Coal Acid Mine Drainage Research Articles

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.

Self-hydrolyzing Submerged Flow Technology for Acid Coal Mine Drainage Treatment: Effective Removal of Iron Ions

In this study, mine wastewater from Leiyang, Hunan Province was taken as the research object to investigate the effect of using the method of self-hydrolytic submerged sedimentation to treat acid coal mine drainage. It was found in this study that the removal rate of sulfate ions and iron ions from the acidic coal mine drainage stock solution at pH=2.7 was very limited by self-hydrolytic sedimentation experiments relying only on pure vertical sedimentation flow treatment, but the hydrolytic treatment could greatly improve the solution environment and promote the formation of secondary minerals of sulfate ions and iron ions in the acidic coal mine drainage, which greatly improved the removal rate of iron ions. Both suspended and precipitated materials produced in the self-hydrolysis sedimentation experiments were hydroxylated iron sulfate secondary minerals- Schwertmannite [Fe8O8(OH)8-2X(SO4)X (1 ≤ x ≤ 175)], the formation of which is inextricably linked to the low pH environment and high concentration of sulfate and iron ions in coal mine wastewater. Self-hydrophoretic submerged flow can remove iron ions from acidic coal mine drainage at low cost and high efficiency, and the total iron removal rate of this system can reach 90.93% after 24 h of treatment, which has a favorable comprehensive utilization value.

Use of a Waste-Derived Linde Type-A Immobilized in Agarose for the Remediation of Water Impacted by Coal Acid Mine Drainage at Pilot Scale.

A new adsorbent based on an immobilized waste-derived LTA zeolite in agarose (AG) has proven to be an innovative and efficient alternative for removing metallic contaminants from water impacted by acid mine drainage (AMD) because the immobilization prevents the solubilization of the zeolite in acidic media and eases its separation from the adsorbed solution. A pilot device was developed containing slices of the sorbent material [AG (1.5%)-LTA (8%)] to be used in a treatment system under an upward continuous flow. High removals of Fe2+ (93.45%), Mn2+ (91.62%), and Al3+ (96.56%) were achieved, thus transforming river water heavily contaminated by metallic ions into water suitable for non-potable use for these parameters, according to Brazilian and/or FAO standards. Breakthrough curves were constructed and the corresponding maximum adsorption capacities (mg/g) (Fe2+, 17.42; Mn2+, 1.38; Al3+, 15.20) calculated from them. Thomas mathematical model was well fitted to the experimental data, indicating the participation of an ion-exchange mechanism in the removal of the metallic ions. The pilot-scale process studied, in addition to being highly efficient in removing metal ions at toxic levels in AMD-impacted water, is linked to the sustainability and circular economy concepts, due to the use as an adsorbent of a synthetic zeolite derived from a hazardous aluminum waste.

Characterization of arsenic (III and V) adsorption on natural schwertmannite formed in acid coal mine drainage: Batch studies and spectroscopic observations

The adsorption behavior of As(III) and As(V) on natural schwertmannite (NSCH) was investigated using batch experiments and spectroscopic observations. NSCH showed comparable As adsorption capacities to synthetic schwertmannite (SSCH); particularly, a much higher affinity toward As(III) than toward As(V) was observed at pH 7, suggesting that NSCH is a promising As(III) adsorbent. As(III) adsorption increased with increasing pH and decreasing ionic strength (IS); effects of pH and IS on As(V) adsorption were opposite and negligible, respectively. These results indicated that the adsorption behaviors of As(III) and As(V) are significantly affected by the solution pH, IS, and As species. Speciation modeling and X-ray spectroscopic analyses revealed limited adsorption of As(V) on NSCH through the formation of only the bidentate binuclear corner-sharing inner-sphere complex, which was suppressed at a pH above the pHPZC because of the electrostatic repulsion between the anionic As(V) and the negatively charged NSCH surface. Compared to As(V), a greater amount of As(III) was adsorbed on NSCH, forming both bidentate mononuclear edge-sharing and bidentate binuclear corner-sharing inner-sphere complexes, including minor outer-sphere complexes. Some of the adsorbed As(III) was oxidized to As(V) during adsorption. Owing to the strong surface complexation, less than 4% of As(III) and As(V) were desorbed, indicating that stable As fixation is possible. These findings provided valuable information for the recycling of acid mine drainage sludge and its use in eco-friendly and cost-effective As attenuation.

Biological and electrochemical treatments of coal mine-impacted water (MIW): toxicological evaluation on the duckweed Landoltia punctata

BackgroundTwo different coal mine-impacted water (MIW) treatments (biological via biostimulation of sulfate-reducing bacteria (SRB), and electrocoagulation (elC)) were proposed, reaching efficiencies of up to 99.79% in relation to SO42−, Fe, Mn, and Al ions, as well as acidity removals. The MIW, a high pollutant potential effluent, consists of river water impacted by coal acid mine drainage (AMD), which is acid, rich in sulfate and dissolved metallic ions, and consequently toxic. The aim of this study was to make a toxicological evaluation of MIW after biological and electrochemical treatments on Landoltia punctata, in order to verify the safeness and usability of the two treated waters. Material and methodsDuckweeds were exposed to different dilutions (0, 25, 50, 75, and 100% of samples) of the two treated waters, and the growth (r) and inhibition of growth (Ir) rates were calculated, based on 50% effect concentration (EC50). ResultsThe water from the biological treatment (microcosm assay) presented the highest toxicity (EC50 = 33.42%), even higher when compared to the raw MIW (EC50 = 42.78%), probably due to the hydrogen sulfide, that even after a purge removal, remained in solution. The results showed that this water, despite being within the standards in physicochemical terms, demonstrated risks in terms of toxicity. The water from electrocoagulation (elC) treatment, in the opposite way, showed much less toxicity, even lower than the control, and therefore not reaching EC50, also suggesting a possible nutrient function of the treated water. Consequently, the treated water by elC could, for example, has potential for non-potable use. ConclusionsThe study made it possible to prove the efficiency of elC treatment (72%, 99.79%, 85%, and 87.36% for SO42−, Fe, Mn, and Al, respectively), the importance of post-treatment toxicological assessments, and the potential of the duckweeds as an option for a test organism in these types of evaluations. Statement of noveltyThis paper with duckweed enabled the identification of the most suitable treatment to allow the treated water to be (re)used, since both treatments presented high efficiencies in terms of sulfate, acidity, and metal removals. This approach therefore gives a complementary view of the treatment then beyond complying with current environmental legislation to the treated effluent.

Biochemical treatment of coal mine drainage in constructed wetlands: Influence of electron donor, biotic–abiotic pathways and microbial diversity

The management and treatment of extremely acidic coal mine drainage (CMD) from Northeastern Coalfield (NEC), Assam, India, remains a perpetual environmental challenge. The present work proposes an effective passive bioremediation strategy for highly acidic (pH of 2.2) synthetic CMD simulated to represent mine discharge from the NEC (in mg L–1) (Fe: 100, Al: 25, Mn: 6, Zn: 5, Co: 1, Ni: 1, Cr: 1 and SO42-: 1000–1200), using a horizontal sub-surface flow constructed wetland (HSSF-CW). Gravel was used as the media in HSSF-CW and operated continuously for 218 days, including acclimatization (I–IV) and treatment (V–VI) phases at a hydraulic retention time of 7 days. COD/SO42- ratio was varied as 0.67 in phase I–V and 0.33 in phase VI. High average metal removal efficiency was achieved for Fe (73%), Al (79%), Zn (98%), Co (95%), Ni (99%) and Cr (100%), but Mn (21%) in the treatment phase. In phase V, high sulfate removal efficiency (74%) conforming sulfidogenesis pathway was observed. The prominence of acidophilic sulfate-reducing bacteria (SRB) (Desulfosporosinus meridiei) was revealed. Sulfate reduction by SRB generated alkalinity and increased pH to 5.1–6.8, which assisted in metal retention (as oxides, hydroxides and sulfides precipitates). At lower COD/SO42-, alkalinity decreased due to incomplete sulfate reduction (45%) as COD became the limiting factor, evident from the lower pH and subsequent remobilization of iron and other adsorbed metals in phase VI. This exploratory study recommends the optimization of COD/SO42- and provides an efficient sustainable solution to mitigate CMD pollution.

Characterization of Arsenic (III and V) Adsorption on Natural Schwertmannite Formed in Acid Coal Mine Drainage: Batch Studies and Spectroscopic Observations

Characterization of Arsenic (III and V) Adsorption on Natural Schwertmannite Formed in Acid Coal Mine Drainage: Batch Studies and Spectroscopic Observations

Different effect of nitrogen sources in autotrophic and mixotrophic culture of Scenedesmus sp for biomass and carotenoids production using acidic coal mine drainage effluents

In the present study, the conditions for autotrophic and mixotrophic culture of Scenedesmus sp were established. Effluents from acidic coal mine drains were used to study biomass and carotenoid production, both under autotrophic and mixotrophic conditions in relation to the effect of different sources of nitrogen: sodium nitrate, urea and ammonium phosphate. Pollutant removal was determined, such as COD, TOC, heavy metals, ions and total suspended solids. Batch cultures lasted nine days and biomass production, carotenoids and pollutant removal were compared in each condition. The highest biomass concentration reached was 1.2 g/L in the mixotrophic culture with urea, followed by the culture with sodium nitrate of 0.9 g/L in a C/N ratio of 6:1. The highest carotenoid specific concentration was reached in the mixotrophic culture with sodium nitrate, 19.43 mg carotenoids /g biomass. The culture with ammonium phosphate was found to be inhibitory for the growth of the microalgae with the lowest results of all the parameters except for the autotrophic culture where the concentration of carotenoids was very similar to those reached with sodium nitrate and urea. Finally, the mixotrophic culture with urea presented the highest removal percentages, being 86.97% for total iron, 58.29% for chlorides and 92.5% for COD.

Rare earth elements and yttrium (REY) in coal mine drainage from Southwest China: Geochemical distribution and resource evaluation

The ever-intensifying global demand and supply shortage of rare earth elements (lanthanides and yttrium, REY) have led to investigations into alternative sources of REY. Coal mine drainage (CMD) has been suggested as an attractive supplementary source of REY primarily due to its high content of dissolved REY, and some CMD is considered critical-REY resource. Guizhou has the fifth largest coal reserve in China and a long history of coal mining activities with the continuous discharge of CMD, which is a long-overlooked likely source of REY. In the present study, 120 CMD samples were collected from the Guizhou coal mine areas of Southwest China to investigate REY concentrations, enrichment trends and potential resources for REY reclamation. The obtained concentrations of REY across all the CMDs vary from less than 0.02 μg/L to more than 8765.66 μg/L, with an average of 684.12 μg/L. The average ΣREY concentrations of CMD from different coal-bearing strata decrease in the following order: Liangshan Formation (LS Fm.; 2337.14 μg/L) > Xiangbai Formation (XB Fm.; 1591.82 μg/L) > Heshan Formation (HS Fm.; 1249.22 μg/L) > Longtan Formation (LT Fm.; 1243.48 μg/L) > Banan Formation (BN Fm.; 534.66 μg/L). When normalized to the North American Shale composite (NASC), most CMD samples generally display middle rare earth element (MREE) enrichment, but some are also enriched in light rare earth element (LREE) and heavy rare earth element (HREE). The REY distribution patterns, Mantel test and geochemical modelling results demonstrate that the geochemical compositions of CMD and the geological conditions are significantly correlated with the behaviours of REY in CMD. CMD with pH ≤ 5.5 contains elevated concentrations of dissolved ΣREY and is also enriched in critical-REY (Nd, Eu, Tb, Dy, Er and Y). Critical-REY in CMD with pH ≤ 5.5 accounts for 19.07%–68.21% of the total REY, and the outlook coefficients (Coutl) of REY reclamation in acidic CMD are in the range of 0.48–4.14. The data of high proportions of critical-REY and the Coutl values presented in this study suggest that CMDs with pH ≤ 5.5 from coal-bearing strata of the LS Fm., LT Fm. and XB Fm. could be a promising alternative source of REY, especially critical-REY.

Genome-Wide Association Study of Natural Variation in Arabidopsis Exposed to Acid Mine Drainage Toxicity and Validation of Associated Genes with Reverse Genetics

Acid mine drainage (AMD) is a huge environmental problem in mountain-top mining regions worldwide, including the Appalachian Mountains in the United States. This study applied a genome-wide association study (GWAS) to uncover genomic loci in Arabidopsis associated with tolerance to AMD toxicity. We characterized five major root phenotypes—cumulative root length, average root diameter, root surface area, root volume, and primary root length—in 180 Arabidopsis accessions in response to AMD-supplemented growth medium. GWAS of natural variation in the panel revealed genes associated with tolerance to an acidic environment. Most of these genes were transcription factors, anion/cation transporters, metal transporters, and unknown proteins. Two T-DNA insertion mutants, At1g63005 (miR399b) and At2g05635 (DEAD helicase RAD3), showed enhanced acidity tolerance. Our GWAS and the reverse genetic approach revealed genes involved in conferring tolerance to coal AMD. Our results indicated that proton resistance in hydroponic conditions could be an important index to improve plant growth in acidic soil, at least in acid-sensitive plant species.

Highly efficient removal of aluminum, iron, and manganese ions using Linde type-A zeolite obtained from hazardous waste

Coal acid mine drainage (AMD) contaminates natural water to form mine-impacted water (MIW), which is characterized by high levels of acidity, sulfate, and metallic ions. This study investigates the use of a Linde Type-A (LTA) zeolite obtained from a hazardous industrial waste for Al3+, Fe2+, and Mn2+ removal from synthetic aqueous solutions. The aim of this study is to stablish a basis for the subsequent treatment of MIW in order to obtain reuse water. In a central composite rotatable design (CCRD) study, 8.25 g L−1 zeolite and 147 rpm were the optimal conditions for treating the multicomponent solution, yielding 99.9, 99.9 and 99.3% removal for Al3+, Fe2+, and Mn2+, respectively. Isothermal studies showed that the affinity of the ions by the zeolite were ranked as Al3+>Mn2+>Fe2+. The best fitting isothermal models for monocomponent solutions were Tóth, Freundlich, and Sips for Al3+, Fe2+, and Mn2+, respectively. In the multicomponent solution, Sips and Freundlich were the better fitting models for Al3+ and Mn2+, respectively, indicating a weakness of the sorbate-sorbent interactions. Kinetic studies revealed that the quantitative removal of Al3+ was achieved in 5 min. The multicomponent solution was transformed into water that was suitable for non-potable use after an optimal time of 60 min. The results demonstrate that LTA zeolite synthetized from hazardous waste has a high potential for remediating contaminated water by metallic ions at low dosages and short times. Using LTA zeolite for remediating contaminated water could make a positive contribution to the circular economy and environmental sustainability.

Critical metal recovery potential of Appalachian acid mine drainage treatment solids

Rare earth elements (REE) are critically important in clean energy technologies, but their mining and refining is energy intensive and generates significant quantities of environmentally harmful waste. The treatment of acid mine drainage (AMD), which is both a global environmental problem and a potential source of these elements, preconcentrates REE and critical metals such as manganese and cobalt into oxide/hydroxide waste products from which they can potentially be recovered. Analysis of 281 treatment solids from coal AMD remediation systems across the northern Appalachian Basin, eastern USA, indicate that the most promising solids (REE value >$400 USD/metric ton) are produced in systems that use limestone or sodium hydroxide to treat low pH (<5) AMD with elevated dissolved aluminum and manganese content. In particular, recovering REE from passive treatment systems could both subsidize treatment of AMD while reducing the environmental footprint of REE extraction.

Multivariate statistical evaluation of dissolved heavy metals and a water quality assessment in the Lake Aha watershed, Southwest China

Heavy metals are of public concern in aquatic ecosystems due to their growing release from industries and mining activities. This study investigated the sources, temporal-spatial distributions and water quality of dissolved heavy metals (Mn, Co, Al, Ni, Ba, V, Sb, Fe, Sr) in the Lake Aha watershed, an area under the influence of sewage and acid mining drainage. These heavy metals displayed significant spatial and temporal variabilities. The water quality index results (WQI values ranged from 3.21 to 15.64) and health risk assessment (all hazard indexes are below 1) indicated that dissolved heavy metals in this study pose a low risk for human health. Correlation analysis and principal component analysis indicated that Fe and Sr mainly presented a natural geological feature in the study area, and Mn, Co, Al and Ni were influenced by the acid coal mine drainage, whereas Ba, V and Sb were under the impact of local industrial or medical activities. This study provides new insights into the risk assessment of heavy metals in small watersheds.

Synthesis of Poly-Alumino-Ferric Sulphate Coagulant from Acid Mine Drainage by Precipitation

The wastes generated from both operational and abandoned coal and metal mining are an environmental concern. These wastes, including acid mine drainage (AMD), are treated to abate the devastating effects they have on the environment before disposal. However, AMD contains valuable resources that can be recovered to subsidize treatment costs. Two of the major constituents of coal AMD are iron and aluminium, which can be recovered and engineered to function as coagulants. This work examines the potential of producing a poly-alumino-ferric sulphate (AMD-PAFS) coagulant from coal acidic drainage solutions. The co-precipitation of iron and aluminium is conducted at pH values of 5.0, 6.0 and 7.0 using sodium hydroxide in order to evaluate the recovery of iron and aluminium as hydroxide precipitates while minimizing the co-precipitation of the other heavy metals. The precipitation at pH 5.0 yields iron and aluminium recovery of 99.9 and 94.7%, respectively. An increase in the pH from 5.0 to 7.0 increases the recovery of aluminium to 99.1%, while the recovery of iron remains the same. The precipitate formed at pH 5.0 is used to produce a coagulant consisting of 89.5% and 10.0% iron and aluminium, respectively. The production of the coagulant is carried out by dissolving the precipitate in 5.0% (w/w) sulphuric acid. Subsequently, the treatment of the brewery wastewater shows that the AMD-PAFS coagulant is as efficient as the conventional poly ferric sulphate (PFS) coagulant. The turbidity removal is 91.9 and 87.8%, while the chemical oxygen demand (COD) removal is 56.0 and 64.0% for AMD-PAFS and PFS coagulants, respectively. The developed process, which can easily be incorporated into existing AMD treatment plants, not only reduces the sludge disposal problems but also creates revenue from waste.

Chitin as a substrate for the biostimulation of sulfate-reducing bacteria in the treatment of mine-impacted water (MIW).

This study aims to know the basis of sulfate-reducing bacteria (SRB) and chitin source relationship for the development of a biotreatment system for mine-impacted water (MIW). The MIW consists of river water impacted by coal acid mine drainage (AMD), an extremely acid effluent, rich in sulfate and dissolved metal ions, with a high pollutant potential. Chitin was used as metal ion sorbent and biostimulant of SRB, whose anaerobic dissimilatory metabolism reduces sulfate to sulfide. Microcosms were built in an oxygen-free atmosphere using chitin from two different sources: commercial chitin and shrimp shell waste, which contains calcium carbonate, an acidity removal agent, in addition to chitin. The results indicate that the shrimp shell performs best in removing sulfate (99.75%), iron (99.04%), aluminum (98.47%), and manganese (100%) ions. The iron ion sorption kinetics of the sediments were also studied; pseudo-second order behavior was observed. High-throughput sequencing analysis revealed the present bacterial community and its abundance in the microcosms after 11 and 30 treatment days: SRB were detected but were not the majority. Thus, this research aims to contribute to the sustainable treatment MIW through the employment of an abundant and low-cost biomaterial.

Sediments and Water Column Contamination by Heavy Metals in Ekulu River, Nigeria: Ecological and Human Health Risk Assessment

Acid mine drainage from a defunct coal mine, agricultural run-off and indiscriminate waste disposal constitute major threat to the quality of Ekulu river of Enugu State, Nigeria. In this study, Ekulu river sediments and water column pollution by heavy metals and the associated ecological and human health exposure risks were assessed. The heavy metals were measured using atomic absorption spectrometry. The parameters used in assessing the pollution of the sediments were contamination factor, contamination degree, geochemical accumulation index and pollution load index whereas the ecological risk of the heavy metals in the sediments was assessed using potential ecological risk index. The parameters employed in assessing the carcinogenic and non-carcinogenic risks of exposure by humans to the heavy metals were hazard index and risk index. The results obtained indicate that the chromium and lead input into the sediments around the defunct coal mine area during the wet season was significant and most probably due to the discharge of acid coal mine drainage into the river. Elevated values of ecological and human health exposure risks around 4 km distance away (Damija) from the defunct coal-mine area are most likely due to anthropogenic activities.

Adsorption of heavy metals from coal acid mine drainage by shrimp shell waste: Isotherm and continuous-flow studies

The main characteristics of coal acid mine drainage (AMD) are low pH and high concentrations of sulfate and different metallic ions. The objective of this research was to study the sorption equilibrium of the removal of metal ions and acids present in coal AMD using shrimp shell in natura (SS) as a biomaterial as well as the behavior of the continuous-flow removal process. The isotherms assays were carried out with synthetic solutions and natural AMD aiming to identify significant differences on metals ions removal by SS. Five isotherm models were studied. R2 values and error statistical functions studies showed that the Freundlich isotherm model was the most appropriate for fitting the experimental data with both synthetic solutions and natural AMD, indicating a metallic removal via a physisorption mechanism. The removal of metal ions in continuous descendent flow was up to 90% Fe and 88% Mn, and the pH increased from 3.49 to 6.77. The adsorption capacities of Fe and Mn resulted in 17.43 and 3.87 mg g−1 SS, respectively. Computing chemical modelling (Visual MINTEQ® software) indicated the sorption was a predominant mechanism on AMD remediation with SS, but with high pH-dependence. This study confirms the suitability of the proposed treatment and provides valuable information for designing a low-cost remediation process for AMD.

Optimization of Fe and Mn Removal from Coal Acid Mine Drainage (AMD) with Waste Biomaterials: Statistical Modeling and Kinetic Study

The main characteristics of coal acid mine drainage (AMD) are a low pH and high concentrations of sulfate and different metallic ions. Response surface methodology using the central composite rotatable design (CCRD) model was used to optimize the parameters for AMD remediation with aquaculture farming waste [shrimp shell (SS) and mussel byssus (MB)]. SS was chosen due to its high chitin (a metal sorbent) and calcium carbonate (an acidity neutralizing agent) content, and MB because of its potential synergistic effect for the treatment. The coefficient of determination and standard error results from the analysis of variance have shown the model to be adequate. The predicted values were in good agreement with the experimental values. The best experimental conditions established from the statistical study were 136 rpm, 11.46 g L−1 SS and 71.6 g L−1 MB. CCRD can efficiently be applied for modeling the AMD remediation with biomaterials and is an economical way of obtaining the maximum amount of information in a short period of time with the fewest number of experiments. Additionally, five kinetic models, i.e., pseudo-first-order, pseudo-second-order, intraparticle diffusion, Bangham and Elovich equation, were tested to investigate the adsorption mechanisms. The kinetic studies revealed that a 200 min contact time is sufficient to transform AMD into water suitable for non-potable reuse. The pseudo-second-order model provided the best fitting of the experimental data, indicating a chemical adsorption mechanism. This research shows the suitability of the proposed treatment, and the information is valuable for designing a low-cost remediation process for AMD.

Iron (Fe) bio-concentration in purun tikus (Eleocharis dulcis) planted on the constructed wetland treating the coal acid mine drainage

Iron (Fe) bio-concentration in purun tikus (Eleocharis dulcis) planted on the constructed wetland treating the coal acid mine drainage

Synthesis of a Goethite Pigment by Selective Precipitation of Iron from Acidic Coal Mine Drainage

Conventional treatment of acid rock drainage (ARD) from coal mines generates large volumes of sludge, which requires further treatment and disposal. The aim of this work was to study the recovery of iron by selective precipitation to synthetize goethite for use as pigment. Goethite particles were successfully produced, and presented a particle distribution in the range of nano- and micro-sizes, varying from 0.04 to 5.0 µm when produced as paste suspension, or from 0.04 to 25.0 µm when dried at 60 °C and converted to a solid powder. The pigment was used to color a white cement paste, giving it a yellow ochre color. ARD treatment plants can adopt this process to reduce waste disposal issues and produce a valuable mineral (e.g., yellow pigment for concrete).