Prevention Of Acid Mine Drainage Research Articles

Treating waste with waste: Lignin acting as both an effective bactericide and passivator to prevent acid mine drainage formation at the source

Acid mine drainage (AMD) induced by pyrite oxidation is a notorious and serious environmental problem, but the management of AMD in an economical and environmentally friendly way remains challenging. Here, lignin, a natural polymer and abundant waste, was employed as both a bactericide and passivator to prevent AMD formation. The addition of lignin to a mimic AMD formation system inoculated with Acidithiobacillus ferrooxidans at a lignin-to-pyrite weight ratio of 2.5: 10 reduced the combined abiotic and biotic oxidation of pyrite by 68.4 % (based on released SO42−). Morphological characterization of Acidithiobacillus ferrooxidans revealed that lignin could act on the cell surface and impair the cell integrity, disrupting its normal growth and preventing biotic oxidation of pyrite accordingly. Moreover, lignin can be used alone as a passivator to form a coating on the pyrite surface, reducing abiotic oxidation by 71.7 % (based on released SO42−). Through multiple technique analysis, it was proposed that the functional groups on lignin may coordinate with iron ions on pyrite, promoting its deposition on the surface. In addition, the inherent antioxidant activity of lignin may also be actively involved in the abatement of pyrite oxidation via the reduction of iron. Overall, this study offered a “treating waste with waste” strategy for preventing AMD formation at the source and opened a new avenue for the management of AMD.

Analysis of PAF and NAF Tests Using NAPP and ANC Methods at Hajak Site, North Barito, Central Borneo

Acid mine drainage (AMD) is a significant challenge for the global coal mining industry, necessitating specialized treatment to prevent its occurrence. A crucial step in AMD prevention is identifying rocks that contribute to its formation. These rocks are classified into Potential Acid-Forming (PAF) rocks and Non-Acid-Forming (NAF) rocks. PAF rocks have the potential to produce acid, while NAF rocks do not. Laboratory analyses, including Maximum Potential Acidity (MPA), Acid Neutralizing Capacity (ANC), Net Acid Producing Potential (NAPP), and Net Acid Generating (NAG) tests, identified 3 sample points with potential PAF characteristics out of 35 samples tested (see Table 3.1). Among these, 2 sample points were classified as Potential Acid Forming-Low Capacity, and 1 sample point was categorized as Potential Acid Forming-Medium Capacity (NAG pH 4.5, NAPP 10 kg H2SO4/ton). The acidity level of mine water resulting from landfilling varies significantly based on the mineral content and landfilling techniques used. Mined material with high carbonate mineral content tends to have lower acidity levels in leachate and can even neutralize formed acid. The stockpiling strategy implemented involves layering PAF material followed by a final cover of NAF material and a rooting zone to mitigate acid formation.

Acid Mine Drainage Prevention through the Dry Coating Method Using Fly Ash and Bottom Ash

Acid Mine Drainage Prevention through the Dry Coating Method Using Fly Ash and Bottom Ash

Inhibition of pyrite oxidation through forming biogenic K-jarosite coatings to prevent acid mine drainage production

This study proposes a novel method by forming biogenic K-jarosite coatings on pyrite surfaces driven by Acidithiobacillus ferrooxidans (A. ferrooxidans) to reduce heavy metal release and prevent acid mine drainage (AMD) production. Different thicknesses of K-jarosite coatings (0.7 to 1.1 μm) were able to form on pyrite surfaces in the presence of A. ferrooxidans, which positively correlated with the initial addition of Fe2+ and K+ concentrations. The inhibiting effect of K-jarosite coatings on pyrite oxidation was studied by electrochemical measurements, chemical oxidation tests, and bio-oxidation tests. The experimental results showed that the best passivation performance was achieved when 20 mM Fe2+ and 6.7 mM K+ were initially introduced with a bacterial concentration of 4 × 108 cells·mL−1, reducing chemical and biological oxidation by 70 % and 98 %, respectively (based on the concentration of total iron dissolved into the solution by pyrite oxidation). Similarly, bio-oxidation tests of two mine waste samples also showed sound inhibition effects, which offers a preliminary demonstration of the potential applicability of this method to actual waste rock. This study presents a new perspective on passivating the oxidation of metal sulfide tailings or waste and preventing AMD.

Inputs and transport of acid mine drainage-derived heavy metals in karst areas of Southwestern China

Heavy metal pollution caused by acid mine drainage (AMD) is a global environmental concern. The processes of migration and transformation of heavy metals carried by AMD are more complicated in karst areas where carbonate rocks are widely distributed. Water, suspended particulate matter (SPM), and sediments are the crucial media in which heavy metals migrate and it is important to elucidate the geochemical behavior of AMD heavy metals in these environments. This study tracked AMD heavy metals from release to migration and transformation in a natural river system in a karst mining area. AMD directly impacted the hydrochemical composition of the karst water environment, but the carbonate rock naturally neutralized the acidity of the AMD. AMD heavy metal concentrations decreased gradually after the tributaries from the mining area entered the main river, with the metals tending to accumulate in SPM and sediments. The forms in which heavy metals were present were influenced by pH and their relative concentrations. Raman spectroscopy and transmission electron microscopy of sediments from the mining area suggested that the presence of an iron phase plays an important role in the fate of AMD-derived heavy metals. It is, therefore, necessary to elucidate the mechanisms of iron phase precipitation from sediments in order to control AMD-derived heavy metals in karst mining areas. This study improves our understanding of the geochemical behavior of heavy metals in karst environments and provides direction for the prevention and control of AMD in affected areas.

Plant ash prevents acid mine drainage from sulfur-bearing tailings through multiple actions — A low-cost alkaline material

Plant ash, an inexpensive alkaline material containing organic nutrients, can provide electron donors for microbial reactions and neutralize water acidity, making it an excellent candidate for use in preventing acid mine drainage production from tailings. However, the efficacy of using plant ash alone to treat tailings and the role of microorganisms remain unclear. Therefore, the effectiveness of plant ash in acid neutralization, inhibiting oxidation of sulfur-bearing minerals, and reducing acid mine drainage production is compared to that of three other alkaline materials—volcanic ash, limestone, and fly ash—in this study. Their potential microbial mechanisms are also explored. The 63-day experimental results showed that all four alkaline materials effectively neutralized the acidity of the sulfur-bearing tailings and dramatically decreased heavy metal leaching (Fe, Mn, Zn, Pb, As, and Cd). Plant ash had a higher removal efficiency of Fe (99.9%), Mn (94.0%), and Zn (99.7%) than the other three materials, which was related to its ability to provide better precipitation and adsorption conditions. XRD observed gypsum in each treatment column, the formation of a new phase of calcium carbonate was observed in the plant ash column, and SEM showed that precipitation wrapped around the surface of tailings inhibited their oxidation process. 16 S rRNA sequencing confirmed that plant ash could inhibit AMD production through microbial action. The plant ash column had higher biodiversity than the control column, and the eutrophic flora in the plant ash column could use organic matter to consume dissolved oxygen, inhibiting tailing oxidation; however, the growth of some reducing flora resulted in As reduction, causing a slight increase in As in the leachate.

Dolomite and organic compost application for preventing acid mine drainage formation in a mesocosm system

Acid mine drainage (AMD) is one of most serious environmental problems facing mining industries. It results from oxidation of sulfide minerals contained in mining wastes, such as rock disposals in mine sites. This study was to investigate AMD formation from waste rocks containing potentially-acid forming (PAF) materials treated with dolomite and compost in a mesocosm system. The system comprised a plastic drum of 150-cm height and 50-cm diameter filled with 15-cm sand at the botom layer, over-laid by 50-cm mixture of PAF+10% of either dolomite or compost, and 35-cm top-soil layer on the top. The drum surface of the sand layer was equipped with a valve to drain leached water into a collecting container. The control was a similar constructed mesocosm without addition of either ameliorant. The drums were installed into the ground of the mined land so that their surfaces were as high as the surrounding soil surface and left under field condition. The leachate samples were taken two-weekly in the early two months and monthly until the day 487. The system demonstrated that both dolomite and compost significantly increased pH from around 3 to pH>6 and reduced dissolved Al and Fe concentrations. However, the dissolved Mn concentration was still high (>20 mg L−1) in all treatments even at the pH reached >6. .

Suppression of pyrite oxidation by co-depositing bio-inspired PropS-SH-tannic acid coatings for the source control acid mine drainage

In previous works, both tannic acid (TA) and organosilane-based passivators have been proven to possess good inhibition effects on pyrite oxidation, which could effectively prevent acid mine drainage (AMD) generation at the source. However, the hydrophilicity of TA passivation film and the complex coating process of organosilane-based passivators (high temperature conditions were required during the process carried out) may limit their further practical use. Therefore, to achieve the purpose of better coating treatment of pyrite under mild conditions, TA and γ-mercaptopropyltrimethoxysilane (PropS-SH) were introduced to synergistically passivate pyrite in this work. Electrochemistry tests and chemical leaching experiments both confirmed that PropS-SH-TA coated pyrite had better oxidation resistance than raw pyrite and single PropS-SH or TA coated pyrite. Additionally, the analyses of scanning electron microscopy (SEM) measurements and static water contact angle tests demonstrated that a scaly coating was formed on PropS-SH-TA coated pyrite surface, which may be the reason for the significant improvement of its surface hydrophobicity. Finally, the study on the film-forming mechanism of PropS-SH-TA composite passivator displayed that the benzoquinone derivatives formed by TA could copolymerize with PropS-SH through Michael addition or Schiff base reaction, which constructed a dense hydrophobic film on pyrite surface. The newly formed composite film could provide a better oxidation barrier for pyrite based on TA passivation film.

Acidification potential of geological materials in a coal mining area in southern Brazil

Acid mine drainage (AMD) is considered the major environmental hazard in coal mined areas. Characterizing the acidification potential of materials from representative geological drilling columns in coal pre-mined areas allows predicting the quality of a future constructed minesoil in post-mining areas. In this sense, acidification potential and neutralization potential quantifications enable selecting materials of the geological column that could be used to naturally neutralize acidifying materials and quantify alkaline materials for acidity correction. Therefore, this study aimed to estimate the probable composition of the constructed soil and its predisposition to cause acid mine drainage, and also estimating their potential to increase acidity in the soils and surface and subsurface waters of post-mining areas. The study was conducted in a coal mining area located in Southern Brazil. Geological material sampling included soil and rocks from six drill holes from the geological column representative of future coal mining areas. The mineralogical analysis was conducted using X-ray diffraction for the complete sample in powder form. The basic materials characterization was carried with chemical analyses: pH of water; pH of CaCl2; exchangeable cations; potential acidity. Results indicate the acidification general tendency in future constructed soils, and that control measures to prevent acid mine drainage generation must be adopted. In this regard, the use of BL and Coal (S2) seams is recommended, since they present an extremely high acidification potential. Furthermore, the controlled placement of sandstone layer with high potential acidity, and its treatment with carbonate materials addition is also recommended. Data regarding soil layers with high sum and base saturation, and the presence of smectite, typical of a Mollisol in F530 drill, reveal to environmental recovery teams the necessity of adapting to another soil condition. This condition must be chemically more fertile, but also physically harder to deal with than the Ultisol normally found in the current mining area.

Straw Biochar at Different Pyrolysis Temperatures Passivates Pyrite by Promoting Electron Transfer from Biochar to Pyrite

To control acid mine drainage (AMD) at source, biochar, a new green and environmentally friendly passivator has been introduced to passivate pyrite. However, the raw material and pyrolysis temperature largely determine the physical and chemical properties of biochar, the causal relationship between biochar and pyrite and the underlying mechanism are still unknown. Here, biochar materials (rice-straw biochar (RSB) and sugarcane bagasse biochar (SBB)) at different pyrolysis temperatures (300–600 °C) were utilized for the passivation of pyrite. The results of our investigations revealed that the passivation ability of RSB was superior to that of SBB. The addition of RSB with higher pyrolysis temperatures could greatly enhance the passivation efficiency of pyrite. RSB-500 (produced at a pyrolysis temperature of 500 °C) achieved the best passivation effect on pyrite. RSB can form Fe-O bonds through C=O bonding with pyrite. Moreover, the addition of RSB created a reducing environment in the mixture system because of its strong electron-donation capacity (EDC) and altered the energy-band structure of pyrite, which promoted the transfer of electrons from biochar to pyrite. On the contrary, the addition of SBB did not result in the formation of Fe-O bonds with pyrite. In addition, the EDC of SBB was also lower than that of RSB and it had almost no effect on the band structure of pyrite. Hence it did not alter the direction of the electron migration. These findings shed light on the mechanism of biochar passivation of pyrite and provide a theoretical foundation for selecting suitable biochar materials for AMD prevention at source.

Resource Utilization of Acid Mine Drainage (AMD): A Review

Acid mine drainage (AMD) is a typical type of pollution originating from complex oxidation interactions that occur under ambient conditions in abandoned and active mines. AMD has high acidity and contains a high concentration of heavy metals and metalloids, posing a serious threat to ecological systems and human health. Over the years, great progress has been made in the prevention and treatment of AMD. Remediation approaches like chemical neutralization precipitation, ion exchange, membrane separation processes, and bioremediation have been extensively reported. Nevertheless, some limitations, such as low efficacy, excessive consumption of chemical reagents, and secondary contamination restrict the application of these technologies. The aim of this review was to provide updated information on the sustainable treatments that have been engaged in the published literature on the resource utilization of AMD. The recovery and reuse of valuable resources (e.g., clean water, sulfuric acid, and metal ions) from AMD can offset the cost of AMD remediation. Iron oxide particles recovered from AMD can be applied as adsorbents for the removal of pollutants from wastewater and for the fabrication of effective catalysts for heterogeneous Fenton reactions. The application of AMD in beneficiation fields, such as activating pyrite and chalcopyrite flotation, regulating pulp pH, and leaching copper-bearing waste rock, provides easy access to the innovative utilization of AMD. A review such as this will help researchers understand the progress in research, and identify the strengths and weaknesses of each treatment technology, which can help shape the direction of future research in this area.

The potential of using alkaline gold mine tailing as a cover material to mitigate AMD formation from acidic gold mine tailing pile at Sabie-Pilgrim's Rest Goldfields, South Africa.

Acid mine drainage (AMD) caused by the oxidation of sulphide minerals found in mine waste is a global environmental concern, especially in water-restricted countries with heavy mining industries. Implementing AMD treatment and prevention programs can be extremely expensive, hence the need to identify environmentally sustainable treatment and preventative techniques to mitigate the potential of AMD formation. Soil covers and blends have been identified as an attractive approach. However, prior studies on the characteristics of the soils concerned and the acid-neutralisation rate should be carried out before considering the implementation of a soil cover or blending system to mitigate AMD formation. This study evaluated the acid generation capabilities of acidic gold mine tailings (AG), alkaline gold mine tailings (AN) and blends (MIX25, MIX50). Acid-base accounting (ABA), net acid generation (NAG) and acid-buffering characteristic curve (ABCC) test methods were used to evaluate the acid-generating and acid-neutralising capabilities of AG, AN, MIX25 and MIX50 samples. Leach column tests were conducted using alkaline gold mine tailings (AN) as the top pH neutralising cover (COV25) to determine the potential of the alkaline gold mine tailing to serve as a pH neutralising cover material to prevent and treat AMD generated by the acidic gold mine tailings. The ABA, NAG and ABCC results showed that AN has a high acid-neutralising capacity while AG has the potential to generate acid. The results further indicated that the AN to AG blend ratio of 1:3 by weight (MIX25) would neutralise the acid generated by AG. Leach column experiment (COV25) found that using AN as a pH neutralising cover would be a feasible option.

Tannic acid as an eco-friendly natural passivator for the inhibition of pyrite oxidation to prevent acid mine drainage at the source

In this study, an eco-friendly natural green polyphenol tannic acid (TA) was utilized as the passivator to inhibit pyrite oxidation. The strong coordination of phenolic hydroxyl groups in TA to Fe ions on pyrite makes TA have the characteristics of simple coating process on pyrite surface. Electrochemical measurements and chemical leaching tests were used to study the inhibition performance of TA on pyrite oxidation. The experimental results indicated that TA passivation coating could provide good antioxidant protection for pyrite and the inhibition ability of TA on pyrite oxidation raised with the increase of TA concentration. Additionally, the morphological changes of pyrite surface before and after TA passivation were further observed by Scanning electron microscopy (SEM). Finally, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied to probe the interaction mechanism of TA with pyrite in detail. The results of surface analyses verified that TA was capable of forming TA-Fe complexes with Fe ions on pyrite through chelation reaction, so as to be chemically deposited on the surface of pyrite that could effectively protect pyrite from oxidation. It is believed that this work can provide a new low-cost and simple way for acid mine drainage (AMD) control.

Managing and Reforesting Degraded Post-Mining Landscape in Indonesia: A Review

Tropical forests are among the most diverse ecosystems in the world, completed by huge biodiversity. An expansion in natural resource extraction through open-pit mining activities leads to increasing land and tropical forest degradation. Proper science-based practices are needed as an effort to reclaim their function. This paper summarizes the existing practice of coal mining, covering the regulatory aspects and their reclamation obligations, the practices of coal mining from various sites with different land characteristics, and the reclamation efforts of the post-mining landscapes in Indonesia. The regulations issued accommodate the difference between mining land inside the forest area and outside the forest area, especially in the aspect of the permit authority and in evaluating the success rate of reclamation. In coal-mining practices, this paper describes starting from land clearing activities and followed by storing soil layers and overburden materials. In this step, proper handling of potentially acid-forming materials is crucial to prevent acid mine drainage. At the reclamation stage, this paper sequentially presents research results and the field applications in rearranging the overburden and soil materials, controlling acid mine drainage and erosion, and managing the drainage system, settling ponds, and pit lakes. Many efforts to reclaim post-coal-mining lands and their success rate have been reported and highlighted. Several success stories describe that post-coal-mining lands can be returned to forests that provide ecosystem services and goods. A set of science-based best management practices for post-coal-mine reforestation is needed to develop to promote the success of forest reclamation and restoration in post-coal-mining lands through the planting of high-value hardwood trees, increasing trees’ survival rates and growth, and accelerating the establishment of forest habitat through the application of proper tree planting technique. The monitoring and evaluation aspect is also crucial, as corrective action may be taken considering the different success rates for different site characteristics.

Geochemical Assessment of Desulphurized Tailings as Cover Material in Cold Climates

It is essential to develop effective mine waste management approaches and mine site reclamation techniques to curtail the adverse effects of mining processes on the natural environment. This study focuses on the use of partially desulphurized tailings as a moisture-retaining layer in an insulation cover with capillary barrier effects (ICCBE). Tailings were obtained from a nickel ultramafic ore processing plant at a mining company located in a continuous permafrost region of northern Québec, Canada. The geochemical response of tailings at two different sulphur contents (0.4 and 0.8 wt%), with and without ICCBEs, was tested by applying eight freeze-thaw and wetting cycles. Desulphurization of the tailings allowed to reduce the content of sulphide minerals by about 90%, from ~22 wt% to around 1.2–2.2 wt%. Column kinetic geochemical tests showed that Ni leaching was significantly reduced to concentrations ranging between 0.01–0.22 mg L−1 compared to 0.63–1.92 mg L−1 from the raw tailings (thanks to the desulphurization process). Zinc release was maintained around 0.04–1.72 mg L−1 compared to 0.4–3.69 mg L−1 from the raw tailing. Although all the columns produced leachates displaying circumneutral to slightly alkaline pH, the columns with ICCBE are expected to prevent acid mine drainage generation longer than the other columns due to reduced sulphide content and a constantly high degree of saturation maintained by capillary barrier effects.

Geochemical behaviour of benign desulphurised waste rocks for mine drainage control and sustainable management

Large volumes of waste rock (WR) are generated in open-pit mines. WR is characterised by high anisotropy in its physical, chemical, mineralogical, and hydrogeological properties. WR is often deposited in unsaturated piles on the mine surface. Mineralogical investigations defined the diameter of physical locking of sulphides (DPLS) allowing the WR to be separated into two fractions: i) a reactive fine fraction (<2.4 mm), and ii) an inert coarse fraction (>2.4 mm). Environmental desulphurisation carried out on the reactive fine fraction decreased the risk of contamination caused by WR oxidation. The geochemical behaviour of three benign desulphurised lithologies (altered greywacke (AGR), carbonated greywacke (CGR) and carbonated porphyry (CPO)) and their corresponding fine fractions (<2.4 mm) were assessed using kinetic weathering cells (WCs). These tests confirmed the effectiveness of environmental desulphurisation to prevent acid mine drainage formation. In fact, geochemical analyses of the leachates from WCs showed that pH values ranged between 7.4 and 8.9. Moreover, instantaneous concentrations of iron and zinc were below 0.5 mg/L and 3 mg/L, respectively. Pyrite oxidation rates, which represent sample reactivity, were higher for head samples (3.01, 4.86, and 2.54 μmol/kg/day for AGR, CGR, and CPO lithologies, respectively) in comparison to the benign desulphurised materials (2.32, 2.4, and 2.25 μmol/kg/day for AGR, CGR, and CPO lithologies, respectively). Pyrite in the dismantled material was only partially liberated or almost encapsulated, making it mineralogically unavailable for oxidation. The benign desulphurised material with low initial sulphide content was potentially non-acid generating at the long-term scale. Upstream environmental desulphurisation has been confirmed as an effective strategy for WR management and valorisation.

Co-Disposal of Coal Gangue and Red Mud for Prevention of Acid Mine Drainage Generation from Self-Heating Gangue Dumps

The seepage and diffusion of acid mine drainage (AMD) generated from self-heating coal gangue tailings caused acid pollution to the surrounding soil and groundwater. Red mud derived from the alumina smelting process has a high alkali content. To explore the feasibility of co-disposal of coal gangue and red mud for prevention of AMD, coal gangue and red mud were sampled from Yangquan (Shanxi Province, China), and dynamic leaching tests were carried out through the automatic temperature-controlled leaching system under the conditions of different temperatures, mass ratios, and storage methods. Our findings indicated that the heating temperature had a significant effect on the release characteristics of acidic pollutants derived from coal gangue, and that the fastest rate of acid production corresponding to temperature was 150 °C. The co-disposal dynamic leaching tests indicated that red mud not only significantly alleviated the release of AMD but also that it had a long-term effect on the treatment of acid pollution. The mass ratio and stacking method were selected to be 12:1 (coal gangue: red mud) and one layer was alternated (coal gangue covered with red mud), respectively, to ensure that the acid-base pollution indices of leachate reached the WHO drinking-water quality for long-term discharge. The results of this study provided a theoretical basis and data support for the industrial field application of solid waste co-treatment.

Long-term zinc contamination and transport at the abandoned Ore Chimney mine

Mine waste-rock piles can release low quality drainage that is harmful to the surrounding environment. Many studies have investigated recently placed waste rock, but fewer have examined geochemical processes within, and downgradient of, old waste rock, even though these processes may be expected to persist for many decades. The Ore Chimney property, in Ontario, Canada, was the site of gold exploration activities that produced a small waste-rock pile; it was abandoned in 1934. Elevated concentrations of Zn are restricted to within 50 m of the waste rock, and pH remains neutral across the site. Water and sediment analyses and geochemical modeling indicate that several processes are involved in pH buffering and contaminant control. Water samples taken at the edge of the waste rock were not acidic, indicating that mechanisms within the waste rock, including carbonate buffering and preferential oxidation of sphalerite over pyrite, are preventing acid mine drainage (AMD). Natural attenuation mechanisms are operating within wetlands at Ore Chimney with the most likely controls for Zn transport in ground and surface water being carbonate mineral precipitation, co-precipitation with Fe and Mn oxides and oxyhydroxide minerals and Al sulphate minerals, and adsorption onto calcite and organic matter. This investigation shows that, after long time frames, natural attenuation mechanisms may act to effectively immobilize metal contaminants.

Evaluation of Non-Acid-Forming material layering for the prevention of acid mine drainage of pyrite and jarosite

Encapsulation is a typical method used to prevent potential acid mine drainage (AMD) in overburden piles. In this method, Potentially Acid-Forming (PAF) material is covered with either Non-Acid-Forming (NAF) material or alkaline material to minimize water infiltration and/or oxygen diffusion through rock pores. The physical and chemical characteristics and thickness of the NAF material layer are critical factors affecting the successful prevention of AMD. Therefore, this study evaluated the method of NAF material layering using laboratory-scale column leaching tests. NAF layers with a ratio of 25 and 50% were used to cover PAF material containing pyrite and jarosite sourced from the Sangatta and Bengalon mining areas, East Kalimantan. The physical and chemical characteristics of leachate collected from samples watered on a weekly wet-dry cycle were analyzed by kinetic tests over a period of 23 weeks. The results showed a trend of increasing pH values and decreasing sulfate and metal concentrations in the leachate. This study shows that NAF layering is an effective method to prevent or minimize the generation of AMD.

Study of Blending Fly Ash with Potentially Acid Forming Material to Prevent Acid Mine Drainage

Acid Mine Drainage (AMD) is one of environmental concerns of mining activities and need to be prevented. One of AMD prevention method is passive method by blending PAF Material with Non-Acid Forming Material. One of constraint often faced by mining companies is the limitation of NAF material. Other Non-Acid Forming Material that is available and abundant near mine site is fly ash from Mine-Mouth Coal-Fired Power Plant Banjarsari. The Study of usage of fly ash as a blending material with PAF material in order to prevent AMD is deemed necessary. Different blending simulations of varying PAF material size (fine and coarse) and varying fly ash-PAF Material ratio (2:1; 1:1; and 0,5:1 by weight) are made and leachate water from kinetic test is physically and chemically tested. This study result shows that variation in OB-Claystone grain size is not influencing the acidity of leachate water. Blending FA with OB-CS with minimum ratio of 1,12:1 (by weight) is effective to prevent AMD generation. Acid-base equilibrium is met when ratio of mole-transfer between neutralizing mineral (periclase, lime and gypsum) to acid-generating mineral (pyrite) is 1:1 (by weight). The higher ratio of FA in blending, the lower oxidation and alkalinity-production rate. Rate of oxidation of pyrite and alkalinity-production rate is the same at OB-CS and FA blending ratio of 1:1,62 (by weight).