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Acid mine drainage (AMD), the very acidic and highly contaminated leachate generated in closed/abandoned mines, is commonly managed by neutralization to raise the pH and precipitate most of the heavy metals. Although effective, this approach does not generate any product of economic value, so it is very costly and unsustainable in the long-term. Un...
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... Acid mine drainage in this site has a pH between 3 and 4, flows at a rate of around 0.04 m 3 /min, and contains substantial amounts of dissolved iron (Fe) (~70 mg/l), Cu (~1 mg/l), Zn (~9 mg/l), and Pb (~0.06 mg/l). It is mostly generated from the tailings dams and underground mine workings and has been treated by neutralization since the 1970s. Fig. 1 shows the plain and cross-sectional views of the tailings dam including the location of borehole core samples. The tailings dam is divided into three sections and is located between a stream and a ...
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... used to simulate AMD formation and flow paths in the tailings dam including the migration of heavy metals. In addition, possible countermeasures like barriers with low permeability and recharge reduction were evaluated using the model. Fig. 2 shows the twodimensional model of the tailings dam formulated based on the cross-sectional line B-B' in Fig. 1 and the measured hydraulic conductivity (K) and Zn distribution coefficient (Kd) of each distinct lithological feature. In all simulations, MODFLOW 2005 and MT3DMS were used to model AMD/groundwater flow and solute migration, ...
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... Acid mine drainage in this site has a pH between 3 and 4, flows at a rate of around 0.04 m 3 /min, and contains substantial amounts of dissolved iron (Fe) (~70 mg/l), Cu (~1 mg/l), Zn (~9 mg/l), and Pb (~0.06 mg/l). It is mostly generated from the tailings dams and underground mine workings and has been treated by neutralization since the 1970s. Fig. 1 shows the plain and cross-sectional views of the tailings dam including the location of borehole core samples. The tailings dam is divided into three sections and is located between a stream and a ...
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... used to simulate AMD formation and flow paths in the tailings dam including the migration of heavy metals. In addition, possible countermeasures like barriers with low permeability and recharge reduction were evaluated using the model. Fig. 2 shows the two- dimensional model of the tailings dam formulated based on the cross-sectional line B-B' in Fig. 1 and the measured hydraulic conductivity (K) and Zn distribution coefficient (Kd) of each distinct lithological feature. In all simulations, MODFLOW 2005 and MT3DMS were used to model AMD/groundwater flow and solute migration, ...
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... AMD can also be generated from old, decommissioned metal and coal mines whose operations have ceased even hundreds of years ago (Johnston et al., 2009;Buzatu et al., 2016). AMD involves the oxidation of metal sulfides, such as pyrite, marcasite, and pyrotite (Khalil et al., 2013;Phillips, 2016;Tabelin et al., 2019). When these minerals are exposed to water and atmospheric oxygen, chemical reactions occur that result in the oxidation of sulfides (Blowes et al., 2003;Jodeiri et al., 2020). ...
Mine tailing deposits may result in environmental issues when abandoned and exposed to environmental conditions. This case study focuses on the “El Lavadero” tailing deposit, an abandoned mining environmental liability located in San Felipe de Jesús, Sonora, Mexico. To forecast its acid mine drainage (AMD) generation potential, the modified acid–base accounting (ABA) test was performed. The results in tailings fluctuated within the following ranges: Eh (257–583 mV), pH (1.7–6.4), E.C. (4425–51,065 µS cm⁻¹), Stotal (2.75–13.23%), SO4²⁻ (4.72–20.77%), and CaCO3 (< DL–12.71%); and PTE (mg kg⁻¹): Cd (12–407), Cr (16–29), Cu (149–685), Fe (95,760–186762), Mn (2432–23,759), Pb (11,258–27,146) and Zn (2212–69,417). These tailings had higher PTE levels than their surrounding agricultural soil, with the following behavior: Fe > Zn > Pb > Mn > Cu > Cd > Cr. PTE levels were significantly higher than those established by both international standards and Mexican environmental regulations. X-ray diffraction and scanning electron microscopic studies conducted in mine tailings and agricultural soil identified primary (i.e., pyrite) and secondary minerals (i.e., gypsum and jarosite). The mobility test showed low mobility rates for Cr and Pb; Cu, Fe, Mn, Zn, and Cd showed higher mobility rates. The modified ABA test indicated that “El Lavadero” deposit tailings were AMD potential generators; therefore, they were classified as hazardous (SEMARNAT, 2003 & 2009). Acidic leachates with high PTE levels can affect the water supply sources of San Felipe de Jesús and effluents discharged into the Sonora River, including the surrounding crops meant for human and animal consumption. Hence, rehabilitation of the "El Lavadero” tailing deposit is recommended to alleviate the environmental impact. Alternatives include the construction of a low-permeability barrier downstream.
... The software has been employed to simulate acid mine drainage in tailings dams, and the simulation results have revealed the migration pathway of heavy metals. The model further predicts that the volume of acidic mine drainage, and the concentration of Zn can be reduced through the installation of a low-permeability barrier downstream of the tailings dam or the utilization of ground-sealing techniques to minimize backfilling [101]. Furthermore, scholars [102] have employed both the MOD-FLOW and MT3DMS models as simulation models, utilizing genetic algorithms as the optimization algorithm, and encoding the optimization process of the genetic algorithm in MATLAB software, thereby achieving the potential of combining models with algorithms. ...
The unreasonable development and pollution of groundwater have caused damage to the groundwater system and environmental problems. To prevent this, the concept of “groundwater vulnerability” was proposed, and various evaluation methods were developed for groundwater protection. However, with changing climatic conditions and human activities, groundwater vulnerability is now emphasizing physical processes. This study aims to review and analyze the principles and applications of process-based groundwater vulnerability methods to achieve the source protection of groundwater resources. It introduces the assessment method and elaborates on pollutant migration processes and numerical simulation technology. Relevant articles from the past 30 years are reviewed to show the evolution of process-based groundwater vulnerability assessment. The study also discusses current research trends and proposes future development paths. It concludes that process-based groundwater vulnerability assessment will become the mainstream method, and modern technologies such as artificial intelligence will be necessary to solve challenges and achieve sustainable development.
... In their research on the migration of heavy metals, scholars have paid more attention to how heavy metal elements migrate in the soil and how they accumulate in rivers and other sediments. Tabelin et al. (2019) used a coal mine as the research object and analyzed the whole process of heavy metal elements from their release to entering the soil and finally leaching into the groundwater and also established a heavy metal migration model. Jiang and Liang (2007) studied the heavy metal migration model in the saturated-unsaturated state and simulated the process of groundwater pollution of coal gangue leachates by using numerical calculations and laid a foundation for the study of pollutant migration patterns. ...
In response to the basic policy of green and low-carbon circular development to solve resource, environmental and ecological problems, gypsum is considered to be a filling material for mine backfilling. To explore the potential risks of gypsum to the groundwater environment due to the backfilling of abandoned mines, a sequential batch leaching experiment was carried out in this paper, which used three types of industrial waste gypsum, namely, phosphorus gypsum (PG), titanium gypsum (TG) and flue gas desulfurization gypsum (FGDG). COMSOL Multiphysics 5.4 software was used to simulate and solve the migration process of the leached metal elements in the mine floor when these three gypsum types were used as filling materials to observe the concentration distributions and diffusion distances of the metal elements from these three gypsum types in the mine floor. The results show that (1) during repeated contact of the three types of industrial waste gypsum with the leaching medium, the pH levels changed, and the changes in pH affected the leaching patterns for the heavy metal elements in the gypsum. (2) Based on the concentrations of the metal elements that were leached from the three types of gypsum, it can be determined that these three types of gypsum are not classified as hazardous solid wastes, but they cannot be ruled out with regard to their risk to the groundwater environment when they are used as mine filling materials. (3) When the three types of gypsum are used as filling materials, the concentration distributions of the metal elements and their migration distances all exhibit significant changes over time. The concentration distributions, diffusion rates and migration distances of the metal elements from the different gypsum types are affected by their initial concentrations in the leachate. The maximum migration distances of Zn in the floor from the PG, FGDG and TG are 8.2, 8.1 and 7.5 m, respectively.
... Active treatment strategies are very effective but become costly and unsustainable in the long-term [26]. This is because AMD formation could persist for hundreds to thousands of years [27,28]. As an alternative, researchers have developed technologies that allow natural chemical and biological treatments for passively treating AMDs [29]. ...
Without treatment, the harmful effects of acid mine drainage (AMD) lead to the destruction of surrounding ecosystems, including serious health impacts to affected communities. Active methods, like chemical neutralization, are the most widely used approach to AMD management. However, these techniques require constant inputs of energy, chemicals, and manpower, which become unsustainable in the long-term. One promising and sustainable alternative for AMD management is to use passive treatment systems with locally available and waste-derived alkalinity-generating materials. In this study, the treatment of synthetic AMD with laterite mine waste (LMW), concrete waste, and limestone in a successive process train was elucidated, and the optimal process train configuration was determined. Six full factorial analyses were performed following a constant ratio of 0.75 mL AMD/g media with a 15-min retention time. The evolution of the pH, redox potential (Eh), total dissolved solids (TDS), heavy metals concentration, and sulfates concentrations were monitored as the basis for evaluating the treatment performance of each run. LMW had the highest metal and sulfates removal, while concrete waste caused the largest pH increase. A ranking system was utilized in which each parameter was normalized based on the Philippine effluent standards (DENR Administrative Order (DAO) 2016–08 and 2021–19). Run 4 (Limestone-LMW-Concrete waste) showed the best performance, that is, the pH increased from 1.35 to 8.08 and removed 39% Fe, 94% Ni, 72% Al, and 52% sulfate. With this, the process train is more effective to treat AMD, and the order of the media in treatment is significant.
... The geogenic sources of SO 4 −2 contain gypsum (CaSO 4 . 2H 2 O), and pyrite (FeS 2 minerals (Nyirenda et al., 2015;Tabelin et al., 2019). However, the anthropogenic sources of SO 4 −2 include metallurgical refineries, coal mining, phosphate refineries, and power plants. ...
This study aimed to determine the fluoride (F−) concentration, fate distribution, source provenance, geochemistry, and health risk exposure through oral ingestion of groundwater. Therefore, 60 groundwater samples were collected from five areas of sub-district Batkhela viz. Batkhela colony, Pirkhel, Selay Patty, Thana, and, Totai. The range concentrations of F− in the groundwater samples collected from the aforementioned areas were 0.50–2.30, 0.90–2.30, 0.50–2.40, 0.30–1.50, and 1.20–2.40 mg/L, and mean were 1.60, 1.50, 1.60, 0.90, and 1.70 mg/L, respectively. The results of fluoride showed that 28.5% of the groundwater samples exceeded the world health organization (WHO) guideline value of 1.5 mg/L. The chemical facies identified three types of groundwater such as CaHCO 3 (55%), NaHCO 3 (32%), and NaCl (13%). Moreover, alkaline pH high HCO3− and Na+ concentration, while depleted Ca++ and Mg++ concentration promote F− dissolution in the groundwater aquifer. The principal component analysis and Gibbs plot define that weathering and dissolution of granite rock minerals play a key role in the control of groundwater chemistry. Additionally, the ion exchange process also plays an important role in releasing F− in the groundwater aquifer. Whereas cluster analysis identified three clusters: C1 was less polluted, C2 was moderately polluted, and C3 was a severely polluted cluster and their percentage contribution was 20%, 58%, and 22%, respectively. Health risk assessment of F− for non-cancer risk in males, females, and children shows high health risk exceeded the recommended value of 0.6 for the community. Therefore, the groundwater sources of the study area are unfit for drinking, and domestic purposes.
... activities (Spitz and Trudinger 2019). The remaining heavy metals (HMs) are biologically toxic substances that are not biodegradable, and long-term exposure to HMs threaten the natural environment and human health (Tabelin et al. 2019;Bari et al. 2020). With the extensive development of iron ore resources, a great number of large-scale iron tailings ponds have been produced. ...
Silicate-iron oxyhydroxide complex formed by mineral weathering has an important influence on the geochemical reactions of heavy metals in mining areas. In this work, tailings were collected from an abandoned iron tailings pond, and the physicochemical properties and distribution of heavy metals were studied under natural weathering and hydraulic processes. The results showed that Fe²⁺ in the iron tailings were transported to the surface during the weathering process, and then the iron oxyhydroxide formed by mineralization adsorbed Cu²⁺ and Zn²⁺. Silicic acid and exchangeable acid were released during the formation of binary agglomerates between hydroxy iron oxide and kaolin, then they migrated to the lower area of a tailing pond via surface runoff. Finally, silicate-iron oxyhydroxide complex were formed. The heavy metals were replaced by H⁺ and penetrated to the bottom layer with water. This research provides an important scientific basis for the prevention and control of heavy metal pollution in mining areas.
... In Japan, for example, chemical neutralization of AMDs from legacy mines has been subsidized by the government to the tune of ~70 B JPY (~US$ 770 M) for the last 40 years (Tomiyama et al., 2019). Although effective, this process generates voluminous sludge that is also a source of secondary pollution and may have to be continued for hundreds to thousands of years (Davis Jr, et al., 2000;Tabelin et al., 2019a;Tabelin et al., 2019b). To address these sustainability issues, several authors proposed the harvesting of other valuable elements, minerals and energy from AMDs to reduce treatment costs (Table 10). ...
Porphyry ores and E-wastes/WEEE are two of the most important copper-bearing materials on the planet. Over 60% of world copper output comes from porphyry copper ores while E-waste(s) is globally the largest copper-bearing waste category since the 1980s. They also contain critical elements for low-carbon technologies essential in the clean energy transition's success. In this review, a critical analysis of ore distribution/processing, metal extraction, E-waste generation and E-waste recycling is presented, focusing on identifying challenges and how to address them with emerging technologies and sustainable socio-environmental strategies. Access to ore deposits is a major hurdle for mine development while the absence of a consistent E-waste classification and legislation, including poor collection rates, remains serious problems in E-waste recycling. As lower grade porphyry ores are exploited, difficulties in processing/extraction due to mineralogical complexities, very fine particles and the generation of “dirty” concentrates will become more prevalent. For E-wastes recycling, current trends are to develop smaller, more mobile, and eco-friendly hydrometallurgical alternatives to pyrometallurgy that can handle localised compositional and feed variabilities. Finally, more sustainable mine waste management strategies, including better LCIA tools with spatial and temporal dimensions, are needed to limit socio-environmental impacts of resources exploitation and maintain the sector's SLO.
... Also, in Japan MTs containing pyrite (FeS2) and substantial quantities of Cu and Zn were reported in a study by Tabelin et al. (2019). For O'Kiep, MSW severely contaminated nearby soils and acidified the soils, thus increasing the mobility of PTEs (Moncho et al., 2017), to areas in the vicinity of the houses (Figure 2-1). ...
South Africa is faced with challenges related to potable water quality, which has periodically deteriorated, coupled with inconsistent supply of tap water to households. On the other hand, South Africa is an important mining region, and nearly every province has remnants of active and closed metalliferous mining sites. Metalliferous mines produce a large quantity of metalliferous solid waste (MSW), which should be effectively managed to minimise the negative effects as it has the potential to produce acid rock drainage (ARD). The mobility of drainage alters the scarce water resources and aquatic species. These challenges are a primary concern to the community in the arid O’Kiep region, which is located in the Namaqualand district, South Africa, whereby the community has few alternatives to groundwater as a source of drinking water. The aim of this study was to assess species dispersion from a closed Namaqualand metalliferous mine into water sources in O’Kiep, Northern Cape province, South Africa. This study aimed to determine the issues related to the deterioration of the surface water quality from the source to the point-of-use (POU) and contributing to the inadequate drinking water supply and shortages in O’Kiep. Quantitative and qualitative assessments of water quality parameters were taken; and the adverse human health outcomes experienced by the residents were surveyed. Furthermore, disease patterns were estimated based on administered questionnaires. Approximately 88% of community members indicated that the water supplied is often turbid, while a high number of people with teeth discolouration (72%) are living in the area and experience diarrhoea-like symptoms, which are likely associated with the ingestion of toxin-contaminated water. This was confirmed by some physicochemical parameters quantified from the drinking water supply system (DWSS), such as sulfate, that were not within the range prescribed for drinking water quality guidelines (SANS241-1, 2015; WHO, 2011). The statistical models did not suggest physicochemical properties as predictors of any of the health symptoms. However, regular monitoring and evaluation of the DWSS are essential for this vulnerable community. From this, it was recommended that a feasible way for water security in O’Kiep might be groundwater resources, as an alternative source to irregular surface water. The hydrogeochemical parameters of groundwater assessed indicated that the continuous consumption of the groundwater without pre-treatment might result in possible human health risks as the groundwater quality index (GWQI) confirmed that the groundwater quality could be classified as being of moderate concern. Furthermore, the hydrogeochemical indices and cationic exchange values indicated that the aquifer is of inland origin, whereas the piper trilinear diagram revealed that the groundwater type in the area is categorised as saline, which was confirmed by sodium adsorption ratio (SAR). Similarly, the seasonal variation of the hydrogeochemical characteristic changes of an open-pit groundwater (OPGW) near a closed metalliferous mine (CMM) were investigated against standards for drinking and irrigation usage. Based on the results, it was evident that the OPGW quality varied seasonally. The PHREEQC model indicated that cation exchanges played a significant role in the groundwater hydrogeochemical characteristic. Furthermore, the seasonal fluctuation in the groundwater quality was attributed to the water-table-level fluctuations, resulting in some instances in a lack of compliance to the drinking water quality guidelines (SANS241-1, 2015; WHO, 2011). Overall, the groundwater was slightly acidic with permissible levels for irrigation purposes. Therefore, excessive usage of the OPGW may have undesirable effects on plant growth. The groundwater hydrogeochemical characteristics of OPGW contamination suggested acid rock drainage formation potential (ARDP). The contamination of the groundwater by potentially toxic elements (PTEs) from soils and MSW in the study area was a matter of concern requiring further investigation. Samples of the metalliferous soils and MSW were then evaluated for their ARDP using an integrated approach, combining geochemical characterisation, static tests and humidity cell tests (HCTs) assessing the balance between acidity potential (AP) and neutralisation potential (NP) of the slurry. Metalliferous soil leachates (MSL), stockpiled metalliferous waste leachates (SMWL) and metalliferous tailing leachates (MTL) were measured and quantified weekly for hydrogeochemical parameters. The static tests suggested that the metalliferous soils had a high acid-producing potential. This was confirmed by the results of the HCTs, which revealed signs of ARDP. Furthermore, the results also demonstrated weathering and production of ARD. The HCT results showed that the soils around the old mining town of O’Kiep are susceptible to ARDP and can release acid for elongated periods. Similarly, this study assessed ARDP from the stockpiled metalliferous waste (SMW) and metalliferous tailings (MTs) in O’Kiep. The static test results for the SMW were inconclusive, whereas the HCTs allowed the classification of the SMW as acid-producing material. In addition, the MTs were classified as acid-producing by the static tests and HCTs, with low mobility of PTEs when compared to SMW. Leaching of the SMW and MTs increases the risk of PTEs and acid contamination of surrounding soil and groundwater bodies in O’Kiep. Additionally, there are increasing concerns over significant potential environmental health effects of the SMW and MTs, including the mobility of PTEs.
... of years (Davis Jr. et al., 2000;Tabelin et al., 2019a), and (2) disposal of huge amounts of bulky and hazardous sludge produced by the treatment (Gazea et al., 1996;Kefeni et al., 2015;Park et al., 2020b;Taylor et al., 2005). ...
Acid mine drainage (AMD) formation is mainly caused by the oxidation of pyrite. Carrier-microencapsulation (CME) using metal-catecholate complexes has been proposed to passivate sulfide minerals by forming surface-protective coatings on their surfaces. Among the various metal-catecholate complexes, Ti-catecholate formed stable coatings having superior acid-resistance, but a thick enough passivating film required considerable time (ca. 14 days) to grow. Meanwhile, Fe-catecholates can form Fe-oxyhydroxide coatings within 2 days, however, they are less stable than Ti-based coating. To address these drawbacks of using a single metal-complex, this study investigated the concurrent use of Fe-catechol and Ti-catechol complexes for accelerating the formation of stable passivating coating on pyrite.
Compared with a single metal-complex system, the coating formation was significantly accelerated in mixed system. Linear sweep voltammetry showed the simultaneous decomposition of [Fe(cat)]⁺ and [Ti(cat)3]2– as the main reason for improved coating formation. Electrochemical properties of coatings formed by single and mixed complex systems, confirmed by electrochemical impedance spectroscopy and cyclic voltammetry, indicated the coating formed in the mixed system had higher resistance and more electrochemically inert than the other cases. The simultaneous use of Fe-catechol and Ti-catechol complexes enhanced pyrite passivation by accelerating metal-complex decomposition and forming more stable coating composed of Fe2TiO5.
... 2020) as well as the improved harvesting ferrites ). These methods have been proven to be effective; unfortunately, the generation of AMD is a lasting process (Orbecido et al. 2019). Therefore, these methods require continuous cost input and monitoring, making them expensive and unsustainable. ...
Pyrite, as one of the most abundant sulfide minerals, can be easily oxidized to generate acid mine drainage (AMD). In the present study, a new composite passivator named PropS-SH/sepiolite (PSPT) using γ-mercaptopropyltrimethoxysilane (PropS-SH) as the main passivator and natural sepiolite particles as filler was fabricated and used to suppress the oxidation of pyrite. Electrochemical tests and chemical leaching experiments were carried out to evaluate the passivation performance of PSPT coatings with different amount of sepiolite particles on pyrite oxidation. The results showed that the addition of appropriate sepiolite could significantly improve the inhibition ability of PropS-SH against pyrite oxidation. However, excessive addition of sepiolite particles weakened the inhibition ability of the PSPT coatings owing to aggregations of sepiolite. Additionally, the coating mechanism of PSPT on pyrite was also proposed based on the characterization of FTIR, XPS, and ²⁹SiNMR measurements, which indicated that sepiolite particles could be embedded in PropS-SH network through oxygen bridges, thus improving the stability of the composite coatings.
