Trans. Nonferrous Met. Soc. China 23(2013) 2743−2750 Mineralogical characterization and leaching behavior of Nigerian ilmenite ore A. A. BABA 1,2 , S. SWAROOPA 2,3 , M. K. GHOSH 2 , F. A. ADEKOLA 1 1. Department of Chemistry, University of Ilorin, P. M. B. 1515, Ilorin 240003, Nigeria; 2. Hydro & Electrometallurgy Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswa 751013, India; 3. CSIR-Central Road Research Institute, New Delhi 110025, India Received 31 October 2012; accepted 6 April 2013 Abstract: The characterization and H 2 SO 4 leaching behavior of a Nigerian ilmenite ore following mechanical activation and alkali roasting were investigated. The effects of NaOH/ore ratio, H 2 SO 4 concentration, leaching and roasting temperature on the Ti recovery from the milled ore were examined. The results show that mechanical activation significantly enhances the dissolution of ilmenite ore. Under the leaching conditions of 90 °C, 60% (v/v) H 2 SO 4 and 4 h, about 72% Ti extraction was obtained from a milled ore roasted at 850 °C with 60% NaOH. X-ray diffraction (XRD) phase analysis of the roasted mass, water treated residue and leach residue supports the reaction mechanism and experimental results. Key words: ilmenite; leaching; mechanical activation; roasting; titanium 1 Introduction Processing of the ilmenite ore for the production of pigment grade TiO 2 often becomes difficult due to high iron content. Because of the limitation in the availability of natural rutile resources, many studies have focused on the beneficiation of ilmenite into synthetic rutile [1,2]. The known reserves of titanium oxides are decreasing, so other titanium minerals must be used, ilmenite being the immediate choice due to its abundance [3,4]. Hydrometallurgical processing of ilmenite requires drastic leaching conditions basically with hot concentrated mineral acids. The main industrial route is the sulfate process. In the sulfate process, the ilmenite ore is dissolved in concentrated sulfuric acid solution (~ 85%) at a temperature of nearly 200 °C to prepare a titanyl sulfate solution. This solution is further purified and hydrolyzed to produce pure TiO 2 [5]. In order to meet the demand for high-grade titanium ores, commercial practices including roasting and smelting are followed to upgrade the ilmenite resources by removing iron oxides and other impurities. Smelting produces a titania-rich slag and a molten iron by-product (South Africa, Canada and Norway). Ilmenite roasting to synthetic rutile involves two process routes, namely Becher process (Australia) using ilmenite grade of 57%−63% TiO 2 and Benelite process-roasting followed by acid leaching step (USA, India and Malaysia) and can treat a wide range of 50%−63% TiO 2 [6]. Although sulfate process constitutes about 50% of global TiO 2 production, but high acid concentration, temperature and exothermic nature of reaction may lead to disastrous operating problem unless well controlled, besides severe environmental problems arising from generation of H 2 S and SO 2 gases and release of waste acid during hydrolysis. In order to achieve enhanced Ti recovery, mechanical activation through high energy ball milling is often employed prior to leaching and has been found to significantly accelerate the dissolution rate by increasing their chemical reactivity [7−9]. Increased reactivity of mechanically activated minerals can be attributed to various reasons such as decrease of particle size and increase of specific surface area, changes in the crystalline structure and disorder, and occurrence of chemical reaction [10,11]. Besides increasing the recovery of valuable components, mechanical activation of mineral leads to the decreased decomposition temperature and reduction of reagent consumption [12,13]. Many practicable routes Corresponding author: A. A. BABA; Tel: +23-48035010302; E-mail: alafara@unilorin.edu.ng DOI: 10.1016/S1003-6326(13)62792-2