Synthetic Acid Mine Drainage Research Articles

Potential for high-grade recovery of rare earth elements and cobalt from acid mine drainage via adsorption to precipitated manganese (IV) oxides

High demand for rare earth elements (REEs) has increased interest in their recovery from unconventional sources, such as acid mine drainage (AMD). AMD contains elevated concentrations of Mn, Fe, and Al, which precipitate as (oxy)hydroxide minerals as pH is raised. These precipitates can remove cations including REEs and Co from solution via sorption and/or coprecipitation. In this study we developed a method to recover these critical minerals by sorption to MnO2, precipitated by oxidation of in situ Mn (II) with added KMnO4 at acidic pH. MnO2 solids were prepared with varying concentrations of KMnO4, SO42−, and Cl−, to elucidate the effects of excess KMnO4, SO42− concentration, and ionic strength on adsorption. When using a stoichiometric ratio of Mn (II) and KMnO4, 100% removal of REEs and Co occurred at approximately pH 3.5, nearly 2 pH units lower than was observed by sorption to Fe and Al hydroxysulfates. When using excess KMnO4 nearly 100% removal of REEs and Co was accomplished at approximately pH 2, although SO42− was found to inhibit REE sorption. From these results, we developed a two-stage process for recovery of REEs from AMD; a preliminary pH adjustment to remove Fe and Al hydroxy-sulfates, followed by adding KMnO4, precipitating MnO2, enabling recovery of REEs and Co. We tested this process in a representative synthetic AMD, achieving a grade of 6.16 mg REEs per g of solid, which is 65 % of the maximum possible grade based on solution composition. Fractionation of REEs was observed, with light REEs (LREEs) preferentially sorbed to MnO2 relative to both medium REEs (MREEs) and heavy REEs (HREEs). In contrast, preferential sorption of HREEs was observed for sorption to Fe and Al oxyhydroxides at all pH ranges. These results suggest the mechanisms of REE sorption differ among the solids and warrant further study.

Association of rare earth elements with secondary mineral phases formed during alkalinization of acid mine drainage

Rare Earth Elements (REE) are present in acid mine drainage (AMD) in micromolar concentrations and AMD discharge may lead to an environmental risk. Alkaline Passive Treatment Systems (PTS) are often used to treat AMD and trap toxic trace elements. This study was set up to identify mechanisms by which REE are trapped in or on secondary phases formed in a PTS. Batch alkalinization experiments were performed to simulate PTS by sequentially increasing the pH of AMD collected from the Tharsis mining area inside the Iberian Pyrite Belt and synthetic AMD water samples via CaCO3 addition. The solids that precipitated up to pH ~4 and between pH 4–6 were collected and characterized by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in combination with Scanning Electron Microscope/Energy Dispersive X-ray spectroscopy (SEM/EDX) and synchrotron-based X-ray Absorption Spectroscopy (XAS) and synchrotron-based Micro-X-ray Fluorescence (μ-XRF). Results reveal that REE are mostly scavenged between pH 4–6 in association with Al and Fe phases, whereas a smaller fraction is scavenged at pH ~4 by association with gypsum. Synchrotron-based analysis evidences the incorporation of La3+ into the gypsum structure by substituting Ca2+, indicating a co-precipitation mechanism with gypsum occurring mainly at low pH. Results from parallel adsorption and co-precipitation tests suggest that the REE scavenging between pH 4–6 could be due to a combination of adsorption and co-precipitation on Al(OH)3 and ferrihydrite. This implies that in PTS, REE would be mainly found in Al- (and Fe-) oxyhydroxides occurring in deeper layers of the PTS, i.e., where higher pH-values occur, though a small fraction, especially the light REE, could also be found incorporated into gypsum in the upper layers.

Application of Low-Pressure Nanofiltration Membranes NF90 and NTR-729HF for Treating Diverse Wastewater Streams for Irrigation Use

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

Bioelectrochemical treatment of acid mine drainage: Microbiome synergy influences sulfidogenesis and acetogenesis

Bioelectrochemical systems (BES) are emerging as potential technologies that can remediate acid mine drainage (AMD) by cathodic reduction of sulfates to metal sulfides. This study evaluated bioelectrochemical remediation of sulfate rich AMD at two applied cathode potentials; BES-1: −1.0 V and BES-2: −0.8 V. Sulfate reducing bacteria were selectively enriched to be used as biocatalyst in BES. Initially, lactate was fed as carbon source and switched to chemolithoautotrophy with only CO2-fed conditions. Both BESs were operated at 3±0.2 g/l of sulfate with synthetic AMD (SAMD) fed first, and gradually changed to 50% AMD from mining site with 50% SAMD. Sulfate reduction was relatively higher with BES-1: 82% than BES-2: 76% coupled with sulfidogenesis. Interestingly, acetogenesis (BES-1: 2.12±0.2 g/l, BES-2: 1.9±0.2 g/l) was also noticed with high reduction currents (BES-1&2: >-70 mA). Microbiome community analysis revealed the dominant presence of sulfate reducers, acetogens, syntrophic bacteria and Methanobacterium, probing microbial synergy aiding sulfate reduction. An added advantage was the iron-sulfide (FeS) particles formation on cathode, which might have contributed to increased reduction currents. This study reveals insights into microbial synergy for autotrophic sulfate reduction within mixed microbiome communities along with the impact of FeS particles as conducive facilitator for electron transfer in BES, thereby enhancing electrosynthetic acetate production.

Continuous co-treatment of mine drainage with municipal wastewater

Acid mine drainage (AMD) and municipal wastewater (MWW) are commonly co-occurring waste streams in mining regions. Co-treating AMD at existing wastewater facilities represents an innovative solution for simultaneous AMD reclamation and improved MWW treatment. However, unknowns related to biological processes and continuous treatment performance block full-scale use. The overarching goal of this work was to address questions related to efficacy and performance of continuous processing of AMD in a biological MWW treatment system. Synthetic AMD was co-treated with synthetic MWW in a continuously-operating bench-scale sequencing batch reactor (SBR). SBRs treated MWW with two strengths of AMD (91 and 720 mg/L as CaCO3 Acidity) to capture the variations of coal AMD chemistry and strength observed in the field. Each co-treatment phases lasted 40+ days, during which clarified effluent and settled sludge quality was routinely monitored to determine impacts of co-treatment relative to conventional MWW treatment performance. Co-treatment produced effluent that met key standards for secondary treatment including biochemical oxygen demand (BOD) < 5 mg/L, total suspended solids (TSS) < 20 mg/L, and pH ∼7.0. Addition of AMD also improved treatment performance, increasing Phosphate (PO4) removal by >60% and pathogen removal by an order of magnitude. Furthermore, AMD co-treatment did not exhibit any major impacts on the overall diversity of the wastewater microbial community. Co-treatment sludge had slightly higher settleability and a lower bound water content, but notable changes in sludge morphology was observed. This study demonstrates co-treatment allows for continuous mitigation of AMD without adversely impacting MWW treatment performance in conventional biological MWW processes.

Bioremediation of acid mine drainage using sulfate-reducing wetland bioreactor: Filling substrates influence, sulfide oxidation and microbial community

Two sulfate-reducing wetland bioreactors (SRB-1 filled with lignocellulosic wastes and SRB-2 with river sand) were applied for synthetic acid mine drainage treatment with bio-waste fermentation liquid as electron donor, and the influence of filling substrates on sulfate reduction, sulfur transformation and microbial community was studied. The presence of lignocellulosic wastes (mixture of cow manure, bark, sawdust, peanut shell and straw) in SRB-1 promoted sulfate reduction efficiency (68.9%), sulfate reduction rate (42.1 ± 11 mg S/(L·d)), dissolved sulfide production rate (27.4 ± 7 mg S/(L·d)), and particularly caused high conversion ratio of sulfate reduction into dissolved sulfide (66.4%). In comparison, the relatively low sulfate reduction efficiency (42.9%), sulfate reduction rate (27.0 ± 10 mg S/(L·d)), dissolved sulfide production rate (5.6 ± 3 mg S/(L·d)) and low dissolved sulfide conversion efficiency (21.2%) occurred in SRB-2. Mixed organic substrates including easily assimilated electron donors (in manure) and lignocellulosic matter were effective to promote quick start and long-term microbial sulfate reduction. More than 98% of produced dissolved sulfide was oxidized dominantly by photoautotrophic green sulfur bacteria (genera Chlorobium and Chlorobaculum), of which 64.6% and 54.5% was converted into elemental sulfur for SRB-1 and SRB-2. The oxidation of sulfide into elemental sulfur for potential recovery rather than sulfate is preferred. Diverse sulfate reducing bacteria and sulfide oxidizing bacteria co-existed in the treatment system, which led to a sustainable sulfur transformation. High metal removal efficiency for Fe (99.6%, 92.5%), Cd (99.9%, 99.9%), Zn (99.4%, 98.5%), Cu (94.5%, 94.6%) except for Mn (9.3%, 3.6%) was achieved, and effluent pH increased to 6.5–7.7 and 6.7–7.7 for SRB-1 and SRB-2, respectively. Microbial community was regulated by filling substrates. Synergism between lignocellulosic decomposing bacteria and sulfate reducing bacteria played a vital role in lignocellulosic bioreactor treating AMD, in addition to fermentation liquid serving as effective electron donor.

Valorization of abandoned mine wastewater for the production of energy in a reverse electrodialysis cell

The study explores the technical feasibility of using abandoned mining site wastewater, specifically acid mine drainage (AMD), as an electrode solution in a reverse electrodialysis (RED) stack for energy production. Through experiments using a RED cell with varying electrode solutions, it was determined that the system achieved a maximum power density of 0.327 W m−2cell pair (5.01 W m−2electrode) when using simple mixtures of Cu2+ and Fe2+ ions, aligning with previous research on the Fe2+/Fe3+ redox pair. Synthetic solutions mimicking AMD composition also yielded promising results. When operating the system with real AMD effluent from an abandoned mine, a slightly lower maximum power density of 0.137 W m−2cell pair was achieved, only 5.5 % lower than with synthetic AMD. An extended-duration test showed a minor increase in pH in the electrode solution, but importantly, no metal deposition occurred on the electrode surface, as the pH consistently remained below 3.5 throughout the test. These findings indicate the potential of AMD as a viable electrode solution, offering a promising avenue for further research in the development of more sustainable RED systems.

Acid mine drainage (AMD) treatment using a novel tannic acid functionalized Boehmite/polyether sulfone nanofiltration membrane

This study focuses on the fabrication of TA-BM/PES membranes by the incorporation of tannic acid functionalized Boehmite nanoparticles into the PES membrane matrix through the phase inversion technique. The presence of TA-BM nanoparticles in the TA-BM/PES membranes was confirmed by analysis of the FT-IR spectra of the embedded membranes. The hydrophilicity, permeability, surface morphology, and fouling resistance properties of membranes modified with TA-BM nanoparticles were compared to those of the naked membrane. The fouling behavior of the modified membranes was assessed in the presence of a foulant solution containing 200 ppm BSA (bovine serum albumin) and 200 ppm Na2SO4. The flux recovery ratio results showed an improvement in all modified membranes, especially M2 membrane. The modified membranes shown remarkable efficiency in the rejection of heavy metal ions (over 72 %), sulfate (over 80 %), and salt (Na2SO4 > 84 % and NaCl>48 %). The M2 membrane was chosen as the most suitable membrane and shown effective performance in eliminating heavy metals (Fe2+ = 65.5, Mn2+ = 88.8, Mg2+ = 83.5 and Ca2+ = 78.6 %) as well as sulfate (SO42− = 83.5 %) from a synthetic acid mine drainage (AMD) wastewater. Based on the findings presented in this research, it can be concluded that the TA-BM/PES nanofiltration membrane has potential for effective use in the treatment of AMD wastewater.

Evaluation of Hydrotalcites Produced in Seawater for Remediation of Metalliferous Acid Mine Drainage and Submarine Placement

Uncontrolled release of acid mine drainage (AMD) causes widespread detrimental impacts on the receiving environment. Thus, effective treatment to neutralise AMD effluent pH and capture a suite of metals is required. In-situ hydrotalcite (HTC) precipitation is an emerging technology for AMD remediation. HTC has an inherent capacity to accommodate a range of cations and anions during in situ formation, offering a method of broad-spectrum contaminant removal. This study explored the feasibility of using seawater as an Mg source and synthetic AMD in HTC formation. The HTC was formed from a stoichiometric combination of synthetic AMD and seawater. While three initial stoichiometric M2+:M3+ ratios of 2:1, 3:1, and 4:1 were investigated, only HTC with an M2+:M3+ ratio of 2:1 was generated, as confirmed by both mineralogical and geochemical analyses. Importantly, the HTC was demonstrated to effectively remove a suite of metals present in AMD such as Cu, Zn, Al, and Mn with removal rates of between 99.97 to 99.99%. The HTC precipitate contained ≈6.6% Cu and 4.1% Zn, and thus shows the potential, if required, for future metal recovery. Since submarine placement is often used in metal mining and processing operations proximal to the coast, the stability of the HTC precipitate in seawater was also investigated. Importantly, only 0.2% of the Cu and 1.1% of the Zn within the HTC were subsequently leaching in decreasing increments into seawater over 30 days with decreasing increments after the initial seven days. This indicates robust element retention and confirms the potential of HTC for AMD remediation with direct submarine placement.

Leaf Scorching due to Foliar Application of Synthetic Acid Mine Drainage and the Effectiveness of an Antitranspirant in Protecting Leaves

Leaf Scorching due to Foliar Application of Synthetic Acid Mine Drainage and the Effectiveness of an Antitranspirant in Protecting Leaves

Effect of organic substrate thickness on synthetic acid mine drainage (AMD) treatment

A Successive Alkalinity Producing System (SAPS) employing an organic substrate of peat soil and limestone aggregate was investigated for the restoration of synthetic Acid Mine Drainage (AMD). The composition, carbon content, and particle size distribution of the peat soil and limestone were determined by characterisation. Iron sulphate (FeSO4) and sulfuric acid were used to create synthetic AMD (H2SO4). The synthetic AMD was acidic (pH4.0) and had a concentration of iron (Fe) of 100 ppm. A laboratory scale physical model of a tailing pond was created. The synthetic AMD was introduced and filtered through the media. Following that, samples of effluent water were collected and examined to ascertain the pH level. Furthermore, the Fe concentration was determined using a UV-Vis test with a retention duration ranging from 6 to 48 hours. After only 6 hours of retention time, the new technology successfully reduced more than 85% iron concentration and neutralised pH. These findings demonstrated that a combination of peat soil and limestone of adequate thickness might potentially be recommended as an additional treatment media for treating AMD with SAPS.

Exploring the Use of Tobacco Waste as a Metal Ion Adsorbent and Substrate for Sulphate-Reducing Bacteria during the Treatment of Acid Mine Drainage

Treatment of acid mine drainage (AMD) was successfully demonstrated using tobacco waste (dust and stem) as a metal cation adsorbent, pH modifier and carbon source for sulphate-reducing bacteria (SRB). Synthetic and industrial AMD wastewaters were used in batch adsorption and SRB facilitated bioremediation experiments. Up to absorbent loading of 80 g/L, metal removal increased. However, increases above 160 g/L did not offer a proportional increase. At an adsorbent loading of 80 g/L, the highest metal removals of 38, 41, 31 and 43% for iron, nickel, copper and zinc respectively were achieved. The iron data fitted well to the Langmuir adsorption isotherm while the Sips adsorption isotherm better-described nickel, copper and zinc adsorption to tobacco waste. SRBs used were able to use tobacco waste as a carbon source while reducing sulphates to metal sulphides in acid mine drainage. In the presence of SRBs, metal removals by both adsorption and sulphide precipitation were 95, 97, 70 and 93% for iron, nickel, copper and zinc, respectively. Copper, however, demonstrated lower removal yields in both adsorption and bioremediation. Bioremediation improved acid mine drainage pH by 2.05 units. The exponential decay function could model both the metal and sulphate removal perfectly. It was concluded that tobacco waste can be confidently used as an adsorbent and carbon source for sulphate-reducing bacteria while facilitating AMD biological treatment.

Recovery of water and valuable metals using low pressure nanofiltration and sequential adsorption from acid mine drainage

Acid mine drainage (AMD) contains an array of valuable resources such as Rare Earth Elements (REE) and Copper (Cu) which can be recovered along with fresh water. Low pressure nanofiltration with NF90 membrane was first studied to recover fresh water from synthetic AMD and concentration of dissolved metals for subsequent efficient selective recovery. Organic matter (OM) present in AMD was found to cause membrane fouling which resulted in significant flux decline. Powdered eggshell was investigated as a low-cost adsorbent for OM removal. The study showed that a 0.2 mg/l dose of powdered eggshell adsorbed 100% of OM and Fe with no significant loss of other dissolved metals. A steady permeate flux of 15.5 ± 0.2 L/m 2 h (LMH) was achieved for pre-treated AMD with a solute rejection rate of more than 98%. A chromium-based metal organic framework (MOF) modified with N - (phosphonomethyl) iminodiacetic acid (PMIDA) and an amine-grafted mesoporous silica (SBA15) material was synthesized for selective recovery of REE and Cu, respectively. The two adsorbents were used sequentially to selectively adsorb REE (91%) and Cu (90%) from pH adjusted concentrated feed. The formation of coordinating complexes with carboxylate and phosphonic groups on MOF was found to be the primary driving force for selective REE adsorption. Selective uptake of Cu onto amine-grafted SBA15 was due to the formation of strong chelating bonds between Cu and amine ligands. Both adsorbents remained structurally stable over 5 regeneration cycles. The findings here highlight the practical potential of membrane/adsorption hybrid systems for water and valuable metal (REE) recovery from AMD. • Low pressure NF achieved 80% permeate recovery while concentrating dissolved ions. • Modified MOF and SBA15-NH 2 selectively adsorbed 91% of REE and 90% of Cu. • REE show high affinity to deprotonated phosphonic and carboxyl groups in MOF. • Chelating bonds between Cu and amine groups in SBA15 promotes high selectivity. • High reuse capacity over multiple cycles recorded for both adsorbents.

Removal of Heavy Metals from Acid Mine Drainage with Lab-Scale Constructed Wetlands Filled with Oyster Shells

The present study investigated the applicability of constructed wetlands (CWs) filled with oyster shells (OSs) for removing heavy metals from acid mine drainage (AMD). Lab-scale CWs consisted of columns (ID 12.5 cm, H 50 cm) packed with OSs or limestone, which were left unplanted or planted with cattails. Synthetic and real AMD containing 7.3 mg/L of Zn, 38.0 mg/L of Fe, and other minerals (pH = 4.0) were fed to the CWs (1 L/column) under a hydraulic retention time of 7 days in a sequencing batch mode. The effluent pH values of the CWs reached 6.9–8.3. Results show that OSs with high CaCO3 contents had higher neutralizing capability for AMD than limestone had. During 7 months of operation, all CWs were highly effective for removing Zn (88.6–99.2%); Fe (98.7–99.7%); and Cd, Cu, Pb, As, and Mn (48.2–98.9%) from both real and synthetic AMD. The mass balance in the CWs indicated accumulation in OSs or limestone as a main pathway for removing heavy metals, representing 44.8–99.3% of all metals, followed by biomass (8.8–29.9%) in the planted CWs. Other processes examined for this study only played a minor role in removing heavy metals. The higher metal treatment performance of OS CWs demonstrated the value of this aquaculture byproduct as a CW substrate.

Application of nano remediation of mine polluted in acid mine drainage water using machine learning model

Acid mine drainage (AMD) is the term used to describe drainage from coal mines with high sulfur-bearing rocks. The oxidative weathering of metal sulfides leads to AMD. The acidic environment corrodes more harmful compounds in the soil, which is spread throughout the working area. One such significant metal is copper, which is extracted in massive quantities from ores rich in sulfide. A copper-extraction resin might be created by combining diatomaceous earth (DE) particles with polyethyleneimine (PEI), which is shown to have great selectivity and affinity for copper. In this effort, PEI-DE particles’ copper absorption level was examined by using synthetic and actual acid mine drainage samples at varied pH values. The findings of the copper uptake particles have been examined through the Support Vector Machine (SVM) model. Using the n-fold 14 cross-validation approach, the quantities of parameters and C are estimated to be 0.001 and 0.01, respectively. The SVM analysis was correct, and the findings indicated that copper could bind to the material efficiently and preferentially at pH 4. Subsequent water elution studies at a pH value of 1 confirmed the pH-reliant interaction between dissolved Cu and PEI by demonstrating full release of the adsorbed Cu. In this research, the copper absorption of PEI-DE particles from synthetic and genuine AMD specimens was studied based on several pH conditions. The findings suggest that copper may attach to the material effectively and preferentially at pH 4. Studies of filtering water at pH1 later confirmed that all of the adsorbed Cu was released. This shows that the interaction between PEI and dissolved Cu depends on PH.

Impact of seasonal variation on the treatment response of constructed wetlands receiving acid mine drainage in a subtropical region

Acid mine drainage (AMD) emanating from coalfields is a severe form of water pollution with adverse ecological impacts. AMD from Makum Coalfield, Assam, India, is highly polluted and unregulated. The present study describes the influence of seasonality on the efficacy of constructed wetlands (CWs) applied for treating synthetic AMD, analogous to mine water characteristics from the Makum Coalfield. Rainfall is predominant in the northeast region of India. The effect of rainfall events on sheltered (SCW) and unsheltered (UCW) CWs was investigated under natural conditions from January to August. Acidic AMD containing Fe, Al, Mn, Zn, Co, Ni, Cr and sulfate concentrations as 100, 25, 6, 5, 1, 1, 1 and 1100 mg L−1 was continuously supplied to CWs at a hydraulic loading rate of 0.014 m3 m−2 d−1. SCW and UCW raised the pH (>5.5) and demonstrated comparable treatment performance in the dry season. Heavy rainfall imposed a highly sensitive and poor treatment response in UCW, resulting in significantly lower sulfate removal in UCW (51.34 %) than SCW (60.29 %). SCW demonstrated superior metal removal for Fe (90 %), Al (79 %), Zn (94 %), Co (92 %), Ni (91 %) and Cr (96 %), which significantly differed from UCW (85 % Fe, 70 % Al, 93 % Zn, 82 % Co, 83 % Ni and 90 % Cr), except Mn. These findings indicated possible shortening of hydraulic retention time in UCW with minimal or insignificant dilution. This experimental study underlines the limitations of wetland systems in the rainfall-affected region and recommends necessary design control measures to manage the effects of rainfall.

Optimisation of semi-upscaled polymer inclusion membrane (PIMs) based device for passive remediation of metal ions in acid mine drainage (AMD)

Acid mine drainage (AMD) has been a source of environmental contamination in many parts of the world. This is because many countries depend on mining as a source of revenue. However, waste tailing dumps often leach out toxic waste with high levels of metal ions and flow downstream to dams and rivers. The current remediation methods (passive and active) are expensive or ineffective for long-term use. In some cases, these methods generate solid slag waste as a major by-product. However, as part of the green and circular economy, waste materials are viewed as potential resources for raw materials. This work then reports on the design, laboratory optimisation and early-stage application of semi-pilot passive remediation device for the possible recovery of metal ions (cadmium, cobalt, copper, iron, and nickel) in AMD generated in the tailings pond. The sampling remediation device consisted of a polymer inclusion membrane composed of polyvinyl chloride and di-(2-ethylhexyl) phosphoric acid as a semi-penetrable barrier. The device had an upscaled chamber made of nylon with 1000 mL of the receiving solution. This developed passive remediation device was used in both synthetic and real AMD samples where a linear uptake of metals was demonstrated from day 6 to over a month with little influence of matrices. During deployment, the pH was increasing in the receiving solution and decreasing in the source solution of the linear region thus indicating the analytes facilitated transport. On day 35 of environmental application accumulated concentrations of target metal ions were Ni (63.42 mg L−1), Cd (47.48 mg L−1), Co (57.34 mg L−1), and Cu (49.86 mg L−1). Further, the characterisation results showed no signs of membrane degradation in this period. This highlights that the PIMs are a promising future for passive remediation and/or recovery of metal ions in mine wastewater before contamination of rivers and dams downstream.

Study of effects of some metals and hydraulic retention time on performance of AMD treatment by SAPS

Acid mine drainage (AMD) is presently observed as one of the major water pollution problems in mining area throughout the world. Proper scientific management of AMD is essential for achieving the national goals for environmental norms. In this studyperformance of AMD treatment by laboratory successive alkalinity producing system (SAPS) by observing the effects of some metals and hydraulic retention time. In this study the experiments were conducted in laboratory successive alkalinity producing system (SAPS) with different synthetic AMDs for five Hydraulic retention times(HRTs). The successive alkalinity producing system shown the promising results during the AMD treatment. The effects of iron, aluminium and manganese were jointly investigated, whichshowed that Net alkalinity generation (NAG) increases with increase in influent metal contents. It was also observed thatNAG also showed increasing tendency with HRT during AMD treatment by SAPS. The obtained findings from this study can be applied for efficient design and operation of successive alkalinity producing system for AMD treatment process in mining industry.

Removal of Iron and Manganese in Acid Mine Drainage Using Natural Zeolite

The environmental problem that often occurs in coal mining is acid mine drainage which can pose a serious threat to human health, animals and ecological systems. Acid mine drainage contains heavy metal contaminants such as iron and manganese. The purpose of this study was to determine the adsorption equilibrium carried out using natural zeolite adsorbents type mordenite from Klaten, Central Java. The application of natural zeolite with a volume of 100 mL synthetic acid mine drainage with concentrations of Fe 41.97 mg/L, Mn 21.75 mg/L and variations in dose of natural zeolite (2, 4, 6, 8, and 10 grams). The highest percent removal was at a dose of 10 grams of zeolite resulted in % removal of 97.94 % for Fe and 67.81 % for Mn. The results obtained using Langmuir and Freundlich adsorption isotherms. The results followed the Freundlich isotherm model with an adsorption parameters Kf = 0.427 mg/g, R2 = 0.991, n = 1.610 Fe metal and Mn metal adsorption parameters are Kf = 0.006 mg/g, R2 = 0.9971, and n = 0.578

Acid Mine Drainage Treatment Using a Process Train with Laterite Mine Waste, Concrete Waste, and Limestone as Treatment Media

Without treatment, the harmful effects of acid mine drainage (AMD) lead to the destruction of surrounding ecosystems, including serious health impacts to affected communities. Active methods, like chemical neutralization, are the most widely used approach to AMD management. However, these techniques require constant inputs of energy, chemicals, and manpower, which become unsustainable in the long-term. One promising and sustainable alternative for AMD management is to use passive treatment systems with locally available and waste-derived alkalinity-generating materials. In this study, the treatment of synthetic AMD with laterite mine waste (LMW), concrete waste, and limestone in a successive process train was elucidated, and the optimal process train configuration was determined. Six full factorial analyses were performed following a constant ratio of 0.75 mL AMD/g media with a 15-min retention time. The evolution of the pH, redox potential (Eh), total dissolved solids (TDS), heavy metals concentration, and sulfates concentrations were monitored as the basis for evaluating the treatment performance of each run. LMW had the highest metal and sulfates removal, while concrete waste caused the largest pH increase. A ranking system was utilized in which each parameter was normalized based on the Philippine effluent standards (DENR Administrative Order (DAO) 2016–08 and 2021–19). Run 4 (Limestone-LMW-Concrete waste) showed the best performance, that is, the pH increased from 1.35 to 8.08 and removed 39% Fe, 94% Ni, 72% Al, and 52% sulfate. With this, the process train is more effective to treat AMD, and the order of the media in treatment is significant.