To Örebro University

Contamination of the environment due to mining and mineral processing is an urgent problem worldwide. It is often desirable to establish a grass cover on old mine waste since it significantly decreases the production of leachates. To obtain sustainable growth, it is often necessary to improve several properties of the waste such as water-holding capacity, nutrient status, and toxicity. This can be done by addition of organic materials such as wood residues, e. g., compost. In this study, we focus on the solution chemistry of the leachates when a substrate containing historic sulfidic mine waste mixed with 30 % (volume) bark compost is overgrown by Agrostis capillaris. The pot experiments also included other growth-promoting additives (alkaline material, mycorrhiza, and metabolizable carbon) to examine whether a more sustainable growth could be obtained. Significant changes in the plant growth and in the leachates composition were observed during 8 weeks of growth. It was concluded that in this time span, the growth of A. capillaris did not affect the composition of the leachates from the pots. Instead, the composition of the leachates was determined by interactions between the bark compost and the mine waste. Best growth of A. capillaris was obtained when alkaline material and mycorrhiza or metabolizable carbon was added to the substrate.

From 1942 to the 1966, oil was produced by pyrolysis of shale, in Kvarntorp, Sweden. This generated some 40 million m³ of metal rich pyrolyzed shale and discarded fines that were piled on site with its original metal content almost intact. The present study focuses on the leaching of vanadium, manganese, iron and molybdenum from fines after addition of wood chips and steel slag, in outdoor 1 m³ reactor systems at low liquid to solid ratio, in order to evaluate the potential environmental impact and recovery of the elements from the leachates. Seasonal variations were observed, with increased leaching during peak summer. For vanadium and molybdenum, high addition of wood chips decreased the leaching, probably due to adsorption. Manganese showed the opposite behavior while leaching of iron was almost independent of the amount of wood chips. Depending on the systems, up to 2200 μg L^-1 vanadium, 90 μg L^-1 molybdenum, 25 mg L^-1 manganese and 500 mg L^-1 iron was found in the aqueous phase. Applied to the 40 million m³ pile, the annual leaching of those elements may reach 14 ton, 0.6 ton, 200 ton and 2400 ton, respectively.

The use of nitrogen as plasma gas for microwave plasma atomic emission spectroscopy (MP AES) is an interesting development in analytical science since the running cost can be significantly reduced in comparison to the inductively coupled argon plasma. Here, we evaluate the performance of the Agilent 4100 MP AES instrument for the analysis of principal metals (Ca, K, Mg, and Na), lithogenic metals (Al, Fe, and Mn) and selected trace metals (As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, V, and Zn) in nitric acid plant digests. The digests were prepared by microwave-assisted dissolution of dry plant material from sunflower (Helianthus annuus) in concentrated nitric acid. Comparisons are made with analysis of the same solutions with ICP-MS (Agilent 7500cx) using the octopole reaction system (ORS) in the collision mode for As, Fe, and V.

The limits of detection were usually in the low μg L-1 range and all principal and lithogenic metals were successfully determined with the MP AES and provided almost identical results with the ICP-MS. The same applies for the selected trace metals except for As, Co and Mo where the concentrations were below the detection limit with the MP AES. For successful analysis we recommend that (i) only atom lines are used, (ii) ionization is minimized (e.g. addition of CsNO3) and (iii) the use of internal standards should be considered to resolve spectral interferences.

In abatement of acid rock drainage (ARD) slag from the Linz-Donawitz steel making process (LD-slag) provides high neutralizing capacity at low cost. A serious drawback for the use of this by-product is its high content of vanadium, which makes it a potential source of toxic vanadium species. The aim of this work was to determine the most common vanadium species, V(IV) and V(V), leached from LD-slag by artificial ARD. Capillary electrophoresis was employed to quantify the species. From the results an initial dominance of V(V) and increasing abundance of V(IV) with increasing artificial ARD L/s ratio was observed.

Uranium-stabilizing ligands can be useful complexing agents for uranium in aqueous solution. The discovery of novel ligand candidates for selective uranium capture in artificial and natural waters could provide scope for their use in water remediation and metal recovery from low- and high grade ores. In this study we used seven fungal strains, isolated from shale waste, to monitor the uranium retention capacity from an aqueous solution. After four weeks of incubation, suspensions containing the fungal strains were filtered, and up to 100% of the total uranium inventory was removed from a 10 mg L-1 solution. Approximately 70% of the total uranium removal is attributed to complexation and/or adsorption by particles in the malt extract and some 10% is adsorbed by the fungal biomass. The additional 20% uranium removed could be related to the excretion of fungal metabolites. From 58% to 90% of the uranium is removed within ten minutes. The formation of colloidal/particulate uranium is proposed to be controlled by organic ligands in the culture medium and organic ligands excreted by the fungi where phosphorus moieties seem to be important. Membrane fouling by the hydrocarbons is also suggested to contribute to a loss of uranium from the aqueous phase.