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  • 1.
    Jia, Yu
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Department of Environment and Minerals ResourcesGreenland Institute of Nature ResourcesNuukGreenland.
    Hamberg, Roger
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Swedish Geological Survey AB, Luleå, Sweden.
    Qureshi, Asif
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Department of Energy and Environment Engineering, Quaid-e-Awam University of Engineering, Science & Technology, Nawabshah, Pakistan.
    Mäkitalo, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Ramböll Sverige AB, Luleå, Sweden.
    Variation of green liquor dregs from different pulp and paper mills for use in mine waste remediation2019In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499Article in journal (Refereed)
    Abstract [en]

    The geotechnical, chemical, and mineralogical properties of green liquor dregs (GLDs) generated as byproducts from five paper mills were investigated to assess their buffering and heavy metal immobilization capacities and their roles as water and oxygen barriers. One type of GLD was further studied to test the effects of the retrieval process and the storage, drying, and hydration of GLD. The high water retention capacity of the GLDs is valuable for limiting O2diffusion. Laboratory results showed that the GLDs had hydraulic conductivities of 3.7 × 10−9–4.6 × 10−8 m/s and varied regularly in plasticity. The chemical and mineralogical compositions of the GLDs varied greatly, reflecting the raw material used to produce paper and the process used to retrieve GLDs. Although they had high total heavy metal contents, none of the leached elements from the GLDs (L/S 10 cm3/kg) exceeded the European Union’s limits for landfills of non-hazardous waste. The GLDs exhibited high buffering capacities. In a supplementary test, the buffering capacities varied (0.0041–0.0114 M H+/g GLD) over 72 d after acid was added to the GLD. Changing the filtration process did not greatly affect the GLDs’ properties but mainly affected the hydraulic conductivity, total heavy metal contents and sulfur content. Analyzing the storage of GLDs is necessary in the mining industry because remediation measures require large amounts of material over short periods. The buffering capacity of the dried GLD decreased slightly. The effect of dewatering caused by the mixing of 2% Na-lignosulfate with GLD (w/w) was low.

  • 2.
    Jia, Yu
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Effect of the alkaline industrial residues fly ash, green liquor dregs, and lime mud on mine tailings oxidation when used as covering material2014In: Environmental Earth Sciences, ISSN 1866-6280, E-ISSN 1866-6299, Vol. 72, no 2, p. 319-334, article id 16Article in journal (Refereed)
    Abstract [en]

    The potential to use the alkaline residue products fly ash, green liquor dregs, and lime mud originating from paper mills as dry cover materials to seal tailings has been investigated. Metals concentration in lime mud and fly ash had the lowest and highest contents, respectively. The tailings (less than 1% sulfur content, primarily pyrite) were disposed about 50 years ago and originated from the former Rönnskär mine site in Sweden. The results of chemical composition analysis shows that the raw unoxidized tailings are active towards oxidation, while the components of the adjacent oxidized tailings are not. To quantify the release of metals from the tailings and to evaluate the effect of a sealing layer on oxidation and weathering of the tailings, batch leaching tests were conducted in which leachate from alkaline residue materials was fed to the tailings. The results show that a higher concentration of most trace elements is leached from the unoxidized tailings than from the oxidized tailings. Except As and Cr, the rest of analyzed metals (Cd, Cu, Ni, Pb) became immobilized in response to the increased pH as a consequence of the amendment. The three tested alkaline amendments show a similar potential for preventing the release of metals (with the exception of As and Cr) from the tailings. Under either aerobic or anaerobic conditions, microbial activity was found to be of minor importance. XRD analysis of the field samples revealed that it was feasible to use alkaline residue products in covering tailings, and that it was advantageous to use ash as a cover material more than dregs.

  • 3. Jia, Yu
    et al.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Metal Mobilization in Tailings Covered with Alkaline Residue Products: Results from a Leaching Test Using Fly Ash, Green Liquor Dregs, and Lime Mud2015In: Mine Water and the Environment, ISSN 1025-9112, E-ISSN 1616-1068, Vol. 34, no 3, p. 270-287Article in journal (Refereed)
    Abstract [en]

    The in situ dynamics of repeated percolation of rainwater through unoxidized mine tailings was simulated using a modified column test to predict long-term weathering characteristics. Fly ash, green liquor dregs, and lime mud waste materials from the paper mill industry were used in the column tests to assess the effect of alkaline paper mill residue on pH buffering and controlling the mobility of metals and semi-metals from the tailings. The experiment was continued for 15 cycles, each comprising reaction, leaching, and idle steps (1 week per step). The cumulative percolated water through the tailings represented a liquid:solid ratio of 1.6. The leached content of inorganic elements decreased with time in both the covered and the uncovered tailings. The presence of the alkaline materials consistently reduced the mobility of most contaminants (e.g. Cd, Co, Cr, Mn, Ni and Zn), but not As. The leachate was modeled using PHREEQC. XRD analysis of the remaining tailings samples after termination of the test showed detectable variations in mineral composition. The alkaline residue products all fulfilled the requirements as a cover material from a geochemical prospective, with the exception of As. The green liquor dregs and lime cover increased the pH of the tailings more rapidly than did the fly ash.

  • 4.
    Jia, Yu
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Mobility of as, Cu, Cr, and Zn from tailings covered with sealing materials using alkaline industrial residues: a comparison between two leaching methods2016In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 23, no 1, p. 648-660Article in journal (Refereed)
    Abstract [en]

    Different alkaline residue materials (fly ash, green liquor dregs, and lime mud) generated from the pulp and paper industry as sealing materials were evaluated to cover aged mine waste tailings (

  • 5.
    Jia, Yu
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Nason, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Degradation of digested sewage sludge residue under anaerobic conditions for mine tailings remediation2014In: Environmental Earth Sciences, ISSN 1866-6280, E-ISSN 1866-6299, Vol. 72, no 9, p. 3643-3654Article in journal (Refereed)
    Abstract [en]

    Previous studies showed that 85 % of total organic matter (TOM) in digested sewage sludge (biosolids) used as a sealing layer material over sulfide tailings at the Kristineberg Mine, northern Sweden had been degraded 8 years after application, resulting in a TOM reduction from 78 % to 14 %. To achieve a better understanding of the field observations, laboratory studies were performed to evaluate biodegradation rates of the TOM under anaerobic conditions. Results reveal that the original biosolid consisted of ca. 60 % TOM (48.0 % lignin and 11.8 % carbohydrates) that had not been fully degraded. The incubation experiments proved that 27.8 % TOM in the biosolid was further degraded anaerobically at 20-22 C during the 230 d incubation period, and that a plateau to the biodegradation rate was approached. Based on model results, the degradation constant was found to be 0.0125 (day-1). The calculated theoretical gas formation potential was ca. 50 % higher than the modeled results based on the average degradation rate. Cumulated H2S equated to 0.65 µmoL*g-1 of biosolid at 230 d. However, the large sulfurous compounds reservoir (1.76 g SO42- kg-1 biosolid) together with anaerobic conditions, can generate high concentrations of this gas over a long-term perspective. Due to the rate of biodegradability identified via anaerobic processes, the function of the biosolid to serve as an effective barrier to inhibit oxygen migration to underlying tailings, may decrease over time. However, a lack of readily degradable organic fractions in the biosolid and a large fraction of organic matter that was recalcitrant to degradation suggests a longer degradation duration, which would prolong the biosolid material’s function and integrity.

  • 6. Jia, Yu
    et al.
    Nason, Peter
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Investigation of biosolids degradation under flooded environments for use in underwater cover designs for mine tailing remediation2015In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 22, no 13, p. 10047-10057Article in journal (Refereed)
    Abstract [en]

    To evaluate the potential suitability of digested sewage sludge (frequently termed biosolids) for use as underwater cover material for mine waste tailings, the degradability of biosolids at 20 − 22 °C under flooded anaerobic conditions was evaluated during incubation for 230 days. Leaching of elements from the flooded anaerobic system was also evaluated. Biosolid degradation was confirmed by the generation and accumulation of CH4 and CO2. Specifically, approximately 1.65 mmoL gas/g biosolids was generated as a result of incubation, corresponding to degradation of 7.68 % of the organic matter, and the residue was stable at the end of the laboratory experiment. Under field conditions in northern Sweden, it is expected that the degradation rate will be much slower than that observed in the present study (Nason et al. Environ Earth Sci 70:30933105, 2013). Although the majority of biosolid fractions (>92 %) were shown to be recalcitrant during the incubation period, long-term monitoring of further degradability of residue is necessary. The leaching results showed that most of the metals and metalloids leached from the biosolids at day 230 were below the limit value for non-hazardous waste, although Ni was the only element approximately three times higher than the limit value for inert material at the landfill site. In conclusion, biosolids have potential for use as covering material for underwater storage of tailings based on their biodegradability and leaching of elements.

  • 7.
    Jia, Yu
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Stahre, Nanna
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. School of Science and Technology, Örebro University, Örebro, Sweden.
    Mäkitalo, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Ramböll Sverige AB, Luleå, Sweden.
    Elemental mobility in sulfidic mine tailings reclaimed with paper mill by-products as sealing materials2017In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 24, no 25, p. 20389-20389Article in journal (Refereed)
    Abstract [en]

    Sealing layers made of two alkaline paper mill by-products, fly ash and green liquor dregs, were placed on top of 50-year-old sulfide-containing tailings as a full-scale remediation approach. The performance and effectiveness of the sealing layers with high water content for an oxygen barrier and low hydraulic conductivity for a sealing layer in preventing the formation of acid rock drainage were evaluated 5 years after the remediation. The leaching behavior of the covered tailings was studied using batch leaching tests (L/S ratio 10 L/kg). The leaching results revealed that, in general, the dregs- and ash-covered tailings released relatively lower concentrations of many elements contained in acid rock drainage compared to those from the uncovered tailings. A change in the chemical composition and mineralogical state of the tailings was observed for the tailings beneath the covers. The increase in pH caused by the alkaline materials promoted metal precipitation. Geochemical modeling using PHREEQC confirmed most of the geochemical changes of the covered tailings. Both the ash and dregs showed potential to function as sealing materials in terms of their geochemical properties. However, mobilization of Zn and Ni from the lower part of the dregs-covered tailings was observed. The same phenomenon was observed for the lower part of the ash-covered tailings. Ash showed advantages over dregs as a cover material; based on geochemical studies, the ash immobilized more elements than the dregs did. Lysimeters were installed below the sealing layers, and infiltrating water chemistry and hydrology were studied to monitor the amount and quality of the leachate percolating through

  • 8.
    Jia, Yu
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Stenman, David
    Mäkitalo, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Use of amended tailings as mine waste cover2013In: Waste and Biomass Valorization, ISSN 1877-2641, E-ISSN 1877-265X, Vol. 4, no 4, p. 709-718Article in journal (Refereed)
    Abstract [en]

    The present study addresses the effectiveness of green liquor dregs (GLD, a residue from paper pulp-making) as a paste additive with different proportions in tailings for stabilizing mine waste by testing of uniaxial compressive strength and hydraulic conductivity. Selected samples were also investigated for freeze–thaw effect on hydraulic conductivity, and the water retention capacity was discussed based on previous results. Fly ash was also added to the paste to study the auxiliary functions such as solidification in the sealing material. GLD have the potential for use as a barrier layer material for stabilizing mine tailings by decreasing water percolation and improving water retention properties. However, the solidified paste of GLD-amended tailings possesses low uniaxial compressive strength, but the addition of fly ash to the paste increased the uniaxial compressive strength by up to 2–3 times 1 month after it was solidified, with a further two- to threefold strength increase after 3-months curing time. Although the hydraulic conductivity of the tailings paste decreased as a consequence of mixing with both GLD and FA, the difference was within one order of magnitude. The hydraulic conductivity was also reduced as the water/solid ratio of pure GLD decreased. The climatic freeze–thaw cyclic process led to 20 % increase in hydraulic conductivity. A proportion of 7:2:1 for tailings:GLD:FA was found to be a geotechnical satisfactory recipe to seal the mine waste. If porosity is reduced, improved water retention capacity and no cracking in the tailings can be assured, oxygen diffusion is limited, and oxidation of the mine waste is decelerated, thus mitigating acid rock drainage.

  • 9.
    Jia, Yu
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Stenman, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Mäkitalo, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Use of rest products as additive in tailings paste for the mitigation of ARD: Effect of green liquor dregs and fly ash addition on geotechnical stabilization of tailings2012In: Proceedings of the 8th International Conference on the Environmental and Technical Implications of Construction with Alternative Materials: WASCON 2012 Conference proceedings / [ed] M. Arm; C. Vandecasteele; J. Heynen; P. Suer; B. Lind, ISCOWA , 2012Conference paper (Refereed)
    Abstract [en]

    This study focuses on the effect of green liquor dregs (GLD) and fly ash (FA) on geotechnical stabilization of tailings, using shear strength test.The objectives were to evaluate thickening of tailings using GLD to paste to improve its water retention and to reduce waste percolation, to identify optimal proportion of additives regarding geotechnical stabilization of tailings, and to study the role of FA in the decrease of porosity and thus to reduce oxygen diffusion via hardening process.The results showed that GLD is a potential material for tailings stabilization by decreasing water percolation and improving water retention property. However, the paste of GLD amended tailings withstands low shear strength. The addition of FA to the paste greatly improves shear strength which is up to 2-3 times higher. Moreover, the fly ash hardening process effectively reinforces the strength of GLD amended tailings paste. Longer curing period (3 months) for specimens leads to up to 2-3 folds higher strength compared to that of 1 month. Hydraulic conductivity is reduced as a result of GLD and FA addition, since the porosity of the tailings decreased. If reduced porosity, improved water retention capacity and no cracks are ensured in the tailings, oxygen diffusion can be limited.

  • 10.
    Lu, Jinmei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Jia, Yu
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Gotthardsson, Jenny
    Boliden Mineral AB.
    Evaluation of the application of dry covers over carbonate-rich sulphide tailings2013In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 244-245, p. 180-194Article in journal (Refereed)
    Abstract [en]

    In this study, four ten years test areas with covered tailings were geochemically evaluated. Three areas were covered with a fly ash and an overlying sludge layer, and one only with a sludge cover, originating from paper mills. The accumulation of As, Fe and Pb in sludge layers, originating from air-borne dust and the depletion of K, Na and P from both cover layers were observed. High release of elements from tailings was observed in the comparison profile due to oxidation and weathering of tailings. In only sludge covered area, the leaching of elements from tailings decreased. In the profiles with thin ash (20 cm and 30 cm), most elements were retained in tailings with pH 7-9. In the profile with the thickest ash (50 cm), elements such as As, Cd, Cu, Mg, Mn, Pb, S and Zn were depleted in the uppermost tailings with pH above 11 and retained deeper in the zone with pH 7-8, which implied that large quantities of fly ash increased the oxidation and weathering of tailings and mobility of elements. Elements excluding K, never reached the groundwater in high concentrations in the covered areas, while the comparison area had high Ca, K, Mn and S concentrations

  • 11.
    Mäkitalo, Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Jia, Yu
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Characterization of Green Liquor Dregs, Potentially Useful for Prevention of the Formation of Acid Rock Drainage2014In: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 4, no 2, p. 330-344Article in journal (Refereed)
    Abstract [en]

    Using alternative materials such as residual products from other industries to mitigate the negative effects of acid rock drainage would simultaneously solve two environmental problems. The main residual product still landfilled by sulphate paper mills is the alkaline material green liquor dregs (GLD). A physical, mineralogical and chemical characterization of four batches of GLD was carried out to evaluate the potential to use it as a sealing layer in the construction of dry covers on sulphide-bearing mine waste. GLD has relatively low hydraulic conductivity (10−8 to 10−9 m/s), a high water retention capacity (WRC) and small particle size. Whilst the chemical and mineralogical composition varied between the different batches, these variations were not reflected in properties such as hydraulic conductivity and WRC. Due to relatively low trace element concentrations, leaching of contaminants from the GLD is not a concern for the environment. However, GLD is a sticky material, difficult to apply on mine waste deposits and the shear strength is insufficient for engineering applications. Therefore, improving the mechanical properties is necessary. In addition, GLD has a high buffering capacity indicating that it could act as an alkaline barrier. Once engineering technicalities have been overcome, the long-term effectiveness of GLD should be studied, especially the effect of aging and how the sealing layer would be engineered in respect to topography and climatic conditions.

  • 12.
    Nason, Peter
    et al.
    Univ Waterloo, Dept Earth & Environm Sci.
    Jia, Yu
    Department of Environment and Raw Material, Greenland Institute of Natural Resources.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Biodegradation of Biosolids Under Aerobic Conditions: Implications for Cover Materials for Sulfide Mine Tailings Remediation2016In: Mine Water and the Environment, ISSN 1025-9112, E-ISSN 1616-1068, Vol. 35, no 3, p. 273-282Article in journal (Refereed)
    Abstract [en]

    Sewage sludge residue (biosolids) was investigated for its potential as a long-term tailings cover. Biosolids may prevent oxygen diffusion into underlying sulfide tailings through microbial aerobic biodegradation of organic matter. Biosolids were investigated at laboratory-, pilot-, and field-scale using analysis of total organic matter (TOM) mass reduction and O2, CO2, CH4 concentrations to quantify the biodegradation rate. A 156-day, open microcosm experiment, in which the loss of biosolids mass over time at differing temperatures, mimicking ambient (20–22 °C), mesophilic (34 °C), and thermophilic (50 °C) conditions, indicated that TOM biodegradation was best in the mesophilic temperature range, with 14.8, 27.2, and 26.7 % mass depletion at ambient, mesophilic, and thermophilic conditions, respectively. The data was correlated to field-scale data that evaluated biodegradation rates via decreasing O2 and increasing CO2 concentrations. Field biodegradation rates were less than laboratory rates because lower mean annual temperatures (0.6–0.7 °C) diminished microbial activity. A calibrated model indicates that 20 % of a field application of biosolids will degrade within 2 years. However, the rate declines with time due to exhaustion of the most readily degradable organic fraction. If biodegradation cannot be maintained, the long-term effectiveness of biosolids as a covering material for mine tailings remains a concern.

  • 13.
    Qureshi, Asif
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Jia, Yu
    Department of Environment and Mineral Resources, Greenland Institute of Natural Resources, 3900 Nuuk.
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Characterisation of fly ashes for minimisation of acid mine drainage from coal mining waste rocks2016In: Mining meets water: conflict and solutions IMWA 2016 in Leipzig, Germany, July 11-15, 2016 / [ed] Carsten Drebenstedt; Michael Paul, Freiberg: TU Bergakademie Freiberg, Institute of Mining and Special Civil Engineering , 2016, p. 977-986Conference paper (Refereed)
    Abstract [en]

    Acid mine drainage (AMD) due to the oxidation of sulphide bearing waste rock (WR) is a common environmental problem associated with coal extraction. Therefore, WRs from a lignite producing coal field in Pakistan and Lignite (PK), bituminous (FI) and biomass (SE) fly ashes (FAs) were mineralogically and chemically characterised to i) estimate the potential of WRs for generating AMD ii) estimate their deteriorating effects on natural waters, and iii) evaluate the FAs for their potential to minimise the impacts of WRs by preventing and/or neutralising AMD. The WRs were composed of quartz, pyrite, arsenopyrite, kaolinite, hematite and gypsum with traces of calcite, malladerite, spangolite, franklinite and birnessite. The major elements Si, Al, Ca and Fe were in the range (wt. %) of 8 – 12, 6 – 9, 0.3 – 3 and 1 – 10, respectively, with high S concentrations (1.94 – 11.33 wt. %). All FAs contained quartz, with iron oxide, anhydrite and magnesioferrite in PK, mullite and lime in FI and calcite and anorthite in SE. The Ca content in SE was 6 and 8 times higher compared to PK and FI, respectively.The WRs had considerable potential for generating AMD with net neutralisation potential corresponding to-70 to-492 kg CaCO3 tonne-1. FAs showed to have sufficient acid neutralisation potential corresponding to 20 – 275 kg CaCO3 tonne-1 , SE being the most alkaline probably due to the higher Ca content. The element leaching varied between the WRs due to their chemical and mineralogical composition and pH conditions during the weathering cell test for 28 weeks. However, in general, the leachates from the more acidic WRs were enriched about 3 to 4 orders of magnitude for certain elements compared to the less acidic WRs. The concentrations of Ca, SO42-, Na and Cl in the leachates were much higher compared to other elements from all FA samples. Iron, Cu and Hg were not detected in any of the FA leachates because of pH ranging from 9 to 13.Overall, the WRs had considerable potential for AMD generation and element leaching, therefore, deteriorate natural waters within the mining area. FAs, on the other hand, possess potential to minimise the impacts of WRs on the environment, due to their buffering capacity. However, the FAs vary in chemical composition and buffering capacity depending on their source, which makes it a possible challenge for utilisation.

  • 14.
    Qureshi, Asif
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Jia, Yu
    Maurice, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Potential of fly ash for neutralisation of acid mine drainage2016In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 23, no 17, p. 17083-17094Article in journal (Refereed)
    Abstract [en]

    Lignite (PK), bituminous (FI) and biomass (SE) fly ashes (FAs) were mineralogically and geochemically characterised, and their element leachability was studied with batch leaching tests. The potential for acid neutralisation (ANP) was quantified by their buffering capacity, reflecting their potential for neutralisation of acid mine drainage. Quartz was the common mineral in FAs detected by XRD with iron oxide, anhydrite, and magnesioferrite in PK, mullite and lime in FI, and calcite and anorthite in SE. All the FAs had high contents of major elements such as Fe, Si, Al and Ca. The Ca content in SE was six and eight times higher compared to PK and FI, respectively. Sulphur content in PK and SE was one magnitude higher than FI. Iron concentrations were higher in PK. The trace element concentrations varied between the FAs. SE had the highest ANP (corresponding to 275 kg CaCO3 tonne-1) which was 15 and 10 times higher than PK and FI, respectively. The concentrations of Ca2+, SO4 2-, Na+ and Cl- in the leachates were much higher compared to other elements from all FA samples. Iron, Cu and Hg were not detected in any of the FA leachates because of their mild to strong alkaline nature with pH ranging from 9 to 13. Potassium leached in much higher quantity from SE than from the other ashes. Arsenic, Mn and Ni leached from PK only, while Co and Pb from SE only. The concentrations of Zn were higher in the leachates from SE. The FAs used in this study have strong potential for the neutralisation of AMD due to their alkaline nature. However, on the other hand, FAs must be further investigated, with scaled-up experiments before full-scale application, because they might leach pronounced concentrations of elements of concern with decreasing pH while neutralising AMD.

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