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Around 25 million tons of coal mine waste rock (CMWR) are stored in many places in Morocco due to coal mining activities. As a result, air and water quality of the neighborhood is polluted and large lands are occupied. This study aimed to investigate the use of an integrated and circular approach based on coal recovery and waste rock recycling. More than 30 drill core samples were taken from the big coal dump reaching a depth of 60 m and analyzed to evaluate the chemical composition variability. Froth flotation was used to recover coal particles using diesel as a collector and Methyl Isobutyl Carbinol as a frother, 100 g/t each. The tailings of coal flotation process (CFT) were used to manufacture fired bricks at a pilot scale. The results of this study highlighted the possibility to valorize the whole waste material toward an objective of zero waste in the future. On a basis of 100t feed, (i) 10-15t can be recovered as high-quality anthracite coal with a calorific value over 7500 kcal/kg using flotation processing at a recovery yield over 80%, (ii) 45-60t can be reused as shales for bricks production with a compressive strength over 16MPa, (iii) 20-30t can be reused as aggregates for concrete production with a compressive strength over 20MPa. The remaining material can be reused as sand. The recovered anthracite can be reused to manufacture coal briquettes or used at it is in the thermal power plant next to the dump site.

The phosphate industry produces huge volumes of waste (hundred million tons per year). These wastes are generally surface landfilled, leading to significant environmental impacts and a large footprint. The current practices of phosphate waste management, the typology of the waste streams and their characteristics, and finally their potential applications are reviewed. All the waste streams generated during the life cycle of phosphoric acid production going from the extraction of phosphate rock to its enrichment and transformation are considered. Great circularity opportunities have been identified and they aim (i) to recover the residual phosphorus and other critical minerals and metals, and (ii) to consider phosphate wastes as alternative resources in the civil engineering and building sectors. The purpose is to shift from linear thinking to circular thinking where synergy between different mining and other industries is highly encouraged. By doing so, opportunities to safeguard natural resources and to minimize the environmental and societal impacts are limitless. However, many challenges are still limiting this shift: economic and technical constraints, societal and policy-makers’ awareness, regulation harmonization and finally knowledge gaps. More efforts and investment in research and development are still required to reach the zero-waste target.

International audience; Phosphate rocks are a vital resource for world food supply and security. They are the primary raw material for phosphoric acid and fertilizers used in agriculture, and are increasingly considered to be a potential source of rare earth elements. Phosphate rocks occur either as sedimentary deposits or igneous ores associated with alkaline rocks. In both cases, the genesis of high-grade phosphate rocks results from complex concentration mechanisms involving several (bio)geochemical processes. Some of these ore-forming processes remain poorly understood and subject to scientific debate. Morocco holds the world’s largest deposits of sedimentary phosphate rocks, and also possesses several alkaline complexes with the potential to bear igneous phosphate ores that are still largely underexplored. This paper summarizes the main geological features and driving processes of sedimentary and igneous phosphates, and discusses their global reserve/resource situation. It also provides a comprehensive review of the published data and information on Moroccan sedimentary and igneous phosphates. It reveals significant knowledge gaps and a lack of data, inter alia, regarding the geochemistry of phosphates and basin-scale correlations. Owing to the unique situation of Moroccan phosphates on the global market, they clearly deserve more thorough studies that may, in turn, help to constrain future resources and/or reserves, and answer outstanding questions on the genesis of phosphates.

Mine tailings exposed to water and oxygen generate acid mine drainage (AMD) when the neutralizing minerals are insufficient to buffer the acid produced by sulfide oxidation. Mineral reactivity, such as sulfide oxidation and carbonate dissolution, leads to several changes within mine tailings in terms of their physical, mineralogical, and geochemical properties, which may lead to the release of metal(oid)s (e.g., As, Cu, Zn, Fe, S) into the environment. Fresh and oxidized tailings were sampled at two vertical profiles in a tailings storage facility (TSF). The TSF contains tailings from gold ore processing at a mine that has been closed for more than 25 years. Oxidized tailings have formed by in-situ oxidation of fresh tailings over more than 20 years. The collected samples were analyzed for: i) chemical composition by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), and total S/C; and ii) mineralogical composition by X-ray diffraction (XRD), Mineral Liberation Analyzer (MLA), Mossbauer spectroscopy, and Fe L-edge X-ray absorption near-edge spectroscopy (XANES). Mineralogically, the fresh tailings included more than 22 wt% carbonates and more than 10 wt% sulfides. In contrast, the oxidized tailings were composed mainly of secondary minerals such as iron oxy-hydroxides and gypsum. Geochemically, the fresh tailings exhibited a circumneutral behavior during weathering cell experiments and contaminants such as As were negligibly released (

The former Eagle and Telbel mine site (hereafter referred to as Joutel mine), located near the town of Joutel in the Nord-du-Quebec (Canada) houses a tailings storage facility (TSF) that has been inactive since 1996. Fresh, unweathered tailings (beneath 10–30 cm of oxidized horizon) are characterized by an average sulfide content of 6–7 wt% and an average Fe-Mn-carbonate content of 20–40 wt%. The oxidation of Joutel's tailings under atmospheric conditions resulted in the precipitation of secondary phases such as ferric oxyhydroxides and gypsum. Accumulation of these secondary phases throughout the TSF caused cementation and agglomeration of grains, which decreased the porosity of the material in a horizon below the surface. This horizon, which is referred to as hardpan, is frequently encountered within fine, reactive tailings. Characterizations showed that hardpans have a highly compact texture. The formation of hardpans limits vertical water infiltration and oxygen diffusion and these layers greatly affect the global geochemical behavior of underlying tailings in the Joutel TSF by protecting the unweathered material from oxidation. As a result, the water quality of the TSF is largely controlled by the reactivity of the upper oxidized tailings horizon. Joutel's oxidized tailings showed an acidic behavior early during laboratory kinetic leaching tests despite the near absence of sulfides and neutralizing minerals. However, when unweathered tailings were added under oxidized tailings, the water became neutral and metal leaching rates were reduced. After over a year of laboratory leaching tests, hardpans formed within the columns and the natural phenomenon was reproduced under laboratory conditions.

Acid mine tailings may affect several environmental matrices. Here, we aimed to stabilize acid-generated mine tailings using several alkaline and cementitious amendments, which were tested in columns for 361 days. The alkaline amendments consisted of 10 and 20 wt.% limestone, while the cementitious amendments consisted of different binders at a total dosage of 5 wt.% binder. The different formulations for the cementitious amendments were: 50% Kruger fly ash and 50% class F fly ash, 20% ordinary Portland cement, 40% Kruger fly ash, and 40% class F fly ash, 80% ordinary Portland cement and 20% Kruger fly ash, and 20% ordinary Portland cement, 40% Kruger fly ash, and 40% fly ash. Kinetic testing on the amendment formulations showed that the pH values increased from &lt, 2.5 to circumneutral values (~7.5). The mobility of various chemical species was greatly reduced. Cumulative Fe released from the unamended tailings was ~342.5 mg/kg, and was &lt, 22 mg/kg for the amended tailings. The main mechanisms responsible for metal(loid) immobilization were the precipitation of secondary phases, such as Fe-oxyhydroxides, physical trapping, and tailing impermeabilization.

Due to the increasing demand for conventional sources of potassium (K) and their inaccessibility by African countries, K-rich igneous rocks are increasingly studied as potential alternative sources. In this study, six potassic igneous rocks (syenites and trachytes) from the Tamazeght, Jbel Boho, Ait Saoun, and El Glo’a regions (Morocco) were sampled and characterized. Then they were hydrothermally treated to enhance their K release for potential use as potassic fertilizers. The raw materials are mainly formed by microcline (up to 74%), orthoclase (20–68%), albite (36–57%), biotite-muscovite (15–23%), and titanite, calcite, hematite, and apatite as accessory minerals. These samples were crushed and milled to reach a particle size &lt, 150 µm and mixed with 4 N NaOH solution in an autoclave. The liquid/solid (L/S) ratio was about 44 mL/50 g. The powders were allowed to react with the solution at 170 °C for 7 h. For all tests, NaOH reacted completely with the powders and no liquid was observed after the treatment. X-ray diffraction (XRD), thermal gravimetric analysis (TGA), infrared spectroscopy (IRTF), and scanning electron microscopy (SEM-EDS) were carried out on treated samples to characterize the mineralogical and structural changes due to the alkali-hydrothermal treatment. Indeed, the treated samples revealed the presence of sodic neoformed phases such as thermonatrite, sodalite, analcime, and cancrinite. The treated material was leached for a week using deionized water and the elements released were measured using inductively coupled plasma–atomic emission spectroscopy (ICP-AES). The hydrothermal process showed a strong effect on structure breakdown as well as on the release of K and other nutrients such as P, Fe, Si, Mg, and Ca. Therefore, the alkali-hydrothermal treatment allowed the release of 50.5 wt% K. Moreover, the release of Mg, Ca, Fe, P, K, and Si were significantly increased. Mg, Ca, Fe, P, K, and Si release within raw materials was about (0.5–3.6), (3.5–31.4), (0.01–0.4), (0.01–0.3), (20–55), and (4.6–8) mg/kg, respectively, whereas treated samples showed a higher release of these elements. Quantitatively, Mg, Ca, Fe, P, K, and Si releases were about (10–11.8), (60–70), (7–20), (1.2–15), (218–1278), and (1119–2759) mg/kg, respectively. Consequently, the treated igneous rocks (syenite and trachyte) could be directly used as potassic fertilizers that would also be a source of other nutrients.

Significant volumes of waste rock are produced in mining operations, particularly in open pit operations. Waste rock is characterized by a high heterogeneity in their mineralogical, hydrogeological, and physical properties, especially in comparison to tailings. The purpose of this study was to develop an improved method to quantify the net acid-generating potential of waste rock by incorporating the degree of liberation of acid-generating and neutralizing minerals. Three lithologies were sampled immediately after waste rock blasting. Each lithology was separated into seven fractions: D 5 cm were not considered. Mineralogical and chemical characterizations showed that sulphides, mainly pyrite, were enriched in the fine to mid-sized fractions (between 0.053 mm and 0.85 mm), and carbonates, mainly calcite, decreased as the particle size increased. Sulphides were more liberated within the fine fractions and their liberation was considered negligible at sizes >2.4 mm. For coarser fractions (>5 mm), sulphides were associated with non-sulphide gangue minerals which was confirmed by micro-computed tomography. The waste rock samples were submitted to both acid base accounting (ABA) and net acid generation (NAG) tests to evaluate their acid-generating potentials. Sixteen size fractions were non-acid generating and five were classified as uncertain. However, standard ABA and NAG tests are based on pulverized samples that don't consider the initial textures of samples. Therefore, ABA results (acid-generating potentials and neutralization potentials) were corrected using the degrees of sulphide and carbonate liberation. The corrected classifications reduced the acid-generating potential of most of the uncertain samples due to the high carbonates content in relation to sulphides. This study also defines a parameter, the diameter of physical locking of sulphides, that can be used to separate waste rock into a reactive and non-reactive fraction based on the relationship between sulphide liberation and particle-size fraction. The reactive fraction refers to waste rock likely to require active acid rock drainage (ARD) management, whereas non-reactive fraction refers to waste rock likely not require active management.

This study investigates the effectiveness of alkaline and cementitious additives in the in situ stabilization of localized acid-generating tailings from a closed gold mine in Abitibi&ndash, T&eacute, miscamingue, Qu&eacute, bec (Eagle/Telbel mine site). Five field cells (including one control) were constructed and equipped with mechanisms for collecting vertical water infiltration and surface runoff. The five cells included: (C1) Control cell, (C2) 5 wt % limestone amendment, (C3) 10 wt % limestone amendment, (C4) 5 wt % half ordinary Portland cement and half fly ash amendment, and (C5) 5 wt % ordinary Portland cement amendment. The control cell showed an acidic behavior (pH &lt, 4.5) with variable concentrations of Fe, Al, Zn, and Cu. The amendments were used to neutralize the acidic leachates and decrease dissolved metal concentrations. Leachates from surface runoff samples of amended cells were less loaded with metals compared to samples of vertical infiltration. All amendment formulations increased the pH of the leachates from approximately 4 to circumneutral values. Furthermore, metal and metalloid concentrations were greatly limited, except for Cr and As for the carbonate-based amendments. Metal(-oid) stabilization was successfully achieved using the different amendment formulations, with the exception of C2, which still released As.

At some orphaned and abandoned mine sites, acid mine drainage can represent a complex challenge due to the advanced tailings&rsquo, oxidation state as well as the combination of other factors. At the field scale, several parameters control sulfides&rsquo, oxidation rates and, therefore, the acidity generation. The objective of this paper is to map the acidity and geochemical properties of oxidized tailings within a closed tailings storage facility. Based on systematic sampling, various geochemical parameters were measured within the oxidized Joutel tailings, including the: Neutralization potential, acid-generating potential, net neutralization potential, neutralization potential ratio, paste pH, thickness of oxidized, hardpan, and transition zones. The different parameters were integrated in geographical information system (GISs) databases to quantify the spatial variability of the acidity and geochemical properties of oxidized tailings. The oxidized tailings were characterized by low sulfide (mainly as pyrite) and carbonate (mainly as siderite/ankerite) contents compared to unweathered tailings. Acidic zones, identified based on paste pH, were located in the eastern portion of the southern zone and at the northern tip of the northern zone.

The anthropogenic pollution of lake ecosystems by human activities (e.g., mining industries) is recognized as a serious issue. The Osisko urban lake located in Rouyn-Noranda (Quebec, Canada) was used partially as a waste disposal facility for many decades, causing a heavy pollution. The main undertakings of this study are (i) assessing the mineralogical and geochemical properties of lake Osisko sediments, and (ii) studying the pollution that occurred within lake water due to the sediments’ reactivity. Water and sediments across the lake were collected in different sensitive locations. Within the sediment samples, two parts were distinguished: a small layer of black vase over grey sediments. The black vase resembled organic matter while the gray sediment seemed close to clean lake sediments. The collected samples were characterized for their physical (particle size distribution, specific gravity and specific surface area), chemical (minor and major elements as well as total sulfur and carbon) and mineralogical (X-ray diffraction and scanning electron microscope) properties. Additionally, the reactivity of sediments was studied using weathering cells to quantify chemical species leaching and their releasing rates. The results showed that the vase was the only contaminated part with high concentrations of sulfur and metals such as copper, zinc and iron. Geochemical data showed that the composite sample and the vase potentially cause contaminated acid drainage if they are exposed to atmospheric conditions. Indeed, the pH values of the leachates from both samples were between 4 and 6, while those corresponding to sediments remained around circumneutral values. Quantitatively, the contaminant release from the tested samples was variable. Indeed, the Fe cumulative concentrations were around 200, 80 and 20 mg/kg for the vase, composite and sediment samples, respectively. Similarly, the Zn cumulative concentrations were around 4500, 4200, and below the detection limit for vase, composite and sediment samples, respectively. The same tendency was observed for Cu, S, and Fe. Thus, sediments within Osisko lake present a risk for water contamination if they are resuspended or dredged out of the lake. Consequently, they should be stabilized before their disposal. The samples’ high Cu contents also offer the possibility of their reprocessing.

This paper investigates the characteristics of nine different wastes from phosphate extraction mines and their potential applications. These materials are generally extracted and landfilled in dumps as they do not present any added value. Therefore, it is aimed to highlight the potential uses of these materials based on their chemical and mineralogical compositions as well as their thermal behavior. Based on the obtained results, those waste materials turn out to offer a great potential for various industrial applications: traditional ceramics, cement industry, geopolymer, alkali activated materials, and acid mine drainage control. Their high content in carbonates could be exploited to produce light weight ceramic products with good acoustic and thermal insulation. Also, due to the high content of CaO, SiO2 and Al2O3, some samples could be mixed with some additives to serve as clinker raw materials or as supplementary cementitious materials. Additionally, high carbonates content provides high neutralization potential to stabilize acid generating tailings. The valorization of such raw materials will allow to decrease the consumption of natural resources in the construction sector as well as resolving the environmental problems linked to these materials.

Prescribing compaction at optimum water content in arid and semi-arid climate regions generally leads to unjustified ecological practices. Indeed, to achieve optimum densities for road embankment compaction, significant volumes of water are required, which is perceived as a very scarce resource in drought-prone areas. Dry compaction with the promotion of the use of materials at their natural moisture content can be a promising alternative that could save water resources. Nevertheless, dry compaction can affect the infrastructures’ stability under flooding conditions. This paper presents field and laboratory tests carried out to investigate the effect of dry compaction on Phosphate Mine Waste Rocks (PMWR) behavior. In situ tests were conducted and the PMWR dry compaction protocol has been defined. Furthermore, the collapse deformation and the shear strength properties were evaluated through double oedometer and triaxial tests, respectively. The microstructural evolution on wetting was evaluated using mercury intrusion porosimetry (MIP) and 3D X-Ray computed tomography techniques. The water retention curve and mineralogical quantification tools were used to explain the influence of hydraulic hysteresis and clay minerals properties on the hydro-geotechnical behavior of PMWR. The results show a significant effect of applied stress level and dry density in addition to the type and amount of clayey expansive minerals on the structural deformation of PMWR on wetting. PMWR showed a maximum collapse settlement of 5.33% under a pressure of 1500 kPa, while no collapse is expected for stress less than 100 kPa. Low content of clays was identified as well as the swelling shrinkage potential within PMWR. The ability of using PMWR as embankment materials at dry moisture content under total overburden stress below 200 kPa ensuring a dry density of at least 95%.σd max is confirmed. The results of this work can also be applied to standard materials with similar hydro-geotechnical characteristics.

Mining operation produces significant volumes of waste rocks (WR) characterised by high heterogeneity in their physical, mineralogical and hydrogeological properties. The purposes of this study were to assess the acid-generating potential, evaluate reprocessing feasibility of polymetallic WR using desulphurisation process (i.e., gravity separation and flotation) and study the geochemical behaviour of desulphurised materials. The fresh WR was collected in the waste dump from Langlois mine at Lebel-sur-Quevillon (Quebec, Canada). The WR sample was divided into six fractions using wet screening: D

Open-pit mining generates a large volume of waste rocks (WR) that are deposited as unsaturated piles on the surface. WR are mainly characterised by the high heterogeneity of their hydrogeological, mineralogical and physical proprieties. The main objectives of this study consist of: i) a detailed characterisation of WR from Canadian Malartic mine in Malartic city (Quebec, Canada), ii) the use of environmental desulphurisation of the three classified waste rocks main lithologies to reduce their acid generation potential and iii) the recovery of the residual precious metals (e.g. Au, Ag). The studied materials were sampled after blasting while ensuring their representativity. Each lithology was first screened based on the DPLS (diameter of physical locking of sulphides) to remove the inert fraction higher than 2.4 mm. Then, the fraction (