The influence of temperature on phase transformations of the minerals present in the red mud: reduction of hematite to magnetite

ABSTRACT In this work a technological route was proposed to analyze the behavior of phase transformations of the minerals present in the red mud during the process of reduction of hematite to magnetite. The fluorescence analysis and X-ray diffraction showed that red mud presented approximately 5% titanium oxide as anatase and 28% iron oxide in the forms of hematite and goethite. Experiments involving the reduction of hematite to magnetite using thermal treatment. The material was calcined at temperatures of 500, 600 and 1000 °C for 2 h. Then, X-ray diffraction and Raman spectroscopy analyzes were performed, which showed that the hematite was reduced to magnetite in all experimental conditions. For the calcination temperatures of 500 and 600 °C, the titanium oxide remained in anatase free form, but for the calcination performed at 1000 ºC, the oxide passed into the form combined with iron (ilmenite). The route proposed in this work allowed to obtain a material with magnetic characteristics, which could be used as source of titanium after extraction of iron compounds by magnetic separation or acid leaching.

摘要：本研究提出一条工艺路线，用以分析赤泥中各矿物在赤铁矿还原为磁铁矿过程中的相变行为。荧光分析与X射线衍射（X-ray diffraction）测试结果显示，赤泥中约含有5%以锐钛矿（anatase）形式存在的氧化钛，以及28%以赤铁矿和针铁矿（goethite）形式存在的氧化铁。本研究通过热处理开展赤铁矿还原为磁铁矿的实验，将物料分别在500℃、600℃与1000℃下煅烧2小时。随后对试样进行X射线衍射与拉曼光谱（Raman spectroscopy）表征，结果表明所有实验条件下赤铁矿均被还原为磁铁矿。当煅烧温度为500℃和600℃时，氧化钛仍以游离态锐钛矿形式存在；而在1000℃煅烧条件下，氧化钛与铁结合生成钛铁矿（ilmenite）。本研究提出的工艺路线可获得具备磁特性的物料，通过磁选或酸浸提取其中的铁化合物后，该物料可作为钛资源进行开发利用。