Acid Mine Water Research Articles

Evaluasi tingkat keberhasilan reklamasi lahan bekas tambang timah di PT Timah Tbk

PT Timah Tbk has operated tin mining for ± 45 years. The ratio between disturbed land reclaimed by PT Timah Tbk indicated a bad ratio. The study aims to analyze and evaluate the land reclamation of former tin mines in Air Jangkang Sinar Rembulan Hamlet. The reclamation is important in that beneficial for the ecologycal, social and economic community. The Decree of the Minister of Energy and Mineral Resources No. 1827K/30/MEM/2018 were reformed. The evaluation was done by comparing the plan and implementationn data. Apparently, the overall reclamation were good in that of backfilling 89%, spreading of top soil 93%, erosion and sedimentation 83%, planting 90%, acid mine water 92%, header closing 100% and maintenance 82%. Canopy cover mine 90%.

Fe(III) Biomineralization in the Surface Microlayer of Acid Mine Waters Catalyzed by Neustonic Fe(II)-Oxidizing Microorganisms

The formation of thin mineral films or encrustations floating on the water surface of low-flow or stagnant zones of acid mine drainage (AMD)-affected streams is probably among the most exotic features that can be found in mining areas. However, most fundamental questions about their origin (biotic vs. abiotic), structure, mineralogy, physical stability and metal-retention capacity remain unanswered. This study aims to reveal the factors promoting their formation and to clarify their composition in detail. With this purpose, the major mineral phases were studied with XRD in surface film samples found in different mine sites of the Iberian Pyrite Belt mining district (SW Spain), and the major oxide and trace metal concentrations were measured with XRF and/or ICP-MS. Fe(III) minerals dominated these formations, with mineralogy controlled by the pH (jarosite at pH~2.0, schwertmannite at pH 2.5–3.5, ferrihydrite at pH > 6.0). Other minerals have also been identified in minor proportions, such as brushite or khademite. These mineral formations show an astounding capacity to concentrate, by orders of magnitude (×102 to ×105), many different trace metals present in the underlying aqueous solutions, either as anionic complexes (e.g., U, Th, As, Cr, V, Sb, P) or as divalent metal cations (e.g., Cu, Zn, Cd, Pb). These floating mineral films are usually formed in Fe(II)-rich acidic waters, so their formation necessarily implies the oxidation of Fe(II) to Fe(III) phases. The potential involvement of Fe(II)-oxidizing microorganisms was investigated through 16S rRNA gene amplicon sequencing of water underneath the Fe(III)-rich floating mineral films. The sequenced reads were dominated by Ferrovum (51.7 ± 0.3%), Acidithiobacillus (18.5 ± 0.9%) and Leptospirillum (3.3 ± 0.1%), three well-known Fe(II)-oxidizing genera. These microorganisms are major contributors to the formation of the ferric mineral films, although other genera most likely also play a role in aspects such as Fe(III) sequestration, nucleation or mineral growth. The floating mineral films found in stagnant acidic mine waters represent hotspots of biosphere/hydrosphere/atmosphere interactions of great value for the study of iron biogeochemistry in redox boundaries.

Removal of Ag, Au, and As from Acid Mine Water Using Lemna gibba and Lemna minor—A Performance Analysis

Mining activities result in the accumulation of pollutants in aquatic environments. This study aimed to investigate the accumulation performances of Ag, Au, and As using Lemna minor and Lemna gibba in the acid mine waters of Maden copper deposit. L. minor and L. gibba are aquatic plants belonging to the duckweed family. They are small, fragile, and free-floating aquatic plants. L. minor and L. gibba were separately placed into two reactors. The plants and water from the reactors were collected daily for eight days. Additionally, the electric conductivity, temperature, and pH of the acid mine water were measured daily. L. minor and L. gibba samples were washed, dried, and burned at 300 °C in a drying oven for 24 h. The water and plant samples were analyzed for Ag, Au, and As content using ICP-MS (Inductively Coupled Plasma Mass Spectroscopy). The acid mine waters of Maden copper deposit contained 9.25 ± 0.4, 0.92 ± 0.02, and 193 ± 12 μg L−1, Ag, Au, and As, respectively. In comparison to control samples, L. gibba and L. minor showed high and effective performances in removing Ag, Au and As from the acid mine waters of Maden copper deposit; 240 and 174 times for Ag; 336 and 394 times for Au; and 30 and 907 times for As, respectively. Overall, the results suggest that L. gibba and L. minor can effectively remove Ag, Au, and As from acid mine waters, highlighting their potential use in environmental remediation.

The Influence Of Rock Mineralogy On Groundwater In The Kampungbaru Formation,Coal Mining Area, Anggana And Surrounding Area, District. Kutai Kartanegara

Coal mining activities using the open pit mining system method will have impacts, both positive and negative impacts, positive impacts will cause changes in improving socio-economic life, while negative impacts will affect changes in hydrogeological conditions and environmental changes such as increasing soil/rock acidity so that it will cause water contaminated. This condition has an impact on decreasing the quality and quantity of groundwater as a source of clean water. The purpose of this study was to determine the hydrogeological conditions around the study site, and the influence of rock mineralogy as a potential source of groundwater contamination, especially in the Kampungbaru Formation. The methods used to obtain data such as; pumping test, rock mineralogy analysis (knowing the characteristics) by conducting studies; petrography, microscopic analysis of ore, XRD analysis, XRF analysis and analysis of the potential of acid mine water, while knowing the chemical characterization of water by analyzing the concentration of anion cations, and classifying water classes. Knowing the characterization of rock mineralogy and water chemistry, the level/value of potential groundwater contamination in the study area will be known. The hope of this research is to know and understand the characteristics of mineralogy of rocks and groundwater chemistry, as well as hydrogeological conditions in Kampungbaru Formation, so that groundwater contamination can be known. Specific benefits of the research, which is to explore more detail hydrogeology of the mine and surrounding areas, to understand the characteristics of rock mineralogy and the characteristics of groundwater chemistry, and to know the source of groundwater contamination of the research area. Practical benefits can provide information to the public and government about the potential of good quality groundwater around the research area and know the groundwater location of good quality. The results of hydrogeological studies, study of mineralogy characterization and groundwater chemistry will be obtained conclusion such as: 1) Characteristics of aquifer in Kampungbaru Formation included in the category of productive aquifers. 2) Mineralogy of rocks affect the chemical concentration .. 3) Kampungbaru Formation has the content of metal mineral elements and water chemical concentrations that contain many sulphide compounds as acid mine formers. Stratigraphy of the study area is included in the Kampungbaru Formation and is part of the Kutai Basin (Kutai Basin). Lithology The Kampungbaru Formation consists of a rocky outcrop with sandstone with coal insertions and sandstone units.
 
 Keywords: Hydrogeology, characteristics of mineralogy and groundwater chemistry, contamination

Pemantauan Dan Pengelolaan Air Pada Tambang Batubara PT Bukit Makmur Mandiri Utama Kabupaten Berau Provinsi Kalimantan Timur

In the mining industry, especially coal mining of PAF materials which are the source of mine acid formation when interacting with water (H2O) and air (O2) Should be managed as best as possible to minimize acid mine water in the pit before the water is pumped out. This research aimed to determine the method used in handling AAT forming material and to discover whether the quality of wastewater from the settling pond is by wastewater quality standard. The stages and processes of research consist of four steps: data retrieval techniques, data processing, data analysis stages, and the report generation stage. The data taken are primary data, such as inlet and outlet pH and the types of PAF and NAF rock and secondary data, which are company profile data required in report writing. After the data is collected, the data is analyzed to determine the method used in PT. Bukit Makmur Mandiri Utama (BUMA) for AAT handling. In the prevention of the establishment of AAT PT. BUMA applies a capsulization method for handling AAT PT. BUMA has WMP. Water quality with pH parameters at inlet zone 4 and outlet 6, TSS ranged from 6 - 4, Fe <0.02, Mn 2.67 – 2.77. the conclusion of this research is handling the establishment of AAT PT. BUMA performs two ways: the capsulization method and provision of lime neutralizing materials; the water pH in the sediment pond that is four while the pH of water issued is 6, and the amount of lime required is 765,534 kg. Water flowed by PT. BUMA has met the wastewater quality standard set by Kep. Men LH no. 113 the year 2003.

EFFECTS OF HEAVY METALS, CONTAINED IN FLOTATION TAILINGS, ON PLANTS USED IN REVEGETATION

During the processing of precious and base metal ores from the Baia Mare mining area, which contained Au, Ag, Cu, Pb and Zn, large amounts of flotation tailings resulted, which were deposited in the Bozânta tailings management facility, located between Săsar and Bozânta Mare villages, 4 km west of Baia Mare. Due to the presence of minerals containing metal sulphides (mainly pyrite), the acid rock drainage (ARD) has become very active, catalysed by iron- and sulphur-oxidizing bacteria, which naturally occur at these sites. Decreasing the surface of the pond as a result of evaporation, combined with the increase of the beach surface and the absence of any protection at the embankment ridge, led to the entrainment of the tailings by wind at considerable distances. They often end up in neighbouring settlements, especially in the two mentioned villages, as a result of prevailing winds from the NE-SW direction. The purpose of the research was to test the resistance of some plant species (Sinapis alba L. – white mustard; Trifolium pratense L. – red clover and Lolium perenne L. – ray grass) to the conditions generated by the tailings on the surface of the depot, in order to create a vegetation cover with a role in diminishing tailings discharges in the adjacent areas. There were tested the effects of the industrial eluate (acid mine water, pH 4.3), obtained from the tailings pond, over seed germination parameters: germination capacity (GC); germinative energy (GE) and relative seed germination (RG). The results of the tests pointed out that the least affected was white mustard: GC – 95.3%; the differences in the values obtained in the control samples and the GE test – 5.3%; the results for RG – 99.3%, confirm that the white mustard seeds were the least influenced by the industrial eluate, followed by ray grass and red clover. In the tests for plant growth on the tailings pond, 5 experimental variants were used: a) soil (S); b) flotation tailings (T); c) mixture of flotation tailings and soil (T+S); d) mixture of flotation tailings and organo-zeolitic material (T+OZ); e) mixture of flotation tailings, organo-zeolitic material and soil (T+OZ+S). It is recommended to use the T+OZ+S mixture on the pond surface and sowing with Sinapis alba and Trifolium pratense. For both species, double seed sowing is recommended.

Ferric Hydroxide Recovery from Iron-Rich Acid Mine Water with Calcium Carbonate and a Gypsum Scale Inhibitor

The focus of this study was to improve the Reverse Osmosis Cooling (ROC) process by using CaCO3 for neutralization and selective recovery of Fe(OH)3 at pH 3.5. By using a specific inhibitor, ferric hydroxide was recovered separately from gypsum and other metals present in mine water. Ferric hydroxide was processed to pigment, a product that is imported and used as colorant in paints and tiles. In addition to pigment recovery, aluminum hydroxide and calcium carbonate can also be recovered from mine water. The following conclusions were made: (i) the rate of gypsum crystallization, in the absence of Fe3+, is influenced by the over saturation concentration in solution, the seed crystal concentration and temperature; (ii) gypsum crystallization from an over-saturated solution, in the presence of Fe(OH)3 sludge, required an inhibitor dosage of 100 mg/L to keep gypsum in solution for a period of 30 min; (iii) gypsum crystallization from an over-saturated solution, in the presence of both Fe(OH)3 sludge and CaCO3 reactant, required a higher inhibitor dosage than 100 mg/L to keep gypsum in solution for a period of 30 min. A dosage of 200 mg/L kept gypsum in solution for the total reaction period; (iv) when only Fe(OH)3 is present in the slurry, gypsum inhibition is more effective when Fe(OH)3 sludge is allowed to settle after the initial mixing; (v) when both Fe(OH)3 and CaCO3 are present in the slurry, gypsum inhibition is more effective when the inhibitor is added over a period of time (10 min) rather than applying the total dosage at time zero; (vi) Fe(OH)3 can be changed to yellow pigment (Goethite) by heating to 150 °C and to red pigment (Hematite) by heating to 800 °C. Pigment of nano particle size was produced; (vii) in the case of Na2CO3, the TDS increased from 12,660 mg/L in the feed to 13,684 mg/L due to the replacement of metal ions (Fe3+, Al3+, Fe2+, Mn2+ and Ca2+) with Na+ in solution. In the case where CaCO3 was used for the removal of Fe3+ and Al3+, Ca(OH)2 for the removal of Fe2+, Mn2+, and Na2CO3 for the removal of Ca2+, the TDS dropped from 12,661 mg/L to 2288 mg/L, due to gypsum precipitation. The alkali cost in the case of calcium alkalis amounted to ZAR29.43/m3 versus ZAR48.46/m3 in the case of Na2CO3.

ANALISIS PENETRALAN AIR ASAM TAMBANG DENGAN METODE AKTIF MENGGUNAKAN POWERBASE DI PIT TIMUR PT DIZAMATRA POWERINDO KABUPATEN LAHAT PROVINSI SUMATERA SELATAN

Acid mine water refers to water resulted from the oxidation of sulphide mineral from a mining process and exposed to water, and it has high acid level which is indicated by the low value of pH that is below 6. Therefore, acid mine water must be treated so that is does not cause pollution in the area around the mine. In this research, the acid mine water treatment applied active method by using jar test with neutralizer media in from of powerbase. This research only calculated the dosage necessity and cost of powerbase with laboratory scale as well as field scale. The need of powerbase for laboratory scale was 80 kg with the powerbase cost of Rp 752,000.00 for once neutralization/hour. With the cost of Rp 7,520,000.00 the powerbase application with 0.6 gram/1000 ml dosage could increase the pH from 4.3 to 7.62.

REMOVAL OF HEAVY METALS FROM SYNTHETIC ACIDIC MINE WATER USING RECYCLED AGGREGATES

Acid mine drainage (AMD), a highly acidic and sulfate (SO42-)-rich solution, is an environmental concern related to the release of metal-containing wastewater from mining areas into the environment. In this study, recycled aggregates (RA) produced from concrete debris were used in the treatment of acidic mine water contaminated with heavy metals. For a model synthetic acidic mine water with a pH of 2.31, SO42- and iron (Fe) concentrations of 5200 mg L-1 and 700 mg L-1, respectively, RA increased the pH value to 11.18 and reduced the SO42- and Fe concentrations by 90.51% and 100%, respectively, at RA/AMD ratio of 100 mg L-1 after 300 minutes of shaking at room temperature in batch experiments. The test results also showed that 100% of copper (Cu), zinc (Zn), manganese (Mn), silver (Pb) and cobalt (Co) concentrations were removed at this ratio and shaking time. This study demonstrates that RA have significant potential to neutralize acidity and remove heavy metals from AMD, a serious problem for ecological systems and health.

DECREASE LEVELS OF IRON (Fe) AND MANGANESE (Mn) IN ACID MINING WATER USING ACTIVE CARBON OF EGG SHELL

Acid mine drainage is acidic water that arises as a result of mining activities. Acidic water has a high acidity, which is often characterized by a low pH and contains high levels of heavy metals Fe and Mn. The purpose of this study was to determine the effect of activated carbon on the adsorption process and the effect of mass of activated carbon on eggshells. The method used in this research is the adsorption method using activated carbon of eggshell which is physically and chemically activated. This study used a mass variation of 5, 10, 15 and 20 grams with a contact time of 30 minutes and an adsorbent size of 200 mesh. The parameters studied were heavy metals iron (Fe) and manganese (Mn). The initial concentration of Fe acid mine waste was 29.179 mg/L, and Mn was 7.9692 mg/L. The results showed that the mass of activated carbon had an effect on decreasing the levels of Fe and Mn metals. On physical activation the average decrease in Fe metal was 99.50% and Mn metal was 53.21%, while on chemical activation the average decrease in Fe metal was 97.72% and Mn metal was 97.97%.Keywords: Acid mine water, Fe, Mn, Activated carbon, egg shell

Metal Bioleaching of Used Lithium-Ion Battery Using <i>Acidophilic ferrooxidans</i> Isolated from Acid Mine Drainage

The cobalt content in LIB (Lithium-ion Battery) can be recycled using green technology through a bioleaching process with the help of microorganisms to have high efficiency, low cost, easy method, and environmentally friendly. The bacterial strain of A. ferrooxidans in the bioleaching process isolated from acid mine water was capable to extracting cobalt in LIB to obtain pure metal ions. The aim of this research is to isolate bacteria A. ferrooxidans from acid mine water in order to extract the element cobalt from a LIB. This study has recovery with culture time of 0-14 days, aerobic systems, inoculum concentrations of 5%, 10%, and 20%. The optimization of bacterial growth was done by aerating the culture. The recovered cobalt were analyzed from the filtrate after the bioleaching process using ICP analysis. LIB and sediment of the bioleaching process were analyzed by XRD, SEM and EDX. The conclusion of this study showed that the recovery of cobalt metal (Co) using the bacterial strain of A. ferrooxidans was obtained at 73.95% for 14 days with the addition of a battery cathode of 1 gram/100 ml at the optimum conditions obtained when the addition of 20% inoculum, pH: 2-4, temperature: 30°C, and the aeration system uses an aerator. Bacterial strains isolated from acid mine drainage have the potential as oxidizing agents for lithium and cobalt metals in bioleaching processes.

Mapping Chini Lake (Pahang, Malaysia) using Sentinel-2 images to determine the effect of acid mine drainage in the pre- to post-COVID-19 restriction period.

Mining activities in the Chini Lake catchment area have been extensive for several years, contributing to acid mine drainage (AMD) events with high concentrations of iron (Fe) and other heavy metals impacting the surface water. However, during the restriction period due to the COVID-19 outbreak, anthropogenic activities have been suspended, which clearly shows a good opportunity for a better environment. Therefore, we aimed to analyze the variation of AMD-associated water pollution in three main zones of the Chini Lake catchment area using Sentinel-2 data for the periods pre-movement control order (MCO), during MCO, and post-MCO from 2019 to 2021. These three zones were chosen due to their proximity to mining areas: zone 1 in the northeastern part, zone 2 in the southeastern part, and zone 3 in the southern part of the Chini Lake area. The acid mine water index (AMWI) was a specific index used to estimate acid mine water. The AMWI values from Sentinel-2 images exhibited that the mean AMWI values in all zones during the MCO period decreased by 14% compared with the pre-MCO period. The spatiotemporal analysis found that the highest polluted zones were recorded in zone 1, followed by zone 3 and zone 2. As compared with during the MCO period, the maximum percentage of increment during post-MCO in all zones was up to 25%. The loosened restriction policy has resulted in more AMD flowing into surface water and increased pollution in Chini Lake. As a whole, our outputs revealed that Sentinel-2 data had a major potential for assessing the AMD-associated pollution of water.

Gibberellic acid improves growth and reduces heavy metal accumulation: A case study in tomato (Solanum lycopersicum L.) seedlings exposed to acid mine water

This study investigated the effect of gibberellic acid (GA3) on the growth of tomato seedlings and heavy metal accumulation within seedlings tissue irrigated with acid mine water (AMW). Three experimental treatments were administered using a completely randomized design with five replicates. The experimental treatments included were gibberellic acid + acid mine water (GA3 + AMW), acid mine water (AMW), and tap water. Seedlings were irrigated directly in pots with 400 mL of 100% AMW at two-day intervals 21 days after planting. Drenching of the seedlings with GA3 was done every 24 h for eight consecutive days from 28 days after planting. Results on the physicochemical analysis showed high concentrations of heavy metals (HMs) in AMW compared to tap water and the experimental treatment significantly affected the measured plant growth parameters. Tomato plants irrigated with AMW alone were shorter (4.00 cm) than plants irrigated with tap water (14.00 cm), while plants treated with AMW and GA3 were much taller (16.50 cm) than the latter (control). Moreover, HM accumulation differed among the three treatments. Seedlings that received AMW with no GA3 accumulated more HMs (Cd, Cr, Cu, Ni, and Zn) in their roots, stems, and leaves while plants treated with GA3 had a decrease in the accumulation and distribution of HMs in the different plant tissues (roots, stems, and leaves) relative to AMW alone and the plants irrigated with tap water alone. The study revealed that GA3 boosted the growth of tomato seedlings irrigated with AMW and also altered HM accumulation with the tissues of the seedlings.

Comparison of two acidophilic sulfidogenic consortia for the treatment of acidic mine water.

Sulfate-reducing bioreactors are a biotechnological alternative for the treatment of acid mine drainage (AMD). In this study, two separate bioreactors with pH and temperature-controlled (Bio I and II) were operated with two different acidophilic microbial consortia to determine their efficiencies in sulfate removal from a synthetic acidic mine water. The bioreactors were operated for 302days in continuous flow mode under the same parameters: fed with a sulfate solution of ∼30mM with a pH of 2.5, the temperature at 30°C, stirred gently at 40rpm and using a continuous stream of nitrogen to help remove the H2S produced in the bioreactor. The glycerol consumption, acetate production, and sulfate removal were monitored throughout the course of the experiment. The community composition and potential metabolic functional groups were analyzed via 16S rRNA partial gene sequencing. Bio I consortium reduced the sulfate, achieving a range of sulfate concentration from 4.7 to 19mM in the effluent liquor. The removal of sulfate in Bio II was between 5.6 and 18mM. Both bioreactors' communities showed the presence of the genus De sulfosporosinus as the main sulfate-reducing bacteria (SRB). Despite differences in microbial composition, both bioreactors have similar potential metabolism, with a higher percentage of microorganisms that can use sulfate in respiration. Overall, both bioreactors showed similar performance in treating acidic mine water containing mostly sulfate using two different acidophilic sulfidogenic consortia obtained from different global locations.

Impact of functional group types in ion exchange resins on rare earth element recovery from treated acid mine waters

Ion-exchange (IX) resins incorporating single functional groups (sulfonic or amino-phosphonic) and two functional groups (sulfonic and phosphonic) were evaluated for selective recovery of Rare Earth Elements (REEs) from acidic mine waters (AMW). The composition of AMW solution, complexing properties of the functional group, and acidity were investigated as key parameters for concentration and separation of REEs from transition elements (TEs). Fe has to be removed from AMW to enable REE recovery and here the AMW was treated with NaOH solutions to reach pH 3.9 where Fe(III) was selectively removed (≤99%) by precipitation of schwertmannite. Single functional IX resin containing a sulfonic group displayed a higher REE recovery efficiency and separation ratio than observed for the bi-functional resin (sulfonic/phosphonic). Concentration factors for REEs between 30 and 40 were achieved using regeneration cycles with H2SO4. The performance of the aminophosphonic resin showed lower separation factors for REEs from TEs than the two resins containing sulfonic groups. IX resins performance was improved by tuning the acidity to match the functional group reactivity, where pH adjustment to the range of 0.5–2.0 provided the highest REE/TE separation factor for the single sulfonic resin followed by the bifunctional resin. The integration of an elution cycle using Na2-EDTA/NH4Cl mixtures strongly increases the concentration factors of REE and Light REE (LREE) concentration factors of up to 260 were achieved for the single functional sulfonic resin.

Recovery of rare earth elements from sulfate-rich acid mine water: Looking through the keyhole the exchange reaction for cationic resin

The ion exchange process for the recovery of rare earth elements (REE) from acid waters is investigated through combined experimental and theoretical approaches. Loading and elution experiments using a strongly acidic cation resin were carried out batchwise and in columns by applying laboratory solutions as well as crude acid mine drainage (AMD). Loading experiments, which assessed the competition of different species during the ion exchange process, showed the preference for La in detriment to Y. The resin was eluted with different inorganic acids and salts to remove the adsorbed REE. The best result was attained with the use of CaCl2 solution, having approximately 80 % of the REE eluted in the batch experiments. It was also noticed that as the flow rate decreased there was an increase in the elution from 80 % to 100 % for light REE and 50–90 % for heavy REE. DFT calculations indicated that the chemical models [LnSO4(H2O)7]+ and [Ln(SO4)2(H2O)5]- (LnLa, Y) are adequate to describe the chemical speciation. Furthermore, these species effectively interact with the resin sulfonic groups in a similar way as to the [Ln(H2O)9]3+ species, explaining why the loading results are high even in the presence of sulfate. For elution, the CaCl2 solution was modeled with the [Ca(H2O)6]2+ species, displacing the La and Y species from the resin. The estimated free energies involved in the mechanisms with and without SO42- are similar. Therefore, DFT calculations indicate that the functional group, which is present in the cation exchange resin, acts as a complexing agent.

Potential for water and metal recovery from acid mine drainage by combining hybrid membrane processes with selective metal precipitation

Acid mining drainage has a serious impact on the environment. Forward osmosis allows the concentration of acid mine waters to favor the formation of enrichment sludges and subsequent selective metal precipitation. In this work, a methodology was proposed to treat mining effluents from the Iberian Pyrite Belt. Forward osmosis experiments were performed using different osmotic pressures from 0.5M to 2.5M NaCl to evaluate water fluxes and recovery. The water recovery obtained was in the range of 50-80%, and the flux remained above 5 (L•m−2•h−1). Four combined processes were modelled to determine the feasibility of eliminating water and precipitating metals. Furthermore, a new hybrid membrane process was proposed to recover at least 75% of water with recovery yields of Al, Fe, Cu, Zn and Mn of greater than 70%. A water production cost of 2.01 $/m3 and a specific energy consumption of 8.03 kWhe/m3 were estimated for the hybrid process.

The role of nanofiltration modelling tools in the design of sustainable valorisation of metal-influenced acidic mine waters: The Aznalcóllar open-pit case

Acid Mine Waters (AMWs) are considered the most challenging environmental problem in the Iberian Pyrite Belt (South of Spain) so far, being characterised by an acidic pH (H2SO4-based), high content of heavy metals (e.g. Co, Pb, rare earth elements (REEs)) and non-metals (e.g. As). Nowadays, AMWs are being contemplated as a source of valuable metals (e.g. Zn, Cu, REEs), and different recovery routes have been studied (e.g. ion-exchange, membrane technologies). Among them, nanofiltration (NF) provides the possibility of water (or H2SO4) recovery and concentration of metals, which can be recovered in a subsequent stage. This work evaluates the performance of the Desal DK NF membrane to treat AMW from Aznalcóllar open-pit, which presents a low pH (2.6) and high contents of Zn (920 mg/L), Mg (2540 mg/L) and REEs (17 mg/L). The effect of solution pH on membrane performance was evaluated. Results showed that the equilibrium SO42-/HSO4- controlled the transport of species. Rejections of sulphate were around 84 % at pH 2.1 (prevalence of HSO4-) and increased to 92 % at pH 3.1 (prevalence of SO42-). Metal rejections remained higher than 74 % (except for monovalent species). Additionally, membrane permeances were determined using the Solution-Electro-Diffusion model coupled with reactive transport, and later used to assess the design of the process treatment of the AMW. Results demonstrated the possibility of concentrating metals and recovering H2SO4 as permeate, but also showed that gypsum and anhydrite precipitation can occur. Additionally, CAPEX and OPEX were estimated for a NF plant treating 2 Hm3/year.

Groundwater risk assessment of abandoned mines based on pressure-state-response—The example of an abandoned mine in southwest China

Due to the exhaustion of coal resources, resource integration, backward production capacity elimination, and other reasons, a large number of coal mines in China have been closed or are close to closing. When a mine is closed and the drainage stops, the water level of the mining area will rise rapidly, resulting in acid mine water (AMD), which carries pollutants through mining-induced fracture faults or poorly closed boreholes into groundwater or surface water, resulting in pollution and safety risks to the water environment. Therefore, it is essential to conduct environmental risk assessments of abandoned mine groundwater for mine environment governance and protection. On this basis and employing the pressure-state-response (PSR) risk evaluation system, and considering the abandoned Chuanbei mine in northern Sichuan province, China, mine water inflow, groundwater water chemistry, and the water environment pollution situation are analyzed, considering the AMD release and its environmental impact, while identifying the drivers and sources of pollution. Considering the mine drainage conditions, three first-level indices of environmental sensitivity response and 12 second-level indices of the redox state of aquifer permeability mine were determined, such as the aquifer thickness and relative location. The results show that the groundwater environmental risk in the study area is high, and the groundwater environmental risk index in the southeast is higher than that in the northwest. Heavy metals and other toxic and harmful substances carried by AMD are found to enter the surrounding waters, posing a direct threat to the health of downstream residents. These results can provide theoretical guidance for the comprehensive remediation of mine environments in this area, and also provide a reference for environmental risk assessment of other similar current mining areas.

Corrosion of Carbon Steel in Extreme Environments by Acid Mine Water: Experimental Study of the Process Using a Factorial Analysis Tool

Acid mine drainage (AMD) is a process resulting from mining activity, which has a potential degrading effect on metallic materials used in machinery and structural installations, mainly carbon steel composites. This work shows how steel is affected and degraded by AMD, as well as the physicochemical changes that occur in the solvent as a consequence of the metal corrosion process. For this purpose, thirty specimens were immersed in AMD for thirty weeks and were removed once per week, observing the changes that had occurred both in the metal and in the solvent to which it was exposed. The results show a material degradation with a loss of weight and alterations in the acid drainage with an increase in pH, total dissolved solids (TDS) and modifications in the rest of the solvent characteristics. The data from the measurements of the plates under study, together with the physicochemical data of the resulting reagent solution, were integrated into matrices for subsequent graphical–statistical processing using Statgraphics Centurion software, a powerful tool for exploratory data analysis, statistical summary, analysis of variance, statistical control, multivariate analysis, time series, etc., and which allows the different variables studied to be classified into categories or proximity ratios.