Prevention Of Acid Mine Drainage Research Articles

Hydrogeochemical Behavior of Reclaimed Highly Reactive Tailings, Part 1: Characterization of Reclamation Materials

The production of solid mine wastes is an integral part of the extraction and metallurgical processing of ores. The reclamation of highly reactive mine waste, with low neutralizing potential, is still a significant challenge for the mining industry, particularly when natural soils are not available close to the site. Some solid mine wastes present interesting hydro-geotechnical properties which can be taken advantage of, particularly for being used in reclamation covers to control acid mine drainage. The main objective of this research was to evaluate the use of mining materials (i.e., tailings and waste rock) in a cover with capillary barrier effects (CCBE) to prevent acid mine drainage (AMD) from highly reactive tailings. The first part of the project reproduced in this article involves context and laboratory validation of mining materials as suitable for a CCBE, while the companion paper reports laboratory and field results of cover systems made with mining materials. The main conclusions of the Part 1 of this study were that the materials studied (low sulfide tailings and waste rocks) had the appropriate geochemical and hydrogeological properties for use as cover materials in a CCBE. Results also showed that the cover mining materials are not acid-generating and that the LaRonde tailings are highly reactive with pH close to 2, with high concentrations of metals and sulfates.

Laboratory study of low-sulfide tailings covers with elevated water table to prevent acid mine drainage

The use of monolayer covers combined with an elevated water table (EWT) is a promising reclamation method that relies on the low gas-diffusivity of water to limit oxygen ingress into potentially acid-generating tailings. A monolayer cover is installed over the sulfidic material and the water table level is controlled to maintain the tailings close to saturation. A protocol including laboratory columns was conducted to evaluate the sensitivity of the technique to parameters including cover thickness, water table level, and the presence of an anti-evaporation layer. Two types of desulfurized tailings were evaluated: silty tailings from Westwood mine and sandy tailings from Goldex mine. Data used to evaluate the covers performances included volumetric water content, suction, oxygen concentrations, and oxygen consumption. Results showed that both cover materials could be used to maintain the reactive tailings at a degree of saturation ≥90% when the EWT level was maintained at a maximum distance of 1 m below the tailings surface. The finer Westwood material showed a better capacity for limiting oxygen migration through the cover, with a maximum flux of 5.7 mol·m−2·year−1 measured near the cover base.

Desulfurization of the Old Tailings at the Au-Ag-Cu Tiouit Mine (Anti-Atlas Morocco)

Tailings from the abandoned Tiouit mine site in Morocco are mainly composed of sulfides, hematite, and quartz. They contain 0.06–1.50 wt % sulfur, mostly in the form of pyrite, pyrrhotite, and chalcopyrite. The tailings also contain gold (3.36–5.00 ppm), silver (24–37 ppm), and copper (0.06–0.08 wt %). Flotation tests were conducted to reprocess the tailings for Au, Ag, and Cu recovery, and at the same time to prevent acid mine drainage (AMD) generation through the oxidation of sulfide minerals, including pyrite, sphalerite, arsenopyrite, chalcopyrite, galena. The flotation results confirmed that environmental desulfurization is effective at reducing the overall sulfide content in the tailings. The recovery of sulfides was between 69% and 75%, while Au recovery weight-yield was between 2.8% and 4.7%. The test that showed the best sulfur recovery rate and weight-yield was carried out with 100 g/t CuSO4 (sulfide activator) and 50 g/t of amyl xanthate (collector). The goal of this study was also to assess the remaining acid-generating potential (AP) and acid-neutralizing potential (NP) of the desulfurized tailing. The geochemical behavior of the initial tailings sample was compared to that of the desulfurized tailings using kinetic weathering cell tests. The leachates from the desulfurized tailings showed higher pH values than those from the initial tailings, which were clearly acid-generating. The residual acidity produced by the desulfurized tailings was most likely caused by the hydrolysis of Fe-oxyhydroxides.

Acid Drainage Potential of Rocks in South-Western Ghana

The generation of acid in reactive sulphide-containing rocks is a major global problem confronting advanced countries, and serving as a wake-up call for developing countries like Ghana. South-western Ghana hosts two major gold belts, which house ten large-scale mining companies, several small-scale mining companies, farms and other activities. The presence of sulphur in the rocks, coupled with the land disturbances stemming from the activities mentioned above, suggests the potential for uncontrolled acid generation. These have thus generated interest in studies on mapping out the acid generating potential of these areas, so that proactive steps can be taken to prevent acid mine drainage. In this study, several samples were taken from mine waste, mineralised waste and ore from a mine concession in Ghana, and subjected to mineralogical, geochemical and Acid-Base Accounting (ABA) studies. Mineralogical studies reported about 75% quartz while carbonates, feldspars, pyroxene, sericites and chlorites accounted for 25% of samples tested. Polish sections showed pyrite content of up to 5% while arsenopyrite accounted for 1%. The results from geochemical and Acid-Base Accounting (ABA) passed 31% of the samples as non-sulphidic, whereas 20% had sulphur content above 0.5%. The sulphur content in excess of 0.5% gives an indication that the rock can generate acid. Analysis of paste pH confirmed that about 80% of the samples were neutral to basic (i.e. pH 6.5-8.5). Further analysis using Net Neutralising Potential (NNP) and ratios of Maximum Neutralisation Potential to Acid Production Potential (NP: AP) placed 35% of the samples as having the potential to generate acid since the NNPs were negative, while the NP: AP had values less than 1. This 35% had the capacity to significantly deteriorate natural water quality. The study concludes that there is a great potential for AMD generation in south-western Ghana, and this calls for periodic monitoring and development of proactive neutralising strategies to arrest the situation.

Acid mine drainage remediation strategies: A review on migration and source controls

Acid mine drainage (AMD) derives from the oxidation of sulfide minerals, primarily pyrite (FeS2), and is the most severe environmental issue facing the minerals industry. The most common short-term approach to AMD treatment is migration control, such as acid neutralization and metal/metalloid and sulfate removal, through the addition of alkaline materials, including lime (Ca (OH)2), limestone (Ca CO3), gangue minerals and industrial wastes. This requires the continuous input of materials and may result in the production of a vast amount of secondary sludge requiring further treatment and disposal. Addition of chemicals is usually more important in metal/metalloid removal than in sulfate removal unless the sulfate is present in very high concentrations. A more promising long-term strategy for AMD prevention is source control through the complete removal of pyritic minerals and encapsulation of potential risk minerals by coating with impermeable surface layers. This is regarded as the most cost-effective approach, although the mechanisms underpinning this and the implementation procedures are yet to be fully elucidated. It is likely that long- and short-term practices can be combined to optimize the remediation of contaminated mining sites. Some factors such as differing geological and mineralogical characteristics and transportation costs must also be considered for the successful implementation of AMD prevention and remediation strategies. This review also considers some implications for AMD remediation, but the promising bioremediation of AMD is not discussed as it has been extensively reviewed.

Geochemical stability of acid-generating pyrrhotite tailings 4 to 5 years after addition of oxygen-consuming organic covers

Oxygen-consuming organic covers can serve as a reactive barrier to minimize sulfide oxidation in acid-generating tailings but may lead to metal mobilization in surface oxidized layers. We evaluated changes in the bio-geochemical stability of acid-generating, Cu-Ni pyrrhotite tailings 4 to 5 years after addition of a 50 cm-thick or a 1 m-thick biosolid cover planted with energy crops. The original tailings (pH 2.5) were oxidized in the first 10 to 40 cm, and goethite was the dominant sink for Cu and Ni, the main metal contaminants in these tailings. Both covers increased pH, nutrient availability, microbial activity and diversity in the oxidized tailings, and led to a reduction of water-soluble Cu, Ni, Fe and Al after 4 to 5 years of application. Changes in pH, humidity, organic C content, and redox conditions resulted in partial dissolution of jarosite and gypsum below the cover but goethite apparently remained stable. Under both covers, total Ni decreased in the oxidized layer, indicating remobilization, but Cu was retained. Significant accumulation of Cu as Cu sulfide at the oxidized/unoxidized tailings interface was detected only under the 1 m-thick cover, suggesting that the thinner cover may not sufficiently decrease the oxidizing conditions to mitigate acid mine drainage. Migration of nitrate and P down to the unoxidized tailings was observed under both covers and raises the concern of continued sulfide oxidation in unoxidized tailings. Although the implementation of thinner covers is economically more sustainable than thick covers, our results indicate that further research is required to establish their long-term suitability and performance to prevent acid mine drainage.

Comparative performance of cover systems to prevent acid mine drainage from pre-oxidized tailings: A numerical hydro-geochemical assessment

The generation of acid mine drainage (AMD) remains a major environmental challenge for the mining industry. The reclamation of old mine sites with pre-oxidized tailings is particularly challenging because of indirect oxidation reactions which can limit the overall effectiveness of an oxygen barrier to prevent AMD. The goal of this project was to quantitatively compare the effectiveness of different cover systems to reclaim two pre-oxidized acid-generating tailings sites, located in Quebec (Canada). Following laboratory column tests, field measurements and observations, coupled hydrogeological and geochemical numerical simulations were conducted to evaluate the effect of various system characteristics. Cover performance was assessed by simulating the evolution of the degree of (water) saturation, pore water pressures, oxygen fluxes and leachate quality. Several reclamation options, including monolayer covers and two- or three-layer covers with capillary barrier effect(s) were simulated. The simulations indicate that because of reduced cover effectiveness with pre-oxidized tailings, the general design targets developed for non-oxidized tailings may not always be directly applicable to already oxidized tailings. The simulations also illustrate how the behaviour and efficiency of a monolayer cover placed over reactive tailings depend on specific factors, including water table position, initial porewater chemistry, and cover materials' hydrogeological properties and thicknesses. The results indicate that under a given set of conditions, a bilayer cover (with a capillary break above the reactive tailings) would not significantly improve cover performance (compared to a monolayer cover) due to water losses by evaporation. The simulations show, however, that a well-designed three-layer cover with capillary barrier effects (CCBE) would be efficient in reducing the oxygen flux and AMD generation, even in the case of highly pre-oxidized tailings. The outcomes from this investigation highlight some of the advantages of carrying out coupled hydrogeological and geochemical simulations to assess the long-term behaviour of reclaimed mining sites.

Mine Drainage: Research and Development

This review summarizes the recent research and development pertaining to the topic of mine drainage which were published in 2016 and early 2017. The review includes three main sections: Mine Drainage and its Environmental Impact, Prediction and Prevention, and Treatment Technologies. The first section covers the characterization of mine drainage and its related environmental impacts, including three subsections focused on physiochemical characterization, microbiological characterization, and environmental impacts. The second section of the review is divided into two subsections focused on either the prediction or prevention of acid mine drainage. The final section focuses on treatment technologies for mine drainage, including physiochemical treatment, biological treatment, passive treatment, and beneficial uses of mine drainage and treatment wastes.

Sulphur removal of iron ore tailings by flotation

ABSTRACTIron ore tailings have become one kind of the most hazardous solid waste. Beneficiation of iron ore tailings is a significant issue in the world steel industries, from the point of view of both pollution control and secondary resources. This investigation addressed the processing of tailings with high sulphur content from an iron ore concentrator to produce pellet feed fines and to prevent acid mine drainage. This study was the lab-scale testing of an integrated method consisting of froth flotation combined with gravity and magnetic separation. Reverse flotation located at the end of the primary treatment circuit (high- and low-intensity magnetic separation) will lower a large amount of the sulphur from magnetic separator concentrate. The effects of various operating parameters such as concentrations of collector, frother, depressant and activator, pH, solid-in-pulp concentration have been studied on the sulphur removal using reverse flotation. According to the data presented in this study, the maximum recovery of total sulphur was obtained when the operational parameters were set to the PAX dosage160 gr/t, MIBC dosage 140 gr/t, CuSo4 100 gr/t, air flow rate 10 l/min, pH 8.5, and pulp density 30%. With these optimum parameters, final concentrate with the grade of 63.7% Fe and 0.085% S was obtained. The results of this study indicated that, with this method, a great amount of iron concentrate is produced and, simultaneously, the sulphidic fraction is separated that can later be managed more easily owing to the reduced volume.

Reactive transport modelling of the hydro-geochemical behaviour of partially oxidized acid-generating mine tailings with a monolayer cover

The efficiency of a monolayer cover to prevent acid mine drainage (AMD) generation from two pre-oxidized tailings impoundments was assessed using the MIN3P code, a finite volume model for coupled groundwater flow, oxygen diffusion and multi-component reactive transport. Numerical simulations were validated using large column tests set up in the laboratory and monitored during 19 wetting and drying cycles, over approximately two years. Results indicate that a monolayer cover made of either non acid-generating tailings or a till was not able to prevent sulfide oxidation in the underlying reactive tailings, both for the conditions applied in the laboratory and under conditions more representative of field observations. The efficiency of the simulated monolayer cover was highly dependent on the position of the water table. Despite improved water quality, the reactive tailings nonetheless continued to oxidize and generate AMD, even when the water table was close to the surface of the tailings (1 m depth). The results from this study indicate that the efficiency criteria for cover systems on fresh unoxidized tailings may not be directly applicable for pre-oxidized tailings. The paper also presents a few modifications to the MIN3P code that were successfully applied to simulate the hydrogeological and geochemical response of pre-oxidized, already acidic and highly contaminated tailings.

Recovery and reuse of sludge from active and passive treatment of mine drainage-impacted waters: a review.

The treatment of mine drainage-impacted waters generates considerable amounts of sludge, which raises several concerns, such as storage and disposal, stability, and potential social and environmental impacts. To alleviate the storage and management costs, as well as to give the mine sludge a second life, recovery and reuse have recently become interesting options. In this review, different recovery and reuse options of sludge originating from active and passive treatment of mine drainage are identified and thoroughly discussed, based on available laboratory and field studies. The most valuable products presently recovered from the mine sludge are the iron oxy-hydroxides (ochre). Other by-products include metals, elemental sulfur, and calcium carbonate. Mine sludge reuse includes the removal of contaminants, such as As, P, dye, and rare earth elements. Mine sludge can also be reused as stabilizer for contaminated soil, as fertilizer in agriculture/horticulture, as substitute material in construction, as cover over tailings for acid mine drainage prevention and control, as material to sequester carbon dioxide, and in cement and pigment industries. The review also stresses out some of the current challenges and research needs. Finally, in order to move forward, studies are needed to better estimate the contribution of sludge recovery/reuse to the overall costs of mine water treatment.

Mine Drainage Generation and Control Options.

This review provides a snapshot of papers published in 2015 relevant to the topic of mine drainage generation and control options. The review is broken into 3 sections: Generation, Prediction and Prevention, and Treatment Options. The first section, mine drainage generation, focuses on the characterization of mine drainage and the environmental impacts. As such, it is broken into three subsections focused on microbiological characterization, physiochemical characterization, and environmental impacts. The second section of the review is divided into two subsections focused on either the prediction or prevention of acid mine drainage. The final section focuses on treatment options for mine drainage and waste sludge. The third section contains subsections on passive treatment, biological treatment, physiochemical treatment, and a new subsection on beneficial uses for mine drainage and treatment wastes.

Biofilm formation and interspecies interactions in mixed cultures of thermo-acidophilic archaea Acidianus spp. and Sulfolobus metallicus

The understanding of biofilm formation by bioleaching microorganisms is of great importance for influencing mineral dissolution rates and to prevent acid mine drainage (AMD). Thermo-acidophilic archaea such as Acidianus, Sulfolobus and Metallosphaera are of special interest due to their ability to perform leaching at high temperatures, thereby enhancing leaching rates. In this work, leaching experiments and visualization by microscopy of cell attachment and biofilm formation patterns of the crenarchaeotes Sulfolobus metallicus DSM 6482T and the Acidianus isolates DSM 29038 and DSM 29099 in pure and mixed cultures on sulfur or pyrite were studied. Confocal laser scanning microscopy (CLSM) combined with fluorescent dyes as well as fluorescently labeled lectins were used to visualize different components (e.g. DNA, proteins or glycoconjugates) of the aforementioned species. The data indicate that cell attachment and the subsequently formed biofilms were species- and substrate-dependent. Pyrite leaching experiments coupled with pre-colonization and further inoculation with a second species suggest that both species may negatively influence each other during pyrite leaching with respect to initial attachment and pyrite dissolution rates. In addition, the investigation of binary biofilms on pyrite showed that both species were heterogeneously distributed on pyrite surfaces in the form of individual cells or microcolonies. Physical contact between the two species seems to occur, as revealed by specific lectins able to specifically bind single species within mixed cultures.

KAJIAN PENANGGULANGAN AIR ASAM TAMBANG PADA SALAH SATU PERUSAHAAN PEMEGANG IJIN USAHA PERTAMBANGAN DI DESA LEMO, KABUPATEN BARITO UTARA, KALIMANTAN TENGAH

This study aims to know the factors that cause the formation of Acid Mine Water, to analyze the methods of prevention of acid mine drainage has been running effectively, to analyze how to prevent the formation of acid mine water at the research area. This research was conducted atLemovillage,North Barito Regency. These results indicate the analysis of water quality in the company with an indication acidic low pH values and high metal values. It is supported by soil pH test results showed low pH, especially on the layer in direct contact or close to coal. Sources of acid mine drainage at the company are from the oxidation of water and oxygen on the wall of rock at pit, water from the dumping area, water flowing from the temporary stockpile into the settling pond 2. From these, we can conclude the results. Recommendations prevention of acid mine drainage can be done by moving the location of the temporary stockpile in accordance with, more effective functioning of sump, controlling the movement of acidic water that has formed, accommodate and neutralize the acidic water that has formed, forming a layer of dry cover, separating the flow of water is not acidic and acidic

Erratum to: Acid mine drainage: electrochemical approaches to prevention and remediation of acidity and toxic metals

Acid mine drainage (AMD), caused by biological oxidation of sulfide minerals in the presence of air and water, is a significant environmental problem because of its acidity and the presence of high concentrations of iron and solubilized toxic metal ions. The focus of this review is to consider the prospects for electrochemical technologies for either prevention or remediation of AMD, with physico-chemical technologies mentioned for comparison.

Construction of Dry Cover System for Prevention of Acid Mine Drainage at Mine Waste Dump in Open Cast Coal Mines, Indonesia

Acid Mine Drainage (AMD) which occurs when sulfide minerals are exposed to water and oxygen with an excavation is one of the serious environmental problems in the world. A dry cover system is generally constructed in waste dump for the prevention of AMD in Indonesia by virtue of low cost and availability of waste rocks for a cover layer. However, the failure of the system caused by the lack of information related to the construction of cover system in mines, which leads to AMD, has been reported recently in Indonesia. In this study, the field investigation was conducted in pit and waste dump in open cast coal mine in Indonesia with the aim of obtaining the information on the construction of a cover layer and backfilling conditions of waste rocks in the waste dump. The rock samples taken in two areas of the mine were analyzed by geochemical analysis and sequential extraction with acids. The results indicated that Net Acid Producing Potential (NAPP) of the rocks in the waste dump down to 100 cm depth in both areas was from 10 to 30 kg H2SO4/ton, suggesting that Potentially Acid Forming (PAF) was backfilled in a cover layer. The backfill of PAF was contrary to the concept of cover system, which caused the failure of constructing a cover layer. The cause of the failure was likely attributed to the shortage of cover rocks which are classified as Non Acid Forming (NAF) or the failure of proper placement of them by an operational problem in the areas. Moreover, the results of the extraction with acids suggested that the form of iron and sulfur has to be taken into account to discuss the occurrence of AMD.

Bluejoint Is an Effective Bio-Barrier Species on Mine Covers.

Covers with capillary barrier effects (CCBE) are used to prevent acid mine drainage from mine wastes in the short term. However, the long-term efficiency of CCBE can be affected by trees because their roots may reduce the ability of covers to limit oxygen migration and also physically damage the CCBE. Two plant species that are native to boreal Canada, bluejoint () and sheep laurel (, were selected as bio-barrier species (BBS) to test if they reduce the growth and root system architecture of trees established on mine covers (balsam poplar [], willow [ spp], and black spruce []). The experiment was established in 2008 on a mine tailings impoundment located in northwestern Quebec, Canada. Trees were measured for height, diameter, and biomass. Coarse roots were excavated from the plots and digitized in three dimensions. Compared with the control (no BBS), bluejoint strongly decreased tree height and diameter increment, biomass, maximum root depth and radial extension, total root length and volume, and number of second- and third-order tree roots. Height and diameter increment, biomass, maximum root depth and volume, and number of second-order roots of balsam poplar increased with sheep laurel compared with control conditions, whereas willow showed no response to this treatment. Most characteristics of black spruce (except root-to-shoot ratio and number of second-order roots) improved in the presence of sheep laurel compared with the control. Thus, bluejoint was a more efficient BBS than sheep laurel. Bio-barriers comprised of bluejoint can be used as a countermeasure for controlling tree invasion of CCBE.

Silicate Covering Layer on Pyrite Surface in the Presence of Silicon–Catechol Complex for Acid Mine Drainage Prevention

Silicate Covering Layer on Pyrite Surface in the Presence of Silicon–Catechol Complex for Acid Mine Drainage Prevention

Valorization of acid mine drainage treatment sludge as remediation component to control acid generation from mine wastes, part 2: Field experimentation

The possibility of using acid mine drainage (AMD) treatment sludge as a cover component to control AMD generation from mine wastes was investigated through laboratory characterization and kinetic column testing (companion paper). The results showed that mixtures of sludge and waste rock, and sludge and tailings, may be integrated in an AMD prevention and control strategy at Doyon mine site (northwestern Quebec, Canada). In order to further investigate these scenarios in realistic climatic conditions, instrumented field test cells were installed on site to evaluate the performance of the mixtures to control AMD generation from tailings and waste rock under natural field conditions. The main findings from two seasons of monitoring are presented in the paper. The waste rock-sludge mixture placed over waste rock was able to reduce the generation of AMD from the waste rock, therefore confirming lab results, and was able to produce a neutral effluent with low concentrations of dissolved metals. The tailings-sludge mixture placed over tailings, with an evaporation protection layer, maintained a high volumetric water content and reduced sulphide oxidation from the tailings as exhibited by a neutral effluent. Monitoring of the field cells will continue to provide valuable information on the possible sludge valorization options.

An Evaluation on Mixture Materials Using Overburden and Flyash as Cover Layer for Acid Mine Drainage Prevention and Underlying Materials of Seedbed in Indonesian Coal Mine

Almost of the coal produced is from open-cut mines in Indonesia. Mining operation of open-cut mines causes a decreasing of a tropical rainforest and gives serious impacts on surrounding environment. Therefore, the environmental reconstruction by revegetation in the disturbed land is required. Mining operation of an open-cut mines requires removal of overburden and placement of them as waste rock dump. However, some of overburden contains sulphide contents which causes Acid Mine Drainage (AMD) and may be undesirable for plant growth because of high salinity, high soluble metal concentrations and high acidity. Furthermore, additional of flyash to waste rock dump for neutralizing AMD is discussed in current researches. As the important object of rehabilitation program is the creation of stable and self-sustaining land surface by vegetation, an assessment of overburden and flyash as planting base have to be discussed. In this study, several geochemical static and kinetic tests for overburden and flyash were carried out to prevent AMD generation and to discuss the impact to plant growth. It was revealed that the adverse effect to plant growth from overburden and flyash can be reduced by effective AMD prevention and preparing appropriate curing period of the ground until the of dissolution of metal ions are decreased.