Acid leaching of ash and coal: Time dependence and trace element occurrences |
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| Authors: | Mehtap Paul Meryem Seferino?lu Gul Asiye Ayç?k Åke Sandström Michael L Smith Jan Paul |
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| Institution: | 1. Turkish Atomic Energy Authority, Ankara Nuclear Research and Training Center, 06100 Be?evler-Ankara, Turkey;2. MTA, Mineral Research and Exploration Directorate, 06520 Balgat-Ankara, Turkey;3. Turkish Atomic Energy Authority, Ankara Nuclear Research and Training Center, 06100 Be?evler-Ankara, Turkey;4. Luleå University of Technology, Division of Process Metallurgy, SE-971 87 Luleå, Sweden;5. Anabolic Laboratories, Inc, 85281, Tempe, AZ, USA;6. Luleå University of Technology, Division of Physics, SE-971 87 Luleå, Sweden |
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| Abstract: | The leaching of coal and coal/asphaltite/wood-ashes in sulfuric acid (pH 1.0, 25 °C, S/L, 1:10) was studied as a function of time; acid consumption and extracted metal concentrations are presented. Whole coals consumed acid rapidly during the first few minutes, followed by slow acid consumption. Wood-, lignite-, and asphaltite-ashes consumed acid in two stages, the rapid phase extending < 30 min and the slow phase extended up to 10 days. The rapid phase was dominated by the dissolution of Ca, K and Mg ions for wood-ash, by Ca, Al and Mg ions for lignite-ash and Ca and Mg ions for asphaltite-ash. The sulfur concentration in solution and the concentrations of Ca, Fe, K, Mg, Na, P, Al and Mn in the aqueous phase verified the neutralizing capacity of the untreated ashes as well as the formation of insoluble sulfates in the residues. The slow phase kinetics differed for different fuels and exhibited leaching of several abundant elements—Fe, Al, K, Na and Mn. Trace elements (Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Th, U, V, Zn) sometimes required up to 32 h for maximal extraction from ashes. Suggestions are presented regarding the chemical nature of trace elements in the untreated coals and ashes and suitable residence times for economical industrial processes. We think it possible to combine bacteriological oxidation of sulfidic concentrates of acid leaching from ash of various qualities or even whole coals. |
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| Keywords: | acid leaching coal leaching ash leaching lignite asphaltite leaching kinetics metal occurrence |
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