Recovery of critical and other raw materials from mining waste and landfills

The transition to a more circular economy is essential to develop a sustainable, low carbon, resource efficient, and competitive economy in the EU. In this context Critical Raw Materials (CRM) are defined as those which are of particularly great importance to the EU economy and at the same time there is a high risk of supply disruptions. First and foremost, improving the circular use of CRM is a key strategy in improving the security of supply and not surprisingly is an objective of various policy documents. This report delivers on action #39 of the Circular Economy Action Plan: "Sharing of best practice for the recovery of critical raw materials from mining waste and landfills". It builds on discussions held during two 2018 workshops and gathers together six examples of existing practices for the recovery of critical, precious, and other materials from extractive waste and landfills, highlighting technological innovation and contributions that have been made to a more comprehensive knowledge-base on raw materials. The report also provides various estimates of potential recovery of certain materials compared to their current demand. Lessons learnt from the practices include awareness that it is very unlikely that recovery processes can target one or just a few specific materials of great interest and disregard other elements or bulk matrixes. Especially in case of very low concentrations, most of the mineral resources and other bulk materials in which they are embedded must be valorised in order to increase economic viability and minimise waste disposal. As recovery processes can be very energy intensive, environmental and land use related aspects are also particularly relevant even though environmental gains may also occur and, moreover, land space can be liberated and reused for new purposes and services. Finally, availability of data and information on secondary materials as well as a harmonized legislative framework within the EU appear to be crucial for the large-scale deployment of recovery practices.JRC.D.3-Land Resource

Bioprocessing low grade copper ores - a promising alternative

International audienceThis paper presents an overview of the work performed by the BRGM team in the last 10 years on the development of bio-hydrometallurgy dedicated to the processing of low-grade copper ores from the Kupferschiefer deposits. It covers selection and adaptation of microbial consortia, optimization of process operating parameters such as solid contents, the relationship between bioleaching performance and mineralogy, testing operating parameters to overcome chalcopyrite recalcitrance, design of process options and economical assessment. The selected bacterial inoculum (autotrophic, working at 42°C) enables to achieve high Cu recovery (up to 95%). In continuous piloting tests the increase of the solid load in the pulp from 15% to 25% doesn’t affect the bioleaching efficiency despite the high and unusual Cu concentration reached in the liquor (40 g l-1). Operating at 25% solid load reduces by 2.3 the size of the leaching tanks compared to 15% solid load, which leads to a significant decreasing of the CAPEX

From mineral processing to waste management and recycling: common challenges and needs for innovation in France

International audienceThe world’s population is constantly growing, the global standard of living is increasing, urbanisation is developing on all continents and both the digital transformation and the necessary energy transition are underway. These different “societal phenomena” have in common that they exponentially increase the need for raw materials (metals and other minerals). For example, the demand for certain strategic metals for manufacturing batteries required for electric mobility and the energy transition is expected to explode. According to the recent raw material score board (2021) from the European commission, the lithium demand will increase by a factor of 20 in 2030; an increase by 5 is expected for cobalt. Projections for copper use show that consumption in the next 25 years will be higher than the total cumulative consumption since the Copper Age (during the Neolithic). To meet these supply challenges whilst respecting the major sustainable development goals adopted by the United Nations, it is necessary to improve the resource efficiency, meaning using the Earth’s limited resources in a sustainable manner whilst minimising impacts on the environment: delivering greater value with less input. In other words, R&D action must help to improve the environmental and societal efficiency of extractive activities, to optimise the use of metals and materials throughout their life cycle by reducing losses, and finally to set up recycling processes as part of a circular economy. The shift from a linear to a circular economy is imperative to ensure that the economic growth is not only based on the use of natural resources. [...] The objective of this paper is not only to show the common challenges faced by ore and waste treatment technologies but also to highlight some specific innovation needs associated with each resources depending of their origin (primary secondary end of life)

Designing bioleaching reactors: challenges and innovations

International audienceBioleaching is a hydrometallurgical technique which uses the metabolic activity of lithotrophic microorganisms for the extraction of metals from sulfide ores. These microorganisms draw their energy from the oxidation of iron and/or reduced inorganic sulfur compounds, producing sulfuric acid and ferric iron. The result is a highly corrosive " bioleaching " solution that dissolves the sulfide minerals by oxidation, releasing the metals to solution. In these reactions oxygen is used as an electron acceptor. Bioleaching is a proven technology already industrially applied. Its main advantages over other processes are to be cost-effective and to provide the same duty in a simpler way in terms of operability. Bioleaching is also attractive insofar as it presents few environmental hazards. However, up to now, it remains a niche application mainly because of the limitations and the unsatisfactory performances of the reactors. One reason to explain this situation is probably the lack of research work dedicated to process development and reactor design in comparison to the great effort devoted worldwide to the biology and physiology of microorganisms. Out of the papers devoted to bioleaching published in the last decade, less than 2% deal with basic process engineering issues (such as heat and mass transfer) and bioreactor design. One of the key factors of bioleaching performances in agitated tanks is mixing. It has to be efficient in order to reach a high level of oxygen transfer rate (OTR) to comply with oxygen uptake rates of about 1500 mg L −1 h −1 , and even distribution of the various components of the slurry throughout the tank. The main costs of bioleaching operations are the investment costs of the tanks and the impellers and the operating costs of gaseous mass transfer. This presentation will give an overview of the recent advances achieved to overcome some of the limitations of bioleaching processes with a particular emphasis on the development of an alternative bioleaching reactor based on the use of floating agitators to mix and to suspend solids in the solution as well as to inject gases in the pulp. This new concept enables to decrease the costs of bioleaching processes by operating (i) in lagoons or ponds instead of tanks, (ii) at higher solid loading (> 15% w/w) than in conventional stirred tank bioreactors (STR). In these conditions of high solid load, the demand for oxygen is significantly increased and air is replaced by oxygen to provide an adequate oxygen supply The experimental testwork performed from lab to pilot scales (2 L up to 2 m 3) has confirmed that this new device operated at solid load up to 30% leads to similar leaching performances (kinetics and metal yields) than those obtained in STR at solid load below 20%. The injection of oxygen instead of air improves OTR but must be managed carefully to avoid high dissolved oxygen (DO) level in the slurry: a decrease of the activity of the bioleach microorganisms was observed when the DO concentration was above 17 ppm, which might be attributed to an oxidative stress due to the formation of toxic reactive oxygen species [1]. [1] IMLAY et al., Annual Review of Biochemistry, 77, 755–776, 2008

Organic and mineral characteristics of Kupferschiefer ore from Lubin mine (Poland): implications for bioleaching of the ore.

International audienceThe ore mineral and organic matter content of the Lubin black shale (LBS) are compared with copper concentrate (LC) obtained by flotation. Study of a mineralized profile shows a good correlation between the S, TOC and Cu, Co and Ag content, suggesting syngenetic bacterial sulfate reduction (BSR) accumulation. The presence of disseminated and fracture filling rather than framboidal Cu-minerals, suggests formation via diagenetic processes. Compared to the black shale, the LC shows a lower HI and a higher OI, and a much more diverse ore mineral content. The black shale ore is composed of 15 vol. % sulfide, this proportion reaches 27 % in the LC whereas the TOC is similar in the LC and LBS. The ore mineral diversity in the LC is due to the contribution of mineralized sandstone and dolomite adjacent the black shale ore

Co-processing of sulfidic mining wastes and metal-rich post-consumer wastes by biohydrometallurgy

International audienceThe consequence of a strong economic growth in emerging countries combined with the rise of the world population is an increase in the demand for raw materials, leading to growing concern regarding their availability and the global efficiency of the supply chain. These tensions reinforce the need to associate the development of the recycling industry to the identification of new resources which could be used for the recovery of valuable materials. The purpose of this study is to develop a novel biological co-processing approach for the recovery of strategic metals in both sulfidic mining wastes and post-consumer wastes (WEEE). The principle of this treatment is based on two steps: mine wastes are biologically oxidized, resulting in the production of a ferric iron-sulfuric acid lixiviant solution which is used to leach base and other soluble metals contained in e-scraps. Batch tests were carried out using flotation tailings wastes containing 60% of pyrite and grinded Printed Circuit Boards (PCB < 750 μm) with a solid load of 2.5%. Two series of tests were conducted in order to study the influence of the ferric iron concentration and of the bacterial activity on metals dissolution. Results showed that a higher ferric iron concentration led to an increase in the dissolution rate of copper which is the main metal contained in the PCBs. Moreover, a dissolution yield of 98.3% was reached for copper after 2 days when bacterial activity was observed, corresponding to an increase of about 20% compared to the tests without bacterial activity. Finally, this study highlights the importance of the availability of ferric iron and of the bacterial oxidation of ferrous iron for the feasibility of this bioleaching process dealing with the recycling of PCBs

Acidophilic microbial communities catalyzing sludge bioleaching monitored by fluorescent in situ hybridization

International audienceBiological autotrophic sulfur oxidation processes have been proposed to remove heavy metals from wastewater treatment sludge by bioleaching. We made a characterization of the microbial population in batch and continuous sludge bioleaching reactors using fluorescent in situ hybridization of fluorescently-labeled oligonucleotidic probes targeting rRNA in a 'top to bottom approach'. Batch incubations of sludge with 0.2% (w/v) elemental sulfur resulted in a pH value of 5. Alpha-Proteobacteria hybridizing with probe ALF1b were dominant in this incubation. Members of the Acidophilium-group (hybridizing with probe Acdp821) of Nitrospira/Leptospirillum phylum (Ntspa712 probe) and from the archaeal domain (ARCH915) were also detected. When sludge was incubated with 1% elemental sulfur in batch or continuous reactor experiments, final pH values were always below 2. Active microbial communities consisted almost exclusively of gamma-Proteobacteria (hybridizing with probe GAM42a). However, further hybridization experiments with probe Thio820 targeting Acidithiobacillus ferroxidans and Acidithiobacillus thioxidans gave negative results. A new probe, named THIO181, encompassing all known members of the genus was designed. Hybridization perfomed with THIO181 and GAM42a showed a perfect co-localization of the hybridization signals. Further hybridization experiments with probe THIO181 and THC642, specific for the species Acidithiobacillus caldus, confirmed that this bacteria was largely responsible for the sulfur oxidation reaction in our acidophilic sludge bioleaching reactors

A review of sulfide minerals microbially assisted leaching in stirred tank reactors

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Evolution of the bacterial population during the batch bioleaching of a cobaltiferous pyrite in a suspended-solids bubble column and comparison with a mechanically agitated reactor

19 ref. DOI:10.1016/S0304-386X(03)00142-7International audienceThe aim of the present work was to compare the bioleaching kinetics and the evolution of bacterial populations between the classical mechanically agitated bioreactor and a suspended-solids column reactor. For this purpose, batch experiments were performed in a 20-L stirred reactor and a 26-L bubble column, respectively. The substrate was a cobaltiferous pyrite. At 20% solids concentration (w/w), the cobalt leaching rates in both reactors were similar. In the bubble column, bioleaching rate increased with gas velocity and at low air-flow rate, dissolved oxygen concentration could decrease down to 0.5 mg/L, oxygen mass transfer being a limiting factor in that situation. These results suggest that bioleaching in the bubble column could be at least as efficient as in the stirred tank. The composition of the bacterial population was determined by sequencing 16S rDNA from biopulp samples: Leptospirillum ferrooxidans, an organism close to Thiobacillus caldus, and a bacterium related to Sulfobacillus thermosulfidooxidans were found. The single-strand conformation polymorphism (SSCP) technique was used to monitor the population. Proportions of bacteria attached to the solids or suspended in the liquid were evaluated. In the liquid, T. caldus is dominant during the first phase of the experiments, then supplanted by L. ferrooxidans. L. ferrooxidans is always in the majority on the solids. S. thermosulfidooxidans is less constant. The growth of this bacterium seems to be favored in the bubble column. The SSCP technique proved to be an interesting and low-cost way to use molecular biology, which is worth developing in the field of bioleaching

Influence of dissolved oxygen on the bioleaching efficiency under oxygen enriched atmosphere

International audienceThe use of oxygen enriched air is a common practice in high-temperature bioleaching tests (> 70°C) to overcome oxygen solubility limitation and reduced the energy costs of the process. Air is usually preferred in medium and low-temperature operations mainly for technical and economic constraints. Nevertheless, under high-sulfide loading conditions - high-grade metal sulfide concentrates and high solids concentration - the microbial and chemical demand for oxygen is significantly increased during the bioleaching process. If not satisfied, this high oxygen demand might limit the oxidation efficiency. Therefore it requires the injection of large amounts of air. Sparging with oxygen enriched gas instead of air may offer an interesting alternative process option to improve gas transfer in the bioleaching reactor and to provide an adequate oxygen supply in order to satisfy the oxygen demand. It might be useful to develop innovative alternative to the classical stirred tank reactor (STR) technology. However, the use of such conditions can lead to much higher dissolved oxygen (DO) concentrations than those encountered with air. Very few papers have been devoted to the study of the optimal range of DO concentrations for bioleaching processes. Most of them reported an inhibitory effect of DO concentrations above 5 ppm. The purpose of this study was to investigate the influence of DO on the bioleaching efficiency under oxygen-enriched atmosphere in 21 L stirred tank reactor at 42°C. Bioleaching experiments were performed in continuous mode with sulfide-rich tailings wastes composed mainly of pyrite (51%) and quartz using the “BRGM-KCC” bacterial consortia. The solid load was close to 20% (w/w). Using various oxygen supply conditions (partial pressure, gas rate), the DO concentration in the reactor varied between 4 and 17 ppm. For a DO ranging from 4 to 13 ppm, a good bacterial oxidizing activity was observed and the sulfide dissolution efficiency increased with the DO concentration. It is assumed that this improvement of the bioleaching efficiency was linked to an increase of the oxygen transfer rate from the gas phase to the liquid phase rather than a direct effect of the DO level. When the DO concentration reached 17 ppm a significant decrease of the microbial activity and consequently of the oxygen consumption was noticed. These results show that there is a critical value above which the DO concentration is detrimental to the activity of the bioleach microorganisms present in the “BRGM-KCC” consortia but this value is much higher than the one usually mentioned in the literature