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Qureshi, A., Maurice, C. & Öhlander, B. (2019). Effects of the co-disposal of lignite fly ash and coal mine waste rocks on AMD and leachate quality. Environmental science and pollution research international, 26(4), 4104-4115
Öppna denna publikation i ny flik eller fönster >>Effects of the co-disposal of lignite fly ash and coal mine waste rocks on AMD and leachate quality
2019 (Engelska)Ingår i: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 26, nr 4, s. 4104-4115Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Lignite fly ash (FA) and waste rocks (WRs) were mixed in three different ratios (1:1, 1:3 and 1:5) and studied to compare the effects of adding FA on acid mine drainage generation from coal mining WRs, leachability of elements and the potential occurrence of the secondary minerals. FA mixed with WRs showed significant differences in pH levels compared to previous research. The 1:1 mixture performed best of all the three mixtures in terms of pH and leachability of elements, mainly due to the higher proportion of FA in the mixture. The pH in the 1:1 mixtures varied between 3.3 and 5.1 compared to other mixtures (2.3–3.5). Iron and SO42− leached considerably less from the 1:1 mixture compared to the others, indicating that the oxidation of sulphides was weaker in this mixture. Aluminium leached to a high degree from all mixtures, with concentrations varying from mg L−1 to g L−1. The reason behind this increase is probably the addition of FA which, due to acidic conditions and the composition of the FA, increases the availability of Al. For the same reason, high concentrations of Mn and Zn were also measured. Geochemical modelling indicates that the 1:1 mixture performs better in terms of precipitation of Al3+ minerals, whereas Fe3+ minerals precipitated more in mixtures containing less FA. These results suggest that, with time, the pores could possibly be filled with these secondary minerals and sulphate salts (followed by a decrease in sulphide oxidation), improving the pore water pH and decreasing the leachability of elements. Since grain size plays a crucial role in the reactivity of sulphides, there is a risk that the results from the leaching tests may have been influenced by crushing and milling of the WR samples.

Ort, förlag, år, upplaga, sidor
Springer, 2019
Nyckelord
Coal mine waste rock, acid mine drainage (AMD), fly ash mixing, weathering cells, PHREEQC, element leaching
Nationell ämneskategori
Geokemi Miljövetenskap Miljöledning Mineral- och gruvteknik
Forskningsämne
Tillämpad geokemi
Identifikatorer
urn:nbn:se:ltu:diva-72667 (URN)10.1007/s11356-018-3896-8 (DOI)30560529 (PubMedID)2-s2.0-85058775217 (Scopus ID)
Anmärkning

Validerad;2019;Nivå 2;2019-02-12 (svasva)

Tillgänglig från: 2019-01-24 Skapad: 2019-01-24 Senast uppdaterad: 2019-02-12Bibliografiskt granskad
Jia, Y., Hamberg, R., Qureshi, A., Mäkitalo, M. & Maurice, C. (2019). Variation of green liquor dregs from different pulp and paper mills for use in mine waste remediation. Environmental science and pollution research international
Öppna denna publikation i ny flik eller fönster >>Variation of green liquor dregs from different pulp and paper mills for use in mine waste remediation
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2019 (Engelska)Ingår i: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499Artikel i tidskrift (Refereegranskat) Epub ahead of print
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.

Ort, förlag, år, upplaga, sidor
Springer, 2019
Nyckelord
Acid neutralization, Buffering capacity, Heavy metals, Water retention, Plasticity, Beneficiation
Nationell ämneskategori
Geoteknik Geokemi
Forskningsämne
Tillämpad geokemi; Geoteknik
Identifikatorer
urn:nbn:se:ltu:diva-75826 (URN)10.1007/s11356-019-06180-0 (DOI)31471848 (PubMedID)
Tillgänglig från: 2019-09-03 Skapad: 2019-09-03 Senast uppdaterad: 2019-09-03
Qureshi, A., Jia, Y., Maurice, C. & Öhlander, B. (2016). Characterisation of fly ashes for minimisation of acid mine drainage from coal mining waste rocks (ed.). In: (Ed.), Carsten Drebenstedt; Michael Paul (Ed.), Mining meets water: conflict and solutions IMWA 2016 in Leipzig, Germany, July 11-15, 2016. Paper presented at International Mine Water Association Annual Conference 2016 : Mining meets Water - Conflicts and solutions 12/07/2016 - 15/07/2016 (pp. 977-986). Freiberg: TU Bergakademie Freiberg, Institute of Mining and Special Civil Engineering
Öppna denna publikation i ny flik eller fönster >>Characterisation of fly ashes for minimisation of acid mine drainage from coal mining waste rocks
2016 (Engelska)Ingår i: 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, s. 977-986Konferensbidrag, Publicerat paper (Refereegranskat)
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.

Ort, förlag, år, upplaga, sidor
Freiberg: TU Bergakademie Freiberg, Institute of Mining and Special Civil Engineering, 2016
Nationell ämneskategori
Geokemi
Forskningsämne
Tillämpad geokemi
Identifikatorer
urn:nbn:se:ltu:diva-29977 (URN)000402663400152 ()39ead8ad-414f-4594-97ca-9e7b37bd4c0d (Lokalt ID)978-3-86012-533-5 (ISBN)39ead8ad-414f-4594-97ca-9e7b37bd4c0d (Arkivnummer)39ead8ad-414f-4594-97ca-9e7b37bd4c0d (OAI)
Konferens
International Mine Water Association Annual Conference 2016 : Mining meets Water - Conflicts and solutions 12/07/2016 - 15/07/2016
Anmärkning

Godkänd; 2016; 20160803 (asiqur)

Tillgänglig från: 2016-09-30 Skapad: 2016-09-30 Senast uppdaterad: 2017-11-25Bibliografiskt granskad
Qureshi, A. (2016). Co-disposal of waste rock and lignite fly ash to mitigate the environmental impact of coal mining. (Doctoral dissertation). Luleå: Luleå University of Technology
Öppna denna publikation i ny flik eller fönster >>Co-disposal of waste rock and lignite fly ash to mitigate the environmental impact of coal mining
2016 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Waste rocks (WRs) from coal mining and fly ash (FA) from coal combustion were studied to determine the potential of the WRs to generate AMD, FAs to neutralise it and estimate their impacts on environment. The ultimate goal was to develop a methodology based on co-disposal to mitigate the environmental problems associated to both wastes. Two methods for co-disposal were tested: i) Mixing WRs and FAs and ii) covering WRs with FAs.

WRs were sampled from the Lakhra coal mines in Pakistan (PK), which has an estimated coal reserves of 1.3 Btonne, varying from lignite to sub-bituminous quality. The FA was sampled from a power plant utilising coal from Lakhra coal mines and is situated in close vicinity (15km) of the mine site. For comparative purposes a bituminous FA from Finland (FI) and biomass FA from Sweden (SE) were also characterised.

The WRs and FA samples were characterised by mineralogical and geochemical methods. Besides organic material (coal traces), quartz, pyrite, kaolinite, hematite, gypsum and traces of calcite, lime, malladerite, spangolite, franklinite and birnessite were identified in WRs by XRD. 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. %) in WRs. The AMD potential of WRs ranged from -70 to -492 kg CaCO3 tonne-1.

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. FAs were enriched in As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn compared to continental crust. The acid neutralising potential of PK was equivalent to 20 kg CaCO3 tonne-1 compared to 275 kg CaCO3 tonne-1 (SE) and 25 kg CaCO3 tonne-1 (FI).

During the period of 192 days in weathering cell experiments (WCE), the pH of leachates from most acidic WRs was maintained from 1 to 2.5, whereas, the less acidic WRs produced leachates of mildly acidic (2.7) to neutral (7.3) pH. The leachates from very acidic WRs ranged in the concentrations of Fe, SO24− and Al from mg L-1 to g L-1.

The samples were subjected to column leaching experiments (CLE) in which mixture (FA:WR; 1:3) and cover (FA:WR; 1:5) cases were mimicked (with 10mm particle size) and effects of particle size (2, 5 and 10mm) on element leaching were studied.

Despite having the lowest acid-neutralisation potential compared to FI and SE, co-disposal of PKFA as mixture readily provides acid buffering minerals, resulting in better start-up pH conditions and leachate quality. However, acidity produced by secondary mineralisation contributes towards the acidification of the system, causing stabilisation of pH at around 4.5−5. Secondary mineralisation (especially Fe- and Al-mineral precipitation) also removes toxic elements such as As, Pb, Cu, Zn, Cd, Co, Ni and Mn, and these secondary minerals can also buffer acidity when the pH tends to be acidic.

In contrast, the pH of the leachates from the PKFA cover scenario gradually increased from strongly acidic to mildly acidic and circumneutral along with decrease in EC and elemental leaching in different WRs. Gradually increasing pH can be attributed to the cover effect, which reduces oxygen ingress, thus sulphide oxidation, causing pH to elevate. Due to the fact that pH~4–5 is sufficient for secondary Fe- and Al-mineral precipitation which also removes toxic elements (such as Cd, Co, Cu, Zn and Ni) by adsorption and/or co-precipitation, the FA cover performs well enough to achieve that pH until the conclusion of the CLE. However, due to the slower reactivity of the buffering system (additional to the initial flush-out), leaching in the beginning could not be restricted.

The co-disposal of FA as cover and/or mixture possesses potential for neutralisation of AMD and improving leachate quality significantly. Particle size of the WRs affected the leaching of the sulphide related elements (such as Fe, S, Zn, Co, Cr, Cu, Mn and Ni) in CLE and WCE. Experiments with ≤1mm particle size constantly produced acidic and metal laden leachates. Co-disposal of FA and WRs as cover and mixture need to be investigated on pilot-scales before full-scale application.

Ort, förlag, år, upplaga, sidor
Luleå: Luleå University of Technology, 2016. s. 50
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Nyckelord
Acid mine drainage (AMD), coal mine waste rocks, coal fly ash, co-disposal, mixing/blending, dry-cover, prevention/neutralisation
Nationell ämneskategori
Geokemi
Forskningsämne
Tillämpad geokemi
Identifikatorer
urn:nbn:se:ltu:diva-60261 (URN)978-91-7583-751-2 (ISBN)978-91-7583-752-9 (ISBN)
Disputation
2016-12-15, F341, F-house, Luleå University of Technology, Luleå, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2016-11-10 Skapad: 2016-11-09 Senast uppdaterad: 2017-11-24Bibliografiskt granskad
Qureshi, A., Maurice, C. & Öhlander, B. (2016). Potential of coal mine waste rock for generating acid mine drainage (ed.). Paper presented at . Journal of Geochemical Exploration, 160, 44-54
Öppna denna publikation i ny flik eller fönster >>Potential of coal mine waste rock for generating acid mine drainage
2016 (Engelska)Ingår i: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 160, s. 44-54Artikel i tidskrift (Refereegranskat) Published
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 the Lakhra coal field in Pakistan, were studied to i) perform a mineralogical and chemical characterisation, ii) determine the AMD generating potential and iii) estimate the leachability of elements. The chemical and mineralogical composition was studied using ICP, XRF, XRD and SEM. Acid base accounting and weathering cell test determined the acid producing potential of WRs. Besides organic material, the WRs were composed of quartz, pyrite, kaolinite, hematite and gypsum with varying amounts of calcite, lime, 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 (19.4–113.3 g/kg). Trace elements were in the range (mg/kg) As (0.3–8), Cd (0.2–0.4), Co (15–75), Cr (67–111), Cu (25–101), Hg (0.1–0.2), Ni (50–107), Pb (8–20) and Zn (75–135). The AMD potential of WRs ranged from − 70 to − 492 kg CaCO3/tonne. During the test period of 192 days, the pH of leachates from very acidic WRs was maintained from 1 to 2.5, whereas, the less acidic WRs produced leachates of mildly acidic (2.7) to neutral (7.3) pH. The leachates from very acidic WRs ranged in the element concentrations of Fe, SO42 − and Al from mg/L to g/L and As, B, Co, Cu, Mn, Ni and Zn from μg/L to mg/L. However, the leachates from less acidic WRs contained all major elements in mg/L and trace elements in μg/L concentrations except for B and Mn that ranged from μg/L to mg/L. The results show that the studied WRs have mild to strong acid producing potential and have the capacity to deteriorate natural water quality significantly. Therefore, necessary preventive or/and acid neutralising measures are strongly suggested.

Nationell ämneskategori
Geokemi
Forskningsämne
Tillämpad geologi
Identifikatorer
urn:nbn:se:ltu:diva-15628 (URN)10.1016/j.gexplo.2015.10.014 (DOI)000365607400004 ()2-s2.0-84947598285 (Scopus ID)f29da7e5-199c-45c9-83de-1564c56d6769 (Lokalt ID)f29da7e5-199c-45c9-83de-1564c56d6769 (Arkivnummer)f29da7e5-199c-45c9-83de-1564c56d6769 (OAI)
Anmärkning
Validerad; 2015; Nivå 2; 20151026 (andbra)Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2018-07-10Bibliografiskt granskad
Qureshi, A., Jia, Y., Maurice, C. & Öhlander, B. (2016). Potential of fly ash for neutralisation of acid mine drainage (ed.). Environmental science and pollution research international, 23(17), 17083-17094
Öppna denna publikation i ny flik eller fönster >>Potential of fly ash for neutralisation of acid mine drainage
2016 (Engelska)Ingår i: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 23, nr 17, s. 17083-17094Artikel i tidskrift (Refereegranskat) Published
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.

Nationell ämneskategori
Geokemi
Forskningsämne
Tillämpad geologi; Tillämpad geokemi
Identifikatorer
urn:nbn:se:ltu:diva-13259 (URN)10.1007/s11356-016-6862-3 (DOI)000382674800019 ()27209637 (PubMedID)2-s2.0-84969850736 (Scopus ID)c73d75aa-70a2-4066-a4b0-cc4ad0bbc97c (Lokalt ID)c73d75aa-70a2-4066-a4b0-cc4ad0bbc97c (Arkivnummer)c73d75aa-70a2-4066-a4b0-cc4ad0bbc97c (OAI)
Anmärkning

Validerad; 2016; Nivå 2; 2016-10-18 (andbra)

Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2018-07-10Bibliografiskt granskad
Qureshi, A. (2014). Potential of fly ashes for neutralisation of acid mine drainage from coal mine waste rock (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Öppna denna publikation i ny flik eller fönster >>Potential of fly ashes for neutralisation of acid mine drainage from coal mine waste rock
2014 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Many countries around the world use coal as fuel for the purpose of power generation. The extraction of coal produces large volumes of waste rock (WR) that are sometimes sulphide rich (principally containing iron sulphides such as pyrite (FeS2) and pyrrhotite (Fe1-xS)), with varying quantities of trace elements such as As, Si, Cu, Zn, Ni, Co, Mo and Cr etc). Such waste is environmentally sensitive due to the risk of oxidation in presence of atmospheric oxygen and water. Sulphide oxidation may result in acidic waters (acid mine drainage, AMD), which often contains high loads of dissolved metals. Coal combustion results in large amounts of fly ash (FA), which also is of environmental concern. However, FA is alkaline and may potentially be used for neutralisation of AMD. Therefore, the AMD producing potential of WR from coal mining and the neutralisation potential of FAs from coal and biomass combustion was studied with the ultimate goal to develop a methodology to decrease the environmental problems related to these materials.WR was sampled form the Lakhra coal field in Pakistan, which has an estimated coal reserve of 1.3 Bton, from lignite to sub-bituminous in quality. The WR samples were characterised by mineralogical and geochemical methods and the acid producing potential was determined by static (Acid Base Accounting) and kinetic (modified humidity cells test) methods. Besides organic material, the WRs are composed of quartz, pyrite, kaolinite, hematite and gypsum with varying amounts of calcite, lime, malladerite, spangolite, franklinite and birnessite. The Lakhra WR has strong potential to generate AMD (-70 to -492 kg CaCO3/ton) and pollute natural waters by leaching of elements such as Cd, Co, Cr, Cu, Ni, Pb, Zn, Fe and SO42-. Three different FAs based on the origin, fuel type and storage methods were studied. They were characterised by mineralogical and geochemical methods, the leachability was studied by batch leaching tests and the potential for buffering acids and neutralisation of AMD was quantified. Fly ash from burning i) brown coal (lignite) in Pakistan (PK), ii) black (bituminous) coal from Finland (FI) and iii) biomass FA provided by a sulphate pulp and paper mill in Sweden (SE) were studied. All ashes contained quarts, PK also iron oxide, anhydrite, and magnesioferrite, FI also mullite and lime, and SE also calcite and anorthite. All ashes were enriched in As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn compared to continental crust, and all ashes had a strong neutralisation potential, the bioash, SE, in particular. The results are encouraging and suggest that it is possible to use FA to mitigate the environmental problems with coal mine WR. Methods for that will be the focus for the continued research.

Ort, förlag, år, upplaga, sidor
Luleå: Luleå tekniska universitet, 2014. s. 71
Serie
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Nationell ämneskategori
Geokemi
Forskningsämne
Tillämpad geologi
Identifikatorer
urn:nbn:se:ltu:diva-17607 (URN)4456163a-5a94-4d85-a621-0167bb0e93f6 (Lokalt ID)978-91-7583-192-3 (ISBN)978-91-7583-193-0 (ISBN)4456163a-5a94-4d85-a621-0167bb0e93f6 (Arkivnummer)4456163a-5a94-4d85-a621-0167bb0e93f6 (OAI)
Anmärkning
Godkänd; 2014; 20141013 (asiqur); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Asif Qureshi Ämne: Tillämpad geologi/Applied Geology Uppsats: Potential of Fly Ashes for Neutralisation of Acid Mine Drainage from Coal Mine Waste Rock Examinator: Professor Björn Öhlander Institutionen för samhällsbyggnad och naturresurser Luleå tekniska universitet Diskutant: Dr Josef Mácsik Ecoloop AB Stockholm Tid: Torsdag den 18 december 2014 kl 13.00 Plats: E246, Luleå tekniska universitetTillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2017-11-24Bibliografiskt granskad
Qureshi, A., Maurice, C. & Öhlander, B.Co-disposal of lignite fly ash and coal mine waste rock for neutralisation of AMD.
Öppna denna publikation i ny flik eller fönster >>Co-disposal of lignite fly ash and coal mine waste rock for neutralisation of AMD
(Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
Abstract [en]

The WRs from a lignite producing coal field and FA produced from a power plant incinerating lignite from this field have been investigated in this study with objectives including the effect of WR particle size, co-disposal of FA (cover and mixture) and WRs on AMD and leachate quality and potential for secondary mineralisation using PHREEQC. The effect of particle size has been clearly observed where smaller particle sizes (2mm) produced low pH (~2) leachates with elevated concentrations of the sulphide related elements (such as Fe, SO42-, Al, Zn, Co, Cr, Cu, Mn and Ni) compared to 5mm (pH~3) and 10mm (pH~3.7) particles, indicating that sulphide oxidation has been pronounced in smaller particles. Co-disposal of FA as mixture readily provides acid buffering minerals, resulting in better pH (~3–6) and leachate quality from the beginning, except initial flush-out on the first rinse. However, acidity produced by secondary mineralisation contributes towards the acidification of the system, causing stabilisation of pH at around 4.5−5. In contrast, the pH of the leachates from the FA cover scenario gradually increases from strongly acidic (pH~2) to mildly acidic (WR1: pH~5 and WR2: pH~4) and circumneutral (WR3: pH~7) along with decrease in EC and elemental leaching. Gradually increasing pH can be attributed to the cover effect, which reduces oxygen ingress, thus sulphide oxidation, causing pH to elevate. Since pH~4–5 is sufficient for the secondary Fe- and Al-mineral precipitation, the FA cover performs very well to achieve that until the conclusion of the column leaching experiment. However, due to slower reactivity of the system, leaching in the beginning cannot restricted. The co-disposal of FA as cover and/or mixture possess potential for neutralisation of AMD and improving leachate quality significantly. However, both systems need to be up-scaled and investigated for AMD neutralisation, leachate quality, kinetic modelling and geotechnical properties.

Nyckelord
Coal mine waste rock, acid mine drainage (AMD), fly ash, co-disposal, dry cover, mixing
Nationell ämneskategori
Miljöledning Mineral- och gruvteknik Miljövetenskap Geokemi Geokemi
Forskningsämne
Tillämpad geokemi
Identifikatorer
urn:nbn:se:ltu:diva-60260 (URN)
Tillgänglig från: 2016-11-09 Skapad: 2016-11-09 Senast uppdaterad: 2017-11-24
Qureshi, A., Maurice, C. & Öhlander, B.Effects of the co-disposal of lignite fly ash and coal mine waste rocks on AMD and leachate quality.
Öppna denna publikation i ny flik eller fönster >>Effects of the co-disposal of lignite fly ash and coal mine waste rocks on AMD and leachate quality
(Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
Abstract [en]

Lignite fly ash (FA) and waste rocks (WRs) were mixed in three different ratios (1:1, 1:3 and 1:5) and studied to compare the effects of adding FA on AMD generation from coal mining WRs, leachability of elements and the potential occurrence of secondary minerals. FA mixed with WRs showed significant differences in pH levels compared to previous research. The 1:1 mixture performed best of all the three mixtures in terms of pH and leachability of elements, mainly due to the higher proportion of FA in the mixture. The pH in the 1:1 mixtures varied between 3.3 – 5.1 compared to other mixtures (2.3­ – 3.5). Iron and SO42- leached considerably less from the 1:1 mixture compared to the others, indicating that the oxidation of sulphides was weaker in this mixture. Aluminium leached to a high degree from all mixtures, with concentrations varying from mg L-1–g L-1. The reason behind this increase is probably the addition of FA which, due to acidic conditions and the composition of the FA, increases the availability of Al. For the same reason, high concentrations of Mn and Zn were also measured. Geochemical modelling indicates that the 1:1 mixture performs better in terms of precipitation of Al3+ minerals, whereas Fe3+ minerals precipitated more in mixtures containing less FA. These results suggest that, with time, the pores could possibly be filled with these secondary minerals and sulphate salts (followed by a decrease in sulphide oxidation), improving the pore water pH and decreasing the leachability of elements. Since grain size plays a crucial role in the reactivity of sulphides, there is a risk that the results from the leaching tests may have been influenced by crushing and milling of the WR samples.

Nyckelord
Coal mine waste rock, acid mine drainage (AMD), fly ash mixing, weathering cells, PHREEQC, element leaching
Nationell ämneskategori
Geokemi Miljövetenskap Miljöledning Mineral- och gruvteknik
Forskningsämne
Tillämpad geokemi
Identifikatorer
urn:nbn:se:ltu:diva-60259 (URN)
Tillgänglig från: 2016-11-09 Skapad: 2016-11-09 Senast uppdaterad: 2017-11-24
Organisationer
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0003-2810-8083

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