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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 mining industry generates acid mine drainage (AMD) characterized with a low pH value and high dissolved metal concentration that leads to the negative impacts on the environment and human health. The objectives of this research were to investigate the growth response of mixed culture of microalgae Chlorella sorokiniana and Monoraphidium neglectum in a liquid media contaminated with AMD; generate the optimum environmental conditions (pH value and contact time) to determine the efficiency biosorption of iron and manganese contained in the solution of AMD into the consortium of microalgae; and quantify the maximum removal amount of iron and manganese contained in the solution of AMD by utilizing microalgae consortium of Chlorella sorokiniana and Monoraphidium neglectum as biosorbent. AMD used in this research was characterized with a pH value of 1.65 with iron and manganese concentrations of 8.28 mg/L and 4.57 mg/L. The research of biosorption was conducted in 150 rpm with pH level variations of 4, 5, and 6, and contact time variations of 60, 120, and 180 min. The maximum value of iron and manganese removals occurred when pH level reached 5 at 180 min of contact time with removal efficiency of 89.73% for iron and 94.53% for manganese. The results proved that the mixed culture of microalgae namely Chlorella sorokiniana and Monoraphidium neglectum can be utilized to remove iron and manganese contained in acid mine drainage. [ABSTRACT FROM AUTHOR]

Sulfate-laden wastewater generated from various natural and industrial activities, including mining, metallurgy, electroplating, and battery manufacturing and recycling, has the potential to contaminate both ground and surface water bodies. It is harmful to all forms of life and the environment. Thus, developing an efficient treatment system to address sulfate pollution is necessary. Biological sulfate reduction (BSR) involving sulfate-reducing bacteria offers a better removal of sulfate than conventional physicochemical methods. BSR offers various advantageous such as lower sludge production, removal and recovery of metals, and production of elemental sulfur. However, the performance of bioreactors depends on wastewater sources, microbes involved, and operating conditions. Currently, limited studies are available encapsulating the current state of the art of biological sulfate remediation aimed at optimization of bioreactor design and operation. Therefore, this paper attempts to provide a comprehensive review of the sources of sulfate, its health and ecological effects, microbes involved in sulfate reduction, and its removal pathways that would be beneficial for future bioreactor design. In addition, theoretical and practical aspects of influencing factors the process parameters have been discussed. Considering the results of the reviewed articles, operating, and set-up conditions are recommended to obtain the higher sulfate removal. It includes dissimilatory sulfate reduction by mixed bacterial culture using sodium lactate as an electron donor with pH near about neutral, mesophilic conditions, COD SO4 2-/ratio of 0.67-1.7, ORP less than -100 mV, and lesser sulfide concentration. This overview helps to develop an effective strategy for bioremediation of sulfate and decreasing the sulfate-rich industrial effluent footprint. [ABSTRACT FROM AUTHOR]

Waste rocks from gold mining operations represents a significant environmental burden and impairs sustainable environmental management in developing countries. This study focused on understanding the leachate properties of different particle sizes (>10mm, 20mm, 30mm and 50mm) from the waste rock dump (WRD) - GPAF in the 30 liters containers to represent waste rocks by using quick static testing to determine a more rational design basis for material storage and management. This study found that small particle sizes of waste rocks with <10 mm showed a strong leaching with a low pH of 3.5, while large particle sizes of 50 mm showed a high pH of 6.5. Metal leaching of small particle sizes had a higher concentration of Manganese, Zinc and Iron than large particle size. Similarly, sulphate concentration from leachate of small particle size of waste rocks had higher levels than large particle size. In addition, this study also demonstrated that the majority of dissolved metals (Mn, Zn and Fe) leached higher in the low pH (3.5) leachate. This study recommended that great emphasis be taken on the separation of small particles from large particle sizes of mine waste rocks during and after mining operations to reduce the risk of metal leaching and the possibility of acid mine drainage (AMD) formation and pollute surface and groundwater. [ABSTRACT FROM AUTHOR]

Pollution is a major threat to the sustainability of the ecosystem. The rapid increase in environmental pollution is a current problem of great concern, affecting the livelihood of land and water dwellers. This can be attributed to anthropogenic and industrial activities, including mining, which often leads to the generation of acid mine drainage (AMD), considered one of the most catastrophic ecological problems. Soil and water use for domestic and industrial purposes has been drastically affected, highlighting the urgent need for remediation. The use of physical, chemical, physicochemical, and thermal methods in the treatment of AMD contamination has been criticized because some of these methods are not environmentally friendly and others result in site recontamination. Bioremediation involves the use of microorganisms to degrade contaminants in a controlled environment. This study critically reviewed various bioremediation methods for the treatment of AMD contamination, factors influencing the application of these methods, cost-benefit and environmental impact analyses, challenges, and prospects of bioremediation technologies for effective treatment. The study shows that bioremediation have proven effective and can serve as a cost-effective and environmentally friendly approach for the remediation of AMD contaminated sites. However, large-scale application remains a challenge. Research is still needed to optimize and develop bioremediation technologies capable of remediating sites with complex mixtures of contaminants that are not evenly distributed in the environment. [ABSTRACT FROM AUTHOR]

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) 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.)

Most copper flotation tailings contain a significant amount of sulfide minerals that can generate effluent resulting from the oxidation of sulfides when they are exposed to oxygen and water. This study aimed to characterize and evaluate the acid drainage potential of five different copper flotation tailings, named samples I, II, III, IV, and V. Sample I was taken from an industrial operation, while Samples II, III, IV, and V were produced in pilot plant tests. All samples were characterized and submitted to static acid drainage tests, such as paste pH, Net Acid Generation (NAG) pH, and Modified Acid-Base Accounting (MABA). The sulfur as sulfide/total sulfur mass ratios varies from 0.40 up to 0.89 showing the presence of a high amount of minerals rich in pyrite and alunite, being higher than 13 wt% of pyrite in samples IV and V and around 19 wt% of alunite in sample III. Samples I and II presented a high number of alkaline elements, totalizing more than 8 wt% of K2O+CaO+MgO, while samples III, IV, and V show the lowest amount of these elements (<4 wt%). Only samples III, IV, and V show Paste pH results lower than 5.0, indicating superficial oxidation on their surfaces and/or the presence of water-soluble acidity minerals. Due to the high pyrite content in samples III and IV, it was not possible to measure their NAG pH due to the high heat released with the addition of hydrogen peroxide. The low NAG pH obtained with sample III (5.30) was due to its high pyrite content (0.30 wt%) in comparison with the results obtained with sample I (NAG pH of 8.15 and 0.10 wt% of pyrite), and sample II (NAG pH of 8.18 and 0.10 wt% of pyrite). The MABA results show that samples III, IV and V presented acid drainage potential due to the neutralization potential (NP)/acidity potential (AP) ratio being lower than 1. On the other hand, samples I and II presented NP/AP ratio higher than 4, not showing potential to generate acid drainage. Due to these results, it is recommended to carry out acid drainage kinetic tests with samples III, IV, and V to determine the long-term weathering rates, evaluate lag time to acid generation and provide reaction rates for geochemical modeling. [ABSTRACT FROM AUTHOR]

The acidified mine water can lead to the release of heavy metal ions in rocks, and its direct discharge deteriorates the surface water ecosystem. Water acidification drives the dynamic transformation of dissolved inorganic carbon (CO2-H2CO3*-HCO3-) and releases large quantities of CO2 into the atmosphere. Thus, this process is a noteworthy source of CO2 that has long been overlooked. From the geochemical perspective, this study analyzes the acidification mechanism of mine water along with its influencing factors. On this basis, the discussion describes the evolutionary characteristics of dissolved inorganic carbon during the migration of acid mine water. In addition, we also clearly demonstrate the characteristics of degassing kinetics and the mechanism of carbon isotope fractionation. There are three fundamental stages of mine water acidification (oxidation of reduced S to SO42-; oxidation of Fe2+ to Fe3+; hydrolysis of Fe3+ to precipitate ferrihydrite). Notably, the corrosion of feldspar silicate minerals also contributes acidity to mine water. The acidification of mine water is controlled by such factors as pH, temperature, dissolved oxygen content, and the action of microorganisms. Evaluating the acid potential of bedrock is vital to any accurate measurement of the total dissolution of carbonate rocks and the carbon emission intensity of mine water. Revealing the DIC sources in mine water, as well as the degassing and carbon isotope fractionation mechanism, is more likely to be accomplished by studying the full-scale evolution of mine water from the aquifer outlet to the mine drainage downstream. Along these lines, the degassing process can be separated into three stages: degassing driven by relieved pressure when mine water pours out during coal mining, degassing arising from the acidification of mine water and the dissolution of carbonate rock, and degassing as a result of the mixture of acid mine drainage and surface waters. [ABSTRACT FROM AUTHOR]

Acid Mine Drainage (AMD) is a significant environmental problem in the mining industry due to its high concentration of hazardous metals and metalloids, sulfate compounds, and low pH levels. Despite the attention that iron oxide magnetic nanoparticles (MNP) have received for AMD remediation, there is still a lack of understanding of the physicochemical mechanisms behind their non-specific adsorption, particularly in distinct variations of AMD, such as Cu-rich AMD. In this study, we synthesized, characterized, and applied MNP to the two-step treatment of Cu-rich AMD. The chemical and physical properties of the MNP and magnetically separated sludges after AMD treatment are characterized. Additionally, the chemical species adsorbed onto the MNP, the oxidation state of the resultant sludge after Cu-rich AMD treatment, and the short-range ordering of metal contaminant species on the surface of the MNP are identified. Finally, first-principles calculations using Density Functional Theory were conducted to understand how different Cu ion species adsorb to the MNP surface depending on the pH of the Cu-rich AMD. The bonding between MNP and Cu species occurs primarily through metal cation-oxygen bonds on the surface of MNP, and this bonding is influenced by the pH of the solution. A combination of experimental and theoretical approaches was the key to arrive at this conclusion. This information can aid in the comprehension of how metal contaminants adhere to the surfaces of MNP and in the precise engineering of these nanoparticles. [Display omitted] • Simple air-exposed co-precipitated MNP and its advanced characterization were done. • The application of MNP significantly reduced total metal content in Cu-rich AMD. • The pH of Cu-rich AMD plays a crucial role in the effectiveness of metal adsorption. • DFT shows that metal cation-oxygen bond surface complexation is the main mechanism. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) pollution leads to the enrichment of sulfate in paddy soil. The interplay between denitrifying and sulfate-reducing bacteria across varying soil depths, and their response to AMD pollution is not yet fully understood. The responses of denitrifying and sulfate-reducing bacteria(SRB) to AMD pollution were analyzed by collecting soil samples at four depths (0–10 cm, 10–20 cm, 20–40 cm, 40–60 cm) under two treatments (AMD-polluted and control soil). AMD pollution resulted in a significant decrease in pH value, elevated SO 4 2- and metal concentrations. Compared to the control soil, denitrifying and sulfate-reducing bacteria in AMD-polluted soils were more sensitive to environmental fluctuations. Co-occurrence analysis revealed that there were more microbiological linkages and nodes in control soil than in polluted soil. Denitrifying and sulfate-reducing bacteria can maintain part of N and S cycle under long-term AMD pollution by increasing the negative correlation in ecological network. Desulfobacca exhibited a positive correlation with nitrate and held a significant position in the symbiotic network, suggesting its potential important role in inhibiting nitrogen loss. This study revealed the intricate ecological network of functional communities, which could have important implications for environmental management and the development of sustainable agricultural practices in areas affected by AMD pollution. [Display omitted] • Denitrifying and sulfate-reducing bacteria were sensitive to environmental variations, particularly in polluted soils. • Desulfobacca occupied a significant position within the ecological network. • Networks were less stable and had fewer connections in contaminated soil. • The networks manifested an increased prevalence of negative associations across diverse soil depths in polluted soils. [ABSTRACT FROM AUTHOR]

Pyrite oxidation causes the generation of acid mine drainage (AMD), posing significant challenges in the management of sulfide tailings. Passivation agents such as humic acid have been tested to prevent pyrite oxidation. The potential of using humate rich food waste compost as a source of passivation agents to suppress pyrite oxidation was explored in this study. Batch leaching tests were conducted at room temperature, involved oxidatively leaching a pure pyrite and a pyrite-containing coal refuse sample, respectively, with and without adding the compost at acidic pH. The involved passivation mechanisms were investigated by solution leaching tests and spectroscopic (XPS) and microscopic (SEM) analysis of the pure pyrite sample and its leaching residues. Compared to the control, adding the compost led to the increases in solution pH, removal of the Fe2+/Fe3+ ions from the solutions by adsorption, and remarkable decreases (≥58 %) in sulfur concentration in both samples. Both SEM and XPS analysis indicated that a coating layer was successfully established on pyrite surface after being leached in the presence of the compost. The coating layer comprised a mixture of organic species (e.g., O-C O and N-H/C groups) and phosphate, potentially improving the likelihood of providing antioxidant protection over acidic pH. As a low-cost material, food waste compost can benefit the source control of AMD not only in terms of its surface passivation, but also its intrinsic alkalinity, metal immobilization, and low environmental risk. [Display omitted] • Compost was used as a source of passivators to inhibit pyrite oxidation. • The compost raised solution pH and retained Fe during pyrite leaching. • The compost significantly reduced pyrite oxidation by forming a coating layer. • XPS results showed that the coating layer comprised organic species and PO 4 3-. • The benefits of using compost in preventing pyrite oxidation were summarized. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD), a common environmental problem around the world, is characterized by low pH, high concentrations of heavy metals and sulfate. AMD treatment technology based on stimulating in-situ microorganisms has received widespread attention, but lack of organic matter is a limiting factor that restricts the remediation by heterotrophic microorganisms such as sulfate-reducing bacteria (SRB). In this study, a pilot scale reactor was set up next to an acid reservoir to evaluate the effect of livestock wastes on the in-situ bioremediation of AMD, focusing on performance assessment, heavy metal removal efficacy, and the evolution of the microbial community. Results indicated that the pH of AMD rises rapidly from 3.23 to 4.11, and metals (e.g., Fe, Cu, and Zn) rapidly got removed in Stage I. However, AMD experienced significant stratification in Stage Ⅱ (biogas slurry supplemented). The pH of surface layer (0.5 m below the surface) gradually dropped to 3.67, and the bottom layer (2.3 m below the surface) remained around 4.1, and the metal removal efficiencies further improved. Microbial communities were dominated by Fe-OB and Fe-RB in surface layer, while SRB dominated in bottom layer. The addition of biogas slurry significantly increased the relative abundance of functional microbe in bioremediation. The growth of SRB in the bottom of the reactor made an important contribution to heavy metal removal. Heavy metals were mainly removed through the formation of insoluble hydroxide and sulfide precipitation and co-precipitation. This study innovatively integrates low-cost, locally sourced livestock waste as nutrient supplements into AMD bioremediation processes, and demonstrated the potential for integrating AMD treatment with livestock waste management, addressing both the nutrient needs for AMD processing and the challenge of livestock waste disposal. The findings contribute to the development of cost-effective and eco-friendly strategies for AMD management while advancing the understanding of microbial mechanisms of in-situ bioremediation. [Display omitted] • Exogenous substrates have obvious effects on AMD bioremediation. • Biogas slurry resulted in stratification of iron oxidation and sulfur reduction. • SRB had a strong competitive advantage in the evolution of microbial communities. [ABSTRACT FROM AUTHOR]

Copyright of Rudarsko-Geolosko-Naftni Zbornik is the property of Faculty of Mining, Geology & Petroleum Engineering 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.)

Historically, the Monongahela, Tygart, and Cheat River watersheds in West Virginia were impaired by acidification from acid mine drainage and Walleye Sander vitreus were extirpated from these watersheds by the 1940s. Walleye were reestablished after water quality improvements following passage of environmental legislation and subsequent reintroduction efforts. We compared population characteristics, with emphasis on growth, of Walleye and used modeling to predict the potential effects of harvest regulations in the Monongahela River and two main‐stem reservoirs in the Cheat River and Tygart River watersheds. Statistical comparisons of von Bertalanffy growth curves and relative growth indices indicated that Walleye growth significantly differed across all water bodies. Relative growth index results suggested that Walleye growth was above average in Cheat Lake, average in the Monongahela River, and below average in Tygart Lake relative to other North American populations. Growth was negatively correlated with Walleye relative abundance and positively correlated with estimates of productivity (total phosphorus, chlorophyll a). Walleye diets significantly differed across all water bodies, with diets dominated by Yellow Perch Perca flavescens and Gizzard Shad Dorosoma cepedianum in Cheat Lake, where growth was fastest. Population modeling suggested that effects of exploitation on yield, spawning potential, and size structure were similar under regulations of no length limit and a minimum length limit (381 mm). Models suggested that removing length limits in Tygart Lake could increase angler harvest opportunities and pose minimal threat to the fishery. Models suggested that a protected slot limit could provide increased protection to the spawning potential of Cheat Lake and the Monongahela River populations. Additionally, models predicted that a protected slot limit could increase the number of large (>630‐mm) Walleye in these waters. Our findings demonstrate the different characteristics that Walleye populations can develop after reestablishment based on abiotic and biotic conditions and the need for watershed‐specific management. [ABSTRACT FROM AUTHOR]

• Sulfuric acid proves to be the most efficient for the acid hydrolysis of molasses. • An optimal hydrolysis was observed at a concentration of 0.15 M sulfuric acid. • Heterotrophic cultivation of C. sorokiniana MB-1-M12 was achieved using molasses. • Using 10 g/L reducing sugars yield 2.57 g/L biomass and 2.1 mg/g lutein content. • The process fulfills the objective of waste recycling and reutilization. Lutein is a xanthophyll carotenoid commonly found in photosynthetic organisms, such as microalgae and plants. It serves as a photosynthetic accessory pigment and possesses antioxidant properties. Lutein is recognized for its prophylactic use in preventing Age-Related Macular Degeneration (AMD) and is widely employed in health supplements. The demand for lutein is steadily increasing. This study utilized Chlorella sorokiniana MB-1-M12 for heterotrophic growth and lutein production, employing molasses as a model of food industrial waste as an alternative carbon source. Molasses was hydrolyzed using acids, and the optimal hydrolysis conditions were determined by varying the types and concentrations of the acids. The resulting hydrolysate, which contains reducing sugars, was then recovered and used to support the heterotrophic growth of C. sorokiniana MB-1-M12 for lutein production. The best efficiency in molasses hydrolysis was achieved using 0.15 M sulfuric acid, resulting in a maximum sugar recovery of 0.721 gs of reducing sugar per gram of molasses. When the molasses hydrolysate reached a sugar concentration of 10 g/L, it yielded a biomass of 2.57 g/L and a lutein content of 2.1 mg/g. These findings indicate that molasses can effectively serve as a substitute for glucose as a carbon source, although it cannot provide all the essential micronutrients required for biomass growth. Consequently, the addition of nutrients in BG-11 medium became necessary. This study successfully demonstrates the upcycling of waste resources, such as molasses, into a high-value product like lutein, all achieved in a cost-effective and resource-efficient manner. [ABSTRACT FROM AUTHOR]

Copyright of Revista Colombiana de Biotecnología is the property of Universidad Nacional de Colombia 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.)

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) 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 Philippines is one of the mineral-rich countries in the world with an estimated US$840 billion worth of untapped mineral wealth, catapulting the mining industry as a significant economic player providing substantial contribution to the national revenue and generating employment opportunities for the Filipino people. However, the detrimental impact of mining to the country has also been heavily criticized as it causes massive potential destruction to environment and wildlife ecology such as acid mine drainage and contaminant leaching, soil erosion, and tailing impoundments among others. These conflicting interests are reflected in the mining discourses stoked or dimmed by media, which influence the readers' construal of meanings in the mining texts, social actors' roles in the mining industry, and the urderlying contexts of the mining reality. Drawing on critical discourse analysis, this study described the linguistic and discursive features of Philippine mining discourse in media texts. The study used 224 news articles published by three online portals within five years. Local news reports and peripheral discourses obtained through interviews with local "symbolic elites" in the identified mining communities and other archival documents supplemented the news texts. The UAM Corpus Tool, a software for linguistic tagging, complemented the manual analysis in identifying the social actor theme. Findings revealed that government actions, economic phenomenon, and political actors are the most prevalent themes in the mining news reports. Moreover, results showed that local news tends to focus more on the mining's environmental impact, whereas the national news tends to put more premium on the mining's economic impact. This means that the media allotted a much lesser spatio-temporal space for the environment and Indigenous Peoples' cause. The findings further invalidate the assumptions that mining discourse is primarily concerned with environmental related issues. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesized a new low-cost adsorbent—oyster shell-modified lignite composite in globular shape (OSL-G). • The OSL-G can effectively remove the Pb2+ and Cd2+ from AMD and increase its alkalinity. • Maximum adsorption capacity of Pb2+ and Cd2+ were 29.878 mg/g and 3.425 mg/g. • Adsorption mechanism was mainly the adsorption-condensation coexistence results of electrostatic adsorption, neutralization precipitation, ion exchange, and surface complexation. • Provided a broad picture of the management and reuse possibilities of fishery wastes and natural mineral resources. A low-cost composite adsorption material has been synthesized from fishery wastes and natural minerals to address challenges such as ecological balance destruction caused by high concentrations of Pb and Cd in acid mine drainage (AMD), unreasonable use of low-caloric lignite, and environmental pollution caused by idle accumulation of oyster shells. This new adsorbent can effectively treat AMD by improving acidity and adsorbing Pb2+ and Cd2+. In this study, oyster shell-modified lignite composite in globular shape (OSL-G) was synthesized by using pyrolyzed oyster shell and lignite, with the addition of bentonite adhesive. The adsorption properties of OSL-G on AMD were evaluated, and the potential mechanism of OSL-G repairing AMD was explored. The results showed that when the mass ratio of oyster shell to lignite was 1:1, oyster shell-modified lignite composite (OSL) was synthesized at 900 °C for 20 min. When the adhesive content was 15.50 %, the roasting temperature was 640 °C, and the roasting time was 2.35 h, OSL-G was synthesized and the adsorption effect was the best. The OSL-G could effectively treat AMD with pH 4 ∼ 5 and initial Pb2+ and Cd2+ concentrations of 10 mg/L within 600 min at a dosage of 4 g/L. The OSL-G adsorption process followed the quasi-second-order kinetic model and the Freundlich model. The maximum adsorption saturation capacities of Pb2+ and Cd2+ were 107.2821 mg/g and 8.3777 mg/g at 298.15 K, respectively. The adsorption process was a multistep controlled spontaneous endothermic process. The potential mechanism was mainly the adsorption-condensation coexistence results of electrostatic adsorption, neutralization precipitation, ion exchange, and surface complexation. The removal rates of Pb2+ and Cd2+ of the recovered OSL-G (ROSL-G) were still high, reaching 57.26 % and 50.38 % after 5 times of adsorption–desorption, respectively. The applicability of ROSL-G after adsorption–desorption for other heavy metal components in AMD proved its good application potential. This study suggested that OSL-G can be used as a promising environmentally friendly adsorbent for AMD. This study provided a broad picture of the management and reuse possibilities of fishery wastes and natural mineral resources, and addressed established, current, and potential strategic needs, particularly in terms of sustainability challenges and ecological civilization construction. [ABSTRACT FROM AUTHOR]

The Huelva estuary is formed by the common mouths of the Odiel and Tinto Rivers, and inside this ecosystem is the biosphere reserve of the Odiel saltmarshes. This ecosystem has been historically affected by acid mine drainage (AMD) and by releases of pollutants from five phosphoric acid industrial plants and phosphogypsum (PG) waste stacks located in the area. This study carried out a comprehensive assessment of the environmental impact of the biosphere reserve of the Odiel saltmarshes. To this end, it was necessary to find a suitable sedimentary background (Piedras River in our case). To quantify this impact, several pollution indexes were used. According to the values reached by the indexes, this impact was classified as "serious" pollution for most trace elements, excepting the deepest layers, and "low-moderate" pollution for the 238U-series radionuclides, while no pollution for the 232Th-series and 40K radionuclides was found as expected. [Display omitted] • An exhaustive environmental impact assessment was carried out for Odiel Saltmarshes. • A suitable sedimentary background was necessary to be previously established. • Several pollution indexes were calculated for trace elements and radionuclides. • The pollution due to AMD and PG/fertilizer plants was traced by Fe and P. • Serious pollution was found for trace elements and 238U-series radionuclides. [ABSTRACT FROM AUTHOR]

Bioremediation using microorganisms is an emerging green technology for the remediation of potentially toxic elements (PTEs) in soils and sediments. However, such technology can differently impact PTEs dynamics (e.g., immobilization and mobilization), ultimately affecting the efficiency of the remediation programs. In this study, we aimed to assess different microbial remediation mechanisms triggered by a microbial consortium to bioremediate Fe-rich mining tailings. The tailings were incubated in a mesocosm system for 35 days with increasing colony-forming units (CFU) of a specific microbial consortium (Azospirillum sp., Pseudomonas sp., Saccharomyces sp., and Rhizobium sp.). At the end of the experiment, we determined the geochemical fractionation of Fe and PTEs in the solid phase to assess the effect of treatments on PTE's bioavailability. Increasing the CFU resulted in higher Fe (15%) and Mn (37%) reductive dissolution compared to the control. As a result, the Fe and Mn concentrations in water increased by 9-fold. In addition, microbial consortium decreased the contents of Fe and Mn associated with oxides (-59% and −79%, respectively) and increased the more bioavailable solid fractions. The microbial consortium also efficiently decreased PTEs pseudo total contents in the mine tailings (Cr: −85%, Cd: −61%, Pb: −55%, and Cu: −49%). In addition, lower CFUs increased PTEs dissolved in the drainage water, indicating a potential for assisting other remediation strategies. Lower CFU also induced high Cr biomineralization (94%). In conclusion, our work provides novel evidence of a microbial consortium for remediating Fe mine tailings through different strategies (biodissolution and biomineralization). In view of the effects of the microbial consortium over Fe and Mn oxyhydroxide dissolution rates, further research should test it on microbially assisted phytoremediation protocols. [Display omitted] • Biosorption and biomineralization efficiently bioremediate Fe mine tailings. • Microbial consortium increased Fe (15%) and Mn (37%) reductive dissolution. • Inoculation increased the Fe and Mn concentrations in water by 9-fold. • Microbial consortium decreased Cd, Cr, Cu, and Pb (∼-63%) in Fe mine tailings. • High Cr pyritization (94%) was found in the inoculated Fe mining tailings. [ABSTRACT FROM AUTHOR]

In this study, a series of bentonite-carbide slag (BCS) mineral composites were developed by modifying bentonite with carbide slag using Na 2 CO 3 as activator, to achieve acid neutralization and mineralized immobilization of Cu2+ in acid mine drainage (AMD). The main factors that affect the structure-activity relationship of the BCS particle, such as material ratio, Na 2 CO 3 dosage, calcination temperature, and calcination time, were investigated in detail to determine the influence rules of each factor and the structure-activity relationship of the BCS particle on the immobilized mineralization of Cu2+ via spontaneous film formation. The results indicated that the optimal preparation parameters for BCS particle were as follows: bentonite/carbide slag mass ratio of 3:7, Na 2 CO 3 amount of 10 wt%, calcination temperature of 500℃ and calcination time of 60 min. During the calcination process, Na 2 SiO 3 and C-S-H were formed under the action of the Na 2 CO 3 activator, which were conducive to bonding between the raw material in BCS particle. The mechanism of OH- alkalinity release of endophytic crystal ions in BCS particle, and the mechanism of spontaneous film formation and immobilization mineralization of Cu2+ in AMD were also proposed with the help of SEM, XRD and FT-IR analysis. This study can provide theoretical guidance for the preparation of composite mineral particle material with endophytic crystal ions, as well as the prevention and control of AMD and the recovery of valuable metals from AMD. [Display omitted] • BCS was prepared to achieve acid neutralization and immobilization of Cu2+ in AMD. • A gap was existed between Cu2+-mineralization film and the BCS particle. • The spontaneous film formation and mineralization mechanism was proposed. [ABSTRACT FROM AUTHOR]

The sulfate-reducing bioreactor presents an auspicious approach for eradicating toxic metals from acid mine drainage (AMD). In earlier studies, the incorporation of rice bran as a substrate in bioreactors was observed to foster the proliferation of a diverse range of microorganisms, consequently leading to the undesirable development of biofilms atop the bioreactor. To selectively stimulate sulfate-reducing bacteria (SRB) within the bioreactor, we examined the consequences of introducing three low-molecular-weight substrates in lieu of rice bran under 12 varying conditions. The sulfate reduction performance was marginally impacted by the incorporation of lactate with corn steep liquor (CSL) compared to ethanol or glucose with CSL, and the microbial composition in the presence of lactate differed significantly from those containing ethanol or glucose. The integration of ethanol and glucose with/without CSL efficiently lowered oxidation-reduction potential and promoted the proliferation of Desulfosporosinus -related SRB (relative abundance: ∼26.6%). Given that the employment of glucose initially activated fermentative bacteria such as Clostridium spp., ethanol emerged as an efficacious alternative substrate to rice bran, which directly fosters the accumulation of Desulfosporosinus sp. without encouraging the growth of other microorganisms that contribute to the unwanted formation of biofilms within the sulfate-reducing bioreactors employed in AMD treatment. [Display omitted] • A sulfate-reducing bioreactor was applied to treat acid mine drainage containing zinc. • Developed bioreactor offers the advantages of being easy to handle. • Microbial compositions were associated with ORP, DO, sulfate, and acetate concentrations. • Addition of ethanol led to the early-stage accumulation of Desulfosporosinus -related SRB. [ABSTRACT FROM AUTHOR]

Lab-scale stirrer bubble and lab-scale stepped continuous flow capillary columns were developed to neutralize lime precipitation treated slaughterhouse wastewater (SWW) and recover the volatilized ammonia, using atmospheric CO 2. These experiments were carried out using central composite design based on the response surface methodology. The carbonation process occurred in both processes. For the bubbling process, numerical optimization indicated a final pH of 8 with calcium and ammonium nitrogen removals of 76.0 and 66.2%, respectively, applying 21 h, air flow rate at 65 L h−1, the stirring speed at 52 rpm, and SWW volume at 178 mL. It was also observed that increasing the air flow rate can avoid the stirring step. For the capillary process, a pH of 8.2 and calcium and ammonium nitrogen removals of 81.0 and 57.5% were achieved, applying a SWW flow rate at 1.2 mL min−1, air flow rate at 90 L h−1, and capillary area at 700 cm2. Under optimal conditions, the flow capillary column was able to neutralize different SWW volumes, 178–478 mL, without significant differences in the collected samples, with the operation time varying between 4.48 and 10.20 h, respectively. [Display omitted] • Bubbling and capillary processes were tested to neutralize alkaline wastewater. • Response surface methodology was used for the optimization of atmospheric CO 2 capture. • Carbonation occurred in both processes but the capillary process had higher CO 2 capture. • The capillarity process remains effective over time regardless of the volume treated. • For both processes studied, the NH 3 capture in the acid medium was about 99±2%. [ABSTRACT FROM AUTHOR]

Electrochemical ellipso-microscopy was combined with the channel flow triple electrode method to evaluate the active-passive transition behavior of Fe-6 mass% Cr in acidic sodium sulfate solutions under the control of mass-transport reaction. During potentiodynamic polarization of the Fe-6 mass% Cr specimen electrode (SE), the SE surface was monitored by ellipso-microscopy and generated Fe(II) and Cr(III) species from the SE were detected at two detector electrodes arranged downstream in parallel. Forced convection of the electrolyte solution affected the mass-transport process of Cr(III) species on the SE surface in the latter half of the active region. In addition, the electrolyte solution flow resulted in enhancement of the passivation process and Cr enrichment on the passive surface. The effects of the electrolyte solution flow on active-passive transition and improvement of the passive film resistance are discussed. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is one of the repercussions that result from earth-moving activities around the sulfide-bearing mineral hosts. The detrimental effects associated with this AMD are driven by its characteristics, which include low pH and high concentrations of sulfate and toxic dissolved metals. Traditionally, the prevention and treatment of AMD are achieved by using technologies that use, amongst other, naturally occurring soils and carbonates. However, the continual use of these materials may eventually lead to their depletion. On the other hand, industrial by-products have been proven to occupying land that could have otherwise been used for profitable businesses. Additionally, the handling and maintenance of landfills are costly. In this current trend of a circular economy that is driven by industrial symbiosis, scientists are concerned with valorizing industrial by-products. One such by-product is the green liquor dregs (GLD) from Kraft mills. The neutralizing and geotechnical properties of these wastes have prompted the research pioneers to seek their potential use in handling the challenges associated with AMD. In this review, the formation AMD, trends in technologies for treatment and prevention of AMD are critically analyzed. This includes the feasibility of using GLD as an alternative, promising sustainable material. [ABSTRACT FROM AUTHOR]

The accessibility of clean water and green environment are the major requirements for survival and sustainable development. In this study, iron-coated sand, derived from acid mine drainage effluent, has been applied as a heterogeneous catalyst. Treatment with H2O2, iron-coated sand, and iron-coated sand-Fenton processes is compared for the COD removals from municipal wastewater effluent. The results showed that the iron-coated sand catalyzed Fenton process could generate hydroxyl radicals (•OH) and oxidize the organic pollutants. Fenton process based on the iron-coated sand catalyst proved to be the most efficient process. The effect of operating conditions such as initial pH and Fenton's reagent doses, i.e. initial H2O2 and iron on the organics oxidation from such wastewater was investigated. The results showed that 70% removal efficiency of COD was obtained within 30 min under optimized conditions (pH 3.0, H2O2 400 mg/L and iron 40 mg/L). The rate equation of iron-coated sand-Fenton system was simply expressed by the second-order equation and the model was found to fit well the data. Thermodynamic analysis of the results indicated that the iron-coated sand-Fenton oxidation is non-spontaneous and endothermic in nature. Regeneration of iron-coated sand was attempted and the catalyst had a good stability and reusability for successive treatments and reducing the quantity of sludge produced in Fenton reactions. Thus, expanding the sustainability scope of iron-coated sand based Fenton catalyst and offer new sustainable and inexpensive alternatives for the classical Fenton process. Article Highlights: Iron recovered from acid mine drainage to prepare iron coated-sand as a Fenton source. Novel Fenton reaction is proposed for treating polymer industry wastewater. The system avoids iron sludge by-product by providing catalyst reusability. The approach points the competitive novel iron waste source to applied as a Fenton technology. [ABSTRACT FROM AUTHOR]

Coal mining is one of the anthropogenic activities that pose serious threats to environment. The coal fields of Salt Range which have the largest coal reserves in Punjab, Pakistan were visited and sampled for soil and water in order to determine the status of pollution around coal mines. Soil sample were collected from the rhizosphere of coal fields after removing the layer of mine spoils from it while water samples were collected from those coal fields only which were draining water from mines. Afterwards the soil and water samples were tested for presence of acidity or alkalinity, hardness, salinity and metal toxicity. The study of soil and water attributes corroborated the presence of alkaline as well as acidic nature of Mine Drainage with a higher level of TDS, salinity and metal toxicity in soil and water. Among heavy metals, Iron followed by Manganese contributed the most in metal toxicity across the mines. The study also confirmed the spread of mine spoils to a larger area with a course of drains to towards River Jehlum which may spread the pollution on a larger scale. Moreover a large variation was observed in pollution around the mines where the site with combined effluents of Salt & Coal Mines and Alkhair Coal Mines were indicated as the most polluted sites of the area. The Agglomerative Hierarchical Clustering (AHC) of soil samples revealed that the samples taken from Munarah Hills (site with no mine spoil or mine drainage) was different from all other sites which validate the role of coal mines in spreading pollution across the area. [ABSTRACT FROM AUTHOR]

• Fe(II) and Al(III) in real AMD were sequentially recovered. • Selective precipitation of iron depended strongly on solution pH. • Al recovery as α-Al(OH) 3 crystals in a continuous FBHC. • Removals of iron and aluminum reached 99.7% and 99.5%, respectively. • FBHC of AMD could bring about a profit of $1.31/m3-AMD. Acid mine drainage (AMD) released from gold and coal mining contains a large quantity of heavy metals, thus being a threat to the surrounding ecosystem. The recovery of metals from AMD can both address the potential contamination and bring more economic profits. In this study, the sequential selective precipitation and fluidized bed homogeneous crystallization (FBHC) were integrated to recover iron(II) and Al(III) from real AMD wastewater. The selective precipitation of Fe was optimized by adjusting pH. The FBHC recovery of Al performed its best at pH 9.25 ± 0.2, molar ratio of [H 2 O 2 ]/[Al(III)] = 2.0 and up-flow velocity (U) = 30.5 m/h. Iron(II) and Al(III) were recovered in the form of iron hydroxide (Fe(OH) 3) and bayerite (α-Al(OH) 3) pellets. Removal efficiencies were as high as 99.7% and 99.3% for Fe(II) and Al(III), respectively. A brief cost-benefit estimation was performed and showed that the estimated profit gained from field-scale recovery of Fe(II) and Al(III) would be $1.31/m3-AMD. [ABSTRACT FROM AUTHOR]

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Copyright of Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales is the property of Academia Colombiana de Ciencias Exactas, Fisicas y Naturales 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.)

Heavy metal pollution caused by acid mine drainage (AMD) is a global environmental concern. The processes of migration and transformation of heavy metals carried by AMD are more complicated in karst areas where carbonate rocks are widely distributed. Water, suspended particulate matter (SPM), and sediments are the crucial media in which heavy metals migrate and it is important to elucidate the geochemical behavior of AMD heavy metals in these environments. This study tracked AMD heavy metals from release to migration and transformation in a natural river system in a karst mining area. AMD directly impacted the hydrochemical composition of the karst water environment, but the carbonate rock naturally neutralized the acidity of the AMD. AMD heavy metal concentrations decreased gradually after the tributaries from the mining area entered the main river, with the metals tending to accumulate in SPM and sediments. The forms in which heavy metals were present were influenced by pH and their relative concentrations. Raman spectroscopy and transmission electron microscopy of sediments from the mining area suggested that the presence of an iron phase plays an important role in the fate of AMD-derived heavy metals. It is, therefore, necessary to elucidate the mechanisms of iron phase precipitation from sediments in order to control AMD-derived heavy metals in karst mining areas. This study improves our understanding of the geochemical behavior of heavy metals in karst environments and provides direction for the prevention and control of AMD in affected areas. [Display omitted] • Mechanisms of heavy metals migration in karst mining areas are elucidated. • Heavy metals migrate mainly in suspended particulate matter and sediments. • Goethite and jarosite are the dominant Fe phases in sediments. • Iron phase precipitation is central to the control of acid mine drainage pollution. [ABSTRACT FROM AUTHOR]

High altitude (alpine) lakes are efficient sentinels of environmental processes, including local pollution and long-range atmospheric transfer, because these lakes are highly vulnerable to ongoing climate changes and increasing anthropogenic pressure. Towards improving the knowledge of trace element geochemistry in the water column of alpine lakes, we assessed 64 physico-chemical parameters, including macro- and micronutrients, major and trace element concentrations in the water column of 18 lakes in the Pyrenees, located along the border between France and Spain. Lake depth, morphology, retention time and watershed rock lithology did not exhibit sizable impact on major and trace element concentrations in the water column. However, acidic (pH = 4.7 ± 0.2) lakes were distinctly different from circumneutral lakes (pH = 6.8 ± 0.5) as they exhibited >10 times higher concentrations of SO 4 2− and trace metals (Fe, Mn, Zn, Cd, Pb, Co, Ni, Be, Al, Ga and REEs). While some of these elements clearly mark the presence of sulphide-rich minerals within the watershed (Fe, Zn, Cd and Pb), the increased mobility of lithogenic elements (Be, Al, Ga and REEs) in acidic lakes may reflect the leaching of these elements from silicate dust derived from atmospheric deposits or surrounding granites. At the same time, compared to circumneutral lakes, acidic lake water displayed lower concentrations of dissolved oxyanions (As, Mo, V, B and W) and elevated SO 4 2− concentrations. The latter could lead to efficient Ba removal from the water column. The exploitation of metal ores within the watershed of three lakes clearly impacted high Zn and Cd concentrations observed in their water column, despite two of these lakes not being acidic. We conclude that local impacts have a greater effect on the water column than long-range atmospheric inputs and that dissolved trace element concentration measurements can be used for revealing sulphide-rich minerals or acid mine drainage within the lakes' watershed. [Display omitted] • Dissolved major and trace elements in water column of 18 alpine lakes. • Solute sensitivity to local lithological context and long-range atmospheric input. • Sulphide mineral weathering controls trace metals in the water column. • Acidic, sulphate-rich waters are rich in trace metals and trivalent lithogenic elements. • Oxyanions are depleted in acidic lakes due to adsorption on mineral particles. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is a form of environmental pollution from mining activity that can negatively affect soil environments by acidification, salinisation, and metal(loid) contamination. The use of plants to remediate (phytoremediation) these impacted environments while generating plant-based value is a promising approach to more accessible and cost-benefiting restoration of post-mining, marginal lands. In this study, a 3-month growth-chamber pot experiment was conducted to investigate the influence of co-cropping two plant species, Chrysopogon zizanioides (vetiver grass) and the legume Medicago truncatula (barrel clover) with a wheat straw biochar amendment on the phytostabilisation of metal(loid)s Cr, Zn, and As and the phytoextraction of rare earth element (REE) in an AMD impacted soil from a gold mining region in South Africa. The results showed that co-cropping with vetiver significantly lowered the legume's Cr, Zn, and As root contents by 80%, 32% and 54%, respectively, and improved the plant's overall metal(loid) tolerance by increasing its translocation from root to shoot tissue. The biochar further inhibited root uptake of Cr and Zn, by 71% and 36%, and increased the legume biomass by 40%. Both plant species and cropping treatments exhibited low REE extraction capabilities by shoot tissue, which accounted for less than 0.2% of total soil REE contents. The study shows that co-cropping with vetiver and biochar amendment are effective tools for the phytoremediation of AMD impacted soil mainly by lowering plant uptake and improving plant metal(loid) tolerance. Likely mechanisms at play include the alteration of rhizosphere chemistry and species-specific physiological and molecular responses. These effects offer support for the phytostabilisation of AMD impacted soil with the generation of plant-based value through dual (and safe) cultivation (phytoprotection) rather than through REE recovery from plant biomass (phytoextraction). These techniques could allow for the simultaneous restoration of post-mining, mining-impacted and marginal lands with agricultural production. [Display omitted] • Co-cropping was investigated as a phytoremediation tool for acid mine drainage impacted soil. • A vetiver grass and legume co-cropping system improved plant metal tolerance. • Vetiver grass could be used for phytoprotection and phytostabilisation in mining polluted soil. • Co-cropping was not an effective strategy for phytoextraction of rare earth elements. [ABSTRACT FROM AUTHOR]

Perfluorooctanoic acid (PFOA) has been widely utilized, leading to serious contamination. Iron (hydr)oxide transformation was varied in media. Whereas, dynamic transformation effect was extensively unclear. Here, iron (hydr)oxide dynamic transformation-induced PFOA transport and attenuation was investigated by emphasizing initial goethite (α -FeOOH) and associated minerals content and groundwater type based on the multi-process attenuation model. Results revealed that groundwater type did not affect the PFOA attenuation pathway. However, it controlled the iron (hydr)oxide dynamic transformation differences. PFOA transport behavior (retardation factor R from 2.61 to 1.91) was significantly affected by iron (hydr)oxide dynamic transformation. Iron (hydr)oxide transformation induced the greatest PFOA transport risk (R = 1.91, attenuation rate λ = 0.0001 min−1) in SO 4 2− environment, where complex α -FeOOH, Fe 3 O 4 , and β -Fe 2 O 3 ·H 2 O transformed to simplex β -FeOOH, leading to instantaneous (K d) and kinetic (α) two-site sorption fraction change. Furthermore, the associated mineral Fe 3 O 4 of goethite was crucial in PFOA attenuation (λ from 0.0001 to 0.0002 min−1). Fe 3 O 4 released Fe2+ and the oxidation of Fe2+ to Fe3+ provided electrons, facilitating the formation of F–(CF 2) 7 –COO· radicals, which played a key role in the following cycle attenuation process. This study provides a theoretical basis for understanding the interaction mechanism of PFOA and iron (hydr)oxide dynamic transformation under groundwater differences. [Display omitted] • Associated mineral Fe 3 O 4 (releasing Fe2+) of goethite plays a key role in PFOA attenuation. • Groundwater type control iron (hydr)oxide dynamic transformation differences. • PFOA transport behavior is significantly affected by iron (hydr)oxide dynamic transformation. • Iron (hydr)oxide transformation induces the greatest PFOA transport risk in SO 4 2− groundwater. • SO 4 2− environment-induce α -FeOOH, Fe 3 O 4 , and β -Fe 2 O 3 ·H 2 O transform to β -FeOOH. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is widely acknowledged as a substantial threat to the biodiversity of aquatic ecosystems. The present study aimed to study the toxicological effects of Cu-rich AMD from the Sulitjelma mine in zebrafish larvae. The AMD from this mine was found to contain elevated levels of dissolved metals including Mg (46.7 mg/L), Al (20.2 mg/L), Cu (18.3 mg/L), Fe (19.8 mg/L) and Zn (10.6 mg/L). To investigate the toxicological effects, the study commenced by exposing zebrafish embryos to various concentrations of AMD (ranging from 0.75% to 9%) to determine the median lethal concentration (LC 50). Results showed that 96 h LC 50 for zebrafish larvae following AMD exposure was 2.86% (95% CI: 2.32–3.52%). Based on acute toxicity results, zebrafish embryos (<2 hpf) were exposed to 0.1% AMD (Cu: 21.7 µg/L) and 0.45% AMD (Cu: 85.7 µg/L) for 96 h to assess development, swimming behaviour, heart rate, respiration and transcriptional responses at 116 hpf. Light microscopy results showed that both 0.1% and 0.45% AMD reduced the body length, eye size and swim bladder area of zebrafish larvae and caused phenotypic abnormalities. Swimming behaviour results showed that 0.45% AMD significantly decreased the locomotion of zebrafish larvae. Heart rate was not affected by AMD exposure. Furthermore, exposure caused a significant increase in oxygen consumption indicating vascular stress in developing larvae. Taken altogether, the study shows that even heavily diluted AMD with environmentally relevant levels of Cu caused toxicity in zebrafish larvae. [Display omitted] • Acid mine drainage (AMD) is a threat to aquatic organisms. • Copper-rich runoff from mines causes phenotypic deformities in fish larvae. • Swimming behavior and respiration impaired by diluted AMD. • Thousand-fold diluted ADM causes toxicity in zebrafish larvae. [ABSTRACT FROM AUTHOR]

"The generation of acidic leachates from phosphogypsum (PGL) stacks is a global problem due to their high pollutant concentrations (As, Cr, Cd, Cu, Ni, Zn, F-, PO 4 3-, SO 4 2-, 210Po and 238,234U). The cleaning treatment of the PGL by neutralization with alkaline reagents is a proper option for removal of pollutants by (co)-precipitation. This study is focused on the characterization of the wastes generated along the cleaning process of PGL using CaCO 3 and Ca(OH) 2 with the aims of diagnosis for their valorization. In addition, a chemical modelling was performed to obtain a general guide on the precipitation behavior (cleaning) of the chemical species when the pH is increased. The main finding was that the fluorine is removed from dissolution as fluorite at pH around 3, precipitating with some gypsum. Nevertheless, calcium phosphate dominates the precipitated phase during the alkaline treatment, where monetite and brushite are the prevailing species formed at neutral pH range and fluorapatite in more basic conditions. These species contain very high concentrations of toxic chemical species and 238U-series radionuclides (mainly 238U-isotopes and 210Pb). Therefore, it is needed to design a valorization process for these two generated wastes, which could contribute to the circular economy and the improvement of the environmental conditions of the PG stacks surroundings." • Phosphogypsum leachates were decontaminated by using CaCO 3 and Ca(OH) 2. • The composition of solids depends on pH and neutralization reagent employed. • Chemical speciation modelling agreed with experimental results. • Major solids are fluorite (pH = 3), and fluorapatite (pH > 7). [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) discharge, particularly from the North Eastern Coalfield (NEC), Assam, has been a major persistent ecological threat. A lab-scale constructed wetland (CW) deriving organic wastes as the wetland media was implemented to treat high acidity (724 mg L–1 as CaCO 3) AMD loaded with sulfate (1000–1300 mg L–1). Metal contents in mine wastewater comprised iron, aluminium, manganese, zinc, cobalt, nickel and chromium as 104, 25, 6.2, 5.1, 1.1, 1.1 and 1.1 mg L–1, respectively. CW operated continuously at a hydraulic loading rate (HLR) of 0.03 m3 m–2 d–1 for 282 days. Effluent water quality was monitored, and resulting shifts in microbial diversity were identified. Results demonstrated 771 mg L–1 (as CaCO 3) alkalinity in effluent and metal removal (87–100%), except Co and Mn, which surpassed effluent discharge criteria. Further, the high-throughput sequencing results revealed significant reformations in bacterial assemblages throughout the operational period. Proteobacteria (45%) and Bacteroidetes (26%) represented the major bacterial groups at the start-up of CW, which later declined due to the elimination of aerobic strains under anaerobic conditions. Additionally, methanogenic archaea suppressed greatly due to the competition from sulfate and iron-reducers. An increase in the relative abundances of key functional bacteria (Firmicutes, Bacteroidetes, Actinobacteria and Acidobacteria) in the treatment phase indicated stable operation. Sulfate reduction (62%) was partial, evidenced by the prominence of sulfate-reducing bacteria (SRB) (Thermodesulfobium , Syntrophobacter , Desulfomonile and Desulfovibrio). This study offers insights into the microbial dynamics within an organic-media-amended CW, which directly influences AMD treatment. [Display omitted] • Effectiveness of HSSF-CW (C) in AMD remediation using organic wastes. • Improvement in effluent pH with residual alkalinity (380–1300 mg L–1 as CaCO 3). • Safe effluent discharge concerning metals (87–100%) and sulfate (24–84%) removal. • Microbial dynamics controlled long-term bio-transformation of metals and sulfate. • Emergence and existence of competition from sulfate-reducing bacteria (SRB). [ABSTRACT FROM AUTHOR]

Pyrite-containing tailings pose an environmental challenge due to the risk of Acid Mine Drainage (AMD) upon storing if not properly managed. AMD can, however, be neutralized with alkali materials like lime which leads to the generation of gypsum that also ends up in the landfill. Instead of landfilling this residue, it can be recycled into potentially useful products. A proposed process involves decomposing pyrite, reduction of pyrrhotite, and finally conversion of gypsum to lime. This study evaluates the recycling/thermochemical conversion process of pyrite tailings and gypsum residues from the Boliden Aitik mine using thermodynamic modeling, simultaneous thermal analyses coupled with mass spectroscopy, and mineralogical composition identification. It was observed that pyrite can undergo complete decomposition into pyrrhotite and release elemental sulfur below 750 °C in an inert atmosphere. Furthermore, successful reduction of pyrrhotite was achieved through the application of biochar in the presence of lime at 950 °C in an inert atmosphere. The study also reveals that gypsum can be effectively converted to lime at 1200 °C in an inert atmosphere when accompanied by calcium sulfide (CaS). Moreover, the energy and material balance of the process was analyzed, considering the conversion of 1 ton of pyrite tailings. The products include 0.4 tons of iron powder, 2.7 tons of SO 2 gas, 0.4 tons of CO 2 gas, and 1.21 tons of excess active lime. The calculated energy consumption for this process was determined to be 2893 kWh. [Display omitted] [ABSTRACT FROM AUTHOR]

We report a preliminary assessment of ferrate [Fe(VI)] for the treatment of acid mine drainage (AMD), focused on precipitation of metals (i.e., iron [Fe] and manganese [Mn]) and subsequent removal. Two dosing approaches were studied to simulate the two commercially viable forms of Fe(VI) production: Fe(VI) only, and Fe(VI) with sodium hydroxide (NaOH). Subsequent metal speciation was assessed via filter fractionation. When only Fe(VI) was added, the pH remained <3.6, and the precipitation of Mn and Fe was <30 and <70%, respectively, at the highest, stoichiometrically excessive Fe(VI) dose. When NaOH and Fe(VI) were added simultaneously, precipitation of Mn was much more complete, at doses near the predicted oxidation stoichiometric requirement. The optimal dosage of Fe(VI) for Mn treatment was 25 μM. The formation of Mn(VII) was noted at Fe(VI) dosages above the stoichiometric requirement, which would be problematic in full‐scale AMD treatment systems. Precipitation of Fe was >99% when only NaOH was added, indicating that oxidation by Fe(VI) did not play a significant role when added. The Fe(III) and Al(III) particles were relatively large, suggesting probable success in subsequent removal through sedimentation. Resultant Mn‐oxide particles were relatively small, indicating that additional particle destabilization may be required to meet Mn effluent goals. Ferrate seems viable for the treatment of AMD, especially when sourced through onsite generation due to the coexistence of NaOH in the product stream. More research on the use of Fe(VI) for AMD treatment is required to answer extant questions. Core Ideas: Ferrate is likely a viable option for acid mine drainage treatment.Oxidation of manganese with ferrate and NaOH approached stoichiometric prediction.Resultant particles may challenge downstream clarification. [ABSTRACT FROM AUTHOR]

Abstract The biological responses of acidobiontic species to extremely acidic waters, as those related with Acid Mine Drainage (AMD) processes, are relevant not only to understand the toxicological degree of the waters as well as the mechanisms responsible for the survival and adaptation of such organisms. Therefore, the objective of this study was to evaluate the effect of acidic pH and metals in biofilms collected in two sites a lentic permanent acid pond (AP) and a temporary acid stream (AS) affected by Acid Mine Drainage (AMD), and taking as control (C), an uncontaminated site with circumneutral pH. The results showed typical conditions of AMD-contaminated waters in sites AS and AP (pH < 3 and high concentrations of Al, Cu, Fe, Mn, Pb and Zn), which are responsible for a substantial decrease in biomass and biodiversity of biofilms (with a dominance of acidobiontic species, such as Pinnularia aljustrelica and Eunotia exigua , comparing to the control site. Also expressed by low values of photosynthetic pigments and reduced amount of proteins. In addition, such extreme acidic conditions also induced biofilms' stress, increasing antioxidant [catalase (CAT), superoxide dismutase (SOD) and biotransformation glutathione S-transferases (GSTs)] enzymes activity and also membrane damage (peroxidized lipids). However, despite the quite similar physico-chemical conditions of both AMD-contaminated sites, differences in the toxicity status between them were indirectly detected through some of the biochemical parameters [GSTs, SOD and CAT], indicating site AS has the most toxic, which fact was attributed to the higher concentrations of Pb2+ in this water. This element is recognized to be highly toxic for biota, and in such acidic conditions remains in solution, easily available to the aquatic organisms. Since pH is similar in the acid sites, the different concentrations of heavy metals in the waters might be responsible for the observed changes in the biological community at these two sites. This fact was translated in a higher capacity of this site's biofilm to cope with the negative effects of the toxicants, evidenced in a higher positive correlation with GSTs, CAT and SOD when compared to biofilms of sites AP and C. Highlights • Lentic and temporary water bodies affected by AMD have different biological behavior. • Antioxidant/biotransformation enzyme activities are higher in AMD affected sites. • Antioxidant/biotransformation enzyme activities determinated from field samples is a new approach. • AMD affected sites have a predominance of acidobiontic species. [ABSTRACT FROM AUTHOR]

Pyrite weathering often occurs in nature and causes heavy metal ion pollution and acid mine drainage during the process. Humic acid (HA) is a critical natural organic material that can bind metal ions, thus affecting metal transfer and transformation. In this work, in situ electrochemical techniques combined with spectroscopic analysis were adopted to investigate the interfacial processes involved in pyrite weathering with/without HA. The results showed that the pyrite weathering mechanism with/without HA is FeS 2 → Fe2+ + 2S0 + 2e−. The presence of HA did not change the pyrite weathering mechanism, but HA adsorbs on the pyrite surface and inhibits the further transformation of sulfur. Furthermore, HA and Fe(II) ions can form complex at 45.0 °C. Increased concentration of HA, decreased HA solution acidity or decreased environmental temperature would all weaken the pyrite weathering, for the above conditions cause pyrite weathering to have a larger resistance of the double layer and a larger passive film resistance. Pyrite will release 73.7 g m−2·y−1 Fe2+ to solution at pH 4.5, and the amount decreases to 36.8 g m−2·y−1 in the presence of 100 mg/L HA. This study provides an in situ electrochemical method for the assessment of pyrite weathering. In-situ electrochemical method combined with spectroscopic techniques was succeeded used to assessment the galena weathering environmental effects with/without HA. Image 1 • HA does not change pyrite weathering mechanism but binds Fe2+ at 45.0 °C. • Higher C HA , pH or lower T weakened pyrite weathering for electrochemical character. • 73.7 and 36.8 g m−2·y−1 Fe2+ released at pH 4.50 when without/with 100 mg/L HA. [ABSTRACT FROM AUTHOR]

In May 2017, a spill from La Zarza pit lake (SW Spain) resulted in the release of approximately 270,000 m3 of extremely acidic waters to the Odiel River. Around 780 × 103 kg of Fe, 170 × 103 kg of Al, 2.15 × 103 kg of As and high amounts of other trace metals and metalloids were spilled. The purpose of this study is to explain the causes, consequences and impacts of the mine spill on the receiving water bodies. To this end, an extensive sampling along the mine site, river and estuary as well as a hydrological model of the pit lake was performed. Around 53 km of the Odiel River's main course, which was already contaminated by acid mine drainage (AMD), were affected. The mine spill resulted in an incremental impact on the Odiel River water quality. Thus, dissolved concentrations of some elements increased in the river up to 450 times; e.g. 435 mg/L of Fe and 0.41 mg/L of As. Due to low pH values (around 2.5), most metals (e.g., Cu, Zn, Mn, Cd) were transported in the dissolved phase to the estuary, exhibiting a conservative behavior and decreasing their concentration only due to dilution. However, dissolved concentrations of Fe, Cr, Pb, Se, Sb, Ti, V and especially As decreased significantly along the river due to Fe precipitation and sorption/coprecipitation processes. At the upper zone of the estuary, a noticeable increment of metal concentrations (up to 77 times) was also recorded. The water balance illustrates the existence of groundwater inputs (at least 16% of total) to the pit lake, due probably to local infiltration of rainwater at the mining zone. The probable existence of an ancient adit connected to the pit lake indicates that potential releases could occur again if adequate prevention measures are not adopted. Image 1 • Around 270,000 m3 of extremely acidic waters were spilled from a pit lake. • An incremental impact after the spill on the already polluted Odiel River and estuary was observed. • Al, Cd, Co, Cu, Mn, Ni, Sc, U and Zn were conservatively transported to the estuary. • Cr, Fe, Se, Pb, Ti, Sb, V and As were removed from water by precipitation/sorption. • The pit lake has not yet reached equilibrium, a new spill could occur in the future. "An accidental discharge (270,000 m3 of acidic and metal-rich waters) from an abandoned pit lake to the Odiel River and its estuary caused a significant additional increase in the contaminant levels". [ABSTRACT FROM AUTHOR]

Thallium (Tl) is a well-recognized hazardous heavy metal with very high toxicity. It is usually concentrated in sulfide minerals, such as pyrite (FeS 2), sphalerite (ZnS), chalcopyrite (CuS) and galena (PbS). Here, this study was carried out to investigate the indigenous microbial communities via 16S rRNA gene sequence analysis in typical surface sediments with various levels of Tl pollution (1.8–16.1 mg/kg) due to acid mine drainage from an active Tl-containing pyrite mining site in South China. It was found with more than 50 phyla from the domain Bacteria and 1 phyla from the domain Archaea. Sequences assigned to the genera Ferroplasma , Leptospirillum , Ferrovum , Metallibacterium , Acidithiobacillus , and Sulfuriferula manifested high relative abundances in all sequencing libraries from the relatively high Tl contamination. Canonical correspondence analysis further uncovered that the overall microbial community in this area was dominantly structured by the geochemical fractionation of Tl and geochemical parameters such as pH and Eh. Spearman's rank correlation analysis indicated a strong positive correlation between acidophilic Fe-metabolizing species and Tl total , Tl oxi , and Tl res. The findings clarify potential roles of such phylotypes in the biogeochemical cycling of Tl, which may facilitate the development of in-situ bioremediation technology for Tl-contaminated sediments. Image 1 • Peculiar microbial community was revealed in typical Tl-contaminated watershed. • Fe and S-cycling related bacteria were enriched in sediments with elevated Tl content. • Microbial communities were mainly shaped by Tl fractions and geochemical parameters. • Fe-metabolizing species were positively correlated with Tl fractions. • The findings may facilitate the in-situ bioremediation of Tl pollution. The relationship of thallium exposure and microbial diversity in the pyrite mining affected sediments was uncovered in an in-situ study. [ABSTRACT FROM AUTHOR]

Silicic acid and soluble Fe are among the most abundant components in acid mine drainage. During the oxidation of Fe(II), the interaction between silicic acid and freshly formed Fe oxides might change the colloidal dynamics, altering surface charge properties. However, the effects of silicic acid on colloidal Fe oxides formed from acid mine drainage are not fully understood. In this work, we examined the colloidal dynamics of freshly formed Fe oxides in synthetic acid mine drainage (prepared from FeSO4 solution) under the effect of silicic acid as a function of changes in pH and ionic strength. The results demonstrate that through adsorption, silicic acid progressively slows oxidation and enhances the dispersion of freshly formed Fe oxides by shifting the surface charge toward more negative values. This effect was most prominent between pH 5 and 9. The current results demonstrate that silicic acid enhances the dispersion and transport of freshly formed Fe oxides and suggest that aggregation‐based techniques for the treatment of Fe‐rich drainage may require further consideration of this effect. Core Ideas: Silicic acid may occur at a significant concentration in Fe‐rich acid mine drainage.During the oxidation of Fe, silicic acid can react and modify the Fe oxide surface charge.By shifting the surface charge to lower levels, silicic acid can favor Fe oxide dispersion.Silicic acid can thus promote the transport of acid mine drainage‐derived Fe(III) oxides. [ABSTRACT FROM AUTHOR]

Abstract Freshwater contamination with mining waste can result with high concentrations of toxic metals in the water and in fish organs. In North-Eastern Macedonia, several rivers (e.g., Zletovska, Kriva) are exposed to acid mine drainage from active Pb/Zn mines. Previous studies confirmed high concentrations of dissolved metals in their water. This study was performed in liver and gills of Vardar chub (Squalius vardarensis Karaman, 1928) from three Macedonian rivers (Bregalnica, Kriva and Zletovska) in spring and autumn 2012. The aim was to establish if increased exposure to certain metals have resulted with their increased bioaccumulation. The concentrations of 19 elements were measured in cytosolic tissue fractions, to obtain information on metabolically available metal species. The following ranges of cytosolic concentrations of highly toxic elements were measured in the Vardar chub liver (in μg/L): Cd, 1.18–184; Cs, 0.25–25.4; Tl, 0.02–5.80; Pb, 0.70–61.1. Their ranges measured in the gills (in μg/L) were the following: Cd, 0.24–59.2; Cs, 0.39–24.4; Tl, 0.01–1.00; Pb, 0.65–87.2. Although the water of the mining impacted Zletovska River was highly contaminated with several essential metals, especially with Mn and Zn, the majority of essential elements (Na, K, Ca, Mg, Co, Cu, Fe, Mn, Mo, and Zn) did not reflect the exposure level. In contrast, seven nonessential elements reflected the level of exposure in the water. Significantly increased hepatic and gill concentrations of Cs, Rb, Sr, and Tl were detected in Vardar chub from the Zletovska River compared to the other two rivers, of Cd and Pb in the Zletovska and Kriva River compared to Bregalnica, and of V in the Bregalnica River compared to Zletovska and Kriva rivers. Observed significant metal bioaccumulation, in particular of highly toxic elements, as a consequence of exposure to water contaminated with mining waste points to necessity of intensified supervision of mining impacted rivers. Graphical abstract Image 100 Highlights • Study of metal pollution of mining impacted rivers of North-Eastern Macedonia. • Analysis of bioaccumulation of 19 elements in gills and liver of Vardar chub. • Essential elements Na, K, Ca, Mg, Co, Cu, Fe, Mn, Mo, Zn kept within narrow ranges. • Toxic elements Cd, Cs, Pb, Rb, Sr, Tl, and V reflected the exposure level. • Pollution of Zletovska River resulted in high toxic metal levels in chub organs. Mining waste presents serious threat and hazard for the health of aquatic animals because it causes high bioaccumulation of very toxic metals, such as Cd, Pb, Cs and Tl, into their organs. [ABSTRACT FROM AUTHOR]