Kinetics of chlorination and microstructural changes of xenotime by carbon tetrachloride

Abstract

Among the rare earth minerals, fluorides, phosphates, and oxides have received attention from the rare earth industry. Traditional methods of decomposition of these minerals, usually alkaline or acid processes, involve several operations. Another possibility to obtain lanthanide chlorides or oxychlorides is reacting the mineral with chlorinating agents, such as gaseous chlorine, hydrogen chloride, thionyl chloride, and carbon tetrachloride, reducing the operation costs and making the process less complicated. In this context, we investigated the decomposition of xenotime using carbon tetrachloride at temperatures from 873 to 1173 K and kinetic and mechanistic studies have been performed. Powder X-ray diffraction, scanning electronic microscopy, energy dispersive X-ray spectrometry, ultra-violet/visible spectroscopy, and thermal analysis techniques were used in this study. The results showed that the reaction follows the shrinking-unreacted-core model with formation of a product layer (lanthanide oxychloride), confirmed by powder X-ray diffraction. Moreover, microstructural changes of xenotime grains during the chlorination reaction were verified.