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Attività scientifiche svolte nel 2021 nell'ambito dell'accordo di cooperazione tra il CNR e il SAV - Accademia delle Scienze Slovacca (anni 2021-2022), progetto "Recovery of critical raw materials from industrial wastes by advanced methods". Rapporto Annuale 2021.

Mining and mineral-processing wastes represent one of the world's largest chronic waste concerns. A number of environmental problems are associated with the disposal of these wastes, including ecological losses, downstream contamination and pronounced landscape transformation. In recent years, difficulties to access raw materials (RMs) lead to progressive resource depletion, increase in metals price and environmental pressures. The recovery of critical raw materials (CRMs) from low-grade ore, steel works by-products and industrial wastes has become an important issue and a global challenge for present and future economy. Due to the continuous need for mining activities to collect RMs to sustain our economy, the recycling and reuse of mining and mineral-processing wastes should be pursued through appropriate innovative management strategies aimed at minimizing the environmental impacts and preserving human health. Furthermore, it is generally difficult to assign a universal method to reuse all kinds of mining and mineral-processing wastes; hence, the choice of possible recycling, reprocessing and reuse strategies should be case-specific. Aim of this paper is to evaluate integrated multidisciplinary strategy for the characterization and analysis of mining waste, their possible recycling and re-use and strategies for CRMs recovery. Proposed strategies have been applied to wastes produced in the Fe-Mn mine in Bichakundi (near Joda West, Odisha-India). In the first phase, in situ sampling campaigns have been carried out; mining wastes have been thoroughly characterized by X-Ray Powder Diffraction (XRPD), X-Ray Fluorescence (XRF) and spectral signatures analysis 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 will be discussed. Furthermore, the potential metals uptake from contaminated soils and their possible recovery from incinerated/lyophilized biomass by hydrometallurgical methods is evaluated also according to preliminary phyto-myco-remediation tests carried out using Helianthus annuus (i.e., sunflower) and Rhizophagus intraradices.

Relazione delle attività scientifiche svolte tra il Luglio 2019 ed il Giugno 2021, nell'ambito dell'accordo di cooperazione CNR/ASM (Academy of Sciences of Moldova), anni 2018-2020. Rapporto Annuale 2021.

Purpose: the metals and industrial minerals contained in the tailings produced by mining and quarrying activities, are cause of environmental damage. The objective of this experimental work is the application of innovative technologies for the treatment and exploitation of mining tailings in Romania, in order to recover materials high grade raw to be placed on the market, reducing the volume of the wastes. Further objective, is to optimize some parameters relating to the dissolution of gold and the subsequent recovery from purified solutions, determining beforehand the technical feasibility of the scheme of process developed on a laboratory scale. Methods: the study is focused on hydrometallurgical process for the recovery of gold. The innovative treatment chosen is the thiosulphate process that, compared to conventional cyanide, has several advantages, first of all the most eco-friendly and non- toxic to humans. The conventional process shows operating limits in the case of auriferous minerals refractory materials, such as Romanian wastes object of the study. Another fundamental characteristic of the ammoniacal thiosulphate solutions, is the best selectivity towards gold, not attacking the majority of the gangue mineral constituents. Results: the dissolution rates of gold reached a final value of 70% Au - working at room temperature - with recoveries of the global process of about 65%, in line with the conventional process. Main conclusions: these results are very encouraging, considering that this is an innovative process, applied to a low content gold ore. The optimization of parameters and operating conditions, and the industrial treatment, continuous and scale greater would certainly permit to reach the best results in terms of process yields and energetic and reagents consumption.

La presente relazione descrive l'attività svolta dal dott. Stefano Ubaldini, Ricercatore dell'Istituto di Geologia Ambientale e Geoingegneria del CNR (Roma) e responsabile italiano del progetto, nel corso del suo soggiorno di studio presso "The Institute of Geotechnics of the Slovak Academy of Science", di Kosice (Repubblica Slovacca) nell'anno 2015, nell'ambito del progetto.

Progetto di ricerca finanziato, svolto per conto di Bioprojectgroup srl, Relazione tecnico-scientifica finale CNR-IGAG, Agosto 2017, Prot. IGAG-CNR n. 0002718 del 04/08/2017.

Attività scientifiche svolte nel 2014 nell'ambito dell'accordo di cooperazione tra il CNR e il SAV - Accademia delle Scienze Slovacca, anni 2013-2015, Progetto CNR n. 1. Rapporto Annuale 2014.

In this work, bio-hydrometallurgical processes have been applied starting from exhaust alkaline batteries. Their disposal constituted a serious environmental problem in terms of heavy metals content when these devices are disposed off in inadequate way. High Mn and Zn content justifies the interest to recover metals from these wastes. The present experimental work involves the application of innovative processes, such as the utilisation of the physical-chemical method (electrowinning) and biological-chemical (bioleaching) method for Mn-Zn recovery from exhaust alkaline batteries. The results have demonstrated the technical feasibility of the application of the bio-hydrometallurgical circuit; in fact, high recoveries of manganese and zinc dissolved in solution were achieved (about 98 % of MnO2 and Zn).

Oggetto della presente convenzione è l'accordo di collaborazione per l'esecuzione di una ricerca dal titolo "Sviluppo di un processo di trattamento di schermi LCD a fine vita e recupero di indio". Obiettivo fondamentale del progetto è quello di estrarre indio da schermi LCD a fine vita attraverso un pretrattamento di macinazione e un'estrazione per via idrometallurgica. Lo studio è stato articolato in diverse attività, sviluppate nelle varie fasi della sperimentazione: 1)triturazione e macinazione degli schermi con separazione di frazioni granulometriche diverse; 2)caratterizzazioni mineralogiche ed elementari delle diverse frazioni; 3)trattamento idrometallurgico finalizzato al recupero di indio. L'attività sperimentale oggetto della presente Convenzione è stata svolta presso i laboratori dell'Istituto di Geologia Ambientale e Geoingegneria (IGAG) del Consiglio Nazionale delle Ricerche (CNR), ubicati presso l'Area della Ricerca di Roma RM 1 - Montelibretti Via Salaria Km 29,300 - C.P. 10 - 00015 Monterotondo Stazione (ROMA). L'IGAG ha messo a disposizione personale preparato, attrezzature e tutta la strumentazione idonea per lo svolgimento delle analisi. I responsabili scientifici, chiamati a sovrintendere le attività oggetto della presente convenzione sono stati, per il DiSVA la Dott.ssa Francesca BEOLCHINI, per l'IGAG il Dott. Stefano UBALDINI.

The present work deals with the bioremediation of a sediment sample contaminated by heavy metals, collected in the Ancona harbour, Italian Adriatic Sea, Mediterranean Sea. Bioleaching of the sediment was performed with a mixed culture of acidophilic, chemi-autotrophic Fe/S oxidising bacteria, in the presence of elemental sulphur as substrate. Such element resulted to be fundamental both for cell growth and for metal dissolution. The effect of an anaerobic biostimulation pre-treatment on the extent of Cd, Cu, Zn, Ni, Pb, Hg, As, Cr extraction by bioleaching was also evaluated: the activity of the Fe/S oxidising bacteria resulted to be significantly enhanced after an anaerobic pretreatment of the sediment. The main advantage of this two-step (anaerobic-aerobic) bioremediation approach is that microbial activity, and the consequent metal mobilisation, is independent from the availability of sulphur. These results open new perspectives for bioleaching applied as a bioremediation strategy for sediment contaminated by heavy metals.

The objectives of this work were to evaluate the use of iron- and sulphur-oxidising bacteria Acidithiobacillus ferrooxidans and sulphate-reducing bacteria Desulfovibrio desulfuricans in the biohydrometallurgical processing of gold-bearing antimony sulphide minerals. Experiments were conducted at laboratory scale on a refractory gold-bearing stibnite coming from Santa Rosa de Capacirca Mine, Bolivia. Involved bacteria were used separately at different conditions for the pre-treatment of the aforementioned sample in order to increase the subsequent gold recovery during cyanidation processes. The application of the bacteria Acidithiobacillus ferrooxidans is based on their ability to oxidize and dissolve pyrite and arsenopyrite, thus releasing the entrapped gold particles. The using of the bacteria Desulfovibrio desulfuricans is based on their ability to the bacterially H2S production for the alkaline leaching of stibnite.

Gjegjan mine there was the biggest cooper mine of Albania. Now this mine does not work, it is abandoned. In the region there are about 10 million tons raw material (wastes) with 0.3 % Cu. It is evident that water passing by the surface and into the gallery results with high content of Cu, Zn, Fe, and SO4 etc the Cu content it is 600 time more than permitted standards. The water is acid with pH 2,5-3,5. This signifies the developing naturally and without administration the processes of bacterial leaching. This alarming status causing high pollution of Fierza Lake(KUKES) enforced to study the bacterial leaching of Gjegjani raw material. The study is carried out in laboratory scale (with grinded material) and in static column with coarse material. -The experiment in static column is carried out with coarse material (+ 6 -50 mm) Material - 6 mm represents 35% of total quantity this is a guaranty that in reality the process will be more effective. Meanwhile in the mine are and pyrite bodies that are main factor of bacteria growth and concentration. The recovery of Cu from raw material (coarse material) during the large scale of experiment results 10 % for about 30 months. These data are represented before, and encouraged us for the treatment the raw material in natural status (heap leaching) -In base of technical-economic data we concluded the project idea of a plant and respective economic evaluation by producing Cu cement concentrate with over 60% Cu. -Meanwhile the building of a plant proposed will resolve the alarmant pollution of water passing by the wastes and poured in Fierza Lake.

The aim of the present work was the application of an hydrometallurgical process for precious metals recovery from polymetallic industrial wastes. Elemental and mineralogical composition hamper an economical treatment by conventional process (cyanidation). By this route, very low gold and silver recoveries were obtained (20-30%), with an high consumption of reagents. Pretreatments have been successful studied in order to eliminate the refractory of the samples. An accurate analysis of the products obtained at the end of the pretreatment was carried out by Scanning Electron Microscope (SEM).

A leaching process of gold-bearing refractory and complex ores has been studied by using chlorine dissolved in brine solutions comparing these results with a standard cyanidation process. Chlorine is locally generated with the same brine solution by electrolysis that also produces the sodium hydroxide needs for the proposed process for the neutralisation phase of the barren solutions. These precipitation reactions restore the presence of NaCl that may be recycled in the process after a suitable pre-treatment. Some simulation and experimental results are present to highlight limits and advantages of the proposed process. A comparison with conventional cyanidation has been also reported.

The aim of this work was to compare a chemical and a biological process as a pretreatment for gold recovery from a refractory gold-bearing stibnite. Experimental tests have been conducted at laboratory scale, utilising an ore sample with gold content of about 20 g/t Au, coming from South America. The chemical pretreatment consisted in alkaline leaching by aqueous sodium sulfide and sodium hydroxide solutions; after chemical leaching, metallic antimony was selectively recovered by electrowinning. The biochemical pretreatment has been carried out in acid environment by bacterial cultures of Thiobacillus genus. The optimisation of the parameters permitted to attain an increasing on gold recovery from 20% Au (not pretreated samples) to about 80% Au, in both processes. Two integrated process flow-sheets have been outlined.

The aim of the work was to decrease the iron content of ferrous quartz sands by fixed-bed column leaching with recycling of the leaching solutions in order to attain a product suitable for industrial use. Dissolution of iron was achieved by treating the sands in an acid medium with a reducing agent (oxalic acid) to convert FeIII into FeII. The factors assumed to affect dissolution of iron, such as temperature, oxalic acid concentration, pH and flow-rate, were studied with a 24 full factorial design in order to assess the main effects and the interactions among the factors. Removal of 46.1% iron gives a product containing 0.0163% Fe2O3 which is fit for industrial applications.

The scope of the paper was to demonstrate the technical feasibility of the remediation processes by electrowinning and selective sequential precipitation, for toxic metals removal from acid mine drainage. By electrochemical experiments, high metals removal has been achieved: in particular, by Zn and Mn electrodeposition, it was possible to achieve about 93-99% Zn and Mn removal (as MnO2), with a relatively low energetic consumption. The principle of the heavy metals selective sequential precipitation is the combined application of sodium hydroxide solution and hydrogen sulfide produced by sulfate-reducing bacteria. For the hydrogen sulfide production the sulphate-reducing bacteria of genus Desulfovibrio was used. The selective sequential precipitation process reaches the selective precipitation of chosen metals with 99% efficiency – Fe, As, Al and Mn in the form of metal hydroxides, Cu and Zn as metal sulfides.