Abstract—A bauxite ore can be utilized in Bayer Process, if the mass ratio of Al 2 O 3 to SiO 2 is greater than 10. Otherwise, its Fe x O y and SiO 2 content should be removed. On the other hand, removal of TiO 2 from the bauxite ore would be beneficial because of both lowering the red mud residue and obtaining a valuable raw material containing TiO 2 mineral. In this study, the low grade diasporic bauxite ore of Yalvaç, Isparta, Turkey was roasted under reducing atmosphere and subjected to magnetic separation. According to the experimental results, 800°C for reduction temperature and 20000 Gauss of magnetic intensity were found to be the optimum parameters for removal of iron oxide and rutile from the non- magnetic ore. On the other hand, 600°C and 5000 Gauss were determined to be the optimum parameters for removal of silica from the non-magnetic ore. Keywords—Low grade diasporic bauxite, magnetic separation, reduction roasting, separation index. I. INTRODUCTION N a bauxite ore, if the mass ratio of Al 2 O 3 to SiO 2 is greater than 10, it can be considered as high-grade bauxite, which can be processed directly by the Bayer process. On the other hand, if this ratio is lower than 8, it is regarded as low-grade bauxite and a pretreatment process should be used before Bayer Process. Although the low grade diasporic bauxite ore of Yalvaç, Isparta in Turkey is a potential raw material for Bayer Process, its high Fe x O y and SiO 2 content flaws its usability. Additionally Fe 2 O 3 content should be max. 2-2.5% for refractory purposes. Therefore removal of iron oxides is required to acquire a beneficial raw material [1], [2]. There are an amount of studies that involve the removal of iron oxides by magnetizing the iron bearing compounds by reduction of Fe 2 O 3 to Fe 3 O 4 , followed by magnetic separation. It was proved to be an effective way to decrease iron content of ores and tailings [2]–[6]. The reduction of hematite is carried out by the following reactions [3]; 3Fe ଶ O ଷ ൅ C → 2Fe ଷ O ସ ൅ CO ሺ୥ሻ (1) 3Fe ଶ O ଷ ൅ CO → 2Fe ଷ O ସ ൅ CO ଶሺ୥ሻ (2) 3Fe ଶ O ଷ ൅H ଶ → 2Fe ଷ O ସ ൅H ଶ O ሺ୥ሻ (3) K.Yılmaz, M.N. Sarıdede, and E. Yiğit are with the Yıldız Technical University, Department of Metallurgical and Materials Engineering, Esenler / İstanbul, 34210, Turkey (e-mail: koksal_1981@yahoo.com, msaridede@gmail.com, erdoganyigit40@yahoo.com) B.Birol is with the Yıldız Technical University, Department of Metallurgical and Materials Engineering, Esenler / İstanbul, 34210, Turkey (corresponding author to provide phone: +90212-383-4620; fax: +90212-383- 4665; e-mail: burak.birol@gmail.com). Rutile (TiO 2 ), which is a valuable mineral, is also present in the bauxite ores. The separation of rutile also lowers the red mud (Bayer process tailing) amount [7]. Cui et al. investigated the magnetic properties of ilmenite, hematite and LR-rutile after reduction roasting. They have concluded that, reduction roasting of ilmenite at 800°C increased its magnetic susceptibility significantly because of the transformation to maghemite (γ-Fe 2 O 3 ). Same magnetic behavior have been encountered at 800 or 1000 °C, in hematite, which reached that of magnetite after 30min of roasting with a charcoal:hematite ratio of either 1:10 or 1:5. Also in the reduction roasting of the LR Rutile have resulted in an increase in its magnetic susceptibility mainly due to the presence of leucoxene [6]. In another study, the authors investigated the recovery of iron oxide from SiO 2 , Fe 2 O 3 , CaO and Al 2 O 3 containing iron ore tailings by reduction roasting. They have asserted that, coal amount, roasting temperature, reduction time, and milling time of roasted samples were the main parameters that affect the recovery of iron minerals. As the result of their experiments, they suggest the optimum conditions of coal: iron ore tailings ratio as 1:100, roasting at 800°C for 30min, and milling 15min of roasted samples. Under these conditions, the grade of magnetic concentrate of 61.3% Fe and recovery rate of iron compounds as 88.2% were obtained [3]. Uwadiale also agrees that the 800°C and high Fe 2 O 3 :C ratio (1:9) give the optimum reduction rates and recovery of iron [8]. On the other hand, a study concerning iron ore refinement by the same process indicates that, best iron recovery results (93%) were obtained from the iron ore samples, which were reduced by H 2 at 450°C for 3min, although most MnO removal was achieved from the experiments conducted for 30 min [9]. Sadler and Venkataraman suggest that a reduction at 500°C for 120min is adequate for the bauxite ores containing 2.7% Fe 2 O 3 transforming into a product containing less than 1.6% Fe 2 O 3 with a recovery of more than 95% of the iron- free bauxite present in the feed [2]. In this work, the pre-beneficiation of low grade diasporic bauxite ore from Yalvaç, Isparta was investigated by reduction roasting and followed by magnetic separation with various parameters. It was aimed to determine the optimum process parameters for removal of iron oxide and silica in order to obtain a high grade ore to be used in Bayer Process. Additionally, the possibility to recover TiO 2 , which is a valuable mineral, was investigated. Pre-beneficiation of Low Grade Diasporic Bauxite Ore by Reduction Roasting K. Yılmaz, B. Birol, M. N. Sarıdede, E. Yiğit I World Academy of Science, Engineering and Technology International Journal of Materials and Metallurgical Engineering Vol:9, No:9, 2015 1084 International Scholarly and Scientific Research & Innovation 9(9) 2015 scholar.waset.org/1307-6892/10002069 International Science Index, Materials and Metallurgical Engineering Vol:9, No:9, 2015 waset.org/Publication/10002069