Search Results (25)

Acid mine drainage (AMD) pollution from closed coal mines in karst regions represents a major environmental challenge in the global mining industry. The complexity of hydrogeological conditions in such regions leads to significant challenges in both predictability and controllability of pollution. Taking the Yudong River Basin in Guizhou Province, Southwest China, as the study area, and based on six years (2017–2023) of systematic remediation practices and monitoring data, this study systematically evaluates the effectiveness and applicable conditions of three types of treatment technologies: centralized treatment stations, source control combined with end-of-pipe treatment, and water-sealing ecological plugging. On this basis, governance models applicable to karst regions are distilled. The results show that after six years of remediation, the number of pollution points in the Yudong River Basin decreased from 27 to 12. At the outflow section, the total Fe reduction rate reached 88.3%, the total Mn reduction rate reached 62.3%, and the proportion of contaminated river length was reduced by 78.5%. Each of the three technologies has its own applicable conditions. Centralized treatment stations, characterized by mature technology but high operational costs, are suitable for emergency transition periods. Source control combined with end-of-pipe treatment addresses both symptoms and root causes, making it applicable to complex pollution points. Water-sealing ecological plugging, although cost-controllable, carries a risk of secondary pollution in karst-developed areas. The failure of water-sealing ecological plugging technology is mainly attributed to two mechanisms: bypass flow through karst conduits and overflow induced by water level rise. Based on the six-year remediation practice, this study proposes a source control model for karst conduits centered on the core concepts of “filling, isolating, plugging, intercepting, draining, and controlling”. The implementation process consists of four stages: detailed investigation, graded optimization, stepwise implementation, and long-term monitoring. The core innovation lies in the cross-disciplinary application of coal mine water control techniques to environmental remediation, achieving a shift from passive end-of-pipe treatment to active source control. This model can provide theoretical reference and practical guidance for karst mining areas in Southwest China and other regions with similar geological conditions. Full article

Acid mine drainages (AMDs) enriched with toxic metals pose a significant environmental risk. Microbial bioremediation offers a sustainable and cost-effective approach for metal removal from AMD. In this study, a wild yeast isolated from the Kavart abandoned mine, identified as Rhodotorula sp., was evaluated for its copper (Cu²⁺) and zinc (Zn²⁺) biosorption ability. Biosorption was strongly pH-dependent. Cu²⁺ and Zn²⁺ removal was most efficient (48.1% or 10.07 mg/g and 35.7% or 6.07 mg/g, respectively) at pH 6. Increasing the biomass to 3 g/L at the same pH enhanced Cu²⁺ removal to 71.5% (26 mg/g). Biosorption kinetic analysis showed an excellent fit to the pseudo-second-order model (R² > 0.99), indicating that the mechanism is chemisorption-dominated. Equilibrium data followed the Langmuir isotherm (R² = 0.93), consistent with monolayer adsorption on homogeneous binding sites. SEM-EDS analysis confirmed Cu²⁺ association with the yeast surface, supporting the ICP-OES results. The results demonstrate the isolate as a promising biosorbent, particularly for Cu²⁺, and highlight its potential application in the remediation of AMD-contaminated waters. Full article

Acid mine drainage (AMD), characterized by low pH and high sulfate concentrations, poses severe environmental risks. Sulfate-reducing bacteria (SRB) are promising for AMD bioremediation, but their activity is often inhibited in such extreme conditions. This study proposed two strategies—SRB pre-cultivation and SRB-enhanced sediment amendment—to address this limitation, and systematically examined the effects of sulfate concentration, pH, inoculum size, and carbon source on sulfate removal. Results showed that pre-cultivation significantly improved SRB’s acid tolerance, expanding the effective AMD treatment pH range from 6.8–8.8 to 4.8–8.8. At pH 7.8, pre-cultivated SRB achieved 50% removal of 11,760 mg/L sulfate within 24 h and complete removal within 150 h. The SRB-enhanced sediment system further enabled efficient and stable remediation of real AMD (sulfate removal > 97%, Fe/Mn co-removal > 90%). This work provides a practical solution to overcome SRB inhibition in harsh AMD environments and contributes to the development of low-cost, sustainable AMD bioremediation technologies. Full article

Biological reduction of sulphates has gradually replaced unit chemical processes for the treatment of acid mine drainage (AMD), which exerts a significant environmental impact due to its elevated acidity and high concentrations of heavy metals. Bioremediation is optimally suited for the treatment of AMD because it is cost-effective and efficient. Anaerobic bioremediation employing sulphate-reducing bacteria (SRB) presents a promising solution by facilitating the reduction of sulphate to sulphide. The formed can precipitate and immobilise heavy metals, assisting them in their removal from contaminated wastewater. This paper examines the current status of SRB-based bioremediation, with an emphasis on recent advances in microbial processes, reactor design, and AMD treatment efficiencies. Reviewed studies showed that SRB-based bioreactors can achieve up to 93.97% of sulphate reduction, with metal recovery rates of 95% for nickel, 98% for iron and copper, and 99% for zinc under optimised conditions. Furthermore, bioreactors that used glycerol and ethanol as a carbon source improved the efficiency of sulphate reduction, achieving a pH neutralisation from 2.8 to 7.5 within 14 days of hydraulic retention time. Despite the promising results achieved so far, several challenges remain. These include the need for optimal environmental conditions, the management of toxic hydrogen sulphide production, and the economic feasibility of large-scale applications. Future directions are proposed to address these challenges, focusing on the genetic engineering of SRB, integration with other treatment technologies, and the development of cost-effective and sustainable bioremediation strategies. Ultimately, this review provides valuable information to improve the efficiency and scalability of SRB-based remediation methods, contributing to more sustainable mining practices and environmental conservation. To ensure relevance and credibility, relevance and regency were used as criteria for the literature search. The literature sourced is directly related to the subject of the review, and the latest research, typically from the last 5 to 10 years, was prioritised. Full article

Mining discharge, namely acid mine drainage (AMD), is a significant environmental issue due to mining activities and site-specific factors. These pose challenges in choosing and executing suitable treatment procedures that are both sustainable and effective. Ceramic membranes, with their durability, long lifespan, and ease of maintenance, are increasingly used in industrial wastewater treatment due to their superior features. This review provides an overview of current remediation techniques for mining effluents, focusing on the use of ceramic membrane technology. It examines pressure-driven ceramic membrane systems like microfiltration, ultrafiltration, and nanofiltration, as well as the potential of vacuum membrane distillation for mine drainage treatment. Research on ceramic membranes in the mining sector is limited due to challenges such as complex effluent composition, low membrane packing density, and poor ion separation efficiency. To assess their effectiveness, this review also considers studies conducted on simulated water. Future research should focus on enhancing capital costs, developing more effective membrane configurations, modifying membrane outer layers, evaluating the long-term stability of the membrane performance, and exploring water recycling during mineral processing. Full article

The presence of toxic and hazardous chemical species in municipal wastewater poses a significant environmental and public health challenge, necessitating innovative, sustainable, and cost-effective treatment solutions. This study pioneers the recovery and valorisation of polycationic metals from real acid mine drainage (AMD) for municipal wastewater treatment, demonstrating a novel approach that integrates resource recovery with wastewater remediation. A key strength of this study is the use of real municipal wastewater (authentic MWW) in the treatment phase, ensuring that the findings accurately reflect real-world conditions. Advanced analytical techniques were employed to characterise both aqueous and solid samples, and batch experiments were conducted to assess the removal efficiency of polycationic metals for key contaminants: ammonium (NH₄⁺), sulphate (SO₄²⁻), phosphate (PO₄³⁻), and nitrate (NO₃⁻). The optimised conditions are 2 g of polycationic metals per 100 mL, 90 min of contact time, and 35 °C. The yielded exceptional removal efficiencies are PO₄³⁻ (>99.9%), NH₄⁺ (>99.7%), NO₃⁻ (>99%), and SO₄²⁻ (>96%), achieving final concentrations of <0.5 mg/L for PO₄³⁻ and NH₄⁺, 2.1 mg/L for NO₃⁻, and 9.1 mg/L for SO₄²⁻. Adsorption kinetics followed a pseudo-first-order model, indicating physisorption, while the Two-Surface Langmuir model suggested a combination of homogeneous and heterogeneous adsorption mechanisms. FTIR, SEM-EDX mapping, and XRF analyses confirmed the retention of P, S, and N in the product sludge, validating the adsorption process. This study is the first of its kind to recover Al-rich Fe species from real AMD and activate them for municipal wastewater remediation using authentic MWW, bridging the gap between laboratory-scale research and real-world applications. By simultaneously addressing AMD pollution and municipal wastewater treatment, this research advances circular economy principles, promotes sustainable water management, and contributes to national and global efforts toward water security and environmental protection. Full article

The acid pollution produced from coal gangue piles is a global environmental problem. Terminal technologies, such as neutralization, precipitation, adsorption, ion exchange, membrane technology, biological treatment, and electrochemistry, have been developed for acid mine drainage (AMD) treatment. These technologies for treating pollutants with low concentrations over a long period of time in coal gangue piles appear to be costly and unsustainable. Conversely, in situ remediation appears to be more cost-effective and material-efficient, but it is a challenge that coal producing countries need to solve urgently. The primary prerequisite for preventing acidic pollutants is to clarify the oxidation mechanisms of coal gangue, which can be summarized as four aspects: pyrite oxidation, microbial action, low-temperature oxidation of coal, and free radical action. The two key factors of oxidation are pyrite and coal, and the four necessary conditions are water, oxygen, microorganisms, and free radicals. The current in situ remediation technologies mainly focus on one or more of the four necessary conditions, forming mixed co-disposal, coverage barriers, passivation coatings, bactericides, coal oxidation inhibitors, microorganisms, plants, and so on. It is necessary to scientifically and systematically carry out in situ remediation coupled with various technologies based on oxidation mechanisms when carrying out large-scale restoration and treatment of acidic coal gangue piles. Full article

Metal sulfides in waste rocks and tailings are susceptible to serious soil and water contamination due to the generation of acid mine drainage (AMD) during stockpiling. The hydrometallurgical process is one of the most essential heavy metal remediation technologies through harmless disposal and resource utilization of the waste sulfides. However, atmospheric hydrometallurgy of sulfides still faces great challenges due to low leaching efficiency and high cost. In this work, we proposed a cooperative leaching system (Fe₂(SO₄)₃-O₃) and investigated the oxidative dissolution process of sphalerite (ZnS). Under the optimal conditions, the extracted zinc reached 97.8%. Reactive oxygen species (ROS) (·OH, ¹O₂ and ·O₂⁻) were identified in the radical quenching experiments. The dissolution of sphalerite did not show passivation due to the ozone’s capability to oxidize the sulfur in sphalerite to sulfate. In addition, stirring rate, O₃ inlet concentration, and Fe₂(SO₄)₃ concentration had a significant effect on the dissolution of sphalerite. Meanwhile, the apparent activation energy was 24.11 kJ/mol based on kinetic fitting, which indicated that the controlling step of the reaction was mainly a diffusion process. This work demonstrated the cooperative effect of sphalerite leaching in the O₃-Fe₂(SO₄)₃ system and provided a theoretical reference for efficient and atmospheric dissolution of sphalerite. Full article

South Africa is the home of major global mining operations, and the acid mine drainage (AMD) contribution has been attributed to abandoned mine sites and huge pyrite-bearing tailings from coal and gold mines. Determining the true economic impact and environmental liability of AMD remains difficult. Researchers have been looking into several treatment technologies over the years as a way to reduce its possible environmental impact. Different methods for active and passive remediation have been developed to treat AMD. The aim of this review was to describe the AMD-impacted environments and critically discuss the properties of AMD and current prediction and preventative methods and technologies available to treat AMD. Furthermore, this study critically analysed case studies in South Africa, gaps in AMD research, and the limitations and prospects offered by AMD. The study outlined future technological interventions aimed at a pattern shift in decreasing sludge volumes and operational costs while effectively improving the treatment of AMD. The various treatment technologies have beneficial results, but they also have related technical problems. To reduce the formation of AMD, it is recommended that more preventive methods be investigated. Moreover, there is a current need for integrated AMD treatment technologies that result in a well-rounded overall approach towards sustainability in AMD treatment. As a result, a sustainable AMD treatment strategy has been made possible due to water reuse and recovery valuable resources such sulphuric acid, rare earth elements, and metals. The cost of AMD treatment can be decreased with the use of recovered water and resources, which is essential for developing a sustainable AMD treatment process. More study is required in the future to improve the effectiveness of the various strategies used, with a focus on reducing the formation of secondary pollutants and recovery of valuable resources. Full article

Gold mining pollution has long-lasting effects on the environment, particularly through acid mine drainage (AMD) and heavy metal contamination. Monitoring and assessing the impact of this pollution is crucial, as well as evaluating the effectiveness of remediation efforts. In our study, conducted in the gold mining area of Zlatna (GMAZ), western Romania, we utilised on-site measurements of water temperature, pH, electrical conductivity, and dissolved oxygen, along with the quantification of culturable aerobic bacteria and microfungi using ready-to-use media plates. We also examined the taxonomic richness of water invertebrates (TRWI) and the environmental features of the sites. Our study found significant negative impacts on the water biota in mining areas, with microbial abundance proving to be a reliable indicator of AMD pollution. While water invertebrates can also serve as indicators of mining effects, their abundance alone may not always accurately reflect pollution levels at every site. This multiple-factor analysis highlights the influences of water type, geological characteristics, air temperature, and precipitation on the structure of the aquatic biota. We observed a natural attenuation of mining pollution in the GMAZ in the last seven years. This study demonstrates that the quantification of microbiota, along with TRWI and basic physicochemical parameters, can offer a cost-effective alternative to expensive monitoring methods for assessing mining pollution. Full article

The highly metal-contaminated Odiel-Tinto River basin, located in the Iberian Pyrite Belt (IPB), has been the focus of many environmental studies as a natural lab for biodiversity and environmentally catastrophic scenarios and as a reference site for mining places with similar conditions. This study demonstrates the feasibility and effectiveness of two different technologies to recover ecosystems affected by acid mine drainage (AMD) in the area of IPB. The current study compiles results of two newest technologies for AMD remediation: passive remediation (dispersed alkaline substrate—DAS) and a new disruptive technology (Adiabatic Sonic Evaporation and Crystallization—ASE&C) that purifies the contaminated water, obtaining two by-products (high-quality water and metal conglomerates) that improve the general quality of the ecosystem including biodiversity by eliminating more than 90% of the contaminants from AMD and mining waters. The removal of contaminants, enhancement of AMD treatment efficiency, and offset operating costs were compared and analyzed for the different uses of the decontaminated effluents, including an old tailing pond failure, the Aznalcóllar mining spill. The efficiency of the removal of elements from the contaminated water is significant using both technologies, although the passive DAS does not still reach the international benchmark for some compounds (such as Fe, sulfates, and Mn); whereas ASE&C obtains distilled water fulfilling all the international benchmarks with conductivity values lower than 120 µS cm⁻¹ or metal concentrations lower than µg/L. Both technologies are eco-friendly and cost-effective as a result of the generation of valuable by-products such as fresh water and metal conglomerates as potentially commercial products while remediating aquatic ecosystems impacted by mining activities. Full article

In the present study, the biosorptive potential of Cyprinus carpio scales for the removal of Fe, Mn, and Zn ions from real acidic mine drainage (AMD) generated at the Rosia Montana gold mine (Romania) was explored for the first time. The collected AMD solution is very acidic, and the concentrations of Fe, Mn, and Zn ions exceed more than 34 to 56 times the disposal standards imposed by legislation. Batch adsorption experiments were carried out to study the effect of the sorbent dosage, sorbent particle size, pH, and contact time on the adsorption performance of the fish scales. Before and after the adsorption process, the biosorbent was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDX). In the investigated experimental conditions, about 100%, 87.1%, and 100% of Fe, Mn, and Zn ions were removed from the AMD after 240 min of contact with the finest-grained Cyprinus carpio scale samples using a solid:liquid ratio of 20:1 (g:L). The adsorption data were analyzed using the pseudo-first order, pseudo-second order, intraparticle diffusion rate, and Elovich equations. The adsorption process was found to follow the pseudo-second-order kinetic model. The maximum adsorption capacities of the fish scales were about 2.46 mg/g for Mn and 0.85 mg/g for Zn ions, respectively. Aside from their significant efficiency in the removal of metals from AMD, Cyprinus carpio scales also have the potential to neutralize the acidic wastewater. Thus, the removal process of metal ions from AMD is ruled by a complex mechanism, including adsorption and iron precipitation. The recycled scales are still able to remove the metal ions from AMD with a better performance during the first regeneration cycle. Based on the obtained results, it might be assessed that the low-cost biowaste of Cyprinus carpio scales have great potential and could be effectively used for the remediation of real acidic mine drainage from a sustainable perspective. Full article

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

Acid mine drainage (AMD) is a global problem with severe consequences for the environment. South Africa’s abandoned mines are a legacy from the country’s economic dependence on the mining sector, with consequent negative impacts on ecosystems. AMD remediation includes active and passive techniques. Constructed wetlands (a passive technique) have lower operational costs but require larger spaces and longer timeframes to achieve the remediation of AMD, and are supported by anaerobic sulphate-reducing bacteria (SRB), which capable of remediating high-sulphate-laden AMD while precipitating dissolved metals from the AMD. Organic substrates supporting these activities are often the limiting factor. When enhancing existing passive AMD remediation technologies, alternative waste material research that may support SRB activity is required to support the circular economy through the reduction in waste products. Chicken feathers show potential as a substrate enhancer, boosting organic carbon availability to SRB, which sustains passive AMD treatment processes by achieving pH elevation, sulphate and metal reductions in AMD water for reuse. Microbial biodiversity is essential to ensure the longevity of passive treatment systems, and chicken feathers are proven to have an association with SRB microbial taxa. However, the longer-term associations between the AMD water parameters, microbial diversity and the selected substrates remain to be further investigated. Full article

This study evaluated the co-remediation performance of an active–passive process comprised of passive permeable reactive barrier acid mine drainage (AMD) pre-treatment and active anaerobic digestion treatment of AMD with effluent as a carbon source. The bioreactor was operated for 24 consecutive days with peak chemical oxygen demand (COD) and sulphate loading rates of 6.6 kg COD/m³/day and 0.89 kg SO₄²⁻/m³/day, respectively. The AMD pre-treatment was capable of removing 99%, 94% and 42% of iron (Fe), potassium (K), and aluminium (Al) concentrations, respectively. The biological treatment process was capable of removing 89.7% and 99% of COD and sulphate concentrations, respectively. The treated wastewater copper (Cu), sulphate (SO₄²⁻), and pH were within the effluent discharge limits and the potable water standards of South Africa. Fe, Al, manganese (Mn), nickel (Ni), and zinc (Zn) concentrations in the treated wastewater were marginally higher than the discharge and potable water limit with all concentrations exceeding the limit by less than 0.65 mg/L. The remediation performance of the process was found to be effective with limited operational inputs, which can enable low cost co-remediation. Full article