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USEFULNESS OF MINERAL WASTES AFTER EXTRACTION OF RARE ELEMNES FOR RECLAMATION PURPOSES

MSc. Anna Pudelko, Assoc. Prof. Dr. Marcin Chodak, Dr. Katarzyna Grzesik

Abstract

Extraction of rare earth elements (REE) from mining wastes may change their physical and chemical properties thus affecting their usefulness for reclamation. The aim of this work was to assess the usefulness for reclamation of mine wastes used for REE production. Samples of mine wastes after an experimental benefication process (n=6) were delivered from Kankberg mine, Sweden. The samples were measured for organic matter (OM) content, specific gravity, maximum water holding capacity (WHC), texture, pH and electric conductivity. The contents of Al, Na, Mg, K, Ca, Fe, Cr, Ni, Cu, Zn, Cd and Pb in the samples were measured after pressure digestion in aqua regia, the C and S contents with elemental autoanalyzer and the N content with Kjeldahl method. The samples were classified as silt loam with moderate WHC (36.0%) and alkali pH (8.7 in water and 8.9 in 1 M KCl). The samples did not contain OM, C and N while the S content was relatively high (0.1%). The concentrations of toxic metals (Cr, Ni, Cu, Zn, Cd and Pb) were low. The studied materials can be used for different types of land reclamation including nature restoration, forestry or agriculture as their texture is favorable and they do not contain excessive amounts of toxic metals. Negative properties of these materials include their high pH, high S content and lack of N. The pH of wastes is high particularly for planting forest tree species that are better adapted to low soil pH. However, this problem may be overcome by oxidation of S present in the wastes which is likely to decrease their pH. However, considering high initial pH of the wastes and relatively high amounts of base cations this process should not lead to excessive acidification. Low N content indicates that extensive N fertilization will be required during reclamation process.

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DOI resolver: doi.org/10.5593/sgem2017/52/s20.142

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