a b s t r a c tUnderstanding of the interactions between iron oxides and flotation reagents is important both for flotation and agglomeration of iron ore. Model systems comprising synthetic iron oxides and pure chemical reagents are commonly applied in experimental work in order to obtain high quality data and to ease the interpretation of the empirical data. Whether the results obtained using model systems are valid for iron ore minerals and commercial reagents is a question seldom addressed in the literature. It is shown in this work that previously reported results obtained from a model system, concerning adsorption of a carboxylate surfactant and sodium metasilicate onto synthetic magnetite nanoparticles, as obtained by in situ ATR-FTIR spectroscopy and contact angle measurements, are applicable to adsorption of flotation reagents on magnetite concentrate. Additionally, the problem of restoring magnetite wetting after flotation is addressed since good wetting of a magnetite concentrate is required to produce iron ore pellets by wet agglomeration. The results from the present work indicate that the wettability of both synthetic magnetite coated with surfactant and magnetite concentrate after flotation can be improved by adsorbing a hydrophilizing agent such as silicate or polyacrylate.
Understanding process water characteristics and variations is important for ensuring high quality processing of iron ore. Large amounts of water are used during refinement, and the water is often recirculated to save energy. Water quality is important for processes such as flotation and agglomeration but recirculation of process water and changes in production can alter water quality significantly. This study was undertaken to better understand the origin of dissolved components in the process water and water quality variations in process water geochemistry at the Kiirunavaara magnetite ore mine, based on analyses from 1989 to 2008. Long-term trends at single sampling stations in the process chain, as well as changes along the process chain, were studied. Ca, S, Na, and Cl are the major elements in the process water, accounting for over 80% of the dissolved concentration. Ca has the highest concentrations with a mean of 183 mg/L and a maximum of 303 mg/L in the clarifying pond. At all investigated sampling stations (influent water and water in the sorting plant, concentration plant, pelletizing plant, and clarifying pond), dissolved elemental concentrations increased during the studied time period. This increase was mainly caused by increased production. The high concentrations of Ca and S probably result from sulfide oxidation and calcite buffering in the drainage area. The high N concentrations come from undetonated explosives while the main source of Na and Cl is fluid inclusions. If production continues to increase, higher concentrations in the process water should be anticipated.
A mixture of sediment and water is formed during the cleansing of catch basins. This paper discusses the concentration levels and distribution of numerous metals and organic carbon (OC) in the water phase of this mixture. The results show that due to the high concentrations of metals in the water phase, the catch basin mixture should be treated before it reaches a recipient. Three sites with different types of area and traffic intensity were sampled. Four fractions were analyzed: unfiltered, dissolved (<0.2 µm), colloidal (0.22 µm to 1 kD [kilodalton]), and truly dissolved (<1 kD). The results of the unfiltered fraction show high concentrations of metals and OC in the catch basin mixture. A comparison of Canadian and Swedish Environmental Protection Agency guidelines and the catch basin mixtures shows that concentrations exceeded the threshold values for As, Cd, Cr, Cu, Ni, Pb, and Zn. Compared with samples from a reference lake in the area, the unfiltered fraction showed high concentrations of all elements. OC seems to have a large impact on the overall speciation of trace metals in the catch basin mixture. To trace the sources of the particulate fraction in the unfiltered samples, Al-normalization was used. Al-normalization indicated that Ca, K, Mg, Na, Mn, Ba, Co, and Cr concentrations could be explained by mineral particles used as traction control. Furthermore, the trace elements As, Cu, Pb, Zn, and Ni were all enriched in the catch basin mixture.
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