Fonte: Journal of the Southern African Institute of Mining and MetallurgyPublicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista CientíficaFormato: text/html
Publicado em 01/01/2008EN
Relevância na Pesquisa
Radioactive elements associated with heavy mineral deposits may be removed from the ilmenite concentrate before smelting or, alternatively, from the high-titanium slag after smelting. Either way, the radioactivity removal process will involve leaching and/or flux-roasting. However, the volume of slag is approximately 50 per cent less than the volume of ilmenite concentrate and it may therefore be more efficient to remove radioactive elements from the slag. Several slags with different compositions (in terms of iron to titanium ratio, silica content and radio activity) were studied. All the slags contain iron-titanium oxide phases with M3O5 (M = Fe2+, Ti3+, Ti4+, Mg2+, Al2+, Cr3+) stoichiometry, silicate phases and a small amount of entrained metal droplets. The silicate phases have variable compositions; in all the samples it was found that droplets of a silica-rich phase (containing about 60% SiO2) unmixes from a low-silica phase (containing about 40% SiO2). Both the highand low-silica phases are considered to be glass, representing quenched, immiscible silicate melt phases. The silicate and oxide phases were analysed by electron microprobe to determine the distribution of thorium in the slag (the concentrations of the radioactive daughter products of the thorium decay series are too low to be detected with the microbeam analytical facilities that were available during the investigation). The results are unequivocal: the concentration of thorium in M3O5 oxide phases is below the detection limit of the technique (500 ppm) while the concentration in the silicate phases is at the one per cent level. Furthermore...