Abstract
The reactivity of ilmenite ore during leaching with hydrochloric acid can be greatly enhanced by reduction in solution using metallic iron. Addition of a particular amount of iron powder after a certain time of reaction will reduce all the dissolved Fe3+ to Fe2+ and reduce a portion of the dissolved Ti4+ to Ti3+. As the leaching continues, any further dissolved Fe3+ will be simultaneously reduced by the action of the formed Ti3+ to produce Fe2+ and Ti4+. As a result, dissolution of the iron and titanium contents from the ore will be improved. Meanwhile, the dissolved Ti4+ will be hydrolysed and precipitated leaving mainly ferrous chloride in the solution. The hydrolysis is accompanied by fast dissolution of the unreacted ore. A reductive leaching process is proposed taking advantages of the recent advances in HCl regeneration from spent leach liquor. The different leaching parameters were optimised to obtain as little iron as possible in the titanium dioxide product. Synthetic rutile of about 90% TiO2 and 0.8% Fe2O3 was obtained from an Egyptian medium-grade ilmenite ore of grain size 100%-75 mum using 20% HCl at boiling temperature (110 degreesC), with addition of 0.11 g iron powder/g ore for 5 h. The product has a low content of colouring elements (total MnO2, Cr2O3 and V2O5 = 0.12%) and chlorine consuming elements (total CaO, MgO and Al2O3 = 0.08%) but contain high silica (SiO2 = 5.8%). The process is applicable for higher grade ilmenite ores which will produce higher quality synthetic rutile. (C) 2004 Elsevier B.V. All rights reserved.