Effects of roasting system on the leaching behavior of iron and aluminum impurities in rare earth concentrates

With the ion-adsorption rare earth concentrate from a smelting enterprise in southern Jiangxi as raw material, the effects of roasting temperature and roasting atmosphere on the leaching of iron, aluminum impurity elements was investigated by means of Inductively coupled plasma spectrometer(ICP), X-ray diffraction analysis(XRD). Its mechanism was revealed. The results show that oxidizing roasting reduces the leaching of iron and aluminum impurities, especially when the roasting temperature exceeds 1300 ℃, the leaching rate of iron and aluminum is less than 5%. However, reducing roasting is not conducive to the solidification of impurities. It is due to the transformation of iron, aluminum and silicon from easily soluble amorphous phase to insoluble crystalline phase under oxidizing roasting conditions for the leaching decrease of impurities, such as iron, aluminum and the like, which are solidified in the form of aluminum-containing polybasic silicate, thereby inhibiting the leaching of iron and aluminum. Whether oxidizing roasting or reducing roasting, the roasting temperature has little effect on the leaching rate of rare earth in the experimental range.