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  • 1.
    Karlsson, Lovisa
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Bäckström, Mattias
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Allard, Bert
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Leaching of sulfidic alum shale waste at different temperatures2012Ingår i: 9th International Conference on Acid Rock Drainage (ICARD 2012) / [ed] Price, W.A., Hogan, C. and Tremblay, G., Red Hook, NY: Curran Associates, Inc., 2012, s. 1015-1025Konferensbidrag (Refereegranskat)
    Abstract [en]

    Four different alum shale waste products (unprocessed shale, weathered fines, processed shale and shale ash) from Kvarntorp, Sweden, were leached at different temperatures (-18°C, +22°C and +70°C) in order to elucidate the influence from freezing (frost wedging) and high temperatures (heat generated during sulfide oxidation). Unprocessed shale and the weathered fine fraction have an acidic pH while the processed shale and the shale ash have circum neutral pH. Leaching was performed at liquid solid ratio of 10:1 at room temperature followed by treatment at different temperatures for 24 hours (cycle repeated 10 times). pH, electrical conductivity, redox, alkalinity, acidity, sulfate, major cat ions and trace elements were measured. pH was almost one pH unit lower in the heat treated shale ash samples compared to the samples kept in the freezer. No significant pH differences were observed for the other samples. Iron and sulfate concentrations were found to be higher in the heat treated samples still containing pyrite (unprocessed shale and weathered fines) indicating a higher rate of oxidation. When it comes to trace elements molybdenum, for instance, significantly higher concentrations were leached from the processed shale compared to the unprocessed shale indicating increased leachability due to transformation of the primary minerals

  • 2.
    Karlsson, Lovisa
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Karlsson, Stefan
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Allard, Bert
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Sjöberg, Viktor
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Bäckström, Mattias
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Release of metals from unprocessed and processed black shale due to natural weathering2013Ingår i: Annual International Mine Water Association Conference: Reliable Mine Water Technology / [ed] Adrian Brown, Linda Figueroa, Christian Wolkersdorfer, Colorado, USA: IMWA , 2013, s. 391-397Konferensbidrag (Refereegranskat)
    Abstract [en]

    Black shale was mined and processed for recovery of hydrocarbons in Kvarntorp, some 200 km SW of Stockholm, Sweden, during 1942–66. Remains from the mining period is a deposit with 40 Mm³ of crushed shale residues: Unprocessed 3ne-grained shale as well as processed shale. The deposit is still hot; oxidation of sulphides as well as burning of hydrocarbons are still in progress some 50 years a1er closure. Weathering of the shale leads to releases of metal-rich leachates which will increase with time. The release of metals from pristine shale as well as weathered shale (exposed to the atmosphere for 50 years) and two di2erent processed shale residues have been studied using water of di2erent pH as leaching solution, to simulate extreme pH-variations in environmental waters: 3.0 (determined by oxidation of iron sulphides), 5.5 (bu2ered by carbon dioxide), 8.5 (bu2ered by calcite) and 12.5 (bu2ered by calcium hydroxide). Extraction of cationic elements was substantial (several percent of the total content) for Ca and Mg, as well as Ni, Co and U at pH 3, and very high (up to 50–60 %) for anionic elements (V, Mo, As) at pH 12.5. Especially the high-temperature processed shale would be a potential source for As and Mo at high pH. The pH-dependence of the weathering processes should be considered when future remediation (or metal recovery) processes and strategies are designed.

  • 3. Karlsson, Lovisa
    et al.
    Sjöberg, Viktor
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Karlsson, Stefan
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Bark compost for removal of Nickel in complex waste water2012Ingår i: / [ed] E. Kothe and G. Büchel, 2012Konferensbidrag (Refereegranskat)
  • 4.
    Karlsson, Stefan
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Karlsson, Lovisa
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Allard, Bert
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Sjöberg, Viktor
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Bäckström, Mattias
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Water quality in a black shale mining area: effects of pH and natural organic acids on weathering and subsequent metal releases2014Ingår i: An Interdisciplinary Response to Mine Water Challenges / [ed] Wanghua Sui, Yajun Sun and Changshen Wang, China University of Mining and Techno logy Press , 2014, s. 136-136Konferensbidrag (Refereegranskat)
    Abstract [en]

    Mining of black shale (alum shale) of Late Cambrium age for the extraction of alum started in the early 17th century in Sweden, and in the late 19th century there was an extensive use of shale, with its high content of organic carbon, as fuel in lime-burning processes. Full-scale recovery of hydrocarbons from shale took place in Kvarntorp during 1942-66, and recovery of uranium in Ranstad during 1965-76. Remains from the historic mining and processing of black shale are some 50 major deposits with processed and unprocessed shale residues, as well as water-filled pits, at the former mining sites. There are also large areas covered with crushed shale, e.g. as road filling material. Studies of the weathering of shale due to exposure to the atmosphere and water with pH within the natural range indicate a high leachability of cationic elements at low pH, as well as anionic elements at high pH. The presence of organic complexing acids of natural origin (microbial exudates and humic acids) may give an enhanced leaching, particularly at pH above 8, when hydroxy-groups would constitute active metal binding sites. Results from studies of weathering and leaching of processed and unprocessed black shale are presented, as well as the effects on the water quality observed at former mining sites and related environmental impact.

  • 5.
    Sjöberg, Viktor
    et al.
    Örebro universitet, Akademin för naturvetenskap och teknik.
    Grandin, Anna
    Örebro universitet, Akademin för naturvetenskap och teknik.
    Karlsson, Lovisa
    Karlsson, Stefan
    Örebro universitet, Akademin för naturvetenskap och teknik.
    Bioleaching of shale: impact of carbon source2011Ingår i: The new uranium mining boom: challenges and lessons learned / [ed] Broder Merkel, Mandy Schipek, Springer Berlin/Heidelberg, 2011, s. 449-454Konferensbidrag (Refereegranskat)
    Abstract [en]

    Bioleaching is often used for processing low-grade shale feedstock and the microbial community used for that purpose is supplied with nutrients such as sugar and/or Fe2+. In the present study, the leaching efficiency was tested when crushed weathered shale was mixed with aspen wood shavings and kept moist, at the mixtures field capacity. The purpose was to investigate whether a more complex carbon source and a lower content of water may be a feasible way of lowering the cost for bioleaching. After 56 days of incubation the amount of uranium mobilized from the shale reached some 1.7% with a minimum of effort and cost.

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