<Original Papers>Ore Dressing Investigations of Titaniferous Iron Placers. (VI) : Recovery of TiO_2-Bearing Minerals in Low-Intensity Magnetic Separation

Thermo-magnetic separation was apllied to recover TiO_2-bearing minerals in low-intensity magnetic concentrate of the titaniferous iron placer from Sinchi, Fukushima Prefecture. The characteristics of the separated products were examined by means of chemical analyses and measurements of specific gravity, X-ray diffraction, intensity of magnetization, and Curie point. The magnetic concentrate mainly consisted of titanomagnetite and the solid solution or the ex-solution of hematite-ilmenite system. Titanomagnetite contained up to about 10% TiO_2 in solid solution. The lattice constant a of titanomagnetite was larger than that of pure magnetite and the intensity of magnetization of the former was smaller than that of the latter. Hemoilmenite was separated from titanomagnetite and ilmenohematite at about 200℃, because the Curie point of the former was lower. Pouillard\u27s theory of limited solubilities of ilmenite in hematite, 2Fe_2O_3=FeTiO_3,and of hematite in ilmenite, Fe_2O_3・2FeTiO_3,were verified. The lattice constants of ilmenohematite, nearly corresponding to 2Fe_2O_3・FeTiO_3,were determined to be α=5.044 A and c=13.83 A, and those of hemoilmenite, nearly corresponding to Fe_2O_3=2FeTiO_3,to be a=5.071～5.073 A and c=13.96～13.97 A. The saturation magnetization of minerals of this system varied considerably with TiO_2 content and its maximum value corresponded to the limit of solubility of hematite in ilmenite, being about 60 gausses. The yield and TiO_2 grade of concentrate and TiO_2 recovery in a Davis magnetic separator were considerably influenced by the temperature of water. The yield and TiO_2 grade of concentrate and TiO_2 recovery decreased with rise in the temperature of water. For example, the yield and TiO_2 grade of concentrate and TiO_2 recovery in the magnetic field intensity of 850 oersteds were 17.6%, 20.0%, and 20.0% respectively at the temperature of water of 4℃, and 9.0%, 9.8%, and 5.1% respectively at 77℃. In conclusion, it is suggested that the TiO_2 concentrate of higher grade might be recovered from iron placers by simply applying wet magnetic separation with the proper control of water temperature