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Zn recovery attempts from a copper-free extreme Acid Mine Drainage with similar to 53 g/L Fe and similar to 2 g/L Zn revealed Fe co-extraction in solvent extraction with 0.9 M D2EHPA or a mixture of 0.72 M D2EHPA and 0.18 M Cyanex 272, and simultaneous precipitation of Fe during zinc sulfide recovery through biogenic sulfide addition. Therefore, alkalinization, solvent extraction with the self-prepared ionic liquid AliCy diluted in kerosene, and combinations of both these methods were studied for the separation of ferric iron (Fe3+) from such water, prior to Zn recovery. The most efficient strategy tested was a solvent extraction cycle with AliCy followed by alkalinization of its aqueous raffinate to pH 3.25 or 3.5. As a result of this approach, similar to 92% of Fe3+ is separated by SX and the remaining is removed by precipitation, with just similar to 12% or similar to 17% Zn losses, respectively. Afterwards, the highest Zn recovery from water resulting from such combination of processes was achieved by precipitation through addition of biogenic sulfide at pH = 3.5. The obtained precipitates are nanoparticles of Wurzite and Sphalerite (ZnS) of sizes between 2 to 22 nm agglomerated into larger structures. This work shows for the first time the potential of AliCy to separate Fe3+ from acidic multimetallic solutions, a known contaminant of several metal recovery processes. METALCHEMBIO info:eu-repo/semantics/publishedVersion

Acid mine drainage is an extraordinarily acidic and highly heavy metal ion-contaminated leachate, seriously threatening the environment. In this work, an industrial solid waste of steel slag is the adsorbent to remediate the simulated acid mine drainage containing a large amount of Fe(II) ions. Due to the excellent physicochemical properties and structures, steel slag exhibited remarkable Fe(II) removal performance. Its maximum removal efficiency was up to 100%. The initial pH, the dosage and particle size of steel slag, and initial concentration of heavy metal ions on Fe(II) removal efficiency were determined. The pseudo-second-order model and Freundlich isotherm model well described the adsorption behavior of steel slag, implying that the adsorption of Fe(II) by steel slag was mainly multilayer chemisorption. The thermodynamic study demonstrated that the adsorption process was endothermic and spontaneous; the enthalpy change was calculated to equal 91.21 kJ/mol. Mechanism study showed that the entire removal process of Fe(II) by steel slag was completed by electrostatic adsorption, chemical precipitation, and surface complexation in cooperation, and the chemical precipitation was the dominant mechanism. Meaningfully, this study provides a valuable strategy and path for engineering applications of AMD remediation by steel slag, which is prospective as an ideal candidate for Fe(II) ions elimination, inspiring the future development of "Treating the wastes with wastes."

Heavy metal pollution is a global environmental problem, and the potential risks associated with heavy metals are increasing. The acid mine drainage (AMD) which is generated by mining activities at Dabaoshan Mine, the largest polymetallic mine in southern China, is harmful to local residents. A detailed regional survey of the ecological and human health risks of this polluted area is urgently needed. In this study, eight sediments and farmland samples were collected along the flow direction of tailing wastewater and Fandong Reservoir; the content of multiple heavy metals in these samples was determined by inductively coupled plasma mass spectrometry. The biological toxicity of water-soluble extracts from the samples was further assessed by referring to different endpoints of Caenorhabditis elegans (C. elegans). The relationship between specific heavy metals and biological toxicity was estimated by partial least squares regression. The results indicated that the risk of heavy metals in Dabaoshan mining area was very high (potential ecological risk index = 721.53) and was related to geographical location. In these samples, the carcinogenic risk (the probability that people are induced carcinogenic diseases or injuries when exposed to carcinogenic pollutants) of arsenic (As) for adults exceeded the standard value 1 × 10−4 and indicated that As presented a high carcinogenic risk to adults, while the high risk of non-carcinogenic effects (the hazard degree of human exposure to non-carcinogenic pollutants) in children was related to lead exposure (hazard index = 1.24). In addition, the heavy metals at high concentration in the water-soluble fraction of sediment and farmland soil extracts, which might easily distribute within the water cycle, inhibited the survival rate and growth of C. elegans. Gene expression and enzymatic activity related to oxidative stress were increased and genes related to apoptosis and metallothionein were also affected. In conclusion, the results of chemical analysis and biological assays provided evidence on the toxicity of soil and sediment extracts in the Dabaoshan mining area and advocated the control and remediation of heavy metal pollution around Dabaoshan Mine.

In March 2019, a well was drilled in the north of the Dashu pyrite mining area in southwest China to extract shale gas from below the pyritic layer. This well passed through the karst water at the top of the Maokou Formation, leading to groundwater flowing into the pit in the north of the underground mining area and producing a large amount of acid mine drainage (AMD) by water-rock interactions with sulfur-bearing minerals. On Jan. 4, 2020, under the dual influence of progressive overpressure generated by water storage and AMD erosion, the underground pit’s wall partially collapsed, resulting in over 280 × 103 m3 of highly polluted AMD entering the Dashu River. About 231 × 103 kg of Fe, 171 × 103 kg of Al, 12 × 103 kg of Ni, and a large amount of other metals and trace elements were discharged. The main purpose of this study was to explain the causes, consequences, and effects of this event. Water and sediment samples were collected from the mine, the river, and the estuary, and a hydrological model of the underground pit was developed. The spill seriously affected the water quality of ≈ 16 km of the Dashu River. Given the low pH (≈ 2.5), most of the metals (Fe, Al, Mn, Cu, Zn, etc.) migrating towards the Dashu estuary were dissolved, but because of dilution and neutralization, much of the dissolved metals precipitated as river sediments, due to Fe and Al precipitation, and adsorption and co-precipitation of other metals. The calculated water balance and monitoring of the underground pit water levels show that the water in the pit mainly came from karst water recharge at the top of the Maokou Formation, increasing mine drainage by at least 17.2 m3/h. Without effective action, serious environmental pollution or secondary geological disasters may occur in the future.

The role of iron- and sulfur- oxidizing microorganisms in the generation of acid mine drainage (AMD) from sulfide ores and tailings is widely recognized. The inhibition of these microorganisms is a very important alternative to mitigate AMD formation and its effects on the environment and ecosystems. Parastrephia quadrangularis (commonly known as Tola–Tola) is a xerophytic plant that usually grows very close to or even on mineral processing tailings located in the Puna region of Argentina. We demonstrate that the aqueous extract of P. quadrangularis is capable of inhibiting the growth of Acidithiobacillus ferrooxidans in suspension. The presence of chlorogenic acid, quinic acid, butyl-1caffeoylquinic, ferulic acid, and euparin, which have already demonstrated antimicrobial action, was detected. The inhibition of A. ferrooxidans could be the basis of a possible alternative to inhibit microbial activity in tailings and thus prevent AMD.

Sulfide-containing mine waste was oxidized to produce acid mine drainage, which lead to acidification of surrounding soil and downstream rivers and posed a threat to the surrounding environment. Quartz often coexists with sulfide minerals and affects the oxidation of sulfide minerals. In order to explore the role of quartz in the bio-oxidation of sulfide minerals in mine solid waste, the mixed minerals of quartz and sulfide minerals were bio-oxidized by Acidithiobacillus ferrooxidans. The results showed that quartz could improve the microbial activity and increase the acid production of sulfide minerals. The larger the proportion of quartz in bio-oxidation of sulfide minerals, the less the production of secondary minerals such as jarosite, and the larger the leaching amount of iron and sulfate. This research provides new ideas for speeding up the bio-oxidation of sulfide mineral to remove iron and sulfate. It provides a new way to solve acid pollution caused by oxidation of sulfide minerals.

Acid mine drainage (AMD) is a serious and persistent environmental pollution problem. At present, many studies have focused on the tailings pond's cover systems. This paper introduced the research results of using tin tailings from Laili mountain to make the covering layer of tailings pond. The first part included a detailed description of tailings characterization and acid production potential. On this basis, the hard layer (HL) was prepared and its feasibility as oxidation barrier was evaluated. It was found that when the proportion of tailings waste was 70%, the immobilization efficiency of heavy metals can reach more than 99.45%, and the pH of leaching solution was about 10.8. Moreover, the beneficial effect of solid waste addition on the HL was also verified. This suggests that HL as a post-mining restorative strategy has strong positive influence on pollution control.

Acid mine drainage (AMD) is the biggest environmental problem of water related to the mining industry in many countries. Recently, coal mining and mineral mining industries use various AMD treatment systems. The main problem, however, is the very expensive and long retention times for treatment of AMD. For this reason, biosorption technology has been tested recently as a promising method for AMD treatment. The authors review presently available or potential biosorption methods to remove and detoxify toxic heavy metals and organic pollutants from AMD. Biosorption technology is evolving as an attractive option to supplement conventional AMD treatment. However, a literature review indicates that there is a lack of studies examining biosorption of AMD treatment. This paper examines a range of subjects, including laboratory scale experiments and the commercial application of biosorption for treatment of AMD. Our review paper will help direct future studies on the development of biosorption technology for treating AMD.

The study focuses on the white secondary mineral precipitate and its environmental response formed in acid mine drainage (AMD) at Jinduicheng Mine (Shaanxi, China). The mineral composition of white precipitate was characterized by Scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), X-ray photoelectron spectroscopy (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Inductively coupled plasma-atomic emission spectrometer (ICP-AES), chemical quantitative calculation and PHREEQC software. The white precipitate was a kind of amorphous crystal with the characteristics of a fine powder, and its main elements were O, Al, S, F, OH- and SO42- groups. Moreover, by comparing the mole number of chemical elements, the main mineral composition of the white precipitate was closest to basaluminite. The geochemical simulation result of the PHREEQC software verified that the white precipitate was basaluminite. According to the analysis of water quality characteristics of water samples, basaluminite can reduce the ions content in the AMD and enrich Cu, Ni, Mo, Cr and F ions, showing an excellent self-purification capacity of the water body. These results are helpful to improve the understanding of secondary mineral and its environmental response, and are of great significance for the environmental protection and sustainable development of mining area.

Passive treatment of coal mining derived acid mine drainage (AMD) utilizes natural processes to neutralize acidity and remove dissolved metal contaminants. In some cases, microbial communities develop without human intervention that can induce the removal of harmful AMD components. To better understand how these beneficial processes might develop, we studied the Huff Run system in eastern Ohio, where a portion of the stream was artificially diverted to prevent direct entry of AMD into the stream. There are now two abandoned stream channels that receive raw AMD and we hypothesized that the increased residence time of the AMD in these abandoned channels could reduce the adverse effects of AMD on Huff Run. We tracked seasonal changes in the aqueous chemistry and microbiology in the two abandoned channels, referred to as Farr and Lyons. The Fe, Al, and Mn were partially removed from solution as AMD moved through the Farr channel, with net alkaline water, and abundant Bacillus and Paenibacillus phylotypes. Dissolved Fe was partially removed in the Lyons channel, but neither Al nor Mn were, and the sediments contained abundant phylotypes attributable to Alicyclobacillus sp., which are capable of oxidative precipitation of Fe(II) under acidic conditions. Our results indicate that enhanced AMD retention in abandoned channels can induce contaminant removal and that abiotic and biotic reactions in the channels are influenced by the AMD chemistry.

In this study, the arsenic (As) removal characteristics of a Mn-Fe binary coating formed on waste sand filter of an acid mine drainage treatment facility are investigated. Owing to the Mn-Fe binary coating forming on the surfaces of the sand grains, its potential for arsenic removal, particularly As(III), was evaluated and characterized through batch experiments and x-ray absorption spectroscopy. Sorption isotherms reveal that the Mn-Fe binary coating exhibits comparable removal efficiencies for As(III) and As(V) under low initial As concentrations. However, at higher initial As(III) and As(V) concentrations, the As(III) removal efficiency increases because of newly formed active adsorption sites from reductive dissolution of Mn. The oxidation of the As(III) and reduction of the Mn oxide phases are verified through As K-edge and Mn K-edge X-ray absorption near edge fine structure analysis. The outstanding As(III) removal efficiency of the Mn-Fe binary coating suggests synergy of Fe- and Mn-oxides, highlighting a potential application for this coating system. The natural formation of binary coating through acid mine drainage treatment reported in this study indicates that similar coating can form naturally in other environments, thus, providing plausible natural attenuation processes for arsenic immobilization.

The prevention of acid generation from sulfidic mine wastes is a problem that challenges the global scientific community for decades. A promising strategy is related to the formation of coating layer around sulfides for inhibiting surface oxidation. In the current research, the conditions favoring the formation of an efficient silicate-based coating around pyrite and arsenopyrite were studied, using batch tests. The coating solutions contained silicate-oxyanions, an oxidant (H2O2) and buffered at pH 6. The effect of Si concentration (0.1–50 mM), liquid/solid ratio (5–100 mL/g) and contact time (up to 24 h) was investigated. Pyrite tailings treated with a solution of 1 mM Si/0.1 M H2O2 at L/S:100 mL/g for 24 h resulted in the optimum formation of a coating, which reduced the amount of SO4−2-released by 72%, compared to the sample treated in the absence of Si. However, silicate treatment had a negative effect on arsenopyrite tailings inducing As mobilization.

Large quantities of sludge produced from acid mine drainage (AMD) treatment require proper disposal due to their potential environmental impacts. Sludge handling and disposal practices are used to address the environmental concerns, and they represent significant economic liability. As a sustainable management strategy, utilization of AMD sludge for beneficial applications can not only eliminate or alleviate the need of disposal, but create value from the materials. In particular, coal mine drainage sludge (CMDS) can potentially be used for various applications due to its high ferric content. However, conventional coal mine drainage (CMD) treatment and sludge disposal practices do not necessarily produce sludge with optimal properties for the applications. This calls for development and implementation of application-driven treatment and sludge management practices to generate sludge materials tailored for the target applications. This study systematically characterized causal linkages between various CMD treatment and sludge disposal factors and sludge properties reported in literature. It also reviewed and documented optimum sludge properties for beneficial applications including adsorptive pollution control, microbially facilitated ferric reduction, and catalytic degradation of wastes. The systematic understanding was then used to develop CMD treatment and sludge disposal guidelines that would facilitate production of application-specific sludge materials. Such an application-driven CMDS management approach, if successfully implemented, is expected to bring about modernization of waste management infrastructure and create values in mineral producing regions.

In this research work, isolation of humic acid from coal of Northeastern region of India is reported. The study is also targeted for application of the coal-derived humic acid in acid mine drainage (AMD) water treatment and electrochemical devices. All the obtained results are compared with the standard humic acid and examined the formation of humic acid from the coal. The isolated coal-derived humic acid is found to be high degree of humifications and relatively stable up to about 200 °C. The FTIR study indicates the formation of metal-humic acid complexes. On treatment with acidic water (AMD), the coal-derived humic acid was found to have the ability to remove toxic metal such as (in order) Pb > Cu > Zn > Cd. In addition, the preliminary electrochemical properties of the isolated humic acid are also discussed in the paper. The specific capacitance of the isolated coal-derived humic acid via cyclic voltammetry and charge-discharge analysis is found to be 7 mF/g at scan rate 10 mV/s and 22 mF/g within the potential window 0.4 V, respectively. The charge-discharge cycles are stable for more than 1000 cycles within the potential window 0.4 V. This study will create a new pathway for the further research in this field.

Made available in DSpace on 2022-04-28T19:40:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-09-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A hydrogeological analysis was conducted of aquifer systems within a sulfide-rich tailings pile and underlying rocks at a uranium mine to understand the generation and transport of AMD. A geophysical investigation was carried out along seven transects spaced 30 m apart using electrical resistivity tomography and a Wenner-Schlumberger array. The results were used as input to 2D and pseudo-3D models of resistivity and chargeability parameters. The geophysical results and models contrasted unaffected saturated zones and zones impacted by AMD, in addition to three areas within the tailings with a high sulfide content. The tailings and underlying fractured bedrock aquifer are hydrologically connected, which promotes the exchange of mine-influenced water into the regional aquifer. Releases from the site’s tailings and other wastes can severely affect regional groundwater. Geosciences and Exact Sciences Institute (IGCE) São Paulo State University, 24-A Avenue, 1515, Bela Vista Geosciences and Exact Sciences Institute (IGCE) São Paulo State University, 24-A Avenue, 1515, Bela Vista FAPESP: 2019/14563-3

The discharge of acid mine drainage from abandoned high sulfur (S) coal mines has caused serious pollution in the Shandi River, Yangquan, Shanxi Province. To determine the impact of long-term acid mine drainage on the microorganisms in the river, we collected river sediments from a polluted tributary (Group P) and the mainstream of Shandi River (Group R) to study the bacterial diversity and community composition. The results showed that the tributary was seriously polluted by acid drainage from abandoned coal mines, with the pH value of the sediment being Metallibacterium, Acidiphilium, and Acidithiobacillus, were the dominant genera in Group P samples, while the Group R was dominated by the neutral anaerobic iron-reducing bacteria Geothrix and Geobacter. Results of principal co-ordinates analysis (PCoA) revealed that the bacterial communities are significantly different between groups P and R, and the significant different species were mainly attributed to phylum Proteobacteria, Actinobacteria, and Acidobacteria. The distribution of the microbial community is mainly influenced by pH, and the Fe and Cd concentrations. Metallicactrium, the dominant genus, is negatively correlated with pH (R2 = − 0.95) and positively correlated with Fe (R2 = 0.99), while Geothrix and Geobacter, are mainly affected by the heavy metals. This study determined the impact of river pollution caused by abandoned coal mine drainage, especially on the microbial diversity and community composition within the river sediment.

The mobility of contaminants from mine waste can be assessed using different extraction methods. Aqua regia (AR) extraction is the most commonly used method in Finland. Another method is the analysis of leachate from net acid generation (NAG) tests, which is primarily designed for acid production potential assessment. We investigated the performance of single-addition NAG test leachate analysis and AR extraction in drainage quality prediction, using waste rock and drainage water samples from several Finnish waste rock sites. Our objective was to improve interpretation of the AR and single-addition NAG test leachate analysis results in drainage quality prediction. The AR extraction effectively reflected elements that occurred in elevated concentrations in drainage water, though it over-predicted Al, As, Cd, Co, Cu, and Ni in some circumneutral drainages, and Cr in general. The single-addition NAG test leachate analysis also performed well in assessing the mobility of contaminants including Al and Cr at acid mine drainage sites. As the contaminants tend to precipitate in neutral NAG test solution, the usability of the method in neutral mine drainage cases should be further investigated. Furthermore, the conclusions presented in this study are limited to waste rock samples collected from the surface of piles; future work will examine waste rock history, dump cores, drainage quality changes, etc. in more detail.

This paper evaluates the effect of remediation at the site Banska Stiavnica – Sobov, which has been defined as an environmental burden. Remediation at the site, which is located in the protected landscape area Stiavnicke vrchy in central Slovakia, was undertaken 20 years ago. The area has been officially registered as an environmental burden since 1995. Mining activity induced soil pollution, surface and underground water pollution, destruction of vegetation cover and lower biodiversity at this site. To minimise these threats to the environment, remediation interventions took place from 1995 to 1999. The interventions were aimed at reducing acid mine drainage (AMD) from the heap. Measurements of basic chemical properties at the study area confirmed ongoing acidification, with an effect on soil properties. Acidification of the soil environment is also reflected in the composition of microscopic filamentous fungi, with the main domination of Penicillium species (20) and the random presence of Zygomycota species. The finding of the species Penicillium vulpinum and Trichophaea abundans was of interest. A low similarity of mycocoenoses was confirmed between a plot without vegetation cover or with only very rarely tufts of grass and showing a high level of water erosion (S1) and a plot covered with acidophilic plant species (S2). Similarity was higher between a plot without vegetation cover or with only very rarely tufts of grass and showing a high level of water erosion (S1) and a plot covered by compact meadow vegetation (S3), and the highest similarity was between samples from plots S2 and S3. It was also confirmed that the structure of microfungal communities is directly influenced by soil reaction (pH) and is closely linked to the soil type.

Metal contamination from base metal sulphide mines is a major environmental challenge that poses many ecological and health risks. We examined the metal concentrations in the Dabaoshan mine in South China in water, sediments, and aquatic organisms and their specific characteristics (i.e. size, body tissue, species, and habitat) along the Hengshi and Wengjiang River courses to assess acid mine drainage remediation efforts. Metal concentrations of arsenic, cadmium, chromium, copper, lead, nickel, thallium, and zinc were examined in tissues (i.e. gills, intestines, and muscles) of 17 freshwater species of fish, shrimps, and crabs. Metals in tissues followed the trend: intestines > gills > muscles; nearly all intestine samples exceeded the safe limits of metals analysed in this study. There is a positive correlation between distance from the mine and metal concentrations related to the flow of surface water and the habitat of aquatic organisms. The concentrations of arsenic, copper, and zinc were the highest in aquatic organisms, and the distribution was influenced by physical (distance from mine, currents, and seasonality), chemical (pH and competing ions), and biological (species, habitat, and predator-prey relation) factors. Large demersal fish and benthic fauna had higher concentrations of metals. Bioaccumulation and biomagnification of metals, as well as the high metal pollution index and target hazard quotient (arsenic, cadmium, copper, lead, thallium, and zinc), occurred in bottom feeders (C. aumtus, X. argentea) and fish belonging to higher trophic levels (P. fulvidraco, O. mossambicus). Lead and cadmium indicated the highest level of biomagnification from prey to predator. Health risks exist from the dietary intake of common aquatic species such as tilapia and carp besides crustaceans due to high arsenic, cadmium, lead, and thallium levels. Further reduction of metals is necessary to improve the effects of acid mine drainage in the catchment. Funding Agencies|Linkoping University-Guangzhou University Research Center on Urban Sustainable Development; Natural Science Foundation of Guangdong Province, ChinaNational Natural Science Foundation of Guangdong Province [2018A030310309]; Joshua Wat proofread the thesis for WSC

Treatment of aqueous leachate from acid mine tailings with pristine biochar (BC) resulted in the removal of more than 90% of the dissolved arsenic with an attendant rapid and sustained pH buffering from 3 to 4. Pine forest waste BC was transformed to a highly effective adsorbent for arsenic remediation of acid mine drainage (AMD) because the dissolved iron induced “activation” of BC through accumulation of highly reactive ferric hydroxide surface sites. Physicochemical properties of the BC surface, and molecular mechanisms of Fe, S, and As phase transfer, were investigated using a multi-method, micro-scale approach (SEM, XRD, FTIR, XANES, EXAFS, and STXM). Co-located carbon and iron analysis with STXM indicated preferential iron neo-precipitates at carboxylic BC surface sites. Iron and arsenic X-ray spectroscopy showed an initial precipitation of ferrihydrite on BC, with concurrent adsorption/coprecipitation of arsenate. The molecular mechanism of arsenic removal involved bidentate, binuclear inner-sphere complexation of arsenate at the surfaces of pioneering ferric precipitates. Nucleation and crystal growth of ferrihydrite and goethite were observed after 1 h of reaction. The high sulfate activity in AMD promoted schwertmannite precipitation beginning at 6 h of reaction. At reaction times beyond 6 h, goethite and schwertmannite accumulated at the expense of ferrihydrite. Results indicate that the highly functionalized surface of BC acts as a scaffolding for the precipitation and activation of positively charged ferric hydroxy(sulf)oxide surface sites from iron-rich AMD, which then complex oxyanion arsenate, effectively removing it from porewaters. Graphical abstract Supplementary Information The online version contains supplementary material available at 10.1007/s11356-021-13869-8.

The focus of this study was on the evaluation of hydrologic and environmental behavior observed in GeoWaste and waste rock test piles. GeoWaste is a mixture of fast-filtered tailings and waste rock prepared as a tailings-dominated mixture. The two test piles included potentially acid-generating (PAG) waste rock and were operated for 26 months to evaluate whether GeoWaste can suppresses sulfide oxidation and production of metal-rich acid mine drainage relative to PAG waste rock. The test piles were constructed in the shape of truncated 5-m-tall pyramids with 25-m base sides and flat 5-m × 5-m top surfaces. Water content, temperature, electrical conductivity, and oxygen concentration were monitored in four layers and at five locations within each layer in both test piles. In addition, 5-m × 5-m lysimeters were installed at the base of each pile to collect leachate. Approximately 2660 mm of water was added to the surfaces of the test piles via precipitation and irrigation (irrigation ≈ 1050 mm applied at an approximately constant rate for 70 days). The measured saturation, oxygen concentration, electrical conductivity, and temperature in the GeoWaste and waste rock piles suggest more sulfide oxidation occurred in the waste rock pile compared to the GeoWaste pile. Observations from the pile experiments suggest that co-managing mine waste in the form of GeoWaste reduced acid generation compared to waste rock alone due to the lower permeability and unsaturated state of the GeoWaste pile that reduced downward migration of moisture and inhibited drainage.

Identification and characterization of endogenous and stress adapted bacterial species, from rat-hole coal mines in Meghalaya, amplify the ambit of bioremediation for eco-restoration. 52 native bacterial isolates, drawn from soil and water samples of these mines, were analysed for bioremediation potential, based on growth and metal tolerance parameters. 12 of these isolates were metal tolerant with Bacillus spp. being the most promising taxon. Three isolates, namely, Serratia marcescens KH-CC, Bacillus altitudinis KH-16F and Bacillus siamensis KH-12A, exhibited high Maximum Tolerable Concentration (MTC) against Fe (500 ppm), Mn (830 ppm) and Pb (1400 ppm). B. siamensis showed highest Fe remediation with 48.34% removal capacity, while maximum removal for Mn and Pb was exhibited by Serratia marcescens at 72.5 and 83%, respectively. The growth profile of the isolates indicated their ability to survive under pH, temperature and salt stress conditions. In vitro growth kinetics studies of the isolates revealed their ability to decrease the acidity of growth media and improve alkalinity from an initial of pH 4.8–5.2 to an alkaline level of pH 8.5–9. These native bacteria, extracted from the stressed coal mine habitat, are potential germane applicants for rehabilitation and eco-restoration of ecologically degraded mine sites.

Mining in the Kizel coal basin (Perm Region, Russia) ceased 20 years ago; however, AMD with high levels of total iron (Fetotal) and trace elements still affects the rivers. In this study, we attempted to estimate inter-annual and seasonal variability of AMD-related surface water contamination using Sentinel-2 images from 2016 to 2019. The acid mine water index (AMWI), which is a normalized difference of spectral reflectance in the red and blue bands, was calculated from Sentinel-2 images. We compared the AMWI values with measured Fetotal concentrations in the surface water. A statistically significant (at a 0.05 significance level) Spearman’s rank correlation between AMWI and Fetotal concentration was found for 5 out of 7 surface water sampling points. We found that surface water contamination reaches a seasonal maximum in July, 1–1.5 months after the end of the snowmelt high water period. Excessive summer rainfalls also contributes to increased contamination, causing contamination to possibly spread more than 200 km from the AMD sources. In contrast, arid summer conditions were associated with a substantially decreased AMD discharge and Fetotal concentrations in the surface water. The main uncertainties in our results are associated with the effect of contaminated bottom and bank sediments and suspended sediments on the spectral characteristics of the water surface, and the relatively coarse (10 m) spatial resolution of Sentinel-2 images. However, despite the data and method limitations, our results show that Sentinel-2 images have substantial potential for monitoring AMD-related contamination of surface water.

Made available in DSpace on 2021-06-25T10:24:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 A determination of the mobility and bioavailability of metals could provide more comprehensive knowledge about the real environmental potential of anaerobic biodigestion and health risks associated with inappropriately treated wastewater. This study aims to determine the distribution of cobalt, copper, iron, manganese, nickel and zinc among the particulate and dissolved fractions in three wastewater types (molasses, vinasse, and acid mine drainage). Affluent and effluent samples from three bioreactors analyzing each wastewater type were collected and separated into dissolved and total fractions; metal partitioning and removal efficiencies from anaerobic treatment were also evaluated. In the influent, substantial proportions of copper and iron (particulate fraction > 70%) are present in the particulate fraction that can be removed more easily than the dissolved fractions of cobalt, nickel, manganese and zinc (dissolved fraction > 53%), requiring subsequent removal techniques, such as ion exchange. For biotechnological applications, this study indicates the substantial potential of the anaerobic treatment for metal removal as an innovative eco-friendly process that minimizes the use of non-renewable resources. Institute of Geosciences and Exact Sciences (IGCE) São Paulo State University (Unesp), Av. 24 A, 1515 - Bela Vista Institute of Geosciences and Exact Sciences (IGCE) São Paulo State University (Unesp), Av. 24 A, 1515 - Bela Vista

Abstract This overview presents the updated physicochemical characteristics of thallium and its stable isotopes (205Tl/203Tl) in the context of their occurrence and fate in abiotic and biotic systems. This also deals with the thallium behavior in geochemical interactions in and between different environmental compartments and describes its natural (geogenic) and industrial sources. The particular emphasis is placed on some extreme environments, including acid mine drainage areas where oxidation processes of Tl-bearing pyrite and other sulfides lead to very high concentrations of this metal in reactive acidic waters. Many geochemical studies have also employed stable thallium isotopes to reconstruct redox conditions in different environmental systems, to fingerprint relative pollution source strengths and to evaluate mobility of this element and its geochemical interactions in the mineral-water and soil–plant systems. This is the reason why this overview also highlights the growing potential of stable Tl isotopes in solving different geologic and environmental issues. Graphic abstract

Background On August 5th, 2015, 3 million gallons of acid mine drainage was accidentally discharged from the Gold King Mine near Silverton, Colorado into Cement Creek which is a tributary to the Animas and San Juan Rivers. The government-initiated risk assessment only assessed a recreational scenario (i.e. hiker drinking from the river), failing to recognize the deep connection of the Dine (Navajo) with the San Juan River. Methods Utilizing a mixed-methods approach we determined the impacts of the 2015 Gold King Mine Spill (GKMS or Spill) on Dine activities. We developed a questionnaire to collect pre- and post-GKMS Dine activity frequency and duration. Navajo Nation Community Health Representatives administered the questionnaire to 63 Dine adults and 27 children living in three Navajo communities along the River. Results Through analysis of the focus group transcripts we identified 43 unique activities between the Dine and San Juan River. There were significant reductions in the total number, frequency, and duration of livelihood, dietary, recreational, cultural/spiritual and arts and craft activities. On average, Dine activities with the San Juan River following the GKMS decreased by 56.2%. Significance The significant reduction in activities following the GKMS may lead to long-term trauma, impacting the ability of the Dine to pass down teachings to their children affecting future generations to come. The 43 distinct activities between the Dine and the San Juan River highlight the importance for scientists and disaster responders to consider cultural and spiritual impacts when responding to environmental disasters and conducting risk assessments among Indigenous communities.

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.

Acid mine drainage (AMD) harbors all three life forms in spite of its toxic and hazardous nature. In comparison to bacterial diversity, an in-depth understanding of the archaeal diversity in AMD and their ecological significance remain less explored. Archaeal populations are known to play significant roles in various biogeochemical cycles within the AMD ecosystem, and it is imperative to have a deeper understanding of archaeal diversity and their functional potential in AMD system. The present study is aimed to understand the archaeal diversity of an AMD sediment of Malanjkhand Copper Project, India through archaea specific V6 region of 16S rRNA gene amplicon sequencing. Geochemical data confirmed the acidic, toxic, heavy metal-rich nature of the sample. Archaea specific V6-16S rRNA gene amplicon data showed a predominance of Thermoplasmata (BSLdp215, uncultured Thermoplasmata, and Thermoplasmataceae) and Nitrososphaeria (Nitrosotaleaceae) members constituting ~ 95% of the archaeal community. Uncultured members of Bathyarchaeia, Group 1.1c, Hydrothermarchaeota, and Methanomassiliicoccales along with Methanobacteriaceae, Methanocellaceae, Haloferaceae, Methanosaetaceae, and Methanoregulaceae constituted the part of rare taxa. Analysis of sequence reads indicated that apart from their close ecological relevance, members of the Thermoplasmata present in Malanjkhand AMD were mostly involved in chemoheterotrophy, Fe/S redox cycling, and with heavy metal resistance, while the Nitrososphaeria members were responsible for ammonia oxidation and fixation of HCO3− through 3-hydroxypropionate/4-hydroxybutyrate cycle at low pH and oligotrophic environment which subsequently played an important role in nitrification process in AMD sediment. Overall, the present study elucidated the biogeochemical significance of archaeal populations inhabiting the toxic AMD environment.

The increasing demand for minerals pressurizing the mining authorities to extract low-grade ore results in more mining waste and degradation of the environment. The main aim of review was to understand the role of climatic factors (temperature, wind, and precipitation) in dispersal and mobility of heavy metals in soil, water, and vegetation in Cu mining region. The major source of contamination in the mining sector is tailings, overburden rocks, and abandoned mines. The contaminates or fine particles of sulfide-rich mining waste follow two major pathways for the dispersal: aerial and leaching. Sulfides on exposure to oxygen and water generate acid mine drainage which results in leaching of heavy metals. The pit water of abandoned mines is also a cause of concern which contaminates the groundwater resources. Climatic factors such as temperature, precipitation, and wind significantly influence the paths of contaminate dispersal. In arid/semi-arid regions, high temperature forms fine-grained efflorescence salts on tailings or exposed surficial mines which are carried away by strong winds/water and contaminates the surroundings. In wet regions, the leaching of heavy metals from both tailings and overburden rocks sulfides results in environmental contamination. The application of impermeable layers is highly recommended. The climatic factors (temperature, wind, and precipitation) significantly control the dispersal and mobility of heavy metals in Cu mining region. The implementation of waste management policies and pollution control technologies is recommended after considering the climatic factors.

Pyrite, as one of the most abundant sulfide minerals, can be easily oxidized to generate acid mine drainage (AMD). In the present study, a new composite passivator named PropS-SH/sepiolite (PSPT) using γ-mercaptopropyltrimethoxysilane (PropS-SH) as the main passivator and natural sepiolite particles as filler was fabricated and used to suppress the oxidation of pyrite. Electrochemical tests and chemical leaching experiments were carried out to evaluate the passivation performance of PSPT coatings with different amount of sepiolite particles on pyrite oxidation. The results showed that the addition of appropriate sepiolite could significantly improve the inhibition ability of PropS-SH against pyrite oxidation. However, excessive addition of sepiolite particles weakened the inhibition ability of the PSPT coatings owing to aggregations of sepiolite. Additionally, the coating mechanism of PSPT on pyrite was also proposed based on the characterization of FTIR, XPS, and 29SiNMR measurements, which indicated that sepiolite particles could be embedded in PropS-SH network through oxygen bridges, thus improving the stability of the composite coatings.

A laboratory-scale up-flow anaerobic sludge blanket (UASB) reactor was developed and constructed for the treatment of landfill leachate and acid mine drainage (AMD). The removal of chemical oxygen demand (COD), sulfate, and metal ions was studied. The maximum COD and sulfate removal efficiency reached 75% and 69%, respectively, during the start-up phase of the UASB. The hydraulic retention time (HRT) had a significant influence on the system. The maximum removal efficiency for COD and sulfate reached 83% and 78%, respectively, at an HRT of 20 h. The methane production process competed with the sulfate reduction process in the UASB. The fractionation of metals in the sludge was analyzed to facilitate metal recovery in a later processing stage. The most abundant sulfate-reducing bacteria was Desulfobulbus, and the methanogen archaeal community in the reactor was mainly composed of Methanobacterium.

The effects of hydraulic retention time (HRT), chemical oxygen demand (COD), and influent Fe2+ concentrations were studied in an up-flow anaerobic sludge blanket reactor for acid mine drainage treatment using whey as a carbon source. The reactor was operated in four phases: phase I: HRT of 16 h, COD/SO42− ratio of 1.0, and an influent Fe2+ of 100 mg/L; phase II: HRT of 16 h, COD/SO42− ratio of 0.8, and an influent Fe2+ of 100 mg/L; phase III: HRT of 24 h, COD/SO42− ratio of 0.8, and an influent Fe2+ of 100 mg/L; and phase IV:HRT of 24 h, COD/SO42− ratio of 0.8, and an influent Fe2+ of 200 mg/L. The best performance was in phase I, with sulfate removal of 70 ± 8%, COD removal of 80.8 ± 7.3%, effluent pH of 6.7 ± 0.17, and sulfide generation of 91.5 ± 30.3 mg/l. The reactor reduced Cu concentrations by 92.4 ± 2.7%, Zn by 48.5 ± 4.0%, and Fe by 99.4 ± 0.4% for the entire study. Increasing the HRT and COD/SO42− ratio caused a decrease in COD and sulfate removal. The increase in influent Fe2+ in phase IV improved the results, but not enough to reestablish the phase I results. Still, the reactor presented steady metal removal and sulfide generation during the entire study.

Acid mine drainage (AMD) often requires management long after mining operations have ceased. Cost-effective long-term passive treatment systems (PTS) are required for closure of mine sites. However, PTS research seldom defines well-constrained operational and financial parameters to enable confident decision making by mining companies. PTS are generally assumed to be a lower-cost alternative to active systems when used in favorable circumstances, but there is little objective information to define when they are more suitable than active treatment. Instead, general ‘rules-of-thumb’ for flow rates or acid loads are used to determine when PTS are best used. We used well-characterized AMD from multiple historic and active coal mine sites in New Zealand to test these rules-of-thumb from a financial perspective by modelling capital and operational costs over a 100 year timeframe. We present static and uncertainty-based cost assessments of a mussel shell reactor PTS compared to typical active AMD treatment systems at six mine drainage sources from the Brunner Coal Measures. We show that for expected AMD characteristics and duration of treatment, savings on operational costs with PTS can exceed the higher initial capital costs. In addition, the financial advantage of PTS over time may be achieved at flow rates and acidity loads that exceed the industry rules-of-thumb PTS limits. However, in some circumstances, cost projections for high up-front capital costs of purchasing all treatment media for the life span of the PTS is less favorable than discounted treatment media in active treatment systems over time. Understanding financial models of AMD treatment options during mine site design can help reduce the costs of operating and closing mine sites.

Acid mine drainage (AMD) is a serious environmental problem due to its high sulfate and heavy metal content. In comparison with the conventionally used physico-chemical methods, biological methods involving sulfate-reducing bacteria (SRB) offer a green and sustainable way to treat AMD. Biological sulfate reduction requires an efficient and low-cost electron donor. This paper overviews different gaseous substrates as electron donor that can be used for sulfate reduction to treat AMD. The use of gaseous substrates as electron donor for sulfate reduction is advantageous as it avoids dilution of wastewater and avoids secondary pollution problems arising from unutilized electron donor. Among the different gaseous substrates for sulfate reduction, hydrogen (H2) is more energetically favourable to the sulfate-reducing microorganisms. Carbon monoxide (CO) is a low-cost waste gas substrate for sulfate reduction, but its toxicity limits its applications. Only a limited number of specialized slow-growing microorganisms can utilize methane (CH4) coupled to sulfate reduction under anaerobic conditions. Different gases (H2, CO and CH4) are evaluated as potential electron donor for biological sulfate reduction to treat AMD. Several bacterial and archaeal species can use these gases as the sole electron donor for reducing sulfate to sulfide. Heavy metals present in the AMD can be removed by sulfidic precipitation although high concentrations of heavy metals can inhibit SRB activity, thus reducing the process efficiency. In addition, proper choice of the bioreactor system has a great influence on the AMD treatment efficiency by biological sulfate reduction using gaseous substrates.

Phragmites australis, which is widely distributed throughout the world, is often used in the phytoremediation of acid mine drainage (AMD) due to its various mechanisms for survival under extremely harsh conditions. To explore the different responses of different aerial organs of P. australis to stress, soil and plant samples were collected from the AMD-polluted area of the Tongling mining area. The contents of manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), and lead (Pb) in the soil and the leaf blades, leaf sheaths, and stems of P. australis as well as the contents/activities of cysteine synthase (CSase), superoxide dismutase (SOD), peroxidase (POD), glutathione (GSH), malondialdehyde (MDA), and proline (Pro) in the organs were determined. Our results revealed that the leaf sheath had the highest potential to store metals of all the organs. The highest translocation factor (TF) for Fe was observed from the stems to the leaf sheaths. A higher bioconcentration factor (BCF) for Mn was found in the leaf blades and leaf sheaths, while higher BCFs for Cd and Zn were observed in the stems. The content/activity of enzymatic and non-enzymatic stress-resistance substances varied from organ to organ. In general, the leaf sheaths remained almost as or slightly less stress-resistant than the leaf blades. It can be concluded that different plant organs play different roles in stress resistance, and understanding the tolerance mechanism of leaf sheaths to metals is essential for the application of phytoremediation procedures.

Sulfate-reducing bacteria (SRB) are an attractive option for treating acid mine drainage (AMD) and are considered to be of great significance in the natural attenuation of AMD, but the available information regarding the highly diverse SRB community in AMD sites is not comprehensive. The Hengshi River, which is continually contaminated by AMD from upstream mining areas, was selected as a study site for investigation of the distribution, diversity, and abundance of SRB. Overall, high-throughput sequencing of the 16S rRNA and dsrB genes revealed the high diversity, richness, and OTU numbers of SRB communities, suggesting the existence of active sulfate reduction in the study area. Further analysis demonstrated that AMD contamination decreased the richness and diversity of the microbial community and SRB community, and led to spatiotemporal shifts in the overall composition and structure of sediment microbial and SRB communities along the Hengshi watershed. However, the sulfate reduction activity was high in the midstream, even though AMD pollution remained heavy in this area. Spatial distributions of SRB community indicated that species of Clostridia may be more tolerant of AMD contamination than other species, because of their predominance in the SRB communities. In addition, the results of CCA revealed that environmental parameters, such as pH, TS content, and Fe content, can significantly influence total microbial and SRB community structure, and dissolved organic carbon was another important factor structuring the SRB community. This study extends our knowledge of the distribution of indigenous SRB communities and their potential roles in natural AMD attenuation.

Acid mine drainage (AMD) is difficult to treat due to its physicochemical characteristics, such as high pH and high heavy metal concentrations, so it causes great harm to the environment and human health. If acid mine drainage is discharged arbitrarily without treatment, it will lead to a series of environmental problems and cause long-term environmental pollution. In this paper, the source and hazards of acid mine drainage are introduced in detail. And the principle, the mechanism, the application, and basic information of the current primary technology of the treatment for acid mine drainage are comprehensively introduced and summarized. The summarized treatment technologies for acid mine drainage mainly include neutralization, sulfidization, constructed wetland method, adsorption method, microbiological method, ion exchange method, membrane technology, and microbial fuel cell technology. Also, the primary technology of treatment for acid mine drainage is systematically compared and evaluated. Moreover, some suggestions on the development direction of water treatment technology in the future are put forward. This paper provides a scientific reference for scientific and technical works to treat acid mine drainage.

Substrate amendments composed of crab shell (CS) waste materials have been shown to significantly improve the longevity and performance of acid mine drainage (AMD) treatment systems containing spent mushroom compost (SMC), yet the development of key microbial populations within these systems has not been investigated. To better understand the effects of CS on microbial dynamics in these systems, clone libraries and real-time quantitative PCR (qPCR) were performed on materials from a laboratory-scale AMD treatment system containing SMC and 0 to 100% CS substrate after receiving a continuous flow of AMD for 148 days (428 pore volumes). The proportion of CS in the substrate positively correlated with the diversity of sulfate-reducing bacteria (SRB) and archaeal clones, but negatively correlated with fungal diversity. CS also impacted microbial community structure, as revealed in Unifrac significance and principal coordinate analysis tests. The column containing 100% CS substrate supported 7 different genera of SRB-the most ever observed in an AMD treatment system. Moreover, the copy numbers of functional genes representing fermenters, sulfate reducers, and chitin degraders increased with increasing proportions of CS. These observations agree well with the chemical performance data, further validating that by supporting more abundant key microbial groups, chitinous substrates may provide benefits for improving both the longevity and performance of AMD treatment systems, and may provide similar benefits for the treatment of other environmental contaminants that are amenable to anaerobic bioremediation.Key points• Crab shell improves the longevity and performance of acid mine drainage treatment.• The diversity of sulfate-reducing bacteria is enhanced with crab shell amendments.• Crab shell supports more abundant key microbial groups than spent mushroom compost.

The mining industry produces billions of tons of mine tailings annually. However, because of their lack of economic value, most of the tailings are discarded near the mining sites, typically under water. The primary environmental concerns of mine tailings are related to their heavy metal and sulfidic mineral content. Oxidation of sulfidic minerals can produce acid mine drainage that leaches heavy metals into the surrounding water. The management of tailing dams requires expensive construction and careful control, and there is the need for stable, sustainable, and economically viable management technologies. Alkali activation as a solidification/stabilization technology offers an attractive way to deal with mine tailings. Alkali activated materials are hardened, concrete-like structures that can be formed from raw materials that are rich in aluminum and silicon, which fortunately, are the main elements in mining residues. Furthermore, alkali activation can immobilize harmful heavy metals within the structure. This review describes the research on alkali activated mine tailings. The reactivity and chemistry of different minerals are discussed. Since many mine tailings are poorly reactive under alkaline conditions, different pretreatment methods and their effects on the mineralogy are reviewed. Possible applications for these materials are also discussed.

The performance of a semi-passive sulfate-reducing bioreactor (SPSRB) was studied for the treatment of highly contaminated AMD (pH = 4.2, [Fe]i: 1600 to 6400 mg/L). The potential mobility of contaminants (metals and sulfates) from AMD post-treatment residue was also evaluated (e.g. metal speciation, weathering cells) to ensure their proper management. Sodium lactate (3500 mg/L) was continuously added to three SPSRBs composed of 60% birch chips, 20% calcite, and 20% poultry manure to enhance microbial activity. The SPSRBs were very effective during the total duration of the experiment (266 days) for the removal of Fe (average removal efficiency of 97.7%), Cd (> 99.4%), Cr (99.3%), Cu (99.9%), Ni (99.2%), Pb (99.8%), Al (92.4%), and Zn (90.7%). The study of the physicochemical stability of the post-treatment residues showed a net positive neutralization potential of 22.4 kg CaCO3/t and a NP/NA ratio of 1.80. Although the metal speciation estimates revealed that Fe, Mn, Ni, and Zn were mainly retained in the biofilter as oxides or hydroxides, a significant proportion of metals were also present in the form of sulfides, or bound to organic matter as exchangeable/soluble sulfate fractions. Finally, the kinetic tests (weathering cells) confirmed the high risk of metal release if the post-treatment residues are disposed of in an oxidizing environment.

The Olifants River in South Africa, is well known to be one of the most polluted rivers in Southern Africa. Water quality issues in the River Catchment are known catchment are known to be primary related to salinity, eutrophication and acid mine drainage. This study aimed to assess the efficiency removal of metal ions in effluent wastewater from a domestic wastewater treatment plant (WWTW), borehole (BH) water contaminated by agriculture and mining activities and acid mine drainage (AMD) effluent from a abandon coal mine. To determine the treatment performance of the adsorbent, the water samples physicochemical parameters; pH, EC, turbidity and COD were measured. The pH and turbidly were within the range while EC and COD values did not fall within the standard discharge limit of industrial effluent by the DWF (1996).The use of shrimp chitosan product cross-linked with glutaraldehyde as an adsorbent was first tested on a certified reference material before applying it to the wastewater, obtained shows exceptional adsorption properties of up to 80% for these elements at concentration above 10 mg/L. However, no reliable results were obtained for samples with less than 1 mg/L. Statistical evaluation of the results at 95% confidence interval using the t-static test shows a standard deviation of ± 7% of the experimental results. Mathematical Modelling employed, results showed AMD effluent presented the power law process, while WWTW effluent, presented a decay process. Finally, for BH we obtained a normal distribution and a mathematical model was employ using the initial condition.

Coal is naturally enriched in trace elements, including mercury (Hg) and selenium (Se). Alkaline mine drainage from mountaintop mining valley fill (MTM-VF)—the dominant form of surface coal mining in Appalachia, USA—releases large quantities of Se into streams draining mined catchments, resulting in elevated bioaccumulation of Se in aquatic and riparian organisms. Yet, the release of Hg into these streams from MTM-VF has not yet been studied. We measured total Hg, methylmercury (MeHg), and Se in stream water, sediment, biofilm, cranefly larvae, and riparian spiders in alkaline streams (pH range 6.9–8.4) across a mining gradient (0–98% watershed mined) in central Appalachia. Hg concentrations ranged from below detection limit (BDL)-6.9 ng/L in unfiltered water, BDL-0.05 µg/g in bulk sediment, 0.016–0.098 µg/g in biofilm, 0.038–0.11 µg/g in cranefly larvae, and 0.046–0.25 µg/g in riparian spiders. In contrast to Se, we found that Hg concentrations in all environmental compartments were not related to the proportion of the watershed mined, suggesting that Hg is not being released from, nor bioaccumulating within, MTM-VF watersheds. We also did not find clear evidence for a reduction in Hg methylation or bioaccumulation under elevated Se concentrations: water, sediment, biofilm, and riparian spiders exhibited no relationship between Hg and Se; only cranefly larvae exhibited a negative relationship (p = 0.0002, r2 = 0.42). We suggest that the type of surface mining matrix rock, with resultant alkaline or acid mine drainage, is important for the speciation, mobility, and bioaccumulation of trace elements within watersheds affected by mining activities.

Engineered covers are commonly used to control the potential environmental problems related to acid mine drainage and contaminated seepage from tailings and waste rock storage facilities. Cyclical environmental weathering processes, such as freeze-thaw and wet-dry cycles, can cause rock degradation. However, these processes are usually not explicitly considered when selecting coarse-grained geomaterials for use as cover materials, even though they could be responsible for a decrease in cover performance over time. This study assesses the durability of a non-potentially acid-generating soapstone waste rock unit with respect to freeze-thaw and wet-dry cycles. This waste rock is intended for use as a cover material for the reclamation of mine tailings and waste rock storage facilities at a site in the Canadian Arctic. An experimental approach was developed based on existing standard and non-standard laboratory methods. Degradation tests were conducted on rock cores, rock slabs, and

In the Karoo coalfields, mining operations that release acid mine drainage (AMD) are threatening groundwater resources. An important parameter controlling the extent and severity of AMD impact is the natural attenuation of rocks in response to AMD. Very little is known about such response of Karoo rocks in saturated and unsaturated conditions, a research gap filled by this paper. Laboratory column leach experiments were used to study the responses of different rock types from the Witbank, Ermelo and Highveld coalfields of South Africa. The results of the experiments show that rock samples with high quartz mineral content offered little attenuation of AMD and those consisting of plagioclase and clays offered some attenuation, while those with high carbonate mineral content, neutralized and reduced the concentration of heavy metals from AMD. The presence of oxygen increased the rate of heavy metal removal from AMD. For all rock samples under saturated and unsaturated conditions, the sulfate and chloride concentrations of AMD remained unchanged after the leaching process, showing that these parameters are conservative and can be used as potential natural tracers of AMD movement in the subsurface. The research shows that laboratory leach tests may be used to rank the various rock types in the Karoo coalfields in terms of their capacity to buffer the impacts of AMD. Such a ranking could inform policy and decision makers in regard to handling and storage of AMD-generating wastes, as well as to location and design of AMD waste storage facilities.

Acid Mine Drainage (AMD) from coal mining is a serious environmental issue which affects water quality, ecology, and the overall landscape of the basin. A large number of coal mine tailings in the mountainous regions of Guizhou Province, China were unattended and iron-rich AMD was directly discharged to the rivers. This discharge leaves the river “yellow” and heavily polluted. This study tries to find an efficient and economical method for treating iron-rich AMD. We sampled AMD water in two sites: Yangliujie town of Duyun city (hereafter, called Yangliujie), and Xinglong Coal Mine, Duliu town of Guiding county (hereafter, called Xinglong). We performed iron removal laboratory experiment with Cement-Bentonite Agent (CBA, 80% cement and 20% bentonite) in 500 mL AMD water from Yangliujie, scale-up experiment in 15 L AMD water from both Yangliujie and Xinglong, and engineering application in Xinglong respectively. Laboratory experiment results showed the iron removal rate can reach 99.8% and the removal rate depends on the CBA dosage and the treatment time. In the scale-up experiment, we found that Fe concentration could be reduced from 587.0 to 0.2 mg/L when adding 20 g/L CBA to the AMD water and aerating for 3 hours. As sampled water in Xinglong has a very high Fe concentration (Fe 1019.8 mg/L) and the concentration varies with seasons, it is not economical to add the CBA directly to the AMD water. Considering the abundant and cheap limestone resources in Guizhou, we used a twostep treatment method, first we added CaCO3 to raise the pH, and then we took the supernatant liquor and added CBA to the liquor. It was shown that 15 g/L of CBA was a good dosage for iron removal with Fe concentration being reduced from 1019.8 to 0.3 mg/L when CaCO3 was used to raise the pH. The best treatment realized over 99.9% iron removal, 99.2% NH3-N removal, 98.9% CODMn removal, and heavy metals in the treated water were reduced to under the limit stipulated in the “Environmental Quality Standards of Surface Water in China”. Thus in the engineering application, we used this two-step treatment method. After the treatment, the pH of the iron-rich AMD (pH 2.86, Fe 2624.6 mg/L) increased to 8.53, the concentration of Fe was reduced to 59.5 mg/L, NH3-N decreased from 16.15 to less than 0.05 mg/L, CODMn decreased from 323.33 to 24.57 mg/L, heavy metals except Fe and Mn were reduced to under the limit of surface water. In conclusion, the use of CBA can effectively remove Fe and other heavy metals from the iron-rich AMD and adjust the pH value to the range of a natural water body.

Many studies on acid mine drainage (AMD) use predictive methods, such as humidity cells (HC), to study this problem, as it is often not possible to predict acid generation from field tests. However, some comparisons of HC testing with reality have proven to be unrealistic. In this study, we compared the results of the HC test with historical data from the Figueira mine, in the State of Parana (southern Brazil). To carry out the work,we collected a fresh coal tailings sample from the Figueira Mine, and compared monthly measurements of pH and electrical conductivity (EC), and concentrations of Fe, Al, Mn, and Zn, over a 5 year period (from 2013 to 2017) with the predictive test results performed following protocol B of the ASTM D5744-13 (2018) standard. The elements were analyzed by ICP-OES. The pH and EC of the HC test were lower than the field data. The HC test underestimated the concentrations of Fe and Mn, while Al and Zn were overestimated. We believe that the overestimations were due to the aluminosilicate buffering capacity and cation exchange capacity of the soil.

Bioleaching is regarded as an essential technology to treat low grade minerals, with the distinctive superiorities of lower-cost and environment-friendly compared with traditional pyrometallurgy method. However, the bioleaching efficiency is unsatisfactory owing to the passivation film formed on the minerals surface. It is of particular interest to know the dissolution and passivation mechanism of sulfide minerals in the presence of microorganism. Although bioleaching can be useful in extracting metals, it is a double-edged sword. Metallurgical activities have caused serious environmental problems such as acid mine drainage (AMD). The understanding of some common sulfide minerals bioleaching processes and protection of Amd environment is reviewed in this article.

Mining equipment and structural elements (e.g. bridges, mining exploration equipment), which are mainly made of steel and concrete, undergo corrosion processes that are strongly accelerated in these extremely acidic environments, with the further aid of acidophilic bacteria that act as catalysts.

Heavy metal contaminations in acid mine drainage (AMD) have posed a serious health and environmental risk. Biosorption is a promising in situ remediation technique to remove heavy metals from AMD. In this study, the potential of thermophilic acidophilus Sulfobacillus thermosulfidooxidans was used as biosorbent to remove heavy metal ions (Cd2+, Cu2+, Zn2+ and Ni2+) from acidic solution. The results indicated that the maximum adsorption capabilities of S. thermosulfidooxidans in the order of Ni2+ > Cd2+ > Zn2+ > Cu2+ at initial heavy metal concentrations range from 0.5 to 6 mM in single-metal system while showed an extremely high affinity toward Cu2+ in quaternary metal coexisting system. pH was positively related to adsorption capacity, and isothermal models also indicated monolayer adsorption played a major role in the biosorption process. Additionally, the deprotonation of carboxyl and phosphoryl contributed to the adsorption of heavy metal ions which were identified by ProtoFit analysis. Fourier transform infrared spectroscopy (FTIR) further proved these two kinds of functional groups as well as amino groups participated in the biosorption process. This study provided a new strategy for in situ bioremediation of heavy metal ions in AMD.

The co-treatment of AMD with other common liquid wastes is a promising synergistic approach, fusing characteristics of active and passive AMD treatment for a sustainable remediation strategy. This paper discusses existing literature on AMD co-treatment approaches, focusing on factors that influence the feasibility of co-treatment, such as mixing proportions, microbiological elements, reactor design, and mixed-water chemistry. Finally, this paper highlights future possibilities, drawing attention to prospects that require exploration.