Abstract
BackgroundIlmenite and rutile are naturally occurring titanium-bearing heavy minerals. Sri Lanka consists of ilmenite and rutile in placer deposits mainly along the northeast coast. The commercial value of rutile is higher than ilmenite. Therefore, the current study focuses to upgrade Sri Lankan ilmenite ores using commercially available activated carbon as a reducing agent. Ilmenite fraction was initially separated from raw beach sand using an industrial-scale magnetic separator (Wet high-intensity magnetic separator: sixteen pole model). The mixtures of ilmenite and activated carbon (4 to 1 ratio by weight) were milled using a planetary ball mill for one to four hours at one-hour intervals.ResultsThe milled samples were subsequently heated for two hours continuously at temperatures of 800 °C, 900 °C, 1000 °C, 1100 °C, and 1200 °C, respectively. Initial and annealed samples were analysed using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and X-ray fluorescence (XRF) analyses. XRD pattern of the initial sample was characterized by less percentage of rutile (TiO2) peaks and low crystallinity. However, the number of rutile peaks and crystallinity were increased with respective milling hours and annealed temperature. Besides, XRD analysis indicates a higher number of sharp and intense rutile and elemental iron peaks in the samples annealed above 1000 °C. FTIR analysis of raw ilmenite indicates mainly stretching vibrations of Fe–O. However, vibrational spectral bands around 700 cm−1 in samples annealed above 1000 °C are assigned to Ti–O–Ti stretching vibrations. High TiO2 and TiO2 + Fe2O3 (total) wt. (%) can also be observed in samples annealed above 1000 °C.ConclusionsThe optimum conditions for carbothermic reduction were obtained at 4 h of ball milling of ilmenite with activated carbon and continuously annealing at 1000 °C for 2 h. Carbothermic reduction is applicable to upgrade Sri Lankan ilmenite ores, and thus this method adds value to heavy mineral resources in Sri Lanka.
Highlights
Ilmenite and rutile are naturally occurring titanium-bearing heavy minerals
The current study examines the value addition potential of Sri Lankan ilmenite at the laboratory scale
The particle size distribution of the mixture of Sri Lankan ilmenite and commercially available activated carbon suggested a significant reduction of grain size after 4 h of ball milling (d50 = 0.08 mm)
Summary
Ilmenite and rutile are naturally occurring titanium-bearing heavy minerals. Sri Lanka consists of ilmenite and rutile in placer deposits mainly along the northeast coast. A large number of high-quality titanium ores such as rutile are required for catering to the escalating global demands of both metal titanium and T iO2 based products, especially in the Asia–Pacific region (Mackey 1994; Dooley 1975; Wang et al 2008). In this case, the production of synthetic rutile (TiO2) is gradually increasing due to a dearth of economically concentrated rutile deposits in the world. Readily available ilmenite gradually became an alternative raw material for synthetic rutile (Chen et al 1997; Wang and Yuan 2006; Wang et al 2008)
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