This investigation identified that ion-exchange chromatography can efficiently remove iron from the leaching of ilmenite by HCl. The strong basic anionic-exchange resin IRA 410 Cl is capable of retaining the negatively charged iron chloro complex from 20% HCl leachate of ilmenite. Oxidative conversion of Fe 2+ to Fe 3+ facilitates the iron exchange to the resin, resulting in an iron-free solution of titanium oxychloride (TiOCl 2 ). This can be directly used to produce synthetic rutile. The procedure is relatively simple and generates little acid waste.
Mercury (Hg) and cadmium (Cd) are contaminants of great environmental concern due to their natural and anthropogenic origin, their ability of bioaccumulate through the food chain and their harmful effects on human health. In this study, the Hg and Cd accumulation in the muscle of 65 yellowfin tuna (
Thunnus albacares
) collected from two different catching sites of the Indian Ocean near Sri Lanka were evaluated. The samples were mineralized using microwave accelerated digestion, and the metals were detected by atomic absorption spectroscopy (AAS). The metal levels were not significantly different between the two sites (p > 0.05), and the average Hg and Cd concentrations were 0.48 ± 0.35 mg/kg and 0.017 ± 0.024 mg/kg, (wet weight basis) respectively. Only 6 (9.2%) and 2 samples (3.1%) exceeded the European Commission limits for Hg (1 mg/kg) and Cd (0.01 mg/kg), respectively. A comparatively strong positive correlation was observed between the THg concentration and the weight of the fish. However, there was no clear relationship between the concentration and size for Cd. These findings provide an understanding of the Hg and Cd distribution in yellowfin tuna in two fishing grounds in the Indian Ocean near Sri Lanka.
The rate of leaching of iron from ilmenite (FeTiO 3 ) in hydrochloric acid (HCl) solutions is greatly enhanced by the presence of ultraviolet (UV) light. The magnitude of the air purged UV light illuminated leaching rate is approximately twofold higher than the N 2 purged leaching rate under dark conditions. The enhanced rate is attributed to the photo dissociation of polymeric titanium oxy species via oxidising radicals OH and HO 2 formed through Fe 3z /Fe 2z /H 2 O Fenton type reactions. Photo dissociation and consequent non-deposition of polymer species in the pores of ilmenite particles cause the chemical reaction between FeTiO 3 and HCl acid in stirred solutions to become the rate determining step. The addition of H 2 O 2 to the reaction mixture, in the presence and absence of UV light, further enhances iron leaching rate, confirming the role of radical species.
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