asbestos-bearing soil/rock. The work aims to introduce a structured composite sampling and processing protocol, to reduce data variability and increase sample representativeness for a specified volume of material under investigation. The protocol is designed to obtain one single aliquot for SEM-EDS quantitative analysis (ca. 10 g) that has all the constituents in the same proportion with a known grade of accuracy and to minimize sample preparation time. Variability in measured asbestos concentration in ophiolitic rocks between discrete samples is due primarily to the texture of rocks and heterogeneity in the distribution of asbestos. To consider the heterogeneous distribution of asbestos, a simulation of size distribution of the material after laboratory size reduction (crushing and grinding) as a function of operating parameters was obtained. It was studied the influence of some parameters, specifically linked to ophiolitic rocks, such as: particles shape factor, granulometric factor, mineralogical factor, asbestos liberation factor, and maximum particle size on the representativeness of the subsamples. The methodology provides reasonably unbiased, reproducible estimates of the mean concentration of asbestos in the specified volume of material.

The application of a new hydrometallurgical process for gold extraction by thiosulphate leaching from Romanian mining wastes, coming from Balan and Deva deposits, was studied. There was obtained 85% of Au extraction after leaching; moreover, an integrated flow-sheet, including recycling of process solution and carbon, was outlined, based on results obtained at a laboratory scale, using a schematic chemical circuit of treatment. Global recovery of the process (leaching-adsorption-desorption-electrodeposition) of about 75-80% of Au was achieved. The developed integrated flow-sheet, allows to recycle the reagents during the process, with a loss of only 5-10%, in particular thiosulphate and alcohol, for each complete circuit of treatment.

A smart economy minimizes the production of waste from mining activities and reuses waste as a potential resource, with the goal of moving towards a near-zero waste society. This paper presents integrated multidisciplinary methodology in order to optimise the management of mining waste. The test site is the FeeMn mine in Odisha (India). The mining waste present in the mine has been collected and afterwards X-Ray Powder Diffraction, X-Ray Fluorescence and spectral signatures analysis have been performed for mineralogical, chemical and spectral characterization of the materials. Finally, the classification and mapping of the characterized mining waste was carried out by Sentinel-2A image.

Mining and mineral-processing wastes have been giving a lot of concern in recent times. This paper has evaluated an integrated multidisciplinary strategy for mining wastes characterization, their possible recycling and reuse, and critical raw materials recovery. After the in situ sampling campaigns, mining wastes have been characterized and the acquired mineralogical, chemical and spectral information have been used to create a map of mining waste deposits by means of the new multispectral satellite Sentinel-2A classification. The use of Fe-Mn rich wastes in arsenic removal and phosphorus recovery from water was discussed. Furthermore, mycorrhizal-assisted phytoextraction of metals from contaminated soils classified as Class 1 to 4 by remote sensing showed a good potential for their possible recovery from biomass, and results indicated that the system was suitable for the uptake of several elements. Results are encouraging and the application of such approach can be important to develop a circular model for sustainable exploitation of mining wastes.

The determination of the asbestos content in ophiolitic rocks is carried out by well-known and standardized analytical techniques (SEM-EDS according to Italian regulation on environmental parameters on spoils, waste and rock and soil). Despite the high resolution and the possibility to obtain elemental information, SEM-EDS is not always able to discriminate serpentine minerals, including chrysotile and non-regulated fibrous antigorite, lizardite, and possibly polygonal serpentine. Moreover, the analytical procedures using electron microscopies are time-consuming and show an intrinsic lack of statistical representativeness, due to the low portion of the analytical sample that is effectively analyzed. Conversely, optical microscopy delivers fast results affected by a lower resolution and unreliable mineral fibre identification. Many sectors related to the realization of geo-engineering projects would take enormous advantages from a more efficient and statistically-sound approach. To evaluate the results obtained from a state-of-the-art optical microscope with automatic image analysis in-line with micro-Raman spectrometer, we designed a study to comparatively determine the asbestos content from a large set of samples deriving from asbestos-bearing rock of the ophiolitic domain. The performance of a Malvern G3 Morphology microscope equipped with a 850 nm laser Raman spectrometer was tested on 40 samples. The same samples, prepared from ophiolitic rocks from the Ligurian Alps comminuted down to top-size = 100 μm, were parallelly analyzed and results compared with SEM-EDS quantitative method described by Italian regulation (Ministerial Decree 6 September 1994, All 1B).

The worldwide mining industry produces millions of tons of rock wastes, raising a considerable burden for managing both economic and environmental issues. The possible reuse of Fe/Mn-rich materials for arsenic removal in water filtration units, along with rock properties, was evaluated. By characterizing and testing 47 samples collected from the Joda West Iron and Manganese Mine in India, we found As removal up to 50.1% at 1 mg/L initial As concentration, with a corresponding adsorption capacity of 0.01–0.46 mgAs/g mining waste. The As removal potential was strictly related to spectral, mineralogical, and elemental composition of rock wastes. Unlike rock crystallinity due to quartz and muscovite, the presence of hematite, goethite, and kaolinite, in association with the amorphous fractions of Fe and Al, enhanced the As adsorption. The natural content of arsenic indicated itself the presence of active sorptive sites. The co-occurrence of site-specific competitors (i.e., phosphate) represented a consequent limitation, whereas the content of Ce, Cu, La, and Pb contributed positively to the As adsorption. Finally, we proposed a simplified multiple linear model as predictive tool to select promising rock wastes suitable for As removal by water filtration in similar mining environments: As predicted = 0.241 + 0.00929[As] + 0.000424[La] + 0.000139[Pb] − 0.00022[P].

This paper presents an overview of the various innovative methodologies used in the recovery of valuable metals and critical raw materials (CRMs) from secondary sources. Valuable metals are interesting due to their vast industrial applications, high market prices and extensively used precious metal. The sanctuary value attributed to valuable metals such as gold during international political and economical crises and the limited resource of this metal, may explain the recent increasing gold share value. This article provides an overview of past achievements and presents scenario of studies carried out on the use of some promising methods which could serve as an economical means for recovering valuable metals and CRMs. The review also highlights the used varieties of application on large scale in real situations and hopes to provide insights into valorization of spent sources.

A new, rapid and selective, HPLC method for simultaneous quantitative estimation of lisinopril and hydrochlorothiazide residues and sampling procedures from pharmaceutical manufacturing equipment surfaces were developed and validated. The sampling procedures have a good recovery (>80%). The limit of quantitation of the HPLC method 0.155 μg/mL and 0.025 μg/mL for lisinopril and hydrochlorothiazide, respectively.