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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]

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]

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]

The successful adoption and widespread implementation of innovative acid mine drainage treatment and resource recovery methods hinge on their capacity to demonstrate enhanced performance, economic viability, and environmental sustainability compared to conventional approaches. Here, an evaluation of the efficacy of chromium-based metal–organic frameworks and amine-grafted SBA15 materials in adsorbing europium (Eu) from actual mining wastewater was conducted. The adsorbents underwent comprehensive characterization and examination for their affinity for Eu. Cr-MIL-PMIDA and SBA15-NH-PMIDA had a highest Langmuir adsorption capacity of 69 mg/g and 86 mg/g, respectively, for an optimum level of pH 4.8. Preferential adsorption tests followed using real AMD collected at a disused mine in the north of Norway. A comparative study utilizing pH-adjusted real AMD revealed that Cr-MIL-PMIDA (88%) exhibited slightly higher selectivity towards Eu compared to SBA15-NH-PMIDA (81%) in real mining wastewater. While Cr-MIL-PMIDA displays excellent properties for the selective recovery of REEs, practical challenges related to production costs and potential susceptibility to chromium leaching make it less appealing for widespread applications. A cost–benefit analysis was then undertaken to quantify the advantages of employing SBA15-NH-PMIDA material. The study disclosed that 193.2 g of EuCl3 with 99% purity can be recovered by treating 1000 m3 of AMD. [ABSTRACT FROM AUTHOR]

The prolonged impact over the Tinto River estuary by both the significant pollution by acid mine drainage (AMD) affecting this river and the polluted releases from phosphogypsum (PG) piles has led to the severe environmental degradation of this ecosystem. The aim of this work was to assess the current environmental quality of the Tinto River estuary through the study of the spatial distribution of metal(loid)s and natural radionuclides in the surface sediments from the channel edge. The sediments contain mean concentrations 5–20 times higher than the background values for pollutants such as Zn, As, Cu, Pb, or U, and up to two orders of magnitude higher for P. The studied sediments are heavily polluted by toxic heavy metals and metalloids (Pb, Zn, Cu, and As) according to the US EPA guidelines. Most of the analyzed sediment samples are also strongly polluted by long-lived natural radionuclides, mainly U-isotopes and 210Pb with concentrations up to one order of magnitude higher than unpolluted sediments, mostly due to the contribution by the PG leachates. The enrichment factors (EF) were extremely high (EF > 50) for As and very severe enrichment (25 ≤ EF < 50) for P, Cd, Zn, Cu, and Pb. [ABSTRACT FROM AUTHOR]

Wetlands are critical ecological infrastructures that improve water quality, serve as habitat for fish and other aquatic life, accumulate floodwaters, and maintain surface water flow during dry periods. However, the health of wetlands has been compromised by anthropogenic activities that affect the constant supply of ecosystem services. This study assessed the impact of anthropogenically modified land use on wetland health in the Witbank Dam Catchment in South Africa, whose land use has been severely modified for agriculture and mining purposes. The study developed a model linking surface runoff generated in the catchment with land use and wetland typology to comprehend diffuse pollution from pollution-source land uses. Runoff data and related wetland spatial information were processed and analysed in a Geographic Information System (GIS) to estimate pollutants (agricultural nutrients and acid mine drainage) from runoff detained and released by wetlands. The analysis facilitated the assessment of the value of wetlands in enhancing water quality, as well as human and environmental health. The runoff volume from pollution-source land uses (urban areas, farmlands, and mining) was used to evaluate annual pollution levels. Wetland types are ranked according to their efficiency levels to filter pollutants. The assumption is that the difference between filtered and unfiltered runoff is the quantity of polluted runoff water discharged into the river system. The analysis has shown that 85% of polluted runoff generated in the catchment ends up in the river system. An important observation is that although wetlands have a substantial ability to absorb excess pollutants, they have finite boundaries. Once they reach their full holding capacity, they can no longer absorb any further pollutants. The excess is discharged into the river system, risking human and environmental health. This explains why the Limpopo River is heavily polluted resulting in the death of fish, crocodiles and other aquatic life. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD), containing large quantities of heavy metals and acidic components, poses a severe threat to the environment and human health. Acidithiobacillus ferrooxidans (A. ferrooxidans) plays a crucial role in the treatment of AMD, but its activity is significantly influenced by environmental conditions. This study systematically analyzes the stress effect of high phosphorus concentration on A. ferrooxidans during AMD treatment and its biomineralization effect. The results indicate that with phosphorus concentrations ranging from 0 g/L to 2 g/L, the system's pH and Fe2+ oxidation rate initially decrease and then increase, with higher phosphorus concentrations delaying the time of increase. When the phosphorus concentration exceeds 2 g/L, both pH and Fe2+ oxidation rates generally show a downward trend. The morphology and elemental composition of the precipitates obtained under different phosphorus concentrations exhibit significant differences, indicating that phosphorus concentration notably affects the oxidation activity of A. ferrooxidans and its mediated biomineralization process. Under high phosphorus concentrations, the activity of A. ferrooxidans is inhibited, hindering the Fe2+ oxidation process and resulting in the formation of a large quantity of amorphous ferric phosphate precipitates. The findings provide a scientific basis for optimizing AMD treatment technologies, suggesting that reasonable control of phosphorus concentration in practical applications can improve AMD treatment efficiency and pretreatment effects. [ABSTRACT FROM AUTHOR]

This article discusses the challenges and importance of accurately annotating transporters in metabolic modeling. It emphasizes the need for investment in accurate functional characterization to improve predictive tools and benefit fields such as personalized medicine, metabolic engineering, and microbial ecology. The text also discusses the types of errors that can occur in transporter annotations and the databases and tools available for transporter annotation. The document is a list of references to various scientific articles and databases related to protein subcellular localization, phenotypic testing, gene function, transporter systems, metabolic modeling, and microbial communities. These resources provide valuable information for researchers studying these areas of biology and can be used as references for further exploration. [Extracted from the article]

The performance of reclamation cover systems could be affected by the colonization of plant roots, which may modify the hydrogeological properties of the construction materials. A four-year field investigation was conducted using six experimental cells with various soil layering designs over AMD-generating tailings reclaimed with an oxygen-barrier cover combined with an elevated water table. Both herbaceous and woody vegetation were installed on top of the cells to compare the influence on the properties of the cover material. Consecutive and undisturbed cores were collected from the cover's functional layer in 2020 and 2021, respectively. Root parameters, such as root length density, and hydrogeological properties were measured on the core samples to assess the possible relationships between the two categories of variables. Root observation trenches were also cut in each cell to better analyze the root density and occurrence profiles. Results showed that, within the four-year monitoring period of the study, both herbaceous and woody vegetation roots mostly colonized the top overburden layer of the cell (>86% visible roots) and barely occupied the functional layer of the reclamation cover (<10% visible roots). The observed maximum desorption rates for the functional layer were lower than the predicted values, which could be a short-term effect of the fine roots. No significant impact of roots on the main hydrogeological variables controlling the oxygen barrier efficiency were noted. At the end of the four-year study period, the hydrogeological behavior of the functional layer in all cells with/without vegetation/additional soil layers was found to be similar. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is one of the main environmental problems associated with mining activity, whether the mine is operational or abandoned. In this work, several precipitates from this mine drainage generated by the oxidation of sulfide minerals, when exposed to weathering, were used as adsorbents. Such AMD precipitates from abandoned Portuguese mines (AGO, AGO-1, CF, and V9) were compared with two raw materials from Morocco (ClayMA and pyrophyllite) in terms of their efficiency in wastewater treatment. Different analytical techniques, such as XRD diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), N2 adsorption isotherms, and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) were used to characterize these natural materials. The adsorption properties were studied by optimizing different experimental factors, such as type of adsorbent, adsorbent mass, and dye concentration by the Box–Behnken Design model, using methylene blue (MB) and crystal violet (CV) compounds as organic pollutants. The obtained kinetic data were examined using the pseudo-first and pseudo-second order equations, and the equilibrium adsorption data were studied using the Freundlich and Langmuir models. The adsorption behavior of the different adsorbents was perfectly fitted by the pseudo-second order kinetic model and the Langmuir isotherm. The most efficient adsorbent for both dyes was AGO-1 due to the presence of the cellulose molecules, with qm equal to 40.5 and 16.0 mg/g for CV and MB, respectively. This study confirms the possibility of employing AMD precipitates to adsorb organic pollutants in water, providing valuable information for developing future affordable solutions to reduce the wastes associated with mining activity. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic pollutants known for their persistence and potential carcinogenicity. Effective removal techniques are required since their presence in wastewater poses serious threats to human health and the environment. In this review study, iron oxide nanomaterials (IONs), a by-product of mining operations, recovered from acid mine water are used to investigate the adsorption of PAHs from wastewater. The mechanisms of PAH adsorption onto IONs are investigated, with a focus on the effects of concentration, temperature, and pH on adsorption efficiency. The better performance, affordability, and reusable nature of IONs are demonstrated by comparative studies with alternative adsorbents such as activated carbon. Economic and environmental ramifications highlight the benefits of employing recovered materials, while case studies and real-world applications show how effective IONs are in removing PAHs in the real world. This review concludes by discussing potential future developments in synthesis processes, areas for more research, and emerging trends in nanomaterial-based adsorption. This research intends to contribute to the development of more effective and sustainable wastewater treatment technologies by offering a thorough assessment of the present and future potential of employing IONs for PAH removal from wastewater. [ABSTRACT FROM AUTHOR]

Copyright of Afyon Kocatepe University Journal of Science & Engineering / Afyon Kocatepe Üniversitesi Fen Ve Mühendislik Bilimleri Dergisi is the property of Afyon Kocatepe University, Faculty of Science & Literature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of this study was to assess the water quality status of the surface water and groundwater resources in the Middelburg area, South Africa. The assessment was addressed using combined water quality indices, investigating selected chemical parameters over four different seasons for a period of five years from 2017 to 2021. A combination of the Canadian Council of Ministers of the Environment water quality index and the comprehensive pollution index was used to analyze the water quality status of surface water and groundwater of the town of Middelburg, situated near coal mining activities in Mpumalanga, South Africa. The combination of the indices indicated that some surface water monitoring sites ranged between poor to fair water quality. Groundwater monitoring points also showed a poor to fair ranking. The comprehensive pollution index confirmed that some sites showed very poor water quality in the summer seasons, exceeding expected limits for the period 2017 to 2021. The principal component analysis further showed that both surface water and groundwater sites had high levels of contamination with increased chemical parameters. The results were compared against the different water quality guidelines. In an extensive monitoring program, water management systems must be properly implemented to mitigate impacts on water resources. [ABSTRACT FROM AUTHOR]

From an engineering standpoint, investigating the effects of rotation speed and fulvic acid concentration on the development of secondary high-iron minerals is crucial for treating acid mine drainage. The Fe2+ oxidation mechanism by Acidithiobacillus (A.) ferrooxidans to synthesise secondary high-iron minerals was examined in this study using shaking flask tests under various conditions: fulvic acid concentrations of 0, 0.2, or 0.4 g/L and rotation speeds of 180 r/min or 100 r/min. The pH, Fe2+ oxidation rate, total iron precipitation rate, secondary high-iron mineral functional groups and ore equivalent indicators were also investigated. The results demonstrated that at a fulvic acid concentration of 0 g/L, the pH decreased from 2.5 to 2.17 at 180 r/min. At 0.2 g/L, it decreased from 2.5 to 2.05. Finally, at 0.4 g/L, it decreased from 2.5 to 2.07. Fe2+ was completely oxidised after 48 h, and the final total iron precipitation rate ranged from 26.2% to 33.4%. The synthesised secondary high-iron minerals were uniformly dispersed in the solution. When the rotation speed was 100 r/min, the pH reduced from 2.5 to 2.25 at a fulvic acid concentration of 0 g/L, from 2.5 to 2.14 at 0.2 g/L, and from 2.5 to 2.19 at 0.4 g/L. Notably, Fe2+ was completely oxidised within 72 h. The experiment's final iron precipitation rate ranged from 23.6 to 29.6%. The synthesised secondary high-iron minerals were blocky and adhered to the bottom of the shaking flask. In summary, at a rotation speed of 180 r/min or 100 r/min, the Fe2+ oxidation rate and total iron precipitation rate of the experimental group with a fulvic acid concentration of 0.2 g/L were higher than those of the control group and the experimental group with a fulvic acid concentration of 0.4 g/L. A fulvic acid concentration of 0.2 g/L enhanced the activity of A. ferrooxidans. The minerals obtained from these experiments were characterised and identified as schwertmannite and jarosite. [ABSTRACT FROM AUTHOR]

The application of low-pressure nanofiltration (NF) was investigated for three different applications: water reuse from acid mine drainage (AMD), surface water containing natural organic matter (NOM) and agricultural reuse of microfiltered biologically treated sewage effluent (MF-BTSE). AMD contains many valuable rare earth elements (REEs) and copper (Cu) that can be recovered with fresh water. The NF90 membrane was investigated for recovery of fresh water from synthetic AMD. A steady permeate flux of 15.5 ± 0.2 L/m2h was achieved for pretreated AMD with over 98% solute rejection. NF90 achieved a high dissolved organic carbon (DOC) rejection of 95% from surface water containing NOM where 80% of the organic fraction was hydrophilic, mainly humics. The NF process maintained a high permeate flux of 52 LMH at 4 bars. The MF-BTSE was treated by NTR-729HF for agricultural reuse. NTR-729HF membranes were capable of rejecting DOC and inorganics such as sulfates and divalent ions (SO42−, Ca2+ and Mg2+) from MF-BTSE, with less than 20% rejection of monovalent (Na+ and Cl−) ions. The sodium adsorption ratio (SAR) was significantly reduced from 39 to 14 after treatment through NTR-729HF at 4 bar. The resulting water was found to be suitable to irrigate salt-sensitive crops. [ABSTRACT FROM AUTHOR]

The generation of acid mine drainage (AMD) characterized by high acidity and elevated levels of toxic metals primarily results from the oxidation and dissolution of sulfide minerals facilitated by microbial catalysis. Although there has been significant research on microbial diversity and community composition in AMD, as well as the relationship between microbes and heavy metals, there remains a gap in understanding the microbial community structure in uranium-enriched AMD sites. In this paper, water samples with varying levels of uranium pollution were collected from an abandoned stone coal mine in Jiangxi Province, China during summer and winter, respectively. Geochemical and high-throughput sequencing analyses were conducted to characterize spatiotemporal variations in bacterial diversity and community composition along pollution groups. The results indicated that uranium was predominantly concentrated in the AMD of new pits with strong acid production capacity, reaching a peak concentration of 9,370 µg/L. This was accompanied by elevated acidity and concentrations of iron and total phosphorus, which were identified as significant drivers shaping the composition of bacterial communities, rather than fluctuations in seasonal conditions. In an extremely polluted environment (pH < 3), bacterial diversity was lowest, with a predominant presence of acidophilic iron-oxidizing bacteria (such as Ferrovum), and a portion of acidophilic heterotrophic bacteria synergistically coexisting. As pollution levels decreased, the microbial community gradually evolved to cohabitation of various pH-neutral heterotrophic species, ultimately reverting back to background level. The pH was the dominant factor determining biogeochemical release of uranium in AMD. Acidophilic and uranium-tolerant bacteria, including Ferrovum, Leptospirillum, Acidiphilium, and Metallibacterium, were identified as playing key roles in this process through mechanisms such as enhancing acid production rate and facilitating organic matter biodegradation. [ABSTRACT FROM AUTHOR]

How to efficiently deal with waste acids and bases produced by industry has constantly been a tough question for scientists and engineers. Such acid–base wastewaters are normally treated by mixing to give neutral products (i.e., water and salts) and heat which is hard to collect and reuse. Therefore, there is a need for innovative approaches with high efficiencies and high-value added products. Here, we report an air/metal hydride battery with the function of both treating acid–base wastewaters and gathering the waste heat energy in the form of electricity. Remarkably, the proposed battery could exhibit a high coulombic efficiency of up to ca. 94%, along with an effective reduction in the acidity/alkalinity of waste acids/bases and a decent amount of electricity. The proposed battery device also demonstrates a stable operation in semi-flow mode over a two-day timescale, showcasing its potential scalability and long-term stability. Moreover, life cycle assessment results indicate that electricity retrieved from the treatment process is a key contributor to reducing environmental impacts. This work offers alternative opportunities for accelerating the transition to a waste acid–base circular economy. [ABSTRACT FROM AUTHOR]

Green liquor dregs (GLD) is an alkaline by-product from the pulp and paper industry with a pH between 10 and 14. Today most of the produced GLD in Sweden is landfilled. As a fine-grained alkaline material, it might be possible to use it for acid-generating mining waste remediation. To increase the utilization, quality characteristics and environmental performance need to be determined. In this study samples were collected 5 times from 16 mills during a period of 2.5 years, and were characterized by analyzing dry matter content, loss on ignition (LOI) 550 °C and LOI 950 °C, elemental analysis, pH, electrical conductivity, and calorific value. The results were then evaluated using multivariate statistics (PCA) as well as being compared to other studies and Swedish till. The results show that even if GLD is heterogenous (both within a mill and between different mills) trends can be seen for samples from most mills. When samples do stand out, it is predominately related to the same four mills. Most of the studied parameters showed characteristics favorable for use as a remediant; however, TOC, sulfur, and some of the elements require further study. In general, this study concludes that GLD can be a viable option for the remediation of small orphaned sulfidic mining sites and thus worthy of further studies on the interaction between GLD and acidic mining waste. Overall, GLD can be a good alternative for cost-effective remediation of smaller orphaned mining sites. It is readily available in large quantities, has the qualities needed for remediation of many orphaned acidic mining sites, and can often be locally sourced near the mining site. The use of GLD for mining site remediation is likely also a more sustainable method compared to traditional remediation methods. [ABSTRACT FROM AUTHOR]

Climate influences near-surface biogeochemical processes and thereby determines the partitioning of carbon dioxide (CO2) in shale, and yet the controls on carbon (C) weathering fluxes remain poorly constrained. Using a dataset that characterizes biogeochemical responses to climate forcing in shale regolith, we implement a numerical model that describes the effects of water infiltration events, gas exchange, and temperature fluctuations on soil respiration and mineral weathering at a seasonal timescale. Our modeling approach allows us to quantitatively disentangle the controls of transient climate forcing and biogeochemical mechanisms on C partitioning. We find that ~3% of soil CO2 (1.02 mol C/m²/y) is exported to the subsurface during large infiltration events. Here, net atmospheric CO2 drawdown primarily occurs during spring snowmelt, governs the aqueous C exports (61%), and exceeds the CO2 flux generated by pyrite and petrogenic organic matter oxidation (~0.2 mol C/m²/y). We show that shale CO2 consumption results from the temporal coupling between soil microbial respiration and carbonate weathering. This coupling is driven by the impacts of hydrologic fluctuations on fresh organic matter availability and CO2 transport to the weathering front. Diffusion-limited transport of gases under transient hydrological conditions exerts an important control on CO2(g) egress patterns and thus must be considered when inferring soil CO2 drawdown from the gas phase composition. Our findings emphasize the importance of seasonal climate forcing in shaping the net contribution of shale weathering to terrestrial C fluxes and suggest that warmer conditions could reduce the potential for shale weathering to act as a CO2 sink. [ABSTRACT FROM AUTHOR]

The progressive decline of the coal industry necessitates the development of effective treatment solutions for acid mine drainage (AMD), which is characterized by high acidity and elevated concentrations of heavy metals. This study proposes an innovative approach leveraging sulfate-reducing bacteria (SRB) acclimated to contaminated anaerobic environments. The research focused on elucidating the physiological characteristics and optimal growth conditions of SRB, particularly in relation to the pH level and temperature. The experimental findings reveal that the SRB exhibited a sulfate removal rate of 88.86% at an optimal temperature of 30 ◦C. Additionally, SRB gel particles were formulated using sodium alginate (SA) and carboxymethyl cellulose (CMC), and their performance was assessed under specific conditions (pH = 6, C/S = 1.5, T = 30 ◦C, CMC = 4.5%, BSNa = 0.4 mol/L, and cross-linking time = 9 h). Under these conditions, the SRB gel particles demonstrated an enhanced sulfate removal efficiency of 91.6%. Thermal analysis via differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) provided further insights into the stability and properties of the SRB gel spheres. The findings underscore the potential of SRBbased bioremediation as a sustainable and efficient method for AMD treatment, offering a novel and environmentally friendly solution to mitigating the adverse effects of environmental contamination. [ABSTRACT FROM AUTHOR]

The present study aims to develop a low-cost and sustainable composite material from solid waste to efficiently treat acid mine drainage (AMD). A modified reactor was used to produce the biochar-CaO composite from solid waste, which was characterized using XRD and SEM to determine the crystal structure, size, and surface morphology. The composite exhibited high adsorption capacity for AMD species, including Fe, Mn, and Mg metals, with an equilibrium point achieved at 300 min of contact time. The percent removal of AMD species varied with pH conditions, and the Langmuir isotherm model was found to describe the adsorption behavior of the composite adequately. The biochar-CaO composite showed a maximum adsorption capacity of 440 mg/g and held significant potential as an economical and efficient solution for AMD remediation. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD), arising from mineral resource exploitation, has transformed into a significant global environmental issue for the mining sector, posing considerable risks to water, soil, ecosystems, and human health. In this study, the current status and cutting-edge dynamics of AMD remediation research were evaluated using a bibliometrics approach. Publications on AMD remediation were collected from the Web of Science Core Collection (WOSCC) database, and the relevant literature was analyzed quantitatively using various statistical methods, including keyword co-occurrence and burst analysis. In total, 2743 articles related to AMD remediation published from 1990 to 2023 were obtained. The number of publications tended to increase annually, with a relatively fast rate of increase in recent years. Recent research related to AMD remediation has mainly focused on the ecological risks, the environmental geochemical cycling, the application of sulfate-reducing bacteria and adsorption, and the recovery of heavy metals (HMs) and rare earth elements (REEs). It is anticipated that these topics of AMD remediation research are expected to be at the forefront of future research endeavors. In addition, the current status, advantages, and challenges of AMD remediation technologies are discussed from both active and passive management perspectives, providing a theoretical basis and reference for AMD remediation. [ABSTRACT FROM AUTHOR]

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%. [ABSTRACT FROM AUTHOR]

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.

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.

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]

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]

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.

Abstract A new idea to alleviate environmental pollution is the development of low-cost adsorbents using natural minerals and fishery wastes to treat high concentrations of heavy metal pollutants in acid mine drainage (AMD). Adsorbent morphology, adsorptive and regenerative capacity, and application potential are limiting factors for their large-scale use. Oyster shells capable of releasing alkalinity were loaded on the surface of lignite to develop two composite adsorbents with different morphologies (powdery and globular) for the treatment of AMD containing Pb(II) and Cd(II). The results show that the ability of the adsorbent to treat AMD is closely related to its morphologies. The pseudo-second-order kinetic model and the Langmuir model are suitable to describe the adsorption process of OS-M(P), and the maximum adsorption saturation capacities of Pb(II) and Cd(II) are 332.6219 mg/g and 318.9854 mg/g, respectively. The pseudo-second-order kinetic model and the Freundlich model are suitable to describe the adsorption process of OS-M(G). A synergistic result of electrostatic adsorption, neutralization precipitation, ion exchange and complex reaction is achieved in the removal of Pb(II) and Cd(II) by two morphologies of adsorbents. The regeneration times (5 times) and recovery rate (75.75%) of OS-M(G) are higher than those of OS-M(P) (3 times) and recovery rate (20%). The ability of OS-M(G) to treat actual AMD wastewater is still better than that of OS-M(P). OS-M(G) can be used as a promising environmentally friendly adsorbent for the long-term remediation of AMD. This study provides a comprehensive picture of resource management and reuse opportunities for natural mineral and fishery wastes.

Abstract Aiming at the acid mine drainage (AMD) in zinc, copper and other heavy metals treatment difficulties, severe pollution of soil and water environment and other problems. Through the ultrasonic precipitation method, this study prepared fly ash-loaded nano-FeS composites (nFeS-F). The effects of nFeS-F dosage, pH, stirring rate, reaction time and initial concentration of the solution on the adsorption of Zn(II) and Cu(II) were investigated. The data were fitted by Lagergren first and second-order kinetic equations, Internal diffusion equation, Langmuir and Freundlich isotherm models, and combined with SEM, TEM, FTIR, TGA, and XPS assays to reveal the mechanism of nFeS-F adsorption of Zn(II) and Cu(II). The results demonstrated that: The removal of Zn(II) and Cu(II) by nFeS-F could reach 83.36% and 70.40%, respectively (The dosage was 8 g/L, pH was 4, time was 150 min, and concentration was 100 mg/L). The adsorption process, mainly chemical adsorption, conforms to the Lagergren second-order kinetic equation (R2 = 0.9952 and 0.9932). The adsorption isotherms have a higher fitting degree with the Langmuir model (R2 = 0.9964 and 0.9966), and the adsorption is a monolayer adsorption process. This study can provide a reference for treating heavy metals in acid mine drainage and resource utilization of fly ash.

Acid Mine Drainage (AMD) contains Fe(II) and Mn(II) metals, which can cause environmental pollution. This research aimed to investigate the potency of activated carbon made from coal as an adsorbent in AMD treatment. The carbon was made of coal and activated with H3PO4 in a weight ratio of 40%, 800 °C for 120 minutes while supplying 1.5 L/min of nitrogen during the carbonization process. The result shows that BET surface area, total pore volume, and iodine number were 296.4 m2/g, 0.156 cc/g, and 1205 mg/g, respectively. The surface contained many fractures, channels, and big holes, as evidenced by the FT-IR and SEM investigations, and it also had acidic surface functional groups. The optimum contact time adsorption for AMD treatment was 30 minutes, and the first concentration of Fe(II) and Mn(II) metals affected the adsorption. The optimum removal of Fe(II) in AMD treatment was 95.27% at an initial concentration of 3.51 ppm, while the optimum removal of Mn(II) was 99.82% at an initial concentration of 5.71 ppm. This activated carbon has a considerable potency to be used as the adsorbent in AMD treatment to reduce Fe(II) and Mn(II) levels.

Acid Mine Drainage (AMD) is a major environmental problem due to low pH, high sulphate content, and dissolved metals. The aim of this study was to investigate the potential of limestone materials for the primary treatment of AMD water. Different doses of limestone were used in this study in the ratio of 0 g/1,000 mL as control, 20 g/1,000 mL, 40 g/1,000 mL, 60 g/1,000 mL, 80 g/1,000 mL, 100 g/1,000 mL, 200 g/100 mL (limestone/AMD) in a batch experiment of 1,500 mL plastic container. The results showed that the pH of AMD water improved to 8.6 at a dose of 100 g/1,000 mL, and the sulphate concentration decreased from 2,277 mg/L to 506 mg/L at a dose of 200 g/1,000 mL. The removal of Fe, Cu, Zn, Mn, and Ni at 200 g/1,000 mL was 99%, 92%, 68%, 96%, and 99%, respectively. The results of this study also showed that the Mn content decreased slowly as the limestone dosage increased. In addition, this study showed that limestone is a good neutralizing agent for increasing the pH of AMD water and reducing sulphate and dissolved metal concentrations. The results of this study indicated that limestone is suitable as a primary treatment agent for AMD water treatment in gold mines in Tanzania.

This paper investigates the intricate interplay between carbon emissions and foreign direct investment within the context of Brazil, Russia, India, China, and South Africa (BRICS) for the period spanning 2000 to 2022. In our comprehensive analysis, we incorporate ecological footprint, renewable energy, globalization, and technological innovations as exogenous variables. Employing a system of simultaneous equations across the BRICS panel, we aim to fully elucidate the proposed relationships. Our empirical findings underscore the following key insights: foreign direct investment, technological innovations, and the adoption of renewable energy sources significantly contribute to the mitigation of carbon emissions in these selected nations. However, it is essential to note that ecological footprints exhibit a positive association with carbon emissions, raising concerns on two fronts: escalating environmental degradation and increased land pressure, both of which contribute to rising ecological footprints in BRICS countries. Additionally, our analysis reveals that foreign direct investment is influenced by its capacity to reduce carbon emissions and bolster renewable energy adoption, while globalization amplifies investment trends within the BRICS nations. To address the environmental repercussions of mining activities, it is imperative to implement stringent control and regulation measures, given their potential adverse impacts, including soil pollution, acid mine drainage, erosion, biodiversity loss, excessive water resource consumption, and wastewater disposal challenges. Nevertheless, proactive steps such as recycling mining waste, adopting environmentally friendly mining equipment, combatting illegal mining, and enhancing overall mining sustainability offer promising avenues to mitigate the environmental footprint of mining operations. [ABSTRACT FROM AUTHOR]

The mining industry generates vast quantities of mine tailings on an annual basis. However, due to their limited economic value, a significant portion of these tailings are deposited close to mining sites, often underwater. The principal environmental apprehensions associated with mine tailings revolve around their elevated levels of heavy metals and sulfidic minerals. The oxidation of these sulfidic minerals can lead to the formation of acid mine drainage, which in turn releases heavy metals into nearby water systems. The effective management of tailing dams requires substantial financial investments for their construction and meticulous control. Consequently, a pressing need exists for stable, sustainable, and economically viable management approaches. One promising method for addressing mine tailings is through alkali activation, a technique that serves as a stabilization process. This approach yields robust, concrete-like structures by utilizing raw materials abundant in aluminum and silicon, which conveniently constitute the primary components of mining residues. This comprehensive review outlines the research on utilizing alkali activation for mine tailings. It delves into the reactivity and chemical attributes of diverse minerals. Numerous mine tailings exhibit an inadequate level of reactivity under alkaline conditions, so various pre-treatment methodologies and their impacts on mineralogy are meticulously explored. [ABSTRACT FROM AUTHOR]

This paper studied the characteristics of the carbon emission of an industrial wastewater treatment plant (IWWTP) and a domestic WWTP (DWWTP) located in a high-tech industrial park of Shaanxi Province, China. The results showed that the total carbon emissions of the IWWTP and DWWTP were 10.13 kg/t and 1.84 kg/t in 2020, respectively. Indirect carbon emissions play a dominant role in the total carbon emission of the IWWTP, which accounts for about 97.6% of the total amount. The direct carbon emissions of greenhouse gases (e.g., CH4, N2O) account for about 62% of the total carbon emissions in the DWWTP, followed by the indirect carbon emissions generated by electricity consumption (31.06%) and chemical consumption (6.94%). Additionally, the centralized recycling and re-utilization of the wastewater could achieve 1.06 kg/t and 1.16 kg/t of carbon emission reduction in the IWWTP and DWWTP, respectively, while the carbon emissions of the DWWTP are inversely proportional to the treatment capacity. Therefore, it is of great value to collect and utilize intensively the recycled water to achieve the goal of regional carbon emission reduction and carbon neutralization of WWTPs in industrial parks. [ABSTRACT FROM AUTHOR]

Iron and sulfur-oxidizing microorganisms play important roles in several natural and industrial processes. Leptospirillum (L.) ferriphilum, is an iron-oxidizing microorganism with a remarkable adaptability to thrive in extreme acidic environments, including heap bioleaching processes, acid mine drainage (AMD) and natural acidic water. A strain of L. ferriphilum (IESL25) was isolated from an industrial bioleaching process in northern Chile. This strain was challenged to grow at increasing concentrations of sulfate in order to assess changes in protein expression profiles, cells shape and to determine potential compatible solute molecules. The results unveiled changes in three proteins: succinyl CoA (SCoA) synthetase, isocitrate dehydrogenase (IDH) and aspartate semialdehyde dehydrogenase (ASD); which were notably overexpressed when the strain grew at elevated concentrations of sulfate. ASD plays a pivotal role in the synthesis of the compatible solute ectoine, which was identified along with hydroxyectoine by using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF). The relationship between IDH, SCoA, and ectoine production could be due to the TCA cycle, in which both enzymes produce metabolites that can be utilized as precursors or intermediates in the biosynthesis of ectoine. In addition, distinct filamentous cellular morphology in L. ferriphilum IESL25 was observed when growing under sulfate stress conditions. This study highlights a new insight into the possible cellular responses of L. ferriphilum under the presence of high sulfate levels, commonly found in bioleaching of sulfide minerals or AMD environments. [ABSTRACT FROM AUTHOR]

Previous studies have reported the role of some species of acidophilic bacteria in accelerating the dissolution of goethite under aerobic and anaerobic conditions. This has relevance for environments impacted by acid mine drainage and for the potential bioleaching of limonitic laterite ores. In this study, natural wellcharacterized goethite mineral samples and synthetic goethite were used in aerobic and anaerobic laboratory batch culture incubation experiments with ferric iron-reducing, acidophilic bacteria, including the lithoautotrophic species Acidithiobacillus (At.) thiooxidans, At. ferrooxidans, and At. caldus, as well as two strains of the organoheterotrophic species Acidiphilium cryptum. All bacteria remained alive throughout the experiments and efficiently reduced soluble ferric iron in solution in positive control assays. However, goethite dissolution was low to negligible in all experimental assays with natural goethite, while some dissolution occurred with synthetic goethite in agreement with previous publications. The results indicate that ferric iron-reducing microbial activity at low pH is less relevant for goethite dissolution than the oxidation of elemental sulfur to sulfuric acid. Microbial ferric iron reduction enhances but does not initiate goethite dissolution in very acidic liquors. [ABSTRACT FROM AUTHOR]

The year 2021 marked a decade of holopelagic sargassum (morphotypes Sargassum natans I and VIII, and Sargassum fluitans III) stranding on the Caribbean and West African coasts. Beaching of millions of tons of sargassum negatively impacts coastal ecosystems, economies, and human health. Additionally, the La Soufrière volcano erupted in St. Vincent in April 2021, at the start of the sargassum season. We investigated potential monthly variations in morphotype abundance and biomass composition of sargassum harvested in Jamaica and assessed the influence of processing methods (shade-drying vs. frozen samples) and of volcanic ash exposure on biochemical and elemental components. S. fluitans III was the most abundant morphotype across the year. Limited monthly variations were observed for key brown algal components (phlorotannins, fucoxanthin, and alginate). Shade-drying did not significantly alter the contents of proteins but affected levels of phlorotannins, fucoxanthin, mannitol, and alginate. Simulation of sargassum and volcanic ash drift combined with age statistics suggested that sargassum potentially shared the surface layer with ash for ~50 d, approximately 100 d before stranding in Jamaica. Integrated elemental analysis of volcanic ash, ambient seawater, and sargassum biomass showed that algae harvested from August had accumulated P, Al, Fe, Mn, Zn, and Ni, probably from the ash, and contained less As. This ash fingerprint confirmed the geographical origin and drift timescale of sargassum. Since environmental conditions and processing methods influence biomass composition, efforts should continue to improve understanding, forecasting, monitoring, and valorizing sargassum, particularly as strandings of sargassum show no sign of abating. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is an environmental issue linked with mining activities, causing the release of toxic water from mining areas. Polyethersulphone (PES) membranes are explored for AMD treatment, but their limited hydrophilicity hinders their performance. Chitosan enhances hydrophilicity, addressing this issue. However, the effectiveness depends on chitosan's degree of deacetylation (DD), determined during the deacetylation process for chitosan production. This study optimized the chitin deacetylation temperature, alkaline (NaOH) concentration, and reaction time, yielding the highest chitosan degree of deacetylation (DD) for PES/chitosan membrane applications. Prior research has shown that high DD chitosan enhances membrane antifouling and hydrophilicity, increasing contaminant rejection and permeate flux. Evaluation of the best deacetylation conditions in terms of temperature (80, 100, 120 °C), NaOH concentration (20, 40, 60 wt.%), and time (2, 4, 6 h) was performed. The highest chitosan DD obtained was 87.11% at 80 °C, 40 wt. %NaOH at 4 h of chitin deacetylation. The PES/0.75 chitosan membrane (87.11%DD) showed an increase in surface hydrophilicity (63.62° contact angle) as compared to the pristine PES membrane (72.83° contact angle). This was an indicated improvement in membrane performance. Thus, presumably leading to high contaminant rejection and permeate flux in the AMD treatment context, postulate to literature. [ABSTRACT FROM AUTHOR]

In the U.S., the state of Pennsylvania has proposed lowering its Mn criterion from 1.0 to 0.3 mg/L. An investigation of the feasibility of meeting this standard with passive treatment was conducted. Existing data from 19 full-scale oxic limestone beds were compiled from literature reports to determine current Mn removal effectiveness and rates. The median system decreased Mn from 20 to 1.7 mg/L at a theoretical retention time of 37 h. Only two passive treatment systems produced effluents with < 0.3 mg/L Mn. In order to explore the capabilities of oxic limestone beds to remove Mn, two experimental oxic aggregate beds were installed at conventional AMD treatment plants and used to experimentally treat a portion of each plant's final effluent. The Hollywood unit was marginally effective, decreasing Mn on average from 0.584 to 0.281 mg/L with a theoretical retention time (TRT) of 3.7 h. The Brandy Camp unit was highly effective, decreasing Mn from 5.85 to 0.095 mg/L when operated at a TRT of 2.3 h. Effective removal of Mn by the Brandy Camp unit required 7 weeks of aggregate ripening. Average Mn removal rates for the Brandy Camp unit were 22.7 g/d/m2, 15.7 g/d/mt, and 2.5 mg/L/hr of theoretical retention time. The half-time of Mn removal was 25 min. After one year of operation, hydraulic problems associated with the accumulation of iron solids on the surface of the aggregate forced termination of the Brandy Camp unit. The results indicate that the 0.3 mg/L effluent criterion can be achieved with oxic aggregate beds at very short retention times, as long as aggregate permeability is maintained. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) prevention or remediation is a major issue of the environmental management of sulfide-bearing active and abandoned mining sites, the main sources of acidic waters being wastes and tailings. The present work intends to check a circular economy approach to such issues in the mining region of Sardinia, where environmental pollution, due to AMD, is a major concern. Tests were conducted on basic drainage-producing feldspar mining wastes that could be recycled as buffering agents of sulfide-bearing tailings. Among the sulfide-bearing abandoned mining sites investigated, Furtei epithermal gold deposit tailings are the most polluting and those that can better test the buffering agent efficacy. Buffering test results show that buffering to near-neutral conditions can be attained following steps similar to those of pure calcite buffer. The buffering potential of the recycled waste is due to both the buffer calcite content, which provides short-term buffering, enhanced by feldspar content that can provide long-term buffering. Buffered waters show a dramatic decrease in the concentration of most of the metals present in the leachate, down to conditions that meet the requirements for the discharge of industrial waters according to Italian legislation. [ABSTRACT FROM AUTHOR]

We address the challenges of limescale deposition and its management in urban construction sites, specifically within the Sumayil North project in Tel Aviv. Jet grouting, a method increasingly favored over conventional dewatering techniques for its minimal environmental impact and efficiency, is scrutinized for its unintended consequences on groundwater chemistry, particularly in relation to limescale formation. Our investigation centers on a dual approach: dissecting the geochemical dynamics leading to limescale deposition following jet grouting operations, and evaluating a remedial acid injection strategy implemented to counteract this phenomenon. We identify the critical factors influencing aquifer water chemistry through a detailed hydro-chemical analysis encompassing the Pleistocene Coastal Aquifer's dynamics. The study reveals that the interaction between grout components and aquifer water significantly alters groundwater pH, driving the precipitation of calcium carbonate. The subsequent implementation of a sulfuric acid injection regimen successfully mitigated limescale accumulation, restoring pumping efficiency and neutralizing pH levels. We propose a workflow to manage and prevent limescale, emphasizing preemptive measures like custom grout compositions and controlled dewatering, with strict post-intervention groundwater monitoring. This approach balances operational efficiency, infrastructure integrity, and environmental stewardship in urban construction projects interfacing with sensitive aquifer systems. [ABSTRACT FROM AUTHOR]

This article contributes a boundary work analysis of the case of acid mine drainage (AMD) in South Africa to the existing boundary work literature. We conduct our analysis by applying a synthesized multi-level boundary work framework to examine whether the knowledge that was produced during the boundary work conducted was usable and influential in decision-making and resulted in successful policy implementation. We conclude that contrary to expectations, a closed, technocratic boundary work process resulted in the relatively successful implementation of a short-term intervention in the AMD problem, whereas a subsequent open and deliberative process did not result in the successful implementation of the long-term policy solution. We ascribe this finding to the influence of critical enabling and constraining factors characterizing the South African socio-political context within which the AMD issue is situated, and therefore, we recommend adding a meta-analytical layer to boundary work analyses, especially in developing country contexts. [ABSTRACT FROM AUTHOR]