Self-sealing isolation and immobilization: a geochemical approach to solve the environmental problem of waste acidic jarosite |
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| Institution: | 1. Flow Process and Rheology Centre, Cape Peninsula University of Technology, South Africa;2. Department of Chemical Engineering, Cape Peninsula University of Technology, South Africa;3. Electron Microscope Unit, University of the Western Cape, South Africa;1. DISTAV, University of Genoa, 26 Corso Europa, Genoa I-16132, Italy;2. DCCI, University of Genoa, 31 Via Dodecaneso, Genoa I-16132, Italy;3. BiGeA, University of Bologna, 1 Piazza S. Donato, Bologna I-40126, Italy;1. Laboratory of Environmental Researches and Nanotechnology Development, Centro Universitário La Salle, Victor Barreto, 2288 Centro, 92010-000 Canoas, RS, Brazil;2. University of the Basque Country (UPV/EHU), Faculty of Science and Technology, Department of Analytical Chemistry, P.O. Box 644, 48080 Bilbao, Spain;1. Centro de Geociencias—UNAM, Campus Juriquilla, Queretaro 76230, Mexico;2. Posgrado en Ciencias de la Tierra, Centro de Geociencias—UNAM, Campus Juriquilla, Queretaro 76230, Mexico;3. Department of Geology, University of Cincinnati, OH 45221, USA;1. Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic;2. Institute of Geosciences, Friedrich-Schiller University, Burgweg 11, D-07749 Jena, Germany;3. Institute of Geology, The Czech Academy of Sciences, v.v.i., Rozvojová 269, 165 00 Prague 6, Czech Republic;4. Czech Geological Survey, Geologická 6, 152 00 Prague 5, Czech Republic |
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| Abstract: | Mimicking geochemical processes to solve environmental problems was implemented in dealing with waste acidic jarosite and alkaline coal fly ash. By placing these two chemically different materials adjacent to one another, a self-sealing layer was formed at the interface between both wastes, isolating and immobilizing chemical constituents in the process. A series of leaching experiments were performed on each material separately to study the release behavior of the principal constituents. Radiotracer experiments were conducted to explore diffusion and reaction of constituents such as Fe3+ in a combined jarosite/fly ash system. A model has been developed to simulate the coupled processes of diffusion and precipitation taking into account porosity change due to pore filling by precipitates. The formation of a self-sealing isolation layer in a hypothetical jarosite/fly ash disposal site was modelled. Leaching results indicate that the release of elements from jarosite is much larger than that from fly ash, and that the highly pH dependent release of Fe, Al, and Zn was controlled by the solubility of their hydroxides. Leaching results also suggest that precipitation reactions can be expected to occur at the interface between jarosite and alkaline coal fly ash where a large pH gradient exists. Radiotracer experiments showed that accumulation of constituents occurred at the interface. Modeled Fe3+ profiles in layered jarosite/fly ash were well validated by experiments. Modeling results also showed that with the accumulation of constituents at the interface, a new layer with low porosity was formed. Application of this model suggests that there is a potential use to form a self-sealing layer in jarosite/fly ash co-disposal sites. |
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