Production Of Acid Mine Drainage Research Articles

The Impact of Moderate Thermophiles on the Production of Acid Mine Drainage and the Dissolution of Ni and Zn from Iron-Bearing Sulfide Minerals

The Impact of Moderate Thermophiles on the Production of Acid Mine Drainage and the Dissolution of Ni and Zn from Iron-Bearing Sulfide Minerals

Geochemical and petrological studies of high sulfur coal and overburden from Makum coalfield (Northeast India) towards understanding and mitigation of acid mine drainage

Opencast coal mining produces trash of soil and rock containing various minerals, that are usually dumped nearby the abandoned sites which causes severe environmental concern including the production of acid mine drainage (AMD) through oxidation pyrite minerals. The current study entailed assessing the potential production of AMD from an opencast coal mining region in Northeast part of India. In order to have a comprehensive overview of the AMD problem in Makum coalfield, the physico-chemical, geochemical, and petrological characteristics of the coal and overburden (OB) samples collected from the Makum coalfield (Northeast India) were thoroughly investigated. The maceral compositions reveal that coal features all three groups of macerals (liptinite, vitrinite, and inertinite), with a high concentration of liptinite indicating the coal of perhydrous, thereby rendering it more reactive. Pyrite (FeS2) oxidation kinetics were studied by conducting the aqueous leaching experiments of coal and (OB) samples to interpret the chemical weathering under controlled laboratory conditions of various temperature and time periods, and to replicate the actual mine site leaching. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was operated to detect the disposal of some precarious elements from coal and OB samples to the leachates during our controlled leaching experiment. The Rare earth element (REE) enrichment in the samples shows the anthropogenic incorporation of the REE in the coal and OB. These experiments reveal the change in conductivity, acid producing tendency, total dissolved solid(TDS), total Iron(Fe) and dissolved Sulfate(SO42−) ions on progress of the leaching experiments. Moreover, the discharge of FeS2 via atmospheric oxidation in laboratory condition undergoes a significant growth with the rise of temperature of the reaction systems in the environment and follows pseudo first order kinetics. A bio-remediative strategies is also reported in this paper to mitigate AMD water by employing size-segregated powdered limestone and water hyacinth plant in an indigenously developed site-specific prototype station. Apart from neutralisation of AMD water, this eco-friendly AMD remediation strategy demonstrates a reduction in PHEs concentrations in the treated AMD water.

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.

Tungsten tailings issues and reprocessing solutions

This paper aims to provide an overview of tungsten (W) tailings properties, detrimental impacts of these tailings, approaches to mitigate these impacts, and a presentation of methods to reprocess them to capture their economic value. Since W is widely used in a variety of industries, it has been extensively mined since the 19th century, and the mining continues to generate significant volumes of tailings. Recent data show that global W production stands at 84 kt per year, and more than 100 Mt of W tailings exist containing over 100 kt of WO3. The tailings contain variable amounts of valuable products and deleterious environmental substances. Some of the contained metals are in great demand for the energy transition. However, these tailings usually contain FeS2/Pyrrhotite and FeAsS minerals, which, when exposed to air and water, can produce acid mine drainage. As such, W tailings may pose environmental and human health risks. Globally, the reprocessing of W tailings presents a potential resource that can be regarded as a paradigm of sustainability and circular economy. Flotation, enhanced gravity separation, and wet high-intensity magnetic separation have been reported to be the common approaches to reprocessing W tailings. However, W processing presents particular difficulties owing to complex material properties, such as fine particle size, surface weathering, similarity in surface properties exhibited by gangue materials (fluorite, apatite, calcite), low concentrations of the elements of interest, and poor mineral liberation.

Mechanical activation for sulfidic tailings treatment by tailings: Environmental aspects and cement consumption reduction

Sulfidic mine tailings are one of the massive hazardous solid wastes, containing large amounts of toxic heavy metals. Poor management of tailings can lead to the production of acid mine drainage and the heavy metal transfer emissions into the environment. Thus, in this study, mechanical activation was used to reuse a combination of carbonate tailings (TC) and sulfidic tailings (TS) for concrete construction purposes and to effectively immobilize heavy metals. The results showed that after tailings treatment, the heavy metal leaching rate was significantly below the allowed criteria based on the toxicity characteristic leaching procedure (TCLP). The mercury intrusion porosimetry (MIP) test results on the specific surface area and porosity after the activation pointed out increase and reduction, respectively. In the concrete sample containing 20 % cement-replacing activated tailings, the critical pore diameter after 28 curing days was 60 nm, which was less than that of the control sample with a critical pore diameter of 150 nm. According to X-ray diffraction (XRD) and scanning electron microscopy (SEM), ettringite and calcium silicate hydrate gel acted as hosts for heavy metals ions and played an inevitable role in stabilizing metal pollutants. Results revealed that the compressive strength of the sample containing 20 % of the activated tailings after 28 curing days was 31.2 MPa, which was higher than the strength of the control sample (26.99 MPa). Overall, it was concluded that the combined mechanically activated mine tailings can be a viable substitute for cement (up to 40 %) for constructing concrete samples. The utilized combined approach led to diminish adverse effect of sulfide content in concrete samples besides the cement consumption reduction.

The Adsorption Characteristics of Heavy Metals in Acid Mine Drainage from Abandoned Tin Mines on Lightweight Expanded Clay Aggregate (LECA)

Abandoned tin mines produce acid mine drainage in their water basin. If not treated well, it will damage environmental ecosystem by entering rivers or other water bodies. This acid mine drainage is attempted to be remediated by adsorption technique. The adsorbent used in this study is Lightweight Expanded Clay Aggregate (LECA) because its base material is natural clay. LECA is commonly used for hydroponics and constructions. LECA is made from natural clay that being heated at temperature over 1100°C. This study aims to determine how significant LECA in adsorbing metals in acid tin mine drainage. This research used two materials namely LECA and tin acid mine drainage. Both materials were contacted for two days in shaker bath. The results of this study were the adsorbing Fe(II) and Cu(II) on LECA could be approached by the Langmuir-Freundlich (LF) combined model where the Cµ,max are 0.406 and 0.020 mg/g of adsorbent, respectively. Unlike the other two metals, Sn(II) was more likely to experience precipitation instead of adsorption because of increasing of pH value. The conclusion, heavy metals in tin acid mine drainage could be remediated well by using LECA.

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.

Geochemical Characterization of Pit Wall Rocks: A Preliminary Step in Predicting the Water Quality of Pit Lake

The quality of pit lake water during development and final condition is affected by various factors, including geochemical characterization of materials of a pit wall, which may consist of in-situ and backfilling materials. This research aims to obtain a geochemical characterization of pit wall materials using 3 main laboratory tests and analysis, namely static test, mineralogical and elemental composition analysis, and kinetic test using free draining column leach test. Static test results show that 5 of 6 samples exhibit low paste pH and NAG pH. Pyrite is found in four samples and is responsible for acid mine drainage production. Some samples contain acid-consuming carbonates and oxides such as calcite and periclase. Four samples exhibit leachates’ pH values lower than 3,00, mostly during all cycles. Alongside the lithostratigraphic distribution of pit wall rocks, these results imply a potential occurrence of acid mine drainage that will become a critical issue for water quality development and final condition in pit lake formation. Therefore, these results become essential feedback for the stakeholders to plan and implement acid mine drainage management to minimize the adverse impact of acid mine drainage in pit lakes. Immediate understanding of the geochemical characteristics of leachates from pit wall rock, which control the overall mine water quality.

Recent Advances and Future Prospects on the Tailing Covering Technology for Oxidation Prevention of Sulfide Tailings.

Acid mine drainage, produced from sulfur-containing mine waste exposed to air, water, and bacteria, is considered as a serious environmental pollutant because of its extremely low pH and excessive heavy metals. In order to solve the ecological environment problems caused by the acid mine drainage, treatment methods such as neutralization, adsorption, passivation, bio-inhibition, and physical coverage have been developed. Nevertheless, these methods are terminal treatment methods, which are unable to prevent the generation of acid mine drainage at the source. Recently, it is noteworthy that the tailing covering technology is particularly emphasized, owing to its superior source control capability. By reducing the contact with air, water, and bacteria, the oxidation of sulfide tailings is significantly reduced, thus avoiding the production of acid mine drainage. To date, massive research has been studied and parts of technologies have been applied, but the review on the principles, processes, and applications of these technologies are still lacking. Thus, the present review aims to increase the knowledge related to the most relevant application of tailing covering technology with the following aspects: (i) the background, concepts, and performance of tailing covering technology; (ii) the applicable conditions for each tailings coverage system and their advantages and limitations; and (iii) the future perspective of this technology.

Mass Balance and Dissolved Metal Loads in the Mamut Copper Mine Temporary Settling Pond

Mining activities which involve certain sulphide bearing minerals generally produce acid mine drainage. The understanding of the characteristics of dissolved metals before they are discharged into streams is important for environmental management. This study focuses on a small water reservoir in the former Mamut Copper Mine, known locally as the Temporary Settling Pond (TSP). The main objective of this study is to estimate the mass balance and load of dissolved metals in the acid mine drainage (from the mine pit to the TSP). Water sampling and discharge measurements were done during baseflow and high flows using water level sensors and dataloggers. The analysis of dissolved elements in water samples was done using ICP-OES, while sulphate was analysed using a ‘HACH’ spectrometer kit. Through the mass balance method, Fe had the highest removal rate followed by Cu, Al, Zn and Mn. The highest dissolved metal load discharged from the TSP was Al followed by Mn, Cu, Zn and Fe.

Water quality implications of the neutralization of acid mine drainage with coal fly ash from India and the United States

Subsurface coal mining often induces the formation of acid mine drainage (AMD) in active and abandoned coal mines while coal combustion generates coal combustion residuals (CCR), including fly ash (FA), with elevated levels of toxic metals. Decades of AMD and CCR production have caused major environmental and human health impacts. Given the typically elevated level of oxides in FA, previous studies have examined its potential to neutralize AMD and remove the associated metals. While the neutralization of AMD through reaction with FA has been demonstrated to successfully remove cationic metals, the fate of oxyanion forming elements are less well studied and is the focus of this study. Here we conducted 49 different experiments in which simulated AMD solutions were interacted with representative U.S. (n = 7) and Indian (n = 6) FA samples through controlled liquid to solid ratios in short-term (24 h) and long-term (up to 5 weeks) lab-scale experiments. We show that Class-F FA, originating from Gondwana and Northeastern Tertiary coals in India, has limited neutralization capacity, while Class-C FA, with high CaO and MgO contents from Powder River coals in the U.S. has the greatest AMD neutralization capacity among the studied fly ashes. The neutralization experiments show that AMD-FA reactions cause the removal of cationic elements (i.e., Fe, Mn, and Al) from solution, while at the same time, leaching oxyanion forming elements (i.e., As, Se, Mo, Cr, B, Tl, and Sb) from the FA, increasing the potential environmental risks from the treated leachates. The magnitude of mobilization of these elements depends on their concentrations in the FA and the pH conditions. We show that using FA from the Appalachian and Illinois coals efficiently neutralizes AMD, but also results in secondary contamination of the treated effluents with oxyanion forming elements to levels exceeding drinking water and ecological standards, which could contaminate the ambient environment, whereas neuralization with Powder River Basin Class-C FA induces only limited contamination.

Utilization of lead–zinc mine tailings as cement substitutes in concrete construction: Effect of sulfide content

Production of acid mine drainage and emission of heavy metals from tailings, especially sulfide tailings, to the environment is one of the serious challenges in the management of mine tailings. The use of cementation process and replacement of cement with mine tailings in the manufacture of concrete is one of the practical approaches to the management of mine tailings. In this study, two different lead-zinc mine tailings (T1 with 0.4% and T2 with 19% sulfide content) were separately used as a cement substitution in concrete construction. Toxicity characteristic leaching procedure (TCLP), acid generation potential, compressive strength tests, and mercury intrusion porosimetry (MIP) were conducted on the constructed concrete samples. The TCLP test results revealed that with increasing the curing time of the samples, the leaching rate of toxic metals (arsenic, cadmium, chromium, cobalt, nickel, copper, zinc, and lead) in all samples was reduced to lower than the permissible criteria, indicating the good stabilization of heavy metals in concrete samples. The MIP test results also revealed that with increasing the curing days and subsequently the hydration process, the intruded mercury volume decreased, indicating that heavy metals were stabilized in concrete samples. The compressive strength test findings revealed that in constructed concrete containing 20% cement-replacing T1, with increasing the curing time of the sample from 28 to 90 days, the compressive strength increased from 16.9 to 19.8 MPa, and the leaching rate of heavy metals decreased from 39.64 to 23.65 μg/L,. In addition, in the sample with 20% T2, the compressive strength increased from 10.59 to 16.4 MPa, and the leaching rate of heavy metals decreased from 44.65 to 26.5 μg/L. Comparing the Scanning Electron Microscope (SEM) and Energy Dispersive X-ray analyzer (EDX) results, it was found that the Ca/Si ratio was lower in the samples prepared with mine tailings compared to the control, indicating insufficient amount of calcium available to form the main hydration product (C–S–H). Therefore, less C–S–H gel was formed in these samples. Also, according to the elemental distribution analysis, it was revealed that other heavy metals were scattered throughout the concrete matrix and stabilized in the concrete structure by forming new compounds. In general, it could be concluded that cement replacement with lead-zinc mine tailings up to 20% without the use of any improvement technique may be possible. Further, the formation of hydration products affected by high sulfide content and causes the production of sulfide salts that attack the concrete sample over time, thereby reducing cementitious properties and strength.

Microbial diversity response to geochemical gradient characteristics on AMD from abandoned Dashu pyrite mine in Southwest China.

The formation and release of acid mine drainage (AMD) have caused extremely serious pollution in the environment around many mining areas. The biological oxidation of metal sulfide minerals causes the production and release of AMD. To understand the interaction mechanism between microbial and AMD, the study uses Southwest Dashu pyrite as an example to investigate the geochemical gradient characteristics and microbial diversity response on AMD from abandoned mine. Through collecting and testing the water samples, the geochemical parameters such as physical and chemical indexes, main ion composition and microbial community composition of seven mine drainage points were obtained. The results showed that the geochemical and microbial community structure the decrease of AMD pollution in the study area with the decrease of altitude has obvious gradient characteristics. Although AMD has the distribution of acid-resistant iron and sulfur bacteria oxidizing bacteria, the microbial community diversity has obvious gradient characteristics. The categories with a relative abundance of > 5% include Proteobacteria, Actinobacteriota, Firmicutes, WPS-2, Chloroflexi, Bacteroidota, and Acidobacteriota. Actinobacteriota, which was common in the AMD, was distributed throughout the samples. The correlation analysis between water quality parameters and microbial community showed that the microbial community structure was affected by environmental factors. With the increase of acidity and metal ion content, the diversity of microbial community decreased, and the content of acid-resistant iron and sulfur oxidizing bacteria increased. The results showed that pH, dissolved oxygen (Do), the total iron (Fe) content (TFe), SO42-, and Al3+ were the five parameters that most affected microbiological diversity and interaction. Hydrogeochemistry and major ions analysis revealed that AMD in the study area mainly comes from the biological oxidation of metal sulfides and the dissolution and cation exchange of other minerals around the deposit. The degree of AMD pollution is related to the hydrogeochemical conditions in the mine. The higher the mine's water level, the lower the pollutants, and the less AMD is produced and released. The findings confirmed that geochemical gradients significantly changed the biota of the mine water and enriched the related microbial diversity adapted to different environmental factors. Therefore, the findings provide strong support for mine containment to inhibit oxidation and lay the foundation for prevention and control strategies of AMD pollution sources.

Evaluation of the Performances of a Monolayer Cover with an Elevated Water Table Used for the Reclamation of the Abandoned Aldermac Mine Site (Québec, Canada)

Until 2008, the Aldermac mine was considered one of the most problematic abandoned mines sites in Québec due to the high production of acid mine drainage caused by mine tailings spread over a large area. The site was reclaimed between 2008 and 2009 to reduce the ecological footprint and to minimize any further tailings oxidation (production of acid mine drainage). For this purpose, a monolayer cover with an elevated water table was used as an oxygen barrier on the north zone of the site. To assess the performance of the monolayer with an elevated water table cover, a network of observation wells was set up to monitor the water table level and collect groundwater samples for the analysis of physical and chemical parameters. Results of water table level measurements show that the cover successfully maintains the tailings within the water table at all times, thus preventing further tailings oxidation. Hydrogeochemical results, interpreted with principal component analysis, show that the quality of water is improving, thus indicating that reclamation is helping to reduce groundwater contamination at the site.

Geochemical Partitioning of Heavy Metals and Metalloids in the Ecosystems of Abandoned Mine Sites: A Case Study within the Moscow Brown Coal Basin

Significant environmental impacts of mining activities connected with high-sulfur materials result from the production of acid mine drainage and potentially toxic elements, which easily migrate to adjacent ecosystems due to the typical absence of vegetation on spoil heaps and toeslope talus mantle. In this paper, we present the results of the first comprehensive study of the ecosystems affected by acidic and metal-enriched (Al, Ca, Co, Cu, Fe, Mg, Mn, Ni, and Zn) mine drainage conducted at spoil heaps and adjacent talus mantle under semihumid climate conditions within the Moscow Brown Coal Basin (Central Russian Upland, Tula Region, Russia). A total of 162 samples were collected, including 98 soil samples, 42 surface water samples, and 22 plant samples (aerial tissues of birch). Coal talus mantle materials of Regosols were characterized by the increased concentration of water-soluble Ca, K, Mg, and S, and all mobile fractions of Al, Co, S, and Zn. The chemical composition of birch samples within the zones affected by acid mine drainage differed insignificantly from those in the unpolluted ecosystems with black soils, due to the high tolerance of birch to such conditions. Differences between the affected and undisturbed sites in terms of the chemical composition decreased in the following order: waters > soils > plants. The geochemical characterization of plants and soils in coal mining areas is essential for the mitigation of negative consequences of mining activities.

Study on the Role of Quartz in the Bio-Oxidation of Sulfide Minerals From Mine Solid Waste.

Sulfide-containing mine waste was oxidized to produce acid mine drainage, which lead to acidification of surrounding soil and downstream rivers and posed a threat to the surrounding environment. Quartz often coexists with sulfide minerals and affects the oxidation of sulfide minerals. In order to explore the role of quartz in the bio-oxidation of sulfide minerals in mine solid waste, the mixed minerals of quartz and sulfide minerals were bio-oxidized by Acidithiobacillus ferrooxidans. The results showed that quartz could improve the microbial activity and increase the acid production of sulfide minerals. The larger the proportion of quartz in bio-oxidation of sulfide minerals, the less the production of secondary minerals such as jarosite, and the larger the leaching amount of iron and sulfate. This research provides new ideas for speeding up the bio-oxidation of sulfide mineral to remove iron and sulfate. It provides a new way to solve acid pollution caused by oxidation of sulfide minerals.

Irrigation with Coal Mining Effluents: Sustainability and Water Quality Considerations (São Pedro da Cova, North Portugal)

Two water effluents that drain from the abandoned coal mine of São Pedro da Cova (NW Portugal) were characterized in terms of their physic-chemical properties and suitability for irrigation purposes. Samples were also collected in a local surface stream, upstream and downstream from the mine drainage points, also used for irrigation by local farmers. Water samples were analyzed for major and minor ions and for trace element concentrations. Sampling campaigns started in 2017 and ended in 2019 and there were 46 water quality parameters tested. There were also proposed all-inclusive indices (the Water Quality Index and the Contamination Index, and also the Trace Element Toxicity Index) based on specific groups of 18 and 17 physic-chemical parameters, respectively, to achieve adequate monitoring requirements for mine effluents and surface water from coalfield. From the physical and chemical aspects of mine water it is inferred that the mine is not producing acid mine drainage. The coal mine water is of medium to high salinity, having almost neutral pH and a high thermal stability during the year, which is a distinguishing feature of the effluents. When compared to international irrigation water quality standards, as Food and Agriculture Organization of the United Nations admissible concentrations, the impacted waters are unsuitable for irrigation. The major outliers to the guidelines were iron, manganese, potassium, magnesium and bicarbonates, being also detected carcinogenic polycyclic aromatic hydrocarbons. Cost-effective ways of monitoring water quality parameters are needed to help control and manage the impact of coal mine effluents that should be treated before releasing into a ditch system that could be then used by local farmers to irrigate their crops.

A Multidisciplinary Approach for the Assessment of Origin, Fate and Ecotoxicity of Metal(loid)s from Legacy Coal Mine Tailings.

Over the course of history, the development of human societies implied the exploitation of mineral resources which generated huge amounts of mining wastes leading to substantial environmental contamination by various metal(loid)s. This is especially the case of coal mine tailings which, subjected to weathering reactions, produce acid mine drainage (AMD), a recurring ecological issue related to current and past mining activities. In this study, we aimed to determine the origin, the fate and the ecotoxicity of metal(loid)s leached from a historical coal tailing heap to the Beuveroux river (Franche-Comté, France) using a combination of mineralogical, chemical and biological approaches. In the constitutive materials of the tailings, we identified galena, tetrahedrite and bournonite as metal-rich minerals and their weathering has led to massive contamination of the water and suspended particles of the river bordering the heap. The ecotoxicity of the AMD has been assessed using Chironomus riparius larvae encaged in the field during a one-month biomonitoring campaign. The larvae showed lethal and sub-lethal (growth and emergence inhibition and delay) impairments at the AMD tributary and near downstream stations. Metal bioaccumulation and subcellular fractionation in the larvae tissues revealed a strong bioavailability of, notably, As, Pb and Tl explaining the observed biological responses. Thus, more than 70 years after the end of mining operations, the coal tailings remain a chronic source of contamination and environmental risks in AMD effluent receiving waters.

Influence of type and amount of organic matters on the iron sorption of acid mine drainage onto reclaimed-mining soils

Mining activity may potentially produce acid mine drainage (AMD), which has relatively high acidity and dissolved heavy metal concentrations. Constructed wetlands is one of the AMD management methods in which organic matter (OM) plays a very important function in reducing the concentration of heavy metals in AMD through absorption and precipitation processes. Three types of OM (empty fruit bunches of oil palm, chicken manure and water hyacinth) and five levels of OM (0, 10, 20, 30 and 40 Mg ha-1) were applied to reclaimed-mining soils (RMS) in an incubation study. A batch experiment was then performed to measure the effect of OM application on the maximum sorption capacity (Qmax) of iron (Fe) from the AMD onto the mixed soil-OM. The application of OM resulted in increases in soil pH, carboxylic groups, and total functional groups, in which these increases varied based on the types and amounts of OM application. This study also revealed that OM application resulted in increasing Fe sorption. The application of OM increased Qmax values from 2077 to 2348-3259 mg kg-1 (water hyacinth), to 2607-3635 mg kg-1 (chicken manure), and to 2219-2992 mg kg-1 (empty fruit bunches of oil palm). Increasing these Qmax values may ascribe to increasing functional groups of the RMS with OM application. The results prove the importance of OM in controlling the sorption of Fe from AMD onto soils.

Pengelolaan Air Asam Tambang dari Batuan Sisa di Pit Barani dan Ramba Joring serta Aplikasi Model Enkapsulasi pada Bendungan Tailing di Tambang Emas Martabe

Acid mine drainage is one of the significant negative impacts of mining activities that can result in environmental degradation. Waste rock is mine waste that is found in large quantities and can produce acid mine drainage (AMD). This study aims to identify waste rock which has the potential to generate acidity (PAF) and do not generate acidity (NAF) in the Barani and Ramba Joring pits and the application of the encapsulation model in tailings dams. The research method with the encapsulation model is a simple method designed in tailings dams to encapsulate the PAF with the NAF. Rock characterization and geochemical analysis will result in the rock being classified as PAF and NAF in both wells . The data used for this study are drilling data (cutting) data that include rock lithology and chemical quality (NAPP and NAG) data. The results identified that the PAF was dominant relative to the NAF both wells and the waste rock in the Barani pit was at a higher risk of producing acidity than the Ramba Joring pit. Measurements of oxygen diffusion and surface water quality indicated that encapsulation of waste rock in the tailings dam may prevent the formation of acidic mine drainage