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The aim of this study was to analyze the radiological hazards and the potential for generating acid mine drainage from the fine coal waste commonly stored in tailings dams. The magnetic susceptibility, natural gamma radioactivity, and net neutralization potential of the tailings are characterized. The results show that the fine coal waste has a uranium equivalent concentration (eU) of 46–48 Bq kg−1, which is 37.14% higher than the world average, and 39–47 Bq kg−1 equivalent concentration of thorium (eTh), which is 56.66% higher than the world average. Also, the absorbed gamma radiation dose rate is higher than the world average. Acid–base balance tests indicate that the net neutralization potential ranged from 0.38 to 2.44. The physical properties indicate a possible radiological risk, while the chemical properties show that generating and non-generating acid drainage can coexist in the fine dam tailings. [ABSTRACT FROM AUTHOR]

Coal mine tailings can lead to a range of environmental problems, including toxic metal contamination, soil erosion, acid mine drainage, and increased salinity. Mine spoils from coal mining activities accumulated as gob piles are difficult to reclaim due to constraints such as a steep slope, unsuitable pH, insufficient nutrient supply, metal toxicity, low water-holding capacity, and poor soil structure. We investigated the efficiency of low-cost amendments on coal gob spoils from Carthage Coal Field (CCF) in New Mexico in improving the quality of coal gob spoils. Gob spoil was incubated for 90 days with various rates of organic amendments such as biochar, compost, and a biochar–compost mix. Gob spoil quality parameters such as the pH, water-holding capacity, and total and plant-available nitrogen and phosphorus content of the gob spoil were measured over a period of 90 days. Both biochar and compost amendment led to a significant increase (40–60% for biochar and 70% for compost, p < 0.05) in water-holding capacity of the coal gob spoil. Plant-available nitrogen content increased from <200 mg N/kg to between 400 and 800 mg N/kg in the amended gob spoil. The period of incubation was a significant factor in the improvement of plant-available nitrogen content. Plant-available phosphorus content also increased; compost amendment was more effective than biochar in increasing plant-available P. This study provides crucial information about the optimum organic amendments that would help in optimizing a sustainable reclamation method for CCF. [ABSTRACT FROM AUTHOR]

The objective of this research was to evaluate the sustainability of a co-treatment system that combines Municipal Wastewater (MW) and Acid Mine Drainage (AMD) through the technique of intermittent electrocoagulation, applied as an advanced solution to improve contaminant removal efficiency and optimize energy balance. Four scenarios were analyzed: Treatment I (with a 1/7 ratio of urban wastewater to AMD), Treatment II (which includes an artificial wetland), Treatment IIIa (which introduces electrocoagulation to enhance sulfate removal and pH regulation), and Treatment IIIb (which employs a 1/15 ratio of AMD to eutrophic water). The methodology focused on calculating key sustainability indicators such as the Net Yield Ratio (EYR), Emergy Inversion Ratio (EIR), Environmental Loading Ratio (ELR), and Sustainability Index (SI), in order to assess the impact of each technology on the energy efficiency and environmental load of the system. The results showed that, although Treatment IIIa was effective in contaminant removal, the EIR increased to 0.18 and the ELR rose to 0.62, indicating a higher reliance on non-renewable inputs due to increased energy demand. However, Treatment IIIb, which combines electrocoagulation with eutrophic water, significantly improved the sustainability of the system, achieving an SI of 2.31 and an ELR of 1.22, reflecting a reduction in energy efficiency due to intensive use of external resources, but overall greater sustainability compared to the other scenarios. This research concludes that intermittent electrocoagulation, when integrated with synergistic resources like eutrophic water, can enhance contaminant removal efficiency and improve the use of renewable resources, minimizing environmental load and increasing the sustainability of wastewater treatment systems. [ABSTRACT FROM AUTHOR]

Iron and Manganese pollution were widespread in the water of northern Chinese mines, exacerbating regional water scarcity and potential ecological issues. This study aimed to remove dissolved iron and manganese from acid mine water using serpentine-loaded manganese oxide (Serp-MO) prepared by a simple coprecipitation-loaded metal method. Serp-MO was microscopically characterized, and the adsorption performance and adsorption mechanism of the Serp-MO composite adsorbent for Fe2+ and Mn2+ were analyzed. After loading, the specific surface area and pore volume of the particles significantly increased, and the surface pore structure improved, which was conducive to the simultaneous adsorption and removal of iron and manganese. The optimal reaction conditions for Serp-MO treatment of composite water samples with Fe2+ and Mn2+ mass concentrations of 20 mg/L and 5 mg/L respectively, were as follows: dosage of Serp-MO 550 mg/L, temperature 35 ℃, oscillation rate 180 r/min, and reaction time 140 min. Under these conditions, the removal rates of Fe2+ and Mn2+ were 99.8% and 99.6%, respectively. The presence of coexistence cations Zn2+ and Cu2+ can inhibit the removal of Fe2+ and Mn2+ by Serp-MO, while SO42- can promote the removal. The pseudo-second-order kinetic model and Langmuir isothermal adsorption model well described the adsorption process of Fe2+ and Mn2+ by the Serp-MO. The maximum adsorption capacities of Serp-MO for Fe2+ and Mn2+ were 14.31 mg/g and 24.04 mg/g, representing improvements of 470.12% and 626.28%, respectively, compared to Serp-MO. The adsorption thermodynamics showed that ΔG was <0 and ΔH and ΔS were greater than 0 at all test temperatures, which was an entropy-increasing reaction, and that increasing the temperature was favorable for the removal of Fe2+ and Mn2+. Based on the analysis of adsorption products, Serp-MO primarily facilitates the precipitation of iron in water, while the removal of manganese was mainly by adsorption. A regeneration study over five cycles indicated that Serp-MO possessed promising reusability potential. Furthermore, the safety leaching test indicated that the material caused minimal secondary pollution. [ABSTRACT FROM AUTHOR]

Heavy metal pollution is a global environmental issue, and microorganisms play a crucial role in the bioremediation of heavy metal-contaminated wastewater. The study isolated heavy metal-resistant bacterium and observed their absorption ability toward Pb2+, Cd2+ and Zn2+. We isolated Agrobacterium tumefaciens S12 from acid mine drainage. The various factors influencing its adsorption performance, including pH, biomass dosage, initial metal ion concentration, and adsorption temperature, were investigated in detail. Chemisorption controls the adsorption rate due to the results better fitted by pseudo-second order kinetics. The maximum adsorption capacities of Pb2+, Cd2+ and Zn2+ on A. tumefaciens S12 were 234, 58 and 51 mg g−1 at 30 °C from Langmuir isotherm, respectively. The adsorption processes for the three heavy metal ions were spontaneous and exothermic in nature. In bimetallic systems, biosorption of Pb2+ ions was preferential to that of Cd2+ and Zn2+. Furthermore, scanning electron microscopy coupled to energy dispersive spectroscopy, Fourier-transform infrared spectra and X-ray photoelectron spectroscopy analysis demonstrated that the adsorption mechanisms include ion-exchange, complexation interaction between the heavy metal ions and the functional groups on the surface of biomass. The obtained results indicated that A. tumefaciens S12 can be applied as an efficient biosorbent in bioremediation technology to sequestrate heavy metal ions from aqueous solution. [ABSTRACT FROM AUTHOR]

The insatiable demand for lithium in portable energy storage necessitates a sustainable and low-carbon approach to its recovery. Conventional hydrometallurgical and pyrometallurgical methods heavily involve hazardous chemicals and significant CO2 emissions. Herein, by integrating electrode oxidation with electrolyte oxidation, we establish a photovoltaic-driven “dual-oxidation” seawater electrolyzer system for low-carbon footprint and high lithium recovery. A 98.96% lithium leaching rate with 99.60% product purity was demonstrated for lithium recovery from spent LiFePO4 cathode materials. In-depth mechanism studies reveal that the electric field-driven electrode oxidation and in situ generated oxidative electrolyte synergetically contributes to lithium ions leaching via a structural framework elements oxidation and particle corrosion splitting synergy. This dual-oxidation mechanism facilitates rapid and efficient lithium extraction with broad universality, offering significant economic and environmental benefits. Our work showcases a promising strategy for integrating dual oxidation within a photovoltaic-driven seawater electrolyzer, paving the way for low-carbon lithium recovery from diverse solid wastes and minerals within a sustainable circular economy. [ABSTRACT FROM AUTHOR]

Discharge of acidic wastewater from mining activities (acid mine drainage (AMD)) is a major global environmental and public health issue. Although several approaches, including chemical precipitation and membrane technology, have been developed to treat AMD, adsorption has emerged as the most promising technology due to its cost-effectiveness and efficacy. Despite the wide adoption of adsorption in treating AMD, the evolution of research in this area remains poorly understood. To address this gap, a bibliometric analysis of the most recent literature involving the application of adsorption in AMD remediation was conducted by merging datasets of articles from Scopus (1127) and the Web of Science Core Collection (1422), over the past decade (2013–2022). This analysis revealed a yearly increase of 11% in research publications, primarily contributed by China, the United States, and South Africa. Keyword analysis revealed that natural schwertmannites and their transformations, activated carbon, zeolites, and clay minerals, are the most extensively employed adsorbents for the removal of common metals (arsenic, chromium, iron, manganese, among others). The findings underscore the need for future focuses on recovering rare earth elements, using nanoparticles and modified materials, pursuing low-cost, sustainable solutions, integrating hybrid technologies, pilot-scale studies, exploring circular economic applications of AMD sludges, and inter-continental collaborations. These insights hold significant future implications, serving as a valuable reference to stakeholders in the mining industry. [ABSTRACT FROM AUTHOR]

Acid mine water (AMD) can cause significant environmental hazards due to its high concentration of metal ions, so the development of effective treatment methods is essential to mitigate its impact. In this study, adsorption experiments were conducted using limestone (LS) and activated carbon (AC) to explore the adsorption efficiency for different concentrations of metal ions. Adsorption was evaluated by static and competitive batch tests. The adsorbent mechanism was investigated using analytical techniques such as SEM, FTIR and XRD. The efficacy of LS and AC for competitive adsorption of Fe, Mn, Zn and Cu ions from AMD was evaluated. The study analyzed the effect of environmental conditions such as initial concentration and ionic strength on the adsorption efficiency. The results showed that LS showed high adsorption capacity for Fe and Cu, but was less effective in competitive adsorption of Mn. AC showed superior adsorption performance for Fe and Cu under competitive conditions due to its high surface area and functional groups. Both adsorbents showed selective efficacy influenced by the physicochemical properties of metal ions. This study helps to guide the optimization of adsorbents in AMD treatment and highlights the importance of selecting suitable materials based on specific metal ion properties. [ABSTRACT FROM AUTHOR]

Chromite is formed in nature in ophiolitic layers and ultrabasic rocks through fractional crystallization. The corresponding mining technologies separate the ore from these ultrabasic rocks, which are considered to be tailings for the process but may be valorized in other applications. The need to utilize this material is due to the large quantities of its production and the special management required to avoid possible secondary pollution. In the present work, the ultrabasic rocks of chromite mining were applied to acid mine drainage (AMD) neutralization. The aim was to increase the technological maturity of the method and promote circular economy principles and sustainability in the mining sector. Ultrabasic rocks were obtained from a chromite mining facility as reference material. Furthermore, an artificial AMD solution was synthesized and applied, aiming to simulate field conditions. According to the results, the sample was successfully utilized in AMD neutralization (pH 7), achieving rapid rates in the first 30 min and maximum efficiency (liquid to solid ratio equal to 8.3) at 24 h. However, the method presented a drawback since Mg was leached, even though the concentration of other typical metals contained in an AMD solution decreased. [ABSTRACT FROM AUTHOR]

This study aims to analyze the cost of using lime and alum in the treatment of acid mine drainage at Settling pond 03, Pit Paku, PT. Rimau Energy Mining. Acid mine drainage, formed through chemical reactions between sulfide minerals and water, requires specialized treatment to mitigate its environmental impact. The use of lime and alum is intended to increase pH and reduce turbidity levels in the acid mine water. Through laboratory experiments with various doses of lime and alum, this research identified the most effective doses to neutralize acid mine drainage, raise pH levels, and reduce turbidity in accordance with established environmental standards. Additionally, the study analyzed the costs associated with each dose combination tested, revealing that the optimal lime and alum dose combinations resulted in more cost-effective treatment compared to previously employed methods. he effective dose to neutralize acid mine water is 1 gram of lime and 2 grams of alum per liter, which successfully increases the pH from 3.88-4.13 to 8.10-8.40, and reduces turbidity from 498-522 NTU to 144.9-196.1 NTU. [ABSTRACT FROM AUTHOR]

Mitigating acid mine drainage (AMD) at its source, specifically within rocks containing pyrite in underwater environments, poses a significant environmental challenge worldwide. Existing passivation techniques are primarily designed for open-air conditions, involving direct contact with coating materials at a solid–liquid interface, making them ineffective beneath a water barrier. In this study, we introduce a novel passivation method inspired by the design of underwater bio-adhesives. Tannic acid (TA) combined with polyethylene glycol (PEG) was employed to form a hydrophobic film directly on the pyrite surface, overcoming water resistance and addressing the limitations of current techniques. Electrochemical experiments and chemical leaching experiments were conducted to evaluate the oxidation resistance of the passivating films. TA–PEG-coated pyrite exhibited a lower oxidation rate and a higher static contact angle of 126.2°, achieving suppression efficiencies of 71.6% for total Fe release and 68.1% for total S release. A comprehensive characterization approach, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), was employed to investigate the passivation mechanism. The results of this study may provide new insights into the preparation of simpler and greener passivating agents to suppress pyrite oxidation at its source in underwater environments. [ABSTRACT FROM AUTHOR]

Mining in the Russian Far East has been developing for more than 100 years, resulting in the formation of mining technogenic systems that negatively affect all components of the environment. The purpose of this paper is to develop and present an ecological and geochemical model of supergene processes in tinsulfide and polymetallic ore mining systems. This paper presents, for the first time, the results of long-term field observations (more than 50 years): studies of numerous secondary minerals (more than 80) identified in mine workings and tailings, their natural associations, as well as the sequence, zonality, and stages of mineral formation as well as the characteristics of hydrochemical samples of river waters, contaminated by acid mine drainage (30 years of observations). Experimental modeling of sulfide oxidation was carried out under laboratory conditions (electrochemical method) and using Selektor software, which made it possible to study the process of acid mine drainage formation and to show the metal ions and ionic complexes composition, to establish Eh-pH parameters of crystallization for 52 secondary minerals, associations of primary and secondary minerals. The influence of water components on the formation of slurry and drainage in different time periods (dry, heavy rainfall, and snowmelt) is shown, and their mixing at the geochemical barrier "acid mine drainage—surface natural waters" is described. Experimental results are verified with numerous in-situ observations and mineralogical studies. The work allowed for the presentation of an environmental–geochemical model of ecosphere pollution, which describes not only the negative impact of sulfide-bearing systems of Russian Far East mining districts but locations all over the world. [ABSTRACT FROM AUTHOR]

Acidophilic sulphate‐reducing bacteria (aSRB) are widespread anaerobic microorganisms that perform dissimilatory sulphate reduction and have key adaptations to tolerate acidic environments (pH <5.0), such as proton impermeability and Donnan potential. This diverse prokaryotic group is of interest from physiological, ecological, and applicational viewpoints. In this review, we summarize the interactions between aSRB and other microbial guilds, such as syntrophy, and their roles in the biogeochemical cycling of sulphur, iron, carbon, and other elements. We discuss the biotechnological applications of aSRB in treating acid mine drainage (AMD, pH <3), focusing on their ability to produce biogenic sulphide and precipitate metals, particularly in the context of utilizing microbial consortia instead of pure isolates. Metal sulphide nanoparticles recovered after AMD treatment have multiple potential technological uses, including in electronics and biomedicine, contributing to a cost‐effective circular economy. The products of aSRB metabolisms, such as biominerals and isotopes, could also serve as biosignatures to understand ancient and extant microbial life in the universe. Overall, aSRB are active components of the sulphur and carbon cycles under acidic conditions, with potential natural and technological implications for the world around us. [ABSTRACT FROM AUTHOR]

During pyrite mining, tailings and waste residues are generated, and the oxidation of exposed metal sulfides leads to significant environmental issues such as acid mine drainage pollution. Studying the oxidation mechanism of pyrite is crucial for inhibiting or preventing the formation of acid mine drainage. Alkaline amino acids were used as electrolytes to explore the electrochemical oxidation mechanism of pyrite. Through electrochemical methods such as OCP, CV, Tafel polarization curve, LSV, and EIS, the electrochemical behavior of pyrite surfaces was measured, confirming the feasibility of pyrite oxidation in an alkaline amino acid system. The oxidation mechanisms of pyrite were consistent across the 3 alkaline amino acids, with the oxidation rate of pyrite following the order: lysine>arginine>histidine. [ABSTRACT FROM AUTHOR]

The Lorraine mine site in Témiscamingue region (Québec, Canada) was reclaimed with a cover with capillary barrier effects (CCBE) to limit acid mine drainage generation. The main objective of this study is to predict the long-term hydrogeological behaviour of the CCBE at Lorraine site, including the influence of vegetation and climate change (CC). Numerical simulations showed that performance of the CCBE is: (1) not affected by forest vegetation and CC in the saturated zone in the north of the Lorraine site and (2) more sensitive to vegetation in the unsaturated zone in the south where the phreatic level is low. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is an environmental concern, and its discharge into the surrounding environment can lead to acidification of water bodies and soil. In this research, red mud (RM) with alkaline pH as aluminum industry waste was implemented as an adsorbent for sulfate removal, which can be available in AMD and adsorption processes as an influential method was applied for AMD treating. Seawater washing (BRM), acid treatment (HRM), and composition with chitosan (CRM) were employed as RM modification methods. Various analytical methods were applied, including x-ray fluorescence spectroscopy (XRF), Fourier-transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET), inductively coupled plasma analysis, and zeta potential, to have a clear comprehension of the sulfate adsorption behaviors and performance of activated methods. These methods have had desirable effects on the sulfate adsorption and adsorption amount, which range from 1.1 mg g−1 for RM reached to 13.4, 39.7, and 67.4 mg g−1 for BRM, HRM, and CRM, respectively. XRF results demonstrated a decrease in calcium and sodium ion amounts that can occur due to their dissolution in the acidic solution. It can create the active surface areas for adsorption onto RM with acid washing. Based on FTIR results, sharp intensity vibration was observed in BRM, HRM, and CRM after sulfate adsorption in the 1,100 cm−1 band that is approximately related to SO42− vibration. BRM porosity decreased from 0.0686 to 0.0345 cm3 g−1 due to various salts' precipitation in seawater, but the porosity volume and specific surface area increased for HRM from 0.0686 to 0.184 cm3 g−1 due to dissolution of ions in HCl. In addition, zeta potential increased to positive amounts from 2.7 to 3.4, 3.8, and 4.5 mv for BRM, HRM, and CRM, respectively. Langmuir isotherm indicated that the highest adsorption amount (qm) as a calculated parameter for BRM, HRM, and CRM was 0.88, 2.45, and 18.6 mg g−1 , respectively. Among modification methods, combination RM and chitosan had the highest impact and increases sulfate removal and adsorption amount at lower pH levels due to further positive charge on the CRM surface. [ABSTRACT FROM AUTHOR]

PT. Singlurus Pratama operates four mining blocks: Sungai Merdeka, Argosari, Margomulyo, and Mutiara. The Sungai Merdeka block has three voids with significant potential as a source of clean water for Nusantara Capital City (IKN), given its location within the city's development area. Surface water flows from the southern ridge to the north, accumulating in the voids of the Sungai Merdeka block, with a total inflow of 449,218,750 m2 per day. This volume can meet the needs of 1,796,875 to 4,492,187 people. One of the geological formations of the Sungai Merdeka block is the Balikpapan Formation, composed of alternating sandstone and clay with intercalations of shale and limestone, which is likely an aquifer. The water quality in voids 1 and 2 falls into the fairly good category (WQI = 70.07 and 70.77), while void 3 has moderate quality (WQI = 64.76). Thus, the water from the Sungai Merdeka voids can be used for personal and household hygiene, as well as raw water for drinking. Additionally, it can be utilized for recreational water facilities, freshwater aquaculture, livestock, and irrigation. However, the void water in the Sungai Merdeka block is indicated to have formed acid mine drainage, as the exposed void walls are contaminated with oxygen and leached by water. This leads to increased acidity, as indicated by the low pH values of the water. The increased acidity also results in higher concentrations of dissolved metals within the voids, necessitating careful management and treatment to ensure the water's safety and usability for various applications. [ABSTRACT FROM AUTHOR]

The mining production industry often leaves large quantities of mine spoil heaps exposed on the surface. The lack of monitoring of these discharges could create sources of pollution; the most common among them is acid mine drainage, which causes the contamination of the environment by heavy metals present in its solutions. Bouaazza’s mine, present in Taza province North-East Morocco, was known for lead and sulfide exploitation for many years, which contributed to the exposure of important quantities of acid spoil heaps on the surface. To assess the impact caused by acid mine drainage in Makhat’s stream plants, sediments, and plant samples were collected along the stream. Physicochemical results for sediments showed pH values below 6. Geochemical results for sediments indicated Pb concentrations higher than the World Surface Rock Average standards (16 ppm), with values over 3000 ppm. As for plants, the values found after ICP-AES analyses were higher than the WHO permissible limit (2 ppm). These results confirm the harmful impact of the lack of environmental monitoring while and after abandoning mining explorations, which leads to environmental disasters. [ABSTRACT FROM AUTHOR]

BACKGROUND: This work studied the treatment of a synthetic sphalerite acid mine drainage (AMD). The treatment was carried out by means of a previous concentration stage using electrodialysis, followed by electrodeposition using a bioelectrochemical system (BES). RESULTS: The best concentration results were obtained when operating the electrodialysis at 8 V and at a diluate/concentrate volume ratio of 3. This treatment yielded a concentrate fraction of about 25% of the volume and a clear fraction of about 75% of the volume. The concentrated fraction was treated in a BES for the electrodeposition of the metal contained. By operating a microbial fuel cell (MFC), the spontaneous reactions took place and, in 2 days, all the Fe3+ was reduced to Fe2+; then, all the Cu2+ was electrodeposited as pure Cu0 in about 8 days. The maximum current density attained in this stage was 0.1 mA cm−2 and the maximum power was 0.05 W cm−2. Then, a subsequent operation of a microbial electrolysis cell (MEC) allowed for the simultaneous recovery of the Fe2+, Ni2+, Zn2+, and Cd2+ as a mixed metal mass. CONCLUSION: The electrodialysis yielded a clear effluent representing 75% of the total volume and a concentrated effluent accounting for 25%. It was possible to treat the concentrated effluent in an MFC, recovering pure Cu0 with a net electricity generation. The non‐spontaneous metal reductions were subsequently accomplished by means of MEC, the electricity requirements being lower than those in the case of the raw AMD due to the higher mass transfer rate and the reduction of the Ohmic loses. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) pollutes natural waters, but some impacted systems show natural attenuation. We sought to identify the biogeochemical mechanisms responsible for the natural attenuation of AMD. We hypothesized that biogenic sulfide-mediated iron reduction is one mechanism and tested this in an experimental model system. We found sulfate reduction occurred under acidic conditions and identified a suite of sulfate-reducing bacteria (SRB) belonging to the groups Desulfotomaculum, Desulfobacter, Desulfovibrio, and Desulfobulbus. Iron reduction was not detected in microcosms when iron-reducing bacteria or SRB were selectively inhibited. SRB also did not reduce iron enzymatically. Rather, the biogenic sulfide produced by SRB was found to be responsible for the reduction of iron at low pH. Addition of organic substrates and nutrients stimulated iron reduction and increased the pH. X-ray diffraction and an electron microprobe analysis revealed that the polycrystalline, black precipitate from SRB bioactive samples exhibited a greater diversity of iron chalcogenide minerals with reduced iron oxidation states, and minerals incorporating multiple metals compared to abiotic controls. The implication of this study is that iron reduction mediated by biogenic sulfide may be more significant than previously thought in acidic environments. This study not only describes an additional mechanism by which SRB attenuate AMD, which has practical implications for AMD-impacted sites, but also provides a link between the biogeochemical cycling of iron and sulfur. [ABSTRACT FROM AUTHOR]

Bioremediation of acid mine drainage (AMD) was often challenged by poor tolerance of sulfate-reducing bacteria (SRB) to heavy metals and low bioactivity. The highly active immobilized particles with Fe0/Fe2+ enhanced SRB (Fe0/2+-SRB) were prepared by the microorganism immobilization technique. Three dynamic columns were constructed to investigate the adsorption capacity of Fe0/2+-SRB for Mn2+ under varying adsorption layer heights, inflow velocity, and initial Mn2+ concentrations. The role of each matrix material in the immobilized particles was explored, the mechanism of AMD remediation by Fe0/2+-SRB was revealed, and the adaptability of Fe0/2+-SRB to AMD under various initial conditions was investigated. The results showed that the prepared Fe0/2+-SRB exhibited a well-developed surface pore structure. When the adsorption layer height was 200 mm, the influent flow rate was 5 × 10−5 m3/s, and the initial manganese ion concentration was 10 mg/L, the maximum dynamic adsorption capacities (qe) of Mn2+ for each dynamic column were 7.8430, 4.7627, and 8.7677 mg/g, respectively. Compared to dynamic columns 1# and 2#, dynamic column 3# showed the best performance in treating AMD, and the Thomas model effectively described the adsorption kinetics of Mn2+ by Fe0/2+-SRB(3#). Microstructural analysis indicated that chemical adsorption, ion exchange, dissimilation–reduction reaction, and surface complexation occurred between the various matrix materials in Fe0/2+-SRB(3#). Mn2+ was primarily removed in the form of metal sulfide (MnS), and Fe0/Fe2+ could promote the dissimilatory reduction of SO42− by SRB to form S2−. Fe0/2+-SRB(3#) was able to adapt to AMD with initial conditions of pH was 2~4, SO42− < 2500 mg/L, and Mn2+ < 20 mg/L. The research results provide new insights into the remediation of AMD, using a combined microbial-adsorption technology. [ABSTRACT FROM AUTHOR]

Cadmium is a toxic heavy metal found in acid mine drainage. It hinders plant and animal growth and accumulates in human organs. In this study, through shake flask experiments, an iron-rich, sulphate-rich environment was simulated, and Acidithiobacillus ferrooxidans was used to mediate the formation of secondary high-iron minerals to explore the effect of calcium ions on the removal of Cd2+ from that environment. Four treatment systems were used: "Blank", "Ca2+-30 mg/L", "Fe/K = 3,Ca2+-30 mg/L", and "Fe/K = 3". The results showed that Cd2+ with an initial concentration of 20 mg/L was effectively removed in each treatment system. The removal efficiencies of Cd2+ in each treatment were 23.46%, 18.42%, 52.88%, and 45.76% respectively. The quantity and type of minerals determined the removal efficiency of Cd2+. The Fe/K = 3 treatment system can significantly increase the amount of mineral formation and improve the removal efficiency of Cd2+. In the Ca2+-30 mg/L, Fe/K = 3 treatment system, the biological oxidation ability was the strongest, and the removal effect of Cd2+ was the best under the combined action of K+ and Ca2+. Co-precipitation was the main way to remove Cd2+ during the formation of biogenic secondary iron minerals, and the removal amount was 5.64 to 14.83 times that of adsorption. Biogenetic secondary iron minerals showed high values in repairing heavy metal pollution. This study provides a theoretical basis for treating heavy metals in acid mine drainage. [ABSTRACT FROM AUTHOR]

Stockpiles containing sulfide minerals are subject to oxidation reactions when exposed to atmospheric conditions, which can result in the formation of acid mine drainage (AMD). Reactive waste rock has limited re-use potential due to the contamination risk associated with the generated drainage water. The re-use of reactive waste rock could lead to a significant reduction in the volume of waste rock as it mitigates the environmental impact of mine waste deposition. Acid mine drainage generation rate depends on sulfide weathering kinetics which are controlled by many parameters such as the mineralogy and the particle size. Fine fractions of waste rock have higher specific surface areas and degree of liberation of sulfides, resulting in greater reactivity than the coarse fractions. The objective of this research was therefore to evaluate the potential of re-use by controlling particle size using the sieving method. Two different potentially acid-generating waste rocks were divided into six fractions and subjected to both static and kinetic tests. Prediction of the geochemical behavior using static test did not consider the liberation of the minerals, and the long-term prediction was therefore overestimated. Results of the kinetic columns showed there was less oxidation of the sulfide minerals in the coarse fractions than in the fine fractions. Additionally, the distribution of sulfidic minerals and neutralizing minerals with particle size is influencing the potential of the re-use of the reactive waste rock. [ABSTRACT FROM AUTHOR]

Brazilian mining ventures aged 30 years or older were studied, revealing historical oversights in environmental planning that have caused substantial environmental liabilities during active mining and decommissioning. Electrical resistivity tomography surveys were conducted in a decommissioning uranium mine in southeast Brazil. The results provided valuable insights into local hydrogeological dynamics, revealing the flow of acid mine drainage in two distinct systems: the porous waste rock pile and the fractured underlying crystalline basement. Geo-electrical sections displayed conductive anomalies indicating hydraulic connectivity between the waste rock pile and the underlying fractured aquifer through crystalline basement fractures. This connection was substantiated by sub-vertical zones of low electrical resistivity interpreted as groundwater influx from the porous system to the fractured aquifer. Consequently, the waste rock pile acted as a localized recharge zone for the regional aquifer, facilitating chemical exchanges between the two systems. Furthermore, the study successfully differentiated less impacted saturated zones (resistivity ≈80 Ω·m) from those associated with acid mine drainage (< 40 Ω·m). Preliminary investigations identified a complex fracture network in the study area, comprising two main fault systems with preferential NE and NW orientations, nearly orthogonal to each other. This fracture network demonstrated continuity, playing a fundamental role in sustaining flow within the local and regional drainage network. [ABSTRACT FROM AUTHOR]

This review critically examines the effects of AMD from the gold mines of South Africa and available options. We also critically analyse case studies, research gaps, and the challenges and opportunities presented by the AMD. Our assessment indicates the availability of potential technological advancements that might flip the paradigm in favour of less sludge being produced, lower operational costs, and more effective AMD treatment strategies. This has led to the development of long-term plans for AMD treatment technologies and the recovery of important minerals. There is currently a demand for integrated AMD technologies that take a holistic approach to long-term AMD treatment. Reusing water and recovering valuable resources like sulphuric acid, rare earth elements, and other metals have received a lot of attention. Continued study and implementation of such strategies will support sustainable gold mining, address the environmental damage caused by AMD, and optimize resource and revenue-generating potentials. [ABSTRACT FROM AUTHOR]

This study focused on treating acid mine drainage (AMD) from a Zn-sulfide mine with a composition that includes Al = 445 mg/L, Fe = 263 mg/L, Mn = 364 mg/L, Cd = 2.8 mg/L, and Zn = 4,830 mg/L. After treatment with regional alkaline minerals, the pH increased from 3.0 to 6.3 and metal concentrations decreased mainly by precipitation, falling below Mexico's permissible limits (MPL) for river discharges, except for Cd2+ and Zn2+, which exceeded their MPLs with concentrations of 0.4 and 1,110 mg/L, respectively. We tested the use of waste materials from a Mn mine containing Mn carbonates (R3) and Mn oxides (R6) for removal of these contaminants. Several Mn oxides have been reported as promising adsorbents and indeed the R6 waste was more efficient than the R3. At a ratio of 0.75 g/L of R6, with 30 h of contact or a ratio of 0.2 with 60 h of contact, Cd2+ and Zn2+ concentrations were decreased to below their MPLs. The evaluation of removal mechanisms was hindered by the complexity of the waste's composition. However, contact with the AMD increased the zeta potential from negative to positive values, indicating a cation sorption process. Mn wastes can be used without prior alkaline mineral treatment, but their technical and economic viability is less. The results suggest that this process is suitable for treating AMD at abandoned mines sites. Additionally, the Mn wastes can potentially be sold as a sorbent material for other processes, offering a recycling option. [ABSTRACT FROM AUTHOR]

The growing demand for valuable metals in recent decades has heightened the economic significance of extracting them from dilute solutions. This research carefully assesses the extraction efficiency of the air-assisted solvent extraction (AASX) process for effectively recovering copper from industrial dilute solutions, such as the raffinate of the solvent extraction (SX) plant and heap leach solutions. The results clearly showed that increasing the frother dosage to 50 mg/L improved the Cu extraction from 83.5% to 90.2%, but increasing the frother dosage beyond 50 mg/L did not change this response significantly. Although varying the extractant concentration and silicone oil dosage in the studied range did not affect Cu extraction, it noticeably led to an increase in the barrier metals recovery. Furthermore, a nine-step AASX system was applied to comprehensively evaluate the extraction efficiency of Cu from dilute heap leach solution. Moreover, an impressive 95.1% of Cu recovery (from a solution containing 890 mg/L Cu, 12.32 g/L Fe, 2.64 g/L Zn, and 4.1 g/L Mn) was achieved with selectivity ratios of 149.6, 153.0, and 93.5, for Cu/Fe, Cu/Zn, Cu/Mn, respectively. It could be concluded that the AASX process is an efficient and promising method for extracting Cu from industrial dilute solutions derived from secondary resources, low-grade ores, and acid mine drainages. [ABSTRACT FROM AUTHOR]

The growing mining industry has led to environmental pollution, primarily from mining waste known as acid mine drainage (AMD). To effectively address AMD, a combination of constructed wetland and biochar treatment is necessary. This study aims to assess the ability of biochar in combination with wetland sediment to reduce sulfate and cadmium (Cd) heavy metals in AMD. The research method involved a laboratory-scale constructed wetland in a microcosmos and a treatment of: T1, biochar mixed with wetland sediment; T2, sediment; T3, biochar; and T4, control with no treatment. Observations included sulfate content, pH determination, heavy metal concentration, and scanning electron microscope (SEM) analysis of the biochar. Results after 30 days of observation showed that T1 reduced sulfate concentration by 72.03%, compared to 63.33% for T2, 63.33% for T3, and 2.50% for T4. The reduction in sulfate was accompanied by a consecutive increase in pH, with T1 at pH 6.9, T2 at pH 6.6, T3 at pH 6.4, and T4 at pH 3.6 after 30 days. T1 treatment reduced heavy metal Cd by 80.16% after 30 days, while T2 of 55.46%. T3 of 65.83% and T4 of 2.31%. This indicates that the constructed wetland method, combined with biochar, is more effective in reducing sulfate and the heavy metal Cd in AMD, compared to using only biochar or wetland sediment treatment. [ABSTRACT FROM AUTHOR]

Environmental desulfurization was investigated as a potential tailings management method in the development of a new orebody. The operators expected variability in the geochemical and mineralogical properties of the minerals within the orebody, therefore a study based on geometallurgy principles was adapted for environmental risk prevention purposes. The objective was to evaluate the variability in the performance of environmental desulfurization by bulk sulphide flotation to produce non-acid generating tailings. The study was performed on 18 drill core samples collected from different zones of the orebody. Physical, chemical, environmental and mineralogical characterizations were done on these 18 ore samples, which were then fed to the desulfurization process. Desulfurization by froth flotation yielded a sulphide concentrate and desulfurized tailings. Similar characterization was performed on these products. The desulfurized tailings were then separated into three groups according to their acid generation potential computed from acid base accounting. Kinetic column tests were performed on six samples, two potentially acid generating, two non-acid generating, and two uncertain, and led to a better classification in acid generation potential, with only one sample confirmed acid generating. The study demonstrated that a detailed characterization of different zones of an orebody is important to identify variability in geochemical and mineralogical properties and their effect on the performance of environmental desulfurization for acid mine drainage prevention. [ABSTRACT FROM AUTHOR]

Elevated concentrations of contaminants have negative impacts on aquatic organisms and their parasites. Changes in parasite infections have been proposed as a technique for monitoring the health of aquatic ecosystems. Furthermore, alterations in physiological responses (biomarkers) of organisms have also been used to delineate ecosystem quality. Lake Heritage is situated along the Crocodile River in Muldersdrift, Gauteng, South Africa, and is subject to contamination by acid mine drainage. Clarias gariepinus is a well‐studied bioindicator species and host to numerous endoparasites and ectoparasites. The aims of this study were to delineate the health status of Lake Heritage through a multifaceted approach by comparing the water quality, biomarker responses, and parasite biodiversity of C. gariepinus, compared to unexposed laboratory‐reared fish. Physical and chemical water quality parameters were determined using a hand‐held probe, test kits, and element analysis with inductively coupled plasma‐mass spectrometry. Biomarker responses in the gill, liver, and muscle tissues from C. gariepinus were assessed for total protein, metallothioneins, superoxide dismutase (SOD), and reduced glutathione (GSH) concentrations and activities of acetylcholinesterase and catalase. Results for water quality variables showed higher pH, nitrate, hardness, and copper levels compared with the South African Target Water Quality Guidelines. Catalase activity and concentrations of SOD and reduced GSH showed a response in C. gariepinus to the water quality. Ectoparasites had lower prevalence and mean intensity than endoparasites. However, there were no differences in the physiological responses between infected and uninfected hosts. The study shows that the eutrophic conditions in Lake Heritage cause biomarker responses in the host when compared to host fish in laboratory conditions. Integr Environ Assess Manag 2024;20:1539–1553. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Key Points: The water quality in this river is impacted by acid mine drainage (AMD), sporadic treatment of AMD, point‐source pollution, and runoff.Inhibition of acetylcholine esterase activity in Clarias gariepinus implies that organophosphate and carbamates are also entering the system, and the lake is eutrophic.Ectoparasite infection intensity, number, and diversity are reduced, while endoparasite numbers and diversity are higher.Water quality has a greater impact on the physiological response of the host, compared to the effect caused by the endoparasites or ectoparasites. [ABSTRACT FROM AUTHOR]

Critical minerals (CMs) are pivotal in modern industries, such as telecommunications, defense, medicine, and aerospace, contributing significantly to regional and global economic growth. However, the reliance on external sources for 26 out of 50 identified CMs raises concerns about supply chain vulnerabilities. To address this, the research focused on developing a hydrometallurgical process for extracting cobalt, manganese, and nickel from acid mine drainage (AMD) treatment by-products, emphasizing the need to diversify CM supply chains within the United States (US). A solution composed of an REE solvent extraction raffinate loaded with cobalt, manganese, nickel, and various impurity metals was utilized as a feedstock in this study. The developed hydrometallurgical process involved initial sodium hydroxide precipitation to remove impurities like aluminum and iron from an SX raffinate solution generated during the extraction of rare earth elements (REEs). Precipitation stages were performed in a pH region ranging from 2 to 12 to identify the optimum pH values, achieving a tradeoff between recovery and impurity removal. A subsequent precipitation process at pH 5–10 yielded a product rich in CMs, such as manganese, cobalt, and nickel. Further separation steps involved nitric acid washing, resulting in a Mn product with a purity of 47.9% by weight and a solution with extractable concentrations of cobalt and nickel. Stagewise precipitation with sodium sulfide subsequently produced three solid products: cobalt and nickel product at pH 1–5, manganese product at pH 5–10, and magnesium at pH 10–12. The study also explored other separation approaches, including solvent extraction, to enhance the separation of nickel from cobalt. Overall, the developed hydrometallurgical process generated the following products with varying degrees of purities: cobalt (9.92 wt.%), nickel (14 wt.%), manganese (47.9 wt.%), and magnesium (27.49 wt.%). This research aimed to contribute to the sustainable extraction of CMs from secondary sources, reducing the US' reliance on imports and promoting a more resilient supply chain for these crucial elements. [ABSTRACT FROM AUTHOR]

This study investigated the Zaalklapspruit valley bottom wetland in South Africa, an ecologically engineered site influenced by acid mine drainage (AMD) from a defunct coal mine upstream. Conducted in 2022, the research aimed to elucidate the dynamics of contaminant dispersal within this wetland, focusing on the sources, pathways, and receptors of metals and sulfur compounds. The analysis revealed that the wetland's bottom sediment is rich in organic material, with pH values ranging from 6.05 to 6.59 and low oxidation-reduction potentials reaching −219.67 mV at Site S3. The significant findings included the highest adsorption rates of manganese, contrasted with iron, which was primarily absorbed by the roots of Typha capensis and the algae Klebsormidium acidophilum. The macrophyte rhizospheres were found to host diverse microbiota, including families such as Helicobacteraceae and Hydrogenophilaceae, pivotal in metal and sulfur processing. This study highlighted the complex biogeochemical interactions involving sediment, macrophyte root systems, periphyton, and microbial populations. These interactions demonstrate the efficacy of ecologically engineered wetlands in mitigating the impacts of acid mine drainage, underscoring their potential for environmental remediation. Importantly, the sustainability of such interventions highlights the need for community involvement and acceptance, acknowledging that local support is essential for the long-term success of ecological engineering solutions that address environmental challenges like AMD. [ABSTRACT FROM AUTHOR]

Abstract Acid mine drainage (AMD), characterized by its acidity and high content of heavy metals, is a significant global environmental problem that harms human health through its impact on rivers. Therefore, this study aims to identify heavy metals in both surface and underground AMD-polluted karst rivers, focusing on the Zhijin River area which is severely affected by AMD, and assess their health risks to residents. Through the collection of 30 surface water samples and 16 groundwater samples from both wet and dry seasons, the study examines the concentration, sources of pollution, and health implications of six heavy metals (Fe, Mn, Cr, Cd, As, and Hg). The results showed that Fe and Mn levels in surface water were highly polluted during both seasons, especially during the wet season, with Fe levels reaching 20.0 mg/L and Mn levels reaching 1.9 mg/L. Further correlation and principal component analyses revealed that mining activities are the primary contributors to the contamination in this region. Health risk assessments and Monte Carlo simulation, including both deterministic and probabilistic, showed that the noncarcinogenic health risk indices for surface water and groundwater were within acceptable limits for both seasons. However, groundwater poses a higher carcinogenic risk to children, with As levels during the wet season and Cr levels during the dry season warranting close monitoring. Factors such as body weight and intake rate played a crucial role in health risk evaluations. This study underscores the need for further attention to groundwater risk, temporal heterogeneity in the Zhijin River.

Abstract Heavy metal pollution is a global environmental issue, and microorganisms play a crucial role in the bioremediation of heavy metal-contaminated wastewater. The study isolated heavy metal-resistant bacterium and observed their absorption ability toward Pb2+, Cd2+ and Zn2+. We isolated Agrobacterium tumefaciens S12 from acid mine drainage. The various factors influencing its adsorption performance, including pH, biomass dosage, initial metal ion concentration, and adsorption temperature, were investigated in detail. Chemisorption controls the adsorption rate due to the results better fitted by pseudo-second order kinetics. The maximum adsorption capacities of Pb2+, Cd2+ and Zn2+ on A. tumefaciens S12 were 234, 58 and 51 mg g−1 at 30 °C from Langmuir isotherm, respectively. The adsorption processes for the three heavy metal ions were spontaneous and exothermic in nature. In bimetallic systems, biosorption of Pb2+ ions was preferential to that of Cd2+ and Zn2+. Furthermore, scanning electron microscopy coupled to energy dispersive spectroscopy, Fourier-transform infrared spectra and X-ray photoelectron spectroscopy analysis demonstrated that the adsorption mechanisms include ion-exchange, complexation interaction between the heavy metal ions and the functional groups on the surface of biomass. The obtained results indicated that A. tumefaciens S12 can be applied as an efficient biosorbent in bioremediation technology to sequestrate heavy metal ions from aqueous solution.

Abstract Acid mine water (AMD) can cause significant environmental hazards due to its high concentration of metal ions, so the development of effective treatment methods is essential to mitigate its impact. In this study, adsorption experiments were conducted using limestone (LS) and activated carbon (AC) to explore the adsorption efficiency for different concentrations of metal ions. Adsorption was evaluated by static and competitive batch tests. The adsorbent mechanism was investigated using analytical techniques such as SEM, FTIR and XRD. The efficacy of LS and AC for competitive adsorption of Fe, Mn, Zn and Cu ions from AMD was evaluated. The study analyzed the effect of environmental conditions such as initial concentration and ionic strength on the adsorption efficiency. The results showed that LS showed high adsorption capacity for Fe and Cu, but was less effective in competitive adsorption of Mn. AC showed superior adsorption performance for Fe and Cu under competitive conditions due to its high surface area and functional groups. Both adsorbents showed selective efficacy influenced by the physicochemical properties of metal ions. This study helps to guide the optimization of adsorbents in AMD treatment and highlights the importance of selecting suitable materials based on specific metal ion properties.

PT. Singlurus Pratama operates four mining blocks: Sungai Merdeka, Argosari, Margomulyo, and Mutiara. he Sungai Merdeka block has three voids with significant potential as a source of clean water for Nusantara Capital City (IKN), given its location within the city's development area. Surface water flows from the southern ridge to the north, accumulating in the voids of the Sungai Merdeka block, with a total inflow of 449,218,750 m³ per day. This volume can meet the needs of 1,796,875 to 4,492,187 people. One of the geological formations of the Sungai Merdeka block is the Balikpapan Formation, composed of alternating sandstone and clay with intercalations of shale and limestone, which is likely an aquifer. The water quality in voids 1 and 2 falls into the fairly good category (WQI = 70.07 and 70.77), while void 3 has moderate quality (WQI = 64.76). Thus, the water from the Sungai Merdeka voids can be used for personal and household hygiene, as well as raw water for drinking. Additionally, it can be utilized for recreational water facilities, freshwater aquaculture, livestock, and irrigation. However, the void water in the Sungai Merdeka block is indicated to have formed acid mine drainage, as the exposed void walls are contaminated with oxygen and leached by water. This leads to increased acidity, as indicated by the low pH values of the water. The increased acidity also results in higher concentrations of dissolved metals within the voids, necessitating careful management and treatment to ensure the water’s safety and usability for various applications.

Acid mine drainage severely affects metallic materials due to the high acidity and oxidising capacity of these lixiviates. A study was carried out to evaluate the time evolution of the mechanical properties of AISI 1020 carbon steel and AW6060 aluminium in contact with acid mine drainage. Weight loss, fatigue and tensile strength were evaluated in two different scenarios, one involving erosion corrosion (dynamic scenario) and the other involving chemical corrosion only (static scenario). Over 80 days of exposure in a static scenario, weight loss is almost 2% for aluminium and 0.5% for steel, fatigue strength is reduced by 28% for steel and ultimate tensile strength is reduced by almost 5% for aluminium and by 2.5% for steel. In a dynamic scenario, the weight loss after 4 days of exposure is 30–35% for both materials, the fatigue strength is reduced by almost 50% for steel, the ultimate tensile strength is reduced by 33% for aluminium and by almost 5% for steel. Acid drainage causes an increase in brittleness and a decrease in stiffness of these materials, much more rapidly in a dynamic environment favoured by the effects of erosion corrosion.

• Sb(III) and Sb(V) fates coupled jarosite formation by A. ferrooxidans were studied. • Sb(III) inhibited the growth of A. ferrooxidans and the formation of jarosite. • Sb(III) formed Sb-O complex with ferrous minerals in a lower crystallization. • Sb(V) is adsorbed on the surface of the mineral as a hydrolyzed substance. • Differential effects of Sb(III) and Sb(V) on bacterial metabolism were revealed. Secondary iron-sulfate minerals such as jarosite, which are easily formed in acid mine drainage, play an important role in controlling metal mobility. In this work, the typical iron-oxidizing bacterium Acidithiobacillus ferrooxidans ATCC 23270 was selected to synthesize jarosite in the presence of antimony ions, during which the solution behavior, synthetic product composition, and bacterial metabolism were studied. The results show that in the presence of Sb(V), Fe2+ was rapidly oxidized to Fe3+ by A. ferrooxidans and Sb(V) had no obvious effect on the biooxidation of Fe2+ under the current experimental conditions. The presence of Sb(III) inhibited bacterial growth and Fe2+ oxidation. For the group with Sb(III), products with amorphous phases were formed 72 hr later, which were mainly ferrous sulfate and pentavalent antimony oxide, and the amorphous precursor was finally transformed into a more stable crystal phase. For the group with Sb(V), the morphology and structure of jarosite were changed in comparison with those without Sb. The biomineralization process was accompanied by the removal of 94% Sb(V) to form jarosite containing the Fe-Sb-O complex. Comparative transcriptome analysis shows differential effects of Sb(III) and Sb(V) on bacterial metabolism. The expression levels of functional genes related to cell components were much more downregulated for the group with Sb(III) but much more regulated for that with Sb(V). Notably, cytochrome c and nitrogen fixation-relevant genes for the A.f _Fe2+_Sb(III) group were enhanced significantly, indicating their role in Sb(III) resistance. This study is of great value for the development of antimony pollution control and remediation technology. Diagram of the mechanism of ferrous oxidation by A. ferrooxidans coupled with antimony conversion. The abbreviation of A. f in the figure represents A. ferrooxidans. [Display omitted] [ABSTRACT FROM AUTHOR]

Sulphate ions removal from Acid mine drainage (AMD) is crucial to mitigate its adverse impact on aquatic and terrestrial ecosystem. Similarly, surplus and unused quantity of the Fly ash, waste from coal-based power plants is also challenging problem. In the present study, Fly ash based low-cost adsorbents (NaOH at 100 oC and HCL at 400 oC) activated Fly ash were synthesized using thermal activation methods. The composition and surface morphology studies were conducted using FTIR, XRD, XRF and SEM-EDX analysis. The Synthesized adsorbents were used to removal of sulphatic ion under various experimental conditions such as initial concentration (5 to 50 mg L−1), contact time (0 to 180 minutes), dose (5 to 40 mg L−1), solution pH (4.5, 5 and 5.5 pH). The optimum removal was 63 ± 1.4 % and 65 ± 1.6 % at room temperature 27 °C, pH 5.5 and 0.6 g L−1 dose of FAZ-HCl and FAZ-NaOH adsorbents respectively. The kinetics models and adsorption isotherm were determined to be pseudo second order (R2 > 0.9919) for FAZ-HCl and pseudo first order which (R2 > 0.9857) was validated and fitted by Freundlich isotherm (R2 > 0.9806 and 0.9932) for FAZ-HCl and FAZ-NaOH. [ABSTRACT FROM AUTHOR]

An in-process technology approach is proposed to identify the source of acid mine drainage (AMD) generation and prevent its formation in a porphyry copper waste rock (WR). Adopting actions before stockpiling the WR enables the establishment of potential contaminants and predicts the more convenient method for AMD prevention. A WR sample was separated into size fractions, and the WR’s net acid-generating potential was quantified using chemical and mineralogical characterization. The diameter of physical locking of sulfides (DPLS) was determined, and the fractions below the DPLS were desulfurized using flotation. Finally, the WR fractions and tailing from the flotation test were submitted to acid-base accounting and weathering tests to evaluate their acid-generating potential. Results show that the WR’s main sulfide mineral is pyrite, and the DPLS was defined as 850 µm. A sulfide recovery of 91% was achieved using a combination of HydroFloat® and Denver cells for a size fraction lower than DPLS. No grinding was conducted. The results show that size fractions greater than DPLS and the desulfurized WR are unlikely to produce AMD. The outcomes show that in-processing technology can be a more proactive approach and an effective tool for avoiding AMD in a porphyry copper WR.

The mining production industry often leaves large quantities of mine spoil heaps exposed on the surface. The lack of monitoring of these discharges could create sources of pollution; the most common among them is acid mine drainage, which causes the contamination of the environment by heavy metals present in its solutions. Bouaazza’s mine, present in Taza province North-East Morocco, was known for lead and sulfide exploitation for many years, which contributed to the exposure of important quantities of acid spoil heaps on the surface. To assess the impact caused by acid mine drainage in Makhat’s stream plants, sediments, and plant samples were collected along the stream. Physicochemical results for sediments showed pH values below 6. Geochemical results for sediments indicated Pb concentrations higher than the World Surface Rock Average standards (16 ppm), with values over 3000 ppm. As for plants, the values found after ICP-AES analyses were higher than the WHO permissible limit (2 ppm). These results confirm the harmful impact of the lack of environmental monitoring while and after abandoning mining explorations, which leads to environmental disasters.

One of the biggest issues in the mining sector is due to acid mine drainage, especially in those abandoned mining operations and active ones that fail to adequately control the quality of their water discharge. The removal degree of copper, iron, lead, and zinc dissolved metals in acid mine drainage was investigated by applying different proportions of mixtures based on neutralizing reagent hydrated lime at 67 % calcium oxide (CaO), with adsorbent material – natural sodium bentonite, compared to the application of neutralizing reagent without mixing, commonly used in the neutralization of acid mining drainage. The obtained results show that the removal degree of dissolved metals in acid mine drainage when treated with a mixture of neutralizing reagent and adsorbent material in a certain proportion, reaches discharge quality, complying with the environmental standard (Maximum Permissible Limit), at a lower pH than when neutralizing material is applied without mixing, registering a net decrease in the consumption unit of neutralizing agent express on 1 kg/m3 of acid mine drainage. Furthermore, the sludge produced in the treatment with a mixture of the neutralizing reagent with adsorbent material has better characteristics than common sludge without bentonite, since it is more suitable for use as cover material, reducing the surface infiltration degree of water into the applied deposit.

The increasing mining activities have led to the problem of acid mine drainage (AMD) pollution. A method that combines biochar treatment as an adsorbent with wetland sediment treatment as a source of sulfate-reducing bacteria is used to address AMD effectively. This research aimed to determine the ability of biochar in combination with wetland sediment treatment to reduce sulfate and heavy metal content in acid mine drainage wastewater. This research was conducted on a laboratory scale in an AMD wastewater treatment reactor with the following treatments of biochar mixed with wetland sediment. Observations included sulfate content, pH, and heavy metal content. Scanning electron microscope (SEM) analysis was also performed on the biochar. SEM observations revealed the presence of small, dense, and irregularly shaped pores on the surface of the biochar. The results on day 30 showed that biochar mixed with wetland sediment was able to reduce sulfate concentration by 74.19% and reduced Pb by 73.79%, compared with treatment sediment only to 64.81% sulfate concentration and reduced Pb by 53.85%, treatment biochar only had reduced sulfate of 46.90% and reduced Pb by 58.67% and control 1.79% sulfate concentration and reduced Pb by 1.87%.

In this study, the safety of a red mud–loess mixture (RM–L) for the remediation of groundwater polluted by acid mine drainage (AMD) containing Cd(II) in mining areas was systematically analyzed and clarified. The effects of the initial concentration, flow rate, and packing height on the breakthrough performance and longevity of RM–L as a permeable reactive barrier (PRB) packing material were explored by column tests. The results show that the breakthrough time, saturation time, and adsorption capacity of Cd(II) in RM–L increased with decreasing initial concentration and flow rate, as well as increasing packing height. Moreover, RM–L had a long-term effective acid buffering capacity for acidic wastewater containing Cd(II). An increase in the packing height led to a longer longevity of the PRB than the theoretical value. In addition, the speciation of Cd on RM–L was dominated by carbonate form and iron–manganese oxide form. The surface of the RM–L particles evolved from a dense lamellar structure to small globular clusters after purifying the acidic wastewater containing Cd(II), due to the corrosion of H+ and the reoccupation and coverage by increasingly enriched adsorbates and precipitates of heavy metal ions. HIGHLIGHTS Focusing on the remediation of AMD-polluted groundwater in mining areas.; Theoretical guidance on the longevity and design of a PRB with RM–L.; Evaluation of the safety and stability of RM–L.;

The study aimed to evaluate the potential of boiler ash from palm oil mills to improve the quality of acid mine drainage (AMD). The experiment was conducted using boiler ash with five doses of 0, 3, 6, 9, 12, and 15 mg. Quicklime was used as a comparison material with doses of 0, 0.02, 0.03, 0.05, 0.1, and 0.3 mg. Boiler ash and quicklime were added to each 500 mL AMD. The parameters of the AMD quality measured were pH, dissolved iron (Fe) and manganese (Mn), and the precipitates of Fe and Mn. The results showed that the addition of boiler ash and quicklime into AMD increased the pH and decreased the concentration of dissolved Fe and Mn and increased the precipitate of Fe and Mn. The pH value of AMD increased with increasing doses of boiler ash and quicklime. An increase in the pH value was followed by a decrease in the dissolved Fe and Mn and anincrease in the Fe and Mn precipitate. The highest pH values, Fe and Mn precipitates, and the lowest dissolved Fe and Mn were obtained by the treatment of 15 mg/L boiler ash and 0.3 mg/L quicklime. The boiler ash showed promising potential as an alternative neutralizing reagent to improve AMD even though the amount of boiler ash needed to repair AMD was more than quicklime.

The article explores the connection between melting permafrost and heavy metals in mountain lakes. It explains that as permafrost melts and glaciers retreat, heavy metals can become more concentrated in streams and lakes, especially in areas with sulfide-containing bedrock. This is due to acid mine drainage, which lowers the pH of the water and causes heavy metals to dissolve. The article also presents a series of experiments that can be used in classrooms to demonstrate the effects of acid mine drainage on water quality. These experiments allow students to observe the pH changes and increased copper content in water samples exposed to pyrite. The experiments provide a hands-on learning experience for high school chemistry and environmental science classes. [Extracted from the article]