Geochemical Behavior of Mine Tailings and Waste Rock at the Abandoned Cu–Mo–W Azegour Mine (Occidental High Atlas, Morocco)

The abandoned Azegour mine is located in the High Atlas Mountains of Marrakesh (Morocco), and was mined for Cu, Mo, and W. About 850,000 t of waste rocks and tailings were deposited on the surface and have been exposed to weathering for 40 years. The remaining acid-producing potential (AP), acid-neutralizing potential, and geochemical behavior of the Azegour Cu-and Mo-rich tailings were investigated. The tailings were found to contain 9.6–19 wt% sulfur, mostly as sulfate (gypsum, anhydrite, and jarosite) while the waste rocks contain less (1.25–6.58 wt%) sulfur. The waste rocks and tailings contain 0.21–9.24 wt% Mo and 0.003–2.78 wt% Cu. The gangue is mostly composed of quartz, talc, chlorite, pyrophyllite, actonolite, clinoptilolite, and alusite. Lead, zinc, cobalt, arsenic, titanium, and nickel are also present. The calcium, which is mainly expressed as calcite, gypsum, scheelite, and powellite, is present at higher concentrations in the waste rocks (18–22 wt% Ca) than in the tailings (4.7–8.6 wt% Ca). Static ABA determinations showed that the Azegour mine wastes still have high AP, 38–205 kg CaCO₃/t in the waste rocks and 46–387.7 kg CaCO₃/t in the tailings. This was confirmed in weathering cell tests, where the Azegour tailings leachate had a pH range of 1.98–3.19 and high concentrations of SO₄ (468–45,400 mg/L), Ca (230–675 mg/L), Fe (3–55,900 mg/L), Mn (0.1–1,430 mg/L), and Cu (2.3–9,000 mg/L). The Mo concentrations were high (35 mg/L) during the two first weeks of kinetics tests; W concentrations were below the 0.005 mg/L detection limit.     

Geochemistry of Mine Tailings from Processing of Siderite–Cu Ores and Mobility of Selected Metals and Metalloids Evaluated by a Pot Leaching Experiment at the Slovinky Impoundment,Eastern Slovakia

This work describes the geochemistry, mineralogy, and mobility of selected metals (Cu, Pb, Zn) and metalloids (As, Sb) in a tailings impoundment in the village of Slovinky (eastern Slovakia). The tailings were covered unevenly by slag from processing of Cu wastes. The tailings and slag both have negligible potential for acid mine drainage formation, thus neutral to alkaline conditions predominate, as shown by high paste pH values of the tailings (7.66–8.83) and neutral drainage, with pH values above 7.50. Weathering of the most abundant primary sulfides (chalcopyrite, pyrite, and arsenopyrite) releases low concentrations of As, Cu, Pb, Sb, and Zn from the tailings impoundment and in leachates from a 150 days pot leaching experiment. This is explained mostly by formation of secondary ferric oxyhydroxides (as weathering rims on the surfaces of primary sulfides or individual grains),which incorporate 4.09 wt% of As, 17.2 wt% of Cu, 1.20 wt% of Pb, 15.0 wt% of Sb, and 1.59 wt% of Zn. Elevated contents of metals and metalloids in weathering rims formed on slag components like glasses, metallic grains, and residues of blast-furnace lining indicate that secondary solid phases are controlling the mobility of the potentially toxic elements. Generally, with the exception of Cu, no separate secondary compounds of the metals or metalloids were found. The potentially toxic elements are mainly immobilized by ferric oxyhydroxides and other iron mineral phases in the tailings impoundment.     

Chemical and Water-Isotope Composition Unravels the Source and Evolution of the Kittilä Underground Mine Water,Kiistala, Finland

Mine Water and the Environment - Assessing the environmental impacts of underground mines requires that the mine water sources and the geochemical processes that alter their chemical composition be...     

The Distribution of Antimony and Arsenic in Waters of the Dúbrava Abandoned Mine Site, Slovak Republic

The abandoned Dúbrava Mine, situated in the northern part of the Nízke Tatry Mts in the middle of Slovakia, was the most significant producer of antimony (Sb) in the former Czechoslovakia. Mine drainage from adits (containing up to 9,300 μg/L of Sb), mine waste dumps, and the leachate from mine tailings contribute Sb and arsenic (As) into nearby Palud?anka Creek and groundwater. Some drinking water resources have been closed due to excessive Sb concentrations; the concentration of Sb in one household well (126 μg/L) far exceeds the Sb drinking water limit of 5 μg/L. Although Sb is attenuated by dilution and adsorption on ferric iron in stream sediment in the Palud?anka Creek, Sb concentrations increase downstream of the mine tailings and then remain almost constant, leading to concentrations of 128 μg/L at the northern boundary of the study area. The dissolved As concentrations in the mine drainage are much lower than Sb, ranging from 4 to 62 μg/L. Flow and transport modeling confirmed the observed contamination pattern and the major role of the mine adits. Results of this study indicate serious Sb contamination, which could be mitigated by treatment of the adit discharges.     

A Note on the Influence of the Mine Tailings Released in the Córrego do Feijão Mine Disaster on the Water Bodies of Brumadinho,Minas Gerais,Brazil

Mine Water and the Environment - The rupture of the Córrego do Feijão iron mine Tailings Dam I killed at least 260 people and had major environmental and social impacts. We analyzed the...     

Prediction of Acid Mine Drainage (AMD) and Metal Release Sources at the Küre Copper Mine Site,Kastamonu, NW Turkey

Mine Water and the Environment - Waste and lithological rocks were subjected to aqueous leaching, acid base accounting (ABA), and net acid generation (NAG) tests, and detailed mineralogical...     

The Geochemical Behaviour of Mine Tailings from the Touiref Pb–Zn District in Tunisia in Weathering Cells Leaching Tests

Flotation tailings associated with the extraction of Pb and Zn in the Touiref mining district, Tunisia, contain galena, sphalerite, pyrite, and marcasite in a carbonate gangue. The geochemical behaviour of oxidized and unoxidised tailings were consistent with their mineralogical and chemical characteristics. The leaching proceeded under neutral to slightly alkaline condition (pH 7.3–8.5), and positive Eh (250–470 mV). The concentrations of sulfate and Ca released during the leaching tests were associated with the neutralization of acidity by carbonates and the dissolution of gypsum initially present in the tailings. The iron precipitated, but significant amounts of Zn (5–3,300 μg/L), Cd (3–18 μg/L), and Pb (28–83 μg/L) were released during leaching, with the latter two exceeding international environmental norms (5 μg/L for Cd and 10 μg/L for Pb).     

Variabilities in Hard Coal Production and Methane Emission in the Myslowice–Wesola Mine

Journal of Mining Science - Hard coal production is a strategic branch of the Polish economy. The exploitation processes at greater depths encounter natural hazards, such as methane hazard. The...     

Phase stabilities and thermodynamic assessment of the system Cu–Pb–S

An equilibration quenching technique was used to evaluate experimentally the phase relations in the Cu–Pb–S system between 763 and 1273 K. At 763–788 K, the formation of a ternary phase was confirmed. In addition, the thermodynamic properties of the Cu–Pb–S ternary system between 763 and 1573 K were critically assessed and optimized by the CALPHAD (CALculation of PHAse Diagrams) method, using the experimental results from this work and critically evaluated literature data. The obtained thermodynamic dataset allows the thermodynamic properties and phase equilibria in the Cu–Pb–S system to be calculated with good agreement to the experimental results. The effects of different process variables on the lead and copper distributions between the metal and matte can be calculated to improve the process control and economics.     

Surface and Groundwater Quality Evolution in the Agrio and Guadiamar Rivers After the Aznalcóllar Mine Spill (SW Spain): Lessons Learned

Mine Water and the Environment - The failure of the tailing dam at the Aznalcóllar mine (SW Spain) in 1998 released ≈ 6 million m3 of pyrite sludge and acidic...     

Comprehensive experiment and evaluation on safety due to fully-mechanized mining under the Xitian River at Linxin Mine

L3414 mechanized mining working face (No.14 coal seam) of Lingxin Mine is under the Xitian River.The mining disturbed zone where rock properties and conditions have been changed due to mining, the safety and environmental protection were concemed greatly. Based on engineering geological environment of L3414 working face and mining factors, the color bore-bole TV inspecting, leakage of drilling fluid monitoring,simulation experiment, numerical computing, in-situ ground stress measurement and subsidence measurement, etal, these programs contribute to the formation of a scientific basis for control water safe mining and normal mining or environmental protection in the condition of existing fully-mechanized mining.     

Nitrate Reduction of the Siilinjärvi/Finland Mine Water with Zero-valent Iron and Iron Waste as Alternative Iron Sources

Mine Water and the Environment - Nitrate reduction was optimized in water from the Siilinjärvi/Finland mine site with iron powder and iron nanoparticles. Iron waste from a mold machining...     

Mobility of Be,Bi, F,Ga, Ge and W in Surface Water and the Water Quality Impact on Epilithic Diatoms Downstream of the Historical Yxsjöberg Mine Site,Sweden

There is a potential risk that the geochemical cycles of several critical metals will be affected when mining of these metals increases to meet the demand of green technology. The geochemistry of Be, Bi, Ga, Ge, and W, herewith called CM5, is lacking, yet is necessary to ensure responsible mine waste and water management. Beryllium, Bi, and W are all considered immobile, but in previous studies of skarn tailings in Yxsjöberg, Sweden, all three elements were mobilized. The tailings are enriched in CM5, together with pyrrhotite, calcite, and fluorite. The mobility and environmental impact of CM5 and F in surface waters downstream of the Yxsjöberg mine site, Sweden, were studied using monthly water samples from seven locations and analysis of diatoms at five of these locations. Bismuth, Ge, and W were present at low concentrations, transported in the particulate phase, and likely settled in the sediments hundreds of meters from the tailings. Beryllium and F were present at high concentrations and dominantly transported in the dissolved phase. At these pH conditions (5.6), Be should form insoluble hydroxides; however, elevated concentrations of dissolved Be were observed more than 5 km from the mine site. Diatoms downstream of the mine site were negatively affected by the mine drainage. The release of low quality neutral mine drainage will continue for hundreds of years if remediation actions are not undertaken since only a small portion of the tailings have weathered during 50–100 years of storage.

     

The role of colloidal precipitates in the interfacial behavior of alkyl amines at gas–liquid and gas–liquid–solid interfaces

Alkyl amines are widely used as cationic collectors in froth flotation. They are generally referred to as weak electrolyte collectors and frequently form solid insoluble precipitates. Much work has been done to measure the interfacial tension and contact angle regarding alkyl amine collectors. However, the role of these colloidal precipitates in adsorption phenomena and the kinetics involved in the adsorption have not been systematically studied and decoupled from those of soluble species in flotation. Using dodecyl amine (DDA) as the model surfactant, four sets of intimately linked measurements were made on the dynamic surface tension of amine true solutions and solutions containing precipitates to demonstrate the difference in the surface activity kinetics of colloidal precipitates and soluble species. The effects of the interfacial kinetics on the bubble size in a two-phase system and on the contact angle in a three-phase system were also studied to understand the migration of precipitates between different interfaces. The experimental data showed that kinetic effects existed whenever precipitates were involved, but were absent from true amine solutions. A three-stage mechanism (migration–adsorption–aggregation) was proposed and tested to explain the kinetic behavior associated with precipitates. The size of air bubbles generated in the true solutions was not affected by the surface age of bubbles, while bubble size was affected by the surface age in the presence of precipitates. The observed kinetics of contact angle evolution suggested that the migration of DDA species between air–water–interfaces occurred.     

Grain Size Effects on Mine Water Quality and Acid/Neutral Rock Drainage Production in Kinetic Testing Using Recsk Porphyry Skarn Cu–Zn Deposit Rocks

The quality of mine drainage from sulphide-containing waste rock dumps is controlled by several factors. To characterize the effects of grain size on acid/neutral rock drainage production, kinetic tests were performed on samples from the Recsk porphyry skarn Cu–Zn deposit in Hungary, an area known to generate ARD. Five columns were used, each containing specific grain size ranges (1–2, 2–4, 4–8, 8–16, and 16–32 mm). Prior to the kinetic tests, a static test was performed for each grain size range to obtain total and available neutralizing potential (NP) and acid potential (AP). Total NP and AP values were roughly similar for all grain size ranges, while available NP increased as grain size decreased. The neutralization potential ratio for all grain size ranges was <1, which suggests a potentially acid-producing material. The kinetic tests, however, had contrasting results; a grain size of 1–4 mm produced a circumneutral pH, while grain size groups >4 mm produced pHs from 5.1 down to 3.6. Higher alkalinity values in the leach water were linked to the finer grain samples, primarily producing circumneutral pH. Grain size correlated with the sulphate release rate during the stable release period: the sulphate release rate was less at larger grain sizes. In contrast, sulphide oxidation calculated from oxygen consumption was highest for the intermediate grain size range, followed by the coarser and then the finer grains. The leaching of metals established an increasing concentration with increasing acidity without a very clear relationship to grain size. The established concept of increased metal mobility with decreasing pH applies, regardless of grain size.